TABLE OF CONTENTS The tensile and compression tests are essential for the determination of constitutive laws. Indeed, they are the only tests that provide a uni-axial stress state and which, thus, do not require an interpretation by inverse-method calculation. Firstly, the tensile test makes it possible to determine the standard characteristics of materials, often required in specifications: proof strength, tensile strength, elongation after fracture. Secondly, it makes it possible to deduce the true stress-strain relation. Despite its simplicity, the tensile test (and the compression test) requires certain precautions, both in its realization and its use.
This chapter begins with a basic description of the test, referring back to the standard for further details; it specifies the standard data provided by the test; it explains the way in which the true stress-strain relation and its most current empirical representations are deduced.
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[1]Chapter written by Dominique FRAN OIS.
This test most often uses cylindrical test pieces of constant cross-section on a sufficient length for the stress to be homogenous. At the two extremities, grip ends are machined with transition curves, the radius of which is large enough to avoid excessive stress concentrations. Fine marks or scribed lines for the measurement of elongation are traced on the parallel length of the test piece, taking care to avoid notches, which could provoke premature fractures.
The standard specifies the ratio between the initial cross-sectional area of the test piece S 0 and the initial length...
