Abstract
Elastomeric materials are widely used for energy absorption applications, often experiencing high strain rate deformations. The mechanical characterization of rubbers at high strain rates presents several experimental difficulties, especially associated with achieving adequate signal to noise ratio and static stress equilibrium, when using a conventional technique such as the split Hopkinson pressure bar. In the present study, these problems are avoided by using the dynamic Virtual Fields Method (VFM) in which acceleration fields, clearly generated by the non-equilibrium state, are utilized as a force measurement with in the frame work of the principle of virtual work equation. In this paper, two dynamic VFM based techniques are used to characterise an EPDM rubber. These are denoted as the linear and nonlinear VFM and are developed for (respectively) medium (drop-weight) and high (gas-gun) strain-rate experiments. The use of the two VFMs combined with high-speed imaging analysed by digital imaging correlation allows the identification of the parameters of a given rubber mechanical model; in this case the Ogden model is used.
Highlights
Rubbers are often used for load mitigation in components that may experience dynamic loading
Many improvements have been made to this traditional technique, the inherent softness of rubber produces experimental difficulties in achieving precise force measurements and a static stress equilibrium state
A similar FEM was used for simulating a gas gun experiment and the nonlinear Virtual Fields Method (VFM) procedure
Summary
Rubbers are often used for load mitigation in components that may experience dynamic loading. Many improvements have been made to this traditional technique, the inherent softness of rubber produces experimental difficulties in achieving precise force measurements and a static stress equilibrium state. These difficulties become more magnified as the strain rate increases. A new experimental technique has been developed for performing dynamic tests [7,8,9] without a traditional force measurement by means of high speed imaging and the dynamic Virtual Fields Method (VFM) [10] This method can be used to identify material parameters of a mechanical model for rubbers (hyperelastic model) using acceleration fields to identify the stress in the specimen. Removing the requirement for a further force measurement is advantageous for dynamic tests on rubbers with regard to the aforementioned experimental difficulties
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