How this calculator works
A uniform bar that cannot change length develops stress when its temperature changes. Positive expansion coefficient with heating produces compression, reported as negative stress. Temperatures are converted to kelvin before subtraction, so Celsius and Fahrenheit inputs work consistently. The model assumes complete axial restraint, constant properties and elastic behaviour; a free bar expands without this stress.
Formula
sigma = -E alpha (Tf - Ti); free thermal strain = alpha (Tf - Ti).
Worked example
With E = 200 GPa, alpha = 12 x 10^-6/K and a 50 K rise, the fully restrained stress is -120 MPa. A 25 K cooling produces +60 MPa tension.
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Frequently asked questions
Why is heating stress negative?
The prevented expansion creates compression under the tension-positive convention.
Can I enter Fahrenheit?
Yes. Enter each temperature with its unit; the engine converts to absolute temperature before finding the difference.
What if restraint is partial?
The support stiffness and member stiffness must be included in a compatibility calculation. This page assumes zero axial extension.