Abstract: The reliability and availability of a Jet Unmanned Aerial Vehicle (JUAV) for balloon downing are evaluated in this third part of the paper. The paper delves into the challenges faced by traditional air defence systems in countering high-altitude balloons, leading to the proposal of substituting missiles with Unmanned Aerial Vehicles (UAVs), specifically the Jet Unmanned Aerial Vehicle (JUAV). The best solution found in the previous section is a derivation of the 1:6 scale RC model of the Lockheed F104C. This is designed for balloon downing, and the essay meticulously analyses its reliability, failure probabilities, and maintenance strategies for various subsystems. The engine is replaced with a more powerful micro-jet, and an 84 mm recoilless cannon is added at the base of the tail. The scaled-down model can use most data derived from the full-scale airplane flight manual, corrected for larger thrust-to-weight and lower wing-loading. Several adjustments and additions are made on sensors, autopilot, On-Line Diagnostic System, communication system, and firing system to increase the reliability of the system. Due to the relatively short design life of the RC model, the Time Between Overhaul (TBO) of the UAV is reduced to 25 h. Consequently, the study emphasizes the importance of simplicity, operational reliability, and adaptability in the development and assessment of modern missile defence systems. The reliability of the JUAVI is presented as 98.14% for 50 consecutive fully automatic missions, highlighting its potential significance in bolstering national security.

Keywords: Aerospace Engineering | availability | balloon killer | cost-effective | D T Pham | Design | Mechanical Engineering | Mechanical Engineering Design | Mechanics | re-usable | Reliability | Transport & Vehicle Engineering | UAV | UK | University of Birmingham

Abstract: The performance of modern, new generation-armored vehicles would greatly benefit from overall engineering, optimization, and integration techniques of advanced diesel engines-electrified transmissions. Modern axial flux electric motors and controllers are perfectly able to replace the classical automatic gearbox and complex steering system of traditional Main Battle Tanks. This study shows a possible design of a serial hybrid electric power pack for very heavy tanks with a weight well over 50 tons. The result is a hybrid power system that improves the overall performance of armored vehicles off-road and on-road, improving the acceleration and the smoothness of the ride. In addition, fuel consumption will be reduced because the internal combustion engine operates at fixed rpm. The electric motors will outperform the traditional engines due to their very high torque output even at “zero speed”. The weight of a hybrid system has also been calculated. In fact, in many cases, it is possible to use all off-the-shelf components. The on-board diagnosis of the subsystems in the hybrid powertrain makes it possible to achieve a Time Between Overhaul (TBO) of 4500 h with a failure probability inferior to one in 10,000.

Keywords: EV | heavy vehicles | hybrid powertrains | MBT

Abstract: The widespread availability of cheap, mass-produced balloons puts a strain on the financial and manufacturing capacities of most aerial interception systems. In the past, high-altitude guided balloons that were between 65,000 ft (19.812 m) and 95,000 ft (27.432 m) in the air have been destroyed successfully by modifying bombers and airplanes to use a high-power laser system. High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAV) with laser systems are also on the market. Nevertheless, the cost to produce and maintain these systems is extremely high. A very cost-effective alternative is to create a mini—Unmanned Aerial Vehicle Interceptor (UAVI) that can intercept and bring down a balloon at a height of 65,000 ft (19.812 m) and has a Maximum Take Off Weight (MTOW) under 100 kg. To enable mass production, the UAVI should make use of readily available components and a simplified carbon fibre reinforced polymers (CFRP) structure. The vehicle also has a commercial microjet engine with an appropriate air intake and nozzle. This paper introduces the design of a cost effective UAVI to minimize the cost this analysis starts from existing, off-the-shelf Radio Commanded (RC) models. An ad-hoc design was then compared.

Keywords: anti-missile systems | cost-effective | re-usable | UAV

Abstract: This paper introduces a method to prepare an engine for very long flights without maintenance. It also gives criteria to estimate time between overhaul by using the sensor data to have an estimation of the engine condition. In-flight refueling has introduced new challenges to UAV (Unmanned Aerial Vehicle) propulsion systems. It is now possible to run continuously an UAV without landing for long periods. For this task, it is necessary to carry a quantity of lubricant sufficient for at least one month (approximately 800h). For extremely long flights, diesel piston engines are better than spark ignition ones due to extremely low fuel consumption. A selection in the assembly line individuates those engines that are suitable for long endurance flight. This is possible because automotive engines are manufactured in thousands per day and many quality controls take place in the assembly process. Moreover, mass produced automotive engines pass several tests during the assembly process including a very short run. The results of these tests are useful for an initial selection. Then, a 25-hour trial with a very thin lubricant is sufficient to forecast the oil consumption up to 1,000 hours. The 25 hours run corresponds to the time necessary to stabilize the oil consumption rate. In addition, during the 25 hours run also the electronic infancy failures are detected. In modern engines, the electronic on board diagnosis, the full redundancy of vital sensors, electronic control units and batteries/generators, make it possible to fly safely without emergencies with random electronic failures of components and wiring. Another major requirement is to forecast the engine failure or an unacceptable deterioration in terms of mechanical performance. This paper introduced a method to evaluate the state of wear of the engine starting from a digital monitoring system. A wear model of the engine based on the real duty cycle is proposed. It is then possible to prolong the life of the engine and to increase the time between overhaul. It is also possible schedule the overhaul operation

