Analysis of restricted earth fault relay application within a shunt capacitor bank design impacting on protection stability
- Authors: Minkley, Warick
- Date: 2013
- Subjects: Electric power systems -- Protection , Electric power transmission -- Equipment and supplies -- Protection
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9604 , http://hdl.handle.net/10948/d1021106
- Description: This research is aimed at analyzing the performance of the restricted earth fault relay used on a 400kV capacitor bank scheme used on the Eskom Transmission network. After the commissioning of two Capacitor Banks using the above mentioned scheme design the plant was energized. As a result of the energization the Shunt Capacitor Bank (SCB) then experienced spurious trips. The cause of the trips was found to be the operation of the restricted earth fault relay. In this research project, restricted earth fault protection on SCBs in the Eskom Transmission environment will be the area of interest. The proposed research will analyze the current SCB protection scheme in service specifically looking at the restricted earth fault circuit design and relay performance. An equivalent model of the SCB from primary plant perspective based on theory will be derived. Recording and analyzing of Comtrade transient waveforms respectively, when the bank is nergized, will be done in order to provide a reference base to work from. Manual alculations of various parameters from the derived model including transient inrush currents and fault currents will be performed to access applicable scheme parameters. Further calculations will include the voltage setting for the restricted earth fault relay. As a result of the analysis a recommendation will be made on a viable solution or a revised design will be put forward, based on the results, to improve the scheme’s performance. The protection scheme is used on the two 400kV 100MVAR capacitor banks 11 and 12 at Hydra Substation.
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- Date Issued: 2013
Analysis of the reliability for the 132/66/22 KV distribution network within ESKOM’s Eastern Cape operating unit
- Authors: Pantshwa, Athini
- Date: 2017
- Subjects: Electric power distribution Electricity -- Supply -- Engineering , Smart power grids
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/19750 , vital:28953
- Description: A stable and reliable electrical power supply system is an inevitable pre-requisite for the technological and economic growth of any nation. Due to this, utilities must strive and ensure that the customer’s reliability requirements are met and that the regulators requirements are satisfied at the lowest possible cost. It is known fact around the world that 90% of the customer service interruptions are caused due to failure in distribution system. Therefore, it is worth considering reliability assessments as it provides an opportunity to incorporate the cost or losses incurred by the utilities customer as a result of power failure. This must be considered in the planning and operating practices. The system modelling and simulation study is carried out on one of the district’s distribution system which consists of 132 kV, 66 kV and 22 kV network in Aliwal North Sector ECOU. The reliability assessment is done on the 22, 66 and 132 kV system to assess the performance of the present system and also predictive reliability analysis for the future system considering load growth and system expansion. The alternative which gives low SAIDI, SAIFI and minimum breakeven costs is being assessed and considered. The reliability of 132 kV system could be further improved by constructing a new 132 kV line from a different source of supply and connecting with line coming from another district (reserve) at reasonable break even cost. The decision base could be further improved by having Aliwal North Sector context interruption cost. However, the historical data which may be used in Aliwal North Sector to acquire interruption costs from the customers are being proposed. The focus should be on improving the power quality on constrained networks first, then the reliability. Therefore for the Aliwal North power system network it is imperative that Eskom invest on the reliability of this network. This dissertation also analysed load reflected economic benefit versus performance expectations that should be optimized through achieving a balance between network performance (SAIDI) improvement, and total life cycle cost (to Eskom as well as the economy). Reliability analysis conducted in this dissertation used Aliwal North power system network as a case study; the results proved that the system is vulnerable to faults, planned and unplanned outages. Reliability evaluation studies were conducted on the system using DigSilent software in conjunction with FME. These two models gave accurate results with acceptable variance in most indices except for the ENS where the variance was quite significant. It can be concluded that DigSilent results are the most accurate results in all three reliability evaluation scenarios for the Aliwal North Power System, best interpretation being that of DigSilent.
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- Date Issued: 2017
Applicability of public-private partnership in provision of water infrastructure to central coastal Namibia mines
- Authors: Kavela, Lukas Tangeni Taukondjo
- Date: 2011
- Subjects: Water-supply -- Namibia , Public-private sector cooperation -- Namibia -- Water-supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9701 , http://hdl.handle.net/10948/d1015641
- Description: This study investigated the potential application of Public-Private Partnerships (PPPs) in water supply, taking cognisance of the water demand and supply in the Central Coastal Namibian (CCN) mines. NamWater does not meet demand for the existing and planned mines in the CCN. Primary objective was to investigate and analyse water demand and supply as well as the effectiveness of PPP as a solution by exploring its potential, successes and challenges. In order to obtain relevant information, literature review was used to collect evidence on water demand and supply in the north-central Namibia as well as the application of PPP in provision of water supply. Multi-case studies were carried out on three operational mines, namely; Rio Tinto Rössing Uranium Mine, Langer Heinrich Uranium Mine and Areva Trekkopje Uranium Mine to attain empirical data on water supply requirements. A self-administered questionnaire was used to collect the data supplemented by interviews with NamWater, operational mines within the study area, government institutions, and knowledgeable consultants on water and the mining environment. The key findings included: institutional weaknesses and lack of legislation frameworks to support PPP projects; skills shortage; and financing problems were identified as major challenges. Results further show that these problems could be resolved by effectively implementing a PPP approach, whereby the Special Purpose Vehicle (SPV) enters into a contract with the public authority. The study concludes that there is a need to increase water output to meet current and future supply requirements to these mines. This situation should be addressed by all stakeholders, from government to private sectors. The study recommends that a sea water desalination plant should be developed to increase water capacity supply to the existing operational and prospective mines in the area. The PPP approach is proposed as a possible solution to water supply infrastructure service delivery problem to ensure long-term water security in the CCN mines.
