Dissertations / Theses on the topic 'Surface pitting'
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Daud, A. R. "The surface chemistry of pitting corrosion." Thesis, University of Surrey, 1985. http://epubs.surrey.ac.uk/770155/.
Full textFranzen, Justin Michael. "Contact Fatigue Evaluation of Ground and Chemically Polished Spur Gears Made of AISI 4118 Alloy Steel." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1370260045.
Full textTilson, Nial Robert. "An Experimental Evaluation of Micro-pitting Performance of Two Bearing Steels." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365695328.
Full textCheong, Kim Hong. "Influence of surface roughness on the pitting corrosion behaviors of stainless steels in different environments." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691159.
Full textChapman-Kpodo, H. "The surface structures associated with the very early stages of pitting corrosion on stainless steels." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/842894/.
Full textNETO, de JESUS ANTONIO C. "Estudo dos parâmetros: teor de NaCl e acabamento superficial, na resistência à corrosão por PITE em tubos de cobre." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11614.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
Klein, Mark Andrew. "An Experimental Investigation of Materials and Surface Treatments on Gear contact Fatigue Life." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243885964.
Full textScarabotto, Mônica. "Estudo da corrosão nas ligas de alumínio 3105 e 5052." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/183156.
Full textThe corrosion resistance of aluminum alloys is related to the exposure medium, chemical composition, presence of intermetallic particles and metallic microstructure, among others. This work investigated corrosion of 3105 H16 and 5052 H34 aluminum alloys commonly used in the bus body industry in aqueous media containing aggressive ions, such as chlorides, sulfates and hydroxyls. The behavior of these alloys with the protective coatings of Nanoceramic, Chromium VI, Chromium III and Paint System in accelerated atmospheric exposure and immersion in different aggressive media was evaluated comparatively. Further studies were restricted to untreated alloys for which accelerated exposure tests were performed on neutral salt spray, acetic salt spray, moisture chamber and natural atmospheric exposure. Field scanning electron microscopy was used to characterize the alloys surface before and after neutral and acetic salt spray tests. The electrochemical statement of the untreated alloys was determined by monitoring the open circuit potential, anodic potentiodynamic polarization curves and electrochemical impedance spectroscopy. Results have shown that the treatment with Chromium VI was the one that obtained better performance in the protection of the aluminum alloys, particularly for 5052 alloy. In general, 5052 aluminum alloy presented greater resistance to corrosion in all tested media, with or without surface treatments. Under salt spray exposure, the corrosion attack appeared mainly in the form of pitting. It has been proven that the effect of Cl- ion is important, but the predominant factor on the corrosion behavior of aluminum alloys is related to the pH of the exposure medium, which is recommended to evaluate protective coatings. Besides the conditions of the medium to which the metal will be exposed, in the selection of anticorrosive treatments it is important to consider the particularities of each alloy, since its compositional and microstructural characteristics exert a relevant influence on the corrosion performance.
Ba, Djiby. "Contribution à l'effet des éléments d'alliage sur la résistance à la corrosion de nuances duplex exposées à des environnements simulant leur marché d'application par le biais d'approches locales." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS060.
Full textDuplex stainless steels (DSS) are characterized by a two-phase structure comprising a mixture of ferrite and austenite. The proportion between the two phases is usually about 50%. They are increasingly used in the chemical, petrochemical, nuclear, marine and paper, mainly because of their excellent mechanical properties coupled with good resistance to pitting corrosion (low grade nickel and molybdenum). The austenite having a different chemical composition than the ferrite, a heterogeneous film is formed on the surface of duplex stainless steels. Furthermore, the two metallic phases having different mechanical properties, a field of heterogeneous stress is generated in the grains. Under certain conditions, these differences may also yield formation of a heterogeneous passive film. In this work, we study the effect of alloying elements on the physico-chemical properties of the passive film and behavior pitting corrosion before and after ageing in chloride media for a reference surface that meet certain criteria ie a smooth surface free from any defects (no hardened layer .. low roughness). The physicochemical properties of the film are studied using Auger and XPS analysis at the microscale. The corrosion behavior of duplex alloys was then determined from CPT tests (determination of the Critical Pitting Temperature). The results before ageing have shown that the passive film is homogeneous on a macroscopic scale and that pitting corrosion appear to be related to the grain size and crystallographic texture described by GOS. After ageing, surface analysis shows a strengthening of passivity by thickening of the passive film and the ratio Cr/Fe are significantly increased which has the effect of improving behavior pitting alloys. Metallurgical criteria for pitting were proposed
Weirich, Timothy Douglas. "Evaluating the Potential for Atmospheric Corrosion of 304 Stainless Steel Used for Dry Storage of Spent Nuclear Fuel." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557098372186951.
