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Gopalan A.,Bhabha Atomic Research Center | Samal M.K.,Reactor Safety Division | Chakravartty J.K.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2015

In this work, fracture behaviour of 20MnMoNi55 reactor pressure vessel (RPV) steel in the ductile to brittle transition regime (DBTT) is characterised. Compact tension (CT) and single edged notched bend (SENB) specimens of two different sizes were tested in the DBTT regime. Reference temperature 'T0' was evaluated according to the ASTM E1921 standard. The effect of size and geometry on the T0 was studied and T0 was found to be lower for SENB geometry. In order to understand the fracture behaviour numerically, finite element (FE) simulations were performed using Beremin's model for cleavage and Rousselier's model for ductile failure mechanisms. The simulated fracture behaviour was found to be in good agreement with the experiment. © 2015 Elsevier B.V. All rights reserved. Source

Rahim A.,Indian Institute of Technology Roorkee | Sharma U.K.,Indian Institute of Technology Roorkee | Murugesan K.,Indian Institute of Technology Roorkee | Arora P.,Reactor Safety Division
MATEC Web of Conferences | Year: 2013

The present experimental program was planned to investigate the effect of type of mineral admixture, pre-load and the presence of confining reinforcement on the spalling behaviour of heated high performance concrete (HPC). Reinforced concrete cylindrical short columns were cast and exposed to four different target temperatures. A compressive preload equal to 25% of the ultimate load capacity of column was maintained on the specimens during heating and cooling. The test results mainly focus on the influence of above said variables on spalling behaviour of reinforced HPC columns. Interesting observations have been made in the paper on the subject matter of the workshop. © Owned by the authors, published by EDP Sciences, 2013. Source

Muralidhara S.,BMS College of Engineering | Raghu Prasad B.K.,Indian Institute of Science | Singh R.K.,Reactor Safety Division
Engineering Fracture Mechanics | Year: 2013

Size independent fracture energy and size effect on fracture energy are the key concerns for characterization of concrete fracture. Although there have been inconsistencies in results, a consensual fact is that the fracture energy from a large specimen is size independent. The fracture energy is proportional to the size of the fracture process zone (FPZ). FPZ size increases with size of the specimen, but the rate of increase of FPZ size decreases with increase in specimen size [1] implying that rate of increase of fracture energy decreases with increase in specimen size, more appropriately with increase in un-cracked ligament length. The ratio of fracture energy to the un-cracked ligament length almost becomes a constant at larger un-cracked ligament lengths. In the present study an attempt is made to obtain size independent fracture energy from fracture energy release rate. © 2012 Elsevier Ltd. Source

Naveen Kumar N.,Bhabha Atomic Research Center | Tewari R.,Materials Science Division | Durgaprasad P.V.,Reactor Safety Division | Dutta B.K.,Reactor Safety Division | Dey G.K.,Materials Science Division
Computational Materials Science | Year: 2013

Molecular dynamics (MD) simulations of nanoindentation of alpha-iron (α-Fe) have shown that all previously observed slip plane families i.e. {1 1 0}, {1 1 2} and {1 2 3} were active in the system. The slip plane families, {1 1 0} and {1 2 3}, were more are less equally active whereas {1 1 2} family was the least active. A small fraction of dislocation density was observed on {1 0 0} slip planes arising due to the formation of a 〈1 0 0 junctions because of the interaction of a/2 〈1 1 1⌠family of dislocations. It was also shown that the line character of dislocations varied uniformly from edge to screw character without any biasing towards a single character of dislocation at temperatures less than 300 K. These results were found to be consistent even with changing the size of domains, shape of the indenter and rate of loading. Present study has shown that for the prediction of deformation behaviour in α-Fe dislocation activities on {1 2 3} slip planes should also be considered along with the activities of {1 1 0} and {1 1 2} slip planes. © 2013 Elsevier B.V. All rights reserved. Source

Muralidhara S.,BMS College of Engineering | Muralidhara S.,Kharazmi University | Eskandari H.,Indian Institute of Science | Prasad B.K.R.,Kharazmi University | Singh R.K.,Reactor Safety Division
Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010 | Year: 2010

In seismology, Gutenberg-Richter relationship log 10 N= a-bM is an empirical relationship between the magnitude of earthquake and its recurrence frequency. The constant 'b', is called the b-value and is the log linear slope of frequency-magnitude distribution. An analogy is drawn between earthquake and failure process in concrete. During the failure process of concrete, Acoustic emission (AE) energy is released in the form of energy waves having certain peak amplitudes. While estimating the b-value during fracture in concrete, peak amplitudes of the AE signals are used. Right from the onset of micro-cracks till failure, the AE events are recorded with their peak amplitudes and AE energies. Interestingly, the AE energy release has been observed to be in "packets" or bursts. These energy packets have been called by the authors as AE quanta. In the estimation of b-value, peak amplitudes of events of groups having a definite number are used. Instead of using amplitudes of arbitrary group of events, quanta are utilized as groups for obtaining the b-value,. Unlike in seismology, wherein the b-value could be nearly unity, it is found that the b-value from quanta is much less than that obtained from the amplitudes. © 2010 Society for Experimental Mechanics Inc. Source

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