Master of Engineering in Manufacturing Systems Engineeringhttp://dl.lib.uom.lk/handle/123/712024-03-29T10:13:10Z2024-03-29T10:13:10ZAnalysis of yarn parameters influencing the knittability of thermoplastic polyurethane yarnsAtapattu DMhttp://dl.lib.uom.lk/handle/123/214842023-10-13T02:35:13Z2021-01-01T00:00:00ZAnalysis of yarn parameters influencing the knittability of thermoplastic polyurethane yarns
Atapattu DM
Knittability specially in synthetic yarns such as polyester and nylon is an essential index
of the performance in ensuring the proper conversion of yarn to a knitted fabric. This can
be affected by various conditions of the yarn manufacturing, yarn storage, knitting
machine, knitting pattern and the environment. In footwear knitting industry,
Thermoplastic Polyurethane synthetic yarn is being used due to its higher heat resistance
and colour fastness properties compared to normal melt spun yarns. One of the major
concerns in the process of knitting is the continuous yarn burst, which occurred
significantly in thermoplastic polyurethane yarn. Occurrence of this burst appeared to be
random and emerged in every yarn knitted areas. This research aimed to identify the
critical factors affecting the yarn burst. After identifying the most critical factors through
literature review, temporary and permanent countermeasures were developed. Initially,
Prisma approach was applied to extract the relevant information from literature. Then,
parameters were categorized into three based on factors related to: yarn compound,
storage environment, and machine and knitting pattern. Under each category the critical
parameters relevant to each factor was identified after analyzing the significance of each
quantitatively and qualitatively. In terms of yarn aging, previous literature explains three
types of tests namely natural exposure, field aging and artificial acceleration. According
to literature, the strength of Thermoplastic Polyurethane yarn deteriorates once it is
subjected to extreme conditions. In this study, the relationship between the Thermoplastic
Polyurethane polymer manufactured date, the yarn lot manufactured date and the yarn
burst was experimentally tested. The correlation with knittability and the yarn
manufacturing dates were found to be not significant. In terms of yarn compound related
factors, yarn unevenness was identified as the most critical parameter. An experimental
set up was developed to measure the unevenness of black and white colourway samples.
These colourways were selected as the defect rate of white colour was the highest while
the black colour was the lowest. Through the statistical analysis of “t” distribution, it was
identified that the statistical variance of the data set was high between the two
colourways. This proves that the factor of yarn unevenness is directly correlated with defect rates. Related to machine and method related factors, the programming structures
were less researched in the literature. According to the relevant footwear application,
initial all needle knit structure is changed to 1*1, 1*2, and 2*2 structures. All 1*1, 1*2
and 2*2 structures prove better knittability compared to initial all needle structure.
Depending on the aesthetic factors, 1*1 structure is considered as the optimum one for
the relevant application. This study was limited to few parameters and the dependence of
other parameters such as temperature, time and moisture absorption has to be further
investigated in future works. Further, the needle knit structure is also an interesting
avenue for further research.
2021-01-01T00:00:00ZLocation planning tool for biomass boilersJeewakaratna SYRhttp://dl.lib.uom.lk/handle/123/159972021-12-22T05:26:34Z2020-01-01T00:00:00ZLocation planning tool for biomass boilers
Jeewakaratna SYR
Steam boilers constitute an important part of a production facility. Though traditionally, fossil fuel has been used predominantly in steam boilers, the environmental impacts of using fossil fuel and the higher economics have fuelled exploration on alternative fuels such as biomass and in 2016 demand for biomass energy in Sri Lanka has been 194.3 PJ out of which 75.8 PJ has been industry demand which is an increase of 300 TJ compared to previous year.
In light of above, this study has been carried out with the aim of mitigating the environmental impacts of using biomass as a fuel for boilers in Sri Lanka and to improve related economics by developing a location planning tool for biomass boilers & with the objectives of assessing factors that would govern the environmental and financial costs associated with the operation of a steam boiler with respect to heavy oil and biomass variants leading to proposing of a framework to rank the fuel variants based on environmental performance and finances.
Methodology followed in this study was carrying out a life cycle assessment (LCA) to assess the environmental loads of each biomass variant in context via data collected in surveys and analysing reports of 60 steam boilers followed by comprehensive financial analysis and sensitivity analysis enabling comparison of relative contribution of each step in the process.
It was identified due to extremely adverse impact of using fossil fuel, using biomass where sustainable has become the best alternative regardless the location of the boiler and subsequent distance from biomass source to the application, in Sri Lankan Context, consequently the threshold points for switching to biomass lie in the economic factors as cost of transportation dominates whether the process is feasible. Sawdust was identified as the most environmentally friendly fuel followed by wood chips, wood logs and husk respectively. Distances from wood log, husk, wood chip, and sawdust biomass sources to the point of application to equal the financial cost of heavy oil-based boiler operation were identified as 530 km, 554 km, 595.5 km and 604 km respectively. It was identified, ranking order of financial performance of fuels, toggle along with distance from respective biomass source to point of application, such that a fuel more feasible compared to another at similar relatively lower distance from fuel source to point of application would not necessarily be so at higher similar distances. Though husk usage is costlier than sawdust at relatively smaller distances, at similar distances over 140 km from respective fuel source to point of application, sawdust becomes the more viable fuel. Similarly, chips usage though expensive at relatively lower similar distances equivalent to other biomass variants, becomes more viable compared to husk and wood logs at similar distances over 460 km and 355 km respectively.
