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Materials scientists and mechanical engineers use specialized test equipment, like the tension test machine in the diagram above, for measuring a material's response to stress. The test equipment can apply a large amount of force. Both the magnitude and duration of the force can be measured with precision. The diagram also shows typical responses of ductile materials under tension.

As you might guess, this type of specialized test equipment is expensive. There are much cheaper methods that you can use to measure stress and strain for your science fair project. For example, see Strength in Numbers?

Why test materials?

Good questions to ask:

• How do we choose materials?
• How do we make sure that what we're making is good?
• How do we make sure it's safe once we've built it?
• How do we make sure it will last?

These are some of the many good reasons for carefully testing materials.

• Research. We need accurate measurements of properties of existing materials so that engineers can choose the right material for a given project. Materials scientists developing new materials need ways to measure progress.
• Quality control in manufacturing. Testing insures that the manufacturing process is working as expected. When materials fail quality-control testing, the cause of the defect(s) can be traced, and the problem in the manufacturing line can be fixed.
• As-fabricated characterization of buildings/devices. When engineers design a product, they have expectations of how their design will perform (based on models and prototypes, known properties of materials, and experience). By taking an actual product fresh from the assembly line and testing it, we can measure how the design holds up in the real world.
• Life cycle testing. Automated testing with repeated cycles of stress can yield information about how long materials can be expected to last under various envrionmental conditions.