ASABE Technical Library - Abstract

Abstract. The Forest Concepts Crumbler® rotary shear comminution machine processes "green" veneer or wood chips through intermeshed rotary cutters so they are "crumbled" into small particles. As the thickness of the cutters gets smaller, understanding the processing forces is important for optimizing the design of appropriately strong cutters. We have modeled the process using the material point method (MPM). In brief, the process involves massive amounts of contact between the wood and the tools (cutters and spacers), large deformation/rotation of the wood material and material failure. These mechanical characteristics suggest that MPM, which has advantages for discretizing the geometry and modeling contact and material behavior, may provide numerical tools that could not be done by other methods. We monitored contact forces and energy during the shearing process and visualized the process in 3D.

Numerical results highlight the effects of wood material strength and hardening, wood/tool friction parameter, and geometry (thickness and width) of the wood and cutters on the tools contact forces. Contact forces increase with the increase of material strength and plastic hardening, the cutters width and the wood sheet thickness. Processing green wood results in contact forces that are 50% lower than dry wood. Contact force curves show significant peaks corresponding to contact of wood with teeth on the cutters.

MPM is a particle-based numerical analysis tool that can run virtual experiments to help optimize equipment for wood comminution. The MPM analysis method may be more accurate than finite element mesh modeling for biomass materials.