Home Forums General Discussion Ask Dr. Peener effect of presetting

hello, i want to know the difference of presetting effect before and after shotpeening

Please give more details of your problem.

i have a leaf spring that is shot peened with an applicated strain of 1600MPa, while peening, i want to know, wich is better, before or after?
by the way i want to ask you, if there is a standard to make a double peening?
thank you

The only standard on double peeing is do the home work. Determine the depth of compression you desire, experiment with shot type/size/velocity, analyze your results, continue practicing until you get it right. There is no cookbook method in shot peening.

Cold bending of a flat steel bar induces a classic residual stress pattern - Z-shaped across the section with compressive residual stress on the convex face and tensile residual stress on the concave face. Shot peening of both faces AFTER bending introduces compressive residual stress on BOTH concave and convex surfaces. It would be wrong to cold bend AFTER peening. That would destroy the surface compressive residual stress.

great thanks SOCRATE
i have an other problem, i want to make the test for the shape control, we are working with the S330 , for the AMS 13165, it says that in a half square inch (0,5x0,5) it's allowable to find only 16 deformed shot in this square, but the problem is that there is no standard how to make this test?
can you help me plz ?
i dont know how to make this test .... i tried to make this with a sheet of paper where i cut a half square inch, but i dont know if it's right or not ????

I also do not know of a standard for making this test. Much depends on the equipment that you have available.
As a background, consider the following: there are about 15 0.033" spheres in a half-inch row. In a square half by half an inch there will therefore be about 15 x 15 spheres as a monolayer. Hence there would be some 225 spheres in the sample area. A layer of real S330 particles would contain rather more particles - say 250. Each S330 particle weighs about 4mg so that the mass of 250 particles is about 1g.
Against that background my own method is to glue a 5 mm length of 1" by 1" square steel tube onto a glass microscope slide. 4g of S330 shot (weighed using scales accurate to 0.1g) is poured into the one square inch 'corral' which is then placed on a 'light box' (to give a transmitted light image). The shot sample is then photographed using a digital camera and the image is then transferred to a computer screen. A computer-drawn square of half the edge of the steel tube section is then superimposed on the center of the digital camera's image to become the sample's test area. The number of deformed shot particles is then counted within this half inch by half inch area. Note that the actual mass of shot used has to be adjusted (up or down) to ensure that a monolayer is present in the 'corral'.
The technique described can easily be modified to suit available facilities. The 'corral' does not even need to be square - it only needs to be large enough to contain a sample area of half inch by half inch. Hence, for example, a section of 25mm diameter round tube could be used.

thank you very much for your answer!!!!! it's really genius !!!!! i will try it to day and i will tell about the result.

I'll throw my 2 cents in here...

A simple way we see media inspection done is by cutting the required square in an index card (rigid paper) and then cover the square hole with shipping tape like a window. The card can be put into the media and patted down onto the card. Remove and gently shake loose media off the card to leave one layer of media in the window.

The card can be placed under a magnification device for inspection. When done, put a piece of shipping tape on the other side of the window to trap the media for archiving purposes.

You can also use a digital microscope to capture the image for record keeping.