jeby philip - Academia.edu (original) (raw)

Papers by jeby philip

Experimental Techniques, Oct 25, 2018

In this paper, simpler methods of measuring various performance parameters, such as pivot point e... more In this paper, simpler methods of measuring various performance parameters, such as pivot point excursions, actuation angles, and symmetry of the nozzle motion of a flex nozzle system (FNS) meant for a large solid rocket booster nozzle are reported. A novel attempt is made to estimate the above parameters using the pivot point coordinates as primary data. Towards this objective, the trajectories of a reference point obtained using one stereo based 3-dimensional Digital Image Correlation (3-D DIC) system, above a nozzle simulator during the vectoring tests, were utilized. A linear least squares (LLS) method is proposed and validated for locating the pivot point from the 3-D DIC trajectory. The pivot point location and the measured DIC displacements were further analyzed to evaluate the target parameters. The results show that use of the 3-D DIC system provides confidence on the performance of the actuators with a simplified measurement scheme. Moreover, it generates useful additional data, as spin-offs, comparable with the conventional measurements. Thereby data reduction, testing time and resource required for characterization of a FNS is expected to reduce considerably. Keywords 3-D DIC • Flex nozzle system (FNS) • Pivot point excursions • Actuation angle • Stroke symmetry • Linear least squares (LLS) method

International Journal of Acoustics and Vibration, Jun 1, 2018

Aluminium Alloy AA 2219 is the principal metal for the production of propellant reservoir used in... more Aluminium Alloy AA 2219 is the principal metal for the production of propellant reservoir used in launch vehicles. The propellant tanks are often proof tested with acoustic emission technique (AET) to ensure its health. Acoustic Emission Testing during the structural health monitoring and proof testing is complex and unrealistic occasionally as it is performed in the noisy environment. Identification of signature corresponds to crack and its extraction from noise signatures is a major challenge in AET. Wavelet Packet Transform is an efficient mathematical tool for the analysis of AE signals. This paper recommends a novel combination of normalized cross correlation, Wavelet Packet Transform and Continuous wavelet transform to detect and extract the event related to failure. Experiments were carried out on AA 2219 tensile coupons at different threshold conditions. The recorded AE hits contain signals related to different events such as atmospheric noise, rubbing noise and other noise signals along with the signals from cracks. By applying the fine tuned wavelet packet transform technique in combination with CWT, the extraction of denoised single event related to crack was executed. Based on the frequency and the wavelet coefficient the crack related hits and the noisy hits are categorized.

Procedia Structural Integrity, 2019

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Journal of Materials Processing Technology, 2007

Hole drilling method, which is relatively simple and fast, is one of the most popularly used semi... more Hole drilling method, which is relatively simple and fast, is one of the most popularly used semi-destructive methods of residual stress evaluation which can provide the measurement of residual stress distribution across the thickness in magnitude, direction and sense. The strains relieved by drilling a small hole of approximately 2 mm diameter are measured using special purpose strain gauges and the residual stresses present in the component are computed from the relieved strains. As a case study, the residual stresses present in aluminium alloy (AA2219) formed and welded components at various locations are presented and compared. The results are compared with the stresses computed from the deflection obtained after chemical milling and EDM.

Lecture Notes in Mechanical Engineering

Lecture Notes in Mechanical Engineering

Materials Research Express, 2021

Measurement of elastic properties, especially the Poisson’s ratio, utilizing non-contact techniqu... more Measurement of elastic properties, especially the Poisson’s ratio, utilizing non-contact techniques in a tensile experiment is very challenging. This is primarily due to the poor spatial resolution and the large strain noise inherent to these techniques. The difficulty level increases many folds when Poisson’s ratio of less elongating, stiffer, and/or brittle materials, like ceramics and ablatives, is measured. This paper reports a newer approach that employs 3-D digital image correlation (3-D DIC) in a Cornu’s experiment to enable accurate measurement of elastic properties in a single test. The deflection field obtained from 3-D DIC in the form of anticlastic surfaces during Cornu’s experiment is utilized for determining Poisson’s ratio. In the same experiment, the elastic modulus is estimated using the center point deflection method. The proposed methods are validated with standard materials and extended to newly developed materials. Cornu’s method with 3-D DIC can provide the ela...

