Browsing Engineering by Issue Date
Now showing 1 - 8 of 8
Results Per Page
- ItemThe effect of mean stress on the high-temperature fatigue behaviour of SAE 1045 steel(Elsevier B V, 2000-06-26) Christa, H .J; Wamukwamba, C. K; H. Mughrabic, H.Specimens of the mild steel SAE 1045 in normalized condition were subjected to stress-controlled push-pull fatigue tests at temperatures ranging from 20 °C to 375 °C. Up to about 250 °C, the steel shows a decrease in cyclic strength and in the number of cycles to failure Nf with increasing temperature. A further increase in temperature leads to an increase in strength due to dynamic strain ageing (DSA) which reaches its maximum effect at a temperature TDSA,max of about 325 °C. As a consequence of the strongly reduced plastic strain amplitude, a maximum of the cyclic lifetime could be observed at a temperature close to TDSA,max. Tests with superimposed mean stresses varying from σm = − 80 MPa to σm = +60 MPa showed that a positive (tensile) mean stress generally increases the plastic strain amplitude and reduces the fatigue life and vice versa. The study of the microstructure revealed dislocation arrangements in the form of debris/bundle structures at TDSA,max and cell structures below and above the temperature range of DSA. At a given temperature in this range, positive mean stresses promote the formation of a cell structure because of the superimposed cyclic creep deformation taking place.
- ItemStochastic Analysis of Wire-Connected Round Timber Trusses Edward(University of Zambia, 2001) Lusambo, EdwardRound timber, as a by-product of forest thinning, can be used for construction of innovative and attractive wooden structures. It forms an inexpensive source of construction material for agricultural structures in developing countries. Several methods of connecting round timber have been proposed and investigated world-wide. This paper considers a method that uses flitch plate and wire lacing connections to achieve stable, low-cost and durable round timber structures. For the structural designer, however, it is also necessary to have methods for structural analysis of such structures. This paper discusses a stochastic finite element analysis procedure that was developed and used to analyse round timber trusses made from eucalyptus poles. Static load versus displacement / characteristics of the trusses were investigated using full-scale trusses. In the deterministic analysis, the wire-connected joints developed for the purpose were modelled using semi-rigid connection elements. The effects of slip at the joints, and the effects of creep and joint movement over a long time were incorporated in the analysis. In the experimental set-up, only the deflection of the mid-point of the bottom chord of the truss was measured. It was observed that the results from the deterministic analysis compared well to full-scale truss tests. Keywords: Timber structures, round timber, stochastic analysis, limit states design.
- ItemMechanical and physical properties of plantation grown timber in Zambia(University of Zambia, 2004-07-18) Mulenga, Micheal; Lusambo, EdwardZambia is endowed with thousands of square kilometers of land on which both plantation grown and indigenous species of timber flourish. The Zambian standard on structural use of locally grown timber. ZS 032,gives physical and mechanical properties for several indigenous species but only two plantation grown species, namely Eucalyptus Grandis (blue gum) and Pinus Kesiya. In view of the economic potential of plantation grown timbers. such as controlled growth and development of plantations and processing plants. country-wide, it is necessary to enhance the utilization of these species for structural, carpentry and other purposes. Greater structural usage. however, can only be reali=ed after determination and dissemination of the physical and mechanical properties. This paper presents test results for physical and mechanical properties of four plantation grown timbers, Eucalyptus Grandis, Eucalyptus Cloesina, Pinus Kesiya, and Pinus Oorcapa, grown by Copper belt Forestry Company The tests were carried out at the Civil and Environmental Engineering laboratories of the University of Zambia. The physical and mechanical properties determined for Eucalyptus Grandis and Pinus Kesiya, exceed those specified in ZS 032 (1986, when the totalfa ctors of safety are applied. The physical and mechanical properties determined in this study for Eucalyptus Cloesina and Pinus Oorcapa are reasonable estimates. in the absence of code values. Keywords: softwood, hardwood, clear specimens, plantation grown, indigenous species, radial, tangential, perpendicular and parallel to grain.
