MESII - 2019

Permanent URI for this collectionhttp://192.248.9.226/handle/123/17182

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Now showing 1 - 20 of 23

item: Conference-Abstract
Effect of penetration of corrosion on the load-bearing capacity of mild steel
(Department of Materials Science and Engineering, 2019-01) Jayasooriya, ED; Munasinghe, RGNDS; Sivahar, V; Sitinamaluwa, HS
The field of Metallurgical Engineering associated with the estimation of the service life of corroded structural members which has been studied in extensive detail, the world over. Most of the research work in this area have focused on the general attack (uniform corrosion) faced by steels across a range of atmospheres. This study sought to contribute to this field by examining whether the penetration of corrosion beyond the general attack has a significant effect on the load-bearing capacity of mild steel. Mild steel samples were corroded in an aggressive atmosphere over a 5-month period, subjected to periodic tensile testing and corrosion mass-loss analyses and examined under optical and electron microscopy. Through the identification and measurement of the penetration of corrosion using scanning electron microscopy, this research managed to correlate corrosion mass-loss and tensile load-loss data with said microscopic measurements. The results showed that the actual fracture loads deviated negatively from the expected load- bearing capacity, which was determined through conventional methods. This deviation showed a close correlation to the increase of penetration of corrosion with time. As a result of this correlation, the research concluded that allowances ought to be made for the penetration of corrosion when the remaining service life of corroded load-bearing members has to be calculated more accurately.
item: Conference-Abstract
Investigation of self discharge mechanism of locally available activated carbon-based super capacitor
(Department of Materials Science and Engineering, 2019-01) Gunarathna, RNP; Muhandiram, DI; Attygalle, D; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
Carbon materials in their various forms are the most used electrode materials in the fabrication of supercapacitors. Activated carbon is derived from a variety of organic parent sources such as lignite, peat, coal, synthetic resins and biomass resources. Sri Lanka holds a global reputation for supplying high quality activated carbon derived from coconut shell with low levels of contaminants, which makes it ideal for incorporating in supercapacitors as the electrode material. The capacitance of supercapacitors, fabricated from activated carbon and an aqueous electrolyte, arises from the charge stored in the electric double layer at the interface between the surface of porous carbon and the electrolyte. Hermann von Helmholtz first proposed the double layer theory for supercapacitors and Gouy, Chapman, Grahame, and Stem later developed it. In electric double layer capacitors, self-discharge has been an inevitable issue which results in the decay of cell voltage and thus loss of stored energy. Further, fast selfdischarge rates restrict practical applications of the supercapacitors. In this research, our major interest was to identify the self-discharge mechanism of the supercapacitor fabricated using locally developed activated carbon in a neutral aqueous electrolyte. The results indicate that self-discharge of the fabricated supercapacitor can be adequately modeled simulating to the diffusion based model.
item: Conference-Abstract
Development of a photosensor based on photo dielectric effect of cadmium sulphide
(Department of Materials Science and Engineering, 2019-01) Kumari, TID; Jayasumana, MASD; Attygalle, D; Sivahar, V; Sitinamaluwa, HS
A photosensor is an electronic component that detects the presence of visible light, infrared transmission (IR), and/or ultraviolet (UV) energy. A photosensor which changes its electrical capacitance in the presence of visible light was developed based on the photo-dielectric effect of Cadmium Sulphide (CdS). This photosensor was fabricated by depositing a CdS thin film on Fluorine-doped Tin Oxide glass (FTO glass). FTO acts as the front electrical contact and an aluminum sheet acts as the back contact, where a 2.0)im - 3.0)im thick CdS thin film acts as the photo-dielectric material. Chemical bath deposition method was used for CdS fabrication and the CdS thin film with optimum photovoltaic and micro structural properties was obtained at a bath temperature interval of 40 - 45 °C, annealing temperature of 180-220 °C. Film thickness was varied by adjusting deposition time and the number of coatings. Thickness variations were determined using a Scanning Electron Microscope (SEM). The transmittance and absorbance spectra are recorded in the range of 200 nm - 1100 nm. CdS thin film fabricated under optimum conditions resulted in a bandgap in the range of 2.30 eV-2.40 eV, which is closely agreeing to the theoretical value of 2.42eV. The photo-capacitance and photoconductivity were measured in a frequency range of 1 kHz to 5 MHz in dark and illuminated conditions. The Cole-Cole plots were analyzed to identify the most sensitive operational frequency for the device.