Full textZhang, Huayu. "Contribution à l'optimisation de la teneur en azote des aciers inoxydables austeno-ferritiques économiques par l'étude du comportement en corrosion à l'aide de sondes locales." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS046.
Full textDuplex stainless steels (DSS) are highly important engineering materials, due to their generally high corrosion resistance combined with high strength and moderate alloy cost (lower nickel and molybdenum content). They are widely used in various industrial sectors. DSS have a complex microstructure with comparable volume of austenite and ferrite. Due to differences in chemical composition between austenite and ferrite, a heterogeneous passive film is formed on both phases. In addition, due to differences in mechanical properties, a heterogeneous stress field may be generated in metallic grains. Under certain conditions, these differences may also yield formation of a heterogeneous passive film. In this work, the influence of long-term ageing in chloride-containing media by on the chemical composition of the passive film was first studied by means of XPS and Auger at the microscale. The corrosion behaviour of some duplex stainless steels was then determined from CPT tests (determination of the critical pitting temperature). Results were analysed taking into account information obtained previously. After ageing, the thickness and the ratio Cr/Fe are significantly increased. The chloride distribution in the passive film was heterogeneous. It was related to the microstructure and the residual strain field. It was shown that this distribution modifies the electrochemical behaviour of samples. The corrosion behaviour was then analysed from local polarization curves and CPT tests. Metallurgical criteria for pitting were proposed
Gravalos, Marcio Tadeu. "Efeitos da usinagem na integridade superficial de um aço inoxidavel superaustenitico." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263125.
Full textDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Foram investigados os efeitos das condições de usinagem em operação de torneamento na integridade superficial do aço inoxidável superaustenítico ASTM A744 Gr.CN3MN. A operação de acabamento foi o foco principal, porém também foram realizados estudos com a operação prévia, de desbaste. As principais variáveis no acabamento foram: ângulo de saída da ferramenta, velocidade de corte, profundidade de corte e avanço. No desbaste variou-se somente o ângulo de saída e a velocidade de corte. Os ensaios foram realizados em um torno horizontal CNC, utilizando fluido de corte. Os parâmetros analisados foram: microestrutura por microscopia ótica, rugosidade, encruamento por ensaio de microdureza e tensão residual por difração de raio-X. Para se estudar a resistência à corrosão por pites, superfícies usinadas foram imersas em solução de cloreto de ferro e examinadas no estereoscópio, medindo-se, por área, a densidade de pites e a perda de massa. Os resultados mostraram a presença de tensão residual de tração e de uma camada encruada em todas as superfícies usinadas. A redução da rugosidade elevou a resistência à corrosão por pite. A melhor combinação das condições de corte encontrada para obter os menores valores de rugosidade e de tensão residual de tração, no acabamento, para profundidade de corte de 0,2 ou 0,4 mm, foi a maior velocidade de corte (120 m/min), o menor avanço (0,1 mm/rot) e o maior ângulo de saída (10º), no desbaste; para a profundidade de corte de 2,5 mm e avanço de 0,25 mm/rot., foi a menor velocidade de corte (60 m/min) e o maior ângulo de saída (10º).
Abstract: An investigation was made of the effects of the machining conditions employed in the turning operation on the surface integrity of ASTM A744 Grade CN3MN superaustenitic stainless steel. The main focus was the finishing operation, but studies were also carried out with a prior roughening operation. The main input variables in finishing were: tool rake angle, cutting speed, cutting depth and feed rate. The only input variables in the roughening operation were rake angle and cutting speed. The tests were conducted on a CNC horizontal lathe, using cutting fluid flood. The following parameters were analyzed: microstructure and roughness - examined by optical microscopy; work hardening - determined by microhardness measurements; and residual stress - analyzed by X-ray diffraction. To study the pitting corrosion resistance, machined surfaces were immersed in a ferric chloride solution and examined under a stereoscope, measuring the pits density and mass loss per area. The results revealed the presence of residual tensile stress and a hardened layer on all the machined surfaces. Reducing the roughness caused the pitting corrosion resistance to increase. To obtain the lowest values of roughness and residual tensile stress in finishing at cutting depths of 0.2 or 0.4 mm, the best combination of cutting conditions was the highest cutting speed (120 m/min), the lowest feed rate (0.1 mm/v), and the highest rake angle (10º). In roughening at a cutting depth of 2.5 mm and a feed rate of 0.25 mm/rot., the best combination was the lowest cutting speed (60 m/min) and the highest rake angle (10º).
