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Papers by Debasis Datta

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, Dec 2, 2023

Polymer Bulletin, Apr 6, 2022

The molecular dynamics simulations based study of graphene (Gr) reinforced polymer nanocomposite ... more The molecular dynamics simulations based study of graphene (Gr) reinforced polymer nanocomposite (PNC) is a very intense research field due to the enormous range of possible applications involving such materials. Current review focuses on the reinforcing mechanisms behind the enhancement of the mechanical, thermal, and tribological properties of Gr-based PNC based on molecular dynamics (MD) simulations. It also reviews the capabilities of MD simulations to reproduce the experimentally measured materials properties and behaviour of Gr-based PNC. This review-based investigation summarizes the current literature of the MD simulation studies as well as comparisons for the tribo-thermo-mechanical properties of Gr-based PNC and identification of the suitable simulation protocols for model development, characterization, and mechanism analysis. The careful review of published MD simulation-based articles indicates that two important factors help to reproduce the experimentally measured materials properties and behaviour of Gr-based PNC. They are mainly (a) simulation models (material used for reinforcement, e.g. Gr and Gr derivatives) development and (b) simulation run parameters. In this review, details about those factors have been discussed keeping major consideration of Gr effect (e.g. shape or length, orientation, clustering, weight fraction, different layer, functionalization, and defective condition). Finally potential applications, current challenges and future prospects are discussed which can be useful to the research community.

Defence Science Journal, May 3, 2012

Light weight armors are usually made up of fibre reinforced plastic composites to suit the requir... more Light weight armors are usually made up of fibre reinforced plastic composites to suit the requirements of human shields in view of their high strength and stiffness to weight ratio. During use, these armors are expected to face projectile or splinter impacts and as such, it is necessary that such composites achieve the desired protection capability against impact. The extent of damage is possibly one of the important areas of interest to both the designer as well as the test and evaluation agencies. Estimation of severity and extent of damage zone due to such impacts can provide valuable inputs for effective fabrication of composite laminates, in terms of selecting the constituents like fibre and resin as well as structural issues like number of plies, ply orientation, stacking sequence, etc. Non-destructive evaluation (NDE) of composites is really challenging due to the fact that apart from being anisotropic and heterogeneous, these materials may involve different damage modes simultaneously. Several investigators have carried out experimental and numerical investigations to study the behavior of composite materials. Henneke 1 and Jones 2 developed a computer controlled ultrasonic scanning and data collection system for NDE of composites. Preuss and Clark 3 used the time of flight of ultrasonic C-scanning for detection, sizing and characterization of defects in carbon-fibre composite components. Abrate 4,5 comprehensively reviewed the response of the material, evaluation of damage and prediction of residual properties. Hosur, et al. presented the results of experimental work on damage of carbon fibre reinforced impacts carried out at energy levels varying from 3 to 30 J where the resulting de lamination damage was determined by immersion type ultrasonic C-scans conducted in pulse echo mode. Datta, et al. 7 performed immersion type C-scans on impacted composite specimens. The impact was created by repeated dropping of weights on the glass fibre reinforced plastic (GFRP) panels. For automated image generation, grouping of signal amplitude data set was done by un-weighted pair group method of arithmetic averages (UPGMA) linkage method, but-based on a preselected number of clusters. The problem faced with all composite materials used for ballistic protection is how to evaluate the damage area after impact. In spite of the availability of different test methods such as liquid penetrant, C-scan ultrasonic, radiographic analysis and digital image analysis in transparent materials, it has not always been possible to discriminate between the main failure modes of a composite material such as fibre breakage, fiber de-bonding, delamination and matrix cracking. However, the size and geometry of the damage area if determined accurately can give reliable information about the ballistic performance of these materials 8 . In an earlier study effect of resin matrix on the ballistic response of aramid laminated composite was reported 9 where the composites made using PP matrix

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

In the present study, finite element analysis were carried out to investigate the ballistic perfo... more In the present study, finite element analysis were carried out to investigate the ballistic performance of Al2O3-Kevlar 29/epoxy armour system impacted by a 4340 steel projectile. The perforation capacity of a 10 mm thick target was studied against a blunt, ogive, and conical shaped projectile with a fixed diameter and mass of 7.56 mm and 10.7 gm, respectively. The simulations were carried out in Ansys/Autodyn by considering the projectile as a deformable body. The variation of the ballistic limit velocity (BLV) and energy, progressive damage of the target, and projectile deformation were studied comprehensively. It was found that the nose configuration of the projectile significantly influence the target’s ballistic performance. The perforation capacity of the blunt projectile was lower than the ogive and conical shape in all the velocity regimes. At higher impact velocity ( Vi >600 m/s), the target’s resistance was better against the ogive projectile than that of the sharp coni...

