Browsing by Author "Piyathilake, SAKVM"

Now showing 1 - 13 of 13

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 carbon content on the correlation between ultrasonic attenuation and corrosion of plain carbon steels
Tennakoon, GAAI; Metthananda, SHGK; Piyathilake, SAKVM; Sivahar, V
The field of Metallurgical Engineering includes a vast range of applications from tiny mechanical components to massive construction applications. Service life of metals is highly concerned and studied extensively. Among all industrial metals, plain carbon steel plays a considerable role. Detecting the actual rate 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 modern methods which can be used to identify the rate 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 rate of 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 non-destructive testing and were correlated so that, using this correlation, rate of corrosion can be determined in a non-destructive way without damaging the components and hence the remaining life time could be predicted.
item: Conference-Abstract
Effect of carbon content on the correlation between ultrasonic attenuation and corrosion of plain carbon steels
Tennakoon, GAAI; Metthananda, SHGK; Piyathilake, SAKVM; Sivahar, V
The field of Metallurgical Engineering includes a vast range of applications from tiny mechanical components to massive construction applications. Service life of metals is highly concerned and studied extensively. Among all industrial metals, plain carbon steel plays a considerable role. Detecting the actual rate 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 modern methods which can be used to identify the rate 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 rate of 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 non-destructive testing and were correlated so that, using this correlation, rate of corrosion can be determined in a non-destructive way without damaging the components and hence the remaining life time 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
Effect of corrosion surface topography on fatigue life of low-carbon steel
Rangana, DMP; Bandara, HMLS; Piyathilake, SAKVM; Abeygunawardane, GA
Sri Lanka’s first research project conducted utilizing fe-safe software by SIMULIA, in the interest area of fatigue life prediction. The field of Metallurgical Engineering associated with the fatigue life of atmospherically corroded structural components has been studied in extensive detail. Most of the researchers in this area have focused on statistical analysis of fatigue strengths of alloy steels and other metals undergone pitting corrosion in a conventional manner. The scope of this work is focused on the fatigue behavior of low carbon steel, exposed to coastal-atmospheric corrosion. The change in surface topography with time, due to atmosphericcorrosion of low-carbon steel is one of the two main areas in this research and other factor is the drop in fatigue strength with changing surface topography. In this research project, effect of surface topography of corroded low carbon steel on their fatigue lives are evaluated with both experimentally and analytically using finite element modelling. The surface topography is evaluated quantitatively, using Scanning Electron Microscopy and a 3D metrology software. The quantitative data obtained on pit geometries are then represented in finite element modelling to evaluate their fatigue lives using fatigue analyzing FEA software. The significance of this work is that it takes into account the surface topography of corroded low carbon steel and helps to explain the difference between simulated and experimentally obtained fatigue strengths of them.
item: Conference-Full-text
Effect of grain size of steel on ultrasonic longitudinal wave velocity to shear wave velocity ratio
(IEEE, 2018-05) Samarasingha, SDM; Ellegama, EGHDB; Piyathilake, SAKVM; Sivahar, V; Chathuranga, D
Determination of the grain size is usually done by microscopic techniques which require special sample preparations. Nondestructive evaluation of grain size becomes important when sample preparation is restricted such as on a finished product. Nondestructive evaluation of grain size could be done through ultrasonic attenuation measurements. However, in such instances the dimensions of the components need to be known. As such, this work focuses on determining the grain size nondestructively when the material thickness is unknown. Hence, this paper presents a method to determine the grain size of a metal through ultrasonic longitudinal wave velocity to shear wave velocity ratio.
item: Conference-Full-text
Effect of penetration of corrosion on the load- bearing capacity of mild steel
(IEEE, 2018-05) Jayasooriya, ED; Piyathilake, SAKVM; Sivahar, V; Munasinghe, RGN De S; Chathuranga, D
The field of Metallurgical Engineering associated with the service life of corroded metallic structures has been studied in extensive detail, the world over. Most of the theses in this area have focused only on the general attack (uniform corrosion) on steel structures in a range of atmospheres. This study sought to examine whether the penetration of corrosion beyond the general attack into the bulk material, has a significant effect on the load-bearing capacity of mild steel structures. 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 breaking loads deviated negatively from the expected loadbearing capacity, which was determined through conventional methods. This deviation showed a close correlation to the increase of penetration of corrosion with time.
item: Conference-Abstract
Prediction of true compressive flow stress of aa 6063 alloy through ultrasonic attenuation
(Department of Materials Science and Engineering, 2020-02) Jurmey, K; Ghimire, NS; Sivahar, V; Abeygunawardana, AAGA; Piyathilake, SAKVM; Abeygunawardane, AAGA
During the compression testing of any material sample, the true compressive flow stress of the material cannot be determined due to the presence of friction between the end surfaces of the specimen and platens (of the compression testing machine) and due to misalignment of the test specimen and platens. Friction causes the barreling of test specimen and material flow at the interface is restrained. However, the material near the mid height position is less restrained by the friction and spreads laterally to a greatest extent. In addition to the compressive stress, a circumferential tensile stress develops as the specimen barrels. Compressive tests are therefore not valid for measurement of bulk elastic or plastic properties of material. The present research work is based on prediction of true compressive flow stress of AA 6063 alloy through ultrasonic attenuation. AA 6063 specimens were compressed to obtain compressive stress and strain. Ultrasonic attenuation coefficient of the each compressed specimens were measured to correlate the variation of stresses with it. Finite Element Analysis (FEA) was performed to validate the frictional and misalignment effects during compression testing and to obtain true compression flow stress. The destructive compression testing method will be eliminated by using nondestructive ultrasonic testing method which is cost effective and time saving.
