A comparison of conventional and ultrasonic seams in swimwear
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
Use of recycled rubber tyres as an alternative ingredient in cementitious building materials
- Authors: Yuill, Robert Mark
- Date: 2018
- Subjects: Building materials , Building materials -- Environmental aspects Sustainable construction Recycled products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/29783 , vital:30777
- Description: The need to incorporate recycled materials in building products is becoming more important than ever before. There is an abundance of waste rubber tyres which in turn results in a waste management issue. The use of waste rubber tyres in cementitious building material provides a possible solution to the problem (Kathomi, 2009:10). Previous research has shown the introduction of recycled rubber tyre crumb can improve the durability, thermal and acoustic performance in residential and commercial buildings. This could result in lives of dwellers in concrete block buildings in South Africa improving due to these characteristics whilst potentially creating a cost-effective, sustainable building material. A grading analysis, loose and compacted bulk densities and relative densities were determined to provide a mix design. Three tests were conducted for this study namely compressive strength, fire and thermal performance and acoustic performance. The testing was conducted on 100mmx100mm cubes at varying rubber replacement percentages. The replacement values were 10%, 20% and 30% tested against a control of ordinary concrete. The waste rubber crumb was a replacement for sand. The research of this study showed 20 % decrease of compression strength at 10 % rubber replacement compared to the control, 55 % decrease at 20 % rubber replacement and 75% decrease at 30 % rubber replacement. The thermal performance test showed a 24 % lower temperature for 10 % rubber replacement compared to the control, 39 % lower temperature at 20 % rubber replacement and 52 % lower temperature at 30 % rubber replacement. All rubber replacement % samples and the control performed adequately in the flame resistance test. The smoke density test showed that all rubber replacement % samples did not release a quantity of smoke which would be deemed dangerous. The acoustic performance test showed the values at 10% rubber replacement was 6 % lower; at 20% rubber replacement; 4% lower and at 30% rubber replacement 14 % lower. Based on these results, the acoustic performance regarding transmission increases with a rubber replacement % higher than 20 %.
- Full Text:
- Date Issued: 2018
- Authors: Yuill, Robert Mark
- Date: 2018
- Subjects: Building materials , Building materials -- Environmental aspects Sustainable construction Recycled products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/29783 , vital:30777
- Description: The need to incorporate recycled materials in building products is becoming more important than ever before. There is an abundance of waste rubber tyres which in turn results in a waste management issue. The use of waste rubber tyres in cementitious building material provides a possible solution to the problem (Kathomi, 2009:10). Previous research has shown the introduction of recycled rubber tyre crumb can improve the durability, thermal and acoustic performance in residential and commercial buildings. This could result in lives of dwellers in concrete block buildings in South Africa improving due to these characteristics whilst potentially creating a cost-effective, sustainable building material. A grading analysis, loose and compacted bulk densities and relative densities were determined to provide a mix design. Three tests were conducted for this study namely compressive strength, fire and thermal performance and acoustic performance. The testing was conducted on 100mmx100mm cubes at varying rubber replacement percentages. The replacement values were 10%, 20% and 30% tested against a control of ordinary concrete. The waste rubber crumb was a replacement for sand. The research of this study showed 20 % decrease of compression strength at 10 % rubber replacement compared to the control, 55 % decrease at 20 % rubber replacement and 75% decrease at 30 % rubber replacement. The thermal performance test showed a 24 % lower temperature for 10 % rubber replacement compared to the control, 39 % lower temperature at 20 % rubber replacement and 52 % lower temperature at 30 % rubber replacement. All rubber replacement % samples and the control performed adequately in the flame resistance test. The smoke density test showed that all rubber replacement % samples did not release a quantity of smoke which would be deemed dangerous. The acoustic performance test showed the values at 10% rubber replacement was 6 % lower; at 20% rubber replacement; 4% lower and at 30% rubber replacement 14 % lower. Based on these results, the acoustic performance regarding transmission increases with a rubber replacement % higher than 20 %.
