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A discussion of aluminum bumper systems, alloy data fabrication performance, and costs are presented. Weights and costs of similar steel, aluminum, and urethane face systems are compared and the effect of weight savings on costs and fuel economy is determined. Areas for product improvements are explored.

A discussion of the impact of a 2.5 mph bumper standard on aluminum sheet and extruded bumpers is presented. Information is presented on energy management systems, bumper shape, and dentability. This information can be used to determine whether a sheet or extruded bumper is the most efficient for a particular application.

This paper compares the construction of an aluminum body with an identical steel body. The design parameters set forth for the steel body governed the overall approach resulting in a realistic comparison between aluminum and steel weight of a body-in-white. The paper discusses specific techniques used in the construction of the aluminum body and outlines areas of difference between aluminum and steel of interest to automotive engineers.

Dynamic denting tests have been conducted on actual autobody components and on simulated panels fabricated from aluminum and steel sheet at impact velocities of 20 to 125 mph. These experiments give additional evidence that dent depth is a linear function of impact velocity. They also show that autobody components fabricated from aluminum sheet can have equal or improved dent resistance compared to the same components fabricated from the steel alloys currently used. Primary factors to be considered in comparing dynamic dent resistance are sheet thickness, yield strength, modulus of elasticity, density and geometric shape.

Dynamic denting properties of aluminum and steel autobody panels have been experimentally measured under controlled conditions. Material, geometric and dynamic factors have been graphically and statistically evaluated to determine design equations. For impact velocities of 20-60 mph and sheet gauges of 0.027-0.040″, dent depths are shown as linear functions of impact velocity. This linear velocity model incorporates sheet thickness, yield strength, density and modulus of elasticity of the alloy used, as well as the geometric shape of the fabricated panel. As an example, for equal dent resistance, a panel of 2036-T4 aluminum would need to be 10-13% thicker than the same panel fabricated from 0.035″ gauge 1010-CQ steel.

Comprehensive exposure tests are underway at Phoenix, Arizona; Chicago, Illinois; Pompano Beach, Florida; and Richmond, Virginia involving full-size aluminum and steel bumpers, bumper-stock panels, bimetallic body panels, and body filling repaired panels. Exposures include 1,2, and 4 yr removals plus control materials. This report includes a summary of the program and evaluations made from 1-yr removals and evaluations at the Phoenix and Florida Sites.

The dent resistance of aluminum and steel autobody panels has been studied under controlled laboratory conditions and by field observations and measurements of actual hailstone damage. Analysis of the results shows that very nearly the same response occurred in the lighter weight aluminum components as occurred in the steel panels. The autobody components were all 1977 model year production panels. Laboratory testing included four steel and four aluminum hoods, both painted and unpainted. The hailstone damaged components included a steel hood, aluminum doors and an aluminum fender. The aluminum and steel panels were damaged in the same hailstorm during May 1977. The analysis of denting resistance presented in this paper is based on insight and experience gained from a four-year cooperative program of Reynolds Research and several automobile companies.

Tailored blanks have been produced by a variety of welding processes. Currently, laser welding and mash seam welding are commonly used to produce steel blanks for automotive stampings. Because of the high electrical and thermal conductivity of aluminum, mash seam welding is generally not suitable for this application. Laser welding is currently in the developmental stage for welding aluminum. Reynolds Metals Company is investigating another existing welding technology -- Gas Tungsten Arc Welding (GTAW)--for welding of aluminum tailored blanks. Using the GTAW process, production weld speeds approximating those of laser systems can be obtained. Additionally, good control of weld geometry and quality can be easily attained. This study focuses on GTA welding process parameters for joining various alloys, tempers, and thickness of aluminum. Additionally, performance of welded joints in terms of strength, ductility, and formability are discussed.

Recent trends in the automotive industry toward improving fuel economy have led to the conversion of many steel applications to aluminum. The use of aluminum reduces vehicle weight while allowing the automaker to continue to use traditional fabricating methods. The primary joining technique used for steel sheet components has been resistance spot welding. While this technique is currently used to join many aluminum components, automakers are reluctant to specify this joining technique due to capital equipment cost, electrode tip life, or reliability concerns. Several alternate joining techniques have been investigated and used. These include adhesive bonding, weld bonding, resistance welding with arc cleaning (1, 2)*, GMA spot welding, clinching, and riveting. Recently, a method of riveting components without prepunching or pre-drilling holes has generated a large amount of interest. This paper is a review of this riveting technique.

One joining technique that is receiving increased attention is mechanical fastening with a steel self-piercing rivet. The use of steel rivets in direct contact with aluminum components raises questions concerning galvanic corrosion. To determine if a corrosion problem exists, aluminum samples were joined by two processes--resistance spot welding and steel self-piercing rivets. Replicate samples using two aluminum alloys were tested for 90 days by alternate immersion in 3.5% NaCl water solution. After alternate immersion exposure, the integrity of the joint was evaluated by shear testing. Joint shear strengths and the metallographic corrosion evaluations are presented in this paper.

The aluminum alloy 2036 is presently being used in the production of automotive body panels. In the study presented, specimens of 2036-T4 with varying crystallographic textures were subjected to tensile testing and limiting dome height (LDH) evaluations in an effort to gauge the effect of texture on formability and stamping performance. To describe the texture, relative magnitudes of ideal texture components were derived from the orientation distribution function. Finite element analysis was used to study the effect of anisotropic properties due to texture on thinning in the LDH test. The impact of textural character on formability is discussed.