## THERMAL SCIENCE

International Scientific Journal

### CALCULATION OF T8/5 BY RESPONSE SURFACE METHODOLOGY FOR ELECTRIC ARC WELDING APPLICATIONS

**ABSTRACT**

One of the greatest difficulties traditionally found in stainless steel constructions has been the execution of welding parts in them. At the present time, the available technology allows us to use arc welding processes for that application without any disadvantage. Response surface methodology is used to optimise a process in which the variables that take part in it are not related to each other by a mathematical law. Therefore, an empiric model must be formulated. With this methodology the optimisation of one selected variable may be done. In this work, the cooling time that takes place from 800 to 500ºC, t8/5, after TIG welding operation, is modelled by the response surface method. The arc power, the welding velocity and the thermal efficiency factor are considered as the variables that have influence on the t8/5 value. Different cooling times,t8/5, for different combinations of values for the variables are previously determined by a numerical method. The input values for the variables have been experimentally established. The results indicate that response surface methodology may be considered as a valid technique for these purposes.

**KEYWORDS**

PAPER SUBMITTED: 2013-04-18

PAPER REVISED: 2013-11-21

PAPER ACCEPTED: 2013-12-04

PUBLISHED ONLINE: 2013-12-22

**THERMAL SCIENCE** YEAR

**2014**, VOLUME

**18**, ISSUE

**Supplement 1**, PAGES [S149 - S158]

- Lazic, V. N., et al, Theoretical-Experimental Determining of Cooling Time (T(8/5)) in Hard Facing of Steels for Forging Dies, Thermal Science, 14, (2010), 1, pp. 235-246, DOI No. 10.2298/TSCI1001235L.
- Ivanovic, I. B.,et al, Numerical Study of Transient Three-Dimensional Heat Conduction Problem with A Moving Heat Source, Thermal Science, 15, (2011),1 , pp. 257-266, DOI No. 10.2298/TSCI1001257I.
- Yeh, R. H., et al, Transient three-dimensional analysis of gas tungsten arc welding plates, Numerical Heat Transfer; Part A: Applications, 51, (2007) 6, pp. 573-592.
- Lazic, V. N., et al, Energetic Analysis of Hard Facing and Weld Cladding of An Air Powered Drop Hammer Damaged Ram, Thermal Science, 14,(2010),suppl, pp. S269-S284, DOI No. 10.2298/TSCI100501021L.
- J. C. L. X.YUE, Continuous Cooling Transformation Behavior in the CGHAZ of Naval Steels, Welding Journal, 91,(2013), 3, pp. S67-S75.
- Leister, B.M. and DuPont, J.N., Fracture toughness of simulated heat affected zones in NuCu-140 steel, Welding Journal, 91, (2012) 2, p. 53s-58s.
- Cieslak, M. J., Hydrogen-Induced Cracking (Cold Cracking), in: ASM HANDOBOOK. VOLUME 6 (Eds. R. M. Nunes et al.), ASM International, New York, USA, 1993, pp. 241-245.
- Kalaba, D. V., et al, Thermomechanical Modelling the Resistance Welding of Pbsb Alloy, Thermal Science, 14, (2010), 2, pp. 437-450, DOI No. 10.2298/TSCI1002437K.
- Al-Sa'ady, M. H., et al, Finite Difference Simulation of Low Carbon Steel Manual Arc Welding, Thermal Science, 15, (2011), 1, pp. 207-214, DOI No . 10.2298/TSCI100206055S.
- Yaghi, A., et al, Residual stress simulation in thin and thick-walled stainless steel pipe welds including pipe diameter effects, International Journal of Pressure Vessels and Piping, 83,(2006), 11-12, pp. 864-874.
- Y.T.iÇ, et al, Design of experiment and goal programing application for the GMAW process, Welding Journal, 91,(2012), p. 106-S - 112-S.
- Montgomery, D.C. and Myers, R.H., Response surface methodology: Process and product in optimization using designed experiments, Jhon Wiley&Sons, New York-USA, 1995.
- CHO, M. H., et al, Simulation of Weld Pool Dynamics in the Stationary Pulsed Gas Metal Arc Welding Process and Final Weld Shape, Welding Journal, 85, (2006), 12, p. 271-s - 283-s.
- Nguyen, N.T., et al, A analytical approximate solution for double ellipsoidal heat source in finite thick plate, Welding Journal, 83, (2004), 3, p. 82-s - 93-s.
- Ohta, A., et al, Analytical solutions for transient temperature of semi-infinite body subjected to 3- D moving heat sources, Welding Journal, 78 (1999), 8, pp. 265-274.
- Martínez-Conesa, E.J., et al, A mathematical approach based on finite differences method for analyzing the temperature field in arc welding of stainless steel thin sheets, Revista de Metalurgia, 46, (2010), 6, pp. pp. 511-519, DOI No 10.3989/revmetalmadrid.1021.
- Maljaars, J., et al, Constitutive model for aluminum alloys exposed to fire conditions, Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, 39A,(2008), 4, pp. 778-789.
- May, J. E. and Menzemer, C. C., Strength of bolted aluminum alloy tension members," Journal of Structural Engineering-Asce, 131, (2005), 7, pp. 1125-1134.
- Aalberg, A., et al, Stiffened aluminium panels subjected to axial compression, Thin-Walled Structures, 39, (2011), 10, pp. 861-885.
- Martínez Conesa, E.J., et al, Optimization of t8/5 for stainless steel Arc Welding, Dyna, 84,(2009), pp. 251-258.
- Box, G.E.P. and Wilson, K.B., On the Experimental attainment of optimum conditions, Journal of the royal Statistical Society Series B-Statical Methodology, 13,(1951), pp. 1-45.
- Kikuchi, N., and Suzuki, K., A homogenization method for shape and topology optimization, Computer methods in applied mechanics and engineering, 93, (1991), pp. 291-318.