In modular hip implants, micro-motion, which leads to fretting corrosion at the head/neck and neck/stem interfaces, has been identified as a major cause of early revision in hip implants, particularly those with heads larger than 32mm. It has been found that the type of fluid used to simulate the fretting corrosion of biomedical materials is crucial for the reliability of laboratory tests. Therefore, to properly understand and effectively design against fretting corrosion damage in modular hips, there is the need to replicate the human body environment as closely as possible during in-vitro testing and validation. In this work, corrosion behavior of CoCrMo in 0.14 M NaCl, phosphate buffered saline (PBS) and clinically relevant simulated body fluid (sbf) is carried out. Also, fretting corrosion studies of the CoCrMo alloy in a clinically relevant novel simulated body fluid (sbf) environment is studied. The presence of phosphate ions in PBS accounted for the higher corrosion rate when compared with 0.14 M NaCl and sbf environment. Despite the low and comparable corrosion rates in 0.14 M NaCl and sbf, the nature of the protective passive film formed in sbf shows the suitability of the novel sbf for future corrosion and fretting corrosion analysis. Finally, the influence of micro-motion at the modular head/neck and neck/stem interfaces on the concentration of metallic ions that goes into the synovial fluid and surrounding tissues is reported.

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on July 15, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Materials Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-05-25T18:39:22Z No. of bitstreams: 1 2017_MarceloAvelarAntunes.pdf: 6625349 bytes, checksum: be484b2964cfc7af247df155d40aebb2 (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2017-06-06T17:41:25Z (GMT) No. of bitstreams: 1 2017_MarceloAvelarAntunes.pdf: 6625349 bytes, checksum: be484b2964cfc7af247df155d40aebb2 (MD5) / Made available in DSpace on 2017-06-06T17:41:25Z (GMT). No. of bitstreams: 1 2017_MarceloAvelarAntunes.pdf: 6625349 bytes, checksum: be484b2964cfc7af247df155d40aebb2 (MD5) Previous issue date: 2017-06-06 / Este trabalho propõe soluções para fadiga por fretting utilizando fatores concentradores de tensão modificados para ligas de aço, alumínio e titânio, os quais são utilizados para se obter fatores de intensidade de tensão na análise com base na Mecânica da Fratura Baseada em Deformação. Primeiramente, um modelo numérico bidimensional com consideração de material elástico, isotrópico e homogêneo foi criado através do método dos elementos finitos. Assumiu-se que a nucleação da trinca ocorreu no ponto de máxima tensão normal na direção da carga remota de fadiga, seguindo uma trajetória retilínea sob tal ponto, da qual se extraíram os campos de tensões atuantes. Uma grande quantidade de campos de tensão foi gerada modificando-se, um de cada vez, parâmetros importantes no estudo de fretting, a saber: o coeficiente de atrito, a carga remota de fadiga, o raio do pad e o material. Todos os modelos propostos seguiram o regime de deslizamento parcial, com bons resultados sido obtidos quando comparados com as soluções analíticas. Através de funções de peso, fatores de intensidade de tensão elásticos sob o modo I foram obtidos, os quais foram então usados para se computar . Uma análise do comportamento de é então apresentada, seguida de sugestões de seu uso para se levarem em conta efeitos de plasticidade, conhecidamente presentes em no fenômeno de fretting. / This study presents modified stress concentration factor solutions for steel, aluminum and titanium materials under fretting fatigue conditions. solutions are used to obtain stress intensity factors in strain-base fracture mechanic analysis. At first, 2D numerical models with elastic, isotropic and homogeneous materials were created using finite element method. It was assumed that under the maximum tangential load in the bulk stress direction, a straight-line crack path was formed and all stress fields in such path were extracted. A vast number of stress fields were obtained by changing - one at a time – important fretting parameters, namely: coefficient of friction, bulk stress intensity, pad radius and material. All configurations respected a partial slip contact condition and the results obtained showed good agreement with the ones obtained analytically. Weight functions were used to obtain stress intensity factors under mode I, which were then used to compute . An analysis of behavior is then presented and discussed, followed by suggestions of its use taking into account plasticity, knowingly involved in fretting fatigue.

