Abstract: In the shipbuilding, construction, automotive, and aerospace industries, welding is still a crucial manufacturing process because it can be utilized to create massive, intricate structures with exact dimensional specifications. These kinds of structures are essential for urbanization considering they are used in applications such as tanks, ships, and bridges. However, one of the most important types of structural damage in welding continues to be fatigue. Therefore, it is necessary to take this phenomenon into account when designing and to assess it while a structure is in use. Although traditional methodologies including strain life, linear elastic fracture mechanics, and stress-based procedures are useful for diagnosing fatigue failures, these techniques are typically geometry restricted, require a lot of computing time, are not self-improving, and have limited automation capabilities. Meanwhile, following the conception of machine learning, which can swiftly discover failure trends, cut costs, and time while also paving the way for automation, many damage problems have shown promise in receiving exceptional solutions. This study seeks to provide a thorough overview of how algorithms of machine learning are utilized to forecast the life span of structures joined with welding. It will also go through their drawbacks and advantages. Specifically, the perspectives examined are from the views of the material type, application, welding method, input parameters, and output parameters. It is seen that input parameters such as arc voltage, welding speed, stress intensity factor range, crack growth parameters, stress histories, thickness, and nugget size influence output parameters in the manner of residual stress, number of cycles to failure, impact strength, and stress concentration factors, amongst others. Steel (including high strength steel and stainless steel) accounted for the highest frequency of material usage, while bridges were the most desired area of application. Meanwhile, the predominant taxonomy of machine learning was the random/hybrid-based type. Thus, the selection of the most appropriate and reliable algorithm for any requisite matter in this area could ultimately be determined, opening new research and development opportunities for automation, testing, structural integrity, structural health monitoring, and damage-tolerant design of welded structures.

Keywords: fatigue | finite element | machine learning | metal | Monte Carlo | neural network | predict | regression | structural health monitoring | weld

Abstract: Increasing the Gear Ratio (GR) while decreasing the gearbox dimension is a contradiction that mechanical designers are challenged to solve. The increasing importance of fine-tuning high power density designs has led to the development of innovative solutions involving cycloidal and hypocycloidal gears. However, when the required GR increases and the number of the stages raises, the gearbox architecture plays a key role in minimizing the overall dimensions. In the present paper, an innovative gearbox architecture is presented. The new design combines three cycloidal and hypocycloidal gearing stages to achieve a higher GR with respect to a traditional two-stage cycloidal gearbox with the same overall dimension. This architecture is called Nested since it involves stages with internal and external gears arranged one inside the other. A comparison of the proposed solution with the more compact two-stage cycloidal architecture (Wolfrom) is shown. The GRs as a function of the total number of meshing features are discussed as well as the torques acting on each component. Eventually, a design solution is illustrated.

Keywords: Cycloid drive | High power density gearbox | Hypocycloidal | Internal gearing | Wolfrom

Abstract: An accurate fracture simulation is often associated with how reliably the material model is represented. Hence, many models dealing with the calibration of ductile damage of materials have already been developed to predict failure initiation. Nevertheless, the challenge remains in obtaining an accurate representation of the fracture growth. Herein, an element deletion algorithm is developed and implemented into finite element open-source software. The deleted elements are replaced by new cells made of a virtual low-stiffness material. To better visualize the failure progression, the final model excludes these virtual cells from the representation. The functionality of the algorithm is tested through a series of two-dimensional simulations on three different geometries with a well-known behavior under uniaxial tension. Moreover, the failure response of a three-dimensional lattice structure is numerically investigated and compared against experimental data. The results of the two-dimensional simulations showed the capability of the algorithm to predict the onset of failure, crack nucleation, and fracture growth. Similarly, the onset and the initial fracture region were accurately captured in the three-dimensional case, with some convergence issues that prevent the visualization of the fracture growth. Overall, the results are encouraging, and the algorithm can be improved to introduce other computational functionalities.

Keywords: Code_Aster | ductile materials | fracture analysis | lattice structure | numerical simulation

Abstract: The acquisition of complex fluxes inside a Tapered Roller Bearing (TRB) via Particle Image Velocimetry (PIV) is an experimental challenge. This can be successfully performed by exploiting a special test rig having the outer ring manufactured with sapphire. In the present paper, the velocity field in the region between cage, rollers and outer race have been captured via PIV in a fully flooded lubricated TRB. The experimental conditions have been reproduced numerically via Computational Fluid Dynamics (CFD). The comparison of PIV results with CFD ones showed excellent consistency. It has been observed that, in the target domain, the tangential velocity of the lubricant is greater than those of the cage. In addition, in the proximity of the edges of the rollers, squeezing effects due to high gradients of pressure have been recorded. The distribution of flow rates due to the pumping effect in different regions of the TRB have been estimated.

Keywords: CFD | Lubrication | OpenFOAM | PIV | Tapered Roller Bearing

Abstract: In the presented work, a parametric multibody simulation model is presented that is capable of predicting the friction torque and kinematics of tapered roller bearings. For a highly accurate prediction of bearing friction, consideration of solid and lubricant friction is mandatory. For tapered roller bearings in particular, the friction in the contact between the rolling element and raceway is of importance. Friction forces in the contact between the rolling element end face and inner ring rib as well as roller cage pocket contacts are also considered in the model. A large number of tests were carried out to validate the model in terms of the simulated frictional torque. Influencing variables such as speed, axial load, radial load, and temperature were investigated. The simulation results show good agreement with the measured friction torque, which confirms that the model is well suited to predict frictional torques and therefore the kinematics of tapered roller bearings.

Keywords: dynamic simulation | experimental validation | friction | modelling | multi body simulation | power losses | rolling bearing | tapered roller bearings | tribology

Abstract: The operation of Tapered Roller Bearings (TRBs) in partially and fully flooded lubricated systems involves relevant lubricant flows; the axial flow rate from the small end to the large end of a TRB is renowned as pumping effect. This effect, which has been studied since the 1970s, affects the cooling process, the static pressure on seals, and the load-independent power losses (PLB0). Then, it influences the design of lubricant supply system. Over the years, analytical formulations to estimate oil flow rates and resistant torques in TRBs have been developed exploiting simplified theories. However, for non-ideal operating conditions, the above formulations may provide incorrect information. To this respect, the development of new tools to support the design of TRBs lubrication systems is needed. Nowadays, novel numerical and experimental techniques allow more detailed analysis of oil behaviors within TRBs. The first goal of the present paper is to introduce Computational Fluid Dynamics (CFD) methods to model and simulate TRBs in the OpenFOAM® environment. In this way, it is possible to estimate fluxes and resistant torques exploiting relatively low computational resources. The second goal is to describe experimental campaigns aimed at measuring loadindependent power losses (PLB0), the oil distribution, and the lubricant velocity field. The latter, exploiting Particle Image Velocimetry (PIV) techniques. Thus, the CFD results can be compared with the experimental ones.

Abstract: To improve roller bearing efficiency, it is essential to identify the sources of power losses and quantify them in the design stage, considering different influencing factors. For oil-lubricated bearings, load-independent power losses ((Formula presented.)) can be the dominant source of dissipation, especially for high-speed and abundant lubrication. In the present work, (Formula presented.) of a 32208 tapered roller bearing were measured experimentally under various operating conditions; that is, different rotational speeds, temperatures, and geometries of the oil reservoir. A numerical tool, based on computational fluid dynamics, to estimate (Formula presented.) and provide useful insights to investigate their causes has been developed in the OpenFOAM® environment. Numerical and experimental results show excellent agreement in most of the operating conditions investigated. Oil flows, (Formula presented.) contributions of different bearing components, and computational effort are discussed in the article.

