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Thick AISI 304L stainless steel plates were welded using the gas metal arc welding process, and through-thickness residual stresses were evaluated by finite element simulation and the deep hole drilling technique. 3D moving heat source-based thermo-mechanical models were implemented to evaluate through-thickness residual stresses. The effects of the weld groove geometries and external restraints on the pattern of through-thickness residual stresses were studied. The maximum magnitude of locked-in residual stresses was recorded beneath the top surface, at a depth of around 6 mm. In comparison to conventional weld groove, the narrow weld groove configuration exhibited a 20–40% reduction in peak residual stresses. A significant rise in residual stresses was observed in constrained welds. The effect of the yield strength of the filler material on the evaluation of the through-thickness residual stress distribution in the course of finite element modeling was illustrated. The evolution of through-thickness residual stresses was also assessed concerning each weld pass.

Fracture studies were carried out on narrow gap welded SA 312 Type 304LN stainless steel straight pipes having circumferential through-wall notch in the weld. Totally six specimens were tested; one specimen was subjected to monotonic loading and the remaining five specimens were subjected to quasi-cyclic loading. Under quasi-cyclic loading, one specimen was tested under incremental displacement-controlled loading and the remaining four specimens were tested constant amplitude load-controlled loading. Based on the load-controlled experimental results, a plot of the cyclic load amplitude versus number of cycles to failure of the specimens was obtained. The experimental results indicate that the piping components subjected to quasi-cyclic loading may fail in very less number of loading cycles even when the load amplitude is sufficiently below the monotonic fracture/collapse load. Crack growth behaviour and cyclic tearing instability in the specimens, which are required for realistic assessment of Leak Before Break applicability, was studied.

Several engineering components are fabricated by joining similar or dissimilar materials. In the present investigation, welded joints between low alloy steel and austenitic stainless steel were considered. This assembly is one of the critical components in the heat transport system of water-cooled reactors of nuclear power plants. 309L austenitic stainless steel and IN 182 alloys were used for buttering low alloy steel during fabrication of joints. Weld metal was 308L austenitic stainless steel and IN 182, respectively, for the two assemblies. Buttering by 309L SS was performed by gas tungsten arc welding, and the same was done by shield metal arc welding at the time of applying IN 182. Joining of 304L SS and buttered assembly in both the cases was carried out by shield metal arc welding. Evaluation of Vickers micro-hardness was done across the weld centerline for both joints. Microstructure of different regions was examined for the joints. Apart from conventional destructive tests, ultrasonic evaluation of joints was also carried out to ensure weld integrity. In this respect, ultrasonic velocity in longitudinal and shear mode was measured along the transverse direction of the weld. Young’s modulus was determined using ultrasonic tests as well as from the average hardness of different regions. The obtained Young’s modulus by two different techniques revealed satisfactory co-relation. The Young’s modulus obtained from ultrasonic measurements was used to determine the yield strength of different regions across the welds. This technique proved to be useful in identifying the failure prone area across the welded joint.

In this study, numerical modelling was utilized to evaluate through-thickness in-plane residual stress fields in a butt-welded joint of pressure vessel steel under restrained condition. The numerical model was validated with experimental results procured through deep hole drilling (DHD) technique to obtain reasonable precision in measurement. Attempts to measure residual stress distribution were made on a welded joint of single V groove geometry, produced by multipass gas metal arc welding (GMAW) process under restrained condition. The degree of restraint constraining the workpiece from deformation was calculated analytically in terms of reaction forces exhibited due to unit transverse shrinkage. The predicted results were found to be in good agreement with the experimentally obtained residual stress profiles. Maximum residual stress magnitude of the weld joint under restrained condition was found to be around 84% of the yield strength of the weld material.

Dissimilar metal welded joints were fabricated between SA508 low alloy and 304LN stainless steel using IN82, IN182, and IN152 as buttering alloys. In-situ tensile testing of the welds demonstrated that the crack initiation and propagation were away from the fusion boundary between low alloy steel and buttering material. The heterogeneities like clustered lath martensite with high dislocation density, Type-I boundary, and Type-II boundary near the interface have a meager role in influencing the tensile properties of the welds. On the contrary, grain structure and second phase distribution in re-solidified buttering alloy played a dominant role in determining the tensile properties of welds. This understanding may pave the way to modify the welding parameters, select appropriate welding consumables, and explore the failure-prone location for such kind of transition joints.

