Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The main goal of the thesis is to validate the ability of discrete element methods (DEM) to predict forced granular flow. Granular flow occurs in a broad spectrum of industrial applications. The thesis focuses on earthmoving processes typical of the mining and agricultural industries. Existing soil mechanics soil-tool models are also investigated and general flow behaviour in and around blades and buckets are established. Soil mechanics theories are used to predict the draft forces on a flat blade moving through granular material. Com and wheat grains are used as material. The rupture (slip) lines in front of the blade are predicted by soil mechanics and compared to experimental results. A two-dimensional test bench is used to visualise the flow of the granular material. Forces and moments that act on the tools are measured. DEM can be used to model industrial granular flow with large displacements. Two types of earthmoving equipment are simulated. The first is a flat blade and the second is a bucket. The forces on these tools are determined using DEM and compared to experimental results. The ability of DEM to predict material compressibility, the flow of material in and around the tools, the rupture lines and the bucket fill rate are investigated. A particle relative displacement method is used to determine the rupture lines. / AFRIKAANSE OPSOMMING: Die hoofdoel van die tesis is om die vermoë van diskrete-element-metodes (DEM) om geforseerde partikelvloei te voorspel, te ondersoek. Partikelvloei word aangetref in 'n breë spektrum van industriële toepassings. Die tesis fokus op grondverskuiwing soos aangetref in myn- en landbouprosesse. Bestaande grondmeganika-modelle word ook ondersoek, asook die algemene gedrag van partikelvloei in en rondom lemme en bakke. Die grondmeganika-modelle word hoofsaaklik gebruik om die kragte op lemme te voorspel. Glip (skuif)-vlakke word ondersoek en vergelyk met eksperimentele resultate. 'n Twee-dimensionele toetsbank word gebruik om die vloei waar te neem. Die kragte en momente op die toerusting word ook gemeet. Mielie- en koringpitte word as materiaal gebruik. DEM kan gebruik word om industriële partikelvloei met groot verplasings te modelleer. Twee tipes toerusting word gesimuleer. Die eerste is 'n plat lem en die tweede 'n bak. Die kragte en momente op dié toerusting word bepaal m.b.V. DEM en dan vergelyk met die eksperimentele resultate. Die vermoë van DEM om materiaalsamedrukking, vloeipatrone, glipvlakke en bakvul-tempo's te voorspel word ondersoek. 'n Partikelrelatiewe- verplasings-metode word gebruik om die glipvlakke te voorspel.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / Please refer to full text to view abstract. / Imported from http://etd.sun.ac.za. / np2011

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: A 1.5 x 1.5 m2 counter-flow fill performance test facility is described in detail. Instrumentation was selected and installed in the cooling tower fill test facility and calibrated to ensure measurement accuracy. A facility control program was written to simplify the operation of the test facility via a user interface. The program calculates automatically the Merkel number and loss coefficients as measures of fill thermal and flow performance respectively. A spray frame was designed and manufactured to ensure uniform water distribution to the fill. The water distribution through different fills with varying fill heights and different water flow rates was measured. The water attached to the walls of the test facility was examined. Film, trickle and splash fills are tested in the upgraded test facility. The film and trickle fill performance determined during testing is deemed acceptable as these fills have minimal migration effects. Fills with poor distribution effects and large migration of water towards the walls of the test facility, like the splash fill tested, cannot to be tested accurately in a 1.5 x 1.5 m2 test section as the results do not represent the performance of the fill in a relatively large