# What is the definite definition of strength?

I have access to definite definition to terminology like stress(Pa), strain(dimensionless), ultimate strength(Pa), yield strength(Pa), etc. But I often get confused when someone just write "strength".

I give an example. Consider the following sentence:

"Titanium has high strength and high stiffness."

What is the strength referring here? Is it a measurable variable, or a qualitative description? If it is measurable, what is its unit, and in a typical stress-strain graph of a ductile material, where is this variable located?

Mapes
Homework Helper
Gold Member
You're not alone in being confused. The word "strength" alone is ambiguous; it could refer to the yield strength in uniaxial tension, the ultimate strength in uniaxial tension, the shear strength, the fatigue strength, etc.

As an everyday (non-precise) term, it probably corresponds to the highest point on the engineering stress-strain diagram (not marked on yours), also known as the "ultimate strength," the point where a metal will begin to neck.

stewartcs
I have access to definite definition to terminology like stress(Pa), strain(dimensionless), ultimate strength(Pa), yield strength(Pa), etc. But I often get confused when someone just write "strength".

I give an example. Consider the following sentence:

"Titanium has high strength and high stiffness."

What is the strength referring here? Is it a measurable variable, or a qualitative description? If it is measurable, what is its unit, and in a typical stress-strain graph of a ductile material, where is this variable located?

Used in that context the word strength generally means the material strength. So if you were to compare Titanium to Steel, you would see a higher overall strength (both yield and ultimate) for Titanium.

But like Mapes said...it's important to clearly define what one is referring to by using a qualifier like yield or ultimate...

CS

Mech_Engineer