Fatigue Behavior of Welded Joints and Weldments in HY-80 Steel Subjected to Axial Loadings

Bureau of Ships, U.S. Navy.Contract N0bs 77137Index No. NS-021-20

Improvements of hybrid laser arc welding for shipbuilding T-joints with 2F position of 8 mm thick steel

One of the main concerns in the early stages of manufacturing flat units of shipbuilding is to ensure the quality of the joints throughout the structure. The flat units are constituted by butt welded flat plates, on which longitudinal T-welded reinforcements are placed to rigidize the structure. Among the different welding technologies, Hybrid Laser Arc Welding (HLAW) is becoming a mature process, profitable and highly productive. In addition, more innovative welding equipment are being developed nowadays, offering greater work flexibility, and raising expectations of achieving better quality, and economic viability. Another key point of HLAW to keep in mind is that structural distortions are reduced, resulting in decreasing the cost and time of straightening work. In the present contribution, the influence of HLAW parameters on the quality of fillet joints of naval steel has been analysed. Experimental HLAW tests were performed with a high power disk laser to join EH36 naval steel plates, with a T configuration. The influence of different processing parameters has been analysed, as the laser power, welding speed, wire feed rate and the configuration of the HLAW processes (including head angle and laser/arc leading process). In addition, FEM simulations were carried out in order to estimate residual stresses and distortion of welded part. The distortion values provided by FEM presented excellent agreement with the measured experimental results. To evaluate the welds, non destructive tests including X-ray tests, metallographic analysis of cross sections, and microhardness mapping tests were performed. Full penetration 8 mm T welds were obtained for the first time at an industrially applicable 2F position with a reasonable HLAW head angle, in one single step without sealing root, and using zero gap square groove edge preparation. The present contribution presents welding rates up to 2.2 m/min for 2F T-joints of this steel thickness, a much higher processing velocity than previously reported for industrial applications

Impact of Gaps on Resource Efficiency in Heavy Welding Industry.

This paper describes a study investigating the current situation concerning plate gaps in welding operations at a company producing welded products. A varying gap between the plates has been identified as a root cause for quality issues and unnecessary costly welds, hence affecting resource efficiency. The result showed signs of vast variations of gaps, both concerning the size of gaps and presence of an extra weld. The investigation indicates a large potential, possible to achieve without heavy investments

On the use of linear-elastic local stresses to design load-carrying fillet-welded steel joints against static loading

This paper uses local linear-elastic stresses to estimate the static strength of steel arc welded joints. The proposed design methodology was developed by taking as a starting point the fundamental concepts on which the Theory of Critical Distances (TCD) is based. The overall accuracy of the devised approach was checked against a number of experimental results taken from the literature and generated by testing a variety of welded geometries. Such a systematic validation exercise demonstrated that the TCD is highly accurate in estimating the static strength of arc welded joints irrespective of the complexity of the assessed welded detail’s geometry

Procedural benchmarks for common fabrication details in plate/shell structures

This report, presents outcomes from the Education and Dissemination Workshops held at Noordwijk and Palma on October 2003 and March 2004 respectively. The results from a 'round-robin' exercise, completed as part of this activity, are also documented. These workshops and the 'round-robin', examined the procedures used in various industry sectors for the modelling and assessment of common fabrication details in plate/shell construction. The primary aim of this exercise was to examine "best practice" in modelling and assessing such detail (with general shell elements) and to disseminate this to the FENET membership and beyond. However, the 'round-robin' was seem as an excellent opportunity to examine such practice and to observe resulting educational and quality assurance related issues