# How to Measure Residual Stress

Measurements – Imperial and Metric explanation

Imperial
Ksi means kilopound per square unit and is derived from psi(lbs/square inch).  Kilo, which is often used in the metric system basically means a thousand (1000).  It comes from the Greek word for 1000. Therefore, a kilopound is 1000 pounds.

Metric
A Megapascal (or MPa) is a variation on a pascal.   Mega in this case means 1,000,000 and again it means “great”.  As you may guess, when using MPa you are usually working with something heavy or with a high pressure!

Both ksi (kilopound per square inch) and megapascal (MPa) are units of pressure measurement – the former is an Imperial unit of measurement and the latter a metric unit.
Ksi values are commonly converted to MPa, as the metric system is the more widely used system of measurement.

# Measurement Of Compressive Residual Stress Using X-ray Diffraction

A sub-surface compressive residual stress profile is measured using x-ray diffraction measuring equipment.

The X-axis is the measurement of the depth in mm or inches the Y-axis is measure of residual stress in ksi or MPa.