divakar canchi - Academia.edu (original) (raw)

Papers by divakar canchi

Research paper thumbnail of A high temperature cell (up to 3300K) for use with a cubic press

Research paper thumbnail of Design and development of an advanced linear reciprocating tribometer

Wear, 2009

With advances in machining technology, the requirements for linear guide ways and industrial lubr... more With advances in machining technology, the requirements for linear guide ways and industrial lubricants are increasing, especially for machine tools which have to meet various demands such as high positioning exactness, low stick-slip coefficient of friction over a wide range of speed. Study of friction and wear of lubricated surfaces plays a prominent role in the development of sliding surfaces for machine tools. The design and development of an advanced linear reciprocating tribometer to study the performance of lubricants and slide way surfaces is presented in this paper. The principle of operation consists of sliding test samples against a stationary counter surface under load and recording the parameters of interest. The novel features include evaluating the stick-slip behaviour and dynamic coefficient of friction over a wide speed range from 0.1 to 6000 mm/min under load. An attempt is made to study the efficiency of different oil groove shapes and geometries with reference to oil flow pattern. Based on these studies, the best oil groove shapes and geometries can be obtained to reduce the friction and wear of lubricated sliding surfaces in machine tool slide ways. Preliminary test results of the frictional behaviour of such lubricated surfaces are presented in this paper.

Research paper thumbnail of Step‐loading technique for tungsten carbide opposed anvil high‐pressure setup

Review of Scientific Instruments

A method is described to achieve a step loading of a tungsten carbide opposed anvil setup. The ri... more A method is described to achieve a step loading of a tungsten carbide opposed anvil setup. The rise time of the pressure pulse is nearly 200 ms and the maximum height of the pressure pulse is 2 GPa. The use of this method in the study of the kineticsof pressure ifiduced transformations under isobaric conditions is illustrated with the help of the data on fcc-bcc (face-centered-cubic and body-centered-cubic) transformation in ytterbium.

Research paper thumbnail of Fabrication of Ceramic-Ceramic Composites at High Pressures Through the Formation of an Intermediate Soft Phase

THE REVIEW OF HIGH PRESSURE SCIENCE AND TECHNOLOGY

eramic-ceramic composites in the Ti-B-C system were fabricated by hot pressing of Ti and B4C powd... more eramic-ceramic composites in the Ti-B-C system were fabricated by hot pressing of Ti and B4C powders. The study describes a method to process fully dense ceramic-ceramic composites (without any sintering aids) through the formation of an intermediate soft phase at moderate pressures and temperatures. The results on the processing and properties of TiB2-TiC and TiB2-TiC-SiC composites are presented. [ sintering, ceramics, composites, reaction synthesis, hot pressing]

Research paper thumbnail of The Kinetics of pressure-induced a-gt;w transformation in TI

The kinetics of the pressure-induced a-transformation in titanium is reported in the pressure ran... more The kinetics of the pressure-induced a-transformation in titanium is reported in the pressure range 5-9GPa. The occurance of this transformation under shock loading has been discussed using the observed pressure dependence of the kinetics

Research paper thumbnail of Synthesis and sintering of ceramic materials under pressure

Research paper thumbnail of Design and fabrication of a 600-ton press for sintering studies

High tonnage presses are required for generating high pressure over large volumes. A 600-ton pres... more High tonnage presses are required for generating high pressure over large volumes. A 600-ton press has been designed and fabrication at the National Aerospace Laboratories for the sintering of ceramic materials at high pressures and high temperatyres. The press is of four-column type, and is fabricated out of hardened EN 24 steel.

Research paper thumbnail of Sintering of a - sic at high pressures and temperatures

The high temperature properties of sintered silicon carbide are critically dependent on additives... more The high temperature properties of sintered silicon carbide are critically dependent on additives which are used for consolidation by conventional hot pressing into pore-free bodies. The sintering aids provide increase in shrink-age rate and high densities at low sintering temperatures. However, the presence of sintering aids results in a second phase at the grain boundaries which13; has adverse effects on the high temperature properties. An effort has been made to produce fully dense self bonded Sic without using sintering aids by high pressure-high temperature sintering. The Sic powder has been sintered13; at pressures (1.7-3.0 GPa) at 18OO0C for 5-30 minutes. The densities 'of the sintered compacts are gt; 99% theoretical density. The compacts show room temperature hardness values in the range 26.7-33.5 GPa. The indentation frac-13; ture toughness values range between 3.5 and 3.9 MPaJ;;E. The microstructural studies have shown that pressure plays an important role in the dens...

