PURSE 1998
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- ItemOn line tool wear monitoring and adptation for enhanced tool life in turning processes(University of Peradeniy, 1998-11-07) Ilamurugan, A.; Pathirana, S. D.Cutting tool wear is a normal phenomenon occurring in any metal cutting process which normally affects the contact conditions at the tool-work interface. The process of tool wear will reduce the work quality and effective machine utilization (due to frequent tool regrinding 1 insert change) while increasing the power consumption, which ultimately increase the production cost. Therefore it is very essential to have an effective on-line tool management system attached to the machine, instead of relying on the subjective judgment of a machinist as to whether or not a tool has reached its wear limit. In addition to this, such a system could also be required to optimize the cutting conditions to enhance the tool life instead of employing conservative feeds and speeds. As a basis for the construction of such a system, we have started a study on turning processes with two objectives. 1. Establishment of a tool change policy:- The tool wear is proposed to be tracked continuously using indirect methods, sensing tool vibration, acoustic emission and dimensional variation of the component in order to establish a tool change policy. 2. Enhancement of tool life :- Development of an adaptive control technique to adjust the machining conditions such as cutting speed, feed and depth of cut in order to enhance the tool life. This paper presents the feasibility study we have conducted to detect the tool wear in order to establish a tool change policy. Experiments were conducted with cast iron (short chips) and bright steel (long chip) work materials using Sandvik TNMA and TNMG tungsten carbide inserts respectively, on T-MAX P lever tool holder, under different cutting conditions such as speed and feed. The acoustic signals emitted during the turning processes were recorded every fifteen minutes on a PC with 12 bits AID converter, built into RTI 800/815 multifunction input/output board using ECM-50PSW condenser microphone along with a control power amplifier. Simultaneously the actual tool wear (flank and carter wear) too was measured using shadow projector and recorded for comparison. The acoustic signals thus obtained were processed off line and found to have an excellent on-line tool wear detection capability. Experiments will be carried out in order to monitor the cutting tool vibration too in determining the validity of such information, for detecting the tool wear. It is planned to devise pneumatic on-line measurement system for detecting the dimensional variation resulting from tool flank wear. The present task is to use the information extracted through these sensors in computing an Autoregressive model representing the cutting process and decision making (tool changing policy) will be based on the calculated model parameters at frequent time intervals.
- ItemOccurrences of two new types of gem deposits in the Okkampitiya-Maligawila gem field(University of Peradeniya, 1998-11-07) Mathavan, V.; Kalubandara, S. T.Okkampitiya - Maligawila gem field occurs within the over thrusted rocks of the Highland Complex. This area is underlain mainly by marble, quartzite, pelitic gneisses, migmatites and basic granulites and surrounded by Vijayan granitic gneisses. Geological mapping of the area reveals that the Highland Complex rocks occur as two 'tongue' shaped bodies which are interpreted as rotated thrust nappes. Most parts of the Okkampitiya - Maligawila area is flat and gently undulating and the area is drain by Kumbukan Oya and its tributaries. Topographically, the area is bounded by mountain ranges in the west and north-east. The main gemstones hosted by Okkampitiya - Maligawila gem field include geuda, sapphires (blue, yellow and colourless), spinel, garnet, tourmaline and zircon in the order of decreasing abundance. Present investigations have shown occurrence of two new types of gem deposits not reported previously from Sri Lanka. Typically, gem bearing gravel and sand deposit occur as thin, discontinuous layers in paleo stream beds and flood plains. However, in the Okkampitiya- Maligawila gem field, most of the gem-bearing gravel and sand deposits are "housed" in solution cavities in the marble beds. The size of these irregular cavities range from several em to dm on the gentle hill slopes and a few meters on the flood plains and the depth ranges from 3 to 6 meters. Formation of these solutions cavities appear to be controlled by short joints and fractures. The stratigraphy of the gem bearing 'illama' which has calcite and dolomite as major components besides quartz, suggest that the flood plains underlain by marble, had been flooded, from time to time with gem bearing alluvial sediments. Worn out crystal faces of geudas and sapphires indicate distant provenance, while spinel and toumaline with distinct crystal faces indicate local derivation, probably from marble and pegmatites. Mining techniques used here differ from those used in other gem fields and include widening the cavities with either explosives or drilling and sieving the 'illama' before panning. In situ occurrences of gem minerals usually, non gem quality, ( e.g. corundum, spinel and tourmaline) have been reported but we report here an occurrence of gem quality, in-situ hessonite (grossular garnet) deposit that has been mined since 1997. This small bed of deposit, has now been completely exhausted except the non gem quality remains. The hessonite in the deposit is characteristically massive and is reddish brown to red in colour. It is associated with scapolite, diopsite, calcite and quartz. Field and petrography suggest that the garnet may have formed by a metasomatic reaction of the form, quartz +scapolite + calcite -> garnet + CO2•
- ItemNovel gas sensors based on polyaniline(University of Peradeniya, 1998-11-07) Premasiri, H. D. S.; Rajapakse, R. M. G.; Bandara, H. M. N.; Tennakoon, D. T. B.; Perera, J. S. H. Q.Polyaniline is a conjugated organic polymer that can exist in six different structural forms depending upon the extent of oxidation andlor protonation of the polymer backbone. These forms are called leuco-emaraldine base, leuco-emaraldine salt, emaraldine base, emaraldine salt, pernigraniline base and pernigraniline salt. First two polymers are in completely reduced forms with neutral and positively charged backbones respectively. These two forms are transparent yellow in colour. The third form which is blue in colour is partially oxidised but deprotonated. Forth form is an electronic conductor with a conductivity around 100 S em" and is green in colour. This form of the polymer exists with a partially oxidised and protonated structure. Fifth and sixth forms of polyaniline are in their fully oxidised states with the former being deprotonated and the latter being protonated. These two forms are violet in colour. These forms of polyaniline are interconvertible by redox andlor acid/base treatments. These changes of the same material can be utilised in several technological applications. In this presentation, we describe novel sensors for gases such as NH3,H2S, CO, CO2, Ch and HCI which are based upon polyaniline attached glass templates. A novel method was developed to covalently attach polyaniline on to ordinary glass surfaces. Such templates were dried at 110 DCand stored in a dry desiccator. The templates were exposed to gases at different pressures and changes of conductivity and the optical absorption were measured. The conductivity of the emaraldine salt form decreases upon exposure to basic gases such as NH3. The colour of the template is changed from green to blue concomitantly. The changes of absorbance and the conductivity were proportional to the gas pressure, while with acidic gases the opposite changes occur. Corresponding changes were observed for reducing and oxidising gases also. With the suitable choice of the polyaniline form it is therefore possible to fabricate electrical and optical sensors for gases that are important environmental pollutants. Since most of the above forms of polyaniline are stable under remote and hostile environmental conditions, these sensors are attractive for the monitoring of industrial atmospheres and those at which geological changes take place. The performance of common gas sensors based upon semiconducting oxides and membranes in remote andlor hostile environments is not very satisfactory.
