木薯块根拔起力的力学模型和数学模型分析

Mechanical and mathematical model analysis of uprooted force on cassava storage root

为了探讨不同块根拔起速度和块根生长状况对块根最大拔起力的影响规律,该文采用物理试验方法、ANSYS/LS-DYNA显式动力学仿真技术及土力学理论分析方法进行物理试验和力学分析,建立了考虑拔起速度影响的木薯块根拔起力的力学模型和数学模型,且对模型进行了试验验证。结果表明,假设木薯块根对土壤的作用为一圆盘和圆盘外延对土壤的共同作用的力学模型合理;圆盘最大拔起力的数学模型精度高,理论值与实测值的相对误差小于16%;木薯块根最大拔起力的数学模型对成圆盘状分布生长的木薯块根拔起力有较高的预测精度,对生长分布较不均匀的木薯块根拔起力的预测精度较低,但理论值与实测值的相对误差也小于27%;木薯块根最大拔起力随拔起速度、块根圆盘直径和圆盘深度的增大而增大;块根圆盘深度对木薯块根的最大拔起力的影响最大,其次是圆盘直径,最后是拔起速度。该文为挖拔式木薯收获机械块根拔起机构系统的设计提供依据。

In order to research on the effects of uprooted speed and distribution status of cassava storage root in soil on the uprooted force on cassava storage root,mechanical and mathematical model of uprooted force on cassava storage root considering the effect of uprooted speed were established by using the physical test method,explicit dynamic simulation software ANSYS/LS-DYNA and soil mechanics theory to have physics experiment and mechanical analysis,and then the models were verified.The results showed that the mechanical model of assumption uprooted force on cassava storage root as interaction of a disc and its extension on the soil was reasonable;mathematical model of maximum uprooted force on disc was highly precision,and the most fractional error between theoretical value and measured value was less than 16%;mathematical model of maximum uprooted force on cassava storage root has higher precision in uprooted force of cassava storage root,which distribution and growth both were like disc-shaped;mathematical model of uprooted force on cassava storage root has lower precision in uprooted force of cassava storage root,which distribution and growth both were uneven,but the most fractional error between the theoretical value and measured value also was less than27%;with the increasing of uprooted speed,the diameter and depth of root disc,the maximum uprooted force on cassava storage root increased.The most influence factor on the maximum uprooted force on cassava storage root is depth of root disc,followed by diameter,and finally uprooted speed.The design foundation is provided for uprooted mechanism system of storage root in dig-uproot cassava harvester.