FUNDAMENTAL STUDY ON A PARALLEL NUMERICAL ANALYSIS FOR PERFORMANCE PREDICTION OF AGRICULTURAL TIRE BY 3D FE-DE METHOD

首先，进行了轮胎用有限元网的制备。我们开发了两个三维有限元网格生成程序；一个用于平滑轮胎，另一个用于牵引轮胎。利用一个典型轮胎数据，成功地论证了牵引轮胎有限元网格的生成。我们的农业系统工程实验室最近开发的2D DEM程序也验证了DEM包含轮耳影响的能力。在开发三维DEM程序时，会遇到计算时间大的问题。探讨了动态FE-DE方法在土-轮胎系统中应用的可能性。我们假设轮胎和深层土层可以用FEM建模，土壤表层可以用DEM建模。我们开发了一个组合式有限元- dem代码来分析农业轮胎-土壤相互作用问题。在计算速度上采用简单接触算法。通过对轮胎在变形土上垂直下沉的小例题的分析，得到了位移场分析的足够精度。对于轮胎滚动问题，发现有限元模型代码可以包含轮胎旋转和平移的功能。基础分析结果表明，变形可以定性分析，但竖向总反力表现出强烈的振动结果。这个问题还需要进一步的详细研究。作为一种可行且有用的工具，我们研究了消息传递并行处理在FE-DEM中的可能应用。澄清以下几点。在开发的有限元DEM程序中，接触检查和接触反应子程序是最耗时的两个部分。如果引入并行处理系统，则FE-DEM程序中的FEM和DEM应分配到两个节点上，并且有可能将DEM中的接触校核回路划分为两个以上的并行过程。

Firstly, the preparation of FE mesh for tire was done. We developed two 3D FE mesh generation programs; one for smoothed tires, and the other for traction tires. Generation of FE mesh for traction tire could successfully demonstrated by using a typical tire data.The capability of DEM to include the effect of wheel lug was also verified by the recent development of 2D DEM program in our Agricultural Systems Engineering Laboratory. The problem of large computational time is expected when 3D DEM program is developed.The possibility of dynamic FE-DE method was investigated in terms of the application in soil-tire system. We assumed that a tire and deep soil layer could be modeled as FEM and soil surface layer as DEM. We developed a combined FE-DEM code to analyze an agricultural tire-soil interaction problem. Simple contact algorithm is adopted in terms of computational speed. Small example problem of vertical tire sinkage on to a deformable soil was analyzed and we found that the sufficient accuracy of analysis for displacement field could be obtained.As for tire rolling problem, it was found that the FE-DEM code could include the function of tire rotation and translation. The result of the basic analysis showed that the deformation could be analyzed qualitatively, but the total vertical reaction exhibited the heavy vibratory result. Further detailed study should be added to this problem.As the one of possible and useful tool, we investigated the possible application of message passing parallel processing for FE-DEM. The following points are clarified.In the developed FE-DEM program, contact check and contact reaction subroutines in DEM are the two most time-consuming parts.If the parallel processing system is introduced, FEM and DEM in FE-DEM program should be allocated to two nodes and there may be possible to devide the contact check loop in DEM into more than two parallel processes.