FEM simulation of spot welding process. Report 4: Characteristics of electrode displacement and nugget formation

Abstract

The real time measurement of the electrode displacement during spot welding is very important to control the spot welding process in order to get a sound weld. In this report, the electrode displacement and nugget formation during spot welding were investigated numerically by means of the finite element method. Important parameters characterizing the relationship between electrode displacement and nugget formation were introduced based on experiment and numerical analysis. The effects of welding current, squeezing force and plate thickness on the electrode displacement and nugget formation were clarified. Through the present study, the following conclusions were drawn: (1) The time when the electrode displacement reaches the maximum value is closely related to the timing of nugget formation and it is influenced by the welding current, the squeezing force and the late thickness. (2) The formation of a sound spot weld with nugget size between 4 x (square root of t) and 5 x (square root of t) can be detected by monitoring the time when the electrode displacement at the top reaches the maximum value, where t is plate thickness.

点溶接プロセスを制御して健全な溶接を得るために、点溶接中の電極変位の実時間測定が非常に重要である。有限要素法を使用して、点溶接中における電極変位とナゲット形成を数値研究した。実験および数値解析に基づいて、電極変位とナゲット形成間の関係を特徴つける重要なパラメータを導入した。電極変位とナゲット形成への、溶接電流、スクイズ力および板厚が及ぼす効果を明らかにした。以下の結果を得た。(1)電極変位が最大に達する時間はナゲット形成のタイミングと密接に関係しており、溶接電流、スクイズ力および板厚の影響を受けた。(2)トップでの電極変位が最大値になる時間をモニタすることで、tを板厚として、ナゲット寸法が4×平方根(t)?5×平方根(t)である健全な点溶接を検出できた。