Browsing by Author "De Silva, GIP"

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item: Article-Full-text
Bond characteristics of CFRP strengthened concrete members bonded using Modified Engineered Cementitious Composite
(Elsevier, 2021) Widanage, C; Gamage, JCPH; De Silva, GIP
This study focuses on the development of an insulating cementitious adhesive for bonding Carbon Fibre Reinforced Polymer (CFRP) fabrics to a concrete surface. The epoxy adhesive which is the generally used adhesive for CFRP shows a low thermal performance. As a potential solution, Engineered Cementitious Composite (ECC) mortar was modified as a cementitious adhesive with improved thermal insulation. The ECC adhesive was developed using locally available class F fly ash, silica sand and Polyethylene terephthalate (PET) fibres other than the generally used cement and water (PET-ECC). The selected mix proportion for PET-ECC achieved a low thermal conductivity of 0.145–0.180 W/mK which limited the heat transfer through the adhesive layer. The effective bond length of the developed PET-ECC adhesive was 125 mm and the corresponding bond strength was 224.9 MPa. The respective bond strength was further enhanced up to 570.28 MPa by sticking river sand on top of CFRP fabric using epoxy adhesive before bonding it to the concrete surface using the PET-ECC adhesive. The use of PET-ECC as the bonding agent to strengthen compression members with CFRP confinement yielded an average strength enhancement of 34%.
item: Conference-Abstract
Development of cellulose fiber reinforced soil-based composite wall panels using selected lignocellulosis materials
(Department of Materials Science and Engineering, University of Moratuwa., 2022-11) Jayaweera, WMIS; Malshan, MMH; De Silva, GIP; Fernando, TN; Abeygunawardana, AAGA
The present study focuses on preparation of composite wall panels, reinforcing with three different pre-treated lignocellulosic material fibers - bagasse (B), paddy straw (PS), and banana stem (BS). Soil-based composite wall panels were prepared by mixing cement, laterite soil, and lignocellulosic materials in the weight ratios of 1: 1: 0.025. Morphological characteristics, water absorption, flexural strength, and thermal conductivity were tested in prepared wall panels after keeping at curing period of 28 days. The characterization results of molded wall panels indicate the variation of flexural strength as 1.85 - 4.05 MPa, percentage of water absorption as 14.7-20.2% and thermal conductivity as 0.131 -0.252 W/mk. The characteristics of some molded wall panels prepared in the present study were at a satisfactory level compared to the market available wall panels.
item: Conference-Abstract
Development of cost-effective cement-based ceiling sheet with the addition of waste foundry dust
(Department of Materials Science and Engineering, University of Moratuwa., 2023-07-28) Mathuran, T; Thulaanchan, K; Fernanado, TN; De Silva, GIP; Sivahar, V
Ceiling sheets are predominantly produced with the addition of asbestos; however, asbestos has been identified as a carcinogenic material. Hence, there is pressing demand for alternative materials to produce ceiling sheets. Waste Foundry Dust (WFD) is a byproduct of metal sand casting process, and there is no effective permanent solution for disposal of the WFD. In this study, the possibility of manufacturing cement-based ceiling sheets with addition of WFD is investigated as a low cost and healty alternative for asbestos based ceiling sheets. Firstly, Ordinary Portland Cement (OPC) was mixed with WFD amount of 30%, 40%, 50% & 60% of total weight to prepare the material. Then, sheets were prepared using compression molding, by applying 2 tons per inch pressure. Also, another set of samples were made by replacing 3 wt% of cement with bentonite, with the same WFD amounts. A series of experiments were conducted to measure flexural strength, thermal conductivity, and water absorption of the prepared samples after 28 days of curing period. All the sample preparations and testing were done according to ASTM C-1185 standard. The results show that the strength and thermal conductivity decrease with increase of WFD while water absorption increase with increasing WFD. Here bentonite is used as binder to increase the binding property, hence improve the properties of prepared samples. WFD mainly acts as filler material to reduce the cost and reduce the adverse effect on environment.
item: Conference-Abstract
Development of soil based composite wall panel using locally available laterite soils
(Department of Materials Science and Engineering, University of Moratuwa., 2022-11) Samarasinghe, MMA; Gunathunga, WPS; De Silva, GIP; Fernando, TN; Abeygunawardana, AAGA
This research focus on developing laterite soil-based composite wall panels by using soil cement mixture, reinforced with cellulose fibers from pretreated cornhusk. In this, effect of various laterite soils and cement proportions of the mixture on the properties of wall panels like flexural strength, water absorption and thermal conductivity were determined. It has been observed high Al2O3+Fe2O3 content, good particle size distribution, lower clay content of soil shows good performance of wall panel properties. Further, lowering the cement content of the mixture reduces the wall panel performance.