Keywords: CFD | experimental validation | hydraulic power losses | lubrication | OpenFOAM^® | Tapered roller bearing

Abstract: To enhance the bearings’ efficiency, it is essential to determine and quantify the sources of power loss in the design stage. In oil-lubricated bearings, load-independent power losses (PLB0 ) can be a significant factor in energy dissipation. This study examines the PLB0 of a double-row Tapered Roller Bearing (32312-A) under different operating conditions, namely various speeds, viscosities, and lubrication conditions, i.e. Feed Lubrication (FEED-L) and Full-Flooded Lubrication (FLO-L). In this respect, a numerical tool based on Computational Fluid Dynamics has been developed within the OpenFOAM® environment. Results highlight that the estimated PLB0 in FLO-L can be an order of magnitude higher than the ones evaluated in FEED-L. The PLB0 in FEED-L are almost exclusively due to inertial effects (99%) and the PLB0 in FLO-L are for the 70% caused by viscous effects. Additionally, it has emerged that the lubricant viscosity has a huge impact on PLB0 for both lubrication conditions. For instance, in the studied configurations, doubling the viscosity can lead to an increase of up to 180% for FEED-L and up to 500% for FLO-L. Moreover, in FEED-L, the flow rate has a significant effect on PLB0 ; on average, doubling the flow rate leads to an increase in PLB0 of more than 15%.

Keywords: Bearing Efficiency | CFD | Hydraulic Power Loss | Lubrication | Open Source | Rolling-Element Bearing

Abstract: The study aims to optimize the topology of the complete disc replacement. In this paper, we present a stress-based topology optimization of a complete disc replacement for the lumbar spine using the finite element level set method (LS). The disc was optimized to reduce stress and strain at the level of two segments. The new modified pro disc design was proposed to increase the space for bone ingrowth and increase the stability of fixation. The intact model was tested in six degrees of freedom (compression, extension, flexion, lateral bending, and torsion). The volume of the intact model was reduced by 50% by optimizing the topology, and validation showed more significant results under biomechanical loading conditions. The Von Mises stress remains the same with minor differences. Topology optimization allows to increase bone ingrowth and reduces stress-shield effects in the cortical bone and cancellous bone.

Keywords: Complete Disc Replacement | Finite Element Method | Lumbar Spine | Topology Optimization

Abstract: Experience and evaluation research on sustainable products’ design is increasingly sup-ported by eye-tracking tools. In particular, many studies have investigated the effect of gazing at or fixating on Areas of Interest on products’ evaluations, and in a number of cases, they have inferred the critical graphical elements leading to the preference of sustainable products. This paper is motivated by the lack of generalizability of the results of these studies, which have predominantly targeted specific products and Areas of Interest. In addition, it has also been overlooked that the observation of some Areas of Interest, despite not specifically targeting sustainable aspects, can lead consumers to prefer or appreciate sustainable products in any case. Furthermore, it has to be noted that sustainable products can be recognized based on their design (shape, material, lack of waste generated) and/or, more diffusedly, information clearly delivered on packaging and in advertising. With reference to the latter, this paper collected and classified Areas of Interest dealt with in past studies, markedly in eco-design and green consumption, and characterized by their potential generalizability. Specifically, the identified classes of Areas of Interest are not peculiar to specific products or economic sectors. These classes were further distinguished into “Content”, i.e., the quality aspect they intend to high-light, and “Form”, i.e., the graphical element used as a form of communication. This framework of Areas of Interest is the major contribution of the paper. Such a framework is needed to study regularities across multiple product categories in terms of how the observation of Areas of Interest leads to product appreciation and value perception. In addition, the potential significant differences between sustainable and commonplace products can be better investigated.

Keywords: areas of interest | brand | eco-design | eco-labels | eye tracking | green consumption | product description | sustainable products | value perception

Abstract: The characterization of new materials for enabling gear design is definitely a fundamental objective in the gear industry and research. Single Tooth Bending Fatigue (STBF) tests can be performed to speed up this process. However, it is well known that STBF tests tend to overestimate material strength compared to tests performed directly on meshing gears (MG) which, in turn, require an excessively long test time. Therefore, it is common practice to use a constant correction factor of 0.9 to translate STBF results for designing actual MG (e.g., via ISO 6336). Recent works involving a combination of Finite Element Models (FEM) and multiaxial (non-proportional) fatigue criteria based on the critical plane concept have highlighted that the assumption of considering as a constant independent of the gear design parameters leads to inaccurate results. However, in previous studies, no correlation between and gear design parameters has emerged. In the present paper, the influence of the normal pressure angle (), the profile shift coefficient (∗), and the normal module () on was investigated by analyzing FEM simulations with the Findley fatigue criterion. 27 gear geometries were studied by varying the above 3 parameters in 3 levels (full factorial DOE). These geometries were simulated in both MG and STBF configurations. The results of the 54 FEM simulations were analyzed by applying the Findley fatigue criterion and the corresponding were calculated. The correlation between and,∗ and was investigated using the Analysis of Variance (ANOVA) technique. The results show that the only gear design parameter influencing is∗ hence, a regression model for including∗ has been developed. This latter has been then adopted for calculating and comparing values from other combination of the parameters found in literature, giving good correspondence.

Keywords: critical plane criteria | Findley | finite element model | gear design | material characterization | multiaxial fatigue | profile shift | single tooth bending fatigue

Abstract: The diffusion of Fab Labs and the continuous development of Additive Manufacturing technologies are undoubtedly two relevant phenomena nowadays. The former fuels the latter and vice versa, but their mutual relationship has not been systematically explored so far. This paper presents an exploratory study based on a survey, in which various aspects of the use of 3D printers in Fab Labs are investigated. The results show how different scales of Fab Labs are present in terms of investments made in 3D printing, as well as work purposes are not negligible for many attendees. In addition, the outcomes of the survey show that 3D printers are considered easy to use, as well as manufactured parts are deemed satisfactory. Despite this, there are still some barriers to boosting the market of domestic 3D printers for Fab Lab visitors.

Keywords: 3D printers | CAD | Design for Additive Manufacturing | Fab Labs | Skills

Abstract: Experimental studies on rolling-element bearing lubrication represent an ambitious engineering challenge. In the present study, the design of a dedicated test rig to perform Particle Image Velocimetry (PIV) measurements on the lubricant inside a tapered roller bearing is presented. Through the usage of a sapphire outer ring, it has been possible to optically access the inside of a bearing without compromising its kinematics. PIV measurements allowed the reconstruction of the lubricant velocity field in the cavity between the cage and the outer ring at different rotational speeds. Results show that as the speed of rotation increases, bubbles due to aeration phenomena tend to appear and modify the behavior of the lubricant considerably.

