Unified Theory and Experimentation for Fatigue and Fracture of High Temperature Shape Memory Alloys

Abstract

In this project, the team has - proposed a new analysis method crack growth under mechanical and actuation loading that provides a unified description for fatigue crack growth in shape memory alloys; - reported the observation of stable crack growth under thermal cycling in shape memory alloys for the first time; - investigated thermal stability of two-way shape memory effect in nano-precipitation hardened NiTiHf high temperature shape memory alloy tubes; - investigated the effects of training on the thermomechanical behavior of nano-precipitation strengthened NiTiHf and NiTiZr high temperature shape memory alloys; -measured fatigue crack growth rates in NiTiHf high temperature shape memory alloys under thermomechanical loading for the first time; - experimentally investigated the thickness dependence of the fracture toughness and fracture micromechanisms in NiTi shape memory alloys; - investigated the stress-induced transformation toughening by measuring the fracture toughness of NiTiHf high temperature shape memory alloys at different temperatures; -studied the effect of microstructure on the fracture toughness of NiTiHf high temperature shape memory alloys by comparing precipitated and solutionized microstructures; -experimentally demonstrated that the toughness enhancement due to crack advance in hysteretic materials may be"reversed" by partial unloading; - numerically investigated void growth and coalescence in shape memory alloys by unit cell simulations and quantified the importance of fracture mechanisms; - simulated crack growth under different thermomechanical loadings using a shape memory alloy constitutive model and validated the results against experimental data; - proposed a phenomenological phase-field model for the formation and growth of fatigue macro-cracks that can reproduce both total life and defect tolerant approaches.

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Document Details

Document Type
Technical Report
Publication Date
Oct 28, 2018
Accession Number
AD1153231

Entities

People

  • Dimitris C Lagoudas
  • Ibrahim Karaman
  • Theocharis Baxevanis

Organizations

  • Texas Engineering Experiment Station

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Air Force Research Laboratories
  • Alloys
  • Crack Propagation
  • Crack Tips
  • Electron Microscopy
  • Engineering
  • Experimental Data
  • Failure Mode And Effect Analysis
  • High Temperature
  • J Integrals
  • Law
  • Materials
  • Materials Science
  • Mechanics
  • Numerical Analysis
  • Phase Transformations
  • Precipitation
  • Resistance
  • Scientific Research
  • Shape Memory Alloys
  • Three Dimensional

Fields of Study

  • Materials science

Readers

  • Materials Science (Mechanical Engineering).
  • Powder metallurgy of Titanium alloys.