Parameter Influence in CO2-laser/MIG Hybrid Welding
Hybrid welding, as the combination of laser beam and arc welding, is an innovative joining technology that has many advantages compared to the single processes. With the hybrid process joint gap ca ...
Effect of Welding Position and Gap between Samples on Hybrid Laser-Arc Welding Efficiency
Influence of welding position and gap between samples on efficiency of hybrid laser-arc welding (HLAW), geometry of melting zone and alloys of filler material depth penetration are presented in the publication. Studies were indicated that maximal efficiency (thermodynamic efficiency about 43%) was achieved at hybrid laser-arc welding in PG welding position. Efficiency at PA and PC welding positions were 31.8% and 33.8% accordingly. Researches were indicated that melting zone, depth penetration alloys of filler materials and efficiency of HLAW increase with increasing gap. Experiments were indicated, that depth penetrate of filler material alloys is 20 mm (gap 1 mm). Proportion of filler material in a top part of metal seam is 50%, in bottom part of metal seam is about 5%.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME