基于DEM/FEM的越野车辆沙地通过性能仿真方法基础研究

The large displacement motions of sand particles and the corresponding wheel slip and sinkage have main influences on the trafficability of an off-road vehicle. The finite element method (FEM), which is based on the continuous theory, is applicable to describe the complex wheel structure, the deformation of the tire and so on. But it is inadequate to model the discontinuous natures of sand terrain. The discrete element method (DEM) has a clear advantage to handle this problem. The purpose of this project is to develop an effective approach which can describe the sand terrain through DEM method and the off-road vehicle via FEM method, the interaction between tire and sand is computed by the coupling method of DEM/FEM.And the appropriative simulation software is developed . The mainly research contents are as follows: the development of the appropriative analysis software , the method of determining the microscopic parameters among elements (including parameters among discrete elements and parameters between discrete element and finite element) is present; based on the pure discrete element sand road sample and the mixed discrete element and finite element sand road sample, an alternate-moving soil bin method is proposed in order to control the model size of sand terrain; a new searching method need to be developed in line with the alternate-moving soil bin method; The parallel computing method based on GPU is developed to enhance the efficiency; the simulation result are validated by soil bin experiments. The successful implementation of this project gives a new method for quickly and effectively simulation of trafficability of Off-road vehicles traveling on sand terrain during the vehicle development stage.

沙石颗粒的大位移运动及车轮沉陷、滑转对越野车辆沙地通过性能有重要影响。有限元方法是基于连续介质理论的数值方法，可以很好地描述车轮的复杂形状、变形等，但不能描述沙地的非连续介质特性。而离散元方法适宜于解决不连续介质问题。本项目用有限元模拟车轮及整车、离散元描述沙粒，通过离散元与有限元耦合方法分析轮胎与沙粒间的相互作用，并开发专用仿真软件。主要内容包括：专用分析软件的开发；单元间细观参数（包括离散单元间、离散单元与有限单元间）的确定方法；提出基于纯离散元样本路面和离散元与有限元混合样本路面的交替移动路面法以控制沙地模型规模；通过基于GPU的并行计算开发使专用软件具备工程应用能力；以室内土槽实验验证仿真评价方法的有效性。本项目的成功实施，有望实现越野车辆开发过程中沙地通过性能快速有效的仿真评价。

越野汽车沙地性能是有别于公路车辆的重要性能之一，通用的有限元方法难以实现相关性能的仿真分析和评价。本项目使用颗粒离散元和有限元耦合分析方法研究越野轮胎的沙地性能，具体研究内容包括：1）专用仿真软件的开发；2）单元细观参数确定方法研究；3）交替移动路面法及接触搜索方法的研究；4）专用软件的GPU并行计算功能开发；5）室内土槽实验设计和评价。.研究成果包括：1）对离散元与有限元耦合计算软件追加轮胎相关有限元计算功能，实现了专用仿真软件对复杂花纹有限元充气轮胎力学性能的仿真计算。2）通过三轴试验、颗粒尺度不变性试验、休止角试验等方法，对砾石和沙粒为介质的离散单元细观参数的确定方法进行了深入研究并得到了有效细观参数，为土槽试验仿真结果的正确性奠定了基础。3）通过交替移动路面法的开发，使一定路面模型规模下越野轮胎任意长度沙石路面行驶性能的仿真评价成为了可能；基于有限元越野轮胎在离散元沙石路面单向行驶的特点，开发了专门处理离散元路面和有限元轮胎接触计算的全局搜索方法和局部搜索方法，大幅提升了接触计算的效率和精度。4）对包含上述性能的专用分析软件进行GPU并行计算功能开发，加速比达到46，极大地提升了仿真计算效率。5）开发了室内土槽试验装置，以砾石和沙粒为介质，实施了不同滑转率和不同车轮水平速度的土槽试验。专用软件计算得到的轮胎驱动力和车轮下陷量仿真结果与试验结果的良好一致性，说明了本项目研究方法的正确性、研究成果的有效性。.目前为止，本项目共发表SCI和EI检索论文13篇、授权发明专利2个、软件著作权1个，培养博士和硕士研究生各3名，研究成果受到相关企业的关注。