Center for Advanced Vehicular Systems

To develop a continuum theoretical frame work for numerical tools to quantify material damage caused by chemical environmental effect.

Chemical Effects on Premature Fracture


Scientific Merit
• To study damage progression from chemical and mechanical effects
• To combine theory, computations, and experiments in a multiscale framework with respect to chemomechanics

Stress Corrosion Cracking Mechanisms
• Tensile stresses cause protective oxide film to rupture and make anodic reactions possible
• Anodic reactions causes material to be removed by electrochemical reactions
from crack tip and further increase the local stress at the tip (in addition to the mechanical load)
• The correlating cathodic reactions produce hydrogen which can diffuse into
the material. Solute hydrogen atoms then can cause hydrogen embrittlement under the tensile loading.
• The coupled electrochemical and mechanical forces cause the crack to grow rapidly until final fracture occurs .



Hydrogen Embrittlement Mechanisms
1. Stress-induced hydride formation and cleavage mechanism

2. The hydrogen-enhanced localized plasticity mechanism

3. The decohesion theory


Combining Mechanical and Chemical Effects on Damage Progression


Multiscale Modeling of Chemical Effects on Metals


Status
• Completed preliminary theoretical frame work on chemical environmental damage effect of engineering materials.

Future Work
• To perform experiments to quantify damage parameters and provide validations for the material model.
• To perform atomistic simulation to aid damage material model.
• To implement chemical environmental damage material model into ABAQUS.