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

在本项目中，我们将轮胎模型和土壤模型相结合，重点研究了轮胎-土壤三维接触问题的数值模拟方法。结果表明：1.在TRAC程序已知轮胎弹性性能的情况下，Nakashima和Wong已经开发的三维轮胎模型可以包含在所开发的接触程序中；2.作为三维土壤模型，Mohr-Coulomb弹塑性模型采用初始应变法，其中采用粘塑性方法；3.现有接触分析程序中采用的接触校核策略在应用于三维Hertz接触问题时具有足够的精度。两种接触单元的结果显示了相似的接触压力分布行为；4.作为当前三维轮胎-土壤接触程序的第一步验证，我们分析了轮胎在弹性土壤上的静态下沉。得到的结果表明了轮胎与土体三维弹性接触分析的基本能力；5.如果进一步进行适当的修正，我们的数值方法将成为应用于土壤压实等实际领域问题的有效工具。而且，只有使用超级计算机进行轮胎-土壤接触分析才能进行计算。

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.