Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Author: search.filters.author.Kulkarni, S.M.

Search Results

Now showing 1 - 10 of 129
  • No Thumbnail Available
    Item
    Ballistic impact analysis of multilayered armour system using finite element analysis
    (Elsevier, 2024) Doddamani, S.; Kulkarni, S.M.; Joladarashi, S.; Mohan Kumar, T.S.; Gurjar, A.K.
    The application of finite element analysis (FEA) to the ballistic impact analysis of polymer composites used in armor is covered in this chapter. This study aims to assess polymer composite armor materials' performance and establish their resistance to high-velocity projectile impacts. The use of FEA enables accurate simulations of the impact process that take into consideration the properties of the materials, the geometry of the projectile and the armor panel, and the impact conditions. The investigation' findings shed important light on how the polymer composite armor responds to impacts and its capacity to absorb and dissipate impact energy. For the development of cutting-edge armor materials and the multiscale modeling method of armor design, this information is essential. The chapter ends with recommendations for further research as well as a discussion of the difficulties and restrictions of employing FEA for ballistic impact analysis. © 2024 Elsevier Ltd. All rights are reserved including those for text and data mining AI training and similar technologies.
  • No Thumbnail Available
    Item
    Strength and failure analysis of cenosphere foam cored glass skin sandwiches
    (2004) Kulkarni, S.M.; Sharnappa; Sandesh, S.
    In weight specific applications, sandwich structures provide a better solution as they can withstand larger bending loads with a lesser net weight of the structure. These structural members consist of two stiff and strong skins and a light weight core. In this case E-glass bidirectional woven fabric as skin and cores made of cenospheres filled in epoxy matrix. Cenospheres used are hollow spherical particles of fly ash separated using a low cost procedure. The size of these particles is in the range 20-200 μm with an average size of 108 μm. The cenosphere concentrations are varied from 25-58%, 58% being the maximum that could be filled in epoxy with dough flowing just enough to fill the mould. The standard three-point bend test was performed on the sandwich samples. Specific strength in bending of sandwiches increased about 17% with an increase in volume fraction initially (35%) and then it declined. This could be attributed to occurrence of debonds in larger particles and poor wetting of the particles by the resin especially at higher volume fractions. In order to reduce the severity of debonds and improve the compatibility, a surface treatment involving coating of a silane agent on the filler is attempted. The effect of the treatment reflected in the improvement of sandwich properties such as maximum increase in specific strength of about 26% is noticed at lower volume fractions. But at higher volume fraction agglomeration of the particles and the resulting poor wetting could have been a dominant phenomenon for reduction in strength. The samples tested under bending were observed in SEM to analyze and account for failure modes. Chiefly, two types of failures could be observed in the samples. Firstly, core failing well before the skin, implying a significant difference in the modulii of skin and core materials. Secondly, delamination observed at the skin-core interface, which could be due to reduced wetting on account of smooth surfaces of skin and core in contact. With compatible values achieved for core properties and with proper sanding of the cores, cenosphere foam cores can be used for realizing a significant cost reduction.
  • No Thumbnail Available
    Item
    Bending strength of cenosphere foam cored jute/glass skin sandwiches
    (2004) Kulkarni, S.M.; Sandesh, S.; Sharnappa
    Sandwich construction is widely used in structural application because of its high bending stiffness coupled with lightweight. In design of sandwiches, skin made of high modulus of elasticity is used with core of high shear modulus. This balance is important so that neither material fails long before the other is stressed to accepted level. In the present study, experiments have been carried out on polymeric foam core sandwich beams with jute/epoxy faces. Syntactic polymeric foam cores, which have high compressive strength compared to open cell foams are made by mixing hollow fly-ash particles called cenospheres in a matrix material. The variable considered is the density of the core varied by differing the volume fraction of cenospheres. Cenospheres used in the present study are obtained from flyash, a waste byproduct of thermal power plants using a low cost separation process. Cores with four different volume fractions are prepared and sandwiched between a set of jute fabric layers. It is noticed that as volume fraction of cenospheres increased density is decreasing (1.12 to 0.98 g/cm3). The sandwich beams cut from the samples are tested using standard three-point bending procedure and the results obtained are compared with the results of glass skin sandwich with similar cores. Results showed a large difference in specific strengths of glass and jute skin sandwiches, which could be attributed to high tensile strength of glass fiber compared to jute fiber. There is a decrease of about 13% and 8% from the maximum specific strength for glass skin and jute skin sandwiches respectively at higher volume fractions of cenospheres. This could be traced to the failure of core well before the skin is stressed to accepted level in case of glass skin sandwiches. The jute skin sandwiches exhibited a little flatter specific strength response with respect to volume fraction of cenospheres indicating matching of the features pertaining to jute skin and the core properties. As the specific strength per unit cost of jute approaches that of glass, jute may be used to replace glass fiber with a significant cost advantage for less demanding applications.
