共查询到20条相似文献,搜索用时 15 毫秒
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Optimal welding parameters for small-scale resistance spot welding with response surface methodology
In this study, Ti–1Al–1Mn thin foils with thickness of 0.05?mm were welded by small-scale resistance spot welding. Welding current, electrode force and welding time have been changed while other welding parameters remained constant. The welded joints were subjected to tensile shear tests for determining the values of shear force and absorption energy. A quadratic model of response surface methodology based on Box–Behnken design was employed in establishing regression equations between input variables (current, electrode force and time) and output variables (shear force, absorption energy, variance of shear force and variance of absorption energy). The models were satisfied in optimising the welding parameters. Besides, the microstructure analysis on the typical spot welds was also conducted. 相似文献
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《Science & Technology of Welding & Joining》2013,18(2):126-132
AbstractThis study investigated the electrode life and the electrode degradation characteristics during continuous resistance spot welding of aluminium alloy sheets. When a long welding time and dome radius type electrode were used, the electrode life was extended more than that when a short welding time and radius type electrode are used. The electrode tip is considered to degrade by the following mechanism: an Al–Cu alloy layer is formed at the electrode tip during continuous welding, and then it peels off from the electrode tip transferring to the surface of aluminium alloy sheet. Its peeling makes the electrode tip indented and finally the electrode tip flattens with increasing diameter of electrode tip. In order to eliminate the direct contact between electrode and worksheet, a special Cu foil insert device for resistance spot welding of aluminium alloy sheets was developed and an extremely long electrode life was achieved. 相似文献
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提出一种将点焊过程动态电极位移信号转化为二值图像的方法.基于图像特征分析,从焊点样本电极位移二值图像中提取出15个隐含特征.针对一系列对应不同焊接质量焊点样本电极位移二值图像特征,利用主成分分析消除图像特征间的互相关性,建立了基于最小风险贝叶斯图像识别技术的焊点质量分类器.分类器有效性测试结果表明,电极位移信号二值图像尽可能多的保留了焊点质量信息,特征提取算法简单、高效、易于实现;同时在小数据样本情况下,贝叶斯图像识别技术能够快速、准确地评判焊点质量,有较好的应用前景. 相似文献
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《Science & Technology of Welding & Joining》2013,18(8):661-670
AbstractThis work numerically investigates the geometrical effects of the electrode containing a coolant hole on transport variables during resistance spot welding. The model accounts for transient magneto-fluid mechanics, heat and species transport, bulk resistance in workpiece, and film and constriction resistances at contact interfaces. The computed results show that electrode cooling due to the coolant hole influences transport processes during not only freezing and cooling periods but also heating and melting periods. Electrode cooling can be interpreted by thermal resistance, depending on the shapes of the electrode and coolant hole within the growing thermal diffusion layer. Major factors affecting electrode cooling are different in distinct time stages. In most cases, enhanced electrode cooling due to the coolant hole decreases the electrode temperature and nugget growth rate. A decrease in the electrode face radius strongly increases nugget growth rate and workpiece temperature and decreases electrode temperature, whereas its effect on cooling rate is insignificant. The optimum design and sensitivity analysis of the electrode shapes subject to required cooling rate, nugget growth rate and welding time are revealed. 相似文献
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H. J. Zhang F. J. Wang W. G. Gao Y. Y. Hou 《Science & Technology of Welding & Joining》2014,19(3):242-249
To improve the efficiency of acquiring monitored features and present a reliable quality assessment method for resistance spot welding, a novel method for converting the electrode displacement signal into binary image is proposed. The probabilistic neural network is adopted to provide a probabilistic viewpoint and a deterministic classification result of weld quality when the image characteristic of displacement signal is selected as monitored features. Test results of the classifier demonstrate that it is feasible and reliable to utilise binary image of the displacement signal to evaluate weld quality. The method reserves weld quality information as much as possible and it avoids complex algorithm for extracting and selecting monitored features. At the same time, when there are small samples, the classifier can identify good or bad weld rapidly and accurately even though the weld is from abnormal welding process, such as expulsion, current shunting and small edge distance condition. 相似文献
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提出一种将点焊过程动态电极位移信号转化为二值图像的方法.基于图像特征分析,从焊点样本电极位移二值图像中提取出15个隐含特征.针对一系列对应不同焊接质量焊点样本电极位移二值图像特征,利用主成分分析消除图像特征间的互相关性,建立了基于最小风险贝叶斯图像识别技术的焊点质量分类器.分类器有效性测试结果表明,电极位移信号二值图像尽可能多的保留了焊点质量信息,特征提取算法简单、高效、易于实现;同时在小数据样本情况下,贝叶斯图像识别技术能够快速、准确地评判焊点质量,有较好的应用前景. 相似文献
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以采集的电阻点焊接头表面的数字图像作为信息源,探索了一种新的点焊质量无损监测方法.首先,通过图像特征分析,焊点表面图像被划分为4个环形特征区域,提取环形特征区域面积作为表征焊点质量的特征参数.其次,根据特征区域面积与焊点抗剪强度的相关性分析结果,选择了相关性显著的3个特征参数作为输入向量,焊点抗剪强度作为输出向量,建立了点焊质量的RBF神经网络监测模型.仿真分析和验证结果表明,基于焊点表面图像特征信息处理监测点焊质量的方法是可行的. 相似文献
