Vijay Petley | Defence Research And Development Organisation (original) (raw)

Papers by Vijay Petley

Advances in Materials Science and Engineering

The main objective of this investigation is to analyze the microstructure, tensile properties, an... more The main objective of this investigation is to analyze the microstructure, tensile properties, and impact toughness of Ti6Al4V alloy joints developed using optimized parameters of linear friction welding (LFW) for gas turbine blisk assembly applications. The 6 mm thick plates of Ti6Al4V alloy were joined using a friction time of 40 sec, a friction pressure of 20 MPa, a forging pressure of 10 MPa, a forging time of 3 sec, and an oscillating frequency of 14 Hz. The different regions of joints were analyzed using a stereo zoom microscope. Optical and scanning electron microscope (SEM) was used for analysing the microstructural features of joints. The room temperature tensile properties, hardness, and impact toughness of LFW-Ti6Al4V alloy joints were evaluated and correlated to the microstructural features of weld region. The fractured sections of tensile and impact toughness specimens of joints were analyzed using SEM and the failure of joints was correlated with the hardness survey. R...

Ti-6Al-4V alloy is a unique material for structural applications of aerospace industry for the ex... more Ti-6Al-4V alloy is a unique material for structural applications of aerospace industry for the excellent strength and lightweight. The fusion welding of this Titanium alloy resulted severe residual stress formation and coarser grains in the fusion zone. To overcome these problems, a solid state linear friction welding (LFW) is a emerge technique to joining of blade and disk assembly in the next generation aero engines. The plastic deformation followed by forging action resulted finer grain structures in welded regions. This investigation elaborated mechanical behavior and microstructural characteristics of linear friction welded joints. The welding parameters established by statistical response surface methodology. The fabricated joints yielded maximum tensile strength and joint efficiency of 1011 MPa and 98%. The lower microhardness recorded in the thermo mechanical affected zone (TMAZ) among the weld cross section. The weld nugget microstructure composed of equiaxed grain structur...

Welding is an integral part of the fabrication process for realization of the components and sub-... more Welding is an integral part of the fabrication process for realization of the components and sub-components for any structural system. The weld process and the evaluation of the weld zone properties become more significant for the critical application like structural components of an aero engine. Standard tensile testing of the welded specimens provides the ductility for the composite joint i.e. the parent, heat affected zone and the weld zone. Standard bend tests (Three point bend) are specified as the qualitative tests for evaluating the ductility of the welded joints. For these bend tests, the ductility of the parent specimens are utilized for calculating the bend test parameters and the bend angles are specified after performing the tests on the parent specimens. But during the bend tests on the TIG welded specimens of specific materials and the thickness combinations like Ti-64 with thickness of 1.2 and 4.0 mm, it was observed that the specimens used to get fractured during ben...

Transactions of the Canadian Society for Mechanical Engineering, 2020

In the present work, experimental trials were conducted with Ti–6Al–4V sheet. The influence of pr... more In the present work, experimental trials were conducted with Ti–6Al–4V sheet. The influence of process parameters on the weld bead geometry of bead on joint welding and butt joint configuration was studied. It was concluded that at high current and low travel speed, the heat input was found to be maximum. This led to a higher linear heat input over the base metal that subsequently yielded a full depth of penetration. The strength and integrity of the welded butt joint configuration were ascertained by tensile and bend tests. The microhardness values of the fusion and heat-affected zones were concluded to be higher compared to the base metal. In addition, an Erichsen cupping test ensured that the formability of the welded specimen was comparable to that of the base metal.

