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Laser cladding surface treatment for enhancement of mechanical propertiesYang, Wen Fu January 2003 (has links)
Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003 / Systematic laser cladding experiments were performed using a mixture of a Nickel
base alloy powder mixed with tungsten carbide powder (percentage contents of
tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder
method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide
powder on EN9 steel substrate was performed with powder injection method as well.
A Finite Element Method for calculating the surface temperature distribution was
used to help prediction of temperature distribution laser cladding results. Composition
of cladding materials was designed; a sticking agent was chosen for the pre-placed
powder method. Clad coatings were obtained for different process parameters for
laser cladding, and a detailed study of the affects of these parameters has been carried
out.
The characteristic microstructure and properties of the clad layers and interface were
investigated by using an optical microscope, a micro hardness tester and a makeshift
wear test. A comprehensive review is presented on the dilution of the coating and the
typical problems experienced with the coating substrate interface.
The results show that microstructure of clad layers comprise three zones: the cladding
layer, bonding zone and heat-affected zone. The results showed that tungsten carbide
particles increased the hardness and wear resistance as expected. Wear resistance of
laser cladding coating is 3.5 times than that of substrate. The micro hardness range of
the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of
substrate. The micro hardness varies from cladding coating to transition layer then to
heat affected zone and substrate along a gradient.
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Investigation of a testing approach for trapezoidal crest fastened metal claddingStephan, Hendrik Christoffel 03 1900 (has links)
Thesis (MscEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Low-rise buildings with crest fastenedmetal cladding are susceptible to failures in the vicinity of the fasteners
during strongwind uplift conditions. These localised failures often lead to the progressive removal of cladding,
which can cause disastrous building damage. In South Africa, the current metal cladding design approach is
inadequate, since it solely relies upon manufacturer design specifications. These specifications are typically
designated as broad design guidelines for the maximum allowable cladding support spacings which are independent
from any specified design loads. This research focuses on the investigation of 0.50 mm ISQ550 IBR
cladding systems to understand basic cladding behaviour during static wind uplift conditions and to quantify
the uplift performance of IBR systems. The research investigation also included the improvement and
performance evaluation of a full-scale cladding test method which applies an air-bag loading method to simulate
static wind uplift conditions according to the revised SANS 10237:201X code of practice. This thesis may
serve as a basis for further cladding research, and the development of suitable standardised metal cladding
test methods in South Africa.
Several experimental investigation methods and limited finite element analyses (FEA) were used to investigate
IBR and the performance of the test methods. Tensile testing was used to determine the material properties of
the cladding metal. The full-scale cladding assembly testing was used to investigate the behaviour of IBR and
to evaluate the performance of the air-bag test rig. The localised behaviour of the cladding around the fasteners
was also investigated with a small cladding subassembly test method. The FEA served as a supplementary
investigation for IBR performance evaluation.
The experimental investigation confirmed that the static wind uplift resistances of IBR systems are mainly
governed by localised deformations of their fastened crests and fastener pull-through failures. The behaviour
and performance of IBR systems are heavily dependent on the crest fastening arrangement. IBR systems with
every crest fastening demonstrated a considerably higher wind uplift resistance than IBR systems with the
standard alternate crest fastening arrangement. The measured fastener loads were independent from span
length, whereas the overall uplift resistance of IBR reduced with increased span lengths. Load-span resistance
data for 0.50 mm ISQ550 IBR was derived from testing to provide a rational framework for design. The FEA
provided a reasonable simulation of IBR subjected to static wind uplift and confirmed the presence of high
stress and strain concentrations around the fastener holes which cause fastener pull-through failures. Therefore,
FEA can be used as an effective tool to investigate the behaviour of IBR. In conclusion, the air-bag test
method used in this research investigation provided an effective method for evaluating the uplift performance of crest fastened metal cladding. However, the air-bag load method is not capable of accurately simulating a
true uniformly distributed uplift load. It is recommended that direct air pressure testing be adopted for any
further research or commercial testing ofmetal cladding because direct air pressure testing is an effective and
proven test method for accurate simulation of static and cyclic wind uplift conditions. / AFRIKAANSE OPSOMMING: Metaalbekleding met kruinvashegting op lae geboue is geneig om te faal by die vashegters tydens toestande
van sterkwind-opheffing. As vashegters faal kan bekleding progressief verwyderwordomrampspoedige skade
aan die gebou te veroorsaak. Die huidige ontwerpmetode vir metaalbekleding in Suid-Afrika is onvoldoende,
aangesien dit slegs gegrond is op vervaardigers se ontwerpspesifikasies. Spesifikasies word gewoonlik verklaar
as breë ontwerpriglyne vir die maksimum toelaatbare spasiërings van ondersteunings sonder enige oorwegings
vir ontwerpbelastings. Hierdie navorsing fokus dus op 0.50mm ISQ550 IBR metaalbekleding omdie basiese
gedrag van bekleding tydens wind-opheffing beter te verstaan en die ophefweerstand van IBR te kwantifiseer
vir ontwerpdoeleindes. Verder ondersoek hierdie navorsing ook die verbetering en evaluasie van ’n
volskaalse bekledingstoetsmetode wat statiese wind-opheffing naboots met verspreide lugsakbelasting volgens
die hersiende SANS 10237:201X gebruikskode. Hierdie proefskrif kan dien as ’n grondslag vir verdere
navorsing en die ontwikkeling van geskikte standaard-toetsmetodes vir metaalbekleding in Suid-Afrika.