The Journal of Strain Analysis for Engineering Design, 2020

Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analys... more Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analysis of metals. Recently, 2-stage and 3-stage R-O variant models have been proposed to replicate stress-strain behavior under large plastic deformation. The complexity of these models increases with the addition of each stage. Moreover, these models have considered deformation till necking only. In this paper, a simplistic multi-stage constitutive model is proposed to capture the strain-hardening non-linearity shown by metals including its post necking behavior. The constitutive parameters of the proposed stress-strain model can be determined using only elastic modulus and yield strength. 3-D digital image correlation was used as an experimental tool for measuring full-field strains on the specimens, which were subsequently utilized to obtain the material parameters. Our constitutive model is demonstrated with an aerospace-grade stainless steel AISI 321 wherein deformation response average...

Acoustic Emission Technique (AET) is one of the most promising non destructive techniques for mon... more Acoustic Emission Technique (AET) is one of the most promising non destructive techniques for monitoring and evaluation of pressure vessels and other structural members. It is an effective way of detecting fracture and fatigue behaviors of materials. Being a volume technique AE can detect the presence of defects like cracks, delaminations, debonds, certain weld defects etc anywhere in the component, which are active, or that can grow under service loading conditions. In certain cases AE can also detect yielding behavior. This technique is being widely used as a reliable tool for structural integrity assessment during qualification and acceptance testing of large number of structural components in aerospace industry. Nickel-Hydrogen cells are used in satellites. The cell case is made of INCONEL-718 alloy and cylindrical in shape capped with tori-spherical end domes. The cell case is made by joining two parts together by means of cirseam TIG weld. The terminals are also welded to the ...

Acoustic Emission (AE) monitoring, which is a real time non-destructive testing method, is extens... more Acoustic Emission (AE) monitoring, which is a real time non-destructive testing method, is extensively used for the structural integrity assessment of pressure vessels during pressure testing. It’s a powerful tool for remote global detection of active defects and its propagation in the components during pressure tests. As liquid propellant tanks are proof pressure tested pneumatically to avoid contamination, the noise due to the pressurization jet is a major hindrance to the proper interpretation of Acoustic Emission data unlike in the case of hydraulic pressurization where normal Acoustic Emission test procedures could be used. In such cases, the characteristics of the emissions from the components during pressure hold phases and repeat test if any are to be relied upon for analysis to interpret the behaviour of the structure. This paper discusses the methodology used for the Structural Integrity assessment of Aluminium alloy tankages tested with pneumatic medium. The parameters co...

In this paper successful application of time average interferometric holography, a w ole field te... more In this paper successful application of time average interferometric holography, a w ole field technique, for quick and complete inspection of a composite sandwich structure with fac e sheets of varying thickness is reported. This techniqueis an established imaging technique used for measu ring the amplitude of vibration ofobjects under excitation and also for identification of defects through mapping its local resonance. However, industrial application of this technique was limited due to thepracticalissues inimplemen tation as an in-situ inspection tool. In this paper, this technique in its advanced form a nd recently developed digital mode ofhologram recording and image reconstruction is utilized for identifyi g various defects. The sensitivity of forced vibration on the resonance of different type of defects in a vary ing thickness face sheets of a sandwich specimen is studied in this paper. Moreover the modal parameters like m ode shape and resonant frequencies of various types...

Acoustic Emission (AE) is an online health monitoring technique for assessing the structural inte... more Acoustic Emission (AE) is an online health monitoring technique for assessing the structural integrity of the hardware and widely used as a mandatory technique to clear all the high pressure Titanium alloy pressure vessels during their hydro pressure test. AE has proven its capability for on line integrity assessments during the proof pressure test. Compared to the AE data of Ti6Al4V gas bottle during proof pressure test, Ti5Al2.5Sn-ELI alpha alloy initial developmental gas bottle has registered more number of AE signals at cir-seam electron-beam weld region. Two of these gas bottles failed in the cir-seam weld region at a pressure above the design ultimate pressure during room temperature burst pressure test. But one of these failed in the same region much below the design pressure in a cyro environment. This paper brings out the results of AE studies carried out during the development phases of Ti5Al2.5SnELI alpha alloy gas bottles.

The crack growth in the engineering materials usually precedes the occurrence of a significant am... more The crack growth in the engineering materials usually precedes the occurrence of a significant amount of plasticity at the crack tip. The plastic deformation and crack opening of the metallic materials usually produce intense acoustic emission. The paper reports on an experimental study carried out to determine the characteristics of the acoustic emission signals emitted from AA2219 Aluminium material during crack opening. Unsupervised pattern recognition analysis of acoustic emission signals captured during the tensile loading of a compact tension specimen is carried out to segregate the genuine AE signals from all the data acquired during tension test. 3 classes of signals segregated through the K-means cluster algorithm has been analyzed in detail. The variation in the magnitude of AE parameters of different clusters is distinct. The signature of crack growth based on the AE parameters viz. amplitude, duration, energy and counts has been obtained through the study.

