B. K. Dutta

B. K. Dutta
Bhabha Atomic Research Centre | BARC

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103
Publications
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Publications

Publications (103)
Article
The present study deals with the determination of fracture properties of a cracked Ni3Al-based intermetallic single crystal turbine blade subjected to tensile load. The analysis has been carried out by accounting the effect of microstructure, strain hardening and damage development under monotonic loading. A continuum damage criterion combined with...
Article
This article investigates the deformation behaviour and fracture characteristics of copper single crystals by uniaxial tensile experiments and compares the results with crystal plasticity simulations. Quasi-static tensile tests were carried out to include different stress–strain states by varying the crystal orientation with respect to specimen axi...
Chapter
Zircaloy-4 is an alloy of zirconium used to make the cladding of nuclear fuel tubes in reactors. The cladding is subjected to neutron irradiation during its service inside the nuclear reactor that leads to degradation of its mechanical properties. In this work, the irradiation hardening and softening of the polycrystalline Zircaloy-4 under various...
Article
The motivation of the present study entails the determination of fracture initiation of a single crystal copper edge-crack specimen subjected to tensile load by considering the influence of crystallographic anisotropy, strain hardening and damage accumulation. To accomplish the purpose of this study, a damage criterion coupled with crystal plastici...
Article
The paper deals with the development of a close form solution to find the stability of flexible symmetric horizontal rigid and tuned flexible rotor mounted on hydrodynamic bearing with squeeze film damper system. The correlations are developed analytically to find the static equilibrium position of a rigid and flexible rotor-bearing-damper system a...
Article
The mechanical and fracture properties of aged materials degrade due to metallurgical and micro- structural changes during service life. Miniaturized specimen testing methodology has been evolved over the years to quantify such degradation mechanisms. Oxygen Free Electronic (OFE) Copper has wide applications in nuclear industry, particularly in fus...
Article
A combined experimental and numerical study on deformation behaviour of single crystal copper is presented in this paper. High purity copper single crystals were fabricated and subjected to uniaxial compression loading at quasi-static strain rate. The stress-strain responses along four different crystallographic orientations were then extracted aft...
Article
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...
Chapter
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...
Article
In the present study, microstructures of Ferritic-martensitic T-91 steel irradiated at room temperature for 5, 10 and 20 dpa using 315 KeV Ar⁺⁹ ions have been characterized by grazing incident X-ray diffraction (GIXRD) and by transmission electron microscopy (TEM). Line profiles of GIXRD patterns have shown that the size of domain continuously redu...
Article
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...
Article
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...
Article
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...
Article
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...
Conference Paper
Full-text available
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...
Conference Paper
Prediction of mechanical properties of irradiated material is a primary issue for the nuclear industry. Experimental determination of mechanical properties is not always viable. This is mainly due to high cost of irradiations and problem of sample activation. Sample activation problem may be avoided by ion (proton) irradiation but irradiation damag...
Article
Understanding of material degradation due to irradiation in structural materials of future reactors is of prime importance for current research as these materials are expected to operate at severe conditions of high temperature and high irradiation doses. The hierarchical multi-scale simulations act as supplement to the costly experiments on irradi...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Fe-Cr based ferritic/martensitic (FM) steels are the candidate structural materials for future fusion reactors. In this work, a multi-scale approach comprising atomistic and dislocation dynamic simulations are used to understand the hardening of these materials due to irradiation. At the atomic scale, molecular dynamics (MD) simulations are used to...
Article
Non-transferability of fracture data from specimen level to component level is a serious limitation of conventional fracture mechanics, as fracture resistance data obtained is largely geometry dependant. The difficulty is largely overcome by GTN model which models the drop in load carrying capacity of a material with the increase in plastic strain,...
Article
Irradiation of materials by energetic particles produces defect clusters like vacancies, self-interstitial atoms and stacking-fault tetrahedra. These defect clusters form loops around existing dislocations, leading to their decoration and immobilization, which ultimately leads to radiation hardening in most of the materials. Effect of irradiation o...
Article
Safe operation of nuclear power plants is one of the major concerns and relies primarily on the integrity of the reactor pressure vessel. Neutron exposure induces temperature dependent embrittlement and can lead to loss of fracture toughness of reactor pressure vessel steel. Conventional fracture mechanics suffers from a serious limitation of non-t...
