PSI - Issue 25

Romanin Luca et al. / Procedia Structural Integrity 25 (2020) 149–158 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Finally, the uncertainties in manual welding, derived from human operator, does not justify the use of such sophisticated tool (say, CWM). Because the welding lengths were relatively short and the space available to an automatic or semi-automatic machine was limiting, welding has been entirely performed manually using the GMAW process. The welds have been mostly carried out in a flat position and the assembly was welded without using clamps. Introducing restrains would have diminished residual deformations but increased residual stresses with the risk to promote hot cracking. The welding process has been divided in three phases (Fig. 5), for each phase more plates were first tack welded before welding.

Fig. 5. Assembly Welding Phases

In the numerical model new plates are activated according to the various welding phases and welding loads are applied according to the established welding sequence. Welding parameters (welding speed, amperage and voltage) have been logged to set up local models for every welded joint type. Local model has been used to extract deformations by means of CWM and calibrate equivalent loads for the single joint. The numerical model has then been validated with a produced workpiece which distortions were measured by means of a laser tracker. Marker points were applied to the assembly. Their coordinates have been measured in the zero state before welding, when all the plates of the assembly have already been tack welded, and after welding. An experimental survey has been conducted to collect welding parameters and create more reliable numerical local models. With the aim to capture the deformation of the single joint as a reference for the simplified model, two-dimensional CWM local models have been developed. The welding parameters such as current, welding speed and voltage have been measured experimentally. Generalized plane strain and a reduced integration method has been employed (Ferro et al. (2006). The reduced integration scheme allows avoiding locking in case of large plastic strains (Lindgren (2007)). Thermal, metallurgical and mechanical properties have been taken into account (Romanin et al. (2018)). 3.1. First Welding Phase The first welding phase analysed is shown in Fig. 6. The core is made of a rectangular plate with 12 holes, a long transversal plate and two main wings transversal to the longitudinal plate. The plates thickness is reported in Fig. 6,