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THE PURPOSE of this experiment was to determine the role of residual stresses in fatigue strength independent of other factors usually involved when residual stresses are introduced. It consisted of an investigation of the influence of residual stresses introduced by shotpeening on the fatigue strength of steel (Rockwell C hardness 48) in unidirectional bending. Residual stresses were varied by peening under various conditions of applied strain. This process introduced substantially the same amount and kind of surface cold working with residual stresses varying over a wide range of values. It was found that shotpeening of steel of this hardness is beneficial primarily because of the nature of the macro-residual-stresses introduced by the process. There is no gain attributable to “strain-hardening” for this material. An effort was made to explain the results on the basis of three failure criteria: distortion energy, maximum shear stress, and maximum stress.*

Automobile body panels made from advanced high strength steel (AHSS) provide high strength-to-mass ratio and thus AHSS are important for automotive light-weighting strategy. However, in order to increase their use, the significant wear damage that AHSS sheets cause to the trim dies should be reduced. The wear of dies has undesirable consequences including deterioration of trimmed parts' edges. In this research, die wear measurement techniques that consisted of white-light optical interferometry methods supported by large depth-of-field optical microscopy were developed. 1.4 mm-thick DP980-type AHSS sheets were trimmed using dies made from AISI D2 steel. A clearance of 10% of the thickness of the sheets was maintained between the upper and lower dies. The wear of the upper and lower dies was evaluated and material abrasion and chipping were identified as the main damage features at the trim edges.

The increasing use of aluminum in the design of Body In White (BIW) structures created the need to develop and verify repair methodologies specific to this substrate. Over the past century, steel has been used as the primary material in the production of automotive BIW systems. While repair methods and techniques in steel have been evolving for decades, aluminum structural repair requires special attention for such common practices as welding, mechanical fastening, and the use of adhesives. This paper outlines some of the advanced verification and testing methodologies used to develop collision repair procedures for the aluminum 2003 Jaguar XJ sedan. It includes the identification of potential failure modes found in production and customer applications, the formulation of testing methodologies, CAE verification testing and component subsystem prove-out. The objective of the testing was to develop repair methodologies that meet or exceed production system performance characteristics.

A computational model of a mid-size sport utility vehicle was developed using MADYMO. The model includes a detailed description of the suspension system and tire characteristics that incorporated the Delft-Tyre magic formula description. The model was correlated by simulating a vehicle suspension kinematics and compliance test. The correlated model was then used to simulate a J-turn vehicle dynamics test maneuver, a roll and non-roll ditch test, corkscrew ramp and a lateral trip test, the results of which are presented in this paper. The results indicate that MADYMO is able to reasonably predict the vehicle and occupant responses in these types of applications and is potentially suited as a tool to help setup a suite of vehicle configurations and test conditions for rollover sensor testing. A suspension system sensitivity study is presented for the laterally tripped non-roll event.

The search for improvements in occupant protection under vehicle impact is hampered by a real lack of reliable biomechanical data. To help fill this void, General Motors has initiated joint research with independent researchers such as the School of Medicine, U. C. L. A. – in this case to study localized head and facial trauma — and has developed such unique laboratory tools as “Tramasaf,” a human-simulating headform, and “MetNet,” a pressure-sensitive metal foam. Research applied directly to product design also has culminated in developments such as the Side-Guard Beam for side impact protection.

The ability to extract and evaluate the time history of structural deformations or crush during vehicle crashes represents a significant challenge to automotive safety researchers. Current methods are limited by the use of electro-mechanical devices such as string pots and/or linear variable displacement transducers (LVDT). Typically, one end of the transducer must be mounted to a point on the structure that will remain un-deformed during the event; the other end is then attached to the point on the structure where the deformation is to be measured. This approach measures the change in distance between these two points and is unable to resolve any movement into its respective X, Y, or Z directions. Also, the accuracy of electro-mechanical transducers is limited by their dynamic response to crash conditions. The photogrammetry technique has been used successfully in a wide variety of applications including aerial surveying, civil engineering and documentation of traffic accidents.

