Dynamically loaded sprocket-chains are used to transmit force and motion, examples include timing chains in motor-vehicle engines, drive chains on motorcycles and transmission uses in machines and plant engineering. In service they are constantly subjected to periodically fluctuating loads and difficult environmental conditions. In addition to tests for fracture resistance and wear resistance, special attention is also paid to the fatigue life and fatigue limiting properties of roller, bush roller and pin chains. ZwickRoell Vibrophores (high-frequency pulsators) represent a particularly cost-effective solution for tests in this area.
Dynamic testing can be carried out on both complete endless chains and on individual chain components (chain suspension bridges). Endless chains can be mounted in the testing machine using either the sprocket intended for their application or special specimen grips. Single or multiple chain-components under test are retained in the specimen grips by means of a locking pin inserted through the last open link. Regardless of how the specimen is clamped, tests are also possible in climatic chambers and liquid mediums such as oils or corrosive substances. Specific test conditions, test loads and number of load changes are defined in the relevant factory standards.
Electromagnetic Vibrophores offer an extremely efficient means of determining the fatigue properties of chains. ZwickRoell Vibrophores in the force range between 5 – 1,000 kN combine low energy-consumption and high testing frequencies. The testing machine is operated in resonance frequency, so that energy consumption is only about 2% of that of a comparable servo-hydraulic testing machine. Typical testing frequencies for chain testing are 50-150 Hz, ensuring a short test duration. Because the test takes place in the resonance range the Vibrophore can detect cracks developing and growing in the chain at a very early point due to minimal changes in frequency.
Vibrophores require no additional power packs for hydraulics, compressed air or water and are considered as wear-free due to their electromagnetic drive.
Other ranges of application for Vibrophores are fracture mechanics investigations on CT specimens and SEB specimens, pre-cracking specimens, fatigue tests on components (e.g. screws and bolts, connecting rods and crankshafts), together with production and quality control for components which are subjected to dynamic loading during their working lives.