
Jayanta ChattopadhyayBhabha Atomic Research Centre | BARC · Reactor Safety Division (Reactor Design)
Jayanta Chattopadhyay
PhD
About
154
Publications
21,659
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2,260
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Introduction
Skills and Expertise
Additional affiliations
August 1989 - present
Homi Bhabha National Institute and Bhabha Atomic Research Centre
Position
- Professor and Senior Scientific Officer
Description
- EPFM, LBB, Fracture tests on full scale piping components, Development of SIF/limit load equations of piping components and limit load based general eqn. of 'eta' and 'gamma' functions to evaluate J-R curve, Master Curve
Publications
Publications (154)
The present study is aimed at analyzing the fatigue crack growth rate data on compact tension (CT) and three‐point‐bend (TPB) specimens of C–Mn steel under different positive load ratios. Detailed elastic–plastic finite element analyses have been performed using nonlinear kinematic hardening rule of Chaboche material model. The numerically calculat...
Present study aims to investigate individual effects of strain gradient and peak equivalent strain amplitude on fatigue life of notched tubes of C‐Mn steel. Remote pure axial and pure torsion strain‐controlled tests have been performed for different strain gradients (owing to different hole diameter in tube specimen) subjected to same peak equivale...
The mechanics and mechanisms of ductile fracture, ahead of a blunting crack tip, have been studied extensively. Several computational studies analyzing the effect of initial void volume fraction, void shape, void spatial distribution and the mode of loading (𝐾𝐼 ,𝐾𝐼𝐼 etc.) on crack-void interaction and its consequence on the mechanism of fracture ha...
In the present study, directional and spatial variations in the mechanical properties are calculated in two nuclear-grade materials. In practice, multiple ASTM standard specimens are tested to measure mechanical properties of any material. The variations obtained in the properties during the tests are generally neglected assuming such variations ar...
Ductile fracture in structural metals and alloys comprises of three distinct stages: namely nucleation, growth, and coalescence of voids. In this failure mode voids, either pre-existing in the material or nucleated during deformation grow until they coalesce to form a continuous fracture path. The larger voids nucleating early in the deformation hi...
Ductile fracture of metals at room temperature has been studied extensively. Since localization of plastic flow is often viewed as a precursor to ductile fracture, several computational studies analyzing the influence of stress triaxiality and the Lode parameter on the critical strain for onset of localization have been reported. The implications o...
Ductile fracture of metals at room temperature has been studied extensively. Since localization of plastic flow is often viewed as a precursor to ductile fracture, several computational studies analyzing the influence of stress triaxiality and the Lode parameter on the critical strain for onset of localization have been reported. The implications o...
Present work is aimed at performing fatigue tests on notched C-Mn steel tubes. Tests were conducted on different sizes of notches under remote axial strain-controlled conditions. Individual effects of peak equivalent strain amplitude and strain gradient are brought out on experimental fatigue life. The localized measured strains are compared with c...
This paper aims to predict the ductile fracture in low alloy steel specimens with pure tension, pure shear and combined shear-tension type loading using modified Madou–Leblond (MML) porous plasticity model, proposed by the present authors in a recent work. This model includes the effect of localised mode of plastic deformation in a narrow band thro...
In service, the piping components (pipes/elbows) are subjected to different operational loadings such as thermal stress, internal pressure, self-weight, external loading from soil movement, flow induced vibration, vortex induced vibrations and third party damage. Structural integrity assessment of these piping components under postulated accidental...
A new ηδ,plLLD$$ {\eta}_{\delta, pl}^{LLD} $$ correlation is proposed to evaluate the plastic component of crack tip opening displacement (δplastic$$ {\delta}_{plastic} $$) of a pre‐cracked small punch test (known as p‐SPT) specimen by using load (P$$ P $$) versus load line displacement ∆$$ \left(\Delta \right) $$ experimental data. Through thickne...
The present study is aimed at understanding the saturated cyclic stress-strain material behaviour of low C-Mn steel under pure axial, pure torsion, proportional axial-torsion and non-proportional axial-torsion test conditions. The axial/shear stress-strain hysteresis loops have been investigated vis-à-vis classical cyclic material modelling rules/c...