cooling tower. Other aspects examined were: • air flow uniformity • air fill bypass effects • location of water inlet and outlet temperature measurement points • location of pressure measurement probes. It was determined that, in the current test facility: • air uniformity is suitable for performance testing • air bypass effects can be ignored for open fills and can be minimised for dense fills by packing sponge between the fill and walls • water inlet and outlet temperatures should be measured in the pipe-work, resulting in a measurement method that is not influenced by the relative weightings of each thermocouple • pressure difference over the fill height measured by the pressure measurement tap is independent of its location on the fill outlet plane provided the pressure measurement points are perpendicular to the air stream and are not against the walls. / AFRIKAANSE OPSOMMING: 'n 1.5 x 1.5 m² Teenvloei pakking werkverrigting toetsfasiliteit word in detail beskryf. Instrumentasie is gekies en geïnstalleer in die koeltoring pakking toetsfasiliteit en gekalibreer om akkuraatheid te verseker. 'n Fasiliteit beheer program is geskryf om die gebruik van die toetsfasiliteit te vereenvoudig. Die program het ‘n vriendelike gebruikers intervalk. Die program bereken outomaties die Merkel-getal en verlies koëffisiënte as mate van pakking termiese- en vloeiwerksverrigting. 'n Sproeiraam is ontwerp en vervaardig om uniforme water verspreiding aan die pakking te verseker. Die water verspreiding deur verskillende pakkings met verskillende pakking hoogtes en water vloei snelhede is gemeet. Die water aangeheg aan die mure van die toetsfasiliteit is ook ondersoek. Film, druppel en spat pakkings word in die opgegradeerde toetsfasiliteit getoets. Die film- en druppelpakking werksverrigting bepaal tydens die toetse is aanvaarbaar, aangesien hierdie pakkings minimale migrasie effekte het. Pakking met swak verspreiding effekte en 'n groot migrasie van water na die wande van die toetsfasiliteit, soos gevind met die spatpakking toetse, kan nie met akkuraatheid in 'n 1.5 x 1.5 m² toets seksie getoets word nie omdat die resultate nie die werkverrigting van die pakking verteenwoordig in 'n relatief groot koeltoring. Ander aspekte wat ondersoek was: • lugvloei uniformiteit • lug omleiding effeckte • die posisie van water in- en uitlaat temperatuur meetpunte • posisie van die drukmeetapparaat. Dit is vasgestel dat, in die huidige toetsfasiliteit • lugvloei eenvormigheid geskik is vir prestasietoetsing • lug omleiding effekte kan geïgnoreer word vir oop pakkings en kan verklein word vir digte pakkings deur spons tussen die pakking en mure te pak • water inlaat- en uitlaattemperature behoort gemeet te word in die pypwerk en lei tot 'n metings metode wat nie beïnvloed word deur die relatiewe gewigte van elke thermokoppel nie • die druk verskil gemeet deur die drupmeetpunte oor die pakkinghoogte is onafhanklik van hul posisie op die pakkinguitlaatvlak op voorwaarde dat die drukmeetpunte loodreg is teen die lugstroom en nie teen die mure nie.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The purpose of this study is to investigate the machinability of commercially pure (CP) titanium, manufactured using the press-and-sinter PM process. To this end, CP titanium powder (-200 mesh) was compacted and sintered in vacuum (10-4 torr) for two hours at 1200°C. Small cylindrical samples were compacted at pressures varying from 350 to 600 MPa in order to determine the compressibility of the powder. Following these tests, four larger stepped-cylinder samples were compacted at pressures close to 400 MPa and sintered under similar conditions. These samples had sintered densities varying between 3.82 and 4.41 g/cm3. They were used to evaluate the machinability of the sintered titanium using face turning machining tests. The samples were machined dry, using uncoated carbide (WC-Co) cutting tool. Cutting speeds between 60-150 m/min were evaluated while keeping the feed rate and depth of cut constant at 0.15 mm/rev and 0.5 mm, respectively. The final machined