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The challenging performance and affordability goals of next generation aircraft have accelerated the demand for advanced structural materials and concepts capable of achieving significant weight and cost (acquisition and operational) reduction. To meet these aggressive weight and structural maintenance reduction targets, future aircraft will require structural solutions that provide increased strength, damage tolerance and corrosion resistance. Alcoa has developed advanced aluminum alloys and third generation aluminum-lithium (Al-Li) alloys with exceptional performance and durability capability. This presentation first introduces the basic properties of the new 2xxx and 7xxx series aerospace aluminum and third generation Al-Li alloys possessing improved strength, fatigue life, crack propagation, fracture toughness, corrosion resistance, and, in the case of Al-Li alloys, reduced density and increased modulus.

A method of developing more representative test factors and respective minimum cycles is proposed in practices such as J328 and J2530. The method includes recent 6061-T6 material fatigue characterization from specimens originating in wheels. The characterization uses a fully reversed (R=−1) loading method and the specimen is in un-notched condition. Results of finite element analyses of different wheel designs are observed to verify the proposition of usage of R= −1 as appropriate for such material characterization. The results of recent fatigue response of 6061-T6 indicate that the accelerated test load factors found in SAE J328 and SAE J2530 can be reduced by 10%, while rendering at least the same structural margin as that of other ferrous and nonferrous materials. SAE J2562 illustrates a methodology for testing the structural adequacy of a wheel design using loads and cycles that more closely replicate on-vehicle service than those of J328 and J2530.

A task group within the SAE Automotive Corrosion and Protection (ACAP) Committee continues to pursue the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. The program is a cooperative effort with OEM, supplier, and consultant participation and is supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels, but correlations between laboratory test results and in-service performance have not been established. The primary objective of this project is to identify an accelerated laboratory test method that correlates with in-service performance. In this paper the type, extent, and chemical nature of cosmetic corrosion observed in the on-vehicle exposures are compared with those from some of the commonly used laboratory tests

Since 2000, an Aluminum Cosmetic Corrosion task group within the SAE Automotive Corrosion and Protection (ACAP) Committee has existed. The task group has pursued the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. A cooperative program uniting OEM, supplier, and consultants has been created and has been supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Prior to this committee's formation, numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels. However, correlations between these laboratory test results and in-service performance have not been established. Thus, the primary objective of this task group's project was to identify an accelerated laboratory test method that correlates well with in-service performance.

The overstress probe fatigue testing method, although codified to characterize fatigue strength, is poorly understood. While it yields data confirming whether minimum fatigue strength may be met, it does not directly reveal the mean fatigue strength. Procedures for conducting the test are somewhat arbitrary and rely on fitting a 3-parameter Weibull model. In this paper, a Monte Carlo procedure is developed to simulate the overstress probe test. The effect of various parameters used in the test is also discussed. A comparison is made between Weibull and Gaussian models. Suggestions for conducting the overstress probe test are provided.

Early in the engineering design cycle, it is difficult to quantify product reliability due to insufficient data or information to model uncertainties. Probability theory can not be therefore, used. Design decisions are usually, based on fuzzy information which is imprecise and incomplete. Recently, evidence theory has been proposed to handle uncertainty with limited information. In this paper, a computationally efficient design optimization method is proposed based on evidence theory, which can handle a mixture of epistemic and random uncertainties. It quickly identifies the vicinity of the optimal point and the active constraints by moving a hyper-ellipse in the original design space, using a reliability-based design optimization (RBDO) algorithm. Subsequently, a derivative-free optimizer calculates the evidence-based optimum, starting from the close-by RBDO optimum, considering only the identified active constraints.

The staircase fatigue test method is a well-established, but poorly understood probe for determining fatigue strength mean and standard deviation. The sensitivity of results to underlying distributions was studied using Monte Carlo simulation by repeatedly sampling known distributions of hypothetical fatigue strength data with the staircase test method. In this paper, the effects of the underlying distribution on staircase test results are presented with emphasis on original normal, lognormal, Weibull and bimodal data. The results indicate that the mean fatigue strength determined by the staircase testing protocol is largely unaffected by the underlying distribution, but the standard deviation is not. Suggestions for conducting staircase tests are provided.

Ultrasonic spot welding is a novel solid-state joining technique for automotive body structures. The residual stresses, caused by the inhomogeneous deformation during the welding process, are considered to be a major factor affecting the strength and quality of the weld. Many conventional measurement methods cannot be applied because of the small size of the spot weld. In this study, the ISSR/ring-core cutting method is applied to measure the residual stresses on the ultrasonic spot weld. The ISSR possesses the short gage length and high sensitivity. The ring-core cutting was conducted on the back of the spot weld. The tensile residual stresses were obtained. The measured tensile residual stresses added to the operation stresses could cause the initiation of the cracks.