Keywords: 800h flight | Aircraft | Piston engine | Tbo evaluation

Abstract: This paper introduces a practical design procedure for Direct Metal Addictive Manufacturing (AM) by Hybrid Selective Laser Sintering or Melting (SLS/SLM). Theoretically AM frees the designer from many design constraints, practically it introduces new problems and it requires a brand new design of the part. Hybrid manufacturing reduces the problems without solving them totally. Supports can be introduced but represent a waste of time during manufacturing and during the post-mill removal. Before a 3D-printed metal part becomes usable, it has already undergone significant postprocessing in the form of CNC milling, hot-hyping, shot-peening or sand-blasting. Powder-bed fusion parts shows a quite rough surface finish. Considering that post-milling will be necessary in any case, surface finish is less important than other issues metal 3D printing. For example, very small cavities form within the part as it is being built. These defects lead to cracks during the part life cycle. Too few power applied by the wiper, too low laser intensity, excessive or inefficient cooling are the most common causes. Geometry of the part, optimized printing pattern and machine parameters are used to address these problems. AM machine operators have to tune their machines for a given material and print job. In the SLS/SLM process, density is achieved with quality powders, optimized build parameters and controlled machine environment. Hot isostatic pressing treatment as a post-process removes the porosity and reveals excessive defect by deforming the part. Residual stress is a result of the printing process. As the powder is melted and cooled, expansion and contraction occur. The residual stress is compressive at the center of the part and tensile at the boundary surfaces. Therefore, thin walled continuous parts are to be preferred. In fact, the classical ribbed structure has several thickness discontinuity requiring continuous adjustment in the build pattern and in laser modulation. To ensure the quality of the part material, the initial layers of the print are removed via CNC milling after the build is complete. Unfortunately, the thermal stress of the substrate will cause the part itself to warp modifying its geometry. Support structures are positioned in the right locations to prevent distortion or warpage. In addition, overhanging surfaces or down-skins faces have poorer surface finish ad are subjected to warping. For this reason, they also need additional supports. For these reasons, the Direct Metal AM part may have a completely different geometry than a cast component. An example of redesigning of a PSRU (Power Speed Reduction Unit) is provided in this paper.

Keywords: Aircraft | Direct metal additive manufacturing | Gear drive | Helicopter | Housing | Psru | Transmission

Abstract: Modern MBTs (Main Battle Tank) are extremely expensive. Many outdated MBTs and other armored vehicles, often lacking the required armor protection, are still kept in depots. It is now convenient to upgrade them to optionally unmanned weapons by adding a humanoid driver, and a robotic arm as a loader. Sensors, an optional automatic driving system, a control and communication suite would complete the transformation. The main armament and secondary armament may be also changed or upgraded. The off-the-shelf huge electronic equipment can be installed wireless inside the hull. The old crew compartment may be spoiled of all the human related parts. Only the driver seat may be kept in order to leave the capability to remove the humanoid, robotized driver and reinstate the human one. This upgrade should also include a diagnostic system for the vehicle, the sensors and the additional systems to reduce the maintenance burden. An additional, specialized, lightweight armor suite should be focused to protect the mobilization system, the robots, the control and the communication system. This second part of the paper introduces a few options to convert the Leopard 1 MBT to an optionally piloted UMBT (Unmanned Main Battle Tank). A first, minimal step, is just the automation of the original tank. In a second step, the weight is reduced by installing a smaller 60mm cannon with a lighter, but more numerous ammunition storage. A third step increases the firepower by installing on the main turret an automated turret with a 12.7 or 30mm cannon with an optional additional 7.62 machinegun. It is also highly advisable to add an APU (Auxiliary Power Unit) and a battery to reduce IR (infrared) signature, improve main engine life and reduce maintenance.

Keywords: Automated turret | Leopard 1 | MBT | UCV | UMBT | Update

Abstract: Modern MBTs (Main Battle Tanks) last more than 30 years. During this period, they will be periodically upgraded in any aspect except the basic structure. Even the main armor is becoming an upgraded accessory that depends on the nature of the threat. The main armament may be also changed or upgraded. The huge electronic equipment is the most upgraded part. The crew compartment may be upgraded in internal armor (for example for spalling), interfaces (optics, displays, commands), safety and protection devices (fire detection and suppression, ejection seats..). This continuous upgrade process should be included in the design of new vehicle, than can be modular for these mid-life upgrades. The vehicle is designed by adding items to the crew compartment and to the mobilization system. As an example, this first part introduces a few options to retrofit the ARIETE MBT. The retrofit cannot be reduced to engine and armor upgrade. A reasoned step approach is outlined in this paper. The first minimal step is based on an active armor and an HMD (Helmet Mounted Display) visual system. The weight increase is compensated by reducing road wheels weight. A second step increases firepower by installing on the main turret an automated turret with an automatic small cannon and a machinegun. The weight increase is compensated by limiting the internal ammunition storage of the main cannon to the anti-tank ones. A third step converts the turret internal ammunition storage into an automatic reloading system. In this way, the crew is reduced from 4 to 3. A fourth step increases crew safety by relocating the driver in the turret and by installing ejection seats. Solutions to reduce ground pressure and to increase the effective “power” available by replacing the final-drives and adding two electric motors on the front sprockets are also briefly examined. It is also highly advisable to add an APU (Auxiliary Power Unit) to reduce IR (infrared) signature, improve main engine life and reduce maintenance.

Keywords: ARIETE | automated turret | MBT | power | updated

Abstract: The main task of this project is the development of a modular heat exchanger to dissipate a TDP (Total Dissipated Power) of 140-180 W on a microprocessor. This exchanger should be able to dissipate the reference target TDP respecting the maximum operating temperatures (above these temperatures the CPU goes into thermal throttle) and the longevity temperatures (lower than the thermal throttle temperatures). This result should be achieved while providing product versatility (based on the concept to adapt the exchanger to each socket), acceptable noise, acceptable size and cost. The heart of the project is the design of a suitable fin surface to protect processors with high TDP. In this case, a significant increase in fan speed and in the size of the finned body is inevitable. In this way, an increase in the heat removal is obtained by larger airflow rate (high number of revolutions of the fan) and the large exchange surface. Considering the impact of these changes, the design of the exchanger is extremely critical in terms of size and noise level. Another physical limit is represented by the progressive and unavoidable phenomenon of electro migration that afflicts each circuit, the more the temperatures separate from those of longevity, the lower the useful life of the CPU. Once the longevity temperature is exceeded, the useful life of the processor decreases with increasing temperatures until the thermal throttle temperature is reached, which causes an abnormal system shutdown. The processors with a TDP from 65W to 95W are the most numerous. For this reason, most aftermarket solutions are designed to dissipate this TDP. The main purpose of this study is to examine the best geometry for a modular exchanger that is able to effectively dissipate the higher TDP (up to 180W) typical of modern high performance processors. For this purpose the Golden-section search is introduced for optimizing the number of fins. The heat exchange is simulated with fluid dynamic simulations (CFD). This new study allows obtaining an optimal design for the construction of the exchanger. The use of an optimal finned surface avoids the use of heat pipes. This approach simplifies the design. Moreover, by using materials with high thermal conductivity (such as copper alloys instead of aluminium alloys) we can certify the heat exchanger for TDP larger than the design one and therefore cope with even higher thermal loads. In this way, we can also effectively dissipate very performant CPUs (very uncommon) with extremely high TDPs such as FX-9590 with a 220W TDP (declared by the manufacturer AMD), maintaining in any case temperatures below the maximum thermal specifications.

