Two figures in, a clear answer out. The shear strain calculator uses angle of twist (φ), displacement due to stress (x), distance from shaft axis (ρ), shaft length (l), shaft radius (c), shear modulus (g), shear stress, transverse dimension (h) and one way to produce maximum shear strain (γmax), shear strain at ρ (γ) and shear strain (x/h), applying the standard relationship for this problem in the order the calculation actually needs it.
What Is the Shear Strain Calculator?
This shear strain calculator is for the kind of problem where you know the physical quantities but not the number you need. It turns angle of twist (φ), displacement due to stress (x), distance from shaft axis (ρ), shaft length (l), shaft radius (c), shear modulus (g), shear stress, transverse dimension (h) and one way into maximum shear strain (γmax), shear strain at ρ (γ) and shear strain (x/h).
Physics calculations go wrong in predictable ways, usually through mixing units or dropping a digit. Work through the result one step at a time and check that the figures are the size you would expect at each stage.
How the Shear Strain Physics Works
The relationship is applied step by step, and each step is a standard piece of physics rather than a single opaque formula. That means you can check the intermediate values against what the theory predicts, which is usually faster than checking only the final answer.
Keep every value in the same unit system throughout the calculation. Mixing metres and feet part way through is the single most common reason a correct formula gives a wrong answer.
Units, Assumptions and the Limits of the Model
The calculation assumes ideal conditions: no air resistance, no heat loss, and dimensions that do not change while you work. Those assumptions are reasonable for most classroom and engineering estimates, and unreasonable for anything more precise.
Where a value is a rate, it has to be quoted for the same period as everything else. A per-hour figure cannot be combined with a per-day figure without converting one of them first.
A Worked Example
Working through an example, with angle of twist (φ) set to 10, displacement due to stress (x) set to 5, distance from shaft axis (ρ) set to 2, the calculator returns shear strain (x/h) of 0.05, and shear strain (γ) of 0.4, and shear strain at ρ (γ) of 0.2. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out maximum shear strain (γmax)?
Enter angle of twist (φ), displacement due to stress (x), distance from shaft axis (ρ), shaft length (l), shaft radius (c), shear modulus (g), shear stress, transverse dimension (h) and one way. The calculator then works through the relationship and reports maximum shear strain (γmax), shear strain at ρ (γ) and shear strain (x/h).
What does the shear strain actually calculate?
It takes angle of twist (φ), displacement due to stress (x), distance from shaft axis (ρ), shaft length (l), shaft radius (c), shear modulus (g), shear stress, transverse dimension (h) and one way and converts them into maximum shear strain (γmax), shear strain at ρ (γ) and shear strain (x/h) using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter angle of twist (φ)?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Can I use this for a quick estimate as well as a precise answer?
Yes. The calculator is built for quick checks, so round your inputs to a sensible number of significant figures and the result will be just as useful. If you need more precision, keep the same method and add digits to the inputs rather than adjusting the method itself.
Is the answer exact?
It is as exact as the formula and the inputs allow. The method itself is the standard one for this problem, so the only sources of error are the figures you enter and the precision you ask for.