Does the fatigue constants which are typically used in fatigue life prediction models, such as fatigue strength coefficient and fatigue ductility coefficient, remain the same for different environment temperatures?
No,fatigue constants does not remain constant in different environment temperatures
No its different as for different environment number cycles to failure corresponding to its max stress is different .
The fatigue constants does not remain constant in different environment temperatures.Because Fatigue decreases with increase in temperature.At low temperatures, the fatigue is brittle fracture and At high temperatures, the fatigue combines with creep process.
No, the fatigue constants very much depend on environmental temperature.
At low temperatures all metals and their alloys exhibit brittle behavior and hence the fatigue life will reduce. Accordingly the fatigue constants get modified.
At moderate temperatures metals and their alloys exhibit ductile behavior and hence the fatigue life will increase. Accordingly the fatigue constants also get altered.
At higher tempers the material becomes creep sensitive and will continuously yield even at normal stress/load conditions and functionally get degraded.
At very high temperatures the material strength may drastically reduce and may not be not be able to hold the normal operating load.
NO, The material - as the most simple self-organised system gives always an "answer" for the external parameters. If the external conditions are changing the response are also changes. BUT, if the MECHANISMS are the same, than a correlation has to be observed between the parameters characterise the response.
Thanks K S Shivakumar Aradhya and Toth Laszlo .
I understand that it changes with environment temperature, as it changes the Microstrcuture. To be more specific I need to understand if they change noticeably for CS 1018 at a temperature round 135 C or lower than that. in other words, does it have to be in the order of 600 C for a steel to start seeing changes, or it can happen at an elevated temperature of around 135 C.
I did not understand well your question. In changing the "material response - i.e. constants" could be reflected both the changing the MICRO STRUCTURE (i.e. the MECHANISM of the DAMAGE) or simply the "rate, speed of the MECHANISM (example: using our legs we are able to walking,, running, etc - "mechanisms" are the same, but the rate are different) . Best regards
Hello Mr.Arash , no it is not possible .fatigue constant depends on the temperature.
Fatigue life and crack extension are temperature, load rate and magnitude-dependent to mention a few. Given different environments (loading conditions) I would construct cycle "blocks" for each one to evaluate inspection intervals. And move forward with standard fatigue and damage tolerance procedures. Much as the case for aircraft that commonly experience various conditions during operation. Regards.
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