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为了提高镁合金电阻点焊接头的力学性能,采用光学显微镜、激光共聚焦扫描显微镜、x射线衍射仪研究了接头的微观组织和相组成.结果表明,接头主要由熔核和热影响区(HAZ)所构成.熔核一般包括两种不同的组织形态,即熔核边缘的胞状树枝晶和熔核中心的等轴树枝晶.熔核是由大量的α-Mg相和少量的β-Mg17Al12相所组成.相对于未熔化的母材晶粒,热影响区晶粒变粗,并伴随晶界熔化.当焊接电流为23 kA,焊接时间为8个周波,电极力为4.5 kN时,熔核边缘的胞状树枝晶细化,而熔核中心的等轴树枝晶有向等轴晶转化的倾向,且平均晶粒尺寸为12.96μm. 相似文献
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Filling technique for keyhole of friction stir spot welding based on the principles of resistance spot welding 下载免费PDF全文
Keyhole at the end of a weld prepared by friction stir welding(FSW) is one of the major issues that impede the application of FSW. To address this issue, a keyhole filling technique was proposed in this paper, which is based on the principles of resistance spot welding(RSW). A three-phase secondary rectifier resistance spot welder was applied as the experimental instrument for filling the keyhole in the center of friction stir spot weld(FSSW). The test sheet is a 2024-T4 aluminium alloy with a thickness of 6.0 mm. The experiments results show that the filled joint strength is improved by 26.12% since the area is increased for the plug in the keyhole. And there are two kinds of dimples in the tensile fracture—equiaxial dimples and long dimples. The filled joint involves the fusion welding zone(FWZ), pressure welding zone(PWZ), melted plug zone(MPZ), and plastic deformation zone(PDZ). The FWZ and the PWZ is the melting bond and diffusion bond between the plug and keyhole, respectively. The MPZ is the center part and the PDZ is upper or lower part of the plug. 相似文献
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热镀锌低碳钢板在车身内外板上获得了广泛应用.在传统的气动焊枪作用下,采用恒定的电极力焊接时,点焊质量不稳定.然而变电极力对镀锌钢板电阻点焊质量的影响很大.因此利用伺服焊枪能够精确控制电极力的特点,运用正交试验设计方法,深入分析了点焊过程中三个阶段电极力,即预压力、焊接力和锻压力对点焊质量的影响,得到了最优的变电极力参数.结果表明,点焊过程中的锻压力是影响点焊质量的重要因素,其次是焊接力,而预压力是最次要因素;最优的变电极力参数能够明显提高热镀锌低碳钢板的焊点拉剪力和熔核直径,这为基于电极力检测的点焊质量实时评价和电极力控制方面的研究奠定了基础. 相似文献
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《Science & Technology of Welding & Joining》2013,18(2):140-145
AbstractElectrode displacement has been used to monitor resistance spot weld quality for long, but the fluctuation of the electrode displacement has not been well studied. This paper analysed the mechanism of the displacement fluctuation by collecting the welding current and electrode displacement during welding process and extracted the incremental pulse expansion of the electrode displacement, which was named as the displacement fluctuation peak. Through metallurgical experiments, the relationship of the displacement fluctuation peak with the weld nugget growth during resistance spot welding process was analysed. The whole process can be divided into four successive stages, and five characteristic points of the displacement fluctuation peak curve were selected to online predict the weld quality. The variation in the displacement fluctuation peak curve under different welding currents was studied, and the results showed that the displacement fluctuation characteristics can be used to effectively evaluate the weld quality. 相似文献
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The end value of the dynamic resistance curve of stainless steel was proved to have strong correlation with nugget size by experiments, so it was an important factor for estimation of weld quality. BP neural network was employed to estimate the weld quality. The end value of the dynamic resistance curve, welding current and welding time were selected as the input variables while the nugget diameter, which is closely related to weld quality, was selected as the output variable. Testing results shows that such network has fine fault tolerance and real-time quality estimation is possible. 相似文献
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通过对电阻点焊过程电极位移和动态电阻信号的实时采集和时域特征分析,利用电阻信号动态特征刻画熔核形成不同阶段,从同步电极位移信号中提取9个特征参量建立输入样本数据集.以焊点接头抗剪强度作为焊点质量的评价指标,将PCA(主成分分析)方法与传统的SVM(支持向量机)回归分析相结合,利用PCA方法对支持向量机的输入样本数据集进行主成分分析,消除了输入特征参量间的自相关性,实现数据降维后作为支持向量机的输入,建立焊点质量映射模型.交叉有效性预测结果表明,基于PCA-SVM的算法增强了SVM的泛化能力,比传统的SVM算法具有更高的预测精度. 相似文献
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Cr-Zr-Cu alloy electrodes for resistance spot welding of aluminiam alloy are treated by deep cryogenic treatment processes.The Cr-Zr-Cu alloy electrodes are analyzed by transmission electron microscope(TEM),and results show that the common dislocation in Cr-Zr-Cu alloy electrodes is changed into the dislocation loop,and twin crystal is found after deep cryogenic treatment.The parallel twin crystal band is observed by selected electron diffraction(SED)and the twin crystal plane is marked as(111).The Cr-Zr-Cu alloy electrode is studied by X-ray diffraction(XRD)and results show that the intensity of diffraction peak is obviously changed after deep cryogenic treatment,and the grain rotates to preferred orientation.The Cr-Zr Cu alloy electrode is studied by positron annihilation technique(PAT)and results indicate that the amount of vacancy defects is less than that of Cr-Zr-Cu alloy before deep crybgenic treatment.The main elements in Cr-Zr-Cu alloy are studied with X ray photoelctron spectroscopy(XPS)and the intensity of spectrum peak is increased after deep cryogenic treatment. 相似文献