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1
Carroll, Robert Ian. "Surface metallurgy and rolling contact fatigue of rail." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/14639/.
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This thesis presents the results of an investigation into the effect of surface metallurgy on the rolling contact fatigue behaviour of rail. The investigation has used laboratory based rolling/sliding twin disc testing of samples with a surface metallurgical feature simulated on them. The samples used in laboratory testing have been compared with samples of rail removed from track. Two surface metallurgical features have been investigated: decarburisation and white etching layer. Decarburisation is the loss of carbon from the surface of the rail due to oxidation at high temperatures, resulting in a softer layer at the surface (180HV compared to 250HV bulk). The decarburised layer has been simulated in this research by heat treating discs in a laboratory furnace with an air atmosphere. The results show that by increasing the depth of decarburisation the growth rate of cracks within the sample, along with the wear rate, increases. At the maximum depth of decarburisation allowed on rail by the standard (O.5mm) there was little difference in the wear or rolling contact fatigue behaviour with or without decarburisation. White etching layer (WEL) forms on the surface of rail due to the action of the wheels and is a very hard layer (>850HV) up to 250mm deep. White etching layer has been simulated in two ways: spot welding and gross sliding of the discs. The results have shown that cracks initiate preferentially at weak spots at the surface, such as the interface between the WEL and pearlite or along proeutectoid ferrite boundaries. It has been found that the growth of cracks below the surface depends on the strain history of the subsurface pearlite. The results indicate that white etching layer is detrimental to rail life through either the promotion of rolling contact fatigue and/or wear.
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Li, Hongchun. "A study on wear and surface roughness of work roll in cold rolling." School of Mechanical, Materials and Mechatronic Engineering - Faculty of Engineering, 2008. http://ro.uow.edu.au/theses/125.
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The objective of this study is to improve our understanding of the evolution and tribological behaviour of work roll surfaces in cold rolling because surface deterioration affects the quality of products and the efficiency of production. The cost of rolls is almost 25% of the cost of cold steel production. An experimental Lateral Set-testing (LST) mini-mill was developed to make use of the Gleeble 3500 thermo-mechanical simulator functions to evaluate, for the first time, the roll material surface features, surface roughness, fast Fourier transform (FFT) and Power Spectral Density (PSD) of frequency distribution, after single and multi-pass rolling. A low carbon-steel was prepared for the paired disc and then experiments on disc-to-disc wear were carried out to test surface deterioration and friction. In the laboratory, material imitating an industrial roll was manufactured. One batch contained 4%Cr and another contained 4%Cr plus approximately 0.1% Ti. These materials were compared against each other in the LST and disc-to-disc experiments. Experiments considered a series of parameters, including strip reduction, speed, and lubrication, while the disc-to-disc experiments considered duration of wear, forward and backward slip and load amplitude. The surfaces of the LST roller and disc were evaluated by surface technologies such as Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and surface profile-meters. Transmission Electron Microscope (TEM) and X-ray diffraction wear properties. Test results from the mini-mill reveal that dominant waviness of the surface roughness still exists on the surface after a single pass of rolling and a 30.5% reduction is a critical reduction level that has a significant influence on the density of power spectrum. A rougher work piece results in a larger power spectrum of the surface profile. It has found that the PSD altitude of the roller surface is significantly affected axially but is more sensitive to its original surface roughness circumferentially. It is distributed in an inverse order to the surface roughness in a high frequency domain. The addition of Ti alters surface deterioration. Lubrication has a significant effect on surfaces containing either 4Cr% or 4%Cr+Ti, affecting surface roughness of rollers containing 4%Cr more significantly. In the disc-to-disc tests, more material was removed in the first 60 minutes from the disc containing Ti than the disc containing only 4%Cr. In general, roll material with 4%Cr+Ti reveals to have better anti-abrasive properties than the roll with only 4%Cr, while lubrication significantly reduced the wear rate and amount of material removed from both materials. The speed of the disc influences the weight loss, ie, the higher the speed the greater the amount of material removed. The slip rate also affects roll wear and weight loss because as the speed increases, so do the slip and loss of weight. The coefficients of friction are between 0.35~0.75 when the contact was dry and 0.06~0.11 when lubrication was applied. Adhesive friction dominated the dry contact while a mixed lubrication regime features friction behaviour when emulsion lubrication was applied. A backward slip of 2% and a forward slip of 1.5% resulted in a different coefficient of friction in dry contact mode although the corresponding torques were similar. The torque and coefficient of friction are found to increase with disc speed in dry contact condition. Lubrication alters the friction of both materials. The coefficient of friction decreases with speed on the disc with added Ti but the effect of load is in the opposite trend, while the disc with 4%Cr was less influenced by speed. The coefficient of friction is more sensitive to load at higher speeds on the disc with 4%Cr than at slower speeds on the disc with Ti added. This indicates that the addition of Ti enhances the tribological behaviour of rollers because the disc with Ti additive is characterised by carbonitrades precipitated in a refined tempered martensitic matrix. Coarse carbides characterise the 4%Cr disc materials. Surface defects of the work rolls, including banding, spalling, marking and welding in a cold strip plant, were investigated. It was found that early failures principally resulted from operational factors and roll material off-specification micro-structure defects rather than wear. It is recommended that different grades materials of the roll and strip with different roughness and hardness to be tested and studied on the evolution and tribological behaviour of roll surfaces in the future.
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McCarthy, Erik L. "Selective Biomolecular Layers for Surface-associated Rolling Circle Amplification." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/McCarthyEL2006.pdf.
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Kim, Tae Hyun. "Fatigue of surface engineered steel in rolling-sliding contact." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325019.
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Lundberg, Oskar Erik. "Vibrations induced by surface roughness in nonlinear rolling contacts." Licentiate thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155049.
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For efficient transportation in either trains, busses or passenger cars, rolling elements such as wheels, tyres, bearings and transmission elements are fundamental. The energy efficiency and the generation of noise and vibrations in rolling contacts depend on the surface roughness of contacting bodies. In order to optimize the surfaces of rolling elements, prediction of its impact on the dynamic response from rolling excitation is required. A computationally efficient method to include surface roughness in the modelling of rolling contacts is presented. More specifically, nonlinear effects on the contact force due to the threedimensional shape and roughness of the contacting surfaces are introduced in a moving point force formulation. As a consequence of the point force approximation follows the assumption that any dynamic wave motion within the contact area is negligible.The rolling contact force is nonlinear due to a varying relative displacement between contacting bodies and is therefore referred to as state-dependent. A study case for the state-dependent method consisting of a steel ball rolling on a steel beam showed good agreement between numerical predictions and measured beam vibrations. Furthermore, an application to the wheel-rail interaction show that roughness-induced contact nonlinearities have a significant impact on the dynamic response caused by rolling excitation.QC 20141103
ECO2 Vehicle Design
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Avcioglu, Emir. "Measurement of surface deflection in rolling bearing by ultrasonic reflection." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21180/.
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Lundberg, Oskar. "On the influence of surface roughness on rolling contact forces." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193935.
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Road vehicle tyres, railway wheels and ball bearings all generate rolling contact forces which are transferred within a finite area of contact between the rolling element and the substrate. Either it is visible or not for the human eye, a certain degree of roughness is always present on the contacting surfaces and it influences the generation of both vertical and lateral contactforces. The purpose of this investigation is to enhance the understanding and modelling of the influence from small-scale surface roughness on the generation of rolling contact forces. To this end, a computationally efficient method to include roughness-induced contact nonlinearities in the dynamic modelling of rolling contacts is proposed. The method is implemented in a time domain model for vertical wheel–track interaction to model rolling-induced rail vibrations, showing good agreement with measurements. Furthermore, a test rig is developed and used for the investigation of tyre–road rolling contact forces. Detailed studies are performed on the influence of substrate roughness on the resulting contact forces for a tyre tread block which is rolling at different operating conditions. The choice of substrate as well as the rolling velocity and the slip ratio is observed to have significant influence on the resulting friction coefficient. For high slip ratios, stick–slip oscillations appear, exhibiting frequency content which is largely dependent on the choice of substrate. The outcomes of this study can potentially be used to improve future tyre–road contacts with respect to wear, traction and noise generation.QC 20161013
Centre for Eco2 Vehicle Design
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Frolish, Michael Fraser. "Design criteria for rolling contact fatigue resistance in back-up rolls." Thesis, University of Sheffield, 2002. http://etheses.whiterose.ac.uk/15083/.
