Finite Element Analysis and Experimental Validation of Residual Stresses in Multipass TIG-Welded Stainless Steel Pressure Vessel Components Used in the Food and Beverage Industry in Nigeria

Residual stresses introduced during multipass welding of stainless steel pressure vessels used in food and beverage processing applications can adversely affect fatigue life, stress corrosion cracking susceptibility, and dimensional stability, with consequences for both product safety and equipment service life in manufacturing facilities across Nigeria. This study applies finite element modelling and experimental validation to characterise residual stress distributions in multipass TIG-welded Type 304 stainless steel plate specimens representative of pressure vessel shell seams at food processing plants in Ogun and Lagos States. A sequentially coupled thermo-mechanical finite element model was developed in ABAQUS, incorporating temperature-dependent material properties, weld deposit progression, and inter-pass cooling cycles. Simulated thermal cycles were validated against experimentally measured weld thermal histories recorded using embedded thermocouples during welding trials. Residual stress distributions in the as-welded condition were predicted from the simulation and experimentally validated using the X-ray diffraction sin-squared-psi technique at multiple measurement locations across the weld and heat-affected zone. Results demonstrated satisfactory agreement between simulated and measured residual stresses within plus or minus 18 percent, lending confidence to model predictions in regions inaccessible to direct measurement. Peak tensile residual stresses of 320 MPa were identified at the weld centreline, approaching the yield strength of the base material. Post-weld heat treatment at 870 degrees Celsius for one hour reduced peak residual stresses by 64 percent. The study provides validated modelling guidance for residual stress management in Nigerian pressure vessel fabrication. Keywords: residual stress, TIG welding, finite element analysis, X-ray diffraction, pressure vessel.