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Compression ratio is the ratio between the volume in the cylinder, when the piston is in bottom dead centre, and the volume, when the piston is in the top dead centre. So: CR=Vbdc/Vtdc Then you have the swept area, the engine displacement, which is: SA=Vbdc-Vtdc Volumetric efficiency is the amount of air/fuel mixture that gets to the piston compared to the swept area - if the same volume of the mixture goes in, you have a 100 % efficiency. Usually it's a bit less, since you are creating a small vacuum when the piston is going down (with naturally aspirated engines) and that doesn't eve

Fatigue is an increase in stress due to crack propagation - which leads to eventual failure. creep is stress relaxation, the material deforms plastically under stress that is less than the yield strength