item: Conference-Abstract
Development of Graphene Oxide based capacitive gas sensor for NO2 detection
(Department of Materials Science and Engineering, 2019-01) Deemantha, MBA; Gunasena, RGSP; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
Parallel plate capacitive gas sensor was assembled using Graphene Oxide (GO) as the transducer material. The sensor was tested with NO2 as the target gas. GO was synthesized according to the Improved Hummer's Method (Tours Method) in which vein graphite was sufficiently oxidized. Synthesized graphene oxide was characterized by Fourier Transform Inirared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) ascertaining that products were well oxidized. Sensor was tested for capacitance variation in the fi^equency and time domains under the influence of constant temperature ramp. The results showed an average response time of about 2 minutes to reach the steady state signal and an equal time to reach the initial reference signal levels once the testing chamber was evacuated of the target gas.
item: Conference-Abstract
Development of nano silver impregnated food packaging materials
(Department of Materials Science and Engineering, 2019-01) Samarasekara, AMPB; Amarasinghe, DAS; Madhushan, WKP; Chathuranga, SN; Sivahar, V; Sitinamaluwa, HS
The growing demand for increased shelf-hfe of food and the need for protection against foodbome diseases, fiiel the development of new food packaging materials. Silver-nanoparticle (AgNp) impregnated packaging materials are promising candidates for active food packaging. These active packaging materials are capable of extending the shelf-life of foods and reducing the risk of pathogens. The current research work is focused on the development of AgNp incorporated coating for polymer-based food packaging. AgNp dispersed in polyvinyl alcohol solution was prepared by in situ reduction method, in which silver nitrate and polyvinyl alcohol (PVA) acted as precursor and capping agent respectively. Presence of silver nanoparticles in the solution was confirmed by photoluminescence spectroscopy and UV-Vis spectroscopy. In order to reduce coating solubility PVA solution was cross-linked. The compatibility of the coating with the substrate was enhanced by plasma treatments. Contact angle measurements were employed to monitor the wettability changes. The solubility of the coating was examined by gravimetric methods. The effects of cross-linked temperature and cross-linked agents on solubility were studied. The presence of silver nanoparticles in the coating was confirmed by surface plasmon resonance and electron micrographs. The modified Kirby-Bauer (disk diffusion) method was employed to measure the anti-bacterial effect of the coating.
item: Conference-Abstract
Extraction of nanocellulose from Sri Lankan agricultural waste
(Department of Materials Science and Engineering, 2019-01) Wickramasinghe, WAWIC; Lasitha, DS; Samarasekara, AMPB; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
Polymers are widely used in domestic and industrial applications because of their diverse functionality, lightweight, low cost and excellent chemical stability. They are mainly classified into naturally occurring or bio-based polymers and synthetic polymers. Bio-based polymers have the potential to replace petroleum-based.synthetic polymers and solve some of the most urgent problems caused by the overuse of petroleum-based polymers, such as environmental pollution especially water and soil pollution and harmful influence to human health. Rice is the major agricultural food and it is cultivated in all parts of Sri Lanka today. Rice straw is the waste product of the rice harvest. Rice straws have a considerable amount of cellulose. Cellulose is the mostly used bio-polymer material for various applications today. Nanocellulose is a light solid substance obtained from agricultural waste which comprises of Nano-sized cellulose fibrils. In this research, rice straw of BG 352 variety was collected from Polgahawela paddy cultivation area in Sri Lanka. Cellulose and nanocellulose materials were extracted from rice straw of BG 352 rice variety. Cellulose was extracted from rice straw using de-waxing, delignification, hemicellulose and silica removal treatments. Extracted cellulose was characterized by Fourier Transform Infrared spectroscopic techniques (FTIR). SEM images indicated that isolated cellulose fibers showed diameters ranging from 2-8|^m. Approximately 21wt. % of cellulose was extracted from the rice straw. Nanocellulose was extracted from cellulose by subjecting to acid hydrolysis, quenching, centrifugation, dialysis, sonication and freeze-drying processes. SEM images showed that extracted nanocellulose materials having 5-70 nm diameters. Therefore, Sri Lankan agricultural waste can be used as a source to synthesis value-added product of nanocellulose
