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To validate the integrity of a commercial vehicle's exhaust system's structural design is a challenging job. An integrated approach to use both simulation/modeling and hardware testing must be employed to reduce product development cost. In addition to the considerations of the geometry and configuration specs of 70-90 parts and joints as well as material's thermal and mechanical property data in model development, representative loading must be used. For base excitation type of loading, such as the one experienced by the vehicle's exhaust system, one must decide whether to conduct the time domain transient analysis or frequency domain random vibration analysis. Although both methods are well known, few discussions can be found in the literature regarding their effective use in the framework of product design and development. Based on our study, the random vibration method should be used first for identifying high stress locations in the system and for design optimization.

This paper describes an analytical process for the design of a brake shoe assembly that consists of the linings, shoe table, webs, and rivets. One fundamental performance requirement for the brake shoe assembly is that the linings will not lose clamp force within the desired service life. Key elements of the analytical process involved developing an FEA model with given loading conditions and developing a mathematical model to study the influence parameters of the forces acting on the lining.

Welding has been used extensively in automotive components design due to its flexibility to be applied in manufacturing, high structural strength and low cost. To improve fuel economy and reduce material cost, weight reduction by optimized structural design has been a high priority in auto industry. In the majority of heavy duty vehicle's chassis components design, the ability to predict the mechanical performance of welded joints is the key to success of structural optimization. FEA (finite element analysis) has been used in the industry to analyze welded parts. However, mesh sensitivity and material properties have been major issues due to geometry irregularity, metallurgical degradation of the base material, and inherent residual stress associated with welded joints. An approach, equilibrium-equivalent structural stress method, led by Battelle and through several joint industrial projects (JIP), has been developed.

In this paper, we describe the development of multi-axis, accelerated durability tests for commercial vehicle suspension systems. The objective of the exercise is to design accelerated durability tests that have well-defined correlation with customer usage. The procedure starts with a definition of the vehicle's duty cycle based on the expected operational parameters, namely: road profile, vehicle speed, and warranty life. The second step is determining the durability proving ground test schedule such that the accumulated pseudo-damage (based on spindle loads) is representative of the vehicle's duty cycle. The third step in the process is developing a multi-axis laboratory rig test for the suspension system, such that the accumulated damage in the proving ground is replicated in a compressed time frame.

Virtual proving ground (VPG) simulations have been popular with passenger vehicles. VPG uses LS-DYNA based non-linear contact Finite Element analysis (FEA) to estimate fully analytical road loads and to predict structural components durability with PG road surfaces and tire represented as Finite elements. Heavy vehicle industry has not used these tools extensively in the past due to the complexity of heavy vehicle systems and especially due to the higher number of tires in the vehicle compared to the passenger car. The higher number tires in the heavy vehicle requires more computational analysis duration compared to the passenger car. However due to the recent advancements in computer hardware, virtual proving ground simulations can be used for heavy vehicles. In this study we have used virtual proving ground based simulation studies to predict the durability performance of a trailer suspension frame.

Engineering specifications, i.e. test bogeys, are criterion for determining the success or failure of durability designs in the product development process. Considerations in the development of the specifications for vehicle structural components, such as axle housings and suspension torque rods, have been presented in a previous SAE paper [1]. This paper has been prepared because the factors on the same subject for vehicle drive train components, such as gears and bearings, are quite different. The center of this study is on “how to define equivalent duty cycles for lab test”. Several issues distinguish this task for drive train components: High cycle fatigue, high accelerated tests, competitive failures and failure modes, empirical component load-life data, loading, field correlation, and system level tests.

A method for predicting the propensity of a drum brake system to produce noise is presented. The method utilizes finite element models of the individual components of the drum brake system, which have been assembled into the system model of the brake assembly. An important step in this process is the tuning of the dynamic characteristics of the FEA model to ensure validation with experimental tests. Friction is the key element, which defines the behavior of the drum brake system. The system FEA model is assembled by coupling the lining and drum at the contact interface to simulate the friction interaction. This process produces an asymmetric stiffness matrix. A complex eigenvalue analysis identifies the system dynamic characteristics such as the frequency and damping for each vibration mode. The damping values reveal which modes are unstable and therefore likely to produce noise.

Nowadays, developing web (World Wide Web) engineering is considered to be a top priority task in many companies. A corporate web information center with broad coverage to support a company's worldwide engineering activities can make the product development and customer support more efficient. First, the archived, readily available product information, knowledge database, and user friendly engineering tools can ease up the more ever demanding engineering jobs. Second, the convenient information storage, retrieval systems and hyperlinks on the web should ensure effective communications among engineers, customers, and suppliers. However, without in-depth planning, the full benefits of web engineering cannot be realized. To be effective, other companion engineering programs must also be instated. This paper reviews the experience we have gained in utilizing web engineering for product development and customer support.

In recent years, several transit agencies have tested buses equipped with hybrid powertrain systems. It has been reported that hybrid powertrains have significant advantages over conventional diesel engine systems, in the area of emissions and fuel economy performance. Presented in this paper are engineering issues and suggestions from an auto component supplier point of view in the design of such a powertrain system. The particular system being considered consists of a downsized diesel engine, a generator, a battery package, two identical AC induction motors, and gearbox systems for the left and right driven wheels. The assembly is supported by an H-shaped suspension sub-structure uniquely designed to achieve the “ultra-low floor” configuration. Our discussion covers the system performance, as well as the durability issues. In particular, the presentation focuses on the durability and the design layout of the gearbox and suspension substructure.

Premature parts breakdown in the final drive of heavy vehicle powertrains in vehicles equipped with high power retarders leads one to believe that the coasting mode gear forces may be higher than anticipated. There is limited experimental data that supports this hypothesis in the observation of high bearing load and gear bending stress in coast mode. However, without an in-depth analysis, it is unclear exactly how the high load is generated. There are several suggested causes: friction, gear geometry, and system compliance. The present study focuses on the effects of hypoid gear friction on the powertrain. Analytical expressions of the gear friction vector as a function of gear pressure, pitch and spiral angles, spiral hand and directions of rotation and applied torque were derived and examined. Attempts were made to correlate test-measured quantities and results from analytical models with and without the consideration of gear friction.

Although the methodology of straight bevel gear tooth form generation has been known for quite some time, few references are available in the literature. Presented in this paper are the general numerical procedures of spherical involute and octoid tooth form generations. We have proven that a tooth form generated from the latter approach, by simulating the rotation of a crown gear, matches exactly with the one from the former approach of unwraping a wire from a base circle. The advantage of using general numerical procedures rather than closed form equations is the flexibility of generating both standard and modified gear tooth profiles. In making the forging die, the gear tooth form must be developed with considerations of both the theoretical optimal geometry, and the dimensional compensation for heat treatment distortion.