SEDL / STP / STP942-EB / STP24482S

Effects of Compression and Compressive Overloads on the Fatigue Behavior of a 2024-T351 Aluminum Alloy and a SAE 1045 Steel

DuQuesnay, DL
M.A.Sc. Candidate, M.A.Sc. Candidate, Professor, and Ph.D. Candidate, University of Waterloo, Waterloo, Ontario

Pompetzki, MA
M.A.Sc. Candidate, M.A.Sc. Candidate, Professor, and Ph.D. Candidate, University of Waterloo, Waterloo, Ontario

Topper, TH
M.A.Sc. Candidate, M.A.Sc. Candidate, Professor, and Ph.D. Candidate, University of Waterloo, Waterloo, Ontario

Yu, MT
M.A.Sc. Candidate, M.A.Sc. Candidate, Professor, and Ph.D. Candidate, University of Waterloo, Waterloo, Ontario

Pages: 11    Published: Jan 1988

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Abstract

Smooth cylindrical specimens of 2024-T351 aluminum alloy and SAE 1045 steel were tested under constant amplitude cycling to study the effect of compressive stress on fatigue life. The results show a reduction in the fatigue life at constant maximum stress as the compressive portion of the stress cycle is increased.

Tests performed to study the effect of a periodic compressive overload on the order of the yield strength show an increasing reduction in fatigue life at constant maximum stress as the frequency of application of the overloads is increased. The compressive overload cycle significantly increases the damage done by subsequent smaller cycles, including those far below the constant amplitude fatigue limit. The results indicate that the present techniques used for damage summation for variable amplitude service histories may give grossly unconservative fatigue life predictions, especially for histories containing large compressive load cycles accompanied by a relatively large number of small cycles. It is suggested that conservative life predictions for such histories can be made using the stress-life curve from constant amplitude tests with compression on the order of the yield stress accompanying every cycle.