The present study is aimed at validation of notch stress/ strain estimation schemes such as classical Neuber, Hoffmann-Seeger and recently developed Ince-Glinka method for Nuclear piping material (low C-Mn steel). The study has considered different constraints, loading conditions, various hole sizes to accommodate strain gradient variations and equ...
Three-dimensional Finite Element Analyses of pre-cracked small punch test (p-SPT) specimens are performed to evaluate plastic constraint factor (m). The m factor is useful to correlate the J-integral with the crack tip opening displacement (CTOD). The through-thickness square pre-cracked specimen is analyzed for this purpose. Parametric studies are...
Diffused and localised plasticity in a narrow band between the pre-existing micro-voids are the dominant modes of deformation in a ductile material. In this paper, a yield function is presented for porous metallic materials accounting for these two modes of deformation. The model has been proposed by modifying Madou and Leblond’s model taking into...
In present study, the notch geometry, constraint conditions, loading conditions and peak equivalent strains have been accounted to review classical hypotheses for estimation of localized stress/strain values. Two dimensional and three dimensional FE analyses have been performed on planner and tube geometry for validation of classical schemes based...
Finite Element Analysis with Gurson-Tvergaard-Needleman (GTN) damage model is used to analyze p-SPT specimens of two structural steels. Load-displacement curves are calculated by parametric variation of GTN parameters. An ANN is trained using load-displacement data as input and GTN parameters as output. Trained ANN is used against p-SPT experimenta...
In the present work, axial-torsion fatigue tests were performed under two loading categories, (i) variable strain paths sequential loading and (ii) asynchronous (different loading frequencies) conditions on low C-Mn steel. Variable strain paths tests brought out that saturated cyclic stress-strain behaviour under a given strain path, is insignifica...
The present study is aimed at assessment of stabilized cyclic elastic–plastic stress/strain response of low C–Mn steel used as the primary piping material of Indian PHWRs. The material model considers von Mises yield criterion, three decomposed non-linear kinematic hardening-based Chaboche model and associative flow rule. Three-dimensional tubular...
Present work is aimed at validation of existing popular cyclic plasticity material models and proposing an improved model for SA 333 Gr. 6 material. Recently reported in-house axial-torsion tests have been used for validation. Present analyses considered Chaboche’s non-linear kinematic hardening rule, Tanaka’s fourth order tensor and Meggiolaro’s n...
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...
Flame Acceleration (FA) and Deflagration to Detonation Transition (DDT) are known risks in scenarios involving accidental release and combustion of hydrogen in nuclear reactors. In the present work, chemical timescale and Borghi diagram analysis of hydrogen combustion have been presented. Based on these, a map of the flame propagation in the GraVen...
The level-3 Leak-Before-Break (LBB) assessment of nuclear piping system is based on simplified fracture mechanics calculations. A postulated through-wall circumferential crack is shown to be stable even under extreme loading conditions. An important aspect of this fracture assessment, which is generally not considered, is the reduction in load at t...
The present studies are aimed at validation of a newly developed critical plane model with respect to large variety of engineering materials used for different applications. This newly developed model has been recently reported by present authors. To strengthen general applicability of this model, multiaxial test database consisting of a wide varie...
Present study is to investigate the dependency of cohesive zone parameters on crack tip stress triaxiality for SA333 Grade 6 steel. An exponential cohesive law is used to simulate ductile fracture behavior of 14 three-point bend specimens made of SA333 Gr. 6 steel. Cohesive parameters are determined by varying peak stress to match experimental resu...
Pre-cracked small punch tests (known as p-SPT) are used to assess fracture properties of aged nuclear materials in cases of limited availability of materials which is insufficient to conduct conventional standard tests. In this paper, the Gurson-Tvergaard-Needleman (GTN) model is used to compute crack growth at peak loads for material 20MnMoNi55 by...
The fracture study of circumferential through-wall cracked (CTWC) pipe under bending load is of interest for integrity assessment of conventional piping system and especially important for Leak-Before-Break (LBB) analysis of primary heat transport piping system of nuclear power plants (NPP). The fracture study in the elastic-plastic regime needs to...