This paper presents outcome of round robin exercise on usage of ball indentation technique to predict strength properties of three different materials which are used in Indian nuclear reactors. The main objectives were to evolve a standardized procedure of determining the mechanical properties by the Ball Indentation technique and quantification of the variation in strength and fracture properties due to ageing through such tests. Standard uniaxial tensile tests were also carried out to quantify the differences between strength properties predicted by ball indentation and those determined using conventional tests. Three different materials studied were, carbon-manganese steel (Grade: SA 333Gr.6), stainless steel (SA312 Type 304LN) and zirconium alloy (Zr-2.5Nb). The carbon-manganese steel and stainless steel materials were drawn from extruded pipes while Zr-2.5Nb was drawn from pressure tubes, used in Indian Pressurized Heavy Water Reactors. Ball indentation tests were carried out on materials in as received and in aged conditions. The ageing was simulated artificially. The carbon-manganese steel and stainless steels were subjected to cold work while Zr-2.5Nb alloy was subjected to heat treatment at different temperatures with varying hold times and in some cases with charged hydrogen. The round robin exercise was conducted within different research centers of Department of Atomic Energy (DAE), India. This was a blind exercise in which all the conventional tests were carried out by a group (who was not involved in Ball Indentation tests) after the completion of ball indentation tests by participants. The paper presents the prediction of strength properties, using ball indentation, by different participants. The reasons of scatter in the results among the various participants and differences with respect to conventional test results are discussed in the paper.

The present paper aims to predict distortions and residual stresses in thick plate weld joints of austenitic stainless steel material prepared by automatic hot wire gas tungsten arc welding (GTAW) process and narrow gap technique using finite element analysis (FEA). The prediction has been validated by carrying out experiments. The variables considered in welding of plate joints are narrow groove configuration, high deposition rate leading to lower heat input (hot wire GTAW), and stress relieving treatment. A suitable stress-relieving treatment has been proposed for relaxing residual stresses and preventing sensitization of the heat-affected zone (HAZ) of the ASS weld joint. Predicted and experimental results of temperature distribution, distortions, and residual stresses were found to be in good agreement. The applicability of prediction of residual stresses for higher weld thicknesses has also been verified. The nature of residual stresses across thickness has also been compared with that given in Structural Integrity Assessment Procedures for European Industry (SINTAP) and BS 7910 standards. Details of the above finding are discussed in this paper.

Purpose Study aim to investigate the possible role of Fok I VDR polymorphism in TB risk assessment. Methods To investigate the role of Fok I VDR polymorphism in TB risk assessment, we collected a blood sample from 106 healthy individuals including both gender. The genomic DNA was isolated and the VDR gene was amplified using gene-specific primers using polymerase chain reaction. The Genotyping of the Fok I polymorphism was performed using Fok I restriction enzyme. The distribution of genotype frequencies of VDR gene polymorphisms was calculated using Hardy-Weinberg equilibrium calculator. Results In the present investigation, the VDR gene was amplified with an undigested DNA band of 265 bp as FF homozygote. Additionally, 169 bp and 96 bp as ff homozygote and three bands ((265 bp, 169 bp, and 96 bp) were observed in the heterozygote. As per our finding, we report a significantly low frequency of susceptible genotypes in Ff (27.4%) and ff (6.6%) compared to average frequency Ff = 41.80% and ff = 8.25% of India. We also reported here the low frequency of mutant allele f in India's central part, i.e., Bhopal division, Madhya Pradesh. Considering our finding, the mutant allele's low frequency in central India, Madhya Pradesh, shows a negligible contribution of Fok I VDR polymorphism in TB prevalence. Conclusions In a comparative analysis with the Northern and Southern India population based on previous reports, the involvement of FoK I polymorphism in the VDR gene was non-significant in Central India. All the studied populations were found in Hardy-Weinberg equilibrium except North India for the Fok1 VDR genotypes.

