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In this article, the authors illustrate the benefits of axiomatic design (AD) for robust optimization and how to integrate axiomatic design into a total robust design process. Similar to traditional robust design, the purpose of axiomatic design is to improve the probability of a design in meeting its functional targets at early concept generation stage. However, axiomatic design is not a standalone method or tool and it needs to be integrated with other tools to be effective in a total robust development process. A total robust development process includes: system design, parameter design, tolerance design, and tolerance specifications [1]. The authors developed a step-by-step procedure for axiomatic design practices in industrial applications for consistent and efficient deliverables. The authors also integrated axiomatic design with the CAD/CAE/statistical/visualization tools and methods to enhance the efficiency of a total robust development process.

In automotive body manufacturing, there are two processes are often applied, Nominal Build and Functional Build. The Nominal Build process requires all individual stamping components meet their nominal dimensions with specified tolerances. While, the Functional Build process emphasizes more on the tolerances of the entire assembly as opposed to those of the individual stamped parts. The common goal of both processes is to build the body assemblies that meet the specified tolerances. Although there is strict tolerance specified for individual stamping parts the finished stampings frequently are released to assembly process with certain levels of dimensioning deviations, or they are within the specified tolerances but require heavy clamping during assembly. It is of high interest to predict the dimensional deviations in the stamping sub-assembly or body-in-white assembly process.

A common occurrence in computer aided design is the need to make changes to an existing CAD model to compensate for shape changes which occur during a manufacturing process. For instance, finite element analysis of die forming or die tryout results may indicate that a stamped panel springs back after the press line operation so that the final shape is different from nominal shape. Springback may be corrected by redesigning the die face so that the stamped panel springs back to the nominal shape. When done manually, this redesign process is often time consuming and expensive. This article presents a computer program, FESHAPE, that reshapes the CAD or finite element mesh models automatically. The method is based on the technique of volume morphing pioneered by Sederberg and Parry [Sederberg 1986] and refined in [Sarraga 2004]. Volume morphing reshapes regions of surfaces or meshes by reshaping volumes containing those regions.

A numerical investigation of automobile sunroof buffeting on a prototype sport utility vehicle (SUV) is presented, including experimental validation. Buffeting is an unpleasant low frequency booming caused by flow-excited Helmholtz resonance of the interior cabin. Accurate prediction of this phenomenon requires accounting for the bi-directional coupling between the transient shear layer aerodynamics (vortex shedding) and the acoustic response of the cabin. Numerical simulations were performed using the PowerFLOW code, a CFD/CAA software package from Exa Corporation based on the Lattice Boltzmann Method (LBM). The well established LBM approach provides the time-dependent solution to the compressible Navier-Stokes equations, and directly captures both turbulent and acoustic pressure fluctuations over a wide range of scales given adequate computational grid resolution.

Tensile measurements and fracture surface analysis of low carbon heat-treated boron steel are reported. Tensile coupons were quasi-statically deformed to fracture in a miniature tensile testing stage with custom data acquisition software. Strain contours were computed via a digital image correlation method that allowed placement of a digital strain gage in the necking region. True stress-true strain data corresponding to the standard tensile testing method are presented for comparison with previous measurements. Fracture surfaces were examined using scanning electron microscopy and the deformation mechanisms were identified.

As a virtual manufacturing press line, line die forming simulation provides a full range math-based engineering tool for stamping die developments of automotive structure and closure panels. Much beyond draw-die-only formability analysis that has been widely used in stamping simulation community during the last decade, the line die formability analysis allows incorporating more manufacturing requirements and resolving more potential failures before die construction and press tryout. Representing the most difficult level in formability analysis, conducting line die formability analysis of automotive body side outers exemplifies the greatest technological challenge to stamping CAE community. This paper discusses some critical issues in line die analysis of the body side outers, describes technical challenges in applications, and finally demonstrates the impact of line die forming simulation on the die development.

