基于HyperMesh和LS-DYNA的玉米籽粒碰撞损伤动态过程的有限元分析  

Finite element analysis of dynamic impact damage process of maize kernel based on HyperMesh and LS-DYNA

作　　者：王博 王俊[1] 杜冬冬[1] WANG Bo;WANG Jun;DU Dongdong(College of Biosystems Engineering and Food Science,Zhejiang University,Hangzhou 310058,China)

机构地区：[1]浙江大学生物系统工程与食品科学学院,杭州310058

出　　处：《浙江大学学报（农业与生命科学版）》2018年第4期465-475,共11页Journal of Zhejiang University:Agriculture and Life Sciences

基　　金：国家重点研发计划(2016YFD070190402)

摘　　要：为了明确玉米在籽粒收获过程中的碰撞损伤机制,寻求较小损伤的收获方式,利用三维扫描技术逆向建立玉米籽粒的三维实体模型,通过基于Hyper Mesh和LS-DYNA的籽粒碰撞有限元分析,研究在不同含水率(11.78%、17.63%、23.45%、29.31%、34.73%)、不同碰撞速度(4、6、8、10、12 m/s)下籽粒损伤动态过程,量化在不同因素水平下的碰撞过程中接触力、Von Mises应力和变形的变化,以确定在不同含水率下籽粒的损伤临界速度;提取关键的数字和图像结果,利用回归分析和响应曲面分析研究单因子及交互效应对响应值的影响规律;结合非线性多目标优化的计算方法,对碰撞参数进行优化计算,以验证所建立的回归模型的合理性。结果表明:玉米籽粒在碰撞时,应力由较小的接触区域向四周扩散,最大接触力、最大Von Mises应力随含水率的增大而减小,随碰撞速度的增大而增大,最大变形则相反;籽粒在含水率为11.78%、17.63%、23.45%、29.31%、34.73%时的临界损伤速度分别为5.51、6.75、8.15、9.36、10.57 m/s;建立的预测模型具有合理的决定系数,最佳碰撞参数组合为含水率26.99%,碰撞速度5.17 m/s,对应的最大接触力为19.30 N,最大应力为40.64 MPa,最大变形为0.73 mm,与实际仿真试验结果的误差小于8%,证明了回归模型的可靠性。This study focuses on exploring the damage susceptibility and the realistic representation of time dependent nonlinear mechanical behaviour of maize kernel under various impact cases with threshing unit.A reverse engineering approach based on three dimensional(3D)scanning technology,finite element method(FEM)-based explicit dynamics simulations and response surface method(RSM)were utilized to investigate contact force,Von Mises stress and displacement characteristics,determine critical velocity of maize kernel.Five moisture contents(11.78%,17.63%,23.45%,29.31%and 34.73%)and five impact velocities(4,6,8,10 and 12 m/s)were considered in the impact simulation scenarios.Useful numerical data and deformation visuals were obtained from the simulation results.These results showed that when impacting,the stress concentrated in the small contact area and spread around and decreased gradually.The maximum contact force,maximum Von Mises stress decreased while maximum displacement increased as the moisture content increased,and the critical velocities of maize kernels with moisture contents of 11.78%,17.63%,23.45%,29.31%and 34.73%were determined as 5.51,6.75,8.15,9.36,10.57 m/s,respectively.In addition,prediction models were successfully established with reasonable coefficient of determination(R2)values.The best parameter combination was obtained through multi-objective optimizing as moisture content of 26.99%with impact velocity of 5.17 m/s,and the corresponding contact force,Von Mises stress and displacement were calculated as 19.30 N,40.64 MPa and 0.73 mm,respectively.Verification checks of the prediction models also indicated that the relative errors between the results of simulation and the empirical model were less than 8%.The above results suggest that these models are reliable to describe the damage susceptibility of the maize kernel for various impact cases.

关 键 词：玉米籽粒 碰撞损伤 逆向工程 有限元分析 临界速度 

分 类 号：S220.1[农业科学—农业机械化工程]