Narrow Results

At high strain rates, the dynamic response of cement mortar, a heterogeneous material with damage, was experimentally studied under three different stress states: (1) one-dimensional stress state by using the SHPB technique, (2) one-dimensional strain state at high pressures from 1 to 5 GPa by using a one-stage gas gun, and (3) quasi one-dimensional strain state by using an improved passive confining SHPB technique. The experimental results indicate that cement mortar is a kind of nonlinear rate-dependent material with internal damage evolution, and that the confining pressure greatly influences its ductility and strength. The main results are given and discussed.

In this paper, we investigate the effect of high modes of buckling on the mechanical behavior of a pre-shaped curved beam. In a first stage, the presented modeling develops further the snapping forces solution and bistability conditions in order to include high modes of buckling. In a second stage, we develop the analytical solution of the stresses inside the beam during deflection between the two sides of buckling. The buckling with or without mechanical conditions on antisymmetric modes, the force characteristics, bistability conditions and stresses are described in this paper based on mathematical approach in order to provide a clear physical understanding of the curved beam behavior and its design parameters. The accurate knowledge of the design parameters is important in order to achieve the best integration of the curved beam in a complete microstructure. The analytical results are compared with and without considering high modes of buckling and have shown to be in excellent agreement with FEM simulations. The results show the importance of the high modes in calculating stresses and snapping forces.

In this paper, the evolution of a ductile damage in the 7075-T6 aluminum alloy is considered based on stress state parameters with a special focus on pre-mechanical working dependency. Uniaxial stress–strain curves are investigated experimentally for two conditions; specimens with shock loaded pre-mechanical working and without it. This kind of loading is applied in order to find out impulsive pressure effects of damage variation procedure. Some experiments are done to take different stress states. Applying two fracture initiations criteria, i.e., Hosford–Coulomb and Xue models, two types of fracture locus of Al-7075-T6 are predicted in terms of plastic strains and stress state parameters under above conditions. By considering experimental data, a new ductile damage evolution model is proposed among plastic behavior. It is introduced by explicating an uncoupled plasticity and related to initial rate dependent stress state. By using both fracture models, our damage evolution model is implemented, phenomenologically as well as the Xue damage model, to compare results.

The impact behavior of cement mortar, a heterogeneous material with damage, were experimentally studied under three different stress states: (1) one-dimensional-stress state by using the SHPB technique, (2) one-dimensional strain state at high pressures from 1 to 5 GPa by using an one stage gas gun and (3) quasi one-dimensional strain state by using an improved passive confining SHPB technique. The experimental results show that cement mortar is a kind of nonlinear rate-dependent material with internal damage evolution, and the confining pressure greatly influence its ductility and strength. The main results are given and discussed.