B - Operations – Transporting – 23 – K
Patent
B - Operations, Transporting
23
K
354/21, 327/90
B23K 11/10 (2006.01) B23K 11/25 (2006.01)
Patent
CA 1202690
METHOD AND APPARATUS FOR DETECTING THE ONSET OF MELTING IN A RESISTANCE SPOT WELD Abstract of the Disclosure During a weld period the weld parameters are monitored and data representing the weld resistance curve and the power curve are acquired and stored for analysis by a suitably programmed computer. The derivative of R, R is calculated and stored and the function is divided by power P to obtain R/P. The resistance curve is searched to obtain the maximum value Rm which occurs during the heating phase and the function R/P is searched prior to the time of Rm to find the maximum of that curve representing the highest rate of resistance increase. Then the R/P curve is searched subsequent to its maximum to deter- mine when the function reaches a specified percentage of the maximum. That value occurs at the knee of the resistance curve and approximates the onset of melting in the weld. A prediction of whether a weld is a nugget or a sticker is made by calculating the ratio of weld energy after the onset of melting to the total weld energy, the ratio of the resistance drop after the resistance peak to the peak resistance, and then a weighted sum of the energy ratio and resistance drop ratio. An edge weld geometry is detected by calcu- lating from the resistance and power curves the weld energy during the period of expulsion, if any, divided by the cumulative energy between the onset of melting and the end of expulsion, a measure of expul- sion intensity based on the maximum degree of resis- tance inflection, and then a weighted sum of the energy value and the inflection value.
444633
Cleveland Dixon
Decina Basil A. Jr.
Havens James R.
Houchens Albert F.
Nagel Gregory L.
General Motors Corporation
Gowling Lafleur Henderson Llp
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