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Technical Paper

Optimization of Split Sleeve Cold Expansion Process for Aerospace Aluminum Alloys

In this work, the application of the split sleeve cold expansion process on different aerospace aluminum alloys was investigated. The study was undertaken for a number of aluminum-lithium alloys in order to provide a recommendation for material / process optimization. The results showed that, in general, these materials can undergo this process without cracking in severe but realistic conditions. In addition, in order to apply the process for the most difficult cases, the performance of a new sleeve design was investigated on a 7085-T7651 aerospace aluminum alloy plate. Although the new design was not optimized, experimental evidence showed that it can significantly reduce cracking near a sleeve split.
Technical Paper

Sheet Metal Forming Simulation for Aluminum Alloy Sheets

This work describes a sheet forming process simulation, cup drawing and redrawing, using a new plane stress anisotropic yield function that describes the anisotropic behavior of aluminum alloy sheets well. The anisotropy of the function was introduced in the formulation using only linear transformations on the Cauchy stress tensor or deviator. The implementation of this constitutive equation in finite element codes was briefly explained. Simulation results were presented and compared with experimental data.
Technical Paper

Sliver Reduction in Trimming Aluminum Autobody Sheet

Aluminum autobody sheets produce appreciable amounts of slivers during trimming operations when trimmed with dies conventionally designed for steel sheets. The slivers can be carried through downstream processes and cause damage to the surface of formed parts which results in significantly increased repair-rates. A systematic experimental investigation was conducted on trimming 6111-T4 and 6022-T4 aluminum autobody sheets using straight cutting blades/pads under unlubricated conditions. It is shown that slivers can be reduced or eliminated by modifying the current trimming tools designed for steel sheets. With appropriate tool design, trimming of 6111-T4 and 6022-T4 sheets actually can be more robust than that of steel sheets, the clearances can be less restrictive and tools may require much less sharpening.
Technical Paper

Filiform Corrosion of Aluminum Auto Body Sheet in Accelerated and Outdoor Environments

This paper discusses a portion of a larger program on filiform corrosion concentrating on test methodologies and environmental mechanisms that contribute to filiform corrosion. It is organized into four sections, the first covers background of filiform corrosion, materials used in the study, and procedures for the sample preparation and testing. Following this, there are sections on outdoor testing, accelerated testing, and environmental parameters all of which include some procedural information, results and conclusions.
Technical Paper

Influence of Surface Treatments on Durability of Painted Aluminum Alloys

Increasing use of aluminum in automotive components has led to lower fuel consumption and enhanced performance of automotive designs. From a manufacturing standpoint, aluminum provides the additional advantage of utilizing same processes as steel. Performance and durability of painted aluminum cars, however, is dependent on proper optimization of process conditions. As part of an extensive study of factors influencing corrosion resistance of painted aluminum, the present study deals with the influence of pretreatment and coating variables and the interaction of alloy composition with zinc phosphate and electrocoat. Interfacial analysis of corrosion products indicates the relative influence of alloying elements on stability of the metal/phosphate/electrocoat interface. As a result, guidelines and recommendations on aluminum processing in an automotive manufacturing floor have been developed.
Technical Paper

Weldbonding of Aluminum Automotive Body Sheet

This paper presents the results of an investigation into the material variables that influence the weldbonding of aluminum. The four major variables that were considered in this study were the aluminum alloy, type of adhesive, the presence of a forming lubricant, and the metal surface treatment. To maximize the amount of information gained from this study, a statistical design of experiments was used. The particular design used here is an example of a screening design, in which a relatively small number of variable combinations is investigated to identify those variables that have a strong impact on the measured responses. The responses in this experiment consist of both quantitative measurements and qualitative judgments that must be taken together to interpret the experimental results. The “quantifiable” responses included weld parameters (current and percent heat); nugget diameter; weld quality ratings (based on a subjective rating system); and tensile strength.
Technical Paper

Lightweighting of Cars with Aluminum for Better Crashworthiness

Societal demands for greater automotive fuel economy, lower environmental impact and improved performance have produced a trend towards lightweighting in automobiles. In this context, the effect of car mass and size on occupant safety is receiving considerable attention in the literature. Concerns have been raised about the safety of occupants of smaller, lighter cars involved in accidents with larger, heavier vehicles. The evidence supporting these concerns comes from crash data of existing steel-bodied cars. In this paper, the possibility of using an aluminum body structure to reduce automobile mass is explored. The use of lightweight aluminum provides the opportunity for a larger low mass structure than could be achieved by traditional steel body construction. This paper provides technical data related to the energy-absorbing characteristics of aluminum components.