This document discusses metal-on-metal hip resurfacing and tribology. It summarizes that metal-on-metal bearings can generate lubricating films through relative motion if engineered properly with smooth surfaces, good sphericity, and optimal clearances. Historical failures were due to poor manufacturing and design issues rather than materials. Current critical issues include wear rates and metal ion release, which in-vitro studies are investigating for large metal-on-metal bearings.
This presentation material is concerned with research results for Ultra High Performance Concrete. The research was focused on the behavior of shrinkage in UHPC.
A slide show of the paper- Tribology of artificial joints, T D Stewart BSc PhD Lecturer in Medical Engineering, Institute of Medical and Biological Engineering, The University of Leeds, Leeds, UK, Journal- ORTHOPAEDICS AND TRAUMA 24:6
- Dislocations are line defects in crystalline materials that allow for plastic deformation through slip and twinning. There are three main types of dislocations: edge, screw, and mixed.
- Slip occurs when a dislocation moves through the crystal on a specific slip plane in a slip direction under an applied shear stress. This motion explains how plastic deformation takes place.
- Strengthening mechanisms like decreasing grain size, solid solution strengthening, strain hardening, and precipitation strengthening make it harder for dislocations to slip by introducing obstacles in their path. This increases the critical resolved shear stress required for plastic deformation.
This lecture helps to understand the basic principles of die forging and the characteristic features of special aluminium die forging processes. It aims at learning about the basic design of dies in order to obtain optimum part qualities and tool life. General understanding of metallurgy and deformation processes is assumed.
The document discusses wear and tribology and answers several questions related to wear mechanisms, friction reduction through lubrication, static and kinetic friction, the effect of normal load on coefficient of friction, comparative wear rates of aluminum and steel, wear behaviors of thermoplastic and thermosetting polymers, and the effect of surface nitriding on steel wear behavior. Specifically, it discusses that surface nitriding of steel increases surface hardness and wear resistance through nitrogen diffusion into the steel surface. It also compares the wear mechanisms and rates of aluminum and steel samples sliding against aluminum and steel plates under dry conditions.
1. The document reports on an experimental lab test investigating wear and tribology using a pin-on-disc machine.
2. Tests were conducted with aluminum and steel pins under various loads and conditions to determine wear rate, friction, and other properties.
3. The results show that wear increases with higher load and dry conditions. Lubrication decreases wear. Surface treatments like nitriding and carburizing improve wear resistance by enhancing surface properties.
Semi-Finished Engineering Plastic Products. TECAFORM is a versatile engineering plastic with high strength and dimensional stability. It is suitable for a wide range of applications due to its resistance to organic solvents and outstanding machinability. TECAFORM has good sliding and abrasion behavior and low water absorption properties. The document provides information on different grades of TECAFORM and their properties, as well as specifications for TECAFORM tubes in various diameters and tolerances.
The document provides information on the thermoplastic polymer polyoxymethylene (POM) including its delivery program, properties, applications, and chemical resistance. POM has a continuous service temperature up to 100°C, high surface strength surpassed by few materials, and good sliding and wear resistance due to its strength and smooth surface. It has applications in bearings, fittings, gears, pumps, and textiles. POM demonstrates resistance to many chemicals at room temperature and 60°C but is not resistant to strong acids or oxidizing agents.
This presentation material is concerned with research results for Ultra High Performance Concrete. The research was focused on the behavior of shrinkage in UHPC.
A slide show of the paper- Tribology of artificial joints, T D Stewart BSc PhD Lecturer in Medical Engineering, Institute of Medical and Biological Engineering, The University of Leeds, Leeds, UK, Journal- ORTHOPAEDICS AND TRAUMA 24:6
- Dislocations are line defects in crystalline materials that allow for plastic deformation through slip and twinning. There are three main types of dislocations: edge, screw, and mixed.
- Slip occurs when a dislocation moves through the crystal on a specific slip plane in a slip direction under an applied shear stress. This motion explains how plastic deformation takes place.
- Strengthening mechanisms like decreasing grain size, solid solution strengthening, strain hardening, and precipitation strengthening make it harder for dislocations to slip by introducing obstacles in their path. This increases the critical resolved shear stress required for plastic deformation.
This lecture helps to understand the basic principles of die forging and the characteristic features of special aluminium die forging processes. It aims at learning about the basic design of dies in order to obtain optimum part qualities and tool life. General understanding of metallurgy and deformation processes is assumed.
The document discusses wear and tribology and answers several questions related to wear mechanisms, friction reduction through lubrication, static and kinetic friction, the effect of normal load on coefficient of friction, comparative wear rates of aluminum and steel, wear behaviors of thermoplastic and thermosetting polymers, and the effect of surface nitriding on steel wear behavior. Specifically, it discusses that surface nitriding of steel increases surface hardness and wear resistance through nitrogen diffusion into the steel surface. It also compares the wear mechanisms and rates of aluminum and steel samples sliding against aluminum and steel plates under dry conditions.
1. The document reports on an experimental lab test investigating wear and tribology using a pin-on-disc machine.
2. Tests were conducted with aluminum and steel pins under various loads and conditions to determine wear rate, friction, and other properties.
3. The results show that wear increases with higher load and dry conditions. Lubrication decreases wear. Surface treatments like nitriding and carburizing improve wear resistance by enhancing surface properties.
Semi-Finished Engineering Plastic Products. TECAFORM is a versatile engineering plastic with high strength and dimensional stability. It is suitable for a wide range of applications due to its resistance to organic solvents and outstanding machinability. TECAFORM has good sliding and abrasion behavior and low water absorption properties. The document provides information on different grades of TECAFORM and their properties, as well as specifications for TECAFORM tubes in various diameters and tolerances.
