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Welding Residual Stress Simulation Technology

The local application of heat in welding leads to the generation of residual stress, which in turn causes cold cracking, brittle fractures, fatigue fractures and stress corrosion cracking. In order to reduce this residual stress, we adopt measures such as post-weld heat treatment (PWHT).
We have succeeded in simulating residual stress and the stress-reducing effects of PWHT through the combination of thermo-elastic plastic analysis and thermo-elastic plastic creep analysis using the fine element method (FEM).
We have applied this technology to large steel structures manufactured by our company such as pressure vessels, boilers, steel manufacturing gears and bridges to improve product reliability and reduce manufacturing costs. Knowing in advance the position at which residual stress increases allows us to adopt suitable countermeasures, while understanding the residual stress-reducing effects of PWHT allows us to perform suitable heat treatment and therefore reduce greenhouse gases.
Fig.1 shows an analysis of butt welding on a 98mm thick plate, and Fig.2 is a comparison of the residual stress distribution near the weld with and without PWHT. The figure shows that PWHT significantly reduces residual stress.

<Machinery & Infrastructure Technology Group, Technical Research Institute>

Fig.1 Welding simulation

(a)As welded

(b)After PWHT

Fig.2 Residual stress distribution near the weld