An algorithm for statistical evaluation of weld toe geometries using laser triangulation

Commonly, to evaluate the influence of the local weld geometry in fatigue test, small-scale specimens are used, assuming those represent a longer weld adequately. In this study, a comparison between short specimens and a long weld is performed. A method is developed for the statistical evaluation of weld toe radii and angles, stress concentration factors and weld quality classes. The results show a strong sampling rate dependence and lower ISO 5817:2014 weld quality results for higher sampling rates. Comparable results between short specimens and a long weld can be achieved using modal values of the parameters assuming a lognormal distribution.

A review of fatigue test data on weld toe grinding and weld profiling

The aim of this paper is to investigate the effects of weld toe grinding and weld profiling on the fatigue strength of welded joints and the main influencing factors. Thus, experimental test results of welds improved by different grinding techniques are reviewed. In total, 445 small- and full-scale fatigue test results of various weld types and steel grades with yield strengths up to 1100 MPa are analysed. The obtained improvements of two FAT classes correspond well with current guidelines; however, a new S–N curve slope of m = 4 is recommended—in line with proposals for other weld geometry improvement techniques.

Numerical stress analysis of tubular joints

The finite element analysis (FEA) presented in this paper pertains to the stress analysis of both the welded tubular T and X joints and is aimed to assess both the importance of the presence of the weld geometry and the suitability of shell and solid elements with regards to the FEA of welded tubular joints and, additionally, to confirm or dispute a correlation between the standards AWS D1.1 and DNVGL-RP-C203 with regards to the minimum size of the weld geometry. Using symmetry, three unit-load cases are investigated: axial loading, in-plane and out-of-plane bending. The results indicate that the FE models acknowledging the presence of the weld geometry and using solid elements are more suitable for the FEA of welded tubular joints and, moreover, the stress concentration factor (SCF) obtained at the chord “crown” location from the FE models subjected to the axial load case either approach, as in the case of the welded tubular T joint, or surpass, as in the case of the welded tubular X joint, the value estimated from the parametric equations as given in DNVGL-RP-C203.

Electron-Beam Welding of Laser Powder-Bed-Fused Inconel 718

This study explores the application of Electron-Beam Welding (EBW) for joining Laser Powder-Bed-Fused Inconel 718 (L-PBF IN718) superalloy. Three different levels of electron beam speed and beam current were explored to give nine different electron beam heat inputs for experimentation. To define the weld characteristics microhardness, tensile, and fractography analysis using scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were conducted. Typical nail-shaped weld geometry was observed with penetration depth proportional to heat input. Most welded samples exceeded the yield strength (600MPa) and tensile strength (920MPa) requirements from the ASTM F3055 specifications for additively manufactured IN718, however, the specimens did not meet the ductility requirements (27%). Brittleness of the weld was attributed to the presence of brittle secondary phases in the weld matrix, and unfused metal powder of adjacent L-PBF layers. Post-processing heat treatments were recommended to improve the weld quality while improving the ductility of EBW joints.