拉丝过程中的缺陷模拟及其在拉拔工艺优化中的应用  

Modeling of the central flaw in wire drawing and its application to processing optimization

作　　者：徐贵娥[1] 孙正华[1] 方峰[2] 李兆霞[1] 蒋建清[2] 

机构地区：[1]东南大学土木工程学院,南京210096 [2]东南大学材料科学与工程系,南京210096

出　　处：《东南大学学报（自然科学版）》2005年第3期409-414,共6页Journal of Southeast University：Natural Science Edition

基　　金：江苏省自然科学基金重点资助项目(BK2001215);国家高技术研究发展计划(863计划)资助项目(2003AA331030);江苏省科技攻关资助项目(BE2003027).

摘　　要：模拟了无缺陷时盘条在高形变区的应力场分布,说明了芯部人字形裂纹形成的机理.然后针对芯部圆盘状裂纹提出轴对称计算模型,基于此计算模型研究模具顶角、摩擦系数等工艺参数对形变区内裂纹尖端应力场分布的影响,得出随着拉丝模具顶角的增大和摩擦系数的减小,裂纹尖端应力集中区域与拉丝轴之间的夹角变小,即形成笔尖状断口的斜角变大,笔尖变得更细长.最后定量研究了模具顶角、摩擦系数、裂纹尺寸对J积分的影响.结果表明:随着裂纹尺寸的增加、模具顶角的增大和摩擦系数的增大,J积分值随之增大;在摩擦系数为0.1时,对于相同尺寸的裂纹,J积分值随着模具顶角的减小而减小,当达到模具顶角8°后,J积分值变化较小,趋于一定值.研究结果应用于拉丝工艺优化,为进一步改进工艺提出了指导性建议.Mechanism of central flaw generation is illuminated by modeling the stress distribution in heavy deformation zone of a wire without defect. An axisymmetrical numerical model is proposed on the basis of the assumption of the central axisymmetrical flaw, and the effects of parameters (die angle and friction coefficient etc.) on the stress field near the crack tip during the wire deformation are analyzed with the developed axisymmetrical finite element model. It can be concluded that the angle between the stress singularity zone near the crack tip and steel central-line decreases (i.e. a greater gradient of the nibbed pencil fracture and a longer neb) with increasing die angle and decreasing friction coefficient. The quantitative analysis of the effects of die angle, friction coefficient and flaw size on J-integral value is carried out by the calculation with ANSYS. It is shown that: J-integral value increases with increasing die angle, friction coefficient and the initial dimension of the flaw. When friction coefficient equals 0.1, J-integral value round the crack tip with the same flaw decreases with decreasing die angle, J-integral value changes slightly and tends to be a constant value when the angle reaches to 8°. The calculated results are then applied to improve the optimization of the technology for wire drawing.

关 键 词：拉拔 钢丝 人字形裂纹 临界尺寸 J积分值 

分 类 号：TG256[金属学及工艺—铸造]