基于FRIDA模型的轮胎-土壤接触特性研究

Research on Contact Properties of Soil-Tyre Based on FRIDA Model

摘要:

利用喷涂法与土壤传感器埋设法测试了不同胎压条件下轮胎-土壤接触特性，旨在研究轮胎气压对轮胎-土壤接触特性影响，对FRIDA模型在华北一年两熟区壤土区适用性进行评价并优化，结果表明，轮胎-土壤接触面面积A的均方根误差（RMSE）从0.022m2降低到0.013m2，标准偏差（Bias）的变化范围为-0.19~0.019m2，模拟值与实测值的回归线决定系数为0.948；轮胎-土壤接触面平均应力及最大应力的模拟值与实测值的相对误差（RE）均小于0.1，参数优化及验证后的FRIDA模型能够模拟华北一年两熟壤土区轮胎-土壤接触特性。通过田间试验结合优化的FRIDA模型，分析轮胎气压、轴载对轮胎-土壤接触特性影响的结果表明，随着轮胎气压增大，接触面形状由矩形到椭圆形再到圆形的变化过程，接触面积减小，应力分布由M型应力集中到凸型应力集中变化；随着轴载增大，轮胎-土壤接触面形状由类椭圆形变为矩形，面积增大，应力分布出现严重M型应力集中现象，且应力逐渐增大。该研究为合理选择拖拉机胎压及配套农机具提供了理论依据。

Abstract:

A lot of study has shown that the distribution of vertical stress in soil just below a loaded tyre is not uniform, and the stress distribution as well as the size and form of the tyre-soil interface are decisive for the topsoil compaction. The distribution of vertical stress was measured in the contact area for three different tyre inflation pressures (85, 100, 120kPa) and load of 21kN. The study took place on a sandy soil in Zhuozhou city, Hebei province. The effects of three different inflation pressures were tested in a randomized block design with three replicates. The vertical stress was measured with load cells located in about 0.1m soil depth. The collected data in the experiment was used to calibrate and validate the FRIDA model. The validated FRIDA was used to predict soil-tyre contact area and the stress distribution across soil-tyre interface. The validation results showed that the RMSE(root mean square errors) and Bias (standard deviation) for soil-tyre contact area were ranged from 0.022m2 to 0.013m2 and from -0.19m2 to 0.019m2, respectively. The decision coefficient of contactarea between the tested and simulated values was 0.948. The relative errors (RE) of measured and predicted values of peak stress and mean stress were generally less than 0.1. Results showed that the FRIDA model could predict the soil compaction problems in sandy soil of north China. The FRIDA model was used to simulate the soil-tyre contact properties and stress distribution at different tyre inflation pressures. At the recommended inflation pressure, tyre displayed a stress distribution across the width of the wheel that could be evaluated as optimal with regard to a minimized topsoil compaction. The FRIDA model seems very well suited for describing the stress distribution at soil-tyre interface, but should be validated with other soil conditions.