31st International Symposium on Ballistics, 2019

Materials behave differently when subjected to loads at different strain rates. The study of this... more Materials behave differently when subjected to loads at different strain rates. The study of this field is very important in the analysis of the behavior and failure of components and structures that are subjected to dynamic loads. In the present work, the high strain rate behavior of steel used in armour applications has been investigated through tensile tests at low and medium strain rates and high rate compression tests in SHPB set up. The study shows that the material exhibits moderate strain rate sensitivity and is fairly constant over a wide range of strain rates.

Polymer Testing, 2002

The ultrasonic technique can be used successfully to monitor the blowing process during the curin... more The ultrasonic technique can be used successfully to monitor the blowing process during the curing cycle of sponge rubber. The measurements have been found to be sensitive to the blowing process. Unlike other tests, the simultaneously formed crosslinks have no fundamental effect on the observed measurements. Furthermore, with the outlined test facility, it is possible to monitor the blowing process in real time.

Non-destructive testing (NDT) of engineering materials, components and structures has steadily in... more Non-destructive testing (NDT) of engineering materials, components and structures has steadily increased in recent years at an unprecedented rate because of all-round thrust for improving material quality, component integrity and performance reliability. Ultrasonic testing is a versatile NDT method, which is applicable to most materials, metallic or non-metallic. The relevance of computed tomography (CT) in state-of-the-art non-destructive evaluation (NDE) is enormous. CT uses computer reconstruction to combine the information obtained from multiple projections. For quicker and reliable results there is a need to have clear ideas regarding performances of reconstruction algorithms. In the present investigation, the NDT of a composite domain using ultrasonic CT is presented. The sample is of rectangular shape and consists of a continuous phase made of steel and a square shaped insert made of resin. Reconstruction is done by ART like algorithms on a set of time-of-flight (TOF) data collected between transducers for multiple ray paths in each of the different views. For each reconstruction, the reconstructed image is compared with the actual one and a corresponding L1 error is calculated. Performance of each algorithm, with different relaxation parameters is studied and compared in terms of accuracy and iteration numbers.

Russian Journal of Nondestructive Testing

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications

The present work is based on numerical simulations of the ballistic behavior of multilayered alum... more The present work is based on numerical simulations of the ballistic behavior of multilayered alumina/aluminum armor plates of varying thicknesses against normal impacts of ogive-nosed steel projectiles. The numerical simulation and the associated models have been validated against published experimental results. A total of nine distinct combinations of ceramic–metal armor plates are impacted normally at different strike velocities, ranging from 200 to 1200 m/sec to determine the residual velocities and ballistic limit velocities of the projectile for each combination of target plate. In a few circumstances, a small air gap has been considered in a combination to compare its ballistic performance to that of a target without an air gap. The optimal ratio of ceramic in a ceramic metal bilayered target plate is determined numerically. This article visualizes the progressive damage of target plates and projectiles at various strike velocities to explore the effects of thicknesses and rel...

Materials evaluation, 2003

Use of the ultrasonic technique has been found to be adequately effective for online detection of... more Use of the ultrasonic technique has been found to be adequately effective for online detection of blowing in industrial rubbers. The blowing process (which forms numerous bubbles) is influenced by several factors including the temperature maintained during blowing, the types of chemicals being used as blowing agents and the degree of natural curing present in rubbers. In the present work, the effect of natural curing of the rubbers on the blowing process is investigated. Using a previously devised ultrasonic detection procedure, investigation is conducted on blowing rubber samples having different degrees of natural curing. The results show that the time domain ultrasonic response is definitely dependent on the extent of curing present in the rubber samples. Certain parameters are also identified from the ultrasonic response that could be used for assessing the extent of curing.

