An extended model for void growth and coalescence

TL;DR: In this article, the authors proposed methods for utilizing 10 kW or more laser energy transmitted deep into the earth with the suppression of associated nonlinear phenomena to enhance the formation of Boreholes.

TL;DR: In this paper, three-dimensional unit cell models were developed to study the damage induced by void growth in ductile materials and special emphasis was given to the influence of the void shape and random spatial void arrangements.

TL;DR: In this article, a non-local plastic-damage potential model is proposed to predict the damage evolution under crash or stamping process, which takes account of void shape effect and anisotropy of the matrix material.

TL;DR: In this paper, the authors concerne l'etude du critere de rupture ductile des materiaux poreux en utilisant les techniques de lhomogeneisation, de l'analyse limite and des methodes d'optimisation of type point interieur.

Abstract: Widely used constitutive laws for engineering materials assume plastic incompressibility, and no effect on yield of the hydrostatic component of stress. However, void nucleation and growth (and thus bulk dilatancy) are commonly observed in some processes which are characterized by large local plastic flow, such as ductile fracture. The purpose of this work is to develop approximate yield criteria and flow rules for porous (dilatant) ductile materials, showing the role of hydrostatic stress in plastic yield and void growth. Other elements of a constitutive theory for porous ductile materials, such as void nucleation, plastic flow and hardening behavior, and a criterion for ductile fracture will be discussed in Part II of this series. The yield criteria are approximated through an upper bound approach. Simplified physical models for ductile porous materials 6ggregates of voids and ductile matrix) are employed, with the matrix material idealized as rigid-perfectly plastic and obeying the von Mises yield criterion. Velocity fields are developed for the matrix which conform to the macroscopic flow behavior of the bulk 4 DISTRIBUTION 0£ :LHIS DOCUMENT IS UNUrv#TE n material. Using a distribution of macroscopic flow fields and working through a dissipation integral, upper bounds to the macroscdpic stress fields required for yield are calculated. Their locus in stress space forms the yield locus. It is shown that normality holds for this yield locus, so a flow rule results. Approximate functional forms for the yield loci are developed.

TL;DR: In this paper, the effect of microscopic voids on the failure mechanism of a ductile material is investigated by considering an elastic-plastic medium containing a boubly periodic array of circular cylindrical voids.