Ahatmct-A
transient problem of propagation of a penny-shaped crack in the plane interface between two different media is solved. The body is twisted by a torque at infinity that tends to shear the bond between the two media. A small initial flaw is assumed to expand uniformly in the plane of the interface at a speed less than the smaller of the SH wave speeds of the two media. The solution is carried out by a combination of two methods: a method of rotational superposition of two-dimensional solutions and the Smimov-Sobolev method of self-similar potentials for twodimensional problems. The dynamic stress intensity factor and the crack tearing displacement are determined. It is found that the stress field near the crack tip has a square root singularity. The maximum crack-tearing displacement is found to occur at close to thresfourths of the way from the crack origin to the running crack tip.
For a homogeneous body, i.e. c(~ = p, and m, = ml, which also imply bl = b2 = b, eq. ( ) can be simplified to K,,,(t) =~,/(nsr) x J(l -s2b-2).
Equation ( ) yields the dynamic stress intensity factor for the penny-shaped crack in an infinite homogeneous material[8], as it certainly should. The dimensionless DSIF is equal to one when the crack-tip speed s = 0 and equal to zero when s = b.