TWI Industrial Member Report Summary 325/1986
By J R Gordon
Although the multiple specimen method is still regarded as the most reliable technique for measuring a material's crack growth resistance curve (R-curve), this method suffers from the drawback that generally a minimum of 5-6 specimens are required. For this reason, several methods of measuring an R-curve from a single specimen have been developed. One of the most popular single specimen methods is the unloading compliance technique. This report describes an investigation to determine the limitations of the unloading compliance method and to identify possible sources of error in an unloading compliance test.