surface finish and the tool wear experienced during the face turning machining tests were monitored in order to evaluate PM titanium’s machining performance. This study showed that it is possible to use the press-and-sinter PM process with CP titanium powder, with a particle size of less than 75 μm (-200 mesh), to manufacture sintered titanium. However, particle shape influences the compressibility of the powder and pressing parts of larger volume, such as the machining test sample shape, is challenging when using such small particle size powder. Processing conditions, such as compaction pressure, sintering temperature and sintering time, influence the sintered density. Results from the machinability tests show that tool wear increases with a decrease in the porosity of the sintered titanium. A more porous sintered material has both lower strength and thermal conductivity. As these factors have opposing effects on the machinability of materials, it is concluded that the strength of the sintered titanium has a stronger influence on its machinability than the thermal conductivity. The cutting tool wear was uniform but showed indications of crater wear. The machined surface of the denser parts had minimal defects compared to less dense parts. Chip shape is long for the dense parts, and spiral for the less dense parts. The chips formed were all segmented, which is typical for titanium. The machinability of the sintered CP titanium was compared to that of wrought titanium alloys. As expected, it was found that the machinability of the sintered titanium was poor in comparison. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om die masjineerbaarheid van kommersieel suiwer (KS) titaan, wat deur die pers-en-sinter poeiermetallurgie (PM) metode vervaardig word, te ondersoek. Om hierdie doel te bereik, is KS titaan poeier (-200 ogiesdraad) gekompakteer en gesinter in ‘n vakuum (10-4 torr) teen 1200°C vir 2 ure. Klein silindriese monsters is tussen drukke van 350en 600 MPa gekompakteer om die samedrukbaarheid van die poeier te bepaal. Na aanleiding van hierdie toetse, is vier groter trapvormige-silinder monsters by drukke naby aan 400MPa gekompakteer en onder soortgelyke omstandighede gesinter. Hierdie monsters het gesinterde digthede tussen 3.82 en 4.41 g/cm3 gehad. Hulle is gebruik om die masjineerbaarheid van die gesinterde titaan te ondersoek deur middel van vlak-draai masjineringstoetse. Die monsters is sonder smeermiddel gemasjineer met onbedekte karbied (WC-Co) snygereedskap. Snysnelhede tussen 60 – 150 m/min is geëvalueer terwyl die voertempo en diepte van die snit konstant by 0.15 mm/rev en 0.5 mm, onderskeidelik, gehou is. Die finale gemasjineerde oppervlak afwerking en gereedskapsslytasie tydens die vlak-draai masjinering toets is van die faktore wat gemonitor is sodat PM titaan se optrede tydens masjinering geëvalueer kan word. Hierdie studie wys dat diepers-en-sinter metode wel met KS titaan poeier, met ‘n partikel grootte van minder as 75 μm (-200 maas), gebruik kan word om gesinterde titaan te vervaardig. Die partikelgrootte beïnvloed wel die samedrukbaarheid van die poeier. Die samedrukking van parte met groter volume, soos bv die masjinerings toetsmonster, is uitdagend wanneer klein partikelgrootte poeier gebruik word. Proses omstandighede, soos kompaksie druk, sinteringstemperatuur en sinteringstyd, beïnvloed die gesinterde digtheid. Resultate van die masjineerbaarheidstoetse wys dat beitelslytasie toeneem met ‘n afname in porositeit van die gesinterede titaan. ‘n Meer poreus gesinterde materiaal het beide laer sterkte en termiese geleidingsvermoë. Aangesien hierdie faktore teenoorgestelde uitwerkings op masjineerbaarheid het, word dit dan afgelei dat die sterkte van gesinterde titaan ‘n groter invloed het op sy masjineerbaarheid as die termiese geleidingsvermoë. Die beitel se slytasie is hoofsaahlik, maar het tekens van kraterslytasie getoon. Die gemasjineerde oppervlak van die meer digte onderdele of toetsmonters het min gebreke gehad in vergelyking met die minder digte dele. Die vorm van die spaanders is lank vir digte parte, en spiraalvormig vir minder digte toetsmonsters. Die spaanders wat gevorm het, was almal gesegmenteerd, wat tipies is vir titaan. Die masjineerbaarheid van die gesinterde KS titaan is met dié van gesmede titaanallooie vergelyk. Soos verwag is, is gevind dat die masjineerbaarheid van die gesinterde titaan in vergelyking swak is.