- Full Text:
- Date Issued: 2018
Scoping of a commercial micro reformer for the production of hydrogen
- Authors: Koorts, Waldo Pieter
- Date: 2016
- Subjects: Hydrogen as fuel , Fuel processors
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8175 , vital:25942
- Description: Hydrogen has gained interest as fuel recently as the harmful effects of fossil fuels on the environment can no longer be ignored. Hydrogen, which produces no pollutants, forms the feed for cleaner fuel cells systems currently in use. Fuel cells, although not as economically viable as fossil fuels, have found a foothold in the energy market in various markets like power backup and use in remote locations. Production of hydrogen is still largely done via fossil fuel reforming and this technology has received renewed interest for use with fuel cells in the form of micro- reformers or fuel processors. This study entailed the performance benchmarking of a so called Best-in-Class commercial micro reformer (as available in 2010), the 1 kW WS FLOX Reformer, and was undertaken under the auspices of the national HySA programme. The study’s focus was primarily on reformate output quality (carbon monoxide concentration), and start up time, thermal efficiency and hydrogen output (15 SCLM). The reformer consisted of a combustion section encased in an outer reforming section consisting of three reactors in series, steam reforming, water gas shift and selective methanation. As-provided temperature control is simplified though the use of only one temperature setpoint in the combustion chamber and temperature control in the CO clean up stages obtained through means of heat transfer with incoming water being evaporated. Combustion takes place through flame combustion or by means of the supplier’s patented FLOX (flameless oxidation) combustion. The purchased FLOX Reformer assembly was integrated into a fully automated unit with all balance of plant components as well as microGC and flue gas analysis for measurement of outlet conditions. The FLOX Reformer was tested at multiple combustion temperatures, combustion flowrates, reforming loads and steam-to-carbon ratios to obtain a wide set of benchmark data. From the testing it was found that the reformer was able to produce the necessary 15 SCLM hydrogen with a carbon monoxide purity of less than 10 ppm as required in fuel cells for all testing if the reaction temperatures were within the recommended limits. Intermediary water gas shift analysis showed methane and carbon monoxide conversion in the reforming and water gas shift stages to be identical to thermodynamic equilibrium conversion – 95% and higher for all temperatures. iii Selective methanation conversion obtained was 99%, but not always at equilibrium conversion due to increased selective methanation temperatures, where carbon dioxide methanation was also observed at the higher temperatures. Temperature control through heat exchange with incoming water in the CO removal stages was found to be less than ideal as the temperature inside these stages fluctuated dramatically due to inaccuracies in the water pump and a lagged response to flowrate changes. Startup times of less than an hour was observed for multiple combustion flowrates and the reformer boasts a standby function to reduce this to less than half an hour. The thermal efficiency was independently confirmed and tested and found to be higher than 70 % for flame combustion and on par with other commercially available fuel processors. The suppliers trademark FLOX combustion only reaching 65% due to decreased combustion efficiency.
