RU2097726C1 - Process testing elastic systems for vibration strength - Google Patents

Abstract

FIELD: tests of shock-absorbing systems of instruments. SUBSTANCE: tested elastic system with concentrated inertial mass is subjected at points of its attachment to action of harmonic vibration with fixed frequency and constant acceleration of inertial mass. Lowest resonance frequency f_r of elastic system and acceleration j_m on inertial mass on frequency f_sp<f_r specified in service forms and records for article are determined in advance to set mode parameters of test. Test are conducted on frequency f_t chosen from relationship f_sp<f_t<f_p with acceleration on inertial mass equal to j_m.. Vibration strength of elastic system is evaluated by change of acceleration at point its attachment. EFFECT: simplified process of test for vibration strength. 2 cl

Description

 The invention relates to test equipment, in particular to methods for testing elastic systems (CSS) for vibration resistance.

A known method of testing the stress test for vibration resistance, according to which the stress test is subjected to harmonic vibration at a frequency f _s specified in the normative and technical documentation, measure and support the acceleration j _s at the point of fastening of the stress test [1]. This method allows testing vibration resistance of both stand-alone US, and several US at the same time (for example, instrument frames, including a housing on which several devices are mounted, rigidly or by means of shock absorbers).

 The disadvantage of this method is the impossibility in some cases of reproducing the vibration loading mode on existing equipment (for example, when simulating transport vibration at low frequencies of 1.20 Hz with a large oscillation amplitude) or the long duration of tests in cases where the vibration loading mode at low frequencies can be reproduced on the existing equipment.

The vibrational strength of the DC is determined by the deformation of the elastic element, which, in turn, depends on the relative amplitude of the oscillations A ₀ and practically does not depend on the frequency. This allows us to test the CSS at higher frequencies compared with the frequency f _s while maintaining the relative amplitude of the vibrations and, consequently, the deformation of the elastic elements.

где f_р низшая резонансная частота;
δ логарифмический декремент колебаний.There is a method of testing the CSS for vibration resistance, according to which the test system with a concentrated inertial mass is subjected to vibration at a resonant (natural) frequency in the place of its fastening, while the acceleration j _m at the inertial mass is determined and supported during the test [2]
As is known

where f _{p is the} lowest resonant frequency;
δ logarithmic decrement of oscillations.

Therefore, for j _m const, the relative amplitude A ₀ (and, therefore, the displacement of the inertial mass relative to the point of fixation of the CS and deformation of the elastic elements) const.

 The method [2] allows to eliminate the disadvantages of the analogue [1] since almost all DCs operating under the influence (or after exposure) of low-frequency, for example, transport loads, are designed so that the resonant frequencies lie above the frequencies of these loads, for example, above the frequencies of the transport range.

 Method [2] is chosen as a prototype, because by its technical nature and the achieved result is the closest to the proposed invention.

 The disadvantage of the prototype is the complexity of the technical implementation (due to the departure of the resonant frequency during the test, a very complex scheme of its automatic phase regulation is used) and the inability to simultaneously test several DCs, which are, for example, part of the instrument frame.

 The objective of the invention is to simplify the implementation of the method while maintaining the accuracy of the test.

The problem is solved in that in the method of testing the CSS for vibration resistance, according to which the test system with a concentrated inertial mass is subjected to harmonic vibration with a fixed frequency in the place of its fastening, the acceleration on the inertial mass is determined and supported during the test, according to the invention, the lower the resonant frequency f _{p of the} elastic system and the acceleration j _m on the inertial mass at a frequency f _s <f _p specified in the normative and technical documentation for the product, and tests about drive at a frequency f _and selected from the relation f _s <f _and <f _p , when accelerating at an inertial mass equal to j _m .

 In addition, in the process of testing, acceleration is measured at the place of fastening of the elastic system, and vibrational stability of the CSS is judged by its change.

In the case of simultaneous testing of several elastic systems, the acceleration j _m is determined on all inertial masses, and during the test, j _{m is} supported on one inertial mass, while the acceleration is measured on the remaining inertial masses and the vibration strength of elastic systems is judged by its change.

The method is as follows. The lowest resonant frequency f _{p is} determined (by calculation or experimentally) and the test frequency f is found _and from the range [f _s , f _p ] The acceleration value j _m on the inertial mass at the frequency f _s specified in the normative technical documentation by calculation or experiment is determined. Tests are carried out at a frequency f _and with a corresponding reduction in test time in proportion to the ratio f _s / f _and ; during the tests, the acceleration value j _m on the inertial mass is measured and maintained. In the case of simultaneous tests of vibration resistance of several DCs, the value of j _m at a frequency of f _s is determined on all inertial masses, and during the tests, the value of j _m const is maintained on one of the inertial masses, while the acceleration is measured on the remaining inertial masses and judged by its change about vibration resistance CSS.

 An example of the method.

Requires determine vibronadezhnost amortized device (vibration damping device and vibration system), which according to specification subjected during operation in a place exposed fastening harmonic vibration at a frequency f _of 1.0 Hz, j _m 0,6g acceleration and the time for 20 hours.

 To determine these characteristics carry out the following steps.

 1. Determine by calculation the amplitude of the vibration acting in the place of fixing.

2. Проводят анализ испытательного оборудования, который показывает, что на существующем испытательном оборудовании создание вибрации с амплитудой 150 мм невозможно.

2. An analysis of the test equipment is carried out, which shows that it is not possible to create vibration with an amplitude of 150 mm on existing test equipment.

 3. Determine the lowest resonant frequency of the damping system, which is 10 Hz.

4. Select from the range of 10 Hz the test frequency f _and 5 Hz, determine the new test time t _and 20 • 1/5 4 hours.

5. Determine by calculation acceleration j _m in the inertial mass - the device at a frequency of 1 Hz and the acceleration _of j 0,6g (the calculation assumed δ 1).

6. Проводят испытания амортизированного прибора на частоте 5 Гц в течение 4 ч, при этом поддерживают на приборе постоянную величину ускорения 0,61g.

6. Test the shock-absorbing device at a frequency of 5 Hz for 4 hours, while maintaining a constant acceleration value of 0.61 g on the device.

 8. During the tests, it was found that the device is vibration-resistant (the additional error does not go beyond the norm), however, after 3 hours of vibration, the acceleration at the fixed point of the shock-absorbed device decreased from 0.47g to 0.26g. The tests were suspended and the lower resonance frequency of the damping system, which was 6 Hz, was re-determined. Thus, the shock-absorbed US device did not pass the test due to insufficient vibration resistance.

Claims (3)

1. The method of testing elastic systems for vibration resistance, according to which the test system with a concentrated inertial mass is subjected to harmonic vibration with a fixed frequency in the place of its fastening, determine the acceleration on the inertial mass and support it during the test, characterized in that the lower resonance frequency is preliminarily determined f _{r of the} elastic system and acceleration j _m on the inertial mass at a frequency f _s <f _p specified in the normative and technical documentation for the product, and the test is carried out at frequencies e f _and selected from the relation f _s <f _and <f _p , when accelerating on an inertial mass equal to j _m  2. The method according to claim 1, characterized in that during the test the acceleration is measured at the place of fastening of the elastic system and its change is used to judge the vibration resistance of the elastic system. 3. The method according to claim 1, characterized in that in the case of simultaneous testing of several elastic systems, the acceleration j _m is determined on all inertial masses, and during the test, j _{m is} supported on one inertial mass, while the acceleration is also measured on the remaining inertial masses and its change is used to judge the vibration resistance of elastic systems.