Research paper thumbnail of Simultaneous synthesis and sintering of silicon carbide under high pressure and temperature

Research paper thumbnail of Machining characteristics of wBN-cBN composite tools

Research paper thumbnail of Wurtzite phase of boron nitride as cutting tool material

Research paper thumbnail of Elastic properties of Ge-Sb-Se glasses under pressure

Research paper thumbnail of Sintering of silicon carbide and silicon nitride under high pressure and high temperature

Research paper thumbnail of The kinetics of pressure-induced alpha-omega transformation in Ti

The kinetics of the high-pressure transformation of the alpha (hcp) phase of titanium to the hexa... more The kinetics of the high-pressure transformation of the alpha (hcp) phase of titanium to the hexagonal omega phase is measured as a function of pressure with a view towards predicting the kinetics under very high pressures. Changes in electrical resistance were used to monitor the extent of the alpha-omega transformation as a function of time at specimen pressures between 6 and 9 GPa. The time dependence of the fractional omega phase concentration is found to obey an exponential law characteristic of a nucleation and growth process. The pressure dependence of the transformation rate implies that the transformation should occur under shock loading conditions at a pressure of 19 GPa, in contrast to experimentally observed values of 35 GPa.

Research paper thumbnail of Determination of the thermodynamic equilibrium pressure of the fcc⇄bcc transformation in ytterbium

Physica B+C, 1986

... DETERMINATION OF THE THERMODYNAMIC EQUILIBRIUM PRESSURE OF THE fcc z: bcc TRANSFORMATION IN Y... more ... DETERMINATION OF THE THERMODYNAMIC EQUILIBRIUM PRESSURE OF THE fcc z: bcc TRANSFORMATION IN YTTERBIUM M. MOHAN, C. DIVAKAR and AK ... 4. Determination of po The time for a given fraction of transformation can be expressed in terms of a pressure ...

Research paper thumbnail of Rapid solidification by application of high pressure

Scripta Metallurgica, 1984

Research paper thumbnail of Self programming synthesis and sintering of dense ceramic materials at high pressures and high temperatures

Research paper thumbnail of Self propagating synthesis and sintering of dense ceramic materials at high pressures and temperatures

Self-propagating synthesis can be an economical method for the preparation of advanced materials ... more Self-propagating synthesis can be an economical method for the preparation of advanced materials if the basis problem of porosity is overcome.The application of pressure during a self-propagating combustion reaction(HPCS)results in dense ceramic materials.Starting from elemental powder,dense compacts of ceramics and ceramic composite materials(TiB2-TiB2-Tic,TiB2-TiN,Ti2SiC2,NiA1-TiB2,etc)were prepared by conducting the simultaneous synthesis and sintering at high pressures and temperatures.

Research paper thumbnail of Processing of ceramic-ceramic composites throgh the formation of a transient phase

Research paper thumbnail of Fabrication of high pressure high temperature cell components using pyrophyllite powder

Research paper thumbnail of A high temperature cell (up to 3300K) for use with a cubic press

Research paper thumbnail of Design and development of an advanced linear reciprocating tribometer

Wear, 2009

With advances in machining technology, the requirements for linear guide ways and industrial lubr... more With advances in machining technology, the requirements for linear guide ways and industrial lubricants are increasing, especially for machine tools which have to meet various demands such as high positioning exactness, low stick-slip coefficient of friction over a wide range of speed. Study of friction and wear of lubricated surfaces plays a prominent role in the development of sliding surfaces for machine tools. The design and development of an advanced linear reciprocating tribometer to study the performance of lubricants and slide way surfaces is presented in this paper. The principle of operation consists of sliding test samples against a stationary counter surface under load and recording the parameters of interest. The novel features include evaluating the stick-slip behaviour and dynamic coefficient of friction over a wide speed range from 0.1 to 6000 mm/min under load. An attempt is made to study the efficiency of different oil groove shapes and geometries with reference to oil flow pattern. Based on these studies, the best oil groove shapes and geometries can be obtained to reduce the friction and wear of lubricated sliding surfaces in machine tool slide ways. Preliminary test results of the frictional behaviour of such lubricated surfaces are presented in this paper.

Research paper thumbnail of Step‐loading technique for tungsten carbide opposed anvil high‐pressure setup

Review of Scientific Instruments

A method is described to achieve a step loading of a tungsten carbide opposed anvil setup. The ri... more A method is described to achieve a step loading of a tungsten carbide opposed anvil setup. The rise time of the pressure pulse is nearly 200 ms and the maximum height of the pressure pulse is 2 GPa. The use of this method in the study of the kineticsof pressure ifiduced transformations under isobaric conditions is illustrated with the help of the data on fcc-bcc (face-centered-cubic and body-centered-cubic) transformation in ytterbium.