Dissimilar metal welds (DMW) of ferritic to austenitic stainless steel are broadly used in steam generators working in power generation industries. Frequent failure of DMWs from the heat-affected zone (HAZ) of the ferritic part necessitates structural integrity assessment of the DMWs in order to determine and extend the lifetime of these components. In this regard, typical DMWs of SA516–309L–304L and SA516–309L/308L–304L attributed to domestic reactors were fabricated under different welding conditions. The effects of conventional and narrow weld groove configurations, buttering layer, and varying buttering layer width on the through-thickness residual stress fields in the DMWs were investigated experimentally and with the help of numerical simulations. Results show that the narrow groove weld is beneficial in reducing the residual stresses in the weld zone. Incorporating an additional buttering layer in the narrow groove joint further reduced the residual stresses across the weld joint. A 6 mm thick buttering layer was found to be competent enough to minimize the residual stresses dispersed across the weld cross-section.

Fracture studies were carried out on bi-metallic pipe weld joints of 324 mm outer diameter having crack at different regions of weld in the circumferential direction. The bi-metallic pipe weld joints were made of low alloy steel (ferritic) and stainless steel (austenitic) materials. Welding consumable used was nickel-based alloy. The initial notch was located in the different regions of the weld joints such as base metals (ferritic and austenitic), centre of weld, buttering (nickel-based alloy on low alloy steel) and heat affected zones. Subsequent to fatigue pre-cracking, fracture tests were carried out under four-point bending under monotonic and cyclic loading. During the fracture tests, load, load-line displacement, deflections, circumferential deformations, surface crack growth, crack mouth opening displacement were recorded. In addition, number of cycles to failure were monitored for tests under cyclic loading. Under monotonic loading, collapse load of the bi-metallic pipe weld joint having initial crack in the centre of buttering reduced by 12% in comparison to the collapse load for crack in the centre of heat affected zone. Crack deviated towards austenitic region for the weld joints having crack in the centre of weld, centre of buttering and heat affected zone. The bi-metallic pipe weld joints subjected to cyclic loading failed at lower number of cycles even when the load amplitude was sufficiently below the collapse load under monotonic loading. Crack growth resistance of bimetallic pipe weld joints under cyclic loading was significantly lower compared to that under monotonic loading under displacement control.

In present study, dissimilar metal weld (DMW) joints between SA508Gr.3cl.1 ferritic steel and SS304LN pipes were prepared using Inconel 82/182, and Inconel 52/152 consumables. Metallurgical properties and their influence on fracture toughness of weldment regions and interfacial regions could play a significant role in integrity assessment of these joints. Ni-based consumables exhibit complex metallurgical properties at interfacial regions. The metallurgical characterization and fracture toughness studies of Inconel 82/182 and Inconel 52/152 joints have been carried out for determining the optimum consumable for DMW joint requirements and the effect of microstructure on fracture toughness in weldment regions. The present codes and procedures for integrity assessment of DMW joints have not given due considerations of metallurgical properties. The requirements for metallurgical properties by considering their effect on fracture toughness properties in integrity assessment have been discussed for reliable analysis. Inconel 82/182 is preferred over Inconel 52/152 joints owing to favorable metallurgical and fracture toughness properties across the interfacial and weldment regions.

The present work aims to evaluate distortion and residual stresses in thick plate weld joints of austenitic stainless steel. Quantification of residual stresses in thick austenitic stainless steel weld joint is important because it is not desirable to carry out stress relieving after welding owing to the susceptibility to sensitization in the heat-affected zone. Therefore, systematic studies were carried out to predict and measure distortion and residual stresses in the austenitic stainless steel plate weld joint. Variables influencing the generation of residual stresses such as heat input, welding speed, constraints during welding were considered. 20 mm thick plate weld joint of austenitic stainless steel material was prepared using gas tungsten arc welding (GTAW) in unclamped condition and distortions were measured during welding after each pass. Sub-surface and through-thickness residual stresses were measured using blind hole drilling (BHD) and deep hole drilling (DHD) techniques respectively. Thereafter, the weld joint was modeled using the finite element method and analyzed for residual stresses and distortions. Thermal analysis was carried out using actual welding parameters and temperature-dependent material properties to generate temperature profile and compare it with the measured values. The temperature profile along with necessary boundary conditions was used for structural analysis to obtain distortion and residual stresses. Experimental and finite element analysis results for distortion and residual stresses compare well. Details of the experimental and numerical analysis results of distortion and residual stresses for thick section plate weld joints have been discussed in this paper. Also, the effects of differences in yield strengths of weld and base metals on distortion and residual stress results have been brought out.