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The optimal design of a heat exchanger for a specified heat transfer, pressure drop and set of ambient conditions entails minimising space, weight, material usage and overall cost. However, the variables which influence the performance as well as the overall cost of a heat exchanger are not related in a simple way and it is not obvious which variables play the most important roles (Perry & Green, 1997:11-44). Air cooled heat exchangers (ACHEs) are normally designed in three stages, by different experts in the field, and with the aid of specially designed software. This project combines these thermal, mechanical and cost estimation processes into a MS Excel model which makes it easier to see the influence that design parameters have on the overall cost of the heat exchanger. A thermal model was created to design an API 661 (2006) ACHE. The results from this model compared well with those of HTRI Xchanger Suite 6.0 software, with HTRI being more conservative in its design mode. A mechanical design model was then developed, which uses as inputs the outputs of the thermal design. The output from this mechanical design model is the minimum material thicknesses based on the stress criteria of Appendix 13 of ASME VIII div 1 (2007) Boiler and Pressure Vessel Code. An experiment on a finned tube bundle was performed in a wind tunnel facility to determine performance characteristics and compare these to existing correlations in literature. The results showed that both the heat transfer coefficient (h) and loss coefficient (Eu) correlations proposed by Ganguli et al. (1985) closely predict the measured data, and were consequently used in the thermal design model. During this experiment it was also shown that the tube bundle reached 8 % - 9 % of its allowable internal fouling factor, due to rust build up inside the tubes, and in a testing period of only nine days. The thermal and mechanical models were then combined with a cost estimation process to perform both a thermal and mechanical parametric study. The thermal study showed that to obtain an optimal solution, the design must attempt to maximise the length, increase the width rather than the number of bays, make use of two bundles per bay with fewer but larger fans and employ a large number of tube rows with the least number of tube passes. These guidelines were used to create an initial design; Excel Solver was then applied to locate the optimum combination of bundle length and width that result in the minimum heat exchanger cost. Two mechanical considerations were investigated, both requiring additional welding and thus increased welding cost. Firstly the use of stay plates result in reduced required plate thicknesses according to the stress criteria since it provides additional stiffness in the header box design. Secondly the use of more (but smaller) nozzles as opposed to less (but larger) nozzles was also considered. The mechanical parametric study showed no specific trends, but both considerations should still be checked as it can be cost beneficial in a specific design. / AFRIKAANSE OPSOMMING: Optimale ontwerp van ’n warmteoordraer vir ’n gespesifiseerde warmteoordrag, drukval en stel van omgewingstoestande behels die minimalisering van ruimte, gewig, materiaalverbruik en algehele koste. Die veranderlikes wat egter die werkverrigting, sowel as die algehele koste, van ’n warmteoordraer beïnvloed, hou nie in ’n eenvoudige sin met mekaar verband nie, en dit is nie vanselfsprekend watter veranderlikes die belangrikste rolle speel nie (Perry & Green, 1997:11-44). Lugverkoelde warmteoordraers (air-cooled heat exchangers of ACHEs) word normaalweg in drie fases ontwerp deur verskillende