Material Tests Flashcards
(14 cards)
Workshop tensile strength test
Tested by applying weights to a test piece and monitor how much the material bends. A ruler or vernier calliper can be used to measure the deflection.
Workshop hardness test
Hit a centre punch into a material and measure the size of the dent. Abrasive wear can be tested by running a file or some glass paper over the surface and compare the number and depth of scratches.
Workshop toughness test
The materials will be held in a vice and you would hit them with the same force. The most brittle materials will snap, and the tough materials will absorb the impact.
Weathering testing
Get pieces of the same size and shape and leave them outside for a period of time and then inspect the damage. Test pieces exposed to the elements can be tested for hardness and how the properties are affected by outdoor use. Can also be used to see the effects of UV on the material.
Workshop flexibility test
Tested by measuring how far a thin piece of the material can be bent before it snaps.
Industrial toughness tests
Charpy and izod tests
Industrial tensile strength test
A tensile strength testing machine clamps the test piece at both ends and pulls it apart until it breaks. A worm drive pulls the clamps apart, at a constant rate, so the distance travelled can be plot.
Industrial hardness tests
Janka’s hardness test measures the ability of the wood to resist scratches and dents. The test measures the force to plunged a 0.44” or 11.28m steel ball halfway into a piece of wood. Other hardness tests include the vickers, Brunel and Rockwell hardness tests.
Charpy and izod tests
Test pieces are prepared to a set size with a 2mm deep notch in the centre. The test piece is positioned carefully before a pendulum is dropped to strike the test piece. The distance the pendulum travels after breaking the test piece is a measure of the toughness of the material. The scale is on the top.
Charpy vs izod test
The starting point of the pendulum in the izod test is lower than the starting position of the Charpy test.
Charpy - test piece is horizontal and the notch is facing away from the hammer.
Izod - test piece is vertical and the notch faces the hammer
Non destructive tests
Can detect faults without damaging or causing any physical damages. They are used to find imperfections bellow the surface of the material.
Ultrasonic testing
Uses sound waves to detect defects. Sound waves are pulsed into the material and the intensity of the reflected waves is recorded. It is highly accurate, quick and portable.
X ray beams
X ray exams are passed through a material and project an image onto a film or screen. Dense materials are opaque and less dense materials are faint. Can detect damage and splitting in woods and provide information about the properties of a timber and how a tree has been affected by its surroundings.
Industry thermal conductivity test
The guarded hot plate test is used. The test sandwiches a material between two temperature controlled plates. One plate is kept hot, and the other is kept cold - the test measures the time taken for the test material to reach a constant temperature. This is one of the most trusted methods, but the test is time consuming, only suitable for solid materials and it cannot perform tests in extreme temperatures.
