High pressure multiaxial extensometry

The development of a multiple degree-of-freedom extensometer to measure axial, torsional, and diametrical strains on a tubular laboratory fatigue specimen is described. It is found that the overall accuracy of the extensometer is limited by cross talk due to torsional displacements in an ambient environment. If only axial and diametrical deformation occur, error induced by cross talk is less than + or - 0.5 percent.