kundiges in die veld en met behulp van spesiaal ontwerpte programmatuur. Hierdie studie kombineer dié termiese, meganiese en kosteberamingsprosesse in ’n MS Excel-model, wat dit makliker maak om van te stel wat die invloed wat ontwerpparameters op die algehele koste van die hitteruiler is. ’n Termiese model is geskep om ’n “API 661 (2006) ACHE” te ontwerp. Die resultate van hierdie model het goed vergelyk met dié van die HTRI Xchanger Suite 6.0-program, met HTRI meer konserwatiew in die ontwerp af. Na die termiese model geskep is, is ’n meganieseontwerp-model ontwikkel, wat as insette die uitsette van die termiese ontwerp gebruik het. Die uitset van hierdie meganieseontwerp-model is die minimum materiaaldikte gebaseer op die spanningskriteria van Bylae 13 van “ASME VIII div 1 (2007) Boiler and Pressure Vessel Code.” Daar is ’n eksperiment op ’n vinbuisbundel in ’n windtonnelfasiliteit uitgevoer om werkverrigtingskarakteristieke te bepaal en dit met bestaande korrelasies in die literatuur te vergelyk. Die resultate het getoon dat sowel die warmteoordragskoëffisiënt (h) en die verlieskoeffisient (Eu) korrelasies, voorgestel deur Ganguli et al. (1985), die data wat gemeet is akkuraat voorspel, en gevolglik is die korrelasies in die termieseontwerp-model gebruik. Gedurende die eksperiment is ook getoon dat die buisbundel 8 % - 9 % van sy toelaatbare interne-aanpakkingfaktor bereik het vanweë roesopbou binne-in die buise, en dit in ’n toetsingtydperk van slegs nege dae. Die termiese en meganiese modelle was toe gekombineer met ’n kosteberamingsproses om ’n termiese sowel as ’n meganiese parametriese studie uit te voer. Die termiese studie het getoon dat, om ’n optimale oplossing te verkry, die ontwerp moet poog om die lengte te maksimeer; die wydte eerder as die aantal strate (bays) te vermeerder; van twee bundels per straat gebruik te maak met minder, maar groter waaiers; en ’n groot aantal buisrye met die kleinste hoeveelheid buisdeurvloeiweë in te span. Hierdie riglyne is gebruik in ’n aanvanklike ontwerp, waarna die Excel Solver gebruik is om die optimale kombinasie van bundellengte en –wydte vas te stel met die oog op die laagste moontlike warmteoordraerkoste. Twee meganiese oorwegings is ondersoek wat albei addisionele sweiswerk sou vereis en dus tot verhoogde sweiskoste sou lei. Eerstens lei die gebruik van ankerplate (stay plates) tot ’n vermindering in die vereiste plaatdiktes volgens die spanningskriteria, aangesien dit addisionele stewigheid in die spruitstukhouerontwerp bied. Tweedens is die gebruik van meer (maar kleiner) spuitstukke teenoor minder (maar groter) spuitstukke ook oorweeg. Die meganiese parametriese studie het geen spesifieke voorkeurneigings getoon nie, maar altwee oorgewings moet nog getoets word want dit kan koste voordelig word in 'n spesifieke ontwerp.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In light of the rapid depletion of the world’s oil reserves, concerns about energy security prompted the exploration of alternative sources of liquid fuels for transportation. One such alternative is the production of synthetic fuels with the indirect coal liquefaction process or Coal-To-Liquids (CTL) process. In this process, coal is burned in a gasifier in the presence of steam and oxygen to produce a synthesis gas or syngas, consisting mainly of hydrogen and carbon monoxide. The syngas is then converted to liquid fuels and a variety of useful chemicals in a Fischer Tropsch synthesis reactor. However, the traditional process for syngas production also produces substantial amounts of carbon dioxide. In fact, only about one third of the carbon in the coal feedstock ends up in the liquid fuel product using traditional CTL technology. If additional hydrogen was available, the carbon utilisation of the process could be improved significantly. The high temperature reactor (HTR) is a gas cooled Generation IV nuclear reactor ideally suited to provide electrical power and high temperature heat for the production of carbon neutral hydrogen via high temperature electrolysis. The integration of an