Electronics TSP-M, Instruction Manual

Page: 13 / 24

Electronics Inc. • (574) 256-5001 • www.electronics-inc.com 13
Appendix
Introduction to Correlation
Almen mini-strips must be compared to standard-size Almen strips to assure compliance with intensity
measurement practices. The comparisons are described in correlation trials where the standard Almen strip is used
to set the requested intensity and the mini-strip is presented to the same blast stream. It is important to document
the test results, especially the parameters and all test conditions. Testing multiple strips and the creation of a
histogram can help validate the process.
The Almen Strips and Correlation Holder
It is convenient to peen the standard-size Almen strip and the mini-strip at the same time using a correlation
holder. There are two methods of affixing the mini-strip to the correlation holder. In the first method, two screws
secure the ends of the mini-strip. For the second method, double-sided adhesive tape or a temporary glue
adhesive, such as rubber cement, secures the mini-strip to the holder. The second method is used only when it is
not possible to attach the mini-strip to the holder with two screws.
For both methods, the standard Almen strip must be affixed to the holder with four screws.
The first image below shows the method using two hold-down screws to secure the mini-strip to the EI Correlation
Holder for mini-strips (Electronics Inc. part number 970070). The strip is positioned next to two protruding back-
stops to help keep it aligned. In the second image, the mini-strip is attached to the holder with double-sided tape.
It is very important to use only one method.
The two hold-down screws will keep the strip firmly secured to the
holder during the blast cycle while the tape or glue may allow some lift-off or curvature. This curvature may
influence the mini strip response. As long as the technique is consistent, the results should be consistent. A
sufficient number of trials should be run to validate the procedure. The examples shown in the next section titled
“Examples of Correlation” use multiple trials and the data is shown in a statistical capability chart (histogram).
When in doubt, run more tests and analyze the data carefully.
Note: When using tape or glue to affix the mini-strip to the holder, make sure the tape and glue are completely
removed from the holder and strip before measuring the strip or reusing the holder.
Two screws holding a mini-strip in place
A mini-strip held in place with double-sided tape. This
method should be used only when the mini-strip
cannot be attached to the holder with screws.