Verskeie eksperimentele toetsmetodes en beperkte eindige-element-analises (EEA) is gebruik om die gedrag
van IBR en die toets-opstellings te ondersoek. Trektoetse is gebruik om die meganiese eienskappe van die bekledingsmetaal
te bepaal. Volskaalse toets-opstellings is gebruik om die weerstand van IBR te ondersoek en
die lugsaktoetsmetode te evalueer. Die gelokaliseerde gedrag van die bekleding rondom die vashegters was
ook ondersoek met klein toets-opstellings. EEA het gedien as ’n aanvullende ondersoek om die gedrag van IBR te evalueer. Die eksperimentele ondersoek het bevestig dat die wind-ophefweerstande van IBR-stelsels hoofsaaklik bepaal
word deur gelokaliseerde deformasies van die vasgehegde kruine en die vashegters se deurtrekweerstand. Die
gedrag en weerstand van IBR-stelsels is ook grootliks afhanklik van die toegepaste vashegtingsmetode. IBR stelsels
met vashegting deur elke kruin het ’n hoër ophefweerstand verskaf as IBR-stelsels met die standaard
vashegtingsmetode deur elke tweede kruin. Die gemete vashegterbelastings was onafhanklik van die spanlengtes,
terwyl die algehele ophefweerstand van IBR verminder het vir langer spanlengtes. Toetsdata is gebruik
om ophefweerstande vir 0.50mm ISQ550 IBR oor verskeie spanlengtes af te lei sodat ’n rasionele raamwerk vir
ontwerp bewerkstellig kan word. Die EEA het die gedrag van IBR tydens toestande van statiese wind-opheffing
redelik goed nageboots en het ook die teenwoordigheid van hoë spannings- en vervormingskonsentrasies
rondom die vashegtergate, wat vashegters laat deurtrek, bevestig. Daarom kan EEA as ’n effektiewe instrument
gebruik word om die gedrag van IBR te ondersoek. Ten slotte word dit afgelei dat die lugsaktoetsmetode van
hierdie navorsingsondersoek ’n effektiewe metode verskaf het vir die gedrag-evaluering van kruinvasgehegte
bekleding tydens wind-opheffing. Die lugsaktoetsmetode kan egter nie ’n ware gelykverspreide ophefbelasting
naboots nie. Daarom word dit voorgestel dat toetsmetodes wat direkte lugdruk aanwend gebruik moet
word vir enige verdere navorsing of kommersiële toetse van metaalbekleding, aangesien dit ’n effektiewe en
bevestigde toetsmetode is wat statiese en sikliese opheftoestande akkuraat kan naboots.
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Laser deposition of titanium and nickel intermetallic coatings on titanium for aerospace applications.Mokgalaka, Mokgadi Nomsa. January 2014 (has links)
M. Tech. Metallurgical Engineering / Titanium alloys exhibit poor tribological characteristic which include abrasion resistance, metal to metal wear resistance and solid particle erosion and cavitation due to low surface hardness and high coefficient of friction. These poor properties have limited the application of titanium alloys as engineering tribological components, tools and parts that operate in severe wear and friction conditions. Laser processing defects such as pores, cracks and segregation pose a huge threat to the quality and the microstructure of the deposited layer. Defects caused by the parameters lead to severe wear and corrosion occurrence, hence, precise control of the parameters are crucial and it depends on the properties of the material used. It is postulated that Nickel Titanium (NiTi) is a promising candidate as reinforcement matrix material for wear resistant alloy. The wear resistance would be further enhanced if NiTi is in-situ incorporated onto titanium matrix by laser cladding to yield hard intermetallic phases. The main goal of the study is to develop corrosive-wear resistant thin surface coatings on Ti-6Al-4V alloy for automotive and aerospace applications by depositing Titanium and Nickel elemental powders to form in-situ NiTi intermetallic using laser cladding technique.
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Surface coatings for 3-piece freight bogie centre bearingsFranklin, Matthew J. January 2008 (has links)
Thesis (M.E.-Res.)--University of Wollongong, 2008. / Typescript. Includes bibliographical references: leaf 226-238.
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