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This paper describes a lightweight magnesium intensive automobile body structure concept developed at DaimlerChrysler to support a high fuel-efficiency vehicle project. This body structure resulted in more than 40% weight reduction over a conventional steel structure while achieving significantly improved structural performance as evaluated through CAE simulations. A business case analysis was conducted and showed promising results. One concept vehicle was built for the purpose of demonstrating concept feasibility. The paper also identifies areas for further development to enable such a vehicle to become a production reality at a later time.

In the automotive industry, in order to characterize and evaluate damping treatments, it is a common practice to employ Oberst bar tests as specified by ASTM E756 and SAE J1637. The ASTM standard provides equations for sandwiched Oberst bars. These equations allow engineers to extract the properties of the visco-elastic core. For certain type of automotive constrained-layer damping treatments, such as the Aluminum Foilback, it is often convenient and desirable to prepare the Oberst bar samples with production-intent configuration. Unfortunately, these configurations are often asymmetric. Therefore, the composite Oberst bar data cannot be post-processed by employing the ASTM equations. In this study, the ASTM equations for sandwiched bars are modified to accommodate for asymmetric Oberst bar configurations. The finite element method is used to validate the derived equations by performing a “Virtual Oberst Bar test.”

Different methodologies to test transfer case imbalance were investigated in this study. One method utilized traditional standard single plane and two plane methods to measure the imbalance of the transfer case when running it on a dynamic balance machine at steady RPM, while a second method utilized accelerometers and a laser vibrometer to measure vertical vibration on the transfer case when running it on a dynamic balance machine in 4 Hi open mode during a run up from 1000 to 4000 RPM with a 40 RPM difference between the input and output shaft speeds. A comparison of all of the measurements for repeatability and accuracy was done with the goal of determining an appropriate and efficient method that generates the most consistent results. By using the traditional method, the test results were not repeatable. This may be due to the internal complexity of transfer cases. With the second method, good correlation between the measurements was obtained.

In the early stages of a vehicle program, it is a common practice to set target ranges for the global body, suspension and powertrain modes. This modal management process allows engineers to avoid potential noise and vibration problems stemming from strong overlap of major global modes. Before the first prototype hardware is built, finite element models of the body, suspension and powertrain are usually exercised to compare predicted versus targeted ranges of the major system modes in the form of a modal management chart. However, uncertainty associated with the design parameters, manufacturing process and other sources can lead to a major departure from the design intent when the first hardware prototype is built. In this study, a first order reliability method is used to predict variance of the eigen values due to parameter uncertainties. This allows the CAE engineers to add a “three sigma” bound on the eigen values reported in the modal management chart.

This paper deals with the effects of various approaches for modeling of strain rate effects for mild and high strength steels (HSS) on impact simulations. The material modeling is discussed in the context of the finite element method (FEM) modeling of progressive crush of energy absorbing automotive components. The characteristics of piecewise linear plasticity strain rate dependent material model are analyzed and various submodels for modeling of impact response of steel structures are investigated. The paper reports on the ranges of strains and strain rates that are calculated in typical FEM models for tube crush and their dependence on the material modeling approaches employed. The models are compared to the experimental results from drop tower tests.

During the design process for a vehicle, the CAD surface geometry becomes available at an early stage so that numerical assessment of aerodynamic performance may accompany the design of the vehicle's shape. Accurate prediction requires open grille models with detailed underhood and underbody geometry with a high level of detail on the upper body surface, such as moldings, trim and parting lines. These details are also needed for aeroacoustics simulations to compute wall-pressure fluctuations, and for thermal management simulations to compute underhood cooling, surface temperatures and heat exchanger effectiveness. This paper presents the results of a significant effort to capitalize on the investment required to build a detailed virtual model of a pickup truck in order to simultaneously assess performance factors for aerodynamics, aeroacoustics and thermal management.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

An advancement in traction control has entered the marketplace this year with the debut of the 1999 Jeep® Grand Cherokee equipped with the Quadra-TracII or Quadra-Drive four wheel drive systems. The new technology that is at the heart of these systems is the progressive coupling. A new passive adaptive traction control device that utilizes much of the hardware normally associated with automatic transmissions but applied to enhance traction. In the following report the function of progressive coupling will be described along with design characteristics and parameter recommendations.

The International Lubricant Standardization and Approval Committee (ILSAC) ATF subcommittee members have compared the two oxidation bench test methods, Aluminum Beaker Oxidation Test (ABOT) and Indiana Stirring Oxidation Stability Test (ISOT), using a number of factory-fill and service-fill ATFs obtained in Japan and in the US. In many cases, the ATFs were more severely oxidized after the ABOT procedure than after the same duration of the ISOT procedure. The relative severity of these two tests was influenced by the composition of the ATFs. The bench test oxidation data were compared with the transmission and the vehicle oxidation test data.

In this paper, the effects of heat exchanger design parameters are investigated. The ease study being investigated here is the parametric analysis of automotive radiator where the hot fluid is the engine coolant and the cold fluid is the ambient air. Key parameters that are considered are the air density, fin thickness, fins height and air temperature. Effect of air density may be a concern since heat exchangers are usually designed, for automotive applications, under atmospheric pressure conditions. Changes in altitude will cause a change in air density. Therefore, the performance of cooling system may be affected by elevation. In this analysis, however, it is shown that the change in air density has very limited or no effect on the cooling system. The fin dimensions play a key role in the overall effectiveness of a heat exchanger. Some cost saving ideas may include reducing fin dimensions such as fin thickness or fin height.

A method to predict the powertrain mount loads is proposed and correlated with measured data. DOE studies are performed to derive the sensitivity of several variables, including the range, root mean square, pseudo-damage values of powertrain mount loads, on some model parameters, including powertrain CG locations, moments of inertia, and mount stiffnesses, respectively. The results show that the proposed method is valid in predicting powertrain mount loads.

