Estimation of the weld pool size in GMAW processes using multiple surface temperatures measurements

This paper describes a detailed procedure for establishing an index to estimate a weld pool size in gas metal arc welding processes using measurements of multiple surface temperatures. Up to now, estimation of a weld pool size based on the surface temperature field formed during welding has been performed using one point temperature. However, owing to the complexity and nonliearity inherent to the welding processes, it is nearly infeasible to specify the temperature field by one point temperature alone, and thereby difficult to consistently quantify the pool size. Therefore, in addition to one point temperature, the temperature differences along and perpendicular to the weld line are adopted to compensate for such a deficiency. To extract the pool size information from these temperature parameters the indices to estimate the respective pool size parameters(top bead width and depth of penetration plus half back bead width) are derived using a multiple regression method. The estimation performance of the indices are investigated through simulation studies and experiments. Advantages of using the index are investigated by comparing with the case of using one point temperature. Eventually, the effectiveness of using the index in practical situation is discussed, in detail.