Nondestructive Testing and Evaluation, 1996

Non destructive evaluation (NDE) of the damaged states in composite materials is far more complic... more Non destructive evaluation (NDE) of the damaged states in composite materials is far more complicated than in case of conventional homogenous and isotropic materials. As composites may contain several types of defects (existing either individually or in combination), analysis of commonly used time-domain features, such as peak amplitude, or time of flight, alone seems to be insufficient for identification of

NDT & E International, 1996

A two-dirnensional plane strain finite element model with absorbing boundary condition has been d... more A two-dirnensional plane strain finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave propagation in isotropic alnd orthotropic media. It is capable of simulating the experimental pulse echo technique to obtain A-scan data, when a short duration pulse is transmitted into a domain with or without a flaw. The flaw can either be a crack or an inclusion of different material such as a Teflon insert or a resin rich zone. After performing FFT on the A-scan data, frequency domain feature analysis is done. The study provides a guideline regarding the suitability of certain harmonics sensitive to certain types of flaw. The simulation shows other important artifacts of wave propagation such as mode con,version and scattering due to the presence of flaws.

Materials Science and Engineering: A, 2015

The behavior of typical armour steel material under large strains, high strain rates and elevated... more The behavior of typical armour steel material under large strains, high strain rates and elevated temperatures needs to be investigated to analyse and reliably predict its response to various types of dynamic loading like impact. An empirical constitutive relation developed by Johnson and Cook (J-C) is widely used to capture strain rate sensitivity of the metals. A failure model proposed by Johnson and Cook is used to model the damage evolution and predict failure in many engineering materials. In this work, model constants of J-C constitutive relation and damage parameters of J-C failure model for a typical armour steel material have been determined experimentally from four types of uniaxial tensile test. Some modifications in the J-C damage model have been suggested and Finite Element simulation of three different tensile tests on armour steel specimens under a relatively high strain rate (10-1 s-1), high triaxiality and elevated temperature respectively has been done in ABAQUS platform using the modified J-C failure model as user material subroutine. The simulation results are validated by the experimental data. Thereafter, a moderately high strain rate event viz. Charpy impact test on armour steel specimen has been simulated using J-C material and failure models with the same

In non-destructive evaluation, it is often necessary to characterize a digitized image in identif... more In non-destructive evaluation, it is often necessary to characterize a digitized image in identification of inserts, if any. Fractal theory can be successfully employed in quantitative assessment of digital images. The word fractal was first coined by Mandelbrot [1] and according to him, the fractal is a “shape made of parts similar to the whole in some way.” The defining parameter of a fractal is the fractal dimension. In respect of a two-dimensional (2-D) digitized surface, the fractal dimension corresponds quite closely to our intuitive notion of roughness. An N by N two-dimensional digitized image contains N 2 pixels, each of which has an individual intensity value attached to it. A 3-D representation of this 2-D image may be conceived by incorporating the third dimension as the intensity of each pixel. Therefore, a 2-D image with different intensity values on its pixels may be thought as an imperfect cube (i.e., a cube with dents) whose fractal dimension should lie between 2 an...

Russian Journal of Nondestructive Testing, 2021

Nitrile rubbers, also known as Nitrile-Butadiene rubbers, belong to the category of synthetic rub... more Nitrile rubbers, also known as Nitrile-Butadiene rubbers, belong to the category of synthetic rubbers and are a better choice as materials for applications requiring higher abrasion resistance and material adhesion. To meet the requirements, vulcanization of such rubbers to the appropriate level is necessary. Earlier, various spectroscopy-based experimental techniques and methods like nuclear magnetic resonance (NMR), chemical analysis, DMA analysis, differential calorimetric have been reported to be used to detect cure reaction of thermosets. In the present work, ultrasonic measurement techniques are employed on the rubber samples in a nondestructive manner via a test setup integrated with a fully automated ultrasonic data acquisition system developed in-house. Real-time monitoring of the vulcanization process of the rubber samples is carried out at different temperatures in order to capture the dependence of the rate of vulcanization on ultrasonic parameters. Tests are carried out at five different temperatures ranging from 140 to 180°C on nitrile rubber samples, and temporal variations of ultrasonic velocity and back wall amplitude are derived by post-processing the digitized data. Ultrasonic responses are observed to identify the rate of vulcanization and completion of the vulcanization process comprehensively. Observations are further consolidated by hardness measurements on the bounding faces of the rubber samples.

