Author
P. V. Kumar
Bio: P. V. Kumar is an academic researcher from Indira Gandhi Centre for Atomic Research. The author has contributed to research in topics: XANES & Heat-affected zone. The author has an hindex of 5, co-authored 9 publications receiving 179 citations.
Papers
More filters
TL;DR: In this article, the peak temperatures attained at different points during deposition of weld beads in stainless steel and low carbon steel weld pads were compared, and the residual stress patterns developed, the change in the peak tensile stress with the deposition of welding beads and the relation between peak temperatures and residual stresses in the weld pads are discussed.
134 citations
TL;DR: In this paper, a three-dimensional computer model based on the control volume method has been developed to predict the temperature distribution in the heat affected zone (HAZ) and in the base plate region of the bead on plate welds, using the weld parameters as input data to the computer model.
Abstract: Welding is a highly reliable and efficient metal joining process. Manual metal arc (MMA) welding is very widely used in industry. The temperature distribution that occurs during welding affects the material microstructure, hardness, and the residual stresses present in the material after welding. In the present work, the temperature distribution during bead on plate welding using MMA welding was experimentally determined for AISI type 304 stainless steel plates and low carbon steel plates of thickness 6 and 12 mm. A three-dimensional computer model based on the control volume method has been developed to predict the temperature distribution in the heat affected zone (HAZ) and in the base plate region of the bead on plate welds, using the weld parameters as input data to the computer model. In this computer model, the heat energy used to melt the electrode is considered as a separate heat flux term and the remaining heat supplied by the welding arc is considered as another heat flux term. A good match between the experimental results and the theoretical predictions was obtained. Using the computer model, the time taken to cool from 800 to 500°C in the coarse grained HAZ (close to the fusion line) of low carbon steel specimens was calculated. From this cooling time and the chemical composition of the material, the maximum hardness in the coarse grained HAZ was predicted. Microhardness measurement in the same region of the welded plates was carried out. The experimentally measured values and predicted results match closely.
18 citations
TL;DR: In this article, the authors used time of flight (ToF) neutron reflectivity (NR) to measure the density of a-C thin films and found that the determination of density of carbon thin films, especially those with a thickness of few tens of nm, may not be accurate with XRR due to a poor scattering contrast between the film and substrate.
14 citations
TL;DR: In this article, changes in physical and chemical properties have been studied for polycarbonate (PC) implanted by 100 keV Ni+ with various fluences from 1 × 1014 to 1 ×1016 ions/cm2.
Abstract: Changes in physical and chemical properties have been studied for polycarbonate (PC) implanted by 100 keV Ni+ with various fluences from 1 × 1014 to 1 × 1016 ions/cm2. Changes in the surface morphology and composition have been observed with atomic force microscopy and X-ray diffraction (XRD). Ni particles as precipitates in PC were observed by cross-section transmission electron microscopy at the 100-nm depth. Ion implantation induces changes in the topography of PC as indicated by a dramatic increase in surface roughness with ion fluence. Implanted metal ions show direct evidence of compound formation on the surface. Chemical changes in the surface region have been observed by Raman spectroscopy and UV–vis spectroscopy. UV–vis absorption analysis indicates a drastic decline in optical band gap from 5.46 to 1.76 eV at an implanted dose of 1 × 1016 ions/cm2. It is shown that partial destruction of the original chemical bonding under ion implantation leads to the creation of new amorphous and graphite-like structures, which are confirmed by Raman spectroscopy. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:143–151, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20130
13 citations
TL;DR: Results show that the composition of boron carbide films is strongly dependent on layer thicknesses, and HAXPES measurements suggest that most of theboron is in the chemical state of B4C in the multilayer structures.
Abstract: W/B4C multilayers (MLs) consisting of ten layer pairs with varying boron carbide layer thicknesses have been investigated. The ML structures were characterized using grazing-incidence hard X-ray reflectivity (GIXR), resonant soft X-ray reflectivity (RSXR), hard X-ray photoelectron spectroscopy (HAXPES) and X-ray absorption near-edge spectroscopy (XANES). Depth-resolved spectroscopic information on the boron carbide layer in W/B4C MLs was extracted with sub-nanometre resolution using reflectivity performed in the vicinity of the B K-edge. Interestingly, these results show that the composition of boron carbide films is strongly dependent on layer thicknesses. HAXPES measurements suggest that most of the boron is in the chemical state of B4C in the multilayer structures. XANES measurements suggest an increase in boron content and C-B-C bonding with increase in boron carbide layer thickness.
9 citations
Cited by
More filters
TL;DR: Based on the ABAQUS software, uncoupled thermal-mechanical three-dimensional and two-dimensional (2-D) finite element models are developed in this article to evaluate the transient temperature and the residual stress fields during welding.
517 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
TL;DR: In this paper, the effect of initial pH and temperature of iron salt solutions on formation of magnetite (Fe3O4) nanoparticles during co-precipitation was reported.
287 citations
01 Oct 2016
TL;DR: The authors of as discussed by the authors greatly acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness (CTQ2014-52687-C3-1-P project) and Marie Sklodowska Curie Initial Training Networks (FP7-PEOPLE-2013-ITN, BIBAFOODS project).
Abstract: The author greatly acknowledges the financial support from the Spanish Ministry of Economy and Competitiveness (CTQ2014-52687-C3-1-P project) and Marie Sklodowska Curie Initial Training Networks (FP7-PEOPLE-2013-ITN, BIBAFOODS project). The author also acknowledges support from Generalitat de Catalunya (2014SGR1655 and TECCIT15-1-0009) and Centro de Investigacion Biomedica en Red de Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN).
285 citations