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Technical Paper

Modeling Costs and Fuel Economy Benefits of Lightweighting Vehicle Closure Panels

2008-04-14
2008-01-0370
This paper illustrates a methodology in which complete material-manufacturing process cases for closure panels, reinforcements, and assembly are modeled and compared in order to identify the preferred option for a lightweight closure design. First, process-based cost models are used to predict the cost of lightweighting the closure set of a sample midsized sports utility vehicle (SUV) via material and process substitution. Weight savings are then analyzed using a powertrain simulation to understand the impact of lightweighting on fuel economy. The results are evaluated in the context of production volume and total mass change.
Technical Paper

Fatigue Strength Effect of Thread Forming Process in Cast Aluminum

2006-04-03
2006-01-0780
Two thread forming processes, rolling and cutting, were studied for their effects on fatigue in cast aluminum 319-T7. Material was excised from cylinder blocks and tested in rotating-bending fatigue in the form of unnotched and notched specimens. The notched specimens were prepared by either rolling or cutting to replicate threads in production-intent parts. Cut threads exhibited conventional notch behavior for notch sensitive materials. In contrast, plastic deformation induced by rolling created residual compressive stresses in the notch root and significantly improved fatigue strength to the point that most of the rolled specimens broke outside the notch. Fractographic and metallographic investigation showed that cracks at the root of rolled notches were deflected upon initiation. This lengthened their incubation period, which effectively increased fatigue resistance.
Technical Paper

Optimum Design of Hood Ajar Switch For Quality

2006-04-03
2006-01-0735
The Hood ajar sensing system provides customer feedback regarding the latch positional state of hood. If the sensing system is not robust to variation due to manufacturing, thermal conditions, and assembly, diagnostic failures can result. Executing various elements of the design for six sigma process can reduce the potential for diagnostic failures. This paper presents a method for achieving quality improvements by developing transfer functions, and using them for sensitivity and variance analysis. Control parameters were optimized to minimize non-conformal situations in the presence of various noise conditions.
Technical Paper

High Temperature Oxidation/Corrosion Performance of Various Materials for Exhaust System Applications

2006-04-03
2006-01-0605
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.
Technical Paper

Tensile Deformation and Fracture of Press Hardened Boron Steel using Digital Image Correlation

2007-04-16
2007-01-0790
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.
Technical Paper

Future Truck Steering Effort Optimization

2007-04-16
2007-01-1155
In an endeavor to improve upon historically subjective and hardware-based steering tuning development, a team was formed to find an optimal and objective solution using Design For Six Sigma (DFSS). The goal was to determine the best valve assembly design within a hydraulic power-steering assist system to yield improved steering effort and feel robustness for all vehicle models in a future truck program. The methodology utilized was not only multifaceted with several Design of Experiments (DOEs), but also took advantage of a CAE-based approach leveraging modeling capabilities in ADAMS for simulating full-vehicle, On-Center Handling behavior. The team investigated thirteen control factors to determine which minimized a realistic, compounded noise strategy while also considering the ideal steering effort function (SEF) desired by the customer. In the end, it was found that response-dependent variability dominated the physics of our valve assembly design concept.
Technical Paper

Expanding the Application of Magnesium Components in the Automotive Industry: A Strategic Vision

2007-04-16
2007-01-1033
There is an increasing global realization about the need for fuel efficient vehicles. An inexpensive way to accomplish this is through mass reduction, and one of the most effective ways that this can occur is through substituting current materials with magnesium, the lightest structural metal. This document describes the results of a U.S. Automotive Materials Partnership (USAMP) sponsored study [1] that examines why magnesium use has only grown 10% per year and identifies how to promote more widespread commercial applications beyond the 5-6 kg of component currently in vehicles. The issues and concerns which have limited magnesium use are discussed via a series of research and development themes. These address concerns associated with corrosion, fastening, and minimal metalworking/non-traditional casting processing. The automotive and magnesium supplier industries have only a limited ability to develop implementation-ready magnesium components.
Technical Paper

Prestrain Effect on Fatigue of DP600 Sheet Steel

2007-04-16
2007-01-0995
The component being formed experiences some type of prestrain that may have an effect on its fatigue strength. This study investigated the forming effects on material fatigue strength of dual phase sheet steel (DP600) subjected to various uniaxial prestrains. In the as-received condition, DP600 specimens were tested for tensile properties to determine the prestraining level based on the uniform elongation corresponding to the maximum strength of DP600 on the stress-strain curve. Three different levels of prestrain at 90%, 70% and 50% of the uniform elongation were applied to uniaxial prestrain specimens for tensile tests and fatigue tests. Fatigue tests were conducted with strain controlled to obtain fatigue properties and compare them with the as-received DP600. The fatigue test results were presented with strain amplitude and Neuber's factor.
Technical Paper

Forming Simulation and Validation of Laminated Steel Panels

2007-04-16
2007-01-1675
Laminated steel has been increasingly applied in automotive products for vibration and noise reduction. One of the major challenges the laminated steel poses is how to simulate forming processes and predict formability severity with acceptable correlation in production environment, which is caused by the fact that a thin polymer core possesses mechanical properties with significant difference in comparison with that of steel skins. In this study a cantilever beam test is conducted for investigating flexural behavior of the laminated steel and a finite element modeling technique is proposed for forming simulation of the laminated steel. Two production panels are analyzed for formability prediction and the results are compared with those from the try-out for validation. This procedure demonstrates that the prediction and try-out are in good agreement for both panels.
Technical Paper