This paper describes the use of Acoustic Emission (AE) monitoring of a pre-cracked CT specimen to... more This paper describes the use of Acoustic Emission (AE) monitoring of a pre-cracked CT specimen to analyse and characterise different stages of failure. Titanium alloy (Ti6Al4V) CT specimens were loaded at a constant crosshead speed until failure. Variations in AE parameters such as amplitude, hit rate, counts were analysed to characterise the crack propagation behaviour. Variation in AE data indicates a correlation with different mechanisms to failure at different loads. Focusing on the microscopic origins of Acoustic Emission during the testing, the resulting macroscopic behaviour at different stages of tensile loading is also discussed.

Acoustic Emission NDT is widely used for the structural integrity assessment of aerospace hardwar... more Acoustic Emission NDT is widely used for the structural integrity assessment of aerospace hardware viz. pressure vessels, tanks and structures. Due to many desirable aerospace properties, the 15CDV6 steel is used for the fabrication of tanks for storing the rocket fuels. To avoid the chemical reactions with the fuels the inner surface of the pressure vessels are coated with an insulating material like epoxy. The AE signals captured from the pressure vessel during the pressure test will be a combination of noise signals and genuine AE signals. In addition to the extraneous noises, the signals generated by the internal resin coating are also a major hindrance for the AE data analysis. Pattern recognition analysis of acoustic emission signals is a widely accepted practice for classifying the various source mechanisms involved by which we can effectively segregate the genuine signal from the noise. This paper gives the details on the analysis carried out on AE data obtained during the p...

Applied Optics, 2021

Digital fringe multiplication is a useful technique for obtaining fractional fringe orders in pho... more Digital fringe multiplication is a useful technique for obtaining fractional fringe orders in photoelasticity at regions with very feeble retardations. In this paper, the effectiveness of the existing fringe multiplication techniques is investigated theoretically and experimentally. A new approach for fringe multiplication, using background nullified fringes, is developed to overcome the prevailing issues. Three options for obtaining background nullified fringe patterns are explained. Further, quadrature transformation of these fringe patterns is carried out to fetch uniform modulation. Moreover, a simplified fringe multiplication method is worked out to obtain fractional fringes from the uniformly modulated fringe patterns. The proposed procedures have been demonstrated through simulated as well as experimental images. A parametric study is carried out to understand the influence of pixel resolution and bit depth of the images on fringe multiplication. A criterion is established fo...

IEEE Sensors Journal, 2018

A reusable passive RFID sensor is reported for wireless strain measurement on metals. The charact... more A reusable passive RFID sensor is reported for wireless strain measurement on metals. The characteristics of the proposed sensor are assessed on aluminum tensile specimens. The Received Signal Strength Intensity (RSSI) from the RFID sensor and the frequency corresponding to the maximum RSSI are used to measure the specimen strain. Besides strain, the yield, ultimate tensile strength and failure points of the specimen could also be identified from the RSSI measurements and correlated with strain gauge load cell data. Digital Image Correlation (DIC) measurements gathered during tensile tests confirm that the sensor does not deform during tensile loading and is reusable. Index Terms-RFID, tag antenna, strain measurement, structural health monitoring I. INTRODUCTION Structural health monitoring (SHM) is essential for engineering infrastructures such as railways, pipelines, dams, bridges and aircrafts to ensure safe and reliable operation [1]. Material degradation such as crack, porosity, and fatigue occurs in engineered structures due to repeated loading during component service. Early identification of the structural damages enables adopting corrective measures to prevent catastrophic failures [2]. Thus, periodic inspection of engineering structures is carried out using non-destructive testing (NDT) and evaluation techniques employing visual, ultrasonic and electromagnetic (EM) tests [3, 4]. Most of the SHM systems used in industry are wired. In case of large structures, wired systems are cumbersome to deploy, maintain and debug. Due to high instrumentation cost, slow inspection time and logistics issues, wireless SHM is gaining significance [5]. Amongst the wireless techniques, there is an increase in the use of radio frequency identification (RFID) systems as they are passive and cost effective NDT solutions which enable pervasive monitoring, wireless and remote inspection [5-7]. The RFID system proposed here consists of the transponder (RFID tag) placed on the material under test (MUT), ultra high