The document provides information on the thermoplastic polymer polyoxymethylene (POM) including its delivery program, properties, applications, and chemical resistance. POM has a continuous service temperature up to 100°C, high surface strength surpassed by few materials, and good sliding and wear resistance due to its strength and smooth surface. It has applications in bearings, fittings, gears, pumps, and textiles. POM demonstrates resistance to many chemicals at room temperature and 60°C but is not resistant to strong acids or oxidizing agents.
Defects in solids can be categorized as point defects, line defects, or area defects. Point defects include vacancies and interstitial atoms, while line defects include dislocations. Area defects include grain boundaries. The number and type of defects can be controlled through processing parameters like temperature. Defects influence material properties and may be desirable or undesirable depending on the application, as dislocations allow plastic deformation but can also decrease strength.
This document outlines Francisco Almeida's doctoral dissertation on studying exchange springs and exchange bias using nuclear methods. The document begins with an outline of the key topics, including magnetism/magnetic interactions, researched systems, and conclusions. It then goes into more depth discussing ferromagnetism and antiferromagnetism, interlayer coupling, and exchange bias. Specific systems researched are a surface spin-flop in an Fe/Cr superlattice studied using polarized neutron reflectometry, and exchange bias in Fe-Pt heterostructures investigated using Mössbauer spectrometry.
Unlock 8.-simulation of fretting fatigue-d. fritzon y otrosWARLO47
This document summarizes the simulation of fretting fatigue in conformal and concentrated contacts. It describes how fretting fatigue models have been implemented in the BEAST bearing simulation toolbox to predict failures. Results are presented from models of an oscillating body in concentrated contact and a deep groove ball bearing in a housing. The concentrated contact model is verified against standalone code and experiments. The ball bearing model shows how fretting fatigue risks are influenced by ball pass frequency and flexibility of the bearing and housing.
The document describes various topics relating to plastic deformation in materials including dislocation motion, slip systems, strengthening mechanisms, and the effects of processing. It defines slip systems for FCC metals as occurring on {111} planes in <110> directions, allowing for 12 total slip systems. Strengthening mechanisms discussed include reducing grain size, solid solution strengthening, precipitation strengthening, and strain hardening. Solid solution strengthening is achieved through lattice strain interactions between solute atoms and dislocations. Strain hardening occurs as dislocation density increases during plastic deformation, causing dislocations to interact and impede further motion. Processing such as cold working was also described as increasing yield strength through dislocation generation and accumulation.
The document discusses the properties of dental amalgam materials used for fillings. It notes that amalgam is strongest in compression but weaker in tension and shear. It also discusses the importance of strength and creep resistance for amalgam alloys, listing typical compressive and tensile strength values. The document describes factors that influence the strength and creep of amalgam, and methods for testing these properties.
There are several mechanisms that can strengthen materials by hindering the movement of dislocations:
1) Grain size reduction - Smaller grain sizes provide more barriers to dislocation movement at grain boundaries. According to the Hall-Petch relationship, smaller grain diameters yield higher yield strengths.
2) Solid solution strengthening - Impurity atoms distort the crystal lattice and generate stress fields that impede dislocation motion. The effectiveness depends on size difference and concentration of solute atoms.
3) Strain hardening - Plastic deformation increases dislocation density within a material, making further dislocation movement more difficult through interactions between dislocations. This causes strain hardened metals to strengthen with increasing plastic deformation.
The document summarizes key concepts from Chapter 7 of the textbook "Introduction to Materials Science" related to strengthening mechanisms in materials. It discusses how plastic deformation occurs through the motion of dislocations in materials and different ways to strengthen materials by impeding dislocation motion, such as reducing grain size, alloying, and increasing dislocation density through strain hardening. It also covers recovery, recrystallization and grain growth processes in materials after plastic deformation.
Wear have been identified as some of the major problem associated with failure of impact sockets. Impact sockets are rotated by impact wrenches. These wrenches are designed to deliver high torque output with minimum exertion by the user. Wear and tear of impact socket takes place because of various reasons. This paper presents an overview of wear failure problem in impact socket and looks at some recent technique of wear prevention and discusses the future development of wear resistant impact socket.
The document discusses optimization of part and mold design for cycle time reduction. It describes 4 concepts for the design of a plastic container: the initial design (Concept 1), a design with thinner walls (Concept 2), a design using conformal cooling channels in the mold (Concept 3), and a design using caloducs cooling (Concept 4). Simulation results showed that Concept 3 could reduce the cooling time and cycle time by over 30% compared to the original design and Concept 2.
NXP Semiconductors is a global semiconductor company with a focus on identification technologies including RFID. They are a leader in various RFID markets including transportation, banking, eGovernment, and tagging. The document discusses NXP's product portfolio, the HF and UHF RFID technologies, important markets and applications, success stories with various customers, and future developments in areas like sensor interfaces and cryptographic processors.
Avantes is a developer and manufacturer of compact spectrometers, light sources, fiber optics, and accessories. It has sold over 17,000 spectrometers since 1994 and has annual worldwide sales of 10 million euros. Avantes uses its core spectrometer technology across multiple markets including life sciences and health, industrial processes, optical diagnosis spectroscopy and imaging, safety and security, agriculture and food, and green energy and environment. The document provides examples of spectroscopy applications for Avantes' products in areas such as LED measurements, solar panel measurements, thin film measurements, blood analyses, and food quality analysis.
Justin Finlay is a second year heavy equipment technician apprentice seeking full-time employment. He has experience working as an apprentice mechanic and shop hand. He is a high school graduate who has also completed his first year of training at NAIT. He has strong mechanical skills, can operate machinery, and has good communication and problem solving abilities. References are available from his past employers and instructors.
The document provides an overview of the office, retail, hotel, and serviced apartment markets in Ho Chi Minh City's central business district (CBD) for February 2016. It includes market performance summaries, current and future supply figures, average rents, occupancy rates, and outlooks for each sector. Tables list significant existing and upcoming projects along with their details. The office market saw improved occupancy for Grade B buildings while rents remained stable. Retail occupancy remained high at 95% on average across the CBD. Hotel and serviced apartment sectors were also performing well overall. The CBD commercial real estate market is expected to see continued healthy performance supported by economic growth.
