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With the renewed current interest in high strength steel and aluminum automotive body and chassis components it has again become important to properly assess the effects of corrosion on the fatigue behavior of structures. The present work summarizes the past work on fatigue and corrosion and presents new results on current automotive materials. The Neuber plasticity correction method, used throughout fatigue software of the ground vehicle industry to account for localized plastic behavior during fatigue, was found to give a very simple and useful technique for the computation of fatigue life of materials in corrosion environments. Data is offered for many common automotive structural materials and a method is given to adapt finite element calculations to compute corrosion fatigue life.

Fatigue properties of sheet steels are examined beginning with a brief overview of the more common strengthening mechanisms used in the manufacturing and processing of sheet products. Cyclic and monotonic flow properties are reviewed with a particular emphasis on processing variables. Strength ductility tradeoffs for sheet steels are discussed and several alloy steels are presented in terms of a Neuber-life cure. The fatigue of cast iron is approached as an internally flawed material. Fatigue life predictions are made by comparing the response of similar structure and composition cast steel to that of cast iron and then applying a Neuber analysis to the results. Fatigue results are given for both non-heat-treatable and heat-treatable aluminum alloys. Finally, the role of residual stresses induced by surface treatments is discussed.

A computer-based technique was used to produce fatigue life predictions for a variety of steels using service histories recorded from several automotive components. The materials considered, both hot and cold-rolled sheets, ranged in yield strength from 200 MPa (30 ksi) to 580 MPa (84 ksi) and included most of the steels currently under consideration for material substitution to achieve vehicle weight reduction. The results of these computations were used to produce estimates of the weight savings potential, in fatigue limited designs, of the substitution of higher strength materials for conventional hot or cold-rolled low carbon steel; the indicated weight savings were from 16 to 50% depending on the nature of the loading of the component. This wide variation in savings is an indication of the importance of design in the engineering for minimum weight. Differences in the fatigue notch sensitivities of the materials were found to be an important factor in the predicted fatigue lives.

Fatigue characteristics of representative cold-rolled, high strength steels, in gages ranging from 0.072 in. (1.83 mm) to 0.055 in. (1.39 mm), were determined in fully-reversed, axial strain cycling at amplitudes up to 0.01. Alloys were selected from three families of high strength steels: recovery annealed steels, conventional microalloyed steels - nitrogenized steel and rephosphorized steel, and dual phase steel. Cold rolled low-carbon steel provided a comparative baseline. Cyclic stress-strain curves are presented to indicate the degree of cyclic stability achievable by various strengthening mechanisms while relative fatigue resistance is determined from strain-life curves. The implications of these behavioral trends to component down gaging are discussed.