The fracture property, J-R curve is an essential material property for assessing the cracked structures for unstable ductile tearing. For obtaining this material property, fracture test is conducted and resultant test data namely load, load line displacement (LLD)and relevant crack extension data are post processed to obtain J-R curve. However, in...
This paper addresses the fracture toughness evaluation procedure of different zones of dissimilar metal weld (DMW). Experiments have been conducted on compact tension specimens from DMW joint having initial notch in centre of weld and fusion boundaries. Plastic eta factors (ηp) and slope of blunting line (bl) for above specimens have been evaluated...
Fracture toughness is the main designing criterion of nuclear power plant. Due to neutron embrittlement, fracture toughness of reactor pressure vessel steel becomes low. This type of phenomenon can also be observed in cryogenic temperature. But in between a certain subzero temperature range, values of fracture toughness of ferritic steel are scatte...
The steels used for manufacturing nuclear reactor pressure vessel are low alloy ferritic steels. There is a range of temperatures at which these steels exhibit transition from ductile to brittle fracture known as the ductile to brittle transition temperature (DBTT). In these range of temperatures, ferritic steels exhibit a scatter in the fracture t...
Cohesive zone models are employed to simulate crack propagation in fracture process zone. It has been demonstrated in the present study that the cohesive zone parameters depend not only on the material, but also on stress triaxiality. To determine cohesive zone parameters, experimental results of 14 three-point bend specimens (TPBB) made of SA333 G...
Determination of fracture properties is important to assess the in-service degradation of nuclear structural materials subjected to thermal fluctuations and irradiation and to calculate the residual life of the component. The pre-cracked small punch test is an alternative method for the determination of fracture properties in case of limited availa...
In this work, variation of the Beremin parameters with temperature for reactor pressure vessel material 20MnMoNi55 steel is studied. Beremin model is used, including the effect of plastic strain as originally formulated in the Beremin model. A set of six tests are performed at a temperature of a '110 °C in order to determine reference temperature (...
Results obtained from the uniaxial tensile tests of 20MnMoNi55 low-alloy RPV steel at different temperatures (varying from 27 to 450 °C) and straining rates (varying from 10⁻⁵ to 10⁻¹ s⁻¹) reveal that the material response is sensitive to both temperature and strain rate. For the range of temperature varying from 200 to 400 °C, in combination with...
Master curve and reference temperature (T0) from three-point bending specimens of 20MnMoNi55 steel for different thicknesses and a/W ratios are determined using Kim Wallin’s master curve methodology (ASTM E1921-02) to study the effect of variation in thickness and a/W ratio at reference temperature (T0). Weibull stress at the crack tip is calculate...
Determination of fracture properties of aged materials is important to assess degradation of structural materials subjected to in-service loads and also to assess residual life of the component. The pre-cracked small punch test is an alternative method for the determination of fracture properties in case of availability of limited quantity of mater...
Conventional η factor equation in ASTM 1820 for CT specimen is based on elastic-perfectly plastic material behavior. Also, it is applicable for deeply cracked specimen (a/W > 0.45). However, actual material always shows strain hardening behavior. Additionally, it may be sometimes needed to test CT specimens with relatively lower a/W (i.e. <0.45) to...
In the present study a phenomenological constitutive model is developed to describe the flow behaviour of 20MnMoNi55 low carbon reactor pressure vessel (RPV) steel at sub-zero temperature under different strain rates. A set of uniaxial tensile tests is done with the variation of strain rates and temperature ranging from 10⁻⁴ s⁻¹ to 10⁻¹ s⁻¹ and -80...
This study explored the determination of J-R curve and Ji (fracture toughness) of nuclear structural materials using small punch test of 3 mm disk. The punch load versus central deflection data are collected up to fracture which is signified by the rapid drop in load carrying capability of the specimens. The experimental data for 20MnMoNi55 materia...
This parametric study explored the correlation between minimum thickness (t/t0) and central deflection (δ/t0) and change in location of fracture point in small punch test specimens due to change in friction coefficient between ball and specimen. A detailed finite element studies were conducted to investigate the effect of parameters that could infl...
Axial fracture toughness of cold worked and stress relieved Zr-2.5Nb pressure tube material containing deuterium between 5 and 200wppm was determined as per ASTM E−1820-15 between 25 and 300 °C using 17 mm wide Curved Compact Tension samples. For deuterium charged materials, the variation of the fracture toughness with test temperature showed typic...
Determination of fracture toughness, J-R curve from experimental test results requires certain geometry factors such as η and γ. These expressions of geometry factors are available for standard geometries and loading configurations. However, these expressions are not available in open literature for complex geometries and loading configurations. R6...
Pre-notched small punch test (p-SPT) samples (10 × 10 × 0.5 mm) have been fabricated to determine the crack initiation toughness. The machined notch profile is fabricated longitudinally from the centre of one side of the sample to the centre of the opposite side, producing a notch depth to thickness ratio a/t = 0.3.
Plastic damage analysis of the p...
The η factor plays an important role in the experimental evaluation of J-integral and J-R curve. While for a deeply cracked SE(B) specimen, established η factor value is available; for shallow cracked specimen, there is a variation in the η values proposed by different researchers. Although, it has been found that η factor depends on the material s...
The miniaturized specimens are used to determine mechanical properties of the materials, such as yield stress, ultimate stress, fracture toughness etc. Use of such specimens is essential whenever limited quantity of material is available for testing, such as aged/irradiated materials. The miniaturized small punch test (SPT) is a technique which is...
The miniaturized specimens are in use to determine mechanical properties of the materials, such as yield strength, ultimate tensile strength, and ductility. Use of such specimens is popular whenever the limited quantity of material is available for testing, such as aged/irradiated material. In this paper, six miniaturized small punch tests have bee...
The paper considers the effect of microstructure degradation on fracture toughness of 20MnMoNi55 pressure vessel steel. This degradation is reflected through the shift of fracture toughness vs. temperature curve along the temperature axis and rise in reference temperature in ductile to brittle transition (DBT) region. Hardness also depends on the m...
Present paper deals with a detailed study on the correlation between minimum thickness (t/t0) and central deflection (δ/t0). Such data are obtained during the deformation of a small punch test of miniaturized specimen. Finite element studies have been carried out to investigate the effect of various parameters which are expected to influence this c...
Elbows are one type of components widely used in various industrial applications in conventional and nuclear power generating plants, chemical processing plants and petroleum refineries. Due to the complexities of geometric structure, elbows are one of the piping components that are prone to failure in the piping system of nuclear power plants (NPP...
It is very important to determine Paris’ power law constants to know the fatigue crack growth rate (FCGR) of a structure containing crack. These constants are generally determined by FCGR test using conventional specimens as specified by ASTM-E647 standard. This standard FCGR test procedure has placed strict size requirements on the conventional sp...
While carrying out fatigue tests on miniature Single Edge Notched Tensile (SENT) specimens, one needs to know the limit load of the specimen to determine the maximum and minimum loads of fatigue cycle. In the literature, several limit load equations, for example, EPRI, Graba, Miller were available. There were large differences in the predicted valu...
In this paper, Digital Image Correlation (DIC) technique has been used to map the full field of displacement and strain for visualizing the fracture growth, fracture propagation and formation of Fracture Process Zone (FPZ) in notched concrete beams under bending. Further, for exact quantification of concrete fracture parameters such as crack openin...
This paper reports defect assessments of experiments on large-scale straight pipes and elbows using failure assessment diagram (FAD) methods. The pipes and elbows were of various pipe diameters and contained a range of sizes of cracks sharpened by fatigue loading. Solutions in the literature for stress intensity factor and limit load have been eval...
Currently the ductile fracture assessment of cracked pipes, under earthquake loading, is based on the monotonic J–R curve where the earthquake load is considered as a one-time applied load monotonically increasing to its maximum magnitude. The cyclic nature of earthquake load and associated cyclic-tearing damage (or cyclic J–R curve) is not explici...
The present work deals with the investigation of a robust analytical scheme to assess the size-independent fracture energy of concrete. The study involves the numerical modelling of three-point bend (TPB) concrete beams that are geometrically similar, having constant length to depth ratio with varying range of notch to depth (a/W) ratios. The uniqu...
