ENGINEERING – MECHANICAL ENGINEERING CALCULATOR
Fatigue Safety Factor
A precise tool.
What is the Fatigue Safety Factor & How does it work?
Fatigue failure is a progressive, localized damage that occurs when a material is subjected to cyclic loading. Even when the applied stresses are below the materialβs static yield strength, repeated loading can initiate cracks that grow with each cycle, eventually leading to catastrophic failure.
The Goodman diagram is a widely used graphical method to assess the combined effect of mean (Ο_m) and alternating (Ο_a) stresses on fatigue life. It assumes a linear interaction between these stresses and the materialβs ultimate tensile strength (S_{ut}) and endurance limit (S_e), providing a conservative estimate of safe operating conditions.
Using the Goodman relation, the fatigue safety factor (n) can be calculated as the reciprocal of the sum of the stress ratios. A higher n indicates a larger margin against fatigue failure.
n = \frac{1}{\frac{\sigma_a}{S_e} + \frac{\sigma_m}{S_{ut}}}
n = safety factor
\sigma_a = alternating stress
\sigma_m = mean stress
S_e = endurance limit
S_{ut} = ultimate tensile strength
\sigma_a = alternating stress
\sigma_m = mean stress
S_e = endurance limit
S_{ut} = ultimate tensile strength
Parameters
Result
β
Frequently Asked Questions
What is fatigue failure?
Fatigue failure is a type of damage that occurs when a material is subjected to repeated cycles of stress, even if the individual stresses are below its static yield strength.
How does the Goodman diagram help in assessing fatigue life?
The Goodman diagram provides a graphical method to assess how mean and alternating stresses interact, helping engineers estimate the fatigue life of materials under cyclic loading.
What are the assumptions made by the Goodman diagram?
The Goodman diagram assumes linear interaction between mean (Ο_m) and alternating (Ο_a) stresses and that fatigue failure occurs when the combined stress reaches a critical value.
How do I interpret the results from the Fatigue Safety Factor calculator?
The result indicates how safe the material is under cyclic loading conditions. A factor greater than 1 suggests safety, while a factor less than 1 indicates potential fatigue failure risks.
Can this calculator be used for any type of material?
This calculator can be adapted for various materials by inputting appropriate material properties such as yield strength and ultimate tensile strength.
What is the difference between mean stress and alternating stress?
Mean stress is the average stress over a cycle, while alternating stress is the deviation from the mean stress that varies cyclically.
How does cyclic loading affect material fatigue life?
Cyclic loading can significantly reduce the fatigue life of materials by causing progressive damage and crack initiation under repeated cycles of stress.
Results are for informational purposes only and do not constitute professional advice.