LOAD INTERACTION EFFECTS DURING FATIGUE-CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING - A LITERATURE-REVIEW - PART I - EMPIRICAL TRENDS

dA summary is given of reported trends in fatigue crack growth observe d in variable amplitude fatigue tests on metallic materials, specifica lly on steels, under both simple and complex load histories. The effec ts of load variables, specimen geometry, material properties, microstr ucture and environment are considered. Attention is given to the thres hold behaviour and small crack effects. The reviewed data suggest that , depending on a particular combination of load parameters, material, geometry and environment, variable amplitude load sequences of the sam e type can produce either retardation or acceleration in fatigue crack growth.