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，对木材断裂过程，特别是木材切割进行了模拟，并将分析结果与实验结果进行了比较。第一个模拟对象是二维木材切削，纵向切削和横向切削的切屑形成结果不同。纵向切削的高级检查得到了很好的模拟，但无法实现横向切削的卷屑过程。造成这种不便的原因在于，程序在计算步长较大时容易发散，导致大变形的模拟变得困难。第二个模拟对象是切削速度对切削表面的影响。与使用悬臂梁形状模型试件的实验结果进行比较，与MDEM模拟结果很好地吻合。今年，对计算程序做了一些改进。现在我可以获得样本中的应力分布，通过这一点，我表明 MEDM 可以像有限元方法一样使用。此外，通过分析作用在元件弹簧上的力，我发现我们也可以模拟切削力。这些结果在国际木材加工研讨会（1995年10月，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.