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The demands placed on back-up rolls in hot strip mills have been investigated by a combination of literature and industrial studies. The tribological operating conditions have been established and the maximum local loads and pressure distributions at the work roll/back-up roll interface have been obtained by processing mill and roll schedule data using a computer program (commercial software developed by V AI Industries (UK) Ltd) and applying the theories of contact mechanics. After a study of the responses of the rolls to these demands and possible failure mechanisms, research has centred on surface initiated damage whereby cracks can propagate into the roll substrate potentially reaching the internal residual stress fields and leading to catastrophic failure. A proposed qualitative contact and fracture mechanics model, for the rolling contact fatigue and spalling failure, has been quantified theoretically using published methods for determining the stress intensity factors at the tips of pressurised and water lubricated, inclined rolling contact fatigue cracks. The predictions of the quantitative model in terms of crack directions and lengths have been validated by microscopic observation of the morphologies cracks produced in test discs used in the "SUROS" Rolling-Sliding Testing Machine and also in a sample of material spalled from a back-up roll. The quantitative failure model includes criteria for crack branching either upwards leading to micro spalling or downwards (potentially catastrophic) and the link between these two cases has been related quantitatively to the value of the mode I threshold for the roll material. After linking mechanics to microstructure and quantifying the interactions between wear and rolling contact fatigue in this case, practical quantitative recommendations have been made for the design of bainitic back-up roll materials, back-up roll redressing procedures and the surface roughness of both the work rolls and back-up rolls presented to the mill.
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Al-Sabti, Sara Louise. "Failure modes of polymethylmethacrylate resulting from rolling line contact." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311264.
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Nordén, Kristina. "Surface and Inner Deformation during Shape Rolling of High Speed Steels." Licentiate thesis, KTH, Materials Science and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4460.
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Shape rolling is a common manufacturing process used to produce long products i.e. bars and wire. One of the problems that might occur during rolling is defect formation leading to rejection of the finished product. This work is a step towards a better understanding of the evolution of some of these defects.
The evolution and reduction of cracks during shape rolling is studied in this thesis. To accomplish this, artificial longitudinal cracks are machined along bars of high speed steel. The cracks are positioned at different sites evenly distributed along the periphery in intervals of 45°. Some of the cracks are left open and some are filled with carbon or stainless steel welds. FE simulations are performed using the commercial code MSC.Marc and the results from the simulations are compared with experimental ones. Generally, simulations predict less reduction than observed experimentally. For most positions, the cracks tend to reduce most effectively followed by carbon steel welds and stainless steel welds.
To evaluate the inner deformation of a cross section during shape rolling in an oval-round-oval-round series, sample bars of M2 high speed steel are prepared with grids made up by stainless steel wires. After collecting samples after each pass, they are X-rayed to create an image of the grid. The deformation of the wires can favorably be described by FE simulations of a bar originally rotated 10° when entering the first pass. The results suggest that the simulations describe the deformation during shape rolling well.
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Nordén, Kristina. "Surface and inner deformation during shape rolling of high speed steels /." Stockholm : Materialvetenskap Materials Science and Engineering, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4460.
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Rycerz, Pawel. "Propagation of surface initiated rolling contact fatigue cracks in bearing steel." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44525.
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The useful life of mechanical components which experience highly stressed rolling/sliding contacts, such as rolling element bearings or gears, is limited by rolling contact fatigue (RCF). Surface initiated pitting is a mode of RCF which has in recent years received particular attention from industry due to its frequent occurrence in service. This work focuses on the growth behaviour of RCF cracks before they develop into surface pits. A three-contact disc machine was used to perform pitting experiments on bearing steel samples. Preliminary tests showed that surface initiated cracks could be reproduced under high contact pressure and mixed lubrication regime. However, it was not possible to detect them using the vibration monitoring system installed on the test rig. This led to the development of a high sensitivity crack detection system which employs the principle of magnetic flux leakage (MFL). The existing test rig was modified to accommodate an inductive sensor and required signal acquisition electronics. In addition, a signal processing procedure was developed to enable analysis in real time. It was shown that the MFL technique is significantly more sensitive than commonly used alternatives. The system is capable of automatically finding cracks down to about 100 μm in length. In addition, results have shown a linear relationship between defect size and signal amplitude which enables in-situ sizing of cracks. Using the crack detector, a procedure to generate cracks and extract their growth rates was established. Crack growth was first studied under high contact pressure. It was found that initiation occurred very early in total life, which was attributed to high asperity stresses due to mixed lubrication regime. Total life to pitting was dominated by crack propagation, the speed of which was shown to depend on crack size. Small cracks grew at a steady and slightly decreasing rate until a critical size is reached at which propagation speed rapidly increases, shortly followed by pitting. Further study at lower loads confirmed that contact pressure is the main parameter controlling propagation speed. In order to identify a suitable crack propagation law, the measured crack growth rates were plotted against a stress intensity parameter expressed in terms of maximum contact pressure and crack size. The results suggest that after reaching certain length, rolling contact fatigue cracks grow according to a Paris-type power law, where the exponent of stress intensity parameter, and therefore contact pressure, was found to be approximately 7.5.
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Lyubenova, Nataliya [Verfasser]. "Comprehensive characterisation and modelling of the surface integrity by deep rolling on flat surface / Nataliya Lyubenova." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1219068640/34.
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Kalil, Richard Charles Jr. "Evaluation of Frictional Characteristics of Precision Machined Surfaces." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5000.
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Precision surface finishes are used in a wide variety of applications. From bearing races and rolling elements to parallel slide ways, the frictional characteristics of these surfaces are critical to the performance of the products. Experimental trial and error has shown that certain surfaces outperform others in certain applications, but the specific surface characteristics that make this true have yet to be fully understood. The research goal was to develop an apparatus that can test the coefficient of rolling/sliding friction of different precision machined surfaces and to combine this data with topographic analysis of the surfaces to correlate specific 3-D parameters with the frictional performance of a surface.
The sample treatments consisted of four different surface textures (hard-turned, ground, honed and isotropic finish) and four different relative surface speeds. By monitoring the torque in the sample-mounting shaft under lubricated conditions the coefficient of rolling/sliding friction of each surface was found. Utilizing white light interferometry measurement of the surfaces, a highly detailed map of each surface was obtained.
Using different characteristic values of each machined surface (RMS roughness, asperity density, lay direction, etc.), the frictional behavior of the surfaces were compared to the surface characteristics yielding insight into the relationship between surface finish and friction in rolling/sliding contact. Friction coefficient was found to correlate most strongly with RMS roughness (Sq) and density of surface summits (Sds). These parameters govern mechanical interference of asperities and surface adhesion respectively. These findings suggest that friction coefficients of surfaces could be optimized through manipulation of three-dimensional surface parameters.
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Kang, J. "Influences of surface quality on the rolling contact fatique behaviour of ceramics." Thesis, Bournemouth University, 2001. http://eprints.bournemouth.ac.uk/309/.