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-08-01T18:45:02Z No. of bitstreams: 1 2017_EduardoMartinsFontesdoRêgo.pdf: 7291379 bytes, checksum: 926fc7bacaecee6dd752d2d7412a3c4c (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2017-08-24T16:43:11Z (GMT) No. of bitstreams: 1 2017_EduardoMartinsFontesdoRêgo.pdf: 7291379 bytes, checksum: 926fc7bacaecee6dd752d2d7412a3c4c (MD5) / Made available in DSpace on 2017-08-24T16:43:11Z (GMT). No. of bitstreams: 1 2017_EduardoMartinsFontesdoRêgo.pdf: 7291379 bytes, checksum: 926fc7bacaecee6dd752d2d7412a3c4c (MD5) Previous issue date: 2017-08-24 / No presente trabalho é proposta uma metodologia para estimar a vida útil de componentes sob fadiga por fretting utilizando o modelo da Mecânica da Fratura Baseada em Deformação (MFBD), que é basicamente um modelo da Mecânica da Fratura Linear Elástica (MFLE) desenvolvido para considerar os efeitos da não linearidade do material. Neste modelo não há necessidade de distinguir a vida em iniciação e propagação de trincas, a vida é considerada como sendo apenas de propagação. Considera-se a modelagem de trinca curta, na qual o comportamento do material é não linear, isto é, fora do domínio da MFLE. A propriedade de plasticidade do material é levada em conta pela curva de Ramberg-Osgood em associação com a regra de Neuber. No final do processo de estimativa de vida, a regra de crescimento de trincas de Paris-Erdogan é aplicada para obter o número de ciclos. O fator de intensidade de tensão é obtido pelo método da Função Peso, no qual as distribuições de tensões são obtidas pelo Método dos Elementos Finitos (MEF) por meio do programa comercial ANSYS, onde considera-se o contato entre dois corpos. A análise numérica apresentada aqui para a estimativa da vida de fadiga por fretting é comparada com dados experimentais do alumínio 7050-T7451. / In the present work, a methodology is proposed to estimate the life of components under fretting fatigue using Strain-based Fracture Mechanics (SBFM) models, which is basically a modification of the Linear Elastic Fracture Mechanics (LEFM) to consider the non-linear properties of materials under the aforementioned condition. This model does not require two steps to model fatigue life, being considered only the life propagation. A short crack behavior is applied here, where the material behavior is non-linear, i.e., outside the LEFM domain. The plasticity property of the material is taken into account by the Ramberg-Osgood curve in association with the Neuber rule. At the end of the process, the Paris-Erdogan crack growth rule is applied to estimate the fatigue life N. The Stress Intensity Factor is obtained by Weight Function method, where the stress distribution are computed by Finite Element Method (FEM) through the commercial program ANSYS, taking in consideration the contact between the surfaces. The numerical analysis presented here for estimation of fretting fatigue life is compared with experimental available data from aluminum 7050-T7451.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2015. / Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2015-12-04T13:07:44Z No. of bitstreams: 1 2015_RaphaelAraujoCardoso.pdf: 4524264 bytes, checksum: 5ea4d3c957b8492a91bd31fad78fdf80 (MD5) / Approved for entry into archive by Guimaraes Jacqueline(jacqueline.guimaraes@bce.unb.br) on 2016-03-28T11:33:00Z (GMT) No. of bitstreams: 1 2015_RaphaelAraujoCardoso.pdf: 4524264 bytes, checksum: 5ea4d3c957b8492a91bd31fad78fdf80 (MD5) / Made available in DSpace on 2016-03-28T11:33:00Z (GMT). No. of bitstreams: 1 2015_RaphaelAraujoCardoso.pdf: 4524264 bytes, checksum: 5ea4d3c957b8492a91bd31fad78fdf80 (MD5) / O objetivo desse trabalho é avaliar o fenômeno de propagação de trincas em condições de fretting. Uma metodologia mais genérica para estimar o fenômeno de parada de trincas curtas foi proposta e diferentes modelos para estimar a direção de iniciação e a posterior propagação de trincas também foram avaliados. Teorias clássicas como o método da distribuição das discordâncias e rotinas robustas em elementos finitos foram utilizadas para calcular os parâmetros mais importantes desse trabalho. Dados experimentais disponíveis na literatura foram utilizados para verificar a acurácia das metodologias em estudo. A metodologia proposta para avaliar o fenômeno de parada de trincas curtas foi capaz fornecer melhores resultados que outras presentes na literatura quando uma curva mais genérica para o fator de intensidade de tensão limiar (Δℎ), baseada no parâmetro material de Bazant, , foi utilizada. A respeito da estimativa da direção de iniciação de trincas, duas metodologias