CLMI graduate assistant Sunday Aduloju participated in the project “Designing Brittle Fracture Specimens to Investigate Environmentally Assisted Crack Growth” through the 3rd Nonlinear Mechanics and Dynamics Summer Research Institute (NOMAD) from June 20 to July 29, 2016, at Sandia National Laboratories and the University of New Mexico in Albuquerque. Sunday worked alongside graduate assistant Wenjia Gu from Cornell University; project mentors were Drs. Scott Grutzik, Dave Reedy, John Emery, and Timothy Truster.
The goal of this project is to design a new specimen for conducting experiments involving environmentally assisted crack growth (EACG). Under inert conditions, a crack in a brittle material will only grow when the stress intensity factor at the crack tip equals the fracture toughness. If water is present, water molecules can interact with material at the crack tip to cause slow crack propagation at lower stresses. EACG is a type of sub-critical crack growth and can cause flaws that would otherwise be stable to grow to a point where they become critical. In the past, EACG has been studied under a variety of conditions but specimens have always required a load to be externally applied. In this project, a new type of test specimen will be designed consisting of a bonded beam with two materials have slightly different coefficient of thermal expansion (CTE). The dimensions of the beam and the material selection will be determined through computational fracture mechanics modeling performed using ABAQUS and FRANC3D. Results from the project will be presented in a group poster at the NOMAD Institute and later published through conference proceedings.