预压紧力对叠层结构制孔层间间隙的影响

为研究预压紧力对叠层结构制孔层间间隙的影响，本文首先采用板壳理论建立叠层结构制孔简化模型；进而运用有限元方法，分析了预压紧力对叠层结构制孔层间间隙的影响，并以单层板的受力响应模型进行结果比对以验证模型正确，进而分析了不同工艺条件下，叠层结构层间间隙的变化规律；最后通过叠层结构钻削试验验证了限元分析结果的正确性.研究结果表明，随着单向预压紧力的逐渐增大，叠层板会经历层间间隙逐渐减小到贴合的过程，其转折点对应着预压紧力的临界值.加工过程中欲达到良好的毛刺抑制效果，预压紧力需满足以下两个条件：Ⅰ)转折点对应的层间间隙DB需小于未施加预压紧力情况下的层间毛刺高度；Ⅱ)其值需高于临界预压紧力FB.此外，减小制孔轴向力或预压紧环直径可有效降低临界预压紧力及对应层间间隙；从提高预压紧力作用效果，减小层间间隙的角度考虑，叠层结构制孔时应将尺寸较厚、模量较高的板材置于叠层结构下层.
To examine the effect of clamping force on the inter-layer gap formed in stacked material drilling, firstly, the drilling deformation state of stacked plates with clamping force was analyzed using elastic shell theory. Further, by finite element method, the drilling deformation model with clamping force was established in consideration of interface contact condition. The accuracy of model was verified by comparing with experimental results of single-plate deformation. Then, the changing process of inter-layer gap was analyzed under different drilling conditions. At last, the experiment was carried out to verify the finite elements analysis results. The results show that, with the increase of clamping force, the inter-layer gap will go through two stages, decreasing rapidly at first and slowly after the turning point. The turning point corresponds to the critical clamping force. To obtain an effective burr height reducing, the following two conditions must be required: Ⅰ) the inter-layer gap DB corresponding to the turning point should be smaller than the drilling burr height without applying the clamping force, Ⅱ) the clamping force should be higher than the critical force FB. Besides, reducing the thrust force, or minimum diameter of the clamping ring can reduce the demand clamping force and inter-layer gap size. To enhance the effects of clamping force and minimize inter-layer gap, the thicker plate and the plate with higher modules should be set as the back plate.