CRACK INSTABILITIES OF A HEATED GLASS STRIP

Recently, Yuse and Sano [Nature (London) 362, 329 (1993)] have observe d that a crack traveling in a glass strip submitted to a nonuniform th ermal diffusion field undergoes numerous instabilities. We study two c ases of quasistatic crack propagation. The crack extension condition i n straight propagation is determined. An asymptotic analysis of the el astic free energy is introduced and scaling laws are derived. A linear stability analysis of the straight propagation is performed, based on the assumption that the crack tip propagation deviates from the cente red straight one as soon as it is submitted to a ''physical'' singular shear stress. It is shown that a straight propagation can become unst able after which a wavy instability appears. The condition for instabi lity as well as the selected wavelength is calculated quantitatively. The results are compared with experiments and the agreement is favorab le.