Geothermal energy is thermal energy generated and stored in the Earth's interior. It originates from the initial formation of the planet and radioactive decay of minerals. The Earth's core remains molten and this magma rises through hotspots, heating groundwater and turning it to steam. Geothermal power plants tap into this steam through pipes in bored rock to rotate turbines and generate electricity in an environmentally friendly manner at geothermal hotspots around the globe.
Este documento presenta el reporte de una práctica de laboratorio sobre un sumador binario de 2 bits. Se explica el funcionamiento teórico mediante álgebra booleana y tablas de verdad, y se muestra el circuito implementado en un protoboard, demostrando el funcionamiento práctico del sumador.
Un navegador web es un software que permite acceder a la Web e interpretar información de archivos y sitios para visualizarlos. El primer navegador, WorldWideWeb, fue desarrollado por Tim Berners-Lee en la CERN a finales de 1990. La función principal de un navegador es descargar documentos HTML y mostrarlos, así como imágenes, sonidos y videos. Algunos de los navegadores más populares son Chrome, Firefox, Internet Explorer, Safari y Opera.
Las plataformas web más comunes son LAMP (Linux, Apache, MySQL y PHP), WAMP (Windows, Apache, MySQL y PHP), Moodle y Facebook que son utilizadas para crear sitios web dinámicos, y Edmodo que es una plataforma de aprendizaje en línea.
Este documento presenta el reporte de una práctica de laboratorio sobre la construcción de un carrito seguidor de líneas. Explica brevemente el objetivo, antecedentes, desarrollo teórico y práctico del proyecto, así como los resultados obtenidos y conclusiones. El carrito funcionó según lo esperado al seguir una línea negra por 10 vueltas antes de agotar la batería.
Defects in solids can be categorized as point defects, line defects, or area defects. Point defects include vacancies and interstitial atoms, while line defects include dislocations. Area defects include grain boundaries. The number and type of defects can be controlled through processing parameters like temperature. Defects influence material properties and may be desirable or undesirable depending on the application, as dislocations allow plastic deformation but can also decrease strength.
This document outlines Francisco Almeida's doctoral dissertation on studying exchange springs and exchange bias using nuclear methods. The document begins with an outline of the key topics, including magnetism/magnetic interactions, researched systems, and conclusions. It then goes into more depth discussing ferromagnetism and antiferromagnetism, interlayer coupling, and exchange bias. Specific systems researched are a surface spin-flop in an Fe/Cr superlattice studied using polarized neutron reflectometry, and exchange bias in Fe-Pt heterostructures investigated using Mössbauer spectrometry.
Unlock 8.-simulation of fretting fatigue-d. fritzon y otrosWARLO47
This document summarizes the simulation of fretting fatigue in conformal and concentrated contacts. It describes how fretting fatigue models have been implemented in the BEAST bearing simulation toolbox to predict failures. Results are presented from models of an oscillating body in concentrated contact and a deep groove ball bearing in a housing. The concentrated contact model is verified against standalone code and experiments. The ball bearing model shows how fretting fatigue risks are influenced by ball pass frequency and flexibility of the bearing and housing.
The document describes various topics relating to plastic deformation in materials including dislocation motion, slip systems, strengthening mechanisms, and the effects of processing. It defines slip systems for FCC metals as occurring on {111} planes in <110> directions, allowing for 12 total slip systems. Strengthening mechanisms discussed include reducing grain size, solid solution strengthening, precipitation strengthening, and strain hardening. Solid solution strengthening is achieved through lattice strain interactions between solute atoms and dislocations. Strain hardening occurs as dislocation density increases during plastic deformation, causing dislocations to interact and impede further motion. Processing such as cold working was also described as increasing yield strength through dislocation generation and accumulation.
The document discusses the properties of dental amalgam materials used for fillings. It notes that amalgam is strongest in compression but weaker in tension and shear. It also discusses the importance of strength and creep resistance for amalgam alloys, listing typical compressive and tensile strength values. The document describes factors that influence the strength and creep of amalgam, and methods for testing these properties.
There are several mechanisms that can strengthen materials by hindering the movement of dislocations:
1) Grain size reduction - Smaller grain sizes provide more barriers to dislocation movement at grain boundaries. According to the Hall-Petch relationship, smaller grain diameters yield higher yield strengths.
2) Solid solution strengthening - Impurity atoms distort the crystal lattice and generate stress fields that impede dislocation motion. The effectiveness depends on size difference and concentration of solute atoms.
3) Strain hardening - Plastic deformation increases dislocation density within a material, making further dislocation movement more difficult through interactions between dislocations. This causes strain hardened metals to strengthen with increasing plastic deformation.
The document summarizes key concepts from Chapter 7 of the textbook "Introduction to Materials Science" related to strengthening mechanisms in materials. It discusses how plastic deformation occurs through the motion of dislocations in materials and different ways to strengthen materials by impeding dislocation motion, such as reducing grain size, alloying, and increasing dislocation density through strain hardening. It also covers recovery, recrystallization and grain growth processes in materials after plastic deformation.
Wear have been identified as some of the major problem associated with failure of impact sockets. Impact sockets are rotated by impact wrenches. These wrenches are designed to deliver high torque output with minimum exertion by the user. Wear and tear of impact socket takes place because of various reasons. This paper presents an overview of wear failure problem in impact socket and looks at some recent technique of wear prevention and discusses the future development of wear resistant impact socket.
The document discusses optimization of part and mold design for cycle time reduction. It describes 4 concepts for the design of a plastic container: the initial design (Concept 1), a design with thinner walls (Concept 2), a design using conformal cooling channels in the mold (Concept 3), and a design using caloducs cooling (Concept 4). Simulation results showed that Concept 3 could reduce the cooling time and cycle time by over 30% compared to the original design and Concept 2.
