挖掘机下车架主件顶环面的平面度

挖掘机下车架主件(Carbody)是由多条空间分布的焊缝连接而成的焊接结构，为保证装配，要求焊后顶环面的平面度小于0．5mm。作者用残余塑变法对下车架主件进行了焊接变形的有限元预测，由于大部分焊缝位于结构重心的上方，焊接后，模型整体出现下沉现象。因此从减小焊接变形的角度考虑，交叉焊接底板焊缝和顶板焊缝是合理的。为考虑焊接顺序提出用残余塑变法对影响顶环面平面度的关键环焊缝进行单独计算，结果表明，环焊缝采取交叉分段焊接有利于减小顶环面的平面度。根据预测结果，挖掘机下车架主件顶环面的平面度为0．68mm，很难达到要求的0．5mm。建议可以通过改变环焊缝的焊接顺序或者适当减小焊角尺寸(即减小焊缝收缩量)来降低顶环面的平面度。

Planeness of upper ring surface of nether frame carbody of grab

Residual plastic strain method is applied to the planeness prediction of the upper ring surface of gragb nether frame carbody where welds are distributed in spatial. For most of welds lie on the above of the gravity, the structure is bending toward bottom after welding. It is reasonable welding bottom plate welds and upper plate welds by turns to decrease of the welding deformation. Residual plastic strain method cannot consider the effect of the welding sequences on the welding deformation. But the effect of parts of welds on the structure can be individualy analyzed by residual plastic strain method. Calculation of the main circle welds showed that it is profit for decreasing the plane degree by welding the circle welds in segments and by turns. The predicted plane degree of the upper ring surface of grag nether frame carbody is 0.68 mm. It seems not easy to meet the demand of 0.5 mm. Welding circles in segments or diminishing the size of welds are suggested to decrease the planeess of the upper ring surface.