Friction materials are used in most industries to induce resistance in several applications that require slow or decreased movement, such as in brake and clutch systems. For example, industrial machinery, automotive equipment, operating systems etc. all require the ability to slow down and/or stop their processes. Disc brake pads, friction pads and linings are common components of these arrangements and these are made of friction materials. They are also referred to as brake materials and clutch materials.
Materials used in the production of friction are usually rough or textured in order to provide added friction and increase efficiency. Smooth surfaces are used to transport materials easily and with little friction, however adding texture to a surface increases the energy required to move over it, thus slowing a moving object more quickly. Heat-resistant materials are often utilized as the process of creating friction typically generates heat energy as a byproduct. While asbestos fibers were once the most popular choice for friction materials, due to health concerns about the use of asbestos, there has been a growth in manufacturing of alternatives such as ceramic brake pads. Ceramic is a durable and highly heat-resistant material which allows for its use in many high friction environments. As the process of friction occurs inevitably with wear and tear, the materials used need to be able to withstand a certain amount of physical stress. There are several applications for which friction materials are essential. Brake pads, clutch sets, brake bands, brake lining, clutch facing, disc brake pads, clutch discs and friction discs, brake shoes and brake blocks all demand friction materials in order to operate at optimum levels. These materials are utilized by a variety of industries such as mining, oil and gas, forestry and construction. The automotive industry relies heavily on these friction material components as well.
Friction is defined as the resistance to relative motion that opposes the travel direction of an object. At its most simple, it is used to slow an object down enough to stop it, or to bring it to a controllable speed. It is created by contact of one solid body with a divergent surface. The type of material suited to a given task is dependent upon the type of friction. Different types of friction include static, kinetic and rolling. Static friction is found between two solid objects that are not moving relative to each other, preventing movement entirely. Slope is an important consideration when utilizing this particular type of friction. Kinetic friction, also known as dynamic, occurs between two objects moving relative to each other. Both surfaces may be moving or one may be sliding along a stationary object. Rolling friction involves wheels or balls. The rough texture of friction materials catches the wheel and stops it from sliding or slipping. A car tire spinning on ice or snow, for instance, is an example of low rolling friction and thus the tire does not catch on the ground, but keeps moving around.
A high coefficient of friction and good energy absorption are the key requirements of all friction materials. It is necessary to know the system for which the material is needed in order to ensure efficiency and effectiveness. In instances where quick stopping is an issue, a material that creates a large amount of friction is needed. In addition to speed, heat generation is an important consideration. Resin bonded asbestos and carbon was once the most popular friction material, but recent technological advances have significantly expanded material possibilities. Ceramic, as aforementioned, has become a popular choice due to its desirable attributes. Semi-metallic brake elements are also available using copper, brass and steel wool bonded by resin as these compounds share many of the long-lasting characteristics of ceramic options.
Braking systems use friction materials to slow and stop wheels and other mechanisms from moving. When a brake is pressed, it activates a system that places friction material against the moving disc in order to slow the connected tire. Friction discs are most often constructed of durable metal. The drawback of metallic components is the inherent grinding noise created by their friction. For this reason several manufacturers coat them with rubber and other high friction materials. Rubber or other materials have the added benefit of increased surface friction. Brake pads, linings, blocks and shoes are different mechanisms engaged by the action of braking which presses them against the disc. Clutch facing and discs function in a similar manner to offer consistent clutch engagement and disengagement. Although it is an important aspect of many other industries, the production of friction materials has more recently become an industry in its own right. While generalizations can be made, manufacturers are often secretive of their specific friction material compositions. The major changes in the industry throughout the years have caused several companies to try and protect their own advancements in order to beat out competitors. The introduction of ceramics, for example, has provided several opportunities for efficient and reliable systems. Faster stopping and lower noise are common claims in brake and clutch related products. Friction materials continue to advance and developments are a consistent occurrence in the industry markets.
Friction materials are used extensively in a range of industries to generate controlled friction. By controlling friction, braking and power transfer is achieved in automobiles and machinery. The products that are made with friction materials are: brake pads, brake lining, friction disc, clutch facing, clutch sets, and brake shoes. For some applications, liners and rolls are also manufactured with friction materials.
There are a number of forms in which friction materials are available for different application.
Friction shoes and pads are the most known form of friction materials that play a major role in braking mechanisms. In disc braking systems, it is these pads or shoes, which are placed in brake calipers and touch the disc, which results into conversion of kinetic energy into thermal energy. As the energy is converted, an automobile loses its momentum and stops.
Friction Clutch Sets or plates
This is another application where friction materials are used extensively; all clutches are fitted with friction materials for smooth transmission action in machines. Friction plates are also used in other transmission devices, such as disc drives and torque limiters.
Friction columns or blocks
You probably have not heard about this, since they have specialized application in mining and oil rigging industry. The cranes components, such as, winches and hoists are fitted with friction blocks that regulate the movement. The blocks, however, have the same function that a brake pad has in an automobile.
Bands are another form of friction material that is used in transmission and machining. Friction bands are used in the machining process known as sawing, where blades running at high angular velocity cut metal.
To make these different forms, a number of friction materials are available, ranging from organic to ceramic to fibers and metallic materials. Ceramic materials are used in heavy loads, since ceramic can endure high temperatures. Ceramic can withstand thermal energy higher than any other alternative, however, it wears pretty fast. Organic friction material makes use of fiberglass and other materials, since asbestos proves to be a hazardous material for humans. Aramide fibers such as Kevlar is also used for making friction materials, it has the property of organic material that helps in smooth engagement of components and braking ability of ceramic pads. The other options involve high-end metallic materials, such as, sintered steel. No other additives are required for making metallic pads; however, they take heavy toll on the machinery, therefore, used only in performance vehicles.
Since there are a number of options in friction material, it is necessary to consider factors that determine its functionality and life. Before buying a friction material, you need to see the following characteristics:
These factors can help you to choose an appropriate friction material that will serve you for longer periods.
"A necessary evil" is an idiom that is used quite often and friction is often referred to as a necessary evil. However, what does that mean? Is friction evil, and if yes, how?
To answer that question you need to know, what friction is? Friction is a natural phenomenon where a surface resists the movement of other surface over it. For most machinery, friction is what that hinders the smooth functioning and leads to wear and tear. That is why machines are lubricated periodically to reduce friction. More or less, friction is an evil that is an ultimate reason for all your operation and maintenance costs.
Now, we know friction indeed is an evil. However, why it is necessary? Why cannot we have a machine that needs no maintenance and works until eternity? The answer is: without friction no machine can work, no gear can transmit movement. Therefore, friction is necessary, too.
Now, moving to, why we need friction materials? This question is interesting and worth writing about. The most extensive use of friction material is in braking and transferring power. Whether it is a car, tank, heavy industrial machinery, all need friction material for generating controlled friction to minimize wear and tear during braking and transferring power.
Motion control products, such as clutch facing, clutch sets, clutch discs, and brake shoes are fitted with different types of friction materials.
Ceramic is one of the conventional friction materials used for making ceramic brake pads and ceramic button-style clutch. Ceramic has a unique property; it does not lose its structural integrity even under extreme temperature. The outer covering of spacecrafts is made from ceramic tiles that act as a shield against the melting temperature when spacecraft enter earth's atmosphere. As the temperature increases, ceramic starts to show better resistance against movement, making it an appropriate material for clutches and brake pads.
Kevlar is a new friction material. After proving its endurance in the armor industry, Kevlar is also used in making clutch and brake pads. Kevlar is a durable friction material that can last two to five times than a conventional friction material. It has the same pulling capabilities of ceramic, but has smooth engagement properties, unlike ceramic. With the use of Kevlar, the life of driveline components, such as, differential gears and universal joints, can be elongated significantly.
The term organic in friction materials industry is not new. Organic brake and clutch sets have existed for more than 70 years. It is one of the oldest friction materials, originally made with asbestos, which has lead to many health issues, including cancer. Therefore, its use is phased out from the manufacturing process, and its place in organic friction material is taken by fiberglass and brass. The organic pad engages clutches smoothly; however, it goes through high wear and tear leading to short life span.
The other alternatives include carbotic and fibertuff, which have the properties of all above mentioned friction material but have longer life.