NXP Semiconductors is a global semiconductor company with a focus on identification technologies including RFID. They are a leader in various RFID markets including transportation, banking, eGovernment, and tagging. The document discusses NXP's product portfolio, the HF and UHF RFID technologies, important markets and applications, success stories with various customers, and future developments in areas like sensor interfaces and cryptographic processors.
Avantes is a developer and manufacturer of compact spectrometers, light sources, fiber optics, and accessories. It has sold over 17,000 spectrometers since 1994 and has annual worldwide sales of 10 million euros. Avantes uses its core spectrometer technology across multiple markets including life sciences and health, industrial processes, optical diagnosis spectroscopy and imaging, safety and security, agriculture and food, and green energy and environment. The document provides examples of spectroscopy applications for Avantes' products in areas such as LED measurements, solar panel measurements, thin film measurements, blood analyses, and food quality analysis.
Justin Finlay is a second year heavy equipment technician apprentice seeking full-time employment. He has experience working as an apprentice mechanic and shop hand. He is a high school graduate who has also completed his first year of training at NAIT. He has strong mechanical skills, can operate machinery, and has good communication and problem solving abilities. References are available from his past employers and instructors.
The document provides an overview of the office, retail, hotel, and serviced apartment markets in Ho Chi Minh City's central business district (CBD) for February 2016. It includes market performance summaries, current and future supply figures, average rents, occupancy rates, and outlooks for each sector. Tables list significant existing and upcoming projects along with their details. The office market saw improved occupancy for Grade B buildings while rents remained stable. Retail occupancy remained high at 95% on average across the CBD. Hotel and serviced apartment sectors were also performing well overall. The CBD commercial real estate market is expected to see continued healthy performance supported by economic growth.
Geothermal energy is thermal energy generated and stored in the Earth's interior. It originates from the initial formation of the planet and radioactive decay of minerals. The Earth's core remains molten and this magma rises through hotspots, heating groundwater and turning it to steam. Geothermal power plants tap into this steam through pipes in bored rock to rotate turbines and generate electricity in an environmentally friendly manner at geothermal hotspots around the globe.
Este documento presenta el reporte de una práctica de laboratorio sobre un sumador binario de 2 bits. Se explica el funcionamiento teórico mediante álgebra booleana y tablas de verdad, y se muestra el circuito implementado en un protoboard, demostrando el funcionamiento práctico del sumador.
Un navegador web es un software que permite acceder a la Web e interpretar información de archivos y sitios para visualizarlos. El primer navegador, WorldWideWeb, fue desarrollado por Tim Berners-Lee en la CERN a finales de 1990. La función principal de un navegador es descargar documentos HTML y mostrarlos, así como imágenes, sonidos y videos. Algunos de los navegadores más populares son Chrome, Firefox, Internet Explorer, Safari y Opera.
Las plataformas web más comunes son LAMP (Linux, Apache, MySQL y PHP), WAMP (Windows, Apache, MySQL y PHP), Moodle y Facebook que son utilizadas para crear sitios web dinámicos, y Edmodo que es una plataforma de aprendizaje en línea.
Este documento presenta el reporte de una práctica de laboratorio sobre la construcción de un carrito seguidor de líneas. Explica brevemente el objetivo, antecedentes, desarrollo teórico y práctico del proyecto, así como los resultados obtenidos y conclusiones. El carrito funcionó según lo esperado al seguir una línea negra por 10 vueltas antes de agotar la batería.
ABC4Trust Architecture and the Benefits for eID SchemesIoannis Krontiris
This document summarizes a research project funded by the European Commission to integrate privacy-enhancing technologies called Privacy-ABCs into existing European electronic identity (eID) card schemes. It outlines some current privacy and security issues with eID systems, such as user tracking and impersonation. The project aims to address these by developing an architecture called ABC4Trust that supports Privacy-ABC features like selective disclosure and unlinkability directly on eID smart cards. This would enhance users' privacy while maintaining usability and performance. The document provides technical details on integrating ABC4Trust into Germany's eID system and making Privacy-ABCs efficient on smart cards with techniques like precomputation.
El documento habla sobre las plataformas web. Define una plataforma web como una aplicación donde se puede desarrollar un sistema para crear variedad de opciones para los usuarios a través de páginas de acceso. Explica que cuando se desarrolla un programa, este funciona en una plataforma específica. Finalmente, menciona diferentes tipos de plataformas como LAMP, WAMP, LAMDA, XATMJ, WXCF, XAMPP y WIMA.
Este documento presenta información sobre políticas y legislación de seguridad industrial en Venezuela. Describe los tipos de organización de seguridad industrial, incluyendo organizaciones en línea y por departamentos. También explica las responsabilidades de seguridad en diferentes niveles de la organización como la dirección, mandos intermedios y trabajadores. Además, proporciona detalles sobre el Comité de Higiene y Seguridad establecido en la legislación venezolana.
Este documento presenta varias plataformas web para desarrollar sitios web, incluyendo LAMP (Linux, Apache, MySQL, PHP), que es la más popular. También describe WAMP para desarrollo en Windows, MAMP para Mac, y Coldfusion. Explica brevemente el propósito de cada plataforma y sus ventajas y desventajas.
Brend Brevé - Philips Industry ConsultingThemadagen
The document discusses lean operations excellence and eliminating waste through lean thinking. It defines lean as creating flow without disruptions by eliminating waste. It then discusses the seven types of waste according to Toyota and explains that lean focuses on increasing value-added activities which are only 5% of total lead time. Finally, it provides the main steps in lean as specifying value, identifying the value stream, making value flow, involving employees, and continuously improving.
This document provides an introduction to the basics of tribology, which is the study of friction, lubrication, and wear between surfaces in contact. It discusses how tribology encompasses many fields of engineering and industry. Surfaces in contact are not flat and have roughness at multiple scales, from nanometers to centimeters. Both the physical roughness and chemical properties of surfaces need to be considered in tribology as they influence contact area, stresses, lubrication, and compatibility. A variety of methods can characterize surface properties. Understanding surfaces is fundamental to tribology as the interaction between surface asperities dictates tribological forces.
