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Professor John A. Nairn, Wood Science & Engineering

Sample Material Point Method (MPM) Movies

The following movies show some interesting simulations done using the material point method (MPM). The emphasis is on problems that are handled well by MPM, but have often been seen as a challenge when using other methods. All simulations were done by John Nairn using his own research code (its source code is publicly available). Click any thumbnail to see a larger movie.

Thumbnail Description
Simulation of orthogonal cutting through a plastic material. The challenging physics concepts, which are all included, are frictional contact between tool and material and explicit crack formation with separation law ahead of the tool tip. This simulation is basis of new research on orthogonal cutting of wood and wood-plastic composites. (22 APR 2010)
Simulation of wedge driving into a plastic material. It could be basis of simulations for driving nails into various materials. (20 APR 2010)
Simulation of copper billet extruding through a right angle corner. The colors show the plastic strain in the x direction. A challenging issue is dealing with wall contact, which was modeled here as frictionless and used multi-material MPM methods. (Collaboration with Vincent Lemiale and Antoine Hurmane, APR 2010)
Compaction of a wood fiber mat. The numerical challenge here was digitizing a realistic 3D structure. The problem was solved by converting pixels in X-Ray CT data into pixels for the wood fibers. The MPM model also handles contact as the mat is compressed. The colors show axial stress. (Collaboration with Eric Badel, 25 FEB 2008)
Compaction of an oriented strand board (OSB). The numerical issues are handling full mechanics (orthotropic with anisotropic yield criterion) of the wood strands and contact between strands (which can be handle several different ways). The final structure shows undulating strands as seen in typical OSB panels. (29 SEP 2008)
Simulation of crack propagation in a material with a process zone. The crack tip propagates by fracture mechanics, the process zone is model with a cohesive law. Unlike FEA modeling with cohesive zones, the cohesive law here dynamically develops as the crack grows, which allows one simulation to combine fracture mechanics and cohesive zones. The inset is the simulated R curve of the material. (15 AUG 2008)
Transverse fracture of Douglas Fir. The challenging numerical issues where modeling full anisotropic properties of earlywood and latewood and digitizing a realistic structure. The latter was done by converting pixels in an optical image into the MPM model and using a radial gradient mask to set radial and tangential orientation directions. The crack path changes as it proceeds through growth rings in a pattern similar to experiments done on the same specimen. (11 MAY 2007)
Transverse compression/densification of Ponderosa Pine. The challenging numerical issues are digitizing a real structure (handled by converting pixels in an optical image into the MPM model) and dealing with cell wall contact at high compaction (which is handled by MPM). The colors show the axial stress. (13 JAN 2006)