Gopal Sanyal | Bhabha Atomic Research Centre (original) (raw)

Papers by Gopal Sanyal

Engineering Fracture Mechanics, 2015

$Research paper thumbnail of Crack resistance curves for thin walled tubes: A fracture mechanics approach$

In this investigation, J-R fracture characteristics of Zr-2.5Nb pressure tube material of Indian ... more In this investigation, J-R fracture characteristics of Zr-2.5Nb pressure tube material of Indian Pressurized Heavy Water Reactor (IPHWR) in cold worked and stress relieved condition have been evaluated over a range of loading rate, hydrogen content and at temperatures of 25 and 300°C. The fracture toughness tests have been carried out using 17 mm width curved compact tension specimens. Prior to testing these specimens have been gaseously hydrogen charged with hydrogen content up to 100 wppm. Both hydrogen charged and uncharged specimens have been tested at 25 and 300°C at five different pulling rates i.e. 0.02, 0.2, 2, 20 and 200 mm/min. The crack length during the fracture toughness tests has been measured using direct current potential drop technique. Various relevant fracture toughness parameters (J Q , J 0.15 , J Max , J 1..5 and dJ/da) have been evaluated as per ASTM standard E1820. It was observed that initiation fracture toughness for as received material did not change monot...

$Research paper thumbnail of Effect of notch geometry on fracture features$

Materials Science and Engineering: A, 2015

International Journal of Advanced Structural Engineering (IJASE), 2014

Radiation Effects and Defects in Solids, 2013

$Research paper thumbnail of A load-separation technique to evaluate crack growth and fracture resistance behaviour of thin-walled axially cracked tubular specimens$

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2012

$Research paper thumbnail of An experimental and numerical study of the fracture behaviour of tubular specimens in a pin-loading-tension set-up$

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2010

Procedia Engineering, 2013

International Journal of Fracture, 2012

Engineering Fracture Mechanics, 2011

Recently, a Pin-Loading-Tension setup has evolved for evaluation of fracture behavior of thin-wal... more Recently, a Pin-Loading-Tension setup has evolved for evaluation of fracture behavior of thin-walled tubular specimens which are machined from nuclear reactor fuel pins. In this work, the geometric functions required for estimation of plastic component of J-integral from experimental load-load-line displacement data has been derived by carrying out a detailed 3D finite element analysis of the Pin-Loading-Tension test setup using the concept of limit load. The fracture resistance behavior (in terms of J-R curve) of the fuel pin specimens have been derived using: (a) multiple-specimen and (b) single specimen loadnormalization technique.

Engineering Failure Analysis, 2011

Nuclear reactor fuel pins act as barriers to the release of radioactive fission products to the c... more Nuclear reactor fuel pins act as barriers to the release of radioactive fission products to the coolant flowing around these thin-walled tubes and hence they prevent the leakage of radioactivity to the surroundings of reactor core. These tubes are of small thickness in order to have less resistance in the path of heat flow from the fuel to the coolant. Investigation of failure behavior of these fuel clad tubes is of utmost importance to the designers and plant operators in order to ensure the maximum residence time of the fuel bundles inside the reactor core as well as to ensure minimal activity during operation and refueling activities. Various types of zirconium based alloys are used to manufacture these pins. The focus is to obtain better strength, ductility, corrosion resistance, oxidation resistance, and minimal creep including those due to irradiation-assisted damage and deformation processes. Two number of such types of alloys, namely, re-crystallization annealed Zircaloy-2 and stress-relief annealed Zircaloy-4, have been investigated in this work for their fracture behavior. As standard fracture mechanics specimens cannot be machined from these thin-walled tubes, non-standard specimens with axial cracks have been used in this work. Load normalization technique has been used to evaluate crack growth during loading of these specimens. It was observed that the re-crystallization annealed Zircaloy-2 specimens have higher initiation fracture toughness as well as higher resistance to crack growth compared to the other type of specimens. In order to understand the micro-structural aspects of the fracture resistance behavior of these materials, further investigation incorporating optical and transmission electron microscopy have also been carried out. It was concluded that the higher fracture resistance behavior of the re-crystallization annealed Zircaloy-2 specimens can be attributed to the presence of finer grain and subgrain micro-structure, very low dislocation density and other defects in the material.

Journal of Alloys and Compounds, 2010

In the present study, alternate routes for the synthesis of a single phase Mo-30 wt% W alloy were... more In the present study, alternate routes for the synthesis of a single phase Mo-30 wt% W alloy were pursued to surmount the limitations experienced in conventional technique. The process essentially consists of preparation of active Mo and W powders by H 2 reduction of the respective oxide intermediates through multiple processing steps and then converting those pure powders into Mo-30 wt% W alloy by mechanical alloying technique (MA) at RT under Ar atmosphere in a high-energy planetary ball mill. The structural evolution of the alloy from the milled powders at different interval of time was studied by X-ray diffraction (XRD) and phase corresponding to Mo-30W alloy was confirmed. The broadening of peaks in XRD pattern was due to crystallite refinement during milling towards the formation of the designated alloy. A high rate of densification for MA powder was achieved during sintering between 900 • C and 1200 • C and density close to theoretical density was attained. The microstructure of sintered alloy exhibited uniform, polyhedral grains with average grain size of about 3 m. The morphological evolution of as-milled powder was studied by Scanning electron microscopy (SEM) which revealed the formation of nano sized crystallites with polyhedral shapes. The crystallites were initially arranged in clusters which later on got distributed uniformly with the progress in milling time. The average crystallite size of MA powder was found to be 7.3 nm after 25 h of milling.

Cladding fracture behavior is an important consideration, particularly in secondary damage of fue... more Cladding fracture behavior is an important consideration, particularly in secondary damage of fuel cladding during service and during handling and storage of discharged fuel. Pin loading tension test is one of the most promising nonstandard procedures with which quantification of initiation and propagation behavior of an axial crack of a thin-walled tubular specimen is possible. This paper focuses on characterisation of the fracture surface of a few different cladding tubes through a detailed fractographic examination and a relative comparison in crack resistance of the tubes in correlation with their fracture pattern.