Keywords: Lubrication | PIV | Tapered Roller Bearing | Test Rig

Abstract: The air-lubricant interaction causes aeration which influences lubrication mechanisms in rolling-element-bearings. The goal of this paper is to develop a Computational Fluid Dynamics (CFD) model capable to take into consideration aeration. A new solver was implemented in the open-source environment OpenFOAM®. A dip lubricated tapered-roller-bearing was simulated with the new and a standard solver. The numerical predictions were compared with experimental data acquired on a dedicated test rig exploiting Particle Image Velocimetry (PIV). The comparison of the standard predictions and the experimental data for high shaft rotational speeds (higher level of aeration) shows discrepant results. On the other hand, the solver that takes aeration into account leads to results which are comparable to the experimental ones in all rotational ranges investigated via PIV.

Keywords: Aeration | CFD | Lubrication | OpenFOAM® | PIV | Tapered roller bearing

Abstract: Despite the large diffusion of additive manufacturing, and markedly fused filament fabrication, some quality aspects of the 3D printed parts have not been dealt with sufficiently. This applies particularly to geometric accuracy and the influence process parameters have on it. The paper describes an experiment in which 27 copies of a part were manufactured by means of a desktop fused filament fabrication device while manipulating layer thickness, printing speed, and number of contours. The effect of such process parameters on five typologies of geometric deviations and the duration of the printing process was assessed. While all the process parameters showed effects on both the printing time and some geometric deviations, the number of contours resulted as the most critical factor. The paper includes a proposal to optimize geometric accuracy and the rapidity of the process, which foresees the maximization of the number of contours, the minimization of the layer thickness, and the use of an intermediate value for printing speed.

Keywords: Coordinate measuring machine | Engineering design | Fused deposition modelling | Geometric tolerances | Process parameters | Rapid prototyping

Abstract: The concept of “Industry 4.0” encourages the use of automated manufacturing processes and the use of advanced technological systems. Some of the most fundamental needs of the Fourth Industrial Revolution can only be met with the help of additive manufacturing. However, the mechanical behavior and reliability of additive-manufactured components are hardly recognized. This paper provides a systematic review of metal additive manufacturing technologies, materials, lattice structures, and fatigue properties as well as the development of numerical simulations. The current state of development in metal alloys and the optimization of cellular structures were presented. In addition, this paper discussed the main challenges in numerical simulation methods, their validation with experimental results, and the limitations of commercial software used. Overall, this paper provides an overview of metal additive manufacturing as well as a survey of its simulation software development to optimize several parameters in industrial and academic research fields. The results were critically analyzed and provided a benchmark for future research and development.

Keywords: fatigue properties | finite element method | laser powder bed fusion | metal additive manufacturing | numerical simulations | structure-process-fatigue properties (SPFP) method

Abstract: According to standards, a fundamental gear design parameter, which heavily influences the sizing of these mechanical components, is the gear tooth root bending strength. To establish this parameter in a reliable way, tests should be performed on running gears (RG) manufactured with the same material and heat treatments under investigation. However, it is common practice in industry and in academia to perform single tooth bending fatigue (STBF) tests, which, on the one hand, are simpler and cheaper to perform, on the other hand, the stress history (t ) they induce is not identical to that obtained during RG meshing. Therefore, it is necessary to apply a correction coefficient (fkorr) to translate data obtained via STBF in RG design data. In recent studies, a method to estimate fkorr through the combination of finite element (FE) simulations and the implementation of multiaxial fatigue criteria (MFC) based on the critical plane concept has been proposed. This method consists of simulating through FE a gear geometry both in the RG load case and in the equivalent STBF condition. Through the load histories recorded on the nodes belonging to the critical area, it is possible, by implementing different MFC, to identify the most critical node and the relative Damage Parameter (DP). The ratio between the obtained critical DP of the STBF case and RG provides the value of fkorr. However, different MFC can lead to different results in terms of fkorr. This is because different MFC differs in the definition of the DP. More specifically, DPs are both functions of material properties, such as the fatigue limit of the material related to symmetric sinusoidal bending stresses (σf) and the fatigue limit at sinusoidal cyclic torsional stresses (τf), and load-dependent characteristics. The goal of this paper is to investigate the effect of different material properties, i.e. σf and τf , on the estimation of fkorr highlighting differences between the various MFC implemented, i.e. Findley, Matake, Papadopoulos, and Susmel et al. To this respect, the above-mentioned numerical method has been applied to a specific gear geometry whose material properties have been systematically varied. Results show that the criteria of Findley and Papadopoulus lead to very similar results and a monotonically increasing relationship between fkorr and τf /σf . A similar trend is observed for the Susmel et al. criterion but with higher value of fkorr Differently, the criterion of Matake leads to a monotonic decreasing relationship between fkorr and τf /σf

Keywords: Critical plane | FEM | gears | material characterization | multiaxial fatigue | STBF

Abstract: Mechanical components, such as gears, are usually subjected to variable loads that induce multiaxial non-proportional stress states, which in turn can lead to failure due to fatigue. However, the material properties are usually available in the forms of bending or shear fatigue limits. Multi-axial fatigue criteria can be used to bridge the gap between the available data and the actual loading conditions. However, different criteria could lead to different results. The main goal of this paper is to evaluate the accuracy of different criteria applied to real mechanical components. With respect to this, five different criteria based on the critical plane concept (i.e., Findley, Matake, McDiarmid, Papadopoulos, and Susmel) have been investigated. These criteria were selected because they not only assess the level of damage, but also predict the direction of crack propagation just after nucle-ation. Therefore, measurements (crack position and direction) on different fractured gear samples tested via Single Tooth Bending Fatigue (STBF) tests on two gear geometries were used as reference. The STBF configuration was numerically simulated via Finite Elements (FE) analyses. The results of FE were elaborated based on the above-mentioned criteria. The numerical results were compared with the experimental ones. The result of the comparison showed that all the fatigue criteria agree in identifying the most critical point. The Findley and Papadopulus criteria proved to be the most accurate in estimating the level of damage. The Susmel criterion turns out to be the most conserva-tive one. With respect to the identification of the direction of early propagation of the crack, the Findley criterion revealed the most appropriate.

Keywords: Critical plane | FEM | Finite Element Model | Gears | Material char-acterization | Multiaxial fatigue | Single Tooth Bending Fatigue | STBF

Abstract: Eco-designed products can contribute to sustainable development if consumers choose them rather than the less environmentally friendly alternatives and if they are used properly. How-ever, eco-design methods have so far failed to address the issue of unsustainable behaviors, whose sources have not been recognized. In light of this deficiency, the authors have analyzed a large number of eco-designed products with the aim to capture the possible unsustainable behaviors arising from their use and consumption. The subsequent characterization of unsustainable behaviors has led to the creation of a framework of unsustainable behaviors, which has been subjected to the evaluation of a pool of experts in the field. In its final version, the framework includes nine classes of unsustainable behaviors, which are categorized into the corresponding product lifecycle phases (purchase, use, end of life), and different kinds of undesired effects (harmful, insufficient, excessive) based on the TRIZ-oriented functional analysis. The classes, whose significance has been checked in the literature, include frequent causes of unsustainable behaviors and corresponding examples. Through the framework, designers can take into due account the possible circumstances that would prevent their developed products from being prone to unsustainable behaviors. In a future step, the classes of unsustainable behaviors are to be linked with indications arising from Design for Sustainable Behavior.