HTR into a CTL process therefore provides an opportunity to improve the thermal and carbon efficiency of the CTL process significantly. This thesis presents a possible process flow scheme for a nuclear assisted CTL process. The system is evaluated in terms of its thermal or syngas production efficiency (defined as the ratio of the heating value of the produced syngas to the sum of the heating value of the coal plus the HTR heat input) as well as its carbon utilisation. If the hydrogen production plant is sized to produce only enough associated oxygen to supply in the needs of the gasification plant, syngas is produced at about 63% thermal efficiency, while 71.5% of the carbon is utilised in this process. It was found that the optimum HTR outlet temperature to produce hydrogen with a high temperature steam electrolysis process is 850°C. If enough process heat and electrical power are available and process equipment capacities are sufficient, the carbon utilisation of the process could be improved even further to values in excess of 90%. / AFRIKAANSE OPSOMMING: Die uitputting van die wêreld se olie-reserwes, asook kommer oor energiesekuriteit het daartoe gelei dat alternatiewe bronne van vloeibare brandstowwe vir vervoer ondersoek moes word. Een so 'n alternatief is die produksie van sintetiese brandstof d.m.v. die indirekte steenkool vervloeiing proses of sogenaamde Coal-To-Liquids (CTL) proses. In hierdie proses word steenkool in die teenwoordigheid van stoom en suurstof in 'n vergasser gebrand om 'n sintesegas of singas te produseer, wat hoofsaaklik uit waterstof en koolstofmonoksied bestaan. Die sintesegas word daarna omgeskakel na vloeibare brandstowwe en 'n verskeidenheid van nuttige chemikalieë in 'n Fischer-Tropsch-sintese reaktor. Ongelukkig produseer die tradisionele proses vir sintesegas produksie ook 'n beduidende hoeveelheid koolstofdioksied. Trouens, slegs sowat een derde van die koolstof in die steenkool roumateriaal eindig in die vloeibare brandstof produk indien van tradisionele CTL-tegnologie gebruik gemaak word. Indien addisionele waterstof beskikbaar was, kon die koolstofbenutting van die proses aansienlik verbeter word. Die hoë temperatuur reaktor (HTR) is 'n gas-verkoelde Generasie IV kernreaktor wat by uitstek geskik is om elektrisiteit en hoë temperatuur hitte te verskaf vir die produksie van koolstofneutrale waterstof d.m.v. hoë temperatuur elektrolise. Die integrasie van 'n HTR in 'n CTL-proses bied dus 'n geleentheid om die termiese- en koolstofdoeltreffendheid van die CTL-proses aansienlik te verbeter. In hierdie ondersoek word 'n moontlike proses vloeidiagram vir 'n kern-gesteunde CTL-proses voorgestel. Die stelsel is geëvalueer in terme van sy termiese- of sintesegas produksie doeltreffendheid (gedefinieer as die verhouding van die hittewaarde van die geproduseerde sintesegas gedeel deur die som van die hittewaarde van die steenkool en die HTR hitte-insette) sowel as sy koolstof-effektiwiteit. Indien die waterstof produksie-aanleg ontwerp word om net genoeg geassosieerde suurstof te voorsien om in die behoeftes van die vergassing-aanleg te voorsien, word sintesegas teen ongeveer 63% termiese doeltreffendheid vervaardig, terwyl 71.5% van die koolstof in hierdie proses benut word. Daar is bevind dat 850°C die optimum HTR uitlaat temperatuur is om waterstof d.m.v. hoë temperatuur stoom-elektrolise te vervaardig. Indien daar genoeg proses hitte en elektrisiteit beskikbaar is en die proses toerusting kapasiteite voldoende is, sou die koolstof-benutting van die proses tot meer as 90% verbeter kon word.