The figure shows a test specimen fixed between upper and lower grips. The knife edges of an extensometer contact the specimen at two points.

A more useful diagram than the load-deformation plot is one showing the relation between stress and strain, called the stress-strain diagram. The stress-strain diagram is more useful because it applies to the material in general, and the information obtained from the stress-strain diagram can be applied to all components, regardless of their dimensions.

The load and elongation data obtained in the tension test can be readily converted to stress and strain data.