Year 1 Design for Industry. Introduction to Engineering John Errington. What structures are made of How they are put together How they work together What makes them active. Engineering materials Construction Mechanics Power sources - Electricity. Topic overview.
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Introduction to Engineering
We think we know what these words mean – but in engineering a new design we need to choose between materials based on their properties. This means we must compare one with another, and to do this we need to have standards by which the hardness, toughness, strength etc can be measured. We start by establishing precise definitions of each term.Common vocabulary
Hardness is the property of a material that allows it to resist plastic deformation, indentation or scratching.
Geologists use the mohs hardness scale to help identify unknown minerals.
Hardness (H) is the resistance offered by a mineral to scratching, as determined by comparison with other minerals of known hardness. A series of ten common minerals ranked in order of increasing hardness comprises the Mohs scale of hardness (listed below). The normal testing procedure is to use samples of these minerals to try to scratch the unknown mineral, cross - checking by trying to scratch them with the unknown.
Finger nails (H = 2 or higher depending on diet), copper pennies (H = 3),plate glass (H = 5.5), and a steel knife or file (H = 6.5) can also be used for comparison, although the hardnesses of these items are variable.
The mohs hardness scale is of little use in engineering as it tells us steel is harder than copper – but not how much harder. We need a more precise way of measuring hardness.
* As measured by Rosiwal cutting resistance test
We will return to examine different engineering materials, their properties and the way they are measured later in the course.