Characterization of Nugget Development under Electrode Wear Conditions in Resistance Spot Welding

Contact areas at both electrode-to-sheet and sheet-to-sheet interfaces are important in the resistance spot welding process. Given electrode force and welding time, contact areas strongly affect the amount of electrical current needed to make a good weld. In production, process variation such as electrode wear and misalignment causes the contact areas to vary. This effect contributes largely to the quality variation of resistance spot welds. This paper proposes a model-based approach to contact area estimation in the resistance spot welding process. A finite element analysis procedure is used to characterize the contact area behaviors. Based on the understanding from the simulations, a lumped parameter model, together with its calibration and estimation procedures, is developed for on-line applications. The proposed method is demonstrated successful under various process conditions including electrode size, force, welding time and current. It provides important information for on-line monitoring and control of the resistance spot welding process.

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Modeling and On-Line Estimation of Electrode Wear in Resistance Spot Welding

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2034516 ◽

2004 ◽

Vol 127 (4) ◽

pp. 709-717 ◽

Cited By ~ 15

Author(s):

Wei Li

Keyword(s):

Contact Area ◽

Resistance Spot Welding ◽

Spot Welding ◽

Welding Process ◽

Welding Current ◽

Estimation Algorithm ◽

Contact Condition ◽

Electrode Wear ◽

Resistance Spot ◽

On Line

Electrode wear is inherent in the resistance spot welding process. It determines the electrical and mechanical contact condition and thus strongly affects the resistance spot weld quality. A practical approach to minimizing the electrode wear effect is to compensate the welding current as the electrodes wear. However, the existing methods for welding current compensation rely on either a predetermined stepper schedule or an expulsion detection algorithm. These methods are not reliable since the welding current is not determined based on the contact condition for each weld made in the welding process. This paper presents an on-line electrode wear estimation approach to determining the contact condition and the welding current needed to make every weld a good weld during the entire life of the electrodes. In the study, an incrementally coupled finite element simulation was first formulated to analyze the contact area behavior in the resistance spot welding process. A lumped parameter model was then developed to characterize the contact area change with the dynamic resistance measurement. A calibration and an estimation algorithm were subsequently devised for on-line applications. The proposed approach has been validated with experimental data. The results have shown that the estimation algorithm is robust under various process conditions including both welding current and electrode force.

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