Experimental Techniques, 2018

The rotor tip clearance is a vital parameter to characterize turbomachinery performance. It is an... more The rotor tip clearance is a vital parameter to characterize turbomachinery performance. It is an essential measurement during engine development and testing. The efficiency of the major modules like fan, compressor and turbine depends on the optimum running clearances. The capacitive sensor is preferred for tip clearance measurements because of various inherent advantages. They are fabricated through complex processes for turbomachinery application and are expensive. These sensors are exposed to harsh engine environments and are likely to exhibit degraded performance. Insulation failure at sensing head, connector contamination and micro-cracks in the MI (Mineral Insulated) cable leads to noise in the signal output. Frequent mechanical failures are also seen due to work hardening of MI cables, lead connector detachments and failure of micro fins at interconnects. Fault fixing of these is tedious and very expensive. This paper presents the concerted effort in developing a simple capacitance sensor addressing potential sensor failure issues. The design features include simple construction, ease of sensor assembly, component realization and troubleshooting. The design also addresses all safety requirements. The sensor has a large sensing area (7.6 mm diameter) producing very stable, high-level signal. The developed sensor produces output that varies from 1 V P-P to 11 V P-P for blade-tip gaps between 3 mm to 0.4 mm respectively. Blade pass simulation studies across the sensor, display almost flat response at minimum clearance. This feature results in very minimal data acquisition errors. The sensor along with RC (Resistance-Capacitance) conditioning electronics was successfully used for clearance measurement on fan stage of gas turbine engine. Test results are in line with the predictions. Extensive tip clearance measurements on the engine validate the design. The current work provides an insight into the development of a simplex capacitance sensor for tip clearance measurement.

Journal of the Mechanical Behavior of Materials, 2014

The strain hardening exponent and strength coefficient of the Ramberg-Osgood flow rule are requir... more The strain hardening exponent and strength coefficient of the Ramberg-Osgood flow rule are required for the accurate design analysis of the materials of aeroengine components. A direct method of deriving these parameters involves the processing of the complete raw data of tensile testing as per ASTM E-646. More often, a first design effort of aeroengine components is made using catalogue data, as the evaluation of material tensile properties is a time-consuming process that takes place concurrently. Catalogue-supplied data on the monotonic loading typically contains elastic modulus, 0.2% proof stress, and ultimate tensile stress along with other data for various temperatures. A methodology was evolved in this work to construct the Ramberg-Osgood flow rule with these three parameters and was validated with laboratory test results and published data through a comparison with ASTM E-646. The strain hardening exponents and strength coefficients were established for a family of aeroengin...

Ceramic Transactions Series, 2013

ABSTRACT The high temperature thermal stability of the CVI generated SiCf/C/SiC composites under ... more ABSTRACT The high temperature thermal stability of the CVI generated SiCf/C/SiC composites under cyclic heat exposure with different quenching rates has been studied. One set of samples was heat exposed at 1073, 1273 K followed by air cooling and water quenching. Second set of samples was exposed to thermal cycling simulating typical aeroengine exhaust conditions in the burner-rig. The degradation of the composites was evaluated by a three point flexure test at room temperature. Severe degradation in the flexural strength was observed for the air cooled as well as water quenched samples exposed at 1273 K and minimum degradation for burner rig tested samples. Matrix micro cracks are observed predominantly in these samples and the fiber matrix interface has been oxidized. The quenching rate was found to have less significance on the flexural strength retention as compared to the total time of exposure at high temperature. The failure patterns of these samples are correlated with their load-displacement response and the flexural strength levels.

Bird strikes on aircraft are well known and cases exist of such strikes causing extensive damage ... more Bird strikes on aircraft are well known and cases exist of such strikes causing extensive damage and even loss of aircraft. While aluminum has been used widely for a number of years for structural components subjected to bird strike, there is interest in using composites and fibre metal laminates in recent years. The need to use these advanced materials has been driven by their distinct advantages in terms of reduction of parts, lower weight, higher fatigue resistance and ability to keep shape when impact loads are low. Energy absorption under high velocity impact by a bird (soft body) is complex due to the highly non-linear effects that occur and the failure modes that can be associated with the materials. It was found appropriate to carry out coupon level impact studies using an airgun, through which soft bodies representing the bird in the form of gelatin cylindrical masses were fired at high speeds. Various coupons of carbon fibre composites, fibre-metal (using aluminum, glass a...

