Comparison of methods for calculating stress intensity factors with quarter-point elements

The quarter-point quadrilateral element is employed with various methods for calculating the stress intensity factor in order to provide guidelines for a 'best' method. These methods include displacement extrapolation, J-integral and Griffith's energy calculations, and the stiffness derivative technique. Three geometries are considered: a central crack, a single edge crack and double edge cracks in a rectangular sheet. For these cases, it is observed that the stiffness derivative method yields the most accurate results, wheres displacement extrapolation is the easiest method to implement and still yields reasonable accuracy. (Author)