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The finite element method (FEM) is used daily in the automotive industry for such purposes as reducing the time of product development and improving the design based on analysis results, followed by later validation by tests in the laboratory and on the proving ground. This paper will present some of the methodology used to develop automotive components by finite element analysis, including procedures to specialize FEM models to obtain quantitative and qualitative results for systems such as body, chassis, and suspension components, as well as validation of the models by experimental data.

The objective of this paper is to provide a review of work covering the effects of constraint in two-dimensional (2D) small scale yielding models of fatigue crack growth under constant and variable spectrum loading. It considers crack propagation and retardation models developed to understand crack propagation processes. The paper also treats numerical 2D finite element method models used to determine the crack opening and closure stress intensity factors. Also presented are procedures used to determine the crack opening and closure under variable amplitude loading.

Various approaches to estimating mean stress effects on stress-life and strain-life behavior are compared with test data for engineering metals. The modified Goodman equation with the ultimate tensile strength is found to be highly inaccurate, and the similar expression of Morrow using the true fracture strength is a considerable improvement. However, the Morrow expression employing the fatigue strength coefficient σ′ƒ may be grossly non-conservative for metals other than steels. The Smith, Watson, and Topper (SWT) method is a reasonable choice that avoids the above difficulties. Another option is the Walker approach, with an adjustable exponent γ that may be fitted to test data, allowing superior accuracy. Handling mean stress effects for strain-life curves is also discussed, including the issue of mathematical consistency with mean stress equations expressed in terms of stress.

This study presents a method to achieve a concise description of multidimensional loading histories for fatigue analysis using the stochastic process theory. For purposes of this study, the load history is considered to have stationary random and non-stationary mean and variance content. The stationary variations are represented by a vector Autoregressive Moving Average (ARMA) model while Fourier series are used to model the non-stationary variations. Justification for this method is provided by comparing the dynamic characteristics of the original loading and reconstruction through their power spectral densities. Further justification is obtained by comparing histograms of principal strain and the corresponding orientation for original loading and reconstruction. Final justification is provided using the resulting fatigue lives of original and simulated loading.