Lecture Notes on Multidisciplinary Industrial Engineering, 2019

The investigation was performed on rolled sheets (2 mm thick) of titanium alloy Ti6Al4V joints wh... more The investigation was performed on rolled sheets (2 mm thick) of titanium alloy Ti6Al4V joints which are diffusion bonded. The objective of this investigation is to study and analyse the effect of holding time on the diffusion bond characteristics. The time for bonding was kept between 15 and 60 min. The pressure and bonding temperature were maintained constantly at 8 MPa and 900 °C, respectively. Metallurgical characteristics were analysed by optical and scanning electron microscopy. The mechanical properties of the Ti6Al4V alloy joints were evaluated. The strength of the bonds was correlated with the microstructures to study the effect of holding time. The microstructure reveals that the defect-free bond can be produced when holding time is increased to a certain limit. The maximum bonding strength and tensile shear fracture load (TSFL) were attained for a holding time of 60 min yields 138 MPa and 40 kN, respectively.

Nickel base super alloys are used for fabrication of hot end components of power plants, automobi... more Nickel base super alloys are used for fabrication of hot end components of power plants, automobiles, aero engines etc. These components are realized by welding & brazing techniques. Welding of super alloys becomes difficult when aluminium & titanium content in the alloys is more than 4.5 % as it may lead formation of deleterious brittle phase Ni3 (Al ,Ti) resulting in weld joint cracking. Therefore, brazing operation is well adopted technique wherein difficult to weld material, inaccessible areas for welding and for batch production & repeatability of the result is important. In this work, Nickel base superalloy GTM SU 263 was brazed in a high vacuum furnace using BNi-9 filler material. Specimens were brazed at 1100 °C for 20 minutes and then heat treated at 1080 °C and 800°C for the duration of 3 hours and 8 hours respectively. The effects of heat treatments were investigated on the microstructure and properties of GTM SU263 braze joint. The resultant microstructures were examined...

SAE International Journal of Aerospace

Metallography, Microstructure, and Analysis

Materials Today: Proceedings

Materials Today: Proceedings

Journal of Manufacturing Engineering

Titanium and its alloys have been considered as one of the best engineering materials for industr... more Titanium and its alloys have been considered as one of the best engineering materials for industrial applications. Excellent combination of properties such as high strength to weight ratio, excellent resistance to corrosion makes them attractive materials for many industrial applications. Recently, considerable research has been performed on Gas Tungsten Constricted Arc welding (GTCAW) process and reported advantages include, lower heat input, reduced residual stresses and distortion. In this investigation, tensile properties of GTCA welded Ti-6Al-4V alloy joints were evaluated. Single pass, autogeneous welds free from volumetric defects were fabricated using optimized GTCAW parameters. The joints were characterized using optical microscopy, scanning electron microscopy and microhardness, survey. Tensile properties of the joints were overmatching with the base metal. The alpha and granular beta grains in the base metal were changed into short acicular alpha martensitic structure in ...

Journal of Manufacturing Engineering

Gas turbine engines demand material with unique properties like high-temperature oxidation and co... more Gas turbine engines demand material with unique properties like high-temperature oxidation and corrosion resistance, high specific strength, etc. All over the world material development to meet these requirements has led to the development of novel alloys. While Titanium base alloys are used in the low-temperature regime of the gas turbine engine, Nickel-basedsuperalloys are used for hot end components of the engine. With the increase in the temperature requirement for the turbine parts, the form of the Ni-based superalloys changed from wrought to cast superalloys. As an inherent process of investment cast superalloy blades and vanes which has serpentine passages for air cooling, these passages are required to be closed after casting. The numerous adapters also need to be joined on the cast superalloy casings for various instrumentation, lube oil ports. These cast superalloys are nonweldable and joining these pose a challenge. In this present investigation, the joining of the Nibase...

