An effective method to investigate short crack growth behaviour by reverse bending testing

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Description/Abstract

A reverse bending rig has the advantage of relatively cheap construction compared with servo-controlled machines, and its robustness and reliability make it ideally suited to long-term testing programmes. In this paper, the details of the mechanical mechanism of a bending rig, the methods of its strain measurement and stress-strain analysis have been presented. A series of tests has been carried out to investigate short crack growth behaviour of AISI type 316 stainless steel under creep-fatigue conditions at 550C. The advantage of this type of test allows a comparison to be made, on one specimen, of the influence of both tensile and compressive hold periods on crack growth behaviour. It has been shown that predominantly intergranular long cracks form on the tensile side and transgranular short cracks on the compressive side and these are a prominent feature between 0.9 – 2.5% strain range.