Keywords: CFD | CPU | Golden-section search | Microprocessors | Thermal analysis

Abstract: In hypersonic aircrafts, the necessity of operating at speed lower than Mach 1.0 obliged the designers to use the complicate propulsion plant of the mixed compression turbojet. Fast commercial passenger transportation will probably shorten the flight time by a factor 5, from the actual 6 hours to 1 hours for the London-NYC flight route. Therefore, the engine will work for a shorter time. The subsonic part of the flight is very limited. For this reason, a possible solution can be to substitute the turbojet with a pulsejet in the ramjet duct. Valveless pulsejets are extremely, simple, reliable, lightweight, fully throttable jet engines. The main limitations of the pulsejet are very low efficiency, relatively low "thrust density" and noise. Noise is naturally reduced as the main working frequency passes from the 150Hz of small pulsejet to the 40Hz of larger ones. Efficiency can be increased inserting the pulsejet in a ramjet-duct. This solution increases the pressure at the pulsejet intake and efficiently recovers heat from the pulsejet walls. Finally, it is possible to decelerate the jet with an ejector exhaust thrust augmenter. The feasibility of this concept is investigated in this paper. For this purpose, it was imagined to develop a transport aircraft with the aerodynamic of the Valkyrie and the new propulsion system. A cruise speed of MACH 3.5@25,000m was simulated with CFD. In this cruise condition the pulsejet works as a combustion stabilizer for the ramjet. Also, the take-off condition was simulated. At take off the thrust is obtained only by the pulsejet.

Keywords: CFD | Hypersonic transportation | Pulsejet | Ramjet | Simulation | Thrust

Abstract: The tandem rotor configuration is particularly convenient for the lift-compound approach in helicopters. In fact, the additional wing is positioned between the two rotors in an area that is marginally interested by the airflow in vertical flight. On the contrary, in horizontal flight, the airflow accelerated by the frontal rotor directly invest the wing improving its lift. A very thin wing with a short chord and a relatively large span can be manufactured with the same technology of the rotor blades. If this wing is fixed without control surfaces, the additional weight can be extremely limited. A concaveconvex high lift airfoil can be used. This airfoil is relatively stiff due to the large bending moment of inertia. A skin stressed structure can be used for the additional wing to obtain also a large torsional stiffness. This lightweight wing can be installed on the helicopter when required and it can be optimized to a defined flight condition. In our case the optimization was performed for cruise. With a very limited weight increment and with a lift penalty within the simulation approximations, the cruise fuel consumption can be halved. The result is impressive for ferrying and long range passenger transport operations, where load capacity can be fully exploited only by increasing the fuel load. In this case a helicopter like the Chinook can perform long range missions with a significant increase in operational capability.

Keywords: Cruise | Helicopter | Lift-compound | Range | Tandem rotor

Abstract: CRDID (Common Rail Direct Injection Diesel), automotive derived engine, main advantage is the enormous amount of experimental data. These engines are produced in millions of units and reliability data based trillions of hours are available. It is also possible to run automotive CRDIDs with jet fuel. It is also possible to mix the two fuels with a proper ECU (Electronic Central Unit) mapping. Therefore, the necessity to refuel in airports can be eliminated. Moreover, the additional mass of CRDIDs is largely compensated by the reduced fuel amount necessary to exploit the same mission/flight. However, an additional cooling system duct should be added. For this purpose, fans are replaced by ejector exhaust (augmenter) that does not need fan additional power. Solid Works Flow Simulation confirmed the feasibility of an ejector-exhaust-powered cooling. However, pressure fields around the helicopter varies in a very significant way in the different flight conditions. High cooling duct efficiency requires pressure and clean air at the intake port and negative pressure at the duct nozzle. Therefore, a optimization of the cooling duct positioning has been carried out on a common light helicopter (Eurocopter EC 120). Several different solutions have been simulated with Solid Works Flow Simulation. CFD confirms the ejector choice and the design criteria. The best configuration is a derivation of a Formula 1 intake duct. This solution proved to be the most effective for the CRDID-exhaust powered cooling duct. The result is that the ejector exhaust (augmenter) is extremely effective. With two small intakes at the side of the mast, the pressure differential between the intake and the nozzle of the duct proved to be extremely stable in every flight condition, even with crosswind.

Keywords: CFD | Cooling | Diesel | Efficiency | Exhaust augmenter | Helicopter

Abstract: CRDID (Common Rail Diesel Engine) main advantage is the extremely high efficiency (up to 52%), the enormous amount of hours run and the flight readiness. Moreover, diesel fuel is safer than jet fuel and it is available everywhere. Therefore, refuelling flights to airports or dedicated supply lines can be avoided. However, diesel engines are generally heavier than turboshafts and require an additional cooling system. This requirement is particularly stringent during near stationary operations of the helicopter. In fact, if fans are used for the cooling system, the available power is reduced with an increased penalty weight for the installation. For this reason the ejector exhaust system can be successfully used in CRDID powered helicopters. A feasibility study of the cooling system for a CRDID (Common Rail Diesel Engine) on a common light helicopter (Eurocopter EC 120-class) is introduced. Optimization of this system is performed. The total mass available for the CRDID is evaluated starting from fuel consumption and helicopter data. A derivative of an automotive engine is proposed for the turboshaft replacement. The result is that the ejector exhaust (augmenter) is extremely effective. Solid Works Flow Simulation confirms the ejector choice and the design criteria.

Keywords: CFD | Cooling | Diesel | Efficiency | Exhaust augmenter | Helicopter

Abstract: The new RPAS (remotely piloted aerial systems) are mostly video cameras with wings whose ownership isn't enshrined in any constitution. Rulers are rushing to do regulate the lack of safety and accountability for RPAS. In Italy ENAC (aviation authority) legislated against random acts of stupidity and probable failures. For the current year of 2015, there is a forecast to sell $1bn worth of RPAS product. For these reasons the installation of RPS (Recovery Parachute System) on commercial RPAS is particularly interesting. A few RPS manufacturers have manufactured specific RPS systems for "drones" both rotary and fixed wing. However, these systems are designed with the same criteria of manned aerial vehicle. This paper demonstrates that the design criteria of RPAS are sensibly different from other applications. In particular the rate of descent during recovery should be reduced from 6m/s to 2m/s. This fact poses new challenges in parachute design. In fact RPS mass depends on parachute diameter that increases with low descent rates. This paper demonstrates that it is possible to design effectively RPS for RPAS up to 80kg by using nonwoven fabric in parachutes. In this way the RPS mass is a small fraction of the RPAS one. Deployment systems are not a problem for RPAS since masses are extremely small and the power necessity are accordingly limited.