Advances in Materials Science and Engineering

The main objective of this investigation is to analyze the microstructure, tensile properties, an... more The main objective of this investigation is to analyze the microstructure, tensile properties, and impact toughness of Ti6Al4V alloy joints developed using optimized parameters of linear friction welding (LFW) for gas turbine blisk assembly applications. The 6 mm thick plates of Ti6Al4V alloy were joined using a friction time of 40 sec, a friction pressure of 20 MPa, a forging pressure of 10 MPa, a forging time of 3 sec, and an oscillating frequency of 14 Hz. The different regions of joints were analyzed using a stereo zoom microscope. Optical and scanning electron microscope (SEM) was used for analysing the microstructural features of joints. The room temperature tensile properties, hardness, and impact toughness of LFW-Ti6Al4V alloy joints were evaluated and correlated to the microstructural features of weld region. The fractured sections of tensile and impact toughness specimens of joints were analyzed using SEM and the failure of joints was correlated with the hardness survey. R...

Ti-6Al-4V alloy is a unique material for structural applications of aerospace industry for the ex... more Ti-6Al-4V alloy is a unique material for structural applications of aerospace industry for the excellent strength and lightweight. The fusion welding of this Titanium alloy resulted severe residual stress formation and coarser grains in the fusion zone. To overcome these problems, a solid state linear friction welding (LFW) is a emerge technique to joining of blade and disk assembly in the next generation aero engines. The plastic deformation followed by forging action resulted finer grain structures in welded regions. This investigation elaborated mechanical behavior and microstructural characteristics of linear friction welded joints. The welding parameters established by statistical response surface methodology. The fabricated joints yielded maximum tensile strength and joint efficiency of 1011 MPa and 98%. The lower microhardness recorded in the thermo mechanical affected zone (TMAZ) among the weld cross section. The weld nugget microstructure composed of equiaxed grain structur...

Welding is an integral part of the fabrication process for realization of the components and sub-... more Welding is an integral part of the fabrication process for realization of the components and sub-components for any structural system. The weld process and the evaluation of the weld zone properties become more significant for the critical application like structural components of an aero engine. Standard tensile testing of the welded specimens provides the ductility for the composite joint i.e. the parent, heat affected zone and the weld zone. Standard bend tests (Three point bend) are specified as the qualitative tests for evaluating the ductility of the welded joints. For these bend tests, the ductility of the parent specimens are utilized for calculating the bend test parameters and the bend angles are specified after performing the tests on the parent specimens. But during the bend tests on the TIG welded specimens of specific materials and the thickness combinations like Ti-64 with thickness of 1.2 and 4.0 mm, it was observed that the specimens used to get fractured during ben...

Transactions of the Canadian Society for Mechanical Engineering, 2020

In the present work, experimental trials were conducted with Ti–6Al–4V sheet. The influence of pr... more In the present work, experimental trials were conducted with Ti–6Al–4V sheet. The influence of process parameters on the weld bead geometry of bead on joint welding and butt joint configuration was studied. It was concluded that at high current and low travel speed, the heat input was found to be maximum. This led to a higher linear heat input over the base metal that subsequently yielded a full depth of penetration. The strength and integrity of the welded butt joint configuration were ascertained by tensile and bend tests. The microhardness values of the fusion and heat-affected zones were concluded to be higher compared to the base metal. In addition, an Erichsen cupping test ensured that the formability of the welded specimen was comparable to that of the base metal.