item: Conference-Abstract
Development of polylactic acid (PLA) based biodegradable packaging materials
(Department of Materials Science and Engineering, 2019-01) Dhanushka, MKDT; Kaushalya, RANC; Samarasekara, AMPB; Sivahar, V; Sitinamaluwa, HS
The key purpose of packaging is to protect the contents or products from external factors. Synthetic polymers do not degrade completely in nature after the usage and create environmental issues. Therefore, there is a tendency to substitute such polymers with natural polymers that are easily biodegraded and less likely to cause environmental pollution. The main objective of this research is to develop a biodegradable packaging material based on Polylactic Acid (PLA) and locally extracted starch. Starch was extracted from cassava tubers by crushing, blending and sedimentation processes. The extracted product was characterized by Fourier Transform Infrared Spectroscopic technique (FTIR). Experimental results indicated that 25 wt.% of starch could be extracted from the cassava that was tested. Biodegradable PLA and starch-based blends were prepared by adding starch as the main additive. The dried starch was incorporated into the PLA and melt-blended using laboratory scale internal mixer. A mixing process was performed for various starch concentrations. The blended samples were then pressed to form thin sheets in a hydraulic press. Soil burial test was performed to analyze the biodegradability of the developed product. The tensile strength and elongation at break of the samples were determined by tensile testing. Weight loss in starch-containing samples gradually increased with time during the soil burial test. Experimental results also indicated that biodegradability of the products increased as the starch content is increased. The mechanical properties such as tensile strength and elongation also decreased as the starch content increased. These results indicated that the addition of starch to PLA is a better method to increase the biodegradability of the PLA -starch blends. These developed biodegradable materials can be used as a sustainable material to create safer environment.
item: Conference-Abstract
Synthesis and characterization of TiO2 nanotube arrays
(Department of Materials Science and Engineering, 2019-01) Chandanayaka, ISP; Madumadawa, GPDLP; Sitinamaluwa, HS; Sivahar, V; Sitinamaluwa, HS
Ti02 is a versatile material that has found applications in a diverse range of devices and applications such as solar cells, photocatalysts, gas sensors, photovoltaics, hydrogen storage, Li-ion batteries etc. In recent years, highly-ordered onedimensional Ti02 nanotubes have attracted much attention due to their distinctive properties in these advanced functional devices. In this study, vertically aligned Ti02 nanotubes were synthesized by anodizing a Ti foil in a non-aqueous electrolyte containing ethylene glycol (97.5 wt.%), NH4F (2 wt.%) and deionized (DI) water (0.5 wt.%). Scanning electron microscopy (SEM) was used to characterize the morphology of prepared nanotubes. Preliminary results showed the formation of tubular structures with a diameter of 1.315 jim and the wall thickness of 209.1 nm. The results indicate that the morphology of the nanotubes depends on the anodization voltage, anodization time and electrolyte composition. In this study, it is expected to establish a relationship between the nanotube morphology with anodization time, anodization voltage and electrolyte composition. The outcome of this study will enable the synthesis of Ti02 nanotube structures with tailored morphologies, for possible applications in a wide range of advanced functional devices.
