Biaxial Testing of Sheet Materials at High Strain Rates Using Viscoelastic Bars
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A dynamic bulge testing technique is developed to perform biaxial tests on metals at high strain rates. The main component of the dynamic testing device is a movable bulge cell which is directly mounted on the measuring end of the input bar of a conventional split Hopkinson pressure bar system. The input bar is used to apply and measure the bulging pressure. The experimental system is analyzed in detail and the measurement accuracy is discussed. It is found that bars made of low impedance materials must be used to achieve a satisfactory pressure measurement accuracy. A series of dynamic experiments is performed on aluminum 6111-T4 sheets using viscoelastic nylon bars to demonstrate the capabilities of the proposed experimental technique. The parameters of the rate-dependent Hollomon–Cowper–Symonds J2 plasticity model of the aluminum are determined using an inverse analysis method in conjunction with finite element simulations.
KeywordsBulge test Biaxial experiments Rate-dependent plasticity Split Hopkinson pressure bar apparatus High strain rates
The partial support by the program “De la mise en forme au comportement dynamique” of the Région Bretagne is gratefully acknowledged. The authors wish to thank Mr. R. Barre from LMS, Mr. H. Bellegou from LG2M and Mr. F. Portanguen from UBS University for their technical assistance.
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