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#481 03/18/04 08:33 PM
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Greetings,
We have a question of interpretation.we have a titanium bracket that the print calls for the part to be shot peen all over per ss 8766. no intensity is specified on the print. ss8766 rev 6 par 3.2.3 states when no intensity is given the values in table II apply. this table is based on part thickness and gives minimum intensity values based on thickness. Our bracket has a variable thickness from .200" - .820". what is the standard industry practice? shoot the part to the thinner material intensity requirements or the thicker? both call outs are within .004A of each other.
thank you,
Olin Anderson

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You would be expected to shot the entire part at one intensity and therefore to use the thinist dimension (lowest intensity), otherwise the higher intensity for the thicker dimension would distort the thin section.

[This message has been edited by jChampaigne (edited December 27, 2004).]

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If the two intensities are within the .004A range specified, isnt the distortion factor already figured in?

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I'm not sure I really understand your last question. Your spec should call out an intensity for material .200" thick and another (higher) intensity for material that is .820" thick. In order to protect the thinner material from distortion you must use the lower intensity. The fact that the higher intensity for the thicker section may be within .004A intensity doesn't affect your requirement to use the lower intensity.

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sorry for the confusion.The spec states that a thickness of .125.250 should be shot to a minimum intensity of .008A. Material greater than .250 the minimum intensity is .012A. the spec goes on to state that if a maximum intensity is not defined, that it should not exceed .004A above the minimum intensity. Since the part in question ranges between the two intensity requirements and those two intensities are within the stated .004A maximum spread, then can you not shoot to the .012A for the whole part? Should you? what happens to the thicker material if it is not shot to the higher "minimum" intensity? what about touch up after rework? If I had to blend in the .250 or above area should we shoot locally to the requirement of .012A?

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My company performs shot peening on hundreds of different parts for Sikorsky. The standard practice is to find the smallest material thickness then go to Table II of SS8766. In your case the minimum intensity would be .008A. However your maximum intensity may or may not be .012A. As stated in SS8766 section 3.2.3 the maximum intensity shall be below the threshold of erosion of the basis material and shall not cause undue warpage on the part.
If you'd like, e-mail me the part number you are trying to peen if we have a Sikorsky Approved technique I will share with you the intensity values we have established.

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