STRAIN-ENERGY RELEASE RATES FOR CRACK-GROWTH IN AN ELASTIC CYLINDER SUBJECTED TO AXIAL SHEAR

Strain energy release rates have been calculated by finite element analysis (FEA) for various modes of failure of a long cylindrical elastic tube bonded between a rigid cylindrical core and a rigid surrounding tube. The core is subjected to an axial load so that the elastic tube is sheared. Fracture loads have been calculated for cracks propagating either along the interface or into the elastic material, at 45-degrees to the interface, using linear elastic fracture mechanics and computed strain energy release rates. They are derived in terms of the initial crack size, the interfacial or bulk fracture energy, and the shear modulus of the elastic material. For an interfacial crack the failure load was found to be proportional to the tube length, the square root of the core radius, and a decreasing function of the elastic tube thickness, R(o)/R(i). For a 45-degrees crack, the presence of the rigid surrounding tube stabilized the crack at a certain size and an increasing load was needed to cause further growth. It is concluded that interfacial cracks am the most likely mode of failure.