Department of Mechanical Engineering

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In the current study, CFD simulations and static structural analysis were carried out to estimate the wind loads for up and downstream wind directions on ground mounted arrayed solar panels. The goal of simulations is to estimate the loads (i.e. drag and lift forces and also moment coefficients) and wind pressure that act upon their surface. Static structural analysis coupled with CFD simulation is done to determine the total deformation due to wind loads on each panel. The motive of the study is to protect the integrity of the solar panels in a situation like cyclone and typhoon so that energy production is not hindered throughout their service life. Simulations were carried out on arrayed nine panels with changing various parameters (i.e. clearance height, inter row spacing between panels and panel inclination) that effect wind loading on the panels Copyright © 2018 ASME.

World University root node

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

Structural analysis of ground mounted solar panel array

Creep strength enhanced ferritic/martensitic 9Cr-1Mo-V-Nb (P91) steel is also designated as ASTM A335 used for out-of-core and in-core (piping, cladding, ducts, wrappers, and pressure vessel) of Gen IV reactors. In present investigation, the dissimilar weld joint of P91 and P92 steel were made using the autogenous tungsten inert gas (TIG) welding with single pass, double side pass and multi-pass gas tungsten arc (GTA) welding with filler wire. Microstructure evolution in sub-zones and mechanical properties of dissimilar welded joints were studied in as-welded and post weld heat treatment (PWHT) condition. Formation of δ-ferrite patches in weld fusion zone and heat affected zones (HAZs) and their influence on the mechanical behaviour of the welded joints were also studied. Presence of higher content of ferrite stabilizer in P92 steel have resulted the formation of δ-ferrite patches in weld fusion zone as well as HAZs. The δ-ferrite was observed in autogenous TIG welds joints. The δ-ferrite patches were formed in as-welded condition and remained in the microstructure after the PWHT. The δ-ferrite patches leads to reduction in Charpy toughness of autogenous TIG welds joint and also lower down the average hardness of weld fusion zone. Peak hardness and poor impact toughness were observed for autogenous TIG welds joint as compared to GTA welds. For microstructure characterization, field-emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS) and optical microscope were utilized. © 2017 Elsevier B.V.

Materials Science and Engineering A

Comparative study of autogenous tungsten inert gas welding and tungsten arc welding with filler wire for dissimilar P91 and P92 steel weld joint

Ferritic/martensitic 9Cr-1Mo-V-Nb steel also designated as ASTM A335 used in construction of several components of power plants operating in temperature range of 600–650 °C. In present investigation, dissimilar weld joints of P91 and P92 steel were prepared using the autogenous tungsten inert gas welding (A-TIG) and multi-pass gas tungsten arc (GTA) welding process. A comparative was performed on evolution of δ-ferrite patches in weld fusion zone and heat affected zone (HAZ) of welded joints. The evolution of δ-ferrite patches was carried out in as-welded and post-weld heat treatment (PWHT) condition. PWHT was carried out at 760 °C for 2 h for both A-TIG and GTA welding process. For A-TIG weld joint higher yield strength, ultimate tensile strength (UTS) and peak hardness were measured due to higher heat input in single pass and higher carbon content in weld fusion zone. Higher heat input, fast cooling rate and higher weight percentage of ferrite stabilizer like vanadium (V) and niobium (Nb) in A-TIG weld joint were resulted in formation ferrite patches in weld fusion zone and heat affected zone. Higher weight percentage of V and Nb in A-TIG weld zone was resulted poor impact toughness of A-TIG weld fusion zone than GTA welds in as-welded condition. After the PWHT at 760 °C–2 h, Charpy toughness of A-TIG weld fusion zone (48 J) just meet the minimum required value as required by the EN: 1557:1997 (47 J). © 2017

Journal of Manufacturing Processes

Dissimilar joining of CFEF steels using autogenous tungsten-inert gas welding and gas tungsten arc welding and their effect on δ-ferrite evolution and mechanical properties

Creep strength enhanced ferritic (CSEF) P91 steel were subjected to room temperature tensile test for quasi-static (less than 10−1/s) strain rate by using the Instron Vertical Tensile Testing Machine. Effect of different type of notch geometry, notch depth and angle on mechanical properties were also considered for different strain rate. In quasi-static rates, the P91 steel showed a positive strain rate sensitivity. On the basis of tensile data, fracture toughness of P91 steel was also calculated numerically. For 1 mm notch depth (constant strain rate), notch strength and fracture toughness were found to be increased with increase in notch angle from 45° to 60° while the maximum value attained in U-type notch. Notch angle and notch depth has found a minute effect on P91 steel strength and fracture toughness. The fracture surface morphology was studied by field emission scanning electron microscopy (FESEM). © 2017 Elsevier B.V.

Journal of Nuclear Materials

Effect of strain rate and notch geometry on tensile properties and fracture mechanism of creep strength enhanced ferritic P91 steel

Friction stir processing (FSP) is a novel process for refinement of microstructure, improvement of material’s mechanical properties and production of surface layer composites. In present investigation, composite reinforced with using Zn/ MoS2 powder in as-cast alloy were developed at tool rotational speed of 664 rpm and tool transverse speed of 26 mm/min using FSP. Microstructural observation of MoS2/Zn reinforced composites confirmed the fine and equiaxed grains in the stir zone (SZ) and distribution of fine reinforced particles of MoS2/Zn in SZ. Moreover, agglomeration of MoS2/Zn particles were not observed. The ultimate tensile strength was measured to be 113 ± 9 and 82 ± 7 MPa for MoS2and Zn reinforced Al-Si alloy, respectively. The sliding wear was studied using pin-on-disk tribometer and it was found that FSP enhanced the wear resistance of the as-cast alloy. The MoS2 reinforced composite showed superior wear resistance than Zn reinforced composite and base material. To understand the acting wear mechanism, the field emission scanning electron microscope (FESEM) of worn out surfaces were performed. © 2018, Springer Science+Business Media B.V., part of Springer Nature.

Silicon

Mechanical Properties and Wear Behavior of Zn and MoS2 Reinforced Surface Composite Al- Si Alloys Using Friction Stir Processing

In present research article, microstructure evolution in P91 steel and their weldments are reviewed in as-virgin and heat treatment and creep exposure condition. The thermal stability of P91 steel is derived from solid solution strengthening, sub-grain hardening and precipitation hardening. The initial microstructure plays an important role in deciding the mechanical properties of P91 steel and their weldment in long-term ageing and creep exposure condition. Effects of various alloying elements present in P91 steel and their related phase have also been discussed in details. The role of grain coarsening, Cr/Fe ratio, lath widening and dislocation density on creep rupture life of base metal and weldments are discussed. The combined effects of lath martensitic microstructure, residual stress and diffusible hydrogen content on performance of P91 steel material are also discussed. © 2018 Elsevier B.V.

Journal of Alloys and Compounds

Some studies on P91 steel and their weldments

Yttria (8%) stabilized zirconia (8YSZ)-alumina-carbon nanotube (CNT) composite coatings were deposited using air plasma spray (APS) technique. Three zirconia alumina (ZA) composite coatings, without CNT reinforcement, and with 1%CNT, 3%CNT reinforcement were deposited using identical process parameters (500 A and 66 V). Indentation method was used to characterize mechanical behavior of coatings. The CNT reinforced composite coating showed superior mechanical properties as compared to the conventional 8YSZ coating. The addition of alumina and 1%CNTs increased the Young's modulus by around 25% and 40%, respectively. However, the increase in CNT content decreased the Young's modulus as a result of CNT agglomeration. The hardness, fracture toughness increased with addition of alumina and CNT. The fracture toughness increased from 0.55 ± 0.26 MPa m1/2 for 8YSZ to 1.76 ± 0.65 MPa m1/2 for 17%alumina-3%CNT reinforcement due to various toughening mechanisms like crack deflection, bridging etc. The maximum displacement of indenter was found to decrease from ~ 176 nm for conventional YSZ coating to ~ 120 nm for 3% CNT reinforced coating. The surface roughness (Ra) was found to be decrease with alumina addition and CNT reinforced coating. The CNT reinforced coating showed surface roughness of around 6 µm. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was used to characterize the coating microstructure and elemental composition respectively. © 2018 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Mechanical property evaluation of carbon nanotubes reinforced plasma sprayed YSZ-alumina composite coating

The aim of the characterization of P911 steel is to determine the consequence of different tempering temperature on nano-size particle evolution and their effect on the mechanical properties. P911 steel was normalized at 1040 °C for 1 h and subjected to varying tempering condition in the range of 720–800 °C for 2 h of tempering time. To study the effect of tempering temperature on nano-size particles distribution and grain size of P911 steel, field-emission scanning electron microscope (FESEM) and optical microscope (OM) were utilized. The other tests were hardness measurement and room-temperature tensile testing was performed to characterize the P911 steel for different tempering condition. The ultimate tensile strength (UTS) and hardness have found a great dependency on the area fraction of precipitates present in the microstructure. The UTS and hardness were observed to be increased continuously with increase in tempering temperature in range of 720–800 °C. © 2017 Elsevier B.V.

Evolution of nano-size precipitates during tempering of 9Cr-1Mo-1W-V-Nb steel and their influence on mechanical properties

In the present work, studies have been carried out on the variations in the microstructure and hardness of P91 base-metal and welded joint. This variations result from the grit blasting and thermal cycle experienced during the thermal spraying process. The microstructural effects have been analyzed in terms of the depth of the deformation zone. Scanning Electron Microscopy and X-ray diffraction were used as characterization techniques. The grit blasting carried out prior to thermal spraying has resulted in the highest change in sub-surface hardness of the heat affected zone (HAZ). However, flame treatment further reduced the subsurface hardness of the heat affected zone. The depth of deformation zone was highest for inter-critical heat affected zone (IC-HAZ). The overall coating process resulted in an increase in subsurface hardness of various regions of HAZ and fusion zone (FZ). The base metal showed a 7% increase in subsurface hardness due to the overall coating process. The IC-HAZ showed maximum variation with 36% increase in subsurface hardness. The coarse grained heat affected zone (CG-HAZ) and FZ did not show any change in subsurface hardness. As a whole, the hardness and microstructure of the welded joint was observed to be more sensitive to the thermal spray coating process as compared to the base metal. © 2018 Polish Academy of Sciences. All Rights Reserved.

Archives of Metallurgy and Materials

Effect of grit blasting and thermal spraying on microstructure evolution of P91 weldment

Ferritic/martensitic 9Cr-1Mo-V-Nb (P91) and 9Cr-0.5Mo-1.8W-V-Nb (P92) steel are used for high temperature (600-650°C) operating components in nuclear and thermal power plants. The present research work deals with the dissimilar joining of P91 and P92 steel using autogenous tungsten inert gas (TIG) welding and multi-pass gas tungsten arc welding (GTAW) with filler. The evolution of δ-ferrite patches in weld fusion zone and heat affected zones (HAZs) were characterized in as-welded and post weld heat treatment (PWHT) condition. PWHT was carried out at 760°C for 2 h and 6 h, for both autogenous-TIG and GTA weld joints. Charpy toughness and microhardness tests were performed for autogenous-TIG welding and GTA welding process under as-welded and PWHT condition. © 2018 Elsevier Ltd.