The aim of the paper is to evaluate the local tensile and fracture toughness properties of the dissimilar metal weld joints between SA508Gr.3 Cl.1 and SA312 Type 304LN pipe. Weld joints have been prepared by manual gas tungsten arc welding (GTAW) process with conventional V-groove and automatic hot wire gas tungsten arc welding with narrow gap using different filler wires/electrode such as Inconel 82/Inconel 182 and ER309L/ER308L. The tensile and fracture toughness test specimens have been machined from different regions of dissimilar metal weld such as heat affected zones, fusion lines, buttering layer, weld metal and both base metals. Tensile and fracture toughness tests have been carried out as per the ASTM standard E8 and E1820 respectively. Tensile and fracture toughness results of all the regions of dissimilar metal weld joints have been discussed in this paper. Metallurgical and fracture surface examinations have also been reported to substantiate the tensile and fracture toughness results. Need for the local properties for integrity assessment of the dissimilar metal weld joints has also been brought out.

The micromechanism of ductile fracture involves processes of void nucleation, growth, and coalescence. The change of void volume fraction with loading in porous metals affects their stress carrying capability. These changes depend upon the stress triaxiality. Though the voids grow under hydrostatic loading conditions, they tend to distort in shear dominant loading conditions leading sometimes to change in porosity. In addition, the voids change their shape and orientation during the loading process which needs to be captured accurately in a material constitutive model in order to predict the deformation behavior. Many of the existing models in literature do not adequately represent the changes in void volume fraction and their shape for a wide range of values of stress triaxilities. In this work, a scheme has been proposed to evaluate the change of average shape of the ellipsoidal and cylindrical voids consistent with their change in volume fraction with loading for different types of loading conditions including those of shear dominated conditions. The results of the proposed method have been validated with 2D and 3D cell model finite element analysis under pure shear, combined tension-shear, and compression-shear loading conditions.

Bi-metallic welded joints are necessary in pressurized and boiling water reactors where heavy section low alloy carbon steel components are connected to stainless steel primary piping systems. The behaviour of such bi-metallic weld joints is very difficult to understand, and very limited experimental data are available in the literature on the fracture behaviour of such joints. It is essential to develop fracture assessment methodologies for these joints and validate them experimentally to ensure safe operation of power plants. In this background, fracture studies were carried out under monotonic bending on seven numbers of bi-metallic pipe weld joints of 324 mm nominal outer diameter having circumferential through-wall crack. The specimens were made of SA 508 Gr.3 Cl-1 low alloy steel (ferritic) pipe on one half and SA312 Type 304LN stainless steel (austenitic) pipe on the other half. The initial through thickness notch was located in the different regions of the weld joints such as weld centre, buttering, heat-affected zones and base metals (low alloys steel and stainless steel). Initial notch angle was either 60° or 90°. Prior to the fracture tests, fatigue pre-cracking was carried out to create sharp crack front. Subsequently, fracture tests were conducted under four-point bending and displacement control. The collapse load of the weld joint having crack in the buttering layer is 12% less compared to that having crack in the heat-affected zone. Increase in the crack angle present in the heat-affected zone from 60° to 90° reduced the collapse load of the weld joint by 19%.

The past two decades have seen an increasing emphasis on the development of flaw assessment procedures accounting for the state of stress (constraint) near the crack tip. In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in a weld or in the regions near the weld. In recent work, the authors have proposed a novel three-parameter scheme to characterize the crack tip opening stress, for small-scale yielding, for a crack lying at the center of a strength mismatched weld. The proposed scheme was validated with detailed finite element analyses using the modified boundary layer formulation. In the present work, the previously proposed scheme is extended to an off-center crack lying in the weld region. Apart from analyzing an off-center crack, studies are performed on an interface crack in a weld having finite width. To validate the proposed scheme, modified boundary layer analyses are carried out for a wide range of offset ratio values (ratio of the crack tip-to-weld center distance to the weld half-width), ranging from 0.33 to 0.9, and strength mismatch ratio values (ratio of yield strength of weld to yield strength of base material), ranging from 0.6 to 1.6. Our studies revealed that the proposed analytical scheme works well for all offset ratios and weld mismatch ratios. For an interface crack, crack tip stresses depend mainly on the strength mismatch ratio between the base and weld material. Practically no significant effect is observed of the weld width on the crack tip opening stress of an interfacial crack.

