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Crack and grinder burn masters

Artificial defects for your crack and grinder burn detection

Parts with defined defect areas of different intensity are needed for assessment of the ability of the eddy current method to detect defects in components and for later monitoring the sensitivity of testing in an industrial environment.

Artificial defects must be able to be defined and reproducibly produced for size, position and kind. In addition, they should preferably generate similar physical test effects like real damage. It is not necessary and it would certainly be in vain to try to produce artificial defects which simulate real damage in all its appearances. The thresholds for sorting the good and bad parts are still determined when testing real parts (validation of process). Parts with differing signals are taken and evaluated with reference methods. Intolerable conditions can be defined and sorting thresholds determined in accordance with the requirements to the component characteristics.

Artificial defects are used to setup the test equipment before testing real parts, especially the needed test sensitivity. Master parts (reference standard) should be run through the test process at certain intervals in order to guarantee that testing is carried out under constant, reproducible conditions. The latter presumes that the master part is not affected by any time-dependent changes which modifies the artificial defect.

Crack masters (EDM)

Notches and dimples with defined depth as per your requirement are inserted in your test parts by the erosion process for verification of the sensitivity of a crack detection. If your customer desires the master parts can be measured in an accredited laboratory and you will receive the parts together with the certificate. Master parts which are regularly tested are naturally subject to high wear. We offer a chromium-plating of the master parts as option which increases the lifetime without affecting the eddy current result.

Grinder burn masters

Manufacturing grinder burn means big problems as it is practically impossible to create specific and reproducible grinder burn with defined size and depth of the area of influence during the grinding process.

An alternative is the production of artificial defects by means of laser burn. Laser burn enables production of defined grinder burn damage on the components. These defects have an analogous behaviour like real damages. They can widely be manufactured and reproduced at defined spots according to your requirements (kind and depth of structure change, special dimension). These defects are used as reference standards for the eddy current test and also for verification of a nital etching process. In line with a preliminary examination the appropriate process parameters for producing laser artificial defects on your components are determined. Afterwards, the determined grinder burn structure is produced with each one mark (dot, stroke, area) at two identical parts. Finally, the evaluation of the microstructure by a metallographic cut is done at one of both parts as control of success. The master part is additionally tested with regard to its eddy current signals before dispatched to you.

On request, an X-ray diffraction analysis for residual stress determination on the surface of the defect can be performed. We work closely together with partner laboratories for this sophisticated topic with whom we could up to now successfully solve each customer requirement. Please contact us – we are looking forward to your exciting projects.

By the way: chromium-plating for grinder burn masters is not possible as the eddy current signal for this kind of defect could be falsified. Lacquering would be a recommendation in order to avoid external impact like rust.