汽车推力杆热铆接质量控制及工艺设计研究进展

近年来,很多学者对重型汽车推力杆的热铆接工艺进行了深入研究,热铆接质量的精确控制以及推力杆铆接工艺则成为了研究的重要课题。为了便于今后研究者工作的开展,本文总结了重型汽车推力杆铆接过程中对铆接工艺参数以及质量控制方面的发展,并指出了今后的研究方向。     

定位桥触点自动铆接工艺与模具设计

通过对电触点铆接方法的工艺改进,制定了定位桥组件的生产工艺及电触点的送进方案,实现了电触点在精密多工位级进模内的自动送入及其与冲制件的装配、铆接。     

DMAIC流程在AC-pin铆接质量改进中的应用

通过对C企业AC-pin铆接过程系统实施六西格玛DMAIC流程来提高AC-pin铆接质量。首先,对问题进行定义,明确项目的改进范围和改进目标。接着,分析AC-pin铆接过程的主要缺陷类型,并对相关测量系统进行评价与改进。在此基础上,进一步分析导致AC-pin铆接缺陷的根本原因,并确定相应的改进方案,使AC-pin铆接缺陷由先前的7000ppm降到500ppm以下,同时产量得到显著提高。最后,对关键质量特性建立相应的控制方案和纠偏措施,以使改进成果得以保持。DMAIC流程在AC-pin铆接质量改进中的成功应用有助于促进六西格玛管理在我国企业的有效实施,提升企业的质量管理水平。     

Comparing mechanical behaviour of aluminium welds produced by laser beam welding (LBW), friction stir welding (FSW), and riveting for aeronautical structures

Three welding processes for aluminium parts have been considered for aircraft fabrication: riveting, friction stir welding (FSW) and laser beam welding (LBW). These processes have advantages and threats, which were analysed in the present work focusing on T-pull and Hoop tensile properties. Concerning T-pull tests, LBW coupons presented higher ability to withstand the applied loads. This was due to the better distribution of loads when the strain is done in the stringer direction. In the case of the Hoop tests, which stress only the skin, the results obtained after FSW were notably higher in terms of ultimate tensile stress, yield stress and maximum strain. It was concluded that both LBW and FSW could replace riveting usually applied for commercial aircraft manufacturing.     

浮动悬臂式折边扣缝模设计

介绍了全自动洗衣机不锈钢内桶成形工艺 ,将折边、扣缝二道工序在1副模具内完成 ,可节省模具费用     

Prediction of Cross-Tension Strength of Self-Piercing Riveted Joints Using Finite Element Simulation and XGBoost Algorithm

Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of researchers.In this work,a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element(FE)simulation and extreme gradient boosting decision tree(XGBoost)algorithm.An FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR joints.The residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints,and cross-tension strengths from FE simulation show a good consistence with the experiment result.Based on the verified FE model,the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints,which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR joints.Results show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regres-sion model with a respective error less than 7.6％ compared to experimental values.     

铝合金自冲铆成形过程最大冲压载荷的反演模型

基于材料塑性变形虚功原理并结合上限定理,展开自冲铆成形过程最大冲压载荷的反演分析。以成形接头几何特征参数(钉脚张开度、铆钉几何尺寸参数、被连接材料的厚度)、铆钉和被连接材料力学性能参数以及冲头与铆钉的接触面接触条件为反演计算模型的控制量,建立最大冲压载荷的反演计算模型;同时,针对多种铝合金自冲铆成形开展最大冲压载荷的验证试验研究。结果表明：所建立的反演模型计算值与试验值的平均误差为7.82%,验证了最大冲压载荷反演计算模型的有效性;最大冲压载荷与铆钉的强度、长度成正比,与铆钉内腔深度成反比,为获得静力学性能较优的自冲铆接头应适当增加铆接最大冲压载荷。此外,在相近的最大冲压载荷作用下,较低硬度的被连接材料搭配较低硬度的铆钉,易获得大张开度的接头。     

Ti45Nb铆钉脉冲电流辅助压铆成形性能分析

为改善Ti45Nb铆钉紧固飞机碳纤维增强复合材料（CFRP）结构时的连接性能,拓宽普通铆钉的适用紧固范围,降低铆接成本,提高连接强度,引入了脉冲电流来辅助压铆。设计了电流前处理辅助铆接试验和同步电流处理辅助铆接试验,围绕两种新工艺及其与常规铆接工艺之间的紧固质量与特性展开了对比研究。测试了不同工艺下铆钉截面的典型硬度,对比观测了铆钉不同区域的微观金相与组织成分,分析了电流导致微观组织差异及元素成分区别的原因,最后评估了不同接头的拉伸强度与破坏行为,测试结果验证了电流辅助铆接工艺的有效性与可行性。     

退火处理对钛合金自冲铆接头疲劳特性的影响

对钛合金自冲铆接头整体进行去应力退火处理,并对热处理前后的接头进行静拉伸及疲劳试验;采用三参数幂函数表达式对热处理前后接头的疲劳试验数据进行拟合,得到热处理前后接头的F-lgN曲线;运用扫描电子显微镜对疲劳失效后接头的铆钉断口进行微观观察,并对比分析去应力退火对接头疲劳特性的影响. 结果表明,铆钉断裂为接头在疲劳试验中的主要失效模式;去应力退火对接头疲劳失效模式有很大影响,使得接头在疲劳试验中的薄弱环节具有由铆钉向基板转变的趋势;去应力退火热处理提高了接头在中等寿命区的疲劳特性,但降低了钛合金自冲铆接头在长寿命区的疲劳特性.     

A Novel Friction Stir Spot Riveting of Al/Cu Dissimilar Materials

In order to eliminate the disadvantages of the keyhole in conventional friction stir spot welding joint and attain the high-strength lap joint of Al/Cu dissimilar metals,a novel welding technique,named as friction stir spot riveting(FSSR),was proposed.A pinless tool and an extra filling stud were employed.The Al/Cu spot joints without keyhole defect were achieved by the FSSR.A Cu anchor-like structure was formed,which greatly increased the mechanical interlocking between the upper Al sheet and lower Cu sheet.The thin intermetallic compounds containing CuAl2 and CuAl at the Al/Cu interface strength-ened the joining interface between the Al sheet and the Cu stud.Increasing rotating velocity increased frictional heat and plastic deformation and then eliminated the interfacial joining defects.The FSSR joint with the maximum tensile shear load of 3.50 kN was achieved at a rotating velocity of 1800 rpm and a dwell time of 20 s,whose fracture path passed through the softened region of upper Al sheet.In summary,the novel FSSR technique has the advantages of strong mechanical interlock-ing and metallurgical bonding between dissimilar materials,thereby attaining the high-strength spot joint.