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The authors' company has established a strong reputation in the application of the Finite Element Method to pistons and has continued to build on this experience, in order to satisfy market needs with respect to increased product durability and reduced development lead times. Results are presented in this paper for gasoline and diesel pistons to illustrate the methodology currently used and the direction in which future piston technology is moving.

This paper analyzes the cooling conditions of articulated piston and their impact on the piston performance. In order to evaluate the piston cooling optimization two configurations of cooling oil jet (single and double) are evaluated on a real time measurement test, together with two articulated piston skirt configuration (single and extended). The results show the influence of engine valves location in the temperatures near the piston top and the influence of cooling oil jet in piston lower part temperatures. The results also show the extended tray efficient behaviour in removing heat from piston undercrown when compared to double jet-single tray configuration.

The duration of piston durability tests is often shortened by increasing mechanical and thermal engine loads and loading frequency. Such durability tests are useful for assessing the structural integrity of new piston designs, but test results are generally not indicative of the expected service life. Furthermore, improper test procedures can introduce illegitimate failure modes which are not present in actual service. Two aluminum pistons were analyzed to gain a fundamental understanding of piston response due to accelerated test loads. The influence of engine speed, fuel/air ratio, intake manifold pressure and crankcase oil temperature on piston fatigue life was studied. Guidelines were established to aid in developing a more effective durability test procedure for natural gas engine pistons.

The use of tailor welded blank sheets for body-in-white applications has brought many new forming challenges. Mechanical properties of tailor welded blanks measured from the tension test showed significantly higher strengths and lower elongations than in the base metal. The forming limit of tailor welded blanks was significantly reduced when compared to that in the base metal. For the weld made from materials with dissimilar thicknesses/strengths, additional formability issues were also raised in addition to those for the weld made from materials with similar thickness/strength. These issues increase the potential for failure in the lesser thickness/lower strength material in the area immediately adjacent to the weld when the difference in thicknesses or strengths of the two materials increases.

This newly developed helical spring can be used at a stress level up to 1300 MPa. The material is composed of Fe-C-Si-Mn-Ni-Cr-Mo-V alloy. Its strength-toughness balance was greatly superior to that of other spring steels. To improve the fatigue strength at a higher stress level, decarburization at the surface upon austenitizing was severely controlled, applying induction heating. Then, a special shot peening process, introduced for the first time, was applied to obtain a surface residual stress at the surface of over 1000 MPa. The spring was first applied to a 1992 TOYOTA model car. Plans are to increase the use since the spring material achieves a weight reduction of at least 30 % and, possibly, 35 to 40 %.

Aluminum sheet forming is entering an era where rapid advances in technology are likely. Combining increased understanding of material behavior, increased understanding of metalworking tribology and improved control of sheet forming processes will result in improved distribution of strain, allowing more complex components to be formed and greater design flexibility. New process control techniques will be developed and implemented to result in improved press actions, control of strain path to effect increased formability and reduced sensitivity to process variables. Improved techniques for assessing producibility and for generating effective tool designs will be developed, perhaps eliminating the need for soft tool tryouts to substantially reduce the total die development time and cost. In this review paper, each of these issues will be discussed.

Increasingly, product engineers must influence customer satisfaction with robust designs, as opposed to waiting for manufacturing to build quality into a product. To enable and facilitate these efforts, simulation and analysis must be used to guide the system to an improved or even optimal state versus merely a functional one. The integration of Multibody System Analysis (MSA) with Design of Experiments (DOE) creates a powerful combination of tools for thorough investigation of a specified design space, identification of the optimal system configuration, and illustration of the effects of system changes on a given output. This paper demonstrates this approach for a specific output: the vertical loads into a suspension's front strut/shock tower due to a severe pothole road event. This event is designed to test the energy management function of a suspension for severe impact events. Improper energy management leads to excessive forces transmitted to the body structure.

Experience has shown that a vehicle equipped with Active suspension and rear wheel steering can be a very powerful tool for research into vehicle dynamics. Passive or “adaptiveu vehicle suspension systems can be emulated. This has considerable potential for shortening vehicle development times. Active systems provide the ability to separate dynamic modes from one another. This enables detailed examination of each effect without the cross coupling normally experienced with passive vehicles. The driver is an important part of the dynamic loop and ultimately it is he/she who must be able to control the vehicle with confidence, precision, and minimum fatigue. An Active vehicle is a powerful way to investigate the feedback and cues needed by the driver, and to produce objective requirements to achieve them. Thus armed, vehicle design, computer simulation and development functions can be more effective in getting better products more quickly to the market.

A control law for integrating 4WS and 4WD systems is presented. It is based upon a non-linear vehicle model in which the lateral force acting on the tires changes according to the tire slip angle, slip ratio and the load. The purpose of the system is to make the actual yaw rate follow the desired yaw rate. A two-degree-of-freedom control structure has been devised and variable transformation is used to linearize the non-linear model so that H∞ control theory can be applied to design the feedback compensator. A new control theory is used to calculate optimum command values for the 4WS and 4WD actuators. Moreover, adaptive logic is added to reduce the desired yaw rate as the tires approach the limits of adhesion. Simulations and experiments prove the system greatly improves stability during cornering.

In the realm of “semi-active” suspension systems, this paper describes a truly “active damping” system. Thorough research and development of low voltage Electro-Rheological Magnetic (ERM) fluids, a revived rotary shock absorber suspension philosophy and a newly developed control algorithm have resulted in an active damping system that resolves the selection between ride comfort and handling performance. The ERM fluid technology, rotary shock absorber configuration and Digital Signal Processor (DSP) technology have advantages of transmitting high forces in a small compact package. The DSP controls the elements that digitize analog sensor signals and through software, result in active damping. We call the actuator the Rotary Active Control Damper (RACD, pronounced “rack-dee”). The variety of on-board sensors makes it possible to adjust vehicle performance through software.

A new 7.3 liter direct-injection turbocharged V-8 diesel engine, T 444E, has been designed by Navistar for use in class 2 through class 8 trucks and buses. The engine incorporates many advanced technology features including Hydraulically actuated, Electronically controlled Unit Injectors (HEUI), and a hydraulically actuated, electronically controlled exhaust backpressure device to provide fast warm-up in cold weather. The direct-injection combustion system and the inherent flexibility of the electronic control system combine to make it possible to meet stringent emission goals while simultaneously satisfying customer demand for improved economy and performance.

Caterpillar Inc. has developed a new diesel engine fuel system, powered by hydraulics and controlled electronically. This Hydraulic Electronic Unit Injector, (HEUI), requires no mechanical actuating or mechanical control devices, and offers many advantages over conventional fuel injection systems. Inherent features of the HEUI Fuel System include injection pressure control independent of engine load or speed, totally flexible injection timing, and full electronic control of injection parameters. Packaging the HEUI Fuel System on an engine is simple, as the injector is compact and available in a variety of configurations. The hydraulic actuating circuit is straightforward, using lubricating oil from the engine sump. Hydraulic lines may be internal to the engine or external. This paper describes the Caterpillar HEUI Fuel System, its operating features, performance advantages, and application to diesel engines.

An important part of vehicle development are design evaluation and validation processes based on testing in the laboratory. At present there are many complete vehicle, body and suspension road simulator configurations. They all are compromised with respect to complexity and cost. They all have certain advantages and disadvantages. Examples for the evolution of such systems will be discussed. It becomes apparent that new solutions are required if not just the optimization of components and subassemblies is aimed at but the exact evaluation of service life in terms of proving ground kilometers. The new concept is a complete car test rig with an active restraint system which restrains the car during maneouvre load simulation and leaves it otherwise relatively uninfluenced. The test rig has in total 20 actuators, four at each wheel and another four at the restrained system. This test rig will be described in some detail.

