New Junker fastener testing reporting requirements can be used globally

Part 4 of 4 of Morten Schiff’s series on the new DIN 25201, written in 2012 for FastenerEurAsia and published here by Vibrationmaster.

No-one used to ask for the test reports on fasteners that had been vibration tested to determine their self-loosening behavior. They were simply never required. Vibrationmaster CEO Morten Schiff explains the new reporting requirements according to the DIN 25201, and how this new format can be used globally.

New consistent Junker Test report requirements

A major departure from the requirements of the old DIN 65151 is the reporting procedures. Effectively, what the new DIN 25201 demands is much greater rigor when recording test results. However, despite the extra effort, the benefits of this new approach are considerable. The new test report requirements will not only provide customers with data about the products they are buying, but will also allow researchers and test engineers to exchange data globally about locking device performance with much greater confidence.

From the outset, detail is a key factor. The report must first describe which test fittings were used in detail, and include the number used, their dimensions, material and surface designations and quality categories. The type of locking mechanism and its fitting position must also be described. Next, the DIN asks the test technician to record the:

• Test frequency
• Clamp-length ratio
• Pre-stressing force
• Effective transverse displacement
• Lubrication used.

The following report specification could be challenging for many, as it asks how the test equipment has been constructed. This could be problematic for some manufacturers, researchers and test-houses that use non-standard test rigs, as it is likely to cast doubt on the validity of the test results. But if a Junker Test Bench from a test equipment manufacturer has been used, then the specification manual that comes with the equipment can be used to detail how it has been constructed.

Time series data reporting can now be automated

Clearly, one of the most important parts of the final test report is the plot of the pre-stressing force against the number of load cycles, as this data demonstrates the effectiveness of the fastener locking mechanism. There are now Junker Test Benches available that can automate this element of the reporting process. The benches can even provide the data in a time series, together with a graph in real-time during testing, and then output the results into standard file formats. That makes it particularly easy to import the information into users’ and clients’ preferred analysis software.

Equally important is the final part of the report. This should detail the exact conditions under which the fastener’s securing element can be used and, if the test determined this, the level of pre-stressing force at which the fastener can be expected to fail. Details such as lubrication, surface coatings and the range of diameters are also requested. The new reporting requirements of DIN 25201 mean that some models of Junker Test Benches, and many bespoke test rigs, will simply be unable to provide the level of detail required, nor in a format that can be easily converted into a report format.

The new DIN 25201 is an important step forward for the fastener industry

There is no doubt that DIN 25201 represents a significant advance for the fastener industry. It will ultimately lead to higher quality specifications and higher quality fastener securing devices and products. Engineers will have greater confidence when specifying fasteners that have been tested to, and shown to comply with, the new standard. And research and development teams will have greater confidence when exchanging data about the performance of specific locking mechanisms.

There will also be a requirement for some manufacturers to rapidly update their product testing and compliance to ensure that all of their products qualify under DIN 25201. Not to do so will lead to their products simply being removed from specification sheets. Fortunately, there is now a new generation of affordable, yet advanced high specification Junker Test Benches and demonstrators available. These can help make this process smooth and swift, ensuring the safety and quality of fasteners and locking mechanisms meets the most demanding standards of the new DIN 25201.

References

• DIN 65151: 2002-08 Dynamic testing of the locking characteristics of fasteners under transverse loading conditions (vibration test), Deutsches Institut für Normung e.V., Berlin 2002
• DIN 25201-4: 2010-03 Annex B Test specification for demonstrating the resistance to self-loosening of secured bolted joints, Deutsches Institut für Normung e.V., Berlin 2010