- Full Text:
- Date Issued: 2011
Application of the theory of critical distance technique to predict fracture toughness in friction stir welded Ti-6Al-4V sheet
- Authors: Rall, William Henry
- Date: 2017
- Subjects: Friction stir welding Fracture mechanics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20351 , vital:29266
- Description: With modern day socioeconomic pressures to deliver more cost effective, higher performance and energy efficient mechanisms and structures, light weight design is coming more to the forefront of design methodologies. These methodologies need to apply lightweight materials in unison with a defect tolerant design strategy. Titanium is certainly not a new material and was used in large quantities in the 1960’s and ‘70s, but mostly in military applications. The main drawback of this material was cost, however due to current design needs as mentioned the consumption of the material is rising rapidly. Friction stir welding is by no means a new technique anymore, however, relatively speaking it is still in its infancy when compared to other traditional welding techniques. It has been applied mostly to low melting temperature metals, more specifically aluminium; however, its application to higher melting temperatures has started to enjoy more attention over the last few years. The lower temperatures at which the weld occurs, when compared to conventional processes, is the main reason for applying this technique to materials melting at a higher temperature such as titanium. Fracture mechanics allows modern-day designers and maintenance engineers to operate structures with an inherent flaw. These flaws may be due to geometric features of the design; fabrication defects or defects such as cracks that have developed over time within an operational structure. Fracture mechanics has evolved significantly since Griffith first proposed it in the early 20th century. The application of the method is often complex and determining the material properties for fracture resistance can be problematic and costly. Many techniques have been proposed over time to simplify the application of this method and one of these techniques would be the theory of critical distance. Since the technique is relatively new and has mostly been applied to more brittle materials, this study aimed not only to apply this technique to a more ductile material but additionally to one that is classified as a sheet material. The initial tests of this study investigated if a common convergent point could be determined by using three notches varying in size. The technique does not have a standard that governs its application. The initial tests did not yield a common intersecting point thus a second study was applied to see if sample width would influence the results. The results from the study indicated that wider samples seemed to yield similar apparent fracture toughness results, however a common convergence point could still not be established. This prompted a more in-depth study which involved various sample widths coupled with varying notch depths. Sharper notches were also applied and samples with controlled cracks were also tested. The results clearly showed that as the plastic zone size increases in relation to the ligament length of the sample, the critical distance becomes larger. The results also suggested that it would perhaps be best to use sample sizes with notches which allow fracture of the sample before the nett section stress reaches the material’s yield strength. The final tests involved testing the friction stir welded material. Various other studies were also done to corroborate the fracture toughness results. The stress relieved samples showed a reduction in the fracture toughness due to possible precipitation hardening during the stress relieving heat treatment process. The welded material showed an increase in the apparent fracture toughness when compared to the parent plate. The results indicate that residual stresses have an influence on the fracture toughness. In terms of the critical distance, it would appear that the value stays unchanged from the parent plate to the welded material; however, what is significant was that the value seemed to stay more or less constant as long as the nett section stress of the notched samples stayed below the yield stress of the material.
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- Date Issued: 2017
Applications of thermal spray technology for surface protection
- Authors: Gorlach, I A
- Subjects: Metal spraying , Surfaces (Technology)
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/21866 , vital:29795
- Description: With the rapid development of modern industry, the quality of surfaces of structures, products and components is important in terms of many aspects such as efficiency, reliability, appearance, maintenance costs and economy. A local failure on the surface usually causes the entire component to be rejected or it may lead to a failure of a machine or structure. It is estimated that in developed countries, the loss caused by corrosion is up to 2-4% of gross national product [1]. Thus, many countries have made great efforts to improve the surface performance of parts in order to enhance the reliability of mechanical equipment and prolong their service life.
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Applying a framework for IT governance in South African higher education institutions
- Authors: Viljoen, Stephen
- Date: 2005
- Subjects: Computer security , Universities and colleges -- Computer networks -- Security measures -- South Africa , Data protection
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9739 , http://hdl.handle.net/10948/416 , Computer security , Universities and colleges -- Computer networks -- Security measures -- South Africa , Data protection
- Description: Background: Higher Education (HE), through HE Institutions, plays a very important role in society. There is thus a need for this sector to be well managed, especially with regards to planning, organising, and controlling. Corporate Governance has received a lot of attention in recent times, especially to engender trust on the part of the stakeholders. There are many similarities, but also significant differences in the governance of HE institutions and public companies. Information Technology (IT) plays an extremely important role in the modern organisation, creating huge opportunities, but also increasing the risk to the organisation. Therefore, effective governance of IT in HE Institutions is of great importance.