A new lumped-parameter equivalent circuit model using three-diodes is presented in this work for large area (∼154.8 cm 2 ) industrial silicon solar cells. The estimation of values of ideality factors n 1 (>1) and n 2 (>2) using a Particle Swarm Optimization (PSO) algorithm for the two-diode model of the industrial samples has been found not to be in conformity with the theoretical values (n 1 = 1 and n 2 = 2 in the literature). The two diodes of the two-diode model are not able to define the different current components of the solar cells clearly. A model with three-diodes has been proposed to better explain the experimental data. In the proposed model, we considered the series resistance, R s , of the solar cell to vary with the current flowing through the solar cell device. All the parameters of the proposed model have been estimated using a PSO algorithm and they were compared with the parameters of the two-diode model. The new model has been found to be a better model to define clearly the different current components of the large size industrial silicon solar cells.

The paper aims at demonstration of reduction in residual stress, distortion and sensitisation in austenitic stainless steel pipe welds. The welding processes considered are Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc welding (SMAW) along with Hot wire GTAW with narrow gap welding technique. It was shown that residual stress is significantly reduced in case of hot wire GTAW. The reduction in residual stress is due to the low heat input and high deposition rate. Lower heat input leads to higher cooling rate giving more margins on sensitization in heat affected zone (HAZ). This has been confirmed by measuring temperature and cooling rate during welding in HAZ of the weld joints. Susceptibility to sensitization of the welds has been compared by carrying out ASTM E262 Practice A and E along with Electo-Potentiokinetic Reactivation (EPR) method. The results of the tests show that values are within acceptable limit for both the cases. However, hot wire GTAW has marginally better sensitization resistance. Fatigue crack growth rate and fracture resistance behavior of the above mentioned weld joints have been compared by carrying out tests on the specimens (Compact Tension) and full scale pipe welds with crack. Fatigue crack growth rate and fracture toughness of the weld joints (hot wire GATW) is superior to conventional GTAW and SMAW. The paper presents the details of the above mentioned studies.

The objective of the present study is to understand the fatigue crack growth behavior in austenitic stainless steel pipes and pipe welds by carrying out analysis/predictions and experiments. The Paris law has been used for the prediction of fatigue crack growth life. To carry out the analysis, Paris constants have been determined for pipe (base) and pipe weld materials by using Compact Tension (CT) specimens machined from the actual pipe/pipe weld. Analyses have been carried out to predict the fatigue crack growth life of the austenitic stainless steel pipes/pipes welds having part through cracks on the outer surface. In the analyses, Stress Intensity Factors ( K ) have been evaluated through two different schemes. The first scheme considers the ‘ K ’ evaluations at two points of the crack front i.e. maximum crack depth and crack tip at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor ( K RMS ) at deepest and surface points. Crack growth and the crack shape with loading cycles have been evaluated. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipe and pipe welds with part through circumferential crack. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor ( K RMS ) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme. Fatigue crack growth in pipe weld (Gas Tungsten Arc Welding) can be predicted well using Paris constants of base material but prediction is non-conservative for pipe weld (Shielded Metal Arc Welding). Further, predictions using fatigue crack growth rate curve of ASME produces conservative results for pipe and GTAW pipe welds and comparable results for SMAW pipe welds.

This paper describes the results of fatigue studies on carbon steel piping materials and components of Indian Pressurized Heavy Water Reactors (PHWRs). The piping components include pipes and elbows, of outer diameter 219 mm, 324 mm and 406 mm, made of carbon steel (SA333 Gr.6 grade) material. Tests on actual pipes and elbows with part through notch were carried out to study the behaviour of crack growth under cyclic loading for different pipe sizes, notch aspect ratios, stress ratios, etc. During the tests, numbers of cycles for crack initiation from blunt notch were recorded with an accuracy of 0.1 mm. In conjunction with component tests, the experimental studies were also conducted on standard specimens to understand the effect of different variables such as size (thickness), type of specimen and components (elbow and pipe), welding, stress ratio, notch orientation on fatigue crack growth rate. The fatigue crack growth curve (da/dN versus ΔK) obtained from three-point bend specimen and pipe was compared with that given in ASME Section XI. The comparison shows that da/dN versus ΔK curves obtained from the specimen and pipe tests are nearly same. The analytical predictions for crack initiation and crack growth for the tested components were compared with experimental results. Such comparisons validate the modeling procedure for crack initiation and growth.

