A METHODOLOGY FOR FATIGUE-CRACK GROWTH AND RESIDUAL STRENGTH PREDICTION WITH APPLICATIONS TO AIRCRAFT FUSELAGES

The FRANC3D/STAGS software system has been developed to model curvilin ear crack growth in aircraft fuselages. Simulations of fatigue crack g rowth have been reported previously (Potyondy et al. 1995). This paper presents two enhancements to this system. One is the generalization o f the representation of cracks that allows the system to represent rea listic damaged structures more accurately. With this capability, param eters that may affect the trajectory of a fatigue crack are studied, R esults are compared with measurements from a full-scale test. The seco nd enhancement is to model stable tearing for residual strength predic tion. A stable tearing simulation along a crack path that captures the material nonlinearities inherent at the crack tip is performed. The C TOA (Crack Tip Opening Angle) is used as a crack growth criterion to c haracterize the fracture process under conditions of general yielding. Residual strength of cracked structures is predicted.