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The paper summarises work which has been carried out to establish the sensitivity of the Alcan AVT weld-bonding system to manufacturing process variability. The robustness of the joint-line to factors such as panel fit-up, bondline thickness, adhesive fillet size and missing adhesive is discussed and their effects demonstrated. Manufacturing factors, such as pretreatment damage during part forming and the cure-cycle window for the adhesive, are considered and their effects on performance are indicated. Finally the effect of a series of manufacturing shortfalls and environmental factors have been put together in one experiment and the resulting strength and fatigue performance of bonded joints has been established.

The recycling and reclamation of metal-matrix composites (MMC's) are critical aspects of the commercialization process. By recycling, we mean the economic processing of MMC scrap for reuse as composite. Reclamation refers to the separation and recovery of the individual components of the composite, i.e., the various aluminum alloys and ceramic particles. Three forms of MMC wrought alloy scrap have been considered; i.e., D. C. (direct chill) cast log ends, extrusion butts, and cut extrusion scrap. Recycling each of these forms of scrap back into D. C. cast extrusion billet has been demonstrated. This has been accomplished by recycling the scrap back through the basic mixing process. Various ratios of scrap to virgin composite have been explored and optimum blends are being studied. Similarly, for MMC foundry alloy (high silicon) gates and risers produced in shape-casting, fluxing and degassing techniques have been developed so these may be recycled back into useful castings.

The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing. The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings.

An A356T61 cast aluminum lower suspension control arm has been put into production for the Lincoln Mark VIII. The mechanical requirements which drive the design for a critical part like this are discussed, together with some of the background knowledge needed to address the issues surrounding alloy and process selection. Particularly as it must be realized that the process impacts the degree to which the potential of the alloy can be realized. With this in mind, some of the research activities which have been spawned in parallel with the production activities are briefly covered. The sequence of events involved in the design and prototyping of the part itself are outlined, as is the implementation of a specialized low pressure casting line to produce the part. Part performance to date has been excellent and the quality controls and test methods which have been put in place to see that this remains so are also covered.

A cold worked and induction hardened SAE1045 steel component exhibited excessive distortion after cold working and straightening, as well as cracking during straightening after induction hardening. Since the problems occurred only in certain heats of electric furnace (EF) steel, in which nitrogen content can vary widely and in some cases be quite high, and never occurred for basic oxygen furnace (BOF) steel for which nitrogen contents are uniformly low it was suspected that the source of the problem was low temperature nitrogen strain aging in heats of EF steel with a high nitrogen content. The measured distortion and mechanical properties at various stages in the fabrication process showed that while nitrogen content had no significant effect on the hot rolled steel the component distortion and strength after cold working and after induction hardening increased with increasing nitrogen content.

This work presents comparisons of finite element model predictions of static and dynamic denting with experimental results. Panels were stamped from 0.81, 0.93 and 1.00mm AA6111-T4 and then paint-baked to produce representative automotive outer body panels. Each type of panel was statically and dynamically dented at three locations using a 25.4mm steel ball. Static denting was accomplished with incremental loading of 22.24N loads up to a maximum of 244.48N. Dynamic denting was accomplished by dropping the steel ball from heights ranging from 200mm to 1200mm. Multi-stage finite element analysis was performed using LS-DYNA1 and ABAQUS2 to predict the entire process of forming, spring-back, denting and final spring-back of the dented panels. The predicted results show good correlation with the experiments, but also highlight the sensitivity of the predictions to formulation of the finite element problem.

Robust lane marking detection remains a challenge, particularly in temperate climates where markings degrade rapidly due to winter conditions and snow removal efforts. In previous work, dynamic Bayesian networks with heuristic features were used with the feature distributions trained using semi-supervised expectation maximization, which greatly reduced sensitivity to initialization. This work has been extended in three important respects. First, the tracking formulation used in previous work has been corrected to prevent false positives in situations where only poor RANSAC hypotheses were generated. Second, the null hypothesis is reformulated to guarantee that detected hypotheses satisfy a minimum likelihood. Third, the computational requirements have been greatly reduced by computing an upper bound on the marginal likelihood of all part hypotheses upon generation and rejecting parts with an upper bound less likely than the null hypothesis.

