Hervé Trumel

On probabilistic aspects in the dynamic degradation of ductile materials

Dynamic loadings produce high stress waves leading to the spallation of ductile materials such as aluminum, copper, magnesium or tantalum. The main mechanism used herein to explain the change of the number of cavities with the stress rate is nucleation inhibition, as induced by the growth of already nucleated cavities. The dependence of the spall strength and critical time with the loading rate is investigated in the framework of a probabilistic model. The present approach, which explains previous experimental findings on the strain-rate dependence of the spall strength, is applied to analyze experimental data on tantalum.

On the Implementation of a Limited Frequency Band Integrator and Application to Energetic Material Ignition Prediction

This paper describes an algorithm for the implementation a fractional order integrator. This algorithm is based on a fractional integrator transfer function approximation by a recursive distribution of poles and zeros. This algorithm is then used to predict the ignition of energetic materials. For these materials, the ignition under low velocity impact can be predicted through the fractional integration of a local function of pressure and of shear strain rate inside the material. It is shown that the proposed algorithm allows obtaining accurate results with a low computational complexity.