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A novel eccentric lapping machine was designed by the author and manufactured in-house, to serve as a test bench to investigate the finishing process parameters in relation to surface quality, as well as the feasibility of accelerating the finishing process of HIPed silicon nitride balls. The kinematics of the eccentric lapping were analysed and discussed. Taguchi Methods were used to optimise the finishing parameters to achieve maximum material removal rate in lapping and to achieve minimum surface roughness value Ra in polishing. Two kinds of HIPed silicon nitride ball blanks were finished by this machine. A finishing rate of 68 µm/hour was achieved which is 15 times higher than the conventional concentric lapping (normally 3'-4µm/hour). The surface roughness and roundness of the polished ball were above grade 5, close to grade 3 precision bearing ball specification. The upper limits of lapping load and lapping speed were determined by aggressive lapping tests. The effects of various finishing parameters on the surface quality generated were studied by detailed surface analysis, including X-ray diffraction residual stress measurement. As a result, the relationship between the finishing process and surface quality has been established. Accelerated rolling contact fatigue tests were performed both under a standard 4-ball and a modified 5-ball rolling configuration, with a ceramic ball as the upper ball and steel balls as lower balls. The tests were conducted at high speed and lubricated conditions under different loads and were run for up to 135-200 million stress cycles. Tests were conducted on commercially finished balls with different surface roughness and with different surface integrity (heterogeneous porosity, star defect, grinding defect and C-cracks). Tests were also conducted on self-finished balls with different finishing parameters and with different surface roughness. After tests, the rolling tracks and failure areas were examined by detailed surface analysis. The residual stresses on the rolling tracks were measured. Finite Element Approaches were also employed to describe the contact stress status. Failure modes in relation to surface quality were discussed. The research has provided an understanding of the finishing process, surface quality and rolling contact fatigue behaviour of HIPed silicon nitride balls.
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Caicedo, Parra Dina Maria. "Mechanism to Quantify Road Surface Degradation and Its Impact on Rolling Resistance." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555430578466857.
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Mirjana, Filipovic. "Evolution of artificial defects during shape rolling." Licentiate thesis, Högskolan Dalarna, Materialvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:du-5215.
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Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs. The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.
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Pärssinen, Mikael. "Studies on dynamic response caused by contact between rough surfaces." Doctoral thesis, KTH, Vehicle Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3196.
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Li, Fan. "Thermo-elasto-plastic modelling of heat treatment processes with particular reference to large steel rolls." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299075.
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Filipovic, Mirjana. "Evolution of artificial defects during shape rolling." Licentiate thesis, Stockholm : Division of Mechanical Metallurgy, Department of Material Science and Engineering, Industrial Engineering and Management, Royal Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4350.
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Tang, Jianning. "A study of oxide scale deformation and surface roughness transformation in hot strip rolling." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061204.162042/index.html.
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Rudkins, Neil Thomas. "A study of surface friction to improve the Finite-Element simulation of Hot Rolling." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511473.
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Bozdana, Ali Tolga. "Surface enhancement of TI-6AL-4V using conventional and ultrasonic deep cold rolling processes." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433989.
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Su, Xiaoyan. "Surface initiated rolling/sliding contact fatigue in pearlitic and low/medium carbon bainitic steels /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,253.
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Santos, Viviane Castro dos. "Occupational vibration in tractor as affected by internal pressure of tires and rolling surface." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17096.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoThe globalized world appreciates the market competition between big companies, having no difference at all when it comes to the agricultural environment, because in order to acquire more customers, the tractor manufacturers tend to invest in technology to increase the machineâs efficiency. These improvements are required and aim to increase production, reduce production costs and to adapt the machines to their users, in order to have more quality within the work. Several factors can influence the machine operation quality, especially noise, temperature and vibration which may directly affect welfare. The present study aimed to evaluate the whole operator body exposure to vibration as well as his hands and arms on a tractor on the following conditions, three different tire air pressure, two different forward speeds and two different shooting surfaces. The experiment was conducted in the experimental area of the Agricultural Machinery Accident Investigation Laboratory belonging to the Department of Agricultural Engineering of the Federal University of CearÃ. The tractor utilized was a 4x2 tractor with auxiliary front wheel drive, Valtra brand, model BM 125i, year 2011 with a power of 91.9 kW (125 HP), maximum speed of 2,300 rotation per minute, equipped with radial tires. The experimental design was a completely randomized factorial 2 x 2 x 3 with two rolling surfaces (uncovered soil and soil covered with (Panicum maximum CV. Mombasa)), two forward speeds (4.3 km. h-1 and 6.4 km h-1), and three different tire air pressure (10, 14 and 18 lbs.pol-2) for the front tires and (12, 16 and 20 lbs.pol-2 ) for the rear tires. The experiment was conducted in accordance with the guidelines determined by the Brazilian operational hygiene standard number 09 and number 10 as well as the international ISO standard 5008, annex A. For the data evaluation, the statistical program ASSISTAT version 7.7 beta was utilized, checked for normality through the symmetry value and kurtosis analysis and consequently subjected to a variance analysis by F test, having the means compared by the Tukey test at 5% significance level. The vibration levels increased due to the increase in speed and the internal air pressure in tires and decreased with the use of the soil covering material. The best working condition was found in the following conditions, operations with soil covering material, at a speed of 4.3 km.h-1, using the tire air pressure at minimum (10 lbs.pol-2 on the front tires and 12 lbs.pol-2 on the rear tires).
O mundo globalizado preza pela concorrÃncia no mercado de grandes empresas e isso nÃo à diferente no meio agrÃcola, para adquirir cada vez mais clientes os fabricantes de trator tendem a investir em tecnologia para aumentar a eficiÃncia de suas mÃquinas. Essas melhorias sÃo necessÃrias nos tratores atuais e visam o aumento da produÃÃo, reduÃÃo de custos de produÃÃo e adequaÃÃo ao usuÃrio para que o mesmo possa desempenhar o trabalho com qualidade. VÃrios fatores podem influenciar na qualidade de operaÃÃo desempenhada pelo operador, principalmente fatores como, ruÃdo, temperatura, vibraÃÃo que interferem diretamente no seu bem estar. O objetivo do trabalho foi avaliar a exposiÃÃo do operador Ãs vibraÃÃes de corpo inteiro e mÃos e braÃos em um trator agrÃcola em funÃÃo da utilizaÃÃo de trÃs pressÃes internas de ar nos pneus, duas velocidades de deslocamento e duas superfÃcies de rolamento. O experimento foi realizado na Ãrea experimental do LaboratÃrio de InvestigaÃÃo de Acidentes com MÃquinas AgrÃcolas, pertencente ao Departamento de Engenharia AgrÃcola da Universidade Federal do CearÃ. O trator utilizado foi um trator 4x2 com traÃÃo dianteira auxiliar (TDA) da marca Valtra modelo BM 125i, ano 2011 com potÃncia do motor de 91,9 kW (125 cv), rotaÃÃo mÃxima de 2300 rpm, equipado com pneus radiais. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2 x 2 x 3, sendo duas superfÃcies de rolamento dos pneus (solo solto e solo com (Panicum maximum cv. MombaÃa) cobertura vegetal), duas velocidades de deslocamento (4,3 km.h-1 e 6,4 km.h-1), e trÃs pressÃes internas nos pneus, sendo (10, 14 e 18 lb.pol-2) para os pneus dianteiros e (12, 16 e 20 lb.pol-2) para os pneus traseiros. O experimento foi realizado de acordo com as diretrizes determinadas pela NHO â 09, NHO â 10 e o anexo A da norma NBR ISO 5008. Para avaliaÃÃo dos dados foi utilizado o programa estatÃstico ASSISTAT versÃo 7.7 beta, onde atravÃs dos valores de simetria e curtose foi verificada a normalidade e entÃo submetidos à anÃlise de variÃncia pelo teste F, e quando significativas, as mÃdias foram comparadas pelo teste de Tukey, a 5% de significÃncia. Os nÃveis de vibraÃÃes aumentaram em funÃÃo do aumento da velocidade e da pressÃo interna de ar nos pneus e diminuÃram com o uso de material de cobertura no solo. A melhor condiÃÃo de trabalho encontrada foi realizar as operaÃÃes com material de cobertura sobre o solo, na velocidade de 4,3 km.h-1 na pressÃo interna de ar nos pneus mÃnima (10 lb.pol-2 nos rodados dianteiros e 12 lb.pol-2 nos rodados traseiros).