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- Date Issued: 2005
Asset management plan for Coega Development Corporation
- Authors: Vabaza, Zolisa
- Date: 2012
- Subjects: Production management , Product life cycle
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9682 , http://hdl.handle.net/10948/2113 , Production management , Product life cycle
- Description: Asset Management, which evolved from maintenance management, is a set of processes, tools and measures that provide a shared understanding of an organisation’s physical assets. The process of asset management involves creation of a register of assets and recording of details of planned work. It also covers scheduling and recording of work done in order to create financial and technical history of assets. The life cycle of an asset consists of the acquisition operation, maintenance and disposal phases. These four aspects of an asset’s life represent the high level framework for asset management. This framework is crucial in development of asset management plans. The plan in turn, creates a road map for asset management excellence. By optimising the performance of asset management practices and processes a positive contribution can be made to the profitability of an organisation. The objective of this study was to develop a plan for the Coega Development Corporation (CDC) that would assist in management, maintenance, tracking and replacement of assets. The research primarily focused on the asset management requirements within the organizational context. The methodology employed in the study included a review of the relevant literature and case study conducted at CDC. The case study approach was very appropriate as it dealt with the current situation at CDC. Primary data was collected through interviews. Secondary data was collected from books, journals and other sources. Data was collected in words instead of numbers. The findings show that the CDC does not have an Asset Management Plan which results into the lack of information in the current asset register, a lack of specialist information systems, a lack of resources and an absence of a planning function in the skills sets of various units within the organisation. The Asset Register should work as a basic system for management of assets. The findings show that asset management can be used to comprehensively address the relevant elements of the organisations’ assets framework.
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- Date Issued: 2012
Autonomous guided vehicle for agricultural application
- Authors: Chikosi, Gerald
- Date: 2014
- Subjects: Autonomous vehicles , Farm equipment
- Language: English
- Type: Thesis , Masters , MEngineering (Mechatronics)
- Identifier: vital:9652 , http://hdl.handle.net/10948/d1016164
- Description: With the world's population expected to reach nine billion by 2050, agricultural production will have to double to meet this growing demand. Hence, a need for better infrastructure to enhance farming efficiency becomes apparent. There are a number of solutions that have been developed to date that are commercially available. They range from genetically modified seeds and bio/green fertilizers to advanced farming machinery amongst others. However most of the farming equipment developed has drawbacks such as: heavy weight – this leads to reduced yields due to soil compacting; human dependency – constant monitoring and controlling is needed; light dependency – excludes usage during the night or when visibility is poor. Therefore, a possible solution will be researched to enhance the evolution of farming equipment. Furthermore, a model will be developed for testing and verifying the research.
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- Date Issued: 2014
Building Information Modelling as a catalyst for an Integrated Construction Project Delivery culture in South Africa
- Authors: Froise, Timothy
- Date: 2014
- Subjects: Construction industry -- South Africa , Construction projects -- South Africa , Acculturation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9716 , http://hdl.handle.net/10948/d1020872
- Description: The importance of technology in construction partnering agreements has been recognised as a vital part of integrated project delivery (IPD) philosophy. Building information modelling (BIM) is increasingly being used by consultants in South Africa during the design phase of construction projects. However, its use is generally not aimed at an integrated project delivery approach, but rather as a tool to generate documentation, as BIM is generally more efficient than traditional computer aided design (CAD) software. For the full benefits of BIM to be realised, a greater degree of acculturation is required between construction project organisations (CPOs). The current cultures of CPOs are separationist in nature and tend to inhibit acculturation within the industry. BIM provides a central source of information that can improve communications between CPOs and foster a collaborative culture. The research examines IPD and BIM in the South African context and investigates how BIM can contribute to IPD. A survey was conducted among registered contractors from the three top grades and architecture practices from two regions in South Africa. The survey was placed in context by a case study that analysed the use of BIM and the resulting communication network seen in a public works project using typical procurement methods. The associated problems with the current accepted paradigm are illuminated by the research.