The structural material for test blanket module of fusion reactor developed in India is
called Indian Reduced Activation Ferritic Martensitic Steel (In-RAFMS). In this study
fracture toughness behaviour of In-RAFM steel is investigated using 0.2T bend samples
in ductile brittle transition regime. The conventional MC estimates a non-conservative ref...
This paper deals with investigation of size-independent fracture energy (GF) of concrete. The study involves numerical modelling of three point bend concrete beams that are geometrically similar having constant length to depth ratio with varying notch to depth ratios. RILEM fracture energy (Gf) values evaluated numerically and experimentally are fo...
The reported investigations undertaken so far on concrete fracture involve limited tests on laboratory size concrete specimens and provide a basic understanding of the fracture phenomenon, but the precise quantification of fracture parameters is still elusive. Therefore purely an experimental approach is not preferably a practicable solution, rathe...
The master curve methodology proposed by Kim Wallin (ASTM E1921-02) has been used to evaluate master curve and reference temperature (T0) from TPB specimen for the material 20MnMoNi55 steel using single temperature and multi-temperature method. The effect of test temperature on reference temperature (T0) has been studied for both TPB and CT specime...
Currently Leak-Before-Break based design and fracture stability assessment considers the earthquake as once applied non-cyclic load, which monotonically increases up to its maximum magnitude. The cyclic character of earthquake load and associated cyclic tearing failure mode (tearing-fatigue regime) are not explicitly considered while demonstrating...
To investigate several unresolved issues and to improve upon the existing equations for integrity assessment of pipes and pipe bends used in nuclear reactors, a comprehensive Component Integrity Test Program (CITP) was initiated at Bhabha Atomic Research Centre (BARC), India. As a part of this program, several fracture tests have been conducted on...
Crack growth is generally measured during fracture experiment of specimen or component. The unloading compliance technique is commonly used for this purpose because of its simplicity. It infers the crack length from unloading compliance of cracked component. The pre-requisite of this technique is the availability of an equation that correlates crac...
Pipe bends or elbows are commonly used components for nuclear power plant piping system. In service, these piping components are subjected to internal pressure in addition to bending loads and the internal pressure is known to have a significant effect on the load carrying capacity of these components. Hence, a systematic study was carried out to i...
Fracture toughness is one of the key input variables to compute critical load of the structural components. The resistance against ductile fracture can be quantified either by the initiation value or by the entire resistance curve. Different standard methods like JSZW, JSME and ASTM: E1820 etc. are mainly used to estimate the critical crack initiat...
In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–plastic conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though...
The master curve methodology proposed by Kim Wallin (ASTM E1921-02) has been used to evaluate master curve reference temperature (T0) from full compact tension (CT) and 1/2T-CT specimens for the material 20MnMoNi55 steel using single temperature and multi-temperature method. The effect of temperature range, number of test temperatures and initial c...
Specimen J–R curve is extensively used for structural integrity of large components. It is well known that J–R curve heavily depends on constraint level ahead of crack tip in remaining ligament. In earlier work, it was demonstrated that J–R curve from Three Point Bending (TPB) specimen is transferable to straight pipe with circumferential through w...
Fracture toughness is an important material property to assess the critical load for structural integrity of reactor pressure vessel steel. In this paper, master curve method proposed by Kim Wallin is used to estimate the fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition regime. Reference temperature (T0) is evaluated usin...
Asymptotic crack tip stress fields are developed for a stationary plane strain crack in incompressible elastic-perfectly plastic material under mode-I loading. Detailed investigations have revealed that in between the two extreme conditions of crack tip constraint, that is, between the fully plastic Prandtl [1] field and the uniform stress field th...
Fracture behaviour under quasi-static tearing load has been studied through fracture toughness tests on SA333 Grade 6 and
20MnMoNi55 steels using single-edge notched bend (SENB) specimens. To understand the response of variation of constraint,
J-R curves were obtained from specimens precracked to a/W ratio in the range of 0.25 to 0.75, in steps of...