Volume 2, Issue 6 (November 1974)
Distinction Between Coaxial and Noncoaxial Strains in Sheet Metal and Its Implications on the Assessment of Material Formability
The distinction between coaxial and noncoaxial strains is explained. It is shown that with noncoaxial strains deformation does not necessarily produce a change of shape, if circles and ellipses are used for strain measurements. If materials are tested in exisymmetrical processes, in which the strains are coaxial, and used in unsymmetrical ones, in which the strains are noncoaxial, then the formability will appear to be overestimated. A test for coaxiality, based on the use of squares and parallelograms for the strain measurements, is presented in the text and the formula used is derived in the Appendix.