Keywords: Parachute | Recovery | Remotely piloted aerial systems | Unmanned aerial vehicles

Abstract: In fixed wind turbine installations, the optimal wind location is difficult to individuate, permissions are difficult to obtain and the production site is distant from the costumers. The large production scale of small wheeled wind turbines keep the cost at minimum and give the possibility to install the windmill close to the final costumers. CFD simulation makes it possible to optimize the matching of a small mobile wind turbine with an automotive commercial alternator. This paper proposes an innovative device to furl the wind turbine around the pole axis in such a way to optimize energy production and avoid over-speed. For this purpose a commercial shock-absorber and a cam mechanism are used. The CFD simulation, in this case with Flow Simulation of Solid Works, makes it possible to design the turbine, the tail vane and the mechanism to maximize energy production. The device includes a shock absorber and a cam mechanism. The system provides optimum matching of the turbine torque output to the generator shaft. The same mechanism also determines the cut-out speed. The automotive generator includes a system to charge a 24V standard battery. Then, a power inverter outputs the electric energy to the grid. The 4m-diameter three-blades-rotor is connected to the 3.6kW automotive alternator through a commercial 2.5:1 speed multiplier.

Keywords: Cam furling mechanism | Energy production | Generator matching | Low cost | Wind turbine

Abstract: Many papers for the analytical solution of the lift distribution on a semi in semi-elliptical wing have been published. These works [1] usually approximate the solution by series expansion. This paper introduces an original method for the closed-form solution of this problem. The solution is possible through the use of symbolic manipulators. The wing of the WWII fighter "Reggiane Re 2005" has been solved analytically with the proposed method. The results are similar to the ones obtained by the panel-method and CFD. A CFD simulation of the Re 2005 at maximum speed demonstrates that these results are reasonable.

Keywords: Analytical closed solution | Elliptical wing | Lift | Load

Abstract: Aircraft fuel consumption depends on engine, engine installation, propeller and aircraft efficiency. The matching of the installed propeller is optimized for a design point and it is a compromise for the other working points. The matching of aircraft optimum lift/drag, the minimum engine fuel consumption and the maximum propeller efficiency is rarely achieved. The hyper simplified model on books does not reach the result. Practically very few aircrafts truly match the three conditions The champion of matching are current airliners that, at least in cruise and with half the fuel, reach the optimum at least at the nominal density altitude. In addition, a few fighters and record aircrafts also achieve the maximum possible speed at the nominal conditions. The large majority of the general aviation aircrafts are far from the optimum matching. Even Unmanned Aerial Vehicles are not champions of propulsion efficiency. Ultralight and sport aircraft are the worst. Turbines are very difficult for matching since their optimum efficiency is reached in a very limited working area. Even spark ignition engines are not efficient in off-design conditions. In fact, the spark ignition engine works with an air to fuel ratio by mass that can ran from 16:1 (lean mixture) down to 12:1 (rich mixture). Even spark ignition direct injection engines the combustion takes place within this range. At the relatively high torque settings typical of aircraft engines, the air inside the combustion chamber is burnt entirely and the power output depends on the engine volumetric efficiency. In diesel engines, the air inside the combustion chamber is never burnt entirely. The minimum air to fuel ratio is around 17:1, but the engine works well with any air to fuel ratio below this value. This means that CRDID (Common Rail Direct Injection Diesel) efficiency or BSFC (Brake Specific Fuel Consumption) curve is flatter than the spark ignition engine one. This fact gives a decisive advantage in the propeller matching and in the fuel consumption. In fact, off-design performance is the strongest point in favour of CRDIDs in general aviation. Therefore, the fuel consumption of CRDID takes advantage not only from the extremely high efficiency of the engine, but also from the better matching. In fact, it is possible to map the CRDID FADEC (Full Authority Digital Electronic Control) to optimize SFC (Specific Fuel Consumption). In the example shown in this paper, a CRDID needs nearly half the fuel necessary to a very good spark ignition engine.

Keywords: Aircraft matching | Diesel engine | Power plant installation efficiency | Propeller | Propeller efficiency | Spark ignition engine

Abstract: This paper shows that the sinkage of the tracked vehicle is the most important parameter in its mobility. Power and fuel consumption follow cubic power law with sinkage. So the usual strategy to increase power is not the more convenient way to improve vehicle off road performance. The Ground Pressure (GP) is the critical parameter. Power requirement goes with the cubic power of sinkage. GP above 0.9 daN/cm2 should be avoided at all costs. The best way to obtain this result on an existing design is to increase track length. However it is easier to work on track width. The easiest modification is to add "Duckbill extensions" in the outer part of the shoe. This system was used on the Sherman Tank when additional armor was added. With modern technology it is perfectly possible to perform experimental tests with new shoes. This can be done by manufacturing prototypes of high stress nitrided steel shoes, usually with 300M high strength steel. Comparative fuel consumption is a good index of vehicle performance. Also wheel diameter and width can be increased to improve off-road performance. Specialized tracks for different terrains should also be designed. The gravity center should be kept slightly rearward. This attitude should not be excessive to keep the pressure value more even possible along the track. In any case the vehicle naturally assumes the backward inclination due to terrain compression. Another important improvement is the addition of computer controlled directional control to improve the accuracy of trajectories. This is particularly important for tracked vehicles where turning involves extremely high energy consumption.

Keywords: Ground pressure | Mobility | Tracked vehicles

Abstract: The primary task in DI (Direct Injection) diesel engines design is the fulfilment of the required emission limits. This result should be achieved while still providing optimum torque-to-rpm curves, acceptable fuel consumption, acceptable power density and affordable purchase and maintenance costs. One method to achieve these objectives is the downsizing. In this case a significant increase in the crankshaft speed and boost pressure is unavoidable. In this way an increase in air flow rate through the intake and exhaust ducts is obtained. Considering the impact of these changes, the duct design is extremely critical due to Mach number. Another physical limit is the CR (Common Rail) injector dynamic performance. This performance decreases with injector size and maximum fuel flow for inertia problems. Automotive engines in the range of 10 to 100 HP per cylinder are the most numerous. For this reason, these injectors are the most updated. Furthermore, their small inertia favors a better dynamic performance. The larger number of nozzles improves combustion performance. In fact, the better surface to volume ratio or the spray improves heat transfer. For this reason, it is convenient to use multiple injectors systems in modern HSDI (High Speed Direct Injection) CR large diesels, as it was common in the past. The primary purpose of this study is to examine the best duct geometry on a modern two-injectors-per-cylinder truck engine. For this purpose a new promising, patented concept is introduced. The study includes flow simulations during the intake phase. This new-patented design enables the formation of two extremely strong homogeneous swirls centered to the injectors, with excellent swirl and flow coefficients. The use of swirl generators on the manifolds avoids the necessity to design helical intake ducts. This approach simplifies head design. Moreover, using a VG (Variable Geometry) arrangement for the volutes (swirl generators) it is possible to tune the swirl index at the optimum for every crankshaft velocity and every load. In this way, the vehicle fuel consumption is reduced.