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate under distorted inflow conditions. These conditions occur due to the prevailing wind conditions, the presence of buildings, and the location of the fan within the ACSC. Fans located on the periphery of the ACSC are affected the most due to their exposure to strong winds and the inner fans drawing in air past them. Distorted inflow conditions cause varying fan blade and gearbox loading conditions. The purpose of the investigation was to simultaneously measure the inlet air flow and the resultant blade and gearbox loading conditions of a single fan located on the periphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocities were measured using a combination of ultrasonic and propeller anemometers while blade loading was measured with strain gauges attached at the neck of the specific blade being monitored. Strain gauges were also attached to the low-speed fan shaft to measure gearbox loading. Measurements were recorded over a period of 8 days where it was found that increased wind resulted in increased air flow in the axial direction of the fan, which then caused a reduction in average blade loading. This was due to a decreased static pressure rise over the fan. The fan blade was found to vibrate at its own natural frequency of 6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading was extracted from the measured data and was found to correlate well with previous experimental work performed by Bredell et al. (2006a). Shaft bending stresses and torque were found to oscillate at the fan’s rotational frequency of 2Hz with a large torque exerted on the shaft during fan start-up. / AFRIKAANSE OPSOMMING: Aksiaalvloeiwaaiers wat by groot lugverkoelde stoomkondensors gebruik word, werk dikwels onder verwronge inlaat lugvloei toestande wat geskied as gevolg van heersende winde, die teenwoordigheid van geboue en die posisie van die waaier in die kondensor. Waaiers wat geleë is op die rand van die kondensor word die meeste beïnvloed as gevolg van blootstelling aan die sterk winde en dwarsvloei wat deur die binneste waaiers geïnduseer word. Verwronge inlaat lugvloei veroorsaak gevolglik variërende waaierlem en ratkas belastingstoestande. Die doel van hierdie ondersoek was om terselfdetyd die inlaat lugvloei asook waaierlem en ratkas belastingstoestande van ’n enkele waaier wat op die rand van ’n grootskaalse lugverkoelde stoomkondensor geleë is, te meet. Waaier inlaat en warmteruiler uitlaat lugvloei snelhede is gemeet met ’n kombinasie van ultrasoniese- en skroefwindsnelheidsmeters terwyl die lem en ratkas belastings gemeet is met rekstrokies. Metings is oor ’n tydperk van 8 dae geneem. Die bevindinge toon dat ’n toename in windsnelheid ’n toename in aksiale lugvloei tempo, deur die waaier veroorsaak. ’n Afname in die gemiddelde lembelasting is waargeneem as gevolg van ’n afname in die waaier statiese druk. Daar is ontdek dat die waaierlem teen ’n natuurlike frekwensie van 6 Hz vibreer wanneer dit opgewek word deur die wisselende aerodinamiese belasting. Die aerodinamiese belasting is verkry uit die gemete data en vergelyk goed met die numeriese werk van Bredell et al. (2006a). Daar is ook bevind dat waaier-as buigspannings en wringkragte ossileer teen die waaier se rotasiefrekwensie van 2Hz met ’n groot wringkrag wat op die as uitgeoefen word wanneer die waaier aangeskakel word. iii

Thesis (MScEng)--Stellenbosch University, 2013. / AFRIKAANSE OPSOMMING: Saamgestelde materiale het baie gewilde materiale in die lugvaart- en motor industrië geword as gevolg van die gewigsbesparende voordele wat dit inhou. Kostes en ander verwerkingsprobleme het tradisioneel die wydverspreide gebruik van spesifiek termoplasties-versterkte vesels in hierdie areas verhinder. Baie van die vervaardigingsprobleme (spesifiek lang siklusse) is aangespreek met die aanvang van termoplastiese matriks materiaal soos Polyphenolien Sulfied (PPS). Hierdie materiaal voldoen ook aan die lugvaart-industrie se brand-, rook- en giftigheidstandaarde. Termoplastiese saamgestelde materiale kan byvoorbeeld gevind word op komponente in vliegtuie se binneruimtes en ook die voorste rand van die vlerke. Hierdie komponente is hoogs vatbaar vir impakskade. Die hoë sterkte en styfheid tot gewig verhoudings van saamgestelde materiale laat toe vir dun materiaal dwarssnitte. Komponente is dus kwesbaar vir uit-vlakkige impak beladings. Saamgestelde materiale kan ook intern deur hierdie beladings beskadig word en kan nie met die blote oog waargeneem kan word nie. Dit is dus nodig om die skade weens hierdie beladings