APPLICATION TECHNOLOGY
Railway operators require secure bolted joints which are crucial for safety in operation and additionally to minimise time consuming inspections
“ Reliability of bolted joints with locking elements for railway vehicle applications” - About the DIN 25201-4 norm
especially under dynamic loads. The securing characteristics of bolted joints are crucial for the safety in operation of railway vehicles. Additionally, regular inspections of bolted joints are not practicable because the operators require a high availability of the railway vehicles. Underfloor inspections are especially time consuming since sufficient visual checks can only be done in depots at inspection pits. During summer 2001 the Suisse Federal Railways (SBB)
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had to withdraw temporarily their entire fleet of tilting intercity railcars (ICN) from operation due to loose or even lost bolts. This incident, and the fact that many commonly used bolt-securing elements emerged to be ineffective, prompted actions to ensure safe railway operations. A comprehensive research, financed by the railway industry, was performed. The aim was to investigate systematically the parameters that influence the loosening of bolts, and to develop a detailed norm procedure in order to evaluate the performance of securing elements. The initiators of this research were Alstom LHB Salzgitter,
Bombardier Transportation Henningsdorf, Siemens Transportation Systems Krefeld, Deutsche Bahn Systemtechnik and three OEMs of securing elements including Nord-Lock GmbH, who were preselected by the above-mentioned companies. The washers of Nord-Lock were the only securing element based on wedge-locking function included in the test.
he modern lightweight construction of railway vehicles results in shorter clamp lengths of bolted joints. However, for the joint integrity a shorter clamp length increases enormously the risk of self-loosening,
The analyses have been done by ‘IMA Materialforschung &
Anwendungstechnik GmbH’ in Dresden and by the Institute for product development and design engineering of the University of Applied Science in Cologne. The influence of these parameters on the self-loosening of a bolted joint was systemically investigated through specific parameter studies, which were determined by means of test rigs. The research
results have been reviewed regarding their relevance for the joining technology and their implementation into the DIN 25201-4. The overall assessment result states that based on this quantitative test result, the securing characteristics of the tested Nord-Lock cam washers are proven to be fully effective. The official
release of the DIN 25201-4 by the DIN Norm Committee is imminent.
126 Fastener + Fixing Magazine • Issue 72 November 2011
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