Keywords: Common Rail | Diesel | Direct injection | Multiple injectors | Swirl index

Abstract: The paper deals with an experimental assessment of the Leap Motion Controller®. This device is able to track the user’s hands in a real environment. Due to low-invasiveness and easiness of use, it is promising for the integration in virtual or augmented reality, research and entertainment scenarios. The assessment is performed in a real context using volunteers that were asked to point with the fingertips to a set of predefined locations in space. A specific test rig has been designed and built. It is comprised of a transparent plate supported by adjustable pillars and mounted over the Leap. The data are processed to assess the errors in tracking the five fingertips of the right hand. Results show that the accuracy and precision of the Leap is suitable for robust tracking of the user’s hand. The results also unveil that there are preferable zones in which the tracking performance is better.

Keywords: Leap controller | Motion capture | Natural interface | Tracking | User interaction

Abstract: Pier Paolo Valentini, PhD in Design of Mechanical Systems, is Associate Professor of Applied Mechanics. He is research fellow of the National Laboratories of Frascati (Rome) of the Italian Institute for the Nuclear Physics and member of the Steering Committee of the Italian Association of Machine Design. He teaches Virtual Prototyping and Simulation of Mechanical Systems and Bio-prosthesis. He has been advisor of more than 130 master and PhD dissertations. He has been principal investigator of more than 40 research projects funded by institutions and industrial partners. He has authored more than 130 papers in international journals and conference proceedings. Eugenio Pezzuti is Associate Professor of Machine Drawing. He is member of the advisory board of the Italian Ministry for Education, University and Research. He has been the principal investigator of three projects funded by national institutions. His fields of interests are the design of machine components, study on optimal tolerance allocations, reverse engineering methodologies and biomechanics. He has authored more than 80 papers in international journals and conference proceedings. The allocation of the right tolerances is one of the most important phases in the design process of mechanical devices and systems. In general, the choice has to take into account the manufacturing costs and limitations, looking at the specific functionality of the device and the assemblability of parts. In the case of flexible components, the designer has to include the evaluation of the compliance effects and the structural resistance. The paper discusses a numerical methodology for addressing the problem of the geometrical tolerance allocation for the compliant ortho-planar spring. The methodology is based on the definition of the functionality and resistance objective functions by means of finite element models. Numerical constrained optimisation is then applied to find the suitable combination of tolerance parameters acting on the main dimensions.

Keywords: Compliant mechanism | Flexible component | Ortho-planar spring | Tolerance allocation

Abstract: In order to optimize the design of the thermodynamic cycle of a turbine (Brayton cycle) for using modern common rail as an “active” combustion chamber, it was intended to write the present paper. About the present case, the “active” combustion chamber produces a large amount of the mechanical energy that drives the fan. The incoming air is compressed by the compressor, then it is refrigerated and inputted in the diesel engine. A high pressure common rail system optimizes the combustion in the diesel combustion chamber and the expansion begins inside the diesel engine. At the exhaust of the combustion chamber, a turbine completes the expansion of the hot gases. A nozzle accelerates the exhaust from the turbine to increase the overall thrust.

Keywords: Aircraft | Diesel engines

Abstract: In order to optimize the design of the thermodynamic cycle of a turbine (Brayton cycle) for using modern common rail as an "active" combustion chamber it was intended to write the present paper. About the present case, the "active" combustion chamber produces a large amount of the mechanical energy that drives the fan. The incoming air is compressed by the compressor, then it is refrigerated and inputted in the diesel engine. A high pressure common rail system optimizes the combustion in the diesel combustion chamber and the expansion begins inside the diesel engine. At the exhaust of the combustion chamber a turbine completes the expansion of the hot gases. A nozzle accelerates the exhaust from the turbine to increase the overall thrust. The mechanical energy from the diesel and from the turbine powers the compressor and the fan. The system can be seen as a turbocharged diesel engine with the turbocharger that outputs energy to the turbofan, increasing the output power and or the efficiency. A diesel-turbine compound can be realized in this way. The coupling of the two systems may be obtained in several different ways. The simplest is to put on the same shaft the compressor, the diesel crankshaft and the turbine. In front of the compressor a speed reducer drives the fan. A second example is to connect the turbine and the diesel on to electric generators. Electric engines are connected to the compressor and to the fan. The traditional turbodiesel has the compressor coupled to the turbine, and the diesel engine that moves the fan. In this latter case, however, the turbine does not energize the fan. Many other hybrid and nonhybrid solutions are possible. The problem is to optimize temperatures, pressures and rpm to the different machines that form the compound. The availability of many experimental data for diesel and turbines makes it possible to obtain a design of a "true" feasible optimum Diesel-Brayton cycle. This efficiency figure justifies the huge manufacturing and development costs of these turbocompound engines [1-4].

Keywords: Feasible optimum Diesel-Brayton cycle

Abstract: Composite structures such as CFRP offer significant weight reduction over the conventional aluminum alloys for aircraft. Weight reduction improves fuel efficiency of the aircraft by approximately 20% which results in cost savings and simultaneously reduces the operational environmental footprint. However, the new aluminum-lithium alloys offer significant improvements and are viable alternatives to CFRP. Aluminum lithium alloy 2195 with Friction Stir Welding is introduced as a successful alternative to CFRP primary structures. A "thick skin" monocoque design with integral stringers as crack stoppers is discussed. An old Macchi 205 WWII fighter plane has been redesigned both in CFRP and 2195-FSW for comparison. The final designs are comparable in weight, but 2195-FSW is more competitive based on mass production costs, reparability, and environmental impact. Macchi 205 airplane is used due to in-depth experience with the original aircraft geometry and loads. Knowledge gained here can be directly transferred to larger structures, from corporate jets to large transport category airplanes [1].