Conference Paper
A centralized version of on-line structural safety evaluation system (BOSSES) has been installed to monitor damage due to creep and fatigue in various critical plant components of multiple thermal power plants. This can be achieved from a centralized BOSSES server. This version is advancement to the earlier version of BOSSES where it was installed...
Article
Boilers and turbines including high-energy piping and headers are operated round-the-clock in the creep regime. For the integrity of such components and equipments, it is essential to have a real-time monitoring system to identify and monitor the critical locations. As per statutory requirement of IBR Act 391A of 1998, a component is to be taken fo...
Article
The actual operating conditions of a component may vary from the original design conditions either constantly or variably as a consequence of deviation from design parameters. Hence, the knowledge of operating temperatures and stresses, both historically and for anticipated future operation is required for an accurate life assessment. A number of h...
Article
Alloy steels of type 9Cr1Mo are being developed worldwide for the boiler and turbine components of supercritical and ultra supercritical thermal power plants and for the pressure vessel of fast breeder reactors. These steels exhibit very complex high temperature creep cavitation processes with coupled influences of creep strain, material softening...
Article
The subject of reliability assessment of plant components is of considerable importance to maintenance and operations engineers. There exist different degradation mechanisms such as creep and fatigue in the plant components operating under conditions of high pressure and temperature. Hence, the safety issue of these components must be addressed by...
Article
Plastic collapse moment (PCM) equations of throughwall axially cracked (TAC) elbow subjected to in-plane closing/opening bending moment were previously proposed by the present authors. However, in actual situation, an elbow may often be subjected to combined internal pressure and bending moment loading. The present work investigates the effect of i...
Article
In this study, the classical Gurson—Tvergaard—Needleman (GTN) model has been extended to a non-local form using damage parameter ‘d’ as a degree of freedom in the finite-element (FE) formulation. The evolution of the non-local damage is related to the actual void volume fraction ‘f’ in ductile fracture using a diffusion type equation. The coupled m...
Article
An on-line structural safety evaluation system (BOSSES) has been developed over the years at Bhabha Atomic Research Centre (BARC), India, which is capable of assessing the damage due to creep and fatigue in critical plant components. The system acquires plant transients in real time and processes them to evaluate the stress, temperature and damage...
Article
Bimetallic welds (BMWs) play a critical and indispensable role in the primary heat transport piping system of nuclear reactors. The primary heat transport system itself is the critical part of a nuclear reactor. Any failure of this system can lead to very grave consequences, not only speaking of huge monetary losses resulting from non-utilization o...
Article
It has been experimentally observed that the piezoceramic materials exhibit different types of non-linearities under different combinations of electrical and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical non-linearities similar to a Duffing oscillator such as jump phenomena and the pres...
Article
Cleavage fracture toughness data often exhibits a considerable amount of scatter and strong dependencies on temperature, loading rate, pre-straining, etc. due to the highly localized nature of the failure mechanism and microstructural inhomogeneity in the ductile-to-brittle transition (DBT) region of a material. Beremin's model is popularly used by...
Article
A throughwall axial crack may develop in an elbow or pipe bend due to service related degradation mechanism. It is very important to know the plastic collapse moment (PCM) of an elbow in the presence of a throughwall axial crack. The existing PCM equations of throughwall axially cracked (TAC) elbows are based on very few test data points of Griffit...
Article
It is now widely recognized in literature that the results of the local damage model are mesh dependent. Regularization methods which use gradients of equivalent plastic strain in the material yield function are also popularly known as gradient plasticity models. Many times, these nonlocal forms of equivalent plastic strain have been used as a meas...
Article
Continuum damage mechanics is applied to compute fracture J-initiation and the J-resistance (J-R) curve for SA333 Gr.6 carbon steel material. A parametric study is carried out to assess the effects of variation of Gurson material parameters on the J-R curve. A difficulty is experienced to obtain a set of Gurson parameters that can compute J-initiat...
Conference Paper
Ductile fracture process involves the typical stages of nucleation, growth and coalescence of voids in the micro-scale. In order to take the effects of these voids on the stress carrying capability of a mechanical continuum during simulation, damage mechanics models, such as those of Rousselier and Gurson-Tvergaard-Needleman (GTN) are widely used....
Article
Full-text available
Piezoceramic materials exhibit different types of nonlinearities depending upon the magnitude of the mechanical and electric field strength within the body. Some of the nonlinear phenomena observed under weak electric fields near resonance frequency excitation are the presence of superharmonics in the response spectra and the jump phenomena etc. In...
