Spring failure analysis

[Fred]

We have problems to understand some spring fracture facies. It works under compression, with probably some times flexion stress.
We are interested in web sites which show fracture facies linked with explications, like initiating, propagation and final break

 

[israelkk]

What kind of spring are you refering too? Helical comtression spring? Helical extension spring? Did you calculate the stresses in the spring? is it for cyclic or static use? What is the spring dimensions, loade etc.?

 

[Fred]

Helical compression spring
I didn't calculate the stresses
It is for cylcic use

Dimensions : wire Ø = 4.5 mm / spring Ø ext = 22.5 mm
Total length in free condition = 46.8 mm
Total length in contiguous spir = 32.35 mm
Spir number = 6.69

Frequency utilisation = 20 Hz

Material : oil quenched wire for dynamic application with shot peening

 

[swall]

Where is the failure location? Under conditions of overstress/underdesign, a compression spring fatigue failure should initiate on the spring I.D. If the origin is elsewhere, look for a configuration issue or material flaw.

 

[Rich2001]

Here is a site with useful FRACTOGRAPHIC information.

http://www.tech.plym.ac.uk/sme/Inte...alysis/Fractography/Fractography_Resource.htm

Vita sine litteris mors est.

 

[Carburize]

There is also a section specific to springs in ASM Handbook Vol 10 "Failure Analysis and Prevention"

 

[israelkk]

Fred

What do you mean by Total length in contiguous spir = 32.35 mm? and by Spir number = 6.69?

Is "spir" means coil? When you say Spir number = 6.69 do you mean number of actice coils or total number of coils?
Is the spring squared and ground?
How much the spring deflects in each cycle and what are the initial and final spring length in each cycle (or initial and final loads)?

What type of oil quenched wire? can you give the AISI number or equivalent?