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.
This book offers fundamentals and a comprehensive overview of tribology in sever conditions. It addresses a comprehensive coverage of classical tribology of solid contacts, friction mechanics, wear mechanisms and lubrication technologies. Characteristics of tribological systems operating under extreme conditions involving extraordinary loads, temperatures, speeds, and vacuum are discussed. Surface coating, surface treatment, and lubrication are argued considering the cutting-edge researches. In addition, tribology of automotive components is presented, as are tribological applications in many practical situations. The tribology of polymer composites, MEMS and NEMS are explored. A basic understanding of failure in tribological systems is covered. Various test methods used in evaluating wear are reviewed. Diverse techniques applied in predicting wear behavior by mathematical models, FE modeling and ANN approach are discussed.
This book offers fundamentals and a comprehensive overview of tribology in sever conditions. It addresses a comprehensive coverage of classical tribology of solid contacts, friction mechanics, wear mechanisms and lubrication technologies. Characteristics of tribological systems operating under extreme conditions involving extraordinary loads, temperatures, speeds, and vacuum are discussed. Surface coating, surface treatment, and lubrication are argued considering the cutting-edge researches. In addition, tribology of automotive components is presented, as are tribological applications in many practical situations. The tribology of polymer composites, MEMS and NEMS are explored. A basic understanding of failure in tribological systems is covered. Various test methods used in evaluating wear are reviewed. Diverse techniques applied in predicting wear behavior by mathematical models, FE modeling and ANN approach are discussed.
Sliding Contact Bearing Theory Prof. Sagar DhotareSagar Dhotare
In present ppt covers following points:
Introduction of Sliding Contact Bearings
Classification
Applications
Different lubrications systems
Hydrodynamic bearing concept and working
Comparison between sliding and rolling contact bearings
PETROFF’S EQUATION For Hydrodynamic Journal Bearing
Dimensionless Parameters used in SCB
Design procedure for Hydrodynamic Journal Bearing
Wear is a process of removal of material from one or both of two solid surfaces in solid state contact, occurring when these two solid surfaces are in sliding or rolling motivation
This presentation is by Flt Lt Dinesh Gupta, Associate Professor (Mechanical Engineering) NIET, Alwar (Rajasthan). It covers topic on Fluctuating Stresses related to Machine Design subject.
Sliding Contact Bearing Theory Prof. Sagar DhotareSagar Dhotare
In present ppt covers following points:
Introduction of Sliding Contact Bearings
Classification
Applications
Different lubrications systems
Hydrodynamic bearing concept and working
Comparison between sliding and rolling contact bearings
PETROFF’S EQUATION For Hydrodynamic Journal Bearing
Dimensionless Parameters used in SCB
Design procedure for Hydrodynamic Journal Bearing
Wear is a process of removal of material from one or both of two solid surfaces in solid state contact, occurring when these two solid surfaces are in sliding or rolling motivation
This presentation is by Flt Lt Dinesh Gupta, Associate Professor (Mechanical Engineering) NIET, Alwar (Rajasthan). It covers topic on Fluctuating Stresses related to Machine Design subject.
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
Teaching How to use the CFD Approach by an Example: Hydrodynamics within a Pa...Nelson García Polanco
The CDF methodology is applied to the study of the air flow around a 2-D car and its interaction with the cabin internal air. The flow visualization or computational works enable engineers to calculate different car characteristics like drag coefficient, external and internal air flow patterns.The results show the physics behavior of the flow and the presence of flow structures, as for instance, indoor air recirculation zones.
In this presentation slides I will discuss about Ocular tribology.
Ocular Tribology is concerned with the mechanisms of
contact lens lubrication.
There are three major driving forces in contact lens design
and development…
a. Cost
b. Convenience
c. Comfort
Wear In Hydrodynamic Journal Bearings: A ReviewIJMER
The importance of friction and wear control cannot be overemphasized for economic reasons
and long-term reliability. This paper presents the reviews of different works in the area of wear and
friction in hydrodynamic journal bearings and tries to find out latest developments and trends available in
industries and other fields in order to minimize the total equipment cost, minimize damages and maximize
the safety of machines, structures and materials. This paper helps us to find out the parameters on which a
hydrodynamic journal bearing is selected for different conditions i.e. dry as well as lubricated conditions.
The tribological properties of textured surfaces of brass and aluminum were compared with untextured surfaces of the same specimens. This was done to research the effect of micro-dimples and their geometry parameters in reducing the wear of samples tested under lubricated contact with a ball-on-flat reciprocating tribometer.
Wear Rate Analysis of Hydrodynamic Journal Bearing In Different ConditionsIJMER
Friction and wear always occur at machine parts which run together. This affects the
efficiency of machines negatively. Hydrodynamic journal bearings are widely used in industry because
of their simplicity, efficiency and low cost. Wear due to relative motion between component surfaces is
one of the primary modes of failure for many engineered systems. Unfortunately, it is difficult to
accurately predict component life due to wear as reported wear rates generally exhibit large scatter.
