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Finite vs. Infinite Life and Fatigue Failure for a Steel Object

Newbie

Finite vs. Infinite Life and Fatigue Failure for a Steel Object

By Mathcad Staff

This worksheet will: 

  • Calculate the fatigue failure, finite or infinite life, and the factor of safety for a rotating beam 
  • Apply to mechanical engineering 
  • Perform using fatigue failure, material properties, yield, ultimate strength, finite life, infinite life, alternating stress, the factor of safety, FS, etc.

This worksheet using PTC Mathcad provides an example of how to calculate for the fatigue failure of a rotating beam specimen made of ductile steel. Fatigue Failures are when machine parts fail due to repeated or fluctuating stresses, mainly because of the very large number of times it is subjected to the fluctuating stresses. Material properties for its yield and ultimate strengths are known and it is subjected to an alternative stress. This example determines if the part will have finite or infinite life. The worksheet first provides you with the parameters which include: 

  • The units MPa and cycles 
  • Alternating stress 
  • Material yield strength 
  • Material ultimate strength.

The worksheet then shows you how to find the value of the factor of safety, FS. When FS is equal to or greater than one, the part will endure at least a million cycles at the applied stress. The worksheet also shows you how you can estimate the number of finite cycles. This worksheet provides you with notation, instruction, all data, formulas, an example, and a solution to aid you in your own calculations.

Download and explore this worksheet yourself! You can download a free lifetime copy of PTC Mathcad Express and get 30 days of full functionality.