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- Date Issued: 2014
Business problems facing potential emerging contractors in CIDB grades 5 to 7
- Authors: Pretorius, Albertus Johannes Hendrik
- Date: 2016
- Subjects: Building trades , Project management , Construction industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3459 , vital:20432
- Description: Considering the vital part which the construction industry plays in the economy of South Africa, as well as the objectives of the reconstruction and development thereof, the failure of contractors, despite all the interventions to identify and eradicate the root of the problem, is a matter of great concern. In November 2000, the Construction Industry Development Board Act (2000) was promulgated which led to the inception of the cidb with a mandate to implement an integrated strategy for the reconstruction, growth and development of the construction industry. The matter of contractor development has been widely studied and investigated since the inception of the cidb in 2000. However, the purpose of this study was to focus on the business problems faced by Grade 5 to 7 CE / GB Potential Emerging Contractors, with regard to construction organisations that make the move from small to medium businesses. The intention was to contribute to the successful transition from small to medium businesses by means of structured initiatives. In order to achieve this, a new business strategy must be adopted. It was therefore necessary to extensively consider the surface and core competencies required for making the transition. Liquidity problems that the transition entails were explored, as well as contractor misconceptions with regard to contractor development. In the course of the study, unethical practices and entitlement issues experienced in the built environment and the effect of this on contractor success were explored. The study aimed to recommend a structured framework for co-ordination between assistance, mentorship, contractor needs, client departments, cidb NCDP best practice guidelines and the most important of all, self-empowerment. This study further endeavoured to find possible solutions regarding the assistance requirements, as well as self-empowering objectives for emerging contractors taking the challenging step from small to medium business and by implication, becoming sustainable contractor enterprises in Grades 6 to 8. Political imperatives need to be weighed against the high unemployment rate. The Gross Fixed Capital Formation (GFCF) indicates that there are not enough sustainable contracting opportunities to allocate to Contractor Development Programmes (CDPs). This is aggravated by the tendency that too many hopeful aspirant entrepreneurs, lacking construction surface and core competencies, are seeing the built environment as an easy industry to enter. Just less than 50% of cidb registered contractors exited the register of active contractors during the last ten years ending 2nd quarter 2015. 45% exited during the last five years. This indicates that there is a serious sustainability problem in the built environment. Considering the GFCF contractor opportunities there are too many cidb registered contractors. However, enterprise failure is not only an Emerging Contractor (EC) problem, but occurs across the board. A dangerous notion that the large national construction firms should no longer qualify for public contracts can have disastrous implications for an already embattled industry. Large national firms are the trend setters in the built environment, which coach the much needed construction surface and core competencies. If upgrading is the measure of success the current CDP statistics do not confirm that the strategic objectives of the National Contractor Development Programme (NCDP) are being achieved. All contractors, including black owned contractors, are faring substantially better than their EC counterparts participating in CDPs. Upgrading should carry less weight and sustainability and high performance should become the focus. A serious lack of construction surface and core competencies was identified. If contractor development is the objective the structure of the cidb grading system should be reviewed. It is recommended that the broad CDP hierarchical structure should streamlined and partly privatised to focus on the core strategic objective of contractor development.
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- Date Issued: 2016
Business process security maturity: a paradigm convergence
- Authors: Box, Debra
- Date: 2008
- Subjects: Management information systems , Reengineering (Management) , Organizational change , Systems engineering , Information resources management
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9785 , http://hdl.handle.net/10948/722 , Management information systems , Reengineering (Management) , Organizational change , Systems engineering , Information resources management
- Description: Information technology developments in software and hardware have enabled radical changes in information systems, culminating in the paradigm Business Process Management. There has been a concomitant rise in the importance of information security and security engineering due to the increased reliance by society on information. Information is seen as a critical success factor which needs protection. Information security is the response to increased hazards created through recent innovations in Web technology and the advent of intra and inter enterprise-wide systems. Security engineering is based on a variety of codes of practice and security metrics which aim at ameliorating these increased security hazards. Its aim is to produce a balanced set of security needs which are integrated into the system activities to establish confidence in the effectiveness of the security counter-measures. It is generally accepted that security should be applied in an integrated approach, for example, in Information Systems development. This has proved to be a noble thought but is the exception to the rule. Security, historically, is generally applied as an after-thought in an Information Technology implementation. This motivated the concept of formulating a model of integrating security inherently within the paradigm of BPM. The overarching requirements of the model are to align the overall organisational security initiatives and ensure continuous improvement through constant evaluation and adaptation of the security processes. It is the intention of this research to show that these requirements are achievable through aligning the process management methodology of BPM, with the security paradigms of Information Security Management (using the ISO 17799 standard) and security engineering (using the Systems Security Engineering Capability Maturity Model – SSE-CMM). The aim of the Business Process Security Maturity model as the output of this research, is to link the SSE-CMM, as the security metric and appraisal method, to the ISO 17799 security standard, which provides the guidance for the information security management framework and security control selection, within the Business Process Management environment. The SSE-CMM, as the security version of the Capability Maturity Model, provides the necessary strategy to control the security engineering processes that support the information systems and it maintains that as processes mature they become more predictable, effective and manageable. The aim of the model is to provide an integrated, mature security strategy within the business process and monitor and correct the security posture of the implemented counter-measures.
