Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aerospace- and automotive industries have an urgency to save space and reduce weight, as well as a need to
increase fuel efficiency and reduce emissions. This has led to the use of lightweight structural materials, such as
Ti6A14V alloy, which is the most widely used titanium alloy in the aerospace industry. This alloy has an
exceptional strength-to-density ratio. The work also covers studies on tool steel 40CrMnMo7 that is used in
applications in the tooling-, aerospace and automotive industry.
In the quest for improved performance new alternative methods of efficiently machining these materials are
investigated. One of the important criteria during machining of these materials is their machinability. This study
discusses current research in high performance machining strategies and techniques for advanced materials such
as Ti6Al4V and 40CrMnMo7. The properties that make these materials advantageous for the use in the
aerospace- and automotive industry also make them difficult to cut. The widespread application of Ti6Al4V in
the aerospace industry has encouraged investigations into cooling strategies or -techniques to maintain and
improve tool life. Ti6Al4V has a low thermal conductivity causing the heat generated during machining to
accumulate on the cutting edge of the tool.
During various experiments the application of external compressed air blow cooling (dry cutting), flood cooling,
high pressure through spindle cooling (HPTSC) and modifications thereof were investigated. The research
project also evaluated the performance of a coating (TiAlN) and various coating treatments. The objectives of
the HPTSC modifications were to improve the coolant stream impingement on the tool surface, effectively
compressing the thermal barrier, and to reduce the chip-tool contact area. This would lead to a decrease in tool
heating and wear. The modified techniques failed to increase tool life but showed signs of increased heat removal capability under
the given conditions. It was observed that air blow cooling (dry cutting) delivered the best results when
considering cutting materials, coating, coating treatment and cooling strategies or –techniques throughout the
experiments conducted. / AFRIKAANSE OPSOMMING: Die Ruimte-en motor-industrie het 'n dringendheid om ruimte te bespaar en gewig te verminder, sowel as 'n
behoefte om brandstofdoeltreffendheid te verbeter en emissies te verminder. Dit het gelei tot die gebruik van
liggewig strukturele materiale, soos Ti6A14V Allooi , wat die mees gebruikte titanium allooi in die Ruimte is.
Hierdie allooi het 'n uitsonderlike krag-tot-digtheid-verhouding. Die studie dek ook gereedskapstaal
40CrMnMo7 wat in die gereedskap, Ruimte-en motor-industrie aangewend word.
In die soeke na verbeterde prestasie word nuwe alternatiewe metodes om effektief bewerking van hierdie
materiaal ondersoek. Een van die belangrikste kriteria tydens bewerking van hierdie materiaal is die bewerkbaar
daarvan. Hierdie studie bespreek die huidige navorsing in hoë prestasie bewerking strategieë en tegnieke vir
gevorderde materiale, soos Ti6Al4V en 40CrMnMo7. Die eienskappe wat hierdie materiaal voordelig maak vir
die gebruik in die lug-en Ruimte-en motor-industrie, maak dit terselfdetyd moeilik om te sny. Die wydverspreide
toepassing van Ti6Al4V in die lug-en Ruimte industrie moedig ondersoeke aan na koelstrategieë of -tegnieke om
die instrumentlewe te handhaaf en te verbeter. Ti6Al4V het lae termiese geleidingsvermoë wat veroorsaak dat
die hitte, wat gegenereer word tydens bewerking, versamel op die voorpunt van die instrument.
Tydens verskillende eksperimente was die toepassing van eksterne saamgeperste lugblaas-verkoeling (droë sny),
vloed verkoeling, hoë-druk-deur-die-spil-afkoeling (HPTSC) en aanpassings daarvan geondersoek. Die
navorsingsprojek het ook die prestasie van 'n bedekkingslaag (TiAlN) en verskeie bedekkingslaagbehandelings
geëvalueer. Die doelwit van die HPTSC aanpassing was om die koelmiddelstroom beklemming op die
instrument oppervlak te verbeter, en effektiewelik die termiese versperring saam te pers, asook die skerf-teenoorinstrument
kontak te verminder. Dit sou lei tot 'n afname in die instrumentverwarming en -slytasie. Die gewysigde tegnieke het daarin misluk om die instrumentlewe te verhoog, maar het tekens getoon van 'n
toename in hitte verwydering vermoë onder die gegewe omstandighede. Dit is dus waargeneem dat lugblaasverkoeling
(droë sny) die beste resultate gelewer het in die oorweging van sny materiale, bedekkingslaag,
bedekkingslaagbehandelings en verkoeling strategieë of -tegnieke wat regdeur die eksperimente uitgevoer was.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80372 |
| Date | 03 1900 |
| Creators | Hammond, Derek |
| Contributors | Dimitrov, D. M., Treurnicht, N. F., Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xvii, 89 p. : ill. |
| Rights | Stellenbosch University |
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