Lecturer, University of Bristol, Bristol,
Edison Welding Institute, Columbus, OH
(Received 10 November 1988; accepted 23 June 1989)
The measurement of displacement in fracture toughness tests is generally accomplished using clip gages. This paper describes an experimental study to examine the performance of a number of clip gages. It is shown that double cantilever clip gages exhibit a non-linear response. The degree of non-linearity is shown to vary with temperature. In relation to fracture mechanics test methods it is demonstrated that in some instances relaxation of the test standards is required to-encompass the gage performance. Where data can be stored digitally, the non-linear response can be accounted for using a third-order polynomial calibration. An analytical study shows that the non-linearity is inherent for the large displacements often incurred in fracture mechanics tests.
Paper ID: JTE12447J