抄録
A fractographic investigation on mode II fatigue crack growth has been made on 7075-T6 and 2017-T4 aluminum alloys. Not like in mode I growth which is known to show a stage I-stage II transition, no transition has been observed in mode II growth but there has been a gradual change in fracture appearance with an increase in ΔKII, whose growth is characterized by crystallographic growth in the lower ΔKII region while in the higher ΔKII region the smooth curved surface which seems to be formed by glide plane decohesion becomes dominant. Another characteristic pattern, which is often observed regardless of the magnitude of ΔKII, is what looks like piled-up thin lamellas. Stress ratio R and superimposed static KI have no influence on the appearance of mode II growth. Mode II growth rate depends on the range of the stress for both cases of R=0 and-1. A model which is to explain these characteristics of mode II growth has been proposed.
