Durability Testing of Components - Chinese University Uses the Largest Vibrophore in the World

Periodic loading of components eventually leads to breaking. In order to ensure maximum reliability, having in-depth knowledge about the durability is essential. Electromagnetic high frequency pulsators (Vibrophores) offer an extremely efficient solution for determining the mechanical properties of materials at high frequencies and forces. Chongqing University in central China will be using a Vibrophore with 1,000 kN in the future. The durability of components provides information about how many load cycles are permitted before leading to failure or break. It is therefore used as a key factor for designing crankshafts, connecting rods, and timing chains in motor-vehicle engines, connection elements in airplanes or concrete-reinforcing steel in power plants. Durability is typically determined through the application of periodic loads in fatigue tests. The resulting limit curve is known as the Wöhler (S-N) curve. It shows the correlation between the number of cycles to failure and the cyclic stress amplitude. The curve diagram is named after August Wöhler who developed the test after a railroad accident in 1875 that was caused by a tire failure. He recognized that periodically loaded components have shorter life spans than those where only static forces are applied. The cause of the wheel failure was not a material defect but rather material fatigue, which was a fundamental realization for future developments in quality assurance.
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Electromagnetic Vibrophores Electromagnetic Vibrophores offer an extremely economical solution for determining the required mechanical properties of materials at high frequencies. ZwickRoell is the only manufacturer that offers a Vibrophore with a force of up to 1,000 kN. This exact machine, weighing over 21 tons, was transported to the Chongqing University in central China via rail approximately 140 years after the first methodical tests by August Wöhler - however, this time the wheels were tested. Due to its considerable weight, the over 10,000 kilometer transport route was made via rail. The testing machine was too heavy for normal air freight and sea freight would have taken too long.
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The Vibrophore up to 1,000 kN developed by ZwickRoell is part of a series for test loads from 5 to 1,000 kN. For specimens that are sufficiently rigid, test frequencies of up to 285 Hz (150 Hz for the Vibrophore 1000) can be achieved. This ensures short testing times and thus high specimen throughput. The operating principle of the ZwickRoell Vibrophore is based on the concept of a mechanical resonator with electro-magnetic drive. The mean force is applied by moving the upper crosshead via a spindle drive. Dynamic (sinusoidal) loading is performed by an oscillating system that operates in resonance mode. High force and displacement amplitudes are achieved at a low energy inputs (around only 2% of the energy consumption of servo-hydraulic testing machines). Both drives are regulated and controlled separately from each other and can be either force, displacement, or strain-controlled. A key feature of the new Vibrophore 1000 is its load frame design. The extremely stiff load frame consists of four columns and therefore exhibits excellent guidance properties. Frequencies from 35 to 150 Hz (eight frequency steps) can be changed by activating/deactivating the weights. At Chongqing University, the Vibrophore is used for performing tests on gears, gear parts, and fastening elements, among other components.
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