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含水沙土颗粒离散元接触模型参数标定及试验

Parameter calibration and experiment of the discrete element contact model of water-containing sandy soil particles

  • 摘要: 含水沙土仿真参数标定研究的缺乏,严重制约着触土部件的理论研究。为获取不同含水率沙土的离散元仿真参数,该研究通过探究含水率对沙土颗粒间接触力学的影响,对不同含水率的沙土进行相关参数标定。以江边沙土为研究对象,借助EDEM软件中Hertz-Mindlin with JKR Cohesion (JKR) 接触模型对4种不同含水率的沙土进行仿真参数标定,以沙土颗粒间的静摩擦因数、恢复系数、动摩擦因数及表面能为标定对象,并以沙土颗粒的仿真堆积角为响应值,基于Box-Behnken的响应面优化方法得到堆积角回归模型,发现JKR表面能对沙土堆积角有显著影响,恢复系数对含水率较高的沙土 (15%和20%) 的堆积角有显著影响(P<0.05),静摩擦因数和动摩擦因数对含水沙土的堆积角影响不显著(P>0.05)。通过Design-expert软件的响应面优化设计,得到仿真参数的较优值,其堆积角仿真结果与物理试验对比后误差均小于5%。为了进一步验证模型的可靠性,对承压物理试验和仿真试验侵入阻力数据进行分析,结果显示试验与仿真的阻力变化趋势基本一致,触土深度在40 mm范围内时误差小于10%;触土深度大于40 mm时,误差较大,表明触土深度较浅时该模型能够近似的代替真实沙土进行仿真模拟。可利用标定后的参数进行含水沙土与触土部件间的离散元仿真,同时也为含水土壤虚拟仿真、农业装备与土壤互作关系、触土部件性能改进优化等研究提供参数选择依据。

     

    Abstract: Soil-engaging components have been severely restricted to the parameters of the water-containing sandy soil. However, it is still lacking in the calibration of simulation parameters. This study aims to clarify the influence of the water content on the contact mechanics among sandy soil particles. Taking the riverside sandy soil as the research object, the Hertz-Mindlin with JKR Cohesion (JKR) contact model was used in the EDEM software. The parameters of sandy soil were then calibrated with four water contents (5%, 10%, 15%, and 20%) using discrete element simulation. The targeted variables of calibration were the static friction coefficient, restitution coefficient, dynamic friction coefficient, and surface energy between sandy soil particles. The simulated angle of the repose of sandy soil particles was taken as the response value. The Box-Behnken response surface method was used for the calibration. A regression model of the angle of repose was also obtained after optimization. It was found that the JKR surface energy shared an extremely significant impact on the angle of repose of sandy soil, and the restitution coefficient had a significant impact on the angle of repose of sandy soil with the higher water contents (15% and 20%), while the static friction coefficient and dynamic friction coefficient had no significant impact on the angle of repose of water - containing sandy soil. The optimal parameters were obtained as follows: for the sandy soil with a water content of 5%, the static friction coefficient between particles was 1.011, the restitution coefficient was 0.41, the dynamic friction coefficient was 0.115, and the JKR surface energy was 0.024 J/m2; for the sandy soil with a water content of 10%, the static friction coefficient between particles was 0.918, the restitution coefficient was 0.532, the dynamic friction coefficient was 0.033, and the JKR surface energy was 0.124 J/m2; for the sandy soil with a water content of 15%, the static friction coefficient between particles was 0.894, the restitution coefficient was 0.835, the dynamic friction coefficient was 0.122, and the JKR surface energy was 1.164 J/m2; for the sandy soil with a water content of 20%, the static friction coefficient between particles was 0.963, the restitution coefficient was 0.893, the dynamic friction coefficient was 0.158, and the JKR surface energy was 3.624 J/m2. The relative errors of the angle of repose between the simulation and the physical tests were all less than 5%. The reliability of the model was validated using the intrusion resistance data from the physical pressure-bearing test and the simulation test. There was essential consistency in the resistance trends from the test and the simulation. Once the soil-engaging depth was within the range of 40 mm, the relative errors were all less than 10%. The calibrated parameters were approximately substituted for the real sandy soil. It was also expected to conduct the discrete element simulations between water-containing sandy soil and soil-engaging components. Meanwhile, the findings can also offer the parameter selection under various research, such as the virtual simulation of water-containing soil, the interaction between agricultural equipment and soil, and the performance of soil-engaging components.

     

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