- ItemStrength and Physical Properties of Zambian Grown Eucalyptus Poles(University of Zambia, 2005-05-20) Lusambo, EdwardPoles used for overhead power and telecommunication lines and buildings are specified by species, physical properties such as moisture content, and dimensions as well as strength properties such as ultimate load. These properties vary from species to species. Design stresses may be determined using testing methods specified in various codes to arrive at grade stresses. For example, in Australia and New Zealand, the poles are assigned one stress grade higher than the highest grade of the same sawn timber. Design stresses jar American preservative-treated round poles were established following tests specified by ASTM Standards D3200. In the United Kingdom, BS 1990 Parts 1 and 2 give specifications for wood poles for overhead power and telecommunication lines. In Zambia, there is no standard that deals specifically with overhead power and telecommunication lines. However, it is necessary to test Zambian plantation-grown poles and establish basic physical and structural properties. This paper aims to present a method that can be used for for establishing a Zambian standard for poles. Eucalyptus poles are used in fencing, overhead power and telecommunication lines, mine props, support structures, building structures and in the production of sawn timber. In all these uses, the physical and strength properties of the poles are of great importance. This paper presents test results on Eucalyptus grandis and Eucalyptus cloesiana poles which were tested following guidelines for testing poles used for overhead power and telecommunication lines are contained in BS 1990 Part 1. Keywords: Poles; Eucalyptus; Structural properties; Testing
- ItemA dynamic model for naturally ventilated Low cost poultry houses(University of Zambia, 2007-10-22) Lusambo, EdwardVentilation as a method of controlling the internal environment in poultry houses serves two main purposes. It provides the desirable levels of temperature and humidity to achieve good poultry performance and it also provides a desired amount of fresh air, without drafts, to all parts of the building. Ventilation also controls ammonia levels to limits appropriate for operating personnel. This paper discusses a simulation model developed to study the dynamic changes of the internal thermal environment in low cost poultry houses in Zambia. The model is based on the interaction of various internal, external and building construction related parameters. The model can be used to predict the temperature in a naturally ventilated poultry house for a given set of input parameters. Furthermore, it can calculate the heating or cooling load required to keep the temperature at desired levels for the birds. It can also be used to study the effects of changing various parameters on the internal thermal environment. The model was validated using data obtained from an open-sided naturally ventilated poultry house housing birds at an average age of 8 weeks. The model was able to predict the internal temperature closely to the measured values. Keywords: Natural ventilation, Dynamic modelling, Poultry houses
- ItemA framework to address the problem of mobile phone theft: a case study of the telecommunications sector in Zambia(University of Zambia, 2020) Akombwa, Benaiah SimuiAs in most nations in Africa, the problem of mobile or cell phone theft is something that local authorities in Zambia are desirous to address. With advances in technology, phones have gotten smaller and of high value. Motivated by this rising challenge, this study purposed to propose an appropriate framework that would help reduce phone thefts. A cross-sectional survey was carried out in which 420 structured questionnaires were distributed among Lusaka residents in four different districts using a multi-stage cluster sampling method. Interviews were also done with various stakeholders such as the Mobile Network Operators, ZICTA and the Police. Data was analysed descriptively using SPSS version 16. Results of the study revealed a 67% phone theft prevalence and confirmed that phone thefts in Zambia have been on the rise, without any seemingly workable remedy from the authorities to counter the issue. Further, Samsung mobile phones topped as the most frequently stolen followed by Nokia. Currently, victims of lost or stolen phones report the matter to the Police then the law enforcement wing tries to recover the phone through a manual process. This study proposed to develop a framework that would help enhance collaboration by interested parties and eventually reduce the prevalence of phone theft by ultimately blocking the handset and preventing its reuse in Zambia once reported stolen. Keywords: Mobile Phone theft, CEIR Zambia, Addressing Cell Phone Theft in Zambia, IMEI Blacklisting in Zambia
- ItemLow-cost high-quality roof construction with round timber(University of Zambia, 2020-05-03) Lusambo, EdwardPole timbers provide an inexpensive source of structural timber in many developing countries and are widely used for traditional buildings. The use of round timber has considerable potential in comparison to the use of sawn timber because of its higher structural strength and its low material cost. There are, however, problems associated with working with non-uniform sections and also with jointing. The traditional methods ofjointing using sisal rope or strips of bark in rural areas do not permit the full strength of the poles to be utilised. Improved low cost methods of connecting poles could lead to stronger structures and more economical use of materials. This paper reviews aspects relating to the use of round timber and describes the design and fabrication of some low-cost, yet high-quality structural systems suitable for roof structures of modern buildings. Keywords: Round timber, Roof structures, Connections, Jointing methods
- ItemChallenges faced In water infrastructure projects implemented by the Zambian government.(The University of Zambia, 2023) Mwale, Marjorie MisoziThe Government of the Republic of Zambia (GRZ) has been undertaking water infrastructure development projects and programs at various levels in both rural and urban areas through the Ministry of Water Development and Sanitation (MWDS) and other line ministries. The implementation of these projects by the Zambian government has come with many challenges, which has led to the non-completion of some projects. In the past 10 years, a number of these projects have been abandoned at various stages of completion. However, no study has been conducted to investigate the cause of this. This study was undertaken to identify challenges that contribute to failures in fully implementing water projects implemented by the Zambian government. The general objective of this study was to establish challenges faced in implementing water infrastructure development projects by the Zambian government. The study was carried out by interviewing different officers from government and donor agencies involved in the water infrastructure projects at different stages, Non-Governmental Organizations (NGOs) and consultants, literature review of the various books and reports and also observation of selected water infrastructure projects. The results indicated that the major challenges of implementation were in the formation and operation of Project Management Teams, lack of financial resources and lengthy procurement process. It was therefore recommended that the Project Management Team should have fully dedicated team members to work solely on the project and must have no government interference, also government should completely fulfil its financial obligations to the projects and the procurement process to be revised to improve efficiency and effectiveness. Keywords: Water infrastructure projects, project management team, government, challenges, implementation.