Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1989-08-18
1991-08-13
Williams, Hezron E.
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
73808, 73814, 73856, G01N 332
Patent
active
050386190
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is a process and an apparatus for testing stabilizers.
For developing vehicle stabilizers and also for the final inspection of standard parts in the manufacture or inspection departments, vehicle stabilizers must be dynamically tested under stress conditions approximate to those in use. This means, in particular, that the stabilizers are exposed to an endurance test for as many as 1,000,000 stress cycles.
2. Related Art
The known testing stands for stabilizers comprise eccentric drives to introduce the test stress either in opposite directions to both legs of the stabilizer or to one leg with firm clamping of the opposite leg. This kind of testing device has the disadvantage that the testing frequency can hardly exceed 5 Hz, since the forces of mass that cannot be compensated lead to extreme vibration of the testing stand, of the floor, etc. The low frequency of the cycling of the load leads to an extremely long duration of the test on the individual part (about 50 hours for 1,000,000 cycles of the load at 5 Hz cycling of the load frequency). The long test time makes the development of stabilizers difficult, and unacceptably delays results of random testing of production parts. Another problem of the eccentric drive is that only oscillation tests with constant amplitudes can be carried out in such test stands.
Servo-hydraulic test systems are known for obtaining stress profiles closer to in use profiles in which a plurality of different amplitudes are applied to the part. These testing systems are not only extremely expensive to manufacture but also cause vibrations on the adjustment location due to forces of gravity that cannot be compensated and are very costly to operate.
OBJECTS AND SUMMARY OF THE INVENTION
Departing from the above mentioned prior art, the object of the invention is a process and an apparatus for testing stabilizers in a simple, economic manner and considerably quicker than formerly accomplished.
According to the process of the invention, this problem is solved by exciting the legs of a stabilizer to be tested together with movable mass elements attached thereto at the resonant frequency of the mass-spring system with out of phase oscillations about a firm zero point. The apparatus of the invention comprises a drive means having movable mass elements which, with the stabilizer, forms a mass-spring resonator. The movably disposed mass elements are each connected with one leg of the stabilizer in a manner such that, via an attached oscillation exciter together with the stabilizer legs, they can be brought to oscillations whose frequency is determined by the mass of the mass elements and the spring tension of the stabilizer.
The principle of the invention is that by attaching the mass to each leg, an intrinsically closed system is formed. The system is capable of oscillating the stabilizer as the test piece and the other parts are two parts located in the testing apparatus. In the process of the invention, the oscillation exciter must only balance the losses occurring in the system, that is, friction resulting from the movement of the apparatus, air damping and material damping. Thus, the resulting requirement of energy is extremely small (below 1 kw for testing the stabilizer of a mid-size passenger car).
Especially suited as an oscillation exciter, because of its adjustability, is a disk armature motor. The disk armature motor causes a mass element to reciprocally rotate. The reciprocally rotatable mass element is rotatably supported about an axle via a shaft and is fastened at one end to the stabilizer leg. The other stabilizer leg is coupled with a second rotatable mass element shaped in a manner such that it can oscillate out of phase with the first mass element. The total load amplitude applied to the stabilizer doubles with a constant oscillation amplitude (angle of rotation) of the oscillation exciter or of the first mass element. The moments of inertia on both sides (seen from the center of the test piece) mu
REFERENCES:
patent: 2157903 (1939-05-01), Lapsley
patent: 3664179 (1972-05-01), Danko et al.
patent: 4283957 (1981-08-01), Zobrist et al.
Finley Rose M.
Industrieanlagen-Betriebsgesellschaft mbH
Williams Hezron E.
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