Materials Technology

II Categorising MaterialsBraking systems

vocabulary useful in this section.

• compound, exotic (material), • ferrous, non-ferrous, ceramic, alloy, • metallic, non-metallic, polymer• consist of, comprise, • made of, made from, made out of

4.1 What do brakes do and how do they work?

Brakes are designed to slow down vehicles or moving parts. Often they work through friction, by applying pressure to pads which are pressed against the sides of a disc, the inside of a drum, or directly against a wheel rim. Alternatives include systems that use electromagnetic force, systems that exploit the braking effects of engines or flywheels (via clutches and gearboxes), aerodynamic braking systems (for example spoilers on aircraft, parachutes on dragsters), and reverse thrusters on jet engines.

4.2 What kinds of materials are used in brake pads and brake discs in different vehicles?

Brake discs are often made of ferrous metals (iron-based – for example steel), or sometimes ceramic materials.Examples of materials used to make pads include: compounds of advanced materials (cars), ferrous metals (trains), rubber (bicycles), ceramics (performance cars).

Green refers to ecological issues. Red refers to heat (red hot means very hot). Also, a hot topic is a current important topic.

5-A Read the article on braking systems. What do colours in the title refer to?

5-B Why do most braking systems waste energy? What are regenerative braking systems, and how do they save energy? What characteristics are required of materials used for the brakes on racing cars?

Answers1. Because they use friction, which wastes energy as

heat 2. They recover heat and use it to power the car.3. The ability to generate high levels of friction, and to

resist the effects of friction and consequent heat4. Heat from the engine being absorbed by the chassis,

which can damage sensitive parts such as electronic components and plastic parts

1(-c)

(1(-c )2-(g

3(-b )( 1-(c) 2-(g

3(-b )4-(f) (1-(c) 2-(g

3(-b )4-(f) 5-(d) (1-(c) 2-(g

3(-b )4-(f) 5-(d) 6-(a) (1-(c) 2-(g

3(-b )4-(f) 5-(d) 6-(a) 7-(e) (1-(c) 2-(g

1 ( -a , b , c)

1 ( -a , b , c) 2 ( -d, e)

1 ( -a , b , c) 2 ( -e , d)

3 ( -d)

1 ( -a , b , c) 2 ( -e , d)

3 ( -d) 4( -e)

1- ( a, b, c )2- ( e, d )3- ( d ) 4- ( e )5- ( a, b, c )