Plasticity Driven Damage and Void Growth

Research output: ThesisDoctoral Thesis (compilation)

Abstract

Plasticity induced damage evolution is considered using a thermodynamical approach. Different postulates on how to include the effects of damage in the constitutive equations have been studied. The results reveal that a mapping, similar to that of the stress, of both the kinematic and isotropic hardening variables is to be preferred. The undesired property that, irrespectively of the postulate employed, the elastic strain will not equal zero as failure takes place, is addressed and a simple modification of the postulate of strain equivalence that does not lead to this property is proposed. From the results it is also concluded that the postulate of (complementary) energy equivalence have some undesirable properties.

A yield criterion for ductile porous materials is proposed based on the lower-bound solution for a cylindrical void model. Comparing the criterion with the Gurson yield criterion and cell model calculations for an axisymmetric cylinder with a spherical void shows good agreement. A constitutive model for porous materials is formulated using the proposed yield function. The corresponding thermodynamic formulation facilitates a natural modeling of damage, in which both the growth and the shrinkage of voids are allowed in the thermodynamic process. Both the elastic and the plastic properties in the model are dependent on the void-volume fraction. The model was found to fit naturally into the thermodynamical framework.

Details

Authors
  • Mattias Olsson
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Mechanical Engineering

Keywords

  • Termisk teknik, termodynamik, Maskinteknik, hydraulik, vakuumteknik, vibrationer, akustik, Thermal engineering, applied thermodynamics, vibration and acoustic engineering, vacuum technology, hydraulics, void growth, Mechanical engineering, damage evolution, elasto-plasticity, thermodynamics
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date2004 Mar 26
Publisher
  • Solid Mechanics, Lund University, P O Box 118, SE-221 00 Lund, Sweden,
Print ISBNs91-628-5995-1
Publication statusPublished - 2004
Publication categoryResearch

Bibliographic note

Defence details Date: 2004-03-26 Time: 10:15 Place: Room M:B, M-building, Ole Römers väg 1, Lund Institute of Technology External reviewer(s) Name: Ståhle, Per Title: Professor Affiliation: Malmö University --- Article: Olsson, M. “Phenomenological aspects on continuum damage mechanics”, Report LUTFD2/(TFHF-1024)/1-142/2000. Lund University, Lund, Sweden, 2000. Article: Olsson, M. and Ristinmaa, M. “Damage evolution in elasto-plastic materials - Material response due to different concepts”, International Journal of Damage Mechanics, Vol. 12, No. 2, pp. 115-139, 2003. Article: Olsson, M. and Ristinmaa, M. “A physically motivated modification of the strain equivalence approach”, accepted for publication in International Journal of Damage Mechanics, 2003. Article: Olsson, M. and Ristinmaa, M. “Yield criterion for ductile porous materials”, submitted for publication, 2003. Article: Wallin, M., Olsson, M. and Ristinmaa, M. “Modeling and computational aspects of ductile void growth at large plastic strains", submitted for publication, 2003.