tydens normale gebruik akkuraat te voorspel. Verder sal dit nuttig wees om die struktuur se gedrag te bepaal in toepassings waar byvoorbeeld passasier veiligheid krities is, soos op vliegtuig ruglenings tydens noodlandings. In hierdie studie is die potensiële vervaardigingsvoordele van termoplastiese saamgestelde materiale gedemonstreer. Daarbenewens is 'n uit-vlakkige impak deur 'n sagte liggaam herbou in 'n laboratorium omgewing. Die primêre doelwit van hierdie studie was om die impak numeries te modelleer. Vervaardigingsvoordele van `n vesel versterkte termoplastiese laminaat is gedemonstreer deur die vervaardiging van 'n konkawe, agt laag laminaat uit 'n vooraf gekonsolideerde geweefde doek. Die totale verwerkingstyd van die plat laminaat na 'n konkawe laminaat was minder as vyf minute. 'n Eenvoudige plat laminaat en 'n konkawe laminaat is onderwerp aan 'n lae snelheid impak deur 'n sagte projektiel. Die impak is gemodelleer deur die evaluering van drie modelleringsmetodes vir die saamgestelde paneel. Die evalueringskriteria het o.a. ingesluit of laminaat se volle gedrag suksesvol gemodelleer kon word met behulp van slegs 2D dop elemente. Die reaksie van die saamgestelde paneel en gepaardgaande faling is met wisselende vlakke van sukses deur die drie geëvalueerde modelle voorspel. Die faling van tussen-laminêre bindings (verwys na as delaminasie) kon nie deur enige van die modelle voorspel word nie. Twee van die modelle het egter in-vlak faling met redelike akkuraatheid voorspel. / ENGLISH ABSTRACT: Due to weight saving advantages composite materials have become a highly popular material in the aerospace and automotive industries. Traditionally processing difficulties and costs have been a barrier to widespread composite material use in these industries. With the advent of thermoplastic matrix materials such as Polyphenoline Sulphide (PPS) the processing difficulties (especially long cycle times) experienced with traditional thermosetting resins can be addressed while maintaining aerospace Fire-Smoke and Toxicity (FST) approval. Thermoplastic composites can for example be found on aircraft interior components and leading edges of the wings. These areas are highly susceptible to impact damage. The high strength- and stiffness to weight ratios of composites allows for thin material cross sections. This leaves the components vulnerable to out-of-plane impact loads. Composite materials may also be damaged internally by these loads, leaving the damage undetectable through visual inspections. It may therefore be necessary to predict the amount of damage a component would sustain during normal operation. Additionally, it would be useful to predict structural response of these materials in applications where passenger safety is crucial, such as aircraft seat backrests during emergency landings. In this study the potential processing benefits of thermoplastic composite materials were demonstrated. Additionally an out-of-plane impact from a soft bodied projectile was reconstructed in a laboratory environment. The primary objective was to numerically model the impact event. Processing benefits of thermoplastics were demonstrated by producing a single curvature eight layered laminate from a pre-consolidated woven sheet. The total processing time from flat panel to a single curvature panel was below five minutes. A simple flat laminate and a single curvature laminate were subjected to a low velocity drop weight impact load from a soft bodied projectile. These impact events were modelled by evaluating three modelling methods for the composite panel structural response and damage evolution. Part of the evaluation criteria included whether laminate failure could be modelled successfully using only 2D shell elements. The response of the composite panel and accompanying failure were predicted with varying levels of success by the three evaluated models. The failure of interlaminar bonds (referred to as delamination) could not be predicted by either model. However two of the models predicted in-plane failure with reasonable accuracy.