- Full Text:
- Date Issued: 2008
C3TO : a scalable architecture for mobile chat based tutoring
- Authors: Butgereit, Laura Lee
- Date: 2010
- Subjects: Intelligent tutoring systems , Instructional systems -- Design
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9746 , http://hdl.handle.net/10948/1511 , Intelligent tutoring systems , Instructional systems -- Design
- Description: C³TO (Chatter Call Centre/Tutoring Online) is a scalable architecture to support mobile online tutoring using chat protocols over cell phones. It is the scalability of this architecture which is the primary focus of this dissertation. Much has been written lamenting the state of mathematics education in South Africa. It is not a pretty story. In order to help solve this mathematical crisis, the “Dr Math” research project was started in January, 2007. “Dr Math” strove to assist school pupils with their mathematics homework by providing access to tutors from a nearby university to help them. The school pupils used MXit on their cell phones and the tutors used normal computer workstations. The original “Dr Math” research project expected no more than twenty to thirty school pupils to participate. Unexpectedly thousands of school pupils started asking “Dr Math” to assist them with their mathematics homework. The original software could not scale. The original software could not cater for the thousands of pupils needing help. The scalability problems which existed in the original “Dr Math” project included: hardware scalability issues, software scalability problems, lack of physical office space for tutors, and tutor time being wasted by trivial questions. C³TO tackled these scalability concerns using an innovative three level approach by implementing a technological feature level, a tactical feature level, and a strategic feature level in the C³TO architecture. The technological level included specific components, utilities, and platforms which promoted scalability. The technological level provided the basic building blocks with which to construct a scalable architecture. The tactical level arranged the basic building blocks of the technological level into a scalable architecture. The tactical level provided short term solutions to scalability concerns by providing easy configurability and decision making. The strategic level attempted to answer the pupils questions before they actually arrived at the tutor thereby reducing the load on the human tutors. C³TO was extensively tested and evaluated. C³TO supported thousands of school pupils with their mathematics homework over a period of ten months. C³TO was used to support a small conference. C³TO was used to encourage people to volunteer their time in participation of Mandela Day. C³TO was used to support “Winter School” during the winter school holiday. In all these cases, C³TO proved itself to be scalable.
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- Date Issued: 2010
Causes and effects of non-payment of residential property rates in Mahikeng
- Authors: Asianoah, Rexford Kofi
- Date: 2014
- Subjects: Debts, Public -- South Africa -- Mahikeng , Municipal default -- South Africa -- Mahikeng , Public utilities -- South Africa -- Mahikeng , Collecting of accounts -- South Africa -- Mahikeng
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9674 , http://hdl.handle.net/10948/d1020076
- Description: One of the major sources of income to South African Municipalities is property rates. Income generated from property rates is meant to develop and deliver services to residents living in the said Municipal area. The main aim of the research was to identify the causes and effects of the non-payment of residential property rates, and also to develop workable strategies to maximise the collection of residential property rates in order to ensure developmental growth sustenance, specifically in Mahikeng Municipal area. Related literature was reviewed on the non-financial viability of Municipalities, maintenance of public infrastructure, service delivery and Municipal development plans in establishing the relationship with non-payment of residential property rates. Four hypotheses were set to guide the research with two testing positive with high level of confidence using the chi square method of testing. The research methodology employed in the research was mainly quantitative where the results and findings obtained from the questionnaire were statistically analysed. The research revealed that: The Mahikeng Local Municipality has failed to find the right medium to send rates bills to clients on time, is not taking active responsibility to recover rates debts, does not provide quality service delivery and the reluctance by locals to pay their property rates. The effects thereof, are the inability of the Municipality to deliver effective and efficient services, lack of maintenance of public infrastructure and development in the area. By implementing various options such as email, sms and the post to send rates bills to property owners, by employing different payment options, for example debit orders, transfers, bank deposits and discounts for property owners and embarking on periodic public awareness campaigns in educating the community regarding the importance of payment of property rates could serve as effective mechanisms to address the non-payment of residential property rates faced by the Mahikeng Local Municipality.