  • No Thumbnail Available
    Item
    A Simple Displacement Function to Determine the Response of a Micro Capacitive Pressure Sensor
    (2011) Simha, A.; Kulkarni, S.M.; Meenatchi Sundaram, S.; Bhat, S.
    The response of a capacitive pressure sensor is generally represented by a fourth order partial differential equation which is complex to solve and does not possess an exact solution. Several attempts have been made earlier through various techniques such as the Galerkin method, Finite Difference Method etc.... In this paper an attempt has been made to develop a simple approximate analytical approach to determine the response of a micro capacitive pressure sensor whose diaphragm is designed to undergo very small deflections (typically less than 25% of the thickness). The non-uniform gap between the electrodes is mathematically expressed as a combination of the initial gap between the electrodes (in the undeformed state) and a displacement function in (x,y). The proposed displacement function is then utilized in evaluating the capacitance as a function of the applied pressure. The results obtained from the analytical approach are benchmarked against those obtained from COMSOL Multiphysics®, a popular Finite Element Analysis tool in the MEMS industry. It is observed that the results obtained from COMSOL Multiphysics® and those from the analytical approach are in good agreement with a maximum deviation of about 8.66%. © 2011 American Institute of Physics.
  • No Thumbnail Available
    Item
    Surface Improvement of Shafts by Turn-Assisted Deep Cold Rolling Process
    (EDP Sciences edps@edpsciences.com, 2016) Prabhu, R.; Sharma, S.S.; Jagannath, K.; Krishna Kumar, K.; Kulkarni, S.M.
    It is well recognized that mechanical surface enhancement methods can significantly improve the characteristics of highly-stressed metallic components. Deep cold rolling is one of such technique which is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In this paper, the effect of turn-assisted deep cold rolling on AISI 4140 steel is examined, with emphasis on the residual stress state. Based on the X-ray diffraction measurements, it is found that turn-assisted deep cold rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in AISI 4140 steel. © The Authors, published by EDP Sciences, 2016.
  • No Thumbnail Available
    Item
    Behaviour of Natural Rubber in Comparison with Structural Steel, Aluminium and Glass Epoxy Composite under Low Velocity Impact Loading
    (Elsevier Ltd, 2017) Mahesh, M.; Joladarashi, S.; Kulkarni, S.M.
    This paper presents the low velocity gravity impact behaviour of various materials (Structural steel, Aluminium, Rubber and Glass Epoxy composite). A comparison of the above said materials is reported considering various parameters such as Total Energy, contact force, deformation, von mises stress and strain and specific energy absorbed are carried out. The results confirmed that rubber absorbs more energy compared to other materials considered thus highlighting its potential use in structural applications subjected to low velocity impact. The natural rubber in many ways is an ideal polymer for dynamic or static engineering applications. It has excellent dynamic properties, with a low hysteresis loss, and good low temperature properties, it can be bonded well to metal parts, has high resistance to tear and abrasion and it is relatively easy to process. Natural rubber composites find technological interest in that they exhibit additional features like biodegradability and renewability, along with the inherent stiffness, low cost and low density. The great advantage of natural rubber based on its linear elasticity, high strength, fatigue life and excellent adhesion to metals makes it well suited for structural or semi structural applications. © 2017 Elsevier Ltd.
  • No Thumbnail Available
    Item
    Synthesis and comparison of mechanical behavior of fly ash-epoxy and silica fumes-epoxy composite
    (Institute of Physics Publishing michael.roberts@iop.org, 2017) Sangamesh, R.; Ravishankar, K.S.; Kulkarni, S.M.
    Present day innovation requires materials with a typical combination of properties that are not possible by conventional metal, alloys, ceramics and polymeric materials. Particulate reinforcements for polymers are selected with the dual objective of improving composite properties and save on the total cost of the system. The point of this study is to utilize and compare the mechanical properties of filler (fly ash and silica fumes) reinforced epoxy composites. The composites of different proportions by percentage of matrix (100%), fillers (5%, 10% and 15%) volume are developed using hand lay-up process are tested for tensile and compression, according to ASTM Standards. From these mechanical properties, the flexural analysis of these composites is simulated. And which are characterized by Scanning electron microscopy for the fracture surface study, which reveals the brittle fracture, this also conforms from the Finite element analysis (FEA). And the overall mechanical properties of the fly ash reinforced polymer composites were found to have better than silica fumes reinforced composites. © Published under licence by IOP Publishing Ltd.
