Goodman diagram for a component designed for Infinite life
Goodman diagram for a component designed for Infinite life
(OP)
Hello
I've done frequency analysis for a component and the stress values are slightly greater than allowaable stress limit.
Is it possible/necessary to check whether the stress values are fitting in goodman diagram.
My component should have infinite life.
Is there any difference between "goodman diagram" and "goodman modified diagram"
I've done frequency analysis for a component and the stress values are slightly greater than allowaable stress limit.
Is it possible/necessary to check whether the stress values are fitting in goodman diagram.
My component should have infinite life.
Is there any difference between "goodman diagram" and "goodman modified diagram"





RE: Goodman diagram for a component designed for Infinite life
have you tried to google for "goodman diagram" ?
Quando Omni Flunkus Moritati
RE: Goodman diagram for a component designed for Infinite life
It is allowable yield stress.. Yes i have tried google. But i couldnt get an clear idea for where goodman diagram should be used.
RE: Goodman diagram for a component designed for Infinite life
i found this description for goodman diagrams ... http://www.engineeringarchives.com/les_machdes_mod....
what fatigue info do you know for your material ??
Quando Omni Flunkus Moritati
RE: Goodman diagram for a component designed for Infinite life
Also, if your stresses are higher than your yield stress and your plasticity is not localized, i.e. you have bulk section yielding with high plasticity, then neither strain life nor stress life fatigue analysis methodology with give you a conservative life prediction and the reasonable thing to do is to optimize your component design to reduce the stress in the structure.
RE: Goodman diagram for a component designed for Infinite life
What Factor of Safety are used in the allowable stress? Are you operating at a resonance?
Achieving infine life would usually require stresses below fatigue limit. If it is steel. For Alu, you would often no have a fatigue limit.
RE: Goodman diagram for a component designed for Infinite life
Thanks,
Regards.
RE: Goodman diagram for a component designed for Infinite life
Goodman is a very conservative approach. After accounting for work hardening, residual stresses, etc., compute the new mean and alternating stresses and plot that point on your Goodman diagram to see if your scenario is in the safe zone or not.
Doug
RE: Goodman diagram for a component designed for Infinite life
RE: Goodman diagram for a component designed for Infinite life
The generalization is correct but there are exceptions. Perhaps most notably, annealed stainless steels can be work hardened significantly. The endurance limit for annealed 304L is higher than the yield strength. ASM Handbook, Volume 19, Fatigue and Fracture cites Fty = 32 and Se = 40. The Handbook of Stainless Steels says 25 and 35 ksi. The first cycle to 40 ksi resets the yield strength, and can be done an "infinite" number of times.
Cyclically hardening materials can have an endurance strength (load / original area) that is higher than the yield strength (load / original area). The strength increases compared to the original condition (I'm not a metallurgist so I can't explain the mechanism) and the cross section is reduced. The %RA for annealed 304SS is about 80%. There's an excellent discussion of the topic in Fatigue and Durability of Structural Materials by Manson & Halford.
Doug
RE: Goodman diagram for a component designed for Infinite life
This annealed 304L steel is a very interesting metal, a true "out of line" case.