- Full Text:
- Date Issued: 2016
- Authors: Koorts, Waldo Pieter
- Date: 2016
- Subjects: Hydrogen as fuel , Fuel processors
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8175 , vital:25942
- Description: Hydrogen has gained interest as fuel recently as the harmful effects of fossil fuels on the environment can no longer be ignored. Hydrogen, which produces no pollutants, forms the feed for cleaner fuel cells systems currently in use. Fuel cells, although not as economically viable as fossil fuels, have found a foothold in the energy market in various markets like power backup and use in remote locations. Production of hydrogen is still largely done via fossil fuel reforming and this technology has received renewed interest for use with fuel cells in the form of micro- reformers or fuel processors. This study entailed the performance benchmarking of a so called Best-in-Class commercial micro reformer (as available in 2010), the 1 kW WS FLOX Reformer, and was undertaken under the auspices of the national HySA programme. The study’s focus was primarily on reformate output quality (carbon monoxide concentration), and start up time, thermal efficiency and hydrogen output (15 SCLM). The reformer consisted of a combustion section encased in an outer reforming section consisting of three reactors in series, steam reforming, water gas shift and selective methanation. As-provided temperature control is simplified though the use of only one temperature setpoint in the combustion chamber and temperature control in the CO clean up stages obtained through means of heat transfer with incoming water being evaporated. Combustion takes place through flame combustion or by means of the supplier’s patented FLOX (flameless oxidation) combustion. The purchased FLOX Reformer assembly was integrated into a fully automated unit with all balance of plant components as well as microGC and flue gas analysis for measurement of outlet conditions. The FLOX Reformer was tested at multiple combustion temperatures, combustion flowrates, reforming loads and steam-to-carbon ratios to obtain a wide set of benchmark data. From the testing it was found that the reformer was able to produce the necessary 15 SCLM hydrogen with a carbon monoxide purity of less than 10 ppm as required in fuel cells for all testing if the reaction temperatures were within the recommended limits. Intermediary water gas shift analysis showed methane and carbon monoxide conversion in the reforming and water gas shift stages to be identical to thermodynamic equilibrium conversion – 95% and higher for all temperatures. iii Selective methanation conversion obtained was 99%, but not always at equilibrium conversion due to increased selective methanation temperatures, where carbon dioxide methanation was also observed at the higher temperatures. Temperature control through heat exchange with incoming water in the CO removal stages was found to be less than ideal as the temperature inside these stages fluctuated dramatically due to inaccuracies in the water pump and a lagged response to flowrate changes. Startup times of less than an hour was observed for multiple combustion flowrates and the reformer boasts a standby function to reduce this to less than half an hour. The thermal efficiency was independently confirmed and tested and found to be higher than 70 % for flame combustion and on par with other commercially available fuel processors. The suppliers trademark FLOX combustion only reaching 65% due to decreased combustion efficiency.
- Full Text:
- Date Issued: 2016
Developing of a supply chain framework for civil engineering SMME's within the Nelson Mandela Bay Municipality
- Authors: Timotheus, Francois
- Date: 2014
- Subjects: Business logistics -- South Africa -- Nelson Mandela Bay Municipality Small business -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/11242 , vital:26901
- Description: A lot of SMME development initiatives have been subsidised from the funds accumulated from taxpayers. In the promotion of sustainability and growth of SMMEs within developing countries particularly within the BRICS, South Africa is lagging despite its efforts over the past 17 years. According to STATS SA, SA’s unemployment rate for 2011 was between 24-36% and economic growth was 3.1%, the Eastern Cape Province is the poorest province within SA and therefore residence within the province is looking at start-up businesses to better their economic situation. The NMBM economic growth and employment is driven largely by its Integrated Development Plan (IDP) 2013/2014. Aims and objectives:To develop a supply chain management policy that addresses the challenges faced by infrastructure officials, supply chain management practitioners and ward councillors with regards to SMME engagement; and, Investigating the strengths, weaknesses and effectiveness of the current supply chain management policy employed within Nelson Mandela Bay Municipality with regards to SMME engagement. Research methodology: A questionnaire was used in this study to conduct quantitative research; the questionnaire was also used as a data collection tool. Valuable information was gathered from SMMEs residing in the Nelson Mandela Bay Municipal area who operate in the civil engineering field. These SMMEs formed the core research sample. Results: The findings suggest that the current supply chain management (SCM) policy of the Nelson Mandela Bay Municipality (NMBM) does not adequately address the challenges encountered by SMMEs. This suggests the SCM policy is inadequate and the policy must be amended to address its short falls:There is a need for a contractor development programme in the NMBM to assist the Potentially Emerging (PE) contractors within its boundaries;The NMBM is regulating the SMME market for competitiveness to some extent with its SCM policy;Even though the market is being regulated for competitiveness, it is not regulated with regards to new entries into the market; There is a need for the NMBM to provide business development services to SMME’s within its boundaries; The majority of SMME’s believed that there is no gender discrimination within the banking sector;The NMBM is an efficient government institution when it comes to settling their debt in a timely manner;The NMBM must appoint a committee to address the problems faced by SMME’s within its boundaries;South Africa’s National Credit Act (NCA) prevents SMME’s from acquiring an uncontrollable amount of debt. Conclusion: SMME’s within the NMBM enjoy a healthy credit record; these SMME’s also pay their suppliers in a timely fashion. Employees of these SMME’s are adequately compensated for their services. Some SMME’s service the equipment regularly and some do not. Some SMME’s are able to cover their overheads from the projects they undertake and some are not. SMME’s residing in the NMBM have experienced a growth in their business over the last financial year, even though they have not received substantial work over this period. The quality of the end product produced by some SMME’s meets the standard required by the NMBM. Recommendations: To address the development needs of the SMME’s the SCM policy needs to be amended to provide business development services and off-the-job training. To address the access to finance needs of the SMME’s the SCM policy needs to be amended to assist SMME’s in acquiring start-up capital, getting a reduced interest rate and creating work opportunities through micro-financing.
