马铃薯跌落碰撞时的接触应力分布特性

    Distribution characteristics of potato contact stress during the drop impact

    • 摘要:
      目的  研究马铃薯跌落碰撞时的损伤原理。
      方法  采用Prescale感压胶片和高速摄像技术测量在不同跌落高度马铃薯与5种材料碰撞时的接触应力分布特性和规律,确定马铃薯损伤和接触应力分布的关系。
      结果  正交试验的响应曲面分析表明,碰撞材料、跌落高度、马铃薯质量对马铃薯碰撞的冲击压缩变形量影响显著,且影响程度由大到小为碰撞材料>跌落高度>马铃薯质量。研究结果发现,碰撞材料为65Mn钢、跌落高度为300 mm时,马铃薯开始出现损伤,碰撞材料为塑料ABS、土块、马铃薯和丁晴橡胶、跌落高度为400 mm时,马铃薯开始出现损伤。跌落高度200~800 mm,接触应力≤0.50 MPa占主要的接触面积,对马铃薯的损伤起主要贡献作用。马铃薯与不同材料碰撞在跌落高度<400 mm (65Mn钢<300 mm)时,接触应力≤0.20 MPa的区域占主要的接触面积,在跌落高度≥400 mm (65Mn钢≥300 mm)后,接触应力(0.20,0.60 MPa的区域为主要接触面积,0.20 MPa为马铃薯跌落碰撞损伤的临界应力。跌落高度与接触面积呈高度线性正相关,决定系数(R2)均大于0.95。接触应力和接触面积的乘积(碰撞冲击力)与冲击压缩变形量呈高度线性相关,R2大于0.96。
      结论  建立的马铃薯碰撞损伤的线性回归模型能够准确预测和评估马铃薯跌落碰撞损伤。

       

      Abstract:
      Objective  To explore the damage principle of potato under drop impact.
      Method  Prescale sensitive film and high speed photogrammetry were used to characterize the contact stress distribution of potato when it collided with five types of materials and dropped from different heights. The relationship between potato damage and contact stress distribution was determined by studying the distribution law of contact stress in potato.
      Result  The response surface analysis of combination orthogonal test for potato showed that collision material, dropping height and potato mass had significant influences on the impact compression deformation amount of potato collision. The influence degree in order was collision material>dropping height>potato mass. When colliding with 65Mn steel, the potato had damage at the dropping height of 300 mm. When colliding with plastic ABS, clods, potatoes and nitrile rubber, the potato had damage at the dropping height of 400 mm. At the dropping height of 200−800 mm, the major contact area was under the contact stress of 0.01−0.50 MPa, which played a major role in potato damage. At the dropping height of <300 mm for 65Mn steel and <400 mm for other collision materials, the major contact area was under the contact stress of ≤0.20 MPa. At the dropping height of ≥300 mm for 65Mn steel and ≥400 mm for other collision materials, the major contact area was under the contact stress of (0.20, 0.60 MPa. The critical stress causing damage of potato was 0.20 MPa under drop impact. Dropping height and contact area showed a highly linear positive correlation, with the determination coefficient (R2) above 0.95. Impact force was the product of contact stress and contact area, which had highly linear correlation with impact compression deformation, and R2 was above 0.96.
      Conclusion  The constructed linear regression model can accurately predict and evaluate damage of potato under drop impact.

       

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