Unit 305 Session 5 PT4 (solid materials)

​Principal properties of solid materials

​Solid materials are made up of many molecules.

How these molecules are arranged and how they behave under certain conditions will determine their properties.

● strength – tensile, compressive and shear
● ductility
● malleability
● hardness
● conductivity – heat and electricity.

​​These properties are:

Open Ended

What do you think Tensile strength means?

​Tensile strength

Is a measure of how well or badly it reacts to being pulled or stretched until it breaks.

Some materials, such as plastics, will stretch or elongate before breaking; others, such as metals, will also deform in a similar way but not by as much, and hard materials such as concrete and brick will not deform at all but will simply snap.

Poll

Which of these do you think would need high tensile strength?

• Steel cables holding a Lift in a buil

• A steel beam bridge

​Compressive strength

Open Ended

What do you think compressive strength means?

​Compressive strength is the maximum stress a material can sustain when being crushed.

Hard materials, such as concrete or cast iron, will shatter under compressive stress, while others, like plastics and some metals, may distort in shape.

Poll

Which of these do you think would need high compressive strength?

• Steel cables holding a Lift in a buil

• A steel beam bridge

​Shear strength

​Shear strength is the stress state caused by a pair of opposing forces acting along parallel lines of a material. for example, cutting paper with scissors or ripping a substance apart.

​Ductility of a material

​Ductility is a mechanical property that describes by how much solid materials can be pulled, pushed, stretched and deformed without breaking.

​Malleability of a material

Malleability can be defined as the property of a material, usually a metal, to be deformed by compressive strength without fracturing.
If a metal can be hammered, rolled or pressed into various shapes without cracking or breaking, it is said to be malleable.

Multiple Choice

What is compressive strength?

• The maximum stress a material can sustain when being stretched.

• The maximum stress a material can sustain when being crushed.

• The stress caused by sliding faces of the material relative to one another.

• The ability of a material to return to its original shape after deformation.

Multiple Choice

Which of the following materials is likely to shatter under compressive stress?

• Plastic

• Rubber

• Concrete

• Aluminium

Multiple Choice

What is shear strength?

• The stress state caused by a pair of opposing forces acting along parallel lines of action through the material.

• The maximum stress a material can sustain when being crushed.

• The ability of a material to be stretched without breaking.

• The stress caused by compressive forces.

Multiple Choice

Which of the following is an example of shear strength?

• Crushing a can

• Cutting paper with scissors

• Stretching a rubber band

• Compressing a spring

Multiple Choice

What does ductility describe?

• The ability of a material to shatter under stress.

• The ability of a material to be pulled, pushed, stretched, and deformed without breaking.

• The ability of a material to resist compressive forces.

• The ability of a material to conduct electricity.

Multiple Choice

Which material property is crucial for applications requiring materials to be stretched into wires?

• Compressive strength

• Shear strength

• Ductility

• Hardness