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
Colin, Dominique. "Obtention, corrosion et analyse de surface d'alliages amorphes inoxydables." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0111.
Full textJesus, Antonio Carlos Neto de. "Estudo dos parâmetros: teor de NaCl e acabamento superficial, na resistência à corrosão localizada e generalizada em tubos de cobre." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-07102011-140611/.
Full textCopper tubes manufactured with C12200 ASTM (99.9% Cu-0015-0040% P) are used worldwide for potable water transport. The largest number of leakages in these tubes is due to pitting, usually related to the water quality, associated to the presence of chloride ions originated from water disinfecting treatment. The literature on the effect of chloride on the corrosion of copper pipelines is controversial. The finishing of the copper tubes inner might also influence pitting corrosion. The lubricating oils used in the manufacture of copper tubes contain carbon and a deleterious film might form during annealing. The objective of this study is to investigate the effect of sodium chloride content and the inner surface finishing of copper tubes used for water transport (ABNT/NBR-13206) on their corrosion resistance. The study was carried out by electrochemical tests in naturally aerated sodium chloride solutions at various concentrations, at 25 °C. The tubes inner surface was observed previous to and after the electrochemical tests by scanning electron microscopy (SEM). The effects of the following surface finishing were investigated: degrease, sand blasting, annealing and the surface without treatment. A loop was built to simulate the operational conditions of the tubes. Results indicated that the corrosion mechanism in chloride solutions with concentrations between 0.06 mol L-1 and 0.12 mol L-1 was localized attack, whereas in the 0.6 mol L-1 solution, generalized attack was the predominant mechanism. The results the surface finishing investigation indicated that the treatments that leads to carbon content reduction are beneficial to corrosion resistance. However, other features must also be considered. For instance, although sand blasting reduces the carbon content on the tubes surface, the increase in roughness due to this treatment decreases the corrosion resistance. The surface treatments that resulted in increased corrosion resistance were those that also resulted in lower carbon levels at the surface, namely degreasing and annealing.
Guillotte, Ismaël. "Films passifs formés par voie industrielle sur aciers inoxydables : relations entre propriétés physicochimiques et électroniques et résistance à la corrosion localisée." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI042.
Full textStainless steels can suffer localized corrosion like pitting corrosion which can damage thestructural integrity of the material. The pit formation is mainly controlled by properties of theprotective layer formed on the stainless steel surface, which is called passive film. Many studies haveexamined pitting mechanism on model surface prepared in the laboratory. This work is dedicated tostudy the relations between physicochemical and electronic properties of industrially processedpassive films and their pitting corrosion resistance.The properties of passive films have been characterized with several methods which can beconventional or in a more innovative way: multi-pitting statistics and electrochemical noise for the useproperty, XPS and SDL for the surface chemistry, electrochemical impedance spectroscopy,chronoamperometry and photo-electrochemistry for semi-conductive properties of the passive films.Multi-pitting statistics and electrochemical transients which were usually used on modelsurfaces have been shown to be accurate for the evaluation of the pitting resistance of industrialsurface finishing samples. Furthermore, the comparison of the results of pitting resistance and of XPSand SDL analyses has shown that the chemical composition of passive films is not sufficient to explainthe difference of pitting resistance behavior among tested industrial passive films. However, the semiconductiveproperties characterizations are able to explain these differences of localized corrosionresistance. They confirm that structuration and defect level are two key parameters of pitting resistanceproperties of passive films.At last, this study highlighted that the pitting resistance of industrial passive films can beimproved by a short nitric acid treatment or by sweep voltammetry in neutral sulfate medium
Cafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/3870.
Full textCafe, Peter F. "Towards reliable contacts of molecular electronic devices to gold electrodes." University of Sydney, 2008. http://hdl.handle.net/2123/3870.
