Abstract: A set of formulae of strain-rate ε sensitivity exponent m are deduced from theories in different typical deforming path by using experimental parameters F (forming load), v (velocity of cross-head) and l (gauge length of specimen), through which the uniform method for measuring ml (strain-rate sensitivity exponent under constant velocity), mv (strain-rate sensitivity exponent under constant velocity) and mF (strain-rate sensitivity exponent under fixed load) is established on experimental curves of constant ε, constant v and fixed F respectively. ml, mv and mF are measured on the same group of curves of constant ε (constant v or fixed F) and their results are different, which is shown that there exists structure sensitivity in super-plastic forming. Whereas, it should be analyzed why the results of ml, mv and mF are different, which are measured with the same measuring formulae on different group of curves under constant ε, constant v and fixed F. Furthermore the structure sensitivity of m-value is analyzed subtly.

Key words: Experimental parameter, Strain-rate sensitivity exponent, Super-plastic tensile forming