Article
There is an increasing awareness of the benefits to be derived from the development and exploitation of smart materials and structures in applications ranging from hydrospace to aerospace. With the ability to respond autonomously to changes in their environment, smart material systems can offer a simplified approach to the control of various materi...
Conference Paper
A throughwall axial crack may develop in an elbow or pipe bend due to service related degradation mechanism. It is very important to know the plastic collapse moment (PCM) of an elbow in the presence of a throughwall axial crack. The existing PCM equations of throughwall axially cracked (TAC) elbows are either too conservative or inadequate to corr...
Conference Paper
Prevention of failure of pressurised and high-energy components and systems has been an important issue in design of all types of power and process plants. Each individual component of these systems must be dimensioned such that it can resist the forces or moments to which it will be subjected during normal service and upset conditions. Design by a...
Article
Full-text available
Irradiation of materials by energetic particles causes significant degradation of the mechanical properties, most notably an increased yield stress and decreased ductility, thus limiting lifetime of materials used in nuclear reactors. Effect of irradiation on materials is to produce vacancies and self-interstitial atoms, and stacking fault tetrahed...
Article
The bimetallic welds (BMWs) play a critical and indispensable role in the primary heat transport piping system of nuclear reactors. The primary heat transport system in itself is the critical part of a nuclear reactor. Any failure of this system can lead to grave consequences, not only speaking of huge monetary losses resulting from non-utilization...
Conference Paper
Irradiation of materials by energetic particles causes significant degradation of the mechanical properties, most notably an increased yield stress and decrease ductility, thus limiting lifetime of materials used in nuclear reactors. The microstructure of irradiated materials evolves over a wide range of length and time scales, making radiation dam...
Article
Full-text available
Piezoceramic materials exhibit different types of nonlinearities under different combinations of electric and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical nonlinearities similar to a Duffing oscillator such as jump phenomena and presence of superharmonics in the response spectra. In or...
Article
Full-text available
When excited near resonance in the presence of weak electric fields, piezoceramic materials exhibit typical nonlinearities similar to a Duffing oscillator such as jump phenomena and presence of superharmonics in the response spectra. In an accompanying paper, a generalized nonlinear 3D finite element formulation has been developed incorporating qua...
Conference Paper
The mechanism of cleavage fracture in reactor structural material is significantly different from ductile fracture. The cleavage fracture in a material usually originates from micro-cracks, which are formed by different mechanisms. The micro-cracks are formed due to non-homogeneous distribution of plastic deformation within the grains, called slip-...
Article
The mesh dependency of the cavity growth model due to Rice and Tracey has been overcome by integrating it over a process zone surrounding the crack tip. This integral represents a modified damage potential. The critical value of the integral for crack initiation in weld material has been determined from a welded CT specimen by comparing the compute...
Article
It has been experimentally observed that piezoceramic materials exhibit different types of nonlinearities under different combinations of electric and mechanical fields. When excited near resonance in the presence of weak e to a Duffinor such as jump phenomena and presence of superharmonics in the response spectra. There has not been much work in t...
Article
Leak-before-break (LBB) assessment of primary heat transport piping of nuclear reactors involves detailed fracture assessment of pipes and elbows with postulated throughwall cracks. Fracture assessment requires the calculation of elastic–plastic J-integral and crack opening displacement (COD)1 for these piping components. Analytical estimation sche...
Article
Fracture assessment of pipe bends or elbows with postulated through wall crack is very essential for leak-before-break qualification of primary heat transport system piping of nuclear power plants. The methodology for fracture assessment of cracked elbows is still in developing stage. Any new development in theoretical aspect requires experimental...
Article
Transferability of the specimen J–R/J–T curve to the component level is an important issue in the field of fracture mechanics. Towards this goal, fracture experiments have been carried out on single-edge bend (SE(B)) and compact tension (CT) specimens and throughwall circumferentially cracked straight pipes/elbows of 200 mm nominal bore (NB) diamet...
Article
The structural integrity of components is usually performed using the specimen fracture resistance curve. However, the specimen fracture resistance curve significantly differs from the component fracture resistance. This is the most serious limitation of classical fracture mechanics. To address this issue, several tests have been carried out on fra...
