婴幼儿奶粉压缩模型参数标定及受力分析

Parameter Calibration and Stress Analysis of the Compression Model of Infant Milk Powder

为研究块状奶粉压缩过程中的受力状态,本试验以市售婴幼儿配方奶粉为对象,休止角试验为基础,利用EDEM软件依次根据Plackett-Burman试验、最陡爬坡试验和Box-Behnken试验,研究粉体颗粒接触参数和模拟休止角之间的回归模型,确定最优接触参数,并研究离散元压缩仿真模型中块状奶粉压缩量变化趋势、表面颗粒与上冲模接触力链分布、断面颗粒间接触力链分布。结果表明,奶粉颗粒间的静摩擦系数为0.359,奶粉颗粒间的滚动摩擦系数为0.099,奶粉颗粒-不锈钢静摩擦系数为0.125。块状奶粉的仿真压缩量与真实压缩量变化趋势基本一致,表明非线性粘结弹性塑形接触(EEPA)模型能够较好地模拟奶粉压缩过程。当压力达到2500 N时,块状奶粉表层颗粒由于无法分载压力产生破碎的可能性高,并且具有由表及里的破碎趋势,与对块状奶粉抗压强度分析结果一致,该离散元压缩模型可以较好地表征奶粉压缩过程中的受力情况。本研究结果为块状奶粉制备工艺参数选择提供了理论依据。

In order to scrutinize the state of stress during compression bulk milk powder,commercially available infant formula was used as a simulation object.Based on the resting angle,regression model between the powder particle and the simulated resting angle was studied to assess the optimal contact parameter by designing diverse parameters with different combination by using the Plackett-Burman test,the steepest climbing test and the Box-Behnken test.Furthermore,the change trend of compression volume of bulk milk powder,contact force chain distribution between surface particles and upper impact dye,and contact force chain distribution between section particles were assessed.The results demonstrated that static friction coefficient between the milk powder particles was 0.359,the rolling friction coefficient was 0.099,and the milk powder particle-stainless steel static friction coefficient was 0.125.The simulated compression trend of bulk milk powder was basically consistent with the real compression trend of change,indicating that the Edinburgh Elasto-Plastic Adhesion(EEPA)contact model could well simulate the compression process of milk powder.When the pressure reaches 2500 N,the surface particles of bulk milk powder were highly likely to break due to the undivided load pressure and had a crushing trend from the surface to the inside.It was constant with the analysis results of the compressive strength of bulk milk powder.The compression model could well represent the stress in the compression process of milk powder.The results of this study provides a theoretical basis for selecting process parameters for bulk milk powder.