Journal of Mechanical Working Technology, 16 (1988) 335-340 335 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands A NOTE ON THE DETERMINATION OF STRAIN GRADIENTS WITHIN DEFORMED SPECIMENS RAFAEL COLAS Tecnologia de Procesos, HYLSA, S.A. de C. V., A.P. 996, 64000 Monterrey, N.L. (Mexico) (Received May 23, 1987; accepted September 28, 1987 ) Industrial Summary A method that can be used to determine the local strain value in deformed pieces or parts is proposed. The equivalent strain value is calculated from the local values of the shear and normal components along the flow lines of a macroscopically etched piece. The values of strain calculated using this method agree with those calculated using other methods. 1. Introduction The prediction of the physical and mechanical properties of a finished part is a goal in mechanical design. Most of these properties are structure-depen- dent, i.e. they depend on the microstructure present in the material. The mi- crostructural evolution can be described by a series of parametric equations [ 1,2 ] in which strain plays an important role, due to the dependence that most of the diffusional transformations have on both the distribution and the den- sity of dislocations. The determination of the local values of strain in bulk pieces has been at- tempted by analytic [ 3-8 ] and metallographic [ 9-12 ] techniques. In the first case, a grid is inscribed on a meridian plane and the local values of strain are deduced from the distorted grid after deformation. The second method implies that the external change of shape is transmitted to the grains, and the strain values are deduced from the aspect ratio. The main disadvantage of the first method is that the test piece has to be sliced and machined and then welded [3] or bolted [6,7] before straining, which might produce a change in the deformational behaviour. The strain values as measured by the second method, are no longer valid when the materials exhibit grain boundary sliding [ 11 ] or dynamic recrystallization [ 12 ]. In this paper, a method for the determination of the local values of strain is presented. The equivalent values of strain are calculated from the shear and normal components along the flow lines of an extruded piece. 0378-3804/88/$03.50 © 1988 Elsevier Science Publishers B.V.