In order to develop an accurate and realistic accelerated life test, vehicle axle acceleration must be correlated to actual road profiles. This paper describes analytical and empirical methods used to correlate vehicle acceleration to road roughness. A quarter-car model was developed to simulate the vertical response of a vehicle. The quarter-car model uses a tire footprint to average the road profile. Pennsylvania Transportation Institute's (PTI) inertial profilometer was used to record road profiles of city streets through out Pennsylvania. Peak axle accelerations from actual accelerometer data were correlated with the profile's International Roughness Index (IRI). Additional road profiles were input to the quarter-car simulation model. The resulting accelerations from the simulation model fit the above correlation constructed with experimental data. Thus, a quarter-car simulation model can be used with road profile data to develop accelerated life tests.

A high-performance road profile measuring system has developed. The measuring system consists of four laser displacement sensors and an optical speed sensor. It has the advantage of making high-accuracy measurements during a regular run, on a public road, and without any traffic restriction. The measurement is hardly affected by bouncing and pitching motions of the vehicle. The four displacement sensors are arranged at unequal intervals in the direction of vehicle. A road profile is calculated from sensor outputs. This paper describes not only the development of this unique measuring system but also its application to a vehicle behavior. Significant measurements of typical and peculiar public roads in Japan and Northern Europe by the measuring vehicle have been performed for the last few years. The features of these roads are described by the power spectrum densities and the profiles.

The design and validation process of a new car requires detailed knowledge of the interaction of dynamic forces and moments introduced into the rotating wheel. These forces are measured under operating conditions with appropriate sensors and transducers. Due to the effects of the dynamic masses, the loads should be sensed as close to the tire/road interface as possible using a wheel load transducer. Currently, existing transducers are quite heavy, not very accurate and elaborate calibrations and computations have to be performed. With the newly developed VEhicle LOad Sensor (VELOS), these deficiencies are overcome. Examples of dynamic force and moment calibrations with the original tire are presented, as well as road load data acquisitions comparing results from the VELOS with those of the axle transducers on a passenger car under different driving maneuvers.

A hydrostatic dynamometer capable of accurately controlling the speed and torque of an engine has been designed and constructed. The thrust of this work is not only to build a better dynamometer, it is the first step in creating a system for laboratory simulation of the actual load environment of engines and powertrains. This paper presents the design, construction, and evaluation of a hydrostatic dynamometer. The evaluation includes speed and torque limits, and bandwidth of the dynamometer. Also, the dynamometer is compared with those in common use, and the feasibility of accurately reproducing the engine or powertrain load environments are assessed. This is the first phase of a development program; future research is discussed.

It is consistently demonstrated by various test groups that the air flow rate, temperature, humidity, and perhaps, pressure entering the combustion process, must be tightly controlled if repeatable tests or studies are to be attained. Combustion Air Conditioning systems are used to supply either a “standard air” inlet condition or other simulated climatic conditions. Flow rates and temperature control are relatively easy, but humidity and pressure control present real challenges to the test engineer and the equipment designer. The intent of this paper is to inform the test engineer how these parameters may be controlled on present day equipment, and to explain various methods and difficulties of achieving each test condition.

Recently, fuel economy, ride comfort and saving resources for automobiles are strongly required. In this situation, energy savings has been required in a power steering system which lessens the driver's fatigue. In order to respond to these needs, we have to increase the efficiency of the oil pump, which is an important piece of equipment of the power steering system. It is an important issue for us to find a solution. Therefore, we have paid attention to the surplus flow at the middle and high revolutions of the fixed displacement vane pump which decreases efficiency. We have developed a variable displacement vane pump which is able to stop the surplus flow and has flow down characteristics to apply to the automotive power steering system while keeping the size of the pump compact as with a conventional pump. The pump uses hydraulic power generated by the pumping action at the bottom of the vane slots for variable displacement mechanism.

Equations predicting cord length per hose pitch, weight per unit hose length, and percent inner-liner coverage for plain stitch knitted automotive heater hoses are presented. These equations help hose manufacturers to determine the reinforcement cost for knitted hoses. A spreadsheet using these derived equations plus a hose burst equation from the literature also offers insight into key cord physical properties for knitted hoses. Cord loop tenacity (loop break strength) falls out as a key element in controlling knitted hose burst pressure.