2019 8th International Conference on Modeling Simulation and Applied Optimization (ICMSAO), 2019

Ultrasonic testing is normally known to be a very useful Non-Destructive Testing (NDT) method for... more Ultrasonic testing is normally known to be a very useful Non-Destructive Testing (NDT) method for detecting defects in materials. In recent years, NDT methods are very much in practice and act as a powerful technique for inspecting and measuring various properties of engineering materials. This paper is based on the interaction between characteristics of ultrasonic waves and rubber hardness. An Ultrasonic NDT set-up was developed in-house for recording digitized ultrasonic data in real time. A transmitting as well as receiving transducer with a central frequency of 1 MHz was used during the experiments to generate and capture longitudinal pulse for both natural and synthetic rubbers, having different shore hardness ranging from 55 to 85. It was found that the ultrasonic velocity was not only sensitive to hardness of rubbers, but also to temperatures. The set-up was specially furnished with temperature controllers for calculating ultrasonic velocity in rubber samples at different temperatures. Dependence of ultrasonic wave velocities with hardness and temperatures were studied from experimental observations. Acoustic impedance, reflection, and transmission coefficients were also calculated for explaining the behavior of ultrasonic waves in normal mode.

Experimental and numerical based investigations are carried out to study the behaviour of Kevlar ... more Experimental and numerical based investigations are carried out to study the behaviour of Kevlar composite panel subjected to ballistic impact. Immersion type ultra sonic C-scan is performed on impacted Kevlar composite panel and extent of damages are identified through Cscan imaging of A-scan data. The methodology, based on segmentation of ultrasonic data i nto different clusters, is implemented for automated generation of the C-scan image of the scanned domain. The core damage area for ballistically impacted composite panel is evaluated from the respective C-scan i m ge. Numerical simulation is also performed to study the impact event on Kevlar/Epoxy panel of different thicknesses struck normally by projectiles (7.62AP shot) with different impact velocities using ABAQUS/Expli cit. A suitable failure criteria is adopted to predict the initiation and subsequent propagation of damage. Resul ts in the form of residual velocity and perforated area show similar trends with those found f...

Ultrasonic inspection might be difficult and tricky when th e bonded specimen has small thickness... more Ultrasonic inspection might be difficult and tricky when th e bonded specimen has small thickness, and substrate material properties have similar acoustic impe dance compared to the bonding material. Conventional signal analysis techniques use signal amplitude, signal energy , o frequency domain quantities obtained from spectral analysis. An alternate starting point as proposed by Hughes is to regard the digitized waveform as a message and to apply the concepts of information theory. In the pr sent work conventional time domain and frequency domain features along with Shannon entropy are computed fro m digitized waveforms for each location of the Cscanned domain of a Glass epoxy composite panel having a Teflon insert. Data set are subjected to systematic grouping as per Ward algorithm and results are used for imaging t he scanned zone. A feature selection procedure based on the ID3 algorithm is also performed on the datas et. It is found that the sensitivities of Shannon Entropy and...

In this paper an alternative way of generating C-scan images using Fractal Dimension (FD) of any ... more In this paper an alternative way of generating C-scan images using Fractal Dimension (FD) of any digitized waveforms as an ultrasonic feature is proposed. The work is carried out on the composite specimen having flaw in the form of inclusion and damage created by the drop weight impact. The technique to estimate FD of a 2D image is modified in this work and a procedure to compute FD of a digitized waveform is evolved. FD is seen to be a representative or a defining parameter of the waveforms received from different regions of the scanned domain for being used in generation of C-scan image. A feature selection procedure based on the ID3 algorithm is also performed on the dataset. It substantiates FD as a potential ultrasonic feature.

Journal of Long-Term Effects of Medical Implants, 2012

There are considerable variations in the femoral geometry of populations across different geograp... more There are considerable variations in the femoral geometry of populations across different geographical locations and ethnic groups. The osteological parameters of the proximal femur are very important for the design of suitably sized prostheses of total hip replacement (THR), especially for cementless implantation. Though total hip prostheses in different sizes are available from manufacturers, best-fit implants are often unavailable for Indian patients. To produce hip prostheses of suitable sizes and shapes for Indian patients, important osteological parameters of the proximal femur in the Indian population are needed. In this study, 100 computed tomography (CT) images of hip joints of members of the Indian population were collected, and 20 anatomical parameters of the proximal femur were analyzed. The mean values of these parameters were compared with those of the populations of a few other countries that were available from the literature. The parameter comparison was also performed between males and females in our subsample of the Indian population. Finally, values of the important parameters were grouped suitably for future design of standard sizes of THR implants for the Indian population. We found variations in the morphology of the proximal femur between the Indian population and that of other countries, which illustrates a need for standardizing THR implant sizes for the Indian population, especially for cementless implantation. The variations of a few important parameters of the proximal femur also occur between the male and female Indian populations. This study is likely to be a significant step toward designing suitably sized cementless THR implants for the Indian population.