Keywords: 2195-FSW | Aircraft structures | Aluminum alloys | CFRP | Composite material

Abstract: In oral implantology, proper execution of the holes for the installation of dental implants is directly related to the correct functioning and durability of the system itself. For this reason, the procedure discussed here, which was once performed freehand in all its phases, is now being implemented through aids with more precision. Masks currently in use are created in resin ad hoc; surgical stents are inserted into the holes that will then be used as a guide. These aids are fixed into the jaw by means of micro bone screws in order to prevent movement during surgery. Despite this, we still use the guides as they are, centered properly with the help of drilling jigs. The same technique is also used in partially edentulous cases through smaller jig fixed on teeth near to the implant zone. In this article, we propose a guidance system for milling cutters used in partially edentulous cases involving from one to three adjacent installations. The purpose of the study was to realize a modular model adaptable to most dental implants, as well as efficient, quick, and low cost by pouring the resin into a plaster mold of the teeth, and then drilling the masks into position in the plants at the required angle.

Keywords: Dental implants | Drilling aid

Abstract: This paper introduces a method to simplify a nonlinear problem in order to use linear finite element analysis. This approach improves calculation time by two orders of magnitude. It is then possible to optimize the geometry of the components even without supercomputers. In this paper the method is applied to a very critical component: the aluminium alloy piston of a modern common rail diesel engine. The method consists in the subdivision of the component, in this case the piston, in several volumes, that have approximately a constant temperature. These volumes are then assembled through congruence constraints. To each volume a proper material is then assigned. It is assumed that material behaviour depends on average temperature, load magnitude and load gradient. This assumption is valid since temperatures varies slowly when compared to pressure (load). In fact pressures propagate with the speed of sound. The method is validated by direct comparison with nonlinear simulation of the same component, the piston, taken as an example. In general, experimental tests have confirmed the cost-effectiveness of this approach [1-4].

Keywords: CAD | FEA | Geometry | Optimization | Simulation

Abstract: This paper introduces an improved Electronic Stability Program for cars that can deal with the sudden burst of a tyre. The Improved Electronic Stability Program (IESP) is based on a fuzzy logic algorithm. The IESP collects data from the same sensors of a standard ESP and acts on brakes/throttle with the same actuators. The IESP reads the driver steering angle and the dynamic condition of the car and selectively acts on throttle and brakes in order to put the car on the required direction even during a tyre burst.

Keywords: ABS | ESP | Fuzzy logic | Tyre road contact

Abstract: Surprisingly, the safety of a flight is still not guaranteed to maximum steam ejection of power during take-off. Moreover, modern aircraft require significant amounts of electricity. It could also be argued that today in many respects the automotive industry appears to be a technology leader with respect to the aerospace industry that, instead, is more conservative. Ferrari has developed, and implemented, on their F1 cars, an electronic device, called KERS, which is able to produce electricity, with peaks of 60 KW for 7s, with a mass of 20 kg, including rechargeable batteries. The main goal of this paper is to explore utilization of turbo-charged aerodiesel engines and conduct feasibility study of the F1-derived KERS to assist power generation in normal and critical flight phases. The KERS' reversible brushless electric motor works as a generator for all aircraft power needs and also provides starting power. It is demonstrated here that such design philosophy improves performance and flight safety of light-to-medium airplanes and helicopter. © 2006-2014 Asian Research Publishing Network (ARPN).

Keywords: Diesel engine | Hybrid aircraft | Kinetic energy recovery system | Li-ion battery systems | Turbine engines

Abstract: Normally in diesel and gasoline engines, common rail systems are employed. The key factors for correct engine power management are pressure, precision and velocity. Digital computers and PID control systems characterize current systems. Recovery strategies are used when anomalies occur and engine performance is significantly reduced. So, restoring normal conditions needs technical assistance. For safety reasons this approach cannot be used in aeronautical, naval and energy-supply applications. In some cases it is necessary to utilize all the possible energy from the power unit causing significant life-reduction of the engine. In this case a progressive reduction strategy should be used and injection law should be reduced accordingly. For this purpose injection control based on fuzzy logic is more effective. In this case, traditional PID control systems are substituted by fuzzy logic control. A reference map is introduced in the Full Authority Digital Electronic Control; this map is interpreted by the fuzzy logic control system that adapts the injection law to the current engine situation. This method has been experimented on a common-rail test bed and results are compared with traditional "binary recovery strategy" FADEC. ©2006-2014 Asian Research Publishing Network (ARPN).

Keywords: Aircraft | Diesel propulsion | Engine control | Fuzzy logic

Abstract: The paper deals with the description of a new methodology for addressing the modelling for static and dynamic simulation of the cross-axis flexural pivot. The proposed methodology is based on the use of the dynamic spline formulation for describing the deformation of the structure using reference points. By using this approach, the very large displacement of the compliant pivot can be modelled using a reduced number of variables. The methodology has been formulated to be also suitable for an integration with an augmented reality interactive design environment. The results coming from the simulations (both static and dynamic) of the proposed model have been compared to those of an equivalent finite element model and show very good accordance. The proposed methodology is able to take into account the nonlinear aspects and it is suitable for real-time computation. An example of implementation in an augmented reality interactive design environment has been successfully implemented. © 2012 Springer-Verlag France.

Keywords: Augmented reality | Cross-axis flexural pivot | Dynamic spline | Interactive design | Simulation

Abstract: A significant issue in aircraft engines is quantifying residual life to overhaul. The algorithm described in this paper calculates with a good level of reliability the residual life of a petrol piston engine. The method was tested on small, latest-generation, naturally-aspirated aircraft and racing piston engines, and has been effective in several experiments. This method is implemented directly on the electronic control system of the engine with very few lines of C-code. The method can also be used in many industrial engines. This innovative method assumes that only two main factors (power level and wear) affect engine durability or time between overhauls. These two factors are considered as separate and combined with worst case criteria. The wear is assumed to follow a logarithmic law and a formula similar to the Miner's law for material fatigue is used, making it possible to calculate the power-level curve with knowledge of only two points. The wear-curve is also related to elapsed engine cycles. The algorithm is very simple and can be implemented with just a few lines of software code accessing data collected from existing sensors. The system is currently used to evaluate actual residual life of racing engines.

