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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.

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.

Several significant process and product developments have enabled single-sided projection welding of 6XXX-T4 automotive aluminum sheet (patent pending). Hem welding was performed on geometries typically encountered on door and hood applications using an enhanced version of the HY-PAK® technology. This process is unique because both electrodes approach from the same side of the component, enabling no visible weld mark on the opposing surface. An experimental design was developed to understand the influence of the major process variables (weld current, weld force, projection height) on the tensile shear and button peel performance. The DOE was performed on single-sided projection welds consisting of 0.8mm 6111-T4 aluminum sheet. The results indicate a range of acceptable process parameters that produced tensile shear strengths on the order of the Aluminum Association's T-10 recommended values for resistance welds of that gauge.

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.

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.

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.

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.

Previous fatigue tests on mechanically fastened aerospace joints showed fatigue cracks often initiated in the countersink of the fastener hole where the fastener head was in contact with and caused fretting on, the hole bore. The work presented here evaluated the potential of a number of possible fastener coatings to reduce fretting and increase the fatigue life of the joint. The coatings were tested in a fretting fatigue test and in a ‘zero load’ fatigue test. The results showed that the best fretting resistance and fatigue life was obtained when aluminum pigmented coating (in accordance with NAS 4006) was used. The results also suggest that both test methods provide a similar ranking of performance. This means that the simpler fretting fatigue test may be useful as an initial screening method. However, more testing is needed to confirm this relationship.

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.

In aerospace fastener industry, all materials used or being considered for fastener applications must meet specified minimum shear strength values. It is widely known that shear strength is dependant on the type of shear test. However despite the suspected test dependencies, no detailed open research literature on the fastener shear test, especially shear strength variation via single and double shear approaches, and factors including surface coatings that affect tested shear values, has been conducted. Thus, the objective of this program is to systematically evaluate the effect of coating tribology on the threaded fasteners shear property tested via single shear and double shear testing methods. Five most common fastener finishes were selected, including uncoated, Aluminum CVD, Hi-KOTE, MoS2 coated, and Anodized.

Significant system efficiency gains can be achieved in high-performance aircraft via a unitized structure that reduces parts count. For instance, reduced parts count leads to substantial engineering logistic cost savings through higher levels of subsystem and mounting hardware integration. It also creates performance benefits by eliminating structural connections. Residual stress management, however, remains a major obstacle to capturing full benefits and broadening the application of unitized structure solutions. This paper describes how Alcoa and others are developing tools to overcome limitations in current testing, evaluation, and design practices attributed to residual stress effects. The authors present recent advancements in fracture toughness and fatigue crack growth characterization, along with a new, integrated approach for improved accounting of residual stress effects during fracture critical component design, manufacturing planning, and life management.