This document discusses bulk metallic glasses (BMGs). It begins by defining BMGs as amorphous materials that were first produced in 1957 through rapid quenching. BMGs have high strength, stiffness, and elastic strain compared to conventional metals. The document then discusses experiments conducted to characterize the mechanical properties and deformation behavior of a Zr-based BMG, including 3-point bending tests, nanoindentation, and wedge indentation. Wedge indentation allowed visualization of shear bands initiating and propagating on the surface. Finite element modeling was also used to model the wedge indentation experiments and simulate shear band nucleation and damage propagation.
Bulk metallic glasses (BMGs) are amorphous alloys that can be formed into bulk samples rather than just thin films. This document discusses BMGs and characterizes a Zr-based BMG alloy. It describes experiments using 3-point bending and wedge indentation to study shear band formation. Wedge indentation showed vein-like structures and shear bands initiating and propagating with increasing load. Nanoindentation found fracture surfaces weaker than the bulk. Finite element modeling used cohesive zone elements to simulate shear band propagation. Future work includes gradient plasticity modeling of nucleation and shear band effects.
The document summarizes an experiment conducted to analyze the effectiveness of different viscoelastic materials in minimizing vibration and noise from rotating machinery. The experiment tested various thicknesses and profiles of natural rubber and PVC sheets placed beneath bearings that supported an unbalanced rotating shaft. Vibration measurements were taken at the bearings under different material configurations and shaft speeds. The results tables show that, in general, thicker viscoelastic materials and those with corrugated profiles performed better at reducing measured vibration levels compared to thinner, plain materials or no isolation.
Tribology is the study of friction, lubrication, and wear between interacting surfaces in relative motion. It helps improve machine reliability and reduce failures. Reynolds' equation, derived in 1886, quantifies fluid film lubrication and allows prediction of hydrodynamic, hydrostatic, and squeeze film mechanisms by modeling pressure as a function of coordinates and time. The equation assumes laminar flow of an incompressible Newtonian fluid with negligible inertia and pressure gradients in the film thickness direction.
1. Total hip arthroplasty has evolved significantly since its origins in the late 1800s through improvements in materials, designs, fixation methods, and surgical techniques.
2. Cementless fixation and improved bearing surfaces have led to improved implant survivorship and reduced osteolysis.
3. Current areas of focus include minimizing wear through novel bearing surfaces and coatings, inhibiting the cellular response to wear debris, and improving surgical techniques through minimal access approaches and computer navigation.
A histomorghometric study of screw-shaped and removal torque titanium implant...Ali Alenezi
This study investigated bone response to titanium implants with different surface topographies over a short follow-up period. Sixty implants with turned, TiO2-blasted, or Al2O3-blasted surfaces were implanted in rabbit femurs and tibias. After 12 weeks, blasted implants had higher removal torque values and bone-to-implant contact percentages, indicating better osseointegration. However, turned implants exhibited greater bone surface area. The results suggest surface topography influences short-term bone response, though differences may not generalize to clinical settings over longer periods.
Experimental Investigation of the Residual Stress and calculate Average Fatig...IJMER
Shot peening procedures developed over the ago in substantial improvements of fatigue properties and Fatigue life. The use of shot peening on aluminium 7075-T6 plates to improve fatigue properties and improve resistance to stress on the corrosion cracking with help of glass beads and various peening methods. When these components subsequently are loaded in tension or bending to a
stress level in the range below the required for yield, the actual tensile stress at the surface is lower than
that calculated on the basis of load and cross sectional area. Fatigue are major problem which normally
start at or near the surface stressed in tension, thus processes that produce residual surface compressive
stresses in components usually enhance the resistance to fatigue. The impact of glass shots which create
resistance after the shot penning process carried out and also control the effects of failure on aluminium
alloys
Engineering design with natural rubber by lindley peter brian (z lib.org)NMTTMN
This document provides an overview of natural rubber and its use in engineering design. It discusses the molecular structure of natural rubber as cis-polyisoprene and how vulcanization through crosslinking transforms raw rubber into a stable, elastic material. The document outlines natural rubber's physical properties, how it is affected by environmental factors, failure mechanisms, and provides stiffness formulas for common rubber spring configurations.
Inaugural lecture for Tomasz Liskiewicz, Professor of Tribology and Surface Engineering, Manchester Metropolitan University, Faculty of Science and Engineering
1. The document discusses sliding contact bearings, which use a layer of lubricant like oil or grease to reduce friction and wear between moving machine elements.
2. Applications include concrete mixers, turbines, motors, and engine crankshafts. Advantages are simple design, compact size, low cost, and good shock resistance, while disadvantages include higher friction losses and need for good lubrication.
3. Bearings are classified by the direction of load (radial or thrust) and the type of contact (sliding or rolling). Sliding contact bearings use layers of materials like babbit metal, bronze, cast iron, or non-metallic alternatives between surfaces.
Lubricants are substances introduced between two relatively moving surfaces to reduce friction and wear. There are three main mechanisms of lubrication: 1) fluid film or hydrodynamic lubrication where a thick lubricant film separates surfaces, 2) boundary lubrication where a thin adsorbed film separates surfaces under high loads/low speeds, and 3) extreme pressure lubrication where additives form protective surface films under high pressures. Lubricants are classified as liquid, semi-solid, or solid based on their physical state. Common liquid lubricants include oils from vegetable, animal, mineral and synthetic sources. Greases are semi-solid lubricants made by thickening oils with soap.
This document discusses the tribology of total hip replacements (THRs). It covers topics like wear, lubrication, friction, bearing materials, and concerns with different bearings. Regarding bearings, it describes hard-on-soft bearings like metal-on-polyethylene, and hard-on-hard bearings like ceramic-on-ceramic and metal-on-metal. It also discusses factors like head size, noting that large heads can decrease dislocation but increase wear.