Precise data on biomass sources in Sri Lanka are lacking and taking measures to develop a biomass resources map would contribute to location planning process of biomass boilers favourably and streamline supply chain process.
2020-01-01T00:00:00ZInvestigation on thermal behavior of NITINOL based actuating elements for biomedical applicationsPerera HSLhttp://dl.lib.uom.lk/handle/123/167352022-06-21T09:05:17Z2020-01-01T00:00:00ZInvestigation on thermal behavior of NITINOL based actuating elements for biomedical applications
Perera HSL
In modern material world, important consideration is given to the group of fascinating materials called shape memory materials (SMMs) which respond quickly to a definite change of heat, light and chemical. The shape memory materials that have been established to date are shape memory alloys (SMA), shape memory polymers (SMPs) and shape memory hybrids (SMH). SMA play a significant role in various applications such as sensors, actuators, clamping devices, etc. Nickel – titanium (NiTiNOL) alloys are heavily used in SMA due to their strain recovery, excellent thermal characteristics, reliability and commercial availability, in addition to being used in macro and micro electro mechanical systems based biomedical applications (BMA) due to high biocompatibility, resistance to corrosion and high fatigue limit.
Previous researches have focused on developing integration between thermal stability and SMA microstructure. But they don't have enough thermal behavior data with different heat treatment temperatures. Although phase transformation temperatures and microstructure patterns with different heat treatment temperatures are unique characteristics of NiTiNOL. The aim of this study is to investigate NiTiNOL characteristics and thermal behavior of SMA based actuating elements for biomedical applications. The overall objective of this research study is to investigate the phase transformation temperatures for NiTiNOL alloy during different heat treatment temperatures and to propose the appropriate geometric shape of the actuating element in BMAs.
Therefore, a number of experiments were done at the laboratory level to characterize the thermal related behavior of the NiTiNOL alloy. Differential scanning calorimetry test measurements are used in this study to analyze the dissimilarities in phase transformation temperatures and properties of NiTiNOL (Ni-54 and Ti-46, weight percentages) alloy due to the variation of heat treatment temperature ranging from 400 °C to 600 °C. Further, microstructure and Energy – dispersive X-ray are determined using Scanning Electron Microscopy. It is found that most critical phase transformations are taken place between heat treatment temperatures of 550 °C and 600 °C and extraordinary unique behavior of phase transformations are exhibited by the respective specimens subjected to these temperatures. Further it is found that thermal behavior of actuator elements is dominated by the changes incurred in the microstructure of the NiTiNOL alloy during heat treatment.
2020-01-01T00:00:00ZPerformance evaluation of white coconut oil based metal working fluidWickramasinghe KChttp://dl.lib.uom.lk/handle/123/166352022-10-12T03:14:26Z2020-01-01T00:00:00ZPerformance evaluation of white coconut oil based metal working fluid
Wickramasinghe KC
Metal Working Fluids (MWFs) play a significant role in metal machining operations and vastly used in aerospace, automotive and marine industries to produce high tech components. The main purpose of using MWF during cutting operation is to facilitate a layer of lubricant between work tool interfaces to abate friction and heat. In the present context, industries practice to use mineral-based MWFs as of its good functional performance. However, health and environmental legislations have bounded the usage due to its carcinogenic behavior and adverse effects to the environment. Therefore, the requirement of ecological and user-friendly cutting fluid has raised substantially in manufacturing industries. Researchers have taken much effort to find an alternative for mineral oils and concluded the importance of vegetable oils as a substitute to use for the MWF. However, neat vegetable oil express poor cooling capability during machining due to its low oxidation stability. The authors have formulated a white coconut oil-based water soluble MWF to overcome the poor cooling ability by using water and permitted food grade surfactants. The main intention of the research is to assess the industrial applicability of the formulated fluid in term of functional performance while ensuring health and safety of the operators and environmental impact. The surface quality, chip curl radius, chip formation of 0.2% C and AISI 304 steels while using formulated novel white coconut oil based MWF, mineral oil based MWF in flood cooling and dry machining configurations have investigated for the conventional turning operation. The machining parameters were selected according to the recommended specifications of the work materials and tool manufacturers. Coated carbide indexable inserts have been used for the turning operation and surface quality of each set of cutting parameters were measured. Further, tool wear was investigated using scanning electron microscope (SEM). Work tool interface temperature was simulated using the DEFORM platform. The invented novel white coconut oil based MWF expressed better values for almost all the set of machining parameters when compared to the other cooling configurations and proven its industrial applicability for the sustainable machining. The performance of the formulated white coconut oil based MWF can be enhanced by adding nanoparticles and it is worthwhile to conduct the machining operations for hard to cut materials for further confirmation of the industrial applicability.
2020-01-01T00:00:00Z