fatigue life for metal bellows
fatigue life for metal bellows
(OP)
Hello everyone,
I 'am studying EJMA code for some time already and I need some help regarding the fatigue life calculation.
Can someone please tell me how to determine the ''material and manufacturing constants a,b and c''? from the formula in the link? you can also see it here. ''Nc=(c/St-b)^a''.
The think is that I found something about this ''a,b,c'' constants in EJMA 9th version, but is for high temperature conditions and in my case I have no high temperature and no pressure for my metal bellows application. Once I have the bellows I need to test them, therefore I need a testing plan and also some formulas to be able to find the constants ''a,b,c'' . Any help would be great.
thank you in advance
I 'am studying EJMA code for some time already and I need some help regarding the fatigue life calculation.
Can someone please tell me how to determine the ''material and manufacturing constants a,b and c''? from the formula in the link? you can also see it here. ''Nc=(c/St-b)^a''.
The think is that I found something about this ''a,b,c'' constants in EJMA 9th version, but is for high temperature conditions and in my case I have no high temperature and no pressure for my metal bellows application. Once I have the bellows I need to test them, therefore I need a testing plan and also some formulas to be able to find the constants ''a,b,c'' . Any help would be great.
thank you in advance





RE: fatigue life for metal bellows
You might consider supplying your design conditions to a manufacturer or two and see what cycle life they calculate. To further muddy things you may see "EJMA" cycles and "ASME" cycles.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: fatigue life for metal bellows
My application for witch I am using metal bellows is a company secret for he moment. But yet I wish that someone can explain me how to get data from a series of metal bellows testing's.
In EJMA they say something about a H (hold time between cycles) witch they use in formulas to determine the constants ''a, b and c''.But I am not sure what this ''H'' coefficient means. I was thinking maybe is about how fast a cycle extension-compression runs, when I am testing a metal bellows.
If is someone ho made fatigue calculations for metal bellows please advice me.