Another deflection photo from a barbell factory. This one is a Wonder Bar shaft (pre-finish) being deflected with 1000kg (~2200lb) of force.
Last week, we talked barbell strength measurement and quantification. This week we are talking about the actual ratings. There are two strength ratings for barbell shafts that matter: the tensile strength and the yield strength.
Tensile strength = ultimate strength
The tensile strength (rated in Pounds per Square Inch/PSI) means the amount of pressure that the steel can take without permanently deforming (aka a bar bending and staying bent after the weight has been removed).
Generally, the higher the PSI, the better. But, we have experimented with high PSI steels in our barbells and found unacceptable brittleness above 250k PSI.
Yield strength = when steel begins bending (but may still go back to true)
The yield strength (also measured in PSI) is the strength beyond which steel experiences "plastic deformation"- it bends, but will return to true (unless the tensile strength has also been breached.)
Tensile - yield = whip
When lifters talk about a "whippy" bar, we're talking about a bar with a decent gap between the tensile and the yield strength- this means the bar will bend under weight, but return to true after the lift.
If you've enjoyed this, buy one of our (tensile and yield strength rated) barbells maybe?