Classical dynamic fracture theories predict the Rayleigh surface wave speed to be the limiting speed for propagation of in-plane cracks in homogeneous, linear-elastic materials subjected to remote loading. However, in the presentudstudy, experimental evidence to the contrary is reported, in which intersonic shear dominated crack growth is seen along weak planes in Homalite-100 under far-field asymmetric loading. It is seen that mode-II (in-plane shear) conditions are essential to attain intersonic crack-tip speeds. The stress field generated byudthe intersonically propagating crack-tip is recorded using photoelasticity and high speed photography. Intersonic shear cracks, featuring shear shock wavesudand large scale crack face frictional contact, are initially highly unstable andudcrack-tip speeds vary from the shear wave speed to the dilatational wave speed of the material. As steady state conditions are achieved, the mode-II intersonicudcracks propagate at a constant speed of √2c_s. These observations have potential implications in geological settings where intersonic rupture velocities have beenudreported for crustal earthquakes.
展开▼
