Developed and predominantly used in the United States QQI Shims, or to give them their official name, AS5371 Notched Shim Indicators have been introduced in to the European market initially by Rolls Royce. These are also now used by other aerospace primes and when working to ASTM E 1444 for Magnetic Particle Inspection.
These notched shims are not necessarily an alternative to the conventional Type 2 laminated strip as they have been designed for use with multi-directional magnetisation in mind. The type 2 strip is more robust, quicker and easier to use and more cost effective however, if you are looking to verify a magnetic particle inspection technique and have a customer requirement then AS5371 Notched Shim Indicators need to be used.
We supply the following types of shim:
|AS 5371 Reference
|0.002" (flaw depths at 20%, 30” and 40% of thickness)
|0.004" (flaw depths at 20%, 30” and 40% of thickness)
When in use it is very important that the shims are in good condition with minimal bends or kinks. It is very easy to distort these shims increasing the artificial flaw depth so take care.
If you are trying to verify a predominantly flat surface then CX-430 or CX4-430 is for you. These are a thicker material so are more robust.
If you have a curved radius to fit a shim to then CX-230 or CX4-230 will be required. These shims are a thinner gauge so are easier to damage but will conform to a curved surface easily.
The 3C2 series consist of concentric rings at different flaw depths. These can be used for multidirectional techniques or when a more quantified level of magnetisation is needed.
When using single direction magnetisation and one leg of the cross is aligned with the direction of magnetisation, the CX series of shims are designed to show the axial part of the cross 90⁰ to the direction of magnetisation and two arcs of the circle at nominally 30 'gauss'.