A Caltech Library Service

Dynamic Crack Propagation in Elastic-Plastic Solids


Deng, Xiaomin (1990) Dynamic Crack Propagation in Elastic-Plastic Solids. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WHJV-C644.


The present finite element study addresses several issues of interest pertaining to the phenomenon of dynamic crack propagation in elastic-plastic solids. Three classes of materials, namely elastic-perfectly plastic materials, linear hardening materials and power-law hardening materials, are considered. The materials are assumed to obey the von Mises yield criterion and the associated flow rule.

Under conditions of Mode I, plane stress, steady state and small scale yielding, we investigated the structures of the near-tip stress and deformation fields. A preliminary asymptotic analysis for crack-tip stress and velocity fields in elastic-perfectly plastic solids was provided to reveal and explain some special features of the crack tip fields observable only in the case of rapid crack propagation. We studied the theoretical basis of a fracture criterion based on the dynamic stress intensity factor for crack growth in materials which fail in a locally ductile manner. We explored the behavior of crack tip fields under non-K-dominance conditions and its effects on the dynamic fracture toughness vs. crack propagation speed relationship.

An Eulerian finite element scheme is employed. Finite element meshes with extremely small elements near the crack tip are carefully designed. The ratio of the crack tip plastic zone size to that of the element nearest to the crack tip is of the order of 1.6 x 10⁴. In order to overcome numerical difficulties associated with crack-tip strain singularities and the use of small near-tip elements, an efficient stress integration algorithm is devised. The existing stress state determination procedure is modified to prevent the occurrence of negative plastic flow and to avoid mistakenly treating elastic unloading as plastic flow. The above measures are proven to be essential for the convergence of the numerical solution.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied mechanics; materials science
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Mechanics
Minor Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Rosakis, Ares J.
Thesis Committee:
  • Rosakis, Ares J. (chair)
  • Hall, John F.
  • Knowles, James K.
  • Vreeland, Thad
  • Knauss, Wolfgang Gustav
Defense Date:3 May 1990
Funding AgencyGrant Number
Josephine de Kármán FellowshipUNSPECIFIED
Li Ming FellowshipUNSPECIFIED
Chinese Government ScholarshipUNSPECIFIED
Office of Naval Research (ONR)N00014-85-K-0596
Office of Naval Research (ONR)N00014-90-J-1340
Record Number:CaltechETD:etd-11062003-112730
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4417
Deposited By: Imported from ETD-db
Deposited On:06 Nov 2003
Last Modified:04 Feb 2022 21:56

Thesis Files

[img] PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page