Analysis of complex composite beam by using timoshenko beam theoryIAEME Publication
This document summarizes an analysis of complex composite beams using Timoshenko beam theory and finite element methods. It begins with an abstract describing the motivation to analyze composite beams and lists some keywords. It then provides background on composite materials and discusses challenges in analyzing complex composite structures due to anisotropy. The document outlines the objectives, introduces Timoshenko beam theory, and describes the methodology used, which involves developing the governing equations, stiffness and mass matrices, and shape functions. It also summarizes the results and discussions, and lists references for further reading.
Edge effect in high speed slurry erosion wear tests of steels and elastomersNiko Ojala
While the slurry transportation via pumping is an increasingly viable alternative for the conventional fine
particle pumping, there are also many applications involving larger particles. However, the published studies
on slurry erosion have mainly been conducted with fine particle sizes. In this work, both fine and large
particle high speed slurry erosion of commercial wear resistant materials is studied.
The high speed slurry-pot wear tester was used with edge protected samples to simulate the wear conditions
in industrial slurry applications, such as tanks and pipelines. Two quenched wear resistant steels together
with natural rubber and polyurethane lining materials were tested, and the results were compared with the
results of the same materials tested without sample edge protection. The tests were performed using 15 m/s
speed, 45° and 90° sample angles, and 9 wt% and 33 wt% slurry concentrations with particle size ranging
from large 8/10 mm granite to fine 0.1/0.6 mm quartz.
With or without edge protection, the steel samples showed stable wear behavior, whereas the elastomers
gave notably inconsistent results in different test conditions. Steels exhibited better wear performance with
large particles and elastomers with fine particles. In general, the wear losses were 40 – 95 % lower without
edge wear, except for elastomers tested with fine quartz at the 45° sample angle, which yielded 25 – 75 %
higher weight losses when the sample edges were protected. With increasing abrasive size, the edge wear
becomes more dominant.
When possible, the full conference paper will be published at https://www.researchgate.net/publication/303881460_Edge_effect_in_high_speed_slurry_erosion_wear_tests_of_steels_and_elastomers
The document discusses chatter theory and how cutting parameters affect machining dynamics at high speeds. It defines chatter as a self-excited vibration between the tool and workpiece when cutting. Chatter can be problematic for high-speed machining. The stability lobe diagram shows the limits of axial depth of cut for different spindle speeds to avoid chatter based on the machine's oriented frequency response function. Process damping provides stability at low speeds by interfering between the tool and workpiece surfaces.
The document discusses chatter theory and how cutting parameters affect machining dynamics at high speeds. It defines chatter as a self-excited vibration between the tool and workpiece during cutting. Chatter can be problematic for high-speed machining. The stability lobe diagram shows the limits of axial depth of cut for different spindle speeds to avoid chatter based on the machine's oriented frequency response function. Process damping provides stability at low speeds by interfering between the tool and workpiece surfaces.
This document discusses ultrasonic machining (USM), including its basic components and mechanisms. USM is a mechanical non-traditional machining process that uses high-frequency vibrations to remove material from hard or brittle materials. The main components of a USM system are the slurry delivery system, feed mechanism, transducer that generates ultrasonic vibrations, and horn that amplifies the vibrations to the tool. Material removal occurs through indentation and cracking caused by the abrasive slurry and ultrasonic vibrations. Factors that affect the material removal rate include vibration amplitude, frequency, feed force, abrasive size and material. An experiment on ultrasonic machining of titanium is also summarized.
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1. Metal on Metal
resurfacing Tot. Hip.
Dr F M C van den Eeden
F.M.C.
Orthopedisch chirurg
M.C.A.
M C A Alkmaar
In 2007 : > 23000 artificial total hips implanted in
the Netherlands
Less than 1000 Resurfacing type
In 2010 RECALL of hipprosthesis by Depuy
orthopedics (Johnson & Johnson)
-ASR Resurfacing system
-ASR XL Acetabular system
2. 13% reoperations before 5 y
p
93000 recall worldwide
Early revisions MOM related to
wear
Metal on Metal Hip Resurfacing
- Tribology and Critical Issues
Jack Thomas
Regional Director - Europe
Corin Group p
p plc
3. Background
Resurfacing is not new
R f i i t
Metal-metal bearings are not new
Development of modern metal-metal resurfacing
What went wrong with historical Resurfacing Arthroplasty
What went wrong with historical Metal-metal Arthroplasty
Technical theory behind the Cormet
Clinical and In Vitro Studies
Clinical Follow-up
p
Hip Tribology
Tribology is: ‘a study that deals with the design,
friction, wear
friction wear, and lubrication of interacting
surfaces in relative motion (as in bearings or gears)’
(WWWebsters)
What factors affect the tribology of hip bearings?
Materials
Loads
Geometry
Sliding speeds
Lubrication theory
L b i ti th
4. Lubrication Theory
y
Lubricating films can separate bearing surfaces
Dental drills, air hockey etc
drills
Thickness of the lubricant thickness primarily depends
on:
Material
Load (up to 3.5x Bw)
Contact stress
Sliding velocity
Conformity
(Radial Clearance/Sphericity) Rotation
frequency
Radial
Clearance
The Bottom line…
h l
Lubricant films are formed during relative motion
If the lubricant film is thicker than the relative
roughness the surfaces will separate
separate.