Keywords: Design for sustainable behavior | Design requirements | Design strategies | Eco-design | Product development | Product lifecycle | TRIZ | Unsustainable behaviors

Abstract: Establishing the actual gear root bending strength is a fundamental aspect in gear design. With this respect, gears materials can be characterized through two types of tests, i.e. on Running Gears (RG) or Single Tooth Bending Fatigue (STBF). The former is able to reproduce the loading conditions of the actual gears and, therefore, leads to the most accurate results. The latter excels in terms of efficiency and simplicity of the experimental campaign but as a drawback, tends usually to overestimate the material strength due to the different stress state histories it induces on the tooth root. Therefore, a common practice is to carry out STBF tests and apply a correction coefficient (fkorr) for exploiting the results in the design of actual gears. In the present paper, an approach to estimate fkorr centered on the combination of numerical simulations and multi-axial fatigue criteria based on the critical plane capable of taking into account non-proportional loading conditions has been proposed. In particular, the same gear geometry has been simulated through Finite Element (FE) models in two conditions, i.e. STBF and RG. The outcomes of the simulations, in terms of stress histories in the tooth root region, have been analyzed with five different fatigue criteria, i.e. Findley, Matake, McDiarmid, Papadopoulos, and Susmel et al. fkorr has been calculated as the ratio between the maximum damage parameter observed in the STBF and RG conditions according to the different fatigue criteria. Results show that fkorr, calculated for three different materials (i.e. 18NiCrMo5, 42CrMoS4, 31CrMo12), differs up to 22% between the RG and the STBF conditions (depending on the criterion considered). Therefore, future studies should aim to understand which fatigue criterion is the most appropriate for this type of analysis.

Keywords: Critical plane | FEM | Gears | Material characterization | Multiaxial fatigue | STBF

Abstract: Shortcomings in manufacturing companies’ capabilities to execute circular economy business modelling have delayed a broader dissemination of circular business models beyond the stage of pilot projects in niche markets. Circular economy poses additional uncertainties for innovation that are not common for manufacturing companies’ traditional activities and business as usual. To cope with such challenges, they lack systematised practices and proactive advice, which are scant in available literature and approaches. The paper presents the development of the tool Circular Economy Business Modelling Expert System within manufacturing companies, intended to address these limitations. Based on systematised business modelling practices for circular economy and proactive advice on potential circular business model configurations, the expert system enhances strategic thinking for circular economy, supporting companies to come up with varied alternative business models with reasonable and viable value propositions to deploy circular benefits accordingly. The expert system was streamlined based on literature review, development, testing and evaluation with 12 practitioners from 10 companies. The paper discusses the main functionalities of the expert system and the results of its application into varied manufacturing companies. The application of the expert system has demonstrated to benefit companies with: inspiration for best practices on circular business modelling, a structured framework for confirming assumptions and a logic structure that prompts decision-making and reduces uncertainties.

Keywords: business model | circular economy | innovation | sustainability | tool

Abstract: Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material properties with respect to tests conducted on Running Gears (RG). Therefore, it is common practice to use a constant correction factor fkorr, of value 0.9 to exploit STBF results to design actual gears, e.g., through ISO 6336. In this paper, the assumption that this coefficient can be considered independent from the gear material, geometry, and loading condition was questioned, and through the combination of numerical simulations with a multiaxial fatigue criterion, a method for the calculation of fkorr was proposed. The implementation of this method using different gear geometries and material properties shows that fkorr varies with the gears geometrical characteristics, the material fatigue strength, and the load ratio (R) set in STBF tests. In particular, by applying the Findley criterion, it was found that, for the same gear geometry, fkorr depends on the material as well. Specifically, fkorr increases with the ratio between the bending and torsional fatigue limits. Moreover, through this method it was shown that the characteristics related to the material and the geometry have a relevant effect in determining the critical point (at the tooth root) where the fracture nucleates.

Keywords: FEM | Findley | Gears | Material characterization | Multiaxial fatigue | STBF

Abstract: Tooth root bending fatigue is the most dangerous failure mode in gears. Indeed, it starts from the nucleation of a crack within the tooth root fillet region and the subsequent propagation up to the complete breakage of the tooth. To investigate this phenomenon, Single Tooth Bending Fatigue (STBF) tests are largely diffused. In these tests, an alternating bending stress at the tooth root is induced by the application of a pulsing force to the gear flank. In addition, this loading condition can be modelled through Finite Elements (FE) to study the stress state in the affected area. However, the application of strength criteria such as von Mises’ can provide the equivalent stresses when the applied force reaches its maximum value but does not provide any insight in terms of fatigue behaviour. Nevertheless, the crack propagation can be investigated by analysing the results of FE analyses (which model the entire load cycle) through fatigue criteria based, for instance, on the critical plane concept. Previous studies conducted by the authors have shown that the different fatigue criteria (to study the tooth bending failure) lead to very different results. Therefore, the objective of the present paper is to compare the results of analyses carried out with different fatigue criteria based on critical plane, i.e. Findley, Matake, McDiarmid, Papadopoulos, and Susmel, with experimental outcomes, i.e. STBF tests on an aeronautical gears, to determine the most appropriate fatigue criterion to characterize the fatigue behaviour of these mechanical components. Results reveal that all fatigue criteria lead to consistent results when the target is to identify the most critical point. However, the Findley and Papadopulus criteria are found to be the most accurate for what concerns the evaluation of the damage. Among the others, Susmel turns out to be the most conservative criterion while the Findley criterion is the only one capable of identifying with good accuracy the direction of crack propagation.

Keywords: Crack | Critical plane | Fatigue | FEM | Gears | STBF

Abstract: The terms that constitute Ideality in TRIZ are extremely appropriate to characterize the conflicting prerogatives of value/functionality, and environmental sustainability and human wellbeing. In a system perspective, the latter are mostly ascribable to harmful functions and consumption of resources. The paper introduces a classification of sustainable design initiatives based on the variations of the factors that contribute to Ideality. The classification urges designers to think of possible win-win solutions in which functionalities are not jeopardized by the search for more environmental-friendly solutions. Combining ideality and sustainability is a trigger towards making sustainable solutions more accepted, and, consequently, more effective in preserving the environment. In particular, the individuation of classes of sustainable design endeavors lay bare that the potential reduction of harmful effects is not a sufficient precondition to create sustainable products. Overall, TRIZ, along with its underlying theory and constructs, has proven to provide an effective key of reading for approaching the eco-design field in terms of the extent to which new products and solutions are promising.

Keywords: Eco-design | Ideality | Super-sustainability | TRIZ | Value

Abstract: To support the transition to sustainable development, eco-design must lead to the development of products that provide additional value when compared to traditional products, ultimately resulting in market success. In this study, creativity principles are explored as leverage points for eco-design implementation, enhancing customer acceptance and market success. The authors have inferred ten eco-design guidelines, which aim to enhance success chances in the development of new products. The proposed guidelines were verified through eco-ideation session and experts’ evaluation. Results support the congruence of objectives between creativity, sustainability, success, and value creation in design. The guidelines represent a promising design tool to be further developed to pursue the objective of making eco-designed products more valuable and successful.