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Stubbs, Richard Edward. "Development of a general three-dimensional model for on-line control of modern rolling processes." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8305.
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Edwards, Matthew. "Prediction and control of rolling noise in buildings." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI097.
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Les nouveaux bâtiments dans les zones urbaines sont divisés en zones commerciales et en zones habitables. Les magasins commerciaux se trouvent généralement au rez-de-chaussée, les résidences privées aux étages supérieurs. Cette utilisation a révélé des perturbations critiques dues au bruit généré par les chariots de livraison lorsque les bâtiments sont principalement occupés (par exemple tôt le matin). Ces chariots génèrent des vibrations à basse fréquence (moins de 100 Hz) qui se propagent facilement dans la structure du bâtiment et aux étages supérieurs, perturbant les habitants qui s'y trouvent. Si des travaux ont été réalisés pour étudier le bruit d'impact, peu de recherches ont été menées dans le domaine du bruit de roulement dans les bâtiments. Cette thèse présente un modèle original du bruit de roulement dans les bâtiments, prenant en compte les facteurs d'influence tels que la rugosité de la roue et du sol, les propriétés matérielles de la roue et du sol, la vitesse du chariot, et la charge sur le chariot. Les irrégularités discrètes, telles que les méplats des roues et les joints de sol, sont également prises en compte. Le modèle est capable de saisir les phénomènes physiques présents dans le contact de roulement à l'intérieur, ainsi que d'estimer l'avantage relatif du niveau sonore de l'ajout d'un revêtement de sol à un système de plancher donné. Le modèle peut être utilisé comme un outil pour étudier comment différents systèmes de revêtement de sol (y compris les systèmes multicouches) réagissent à l'excitation par roulement, dans le but de développer des solutions de construction à plusieurs étages qui sont mieux équipées pour combattre ce type de source de bruitNew buildings in urban areas are divided into commercial and residential areas. Commercial stores are generally located on the ground floor, private residences on the upper floors. This use has revealed critical disturbances due to noise generated by delivery carts when buildings are mainly occupied (e.g. early morning). These carts generate low frequency vibrations (less than 100 Hz) which easily propagate through the building structure and to the upper floors, disturbing the residents therein. While work has been done to study impact noise, little research has been done in the area of rolling noise in buildings. This thesis presents an original model for rolling noise in buildings: taking into account the influencing factors such as the roughness of the wheel and floor, the material properties of the wheel and floor, the speed of the trolley, and the load on the trolley. Discrete irregularities, such as wheel flats and floor joints, are also taken into account. The model is capable of capturing the physical phenomena present in the rolling contact indoors, as well as estimating the relative noise benefit of adding a floor covering to a given floor system. The model can be used as a tool to study how different flooring systems (including multi-layer systems) respond to rolling excitation, with the aim of developing multi-story building solutions that are better equipped to combat this type of noise source
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Hannes, Dave. "Modelling of surface initiated rolling contact fatigue crack growth using the asperity point load mechanism." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34005.
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Hedmark, Björn, and Per Wallgren. "Influence of ANS Triboconditioning on friction and fatigue in rolling contact configurations." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75597.
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The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.
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Zhao, Ping. "Three-dimensional boundary element and experimental analysis of lubricant ceramic surface ring cracks in rolling contact." Thesis, Bournemouth University, 2006. http://eprints.bournemouth.ac.uk/10552/.
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Surface defects such as ring cracks are located on silicon nitride ceramic rolling elements.The random nature of ring crack position creates difficulties in predicting rolling contact fatigue (RCF) life. The influence of the lubricant, contact pressure and crack geometry on the RCF mechanism is difficult to determine due to the variable nature of RCF life when the crack location is not defined. In this study, rolling contact fatigue was tested using a novel experimental technique. The test ceramic ball specimen with identified surface ring cracks was precisely located in the contact path. The rolling contact fatigue tests were conducted using a modified four-ball machine in a hybrid ceramic/steel combination with five different types of lubricating mediums at various contact pressures. Detailed analysis of damage progression was carried out to study the mechanisms of fatigue failure. A boundary element analysis was used to determine the stress intensity factors around the crack front and stress distributions on the surface in the presence of the surface crack. The RCF tests of silicon nitride balls with surface ring cracks showed that fatigue life was strongly influenced by load/contact stress, crack size,lubricant and material type. Ring crack spalling failure is not only influenced by sub-surface fatigue crack propagation but also strongly influenced by secondary surface cracks. The formation of the secondary surface cracks is a key factor which dominates spalling of rolling contact fatigue. Modelling work showed that the crack length was an important parameter.Increasing the crack length for given crack radius resulted in higher tensile surface stresses ahead of the original ring crack and also gave higher absolute K11 values. In addition, the crack gap and crack face friction had a significant effect on the formation of secondary surface cracks and fatigue crack propagation behaviour. Increasing the crack face friction decreased both the surface tensile stress and absolute magnitude of K11. Numerical calculation results were consistent with the experimental observations.
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Nioi, Manuel. "Surface defect evolution analysis in high silicon steels during hot rolling processes : experimental and numerical simulation." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18308/.
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Experimental and numerical approaches were used in the current research to investigate the evolution of superficial defects that develop on slabs of High Silicon content during the first stand of hot rolling processes. Understanding the deformation mechanisms of the initial surface features is essential for the prevention of critical defect formation on final products. Hot rolling experiments were carried out to determine the evolution of superficial cavities when the slabs are subjected to hot rolling. In addition, descaling experiments and hot ring compression tests were carried out to identify the friction coefficient present during the process. A model reproducing the hot rolling experiment was produced and a multilevel modelling approach was used to refine the mesh in the defects zone. The predictions are found in good agreement with the experiments. The results obtained from hot rolling experiments indicated the buckling of the lateral sides of the cavity to be the main cause of oxide entrapment and consequent defect formation. This is because the oxide inclusions beneath flaps of metal are most likely to resurface during successive slab thickness reductions appearing as surface defects. Experiments demonstrated the importance of depth to width aspect ratio of the initial surface features on the severity of the final defect. With regards to friction, isothermal ring tests demonstrate that friction coefficient increases with temperature and decreases with the thickness of the oxide present on the surface of the slab. The material models, the contact conditions and the modelling approaches developed are used to reproduce a full scale single rolling stand of a hot rolling process. The full-scale model was used to test the effect of different process parameters on the defects evolution and of different geometries on the deformation mechanisms. The model developed revealed that the friction is the main process parameter affecting the defect evolution during rolling. Higher friction coefficients facilitate the closure of the defect, increasing the severity of the final features formed. The geometry of the initial indentation before rolling was identified to be the main parameter which determines its deformation mechanisms. In particular, spherical cavities are easily eliminated during rolling. Conversely, pyramidal and cubical features tend to deform in a more severe way. For a given initial geometry, the initial aspect ratio of the defect was confirmed to play an important role in the final severity. The major limitation of the model was the excessive simplicity of the contact conditions between roll and slab in the defect zone. Nevertheless, the approaches used to produce the models can be extended to predict the deformation of different initial features presents on the surface of slab subjected to hot rolling processes and to reproduce the behaviour of defects for multistand rolling procedures.
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Wilke, Jeffrey A. (Jefrey Allan). "An economic analysis of defect flow and system-wide surface inspection at an aluminum rolling facility." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12395.