Define lambda ratio:
Minimum Film Thickness
O
Cumulative Surface Roughness
5. Hydrodynamic Lubrication O ! 3
Lubricant film fully separates the surfaces
This is the ideal regime – effectively zero wear
Motion
M ti Bearing Surface
B i S f
Bearing Surface Motion
Boundary Lubrication O < 1
Lubricant is present but not thick enough to separate the
surfaces
Surfaces can be protected b b
S f b t t d by boundary l b i
d lubricants ( t i
t (proteins,
lipids etc)
Asperities on opposing surfaces contact leading to friction and
p pp g g
wear
Motion Bearing Surface
Bearing Surface
Motion
6. Mixed Lubrication 1 < O < 3
Combination of boundary and fluid film lubrication
Occurs with intermittent motions
Sometimes the surfaces are separated and sometimes not
There is occasional surface contact leading to some surface
wear
Bearing Surface
g
Motion
Bearing Surface Motion
So…
So How do we engineer
Hydrodynamic Lubrication?
1. Engineer the materials
2. Engineer the geometry
Diameter
Radial Clearance
Sphericity
7. Effect of Material
Stiffness (Elastic modulus)
Surface roughness
Bearing Material Elastic Modulus (Gpa) Typical Surface
Roughness, Ra (microns)
Alumina 400 0.005
High Carbon CoCr 200 0.005-0.01
UHMWPE 1 1
Stiffness has a small effect on lubricating film thickness
Surface roughness has a massive effect:
UHMWPE is 200 times rougher than metal or ceramic
Minimum Fil Thi k
Mi i Film Thickness
O
Cumulative Surface Roughness
Effect of Bearing Diameter
Large Bearing Diameters
Large bearing = lower contact stress
Increased sliding speed generates an increased fluid film
BUT sliding distance is increased!
8. What does it all mean?
Metal/ceramic UHMWPE bearings
Rough surfaces/Large radial clearances/Poor sphericity
R h f /L di l l /P h i i
¾ Boundary lubrication
¾ Wear is directly proportional to load and sliding distance
¾ More wear with larger bearing diameters
For Example…
Example
THARIES/Wagner/Freeman Metal-UHMWPE Resurfacings
Massive wear due to large diameter Metal-UHMWPE articulation
Metal UHMWPE
- Wrong Tribology
9. What does it all mean?
Metal on metal bearings
We can achieve very smooth surfaces
(Ra = 0.05 microns)
0 05
We can achieve excellent sphericity (<10 microns)
We can achieve optimum radial clearances
Therefore we can achieve a
lubricated contact!
• Especially with
Larger diameter bearings
For Example:
Metal on metal simulator study, Smith et al*
study al
7
llion cycles
s
6
5
We Rate mm per mil
4
m3
3
2
ear
1
0
16mm
16 22.225mm
22 225 28mm (new)
28 ( ) 28mm (worn)
28 ( ) 36mm
36
Joint Diameter
* Proc Inst Mech Eng [H] 2001; 215(2): 161-170
10. What went wrong with Historical M-M
h ih i i l
Hip Arthroplasty?
p p y
Poor Manufacturing tolerances
Equatorial bearing!
Poor design
Component fixation
Impingement
p g
The result?
Early incidence of loosening with metallosis
No such problems with the Charnley at the time.
Summary of Tribology
We know how to engineer the bearing
We know what not to do with
reference to historical Resurfacing and
Metal-metal THRs
So what are the current critical issues
in Metal-metal Hip Resurfacing?
11. Critical Issues?
C iti l I ?
Wear
Do Standard Heat-Treatment Processes Influence
Heat-
Large Diameter Metal-on-Metal Wear ?
Metal-on-
– An In Vitro Study Under Normal & Adverse Gait Conditions
John G. Bowsher, Jim Nevelos, Julia C. Shelton
Trans 49th ORS, New Orleans, 2003
Metal Ion Release
Medium Term Serum Cobalt and Chromium Levels in Patients with
Metal-metal Resurfacing
V Reddy MD, J Dorairajan MD, J Nevelos PhD, S Krikler PhD FRCS(Orth).
Trans 70th AAOS, New Orleans, 2003.
Do Standard Heat-Treatment Processes Influence
Heat-
Large Diameter Metal-on-Metal Wear ?
Metal-on-
– An In Vitro Study Under Normal & Adverse Gait Conditions
Physiological Hip Self-Centring Bearing
Anti-Rotate
Anti Rotate Arm (x2)
Simulator Study Horizontal Torque
y Cell ± 20 Nm
z
As Cast vs HIPed Torque Cell Adapter
x
and Solution
d S l ti Cup Fixturing
Annealed 40mm Serum
Chamber
Direction
of Torque
Measurement T
Bearings 360q
(y-axis)
23q Fixed in
Standard and y-x plane
Severe Testing r23q Biaxial Rocking
Motion
g
Joint
Conditions Force ABD / ADD
FLEX / EXT
(a)(b)
Fig. 1. Schematics showing (a) hip joint simulator, and (b) torque
measurement and definition of biaxial rocking motion.
12. Results
(a) Running-In (b) Steady-State (c) Simulated (d) Simulated
0 to 1 mc 1-3, 4-6 mc Fast Walking Fast Jogging
Normal Walking Normal Walking
7.0 **
6.0 **
(m m 3 /1 0 6 C y c le s )
M ean W ear R ate
5.0
**
4.0
3.0
2.0
m
1.0
0.0
(n=6) (n=8) (n=18) (n=22) (n=6) (n=6) (n=8) (n =8)
(n`=8)
As cast HIPed & Solution Annealed
** - statistically significant
Conclusions – Wear Study
r HIPing and solution annealing did not adversely affect the wear
rates of large diameter metal-on-metal articulations, even under
severe gait conditions.
r Both alloys possessed very different micro-structures and surface carbide
structure, Fig 2a-2b, however, this appeared to have little affect on the
wear mechanisms
mechanisms.
r A combined head and cup wear rate of 0.45 mm3/106 cycles (k = 1.5 x10-8
mm3 N-1 m-1) for the 40 mm diameter metal bearings is lower than that
reported for smaller head diameters, thus suggesting improved lubrication
for larger bearing sizes.
r The wear of both groups was found to be highly sensitive to the type of
patient activity tested, with fast jogging activities generating a 10–fold
increase in metal wear generation compared to normal walking, k = 2.4
x10-7 mm3 N-1 m-1.
