* International Review of Aerospace Engineering (I.RE.AS.E), Vol. l, N. 5 October 2008 wiTvtkj fviu Al to A5 Cp hoo I - K Q rx,ryav, r var S t T T oo TG Ti yu. T p U V V;; x,y BM Thermal Simulation and Experimental Characterizations of Aeronautic Stainless Steel Welded by TIG Process M. Aissani J ,4, D. H. Bassir 2 ,4, Y. Benkedda 3 Abstract - In arder ta study the thermal behaviour of aeronautic stainless steel welded by TIG process, we have improved the energetic distribution formulation by adapting the geometric configuration into a bi-elliptic form with Gaussian surface heat jlow distributions of the welding source. The Thermal transie nt fields and thermal cycles are evaluated ta determine dimensions of the risky zones (Heat Affected Zone and Fusion Zone) and the welded joint is characterized by tension tests, miero-hardness (Hv) and micrographies. A metal/agraphie analysis is prepared ta differentiate al/ zones as wel/ as the grain sizes, and ta eorifirm theirs widths. Computations are earried out by finite volume method, where thermo-physic 's properties and boundary conditions are infunetion oftemperature. The reliability of the model is evaluated by the comparison of the simulated results with those obtained by thermal cycle reeordings ta evaluate the size of the risky zones. Bath, theoretieal and experimental approaches have good agreement and give an enhaneement of a previous work. Copyright © 2008 Praise Worthy Prize S. r. 1. - AIl rights reserved Keywords: Aeronautie Stainless steel, Meehanieal and Metal/urgieal Characterization, TIG Welding, Thermal Simulation Nomenclature Temperature coefficients after discretization Thermocouple position Specific heat (J/kg/K) Convection coefficient (W/m 2 /K) CUITent intensity (A) Thermal conductivity of the material (W/mIK) Point used to determine the finite volume V;; Arc energy coming on the surface of sheets (W) Heat flow (W 1m2) Radii's of the bi-ellipse shape (m) Heat source function (J/m 3 /s) Time (s) Temperature (K) Ambient temperature Initial temperature in the material Temperature at point Pi (i 0 {E, w,N,S}) Temperature at the previous iteration Temperature at point 'P' Welding voltage (Volt) Wei ding velocity (mis) Control volume sUITounding point Pu Bi-dimensional coordinates (m) of P Base Metal FZ HAZ TIG P 77 (J (; (j'max b'x, b'y Fusion Zone Heat Affected Zone Tungsten Inert Gas weI ding process Density of material (kg/m 3 ) Arc efficiency (%) Stephan Boltzman constant Emissivity Tensile strength (MPa) Distance between points of the mesh in x and y direction respectively Parameters defining the size of Control Volume 1. Introduction Nowadays, joining technologies and technical advances, specially welding process, allow complex assembling of metallic structures with different shape and size. However, security and economy factors must be the most important parameters of the constructions reliability, in the aeronautical industry [1], [2] and others industrial fields as the nuclear and robotic [3]- [5]. The arc welding process that involves fusion of the material assembled edges undergoes a great number of metallurgical and mechanical modifications, which are induced by strong temperature gradients. These modifications determine the final characteristics of the welding. Nevertheless, problems of weld-ability can be Manuscript received and revised September 2008, accepted October2008 Copyright © 2008 Praise Worthy Prize S.r.l. - Ali rights reserved 481