Keywords: polyurethane shock programmer, Mooney-Rivlin constitutive model, impact test..

In this paper, the validity of the Mooney-Rivlin constitutive equation to depict the behaviour of a hyperelastic material was evaluated. The results were based on the study of the parameter affecting various shock waves. Three main typesof impact test system are used: the drop-type, rotation-type, and lateral-type. The impact test system was composed of an impactor, which was moved, and the test bed on which the specimen was mounted. To evaluate the impact resistance of the specimen, various shock waves were transmitted to the specimen. The typical shock waves used in the impact test were the half-sine, saw-tooth, and rectangular waves. To control the shape of the shock wave, the specific structure was mounted between the impactor and the testbed. The structure was called the shock programmer. Various materials were used for the shock programmer. The geometry and material of the shock programmer were determined from the mass and impact velocity of the impactor because the mass and impact velocity of the impactor were related to the kinetic energy of the impactor.

In this paper, because the restitutive characteristic of the hyperelastic material was more than the restitutive characteristic of other metals, the shock programmer using hyperelastic material was considered. To simulate the hyperelastic material in the simulation, various constitutive material models such as the Mooney-Rivlin, Yeoh, Ogden constitutive models were used.

The original Mooney-Rivlin hyper-elastic model was considered as the constitutive model to depict hyperelastic material behaviour. As the stress-strain curve of the hyperelastic material was dependent on the strain rate, the velocity of the impactor was one of parameters. In this paper, using the Mooney-Rivlin constitutive equation, the stress-strain curve of the hyper-elastic material was predicted for various velocities of the impactor. The constants of the Mooney-Rivlin constitutive equation were calculated. To calculate the constants, the impact test was performed. Poly-urethane Shore 95A was used as the material for the shock programmer. The shape of the shock programmer was of the cylindrical type. The impact test with various velocities for the impactor was performed. The time history on the force and compressive displacement was obtained and a force-displacement curve was generated. Using the force-displacement curve of the polyurethane shock programmer, constants of the Mooney-Rivlin constitutive equation were calculated for various velocities of the impactor. In this paper, the validity of the Mooney- Rivlin constitutive equation to depict hyperelastic material behaviour was evaluated and the results were based the parameters affecting various shock waves.

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