Dynamic Tensile Response of Caprine Muscles Using Split Hopkinson Pressure Bar

Abstract

Computer modeling and numerical simulation has become an efficient diagnostic tool to predict the human body injuries caused due to high speed automotive impacts, blast and ballistic impacts. Soft tissues such as muscles and skin in human body are exposed to varying strain rates under dynamic loadings during impacts. The prediction of impact-induced injuries requires a thorough understanding of mechanical behaviour of soft tissues for computational modeling of human body. In the present study, uniaxial tensile tests were conducted on caprine lower extremity muscles in the strain rate range of (500s^-1-3500s^-1) using custom-made split Hopkinson pressure bar (SHPB) apparatus. The challenges in the dynamic testing of soft tissues such as measurement of weak transmitted signals, use of viscoelastic pressure bars, tensile loading of specimen and generation of constant strain rate were addressed in dynamic tensile testing of soft tissues using polymeric SHPB. The attenuation and dispersion in waves are corrected using isolated incident bar tests. The stress-strain results were determined from the reconstructed waves for the tests conducted on lower extremity caprine muscles. The muscle specimens were tested along and perpendicular to the fiber direction to study the directional dependency of tissue behaviour. The stress-strain response was found to be non-linear and significant dependant on strain rate when tested along and perpendicular to fiber direction at same strain rates. It is also observed that at the same strain rate, the specimen stress of caprine muscle along the perpendicular fiber direction is higher than that along the fiber direction. The obtained results may further be used to develop finite element human body models and safety systems for human body in high rate scenario.