Simulation Tests for PWHT and Welding Processes

Welding and post weld heat treatment (PWHT) processes have the ability to drastically change the mechanical properties of welded structures, so advanced simulations and compliance with industry codes help ensure pressure vessels meet safety and performance standards post PWHT.

FEA allows engineers to predict how a structure will deform during heating and cooling cycles, enabling them to design the optimal heating cycle to avoid distortion and cracking. Load-punch displacement curves for weld metal (WM) and coarse grain from heat-affected zone (CGHAZ) tend to converge upon PWHT, aligning closely with those for base metal (BM), showing significant homogenization of mechanical behavior.

Structural Analysis

Post-Weld Heat Treatment (PWHT) is an integral step in the production of pressure vessels. PWHT can relax welding stress, avoid delayed cracking and increase toughness, creep resistance, service life and toughness of components that have been welded together.

FEA allows for simulation of the PWHT process on vessel’s structural integrity, assuring compliance with mechanical design codes and safety standards. Furthermore, it helps predict geometric distortions during PWHT, so as to optimize heating/cooling rates in order to minimize distortions.

FEA modeling results of G91/C22 weld geometry and residual stress are in excellent agreement with experimental data. When simulating weld metal microstructure and stress distribution, incomplete austenite to martensite transformations, welding-induced distortion, soft regions in the heat-affected zone and thermal strain mismatch between base and clad materials were taken into consideration as factors. Regardless of these inhomogeneities, however, the model predicts that PWHT reduces weld-related residual stresses as well as stress gradients at bonding interface.

Finite Element Analysis (FEA)

Finite Element Analysis (FEA) is an engineering technique that uses mathematics to simulate real-world behavior without building physical prototypes. FEA plays an essential role in modern engineering, helping manufacturers reduce product development costs while meeting stringent safety and performance standards.

FEA analysis can accurately simulate the distribution and effect of PWHT treatment on residual stresses in welded structures, as well as geometric distortions and material property changes caused by heat treatment processes, providing engineers with information to optimize PWHT parameters accordingly.

However, the accuracy of FEA models depends on the quality of input data. With software like Simcenter Femap, you can easily verify the integrity of your models using advanced design verification and inspection tools such as SDC Verifier to quickly inspect code changes directly within FEA workflows for faster design process acceleration with one click – you can even apply standard rules or create your own customized checks!

Thermal Analysis

As pressure equipment requires postweld heat treatment (PWHT), engineers should conduct a structural analysis to identify potential weak points and areas susceptible to deformation – this allows engineers to optimize design and enhance safety.

Engineers use finite element analysis (FEA) to accurately forecast geometric distortions caused by uneven heating and cooling, allowing them to fine-tune their PWHT process so as to heat material evenly with minimal distortions.

Under the ASME Boiler and Pressure Vessel Code, various experimental tests must be conducted on steel plate to satisfy ASME regulations for acceptance. One such experimental test is post-weld heat treatment (PWHT). Mechanical test coupons representing plates supplied by plate suppliers undergo PWHT simulation by their supplier, with their mechanical properties meeting specified requirements upon simulated postweld heat treatment (PWHT). Unfortunately, however, due to inadequate testing methods available and simplistic qualitative approaches being employed that don’t take into account real heat treatment processes being simulated; neither do actual performances understand.

Material Testing

Post weld heat treatment (PWHT) is an increasingly popular practice to enhance the microstructure and mechanical properties of welded components, including residual stress reduction, postponed cracking prevention, improved toughness and creep limit of structures as well as increasing toughness/lasting creep limits.

Engineering analysis must be performed carefully in order to ensure that PWHT does not result in distortion, warping or undesirable material properties in the weld structure. Finite element analysis (FEA) helps engineers accurately predict thermal and mechanical behaviors as a structure heats and cools during this process.

Many methods exist for measuring residual stresses in weldments, including the widely-known XRD and hole drilling methods. But due to their destructive nature and inevitable test errors, FEA is an invaluable tool for supporting experimental results and clarifying experimental outcomes. By helping identify areas where high concentrations of residual stresses exist and suggesting ways they may be reduced during PWHT processing, manufacturers can optimize PWHT processes and produce consistent, repeatable results that deliver repeatable performance.