item: Article-Full-text
Development of sustainable mortar using waste rice husk ash from rice mill plant: Physical and thermal properties
(Elsevier, 2021) Selvaranjan, Kajanan; Gamage, JCPH; De Silva, GIP; Navaratnam, S
The rice processing industry generates a significant amount of rice husk ash (RHA) waste, which is considered as cost-efficient and environmentally friendly pozzolanic material. This study used RHA as a replacement for filler material/fine aggregate in the mortar. The mechanical, thermal, and environmental performance of mortar comprising RHA waste as a replacement of river sand in different contents (0, 10, 20, 30 and 50% by weight of river sand) were investigated through experimental tests and environmental impact assessment. The RHAs were obtained from both controlled burnt (CBRHA) and opened burnt (OBRHA) processes and used to produce the mortar mixtures. Results show that OBRHA can be used as a partial replacement for river sand for up to 30% of weight to improve the thermal performance by reducing thermal conductivity up to 62% while keeping the adequate compressive strength. Further, the replacement of 30% weight of sand with OBRHA in conventional mortar production significantly reduces greenhouse gas emissions (i.e. 13% reduction per kg) and cost (4% reduction per kg).
item: Thesis-Abstract
Enhancement of surface quality brass castings cost effectively using naturally available sand and clay available in Sri Lanka
(7/2/2011) De Silva, GIP; Munasinghe, N
Through a survey done for the Sri Lankan foundry industry using a structured questionnaire it was revealed that one of the most significant quality parameter of the brass casting is the high surface roughness. Properties of the sand clay- mixture, the gating system of the mould, composition of the material to be melted and pouring temperature are the factors, which affect the surface roughness. Out of these factors the attention was focused in this work to the properties of the sand-clay mixture like fineness no., clay content, moisture content and permeability etc. to reduce the surface roughness. A synthetically unmodified sand-clay mixtures consisting of natural sand and clay from different locations in Sri Lanka were analyzed with respect to the reference sand sample (naturally bonded sand-clay mixture) imported from Japan, which gives a considerably low surface roughness. In this research work the attention was also directed to develop a non-contact method to measure the surface roughness of castings using ultrasonic echo amplitude technique. With this method it is possible to measure the surface roughness of castings with improved accuracy and minimized cost. The results of the experimental work done in this work show that it is possible to produce several number of mixtures made by mixing different sand and clay available in Sri Lanka and those mixtures give a relatively good surface roughness for the brass castings with compared to the casting made with Japanese reference sample.
item: Conference-Abstract
Influence of low-amplitude high-frequency pulsed current on the deformation characteristics of low and medium carbon steels
(Department of Materials Science and Engineering, 2020-02) Hendeniya, HMND; Shiranga, WMP; Abeygunawardane, AAGA; De Silva, GIP; Abeygunawardane, AAGA
When electrical pulses are applied to a metal during deformation, the resistance to deformation is dramatically reduced while the plasticity increases significantly. This phenomenon is introduced as electroplasticity. Macroscopic observations of yield stress reduction under current pulsation due to uniaxial tension, creep and stress relaxation is in the center of attention recently. Traditional manufacturing processes such as drawing, and rolling be contingent on the use of heat to reduce the forces associated with the fabricated parts. The high-temperature requirement is potentially leading to stress, warpage, and reduced tolerance control. Therefore, Electrically Assisted Manufacturing is introduced as an effective way of simplifying the fabrication while enhancing end- product properties. The electroplastic deformation of low and medium carbon steels under uniaxial tensile conditions were investigated with respect to the universal uniaxial tensile testing conditions. A significant reduction of yield stress of low and medium carbon steel with different carbon content were observed due to electroplasticity effect. A qualitative and quantitative analysis of yield stress reduction was carried out. Microstructural behavior and morphological aspects of fractured and strained surfaces of low and medium carbon steel specimens were observed. Keywords: Electro plasticity, Electron wind force, Dislocations, Uniaxial tensile test, Electrically assisted manufacturing, Low and medium carbon steel, Plasticity
item: Conference-Full-text
An investigation of the effect of precipitate size distribution on mechanical properties of aluminum 6063 extrudates used for window frames
(IEEE, 2021-07) Dilrukshi, LWUR; De Silva, GIP; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
This work focused on presenting an interpretation for the effect of precipitate size distribution on hardness and strength of the aluminum 6063 extrudates produced in local industry. The same heat treatment process applied in the local industry comprising solution treatment: keeping at 530°C for 4 hours, followed by age hardening treatment: keeping at 205°C for 150 minutes and air cooling, was carried out at laboratory scale. The average hardness and strength of heat-treated samples were measured as 66.5 HV and 210.5 MPa, respectively. Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy (SEM/EDS) examination showed that secondary phase precipitates formed during this aging treatment belong to two types of precipitates, they are Silicon-Iron rich and Magnesium-Silicon-Iron rich precipitates. The average number of precipitates, precipitate size and area covered by precipitates were calculated by Image J software. Percentages of precipitates belong to three different size ranges were analyzed as 50.10 percent, 45.13 percent, and 4.77 percent for 0.0−0.2 μm,0.2−1.5 μm and above 1.5 μm , respectively. The present work can be extended towards the development of a mathematical model to relate the ageing parameters and precipitate size distribution to hardness and strength of Al 6063 extrudates.
