SU1180718A1 - Method of article vibration testing on resonance frequencies and apparatus for accomplishment of same - Google Patents

Abstract

1. A method of vibration testing of products at resonant frequencies, implying that the vibration load is stepwise changed after a predetermined number of cycles has been worked out by a step change in the level of the excitation signal, in order to increase the reliability of the test results by reducing the time transient processes, after testing a specified number of cycles, first they switch to the resonance excitation frequency, then the vibration load level is changed at the resonance frequency and ie it proceeds to the resonance frequency of the excitation. 2. A device for vibration testing of products at resonant frequencies, containing a series-connected master oscillator, an excitation signal level regulator, a power amplifier and a vibration exciter, a communication processing circuit including a vibrator, a matching amplifier, a rectifier, a low-pass filter and a unit the comparison, the output of which is i; is connected to the control input of the regulator of the level of the exciting signal, the unit of the number of cycles connected to its output of the program of the first level, the output of which The second input is connected to the second input of the comparison unit, and the trigger, the installation input of which is connected to the output of the cycle number setter, characterized in that 00 the cycle number setter is connected to the level programmer via a sequentially switched on multivibrator, first and second differentiators, the output of the first digifiertiator connected to the zero input of the trigger, and the output of the trigger - to the switch of the frequency of the master oscillator.

Description

Iuse:

The invention relates to an experimental technique, namely, a method and apparatus for vibration testing of products at resonant frequencies.

The aim of the invention is to increase the reliability of test results by reducing the time of transients.

FIG. 1 shows a block diagram of a device for vibration testing of products at resonant frequencies; in fig. 2 - time diagrams of the device; in fig. 3 - oscillograms of transient loading processes.

The device contains a sequence of 5 but connected master oscillator 1, regulator 2 of the excitation signal level, power amplifier 3 and vibration exciter 4 with test subject 2 installed on its moving part (G class 5, negative feedback circuit including vibration transducer 6 , matching amplifier 7, rectifier 8, low-frequency filter 9 and comparison unit 10, the output of which 25 is connected to the control input of the level controller 2, connected in series to the number of cycles setting device 11, the waiting multivibrator 12, the first differentiator p 13, second differentiator 10 14, programmer 15 level, the output of which is connected to the second input of the comparison unit 10, trigger 16, the installation input of which is connected to the output of the setting device 11 and combined with the 35 input of the waiting multivibrator 12, and the zero input connected to the output of the first differentiator 13 , the switch 17 of the frequency of the master oscillator 1, to the inputs of which (switch 40) the reference voltages and and U | are supplied. The control input of the frequency switch 17 is connected to the output of the trigger 16.

The vibration test method 45 is performed using the device as follows.

The harmonic signal from the master oscillator 1 through the level 2 regulator and the power amplifier 3 supplies 50 to the exciter 4 with the test article 5 mounted on it. The resonant value of the oscillation frequency is set by a predetermined reference voltage. The feedback signal 55 is fed to the first input of the comparator unit 10, to the second input of which a control signal is supplied

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from programmer 15, which delivers a discretely varying direct voltage when a pulse enabling signal is applied to the input. The switching time is determined by the number of cycts setting device 11, which generates a switching signal to another level (Fig. 2a) when a given number of cycles are processed at the previous loading stage,

This signal is fed to the setup input of the trigger, 16, setting it to a single state |) ig.26). The output signal of the trigger 16 is supplied to the control input of the switch 17, while the reference voltage U / is applied to the master oscillator 1, which corresponds to the resopans frequency value, i.e. the oscillation frequency of the test article 5 changes (Fig. 2g, h).

The signal from the setting unit 11 of the number of cycles simultaneously enters the input of the waiting multivibrator 12, which generates a pulse, the duration of which is chosen, based on the time of the transition process in the system (figv). This impulse arrives at the first differentiator 13, which emits two pulses: one - on the leading front of the im- pulse of the waiting multivibrator 12, the other - on the back (fig.2g). The first pulse arrives at the second differentiator 14, which also generates two short pulses along the leading and trailing edges of the pulse of the first differentiator 13 (Figure 2d. The pulse at the falling edge from the second differentiator 14 switches the programmer 15 to a new load level in the resonant frequency domain (FIG. , 2e, h). The pulse on the falling edge from the first differentiator 13 returns to the zero state of the trigger 16 and thereby returns the switch 17 to the initial state - connection U, corresponding its resonant frequency value (Fig.26, g, h).

The proposed apparatus relates to linear systems. The differential equation of the system is determined by the model of the product being tested, the vibration exciter and the low pass filter used. The transition process when switching load steps at a resonant frequency is oscillatory. In linear systems, the transition process in terms of the oscillation frequency is inertialess, and the switching of load stations in the resonance region with a low amplitude of oscillations allows one to shorten the time of the transient process. When switching the frequency from the resonant value to the resonance region of the transitional process, the oscillation amplitudes are lowered, which does not affect the accumulation of damage in the tested product. The transition process in the system when switching from a higher frequency to a resonant one is aperiodic in nature and its time t is much less than when switching steps at a resonant frequency. FIG. Figure 3 shows the oscillograms of the trans: slice processes for the well-known (Fig. 3a) and the proposed (Fig. 36). Where from here it can be seen that t, 7 t.j.

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Claims (2)

1. The method of vibration testing of products at resonant frequencies, namely, that the vibration load is changed stepwise after working out a predetermined number of cycles by stepwise changing the level of the exciting signal, characterized in that, in order to increase the reliability of the test results by reducing the transient time, after practicing a predetermined number of cycles, first they switch to a resonant excitation frequency, then, at a resonant frequency, the vibration load level is changed, and after that on moving to a resonant "frequency of excitation. 2. A device for vibration testing of products at resonant frequencies, containing a serially connected master oscillator, a regulator of the level of the exciting signal, a power amplifier and a vibration exciter, a negative communication processing circuit including a vibration transducer, a matching amplifier, a rectifier, a low-pass filter and a comparison unit, the output of which ! connected to the control input of the * g regulator of the level of the exciting signal, the number of cycles controller connected to its program level output, the output of which is is connected to the second input of the comparison unit, and the trigger, the installation input of which is connected to the output of the number of cycles setter, characterized in that the cycle number setter is connected to the level programmer through sequentially turned on standby multivibrator, the first and second differentiators, the output of the first differentiator connected to the zero input of the trigger, and the output of the trigger to the frequency switch of the master oscillator.