Welding residual stresses can predominantly damage the reliability and performance of the welded structures. In this experimental study the effect of constant and pulse arc TIG welding processes, the ...development of thermal fields and residual stresses in dissimilar weldments of SS 316 and Monel 400 are investigated. During the welding process, the temperature distribution over the surface of the weldments has been captured using Infra-Red Thermography. The developed residual stresses have been measured experimentally by using the x-ray diffraction technique. The nature of residual stresses in constant and pulse arc weldments have been observed and compared. The experimental results of constant current weldments are validated against finite element analysis using ANSYS software. Transient thermal analysis is performed to determine heat dissipation during the welding process in different modes such as conduction, convection and radiation. Also, the elemental birth and death techniques are considered for the effect of filler wire owing simulation. From the results, the experimental and numerical analysis of constant arc welding process show good agreement to each other in temperature fields and residual stresses.
This research manuscript explores the residual stress analysis, mechanical and metallurgical aspects of dissimilar welded joints between AISI 316 and Monel 400 developed by constant, pulse and ...Interpulse current TIG welding processes. The induced residual stresses have been measured experimentally by employing X-ray diffraction. The mechanical properties of welded joints have been determined by conducting tensile and Vickers hardness testing. The metallurgical properties of weldments have been analyzed by employing optical and scanning electron microscopy. From the experimental results, lower residual stresses have been observed in Interpulse current TIG weldment than the other two weldments. The tensile properties of the Interpulse current TIG weldment were observed to be higher than the other two weldments. In Interpulse TIG weldments, grain refinement and reduced heat affected zone near the fusion zone have been observed.
Hastelloy C-276 nickel alloy is widely preferred for nuclear power plant applications where steam generators operate at 600 °C. However, stainless steels are still used for tubes in steam gas ...reformers which necessitates welds between dissimilar materials. In this study, hastelloy C-276 and SS 316 L alloys were joined using GTAW process. The welding parameters of GTAW were optimized to minimize the defects in samples of similar (SS 316 L-SS 316 L, HAS C-276-HAS C-276), and dissimilar (HAS C-276-SS 316 L) joints. SEM/EDS results confirm the presence of columnar dendritic and cellular structure in fusion zone for dissimilar weldments (HAS C-276-SS 316 L). EDS results also revealed the presence of larger amount of Mo, W and lower amount of Ni in the subgrain boundary as compared to the subgrain body. Compared to the similar (HAS C-276- Has C-276) and dissimilar (HAS C-276-SS 316 L) welded joints FZs, the enrichment of Mo is lesser in SS 316 L-SS 316 L similar welded joints. Higher UTS was obtained for dissimilar (HAS C-276-SS 316 L) GTAW joints 780 MPa compared to the similar welded joints of SS316 (552 MPa) and HAS C-276 (740 MPa). The average microhardness for the dissimilar SS 316 L and HAS C-276 is 220 Hv, which is higher compared to the similar welded joints, SS 316 L and HAS C-276, i.e., 190 Hv and 210 Hv, respectively. This study shows that GTAW process is suitable to fabricate sound weld joints of similar (SS 316 L- SS 316 L, HAS C-276-HAS C-276), and dissimilar (HAS C-276-SS 316 L) alloys which are useful for the nuclear power plant boilers.
Dissimilar weldments of AISI 316 and Monel 400 are extensively used in boiler feed water heaters where the weld roots are exposed to high pressure and hot corrosive environments. In this research, ...metallurgical and mechanical properties of dissimilar weldments of AISI 316 and Monel 400 obtained by pulsed current gas tungsten arc welding (PCGTAW) and constant current gas tungsten arc welding (CCGTAW) processes were compared. The heat input rate and filler wire were same in both welding techniques. Metallurgical properties are studied by employing optical microscope (OM) and scanning electron microscope (SEM). Mechanical properties of dissimilar weldments are determined by tension test and Vickers hardness. The metallurgical study has revealed fine grain structures with clear grain boundaries at the heat-affected zone in PCGTAW weldment. The ultimate tensile strength in PCGTAW and CCGTAW weldments was observed as 554 and 542 MPa, respectively. The ratio of yield strength to ultimate tensile strength is higher in PCGTAW weldment than CCGTAW weldment. The weldment developed by using PCGTAW technique has shown a higher microhardness value at HAZ of both the base metals than the weldment developed in CCGTAW technique.
