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Dissipated Energy at a Bimaterial Crack Tip Under Cyclic Loading

Daily, Jeremy S

Abstract Details

2006, Doctor of Philosophy (PhD), Wright State University, Engineering PhD.
A new theory of fatigue crack growth in ductile solids has recently been proposed based on the total plastic energy dissipation per cycle ahead of the crack. This, and previous energy-based approaches in the literature, suggest that the total plastic dissipation per cycle can be closely correlated with fatigue crack growth rates under mode I loading. The goal of the current research is to extend the dissipated energy approach to steady-state crack growth under mixed-mode I/II loading conditions, with application to cyclic delamination of ductile bimaterial interfaces. Such systems can occur in brazing, soldering, welding, and a variety of layered manufacturing applications, where high-temperature material deposition can result in a mismatch in mechanical properties between the deposited material and the substrate. The total plastic dissipation per cycle is obtained by 2-D elastic-plastic finite element analysis of a stationary crack in a general mixed-mode specimen geometry under constant amplitude loading. Numerical results for a dimensionless plastic dissipation per cycle are presented over the full range of relevant material combinations and mixed-mode loading conditions. Results suggest that while applied mode-mix ratio is the dominant parameter, mismatches in yield strength and hardening modulus can have a significant effect on the total plastic dissipation per cycle, which is dominated by the weaker/softer material. Results extended to general elastic-plastic mismatches provide substantial insight into the effects of crack-tip constraint, material hardening behavior and applied mode-mix ratio on the dissipated energy during fatigue crack growth. A consistent definition of the mode mix ratio is presented based on minimizing the elastic strain energy at a crack tip. Next, application of the current theory is demonstrated for thermomechanical fatigue of bonded bimaterials. Finally, the plastic dissipation computations are erformed in a probabilistic framework in an attempt to assess the variability of the fatigue crack growth rate based on variation in bulk properties.
Nathan Klingbeil (Advisor)
202 p.

Recommended Citations

Citations

  • Daily, J. S. (2006). Dissipated Energy at a Bimaterial Crack Tip Under Cyclic Loading [Doctoral dissertation, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1150865012

    APA Style (7th edition)

  • Daily, Jeremy. Dissipated Energy at a Bimaterial Crack Tip Under Cyclic Loading. 2006. Wright State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1150865012.

    MLA Style (8th edition)

  • Daily, Jeremy. "Dissipated Energy at a Bimaterial Crack Tip Under Cyclic Loading." Doctoral dissertation, Wright State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1150865012

    Chicago Manual of Style (17th edition)