Indian Welding Journal, 2006

Procedia Structural Integrity, 2019

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Experimental Techniques, Oct 25, 2018

In this paper, simpler methods of measuring various performance parameters, such as pivot point e... more In this paper, simpler methods of measuring various performance parameters, such as pivot point excursions, actuation angles, and symmetry of the nozzle motion of a flex nozzle system (FNS) meant for a large solid rocket booster nozzle are reported. A novel attempt is made to estimate the above parameters using the pivot point coordinates as primary data. Towards this objective, the trajectories of a reference point obtained using one stereo based 3-dimensional Digital Image Correlation (3-D DIC) system, above a nozzle simulator during the vectoring tests, were utilized. A linear least squares (LLS) method is proposed and validated for locating the pivot point from the 3-D DIC trajectory. The pivot point location and the measured DIC displacements were further analyzed to evaluate the target parameters. The results show that use of the 3-D DIC system provides confidence on the performance of the actuators with a simplified measurement scheme. Moreover, it generates useful additional data, as spin-offs, comparable with the conventional measurements. Thereby data reduction, testing time and resource required for characterization of a FNS is expected to reduce considerably. Keywords 3-D DIC • Flex nozzle system (FNS) • Pivot point excursions • Actuation angle • Stroke symmetry • Linear least squares (LLS) method

International Journal of Acoustics and Vibration, Jun 1, 2018

Aluminium Alloy AA 2219 is the principal metal for the production of propellant reservoir used in... more Aluminium Alloy AA 2219 is the principal metal for the production of propellant reservoir used in launch vehicles. The propellant tanks are often proof tested with acoustic emission technique (AET) to ensure its health. Acoustic Emission Testing during the structural health monitoring and proof testing is complex and unrealistic occasionally as it is performed in the noisy environment. Identification of signature corresponds to crack and its extraction from noise signatures is a major challenge in AET. Wavelet Packet Transform is an efficient mathematical tool for the analysis of AE signals. This paper recommends a novel combination of normalized cross correlation, Wavelet Packet Transform and Continuous wavelet transform to detect and extract the event related to failure. Experiments were carried out on AA 2219 tensile coupons at different threshold conditions. The recorded AE hits contain signals related to different events such as atmospheric noise, rubbing noise and other noise signals along with the signals from cracks. By applying the fine tuned wavelet packet transform technique in combination with CWT, the extraction of denoised single event related to crack was executed. Based on the frequency and the wavelet coefficient the crack related hits and the noisy hits are categorized.

Procedia Structural Integrity, 2019

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Journal of Materials Processing Technology, 2007

Hole drilling method, which is relatively simple and fast, is one of the most popularly used semi... more Hole drilling method, which is relatively simple and fast, is one of the most popularly used semi-destructive methods of residual stress evaluation which can provide the measurement of residual stress distribution across the thickness in magnitude, direction and sense. The strains relieved by drilling a small hole of approximately 2 mm diameter are measured using special purpose strain gauges and the residual stresses present in the component are computed from the relieved strains. As a case study, the residual stresses present in aluminium alloy (AA2219) formed and welded components at various locations are presented and compared. The results are compared with the stresses computed from the deflection obtained after chemical milling and EDM.

Lecture Notes in Mechanical Engineering

Lecture Notes in Mechanical Engineering

Materials Research Express, 2021

Measurement of elastic properties, especially the Poisson’s ratio, utilizing non-contact techniqu... more Measurement of elastic properties, especially the Poisson’s ratio, utilizing non-contact techniques in a tensile experiment is very challenging. This is primarily due to the poor spatial resolution and the large strain noise inherent to these techniques. The difficulty level increases many folds when Poisson’s ratio of less elongating, stiffer, and/or brittle materials, like ceramics and ablatives, is measured. This paper reports a newer approach that employs 3-D digital image correlation (3-D DIC) in a Cornu’s experiment to enable accurate measurement of elastic properties in a single test. The deflection field obtained from 3-D DIC in the form of anticlastic surfaces during Cornu’s experiment is utilized for determining Poisson’s ratio. In the same experiment, the elastic modulus is estimated using the center point deflection method. The proposed methods are validated with standard materials and extended to newly developed materials. Cornu’s method with 3-D DIC can provide the ela...