The focus of this research effort was to develop a technique to measure the cyclic variability of the mass injected by fuel injectors. Successful implementation of the measurement technique introduced in this paper can be used to evaluate injectors and improve their designs. More consistent and precise fuel injectors have the potential to improve fuel efficiency, engine performance, and reduce emissions. The experiments for this study were conducted at the Michigan State University Automotive Research Experiment Station. The setup consists of a fuel supply vessel pressurized by compressed nitrogen, a Dantec laser Doppler anemometry (LDA) system to measure the centerline velocity of fuel, a quartz tube for optical access, and a Cosworth IC 5460 to control the injector. The detector on the LDA system is capable of resolving Doppler bursts as short as 6μs, depending on the level of seeding, thus giving a detailed time/velocity profile.

Durability requirements for exhaust materials have resulted in the increased use of stainless steels throughout the exhaust system. The conversion of carbon steel exhaust flanges to stainless steel has occurred on many vehicles. Ferritic stainless steels are commonly used for exhaust flanges. Flange construction methods include stamped sheet steel, thick plate flanges and powder metal designs. Flange material selection criteria may include strength, oxidation resistance, weldability and cold temperature impact resistance. Flange geometry considerations include desired stiffness criteria, flange rotation, gasket/sealing technique and vehicle packaging. Both the material selection and flange geometry are considered in terms of meeting the desired durability and cost. The cyclic oxidation performance of the material is a key consideration when selecting flange materials.

This paper will describe an investigation of the formability of high strength steel (HSS) laser welded blanks (LWBs). Anticipated combinations of thickness and steel grades, including high strength low alloy (HSLA) and dual phase (DP) steels were selected. The blanks were characterized through chemical analysis and mechanical testing, as well as microstructural analysis of the weld. Samples were strained in a limiting dome height tester. Weld line movement, dome height and strain at failure were then measured. Data from these tests resulted in development of forming limit diagrams, and allowed correlation of weld line movement to forming conditions. In part, the results showed that the presence of the weld has a negative influence on formability, and that balancing the load carrying capacity of each side of the blank results in minimum weld line movement in the blanks.

Sheet metal forming processes change the material properties due to work hardening (or softening) in the thickness direction as well as throughout the entire part. At the same time, uneven thickness distribution, mostly thinning, occurs as the result of forming. This is true for all commonly used sheet metal forming processes including stamping (deep drawing), tube hydroforming, sheet hydroforming and super plastic forming. The effects from forming can sometimes strongly influence the structural performance. Though the CAE analysts have been trying to consider forming effect in their models for performance simulations, there was no easy way to do it consistently and reliably. Some analysts have been trying to modify the initial gage or yield strength to compensate for the property change due to forming. Replace the model with the formed panel is not feasible due to the mesh density difference.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

A novel design tool that produces solid model geometry from computer-generated sketches was developed to dramatically increase the speed of component development. An understanding of component part break-up and section shape early in the design process can lead to earlier part design releases. The concept provides for a method to create 3-dimensional (3D) solid models from 2-dimensional (2D) digital image sketches. The traditional method of creating 3-dimensional surface models from sketches or images involves creation of typical sections and math surfaces by referencing the image only. There is no real use of the sketch within the math environment. An interior instrument panel and steering wheel is described as an example. The engineer begins with a 2-dimensional concept sketch or digital image. The sketch is scaled first by determining at least three known feature diameters.

Automotive manufacturers have intensified their efforts to increase vehicle fuel economy by reducing weight without sacrificing vehicle size and comfort. Vehicle areas that offer the potential to reduce weight include chassis structural components. A cradle or a subframe is a chassis structural component that is utilized to support the engine/powertrain in front wheel drive vehicles. Traditionally, engine cradles have been manufactured by using stamped steel weldments. Recently, automotive designers are considering alternative processes, i.e., hydro-forming, as well as fabricating engine cradles using lightweight materials. The objective of this paper is to describe the development of an aluminum engine cradle for a General Motors's midsize vehicle. The design criteria and structural performance requirements for this cradle are presented along with an overview of the manufacturing processes used to produce this lightweight structural part.

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.