Springback is one of the main detrimental factors affecting the dimensional quality of stamped parts in automotive industry. Accurate determination of springback is vital to the design of tools used in the automotive sheet stamping operations. Generally the least distance from a point on a stamped part to the die surface is used as a measurement of the amount of springback. This paper presents a reversed finite element method for assessing the springback of stamped parts. First, the point cloud (coordinate measurement data) scanned from actual stamped parts is triangulated to generate a finite element mesh with triangles. Contrary to the traditional finite element mesh from an existing CAD model, this is a reversed process in which the actual CAD data for the surface is unknown. Then finite element method is utilized to determine the deformation the stamped part needed to conform to the die surface using the minimum amount of work.

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.

Correlation between accelerated laboratory tests and field tests for filiform corrosion of painted aluminum alloy sheets for automobile was investigated by conducting six kinds of laboratory tests with different pH, dry-wet condition, etc., and two sites of outdoor exposure tests, and vehicle test. It was found that susceptibility to filiform corrosion in the laboratory tests increased with the decrease of pH and/or the increase of repetition rate of wet/dry cycle. The susceptibility in the laboratory tests also increased with the increase of Cu contents in the alloy or with the sanding treatment before painting. The same tendency was obtained in the outdoor exposure tests and vehicle test. However, the correlation of the outdoor exposure tests and the vehicle test was low. In conclusion, the laboratory tests with relatively low wet ratio (70%) correlated well with the outdoor exposure tests, and the tests with relatively high wet ratio (95%) correlated well the vehicle tests.

When the finite element model of a complex structure is partitioned into substructures in order to enable component mode synthesis, the reduced order model obtained from the Craig-Bampton method often features a large number of interface degrees of freedom (DOF). The authors have recently developed a method to reduce the interface DOF by using a set of so-called characteristic constraint (CC) modes. The resultant, highly compact CC-mode-based reduced order model provides a good platform to calculate the power flow between substructures. In this paper, the CC-mode method is applied to the finite element model of a vehicle structure with about 1.5 million DOF. A convergence study is conducted to find optimal mode selection criteria, and a 2124 DOF reduced order model is obtained for the 0-200 Hz range by using the CC-mode method.

The Automotive Aluminum Alliance in conjunction with SAE ACAP founded a corrosion task group in 2000 with a goal to establish an in-laboratory cosmetic corrosion test for finished aluminum auto body panels, which provides a good correlation with in-service performance. Development of this test involves a number of key steps that include: (1) Establishing a reservoir of standard test materials to provide a well-defined and consistent frame of reference for comparing test results; (2) Defining a real-world performance for the reference materials through on-vehicle tests conducted in the U.S. and Canada; (3) Evaluating existing laboratory, proving ground, and outdoor tests; (4) Conducting statistically designed experiments to evaluate the effects of cyclic-test variables; (5) Comparing corrosion mechanisms of laboratory and on-vehicle tests; and (6) Conducting a round robin test program to determine the precision of the new test. Several of these key steps have been accomplished.

With the revolutionary advances in computing power and software technology, the future trend of integrating design and CFD analysis software package to realize an automated design optimization has been explored in this study. The integrated process of UG, ICEMCFD, and FLUENT was accomplished using iSIGHT for vehicle Aero/Thermal applications. Process integration, CFD solution strategy, optimization algorithm and the practicality for real world problem of this process have been studied, and will be discussed in this paper. As an example of this application, the results of an underhood thermal design will be presented. The advantage of systematical and rapid design exploration is demonstrated by using this integrated process. It also shows the great potential of computer based design automation in vehicle Aero/Thermal development.

In an effort to reduce anisotropy, which affects sheet forming performance, special actions were taken in the production of 6009-T4 sheet. To further reduce anisotropy in forming behavior, the modified 6009-T4 sheet was given an electro-discharge texture (EDT) surface topography to make friction behavior nondirectional. The modified 6009-T4 was compared to standard 6009-T4 in terms of metallurgical characteristics, laboratory test results and field forming results. The modified sheet yielded reduced planar anisotropy and improved formability. EDT completely removed directionality in friction behavior and led to an improvement in performance in the forming trials.

Aluminum sheet forming is entering an era where rapid advances in technology are likely. Combining increased understanding of material behavior, increased understanding of metalworking tribology and improved control of sheet forming processes will result in improved distribution of strain, allowing more complex components to be formed and greater design flexibility. New process control techniques will be developed and implemented to result in improved press actions, control of strain path to effect increased formability and reduced sensitivity to process variables. Improved techniques for assessing producibility and for generating effective tool designs will be developed, perhaps eliminating the need for soft tool tryouts to substantially reduce the total die development time and cost. In this review paper, each of these issues will be discussed.