Keywords: design creativity | eco-design | Ideation | success | value perception

Abstract: On the one hand, many mechanical components manufactured through additive technologies are optimized in terms of stiffness/weight or strength/weight thanks to lattice structures. On the other hand, the high complexity of these components often impedes further finishing operations and, therefore, the fatigue strength can be compromised. The high surface to volume ratio together with the high roughness, typical of additive manufactured components, promote the crack nucleation. In this paper, the High-Cycle-Fatigue (HCF) behavior of the 17-4 PH stainless steel (SS) was characterized. Cylindrical samples, manufactured via Selective Laser Melting (SLM) with an EOS M280, were tested in the as-build condition through a STEPLab UD04 fatigue-testing machine. In particular, a preliminary quasi-static traction test was performed on a sample to obtain the yield strength (σY = 570 MPa) and the ultimate tensile strength (UTS = 1027 MPa). Fatigue tests were performed on samples at different stress levels in order to characterize the whole Stress-Number of cycles (S-N) curve (Wöhler diagram). More specifically, the stair-case method combined with the Dixon approach were exploited to calculate the fatigue limit (σF = 271 MPa). The obtained results were compared with those present in literature for the same material and they are coherent with previous researches.

Keywords: 17-4 PH | Additive manufacturing | HCF | SLM

Abstract: In this paper, the static and low-cycle-fatigue (LCF) behavior of wrought samples of 17-4 PH stainless steel (SS) manufactured via Selective Laser Melting (SLM) are presented. On the one hand, several scholars have studied SLM materials and literature reports a huge amount of data as for the high-cycle-fatigue (HCF) behavior. On the other hand, few are the data available on the LCF behavior of those materials. The aim of the present research is to provide reliable data for an as-build 17-4 PH steel manufactured via SLM techniques. Only with quantitative data, indeed, it is possible to exploit all the advantages that this technology can offer. In this regard, both quasi-static (QS) and low-cycle-fatigue tests were performed on Additive Manufacturing (AM) cylindrical samples. Through QS tests, the constitutive low has been defined. Strain-controlled fatigue tests on an electromechanical machine were performed on 12 samples designed according to the ASTM standard. Tests were continued also after the stabilization was reached (needed for the cyclic curve described with the Ramberg-Osgood equation) to obtain also the fatigue (ε-N) curve. Results show that the material has a softening behavior. The Basquin-Coffin-Manson (BCM) parameters were tuned on the basis of the ε-N combinations after rupture.

Keywords: 17-4 PH | Additive manufacturing | LCF | SLM

Abstract: The relationships between the creation of value for both the environment and consumers have been insightfully investigated by the authors in previous studies. The results achieved in these studies have allowed the authors to deduce some design recommendations and represent the basis for further analyses of the perception of eco-designed products through quantitative data. In this paper, a sample of indications intended to support designers in developing sustainable and successful products was fine-tuned. These indications, embodied in eco-design guidelines, have been partially deducted from the evidence that emerged in previous works and partially inferred through a specific elaboration of data regarding the value perception of eco-design strategies. The guidelines have been evaluated by (eco-)design practitioners, whose evaluation shows the high perceived relevance of the guidelines.

Keywords: Eco-design guidelines | Success | Value perception

Abstract: The lubrication of the mechanical components reduces friction, and increases the efficiency and the reliability. However, the interaction of moving components with the lubricant leads to power losses due to viscous and inertial effects. Nowadays, the study of lubricant behavior can be carried out through computational fluid dynamics (CFD) simulations. Nevertheless, the modeling of the computational domain within complex mechanical systems (e.g., ordinary, planetary and cycloidal gearboxes, roller bearings, and pumps) requires the exploitation of specific CFD techniques. In the last decades, many mesh‐based or meshless approaches have been developed to deal with the complex management of the topological changes of the computational domain or the modeling of complex kinematics. This paper aims to collect and to classify the scientific literature where these approaches have been exploited for the study of lubricated mechanical systems. The goal of this research is to shed a light on the current state of the art in performing CFD analysis of these systems. Moreover, the objective of this study is to stress the limits and the capabilities of the main CFD techniques applied in this field of research. Results show the main differences in terms of accuracy achievable and the level of complexity that can be managed with the different CFD approaches.

Keywords: CFD | Gears | Lubrication | Mesh handling techniques | Meshless | Overlapping grids | Remeshing approaches | Rigid mesh motion | Sliding meshes

Abstract: In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability. The so-called 'thermal limit', i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past. The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses. The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution. Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios.

Keywords: CFD | Cycloidal gear | Efficiency | Lubrication | Multiphase | Power losses

Abstract: Cor-Ten is a weathering steel exploited in the last decade for several applications such as bridges, artworks, building facades, etc. Besides a good strength, it naturally oxides creating a protective layer. This oxide, unlike rust, has the same specific volume of the pure metal. This characteristic allows overcoming the need of protecting treatments like galvanization, etc. While its properties promote its exploitation in civil applications, there are also some examples of application where safety is a fundamental requirement. In the northern part of Italy, Cor-Ten is used for safety barriers (guard rails) along the highways. It is, therefore, fundamental to know the ductile behavior of this material, for which few data are available in literature. Quasi-static experimental tensile tests have been performed on eight samples having different shapes. Numerical simulations carried out with an open-source code (Code_Aster) reproduced the experimental setup. In this way, it was possible to calculate the stress state and the plastic strain at failure needed for the calibration of the ductile damage model. The material model is based on classical incremental plastic response with isotropic hardening and phenomenological concept of damage.

Keywords: Code_Aster | Cor-Ten | Ductile fracture | Experiments | FEM | Fracture locus

Abstract: Idea generation is acknowledged to benefit from intentionally administered stimuli or designers’ processes that include the search for external sources of inspiration. Text-based and graphic forms of stimuli are the most leveraged in design literature, but it has not been yet demonstrated which form is most effective for boosting creativity. This is due to the fact that previous studies have employed many varying conditions which do not allow for comparisons to be made. The present paper presents an experiment in which three groups of 27 participants were asked to generate new ideas for new-borns’ outfits. To perform the task, the participants first considered five stimuli presented to them in one of the forms depending on which group the participants had been assigned to, i.e. textual, pictorial or combined (juxtaposition of the two). The stimuli were intended to share the semantic content, thus limiting potential bias due to different meanings. The outcomes of the experiment were evaluated in terms of creativity and non-obviousness. The presence of a pictorial dimension resulted in a significant increase in terms of rarity and non-obviousness of ideas, but did not affect quality, originality or quantity. The limited overlap among ideas emerging from the three forms suggests the potential value of developing design tools for idea generation that mix multiple forms of stimuli.

Keywords: analogical reasoning | creativity evaluation | Idea generation | inspiration

Abstract: The market for agricultural machinery is characterized by products with a high degree of maturity in the product life cycle. Consequently, current improvements in new machinery are predominantly incremental and new projects basically use solutions that are already consolidated. This makes this domain appropriate for benchmarking existing systems and envisioning new value propositions. The present paper deals primarily with the former and uses the value curves as a means to structure the comparison among different families of technical systems; in particular, harvesting machines for shell fruits from the ground surface, e.g., chestnuts, walnuts, and hazelnuts, were investigated here. The process of building value curves requires the identification of currently fulfilled requirements. Despite the attention paid by engineering design research to requirements, a structured process is lacking to extract relevant information and create value curves or other representations useful for benchmarking. The present paper approaches this problem and presents how the authors have individuated relevant knowledge for characterizing different categories of harvesting machines. Namely, after an extensive search of the scientific literature and patents, a critical review of existing machines, aimed at individuating their functioning principles, architecture, and attitude in fulfilling specific design requirements, was performed. Then, existing machines were classified in 8 main categories, and their strengths and weaknesses were identified with reference to 11 competing factors. The consequent construction of value curves enabled the identification of possible points of intervention by hypothesizing possible future evolutions of such machinery, both in a structural and in a value-based perspective. Limitations about the repeatability of the followed approach and possible repercussions on design research are discussed.