Virtual Manufacturing of Automotive Body Side Outers Using Advanced Line Die Forming Simulation

2007-04-16
2007-01-1688
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.
Technical Paper

Drum Brake Out of Roundness Reduction to Improve Brake Pulsation

2008-04-14
2008-01-0825
The drum brake pulsation is an issue that may cause a major customer complaint. One of the root causes of the drum pulsation is the deformation of the drum to an out of roundness (OOR) shape during the wheel-drum-axle assembly process under the presence of the uneven wheel flatness. This paper summarizes the newly developed OOR simulation method using ABAQUS and the counter-measures to reduce the OOR, and subsequently pulsation, by identifying the drum design parameter effects on OOR.
Technical Paper

Improved Simulation of Local Necks in Quick Plastic Forming

2008-04-14
2008-01-1441
Two alternative finite element formulations are described which consider the influence of normal stress components on sheet deformations in Quick Plastic Forming [1]. The new formulations, single field bricks and multi-field shells, were implemented in the forming simulation program PAM-STAMP [2] using a non-linear viscoelastic constitutive relation [3,4]. Simulations of two industrial components indicate that both new elements simulate local necking more accurately than the standard shells which ignore normal stresses. The multi-field shells require slightly more calculation time than the standard shells and significantly less than equivalent brick models.
Technical Paper

Volume Morphing to Compensate Stamping Springback

2009-04-20
2009-01-0982
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.
Technical Paper

Advanced Simulation Technology Using LS-DYNA® for Automotive Body Manufacturing Process: From Stamping To Assembly

2009-04-20
2009-01-0983
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.
Technical Paper

Robust Analysis of Clamp Load Loss in Aluminum Threads due to Thermal Cycling

2009-04-20
2009-01-0989
A DFSS study identified a new mechanism for clamp load loss in aluminum threads due to thermal cycling. In bolted joints tightened to yield, the difference in thermal expansion between the aluminum and steel threads can result in a loss of clamp load with each thermal cycle. This clamp load loss is significantly greater than the loss that can be explained by creep alone. A math model was created and used to conduct a robust analysis. This analysis led to an understanding of the design factors necessary to reduce the cyclic clamp load loss in the aluminum threads. This understanding was then used to create optimized design solutions that satisfy constraints common to powertrain applications. Estimations of clamp load loss due to thermal cycling from the math model will be presented. The estimates of the model will be compared to observed physical test data. A robust analysis, including S/N and mean effect summary will be presented.
Technical Paper

Local Mechanical Property Variations of AZ31B Magnesium Sheet due to Elevated Temperature Forming

2009-04-20
2009-01-0864
The influence of elevated temperature forming on local mechanical properties of AZ31B magnesium (Mg) sheet material was investigated. The Mg sheet was formed into a closure component with high temperature gas pressure at 485°C. Miniature tensile testing specimens were cut from selected areas of the component where different levels of thinning occurred. The specimens were strained in tension to fracture using a miniature tensile stage. The two-dimensional strain distribution in the necking region along with true stress-true strain curves were computed using a digital image correlation technique to assess the influence of the forming-induced thinning on tensile strength and percent elongation at fracture.
Technical Paper

Dynamic Spot Weld Testing

2009-04-20
2009-01-0032
Static and dynamic strength tests were performed on spot welded specimens made of dual-phase (DP) 780 and mild steels (DQSK). Lap-shear (LS) and cross-tension (CT) as well as a new mixed mode specimen were studied using MTS hydraulic universal testing machine for static tests and drop weight tower for dynamic tests. Three weld nugget sizes were made for each steel and CT and LS. DP780 with one weld size was also tested in mixed mode. Load and displacement as functions of time and fracture mode of the spot welds were recorded. Representative data are reported in this paper.
Technical Paper

Integrating Metal Forming With Other Performance Analyses Using a Mapping Strategy

2005-04-11
2005-01-0357
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.
Technical Paper

Simulation Based Development of Quick Plastic Forming

2005-04-11
2005-01-0088
A computer assisted development technique for Quick Plastic Forming parts [1] is described, based on the simulation program PAM-STAMP [2]. The technique allows thickness changes during forming to be accurately considered in the development process without physical trials. Process pressure cycles, which provide for maximal material formability, can be determined with a single simulation. The paper describes new program features, which reduce modeling effort and increase simulation accuracy. Various validation examples and industrial case studies are also presented, demonstrating current capabilities.
Technical Paper

Inertia Effect in Dynamic Impact Tests

2004-03-08
2004-01-0814
Inertia force during dynamic testing exists in any testing system. A generic system is analyzed using the principle of rigid body dynamics. It is shown that the load recorded by a load cell includes both the load experienced by the test specimen and the inertia force from the mass between the specimen and the load cell, when the load cell is placed on the fixed side of the test specimen. An impact fixture designed for spot weld strength test was then studied as an example. Test data were collected and analyzed to show the effect of inertia on the impact strength of the spot weld.
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