These notes summarise the entirety of the AQA Design and Technology AS/A Level textbook. They are easy to read and follow and contain all of the most important information in a clear and easy to read format.
Destructie testnn refers to a ranne of tests that ultimately results in the destructon of a test piece.
Hardness tests
Hardness is the ability of a imaterial to resist abrasiie wear, indentaton or deforimaton.
Brinell test- a hardened steel ball is forced into the imaterial’s surface by imeans of a suitable
load. The resultnn surface area of the indent is imeasured, and used to calculate a hardness
nuimber.
Vickers test- this uses a diaimond pyraimid to indent the imaterial. This is imeasured usinn a
imicroscope to niie the hardness ialue.
Rockwell test- this is imore appropriate for a quality control testnn of fnished products. It is
a relatiely rapid test, with the hardness ialue beinn indicated on an atached dial, thus
aioidinn the need to imeasure a simall indentaton.
Tensile testing
Tensile testnn iniolies putnn the imaterial under tension by stretchinn to proiide inforimaton
renardinn tensile strennth, elastcity and plastc propertes, such as ductlity and imalleability. A
standard test piece is held between two nrips. One of the nrips is fied while the other is atached to
a iertcal slide operated by an electric imotor. The test piece is then put under tension at a constant
rate untl it breaks or it stretches beyond the liimits of the imachine.
Impact tests
Iimpact tests indicate the tounhness of a imaterial and its resistance to imechanical shock. Tounhness
is ofen not reiealed by a tensile test.
Wear resistance
Wear resistance of a imaterial can be deterimined by rubbinn with an abrasiie. A standard test
iniolies weinhinn a disc of imaterial and rubbinn it anainst the imaterial a niien nuimber of times, at a
niien pressure, followed by re-weinhinn to niie a quantatie ialue of abrasiie wear.
Non-destructive testing
Surface crack detection
Sound and touch- these are imethods of testnn that can be applied to a iariety of products
and use basic quality control techniques.
Rinninn- A bell can’t rinn if its cracked, this imethod of testnn a product is used in both the
castnn and potery industries.
Liquid penetrant- the liquid penetrant is sprayed onto the surface of the product. Any eicess
is reimoied leaiinn only the penetrant in the cracks.
Magnetic testing
The coimponent is imannetsed by imakinn part of an electroimannetc circuit. Iron partcles are dusted
oier the area, which then hinhlinht where the imannetc lines of force are broken by defect.
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