The Corrosion Task Force of the Automotive/Steel Partnership has developed the SAE J2334 cyclic laboratory test for evaluating the cosmetic corrosion resistance of auto body steel sheet. [Ref. 1] Since the publishing of this test in 1997, further work has improved the precision of J2334. In this paper, the results of this work along with the revisions to the J2334 test will be discussed.

The proliferation of Unibody construction, for vehicle weight reduction, and the expanded use of precoated steel, for improvement in outer body rust-through protection, has significantly increased the number of bimetallic and crevice unions on U.S. manufactured vehicles. Cyclic corrosion and proving ground testing has shown that these unions are highly active electrochemically, resulting in extensive anodic corrosion and cathodic de-lamination of the paint film. This work examines the individual contribution of each layer of the applied protective coatings package, with respect to applied film thickness, to the reduction of permeation by water, oxygen, and NaCl and resultant corrosion.

Variations in human skull thickness affecting human head dynamic impact responses were studied by finite element modeling techniques, experimental measurements, and histology examinations. The aims of the study were to better understand the influences of skull thickness variations on human head dynamic impact responses and the injury mechanisms of human head during direct impact. The thicknesses of the frontal bone of seven human cadaver skulls were measured using ultrasonic technology. These measurements were compared with previous experimental data. Histology of the skull was recorded and examined. The measured data were analyzed and then served as a reference to vary the skull thickness of a previously published three-dimensional finite element human head model to create four models with different skull thickness. The skull thicknesses modeled are 4.6 mm, 5.98 mm, 7.68 mm, and 9.61 mm.

This study evaluated multi-layer steel and composite head gaskets of various thicknesses (0.43 to 1.5 mm) and fire-ring diameters to determine the influence of head gasket crevices on engine-out hydrocarbon (HC) emissions. The upper limit in the percent reduction in HC emissions from gasket-design modifications is estimated to be about 15%. At part-load conditions, the lowest HC emissions were measured for head-gasket thickness of about 1 mm. Significantly smaller thicknesses of the order of 0.4 mm result in an increase in HC emissions. Substantial hydrocarbon-emissions advantage may be realized by minimizing the gasket-to-cylinder bore offset.

The dilemma of using a shoulder belt force limiter with a 3-point belt system is selecting a limit load that will balance the reduced risk of significant thoracic injury due to the shoulder belt loading of the chest against the increased risk of significant head injury due to the greater upper torso motion allowed by the shoulder belt load limiter. However, with the use of air bags, this dilemma is more manageable since it only occurs for non-deploy accidents where the risk of significant head injury is low even for the unbelted occupant. A study was done using a validated occupant dynamics model of the Hybrid III dummy to investigate the effects that a prescribed set of shoulder belt force limits had on head and thoracic responses for 48 and 56 km/h barrier simulations with driver air bag deployment and for threshold crash severity simulations with no air bag deployment.

The effect of friction modifiers on the low-speed frictional properties of automatic transmission fluids (ATFs) was investigated by scanning force microscopy (SFM). A clutch lining material was covered by a droplet of test ATF, and a steel tip was scanned over the sample. The scanning speeds were varied from 0.13 to 8.56 mm /sec, and the frictional force was deduced from the torsion of the SFM cantilever. A reduction in dynamic friction due to the addition of the friction modifier was clearly observed over the entire speed range. This indicates that the boundary lubrication mechanism is dominant under this condition, and therefore surface-active friction modifiers can effectively improve the frictional characteristics. The friction reduction was more pronounced at lower sliding speeds. Thus addition of friction modifiers produced a more positive slope in the μ-ν (friction vs. sliding speed) plots, and would contribute to make wet clutch systems less susceptible to shudder vibrations.

Technical Standards are essential for the expanded use of any engineering material. The Society of Automotive Engineers (SAE) Iron and Steel Castings Committee has been reworking existing, (and issuing new), standards for automotive iron and steel castings. This paper will review the status of the SAE standards for Ductile Iron, Austempered Ductile Iron (ADI), Compacted Graphite Iron (CGI) and high Silicon-Molybdenum (Si-Mo) Ductile Iron, Gray Iron and Steel Castings. The SAE Standards, (and draft standards), will be critically compared to those for ASTM and ISO. Salient differences in the standards will be discussed and implications to design engineers will be addressed. Comparisons to other, competitive materials (and their standards) will be made.

