JUSTIFICATION AND IMPROVEMENT OF KIENZLER AND HERRMANN ESTIMATE OF STRESS INTENSITY FACTORS OF CRACKED BEAM

Kienzler and Herman recently showed that good and remarkably simple approximations of the stress intensity factors of cracks in beams can be obtained by bending theory estimations of the strain energy release as the crack is widened into a band of finite width. Their method has been based on equating this energy release to the energy release rate due to crack length extension, which has been postulated as a hypothesis. This note presents a justification of this hypothesis and further shows a possibility of improvement by introduction of an additional factor. The improvement is demonstrated by numerical comparison with the exact solution of a cracked beam. The aforementioned factor, however, can be determined only by optimum fitting of the exact solution. © 1990.