Development of a Procedure for the Acoustic-Emission Checking of Resistance Spot Welding
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DEVELOPMENT OF A PROCEDURE FOR THE ACOUSTIC-EMISSION CHECKING OF RESISTANCE SPOT WELDING E. V. Shapovalov,1 R. M. Galagan,2, 3 and F. S. Klishchar1 We study the possibility of application of the acoustic-emission method for the monitoring of resistance spot welding. We develop a specialized system for the reception and processing of acoustic emissionsignals and criteria for synthesizing the quality index of a spot-welded joint. For the formation of the quality index of spot-welded joint, it is proposed to use the method of convolution of the template signal and a signal obtained by checking of the current weld spot. Keywords: acoustic emission, resistance spot welding, quality, checking.
Formulation of the Problem Resistance spot welding (RSW) is one of the most widespread procedures for getting permanent joints used in automobile construction, shipbuilding, instrument making, and other branches of industry. It is customary to make high demands to the reliability and stability of quality of spot-welded joints. Thus, various methods are used to verify the realization of these requirements. One can improve their quality by checking the modes of operation of welding equipment: welding current, voltage drop between the electrodes, the force of their compression, the resistance of the weld spot, etc. Another approach is connected with checking the process of welding with application of the methods of nondestructive testing: ultrasound, thermal, eddy-current, etc. [1]. At present, the traditional methods used for the nondestructive testing of welding are supplemented with the acoustic-emission (AE) method. However, its application is restricted by a series of factors one of which is connected with the existing difficulties in reliable and single-valued reception of AE signals against the background of noise caused by the operation of welding equipment. This method was developed in the works [2, 3] devoted to the analysis of the sources of AE signals and noise against the background of which it is necessary to detect these signals and to recommendations concerning the choice of sites for placing the AE transducers. In [4], it is proposed to use “fractal theory” for the description of the characteristics of AE signals. The AE signals emitted in the course of formation of cast nuggets are studied in [5]. The results of these experiments show that the AE method is quite promising for checking the quality of spot-welded joints. However, due to the absence of specialized equipment and criteria capable of predicting the quality of spot-welded joints according to the results of the analysis of AE signals, it is impossible to completely use all possibilities of this method aimed at checking RSW. The aim of the present work is to develop an efficient procedure for processing the informative parameters of AE signals formed in the course of RSW and synthesize a criterion of the quality of spot-welded joints. 1 2 3
Paton Institute of Electric Welding, Ukrainian National Academy of Sciences, Kiev, Ukraine.
“KPI” National Technical Un
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