There has been a general consensus in the scientific literature that a rim gouging, not scraping, into a roadway surface generates very high forces which can cause a vehicle to overturn in some situations. However, a paper published in 2004 attempts to minimize the forces created during wheel rim gouging and the effect on vehicle rollover. This paper relied largely on heavily filtered lateral acceleration data and discounted additional test runs by the authors and NHTSA that did not support the supposed conclusions. This paper will discuss the effect of rim gouging using accepted scientific methods, including full vehicle testing where vehicle accelerations were measured during actual rim gouging events and static testing of side forces exerted by wheels mounted on a moving test fixture. The data analyzed in this paper clearly shows that forces created by rim gouges on pavement can be thousands of Newtons and can contribute to vehicle rollover.

The bulge test in hydroforming is a simple fundamental experiment used to obtain basic knowledge in tube expansion. The results can be used to assist design and manufacturing of hydroformed automotive parts. It also can be used to develop a failure criterion for tubes in hydroforming. For these purposes, a section of a long unsupported tube with fixed ends was simulated numerically to obtain the mechanical states of the tube subjected to internal pressure. Steel and aluminum tubes are used. For the bulge tests, the internal pressure reaches a maximum and then decreases in value without failure while the stress, strain and volume of the tube keep increasing. A failure criterion for the bursting of a tube is proposed based on the stress-strain curve of the material.

This paper describes (1) the findings from the implementation of a component test methodology for body, engine and transmission mounts [1, 2 and 3], and (2) the associated CAE model development and mount design robustness enhancement. A series of component tests on light truck body, engine and transmission mounts have been conducted to not only obtain their characteristics as inputs for crashworthiness analysis, but also drive mount design direction for frontal impacts.

The front rail plays an important role in the performance of body-on-frame (BOF) vehicles in frontal crashes. New developments in materials and forming technology have led to the exploration of different configurations to improve crash performance. This paper presents the initial stages of an ongoing study to investigate the effects of the cross section of steel columns on crash performance in automotive applications. Because accurate prediction of the performance of these rails can help reduce the amount of physical crash testing necessary, the focus of this paper is on appropriate testing and modeling procedures for different rail configurations. In the first part of this paper, the Finite Element Analysis (FEA) methodology is presented with respect to correlation with real world tests. The effects of various parameters are described, along with the optimum configuration for model correlation.

The front end module technology is a system developed to make the interface with vehicle body in accordance with costumer requirements. This modular system also has characteristics to reinforce the structure (chassis, main rails, shotguns), respecting its robustness (tolerances of the body) in accordance with NVH performance. The decision of having a FEM design made by steel and plastic was taken due to NVH specification, impact and safety requirements. Other items were either considered such as: fixation on the body of the vehicle, constraints between bumper beam and engine cooling module. Simulation tools including: durability test (static and dynamic) and modal F.E.A analysis, CAE system, crash test performance, aerodynamics required to insure results desired results.

The optimization method and CAE analysis have been widely used in structure design for crash safety. Combining the CAE analysis and optimization approach, vehicle structure design for crash can be implemented more efficiently. One of the recent safety desirables in structure design is to reduce vehicle pitch and drop. At frontal impact tests with unbelted occupants, the interaction between occupant's head and interior header/sun visor, which is caused by excessive vehicle pitch and drop, is not desired in vehicle crash development. In order to comply with the federal frontal crash requirements for unbelted occupant, it is necessary to manage the vehicle pitch and drop by improving structure design. In this paper, a systematic process of CAE analysis with optimization approach is applied for discovering the major structural components affecting vehicle pitch and drop.

In vehicle safety engineering, it is important to determine the severity of occupant injury during a crash. Computer simulations are widely used to study how occupants move in a crash, what they collide during the crash and thus how they are injured. The vehicle motion is typically defined for the occupant simulation by specifying a crash pulse. Many computer models used to analyze occupant kinematics do not calculate both vehicle motion and occupant motion at the same time. This paper presents a framework of response surface methodology for the crash pulse prediction and vehicle structure design optimization. The process is composed of running simulation at DOE sampling data points, generating surrogate models (response surface models), performing sensitivity analysis and structure design optimization for time history data (e.g., crash pulse).