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Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1993, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1993.Includes bibliographical references (p. 119-120).
by Jeffrey A. Wilke.
M.S.
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Hasan, Mushfiq. "Investigation of micropitting and wear in rolling/sliding contacts operating under boundary lubrication conditions." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87215.
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Bjurström, Henrik. "Non-contact surface wave measurements on pavements." Doctoral thesis, KTH, Jord- och bergmekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201147.
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In this thesis, nondestructive surface wave measurements are presented for characterization of dynamic modulus and layer thickness on different pavements and cement concrete slabs. Air-coupled microphones enable rapid data acquisition without physical contact with the pavement surface. Quality control of asphalt concrete pavements is crucial to verify the specified properties and to prevent premature failure. Testing today is primarily based on destructive testing and the evaluation of core samples to verify the degree of compaction through determination of density and air void content. However, mechanical properties are generally not evaluated since conventional testing is time-consuming, expensive, and complicated to perform. Recent developments demonstrate the ability to accurately determine the complex modulus as a function of loading time (frequency) and temperature using seismic laboratory testing. Therefore, there is an increasing interest for faster, continuous field data evaluation methods that can be linked to the results obtained in the laboratory, for future quality control of pavements based on mechanical properties. Surface wave data acquisition using accelerometers has successfully been used to determine dynamic modulus and thickness of the top asphalt concrete layer in the field. However, accelerometers require a new setup for each individual measurement and are therefore slow when testing is performed in multiple positions. Non-contact sensors, such as air-coupled microphones, are in this thesis established to enable faster surface wave testing performed on-the-fly. For this project, a new data acquisition system is designed and built to enable rapid surface wave measurements while rolling a data acquisition trolley. A series of 48 air-coupled micro-electro-mechanical sensor (MEMS) microphones are mounted on a straight array to realize instant collection of multichannel data records from a single impact. The data acquisition and evaluation is shown to provide robust, high resolution results comparable to conventional accelerometer measurements. The importance of a perfect alignment between the tested structure’s surface and the microphone array is investigated by numerical analyses. Evaluated multichannel measurements collected in the field are compared to resonance testing on core specimens extracted from the same positions, indicating small differences. Rolling surface wave measurements obtained in the field at different temperatures also demonstrate the strong temperature dependency of asphalt concrete. A new innovative method is also presented to determine the thickness of plate like structures. The Impact Echo (IE) method, commonly applied to determine thickness of cement concrete slabs using an accelerometer, is not ideal when air-coupled microphones are employed due to low signal-to-noise ratio. Instead, it is established how non-contact receivers are able to identify the frequency of propagating waves with counter-directed phase velocity and group velocity, directly linked to the IE thickness resonance frequency. The presented non-contact surface wave testing indicates good potential for future rolling quality control of asphalt concrete pavements.QC 20170209
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Biswas, Souvik. "Simulation of thermo-mechanical deformation in high speed rolling of long steel products." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-1027103-203032/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: product geometry; hot rolling; high speed rolling; rolling simulation; bar and rod rolling; free surface; finite element analysis. Includes bibliographical references (p. 69-75).
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Hannes, Dave. "On fatigue crack growth modelling of surface initiated rolling contact fatigue using the asperity point load mechanism." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141151.
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Load transfer in applications or between machine components is generally achieved through contact. In case of recurrent high contact loads in combination with a rolling motion, i.e. with a relatively small amount of slip, the contact surface may eventually suffer from rolling contact fatigue (RCF). The damage consists then of cracks and craters or spalls, which can cause dysfunctionality of the application leading to inefficiency or increased maintenance costs. Ultimately the damage may cause total failure of the machine component. The damage process is still not fully understood due to the complexity of the problem. Different mechanisms have been suggested to explain initiation and propagation of RCF damage. The current work focused on crack growth modelling of surface initiated RCF in case hardened gear steel. The study was based on the asperity point load mechanism, which emphasizes the importance of the surface roughness in the damage process. Asperities on the contact surface act as stress raisers inducing locally high tensile surface stress when entering the contact. Improved understanding of the damage process and further validation of the asperity point load mechanism was achieved. In Paper A, the crack path of surface initiated RCF was simulated in the symmetry plane of the damage with the trajectory of the largest principal stress in the uncracked material. The mode I fracture mechanism was found applicable as well as linear elastic fracture mechanics (LEFM). The evolvement of the asperity contact parameters during the load cycle was determined through a finite element (FE) contact model based on an equivalent contact geometry. The predicted RCF crack path agreed with experimental spall profiles both in entry details as in overall shape. An experimental series was performed in Paper B to investigate the crack closure behaviour in presence of large negative minimum loads. The experimental results suggested a crack closure limit close to zero. The choice of the equivalent mixed-mode stress intensity factor range and especially the crack closure limit had a significant effect on the predicted RCF or spalling life. The two-dimensional crack growth model was further developed in Paper C and used to investigate the influence of asperity size, friction and residual surface stress on the simulated RCF damage. The simulations agreed qualitatively with experimental observations where reduced surface roughness, improved lubrication and compressive residual surface stress increased RCF resistance. In Paper D, a three-dimensional stationary crack was studied using an FE model and a simplified RCF load. A new crack geometry was proposed allowing the investigation of the spall opening angle of the typical vshaped damage. Crack arrest through crack closure was suggested as explaining mechanism. A qualitative study indicated increased spread of the surface damage with increased friction. The results also depended on the crack inclination angle. The different studies supported the asperity point load mechanism to explain not only fatigue initiation but also fatigue crack propagation.QC 20140210
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Stewart, William Elliott. "A Response Surface Exit Crown Model Built from the Finite Element Analysis of a Hot-Rolling Mill." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/45203.
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Nine independent and four dependent variables are used to build a response surface to calculate strip crown using the difference in the industry standard strip height measurements. The single element response surface in use provides the advantages of continuous derivatives and decouples rolling load from the determination of exit height. The data points to build the response surface are the product of a calibrated finite element model. The rolling dynamics in the finite element model creates a transient that requires nonlinear regression to find the system steady-state values.
Weighted-least squares is used to build a response surface using isoparametric interpolation with the non-rectangular domain of the mill stands represented as a single element. The regression statistics, the 1-D projections, comparisons against other response surface models and the comparisons against an existing strip crown model are part the validation of the response surface generated.
A four-high mill stand is modeled as a quarter-symmetry 3-D finite element model with an elastic-plastic material model. A comparison of the pressure distribution under the arc of contact with existing research supports the pressure distribution found with experiments conducted by Siebel and Lueg [16] and it also suggests the need for one improvement in the initial velocity for the strip in the finite element model.
The strip exit heights show more sensitivity to change than strip exit crown in seven out of the nine independent variables, so a response surface built with the strip exit height is statistically superior to using the derived dependent variable strip exit crown. Sensitivity of strip exit crown and the strip exit heights to changes in work-roll crown are about equal. Backup-roll diameter sensitivity is small enough that oversampling for the mean trend has to be considered or ignore backup-roll altogether. Strip entry velocity is a new independent variable, unless the response surface is built from the derived variable, strip exit crown.
A problem found is that the sensitivity of strip entry crown and work-roll crown requires a larger than typical incremental change to get a reliable measure of the change strip exit crown. A narrow choice of high and low strip entry crowns limits the usefulness of the final response surface. A recommendation is to consider the use of the strip cross-section as an exit crown predictor.Master of Science
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Paik, Kwang Jun. "Simulation of fluid-structure interaction for surface ships with linear/nonlinear deformations." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/569.
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The present research develops a numerical fluid-structure interaction (FSI) code based on CFDShip-Iowa version 4, a general-purpose URANS/DES overset fluid solver. Linear and nonlinear FSI methods are developed to compute structural responses on surface ships or marine structures. The modal superposition transient analysis and the nonlinear FEM structure solver are used for small and large deformation FSI problems, respectively.
