Abstract:

In order to achieve low energy consumption and lightweight simplification of the excavation mechanism for planting machine， this article carried out structural design and parameter optimization for the drill bit. The discrete element method was applied to construct soil model， while the dynamics of the drilling process was simulated by EDEM software. Design-expert software was used to design the response surface method test scheme. Taking the cutting edge angle， helical airfoil lift angle and rotational speed as independent variables， and the resistance moment of drill bit as response value， the regression equation of resistance moment was constructed and the variance analysis was performed. The optimal parameter combination was obtained as follows： cutting edge angle of 32.778°， helical airfoil lift angle of 28.316°， drill bit rotational speed of 160.346 r·min^-1， and under the above parameter combination the resistance moment was 275.137 N·m， with verification error of only 4.38%. Optimization of the drill bit parameters was conducted by ANSYS，and the results showed that there was a 34.39% reduction in weight after optimization. the stress increased by 76.28% with a safety factor of 2.61； the deformation increased by 59.79% which still was below 1 mm. Modal analysis was also carried out on the drill bit after optimization， and the various orders of inherent frequency avoided the main excitation frequency， preventing resonance from occurring. These research results provided references for parameter optimization of the excavation mechanism.

Key words: excavation mechanism, spiral drill bit, discrete element method, response surface methodology, modal analysis

摘要：

为实现植树机挖坑机构的低能耗和轻简化，对钻头进行了结构设计和参数优化。应用离散元法建立土壤模型，通过EDEM软件对钻头钻土过程进行动力学仿真。采用Design-Expert软件进行响应面试验方案设计，以切刀刃角、螺旋翼片升角、转速3个因素为自变量，以钻头受到的阻力矩为响应值，构建阻力矩的回归方程并进行方差分析。得出最优参数组合为：切刀刃角为32.778°、螺旋翼片升角为28.316°、转速为160.346 r·min^-1，以上参数组合下阻力矩为275.137 N·m，通过验证试验得出误差仅4.38%。通过ANSYS对钻头进行参数优化，优化后质量减轻了34.39%，应力增大了76.28%，此时的安全系数为2.61；变形增大了59.79%，但仍小于1 mm。对优化后钻头进行模态分析发现，各阶固有频率均避开了主要激励频率，避免了共振的发生。以上研究结果可为挖坑机构参数优化提供参考。

关键词: 挖坑机构, 螺旋式钻头, 离散元法, 响应面法, 模态分析