Stress resistance parameters of brittle solids under laser/plasma pulse heating

The present study analyses the stress and fracture response of brittle materials under the effect of high-power pulse laser/plasma sources. It establishes the relationship between the material properties and the degree of fracture damage and threshold loading parameters which initiate fracture. The crack stability is analyzed using the generalized fracture mechanics approach for a non-uniform stress distribution. The thermal stress field is determined using a quasi-static thermomechanical diagram appropriate for a pulsed heating under a uniaxial temperature variation. The stress intensity factor is calculated for a crack propagating in the stressed layer considered to be much smaller compared to the body dimensions. The calculations show that stress intensity versus crack length curves display maxima which allow one to determine the critical conditions under which the existing cracks start to propagate and the advancing cracks are arrested. The results are used to evaluate the thermal stress resistance and the degree of fracture damage as a function of thermal and mechanical properties of materials and the intensity and duration of thermal shock loading. The critical temperature variation within which the crack stability is independent of the crack size is established. The relation of this parameter to the thermomechanical properties of materials is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.