elec mt Flashcards by Unknown Unknown

is the resistance generated when two surfaces slide against each other. While
it serves important functions in applications such as braking and traction, excessive friction in
machinery leads to energy loss, heat buildup, and material damage. To minimize these
effects, lubricants are used to create a separating film that prevents direct asperity contact
between surfaces. Under boundary lubrication conditions, friction modifiers play a significant
role in reducing surface interaction and improving motion smoothness. Furthermore, the
oiliness property of lubricants helps decrease the coefficient of friction beyond the effect of
viscosity alone, ensuring efficient mechanical operation.

Friction

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refers to the gradual loss of material from a surface as a result of mechanical
interaction. It commonly occurs in various forms, including adhesive, abrasive, and corrosive
wear, each of which can reduce dimensional accuracy and impair machine performance. To
mitigate these effects, additives such as anti-wear agents and extreme-pressure compounds
are utilized to form protective tribofilms on surfaces. These films help reduce direct contact

and wear, especially under high loads and demanding operating conditions, thereby extending
the service life of components.

Wear

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is the process of introducing a fluid, semi-solid, or solid substance
between moving surfaces to lessen friction and wear. Lubricants generally consist of base oils
combined with additives that enhance their performance and stability. The effectiveness of a
lubricant depends on its key properties, including viscosity, viscosity index, oxidation
stability, thermal resistance, flash point, and pour point. These properties determine a
lubricant’s suitability for specific operating conditions. Proper lubrication ensures smoother
motion, reduced energy loss, and longer equipment life, making it a crucial factor in
achieving efficient and reliable mechanical operation.

Lubrication

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describes the small-scale irregularities present on solid surfaces.
Increased roughness promotes greater asperity contact, which consequently raises both
friction and wear. The use of lubricants helps counter these effects by forming protective
films that fill in surface imperfections, minimizing direct contact and wear. Additives such as
friction modifiers enhance efficiency in boundary lubrication conditions, while detergents
maintain surface cleanliness and prevent deposit buildup that could affect performance.

Surface roughness

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are fundamental mechanical components responsible for transmitting power
from one shaft to another and are utilized in a wide range of industrial applications.

Gears

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failure generally results from scuffing or wear that occurs when
two mating surfaces come into contact. In contrast, in tungsten carbide (WC)-coated gears,
failure is primarily caused by the gradual thinning of the coating rather than by direct wear.

In carburized gears,

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These gears are made from polymer materials with teeth on their surface,
typically manufactured through the injection molding process.

polymer gears

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play a crucial role in supporting various rotating
elements such as shafts.

bearings

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are used to support cylindrical
rotating shafts.

Journal bearings,

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Utilize precision-ground balls as rolling elements and are capable of handling
both substantial thrust and radial loads. They are particularly suitable for high-speed
applications such as gearboxes and pumps due to their low friction and smooth
operation.

Ball bearings

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the shaft is slightly elevated from its original position and
rotates while remaining separated from the bearing surface. This prevents direct contact and,
therefore, eliminates wear during normal operation.

In hydrostatic lift bearings,

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On the other hand, they are designed for applications involving heavier radial
loads. While similar in function to ball bearings, they differ in that their rolling
elements are cylindrical rather than spherical. A specific subtype, known as needle
bearings, features very thin cylindrical rollers that allow them to sustain high load
capacities despite their compact design. Common applications of roller and needle
bearings include automotive power transmission systems, drive shafts, and air
compressors.

Roller bearings

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Also referred to as plain bearings, they operate without rolling elements.
These bearings function through sliding motion between surfaces and are often
one-dimensional in design. They typically require little to no lubrication, exhibit low

friction, and possess a high load-bearing capacity. Slide bearings are especially
advantageous for structural support applications, with common uses in compressors,
ship propeller shafts, and seat slider mechanisms.

Slide bearings

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Bearings are a type of slide bearing made from synthetic jewel materials such
as sapphire or ruby, which provide exceptional resistance to friction and wear. These
bearings are primarily used in applications requiring miniature size, high precision,
and excellent wear resistance, such as mechanical watches and precision instruments.

Jewel

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Operate by supporting the load on a thin film of rapidly moving, pressurized
liquid or gas situated between the bearing surfaces. The working fluid—typically
water, oil, or air—is pressurized using a pump to create a stable lubricating layer. This
design minimizes direct surface contact, resulting in extremely low friction and high
efficiency. Fluid bearings are particularly suitable for high-speed and precision
applications, including hard disk drives, turbines, and industrial machinery.

Fluid bearings

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A type of rotary bearing specifically designed to support axial loads. They are
generally composed of ball bearings arranged in a ring formation to accommodate
forces parallel to the shaft. Certain types of fluid bearings also function as thrust
bearings due to their ability to support axial loads through fluid pressure. Thrust
bearings are widely used in clutch release systems, automotive air-conditioning
compressors, and other rotary mechanisms that require smooth axial motion and
reduced friction.

