异种材质自冲铆接接头成形质量研究

以汽车零/部件常用材质双相钢和铝合金的自冲铆接接头为研究对象,采用Simufact.forming有限元模拟仿真软件建立双相钢DP600和铝合金AA6061的自冲铆模型,按基板的不同叠放顺序和铆钉规格进行自冲铆接数值模拟。通过分析铆接接头的钉头高度等参数,找出了铆钉长度和基板的叠放顺序对上下2种叠层材料自冲铆接过程及接头连接质量的影响规律。结果表明:DP600和AA6061为基板的自冲铆接模拟仿真试验中,铆钉长度为6.0 mm时的连接质量最优;铆钉相同而基板叠放顺序互换时,上层为DP600和下层为AA6061的铆接接头质量优于基板叠放顺序互换的铆接接头质量;铆钉长度在一定范围内增大可提高自冲铆接接头的自锁性能,提升自冲铆接接头的质量。     

泡沫镍夹层结构自冲铆接头的成形特征及失效机理分析

为揭示泡沫镍夹层结构自冲铆接头的成形特征及失效机理,本文制备了以AA5052铝合金为基板,泡沫镍为夹层的自冲铆接头;采用理论分析与微观组织观察相结合的方法对夹层结构接头成形特征进行系统研究,通过拉伸-剪切试验研究接头的静失效载荷及失效位移,探究了接头的失效机理。结果表明:泡沫镍夹层可增大接头的钉脚张开度,并改善应力分布;铆接过程中泡沫镍能在铆接界面间形成牢固的自润滑物理吸附膜,可提高接头的耐腐蚀性;1mm泡沫镍夹层使接头静失效载荷增加了8.9%;随着泡沫镍夹层厚度的增加,接头的抗拉强度呈降低趋势;泡沫镍夹层结构自冲铆接头的失效模式为铆钉脱离下板,上板主要承受拉伸载荷,下板承受压缩载荷。     

铝板无铆钉自冲铆接质量及强度的试验研究

由于具有传统点焊连接无法替代的优势,无铆钉自冲铆接技术在汽车、家电等行业中得到了较广泛的应用.铆接接头的质量及强度是人们关注的热点问题,而铆接工艺参数和模具结构参数是影响接头质量和强度的主要因素.通过对同种铝板件L5在不同的压边力及模具结构参数下的无铆钉自冲铆接的试验研究,分析这些参数对铆接接头的失效形式、断面质量和剪切强度的影响规律.研究结果表明:接头剪切时的主要失效形式是剪断;合理的铆接工艺参数及模具结构参数可以得到比较理想的接头断面质量及较高的接头剪切强度.     

模具工艺参数对自冲铆接工艺过程及铆接质量的影响

通过对6063铝合金板料自冲铆接过程的实验和数值模拟,分析了自冲铆接工艺过程中半空心铆钉和板料的变形和受力.对比研究了铆接过程中铆钉载荷与位移的关系曲线,探讨了模具的深度、模具凸台高度和模具圆角半径对铆接质量的影响.研究表明,计算机模拟与实验结果吻合良好,自冲铆接工艺参数的探讨为提高铆接质量提供了理论依据.     

自冲铆接质量无损监测技术进展

自冲铆接的工艺特点决定了铆接质量受到板材、铆钉等多种因素的影响,需要采用合理的缺陷分析与监测方法。文章系统的概述了自冲铆接接头质量无损监测技术,并对比和评价各项技术的优缺点、应用现状和研究进展,为自冲铆接工艺的研究和发展提供借鉴。     

铝合金与静音钢异种材料匹配无铆钉铆接成形特性

无铆钉铆接以其无热入、自动化程度高等优势成为异种材料连接的重要手段之一,已在汽车工业得到广泛应用。通过实验方法,研究了铝合金与静音钢这一特殊异种材料匹配的无铆钉铆接接头成形机理。结合成形过程力-位移曲线和接头各阶段断面宏观形貌,将无铆钉铆接接头成形过程分为三个阶段,并具体分析了接头形貌特征的演化规律,得到了特定模具匹配下的最优压入深度参数。通过不同模具匹配实验,研究了凸模铆头直径和凹模沉孔深度对接头几何形貌的影响规律,为工艺优化提供借鉴。     

自冲铆接工艺参数对接头性能影响的研究

随着新能源汽车车身轻量化的发展,铝合金复合材料在车身上逐渐被采用。由于传统焊接不适用于铝合金材料的连接,自冲铆接技术在全铝车身上的应用得到了重视。自冲铆接技术是一种冷连接技术,多片材料无需预先穿孔即可连接在一起。因此,研究自冲铆接工艺的接头性能和质量对车身轻量化有着重要的意义。基于国内外自冲铆接技术的发展现状,综合评述了接头性能的评价参数,归纳了铆钉、凹模、冲头和板料工艺参数对接头性能影响的特点,分析了其关键作用和优先程度,可用于指导自冲铆接技术工艺的开发过程。此外,通过对国外根据工艺参数对接头几何性能和抗剪强度进行预测的方法的总结,分析了国内与国外在强度预测方面存在的差距,提出了我国自冲铆接技术进一步研究的方向。     