An attempt has been made to study the influence of wear parameters like load, speed, type of lubricant
used, temperature, and viscosity of lubricant. The main objective of the study is to evaluate the wear
rate of different journalbearing materials (brass and white metal) under similar conditions. The
materials are tested in dry and wet lubrication under similar operating conditions. For this purpose we
use Pin-on-disc apparatus. It was found that the wear rate of both materials is more in dry conditions
compared to lubricated conditions (when tested under similar working conditions). We also found that
wear rate of white metal is more as compared to brass and higher frictional force is observed in case
of brass material
Microstructure and sliding wear behaviour of stircast ti gr and ti –fe metal ...eSAT Journals
Abstract
The type and weight percentage of reinforcement play important role in microstructure and sliding wear resistance of the composite. The low melting point nonferrous metal matrix composites Tin- Graphite and Tin-Iron metal matrix composites are cast by the liquid stir casting technique with up to 5 and 15 weight percentages of carbon and iron respectively as reinforcements. The sliding wear characteristics are important if the specimens are used as bearing materials for light duty applications. The specimens are polished and etched for microstructure examination to verify the homogeneous dispersion of reinforcements in the matrix. The microstructure examination reveals the uniform dispersion of reinforcements in the matrix. The specimens are also subjected to dry sliding wear on Pin –on –disc wear testing equipment and the weight loss method technique was used to find specific wear rate at the respective sliding distance. The cumulative specific wear rates and friction coefficients are plotted against sliding distance. The specific wear rate curves show the necessity of an optimum weight percentage of reinforcements in the composite to reduce the wear rate. The frictional coefficient versus sliding distance curves show the decrease in frictional force at higher sliding distances as the weight percentage of particulates increases. At higher sliding distances, in case of the Tin –Graphite composite the surface of the specimen observed to be smooth which makes the graphite particles to expose as flakes and act as solid lubricant to reduce wear. The scanning electron microscope image of the surface which is normal to the sliding surface also studied to verify the flake formation during wear. Both mild and severe wear regions are observed.
Keywords: particulate, metal matrix composites, stir casting, specific wear rate, friction coefficient.
What is and what is the function of a rubber seal
The Increasing of the speed of mechanical systems, driven by the desire for greater productivity, leads to higher operating temperatures and reduced fluid viscosities. This, coupled with higher pressures, causes an increasing tendency for fluid to leak. This leak in fuel systems that handle highly flammable solvents cannot be overlooked as there is a high probability of a fire hazard.
For this reason it has become common practice to include a safe leak path in the system design, to an escape or collection point, in order to minimize risk.
Seals prevent fluid from escaping from a hollow cylinder when a shaft penetrates the cylinder wall. Most commonly, the axis will have a rotary or linear motion. If a seal is not made for functional requirements, or installed and maintained properly, it can fail, causing fluid loss. The two main functions of a seal are to keep the fluid in while keeping dirt and debris out.
Study of sliding wear rate of hot rolled steel specimen subjected to Zirconia...IJERA Editor
Wear is nothing but loss of material by usage. In a mechanical industry mechanical components will operate
under severe load, temperature and high speeds. Under such a type of situation, when metal to metal contact take
place the surfaces that comes in contact is subjected to wear. These should be considered as a serious affair in an
industry because if the process of wear continues it can reduce service life of the component and also to the
entire mechanical system to which the component has been used. In the light of the above the present work
mainly deals with the study of wear behavior of hot rolled steel with and without zirconia coating on the contact
surface and the effect of zirconia coating with varying thickness.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Normal Labour/ Stages of Labour/ Mechanism of LabourWasim Ak
Normal labor is also termed spontaneous labor, defined as the natural physiological process through which the fetus, placenta, and membranes are expelled from the uterus through the birth canal at term (37 to 42 weeks
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
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Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
2. What is Tribology ?
• Tribology is derived from the Greek word “Tribos”. Meaning of
Tribos is Rubbing.
• Tribology is a science that deals with friction, lubrication and
wear in all contacting pairs.
• Tribological knowledge helps to improve service life, safety and
reliability of interacting machine components; and yields
substantial economic benefits.
3. Consider few failed machine components, failure of which could had been avoided using
tribological knowledge.
Example 1 CAM
Example 1 is related to pitting wear on the cam surface. Cams are used to transmit rotary
motion in reciprocating motion. These components are subjected to jerks in sliding
distance, which leads to form some pits on the cam surface. Creation of pits on cam surface
increases noise pollution and reduces mechanical performance. Understanding the
mechanism of pit formation helps to estimate the life of component and find methods to
reduce such pitting failures.
