Smoothly waning, symmetrically expanding, cavity-pressure loads in earth materials

An approximate solution for the pressure loading required to expand a spherical cavity in rock and soil targets is derived. A dual characterization of fracture and flow material model is used. Frictional resistance to flow is also included. Non-linear volumetric strain hardening is modeled with bi-linear curves and unloading is assumed to be non-dilative. Applications of this solution form to the prediction of pressure loading on slender, convex-nosed earth penetrators and on spherically-nosed water entry vehicles are discussed

Experimental-analytical comparison of the ductile failure of notched tensile bars

Experimental results of the ductile failure of 7075-T6 aluminum notched tensile bars are compared with finite strain, nonlinear, finite element calculations. This comparison allows the investigation of mean stress dependent macroscopic theories for ductile fracture. Two such theories are examined and the results are presented in graphical form. 14 figures, 2 tables

Experimental aspects of an investigation of macroscopic ductile failure criteria

Experimental results for the ductile failure of 7075-T651 aluminum are presented. Four separate shapes were tested to investigate the importance that macroscopic effective shear stress, hydrostatic stress, and plastic strain play in describing ductile failure of materials. The specimens used were: thin wall torsion tubes to create a state of pure shear, uniform hollow tubes to create a state of uniaxial stress; hour-glass shaped hollow tubes to create a state of biaxial stress; and notched round bars to create a state of triaxial stress. Two proposed ductile failure criteria are discussed in conjunction with the experimental results presented