The way a powertrain is mounted plays an important role in improving vehicle noise and vibration caused by the engine firing forces and can be an effective role in improving vehicle ride comfort. This paper describes the basic concepts in powertrain mounting and derives a new concept of evaluating powertrain mounting. It is well known in publications that a decoupled powertrain mounting system has better NVH characteristics[3][4][6]. But how to relate percentage of decouple to powertrain mounts transmitted forces, what “decoupled” really means, and how to evaluate how much it is decoupled are still ambiguous to many engineers. The traditional “one coordinate system” kinetic energy fraction (KEF) index can't give a clear picture of how much the engine mounting is decoupled and is often misleading. The new concept focuses on the excitations acting on the powertrain system.

The objective of this paper is to present a simple and comprehensive integrated Design for Six Sigma (DFSS) approach to design robustness. The approach is hinged on conceptual components for axiomatic design, robust design and Six Sigma. An automatic transmission planetary case study is provided as an illustration vehicle. Specifically, this paper will explore the cascading process of functional requirements to design parameters and features while providing an initial robustness assessment against the common sources of variation. A Six Sigma design quality level is pursued as an objective. The approach presented in this paper represents a stream of development to achieve excellence by improving customer satisfaction through quality enhancement efforts. It can be viewed as a process with detailed steps needed to cast a complete understanding of how to achieve desired breakthrough design improvement.

The automotive industry is rapidly implementing computer simulation in every aspect of their processes mainly to decrease the time required to bring new models to market. Computer simulation can also be used to reduce the cost of vehicle development and manufacturing. A major portion of the manufacturing cost associated with automotive stamping lies in the process design, build and tryout of production dies and in automation of the transfer equipment. Press home-line tryout is largely a trial-and-error process relying heavily on the skills and experience of tool and die makers. To reduce this dependence on human skills and effort, press-line simulation can be effectively utilized to verify the design accuracy thereby reducing the changes needed to rework the production die/tool. The entire press-line with all its complete accessories can be modeled and checked for design errors similar to the try-out conducted in the production plant.

The US Automotive Materials Partnership (USAMP) and the US Department of Energy launched the Magnesium Powertrain Cast Components Project in 2001 to determine the feasibility and desirability of producing a magnesium-intensive engine; a V6 engine with a magnesium block, bedplate, oil pan, and front cover. In 2003 the Project reached mid-point and accomplished a successful Decision Gate Review for entry into the second half (Phase II) of the Project. Three tasks, comprising Phase I were completed: (1) evaluation of the most promising low-cost, creep-resistant magnesium alloys, (2) design of the engine components using the properties of the optimized alloys and creation of cost model to assess the cost/benefit of the magnesium-intensive engine, and (3) identification and prioritization of scientific research areas deemed by the project team to be critical for the use of magnesium in powertrain applications.

In this study, a simplified approach to modeling the dynamics of damping treatments in FEA (Finite Element)/ SEA (Statistical Energy) models is presented. The basic idea is to represent multi-layered composite structures with an equivalent layer. The properties of the equivalent layer are obtained by using the RKU (Ross, Kerwin and Ungar) method. The procedure presented here does not require any special pre-processing of the finite element input file and it does not increase the number of active degrees of freedom in the model, thereby making it possible to include the effect of these treatments in large system/subsystem level models. The equivalent properties obtained from RKU analysis can also be used in the SEA system models. In this study, both unconstrained and constrained layer damping treatments applied to simple structures (e.g., flat panels) as well as production vehicle components are examined.

A design is robust when the performance targets have been achieved and the effects of variation have been minimized without eliminating the causes of the variation such as manufacturing tolerances, material properties, environmental temperature, humidity, operational wear etc. In recent years several robust design concepts have been introduced in an effort to obtain optimum designs and minimize the variation in the product characteristics [1,2]. In this study, a probabilistic design analysis was performed on a catalytic converter substrate in order to determine the required manufacturing tolerance that results in a robust design. Variation in circularity (roundness) and the ultimate shear stress of the substrate material were considered. The required manufacturing tolerance for a robust design with 1,2 and 3 sigma quality levels was determined. The same manufacturing tolerance for a reliability based design with reliability levels of 85%, 90% and 95% was also determined and compared.

This paper describes the use of robust engineering in engine cooling system design. 1-D thermal-fluid network simulation software has been used in conjunction with statistical variation analysis software. It shows how we can increase the reliability of an automotive engine cooling system by considering the variations of all factors of design. Design of experiment (DOE) and Monte Carlo simulation techniques have been used to optimize the engine cooling system design.

The quality of engine lubrication depends upon how much oil is supplied and how the lubricant is pressurized to the lubricated components. These variables strongly affect the safe operation and lifespan of an engine. During the conceptual design stage of an engine, its lubrication system cannot be verified experimentally. It is highly desirable for design engineers to utilize computer simulations and robust design methodology in order to achieve their goal of optimizing the engine lubrication system. The heuristic design principle is a relatively routine resource for design engineers to pursue although it is time consuming and sacrifices valuable developing time. This paper introduces an unusual design methodology in which design engineers were involved in analyzing their own designs along with lubrication system analyst to establish a link between two sophisticated software packages.

This paper identifies the difference in powertrain cooling system content levels using a nominal and a +3 Standard deviation maximum temperature design approach. Variation simulation analysis tools are used along with a 1-D cooling system performance model to predict resulting temperature distribution for different combinations of input variable populations. The analysis will show differential in powertrain cooling system content, mass, and impact to fuel economy for a nominal vs. +3 sigma design approach.