item: Conference-Abstract
Extraction of natural dye from flowers of chenille plant (Acalypha hispida) for fabrics
(Department of Materials Science and Engineering, 2019-01) Yasassri, MAH; Weerasinghe, WDC; Udayakumara, SV; Sivahar, V; Sitinamaluwa, HS
Today many countries use the eco-friendly concept and various steps are being taken to preserve the environment and to reduce pollution. As the textile industry is becoming one of the main industries in the world, it emits various kinds of pollutants to the environment that can cause serious damages to the bio-system. Thus, industries tend to use non-toxic and eco-friendly natural dyes instead of hazardous synthetic dyes on textiles to minimize the pollution. Natural dyes can be obtained from various parts of plants including roots, bark, leaves, flowers, and fruits. These sources are freely available, and their dyes do not harm the environment. The aim of this research is to extract dyes form the flowers of Chenille Plant {Acalypha hispida), under aqueous, acidic, alkaline and alcoholic conditions. Aqueous extraction method showed best results among all extraction methods. The extraction parameters used for aqueous method i.e. temperature, time and mass to liquid ratio were 100 °C, 2hr and 1:5 respectively. Stability of dyestuff was increased by adding known amount of acetic acid. Cotton fibers were treated with 4% tannic acid before application of dyestuff. Adhesion of dye to cotton fabric accompanied by a pre-mordanting method with the mordants such as alum, chrome, copper sulfate, ferrous sulfate and stannous chloride. Light fastness, wash fastness, variations of surface colour strength (K/S) values, L*, a*, b* color coordinates, and brightness index were obtained from mordanted cotton fabrics with different mordants. Potassium dichromate showed the highest colour value (K/S =60.366) while aluminium sulphate gave the lowest value (K/S = 17.535).
item: Conference-Abstract
Development of cement, sand and sawdust based composite material to use as plaster for walls
(Department of Materials Science and Engineering, 2019-01) Ekanayaka, EMCHB; Fernando, KKA; Udayakumara, SV; Sivahar, V; Sitinamaluwa, HS
With the arisen development around the world, the demand for natural construction materials has been increased. Increasing consumption levels decrease the amount of available natural resources. The importance of material efficiency and the need to improve it can be studied from several perspectives. Limited availability or scarcity of materials may lead to threats to the economy, and the production processes of materials can have significant environmental impacts. This study was concentrated on the use of sawdust as a partial replacement for fine aggregates in cement-based wall plaster material. Mahogany sawdust produced in local timber mills was selected for the study. Sawdust was incorporated into the plaster mixture in the raw form as well as in burnt form (saw dust ash). Composites were prepared by incorporating 5% and 10% saw dust by weight and sawdust ash by weight. Prepared composites were tested for flexural strength and tensile strength according to BS EN 1015 standard. Lee's disc method was used to compare the thermal properties of the composites. Composite with 5% saw dust ash showed better properties compared to the composites with other sawdust combinations.
item: Conference-Abstract
Determination of moisture content of wood using ultrasonic pulse velocity
(Department of Materials Science and Engineering, 2019-01) Vithanage, VSC; Wijesinghe, MPMC; Piyathilake, SAKVM; Sivahar, V; Sivahar, V; Sitinamaluwa, HS
Wood is one of the conventional materials still used in many engineering applications. As a natural material, it is subjected to dynamic property variations. One of the major reasons for the property variation of wood is the moisture absorption. The main aim of this research is to estimate the degree of decay in the compressive strength of selected wood types against the amount of moisture using ultrasound waves. Teak (Tectonagrandis), a hardwood and Pine (Pinusthaeda), a softwood are two types of wood which are commonly used in Sri Lankan wood industry. Samples of each wood type were kept for moisture absorption and the ultrasonic pulse velocities were measured in each sample. A 54 kHz normal probe was used. Through transmission technique was carried out in longitudinal and transverse directions. The corresponding compressive strength was also tested for each moisture level in the defined directions. In the transverse direction, ultrasonic velocity and compressive strength showed relatively lower values than those in the longitudinal direction. The ultrasound velocity was found to drop with the increase in moisture content. The rate at which the velocity drops changed at a particular moisture content. It was noted that this moisture content is the Fiber saturation point (FSP) of the wood tested. This phenomenon is common for both the wood types in both the directions. The fiber saturation point of each sample was confirmed with DSC (Differential Scanning Calorimetric) analysis. The established relationships can be used to estimate the compressive strength of wood nondestructively for a known moisture content.
item: Conference-Abstract
Effect of carbon content on the correlation between ultrasonic attenuation and corrosion of plain carbon steel
(Department of Materials Science and Engineering, 2019-01) Metthananda, SHGK; Tennakoon, GAAI; Sivahar, V; Piyathilake, SAKVM; Sivahar, V; Sitinamaluwa, HS
The field of Metallurgical Engineering includes a vast range of applications from tiny mechanical components to massive construction applications. The service life of metals is highly concerned and studied extensively. Among all industrial metals, plain carbon steel plays a considerable role. Detecting the actual amount of corrosion has become very vital and critical since the failures occurring due to corrosion is still a substantial problem. Ultrasonic Testing is one of the modem methods which can be used to identify the degree of corrosion of a metallic component accurately, without causing any destruction. This study sought to contribute the field of metallurgical engineering by identifying the effect of carbon content and ultrasonic attenuation towards the corrosion of plain carbon steels. Plain carbon steel samples of different carbon contents were allowed to corrode under accelerated environment and periodically tested for ultrasonic attenuation and weight loss measurements. In addition, corrosion penetration of the samples was examined under optical and scanning electron microscopes. Observations were taken for both destructive and nondestructive testing and were correlated so that, using this correlation, the degree of corrosion can be determined in a non-destructive way without damaging the components and hence the remaining service lifetime could be predicted.
item: Conference-Abstract
Effect of corrosion surface topography on fatigue life of low carbon steel
(Department of Materials Science and Engineering, 2019-01) Munasinghe, RGNDS; Piyathilake, SAKVM; Bandara, HMLS; Rangana, DMP; Sivahar, V
One of the main research areas of Metallurgical Engineering is associated with the estimation of fatigue life of atmospherically corroded metallic structural components. It has been studied extensively worldwide and most of the researchers in this area have focused on statistical analysis of fatigue strength of alloy steels and other metals deteriorated due to pitting corrosion. The scope of this work is focused on the fatigue behavior of low carbon steel, exposed to coastal-atmospheric corrosion which omits pitting. Studying the change in surface topography with exposure time, due to atmospheric corrosion is one of the two main objectives of this research. Evaluating the change in fatigue life of corroded samples with changing surface topography due to corrosion is the second objective. Fatigue life is taken as the number of cycles to failure, and it is evaluated by experimental and numerical methods (FEA). The surface topography is evaluated quantitatively using Scanning Electron Microscopy and 3D MountainMaps^"^ software. The quantitative data obtained on surface features are then represented in a finite element model to evaluate their fatigue performance using fatigue analyzing FEA software. The significance of this work is that it helps to explain the difference between simulated and experimentally determined fatigue life of atmospherically corroded low carbon steel, which can be ultimately used in estimating the life expectancy of corroded structural steel components.
item: Conference-Abstract
Suitability of limestone and red sand in Aruwakkalu to produce paving blocks used in class a and class b roads
(Department of Materials Science and Engineering, 2019-01) Pirashanth, K; Prashanthan, R; Guluwita, SP; Nanayakkara, SMA; Sivahar, V; Sitinamaluwa, HS
Paving blocks are used as a top layer of road structures to replace asphalt. Concrete paving slabs are usually made by mixing materials such as Portland cement or other bonding materials, water and aggregates. Compared to other pavements such as concrete or asphalt, there is an increasing demand for paving blocks. The advantages of paving blocks include environmental friendliness, aid in soil conservation, fast completion time, easy installation and maintenance, aesthetic beauty and low cost. This research aims to prepare paving blocks using Aruwakkalu red sand and lime stone as coarse aggregates and fine aggregates instead of stone aggregates and river sand. Samples were prepared using a mixture of limestone and red sand using cement: fine aggregate: coarse aggregate mixing ratio of 1:2:2. The maximum compressive strength of 60.1 MPa in 28 days of curing time for grade 50 mix design. Trial mixes were cast and tested for compression after 7 days and 28 days of curing time. Paving blocks are mix designed as per the DOE concrete mix design method. Quantities of constituents were estimated for characteristic compressive strengths of 40 N/mm^ and 50 N/mml 40 N/mm^ was selected for the class B roads and 50N/mm was selected for the class A roads.
