No abstract

A simple, 3-D yield function that is quadratic in stresses was proposed to describe the plastic behavior of fiber composites. It relaxes the two usually used assumptions that hydrostatic stress does not influence plastic deformation and that the total plastic dilatation is incompressible. It is also general in nature to allow for composites with various fiber volume fractions and different fiber arrays. The applicability of this quadratic yield function to fiber composites was examined, and the accuracy of the elasto-plasticity model was verified by using the macro stress-strain data generated by a 3-D nonlinear micromechanics model. Because this anisotropic plasticity model is simple and is in the general form of those widely used in existing numerical plasticity codes, it can easily be incorporated into the existing codes with little effort.

No abstract

No abstract

We investigate shock-induced detonation of high explosives confined in an open-ended steel cylinder by a normal impact to the cylindrical surface using three-dimensional finite element analysis. Three types of steel projectiles are considered: a cube, a sphere and a square plate. For the encased LX-17 explosive the calculated threshold impact velocities that lead to deflagration and detonation are higher for a sphere than for a cube of the same mass. It is found that detonation of the encased PBXN-110 explosive with the cubical projectile could occur immediately once a full reaction is initiated in the region near the impact site. The threshold detonation velocity is much lower for PBXN-110 than for LX-17. In addition, we discuss the threshold conditions of detonation predicted by different equations of state and failure models for the steel casing and projectile.