This paper describes the experimental studies carried out on cracked austenitic stainless steel pipe and pipe welds under bending loads. Pipe welds were produced by gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW). Fracture resistance curves for pipe and pipe welds were compared. Results indicate that the fracture resistance of pipe and pipe weld (GTAW) is comparable but that of pipe weld (GTAW+SMAW) is inferior. Cracks do not deviate from their original plane during propagation as observed in the cases of carbon steel pipe and pipe welds. The fracture resistance of pipe welds does not depend on the loading histories to which it has been subjected prior to fracture test. Initiation and crack propagation were observed prior to the maximum moment. An existing limit load expression is applicable for the pipe base material but gives non-conservative results for the pipe welds. Multiplication factors have been suggested for the pipe welds for evaluation of limit loads using the existing expression. Fracture resistance for the pipe and compact tension specimens have also been compared for base material and welds.

Weld joints of SA 333 Gr. 6 steel pipe have been prepared using GTAW root pass and SMAW filling of V-groove according to welding procedure specifications (WPS) conforming to ASME Sec IX, a procedure commonly used to fabricate nuclear piping system components. The objective of the present study was to characterise the base metal, weld deposit and HAZ of the pipe weld in terms of their chemical composition and metallurgical, mechanical and fracture mechanics properties. The fracture toughness behaviour of the welds and HAZ has been characterised by J-integral parameters. The fatigue crack growth rate has been characterised by Paris Law. The stretched zone width (SZW) at the fracture surface has been measured with SEM to evaluate the initiation fracture toughness. The values of initiation fracture toughness estimated on the basis of SZW and blunting line from EGF recommendation have been compared. The fracture mechanics properties of the base metal, weld and HAZ have been compared and correlated. Fra...

A hybrid approach of forming a stabilizing layer of bonded carbon on porous silicon (PSi) surface by photoassisted reaction of acetylene gas at low temperatures is described. The PSi samples were made by anodization in a HF/H 2 O 2 electrolyte at a current density of 80 mA/cm 2 . Samples show a strong luminescence with a peak at 644±4 nm. The photoluminescence (PL) intensity shows a very strong quenching under the influence of continuous laser illumination (∼0.25 W/cm 2 , 488 nm). The PSi samples were subjected to flowing acetylene under optical illumination from quartz halogen lamp (20 mW/cm 2 ). The PL intensity is initially quenched to very low values (less than 5% of initial value) and then recovers on further exposure to acetylene to a final value ∼30% of the initial value. No quenching is observed on further exposure to laser illumination in ambient air instead an improvement of 15–25% in PL intensity is observed. This behaviour is a good indicator of the formation of a practically stable PSi surface.

Memory window (MW) and the retention of single-layer (SL) and dual-layer (DL) platinum (Pt) nanocrystal (NC) devices are extensively studied before and after program/erase (P/E) cycling. DL devices show better charge storage capability and reliability over the SL devices. Up to 50% improvement in the stored charge is estimated in the DL device over SL when P/E is performed at equal field. Excellent high temperature and postcycling retention capabilities of SL and DL devices are shown. The impact of the interlayer film (ILF) thickness on the retention of the DL structure is reported. While SL devices show poor P/E cycling endurance, DL cycling is shown to meet the minimum requirements of the multilevel cell (MLC) operation.

Most of the current high-density Flash cells use multi-level-cell (MLC) technology to store 2-bits/cell to increase memory density. In this work, dual layer metal nanocrystal (NC) flash EEPROM device, with large memory window, good retention and 10 4 cycle endurance is reported. High-temperature retention, gate bias accelerated retention, read disturb and post- cycling retention measurements show excellent reliability of the NC devices which make them suitable for the MLC application.

