Analysis and Modeling of GTAW Weld Pool Geometry - Intelligent Computing for Sustainable Energy and Environment - page 287

3 Characteristic Parameters Definition

In previous works, some characteristic parameters were given to describe the weld
pool [12], [16], [17], [25]. All the parameters mentioned in above works are in two
dimension plane. In [24] the weld pool width, length, and convexity were proposed as
the characterization parameters of the weld pool surface. Some parameters reflecting
more detailed three dimensional characteristics are presented in this paper.
In Fig.4, and give the basic description of weld pool in two dimensional,
and present more information about the rear part of weld pool. , W , and
are the length, width, half length, half width of the weld pool respectively. H , S ,
and ∆S describe the characteristic in YZ plane. , , and ∆ denote the height of
the weld pool, the cross-section area, and the pool concavity area. Based on Fig.4 (a),
the area of the weld pool in horizon can be calculated. Here the area is considered as
circular, and radius of the circle can be obtained, which is denoted with . Among
these parameters, , ∆ and are introduced to characterize the weld pool for their
correlation with the penetration at the first time.
Based on the above analysis, ,, , ,,,, are selected as characteristic
parameters to describe the weld pool. , are parameters describing the
penetration status, where is the backside height, and is the backside width.
Normally, a camera will be applied to obtain the value of in real time, but the
cost is high and it is difficult to place the vision system in some conditions (e.g., the
accessibility is poor). can be measured when the weld pool solidifies, but some
delay will exist. In order to sense these two variables in real time, soft-sensing model
thus is presented as an alternative to estimate them online. Based on the three
dimensional weld pool sensing technology and weld pool reconstruction,
L,W,L ,W ,H,S,ΔS,R of the weld pool shape will be calculated in real-time.
,, , ,and are calculated based on Fig.4 (a); ,, are obtained from
Fig.4(b). , are measured after welding. Then the correlation between the
characteristic parameters and , will be studied, and the soft sensing model will
be established.

(a) ܮǡܹǡܮ ௛ ǡܹ ௛ (b) ܪǡܵǡ߂ܵ

Fig. 4. Weld pool characteristic parameters description

From the above analysis, characteristic parameters of the front weld pool were
defined to correlate with the penetration status. Experiments were conducted to obtain
relative data, and the relationships between the characteristic parameters and