Thrust bearings

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one of the most critical components of any vehicle as they are
responsible for safely reducing speed or completely stopping the vehicle.

● BRAKES

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A type of brake that operates by utilizing friction produced when a set of shoes
or pad exerts pressure outward on the inside of a rotating, cylinder-shaped component
known as brake drum. The friction is what stops or slows the rotation. The term
“drum brake” refers to a breaking mechanism in which the shoe applies pressure to
the inner surface of the drum. It is commonly found in older vehicles and some
rear-wheel brakes.

Drum Brake

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are mechanical components used to regulate the motion of
rotating shafts in machinery. This works by applying a force that opposes the motion,
thereby slowing the rotating shaft’s movement. These brakes are commonly utilized in
heavy equipment such as industrial machines, elevators, and cranes that often require
precise motion control.

Cone Brake

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A fundamental component in modern automotive braking systems, known for
their high efficiency. This type of brake has enhanced stopping power, has a high
ability to dissipate heat quickly, and greater durability which outperforms older or
traditional drum brakes.

Disc Brake

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Is often employed within an automatic transmission system, where it fits
around the clutch drum and does not demand additional space. The braking force it
generates is influenced by the layer of oil film present between the band and the drum.
Heavier lubrication and lower pressure reduces friction, affecting the band brake’s
ability to slow or stop the movement. The recommended lubricant for this is light
machine oil or grease since it lubricates band pivot points, lever arms, and other
moving parts. Its low viscosity allows it to enter tight spaces and reduce friction and
also prevent rust and corrosion.

Band Brake

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are essential components in all mechanical systems, as they prevent leaks and
ensure the integrity of the system.

Seals

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Are static seals made from flat, elastomeric, or compressible materials such as
rubber or cork. They are designed to fill the space between the surfaces of stationary
components, compensating for irregularities to create a tight seal. Leading gasket
manufacturers ensure that these seals are produced in various materials and sizes to
meet the requirements of specific applications. Gaskets offer excellent fluid
compatibility and resist both pressure and temperature, making them suitable for use
in machinery, flanges, motors, and pipelines.

Gaskets

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Are circular, ring-shaped mechanical seals typically made from rubber or
elastomeric materials. They are versatile seals suitable for both static and dynamic
applications. When inserted and compressed between two mating surfaces, O-Rings
create a tight seal that prevents fluid or gas leakage. They are specifically designed to
fit within grooves or housings of components and can withstand extreme temperatures
and pressures. O-Rings exhibit high resilience, flexibility, and chemical resistance,

making them ideal for use in hydraulic systems, pumps, valves, and various
mechanical assemblies.

O-Rings

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Also known as plain washers, are thin, flat discs with a central hole. Their primary function is to distribute load and provide a sealing interface between bolts or nuts and the mating surface. While not primarily designed for sealing, flat washers can help prevent leakage and contamination from external elements, reducing the risk of surface damage or distortion. Flat washers are made from both metallic and non-metallic materials and are commonly used in industries such as construction, automotive, and machinery.

3. Flat washers

Are designed specifically for reciprocating motion in hydraulic and pneumatic systems. They are positioned between the piston and the cylinder bore to prevent leakage and maintain system pressure. Piston seals are engineered to withstand a range of operating conditions, including high pressures, ensuring reliable performance in demanding applications.

1. Piston Seals

Also known as shaft seals or oil seals, are installed between the housing bore and the reciprocating rod or shaft to prevent fluid leakage and protect against external contamination. They are commonly used in hydraulic and pneumatic cylinders. Rod seals are designed to handle radial loads, reciprocating motion, and exposure to varying fluids and temperatures. Additionally, they can be equipped with features such as wipers or scrapers to enhance performance and extend service life.

2. Rod Seals

Causes of Friction:

Surface Irregularities: Material Properties: Adhesion:

Effects of Friction:

Increase in Temperature: Machine Failure: Surface Quality: Deformation: Tool Wear:

Effects of Wear:

Loss of Material: Surface Damage: Increased Friction: Component Failure:

occurs when metal-to-metal contact exists between two moving surfaces. This regime develops when a fluid film cannot form or be sustained due to heavy loads, low operating speeds, high surface roughness, or insufficient lubricant supply. This condition often arises during the start-up or shutdown of equipment such as journal bearings or under heavily loaded applications like construction equipment pins and bushings.

Boundary lubrication

occurs when two or more lubrication mechanisms operate simultaneously. In this regime, partial solid contact exists between the surfaces, while other sections are supported by a thin hydrodynamic fluid layer.

Mixed lubrication

typically occurs in friction pairs that experience elastic contact under very high pressure, such as ball bearings and gears. This regime arises when a rolling motion occurs between moving elements, and the contact zone has a low degree of conformity.

