Papers by Keyword: Nugget Size

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Authors: Zhi Gang Hou, Jun Zhao, Li Qiang Xu, Zhong Guo
Abstract: In order to theoretically simulate the welding process of complex structure with large quantities of welding spots, a simplified method for analyzing a single spot welding should be developed firstly. In this paper, a 2D axisymmetric model of thermoelectric Finite Element Method (FEM) is developed to analyze the transient thermal behavior of Resistance Spot Welding (RSW) process using ANSYS. The determination of the contact resistance at the faying surface is moderately simplified to reduce the calculating time, while the temperature dependent material properties, phase change and convectional boundary conditions are taken into account for the improvement of the calculated accuracy. The thermal history of the whole process and temperature distributions for any position in the weldment is obtained through the analysis. The model can also predict the weld nugget size and the width of the Heat Affected Zone (HAZ).
Authors: Taehyung Kim, Yong Suk Lee, Jonggu Lee, Se Hun Rhee
Authors: Chun Tao Ji, Li Peng Deng
Abstract: The behaviors of electrode displacement and force during spot welding were studied. Tests were conducted on a 170KVA MFDC spot welder. Data were collected via a multi-channel high speed data acquisition system, and were analyzed with MATLAB. Behaviors of 5182 aluminium and mild steel in spot welding were compared. Results showed that nugget expansion rate did not reach zero for aluminium as it did for mild steel as nugget grew to a certain size. An electrode force peak was observed and was believed relevant to sufficient nugget size.
Authors: Prachya Peasura
Abstract: This research was to effect of electrode force on the tensile shear and nugget size of the resistance spot welding. The specimen was austenitic stainless steel 304 grade sheet metal 1.2 mm thickness. The electrode force are 1, 1.5, 2.0, 2.5, and 3.0 kN apply to the specimen. The replications in each treatment are 20 follow JIS Z 3136:1999 and JIS Z 3139:1978. Factor control, welding current 7 kA., time current flow 7 cycle and electrode tip diameter 6 mm. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999, macro structure testing according to JIS Z 3139: 1978 and analysis results by using One-way ANOVA .The result showed that electrode force had affected on tensile shear and nugget size at 95% confidential (P value > 0.05). The low force induced the gab between specimen increasing then the current flow difficult to pass and both of gab between specimen and nugget seize had increase (Q=I2Rt). When the resistance increased so that fusion zone will have a high heating. It had affected to nugget size, heat affected zone and mechanical properties decreasing. The electrode forces are complete 2.5 kN. tensile shear 9.21 kN and nugget size 5.82 mm. The data can be applied to be used as process monitoring of resistance spot weld quality
Authors: Kuang Hung Tseng, Ko Jui Chuang
Abstract: The objective of this work is to investigate the relationship between nugget development and electrode displacement curves during micro RSW of stainless steel sheets. A DC transistor type micro RSW machine equipped with a real-time monitoring system was employed for this study. A laser displacement sensor was used to detect the displacement signals in the movement of upper electrode. This research can provide references for monitoring and control micro RSW quality using maximum electrode displacement. The results showed that electrode displacement increased rapidly at the initial heating stage of welding, and then at a reducing rate under normal cooling stage. The maximum electrode displacement is proportional to the weld current and is inversely proportional to the electrode force. An electrode displacement curve is an ideal monitoring signal can reflect the formation and growth of a nugget during micro RSW.
Authors: Kyung Cho Kim, Roman Gr. Maev
Authors: Chen Yan Xu, Ikuo Ihara, Kohmei Kenzaki, Manabu Takahashi
Abstract: Spot welding is widely used in the various fields of engineering and industries. Since the size, shape and mechanical properties of a nugget which is a zone melted and re-solidified during welding are closely related to the strength of the welded structure, quantitative evaluations of them are strongly required. In this work, an air-coupled ultrasound technique with focused transducers has been used for non-contact measurements of spot welds of steel plates. One-dimensional scanning in transmission configuration using a pair of focused air-coupled ultrasonic transducers operating with tone burst waves at 0.3 MHz is performed to obtain the amplitude profile of the transmitted ultrasound through the nugget area of a spot weld. A simple method for determining the nugget size from the profile of the transmitted ultrasound is proposed. To verify the validity of the method, calibration samples which imitate spot welds having different sizes of nuggets are prepared and used for demonstrating nugget size determinations. In addition, the proposed method has been applied to evaluate several spot welds fabricated with different electric currents (5 kA – 9 kA).
Authors: Prachya Peasura
Abstract: This research was study the effect of resistance spot welding process on physical properties. The specimen was mild steel sheet metal. The experiments with full factorial design. The factors used in this study are welding current, welding time and electrode force. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999 and macro structure testing according to JIS Z 3139: 1978. The result showed that both of welding current, welding time and electrode force had interaction on tensile shear and nugget size at 95% confidential (P value < 0.05). Factors affecting the tensile shear and nugget size are the most welding current 10,000 amp., welding time 10 cycle and electrode force 1 kN. were tensile shear 7.13 kN. and nugget size maximum 6.75 mm. This research can bring information to the foundation in choosing the appropriate parameters to resistance spot welding process.
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