- Full Text:
- Date Issued: 2014
Challenges facing the state of construction health and safety management practices within the Eastern Cape: a case of the Sarah Baartman District
- Authors: Mafuya, Nomakhwezi
- Date: 2018
- Subjects: Industrial safety -- Management , Construction industry -- South Africa -- Eastern Cape Construction industry -- Safety measures -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31532 , vital:31504
- Description: The construction industry has a poor Health and Safety (H&S) record globally and South Africa is no exception (Haupt, 2016: 1). The construction industry is integrally a high-impact and dangerous industry with less than a 50% ratio in compliance to H&S standards (PricewaterhouseCoppers (PwC), 2016). This study is aimed towards evolving a solution to mitigate the fatalities and injuries, occupational health hazards, non-compliance with legislation and design originated hazards and the reoccurring problems experienced by the Eastern Cape Department of Public Works (ECDPW) on projects. Literature points out that H&S performance is attributable to a lack of management commitment, inadequate supervision, inadequate H&S training, and lack of worker involvement (construction industry development board (cidb), 2009: 36). Huang and Hinze (2006: 179) contend that clients‟ participation in project H&S can significantly influence project performance. Various researchers have amplified the importance of leadership roles and involvement of clients in H&S. A quantitative survey and qualitative inquiry were utilised to gather and analyse data within the Eastern Cape province of South Africa. Three questionnaires were developed and distributed to a target population, and interviews were conducted. The study focuses on seven schools, namely; Stormsriver, Jubilee, Mfesane, Bongweni, David Livingstone, Kaiser Ngxwane and Bethelsdorp, which are on-going for the 2016/2017 financial period during which the research study was conducted. A total of 136 responses were used to analyse the data. All project stakeholders, namely: project managers, contractors‟ site managers, and workers contributed to the study. The frequency of H&S actions varied with each stakeholder dependent on the stage in which they were involved. The study determined that extensive inadequacy of construction expertise in terms of H&S including H&S consultants and departmental H&S personnel, inadequate management and supervision on site, inadequate workers participation, inadequate H&S training, inadequate expertise in H&S management, inadequate designer report, inadequate H&S knowledge and awareness, negligence, unsafe acts, unskilled workers, unsafe conditions, non-compliance with H&S regulations, Safe v Operating Procedure (SOPs) and Safe Working Procedures (SWPs), inadequate commitment of various project stakeholders, ignorance, poor client H&S leadership throughout certain aspects of the ECDPW projects are the primary cause of fatalities and injuries, ill-health, design originated hazards, non-compliance and the reoccurrence of problems. Recommendations were for H&S to be integrated within the Departments internal project systems from project inception to project close out, and to enhance H&S knowledge and skills in order to mitigate the reoccurrences of problems on projects.
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- Date Issued: 2018
Characterisation of dissimilar friction stir welds between 5754 Aluminium alloy and C11000 copper
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
Characterisation of Young's modulus and loss factor of damping materials
- Authors: Nortemann, Markus
- Date: 2014
- Subjects: Elasticity , Simulation methods , Damping (Mechanics)
- Language: English
- Type: Thesis , Masters , MEngineering (Mechatronics)
- Identifier: vital:9662 , http://hdl.handle.net/10948/d1021036
- Description: Given the importance of simulation techniques in automotive engineering, there is a lack of implementation regarding these techniques in the acoustics of damping materials for air-borne sound. Biot’s calculations have proven its abilities to simulate the acoustic characteristics of these damping materials. However, the characterisation of essential structural parameters, such as Young’s modulus and loss factor, in order to conduct Biot’s calculations have been inconclusive. Thus, the primary research objective of this study is to propose a new measurement system for the structural Biot parameters. After a comprehensive literature review has been undertaken on damping materials, as well as measurement apparatuses for Young’s modulus and loss factor of damping materials, two causes of measurement errors have been identified. Unknown stresses in measurement apparatuses and inhomogeneous, polytrophic and viscoelastic behaviour of specimens. A new measurement system that does not affect the specimens with unknown stresses and accounts for their complex behaviour required investigation. Non-contact ultrasound had been selected as a solution to determine the aforementioned parameters, since these methods do not necessarily touch or compress the specimen, which led to unknown stresses and neglection of the complex specimen behaviour with the aforementioned techniques. Although ultrasound had been used to determine structural parameters on various types of materials, it has never been used to measure soft porous damping materials. In order to find possible solutions, various sources using ultrasonics to investigate struc- tural parameters had been reviewed. In order to calculate structural parameters, the longitudinal and transversal wave velocity inside the specimen had to be determined. The main findings showed that non-contact ultrasound will be able to evaluate the Young’s modulus, loss factor as well as Poisson’s ratio. Consequently, it was shown that longitudinal velocity measurements could be conducted using well known transmission measurements. However, well known approaches would not be sufficient measuring the transversal wave velocity in soft damping materials. This problem was addressed with a special gas to be used, with lower sound speed velocity in the fluid than in the solid. Moreso, a new method determining the transversal wave velocity had been found, as it would enable the use of an even larger range of damping materials, especially ones with heavy frames and lower porosity. It will use refracted waves inside the specimen and the determination of the convertion position of the transversal to the longitudinal wave at the rear specimen surface. At the end of the study, hardware components were selected and a test rig was constructed, which should be able to prove that a determination of structural Biot parameters with non-contact ultrasound is possible with less errors instead of using mechanical transfer function systems. The development of measurement software as well as the testing of the measurement system and its validation was not under investigation in this dissertation. This study has expanded on the body of literature knowledge regarding non-contact ultrasound. Furthermore, a significant contribution has been made towards a new measurement system measuring Young’s modulus and loss factor which circumvents errors in mechanical transfer function systems. This will contribute to more precise simulations of damping materials and damped enclosures, which may ultimately result in enhanced efficiency of damping materials as well as the acoustic packaging of cars.