This paper will describe the main features of two newly-developed enabling technologies for the future establishment of an integrated system to recover the full value of the aluminum from scrapped aluminum intensive vehicles. These technologies are fluidized bed decoating and alloy sorting using analysis by laser induced optical emission spectroscopy. Aluminum Intensive Vehicles will employ substantial quantities of sheet material, most of which will have fairly heavy paint coatings and possibly adhesives. While it may be possible to remove and segregate some of the closure panels and the major aluminum castings, the main body structure will need to be shredded to facilitate both the separation of the various aluminum and other materials and also the subsequent thermal decoating of paint films and adhesives. The decoating is necessary to ensure complete pyrolysis of the coatings and to avoid the excessive dross losses encountered when as-painted scrap is remelted.

Vehicle weight reduction through the use of components made of magnesium alloys is an effective way to reduce carbon dioxide emission and improve fuel economy. In the design of these components, which are mostly under cyclic loading, notches are inevitably present. In this study, surface strain distribution and crack initiation sites in the notch region of AZ31B-H24 magnesium alloy notched specimens under uniaxial load are measured via digital image correlation. Predicted strains from finite element analysis using Abaqus and LS-DYNA material types 124 and 233 are then compared against the experimental measurements during quasi-static and cyclic loading. It is concluded that MAT_233, when calibrated using cyclic tensile and compressive stress-strain curves, is capable of predicting strain at the notch root. Finally, employing Smith-Watson-Topper model together with MAT_233 results, fatigue lives of the notched specimens are estimated and compared with experimental results.

This paper presents the numerical validation of the impact response of a hot formed B-pillar component with tailored properties. A laboratory-scale B-pillar tool is considered with integral heating and cooling sections in an effort to locally control the cooling rate of an austenitized blank, thereby producing a part with tailored microstructures to potentially improve the impact response of these components. An instrumented falling-weight drop tower was used to impact the lab-scale B-pillars in a modified 3-point bend configuration to assess the difference between a component in the fully hardened (martensitic) state and a component with a tailored region (consisting of bainite and ferrite). Numerical models were developed using LS-DYNA to simulate the forming and thermal history of the part to estimate the final thickness and strain distributions as well as the predicted microstructures.

The objective of this study was to assess the formability of two 3rd generation advanced high strength steels (3rd Gen AHSS) with ultimate strengths of 980 and 1180 MPa and evaluate their applicability to a structural B-Pillar for a mid-sized sport utility vehicle. The constitutive behavior including strain-rate effects and formability were characterized to generate the material models for use within AutoForm R8 software to design the B-pillar tooling and forming process. An extended Bressan-Williams instability model was able to deterministically predict the forming limit curves obtained using Marciniak tests. The tooling for the representative B-pillar was designed and fabricated with Bowman Precision Tooling and forming trials conducted for both 3rd Gen steels that had a thickness of 1.4 mm.

The choice of an appropriate material model with parameters derived from testing and proper modeling of stress-strain response during cyclic loading are the critical steps for accurate fatigue-life prediction of complex automotive subsystems. Most materials used in an automotive substructure, like a chassis system, exhibit combined hardening behavior and it is essential to capture this behavior in the CAE model in order to accurately predict the fatigue life. This study illustrates, with examples, the strain-controlled testing of material coupons, and the calculations of material parameters from test data for the combined hardening material model used in the Abaqus solver. Stress-strain response curves and fatigue results from other simpler material models like the isotropic hardening model and the linear material model with Neuber correction are also discussed in light of the respective fatigue theories.