Keywords: Aircraft | Algorithm | Durability | Engine

Abstract: The KAD (Knowledge Aided Design) tool is developed to predict the performance of an F1 car in different driving conditions and with different configurations. The regulations to put in trimming a car, also in the exasperated technology of the competitions, still demand a remarkable dose of luck and an elevated number of tests. It is then important to know a set of regulations close to the optimal trim before testing the car on the track. The difficult phase of this process is to evaluate the lap time. As a matter of fact driving style, track conditions and car behavior should be simulated. The optimisation of the fuzzy controller that simulates the pilot for an F1 racing car is difficult due to handling problems and velocity of response. For this purpose a specific Genetic Algorithm (GA) was conceived and tuned to work with a lumped mass model of an F1 racing car for the optimization of the fuzzy controller that simulates the pilot. A new mutation and a new crossover operator were defined to complement the standard crossover and mutation operators of the basic Holland's GA. This was necessary in order to increase the overall performance of the fuzzy pilot. This approach was tested on an F1 car due to the huge amount of data available (Donnarumma, 1998; Moelenbein, 1989; Lee and Takagi, 1993).

Keywords: Control | Fuzzy logic | KAD | Performance

Abstract: A main problem in aircraft engines is the evaluation of residual life to TBO. The algorithm described in this paper calculates with good reliability the residual life to TBO of a petrol piston engine. The method was tested on small last-generation naturally-aspirated-avio piston engine, and has demonstrated to be effective in several experimental tests. This method is implemented directly in the FADEC or ECU of the engine with very few lines of C-Code. The method can be used also in many industrial engines. This innovative method assumes that only two main factors (load and wear) affect engine durability or Time Between Overhauls (TBO). These two factors are considered as separate and combined with the worst case criteria. The load is assumed to follow a logarithmic law and a formula similar to the Miner's law for material fatigue is used, making possible to calculate the "load curve" with die knowledge of only two points. The "wear" curve is related to elapsed engine cycles, and is easy to implement since it is related to technological. The resulting algorithm is very simple and can be implemented in very few software lines with data collected from the already existing sensors.

Abstract: In this chapter the authors discuss several approaches in order to integrate computeraided engineering instruments into Augmented Reality environment. Engineers and designers often develop their creative ideas in front of a computer monitor using mouse and keyboard. Although the integration between numerical computation and graphics leads to the generation of very realistic digital mock-ups, they are still far from the real context and the user has limited interaction with them. The purpose is to illustrate how recent development in computer graphics and image processing can improve the realism and interactivity with digital mock-ups. Starting from the interactive modeling of 3d shapes, the chapter presents some examples about the integration of real-time mechanism motion simulation, structural and fluid dynamics analysis post-processing. © 2010 by Nova Science Publishers, Inc. All rights reserved.

Keywords: Augmented reality | Computer-aided design | Simulation | Virtual engineering

Abstract: Active antiskid systems for high performance motorbikes are difficult to implement due to the necessity to combine performance, equilibrium, handling and safety. In order to design and optimize a fuzzy controlled antiskid system for motorbikes a fuzzy model of the pilot was applied to a lumped-mass model of the motorcycle (two different models have been considered). The fuzzy pilot acts on the steering angle to control trajectory, yaw angle, yaw velocity and roll angle. Throttle position vs. time curve, gear and an adherence model between tire and road are given as input. The fuzzy pilot is implemented with Matlab/Simulink, and simply tries to keep equilibrium. Only measurable inputs were given as input variables of the antiskid fuzzy controller. The output is the percent reduction in throttle position. The motorcycle-fuzzy-pilot model proved to be quite accurate. Motorcycle maximum velocity resulted higher than the real one due to the simplifying hypothesis. In curves the fuzzy pilot is less efficient than the real pilot. In fact there was a low frequency oscillation around the optimum steering angle. This fuzzy controlled antiskid proved to work quite well since equilibrium is attained also in critical situations where the motorcycle-fuzzy-pilot model alone fails to keep equilibrium.

Abstract: The progressive increase of tire-size has concurred to a sensitive improvement of the adherence with consequent increase of car safety. However, the wide tires have problems to expel the water in excess in heavy rain condition. For this reason the phenomenon of the aquaplaning is increasingly felt and is the cause of several automotive accidents. It is not a case that nearly all tire manufacturers supply "rain" tires and adherence in wet conditions is highly advertised. A typical accident happens when aquaplaning occurs in motorway at high speed. One or more tires lose adherence and the car begins to spin. If the pilot is not able to regain the initial direction, the car may hit the guardrail or another car. In this case the modern control systems like the ESP (Electronic Stability Program) and the ASR (Anti Skid Regelung) do not have time or are not able to manage a pre-spin or spin situation at elevated slip-angles. In this paper, a fuzzy control system able to deal with these conditions is introduced. The car has been simulated with a 9 DOF lumped-mass model that does not take into account suspensions and it considers a rigid car on smooth asphalt. The model of adhesion of the tire, instead, takes into account the effect of transverse forces on the longitudinal adherence. An expert pilot controls a high-speed spin with difficulty also. In this paper, a fuzzy control system that is able to control the brake torque on each single tire has been considered. The fuzzy control system works quite well and the car does not even enter in a true spin if enough adherence is present or if the slippery zone on asphalt is limited.

Abstract: The paper deals with the investigation of the influence of geometrical and dimensional errors on performance of the Tracta coupling. It is one of the most simple constant-velocity joints which has been used in front-wheel drive automobiles, all-wheel drive military vehicles, heavy vehicles and various other applications. The proposed study is based on building and simulating a parametric spatial multibody model of the full joint. Both kinematic and dynamic behaviour have been investigated. Five different linear and angular errors have been studied. The sensitivity of kinema-tics and dynamics irregularities to these errors has been computed and summarized in design charts. The results can be used in optimal toleran-ce allocation and accurate vehicle system simulation with the coupling joint sub-model.

Keywords: Mechanical error | Multibody model | Tolerance | Tracta joint

Abstract: In this paper, the authors discuss a methodology to enhance multibody systems simulations using Augmented Reality (AR) implementation. The AR deals with the use of live video imagery which is digitally processed and augmented by the addition of computer generated graphics. The purpose is to illustrate how recent developments in computer-aided design and augmented reality can improve the realism and interactivity when simulating the movement of digital mock-ups. The paper discusses hardware and software implementations and an overview of several illustrative examples. The basic idea is described starting from a simple simulation of a falling body subjected to gravity with the initial conditions set interactively by the user. Then, a more complex interactive simulation of the kinematics of a robot whose end-effector can be grabbed and moved by the user is presented. Finally, the real time dynamic simulation of a slider crank mechanism is discussed. The integration between AR and multibody simulation has revealed to be very useful for didactical purposes and collaborative design.

