Lesson Notes By Weeks and Term v4 - SHS 3
Properties of Materials
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Properties of Materials
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Subject: Manufacturing Engineering
Class: SHS 3
Term: 2nd Term
Week: 11
Grade code: 3.1.2.LI.2
Strand code: 1
Sub-strand code: 2
Content standard code: 3.1.2.CS.2
Indicator code: 3.1.2.LI.2
Theme: Manufacturing Materials and Technologies
Subtheme: Properties of Materials
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Welcome, future engineers! Have you ever wondered why a plastic chair left in the hot Ghanaian sun for many months starts to sag and deform, even when no one is sitting on it? Or why the metal leaf spring on a trotro can suddenly snap after years of driving on bumpy roads, even though it never seemed to bend too much at any one time? These are examples of material failure. As engineers and manufacturers, understanding *why* and *how* materials fail is one of the most important parts of our job. It allows us to design safe, reliable, and long-lasting products, from simple household items to large structures like the Adomi Bridge.
Before we discuss the specific types of failure, let's define material failure itself.
Material Failure: This is the inability of a material to perform its intended function. It occurs when a component or structure can no longer safely support the load it was designed to carry. This can happen through breaking, excessive deformation, or a loss of stiffness.
Now, let's explore the three specific modes of failure for today's lesson. A. Creep
Definition: Creep is the slow, progressive, and permanent deformation of a material under a constant stress over a long period, especially at high temperatures.