compression spring fatigue/life
compression spring fatigue/life
(OP)
OD: .296 in
fl: .630 in
sl: .380 in
k: 148 lbs/in
material: sst
The spring is being used in a "detent" mechanism.
It's usually preloaded at least .06" but can be adjusted to a total of .150" When the mechanism goes through the detent the spring also travels .085" of further deflection.
Total deflection can range from .145" to .235"
This is a low cyclic application, however I need a rather good estimate on how many cycles it can take. Can someone help me get the results for .145" to .235" deflection every .020"? Any help appreciated.
P.S. is there any programs that do these calculations? Many thanks.
fl: .630 in
sl: .380 in
k: 148 lbs/in
material: sst
The spring is being used in a "detent" mechanism.
It's usually preloaded at least .06" but can be adjusted to a total of .150" When the mechanism goes through the detent the spring also travels .085" of further deflection.
Total deflection can range from .145" to .235"
This is a low cyclic application, however I need a rather good estimate on how many cycles it can take. Can someone help me get the results for .145" to .235" deflection every .020"? Any help appreciated.
P.S. is there any programs that do these calculations? Many thanks.





RE: compression spring fatigue/life
RE: compression spring fatigue/life
thanks
RE: compression spring fatigue/life
RE: compression spring fatigue/life
RE: compression spring fatigue/life
RE: compression spring fatigue/life
RE: compression spring fatigue/life
I am not designing a spring or anything. It is a catalogue spring.
I attached a quick sketch, since im not at work anymore, not to scale, sizes are greatly exaggerated
free length is .630"
solid length is .380"
At the position you see in the sketch the spring is preloaded to a total length of .570" (.06 deflection) This length can be adjusted to a total length of .480" (.150 deflection). You can see object 1 moves horizontally, as it passes by the triangular extension of object 2, object 2 is pushed it up. This object pivots on the pin (3). Now the total length it can move vertically (at the spring location) is .085". So now the spring deflects another ~.085". So the least the spring could be deflected is .145 (.485 total spring length), and the most .235 (total spring length).
Now I would like to know how many times can object 1 pass horizontally through object 2 at the specified preload positions.
Hopefully this makes it clear, or am I missing something?.
Sorry for the bad explanations, English is my second language :)
RE: compression spring fatigue/life
The 0.235" is the total deflection of the spring not the total spring length. The spring length after 0.235 deflection is 0.63"-0.235" = 0.395".
According to my calculations this spring can not be used for cycling in any of the two modes, 0.06" to 0.145" (~8.8 lb to ~21.5 lb) and the 0.15" to 0.235" (~22 lb to ~34 lb) at those loads the stresses are too high for any guarantied number of cyclic operations.
RE: compression spring fatigue/life
yes I know its the deflection, I forgot to include the .395" in the paranthesis,
would peening have any "good" affect?
Isrelkk, do you have a good source for fatigue calculations?
thanks
RE: compression spring fatigue/life
RE: compression spring fatigue/life
You can download a free three day trial of the software at www.uts.us.com
Shot peening can commonly impart up to 50% of the UTS in surface compression stresses at a depth of about 0.003 to 0.005" - depending on application an increase of at least 50% in fatigue life is common. SS springs should be shotpeened with either SS shot or ceramic balls and passivation per ASTM A380 after peening is recommended.