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

今年，利用去年开发的一种改进的木材离散元方法，对木材的劈裂过程，特别是木材的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。第一个仿真对象为二次元木材切削，纵向切削与横向切削的切屑形成结果不同。对纵向切削的高级校核进行了较好的模拟，但无法实现横向切削的切屑卷曲过程。造成这种不便的原因是程序在较大的计算步长中容易出现发散，从而给大变形的模拟带来困难。第二个仿真对象是切削速度对切削表面的影响。采用悬臂形模型试件与试验结果进行对比，结果与MDEM仿真结果吻合较好。今年，对计算程序做了一点改进。现在我可以得到试样的应力分布，通过这个，我表明MEDM可以类似于有限元法。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）上提出，并得到很好的反应。

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.