School of Mechanical Engineering Prof. Adrian J. Lew1
School of Mechanical Engineering Seminar
Monday, May 15, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
HIGH-FIDELITY SIMULATION OF BRITTLE FRACTURE PROBLEMS
WITH UNIVERSAL MESHES
Prof. Adrian J. Lew1
1 Department of Mechanical Engineering, Stanford University
Durand 207, Stanford, USA
We describe our approach to simulating curvilinear brittle fractures in two-dimensions based on the use of Universal Meshes. A Universal Mesh is one that can be used to mesh a class of geometries by slightly perturbing some nodes in the mesh, and hence the name universal. In this way, as the crack evolves, the Universal Mesh is always deformed so as to exactly mesh the crack surface. The advantages of such an approach are: (a) no elements are cut by the crack, (b) new meshes are automatically obtained as the crack evolves, (c) the crack faces are exactly meshed with a conforming mesh at all times, and the quality of the surface meshing guaranteed to be good, and (d) apart from duplicating degrees of freedom when the crack grows, the connectivity of the mesh and the sparsity of the associated stiffness matrix remains unaltered. In addition to the mesh, we are now able to compute stress intensity factors with any order of convergence, which gives us unprecedented accuracy in computing the crack evolution. As a result, we observe first-order convergence of the crack path as well as the tangent to the crack path in a number of different examples. In the presentation I will introduce the notion of a Universal Mesh, illustrate the progress we have made so far with some examples, and then focus on the simulation of curvilinear fractures, and on the tools we created to compute stress intensity factors. In particular, showing examples in which the computed crack path converges to the exact crack path, regardless of the mesh. If time permits, simulation of thermally induced fracture and hydraulic fractures will be discussed.
Adrian J. Lew is an Associate Professor of Mechanical Engineering at Stanford University, and the Lee Otterson Faculty Scholar. He graduated with the degree of Nuclear Engineer from the Instituto Balseiro in Argentina and received his M.Sc. and doctoral degrees in Aeronautics from the CalTech. He has been awarded Young Investigator Award by the International Association for Computational Mechanics, the ONR Young Investigator Award, the NSF Career Award, and the Ferdinand P. Beer & Russel Johnston, Jr., Outstanding New Mechanics Educator Award from the American Society of Engineering Education. He has also received an honorable mention by the Federal Communication Commission for the creation of the Virtual Braille Keyboard. He served as the North-American co-chair of the XII Pan American Congress in Applied Mechanics, which took place in January 2012, and in the organizing committee of the first Pan American Congress on Computational Mechanics, which took place in Buenos Aires in April 2015. He has also co-founded iBrailler, which produces iBrailler Notes, an app to type Braille in an iPad.