The gluing method is applied to transfer the forces and displacements on non-matching grids for fluid and structure domains. The linear FEM solver is applied to deform the boundary layer grid with large deformation in the fluid domain, while the deformation is ignored in small deformation problems. Deformation of an interior point in the boundary layer grid is obtained using linear interpolation in both linear and nonlinear deformation problems.
The S175 containership is studied in regular waves as an application example for the linear problem. Heave and pitch responses are compared with the experiments, showing good agreement. Time histories of vertical bending moment (VBM) are calculated using rigid model, one-way coupling, and two-way coupling approaches. The elastic models are able to capture the ringing of the VBM induced by slamming, while the rigid model shows a peak at the moment of slamming without further fluctuations. The two-way coupling method shows the effects of hull deformation on the amplitude and phase of VBM as well as the accelerations of heave and pitch.
For the nonlinear deformation problem three sloshing tanks with an elastic bar clamped to its bottom or top are simulated and compared with the experiments and other numerical simulation results. The present simulation results show reasonable agreement with the experiments for bar deformation and free surface elevation. A secondary wave on the free surface is creadted by the vorticity generated from the free surface. The effect of the bar on the sloshing impact is studied comparing dynamic pressure acting on the tank wall without bar, with an elatic bar, and with a rigid bar.
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Qiao, Hua. "Prediction of contact fatigue for the rough surface elastohydrodynamic lubrication line contact problem under rolling and sliding conditions." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56019/.
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The study of elastohydrodynamic lubrication (EHL) with rough surfaces results in a transient problem due to time varying geometry. In conditions where the A ratio (the ratio of smooth surface film thickness to composite roughness) is low, significant pressure deviations from the corresponding smooth surface results occur. The relative motion of asperity features on the two surfaces leads to cycling of these pressure deviations as surface features move through the nominal contact area. Micropitting, which is a form of surface distress seen in gears, may well be viewed as rolling contact fatigue at the roughness asperity scale as a result of this load cycling. In order to understand the failure mechanism associated with rough surface EHL, a full theoretical model of lubrication of gear contacts under low A conditions is presented in this thesis. The model takes account of the real gear operating conditions in terms of loads, speeds, surface roughness and lubricant properties to predict pressures, film thickness, temperatures, and friction between the teeth. Subsequent contact stress analysis was performed to determine the stress history developed in the contacting solids. Conventional pitting is usually associated with failure beneath the surface of a rolling contact and in the past has been linked with the occurrence of the maximum shear stress that occurs in the classical Hertzian solution for smooth surfaces. In this thesis, a numerical procedure for predicting contact fatigue damage in an EHL line contact between two rough surfaces is developed to take the features of variable amplitude multiaxial fatigue into account due to the roughness effect. The way in which the calculated fatigue damage varies with changes in factors such as slide roll ratio, speed, viscosity, rough surface profiles, and A ratio adopted for the analysis is demonstrated in a series of numerical examples using roughness profiles taken from gears in micropitting experiments.
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Goodchild, Joanne. "The design of a laboratory test machine to simulate surface damage to work rolls for hot strip rolling." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247175.
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Cabut, Damien. "Characterisation of the flow in a water-puddle under a rolling tire with refracted PIV method." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEC025.
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L’écoulement au sein d’une flaque d’eau lors du passage d’un pneumatique en roulement est étudié dans ce travail. Une méthode de mesure adaptée aux mesures sur piste sous un véhicule en roulement est développée dans un premier temps. Cette méthode basée sur la méthode PIV (Vélocimétrie par Images de Particules), consiste en la réfraction de la nappe laser à l’interface hublot/écoulement afin de pouvoir éclairer les particules par le même accès optique que la collection d’images. Cette technique appelée refracted PIV (R-PIV) est caractérisée dans un premier temps sur un écoulement contrôlé en laboratoire. Cette technique est ensuite adaptée au cas de la piste pour les mesures in-situ. Ces mesures appliquées à la piste ont permis de mettre en évidence différents comportements de l’écoulement dans la flaque d’eau en amont du pneumatique mais également au sein des sillons pneumatiques. En amont du pneumatique les évolutions linéaires de la vitesse du fluide en fonction de la vitesse du véhicule est mise en évidence dans ce travail. Des effets non linéaires sont également observés et mis en lien avec la réduction de l’aire de contact pneu chaussée. Dans un second temps, l’étude de l’écoulement au sein des sculptures du pneumatique dans l’aire de contact nous permet de mettre en évidence deux grands types de sculptures. Le premier est composé de tous les sillons longitudinaux du pneumatique. Dans ces sillons, la vitesse de l’écoulement à travers ces sculptures dépend de la vitesse véhicule mais également de la présence du témoin d’usure du pneumatique. Un écoulement secondaire tourbillonnaire a également été mis en évidence grâce à nos mesures sur piste. Dans le second type des sillons composés de toutes les sculptures orientées transversalement, la vitesse du fluide, en leur sein, dépend de leur position dans l’aire de contact. Cette évolution semble être fonction de la déformation du pneumatique dans l’aire de contact. Pour finir, les interactions entre ces différents types de sculptures sont également discutées dans ces travaux permettant d’expliquer certains comportements spécifiquesIn this work, the fluid flow in a water puddle while a rolling tire crosses the puddle is studied. A measurement method adapted to track measurements under a rolling tire is developed. This method, based on PIV (Particle Image Velocimetry), is based on the refraction of the laser light sheet at the flow/window interface. This allows us to illuminate particles and record their images from a single optical access. This technique called refracted PIV (R-PIV) is characterised with a laboratory controlled experiment. When characterised, this technique is applied to in-situ measurements on the track. Measurements performed allow to highlight specific behaviours in different parts of the flow, in front of the tire and inside tire grooves in the contact patch area between the tire and the road. In front of the tire, the linear evolution of the water velocity in the puddle as a function of the vehicle speed is demonstrated. At high vehicle speed, non-linear effects are highlighted and linked to the shape of the contact patch area which evolves at high vehicle speed. Under the tire contact patch area, two main types of grooves contribute to the draining of water. Firstly, the longitudinal grooves are the straight grooves aligned with the rolling direction. In these grooves, the velocity of the fluid flow depends on the vehicle speed and also on the presence or not of the wear indicator. A secondary vortex like flow structure is also demonstrated in this work. The second type of grooves are the transverse grooves which are the grooves oriented with a certain angle compared to the car rolling direction. In these grooves, this work proved that the velocity is dependent on the groove location in the contact patch area. This seems to be linked to the tire deformation with the load of the car in the contact patch area. Finally, this work discussed the link between the different tire groove types to explain different specific behaviours
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Bombana, Lucas Tadeu Amarante. "Influência da qualidade e tipo de esmerilhamento de tarugos na geração de defeitos superficias de barras laminadas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/70682.
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Este trabalho avalia a influência do método e qualidade do esmerilhamento de tarugos na qualidade superficial de barras redondas de aço laminadas. Foi avaliada a rejeição de barras laminadas para três condições diferentes de acabamento superficial de tarugo – não esmerilhado, esmerilhado total simples, e esmerilhamento total duplo. Constatou-se que o esmerilhamento superficial de tarugos melhora a qualidade superficial de barras laminadas e, para os aços testados, o esmerilhamento total simples ofereceu melhor custo beneficio entre rendimento metálico e rejeição de barras por defeito superficial. Também se constatou que a profundidade de remoção da camada superficial do tarugo no esmerilhamento não é proporcional à redução de defeitos no produto laminado, sendo a aproximação da camada colunar uma variável com provável influência em tal resultado, assim como a presença de defeitos internos subsuperficiais, que tendem a aflorar com a redução da distância até a superfície da peça.This work evaluates the influence of billet grinding method and quality in surface defects of hot rolling steel bars. It was evaluated bar rejection rates due to surface defects for three different billet surface conditions: without grinding, bright grinding of the entire surface and double bright grinding of the entire surface. The results show that the bright grinding of the entire surface with a single pass results in better cost benefit between yield loss and bar rejection rates. It was also observed that the grinding depth of the superficial layer of the billet is not proportional to the reduction of defects in the rolled product. This may occur in consequence of the reduction of the chill zone thickness, or even by the presence of sub superficial defects that can emerge to the surface with the reduction of the defect distance to the billet surface
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Selvaratnam, Thevapriya. "Optimization and characterization of a centrally functionalized quartz crystal microbalance sensor surface for Norovirus detection : Optimering och karakterisering av en centralt funktionaliserad kvartskristall mikrovåg sensoryta för norovirus detektion." Thesis, KTH, Skolan för teknik och hälsa (STH), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172550.
