The Behaviour of Fatigue Cracks Subject to Applied Biaxial Stress: A Review of Experimental Evidence

Abstract

Experimental studies aimed at understanding the fatigue process in metals and polymers have usually been performed under uniaxial stress. Only in the last two decades or so has much experimentation been carried out on fatigue crack propagation under biaxial stress. This paper reviews the available published data. Crack propagation behaviour under biaxial stress is dictated by 3 parameters: stress biaxiality itself, which is defined here as the ratio of the in-plane principal stresses, crack angle with respect to the applied principal stress directions and stress intensity factor range. Depending on the first two parameters. cracks may grow in Mode I, Mode 11 or Mixed-Mode. Crack growth data have been presented using these three divisions. Two short sections have been included on initiation and cyclic stress/strain behaviour under biaxial stress to emphasise the fact that crack growth cannot be fully understood without knowing something of them. The accumulated data do not lead to adequate conclusions on either the qualitative or quantitative behaviour of cracks subject to cyclic in-plane biaxial stress. Reasons for the confusion and even contradiction of independent results are put forward and some discussion given to the possible directions of future experimental work.

Fatigue Crack Growth Under Mode Ii Loading

“…His conclusion was that a fatigue crack usually grows in Mode I but it can grow in Mode I1 when (i) the fatigue crack is initially propagating along a shear band, (6) the cyclic stress has a strong compression component or (iii) the net-sectional shear stress approaches or exceeds the cyclic shear yield strength of the material. Reviews on shear mode or mixed mode crack growth are also available by Smith and Pascoe [16] and Bold et al [17]; some conclusions on shear mode crack growth were similar to Liu's.…”

Closure and Growth of Mode I Cracks in Biaxial Fatigue

“…Other researchers [18,191 reported no significant change in fatigue crack growth rates with biaxiality. A more detailed review of some of this data is given by Smith and Pascoe [20]. Note that in this article, discussion will be limited to mode I cracks under loading which is proportional, either fully in-phase (e.g.…”

Fatigue Crack Growth Behaviour of Sm45c Steel Under Mixed‐mode I and Ii Loading

“…Regions 1, 2 and 3 are shown in Fig. 5( b), roughness-induced closure effect and the excessive residual plastic deformation due to the supplement of the shear stress on a mixed-mode fatigue crack [17][18][19][20].…”