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Modern automobile diesel engines make use of aluminium cylinder heads that experience both high pressure and thermal loads. Maximum temperatures are above 250°C in the valve bridge area, generating microstructural transformations in the material and thus local evolution of the mechanical properties. To be able to predict the life time of this component with a reasonable amount of confidence, it is therefore necessary to describe these changes in the material. This has been done on a variety of casting materials, with various amount of silicon and copper. Two of them have been taken as references, namely the A356 and 319 type of alloys, making extensive use of Transmission Electron Microscope (TEM) associated with Automatic Image Analysis for quantitative analysis of the precipitation stages during different heat treatments, from the as-received state to saturated aging state.

Increasing demands on engine efficiency and specific power have resulted in progressively higher loadings on internal components of combustion engines. Therefore the durability assessment of such components is increasingly in demand, triggered by both reliability and economic requirements. Within this context the TMF cylinder head simulation process established at BMW is presented in the following article. The numerical model is able to account for thermo-mechanical loading histories. These lead to a transient evolution of the material characteristics during the lifetime due to aging in aluminum alloys. Therefore a viscoplastic constitutive model is coupled with an aging model to handle the change in precipitation structure and the effect on the material properties, especially for non heat-treated secondary aluminum alloys. The local damage evolution is modeled based on the growth of micro cracks.

Statistical studies of collision and non-collision fires abound, founded upon information in publicly available collision and fire incident data bases. Recent efforts to improve the quality and reliability of the data within such databases have included the development of vehicle fire investigator training materials for motor vehicle crash investigators. These materials will be available to investigators both as a computer-based training system for remote learning and as a classroom seminar. When completed, the computer-based training course will be publicly available. The computer-based training course is based on published and unpublished research on vehicle fires, material properties and ignition characteristics. Topics include a discussion of combustible fluids and materials, ignition sources, burn patterns, arson, hybrid vehicles and vehicle design, as well as background information on fire science, automotive systems, and design and investigation standards.

Ultrasonic fatigue testing machines working at approximately 20 kHz allow extending the number of testing cycles to the 108-1010 range, which would be prohibitive using conventional servo-hydraulic machines (up to 100 Hz). One of the questions that arise, however, is if the results from these very high frequency tests are comparable to the ones obtained from conventional tests performed at lower frequencies. This paper compares the high cycle fatigue (HCF) behavior of four cast aluminum alloys under two test frequencies (75 Hz and 20 kHz). It is shown that the S-N curve for some alloys is very sensitive to the testing frequency.

Explicit finite element simulations were conducted on an aluminum wheel model where a rotating bend moment was applied on its hub to simulate wheel cornering fatigue testing. A post-processor was developed to calculate equivalent von Mises alternating and mean stresses from stress tensor. The safety factors of fatigue design for each finite element were determined to assess the fatigue performance by utilizing the Goodman linear relationship. Elements with low safety factors were identified due to the prescribed boundary conditions and stress concentrations arising from wheel geometry.

Prediction of fatigue performance of large structures and components is generally done through the use of a fatigue analysis software, FEA stress/strain analysis, load spectra, and materials properties generated from laboratory tests with small specimens. Prior experience and test data has shown that a specimen size effect exists, i.e. the fatigue strength or endurance limit of large members is lower than that of small specimens made of same material. Obviously, the size effect is an important issue in fatigue design of large components. However a precise experimental study of the size effect is very difficult for several reasons. It is difficult to prepare geometrically similar specimens with increased volume which have the same microstructures and residual stress distributions throughout the entire material volume to be tested. Fatigue testing of large samples can also be a problem due to the limitation of load capacity of the test systems available.

The analytic solution of the mode I stress intensity factor for spot welds in lap-shear specimens is investigated based on the classical Kirchhoff plate theory for linear elastic materials. Approximate closed-form solutions for a finite square plate containing a rigid inclusion under counter bending conditions are first derived. Based on the J integral, the closed-form structural stress solution is used to develop the analytic solution of the mode I stress intensity factor for spot welds in lap-shear specimens of finite size. Finally, the analytic solution of the mode I stress intensity factor based on the stress solution for a finite square plate with an inclusion is compared with the results of the three-dimensional finite element computations for lap-shear specimens with various ratios of the specimen half width to the nugget radius.

