NUMERICAL SIMULATION OF AGRICULTURAL TIRE-SOIL CONTACT PROBLEM BY 3D FINITE ELEMENT METHOD

本课题主要研究轮胎模型与土壤模型相结合的三维轮胎-土壤接触问题的数值模拟方法。我们得到了以下结果：1.如果轮胎的弹性特性已经通过TRAC程序知道，那么Nakashima和Wong已经开发的三维轮胎模型可以包含在开发的接触程序中; 2.作为三维土体模型，考虑了Mohr-Coulomb弹塑性模型，采用了粘塑性方法，并采用了初始应变法;在目前的接触分析程序中使用的接触检查策略被发现具有足够的精度时，适用于三维赫兹接触问题。两种接触单元的计算结果显示了相似的接触压力分布规律;作为对现有三维轮胎-土壤接触程序的初步验证，本文分析了轮胎在弹性土壤上的静态下沉。计算结果表明了轮胎-土壤系统三维弹性接触分析的基本能力;如果适当的修改，进一步应用，我们的数值方法将是一个有效的工具时，应用于实际领域的问题，如土壤压实。而且，这种计算只有在超级计算机上才能进行。

In this project, we focused on the development of numerical simulation method for three-dimensional tire-soil contact problems by the combination of tire model and soil model. We obtained the results : 1. The three-dimensional tire model which has already been developed by Nakashima and Wong can be included in the developed contact program if the elastic properties of tire is already known by TRAC procedure ; 2. As the three-dimensional soil model, Mohr-Coulomb elasto-Plastic model is considered with the initial strain method where the visco-plastic approach is employed ; 3. Contact check strategy used in the current program for contact analysis is found to work with sufficient accuracy when applied to three-dimensional Hertz contact problem. The result of two types of contact element shows the similar behavior of contact pressure distribution ; 4. As the first step verification of current three-dimensional tire-soil contact program, we analyzed the static sinkage of tire onto elastic soil. The obtained result shows the fundamental capability of three-dimensional elastic contact analysis of tire and soil system ; 5. If appropriate modification is further applied, our numerical method will be an effective tool when applied in practical field problems such as soil compaction. Moreover, it turned out that the computation is only possible by using a super computer for tire-soil contact analysis.