Home Forums General Discussion Shot Peening Process, Intensity, Coverage coverage of 80% or 100%??

hi!!

Some time ago I read an article which referred to the desire to achieve coverage of 80 % instead of 100 %.

A small open debate on this issue .

what you think about it?

thanks

I am aware of spring manufacturers in Japan using the Toyo Seiko coverage checker and performing 80% coverage (in about 20% of the time needed for full or 100% coverage). See this article by Dr. John Cammett
http://www.shotpeener.com/library/pdf/2002038.pdf

Hi!!

The first, Thanks for your quickly reply, Jack.

first of all say that I am passionate peening operator and do not intend to put in between said John Cammet . God forbid!! hahahaha

but if we see the graph of the mechanical effect of the shot peening . There is a point where what is produced is a balance of tensions. I understand that if there is not shotpeened areas .

Does this not cause the balance toward one of the two tensions is decanted and facilitate the cracks ?


Thanks

I'm not clear about your question. Can you send me an example stress profile?

Sorry , my English is very bad. Maybe that's why you can not understand.

According to Newton 's third law, when I peened at each point, a balance of tensions ( action-reaction ) occurs. Right?

My question is. If I leave areas without peening, when that piece is working ( subjected to external forces).
Will this help the generation and propagation of cracks for not being all surface shotpeened?

Thanks

The areas that you leave without peening may have either compressive or tensile stresses (residual) from earlier processing (cutting, grinding, turning etc). If those stresses are tensile then you could expect fatigue failures with applied tensile stress. If those residual stresses are compressive you would expect longer fatigue life, depending upon stress levels (applied versus the residual).
The above is considering large areas, not the small areas in a 80% peening application. In this case the dents are evenly distributed and only very small areas are left "original". These untreated areas are typically smaller then the peening dents. However, since the affected zone for peening, below the surface, is generally three times the area seen on the surface, there is no problem. The sub-surface peened zone will offer complete protection underneath the dents seen on the surface that appear to have gaps from dent to dent.