A linear elastic fracture mechanics study of the size effect on fatigue behaviour.

摘要

Experimental results show that the bending endurance limits of plain and notched specimens decrease as specimen size increases. Several theories have been suggested to account for this effect, but, although Fatigue is now understood to be a Fracture Mechanics phenomenon, there has been no attempt to explain the size effect using a Fracture mechanics approach.; In this thesis, specimen size effect in Aluminium alloy 7075-T6 is analysed by Linear Elastic Fracture Mechanics (L.E.F.M.) approach. The analysis is performed on smooth round specimens and on edge notched plates subjected to bending and axial loads, using analytical and numerical methods. For the numerical approach, two-dimensional finite element and boundary integral element programs were used. The results were then compared with published data, and they both show that stress gradient is indeed the governing factor. Finally, concluding remarks and recommendation for further analysis are also included.