Research paper thumbnail of Fabrication of Ceramic-Ceramic Composites at High Pressures Through the Formation of an Intermediate Soft Phase

THE REVIEW OF HIGH PRESSURE SCIENCE AND TECHNOLOGY

eramic-ceramic composites in the Ti-B-C system were fabricated by hot pressing of Ti and B4C powd... more eramic-ceramic composites in the Ti-B-C system were fabricated by hot pressing of Ti and B4C powders. The study describes a method to process fully dense ceramic-ceramic composites (without any sintering aids) through the formation of an intermediate soft phase at moderate pressures and temperatures. The results on the processing and properties of TiB2-TiC and TiB2-TiC-SiC composites are presented. [ sintering, ceramics, composites, reaction synthesis, hot pressing]

Research paper thumbnail of The Kinetics of pressure-induced a-gt;w transformation in TI

The kinetics of the pressure-induced a-transformation in titanium is reported in the pressure ran... more The kinetics of the pressure-induced a-transformation in titanium is reported in the pressure range 5-9GPa. The occurance of this transformation under shock loading has been discussed using the observed pressure dependence of the kinetics

Research paper thumbnail of Synthesis and sintering of ceramic materials under pressure

Research paper thumbnail of Design and fabrication of a 600-ton press for sintering studies

High tonnage presses are required for generating high pressure over large volumes. A 600-ton pres... more High tonnage presses are required for generating high pressure over large volumes. A 600-ton press has been designed and fabrication at the National Aerospace Laboratories for the sintering of ceramic materials at high pressures and high temperatyres. The press is of four-column type, and is fabricated out of hardened EN 24 steel.

Research paper thumbnail of Sintering of a - sic at high pressures and temperatures

The high temperature properties of sintered silicon carbide are critically dependent on additives... more The high temperature properties of sintered silicon carbide are critically dependent on additives which are used for consolidation by conventional hot pressing into pore-free bodies. The sintering aids provide increase in shrink-age rate and high densities at low sintering temperatures. However, the presence of sintering aids results in a second phase at the grain boundaries which13; has adverse effects on the high temperature properties. An effort has been made to produce fully dense self bonded Sic without using sintering aids by high pressure-high temperature sintering. The Sic powder has been sintered13; at pressures (1.7-3.0 GPa) at 18OO0C for 5-30 minutes. The densities 'of the sintered compacts are gt; 99% theoretical density. The compacts show room temperature hardness values in the range 26.7-33.5 GPa. The indentation frac-13; ture toughness values range between 3.5 and 3.9 MPaJ;;E. The microstructural studies have shown that pressure plays an important role in the dens...

Research paper thumbnail of Simultaneous synthesis and sintering of silicon carbide under high pressure and temperature

Research paper thumbnail of Machining characteristics of wBN-cBN composite tools

Research paper thumbnail of Wurtzite phase of boron nitride as cutting tool material

Research paper thumbnail of Elastic properties of Ge-Sb-Se glasses under pressure

Research paper thumbnail of Sintering of silicon carbide and silicon nitride under high pressure and high temperature

Research paper thumbnail of The kinetics of pressure-induced alpha-omega transformation in Ti

The kinetics of the high-pressure transformation of the alpha (hcp) phase of titanium to the hexa... more The kinetics of the high-pressure transformation of the alpha (hcp) phase of titanium to the hexagonal omega phase is measured as a function of pressure with a view towards predicting the kinetics under very high pressures. Changes in electrical resistance were used to monitor the extent of the alpha-omega transformation as a function of time at specimen pressures between 6 and 9 GPa. The time dependence of the fractional omega phase concentration is found to obey an exponential law characteristic of a nucleation and growth process. The pressure dependence of the transformation rate implies that the transformation should occur under shock loading conditions at a pressure of 19 GPa, in contrast to experimentally observed values of 35 GPa.

Research paper thumbnail of Determination of the thermodynamic equilibrium pressure of the fcc⇄bcc transformation in ytterbium

Physica B+C, 1986

... DETERMINATION OF THE THERMODYNAMIC EQUILIBRIUM PRESSURE OF THE fcc z: bcc TRANSFORMATION IN Y... more ... DETERMINATION OF THE THERMODYNAMIC EQUILIBRIUM PRESSURE OF THE fcc z: bcc TRANSFORMATION IN YTTERBIUM M. MOHAN, C. DIVAKAR and AK ... 4. Determination of po The time for a given fraction of transformation can be expressed in terms of a pressure ...

Research paper thumbnail of Rapid solidification by application of high pressure

Scripta Metallurgica, 1984

Research paper thumbnail of Self programming synthesis and sintering of dense ceramic materials at high pressures and high temperatures

Research paper thumbnail of Self propagating synthesis and sintering of dense ceramic materials at high pressures and temperatures

Self-propagating synthesis can be an economical method for the preparation of advanced materials ... more Self-propagating synthesis can be an economical method for the preparation of advanced materials if the basis problem of porosity is overcome.The application of pressure during a self-propagating combustion reaction(HPCS)results in dense ceramic materials.Starting from elemental powder,dense compacts of ceramics and ceramic composite materials(TiB2-TiB2-Tic,TiB2-TiN,Ti2SiC2,NiA1-TiB2,etc)were prepared by conducting the simultaneous synthesis and sintering at high pressures and temperatures.

Research paper thumbnail of Processing of ceramic-ceramic composites throgh the formation of a transient phase

Research paper thumbnail of Fabrication of high pressure high temperature cell components using pyrophyllite powder