Reinforcing and stiffening
Forces act on materials all the time - even if a material appears stationary it still has a force acting on it. There are five terms used to describe what type of force can act on a material:
- Pulling force exerted by each end of an object such as a string or rope. - a pulling force
- Being squashed. - a pushing force
- A force across a material, eg scissors cut by applying a shear force. - forces acting across the material
- electrical - ability to conduct electricity
- magnetic - magnets will attract metals that contain iron
Each metal type has different The mechanical, physical or optical properties of materials that define how they behave in use. in relation to the way they react to each of the five forces. It is therefore important to know how to test a metal so the correct one can be chosen for the specific task.
Tension can be tested by pulling opposite ends of the metal. The The tension a material can withstand without breaking. can be tested to see if the chosen metal will be fit for purpose by fixing a piece of metal to a point and then loading it with a pulling force.
Compression can be tested by applying a force on top of the piece of metal. If the metal compresses, then To strengthen a material that could weaken when a force is applied. the metal could be an option.
Often the shape of the metal plays a big part in how it will react to a force. A ‘rolled steel joist’ (RSJ) is used in construction work as the shape withstands bending and compression.
Shear forces act in different directions and cut across a material, but a huge amount of force is needed to shear through a piece of metal. If a piece of metal is cut using A tool for cutting metal by providing a shear force., the cut will have been made by a shear force.
Electrical conductivity can be tested by making a simple circuit and passing a current through it. If the circuit is complete, then the current will pass through the material - in the example below passing through the paperclip, causing the bulb to light up.
Magnetic materials can be tested through the use of a magnet. If the material is attracted to the magnet, then the material will be classed as magnetic.