A ferritic-pearlitic nodular iron automobile suspension knuckle was fatigue tested in the laboratory using a constant amplitude load level that simulated a severe service condition. It was found that cracks always initiated from surface casting defects and that the fatigue life could be extended significantly by machining away the as-cast surface in the fatigue sensitive locations. Both local strain and fracture mechanics approaches were used successfully to predict the fatigue life of the component.

The movement towards extended warranties in the automobile industry has focussed attention on corrosion performance of many components, particularly cast aluminum wheels. Filiform corrosion is of particular concern since it can severely affect the appearance of the wheel. The appearance and the choice of wheel design are the most attractive features to customers. In order to enhance the filiform corrosion resistance of cast aluminum wheels, cleaning, pretreatment, coating and alloy parameters are critical and need to be optimized. In this paper, the effects of alloy composition and condition on filiform corrosion are reviewed. A series of cast discs were prepared with variations in iron, zinc and copper levels around the standard A356.2 alloy composition. Apart from composition, certain specimens were subjected to different heat treatment and ageing conditions. The effects of porosity and different machining procedures were also evaluated.

The effect of stress triaxiality on failure strain in as-cast magnesium alloy AM60B is examined. Experiments using one uniaxial and two notched tensile geometries were used to study the effect of stress triaxiality on the quasi-static constitutive response of super vacuum die cast AM60B castings. For all tests, local strains, failure location and specimen elongation were tracked using two-dimensional digital image correlation (DIC) analysis. The uniaxial specimens were tested in two orthogonal directions to determine the anisotropy of the casting. Finite element models were developed to estimate effective plastic strain histories and stress state (triaxiality) as a function of notch severity. It was found that there is minimal, if any, anisotropy present in AM60B castings. Higher stress triaxiality levels caused increases in maximum stress and decreases in elongation and local effective plastic strain at failure.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

The characterization of sheet metals under in-plane uniaxial bending is challenging due to the aspect ratios involved that can cause buckling. Anti-buckling plates can be employed but require compensation for contact pressure and friction effects. Recently, a novel in-plane bending fixture was developed to allow for unconstrained sample rotation that does not require an anti-buckling device. The objective of the present study is to design the sample geometry for sheared edge fracture characterization under in-plane bending along with a methodology to resolve the strains exactly at the edge. A series of virtual experiments were conducted for a 1.0 mm thick model material with different hardening rates to identify the influence of gage section length, height, and the radius of the transition region on the bend ratio and potential for buckling. Two specimen geometries are proposed with one suited for constitutive characterization and the other for sheared edge fracture.

This work outlines the evaluation of static and dynamic dent resistance of medium scale structural assemblies fabricated using AA6111 and AA5754. The assemblies fabricated attempt to mimic common automotive hood designs allowing for a parametric study of the support spacing, sheet thickness and panel curvature. Closure panels of AA6111, of two thicknesses (0.8, and 0.9mm), are bonded to re-usable inner panels fabricated using AA5754 to form the structural assemblies tested. While normal practice would use the same alloy for both the inner and the outer, in the current work, AA5754 was adopted for ease of welding. Numerical simulations were performed using LS DYNA. A comparison of experimental and numerically simulated results is presented. The study attempts to establish an understanding of the relationship between structural support conditions and resulting dent depths for both static and dynamic loading conditions.

Process consistency and long electrode-life are essential requirements for users of resistance spot welding (RSW) in the automotive industry. RSW is the dominant joining process for manufacturing automotive body structures from sheet materials. The technique is cost effective (particularly in high-volume production), makes joints rapidly, is easy to automate, and it has no per-joint consumables. These beneficial attributes apply equally to RSW of aluminium automotive structures. However, there has been some reluctance in the industry to embrace spot welding for aluminium. This is because the electrode-life is much shorter than that experienced when welding traditional uncoated, plain-carbon steels, and there is a general lack of confidence in the consistency of the process. This paper describes a potentially non-intrusive method that addresses these concerns.