Full textSYNOPSIS OF THIS THESIS The aim of this thesis is to more fully understand and explain the binding mechanism of organic molecules to the Au(111) surface and to explore the conduction of such molecules. It consists of five discreet chapters connected to each other by the central theme of “The Single Molecule Device: Conductance and Binding”. There is a deliberate concentration on azine linkers, in particular those with a 1,10-phenanthroline-type bidentate configuration at each end. This linker unit is called a “molecular alligator clip” and is investigated as an alternative to the thiol linker unit more commonly used. Chapter 1 places the work in the broad context of Molecular Electronics and establishes the need for this research. In Chapter 2 the multiple break-junction technique (using a Scanning Tunnelling Microscope or similar device) was used to investigate the conductance of various molecules with azine linkers. A major finding of those experiments is that solvent interactions are a key factor in the conductance signal of particular molecules. Some solvents interfere with the molecule’s interaction with and attachment to the gold electrodes. One indicator of the degree of this interference is the extent of the enhancement or otherwise of the gold quantized conduction peak at 1.0 G0. Below 1.0 G0 a broad range for which the molecule enhances conduction indicates that solvent interactions contribute to a variety of structures which could bridge the electrodes, each with their own specific conductance value. The use of histograms with a Log10 scale for conductance proved useful for observing broad range features. vi Another factor which affects the conductance signal is the geometric alignment of the molecule (or the molecule-solvent structure) to the gold electrode, and the molecular alignment is explored in Chapters 3 for 1,10-phenanthroline (PHEN) and Chapter 4 for thiols. In Chapter 3 STM images, electrochemistry, and Density Functional Theory (DFT) are used to determine 1,10-phenanthroline (PHEN) structures on the Au(111) surface. It is established that PHEN binds in two modes, a physisorbed state and a chemisorbed state. The chemisorbed state is more stable and involves the extraction of gold from the bulk to form adatom-PHEN entities which are highly mobile on the gold surface. Surface pitting is viewed as evidential of the formation of the adatom-molecule entities. DFT calculations in this chapter were performed by Ante Bilic and Jeffery Reimers. The conclusions to Chapter 3 implicate the adatom as a binding mode of thiols to gold and this is explored in Chapter 4 by a timely review of nascent research in the field. The adatom motif is identified as the major binding structure for thiol terminated molecules to gold, using the explanation of surface pitting in Chapter 3 as major evidence and substantiated by emergent literature, both experimental and theoretical. Furthermore, the effect of this binding mode on conductance is explored and structures relevant to the break-junction experiment of Chapter 2 are identified and their conductance values compared. Finally, as a result of researching extensive reports of molecular conductance values, and having attempted the same, a simple method for predicting the conductance of single molecules is presented based upon the tunneling conductance formula.
Coudert, Jean-Baptiste. "Impact de l'usinage de superfinition sur la zone affectée par le procédé : application à un matériau multiphasé." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS074.
Full textDuring machining, pressure and temperature conditions at the machined surface are veryintensive. Machined material microstructure and mechanical state are changed, whichimpacts the chemical reactivity of the machined surface. In this PhD study, we focus onsuperfinish turning of heat treated martensitic stainless steel X4CrNiMo16-5-1 (namedoptimized APX4). It has to be mentioned that this material has a multiphased microstructureat ambient temperature (martensite, ferrite and austenite). The aim is then to quantifyrelationships between cutting conditions, properties and the deterioration (corrosion) ofmachined surfaces. Machining trials in orthogonal cutting configuration (QST) have beenrealized in order to compare experimental results directly to 2D numerical forecast ofmachined surfaces.Material phase transformations have been studied by calorimetry tests until 1200°C. Testshave evidenced different metallurgical transformations. The complementary bibliographystudy allows to conclude that phase transformation possibilities during machining are veryquasi nonexistent due to extremely high heating kinetics in turning.Machined samples have been characterized by a microstructural study by opticalmicrography and SEM-EBSD. Both techniques highlight high strains in extreme machinedsurface as indicated by the stretching of ferrite islands in parallel to the machined surface.Microstructural results have been linked to the Vickers microhardness results. Surfacehardness has been expressed as a function of the cutting conditions.EBSD measurements have shown for machined samples in the most severe conditionsstraining of the ferrite with low angle grain boundaries, microstructural refining ofmartensite and heightening of martensitic matrix close to the strained ferrite.A numerical simulation predicting strains at the macroscopic scale has been carried out.These numerical results have been compared to strain and microhardness results arise fromone trials campaign. Further numerical simulations applied at the microstructure level(considered as biphased material) allow understanding of ferritic phase strain and its localinfluence on martensitic matrix strain. These results are consistent with experimentalresults.Pitting corrosion phenomenon has been studied by polarization testing using theelectrochemical microcell and specific pulsed testing. Last used method has been conductedto analyze the generated pits (diameter and density). Localized corrosion resistance ofmachined martensitic stainless steel surfaces remains good, even improved (few times lowerpitting density than the reference state). This behaviour is corroborated to the compressivestate of the surface.Surface microhardness, which is mainly controlled by the feed rate, conditions the criticalpitting potential. Increased pitting diameter has been linked to microstructural refining(observed above a surface microhardness level)
Vrček, Aleks. "Micro-pitting and wear characterization for crankshaft roller bearing application." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68418.
