磨介球对小麦麸皮振动冲击破碎性能的影响

The influence of grinding ball on the vibration-impact crushing properties of wheat bran

充分考虑振动磨机磨介球在磨筒内的运动形态,根据相似原理提出了“磨介-小麦麸皮-磨介”双边冲击计算模型,克服了单边冲击计算模型无法模拟冲击剪切的不足,同时给出了该模型的材料参数以及利用该模型进行有限元数值模拟计算的求解设置。在此基础上,针对影响小麦麸皮破碎性能的运动特性、质量特性以及破碎形式等因素,利用LS-DYNA进行了有限元数值模拟计算。计算结果表明:磨介球对小麦麸皮破碎性能的影响是显著的。在运动特性方面,磨介球冲击速度越大,麸皮破碎性能越好;磨介球冲击角越大,麸皮破碎性能越差。在质量特性方面,磨介球密度越大,麸皮破碎性能越好;磨介球直径越大,接触力越大,麸皮接触区域也越大,但接触次数会降低。在破碎形式方面,冲击剪切与冲击挤压产生的接触力、接触时间、接触面积的差异较小,但冲击挤压引起的麸皮中心单元有效塑形应变大于冲击剪切;对于大尺寸麸皮应以冲击挤压为主要破碎形式,对于小尺寸麸皮应以冲击剪切为主要破碎形式。以上研究初步探明了磨介球对麸皮破碎性能的影响规律,为全面探索振动磨机物料破碎性能的影响规律提供了一条新途径。

On the basis of fully considering the movement modes of the grinding ball in a vibration mill grinding tube,a bilateral impact calculation model named"grinding medium-wheat bran-grinding medium"was proposed based on the similarity principle.This model overcomes the shortage of the single side impact calculation model which can not simulate impact shear.At the same time,the material parameters of the model and the solution setting of the finite element simulation calculation were given.On this basis,the finite element numerical simulation was carried out on the movement characteristics,quality characteristics and crushing forms of wheat bran breaking properties by using the LS-DYNA.The results show that the effect of milling medium on the crushing properties of wheat bran is significant.In terms of the motion characteristics,the higher the impact speed of the grinding ball,the better the crushing performance of wheat bran.However,the greater the impact angles of the grinding ball,the worse the crushing performance of wheat bran.In terms of quality characteristics,the greater the density parameters of the grinding ball,the better the crushing performance of wheat bran;the greater the diameter of the ball,the greater the contact force;the greater the contact area of the wheat bran,but the contact number will be reduced.In the aspect of crushing form,the difference between impact shear and impact extrusion in contact force,contact time and contact area is small,but the effective plastic strain of bran center unit caused by impact extrusion is greater than that of impact shear.For large size bran,impact extrusion should be applied as the main form of crushing;and for small size bran,impact shear should be used.The above research preliminarily found out the effect of grinding ball on the crushing performance of wheat bran,and provided a new way to explore the influence law of material crushing performance of vibration mill comprehensively.