FINITE-ELEMENT MODELING OF CRACK-PROPAGATION IN ELASTIC-PLASTIC MEDIA.2. HORIZONTAL SUBSURFACE CRACKS

Horizontal subsurface cracks in an elastic-plastic material are analys ed using finite-element techniques. The sliding surface is modelled as a rigid cylinder. The effect of such parameters as the friction betwe en the cylinder and the material being indented, the elastic and plast ic modulus of the material and the depth of crack location on the J-in tegral values at the left and right tips of a horizontal subsurface cr ack is considered. The prospective crack propagation direction is take n as the direction along which the J integral assumes a maximum as the indenter slides along the material surface. The left and right tip cr acks were found likely to propagate at about 10 degrees to the horizon tal. This propagation direction was found to depend strongly on the lo cation of the crack. Both crack tips are expected to propagate closer to the vertical direction as the depth of crack location is reduced. A lso, horizontal cracks closer to the surface are found to have higher J integral values. While friction between the slider and the specimen did not affect the crack propagation direction, the crack-tip plastici ty reduced the propagation direction, with respect to the horizontal.