Analysis of the fracture process of wood by Modified Distinct Element Method.

今年，利用去年开发的改进的木材离散元方法，对木材的断裂过程，特别是木材切割过程进行了模拟，并将分析结果与实验结果进行了比较。第一个仿真对象是二维木材切割，它给出了纵切削和横切削不同的切屑形成结果。纵切削的高级校核得到了较好的模拟，但无法实现横切削的卷屑过程。这种不便是因为程序在大的计算步骤中容易发散，从而使大变形的模拟变得困难。第二个模拟对象是切割速度对切削面的影响。与悬臂形模型试件的试验结果进行了对比，与MDEM模拟结果吻合较好。今年，计算程序做了一些改进。现在我可以得到试件中的应力分布，从而表明MEDM可以类似于有限元方法使用。此外，通过对单元弹簧的受力分析，我发现我们也可以模拟切削力。这些结果在1995年10月的国际木材加工研讨会(京都)上发表，并得到了良好的反响。

This year, using a Modified Distinct Element Method for wood, which was developed last year, simulations on wood fracturing processes, especially on wood cutting, were made and analyzed results were compared with the experimental ones. First simulation object was the second-dimensional wood cutting, which gave different results of chip formation between longitudinal cutting and lateral cutting. The advanced checking in logitudinal cutting was well simulated, but the chip curling process of lateral cutting could not be realized. This inconvenience became from the fact that the program was apt to diverge in large calculating steps and then the simulation of large deformation was difficult. Second simulation object was the effect of the cutting velocity on the cut surfaces. The comparison with the experimental results used cantilever shaped model specimens gave good accordance to the MDEM simulation results. This year, a little improvement was done to the calculating program. Now I can obtain stress distribution in the specimen, and by this, I showed that MEDM could be used similary as a Finite Element Method. Further more, by analyzing the forces acting on the element springs, I found that we can simulate the cutting forces also.These results were presented at the International Wood Machining Seminar (Oct.1995, Kyoto) and received good response.