The influence of specimen geometry on the strain rate sensitivity index–strain (m–δ) relationship has been determined for a Zn–5Al (wt-%) eutectic alloy at a strain rate ɛ of 0.025 min−1 and a temperature of 250°C. It was found that all the m–δ curves were of the type mL=mmaxm0 and > mF for δ0 < δL < δF, where mL is the strain rate sensitivity corresponding to the ‘limit strain’ δL; δ0 (=0) is the initial strain; and δF is the total elongation at fracture. Tests were performed for five values of specimen width/length w0/l0 between 0.15 and 0.39. With increase in w0/l0, it was observed that the m–σ curves shifted to higher positions; the values of total elongation at fracture δF and strain rate sensitivity index at zero strain (δ0) m0 and at the limit strain (δL) mL increased; and the strain rate sensitivity index at fracture strain (δF) mF varied little. Consistent with these findings, increasing the thickness of the specimen from 1 to 2 mm at constant w0/l0caused a shift in the m–σ curve to the right and increased the value of δF and also the limit strain at maximum value of m. From the m–δ data obtained, a modification to the Chin Liu equation is proposed to take into account specimen geometry δF=(C3, F(m′0− m′L)/(w0l0)ɛmF−1[ (m′0(w0l0)]−1)100%, where C is the slope of the m-δ curve; (m′0 (w0/l0)=m0, m′0m0 and (m′L(w0/l0)=mL, m′Lm0 for w0/l0 between 0.15 and 0.39. When w0/l0=1(or w0=l0), the notch effect is eliminated and the total elongation at fracture will take its maximum value. © 1990 The Institute of Metals.