  • No Thumbnail Available
    Item
    Modelling and Analysis of Material Behaviour under Normal and Oblique Low Velocity Impact
    (Elsevier Ltd, 2018) Mahesh, M.; Joladarashi, S.; Kulkarni, S.M.
    The present article deals with analysis of various engineering materials (rubber, steel, aluminum and glass epoxy) under low velocity gravity impact loading normal to the plate as well as at an oblique angle of 20 degrees. Impact damage remains a major concern for structural components; the impact of objects can create internal damage that can significantly reduce their structural strength, because of its complex nature. The investigation of low velocity impact remains an area of interest and has received much attention. Very few research work have been done on the oblique impact behaviour of composites, where most of them concentrates on high-velocity impact conditions. The study on low-velocity oblique impact of composites are scare. Comparison of the above said materials is reported considering various parameters such as total energy, contact force, deformation, von Mises stress and strain and specific energy absorbed. Specific energy absorbed by each material considered are compared both under normal impact and oblique impact and the results confirmed that rubber absorbs 11.72 times more energy than structural steel, 3.24 times more energy than aluminium and 1.8 times more energy than glass epoxy, when subjected to normal impact. In case of oblique impact at 20 degrees rubber absorbs 47.6 times more energy than structural steel, 14 times more energy than aluminium and 8.6 times more energy than glass epoxy. This makes rubber as an ideal polymer for dynamic structural applications subjected to low velocity impact under oblique condition. © 2017 Elsevier Ltd.
  • No Thumbnail Available
    Item
    Ballistic Impact Study on Jute-Epoxy and Natural Rubber Sandwich Composites
    (Elsevier Ltd, 2018) Sangamesh, R.; Ravishankar, K.S.; Kulkarni, S.M.
    Since ages, human beings have used different methods to protect themselves and their armors from the impact of bullets/projectiles by using structures made up of wood, metals, glass and sand bags etc. These protective structures are heavy and incur cost and inconvenience to transport. Of late, they are replaced by structures of polymers and their composites, because of their light weight and good corrosion resistance. Ballistic impact analysis of composite materials is necessary in order to establish their use in military, aerospace and automotive applications either through experimental studies or using modeling techniques. The aim of the present investigation is to model and analyze the behavior of composites for ballistic impact. Residual velocity, energy absorption and ballistic limit for three different materials Jute-Epoxy (JE), Rubber (Ru), Jute-Epoxy-Rubber sandwich (JRE) for three thicknesses (5, 10, 15mm) and at three velocities (150, 250, 350 m/s) is studied. The study exhibits a significant amount of energy absorption in rubber, almost 10 times as compared to JE plate. Also damage observed was ductile in the case of rubber, while brittle in JE. Sandwich composites (JRE) displayed energy absorption and ballistic limit on par with rubber plates. Thus the applicability of these sandwiches in ballistic impact is established as better energy absorbing protective target structures. © 2017 Elsevier Ltd.
  • No Thumbnail Available
    Item
    Study on ballistic energy absorption capability of glass-epoxy and jute-epoxy-rubber sandwich composites
    (Trans Tech Publications Ltd ttp@transtec.ch, 2018) Rajole, S.; Ravishankar, K.S.; Kulkarni, S.M.
    High velocity impact analysis of natural fiber reinforced composites is essential as the trend is focused towards the development of light weight, environment-friendly, non-corrosive and economical materials. At present, the defence, aerospace and automobile sectors are using synthetic fiber composites which are expensive and non-eco-friendly. In the present study ballistic impact of jute-epoxy (JEC), glass-epoxy (GEC), jute-epoxy-rubber (JERC) sandwich composites are simulated with different thickness (1, 2 and 3 mm) and velocity variations (100, 200 and 300m/s) using Finite Element analysis software. Although different approaches to the analysis of the effect response of composite structures are available, numerical modeling is based on strict constitutive models is often preferred because it can provide valuable detailed information about the spatial and temporal distribution of damage during the impact. The ballistic parameters such as energy absorption, ballistic limit and fracture behaviors are predicted. The composite is made of 8 noded linear brick elements and the bullet/projectile is modeled as a discrete rigid element in which deformation behavior, energy absorption and penetration behaviors obtained are clearly represented. The simulation results predicted match well with the analytical results obtained. Among all the combination of the materials simulated, the sandwiches have better ballistic qualities. Energy absorption of sandwich(JERC) was found 67 percentage higher than GEC and 56 percentage higher than JEC laminate. In future, these materials can be the alternative materials for defence sector for bullet proofing. © 2018 Trans Tech Publications, Switzerland.