SPFC440钢/5052铝自冲铆接头与胶铆复合接头腐蚀性能对比

为研究SPFC440钢与5052铝合金自冲铆接头的腐蚀性能,分别制备了自冲铆接和胶铆复合两种接头。通过对不同腐蚀时长下的两种接头试样进行疲劳性能测试,分析了粘胶剂对铆接接头腐蚀疲劳性能的影响,并对疲劳断口、裂纹扩展进行SEM和EDS检测。结果表明：粘胶剂的存在不仅提高了接头强度,还保护了金属界面,减小了电偶腐蚀的影响;随着腐蚀时间的增长,复合接头的最大静载荷值不断减小,自冲铆接接头最大静载荷先增大后减小;复合接头的拉伸失效模式与自冲铆接接头的失效形式相似;自冲铆接接头的疲劳裂纹主要集中在下板料的铆钉周围,复合接头主要为下基板的断裂;铆钉与下板相互接触区域以及两板间接触面出现了严重微动磨损。     

基于神经网络无铆钉自冲铆接头力学性能预测

为研究钢铝一体化结构车身无铆钉自冲铆接接头力学性能,引入反向传播神经网络模型来描述板材厚度、板材硬度和成形接头底部直径等工艺参数与接头剪切力及剥离力强度等力学性能的映射关系.由于标准反向传播网络存在训练精度低、收敛速度慢及泛化能力差等缺陷,采用归一化法与Levenberg-Marquardt算法相结合的算法来优化神经网络预测模型连接权值,提高了神经网络模型的预测精度和泛化能力.对神经网络的预测结果进行检验的结果表明,训练后的神经网络模型能够准确有效地预测无铆钉自冲铆接接头力学性能,证实了神经元网络应用于无铆钉自冲铆接接头力学性能预测的可行性与可靠性,为优质的钢与铝无铆钉自冲铆接接头的设计提供了依据.     

平点自冲铆接过程的数值模拟分析

为研究平点自冲铆接过程,以两层厚度均为1mm的铝板AL-1100以及材质结构为合金结构钢DIN 14NiCr14的半空心铆钉为研究对象,借助于有限元分析软件Deform-2D进行数值模拟并得到强度合适的接头以及冲头载荷随位移变化的曲线;选取接头自锁量和底部最小厚度作为评价指标,研究了不同铆钉高度对接头的影响。结果表明:平点自冲铆接技术是可行的;铆钉腿部的变形是引起冲头载荷迅速增加的主要因素;随着铆钉高度的增加,两个评价指标的变化曲线几乎呈线性关系。     

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...     

高速透平机械轴位移故障自愈调控系统研究

在机器故障停机前能做些什么?机器故障可否在运行中自行消除?本文对轴位移故障自愈调控系统做了研究。这套系统是通过调整平衡盘两侧的压力差来调整高速透平机械转子的残余轴向力。首先总结了轴位移故障的特征和导致故障的直接原因,将它们和可倾瓦止推轴承的性能相结合,组成一故障诊断专家系统。接着,通过在线实时检测机器的轴位移、轴向力以及轴承温度,由专家系统决定是否需要故障自愈调控系统。最后介绍了关于该自愈调控系统的试验设备。     

Modeling small-scale resistance spot welding machine dynamics for process control

Electrode displacement is generally regarded as a variable that can provide real-time information useful for monitoring and controlling resistance spot welding (RSW) process quality. However, in small-scale RSW production, it is difficult to measure the displacement because its magnitude is very small. By contrast, force signals are relatively large and thus are less susceptible to measurement noise. In this article, an empirical model is proposed to simulate the dynamics of an SSRSW head with the objective of calculating electrode displacement from the variation of electrode clamping force measured during welding. The parameters in the model were determined by fitting experimental force and displacement signals with polynomials and then performing an optimization search for parameters of first-order dynamic models. To verify the models’ accuracy, they were subsequently applied to simulate the electrode displacement curves of welds with expulsion and without expulsion. The calculated displacement curves agreed well with experimental measurements, and the occurrence of expulsion was clearly indicated by the model predictions. A more comprehensive model is under construction with an objective to eliminate displacement sensor in the monitoring and control of SSRSW process.     