Keywords: Agricultural equipment | Competing factors | Engineering design | Patent search | Requirements elicitation | Shell fruits-harvesting machines | Value curve

Abstract: Design is inherently affected by human-related factors and it is of no surprise that the fine-Tuning of instruments capable of measuring aspects of human behavior has attracted interest in the design field. The recalled instruments include a variety of devices that capture and quantitatively assess people's unintentional and unconscious reactions and that are generally referred as neurophysiological or biometric. The number of experimental applications of these instruments in design was extremely limited as of 2016, when Lohmeyer and Meboldt published a first report on relevant measures and their interpretation in design. In the last few years, the number of relevant publications has increased dramatically and this determines the opportunity to carry out a comprehensive review in the field. The reviewed contributions are analyzed and classified according to, among others, instruments used, the kind of stakeholders involved and the supported design research activities. The role of biometric measures with respect to traditional research methods is emphasized too. The discussed instruments can represent supports or substitutes for traditional approaches, as well as they are capable of exploring phenomena that could not be addressed hitherto. The intensity of research concerning experiments with biometric measurements is discussed too; a particular focus of the final discussion is the individuation of obstacles that prevent them from becoming commonplace in design research.

Keywords: Biometric versus traditional measures | design cognition | electroencephalography | eye-Tracking | product evaluation

Abstract: The paper offers insights into people's exploration of creative products shown on a computer screen within the overall task of capturing artifacts' original features and functions. In particular, the study presented here analyzes the effects of different forms of representations, i.e., static pictures and videos. While the relevance of changing stimuli's forms of representation is acknowledged in both engineering design and human-computer interaction, scarce attention has been paid to this issue hitherto when creative products are in play. Six creative products have been presented to twenty-eight subjects through either pictures or videos in an Eye-Tracking-supported experiment. The results show that major attention is paid by people to original product features and functional elements when products are displayed by means of videos. This aspect is of paramount importance, as original shapes, parts, or characteristics of creative products might be inconsistent with people's habits and cast doubts about their rationale and utility. In this sense, videos seemingly emphasize said original elements and likely lead to their explanation/resolution. Overall, the outcomes of the study strengthen the need to match appropriate forms of representation with different design stages in light of the needs for designs' evaluation and testing user experience.

Keywords: Areas of interest | Creative products | Eye-Tracking | Human-computer interaction | Images | User experience | Videos

Abstract: Object of this work is the design of a speed reducer which introduces two distinctive innovations: adoption of a Wolfrom layout and adoption of polymeric materials. This solution is innovative respect to current literature also for proposed application, concrete mixes and other machines for construction yards. In this work, features of proposed solution are critically compared with pre-existing ones demonstrating its potential industrial interest for applications constrained by cost limitations and exposition to severe environmental conditions. A preliminary design is then performed on benchmark case study also introducing finite element modelling of contact conditions of proposed polymeric gears. Results are quite promising and more generally adequate to demonstrate feasibility and potential utility of proposed solution.

Keywords: Construction Yards | Cycloidal Drive | Harmonic Drive | Mechatronics | Wolfrom Drive

Abstract: The fields of eco-design and design creativity have not found strategic synergies yet. This applies despite the fact that the paramount objective of eco-design, i.e. sustainable development, might benefit from the radical design changes creativity can engender. In parallel, those significant changes should also support the transformation of products towards designs that exhibit major success chances, which is still in line with the perspectives of sustainable development. The authors have developed ten guidelines to guide eco-design towards creative and successful outcomes and the present paper illustrates the first experimentation thereof. The results of the experiment show that the compliance with the guidelines determines a satisfactory trade-off between environmental friendliness and success chances, as well as fully increasing the novelty of ideas. The outcomes are however affected by a remarked misalignment between the views of the two evaluators, i.e. an industrial player and an academic expert in eco-design.

Keywords: Design creativity | Eco-design guidelines | Eco-ideation | Success

Abstract: This paper aims to create a conceptual map of problems and solutions concerning High Power Density Speed Reducers (HPDSRs), i.e. planetary gearboxes, cycloidal gears and harmonic drives. The existing designs of HPDSRs are explored and classified through the Problem Solution Network (PSN), i.e. a method based on the Network of Problems from the TRIZ base of knowledge that considers different levels of abstraction. Through the PSN, it was possible to highlight conceptual design differences and communalities among the various HPDSRs in order to clarify the working principles of existing solutions. HPDSRs carry out the speed reduction through components that perform planetary motions. Therefore, a first distinction has been made based on input and output motions. Cycloidal and harmonic solutions have as output the rotation motion of the planet while planetary gear trains have as output the revolution motion of the planetary pinion. A second classification has been made on the strategy for avoiding the secondary path of contact, i.e. the unwanted contact between two components outside of the expected contact area. Cycloidal solutions modify the tooth profile while harmonic solutions deform the planetary pinion. Further considerations have been made on multi-stage solutions that take into account differential principles to multiply the useful function.

Keywords: Conceptual design | Cycloidal gears | Harmonic drive | Planetary gearbox | Problem solution network | TRIZ

Abstract: Eco-Design Strategies lead to both enhanced environmental sustainability and product differentiation, which, however, takes place only if observers recognize and value these advantages. To study this aspect, a sample of 40 product pictures has been administered to 12 subjects with experience in eco-design. They were asked to evaluate whether one or more Eco-Design Strategies (in Vezzoli and Manzini's version) were implemented in each depicted product. The outcome of the evaluation was an overall fair agreement. Useful information for eco-design is inferred from nuances of the results.

Keywords: design evaluation | ecodesign strategies | product design | sustainable design

Abstract: The paper investigates the relationship between the forms through which products are represented and the outcomes of evaluations made by observers. In particular, the study focuses on perceived affordances of creative designs, meant as the capability of capturing original elements and corresponding functions, for products presented through static images or videos. Also thanks to the use of Eye Tracking, the experimental results show how dynamic effects that involve salient aspects of products, as well as creative features, are critical to observers' capability of capturing design intentions.

Keywords: design affordance | design creativity | design evaluation | forms of representation | product design

Abstract: A considerable part of the design literature focuses on creativity and puts forward means to enhance creativity. It is assumed that boosting creativity results in product improvements and benefits for many stakeholders, starting from the recipients of design deliverables. However, the actual outcomes of creative endeavors and, especially, creative products have never been assessed systematically. Within this overall goal, the present paper compares the results of two experiments in which the same participants were involved. Both experiments were meant to evaluate according to multiple dimensions couples of products, where an element of the pair was subjected to some variations. The experiments foresaw the use of eye-trackers to achieve additional behavioral information. As creativity or variations thereof (novelty, unusualness) were assessed, it is possible to infer dimensions of value that are affected by creativity in multiple settings. The outcomes show that creative products significantly give rise to increased exploration time and efforts to make sense out of objects, but this process leads nevertheless to difficulties in understanding the products and to the identification of some disadvantages. According to these preliminary results, the relationship between creativity and perceived value, as well as their measurement, is overall dubious and highly depending on circumstances. While the authors support the relevance of design creativity, the paper urges to consider value at the same time.