- Full Text:
- Date Issued: 2014
- Authors: Timotheus, Francois
- Date: 2014
- Subjects: Business logistics -- South Africa -- Nelson Mandela Bay Municipality Small business -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/11242 , vital:26901
- Description: A lot of SMME development initiatives have been subsidised from the funds accumulated from taxpayers. In the promotion of sustainability and growth of SMMEs within developing countries particularly within the BRICS, South Africa is lagging despite its efforts over the past 17 years. According to STATS SA, SA’s unemployment rate for 2011 was between 24-36% and economic growth was 3.1%, the Eastern Cape Province is the poorest province within SA and therefore residence within the province is looking at start-up businesses to better their economic situation. The NMBM economic growth and employment is driven largely by its Integrated Development Plan (IDP) 2013/2014. Aims and objectives:To develop a supply chain management policy that addresses the challenges faced by infrastructure officials, supply chain management practitioners and ward councillors with regards to SMME engagement; and, Investigating the strengths, weaknesses and effectiveness of the current supply chain management policy employed within Nelson Mandela Bay Municipality with regards to SMME engagement. Research methodology: A questionnaire was used in this study to conduct quantitative research; the questionnaire was also used as a data collection tool. Valuable information was gathered from SMMEs residing in the Nelson Mandela Bay Municipal area who operate in the civil engineering field. These SMMEs formed the core research sample. Results: The findings suggest that the current supply chain management (SCM) policy of the Nelson Mandela Bay Municipality (NMBM) does not adequately address the challenges encountered by SMMEs. This suggests the SCM policy is inadequate and the policy must be amended to address its short falls:There is a need for a contractor development programme in the NMBM to assist the Potentially Emerging (PE) contractors within its boundaries;The NMBM is regulating the SMME market for competitiveness to some extent with its SCM policy;Even though the market is being regulated for competitiveness, it is not regulated with regards to new entries into the market; There is a need for the NMBM to provide business development services to SMME’s within its boundaries; The majority of SMME’s believed that there is no gender discrimination within the banking sector;The NMBM is an efficient government institution when it comes to settling their debt in a timely manner;The NMBM must appoint a committee to address the problems faced by SMME’s within its boundaries;South Africa’s National Credit Act (NCA) prevents SMME’s from acquiring an uncontrollable amount of debt. Conclusion: SMME’s within the NMBM enjoy a healthy credit record; these SMME’s also pay their suppliers in a timely fashion. Employees of these SMME’s are adequately compensated for their services. Some SMME’s service the equipment regularly and some do not. Some SMME’s are able to cover their overheads from the projects they undertake and some are not. SMME’s residing in the NMBM have experienced a growth in their business over the last financial year, even though they have not received substantial work over this period. The quality of the end product produced by some SMME’s meets the standard required by the NMBM. Recommendations: To address the development needs of the SMME’s the SCM policy needs to be amended to provide business development services and off-the-job training. To address the access to finance needs of the SMME’s the SCM policy needs to be amended to assist SMME’s in acquiring start-up capital, getting a reduced interest rate and creating work opportunities through micro-financing.
- Full Text:
- Date Issued: 2014
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