The nonvolatile memory properties of the partially crystallized HfO2 charge storage layer are investigated using short-channel devices of gate length L-g down to 80 nm. Highly efficient two-bit and four-level device operation is demonstrated by channel hot electron injection programming and hot hole injection erasing for devices of L-g > 170 mn, although the reduction of the memory window is observed for devices of L-g < 170 nm. A memory window of 5.5 V, ten-year retention Of Vth clearance larger than 1.5 V between adjacent levels, endurance for 10(5) programming/erasing cycles, and immunity to programming disturbances are demonstrated. Flash memory with partially crystallized HfO2 shows a larger memory window than HfO2 nanodot memory, assisted by the enhanced electron capture efficiency of an amorphous HfO2 matrix, which is lacking in other types of reported nanodot memory. The scalability, programming speed, V-th control for two-bit and four-level operation, endurance, and retention are also improved, compared with NROM devices that use a Si3N4 trapping layer.

SA312 type 304LN stainless steel material, having closer control over impurities and inclusion content, is the intended piping material in the Advanced Heavy Water Reactors. Deformation, fatigue and fracture behaviour of this material and its weldments have been characterized at ambient temperature and at 558K. The details of the fractographic investigations and stretch zone width measurements are also discussed. The base metals shows high initiation toughness (>500 kJ/m2 ) and large tearing modulus at ambient and operating temperatures. Shielded Metal Arc Welding (SMAW) weld metal shows much much reduced initiation toughness and tearing resistance in comparison to base metal and Gas Tungsten Arc Welding (GTAW) welds. This is attributed to larger density of second phase inclusions in the SMAW weld metal. SZW measurements give a good alternate estimate of the toughness of the materials. Fatigue crack growth rate in SMAW weld metal was found to be comparable to base metal at higher load ratios.Copyright © 2006 by ASME

A novel hardware implementable model for MOS devices in an integrated circuit is proposed that negates the thermal effects. It applies a correction to the device whose magnitude varies in accordance with the amount of error introduced in the device due to thermal gradient. This model introduces corrections by a suitable circuit external to the device. The FTGMOS model can be applied to all the devices in an integrated circuit to obtain the circuit performance as if thermal effects are absent altogether.

Fine grain BaTiO3 thin films with a grain size ranging between 100 and 1000 A were deposited using the reactive partially ionized beam deposition technique at 550–600 °C. A metal/insulator/metal structure of these materials was fabricated and the dielectric response was measured up to 40 GHz using a network analyzer. It is shown that these films are not ferroelectric. However, these films show a dielectric relaxation in the frequency interval between several MHz and 1 GHz. We propose that this indicates a relaxation mechanism not related to the ferroelectric domain walls.

The transition from the system level to the transistor level design of sigma delta modulator involves degradation in performance due to circuit imperfections, the extent of which depends on the architecture. A systematic understanding of the sensitivity is essential to accomplish a robust design. Smart behavioral modeling allows us to compare architectures and to derive minimum specifications for op-amp and system design.

Parallel plate capacitors for the broadband dielectric characterisation of both high (amorphous BaTiO3 and amorphous TaOx) and low (parylene) dielectric constant thin films were fabricated at low temperature (< 200 °C). The dielectric constant and loss tangent were dermined through the measurement of C, G and the S parameters of the capacitors. These thin film dielectrics exhibit no dispersion in the frequency range 1 kHz – 40 GHz.

The objective of the present study is to understand the fatigue crack growth behavior and validate analytical procedures for austenitic stainless steel and carbon steel pipes, pipe welds and elbows. The study involved fatigue tests on actual components and specimens. The Paris law has been used for the prediction of fatigue crack growth life. Paris constants have been determined for pipe (base), pipe weld and pipe elbow materials by using Compact Tension (CT)/Three Point Bend (TPB) specimens machined from the actual pipe, pipe weld and pipe elbow. Analyses have been carried out to predict the fatigue crack growth life of these piping components having part through cracks on the outer surface. In the analyses, Stress Intensity Factor ( K ) has been evaluated through two different schemes. The first scheme considers the ‘ K’ evaluations at two points of the crack front i.e. maximum crack depth and crack tip end at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor (KRMS) at deepest and surface points. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipes, pipe welds with part through circumferential crack. The tests have also been conducted on the full scale carbon steel elbows having part-through circumferential notch at intrados location and axial notch at crown location on the outer surface. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor (KRMS) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme.