Modelling wood fracture mechanics in primary wood products manufacturing

直径为2.5至30英寸的原木的初级破碎通常使用削片机进行，该削片机在一次操作中产生斜面和碎片，同时最大限度地减少锯屑的产生。然而，由于切削方向沿着刀具路径变化，切削动作相当复杂。由于切削方向取决于刀盘和原木直径，因此已根据经验对切屑和斜面质量进行了工艺优化。因此，没有数据是可用的切削力和/或断裂力学，管理木材工具的相互作用，在削片机中心。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的研究一直集中在正交切削。这些模型，金属切削理论的基础上，产生了良好的相关性，但不考虑断裂力学在细胞水平。建立了一种用于研究正交横晶切削破坏机理的混合元胞/宏观有限元模型。作者能够证明宏观和微观建模的必要性。我的研究计划的重点是获取实验数据，将用于开发一个混合有限元模型的木材周边切削过程。该方法包括获取有关切削力、断裂力学、切屑形成和质量以及表面质量的全面实验数据。这将提供有关不同切削方向的切削动力学的定量和定性信息。这些研究结果将与切削力，芯片质量和表面质量的测量在工业上。其次，将针对不同的切削方向建立混合的细胞/宏观周边切削有限元模型。这将提高我们对周边切削中切削动力学的认识。最后，将使用实验和工业数据来验证模型。从长远来看，该模型将进一步适应特定的切削加工操作的削片机，所以改变切割方向沿着切割路径将被引入作为一个功能的刀盘和日志直径。然后，该模型将被用来研究不同的切削参数对切削动力学，切屑形成和表面质量的切屑中心的影响。

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.