This page contains a Flash digital edition of a book.
MANUFACTURING TECHNOLOGY


DIN 25201 - Important new standard for testing fasteners


By Morten Schiff, Vibrationmaster ApS


Not re-testing fastener stock to DIN 25201 could cause product ranges to become obsolete. The following explains the important differences between DIN 25201 and its predecessor, DIN 65151, when conducting Junker Testing of fasteners for self-loosening behaviour.


A


new age of fastener testing was heralded in 1969 when Gerhard Junker published his classic paper, ‘New criteria for self-


loosening of fasteners under vibration’, in the Transactions of the Society of Automotive Engineers. The Junker Test, as it became known and was later prescribed by the original DIN 65151, tested the self-loosening behaviour of fasteners under transverse loading conditions by vibration testing. It has been a byword of trust, safety and security in the fastener industry. But now that has all changed with the


publication in 2010 of the new DIN 25201. Certainly the new DIN standard builds on the original DIN 65151 defined by Junker, but it also takes things much further in setting out exactly how to conduct vibration testing of fasteners. For the first time, the new DIN allows researchers, test engineers and clients worldwide to conduct fastener vibration tests that genuinely compare like with like. This also gives greater confidence


to engineers specifying components, because the testing standards of critical fasteners are so much tougher than under DIN 65151. But there are still manufacturers and customers in the fastener industry unaware that the old standard, DIN 65151, has been superseded, and that a much tougher new test regime is in place. They are in danger of losing competitive advantage, and their products could simply drop out of the market. That’s because, unless a re-testing programme is initiated, many fastener products lacking test certification to DIN 25201 will begin to disappear from engineers’ specifications.


Demanding new test requirements While the original DIN 65151 only


specified that vibration testing must be conducted using a Junker Test Bench, the new DIN 25201 sets out exactly how the


testing must be completed. It introduces new mandatory requirements to conduct reference and verification tests that compare the self-loosening behaviour of bolted joints, requires the use of a washer during testing and sets out strict test reporting procedures. Vibration testing must be completed


using a test block that, when the schematic provided of the test equipment to be used is examined, is to all intents and purposes a Junker Test Bench. A considerable advance on the old DIN test conditions is that the new test must match the likely application and operating conditions of the fastener as closely as possible. The first stage of the test is called the


‘reference test’. The aim is to discover the effective displacement at which the bolt starts to self-loosen, so that the performance of the securing element, or locking mechanism, can be effectively tested. The rest of the testing programme will depend on this initial stage.


A washer meeting specific DIN standards must be included The new DIN spells out in detail that


the test fittings should include the bolt and nut in standardised dimensions, and a washer, which is another new feature. The washer is now included to play the part of the surface that would normally support the fastener when used in practice. All test subjects must be new, unused and not previously tested or stressed. They should conform to a manufacturer’s standard product specification so that the results can apply to a range of standard fastener products made of the same materials and to identical specification. The quality standards of the test fittings should be in quality categories A or B. Even the washer’s parameters are


detailed. The parameters must be compliant with DIN EN ISO 7093-1, the surface of the washer must be ground,


124 Fastener + Fixing Magazine • Issue 71 September 2011


The new DIN 25201 at a glance


• Introduces a comparative assessment of the self-loosening characteristics of bolted joints.


• Introduces a reference test to determine at what effective displacement the unsecured bolted joint loses its preload.


• Introduces verification tests on a secured bolted joint, which confirms that the preload is not lost at the same effective displacement at which it was lost in the reference test.


• Details exact methodology of how the reference and verification tests must be conducted.


• Requires a surface washer compliant with DIN EN ISO 7093-1 for hardness/ roughness and DIN EN ISO 4759-3 for plane parallelism and flatness.


• Introduces strict reporting requirements.


• Specifies the test equipment to be used, such as a Junker Test Bench (as it was with DIN 65151).


• Demands that every bolt size must undergo testing —the results of testing one fastener size can no longer be applied to another.


• To learn more about the important differences between DIN 25201 and its predecessor, DIN 65151, when conducting Junker Testing of fasteners for self-loosening behaviour, contact the author or visit the Vibrationmaster website at: www.vibrationmaster.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172