PSI - Issue 5

Zuheir Barsoum et al. / Procedia Structural Integrity 5 (2017) 1401–1408 Zuheir Barsoum / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig 4. ultimate strength vs displacement (a) for full penetration (b) effect of penetration ratio (c) failure locations.

For the S700 butt welded joints no significant difference in the load capacity is observed in the different cases, except the deformation capacity (i.e. overall ductility in the joint). Failure in these joints started in the weld root and propagated along the HAZ (Heat Affected Zone). For the S960 butt welded joints, matching weld metal showed higher hardness, whereas under-matching weld metal has lower hardness in comparison to the base material. Failure for matching joints occurred in the base plate. In case of under-matching joints, the load carrying capacity of the base plate could be achieved but the deformation capacity was decreased. Failure of these joints occurred in between the weld metal and the HAZ. ABAQUS/EXPLICIT 6.11 has been used for nonlinear finite element analysis to evaluate the behavior of the joints for different cases. The stress singularities at sharp edges where removed using effective notch stress concept, Barsoum et al (2012). Weld metal, base plate and HAZ were assigned material properties based on the hardness measurements based on correlation between hardness, yield and tensile strength Barsoum et al (2014). The failure criteria for load carrying capacity was based on limited plastic strain distribution across the critical section of the joint. For conservative approaches where no plastic deformation is allowed, 0.2% plastic strain distribution across the critical section of the joint can be used. In case of fully penetrated joints, base material is the critical section, while in case of partially penetrated joints, the weld throat plane is the critical section. Fig 5 shows examples of estimated failure locations, experimentally and FEA, for full and partial penetrated butt welds.

Fig 5. Failure location for partial-and full penetrated butt welds.

5. Comparison design codes, FEA and experiments

5.1. Fillet welds

In Fig 6 the ultimate strength capacities for fully penetrated joints with different filler materials evaluated by FEA, testing and design codes are in close agreement. Also, the failure location is verified by the standards. Both