Experimental Techniques, 2018

The rotor tip clearance is a vital parameter to characterize turbomachinery performance. It is an... more The rotor tip clearance is a vital parameter to characterize turbomachinery performance. It is an essential measurement during engine development and testing. The efficiency of the major modules like fan, compressor and turbine depends on the optimum running clearances. The capacitive sensor is preferred for tip clearance measurements because of various inherent advantages. They are fabricated through complex processes for turbomachinery application and are expensive. These sensors are exposed to harsh engine environments and are likely to exhibit degraded performance. Insulation failure at sensing head, connector contamination and micro-cracks in the MI (Mineral Insulated) cable leads to noise in the signal output. Frequent mechanical failures are also seen due to work hardening of MI cables, lead connector detachments and failure of micro fins at interconnects. Fault fixing of these is tedious and very expensive. This paper presents the concerted effort in developing a simple capacitance sensor addressing potential sensor failure issues. The design features include simple construction, ease of sensor assembly, component realization and troubleshooting. The design also addresses all safety requirements. The sensor has a large sensing area (7.6 mm diameter) producing very stable, high-level signal. The developed sensor produces output that varies from 1 V P-P to 11 V P-P for blade-tip gaps between 3 mm to 0.4 mm respectively. Blade pass simulation studies across the sensor, display almost flat response at minimum clearance. This feature results in very minimal data acquisition errors. The sensor along with RC (Resistance-Capacitance) conditioning electronics was successfully used for clearance measurement on fan stage of gas turbine engine. Test results are in line with the predictions. Extensive tip clearance measurements on the engine validate the design. The current work provides an insight into the development of a simplex capacitance sensor for tip clearance measurement.

Journal of the Mechanical Behavior of Materials, 2014

The strain hardening exponent and strength coefficient of the Ramberg-Osgood flow rule are requir... more The strain hardening exponent and strength coefficient of the Ramberg-Osgood flow rule are required for the accurate design analysis of the materials of aeroengine components. A direct method of deriving these parameters involves the processing of the complete raw data of tensile testing as per ASTM E-646. More often, a first design effort of aeroengine components is made using catalogue data, as the evaluation of material tensile properties is a time-consuming process that takes place concurrently. Catalogue-supplied data on the monotonic loading typically contains elastic modulus, 0.2% proof stress, and ultimate tensile stress along with other data for various temperatures. A methodology was evolved in this work to construct the Ramberg-Osgood flow rule with these three parameters and was validated with laboratory test results and published data through a comparison with ASTM E-646. The strain hardening exponents and strength coefficients were established for a family of aeroengin...

Ceramic Transactions Series, 2013

ABSTRACT The high temperature thermal stability of the CVI generated SiCf/C/SiC composites under ... more ABSTRACT The high temperature thermal stability of the CVI generated SiCf/C/SiC composites under cyclic heat exposure with different quenching rates has been studied. One set of samples was heat exposed at 1073, 1273 K followed by air cooling and water quenching. Second set of samples was exposed to thermal cycling simulating typical aeroengine exhaust conditions in the burner-rig. The degradation of the composites was evaluated by a three point flexure test at room temperature. Severe degradation in the flexural strength was observed for the air cooled as well as water quenched samples exposed at 1273 K and minimum degradation for burner rig tested samples. Matrix micro cracks are observed predominantly in these samples and the fiber matrix interface has been oxidized. The quenching rate was found to have less significance on the flexural strength retention as compared to the total time of exposure at high temperature. The failure patterns of these samples are correlated with their load-displacement response and the flexural strength levels.

Bird strikes on aircraft are well known and cases exist of such strikes causing extensive damage ... more Bird strikes on aircraft are well known and cases exist of such strikes causing extensive damage and even loss of aircraft. While aluminum has been used widely for a number of years for structural components subjected to bird strike, there is interest in using composites and fibre metal laminates in recent years. The need to use these advanced materials has been driven by their distinct advantages in terms of reduction of parts, lower weight, higher fatigue resistance and ability to keep shape when impact loads are low. Energy absorption under high velocity impact by a bird (soft body) is complex due to the highly non-linear effects that occur and the failure modes that can be associated with the materials. It was found appropriate to carry out coupon level impact studies using an airgun, through which soft bodies representing the bird in the form of gelatin cylindrical masses were fired at high speeds. Various coupons of carbon fibre composites, fibre-metal (using aluminum, glass a...