Fatigue strength mean and standard deviation may be estimated by the Probit and 2-Point test methods. In this paper, methodologies for conducting the tests are developed and results from Monte Carlo simulation are presented. The results are compared with those from concurrent testing with the staircase method. While the Probit and 2-Point methods are intuitively attractive, their results are significantly different from those from the staircase method. The latter remains the best of the three.

Experimental quick plastic forming (QPF) of commercially available magnesium alloy AZ31B sheet into Cadillac STS decklid inner panels was done successfully with existing QPF tools and processes developed for forming QPF-grade AA5083 aluminum sheet. This demonstrates that QPF parts designed for aluminum can be made with magnesium. The post-formed properties of the formed panel were investigated. Thinning of the magnesium alloy sheet in the successfully formed panel was limited to just under 50%, which is normally considered acceptable in QPF aluminum panels. The basal crystallographic texture of the sheet material was essentially maintained through the forming process. Tensile properties of samples cut from the formed panels exceed the specified minimums for the O-temper AZ31 sheet. Significant reduction in cycle time is expected based on the results of this work.

High pressure die casting (HPDC) is the dominant process for the production of magnesium components with complex configuration having typically thin to medium wall thickness. The growing use of die cast Mg alloys in the automotive industry, particularly for the production of drive-train components, has led to the development of creep resistant alloys, MRI153M and MRI230D, which were launched into the market several years ago. The present paper aims at exploring the effect of the HPDC process parameters on the porosity and, as a result, on the properties of the two MRI's developed alloys in comparison with common alloys AZ91D and AM50A that are usually considered as benchmark die casting alloys. The outcome of the research performed includes processing guidelines and recommendations, which allow obtaining high quality sound castings. These recommendations should be implemented in the course of design, optimization and production of high-performance components for various applications.

This paper describes a lightweight magnesium intensive automobile body structure concept developed at DaimlerChrysler to support a high fuel-efficiency vehicle project. This body structure resulted in more than 40% weight reduction over a conventional steel structure while achieving significantly improved structural performance as evaluated through CAE simulations. A business case analysis was conducted and showed promising results. One concept vehicle was built for the purpose of demonstrating concept feasibility. The paper also identifies areas for further development to enable such a vehicle to become a production reality at a later time.

Image Correlation technique has been proven to be a flexible and useful for deformation analysis. It’s a robust method for measuring full-field absolute displacement and strains. In this paper we describe a new Digital Image Correlation (DIC) system, where all components (hardware and software) are fully integrated in order to build a self-contained measurement system. Due to a modular structure for hardware components as well as for the software in combination with high speed cameras this can be used for investigations on transient events. The calibration of a DIC system is the most important action, which is needed to generate accurate results. Therefore we describe the procedure, which allows an easy to use, reliable and fast calibration as an integrated part of the system. Results of measurement performed on a vibrating membrane and a tensile test sample are show typical features of the system.

Planetary gearboxes are used to transmit power and motion between rotating shafts using high reduction ratio. Design optimization of such gears requires information about the stress level on contacting surfaces of meshing gears, as it may influence durability and efficiency of the gearbox. Stress distribution in gears and pinions was estimated using following methods: a) Image correlation – photogrammetry – technique b) Holographic interferometry – holometry – technique c) Finite element analysis of contact problems. Image correlation is the white light technology. For the image correlation methodology digital pictures of the measured object taken simultaneously by two cameras are automatically correlated in ARAMIS 3D system. By means of triangulation calculation of coordinates of all the points in the images can be performed. Accuracy of the method depends on the field of view so very limited view area was considered for measurements.

Applications using two-dimensional and three-dimensional computer vision for deformation and shape measurements are described. First, the use of 2D image correlation for estimation of properties in heterogeneous materials is demonstrated. Second, the use of 3D computer vision for shape and deformation measurements in large, flawed panels is presented. Finally, the use of 3D computer vision for deformation measurement in cracked, ductile materials undergoing complex loading conditions is shown.