Conference Paper
Integrity assessment of piping components is very essential for safe and reliable operation of power plants. Over the last several decades, considerable work has been done throughout the world to develop a methodology for integrity assessment of pipes and elbows, appropriate for the material involved. However, there is scope of further development/...
Conference Paper
Leak-before-break (LBB) assessment of primary heat transport piping of nuclear reactors involves detailed fracture assessment of pipes and elbows with postulated throughwall cracks. Fracture assessment requires the calculation of elastic-plastic J-integral and crack opening displacement (COD) for these piping components. Analytical estimation schem...
Conference Paper
Continuum damage mechanics is applied from specimen to component level to compute fracture behaviour. The computed parameters are load-displacement and J-Δa curves. A parametric study is done to show the effect of variation of f0 and fn on J-R curve. It is suggested to use a variation of q2 parameter near crack tip instead of a constant value in Gu...
Conference Paper
The mesh dependency of Rice and Tracey cavity growth factor (CGF) is overcome by integrating the CGF over a process zone surrounding the crack tip. This integral represents a modified damage potential. The critical value of the integral for crack initiation in weld material has been determined analyzing a welded CT specimen and comparing the comput...
Conference Paper
An ageing in-service Hot Reheat (HRH) pipe bend before Intermediate Pressure (IP) Stop/ Control Valve of a Utility was identified for real-time creep-fatigue damage assessment. A data acquisition system has been installed to record thermal hydraulic parameters, such as pressure, temperature and flow on real time basis. The HRH piping including low...
Article
Experimental evaluation of J–R curve in a crack growth situation requires `ηpl' and `γ' functions that are specific to a cracked geometry and loading condition. All derivations of existing `ηpl' and `γ' functions are for specific cracked geometry and loading. In this paper, direct limit load based general equations of `ηpl' and `γ' functions have b...
Article
Experimental evaluation of J–R curve in a crack growth situation requires `ηpl' and `γ' functions that are specific to a cracked geometry and loading condition. In Part I [Engng. Fract. Mech., in press] of this paper, new ηpl and γ functions, which are not available in the literature, for pipe and elbow geometry with various crack configurations un...
Article
Integrity assessment of piping components with postulated cracks is very important for safe and reliable operation of power plants. Pipe bends or elbows are among the very important piping components in any power plant. The existing equations of limit load of elbows have various shortcomings. Additionally, there is only limited test data on elbows...
Article
Full-text available
A large throughwall circumferential crack in an elbow subjected to in-plane bending moment can significantly reduce its collapse load. Therefore, it is very important to know the collapse moment of an elbow in the presence of a throughwall circumferential crack. The existing closed-form collapse moment equations of throughwall circumferentially cra...
Article
Integrity assessment of piping components with postulated cracks is important for safe and reliable operation of power plants. While various equations and methods are available for prediction of the load bearing capacity of pipes and elbows, it is very important to choose the correct equation and method whose predictions are consistent, safe but no...
Article
Local approach has been used to compute a) Jinitiation and JR curves at different temperatures and b) fracture toughness transition curves at different probability of failure. The material under investigation is the Reactor Pressure Vessel Steel 22NiMoCr37. Ductile fracture has been analyzed using Gurson material constitutive model and probability...
Article
Mesh dependency of cavity growth model due to Rice and Tracey has been overcome by integrating it over a process zone surrounding the crack tip. This integral represents a modified damage potential. The critical value of the integral for crack initiation in SA333Gr.6 material has been determined analysing a CT specimen and comparing the computed J...
Conference Paper
Integrity assessment of piping components with postulated cracks is very important for safe and reliable operation of power plants. Pipe bends or elbows are one of the very important piping components in any power plant. The existing equations of limit load of elbows have various shortcomings. Additionally, the test data on elbows are not so abunda...
Conference Paper
Conventional elastic plastic fracture analysis does not consider the crack growth and thus it cannot give the complete load deformation behaviour of cracked components. In the present paper numerical methodology is proposed to simulated the load deformation behaviour of cracked components considering the crack growth. In the present analysis, the c...
Conference Paper
Local approach has been used to compute a) Jinitiation and JR curves at different temperatures and b) fracture toughness transition curves for German Reactor Pressure Vessel Steel 22NiMoCr37. Ductile fracture has been analyzed using Gurson material constitutive model and probability of cleavage failure is calculated using Beremin’s model. A variati...