Keywords: Design creativity | Eye-tracking | Fused Deposition Modelling | Perceived value | Product evaluation

Abstract: Recently, an increasing need for sophisticated multimedia analytics tools has been observed, which is triggered by a rapid growth of multimedia collections and by an increasing number of scientific fields embedding images in their studies. Although temporal data is ubiquitous and crucial in many applications, such tools typically do not support the analysis of data along the temporal dimension, especially for time periods. An appropriate visualization and comparison of period data associated with multimedia collections would help users to infer new information from such collections. In this paper, we present a novel multimedia analytics application for summarizing and analyzing temporal data from eye-tracking experiments. The application combines three different visual approaches: Time∘diff, visual-information-seeking mantra, and multi-viewpoint. A qualitative evaluation with domain experts confirmed that our application helps decision makers to summarize and analyze multimedia collections containing period data.

Keywords: Data visualization | Multimedia analytics | Multimedia application | Period data

Abstract: Despite the potential to lead to enhanced environmental performance, the extent to which eco-design leads to success is still unclear. In order to lay bare the effects of eco-design implementation, this paper focuses on understanding the correlations between specific eco-design principles and success through an exploratory study. A sample of 178 products, characterized in terms of their success levels and implemented eco-design principles, was statistically analyzed. The results indicate a number of positive correlations for principles that tend to favor success (e.g. intensified use and product/service systems) and negative correlations for principles that tend to moderate the chances of success (e.g. minimize packaging). Although the mechanisms that cause this phenomenon should be further investigated, the findings can provide designers with additional recommendations for the selection of eco-design principles.

Keywords: Eco-design principles | New product development | Product life cycle | Success catalysts | Sustainable products

Abstract: Previous studies have failed to provide a comprehensive view on the value perception of green products. The present research takes up this challenge through an experiment in which 43 participants have interacted with and evaluated 40 products-20 baseline products and 20 green products of the same categories. The experiment included both self-assessments to monitor conscious evaluations of the products and biometric measurements (Eye-Tracking and Galvanic Skin Response) to capture unconscious aspects. The results show that different forms of perceived value emerge clearly. Green products, for which participants required greater efforts in the search for relevant information, boost the value attributed to creative solutions still believed of high quality. This effect is significantly more evident for participants showing remarkable interest for sustainability issues. Conversely, alternative products feature greater value perception because they are acknowledged to be functional and reliable.

Keywords: Attitude-behavior gap | Biometric measures | Creativity | Eco-design | Estimated price | Eye-tracking | Green products | Principal component analysis | Value perception | Willingness to pay

Abstract: Biometric devices and especially eye tracking systems have been used in various sectors such as neuroscience, clinical research, training and learning, linguistics, biomechanics, ergonomics and market research. So far, there are only a few applications of eye tracking in industrial environments such as engineering design and manufacturing or assembly. The aim of this research is to review why and to what extent biometric devices such as eye tracking systems can be used in industry. The research provides an overview of the state of the art in using these technologies in industrial engineering with a special focus to design and manufacturing. In addition, this paper briefly describes two currently running test series of the research team to investigate the usability of these systems in industrial engineering.

Keywords: assembly | assistance systems in production | biometric devices | biometric measurement | design | eye tracking | industry 4.0 | manufacturing

Abstract: In order to protect low-alloy steel from corrosion in outdoor applications, it is common practice to use surface treatments e.g. painting or galvanization. The costs of these specific treatments and further maintenance can be reduced by exploiting weathering steel, the so-called CORTEN steel. The rust of this material forms a protective layer, adherent and self-regenerative, capable to stop the oxidation of the raw material. This characteristic, called self-passivation, is achieved by adding Cu, Cr and P in the alloy. Furthermore, its natural rust-color inspired architects, artists and civil engineers that start using CORTEN for bridges, building facades, artworks etc.. The harmony of CORTEN with natural environments boosts its application for guardrails (safety barriers) along the highway and alpine roads of the South-Tyrolean region. These components, in addition to aesthetic characteristics, have to fulfill safety requirements, especially during crash events. During an impact, the main goal of guardrails is to absorb and dissipate energy. Large deformations take place. Therefore, the most important mechanical characteristic for guardrails' materials is the tenacity related to the ductile behavior. However, despite CORTEN guardrails are homologated through experimental tests, in some specific conditions the passivation process could fail. Therefore, its energy absorption capabilities can be jeopardized by corrosion. In order to verify and/or optimize specific guardrails' geometries for safety applications, it is important to be able to model the ductile behavior and fracture locus of CORTEN within finite elements. The goal of this paper is to characterize the ductile behavior of CORTEN through experimental quasi-static tests with different geometries, thus different level of triaxiality. The test configurations were numerically reproduced, to retrieve the actual stress state, quantify the plastic strain at failure and calibrate a ductile damage model.

Keywords: CORTEN | DIC | Ductile damage | Experiments | FEM | Fracture locus

Abstract: Additive Manufacturing (AM) is a potentially revolutionary technique in industry with claims of high skills shortage in the recent days. It is assumed that full exploitation of AM capabilities can be made possible by a paradigm shift steered by engineering design. Future generations of engineers might benefit from Design for Additive Manufacturing (DfAM), which targets AM potential and enables design freedoms. In this context, the paper investigates AM education for a better understanding of the main AM-related subjects taught in universities. To this scope, the authors gathered 52 syllabi of courses taught in highly-ranked technical universities worldwide that relate to AM. From the investigation, it emerges that AM is the core discipline of the course in 42 out of 52 cases and considered widely as an independent domain to date. As for taught subjects, it was found that design aspects in AM and DfAM are poorly focused on, while manufacturing and process areas are the most popular. This poses a challenge especially to the design community, as the current situation might limit the exploitation of AM capabilities.

Keywords: Additive Manufacturing | Computer Aided Design (CAD) | Design education | Design for Additive Manufacturing (DfAM)

Abstract: Weathering steel, specifically Cor-Ten (or CORTEN) steel is a material particularly exploited in the last century for various outdoor applications, e.g. bridges, building facades, artworks etc. In addition to a tensile strength comparable with other construction steels, the natural oxide of this material, that is common rust, has the same specific volume as the metallic core. This ensures the adhesion of the oxidized protective layer as for aluminium. Therefore, the stable rust layer protects the raw material from further corrosion. This characteristic overcomes the need for painting and maintenance. These properties boost the exploitation of Cor-Ten in several civil applications, also where safety is a fundamental requirement, e.g. guard rails used, for example, in the South-Tyrolean region along the highways. With the aim of verifying or optimizing such safety applications, it is important to know the ductile behavior of the material. Indeed, during an impact, the main purpose of the structure is to absorb energy and this implies that large deformations will take place. Experimental quasi-static tests were performed on several sample geometries made of Cor-Ten. The same tests were also numerically reproduced, to retrieve the actual stress state, quantify the plastic strain at failure and calibrate a ductile damage model. The material model is based on both the classical incremental model of plastic response with isotropic hardening and the phenomenological concept of damage in continuum mechanics.