In this paper, an effective approach, Taguchi grey relational analysis, has been applied to experimental results of wire cut electrical discharge machining (WEDM) on Inconel 825 with consideration of ...multiple response measures. The approach combines the orthogonal array design of experiment with grey relational analysis. The main objective of this study is to obtain improved material removal rate, surface roughness, and spark gap. Grey relational theory is adopted to determine the best process parameters that optimize the response measures. The experiment has been done by using Taguchi’s orthogonal array L36 (2
1
× 3
7
). Each experiment was conducted under different conditions of input parameters. The response table and the grey relational grade for each level of the machining parameters have been established. From 36 experiments, the best combination of parameters was found. The experimental results confirm that the proposed method in this study effectively improves the machining performance of WEDM process.
The article investigates the residual stress distribution and surface deformation induced with Laser Shock Peening (LSP) using Finite Element Method (FEM) model.LSP surface treatment is complex ...phenomenon with huge number of parameters interaction in nanosecond span of time to induce deep residual stress. ABAQUS Explicit Dynamic FEM is used with Johnson-Cook material model for analysing non linear constitutive behaviour of Ti6Al4V and compared with published experimental results. A fine correlation is observed for simulated model and literature results at particular peening condition. A Design of Experiment based simulation of LSP is performed to analyse the effect of Laser spot diameter, laser spot overlapping rate, Laser power density, Number of laser shots and laser pulse time on residual stress distribution and surface deformation. Fractional factorial design is adopted for designing the experiments with five factors having three levels each. Equal in levels of laser spot overlap, laser power density and number of shots will gradually increase in residual stress induced and huge surface deformation with respect to laser pulse duration. Random interactions of these parameter levels have two different type of results; deep compressive stress with minimum deformation and reversal of compressive to tensile stress with huge deformation on surface followed by deep compressive stress.
Hydrogen embrittlement of Ti6Al4V alloy was investigated under electrochemical cathodic hydrogen charging. Advanced surface treatment and material characterisation, laser shock peening (LSP) or laser ...peening (LP), atom probe tomography, slow strain rate tensile (SSRT) test, and XRD residual stress are employed for analysis. Results obtained exposed the opportunity to implement surface treatment for controlling hydrogen embrittlement. Induced grain refinement and compressive residual stress restrict the hydrogen uptake in Ti6Al4Valloy. Furthermore, APT results gave wt. % of TiH (titanium hydride) in laser peened hydrogen charged and untreated hydrogen-charged specimens. Thus, it is concluded that compressive stress induced by laser peening process controlled uptake of hydrogen by Ti6Al4V alloy.
Purpose
In any machining process, the surface profile of the workpiece is continuously changing with respect to time and input parameters. In a conventional machining process, input parameters are ...feed and depth of cut whilst other parameters are considered to be constant throughout the process.
Design/methodology/approach
The direct and indirect participation of this instantaneous curvature can be used to optimize the strategy of cutting operation in terms of different parameters like heat generation-induced stresses, etc. The concepts of the metric tensor and Riemannian curvature tensor are made use in this study as a representation of curvature itself. The objective of this study is to create a mathematical methodology that can be implemented on a highly flexible machining process to find an optimum cutting strategy for a particular output parameter.
Findings
The study also includes different case studies for the validation of this newly introduced mathematical methodology.
Originality/value
The study will also find its position in other mechanical processes like forging and casting where instantaneous curvature affects various mechanical properties.
In this research, the dissimilar metals of AA5052 and AA7075 were joined by employing gas tungsten arc welding process using ER4043 as filler metal. During welding, the temperature distribution over ...the weld surface was measured using Infrared thermography. Using X-ray diffraction technique, residual stresses were measured in each welding pass on different weld zones. From thermography results, the peak temperature of 712, 789 and 816 °C was recorded in pass-1, pass-2 and pass-3, respectively. Higher temperature values were recorded at the HAZ of AA5052 than at the HAZ of AA7075. Peak residual stress of 66, 28 and 45 MPa was observed in pass-1, 2 and 3, respectively. Minimum residual stresses were observed at the HAZ of AA5052 than HAZ of AA7075.
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