Full textPacquentin, Wilfried. "Contribution à l'étude des propriétés physico-chimiques des surfaces modifiées par traitement laser : application à l'amélioration de la résistance à la corrosion localisée des aciers inoxydables." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00676332.
Full textFreitas, De Abreu Marcio. "Experimental Study of Metallic Surfaces Exposed to Cavitation." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231937.
Full textMoscatelli, Michel. "Role du molybdene dans la dissolution et la passivation d'alliages nickel-molybdene : influence du soufre." Paris 6, 1987. http://www.theses.fr/1987PA066542.
Full textLin, Chung-Ming, and 林忠民. "Fundamental Studies on Electrical Pitting Mechanism of Lubricated Metal Surface." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/88611386608226108658.
Full text國立中山大學
機械與機電工程學系研究所
91
Abstract The electrical pitting often occurs at the bearing of the ro-tating machinery due to the actions of the shaft voltage and the shaft current resulting in the arcing effect on the lubricated surface and causing the bearing failure. Since the mechanism of the electrical pitting cannot be microscopically observed in process, it is difficult to prevent the bearing damage. Hence, this study uses a static electrical pitting tester with sub -micrometer accuracy to experimentally investigate the effects of supply voltage, supply current, oil film thickness, and ad-ditive on the threshold condition of electrical pitting under the conventional bearing material pairs. Moreover, according to the SEM micrograph and EDS analysis, the mechanism of the pitted surfaces is investigated. According to the experimental results and the surface ob-servations of steel/steel pair using a paraffin base oil, three electrical pitting regimes are found under the influences of shaft voltage and oil film thickness, namely, pitting, transition, and no-pitting regimes. In the electrical pitting regime, the interface voltage, interface impedance, and interface power increases slightly with increasing oil film thickness at a certain supply current. However, the interface voltage and interface power increases with increasing supply current, and the inter-face impedance decreases with increasing supply current at a certain film thickness. Furthermore, the pitting area versus the interface power relationship is a cubic function. According to the experimental results and the surface ob-servations of babbitt alloy/steel pair using a paraffin base oil, two electrical pitting regimes are found under the influences of shaft voltage, oil film thickness, and melting point of material, namely, pitting and no-pitting regimes. The mechanism of electrical pitting on the babbitt alloy surface is significantly influenced by the interface power and the oil film thickness. At the smaller oil film thickness, the eroded surface of babbitt alloy exhibits a concave crater with a few micro-porosity in the vicinity of center region with a plateau on its surrounding, especially at high supply current. The polished track can be observed at the plateau. A large amount of tin element trans-fers to the steel ball surface because the molten tin contacts the ball. At the higher oil film thickness, only a little amount of metal element transfers to each other. The major pitting area of the babbitt alloy is caused at the initial stage of the arc dis-charge. With increasing arc discharge time, the pitting area increases slightly, and finally reaches a saturated value. According to the experimental results and the surface ob-servations of babbitt alloy/steel pair using an additive of MoS2 in a paraffin base oil, two electrical pitting regimes are found under the influences of shaft voltage, oil film thickness, and particle concentration of additive, namely, pitting and no-pitting regimes. The area of pitting regime increases with increasing additive concentration and supply current. Fur-thermore, the ratio of pitting area to the interface power in-creases with increasing additive concentration and supply current at the oil film thickness smaller than 6 mm. However, this ratio increases rapidly to about 10 times with increasing additive concentration and supply current as the oil film thickness increases from 6 mm to 10 mm. This results from the molten plateau that directly connects two specimens, and the interface power is mainly consumed at the heating of the pla-teau and the interfacial materials. According to the above re-sults, the growth model of the plateau on the pitting surface is proposed at the lubricated condition using an additive of MoS2 in paraffin base oil.