- ItemNon medical risk factors of low birth weight(University of Peradeniya, 1998-11-07) Kumarasiri, P. V. R.Many research works have been conducted to identify the possible obstetric and medical risk factors of low birth weight. Few studies have been done to identify the possible non medical risk factors. Having understood the importance and the gravity of the problem, this study was planned to identify the demographic, socioeconomic and environmental factors associated with the birth weight. This was a follow up study to find out the association between the birth weights and the demographic, socio-economic and environmental factors. Demographic variables were the age of the father and mother, number of children in the family, ethnicity and the religion of the father, height of the father and mother in cent meters. The socio-economic data were occupation, education of the parents, monthly income of the family. The environmental data were the source of water supply and the type of toilet facilities available, ventilation of the bedroom, per person cubic area of the bedroom, condition of the roof, walls, and floor of the house. In addition to this information, smoking habits of the father and the other family members, and the alcohol consumption of father was collected. Mothers residing in the Hindagala Community Project Area, who have delivered babies from 1st of September 1997 to 30th of August 1998, were recruited in this study. Mothers who had known obstretic and medical causes of low birth weight and pre term babies were excluded from the study. There were 301mothers qualified for the enrolment in the study. Of the 310 births occurred in the area 71 had less than 2500 grams, calculated 23.6%. Among the 18 variables (demographic, socio-economic and environmental) studied, the multiple regression model identified only three statistically significant variables. They are the father's occupation, mother's education and the number of children at home. This indicate the babies born to the families where the father is a manual or skilled labourers are more prone to get low birth weight babies compared to the other occupations. On the other hand the birth weight increases with the mother's educational levels. The results also revealed that the birth weight of the second baby of the family was more than the first baby.
- ItemMulticriteria fuzzy optimisation of structural systems(University of Peradeniya, 1998-11-07) Dissanayake, P. B. R.There are a number of different characteristic objectives which in practical structural design problem designers have to consider. Each objective is evaluated relative to the other objective functions being considered. Conflicts can arise between these objectives, for example, economy versus safety and functionality. Moreover, the value of each objective function has to obtain client and/or general consent, as well as satisfy the designer's preferences and design emphases. Furthermore, relative evaluations of these objectives have some fuzziness. Therefore, designers are always faced with determining a best-compromise solution by evaluating each different characteristic objective relative to the others being considered, whilst satisfying the design requirements. This optimum decision-making problem can be recognised as a multicriteria optimum design problem with fuzziness. This study proposes an efficient and systematic multicriteria fuzzy optimum design method which can deal with multiobjectives, fuzziness in the decision-making, design emphases, designer's preferences and so on. The proposed design method is developed using suboptimisation, introduction of measure membership functions and fuzzy decision-making techniques. Each objective function is suboptimised first for all discrete sets of common design variables and design parameters. To make the relative evaluation of suboptimised data of objective functions rationality and systematically, and involving the fuzziness in the decision- making process and design emphases, the measure membership functions are introduced for all objective functions. The membership functions of the suboptimised objective functions are determined simply using the corresponding measure membership functions as datum. A hybrid decision-making process is deve\ojled combi.ning the wei.ghted operato! meiliod, comparison processes of maximum membership values and backward interpolation processes for the determination of the global optimum solution. The proposed design method is applied to a large-scale prestressed concrete bridge system in which the two primary objectives to be considered are the total expected cost after an earthquake and the aesthetics of the bridge system. The total expected cost is calculated as the sum of the suboptimized total construction cost of the bridge system and the expected losses caused by collapse of bridge system due to an earthquake. The expected losses are assumed to be calculated as a product of certain amount of social losses, which is the sum of the cost of demolition after collapse and all other expenses directly or indirectly involve due to the failure of the bridge system, and failure probability of the bridge system. Since the failure probability of the bridge system is affected so much by the safety parameter used in the design of substructures, the safety parameter is dealt with as the design parameter, while the span ratio and web height are dealt with as the common design variables. The bridge system is suboptimized on the total construction cost at discrete combinations of span ratio web height and safety parameter. The measure membership function of total expected cost is introduced by inspecting the total expected cost at all discrete combinations of span ratio, web height and the safety parameter. The membership values of total expected cost are determined simply using the measure membership function as datum. The measure membership function of aesthetic of the bridge system and the membership values for every discrete span ratio and web height are introduced by comparing the aesthetics of corresponding perspectives of the bridge system relatively.