baseadas na Teoria das Distâncias Críticas foram avaliadas e um delas (o Método da Direção Crítica) foi capaz de fornecer satisfatoriamente a direção de iniciação das trincas, enquanto que a outra metodologia baseada em uma abordagem não-local de plano crítico levou a grandes erros nas estimativas. Duas outras diferentes metodologias também foram testadas para prever o caminho de propagação de trincas sendo que uma delas, baseada no cálculo do fator de intensidade de tensão de uma trinca infinitesimal emergindo de uma trinca preexistente, foi capaz de fornecer bons resultados, enquanto que a outra metodologia, baseada na faixa de tensão cisalhante nas proximidades da ponta da trinca, conduziu a resultados discrepantes em relação as observações experimentais. _____________________________________________________________________________________ ABSTRACT / The aim of this work is to evaluate the crack behaviour under fretting conditions. A more generic methodology was proposed to predict the short crack arrest phenomenon and different models to estimate the direction of crack initiation and further propagation were also assessed. Classical theories as the distribution dislocation technique and robust commercial FEM routines were used to calculate the most important mechanical parameters involved in these theories. Available experimental data were collected to verify the accuracy of the present methodologies. The methodology proposed here to evaluate short crack arrest was able to provide better estimates than other available in the literature when a more generic curve for the stress intensity factor threshold (Δℎ), based on the Bezant’s material parameter, , was used. Concerning the estimate of crack initiation direction, two methodologies based on the Theory of Critical Distances were assessed and one of them (the Critical Direction Method) could satisfactory provide the direction of crack initiation, whereas the other model, based on a non-local critical plane approach, led to high discrepancies. Two methodologies were also tested to predict crack propagation path and one of them, based on the calculation of the stress intensity factor of an infinitesimal kinked crack emerging from the original one, was able to provide good results, whereas the other methodology, based on the shear stress range near to the crack tip, led to inaccurate results.

A challenge in engineering coupling design is the understanding of performance of contact geometry for a given application. “Wear” is one of a number of mechanical failures that can occur in mechanical coupling design. “Fretting wear” occurs where surfaces in contact are subjected to oscillating load and very small relative motion over a period of time. Fretting has been observed in many mechanical interactions and is known to be a reason for failure in many designs. Recent evidence suggests that fretting wear occurs at the taper junction of modular total hip replacements and leads to failure of the implants. Experimental testing to determine the wear behaviour that occurs in mechanical devices is time consuming, expensive and complicated. Computational wear modelling is an alternative method which is faster and cheaper than real testing and can be used in addition to testing to help improve component design and enhance wear characteristics. Developing an algorithm that can accurately predict fretting wear considering linear wear, volumetric wear and surface wear damage is the main focus of this thesis. The thesis proposes a new computational methodology incorporating published wear laws into commercial finite element code to predict fretting wear which could occur at the taper junction of total hip replacements. The assessment of wear in this study is solely based on mechanical wear (fretting) as being the primary mechanism causing surface damage. The method is novel in that it simulates the weakening of the initial taper ‘fixation’ (created at impaction of the head onto the stem in surgery) due to the wearing process. The taper fixation is modelled using a contact analysis with overlapped meshes at the taper junction. The reduction in fixation is modelled by progressive removal of the overlap between components based on calculated wear depth and material loss. The method has been used for three different studies to determine surface wear damage, linear and volumetric wear rates that could occur at taper junction of total hip replacements over time. The results obtained are consistent with those found from observation and measurement of retrieved prostheses. The fretting wear analysis approach has been shown to model the evolution of wear effectively; however, it has been shown that accurate, quantitative values for wear are critically dependant on mesh refinement, wear fraction and scaling factor, wear coefficient used and knowledge of the device loading history. The numerical method presented could be used to consider the effect of design changes and clinical technique on subsequent fretting wear in modular prosthetic devices or other mechanically coupled designs.