Design and Simulation of a Laser Measurement Technique in Split Hopkinson Pressure Bar Test

The Split Hopkinson Pressure Bar (SHPB) is a commonly used technique to measure the stress-strain behavior of materials at high strain rates. Using Utilizing the strain records signals recorded in the input and output bars, the average stress, -strain and strain rate in the sample can be calculatedis determined by the one-dimensional wave propagation equations of SHPB formulas based on the one-dimensional wave propagation theory. The accuracy of a SHPB test is based on this assumption as well as dynamic equilibrium. In this paperarticlework, the possibility feasibility of using a laser measuring system to obtain the dynamic properties of a wide range ofvarious materials using split Hopkinson pressure bar without strain gages is studied. In this method which is a non-contact one, the displacements of bar/sample interfaces are measured directly using a laser extensometer technique. After designing a proper set of optical elements, the operation of the method is evaluated using numerical simulation in ABAQUS/Explicit. Cast iron, aluminum and polypropylene samples, which represent the properties of hard to soft, respectively, were studied to evaluate the proposed measurement method for different materials. The comparison with other strain gage methods shows good agreement and lower fluctuation in stress-strain curves. Moreover, since the one-dimensional wave propagation is not used in this method, we show by numerical simulation that the proposed method can be used even with shorter pressure bars which can reduce the cost of manufacturing and maintaining the SHPB apparatus.