Engineering plastics provide superior performance to ordinary plastics for wide range of the use. For polymer materials, dynamic stress and strain rate may be major factors to be considered when the strength is evaluated. Recently, high‐speed tensile test is being recognized as a standard testing method to confirm the strength under dynamic loads. In this study, therefore, high‐speed tensile test is analysed by the finite element method; then, the maximum dynamic stress and strain rate are discussed with varying the tensile speed and maximum forced displacement. The maximum strain rate increases with increasing the tensile speed u/t, but the strain rate concentration factor italicKtitalicεtrue˙italict=trueε˙italicyAitalict/trueε˙italicynomitalict is found to be constant independent of tensile speed, which is defined as the maximum strain rate italicεtrue˙italicyA,max appearing at the notch root over the average nominal strain rate at the minimum section trueε˙italicynomitalict. It is found that the strain rate at the notch root depends on the dynamic stress rate at the notch root and independent of the notch root radius ρ. It is found that the difference between the static and dynamic maximum stress concentration (σyA,max − σyA,st) at the notch root is proportional to the tensile speed when u/t = 5000 mm/s. Strain rate concentration factors are also discussed with varying the notch depth and specimen length. Based on the elastic strain rate concentration factor, the master curve is obtained useful for understanding the impact fracture of polycarbonate for the wide range of temperature and impact speed.

Engineering plastics provide superior performance to ordinary plastics for a wide range of the use. For polymer materials, dynamic stress and strain rate are major factors to be considered when the strength is evaluated. Recently, high speed tensile test is recognized as a standard testing method to confirm the strength under dynamic loads, and it is analyzed by the finite element method; then, the maximum dynamic stress and strain rate are discussed with varying both the tensile speed and the maximum forced displacement. The strain rate concentration factor is found to be constant independent of the tensile speed, which is defined as the maximum strain rate appears at the notch root over the average nominal strain rate at the minimum section. The maximum strain rate is controlled by the tensile speed alone independent of the magnitude of the forced displacement. It is found that the difference between static and dynamic maximum stress concentrations ( max st σ σ − ) at the notch root is proportional to the tensile speed when u/t≦5000mm/s.