Keywords: Cor-Ten | Ductile fracture | Experimental | FEM | Fracture locus

Abstract: Understanding the impact of inventive solutions on consumers’ value perception is essential to develop successful products. This applies particularly to sustainable solutions, which need to penetrate the market to pursue environmental objectives. This paper explores the value perception of three categories of TRIZ-oriented sustainable solutions, namely designs that have undergone dynamization, change of the physical state or the field exploited. Through an experimental study with 43 participants, supported by a specific questionnaire and biometric measures (eye tracking, skin conductance), self-assessments and unconscious behavioral aspects were gathered while a series of 18 product pictures was shown. Out of them, 9 products implement one of the above TRIZ-oriented principles and 9 constitute same-category products with a higher environmental impact. The results show that the different categories of TRIZ solutions give rise to diverse nuances of value perception. This outcome triggers further considerations concerning the ease of interpreting design modifications steered by TRIZ concepts and heuristics.

Keywords: Biometric measures | Eco-design | Eco-innovation | Human perception | TRIZ-oriented sustainable solutions

Abstract: In recent years, the increasing demand for more and more compact and efficient solutions has highlighted the need to have appropriate tools in order to optimize the internal design, to avoid thermal problems, ensuring proper lubrication and to increase the reliability of the systems. Typical high power density gearbox designs are based on planetary, harmonic and cycloidal architectures. Although many analytical and numerical models are already available for the prediction of the power losses related to gear meshing (sliding), bearings and seals, literature is lacking in terms of hydraulic power loss models (deep lubrication, churning, windage and squeezing). Some numerical multiphase CFD and experimental studies on parallel axis and planetary gear sets have been already performed by the authors in previous research. The aim of this paper is to extend the applicability of the previously developed numerical techniques to cycloidal architectures, taking into account the typical lubricants used for these type of drives. With respect to the load independent power losses (related to the interaction of the mechanical component and the surrounding lubricant), the cycloidal gear set has been numerically simulated with an especially developed CFD code implemented in the OpenFOAM® environment. A specific mesh handling technique allows us to manage the topological changes of the domain ensuring the numerical stability of the simulation and the correct calculation of the complex multiphase flows that take place in gearboxes. The results have been compared with those already available for other gear architectures with similar performances (dimensions, reduction ratios and loads).

Keywords: CFD | Cycloidal drive | Efficiency maps | Multiphase | Power losses

Abstract: Many outputs of the application of eco-design principles and guidelines result in solutions that slightly differ from previous ones. Although the environmental advantages of new solutions are evident, the extent of achieved benefits fails to pursue the objectives of sustainable development. The latter requires disruptive change and the contextual demise of old generations of products with worse environmental performance. This is made possible just when environmental friendly product transformations positively capture the social and the economic dimension too, as these are accompanied by changes in people’s habits and fueled by customer satisfaction. However, few enterprises are available to engage in radical innovation, as it is generally understood as a risky endeavor. The situation is made more complicated by the relatively poor availability of design methods that target radical product redesign. Proactive design methods and thinking strategies are commonly in play when substantial design changes are expected, but no standard methodological reference has been established so far. Based on theoretical reflections and literature evidence, the paper outlines the need for new knowledge, as the foundation of new methodological frameworks to enable the design of products whose environmental, social, and economic sustainability is ensured.

Keywords: Design methods | Eco-design | Radical innovation

Abstract: Structured approaches to diminishing products’ environmental footprint include the identification of hotspots, e.g., lifecycle phases or aspects that feature criticalities in terms of environmental sustainability. Still in these approaches, measures are taken consistently by investing eco-design efforts to improve the situation in the identified hotspots. However, many products implement eco-design principles irrespective of hotspots, i.e., without taking into account the major sources of environmental footprint. A sample of products has been analyzed in terms of hotspots, and lifecycle stages are affected by the implementation of eco-design principles and achieved success. The study reveals that, while eco-design principles in the use phase of the product favor success, the consistency between the hotspot and the lifecycle stage does not modulate the relationship between implemented eco-design principles and success. As a result, while the identification of hotspots is a best practice as for the attempt to maximize environmental benefits brought on by eco-design initiatives, it plays a limited role in terms of customer’s acceptability and appreciation of new products.

Keywords: Eco-design principles | Lifecycle hotspots | Success

Abstract: The outreach of application domains for Additive Manufacturing (AM) is expanding and end-use products represent their next frontier. Contextually, design methods are developed for exploiting the unique AM capabilities. They largely benefit from the knowledge about peculiarities, constraints and technical performances of the various AM processes and devices. However, while the mechanical properties of objects created with AM are widely studied, there is lack of research on emotional and perceptual aspects. This is of great relevance in the mentioned perspective of employing AM for end-use products. The paper aims to elucidate which perceptual mechanisms are activated when a user observes an object generated with AM instead of traditional technologies. An experiment has involved 43 participants who have evaluated ten pairs of objects, constituted by a commercial product and a replica made with Fused Deposition Modelling. Testers have answered a questionnaire, as well as their visual behavior has been recorded with eye-tracking glasses. Based on results, replicas suffer from poor attractiveness and especially low perceived quality. They have also given rise to more careful exploratory behaviors because they likely require a lengthier examination for testers’ assessment or they arouse curiosity. It can be inferred that Fused Deposition Modelling does not exhibit sufficient accuracy to achieve acceptability with reference to everyday products. Nevertheless, it is also deemed that limited improvements might compensate for the perception of technical unsuitability this technology engenders. This can be verified by repeating the experiment with more sophisticated and precise AM devices.

Keywords: Design for additive manufacturing | End-use products | Eye-tracking | Fused deposition modelling

Abstract: Aging societies have an extended need for transportation solutions that enhance elderly's independence. However, the solutions needed are as manifold as the elderly's lifestyles are. This study uses Usercentred Design principles as a structuring tool to manage this complexity of requirements. By not just focusing on specific functionalities but also reflecting product life cycle and usage context, new types of requirements can be revealed. Through a case study, this article shows how a participatory design approach can lead to integrated solutions that better fit the user's needs.

Keywords: Co-design | Human centred design | Integrated product development | Requirements management | Teamwork

Abstract: Although product design targets success, the achievement of success is rarely verified or insightfully explored because of difficulties in measuring this term. The present paper addresses design research by proposing a procedure to extrapolate success of products by means of the vast knowledge made available by the scientific literature and the Internet at large. The final achievements are constituted by an algorithm to perform information search about product success and a success scale to be used as an ordinal variable in a posteriori studies involving large numbers of products.

Keywords: Information retrieval | Product development | Product failure | Product success | Sustainable design

Abstract: As creativity is increasingly important in order to achieve differentiation and competitiveness in industry, designers face the challenge of conceiving and rating large numbers of new product development options. The authors’ recent studies show the effectiveness of ideation procedures guided by stimuli that are submitted to designers in the form of abstract benefits. A rich collection of said benefits has been created to this scope; more specifically, the authors have performed a detailed clustering of the categories described in TRIZ ideality, i.e. useful functions, attenuation of undesired effects and reduction of consumed resources. Aspects related to sustainability and environmental friendliness manifestly appear in the list of stimuli and these issues are reflected in several ideas emerged in initial experiments. However, many promising product development objectives conflict with sustainability or, at least, their adherence to eco-design is arguable. The paper assesses the share of ideas that are supposed to comply with sustainability in experiments described in recent literature. Subsequently, it intends to stimulate a discussion about the introduction of measures to attract attention of designers on sustainability in the critical early product development stages also when green aspects do not represent the fundamental driver to achieve greater customer value. As well, it discusses which sustainability aspects are worth being considered adequately during the very early design phases and which ones could result as exceedingly constraining.

Keywords: Idea generation | Product value | Sustainability | TRIZ | Very early design phases