Keywords: Augmented Reality | Interactive simulation | Multibody

Abstract: In this paper an integration between a computer aided 3D modeller and an augmented reality environment is presented. The system is based on an high resolution web cam to acquire video stream from the real world and an electromagnetic tracking system (Flock of Bird by Ascension) which allows the user to interact with real and virtual objects in the augmented scene. The software to manage user interaction and data flow is implemented in Visual C++ and it makes use of the Artoolkit libraries, the OpenGL libraries and the Flock of Birds libraries. The purpose of the system is to speed up reverse engineering and prototyping processes, because the user can relate real object features in the scene to model its virtual entities or acquire geometrical features of existing parts. Moreover, the user can export the virtual models into CAD system or import external models to see how they fit in their real environment.

Keywords: Augmented reality | CAD | Motion tracking

Abstract: In this paper a complex prosthesis of dental implants, inserted in a mandible bone, has been analyzed using a virtual model. The study has been performed by means of a three-dimensional finite element model including the implants, the bridging structure and the bone. The interaction between implant screws and bone has been simulated in detail. Four different load conditions has been implemented to mimic the masticatory phase. The stress distribution in the implants and in the bone has been evaluated. Effects of possible temperature variation and assembling errors have been also taken into account. Moreover, the stiffening effect of the stabilizing bar that connect the implants has been also discussed. Starting from the results of the numerical investigations an optimization of the shape of the implants has been proposed in order to optimize the assembling procedure. © 2008, The Japan Society of Mechanical Engineers. All rights reserved.

Keywords: Dental Biomechanics | Finite Element Modeling | Immediate Loading Implants | Virtual Model

Abstract: This paper develops a method for optimum tolerancing of components in assemblies. This approach, based on the solution of a constrained optimisation problem, has been applied to an industrial case of an opening door system. The equation to minimise is a manufacturing cost-tolerance function that describes the relationship between tolerance values and manufacturing cost. A set of equations, representing the constraints used in the optimisation problem, is formulated based on the design constraints and assembly requirements. The equations obtained for the optimisation problem are solved to determine the optimum tolerances satisfying all the assembly requirements and all tolerance constraints. Copyright © 2008 Inderscience Enterprises Ltd.

Keywords: Constrained optimisation | Dimensional and geometrical tolerance synthesis | Opening door system

Abstract: For medical and surgical applications, human modelling and simulation have to be very accurate and realistic. This means that both geometries and movements have to be reproduced precisely, investigating both physiological properties and anatomical shapes. This paper deals with the description of geometrical constraints to mimic the movement of the upper limb segments subjected to physical joints. Anatomical studies show that relative motion cannot be approximated with basic constraints such as revolute or spherical joints, but requires the definition of specific geometrical and kinematic pairs. For this purpose, for each joint the authors deduce a set of equations which can be embedded into a virtual environment in order to simulate the relative motion among body segments in a detailed way. © 2007 Elsevier Ltd. All rights reserved.

Keywords: Geometrical constraint | Human modelling | Physical joint | Upper limb

Abstract: Italy has plenty of cultural heritages. The masterpieces are often placed in locations which are difficult to reach, moreover many artifacts, coming from man's creativity, have very complex functioning. The authors of this paper describe their experience in using the computer graphics capabilities in order to reproduce four ancient clocks functioning coming from different Italian regions. The study is based not only on the 3D-shapes reconstruction but also on the simulation of their complex mechanisms in order to mimic their functioning. The realism of the reconstruction allows to use the graphical products in exhibits, museums and also for maintenance programs. The rendering techniques together with an accurate camera path, allow to get into the clock mechanisms and to appreciate all the features (and even secrets) that a simple glance cannot reveal. Copyright © 2006 John Wiley & Sons, Ltd.

Keywords: Ancient clock | Computer-aided simulation | Cultural heritage | Virtual museum

Abstract: Tolerance allocation influences production costs in a big way. For this reason it is very important to have an accurate study about the effects of manufacturing errors on the functioning and performances of linkages. In this paper, the authors present a computer-aided methodology based on a 3D geometrical approach using the dual-algebra fundamentals. The purpose is to give an useful tool which can be integrated into CAD software in order to evaluate the performances of spatial mechanisms with mechanical errors. The proposed methodology has been validated by means of experimental tests on a Cardan joint mechanism with clearances, misalignments and dimensional errors. Copyright © 2005 John Wiley & Sons, Ltd.

Keywords: Computer-aided simulation | Dual algebra | Spatial linkages | Tolerance allocation

Abstract: In this paper an easy procedure to integrate three dimensional cam profile synthesis and Computer Aided Design is presented. The aim of the proposed method is to combine an accurate kinematic analysis with shape modelling using CAD programmes. In many cases the manufacturing process and cutting approximation cannot be neglected and affect the final drawing. For specific needs, as spatial cams, an appropriate and more accurate synthesis is required. On the other hand, the only geometrical design misses all the advantages of modelling, for example the correct calculation of mass properties, interferences, and the possibility to perform dynamical and stress analysis. The authors develop an integrated tool which interacts with both CAD software and algebraic solver in order to draw an accurate cam model and to compute performances as regards errors on position, acceleration, jerk and jounce. This methodology can help the designers in the definition of digital mock-up. Copyright © 2005 Inderscience Enterprises Ltd.

Keywords: 3D barrel cam design | Cad modelling

Abstract: Aluminium alloys are used extensively, whenever the advantages of high strength-to-density ratio, reduction of dead weight and corrosion resistance, make these alloys competitive with other materials. The major markets for structural application of aluminium alloys are civil engineering and the transport industry, in particular, aircraft construction and more recently, that of electric and low emission cars. One of the difficulties to be overcome in using aluminium alloys is the reduction of mechanical properties due to HAZ (Heat Affected Zone) deterioration caused by welding. The mechanical and microstructural characteristics of MIG welded joints in 6082-T6 plate alloy were investigated by means of tensile tests, fatigue bending tests, microhardness analysis, and optical and SEM metallography. The reduced hardness and tensile strength in the HAZ have been linked to the mechanisms of deterioration of constituents initially present in the alloy, originating from quenching and thermal ageing treatment. © 1997 Taylor and Francis Group, LLC.