Studying the effect of residual stress on fracture using fixed displacement four-point bending

A novel method for applying residual stress to a fracture specimen has been designed. Residual stress is applied to an edge-cracked beam using fixed-displacement four-point bending. The beam is then simultaneously loaded in tension which represents applied load. Finite element analysis has been used to design the geometry of the fracture specimen so that the bending load behaves like residual stress. A notch needs to be machined opposite the crack to prevent significant residual stress relaxation due to a geometry effect. This novel system enables residual stress to be easily monitored using a load cell as the magnitude of applied load increases, and so the magnitude of both the applied load and residual stress are known at failure. It is difficult to achieve this with traditional methods of applying residual stress to fracture specimens, and so this system is expected to contribute significant insight into the effect of residual stress on fracture.