LIBRARY ı6ıul 0) - Cranfield University

Pen is the weld penetration (side penetration, Pen,, and bottom penetration, Penb);
a7 and (37 are regression coefficients.
Possibility measure of undercut, Pr(und)
Pr(und)=a, WFS+ß, WFS SO +s, v"s;, (3.8)
where as , ßs and 5s are regression coefficients.
c) Models for predicting process stability
Possibility measure of bad arc ignition
Pr(arc) =1-
WFS,,.
=1 VSet
- a9
WFS, R9 S,,
t
where
WFS, is the ideal
gn
wire feed speed required to give good arc ignition;
WFS5,, is the set-up wire feed speed;
Vtet is the set-up voltage;
(X9
, 09 are regression coefficients obtained by fitting a linear relationship to
VSe WFS, gn).
Model for predicting power ratio (PR)
PR =ago +ß10, +810V
ean
2
where a1o , ßio and Slo are regression constants.
(3.9)
(3.10)
The coefficients of the models are dependent on the wire type (diameter and
composition), the shielding gas type and the joint type. In this work, the coefficients
obtained by Ogunbiyi [ref. 51] were utilised as a starting point (see Table 3.1). These
coefficients were obtained for 1 mm mild steel welding wire3,1.6 mm and 3.2 mm
thick mild steel sheets set in fillet joints in the horizontal vertical (2F) position and
BOC Argonshield 54 shielding gas, using a Migatronic BDH 320 inverter power
source. Although the models were obtained using 1.6 mm and 3.2 mm thick mild steel
sheets, the author [ref. 51] suggests that they can be used for prediction purposes in
the range from 1.0 mm to 6.0 mm thick mild steel sheets.
3 Oerlikon (BS 290LA18)
Ar + S%COZ + 2%02 gas mixture
70