一种钛合金热铆机的研制

根据电阻加热原理,研制开发了一种钛合金热铆机,并进行了热铆性能测试。研究表明,该钛合金热铆机性能稳定,安全可靠,操作方便,实现了钛合金铆钉的快速热铆,提高了铆接质量。     

摆碾铆接过程数值模拟分析

应用DEFORM-3D有限元分析软件建立碾压铆接有限元模型,对摆碾铆接工艺过程进行数值模拟。分析了其成形过程的三个阶段、应力应变和行程载荷曲线的变化趋势,结果表明最大应力应变都集中在铆钉头部边缘区,边缘区点最先受到旋压力开始变形,最早发生屈服现象并进入弹塑性变形阶段;铆钉在相同行程下达到相同的成形效果时,碾压铆接需要的载荷要远远低于传统铆接的载荷。最后分析了影响碾压铆接质量的几个核心因素,如铆头速度、铆头倾斜角度等,为有效地进行碾压铆接工艺研究提了供理论依据。     

基于几何法的管道焊缝扫查七关节机器人逆运动学分析

设计了一种在线夹持式的相贯线扫查冗余机器人,可用于核工业插接管道焊缝的超声探伤。对该机器人进行了运动学分析,通过几何法和D-H矩阵变换求解了机器人关节空间内的逆运动学问题,得到了任务空间中基于管道扫查特征参数的关节变量表达式,为相贯线扫描路径参数的在线优化提供了设计途径。分析结果和方法可普遍适用于插接管道在线作业机器人的轨迹规划。     

Active magnetic bearings used as exciters for rolling element bearing outer race defect diagnosis

The active health monitoring of rotordynamic systems in the presence of bearing outer race defect is considered in this paper. The shaft is assumed to be supported by conventional mechanical bearings and an active magnetic bearing (AMB) is used in the mid of the shaft location as an exciter to apply electromagnetic force to the system. We investigate a nonlinear bearing-pedestal system model with the outer race defect under the electromagnetic force. The nonlinear differential equations are integrated using the fourth-order Runge–Kutta algorithm. The simulation and experimental results show that the characteristic signal of outer race incipient defect is significantly amplified under the electromagnetic force through the AMBs, which is helpful to improve the diagnosis accuracy of rolling element bearing׳s incipient outer race defect.     

An experimental study of contact pressure distribution in panel stamping operations

This paper presents an analysis of the dynamic contact pressure distribution at the sheet metal-tooling interface in normal and defective panel stamping operations. Specifically, the stamping of a 1.27?×?20?×?15?cm rectangular aluminum alloy panel has been simulated using finite-element modeling methods. The modeling results are leveraged to determine the forces acting on sensors embedded in the die structure. Based on these results, a customized stamping test bed has been designed, which incorporates an array of force sensors embedded into the stamping die to enable online measurement of the forces in the die. The force measurements are processed by the thin plate spline numeric surface interpolation method to evaluate a continuous contact pressure distribution map of the die cavity. The pressure distribution in the die cavity in normal and defective scenarios has been presented along with a suggested volume thresholding method for automated defect detection. By leveraging the numeric surface generation method to analyze experimental data, the present study establishes the basis for intelligent tooling and in-process monitoring for improved observability in sheet metal stamping.     

Quality monitoring based on dynamic resistance and principal component analysis in small scale resistance spot welding process

The present study aims at solving weld quality monitoring problem in small scale resistance spot welding of titanium alloy. Typical dynamic resistance curves were divided into several stages based on the weld nugget formation process. A smaller electrode force or lower welding current was found to promote the initial resistance peak. The bulk material heating stage could not be detected under very high welding current condition. Electrode force effect on dynamic resistance and failure load was much smaller than that of welding current. Principal component analysis was made on discrete dynamic resistance values. The first principal component was selected as independent variable in regression analysis for quality estimation. A back propagation neural network model was then proposed to simultaneously predict the nugget size and failure load. The electrode force, welding current, welding time, and first five principal components were designed as network inputs. Effectiveness of the developed model was validated through data training, testing, and validation. The realtime and online quality monitoring purpose could be realized.     

迈步式超前支护过渡过程的支撑力控制策略

为解决迈步式超前支护过渡过程支撑力波动问题,提高支护效率,采用先进的电液比例控制技术,结合阀控缸的理论基础,提出通过调节比例换向阀阀芯位移来控制超前支护支撑力的控制策略。基于超前支护的机电液系统,建立控制系统的数学模型及仿真模型,利用AMESim软件对系统进行仿真,分析不同阀芯位移控制曲线在升架和降架过程中对支撑力的控制效果。结果表明,基于体积增量原理的阀芯位移控制曲线符合实际工况要求。结合对样机的实验研究,对比分析了实验与仿真的控制规律,结果验证了所提出控制策略的合理性。