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- Date Issued: 2014
Characterising the stress-life response of mechanical and laser formed titanium components
- Authors: Fidder, Herman
- Date: 2012
- Subjects: Titanium alloys -- Fatigue , Titanium --- Fatigue , Materials -- Mechanical properties
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9634 , http://hdl.handle.net/10948/d1018462
- Description: This dissertation involves the experimental investigation of commercially pure titanium (CP Ti) which was subjected to laser forming and mechanical forming processes. Commercially pure titanium grade 2 was formed to a radius of curvature of approximately 120 mm using three forming procedures, i.e. i) laser forming; ii) mechanical forming (stretched forming) and iii) a combined forming process (laser-mechanical forming). Fatigue testing revealed, for all the forming processes, that samples produced by laser forming performed the best at high load settings. However, mechanically formed specimens performed the best at low load settings, whereas the laser-mechanical process resulted in midway performance between laser and mechanical processing. Considering microstructure vs fatigue; impact vs fatigue; and residual stress vs fatigue; at high load settings it is evident that the microstructure is the dominant contributor to crack initiation and growth. Crack morphology of fatigue samples revealed that secondary cracks (parallel to main crack front) followed the grain boundaries of the Widmanstätten microstructure, whereas irregular secondary cracks grew parallel and through the twinning planes and along the grain boundaries of the equiaxed microstructure. Laser forming resulted in microstructural changes from equiaxed grains to a Widmanstätten structure due to fast cooling rates. Excessive twinning is developed within the equiaxed microstructure after the mechanical forming procedure. This is due to cold working / strain hardening. The combined process shows a combination of equiaxed grains and Widmanstätten microstructure. Residual stress relieved for all forming processes revealed an increase in the magnitude of the residual stress compared to the parent plate and that the maximum values were obtained at the inner radius of curvature (i.e. 118.4 mm). Laser forming revealed the highest values in residual stress whereas the other two processes i.e. mechanical and laser-mechanical forming exhibited an increase midway between the parent plate and laser forming. The second most influential factor with regards to fatigue was the magnitude of the residual stress, especially at medium to low load settings. When considering theoretical models to predict fatigue life it was found that the Goodman model showed the closest relation to the actual fatigue data when considering the entire theoretical curve. Vickers microhardness profiling was applied to the thickness of the samples for the parent plate and all forming processes. No significant hardening occurred due to the forming processes and differences in hardness were considered negligible. Charpy impact testing revealed that the laser formed specimens exhibited the most brittle behaviour when compared to the parent plate results. Mechanical formed specimens showed a slight increase in brittleness compared to parent plate whereas the combined process yielded results midway between the laser and mechanically formed specimens. Mathematical equations are formulated and presented for predicting the fatigue life of CP Ti grade 2 for the parent plate and the three forming processes. This study proved that the laser forming process can be successfully used as a production stage in the forming of CP Ti grade 2.
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- Date Issued: 2012
Characterising the stress-life response of mechanical formed AISI-1008 steel plate components
- Authors: Müller, Ruan
- Date: 2012
- Subjects: Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9616 , http://hdl.handle.net/10948/d1008102 , Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Description: The main purpose of this research project was to determine the fatigue-life behaviour of AISI 1008 sheet steel which has been mechanically formed to a radius of curvature of 120mm and then to correlate the fatigue-life behaviour to that of the parent or “as manufactured” material. During the forming process it was felt important to induce plastic strain through stretch-bending by clamping the sides of a plate sample’s (width) edges in the bending fixture before being bent by a single acting mechanical press. It was determined through actual testing that there was a decrease in fatigue-life when the mechanical formed data was compared to fatigue data of the parent material. Standard fatigue mathematical models were used to relate the actual fatigue data. Due to the material being cold formed to a radius of curvature of 120mm, residual stresses induced during the forming process played an essential role during the fatigue-life prediction calculations. The maximum relieved stress in the parent material was compressive in nature having a magnitude of 11percent of the “as manufactured” yield strength (265 MPa). For the mechanical formed material compressive residual stresses were measured on the outer surface while tensile stresses were measured on the inner surface. The difference between actual number of cycles to failure to that calculated using the standard mathematical models for the parent material, ranged between 48 percent and 18 percent and for the mechanical formed samples between 35 percent and 1percent, depending on the strain amplitude used. An important aspect of this study was to determine the criteria required for mathematical modelling of the parent material as testing occurred between the limit of proportionality and yield point. Although this aspect requires further investigation the mathematical results obtained during this study were considered to be acceptable.
