冷鲜波尔山羊肋骨弯曲破坏离散元参数标定

    Calibration of discrete element parameters for the bending failure on the chilled Boer goat ribs

    • 摘要: 针对羊胴体自动化屠宰中分割等关键环节离散元仿真缺乏准确模型的问题,以冷鲜波尔山羊肋骨为研究对象,基于EDEM仿真软件开展羊肋骨弯曲破坏离散元仿真建模和各参数标定的研究。首先通过单轴压缩试验测量确定羊肋骨的基本本征参数,其中泊松比为0.34,剪切模量为4.52×108 Pa,弹性模量为1.21×109 Pa。基于碰撞、斜面法等摩擦方法及摩擦系数仪分别测定了羊肋骨的骨-骨、骨-钢的碰撞恢复系数、静摩擦系数及滚动摩擦系数。然后结合EDEM的Hertz-Mindlin with bonding(HMB)接触模型进行了羊肋骨弯曲破坏仿真模型构建。经最陡爬坡试验确定了羊肋骨离散元仿真模型的黏结参数范围,运用响应曲面法分析得出羊肋骨颗粒包括法向接触刚度、切向接触刚度、临界法向应力与临界切向应力等4个黏结参数的最优值,分别为7.07×1013 N/m3、6.22×1012 N/m3、1.34×108 Pa和1.87×108 Pa。最后针对建立的羊肋骨弯曲破坏离散元仿真模型开展了5组不同外形尺寸对比试验验证,研究结果表明,仿真破坏力与实测破坏力的相对误差不大于6.49%,平均相对误差为4.19%,本文标定方法正确可行,仿真模型的标定参数准确可靠。本研究结果可为分析羊胴体分割刀具的作业机理进而优化分割刀具设计提供理论依据和方法参考。

       

      Abstract: Large-scale mutton processing is ever-expanding with the increasing demand for meat production. Mechanized carcass segmentation has been one of the key steps to upgrade the mutton industries. Among them, the goat rib has been the main obstacle during segmentation. A scientific and reliable discrete element model of goat rib can be expected to provide both the analysis of mechanized goat carcass segmentation and the optimization of tool parameters. Taking the chilled Boer goat rib as the research object, this study aims to calibrate the discrete element parameters of the bending failure model using EDEM software. Firstly, a series of tests were carried out to determine the profile, density, Poisson’s ratio, and shear modulus of the goat rib. Next, the collision, inclined plane friction and friction coefficient measurement tests were conducted to measure the contact parameters, such as static friction coefficient, rolling friction coefficient, and collision recovery coefficient. The bending failure test of the goat rib was carried out on the texture analyzer to obtain the peak failure force and cutting position, which were the target values of the simulation. According to the actual test conditions, the discrete element model of goat rib was established to simulate the bending failure using Hertz-Mindlin with the bonding model in EDEM software. The path of the steepest ascent was used to determine the optimal parameters, including the optimal value of bonding parameters. A quadratic polynomial regression model was then optimized between the peak failure force and the four bonding parameters using response surface analysis. The optimal combination of four significant influencing factors was also obtained to solve the regression equation. The results illustrated that the normal stiffness per unit area was 7.07×1013 N∙m-1, the shear stiffness per unit area was 6.22×1012 N∙m-1, the critical normal stress was 1.34×108 Pa, and the critical shear stress was 1.87×108 Pa. Finally, the bending failure of five goat ribs was simulated to verify the accuracy and reliability of calibration. The maximum relative error between the simulated and the actual values was less than 6.46%, and the average relative error was 4.19%, indicating the credible calibration. This finding can also provide a theoretical basis for parameter optimization in the mechanized segmentation of goat rib during mutton processing.

       

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