item: Conference-Full-text
Remote estimation of degree of corrosion using ultrasonic pulse echo methods
(IEEE, 2018-05) Nawfi, NM; Sarusan, N; Piyathilake, SAKVM; Sivahar, V; Munasinghe, RGNDeS; Chathuranga, D
Even though the engineering structures are designed to achieve the potential to be very durable and capable of withstanding the degradation caused by adverse environmental conditions, failures in the structures do still happen; predominantly due to corrosion. Even though there are many conventional methods to evaluate the degree of corrosion, most of them are destructive. Though there are significant efforts made to estimate the degree of corrosion nondestructively, reliable methods are yet to be established especially, for hidden or inaccessible corrosion. Moreover, the available methods, whether destructive or nondestructive, focus only on the surface corrosion (except in the cases of intergranular corrosion [IGC] of stainless steel) completely ignoring the corrosion pits that form beyond the limits of surface corrosion. Hence, this study includes these corrosion pits in estimating the degree of corrosion. In this study, selected steel samples were subjected to accelerated corrosion conditions and then tested ultrasonically. Ultrasonic longitudinal wave velocity to shear wave velocity ratio and the attenuation coefficient were measured using Ultrasonic Flaw Detector. These measurements were done even after removing the corrosion products from the surface. SEM analysis and the conventional weight loss measurements were also carried out. The correlations obtained between the degree of corrosion and ultrasonic parameters are presented.
item: Conference-Abstract
Retrospective determination of water-to-cement ratio (w/c) of concrete through ultrasonic pulse velocity measurements
(Department of Materials Science and Engineering, 2020-06) Anushan, R; Dilaittan, V; Sivahar, V; Piyathilake, SAKVM; Gamage, JCPH; Abeygunawardane, AAGA
The objective of this research is to find a method to determine the water-cement ratio that has been used in a concrete during construction, retrospectively. Water-Cement ratio affects the properties of concrete including its strength. Ultrasonic Pulse Velocity (UPV) of concrete can be related to its strength. These inter-relations can be used as the tool to achieve our objective. Different grades of concrete with varying water-cement ratios were used in this study. 28-day strength was measured using the standard concrete cubes and UPV measurements also were done for the same samples. 28-day strength of concrete can be considered as its long-term strength, as it does not change much after 28 days. UPV and 28-day strength of concrete, both found to decrease with the increase of water- cement ratio. These reductions were due to increased volume of capillary voids and micro- cracks within concrete transition zone and porous structure within the interconnected hydrates. The relationships established can be used to predict the water-cement ratios used in concrete structures retrospectively.
item: Conference-Abstract
Ultrasonic nondestructive evaluation of corrosion damage In concrete reinforcement bars
(2017) Maddumahewa, KK; Madusanka, NPA; Piyathilake, SAKVM; Sivahar, V
Corrosion of reinforcement bars which are embedded in concrete is one of the significant problems encountered in reinforced concrete structures. Despite the fact that concrete gives protection against corrosion, aggressive environmental conditions can lead to the corrosion of the reinforcement bars embedded in concrete. This may affect the strength of the concrete structures which leads to catastrophic failures during the service. Assessment of the extent of corrosion in embedded reinforcement bars nondestructively is the main objective of this research work. Grade M30 concrete mixture was used for the preparation of rectangular square blocks as testingsamples. Concrete specimens with embedded steel bars of 10 mm, 16 mm, 20 mm and 25 mm diameters have been subjected to accelerated corrosion using ‘Impressed Current Technique’ for different time periods. The ultrasonic velocities through the concrete samples with corroded reinforcement bars were measured against the corrosion time and the bar diameters. For these measurements Portable Ultrasonic Nondestructive Digital Indicating Tester (PUNDIT) was used. The weight loss due to corrosion of the reinforcement bars were measured subsequently, and those readings were evaluated against the ultrasonic velocities. The ultrasonic velocity decreases with the time and the extent of corrosion.
item: Conference-Abstract
Utilization of fruit waste to produce biodegradable polymer composites
(2011) Samarasekara, AMPB; Piyathilake, SAKVM; Kumarage, DIU
Polymers play an essential and ubiquitous role in everyday life due to their extraordinary range of properties. However, Polymer wastes create formidable problems to the society today. Biodegradable polymers are significant and of great importance for the future of the planet. Biodegradation is the decomposition of polymer materials by microorganisms. Biodegradable Low Density Polyethylene (LDPE) based composite was prepared by adding pectin as the main additive. Pectin was extracted using passion fruit waste. The biodegradability imparted by pectin can be improved by incorporating natural enzymes. Papain and Bromelain were two natural enzymes extracted from fruits of papaya and pineapple waste. The extracted products were analysed and characterized using Fourier Transform Infrared Spectroscopy (FTIR). These extracted natural enzymes can be used to produce biodegradable LDPE — Pectin polymer composite to preserve the environment for future generations.