Assessment of the Structural Parameters Significance Using the Experiment Design in the Production of Pressure Vessel Heads

The production of pressure vessel heads by the incremental sheet forming (ISF) causes local deformation and surface hardening. This phenomenon, special in combination with welding and residual stresses, can cause the appearance of brittle fracture. The focus of the research is the heat-affected zone in the welded joint. Using the experiment design and plan matrix, the experimental determination of the fracture toughness, K_Ic, as well as the total impact energy KV on the specimens taken from the plastically deformed vessel heads is carried out. A three-factor experiment plan is applied in two blocks, with and without post weld heat treatment (PWHT). Two output parameters, K_JIC and KV, were analysed. The influence of the combination of analysed input parameters on the parameter KV exists, as indicated by the good agreement of the regression model and experimental data. At the same time, the analysis shown ‘inadequate’ agreement of the regression model and experimental data with the output parameter K_JIC as objective function.