On loading ceramic-like materials using split Hopkinson pressure bar

摘要

In Hopkinson pressure bar experiments on ceramics, the stress inequilibrium and indentation of the specimen to bar ends are critical issues due to the brittle nature and high strength of ceramics. Theoretical analysis is employed to reconstruct the loading process for investigating the influence of the stress inequilibrium. The results indicate that it has little influence on the accuracy of stress-strain curves and accurate peak stress measurements during the dynamic test can be made. The optimized bilinear incident wave is formulated for achieving the stress equilibrium and constant strain rate loading on the specimen, and the experimental verification demonstrates the feasibility and merits of the bilinear wave in testing brittle materials. Numerical simulations are also performed to see the effect of bar indentation on stress-strain curves, and simulation results show strain concentration at both ends of the specimens resulting in premature failure. A specimen with a dogbone configuration is proposed which can greatly reduce the strain concentration and facilitate the accurate measurement of stress-strain for brittle materials.