Optimal Pulse Shapes for SHPB Tests on Soft Materials

摘要: For split Hopkinson pressure bar (SHPB) tests on soft materials, the goals of homogeneous deformation and uniform uniaxial stress in specimen present experimental challenges, particularly at higher strain rates. It has been known for some time that attainment these conditions is facilitated by reducing thickness or appropriately shaping loading pulse. Typically, both methods must be employed. Pulse shapes are often tailored to deliver a smooth sufficiently slow rise constant axial rate, as this promotes equality mean two faces specimen, condition referred dynamic equilibrium. However, rate does not eliminate radial acceleration, which may result large hoop stresses variations radial, stresses. An approximate analysis (assuming incompressibility) indicates inertia effects would eliminated if were constant. Motivated result, we consider pulses after an initial ramp-up. The corresponding no longer any interval, but thin specimens resulting departure from equilibrium small enough tolerable. This explored here comparing analytical predictions conventional “optimal” pulse with numerical simulations SHPB soft, nearly incompressible material.