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In this study a biosensor based on real time quartz crystal microbalance (QCM) monitoring is optimized and characterized for the application in the Norosensor. This biosensor is aimed to recognise, capture and amplify Norovirus (NoV). In an initial step a simplified bioassay was developed that focuses on the latter parts of the assay which consists of DNA-guided probing and amplification of the captured virus and includes the development of an amplification model assay directly to the functionalised crystal surface. A padlock probe with matching sequence to the conjugated oligonucleotide on the quartz crystal surface is used as target in the model assay. Although a number of studies have been carried out based on padlock probe ligation and rolling circle amplification (RCA) based QCM sensing, these studies utilize the entire crystal surface to capture and amplify the biomolecule. In this research work the QCM monitoring is explored on a centrally functionalised electrode surface through conjugation only at the centre of the electrode for increased mass sensitivity. Thus, allowing capture and amplification of the padlock probe only at the centre of the quartz crystal. A 14mm diameter, thermoncompensated AT-cut, nonpolished quartz crystal with a 10mm diameter gold surface coating acting as electrode was utilized for QCM measurements. The detection system is based on mass binding and amplification on the QCM to produce a negative frequency shift in the fundamental frequency of the vibrating quartz crystal. The amplification products were additionally fluorescently labelled and fluorescent microscopy images were also obtained at the end of every experiment to verify the presence or absence of DNA capture and amplification. Experimental findings show that the current flow chamber with a 15ul capacity is able to detect a specific padlock probe concentration of 1nM on a conjugated region of ~2.5mm diameter. RCA amplified the mass with an average frequency shift of -80Hz in 60mins RCA incubation time. Further, the specificity and sensitivity of the QCM system was explored. However, the system has limitations where sensor binding of reaction proteins, such as DNA ligase and BSA, to some extent is observed. The storage stability of the functionalized self-assembled monolayer (SAM) on the QCM is also observed to deteriorate and thus, is of concern. Nevertheless the combination of RCA based amplification with QCM real-time monitoring has the potential for rapid and simple, low cost detection of the Norovirus.I det här arbetet har vi optimerat och karateriserat en biosensor för detektion av Norovirus som orsakar häftiga utbrott av kräksjuka under vinterhalvåret vilket leder till både försämrad vård samt stora ekonomiska förluster för samhället. Målet inom EU projektet “Norosensor” är att utveckla ett snabbtest som kan tillämpas efter ett utbrott på till exempel en vårdavdelning och som ska mäta mängden virus i luften vilket kan fungera som riktlinje för om en avdelning är säker att användas eller ej. Tekniskt är målet med testet att fånga in viruspartiklar från luften som specifikt binds till sensorytan. Därefter ökar vi känsligheten från bundna partiklar genom en DNA-baserad amplifiering. Detta genererar specifik, viruskorrelerad massa som mäts med en kvartskristall mikrovågs sensor. När massan ökar minskar frekvenser vid vilken kristallen vibrerar och detta mäts i realtid. Det här arbetet har inte behandlat infångande eller inbindning av virus utan har fokuserat på den senare delen av protokollet som omfattar amplifieringen på sensorytan. En modell-assay har därför utvecklats där viruspartikeln istället representeras av en så kallad “padlock probe” (hänglås probe). Då sensorn är mycket känslig har först olika protokoll testats för effektiv rengöring av ytan med hjälp av ultraljud. I nästa steg har ytan funktionaliserats med thiol-modifierade syntetiska DNA molekyler som används för infångningen av målmolekylen på sensorytan (virus eller i detta fall padlock proben). Det har tidigare uppskattats att för att få maximal känslighet i massmätningen så är det fördelaktigt att binda viruset endast i mitten på en mycket liten yta av kristallen. Den här avhandlingen har därför fokuserat på att utveckla protokoll för detta där ytan först funtionaliserats i mitten innan resten av ytan blockats för att undvika ospecific inbindning. Resultaten visar att vi kan generera en centrerad funtionalisering och att vi får låg ospecifik binding. Protokollet består av flera biokemiska reakionssteg såsom (i) inbindning och lingering av padlock probe och (ii) amplifiering av den ligerade proben genom “rolling circle amplification”. För att kunna verifiera att vi fått amplifieringsprodukter på ytan har vi dels mätt frekvensändringen på grund av ökad massa men också märkt in dem med fluorescerande molekyler och detekterat dem i microskop. Under arbetets gång har ett flertal olika typer av kristaller testats. Det visade sig att om en polerad yta används (1μm grovhet) så migrerade molekylerna iväg från mitten när vi oscillerade kristallen medan vi fick bättre resultat om något grövre (3μm) ytor användes. Vi testade även ett flertal olika flödesceller av olika material och med olika reaktionsvolymer. Eftersom kristallen är mycket känslig så påverkar faktorer som flödeshastigheter och eventuella luftbubblor frekvensen. Vi optimerade därför detta och körde mätningarna vi6konstant flöde men med alternerande, låga hastigheter när vi tillsatte nya reagens eller inkuberade reaktionerna. Vi förvärmde även reaktionsmixarna för att minska ospeficika effekter och konstaterade att den funktionaliserade ytan påverkades av lagring över tid. I våra försök såg vi att protein såsom ligeringsenzymet och albumin, vilka har förhållandevis stor massa, hade effekter på frekvensen redan i sig genom att binda till ytan. Ytterligare optimeringar måste därför göras framöver för att minska denna inbinding bland annat genom bättre tvättsteg. Vi kunde dock påvisa linjär massökning med ökad amplifieringstid och har bevisad hög specificitet. Slutligen utvecklades ett litet mjukvaruprogram för att automatisera analysen och minska bruset. Sammanfattingsvis har vi lyckats utveckla ett enkelt och snabbt system för specifik massamplifering av Norovirus.
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Li, Kai. "Origins and evolution of near-surface microstructures and their influence on the optical property of AA3104 aluminium alloy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/origins-and-evolution-of-nearsurface-microstructures-and-their-influence-on-the-optical-property-of-aa3104-aluminium-alloy(69670a59-c416-40a1-920f-a246959791a4).html.
