A Novel Method for Strain Controlled Tests

Abstract

The present paper aims at providing a contribution to the testing strategies in the field of mechanics of materials, with particular reference to low cycle fatigue in the strain control mode. After a detailed analysis of the state of the art on possible techniques for strain controlling, the paper points out the difficulties that could be encountered when a conventional longitudinal contact extensometer cannot be used. This methodology, based on controlling the strain at a particular specimen location, by controlling the relative displacement between its ends, was developed to provide an alternative solution in such occurrences. The paper introduces its analytical fundamentals for its most general application in the execution of fatigue or even static tests. Particular attention was devoted to the validation of the proposed methodology: this task was conducted by applying the suggested technique to both static and fatigue testing of hourglass specimens, by analyzing results also in comparison to other experimentations or numerical simulations, always observing a good agreement. The methodology proved to be efficient and reliable on a wide range of strain amplitudes.