Article
Full-text available
The evaluation of J-integral from experimental data requires the eta(pl) and gamma functions. However these functions are available for limited geometry in the literature. In this paper limit-load-based general expressions of eta(pl) and gamma functions have been derived. These general expressions are then utilized to derive the eta(pl) and gamma f...
Article
Experimental evaluation of the J-integral requires the ‘ηpl’ function, proposed by Rice et al. [Progress in flaw growth and fracture toughness testing (1973) 231], to multiply the area under the load vs. plastic load-line-displacement curve. However, the J-integral, thus evaluated, requires modification if crack growth occurs. A ‘γ’ term was propos...
Article
Full-text available
Elastic-plastic finite element analysis has been carried out to evaluate collapse moments of six elbows with factors varying from 0.24 to 0.6. The loading conditions of combined in-plane closing/opening bending moment and varying degree of internal pressure are considered in the analysis. For each case, collapse moment is obtained by twice elastic...
Article
A system has been developed for on-line monitoring of various aging effects e.g. creep, fatigue and creep fatigue interaction. The earlier developed fatigue monitoring system has been modified to account for creep damage and creep-fatigue interaction. The present system is based on the finite element method. The system can take care of the fluctuat...
Article
The ductile fracture phenomenon is a local mechanism, which consists of nucleation, growth and coalescence of microscopic voids. These microscopic voids are generally formed around the second phase particles because of the debonding of these particles from the parent matrix or the cracking of these particles themselves. In the present work, the duc...
Article
The advent of Leak-Before-Break (LBB) concept has now replaced the traditional design basis event of the Double-Ended-Guillotine-Break (DEGB) to design the Primary Heat Transport (PHT) system piping of the Pressurised Heavy Water Reactor (PHWR) and Pressurised Water Reactor (PWR). This approach is being adopted to design the PHT system piping of 50...
Article
A finite element based fatigue monitoring system has been developed for on-line monitoring of fatigue degradation of components used in various plants. The system can take care of the fluctuations of the process fluid temperature, pressure and flow rate. This can also account for the system induced loads such as axial forces and bending moments. Th...
Article
Numerical investigations were carried out to assess the integrity of reactor pressure vessels under pressurised thermal shock (PTS). The 4-loop reactor pressure vessel with cladding was subjected to thermo-mechanical loading owing to loss of coolant accident. The loss of coolant accident corresponding to small break as well as hot leg breaks were c...
Article
Full-text available
The concept of Leak-Before-Break (LBB) is being applied to design the 500 MWe Indian Pressurised Heavy Water Reactor (PHWR) primary heat transport (PHT) piping system. Towards this goal, a detailed non-linear fracture analysis has been carried out on all the straight pipes and elbows of the 500 MWe PHWR PHT system. In this analysis, leakage size cr...
Article
Numerical investigations are carried out to assess the integrity of reactor pressure vessels (RPVs) under pressurised thermal shock (PTS). The 4-loop RPV with cladding is subjected to thermo-mechanical loading due to loss of coolant accident (LOCA). Both small break LOCA and hot leg breaks are considered to assume axisymmetric and asymmetric therma...
Article
A numerical modelling of pressurised thermal shock (PTS) accidents has been performed. Crack growth and crack arrest are numerically simulated using the finite-element method. The analysis is done in two steps. In the first the observed crack growth phenomena has been used as input to compute parameters such as crack mouth opening displacement, J-i...
Article
The use of the leak-before-break concept in the design of a Primary Heat Transport (PHT) piping system for nuclear power plants requires postulation of the largest credible flaws at highly stressed points and demonstration of system stability under the most severe loading conditions. In the PHT piping system, the elbows and branch tees are normally...
Article
Fatigue is one of the most important aging effects of power plant components. Information about fatigue helps in assessing structural degradation of the components and so assists in planning in-service inspection and maintenance. It may also support the future life extension programme of a power plant. In the present paper, the development of a met...
Article
The problems of crack-microcrack interactions and doubly kinked cracks have been analysed by the finite element method. In the first case the main crack tip SIF has been evaluated for different length of a collinear microcrack, which is located at a fixed distance. Through another case study the influence of a pair of stacked parallel microcracks o...
Article
Full-text available
A formulation for incorporating two singular points (TSP) of variable orders in a single finite element is presented. Though the element does not satisfy any of the convergence criterion, its performance is found to be good, which has bee