The Journal of Strain Analysis for Engineering Design, 2020

Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analys... more Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analysis of metals. Recently, 2-stage and 3-stage R-O variant models have been proposed to replicate stress-strain behavior under large plastic deformation. The complexity of these models increases with the addition of each stage. Moreover, these models have considered deformation till necking only. In this paper, a simplistic multi-stage constitutive model is proposed to capture the strain-hardening non-linearity shown by metals including its post necking behavior. The constitutive parameters of the proposed stress-strain model can be determined using only elastic modulus and yield strength. 3-D digital image correlation was used as an experimental tool for measuring full-field strains on the specimens, which were subsequently utilized to obtain the material parameters. Our constitutive model is demonstrated with an aerospace-grade stainless steel AISI 321 wherein deformation response average...

Acoustic Emission Technique (AET) is one of the most promising non destructive techniques for mon... more Acoustic Emission Technique (AET) is one of the most promising non destructive techniques for monitoring and evaluation of pressure vessels and other structural members. It is an effective way of detecting fracture and fatigue behaviors of materials. Being a volume technique AE can detect the presence of defects like cracks, delaminations, debonds, certain weld defects etc anywhere in the component, which are active, or that can grow under service loading conditions. In certain cases AE can also detect yielding behavior. This technique is being widely used as a reliable tool for structural integrity assessment during qualification and acceptance testing of large number of structural components in aerospace industry. Nickel-Hydrogen cells are used in satellites. The cell case is made of INCONEL-718 alloy and cylindrical in shape capped with tori-spherical end domes. The cell case is made by joining two parts together by means of cirseam TIG weld. The terminals are also welded to the ...

Acoustic Emission (AE) monitoring, which is a real time non-destructive testing method, is extens... more Acoustic Emission (AE) monitoring, which is a real time non-destructive testing method, is extensively used for the structural integrity assessment of pressure vessels during pressure testing. It’s a powerful tool for remote global detection of active defects and its propagation in the components during pressure tests. As liquid propellant tanks are proof pressure tested pneumatically to avoid contamination, the noise due to the pressurization jet is a major hindrance to the proper interpretation of Acoustic Emission data unlike in the case of hydraulic pressurization where normal Acoustic Emission test procedures could be used. In such cases, the characteristics of the emissions from the components during pressure hold phases and repeat test if any are to be relied upon for analysis to interpret the behaviour of the structure. This paper discusses the methodology used for the Structural Integrity assessment of Aluminium alloy tankages tested with pneumatic medium. The parameters co...

In this paper successful application of time average interferometric holography, a w ole field te... more In this paper successful application of time average interferometric holography, a w ole field technique, for quick and complete inspection of a composite sandwich structure with fac e sheets of varying thickness is reported. This techniqueis an established imaging technique used for measu ring the amplitude of vibration ofobjects under excitation and also for identification of defects through mapping its local resonance. However, industrial application of this technique was limited due to thepracticalissues inimplemen tation as an in-situ inspection tool. In this paper, this technique in its advanced form a nd recently developed digital mode ofhologram recording and image reconstruction is utilized for identifyi g various defects. The sensitivity of forced vibration on the resonance of different type of defects in a vary ing thickness face sheets of a sandwich specimen is studied in this paper. Moreover the modal parameters like m ode shape and resonant frequencies of various types...

Acoustic Emission (AE) is an online health monitoring technique for assessing the structural inte... more Acoustic Emission (AE) is an online health monitoring technique for assessing the structural integrity of the hardware and widely used as a mandatory technique to clear all the high pressure Titanium alloy pressure vessels during their hydro pressure test. AE has proven its capability for on line integrity assessments during the proof pressure test. Compared to the AE data of Ti6Al4V gas bottle during proof pressure test, Ti5Al2.5Sn-ELI alpha alloy initial developmental gas bottle has registered more number of AE signals at cir-seam electron-beam weld region. Two of these gas bottles failed in the cir-seam weld region at a pressure above the design ultimate pressure during room temperature burst pressure test. But one of these failed in the same region much below the design pressure in a cyro environment. This paper brings out the results of AE studies carried out during the development phases of Ti5Al2.5SnELI alpha alloy gas bottles.

The crack growth in the engineering materials usually precedes the occurrence of a significant am... more The crack growth in the engineering materials usually precedes the occurrence of a significant amount of plasticity at the crack tip. The plastic deformation and crack opening of the metallic materials usually produce intense acoustic emission. The paper reports on an experimental study carried out to determine the characteristics of the acoustic emission signals emitted from AA2219 Aluminium material during crack opening. Unsupervised pattern recognition analysis of acoustic emission signals captured during the tensile loading of a compact tension specimen is carried out to segregate the genuine AE signals from all the data acquired during tension test. 3 classes of signals segregated through the K-means cluster algorithm has been analyzed in detail. The variation in the magnitude of AE parameters of different clusters is distinct. The signature of crack growth based on the AE parameters viz. amplitude, duration, energy and counts has been obtained through the study.

