Fatigue Test

Hi everyone, today i want to share about fatugue testing uses as my presentation in Manufacturing Process lecture in last yesterday.

First, fatigue is a  fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material. (Wikipedia). 

Mechanical failure contain 3 step,

  1. Crack Initiation
  2. Crack Propagation
  3. Final Crack

For what fatigue testing?

Fatigue testing is made for several reason, they are:

  1. To  predict material life time
  2. Design to keep stress below of fatigue limit
  3. Instruct the user to inspect the part periodically for crack and replace the part when a crack exceeds a critical length.

Many company using the fatigue test to know the limit of their product.

Example, Boeing using fatigue testing in their Boeing 787 in their factory. They testing to break the airplane for knowing the limit each part of the plane, from wing, tail, body, etc. They test it for 3 years 24/7. Also using “GAG” test mode, Ground-Air-Ground, that’s they test for a real life from terminal-taxy-take off-cruise-landing-taxy-terminal. They test it until 100.000 flight, or 3 times bigger from normal life time.

 

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