Semi-analytic inverse method for rubber testing at high strain rates

Abstract

Keywords:High strain rate Soft material Stress heterogeneity Elastomer Hopkinson bar Because of their low mechanical wave speed, high strain rate testing of rubber is highly difficult. Indeed, stress and strain homogeneity is hard to achieve. In this paper, a semi-analytic inverse solution is proposed. This solution is based on a uni-axial stress state assumption in the specimen. Moreover, a new-Hookean law is assumed for rubber. The new method is successfully applied to a high strain rate test on a synthetic rubber.

Tensile Behavior of Polyetheretherketone over a Wide Range of Strain Rates

“…Subsequently, the axial and transverse strains, assumed homogeneous in this elementary volume, are considered. The transverse strain is used in calculating the change of the crosssectional area [15,[27][28][29]. Both transverse and axial strains are needed to calculate the volume change.…”

A Drop‐Bar Setup for the Compressive Testing of Rubber‐Like Materials in the Intermediate Strain Rate Range

“…A thick steel disc is screwed to the lower end of this instrumented bar to maintain surface contact with the specimen; its thickness is 5 mm, which is much lower than the excited wavelengths. Thus, it will influence the wave propagation in the aluminium tubular bar . The specimen rests upon a flat horizontal rigid support.…”

“…And, if a specific strain level is needed, the number of parts in the steel bar can be adjusted.A tubular aluminium bar is used as a force transducer: this reduces its cross‐sectional area and then its mechanical impedance as suggested in Refs. . Assuming that the force that acts on the specimen is about 100 N, strain induced in the aluminium bar is about 10 −5 , i.e.…”

“…Besides, multiple works have investigated the use of pulse shaping technique, which allows for a rapid establishment of the dynamic equilibrium . Alternatively, some authors propose to directly determine the heterogeneous stress field using either a non‐parametric method or an inverse method, both based on boundary force and full‐field displacement measurements . Second, the small stiffness of rubber‐like materials leads to low‐level force signals; then, adequate force transducers must be used to increase the signal‐to‐noise ratio.…”

“…Second, the small stiffness of rubber‐like materials leads to low‐level force signals; then, adequate force transducers must be used to increase the signal‐to‐noise ratio. In this way, tubular and polymeric Hopkinson bars have been proposed in order to reduce their impedance as compared with the one of the rubber samples. Besides, Hopkinson bar setups can be instrumented with polyvinylidene fluoride thin‐film sensors in order to first increase the signal‐to‐noise ratio and second increase the test duration .…”