Home Forums General Discussion Shot Peening Process, Intensity, Coverage Intensity Verification Locations

Pandora’s box?

Standard callout on an engineering drawing:
Shot Peen all over to an Intensity of 8-12A with 200% coverage using ASH-230 shot.

Typically the engineering drawing fails to call out the locations for intensity verification. However, since the drawing states 8-12A all over it appears to me that the organization performing the peening is putting itself in potentially dangerous position. What if at some point down the road someone questions the intensity in an area where it was not previously measured? What happens when it’s not within the specified range? What if the part failed at location where the intensity was not within the specified range and there was a loss of life, who’s to blame, the Shot Peen process house or the OEM?

Most often it’s up to the shot peener to determine the locations intensity will be verified. At times these locations are agreed to by the customer but not all. Even when they are it’s been my experience that rarely are these locations approved by someone with design authority. Typically it’s done by a process engineer if that. I think there is potential for a major disconnect between what the design engineer envisioned and reality. For several years I have brought this up at SAE AMEC meetings, to date not much has been done.

It makes me wonder why we are forced to so tightly control our process when the locations of measurement are not defined on the drawing.
Nor is there is any guidance whatsoever as to how accurately the intensity verification fixture needs to be made.

It’s time to address this White Elephant.

Please comment....

I feel your pain. When an inspector asks you to locate an Almen holder in a "new" area can you suggest that you need permission from the customer prior to any "experiments"? I suppose the alternative is to reject job requests that do not have sufficient information for holder locations. Another possibility is to use a large number of holders and build that into the quote.

Unfortunately none of these options are things any of us can really do. Failure to do something a government inspector asks for would be the equivalent of failing to take a sobriety test when pulled over by the police. Rejecting the jobs that don’t specify the locations for intensity verification would put me out of business as would putting an obscene amount of test blocks on any given part.

At a minimum I would like to see AMS 2430 add the following:

Process Verification – Each part shall have the saturation point determined at specific locations as specified on the engineering drawing.
In the event the engineering drawing does not specify the locations the locations may be developed by the shot peen source. In some cases these locations may require cognizant engineering approval. It is highly recommended that the shot peen source obtain written authorization detailing the intensity verification locations even if it is not a requirement. The saturation point for each location shall be within the specified Intensity range on the engineering drawing. Intensity verification is not required outside of the locations as shown on the engineering drawing and or the shot peening schedule. All areas requiring shot peening shall also exhibit full coverage in accordance with the engineering drawing. Ref SAE J442, J443 and SAE J2277.