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2014. / Submitted by Larissa Stefane Vieira Rodrigues (larissarodrigues@bce.unb.br) on 2014-10-31T17:48:59Z No. of bitstreams: 1 2014_EstarleRobertoFerreiraDeSouzaCampos.pdf: 3382079 bytes, checksum: 0ad9c998938a983b1046eaf2ed5f7f59 (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2014-11-03T15:09:07Z (GMT) No. of bitstreams: 1 2014_EstarleRobertoFerreiraDeSouzaCampos.pdf: 3382079 bytes, checksum: 0ad9c998938a983b1046eaf2ed5f7f59 (MD5) / Made available in DSpace on 2014-11-03T15:09:07Z (GMT). No. of bitstreams: 1 2014_EstarleRobertoFerreiraDeSouzaCampos.pdf: 3382079 bytes, checksum: 0ad9c998938a983b1046eaf2ed5f7f59 (MD5) / O presente trabalho tem como principal objetivo a previsão da parada de trincas curtas, em corpos submetidos a condições de fretting. O modelo proposto se baseia na determinação do Fator Intensidade de Tensão dentro da zona de processo, sob à ação de cargas de contato, e posterior comparação com dois critérios de limiar de propagação de trincas curtas: El-Haddad e Kitagawa-Takahashi. Os resultados encontrados foram confrontados com dados experimentais da literatura. Todos os casos estudados utilizaram contato entre cilindro e plano feitos de aço 52100 e AISI 1034, respectivamente. Os testes foram conduzidos em regime de escorregamento parcial, sem a presença de carga remota de fadiga. Para estes dados à metodologia que forneceu as melhores estimativas para o tamanho da trinca parada baseou-se no cálculo de um fator intensidade de tensão efetivo (Modo I e Modo II) e na curva limiar de Kitagawa-Takahashi. Para determinar a priori o ângulo de propagação da trinca utilizou-se um critério de fadiga multiaxial de Plano Crítico associado à Teoria das Distâncias. Concluiu-se a escolha do modelo mais apropriado para estimar a parada do crescimento de trincas curtas depende fortemente do material estudado e de seu fator de Bazant. ______________________________________________________________________________ ABSTRACT / The aim of this work is to estimate the arrest size of short cracks in bodies subjected to conditions of fretting. The proposed model is based on determining the Stress Intensity Factor within the process zone under the action of contact loads, and later compare with two threshold criteria for of short propagating cracks, El-Haddad and Kitagawa- Takahashi. The results were compared with experimental data from literature . All case studies used contact between cylinder and plane made of steel AISI 52100 and 1034, respectively. The tests were conducted in partial slip regime, without the presence of bulk stress. For these data the methodology that provided the best estimates for the size of the crack arrest was based on the calculation of an effective stress intensity fator ( Mode I and Mode II ) and the threshold curve Kitagawa - Takahashi . To determine a priori the angle of crack propagation used a criterion of multiaxial fatigue associated with Critical Theory Plan of distance. It was concluded the choice of the most appropriate model to estimate the growth arrest of short cracks strongly depends on the material studied and its factor Bazant.

Electrical connectors are widely utilized for signal communications in automotive electronic systems whose performance is related to the reliability of the entire system. Electrical connectors are frequently affected by the engine vibration, resulting in fretting damages on electrical connector. In this thesis, the main propose is to find a signal analysis method to predict the fretting damages on fuel pump connector induced by engine vibration. The data of the fuel pump connector is studied from a vibration test of the four-cylinder engine and the dominating frequencies are used in the fretting test to verify the analysis method. The fretting damage is identified through visual inspection by microscope. The model of the connector is built in COMSOL to explain the fretting on the contact surfaces. The results present the signal analysis method can be directly used to predict the risk of fretting damages during the engine vibration. Some significant frequencies are pointed out as guidelines for future tests and optimization.

