ABSTRACT
This chapter introduces the method of fracture mechanics which complements the strain method for more accurate results of an entire destruction process. Strain method concerns itself with the initial stage, while fracture mechanics analyzes the crack propagation in its entirety. The theory defines the bounds of elastic energy within which the crack propagation takes place. Experiments show that when to the regular loads, fluctuating at constant amplitude, is added occasional overloads the crack propagation is retarded. The problems reviewed heretofore have been concerned with one-dimensional loadings within plane space, ignoring in the solutions mixed loading, crack propagation changing directions and multiaxial effects. Fatigue crack propagation in mixed loading the crack propagates along a path continuously changing direction. There a broken part due to fatigue has a different surface up to the rupture zone, signalling that the stress intensity factor reached the critical value.