The reliable function of the system piston - piston ring -liner depends strongly on the correct quantity of oil. A balance between the sufficient oil offer and minimum emission is to be found. For this system numerous computation programs exist however their results strongly depends from the boundary conditions. To assist in the understanding of this system it is to be used necessarily optical research methods. So that the lubricating film at the piston and at the piston rings can be examined, a cylinder of an engine had to be completely made of glass. The used glass must have the wetting characteristics of grey cast iron, so that the results are transferable. The used tracers to visualize the oil may not change the characteristics of the oil. Different photograph procedures were necessary, in order to identify the fundamental presence of oil and the bearing oil film. In this paper the test set-ups and results are described.

Current simulation tools for the investigation of the dynamic system response as well as for the component stresses on the basis of multi-body and finite-element techniques are integral part of today's powertrain development efforts. These tools are typical used for the analysis and optimization of shafts, clutches, chain/belt drives, bearings, levers, brackets, housings and many other components. An exception is made by gears which today are still frequently investigated by the help of semi-empirical methods based on DIN, ISO, AGMA and the specific knowledge base of well experienced developers. The main difficulty is that the gears are rolling off via large contact surfaces with complex nonlinear mechanical contact properties. Within the scope of research work FEV developed a new method for the analysis and optimization of gear drives based on comercial multi-body and finite-element software platforms.

An exact approach to linearize the equations of motion of multibody systems is presented. The method has general applicability and it is well suited to linearize the index-3 Differential Algebraic Equations (DAE) governing the state of a dynamical system. Moreover, the method was extended to linearize a dynamical system in terms of user-defined coordinates without the need to reformulate the governing equations; this feature is of particular interest in disciplines like rotordynamics where eigensolutions are requested in terms of coordinates defined in a rotating frame. Contrary to other linearization methods, the proposed approach implements a closed-form computation of the linearized equations of motion; all second order effects are taken into account and no numerical differentiation is required. The proposed method inflates the governing equations and then computes a set of sensitivities that provide the linearization of interest.

This paper presents a shape optimization method for the rigidity design of sheet metal structures under multiple loading conditions with the aim of weight reduction. In order to maintain the curvatures of the given initial shape, it is assumed that the design domain is varied in the in-plane direction. Using compliance as an index of the rigidity, a volume minimization problem subjected to multiple rigidity constraints is formulated as a non-parametric shape optimization problem. The shape gradient function and the optimality conditions are theoretically derived for this problem. The traction method is applied to determine the smooth in-plane domain variation that minimizes the objective functional. The calculated results of fundamental design examples and actual automotive chassis components will show the effectiveness and practical utility of the proposed method in solving shape optimization problems of sheet metal structures.

Blow moulding is one of the most important polymer processing method for producing plastic automotive parts. Yet, there are still several problems that affect the overall success of forming these parts. Among them, are thermally induced stresses, relevant shrinkage and part warpage caused by inappropriate solidification conditions. This work presents a finite element model that allows for predicting residual stresses and subsequent deformations that arise during the cooling stage of finished parts. It is expected that the virtual presence of the flash zone has an influence on the development of residual stresses in the numerical model. Deflashing is usually performed immediately after part removal from the mould, therefore, the numerical model is adapted to take this into account. Numerical results obtained with and without flash for a simple part, as well as a complex automotive part, are compared to determine accuracy and limitations of the model.

For efficient prediction of single and multiple impacts on bumper energy-absorber systems, it is necessary to have certain important aspects represented by the model that represents the material of construction. These aspects include true stress-strain behavior, strain rate effects, hydrostatic effects, multiple failure criteria and recovery of material during unloading. An existing material model in the explicit solver LS-DYNA covers these aspects, and this paper aims at exploring the sensitivity of this model to finite element parameters. This is done by simulating multiple impacts on two designs, and comparing with test data. Results indicate that FE model parameters, stiffness variation, and contact definitions play a vital role in obtaining a solution.