item: Conference-Abstract
Suitability of aruwakkalu red sand as the molding sand for cast iron casting
(Department of Materials Science and Engineering, 2019-01) Hettiarachchi, HC; Jayasinghe, KC; Guluwita, SP; Sivahar, V; Sitinamaluwa, HS
Sand casting is a common casting method used for the production of metalUc components. Normally Silica sand and Bentonite clay are used as the main ingredients of molding sand. There is a vast deposit of red sand in Aruwakkalu and currently it is not used for industrial applications. The particle size distribution of Red Sand is very much similar to Silica sand and there is a clay content in it as well. Therefore, there is a possibility of partially replacing Silica sand and Bentonite with Aruwakkalu Red Sand. In this study, the Silica sand was replaced from 100% to 10% by red sand and the properties of molding sand were analyzed. The test results were compared with the requirements of the AFS standards. The optimum percentage of Aruwakkalu Red Sand, Silica sand, and Bentonite clay is 11.4%, 77.9% and 7.1% by weight respectively. The moisture content was kept at 3.6%. Therefore 9.8% of silica sand and 0.8% of Bentonite clay can be reduced compared to the conventional molding sand when Aruwakkalu Red Sand is added.
item: Conference-Abstract
Solar powered domestic waste dryer
(2019-01) Alahakoon, AMMT; Kandewaththa, TH; Galhenage, AS; Sivahar, V; Sitinamaluwa, HS
Kitchen garbage, in general, is getting to be a big problem in urbanized area. Usually, in Sri Lanka municipal councils collect kitchen garbage once a week. Thus, week-long garbage at homes creates a strong unpleasant smell. One of the main reasons for the bad smell is moisture content in the garbage. The purpose of this study is to reduce the moisture content in the kitchen garbage using solar energy. Used coconut pulp is used as the representative for the experiments as it contains a high amount of moisture. Variation of the moisture content with temperature was analyzed using TGA/DTA analysis. An affordable solar dryer was designed to dry the kitchen garbage before being stored for the weekly collection. There are two compartments in the design, namely, a solar collecting chamber and a sample chamber. Current performance of the dryer shows a temperature of about 60 °C in the sample chamber and it can remove about 20% of the moisture present in the used coconut pulp.
item: Conference-Abstract
Studying the effects of quenching mediums on the mechanical properties of EN8 steel
(Department of Materials Science and Engineering, 2019-01) Samaraweera, PDIP; Bandara, MMEN; Fernando, WSMGS; De Silva, GIP; Sivahar, V; Sitinamaluwa, HS
Presently, ENS steel is widely used for induction hardened gear wheels due to its superior mechanical properties which are essential for gear wheels. This project focuses on achieving the required level of mechanical properties for a gear wheel of a starter motor using a low-cost quenching medium. Specimens of ENS alloy steel were examined after heating between S00°C-850°C using an Induction Furnace and quenched in different quenching mediums such as natural oils and heavy vehicle radiator coolants. The mechanical properties such as hardness and impact toughness are determined using the micro hardness tester and Charpy impact testing machine respectively. When replacing the AH Metalworking Fluid (Active Heavy duty) which is the industrially used quenching medium, with above-mentioned low-cost quenching medium, soaking time and temperature at the metal surface during induction hardening need to be varied in order to obtain the required level of hardness and impact toughness. The micro hardness of the case was measured as per the linear point system across the center point of the cross section of the samples. The basic properties of the quenching mediums such as viscosity, heat capacity, water content and flash points were measured and compared with the presently used oil.