Friction materials serve a great purpose-- stopping or reducing the speed of moving things. They have found their use in the automotive, aircraft, aerospace, railroad, heavy machine manufacturing, and defense industries. Friction is a force we encounter all the time-sometimes, it is undesirable; the other times, we use it to our advantage. One beneficial use is motion control products such as ceramic brake pads and brake lining; these products are used in a brake system of a vehicle. They help to control the motion of the vehicle; an uncontrollable automobile is undesirable and unusable. By allowing us control a car or an automobile, these friction materials facilitate smooth and safe rides. Therefore, if you have just taken a car ride, you need to acknowledge these items as much as you need to thank the driver for driving responsibly.
When two surfaces slide against each other, a resisting force is generated-this force is called friction. Several parts in automobiles use this force to facilitate movement or control it. Brake shoes or brake lining, clutch facing, clutch disks-all use friction. When you press the brake pedal, brake pads are rubbed against the friction disks in the brake system (or drums in drum brakes), creating friction that stops the car or reduces its speed. Other components of the vehicle, such as clutch facing and clutch discs also use the force. A clutch works as a bridge between the engine and the transmission; to facilitate movement and stoppage, the engine needs to be engaged and disengaged from the transmission, these items make that happen.
The brake system in a vehicle is one of its most crucial elements. There are ceramic brake pads and there are brake shoes made from a variety of materials such as advanced fibers and different metal alloys. As the speed of cars has increased over time, the need for a powerful and efficient braking system also increased. Sports cars, super cars, and heavy-haul vehicles need far more powerful brake power than other vehicles. In these cases, ceramics are used, which is more durable than other friction materials.
Unlike a braking system where friction is used to our benefit, there are areas where friction is generated but that is unwanted. In such scenarios, lubricants are used to reduce the friction coefficient. Engines, wheels, transmissions are example of such components.
A traditional braking system prevents motion by means of friction, converting kinetic energy of the vehicle or a moving object to heat. However, in regenerative braking, which is relatively a new concept, the kinetic energy is converted into electrical energy. This is found in hybrid or electric vehicles.
Friction is with us all the time, so are friction materials. Without these materials, the concept of an automobile and many other things is simply not possible. When we create momentum, there is also the need to control it. A brake lining or a friction disk aids you to do that, when talk about vehicular momentum. Thanks to friction, you can enjoy a peaceful and safe journey in an automobile.
- The process by which overheated or spoiled brake fluid and air bubbles are removed from the brake system.
- Metal housing bolted to an axle and vehicle wheel that looks like a large jar lid. Brake shoes are forced against the drum to stop rotating wheels.
- Heat-resistant friction material that presses against the disc/drum to create braking force.
- Made of friction materials and bonded to metal plates. Brake pads need to be replaced occasionally due to heavy wear.
- Process of wearing in brakes so that the contact between the friction material and the rotor or drum becomes stable.
- The assembly that houses the brake pad(s) and applies them to the rotor. This also houses the hydraulically operated pistons to which the pads are bonded.
- Any of various contraptions used to engage and disengage two moving parts of a shaft or shaft and driving mechanism. When changing gears, the clutch pedal is pressed, disengaging the clutch and allowing the gear change; when released, the clutch engages and transfers the rotating motion throughout the entire driveshaft.
- The ratio of force necessary to move an object compared to the weight of the object itself.
- Consists of brake pads, caliper and rotor. This is the part of the brake system that actually stops the vehicle.
- A large circular metal housing that looks like an oversized jar lid and is bolted to a vehicle's axle and wheel. Brake shoes are forced against the inner section of the drum, which then stops the rotating wheel.
- Apparatus in a laboratory used to test brake system performance.
- Temporary reduced braking power. Fade results from overheating of the friction material.
- Grooves on friction material that help dispel heat, get rid of fluid and eliminate noise.
- The cylinder that contains hydraulic fluid and a piston. It is connected directly to the brake pedal and transmits pressure to the brake operating system.
- The return of braking performance to a normal level after fade has diminished. This measures friction materials' ability to perform after overheating.
- Also referred to as a disc or drum, this is the circular metal object to which the brake pads are applied, creating friction to slow and stop the vehicle.
- A steel semicircular form coated with a friction agent that presses against the inside of a drum when activated.
- High-pitched noise made when braking. Squeal indicates that brakes should be inspected for wear.