Abstract：Both gradient-dependent and rate-dependent constitutive models introduce intrinsic length scales in dynamic strain localization analysis of engineering materials. The intrinsic length scales in the two different constitutive models are discussed，respectively. The ways to predict the intrinsic length scales the two constitutive models are different and the expressions of the intrinsic length scale are also different from each other. To give a prediction of the intrinsic length scales for the general case with the two models，both the length curves corresponding to the damping effect and wave length versus wave number are computed. The internal length scales derived respectively from the damping effect，which is typical for the visco-plastic model，and the wave length is obtained from the critical wave number with unimaginary velocity. An intrinsic length scale domain with upper and lower bound values is obtained which includes the actual length scale. The proposed method can explain the results obtained with the two models. The way proposed here for prediction of the intrinsic length scale is more general than those commonly used to explain the phenomena observed in both the viscoplastic and gradient dependent models. Moreover，it has also been found that the sensitivity of the internal length scale for the visco-plastic parameter is higher than that for the gradient dependent parameter. Numerical example is given and the results are confirmed with those of theoretical analysis.
