How do you predict and control welding distortion in complex fabrications?

Weld distortion prediction and control involves: Analytical methods (shrinkage force approach, inherent strain method), FEA simulation (thermo-mechanical analysis in SYSWELD, ABAQUS), and Empirical correlations. Control strategies: Design phase (balanced welds, neutral axis placement, weld sizing), Sequence optimization (backstep, skip welding, symmetric sequences), Fixturing and restraint (careful - may cause residual stress), Pre-setting and pre-cambering, Thermal management (preheat, interpass control), Low heat input processes (laser, electron beam), and Post-weld correction (mechanical straightening, stress relief). For critical structures like ship hulls or aerospace frames, combine simulation-based prediction with proven mitigation strategies.