Stress Intensity Factors in the Third-Stage Fan Disk of the TF-30Turbine Engine.

摘要

A photoelastic determination of the mixed-mode stress-intensity factors in a scale model of the third-stage fan disk of the TF-30 turbine engine has been performed. A series of 23 tests were conducted to obtain isochromatic fringe patterns at the tip of a simulated crack as it was incrementally extended through the lug along the observed failure path. The isochromatic fringe patterns were analyzed by employing a newly developed method which permits determination of both opening and shearing mode stress-intensity factors K sub I and K sub II in the presence of far-field stresses sigma sub ox. Although both K sub I and K sub II varied as the crack extended from its initiation point to its turning point, the effective stress intensity factor K sub eff, equal to the square root of the sum of the squares of K sub I and K sub II, remained essentially constant over most of the length of the fracture path. After the crack turns, the propagation is predominantly mode I and the value of K sub eff increases dramatically with increasing crack length. (Author)