13. Medium Term Serum C b l and Chromium Levels
di S Cobalt d Ch i l
in Patients with Metal-metal Resurfacing
Metal-
39 patients followed for up to 6 years
Blood serum levels of Co and Cr measured using a standardized
technique
Two distinct patient groups:
General Population
Outliers
No effect:
Corin McMinn vs. Cormet resurfacing
Bilateral (few data points)
Results – General Population
250 Ov e rall av e rage ion le v e ls
Co
Cr
200
ion level (nmo l/l)
150
100
n
50
0
Pre
Pre- 3 10 16 22 28 34 38 45 52 57 63 76
op Time (months)
14. Younger vs. Older Patient Groups
250 250
ion levels patients under 50 at primary operation ion levels patients over 60 at primary operation
Co
200 200 Co
Cr
Cr
ion level nmol/l
l
150 150
ion level nmol/l
100 100
50 50
0 0
0 3 10 16 22 28 34 39 46 54 0 4 10 16 22 28 33 38 53
Months months
Decrease in ion levels could be due to a decrease in wear after
‘running-in’ plus improved joint stability.
Outliers - Results
4000
AP Co Outliers Compared with Average Population
AP Cr
LB Co
3500
LB Cr
SM Co
3000 SM Cr
Ave Co
Ave Cr
2500
Ion level (nm ol/l)
2000
1500
1000
500
0
0 12 24 36 48 60 72
Months Post-op
15. Conclusions – Metal Ion Study
In the vast majority of patients with metal-metal
hip resurfacing there is a small but early rise in
serum metal ions over the first 2-3 years but the
levels then gradually diminish over time .
g y
Steep cups seem to be associated with increased
levels, which could be due to wear and therefore
increased ion release into the body.
Summary
Cormet has the right tribology for clinical
success and is the product of 11 years
continuous controlled evolution
Cormet is the only resurfacing hi prosthesis
C t i th l f i hip th i
with peer reviewed published wear data and
l
long term i release measurements
t ion l t
16. Cormet Update – July ‘03
Jack Thomas
Regional Director - Europe
Corin Group p
p plc
17. Latest Developments
p
McMinn published a paper in Hip
International
The paper attacks Cormet and
g
heat treatments in general
General
Paper is in a Supplement with the proceedings
from a symposium at EFORT 2002
o sy pos u O 00
Guest editor was G Bannister (MMT user)
Not peer reviewed as such
Lots of inaccuracies
Lots of very poor science
No surprises there then
18. Key points
Alleged: ’94 –HIPed; ’95 – SA ’96 – HIP d and SA
All d HIP d SA, HIPed d
Fact: ’91-’95 – Trucast (94% HIPed)
Fact 1996 – C
F Centaur HIP d and SA (
HIPed d (reverse engineered
i d
from the original McMinn castings).
Difference between HIPed and HIPed and SA?
Negligible
Current Cormet Metallurgy
Unchanged and re-validated
19. More failures in 1996 ??
94-95 – three failures (1 infection, 1 head collapse,
1 loosening with dysplasia)
1996 - 5 failures (1 infection, 3 cup loosenings, 1
awaiting revision)
Metallosis and osteolysis seen with the cup
loosenings
Plus one from Belgium with pain (and alleged severe
wear) at 50 months but well fixed.
)
McMinn Sales by Year
Year No of Implantations.
1991 23
1992 56
1993 57
1994 95
1995 238
1996 440
Total 909
20. Failures with wear
Case from Belgium
with l
ith low carbide
bid
content (allegedly)
Cup is open and
anteverted.
Could be a
yp y
hypersensitivity
reaction
Cup Loosenings
Cups have tilted
HA on smooth
Wear secondary to cup
movement or cup
movement secondary
to wear?
21. Wear as related to carbide content
MMT data (Calowear) from Treacy presentation
1.4E-03
1 4E 03
Error Bars = 1 standard
90% confidence interval
1.2E-03
Wear Coefficien K (mm3 N-1 m-1)
1.0E-03
1.26E-03
1.03E-03
1.03E-03
8.0E-04
9.46E-04
nt,
6.0E-04
4.0E-04
W
2.0E-04
0.0E+00
As Cast HT High N2 HIP & HT
Material Type
100,000 times the wear factors seen clinically!!
Hang on.
McMinn alleges that some 1996
resurfacings are fine and other have
metallosis
Ah, this is because HIP and SA produces
a range of microstructures.
microstructures
A very convenient excuse .
HIP and SA is used because it gives the
most reproducible results
22. Remember…
The data shown by McMinn would lead us to believe
that forged materials also have high wear
200,000 Metasul since 1988 would suggest otherwise
Conserve plus is also HIP and SA with no reported
problems with wear
These arguments are fabrications made up to
support a faulty hypothesis
Published wear data
Mean Volumetric Wear at 3M cycles
7
6
metic Wear (m )
3
mm
5
4
3
Volum
2
1
0
28mm low C 36mm wrought, 36mm wrought, 36mm wrought, 40mm as cast 40mm HIPed and 54mm as cast, 54.5mm as cast,
head/High C cup mean 143 (142-146, mean 123 (120-126, mean 105 (105, (mean 220) SA Mean 220 mean 276 (254-307, mean 108 (83-129,
mean 50 n=3) n=4) n=3) n=3) n=4)
23. Wear Data
Wear is dependant on head size and radial clearance
and NOT metallurgy
Although low carbon/low carbon couples are not great
This was supported at the recent Second International
Conference on Metal-metal Hip Prostheses: Past
Performance and Future Directions. Montreal 2003.
Directions 2003
McMinn d
M Mi and MMT are b becoming i
i increasingly i l t d
i l isolated
by the scientific community and are losing credibility
in the eyes of surgeons.
surgeons
Thank you