Abstract
The Split Hopkinson Pressure Bar Method with viscoelastic stress bars is widely used as a technique for the evaluation of the dynamic properties of such materials. The validity of the Viscoelastic SHPB Method is examined. In this method, the stress and the strain of a specimen are calculated by considering the average of the data collected from both ends of the specimen. Therefore, the accuracy of the dynamic properties of viscoelastic materials depends on the experimental condition. The shape of the waves at the boundary side of the stress bar and the specimen are obtained numerically by using the Elementary theory, and the stress distribution in the specimen is analysed. It is necessary to measure the reflected and transmitted strain waves of moderate size and to almost equal the load on both ends of the specimen with this method. When the ratio of the stress bar and the specimen of mechanical impedance is about 15-20%, these requirements are met, and the dynamic properties of viscoelastic materials can be evaluated with good precision. The value of the complex compliance comes to vary, except under this condition, so this method can not be used well.