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- Date Issued: 2012
Characterising the structural integrity of mechanical formed low carbon steel
- Authors: Victor, Ngea Njoume
- Date: 2012
- Subjects: Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9627 , http://hdl.handle.net/10948/d1012089 , Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Description: The contribution of the clamping force in the technique used in this study to stretch-bend low carbon steel samples was investigated to support the subsequent changes in the microstructure and properties of the formed material with regard to parent material. Although plastic deformation by cold working is known to induce texture or preferred orientation to the grains of a formed material while decreasing its ductility and increasing the strength, as well as inducing residual stress, it is not known how the different directions (rolling, transverse and oblique/45°) of the sheet steel will respond to this stretch bending technique. The first part of the research work involved a thorough literature review on sheet metal forming processes and their effect on the formed material with interest on the above mentioned directions of the sheet. It became clear from the literature overview that cold working of a material will induce strain-hardening which varies with the magnitude of cold work, resulting in changes in the strength and ductility of the material. Besides, when plastic deformation is not uniform (e.g., tensile and compressive) throughout the entire cross section of the formed part, residual stresses remain in the material with the grains been elongated along the direction of the maximum strain. The main parameters that were considered and controlled in this study are as follows: strain experienced / stress induced into the form sample, the sample direction, the stroke length and the clamping torque, the generated radius of curvature. The chapters that follow the literature review, deal with the set-up of the different equipment used in this study, the specimen preparation as well as the recording, the calculation and interpretation of the results. It was found that the stress magnitude that generated the different radii of curvature (120 mm, 150 mm and 185 mm) was between 1 percent & 13 percent higher than the parent material’s yield strength with the lower stress been associated to the smaller radius of curvature and the higher stress to the higher radius. The stress induced into the sample during forming was not only proportional to the stroke length but also to the distance between the punch’s tip and the sample and the sample to the die’s nadir. The clamping torque adopted was restricted to the manual capacity of the operator who used a preset torque wrench to fasten the plate sample into the jig. Plate samples of low carbon steel were cut to angles of 0°, 45°, and 90° to the rolling direction of the sheet material and stretch-bent on a single-action mechanical press to 120 mm, 150 mm, and 185 mm radii of curvature. The preliminary results indicate that stretch-bent samples had increased hardness to the parent plate, in particular below the surface layers up to around 1.1 mm depth. Since there is a well established relationship between hardness, yield and tensile strengths for steel, the yield and tensile strengths of the formed material were estimated using the Nobre et al [34] incremental relation, which relates the linearity between relative increments of hardness and yield strength. Changes were not noticeable at the microstructural level of the formed samples. Meanwhile, samples from which higher plastic deformation stress values were calculated were not those absorbing higher impact energy when Charpy specimen cut from plate and stretch-bent samples were tested. The maximum relieved residual stress in the parent material was predominantly compressive and represents in magnitude approximately 12 percent (average for the three directions) of its original yield strength. In the stretch-bent samples, the relieved residual stress was compressive in the outer curved section with a magnitude about 50 percent of the parent material yield strength and tensile in the inner curved section with a magnitude approximately 25 percent of the parent material yield strength.
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- Date Issued: 2012
Characterization of friction hydro pillar process weld properties as applied to 10CrMo910 creep resistant steel for application in the power generation Industry
- Authors: Bulbring, Daniel Louis Hans
- Subjects: Materials -- Creep , Friction welding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9636 , http://hdl.handle.net/10948/d1020586
- Description: Creep degradation of steam carrying vessels in the power generation industry is a concern that needs to be constantly monitored. The Weldcore® process has been earmarked as a potential method of creep sampling which will allow for thick-walled sections to be analysed. A component of the process involves plugging the resultant hole after removing a creep sample using a novel welding technique called friction hydro pillar processing. At the commencement of this study, insufficient data was available to warrant safe industrial application of the process. This research was conducted to evaluate the performance of 10CrMo910 friction hydro pillar process welds. The effects of downward force, stud taper angle, hole taper angle and hole base diameter on process response, defect population, static properties and dynamic performance were evaluated. The variation of downward force showed that higher forces produce significantly smaller defects and higher fatigue life. The occurrence of defects was linked to process parameters and geometry thereby identifying the correct parameters for safe use in the power generation industry. Flash formation was identified as an early indicator of weld defects and can assist with quality control in industrial applications. Methods of standardising the plunge depth and forge force were developed to identify the correct magnitudes for different geometries, without the need for testing. Defects were shown to populate specific regions of the weld and produce variations in fatigue life. Crack initiation sites were detected which will aid in identifying areas of focus in further research and development. Temperature measurements were linked to the occurrence of defects and crack initiation sites and have been identified as a method of identifying defective welds. The effects of process parameters and stud and hole taper angles on energy inputs and near interface temperatures were statistically evaluated. Downward force was shown to have the largest effect on energy input rates, total energy input and temperatures at the 11.5mm and 20.5mm positions. Smaller hole and stud taper angles produced lower energy inputs and were identified as more energy efficient than the larger taper angles. A regression model was also developed to predict the fatigue life of welds and can assist with critical process related decision making. A range of hole base diameters were identified which produced welds with low defect populations and fatigue performance similar to that of the parent plate. Larger hole base diameters were shown to produce significant defects along the hole bottom fillet, in the weld nugget and along the bond line. Temperature measurements of the larger diameter welds showed a delay in response and are attributed to a delayed contact of plasticised stud material with the sidewall. Welds with hole base diameters larger than 11mm produced unrepeatable and defective welds, and also required higher energy inputs making smaller diameters more desirable. Analysis of all welds in this study revealed that clearance and interfacial pressures characterise the quality of friction hydro pillar process welds, therefore models were developed to aid in critical decision making with respect to downward force and geometry. This study has successfully evaluated the effects of process parameters and geometry on the properties of friction hydro pillar process welds and thereby has increased understanding of the process.
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