item: Conference-Abstract
A study of the effect of load on the depth of sulphide stress corrosion of steel used in petroleum pipelines
(Department of Materials Science and Engineering, 2020-02) Rathnayaka, RMMB; Madushan, HEMD; De Silva, GIP; Abeygunawardane, AAGA
The phenomenon of sulfide stress corrosion (SSC) can result in catastrophic failures in pressurized equipment and piping leading to extensive damages, injuries and possible fatalities. Sulfide stress corrosion, a major degradation process in metals, is commonly associated with the petroleum industry where a high concentration of H2S is involved. This research focuses on developing a relation between depth of SSC and applied load under a constant H2S concentration for a given time period. Furthermore, the mechanism of the propagation of sulfide stress corrosion is studied via microstructural analysis. According to the NACE standard solution "B" at the room temperature, the corrosion behavior of pipeline steel was evaluated. A special apparatus according to the NACE standards was fabricated for the testing process. The prepared samples of pipeline steel API 5L Grade B was tested under set of pre-determined loads while maintaining constant H2S concentration and pH value of 3.0 ± 0.5 for a constant time period. Thereafter, SEM microscopy and EDAX analysis were performed on the cross sections of corroded specimens. Relations of depth of corrosion versus applied load, and load at fracture versus applied load have been developed. Also, an interpretation is given for the propagation mechanism of SCC in terms of microstructural analysis. The ultimate objective of this work is to develop a model to predict the depth of corrosion occurred under different H2S concentrations, loads/pressure and exposure time periods.
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.
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Study of the Effects of Two Step Age Hardening Process on Mechanical Properties of Aluminum 6063-T5 Alloy
(2015-07-21) De Silva, GIP; Perera, RAD; Ranasinghe, PVSK
Aluminum 6063 T5 is an alloy and containing magnesium (0.45-0.9%) and silicon (0.2-0.6%) as the main alloying elements. T5 denotes the heat treatment process: cooling from hot working and artificially aged. Aging process is used to harden this alloy by forming second phase particles of Mg2Si. This work is mainly focused on the enhancement of hardness of Aluminum 6063 T5 extrudates, and increasing the production rate cost effectively. Two step age hardening treatment is developed as a substitute for the existing single step age hardening treatment used in local industry, to reduce the total time period and temperatures while improving the hardness. In this research work, average hardness value of extrudates produced in local industries is taken as the reference point and that is improved up to the required level by varying the time periods and temperatures of two step age hardening treatment.
item: Conference-Abstract
A study on reducing casting defects of sand casted water pumps
(Department of Materials Science and Engineering, 2020-02) Dawa, T; Lhamo, T; De Silva, GIP; Abeygunawardane, AAGA
Casting is one of the useful processes in producing products from utensils to machinery components. However, major disadvantage of this process is accompanying of casting defects, which bring great loss to the industry. Casting defects occur due to various reasons which are hard to control under the industrial environment. Many researchers have conducted experiments to find the best combination of process parameters which causes minimum casting defects. In such efforts, casting defects has been considerably reduced (up to 6%) by varying the moulding sand properties. Jinasena(Pvt) Ltd is one of the oldest pump manufacturers in Sri Lanka, however, currently they are suffering from high rate of sand-casting defects of 12% which leads to water leakage. This research focuses on analysis of these casting defects quantitatively and qualitatively, determining the causes, and suggesting effective solutions. It was found that shrinkage and blowholes were two critical defects leading to water leakage of water pump casing. Generally, it is well known that molding sand properties, metal pouring temperature, design of gating system and chemical composition of the raw material are vital factors that lead to the formation of casting defects. The influence of these major factors on formation of shrinkage and blowholes was studied in this work. The experimental results showed that improper design of gating system and deviation of the moulding sand properties dominantly affect the shrinkage and blowhole defects.
item: Conference-Abstract
Studying the effect of quenching medium and the aging temperature on hardness of al6063 alloy
(Department of Materials Science and Engineering, University of Moratuwa., 2023) Bandara, HMP; Kumarasingha, POAB; De Silva, GIP; Sivahar, V
This study investigates the influence of different combinations of quenching mediums and aging temperatures on the hardness of Al 6063 billets. To of finding maximum hardness, samples underwent quenching in air, water, and a salt bath and aging at temperatures of 170°C, 190°C, and 210°C. Microstructure images were obtained after quenching and after aging to compare the grain structures. Scanning Electron Microscope/Energy Dispersive Spectroscopy (SEM/ EDS) analysis is utilized to examine the composition of both the inside and outside of the particles present in the samples of after aging, use to identify and characterize the precipitates formed during the aging process. Scanning electron microscopy (SEM) images are obtained for samples representing the highest, lowest, and medium hardness values after aging, to investigate the relationship between hardness and particle sizes distribution. The major results of this research revealed that the combination of quenched medium as salt and an aging temperature of 190°C resulted in the highest hardness value of 85.46HV. This optimized process can serve as a practical guideline for industries seeking to enhance the mechanical properties of Al6063 alloy, ensuring they can achieve the desired hardness levels efficiently and reliably. The exploration of this novel quenching medium presents an opportunity for local industries to adopt this approach and potentially improve their manufacturing processes by capitalizing on the benefits of salt quenching.
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.