Effects of Temperature and Strain Rate on Numerical Sigmoid Curve for AZ41 Magnesium Alloy

Abstract

One of the ways for determination of flow curves is the application of a ring test. Using this method, friction in the interface between the die and the specimen leads to a bulging of the sample and thereby to an inhomogeneous stress and strain state. The calculation of the flow stress from experimentally determined force–displacement curves implies a uniaxial stress state, but this will produce an error because of the above-mentioned bulging, when friction occurs. One method of avoiding these sources of error is to use the sigmoid curves, but the sigmoid curves are varied by the change of temperature and strain rate. Calculations of numerical sigmoid curves were done by the use of an iterative procedure, applying a corrective function. The paper presents a complete investigation of the AZ41 magnesium alloy sigmoid curves at temperature ranging between 473 K and 513 K and strain rates ranging between 0.025 s-1 and 0.00025 s-1 . Ring tests are used to determine the numerical sigmoid curves sensitivity to temperature and strain rate.