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

今年，使用一个修改的木材离散元法，这是去年开发的，模拟木材断裂过程，特别是木材切削，并分析结果与实验结果进行了比较。首先以二维木材切削为仿真对象，给出了纵向切削和横向切削时切屑形成的不同结果。该模型较好地模拟了横截切削中的先进检测，但无法实现横截切削中的切屑卷曲过程。这是由于程序计算步长大，容易发散，难以模拟大变形。第二个仿真对象是切削速度对切削表面的影响。与悬臂梁模型试件的试验结果进行了比较，结果与MDEM模拟结果吻合较好。今年，对计算程序做了一点改进。这样我就可以得到试件中的应力分布，并由此表明，电火花线切割可以类似于有限元法来使用。通过对单元弹簧的受力分析，发现该方法也可以模拟切削力，并在1995年10月京都国际木材加工研讨会上作了介绍，得到了很好的反响。

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.