4. Example 2 JOURNAL BEARING
In these examples of journal bearing, wear increases the clearance between shaft and
bearing and leads to reduction in load support capacity of the bearing. Often such
failures occur in absence of sufficient lubricant hydrodynamic film thickness due to
relatively low speed. Learning tribology cultivates an understanding that at low
speeds, the main purpose of oil is the lubrication and high viscosity oil will be
preferred to low viscosity oil, while at high speeds the major purpose of oil is to act as
a coolant and low viscosity lubricants are preferred to carry away frictional heat of
operation. Here lubrication is a secondary consideration.
5. Example 3 Multi-row Roller Bearing
Here cracking means deep cracks which breaks outer ring in number of pieces. Such
failure occurs due to faulty manufacturing and wrong assembly of roller bearing.
Tribological relations help estimating increase in contact stresses due to misalignment
of shaft and improper mounting of bearing surfaces. Hence an approximation on
reduction in service life can be estimated.
6. Example 4 Gear
The pit generally occurs due to excessive contact stress. Understanding the effect of contact
stress helps in developing an equation for estimation of perspective gear life.
7. Need of Tribology as subject
• Most tribological phenomenon are inherently complicated and interconnected, making it
necessary to understand the concepts of TRIBOLOGY in details.
• Integration of knowledge from multifaceted disciplines(solid mechanics, fluid mechanics,
material science, chemistry etc) is essential and therefore a separate subject is required.
• Solid Mechanics: Focus is on expressions of contact stresses/deformations and surface
temperatures due to rolling/sliding.
• Fluid Mechanics: Study of lubricant film formed between various geometric shapes of
rolling/sliding surfaces.
• Material Science: Focus is on atomic and micro scales mechanisms whereby solid surface
degradation or alteration occurs during relative motion.
• Chemistry: Deals with reactivity between lubricants and solid surfaces.
• Thermodynamics: Heat and mass transfer in fluids and bounding solids.
8. Fluid Film Lubrication
Fluid Mechanics Concepts : Fluid is defined as a substance that easily moves and
changes its relative position without a separation from the bulk mass.
• Lubrication makes relative motion between two surfaces very smooth. It reduces
the friction and minimizes the wear.
• In general, real area of contact between tribo-pair is hardly ten percent of
apparent area.
• Here, stress-state always exceeds the elastic/fracture point of all known solids. It
results in high plastic deformation in ductile materials, while generates cracks in
brittle materials, which causes excessive wear.
• Therefore, it is essential to reduce the normal stresses imposed by applied load
and to reduce the shear stresses induced due to relative motion.
There are some ways to reduce the normal and shear stresses shown on
next slide.
9.
10. In hydrostatic lubrication that separates two surfaces by an external pressure source.
It is suitable for extremely high load carrying capacity at low speed or at highly
controlled precision works.
• As pressure is generated and supplied by external sources, it is one of the
expensive approaches to separate two surfaces.
• If applied load is reduced, the film thickness (separation between tribo-pair) will
increase. Similarly if more load is added to the moving surface, the film thickness
will decrease.
• To compensate cost, often a hybrid concept of hydrodynamic + hydrostatic is used
to achieve best of both the mechanisms of fluid film lubrications.
11. In a hydrodynamic lubrication mechanism, a fluid is drawn into the region between
the relatively-moving surface by the virtue of its viscosity and adhesion to the
surfaces.
Due to the converging geometry of the surfaces, a pressure is generated within the
fluid that separates the tribo-surfaces. The separating film is only generated when the
there is relative motion.
13. In 1886, Reynolds derived an equation for estimation of
pressure distribution for “Fluid Film Lubrication”.
• Quantification of fluid film lubrication can be made by
solving Reynolds’ Equation, which provides fluid film
pressure as a function of coordinates and time. Reynolds
equation helps to predict hydrodynamic, squeeze, and
hydrostatic film mechanisms.
14. Derivation of Reynolds’ Equation :
To model the pressure as a function of angle of inclination, let us consider a fluid
element subjected to pressure and viscous forces, assuming gravity and inertia forces
acting on fluid element can be neglected.
Fig: Fluid element subjected to pressure & viscous forces.
On balancing forces shown in figure-
15. For laminar flow of Newtonian fluid,
On substitution
Equation is based on following assumptions :
1. Negligible inertia terms
2. Negligible pressure gradient in the direction of film thickness
3. Newtonian fluid
17. Assuming no slip at liquid-solid boundary;
y = 0, u = U2
y = h, u = U1
Utilizing these boundary conditions, values of integration constants can be evaluated.
18. This equation is applicable for following assumptions :
1. Negligible inertia terms.
2. Negligible pressure gradient in the direction of film thickness.
3. Newtonian fluid.
4. Constant value of viscosity.
5. No slip at liquid solid boundary.
In that equation, on right hand side there are three terms, two velocity terms and one
pressure term. Velocity terms represent “shear flow” also known as “Couette flow”.
Flow due to pressure gradient is termed as “Poiseuille flow”. similarly flow velocity in z
direction.