The present paper deals with the effect of welding conditions, plate length and tack weld pitch on changes of root gap during welding in butt weld joints. The calculations of changes of root gap during welding are carried out under various conditions of heat input, plate length and tack weld pitch, using the finite element method explained in the previous report. In this case it is assumed that the rigidity of tack weld is infinite.
The main conclusions obtained in this report are summarized as follows:
(1) In case of butt weld joints with tack welds under the condition of relative small tack weld pitch, the root gap at heat source closes between the weld start position and the first tack weld position. The behaviour of released displacement at tack weld position is devided into the following classes. In the first case the released displacement at tack weld position increases as the heat source moves. In the second case the released displacement increases after decreasing as the heat source moves.
(2) The maximum closing displacement between the weld start position and the first tack weld position ((uH)
s) and the released displacement at the end tack weld ((uH)
e) have the following characteristics.
The remarcable displacement ((uH)
s) increases as the heat input (q/υh) increases under the condition of constant molten pool length lead from the mechanical point of view (lM). It decreases as the molten pool length (lM) increases under the condition of constant q/hυ.
The remarkable displacement ((uH)
e) increases as the heat input (q/υh) increases under the condition of constant lM.
Effect of plate length(L) on (uH)
e depends on the welding conditions (q/υh, lM) and the range of plate length.
The remarkable displacement (uH)
e increases as the tack weld pitch increases.
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