SU879300A1 - Device for measuring forces affecting tested structure - Google Patents

Description

The invention relates to ultrasonic non-destructive testing and can be used to record both local and general loss of stability of complex structures in the case when visual collision with a test object or using other methods of ascertaining a critical state is impossible.

A device is known for measuring the forces acting on a test structure, comprising a surface acoustic wave generator formed by two transducers that are remote from each other and mounted on piezoelectric substrates that undergo elastic deformation under the influence of the measured force and are connected to an amplifier. The frequency of the generator is a function of the measured force [12.

However, this device cannot provide prediction of the critical force acting on the structure and registration of the initial stages by the loss of its stability.

Closest to the technical nature of the invention is a device for measuring the forces acting on a structure containing an exciter of acoustic waves and a receiver with a piezoelectric element [2].

However, this device also does not provide prediction of the critical force acting on the structure and registration of the initial stages of loss of its stability.

The aim of the invention is to provide a forecast of the critical force acting on the structure, and registration of the initial stages of loss of stability.

This goal is achieved by the fact that the device is equipped with 15 connected in series with a multi-channel amplifier, detector, adder and a unit for recording the extremum of the output signal and at least two additional piezoelectric elements spaced apart from each other by a distance not equal to half the wavelength and electrically connected to the corresponding amplifier inputs.

The drawing shows a block diagram of the proposed device.

The device contains an acoustic wave exciter 1, including an ultrasonic generator 2, to which a transducer 3, 30 is mounted mounted on a piezoelectric substrate attached to the test structure 4.

In structure 4, a receiver 5 attached akustycheskih waves with three piezoelements 6-8, remote from each other by a distance not equal to half the wavelength in order nepopa- ³ Denmark at least one of three sensors in a standing acoustic wave trough area, propagating in designs 4.

The device is equipped with a series-connected three-channel amplifier 9, a detector 10, an adder 11 and an extremum registration unit 12 of the output signal. The piezoelectric elements 6-8 of the receiver 5 are electrically connected to. 15 inputs of the corresponding channels of the amplifier 9.

Block 13 serves to control the loading mechanism of the structure 4.

The device operates as follows 20 times.

P [and loading of the test structure 4 by the force P in the initial stages of buckling, i.e. at critical values of force P, the piezoelectric elements »6-8 of receiver 5 fix the extreme value of the acoustic signal and transmit it through amplifier 9, detector 10, adder 11 to the output signal extremum recording unit 12, which, when the sign changes, the derivative with respect to time function of the signal of the adder gives a control signal to turn off the unit 13, which controls the mechanism of loading the structure with force R.

The magnitude of the load P at the moment of operation of the registration unit 12 is critical.

Using the described device will allow for non-destructive testing mainly for local loss of the widest range of complex structures of mechanical engineering, aircraft industry, construction in various types of static tests.

Claims (2)

a substrate attached to the test structure 4. On the structure 4, a receiver of 5 acoustic waves is attached with three peso-elements 6-8 spaced at a distance not equal to half the wavelength, in order to avoid one of the three sensitive elements in the zone cavities of a standing acoustic wave propagating in construction 4. The device is equipped with a series-connected three-channel amplifier 9, a detector 10, an adder 1 and a block 12 for recording the extremum of the output signal. Piezoelectric elements 6-8 of the receiver 5 are electrically connected with. the inputs of the corresponding channels of the amplifier 9. The block 13 serves to control the loading mechanism of the structure 4. The device operates as follows. Conductance loading test structure 4 by force P in the initial stages of the stability loss, i.e. at critical values of force P, the piezoelement 6-8 of receiver 5 fixes the extreme value of the acoustic signal and passes it through amplifier 9, detector 10, adder 11 to the output signal extremum recording unit 12, which, when the sign is changed, the time-derived signal function The adder issues a control signal to turn off the block 13, which controls the structure loading mechanism with force P. The load P is critical at the instant the detection block 12 is triggered. The use of the described device will allow nondestructive testing to be carried out mainly on the local loss of the widest range of complex engineering structures, aircraft industry, and construction with various types of static tests. Claims An apparatus for measuring forces acting on a structure under test, comprising an acoustic wave driver and a receiver with a piezoelectric element, with which; that, in order to ensure the prediction of the critical force acting on the structure and registering the initial stages of losing its stability, it is equipped with series-connected multi-channel amplifier, detector, adder and unit for recording the extremum of the output signal and at least two additional piezoelectric elements distant from each other distance, not equal to half the wavelength, and electrically connected with the corresponding inputs of the amplifier. Sources of information taken into account in the examination 1. For Britain, UK No. 1486155, cl. H 4 D, 1978. 2. For the UK of UK No. 1488155, class H 4 Oh, 1978 (prototype).