Elastohydrodynamic lubrication

also known as full-film or thick-film lubrication, occurs when the fluid film is thick enough to completely separate the moving surfaces. In this regime, the friction-coupled elements operate without direct contact, significantly minimizing wear and energy loss.

Hydrodynamic Lubrication

are advanced fluids produced by dispersing nanosized particles into conventional base fluids like water or oil.

Nano-lubricants

are thin films applied to sliding surfaces using techniques such as aerosol spraying, burnishing, or tumbling.

Solid Lubricant Coatings

involves determining the pressure–deformation relationship between two bodies in CONTACT. It focuses on how pressure is distributed across the contact region, influencing product quality, wear, and potential failure in processes such as metal forming or machine component operation.

Contact mechanics

refers to the measurement of a surface’s texture, expressed through microscopic deviations from its true form.

Surface roughness

such as turning, milling, drilling, and cutting involve direct contact between the cutting tool and the workpiece. This interaction generates significant friction and heat at the tool–chip and tool–workpiece interfaces.

Machining operations

processes—such as forging, rolling, extrusion, and stamping—involve large plastic deformations where metal flows between tool surfaces. Friction at the interface significantly affects forming load, surface quality, and die wear.

3.2 Metal Forming

involves pouring molten metal into a mold where it solidifies into a specific shape. Although not primarily a surface-contact process, tribological factors affect interactions between molten metal, mold surfaces, and cores—especially in die casting.

Casting

builds components layer by layer using metals, polymers, or ceramics. Though distinct from conventional processes, tribology still influences powder flow, layer adhesion, and surface finishing.

Additive manufacturing (AM)

is a precision finishing process where abrasive particles remove material from the workpiece. Due to high sliding speeds and small contact areas, it generates intense heat and stresses.

3.5 Grinding

is one of the most fundamental sliding wear tests in tribology. In this setup, a stationary pin is pressed under a controlled load against a rotating flat disk. The resulting frictional interaction produces measurable frictional forces—expressed as the coefficient of friction (COF)—and wear data.

3.6.1 Pin-on-Disk Test

is primarily used to assess lubricants, especially oils and greases, under high point-contact sliding conditions. The setup includes three stationary balls forming a cradle immersed in the lubricant, while a rotating upper ball is pressed against them under a constant load.

The four-ball wear test

evaluates the tribological performance of materials, coatings, and lubricants in line-contact configurations—conditions that closely represent many industrial applications. In this test, a block specimen is pressed against a rotating ring under a controlled load, creating a consistent line contact where friction and wear are measured.

The block-on-ring test

refers to the deliberate modification of the outermost layers of a material so that its surface properties—such as hardness, friction, wear resistance, fatigue life, corrosion resistance, or a combination thereof—are significantly improved relative to the untreated bulk substrate.

Surface engineering

is used to assess coating adhesion, surface durability, and failure mechanisms under applied sliding stress. In this test, a diamond indenter is drawn across a coated surface under either constant or increasing load while monitoring friction, acoustic emission, and visible coating failures such as cracking or delamination.

Scratch testing

converts fuel to mechanical power for pumps and systems

Engine

powers boom/arm/bucket; needs clean, well-oiled fluid

Hydraulic system

It is used for the smooth operation of the machinery engine. It has high temperatures and pressure while providing strong protection against wear and corrosion.

Engine Oils

- It is formulated to provide extreme pressure protection to ensure the smooth operation under heavy loads.

Gear Oils

It is a semi-solid lubricant that stays in place, it is usually used in areas that are prone to high pressure. Shock loads, and constant movement.

Grease

- It is used to ensure the transmission of power from the engine to the wheels efficiently to lubricate the transmission system, reduce wear, and keep the machinery running smoothly.

Transmission Fluids

- It is specifically designed to transmit power within the hydraulic system while also providing lubrication to the moving parts, also called as the heart of the construction machinery.

Hydraulic Oils

most cost friendly fire resistant fluid which consist of 35% water and 65% oil. A mix of 40% water glycol with 60% additives maintains proper viscosity and prevents corrosion.

Water-based hydraulic fluid

- this is best to use during high temperature scenarios - It is also fire resistant and has smooth viscosity for a higher performance of lubrication.

Synthetic Blend

most common type of hydraulic oil - Typically based on zinc dialkyldithiophosphates (ZDDP)

Anti-wear Hydraulic Oils (AW)

- it is an eco-friendly fluid that serves as an alternative. This fluid contains soybean, rapeseed, and sunflower oil.

Biodegradable

most reliable hydraulic lubricators offered in the market for it increases the machinery’s performance and product outcomes - It also eliminates contaminants and hydrocarbons.

Petroleum Based

- used for construction machinery have different types and each of them has been designed for specific parts of the equipment. It depends on the base oil type, the lubricants can be mineral and synthetic.

Oils and lubricants -

Key methods in monitoring lubrication systems

Visual inspection Oil analysis Ultrasonic monitoring Sensor based monitoring

elec mt Flashcards

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