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The microstructures of the near-surface layers on AA3104 aluminium alloys and their evolution through rolling and deep drawing processes have been investigated. The effect of the near-surface layers on the optical property of AA3104 aluminium alloy has also been assessed. It was revealed that two types of near-surface deformed layers, both with different microstructures different from the underlying bulk alloy, were generated on the surface of AA3104 aluminium alloy during rolling. Both of them are characterized by ultrafine, equiaxed grains, with diameters <100 nm for type A near-surface deformed layer and <200 nm for type B near-surface deformed layer. A high population density of nano-sized, oxygen-rich particles is present along grain boundaries within type A deformed layer. But type B deformed layer is free of oxygen-rich particles. Type A deformed layer was generated through two mechanisms, i.e. geometric dynamic recrystallization and mechanical alloying. Rolling introduced plastic strain in the surface/near-surface region of aluminium sheet was of sufficient magnitude to cause geometric dynamic recrystallization and thus microstructure refinement. In addition, the incorporation of oxides into the near-surface region was also involved in the formation of type A deformed layer. However, the formation of type B deformed layer was only attributed to severe strain induced geometric dynamic recrystallization. Type A deformed layer was mainly formed at the early stages of hot rolling. The subsequent rolling and deep drawing reduced the thickness of type A deformed layer by distributing it over a larger surface area. During cold rolling, type A deformed layer broke into patches with the extension of alloy surface. Type B deformed layer may be generated on the nascent surface if the strain is sufficiently severe to cause geometric dynamic recrystallization. For the hot rolled alloy sheets, the surface/near-surface region is mainly covered by type A deformed layer. However, for the alloys after cold rolling, only limited area is covered with type A deformed layer. The thicknesses of the near-surface deformed layers are not uniform across the surface of AA3104 aluminium alloy. The maximum thickness of type A deformed layer on transfer slab is approximately 4 µm, while that on re-roll gauge sheet is ~1 µm, and ~0.8 µm on the final gauge sheet, ~400 nm on formed cup and ~100 nm on formed can. Type A deformed layer is randomly distributed as patches on the cold rolled aluminium sheet. The reflectivity of oxygen-rich particles is lower compared with the reflectivity of aluminium. As a result, the type A deformed layer patches absorb more incident light than the area without type A deformed layer. Further, there are plenty of micro-scale mini-cracks present on type A deformed layer, their opening sizes are in the equivalent scale of the wavelength of visible light. The incident light may not able to be reflected out if they go into these mini-cracks. It is more prone to happen for short wavelength light since it is easier for them to go into the mini-cracks than long wavelength light. As a result, less short wavelength visible light is reflected from the type A deformed layer patches. Thus, such patches exhibit a yellow appearance while the surrounding area appears the original silver white aluminium appearance. The aluminium sheet with a high coverage of type A deformed layer exhibits a low total reflectance. Further, its total reflectance is with a significant “red shift”. Neither the macro-scale surface roughness nor the ultrafine grain size affects the total reflectance of aluminium alloys. The total reflectance of aluminium alloys is primarily dependent on the presence of type A deformed layer.
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Moshaei, Mohammad Hossein. "Adhesion of Rolling Cell to Deformable Substrates in Shear Flow." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou153373230467728.
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Biscolla, Laura Maria da Cunha Canto Oliva. ""Controlabilidade do rolamento de uma esfera sobre uma superfície de revolução"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/45/45132/tde-31072006-141249/.
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O trabalho apresenta inicialmente os conceitos clássicos de rolamento (sem escorregamento e sem pivotamento) de uma superfície sobre outra usando os triedros de Darboux das duas superfícies ao longo das respectivas curvas de contato. Mostra, ainda, a equivalência desses conceitos com outras definições. A seguir, estuda-se a controlabilidade no problema do rolamento de uma esfera sobre uma superfície S de revolução, tanto no caso de rolar sem escorregar como no caso de não escorregar e não pivotar; a controlabilidade visa determinar a atingibilidade entre dois 'estados' da esfera (posição em S e orientação), isto é, de elementos do espaço das configurações S×SO(3). Na seqüência, estabelecem-se condições nos controles para que os rolamentos sem escorregamento e sem pivotamento ocorram sobre geodésicas de S e obtém-se, também, a controlabilidade nesta situação. Finalmente, verifica-se que, quando S é um plano, 3 ou 4 rolamentos retilíneos, sem escorregamento e sem pivotamento, são suficientes para garantir a atingibilidade entre dois estados da esfera.This work starts by presenting the classical concepts of rolling (without slipping and without slipping or twisting) of a surface over another one, using the Darboux referential frames of the two surfaces along their contact curves. It shows the equivalence between these concepts with other definitions. In the sequel one studies the controllability in the rolling problem of a ball over a surface of revolution S, including both: the non slipping and the non slipping or twisting cases; controllability aims to determine the reachability between two 'states'of the ball (position on S and orientation), that is, two elements of the configuration space S × SO(3). It follows by establishing conditions on controls in order that the rollings occur along geodesics of S and by studying the controllability in this situation. Finally, it is shown that if S is the plane, 3 or 4 retilinear moves without slipping or twisting are enough to guarantee reachability between two states of the ball.
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Shon, Samuel. "An Experimental Study on the Impact of Various Surface Treatments on Friction, Scuffing, and Wear Characteristics of Lubricated Rolling-Sliding Contacts." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1351629351.
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Šamánek, Otakar. "Snížení tření a opotřebení strojních částí cílenou modifikací topografie třecích povrchů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-234152.
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This thesis describes a study of the influence of surface texturing on rolling contact fatigue of non-conformal contacts. The texture depth and density have been considered during experiments. It also presents the methodology and the procedure of creation of micro-dents on sample surfaces. Described results suggested that properly designed surface texturing should not necessarily increase the risk of fatigue failure of rubbing surfaces.
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Maluf, Omar. ""Influência do roleteamento no comportamento em fadiga de um ferro fundido nodular perlítico"." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-17032004-163144/.
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O processo de roleteamento é um tratamento superficial, comumente utilizado em peças fabricadas em aços e ferros fundidos nodulares, em regiões onde há concentradores de tensões, com o intuito de melhorar as propriedades de resistência à fadiga. Este processo endurece e introduz tensões residuais compressivas na camada superficial do material, através de deformação controlada, provocando uma redução das tensões de tração que atuam na superfície da peça submetida a carregamentos cíclicos. Este trabalho teve como principal objetivo o estudo do efeito do roleteamento superficial sobre o comportamento em fadiga de um ferro fundido nodular de matriz perlítica, utilizado na fabricação de virabrequins pela indústria automobilística. Foram realizados ensaios de fadiga por flexão rotativa em corpos de prova lisos e com entalhe. Os corpos de prova com entalhe foram divididos em dois grupos, com e sem roleteamento superficial. Foi utilizado entalhe com geometria semicircular com raio de 1,20mm e profundidade de 0,70mm. Para o processo de roleteamento foi utilizado um rolete com diâmetro de 15,00mm e com raio de curvatura de 1,30mm e aplicada uma força de compressão de 2390N. A introdução de tensões residuais compressivas pelo trabalho a frio, dificultou a nucleação e a propagação de trincas na camada superficial dos entalhes roleteados. Isto ficou evidenciado pelo aumento do valor do limite de fadiga para 483MPa obtido para o material entalhado e roleteado, enquanto que para o material nas condições de sem entalhe e somente entalhado estes valores foram de 300MPa e 168Mpa, respectivamente.Surface rolling is a mechanical treatment commonly used in parts fabricated with steel and ductile cast iron, specifically in stress concentration regions, to improve fatigue properties. This process hardens and introduces compressive residual stresses to the surface of the material through the application of controlled strains, thus provoking a reduction of resulting tensile stress at its surface under cyclic loading. This work deals with the effect of surface rolling on high cycle fatigue behavior of a pearlitic ductile cast iron used in crankshaft by automotive industries. Rotating bending fatigue tests were performed in both smooth and notched specimens. The notched specimens were divided into two groups: with and without surface rolling treatment. The specimens notch geometry was semicircular with radius of 1.20mm and depth of 0.70mm. The rolling treatment was carried out using a roller with diameter of 15,00mm, curvature radius of 1.30mm and a compression force of 2390N. The introduction of compressive residual stresses under cold work made difficult the nucleation and propagation of the crack on the rolled surface of the notch. It was confirmed by the increase of the endurance limit of the surface rolled specimens to 483MPa in comparison with the smooth and notched specimens, respectively, 300MPa and 168 MPa.
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Qin, Yang. "Grain Boundary Engineering for Improving Intergranular Corrosion resistance of Type 316 Stainless Steel." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1505210960237495.
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