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Materials - Objectives

Content

• Tensile stress and strain

• Elastic and plastic behaviour

Learning Outcomes

Candidates should be able to:

• define and use the equation density = mass/volume.
• appreciate that deformation is caused by a pair of forces and that, in one dimension, the deformation can be tensile or compressive.
• describe the behaviour of springs and wires in terms of load, extension, Hooke’s law and the spring constant.
• define and use the terms elastic limit, tensile stress, tensile strain and the Young modulus.
• describe an experiment to determine the Young modulus of a metal in the form of a wire.
• distinguish between elastic and plastic deformation of a material.
• describe plastic behaviour, fracture and brittle behaviour linked to force-extension graphs.
• understand the term breaking stress.
• deduce the strain energy in a deformed material from the area under the force/extension graph.
• demonstrate knowledge of the force-extension graphs for typical ductile, brittle and polymeric materials, including an understanding of ultimate tensile stress.
• intepret simple stress-strain graphs.
• apply conservation of energy to qualitative and quantitative examples involving elastic/strain energy and the energy to deform as well as kinetic energy and gravitational potential energy.
• appreciate energy conservation issues in the context of ethical transport design.
• REQUIRED PRACTICAL - determination of the Young Modulus of a material by a simple method.

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