item: Conference-Abstract
Study of the effects of sulphide stress corrosion on tensile strength of pipeline steel used in petroleum industry
(Department of Materials Science and Engineering, 2019-01) Peiris, MDHC; Perera, LWL; De Silva, GIP; Sivahar, V; Sitinamaluwa, HS
The phenomenon of sulfide stress corrosion (SSC) can result in catastrophic failures of pressurized equipment and piping, resulting in extensive damage, injuries and possible fatalities. Sulfide stress corrosion, a major degradation process in metals, is commonly associated with the petroleum industry where high concentrations of H2S is involved. The term, "Sulphide Stress Corrosion", is a customary term for aqueous corrosion in the presence of hydrogen sulfide (H2S) at a level high enough to significantly affect the corrosion behavior and corrosion products compared with the same conditions without H2S. Sulphide stress corrosion resistance of pipe line steel is evaluated in NACE "B" solution at room temperature This research focuses on the corrosion mechanism and variation of tensile strength with time. A constant stress of 40 MPa that is 10% of yield stress of the API 5L Grade B steel was applied to a set of samples and they were kept at a constant H2S environment for a predetermined time period. Thereafter, microstructural analysis was carried out for cross sections of the corroded specimens using SEM /EDS. The depth of corrosion versus exposure time and tensile strength versus exposure time graphs were plotted while monitoring corrosion propagation within the pre-determined time slots.
item: Conference-Abstract
Development of a vibration and shock sensor using piezoelectric ceramics
(Department of Materials Science and Engineering, 2019-01) De Silva, HTTM; Dayananda, RKAS; Adikary, SU; Sivahar, V; Sitinamaluwa, HS
When buildings are exposed to vibration or shock, those buildings can be damaged partially or fully depending on the energy of vibration. Hence, quantitative analysis of building vibration has become popular among researchers. In this research, a vibration sensor was developed using a piezoelectric ceramic cantilever beam and a tip mass to confirm that the vibration frequency of the building does not exceed the cosmetic damage range. As the first step, a mathematical model was developed to calculate the resonance frequency of the cantilever beam with a tip mass. At the resonance frequency, maximum amplitude could be achieved resulting in a higher output voltage of the piezoelectric sensor. The developed mathematical model and finite element analysis were used to determine the accurate dimensions of the cantilever beam based piezoelectric sensor. According to the calculations, width, length and thickness of the piezoelectric material, copper beam and tip mass are 10x20x1, 10x100x0.3 and 10x30x3 mm respectively. Hence, the piezoelectric sensor output voltage was calculated using finite element analysis at the vibration frequency range that corresponds to the cosmetic damage. According to the calculations, threshold voltage level and frequency of the sensor to activate the alarm were 4.35 mv and 9.5 Hz respectively. Arduino software was used to analyze the output signal of the sensor. Vibration source was used to verify the calculation steps. Finally, liquid crystal display and small buzzer were added to show the frequency and give a warning when vibration frequency exceeds the required level.
item: Conference-Abstract
Investigation of cause of uncured resin in carbon fiber razor cables
(Department of Materials Science and Engineering, 2019-01) De Seram, HSNP; Rathnayake, RMM; Weragoda, VSC; Sivahar, V; Sitinamaluwa, HS
This research project investigates a mechanical failure of razor cables manufactured by a leading carbon fiber boom, rigging and spars manufacturing company in Sri Lanka. This project was aimed at detecting the cause of failure of razor cables when subjected to coiling for transportation. In preliminary studies, it was apparent that the localized variations in the curing process could be a possible cause for the failure. Also, other factors such as the presence of moisture, the behavior of the epoxy resin, curing method could affect the outcome of the curing process. Through this project, authors attempted to establish the most probable cause for the failure and to determine a method to identify the areas susceptible to failure to minimize the production of potentially defective products. It was hypothesized that the uneven curing of the razor cables could be a major reason for failure. To test that, eddy current and di-electrometry techniques were used as the test methods for monitoring of the degree of curing. However, it was observed that eddy current method did not give any useful indications about the degree of curing. The di-electrometric technique showed different dielectric capacitance values for cured and uncured resins. Therefore, using dielectric capacitance theory, a test probe was designed to distinguish the cured product from the non-cured product. A combination of experimental and theoretical study was carried out to verify whether the curing cycle used is sufficient to complete the curing process. The mathematical model shows that, the curing cycle time was sufficient for complete curing of the epoxy resin. Therefore, it is suggested that the cause of failure could be either a material or pre-curing process related.

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