Fretting wear occurs when two bodies in contact are subject to small oscillatory displacements. This wear phenomenon is common in many industrial applications, such as gears, couplings, bearings, screws, valves and joints where vibrations occur. It has been shown that many factors affect the fretting wear rate, e.g. the normal load, sliding distance, geometry of the bodies, surface roughness, material properties, lubrication status, temperature and presence of third bodies. Fatigue has also been the subject of much investigation over the past century. Fatigue damage is observed in the form of microcracks, debonding, etc. in the vicinity of stress risers (e.g. inclusions, voids etc.) within the materials. The stress component causing fatigue failure can be normal, shear, or a combination due to a compound state of loading. In order to investigate the shear mode of fatigue failure, torsional fatigue testing has been the subject of many studies. Shear mode of failure is of significant importance in triaxial state of stress present for ball and rolling element bearings and machine component which are subject to fretting fatigue. A number of different experimental and numerical techniques have developed to study the torsion fatigue and fretting wear of materials at different conditions. An in-situ fretting wear measurement technique was developed to investigate the effects of temperature on the coefficient of friction and wear rate of Inconel 617 in fretting wear in air and helium environments. Due to the importance of the shear mode of stress in fretting fatigue phenomenon, another set of experiments were designed to measure high cycle torsional fatigue properties of Inconel 617 at elevated temperatures. An MTS torsional fatigue test rig was modified with customized mechanical grips and cooling fins. In order to achieve the objectives of analytical aspects of this investigation, a 3D elastic-plastic finite element model was developed to examine the torsional fatigue damage in Inconel 617 material at high temperatures. Then, a 3D finite element model was developed to study fretting wear of similar materials in Hertzian line and circular contacts. The wear law incorporated in this model is based on the accumulated dissipated energy law. The FEM was used to investigate partial slip regime. Then, the model was verified by performing several experimental tests for the circular contact configuration. During fretting wear, the generated wear debris is of significant importance. A finite element model was created to study the third body effects on fretting wear of Hertzian contacts in the partial slip regime. Both first bodies and third bodies were modeled as elastic-plastic materials. The effect of the third body particles on contact stresses and stick-slip behavior was investigated. The influence of the number of third body particles and material properties including modulus of elasticity, hardening modulus, and yield strength were analyzed. Finally, A new thermally cured polymer-graphene-zinc oxide-based solid lubricant was developed that reduced friction and wear significantly during the sliding wear of bearing steel under extreme contact pressure and long duration. The dry solid coating composite was made from a mixture of graphene, zinc oxide, and a specific industrial binder and then laminated on the surface of 52100 steel disks using the spin-coating technique. After ∼3000 cycles, the 15 μm thick coating created a significant reduction in the steel's coefficient of friction (approximately 82%) and wear loss compared to the uncoated surfaces. Following the tribological<a></a> examination, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy were conducted to determine the topography and morphology of the composite coating and resultant wear scars.

Direct measurements of surface temperatures produced during fretting contact are an unknown area in the discipline of tribology; in addition, the possible effects of such temperatures on the behavior of protective anti-fretting coatings (e.g., polymeric) have never been investigated. An oscillating contact device was designed and built to study fretting contact behavior in tribological processes. The contact geometry consisted of a stationary spherical test specimen loaded against a vibrating sapphire disk driven by an electromagnetic shaker. Surface temperatures generated by frictional heating were measured during fretting contact using an infrared microscope. A photo/video technique was developed to view the fretting contact interface during an experiment and to measure the size and distribution of real area(s) of contact. The effects of size and distribution of the areas on the experimental surface temperatures for polymer-coated steel spheres-on- sapphire were investigated. Archard's theoretical model was also modified to account for multiple contact areas, and the calculated surface temperatures were compared to the experimental results. Polymeric coatings - including polystyrene (PS), polymethylmethacrylate (PMMA), polysulfone (PSO), polyvinylchloride (PVC), and polyvinylidenechloride (PVDC) were studied at a given load (20 N), frequency (150 Hz), amplitude (100 JLm), and film thickness (55 p.m). The surface temperatures generated were generally low and below the glass transition temperatures of the rigid polymers studied. The magnitude of the surface temperatures was found to be particularly dependent on the size and distribution of real area(s) of contact. The most extensive studies were performed using polystyrene coatings. Effects of load, frequency, amplitude, and film thickness on surface temperature rise and the size and distributions of real area of contact were examined. In addition, uncoated steel specimens were studied under various loads and fretting amplitudes. The observed formation of iron oxide at low surface temperature (60°C) tribologica1 experiments was explained in terms of exoelectron emission. There were considerable differences observed in the behavior of polymeric coatings under various fretting conditions. The fretting behavior of the coatings was explained in terms of mechanical and thermo-elastic effects. Thermo-elastic predictions of size distributions of real contact areas (patches) showed good agreement with the observed photo/video studies. A mechanism was proposed for tribological behavior and fretting protection of polystyrene coatings. / Ph. D.