Lecture Notes on Multidisciplinary Industrial Engineering, 2019

The investigation was performed on rolled sheets (2 mm thick) of titanium alloy Ti6Al4V joints wh... more The investigation was performed on rolled sheets (2 mm thick) of titanium alloy Ti6Al4V joints which are diffusion bonded. The objective of this investigation is to study and analyse the effect of holding time on the diffusion bond characteristics. The time for bonding was kept between 15 and 60 min. The pressure and bonding temperature were maintained constantly at 8 MPa and 900 °C, respectively. Metallurgical characteristics were analysed by optical and scanning electron microscopy. The mechanical properties of the Ti6Al4V alloy joints were evaluated. The strength of the bonds was correlated with the microstructures to study the effect of holding time. The microstructure reveals that the defect-free bond can be produced when holding time is increased to a certain limit. The maximum bonding strength and tensile shear fracture load (TSFL) were attained for a holding time of 60 min yields 138 MPa and 40 kN, respectively.

Nickel base super alloys are used for fabrication of hot end components of power plants, automobi... more Nickel base super alloys are used for fabrication of hot end components of power plants, automobiles, aero engines etc. These components are realized by welding & brazing techniques. Welding of super alloys becomes difficult when aluminium & titanium content in the alloys is more than 4.5 % as it may lead formation of deleterious brittle phase Ni3 (Al ,Ti) resulting in weld joint cracking. Therefore, brazing operation is well adopted technique wherein difficult to weld material, inaccessible areas for welding and for batch production & repeatability of the result is important. In this work, Nickel base superalloy GTM SU 263 was brazed in a high vacuum furnace using BNi-9 filler material. Specimens were brazed at 1100 °C for 20 minutes and then heat treated at 1080 °C and 800°C for the duration of 3 hours and 8 hours respectively. The effects of heat treatments were investigated on the microstructure and properties of GTM SU263 braze joint. The resultant microstructures were examined...

SAE International Journal of Aerospace

Metallography, Microstructure, and Analysis

Materials Today: Proceedings

Materials Today: Proceedings

Journal of Manufacturing Engineering

Titanium and its alloys have been considered as one of the best engineering materials for industr... more Titanium and its alloys have been considered as one of the best engineering materials for industrial applications. Excellent combination of properties such as high strength to weight ratio, excellent resistance to corrosion makes them attractive materials for many industrial applications. Recently, considerable research has been performed on Gas Tungsten Constricted Arc welding (GTCAW) process and reported advantages include, lower heat input, reduced residual stresses and distortion. In this investigation, tensile properties of GTCA welded Ti-6Al-4V alloy joints were evaluated. Single pass, autogeneous welds free from volumetric defects were fabricated using optimized GTCAW parameters. The joints were characterized using optical microscopy, scanning electron microscopy and microhardness, survey. Tensile properties of the joints were overmatching with the base metal. The alpha and granular beta grains in the base metal were changed into short acicular alpha martensitic structure in ...

Journal of Manufacturing Engineering

Gas turbine engines demand material with unique properties like high-temperature oxidation and co... more Gas turbine engines demand material with unique properties like high-temperature oxidation and corrosion resistance, high specific strength, etc. All over the world material development to meet these requirements has led to the development of novel alloys. While Titanium base alloys are used in the low-temperature regime of the gas turbine engine, Nickel-basedsuperalloys are used for hot end components of the engine. With the increase in the temperature requirement for the turbine parts, the form of the Ni-based superalloys changed from wrought to cast superalloys. As an inherent process of investment cast superalloy blades and vanes which has serpentine passages for air cooling, these passages are required to be closed after casting. The numerous adapters also need to be joined on the cast superalloy casings for various instrumentation, lube oil ports. These cast superalloys are nonweldable and joining these pose a challenge. In this present investigation, the joining of the Nibase...