Chou, Chau-Chang, and 周昭昌. "Tribological Effects of Surface Roughness and EP additive on the Run-In Process and Pitting Behavior of Oil-Lubricated Line Contacts." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/23059756718786907571.
Full text國立成功大學
機械工程學系
86
A gear/cam adapter was employed to study various aspects of line-contact lubrication, using oil with extreme-pressure at two different concentrations. The effect of run-in on the tribological performance of rollers with two different surface roughnesses was investigated in terms of friction coefficient, wear loss, oil temperature, specimen roughness and electrical resistanc?蒞he relation between roller wear loss and the time rate of electrical resistance change was established. The run-in effect on roller wear loss in smooth rollers is opposed to that in rough rollers. The asperity height of the smooth rollers was increased by wear testing irrespective of run-in; however, run- in enhanced the increase in surface roughness. The extreme- pressure additive concentration instead of run-in was the decisive factor in electrical resistance. Friction coefficient during testing showed a strong positive relation with composite surface roughness. The pitting behavior of rollers with two different surface roghnesses was investigated in terms of crack length, chemical reaction thin film, pitting area, pitting depth, and specimen''s life. Rollers with a rough contact surface induced a longer life by means of a shallower stress distribution in the subsurface. The presence of extreme-pressure additive in the base oil reduced Weibull slope and promoted the L50 life. The results were confirmed due to the plastic flowing of Beilby layer, which restrained the propagation of cracks.
Klages, Peter E. "In Situ Real-time Visualization and Corrosion Testing of Stainless Steel 316LVM with Emphasis on Digital In-line Holographic Microscopy." 2012. http://hdl.handle.net/10222/15397.
Full textLin, Shin-Min, and 林欣民. "Effect of kinematic parameters on electrical pitting formation mechanism for the lubricated surfaces." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/13360882680151672446.
Full text國立中山大學
機械與機電工程學系研究所
91
When the shaft current passes through the bearing under lubrication condition, the arc often occurs and the pitting can be observed on the surface of bearing. Consequently, the life of bearing is shortened. The pitting resulting from discharge is dependent upon the shaft voltage, the oil film thickness, and the insulation of lubricant. To simulate the pitting, the dynamic pitting tester is developed to investigate the effects of the kinematics parameters on the electrical pitting formation mechanism for the common material of bearing by changing the supply voltage current and the oil film thickness. Result show that in the static condition, since the arc action causes the surface melting of two specimens, and the actions of coulomb force and electrostatic force cause the specimens to attract each other, the plateau can be observed on the surfaces of specimens. The plateau is like a bridge to connect two specimens. In this moment the plateau accumulates continuously and causes two specimens to produce the repulsive force. In the dynamic condition, the formation of pitting at the initial stage is quite similar to that in the static condition. Since the effect of sliding speed, the bridge is sheared and the friction force increases. Under the actions of joule heat and friction force, the surfaces of two specimens melt and scratch continuously. When the dynamic pitting occurs, the pitting width of square specimen, the normal force and the friction force increases with increasing supply voltage, supply current, and oil film thickness. When the interface power is larger, the melting phenomenon is more obvious, and the pitting width becomes larger. Because the surface melting and the actions of Coulomb force and electrostatic force cause the material accumulates continuously, the normal force and the friction force increase with increasing the interface power. To investigate all effects of experimental parameters on the pitting width, the empirical formula for the pitting width is established in terms of supply voltage, supply current, and oil film thickness. This formula can be used to predict oil film thickness or the size of pitting width on the bearing surface for diagnosing the lubricant condition of bearing.
CHANG, SHEN CHENG, and 沈政昌. "Studies on the Electrical Pitting Mechanism of the Contact Surfaces for Steel Pairs Under AC Electric Field." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/82574480198388386697.
Full text