Modelling wood fracture mechanics in primary wood products manufacturing

直径从2.5英寸到30英寸的原木的主要分解通常是使用切削机进行的，这种切削机在一次操作中就能产生铁路超高和碎屑，同时最大限度地减少木屑的产生。然而，由于切割方向沿刀具路径变化，因此切割动作相当复杂。由于切割方向取决于刀盘和原木直径，因此对切屑和斜面的表面质量进行了经验优化。因此，没有关于切削力和/或断裂力学的数据，这些数据支配着削片机-刀具之间的相互作用。这种知识的缺乏可以通过使用有限元建模来克服。然而，木材加工过程的有限元建模研究一直集中在正交切削上。这些基于金属切割理论的模型产生了很好的相关性，但没有考虑细胞水平上的断裂力学。提出了一种元胞/宏观混合有限元模型，用于研究正交切割过程中的失效机理。作者能够证明宏观和微观建模的必要性。我的研究计划专注于获取实验数据，这些数据将用于开发木材周边切割过程的混合有限元模型。该方法包括获得关于切削力、断裂力学、切屑形成和质量以及表面质量的全面实验数据。这将给出不同切割方向所涉及的切割动力学的定量和定性信息。这些发现将与行业中的切削力、切屑质量和表面质量测量相关联。其次，针对不同的切割方向，建立了单元/宏观混合周边切割有限元模型。这应该会增强我们对周边切割所涉及的切割动力学的了解。最后，实验和工业数据将被用来验证该模型。从长远来看，该模型将进一步适应削片-刀具的特定加工操作，因此沿切割路径的切割方向的变化将作为刀盘和原木直径的函数来引入。该模型将被用来研究不同的切削参数对切屑动力学、切屑形成和切屑表面质量的影响。

Primary breakdown of logs having a diameter ranging from 2.5 to 30 inches is often done using a chipper-canter that produces, in a single operation, a cant and chips while minimizing sawdust production. However, the cutting action is quite complex since cutting direction changes along the tool path. As cutting direction depends on cutterhead and log diameters, process optimization has been done empirically for chip and cant surface quality. Therefore, no data is available on the cutting forces and/or the fracture mechanics that govern the wood-tool interaction in chipper-canters. This lack in knowledge could be overcome by using finite element modelling. However, research on finite element modelling of wood machining processes has been focused on orthogonal cutting. These models, based on metal cutting theories, have yielded good correlations but do not take into account fracture mechanics at the cellular level. A hybrid cellular/macroscopic finite element model has been developed to study failure mechanism in orthogonal cutting across the grain. The authors were able to demonstrate the need for both macroscopic and microscopic modelling. My research program focuses on acquiring experimental data that will be used to develop a hybrid finite element model of wood peripheral cutting process. The approach consists in acquiring thorough experimental data on cutting forces, fracture mechanics, chip formation and quality, as well as surface quality. This will give quantitative and qualitative information on cutting dynamics involved in different cutting direction. These findings will be correlated with cutting force, chip quality, and surface quality measurements made in the industry. Second, a hybrid cellular/macroscopic peripheral cutting finite element model will be developed for different cutting direction. This should enhance our knowledge of the cutting dynamics involved in peripheral cutting. Finally, the experimental and industrial data will be used to validate the model. In the long-term, this model will be further adapted to the particular machining operations of chipper-canters so change in cutting direction along the cutting path will be introduced as a function of cutterhead and log diameters. The model will then be used to study the impact of different cutting parameters on cutting dynamics, chip formation, and surface quality of chipper-canters.