Tapered vs grinded springs ends

[tanak]

Can somebody tell me which ends (tapered or grinding) are better for compresson coil spring for rail industry? I know that standards dont deal whit it. But can it make differences in fatigue life, lateral characteristic of springs or so...?

 

[TVP]

Ground ends are always better for reducing side load, and allow higher fatigue strength/life. There are some very good spring references from SMI (

http://www/smihq.org)

or IST (

http://www.ist.org.uk/)

that discuss the technical aspects of springs.

 

[tanak]

I measured lateral rate of those two springs and compared them. Rate of springs with tapered ends was lower which quite suprised me.
So in my opinion lateral characteristic has more to do with design of end coil (I mean the gap between end of spring and active coil and of course the cross coil).

 

[israelkk]

What to you mean by tapered ends? It usually has four those four types of end:

1. Squared and ground
2. Plain ends
3. Squared or closed ends
4. Plain ends ground

http://www.webspawner.com/users/israelkk/

http://www.efunda.com/DesignStandards/springs/spring_design.cfm

 

[TVP]

Thanks for the clarification israelkk. I was assuming that the ends were closed, which was not necessarily a good assumption, especially if these springs use large diameter wire (say greater than 12 mm) and are hot wound.

 

[tanak]

Wire diameter is bigger then 12 and hot wound. The ends are closed. But made by different technology. Grinding or tapering. And they are also shot peened both.
In my opinion there could be just bigger decarburization in case of tapered ends cause of one more heating. And then lower fatigue life...

 

[israelkk]

I do not think that decarburization should be allowed at all or at least should be minimized. The heat treatment can be conducted in a protective environment such as an Argon gas or a carbon enriched envirnment to avoid decarburization.

http://www.webspawner.com/users/israelkk/