Characterization of elastomers under simultaneous tension and torsion for application to engine mounts

ABSTRACT: A general procedure is proposed to develop relevant multiaxial tension-torsion experiments that mimic the complex loading conditions undergone by engine mounts in service. First, displacements and forces exerted on the engine mount are measured on an instrumented vehicle. For several loading conditions, the displacements are introduced in a finite element model of the engine mount to determine the corresponding strain fields. To characterize and compare these strain fields, we consider the invariants of the Hencky strain tensor. For a given set of invariants, we determine displacements and angles that must be applied on the samples to reproduce the deformation of the engine mount. The present work focuses on the subsequent experimental campaign. Firstly, a new rubber specimen is designed for simultaneous tension-torsion tests. Its principal re- quirement is that the finite element strain field must be as close as possible to the analytical solution of the simultaneous extension and torsion of a cylinder. The geometry of the new sample is validated with the help of stereo digital images correlation (SDIC) on the lateral surface of the specimen. From SDIC results, rela- tionships between global axial displacement and local extension λ on the one hand, and between global angle and local angle per unit of height τ on the other hand are established. This validated method will be consid- ered in a next future to perform multiaxial quasi-static and dynamic experiments, leading to identification of a visco-hyperelastic model.

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