This paper describes the use of Acoustic Emission (AE) monitoring of a pre-cracked CT specimen to... more This paper describes the use of Acoustic Emission (AE) monitoring of a pre-cracked CT specimen to analyse and characterise different stages of failure. Titanium alloy (Ti6Al4V) CT specimens were loaded at a constant crosshead speed until failure. Variations in AE parameters such as amplitude, hit rate, counts were analysed to characterise the crack propagation behaviour. Variation in AE data indicates a correlation with different mechanisms to failure at different loads. Focusing on the microscopic origins of Acoustic Emission during the testing, the resulting macroscopic behaviour at different stages of tensile loading is also discussed.

Acoustic Emission NDT is widely used for the structural integrity assessment of aerospace hardwar... more Acoustic Emission NDT is widely used for the structural integrity assessment of aerospace hardware viz. pressure vessels, tanks and structures. Due to many desirable aerospace properties, the 15CDV6 steel is used for the fabrication of tanks for storing the rocket fuels. To avoid the chemical reactions with the fuels the inner surface of the pressure vessels are coated with an insulating material like epoxy. The AE signals captured from the pressure vessel during the pressure test will be a combination of noise signals and genuine AE signals. In addition to the extraneous noises, the signals generated by the internal resin coating are also a major hindrance for the AE data analysis. Pattern recognition analysis of acoustic emission signals is a widely accepted practice for classifying the various source mechanisms involved by which we can effectively segregate the genuine signal from the noise. This paper gives the details on the analysis carried out on AE data obtained during the p...

Applied Optics, 2021

Digital fringe multiplication is a useful technique for obtaining fractional fringe orders in pho... more Digital fringe multiplication is a useful technique for obtaining fractional fringe orders in photoelasticity at regions with very feeble retardations. In this paper, the effectiveness of the existing fringe multiplication techniques is investigated theoretically and experimentally. A new approach for fringe multiplication, using background nullified fringes, is developed to overcome the prevailing issues. Three options for obtaining background nullified fringe patterns are explained. Further, quadrature transformation of these fringe patterns is carried out to fetch uniform modulation. Moreover, a simplified fringe multiplication method is worked out to obtain fractional fringes from the uniformly modulated fringe patterns. The proposed procedures have been demonstrated through simulated as well as experimental images. A parametric study is carried out to understand the influence of pixel resolution and bit depth of the images on fringe multiplication. A criterion is established fo...

IEEE Sensors Journal, 2018

A reusable passive RFID sensor is reported for wireless strain measurement on metals. The charact... more A reusable passive RFID sensor is reported for wireless strain measurement on metals. The characteristics of the proposed sensor are assessed on aluminum tensile specimens. The Received Signal Strength Intensity (RSSI) from the RFID sensor and the frequency corresponding to the maximum RSSI are used to measure the specimen strain. Besides strain, the yield, ultimate tensile strength and failure points of the specimen could also be identified from the RSSI measurements and correlated with strain gauge load cell data. Digital Image Correlation (DIC) measurements gathered during tensile tests confirm that the sensor does not deform during tensile loading and is reusable. Index Terms-RFID, tag antenna, strain measurement, structural health monitoring I. INTRODUCTION Structural health monitoring (SHM) is essential for engineering infrastructures such as railways, pipelines, dams, bridges and aircrafts to ensure safe and reliable operation [1]. Material degradation such as crack, porosity, and fatigue occurs in engineered structures due to repeated loading during component service. Early identification of the structural damages enables adopting corrective measures to prevent catastrophic failures [2]. Thus, periodic inspection of engineering structures is carried out using non-destructive testing (NDT) and evaluation techniques employing visual, ultrasonic and electromagnetic (EM) tests [3, 4]. Most of the SHM systems used in industry are wired. In case of large structures, wired systems are cumbersome to deploy, maintain and debug. Due to high instrumentation cost, slow inspection time and logistics issues, wireless SHM is gaining significance [5]. Amongst the wireless techniques, there is an increase in the use of radio frequency identification (RFID) systems as they are passive and cost effective NDT solutions which enable pervasive monitoring, wireless and remote inspection [5-7]. The RFID system proposed here consists of the transponder (RFID tag) placed on the material under test (MUT), ultra high

Indian Welding Journal, 2006

Procedia Structural Integrity, 2019

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.