Home Forums General Discussion Specifications J443 changes for intensity verification

Saturation curves for new set-ups are (usuallly) understood and practiced approproiately. Intensity verification has often been performed without regard for requirement that the strip be presented to blast stream for the T1 saturation curve time (often using machine settings for full coverage or cycle time). This is especially troublesome when multiple holders are on a fixture. Many times (almost all?) the strips are presented at the latest saturation time and then hope to get all holder arc heights to fall within the tolerance band. This is often futile, and doesn't comply with the J443 directive to expose each strip at it's own T1 time. Revisions being discussed for J443 would allow a target arc height approach whereby the arc heights of each holder at the latest T1 time are then recorded for verification runs. These verification arc heights must then be within ±0.015 inch of the target arc height and may (or may not) still fall within the tolerance band.

A modification of this approach would involve translating the tolerance band for each new target arc height thus preserving the intention of the original tolerance. This would be helpful for instance when the intensity is determined to be .0118 and is accepted for a tolerance band of .009-.012. If the target arc height then becomes, for example, .0130 ±0.015 then this holder position may be allowed to receive to high of an intensity if it was later verified to be .0145.

Intensity verification requires proof that the T1 arc height established at process setup is still within the required intensity range for subsequent parts. It requires running a new Almen strip at T1 time. For Almen fixtures with multiple Almen locations with different T1 times it should be allowed to select one of the T1 times to run all strips provided that for the different T1 time strips the positions of their T1 arc heights in the range are translated to the common T1 time on the saturation curve of each. Thus there will be a new "range" for each strip

We like the proposal for changing J443. Our studies in the past have concluded that it is practical to run to target arc heights for verification. Can I suggest that you meant to write ±.0015 (instead of ±.015) in your example?

On a side note we suggest dropping the word "Saturation" and moving forward with the term "Intensity Determination Curve. This is something we think helps clear any confusion with all the rookies who are tempted to think that intensity calculations tell you something about coverage. This new term also brings a very convenient easy to say & write acronym "IDC".

From Pete Bailey's reply, it is unclear to me on how a new "range" would be developed for each strip location of a multiple strip intensity verification. I agree with the proposed change of running intensity verification to a selected target arc height, with an allowed variation of +/-.0015. The target arc height is selected from each strips' saturation curve, at the time for the strip that took the longest time (longest T1 time) to saturate.

I see two basic problems with J443 verification.
The first is that the derived peening intensity time, T1, rarely corresponds to an integral number of passes/strokes/rotations. Target verification arc height at an integral number can easily be calculated using the equation derived for the saturation curve (assuming computer-based analysis of data sets is being used). A convenient integral number of passes is substituted into the equation and out pops the corresponding point on the saturation curve. This technique is available as a simple add-on to any of the Solver programs.
The second problem relates to multiple holders. Again, target verification arc heights can be generated by substituting into the corresponding equations for each holder. It seems logical to adopt a precise 'rule' governing choice of peening 'time'. Why not take the average of the several T1 times and round that up to the nearest integral number of passes? Conversely, it seems illogical to insist on a blanket +/-0.0015" variation. Some users may be happy with a larger variation and some may require a smaller variation - especially for critical components. The significance of +/-0.0015" also depends on the required intensity limits.

See additional discussion in my last post.