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New Junker test machine


April 2011


The Research & Development laboratory of Growermetal has been provided by a sophisticated test machine capable of simulating the behavior of fasteners under vibration and dynamic loads (Junker test machine).
The machine can perform the test according to DIN 65151 (testing of the Dynamic Characteristics of locking fasteners under transverse loading conditions – vibration test), with the regulation settings according to DIN 25201:2010 Part 4, Annex B (Design Their guide for railway vehicles and components – Bolted joints – Part 2: Design – Mechanical applications). The tested washer is combined with a screw and a nut, bolted to a determined axial clamping force and subjected to a transversal dynamic load with predefined amplitude and frequency oscillation.
Thanks to the software, the machine is able to record continuously the variations of many parameters, such as the residual clamping force, the angle of rotation of the screw, the strength of the transverse stress, the actual transverse movement and the number of cycles of oscillation that has been made.
The tests provide important information to the technical staff of Growermetal and enable continuous improvements of the performances of safety fastening systems in the presence of vibrations and the comparison of the unscrewing performances with different surface coatings. The new Junker test machine will allow Growermetal to provide its customers with advanced technical support in order to help them to always choose the most appropriate fixing solution.
Examples of Growermetal’s products tested according to the Junker test: Conical Contact washers, Conical Sperrkant washers, Rippen Flat washers and the new Grower Twin-Lock®.