SU1620933A1 - Acoustic device for checking qualities of surface of cylindrical articles - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to monitor the state of the surface of cylindrical products and determine the location of localized damage. The purpose of the invention is to increase the reliability of control by reducing the effect of the variable intensity noise signal on the measurement results, which is achieved by forming a Floating Comparison Threshold in the amplitude discriminator of the device that generates a defect signal. The registration of the amplitude of the signal above the floating comparison threshold provides information on the size of the local defect, the signal envelope (the floating comparison level) gives an integral assessment of the surface state of the product. 1 il.

Description

The invention relates to a non-destructive testing technique and can be used to monitor the state of the surface of cylindrical products and determine the location of localized damage.

The purpose of the invention is to increase the reliability of monitoring by reducing the influence of the noise signal of a variable intensity on the measurement results.

The drawing shows a bpock diagram of an acoustic device for controlling the surface quality of cylindrical products.

The acoustic device for controlling the surface quality of cylindrical products contains the surface scanning mechanism 1 of the product under test, a probe 2 with an acoustic transducer 3, mechanically connected with the scanning mechanism 1, connected in series to a preamplifier 4, a band filter 5, a rectifier 6, a bottom filter 7

frequency (low pass filter). the amplifier 8, the amplitude discriminator 9. the pulling node 10 and the recorder 11 and series-connected reference voltage unit 12, the comparator 13 and the indicator 14, the second input of the amplitude discriminator 9 is connected to the output of the bandpass filter 5, the second inputs of the recorder 11 and the comparator 13 are connected to output of the amplifier 8. The position 15 indicates a controlled product.

The device works as follows.

The scanning mechanism 1 performs translational-rotational movement of the probe 2 with the acoustic transducer 3 along the surface of the tested product along a spiral path with a step determined by the formula

w

Yo

ABOUT

yoo yu with

h 2 # V / u),

(one)

where V is the speed of the translational movement of the probe 2 and the acoustic transducer 3 along the product 15;

(D is the angular velocity of rotation of the product.

In this case, the mechanical interaction of the probe 2 with the relief of the test surface: delamination areas (or layering), cracks, etc. is carried out. The electrical signal taken from the acoustic transducer 3 is amplified by the preamplifier A. The band-pass filter 5 separates the signals in the working frequency band (this suppresses interference caused by low-frequency equipment vibration and electrical interference). Rectifier 6 and FTS 7 highlight the signal envelope. The magnitude of the signal at the output of the low-pass filter 7 characterizes the quality of the surface area currently monitored (it is advisable to choose the time constant of the low pass filter 7 equal to the time of one or several turns of the product 15). When probe 2 passes through a section of a surface with a defect such as a crack, an abrupt change in the trajectory of movement of the tip of probe 2 occurs. At the same time, probe 2 (which is also a waveguide) causes a propagation of acoustic waves to: acoustic transducer 3, which leads to an increase in electrical the output signal of the acoustic transducer 3. The amplitude discriminator 9 transmits only that part of the amplitude that exceeds the envelope of the signal amplified a given number of times with the help of amplifier 8. To ensure the recording of the amplitude value by the recorder 11, the pulling unit 10 pulling the signal from the output of the amplitude discriminator 9. At the same time, the decay time constant is chosen to be slightly longer than the time of passage, above the 2 longitudinal crack of maximum width. The recorder 11 records a signal envelope under one channel, which makes it possible to assess the overall surface state of the monitored product. Recording on a different channel of signals exceeding the envelope of a signal a predetermined number of times allows locating local damage to the surface (such as a crack) to be determined, and the degree of damage can be estimated from the signal amplitude.

If the control process is disturbed, for example, due to the lack of contact between the probe 2 and the surface, the magnitude of the signal envelope decreases. By reducing the value to a threshold value determined by the block 12 of the reference voltage,

the comparator 13 generates a signal on which the indicator 14 is turned on.

In the proposed device, as a scanning mechanism 1, which provides translational-rotational movement of the probe 2 with the acoustic transducer 3 relative to the surface of the tested product, a lathe can be used, for example.

(in this case, the controlled article is fixed in the cartridge, and the probe 2 and the acoustic transducer 3 are mounted on the tool holder). The rotational movement of the product relative to the probe 2 is provided by the cartridge, and the translational movement is achieved by feeding the toolholder along the axis of the product.

As probe 2 and acoustic transducer 3 can be used

piezoelectric adapter type GZK-661. The preamplifier 4 and the amplifier 8 can be performed on the K544UD1 integrated circuits. Band-pass filter 5 and low-pass filter 7 are active RC filters,

performed, for example, on operational amplifiers (op-amps) K544UD1, Rectifier b is an op-amp K544UD1 with a diode included in the feedback. Amplitude discriminator 9 is assembled according to the scheme of the subtracting opamp. As a two-channel recorder 11, a recorder of type H-327 can be used. The reference voltage block 12 is a resistive divider connected between buses

power and zero potential. The comparator 13 is made on the chip K521SA1. As the indicator 14 can be used led AL307. In comparison with the known, the proposed device allows to control the surface of cylindrical helix, provides localization of defects. Use for amplitude discriminator floating threshold level (amplified signal with

the output of the low pass filter 7) allows the device to automatically adapt to the surface relief and against the background of a noise signal (e.g. a layering) separate the pulse signal from a local defect (e.g. a crack). The recording of the amplitude of the signal above the floating threshold provides information on the size of the local defect. At the same time, the recording of the signal envelope provides an integral assessment of the state of the product surface. Comparison of the data obtained using the proposed device with periodically repeated monitoring of the products in use allows us to judge the development of defects and the appearance of new defects.

The device makes it possible to significantly increase the reliability of monitoring through the use of a seri- ous threshold, which allows one to smoothly monitor the state of the surface and, with the help of an indicator, quickly diagnose the monitoring process itself.

Claims (1)

An Acoustic Device for Quality Control of the Surface of Cylindrical Products, Containing Acoustic Transducer and Preamplifier In Series, As well as Amplifier and Comparator, In order to increase the reliability of control, it is equipped with a probe connected to an acoustic transducer to scan mechanisms. performing translational-rotational movement of a probe with an acoustic transducer with respect to the surface of the product under test, serially connected by a band-pass filter, a rectifier and a low-pass filter, connected in series with an amplitude discriminator, a pulling unit and a two-channel recorder, a reference voltage unit and an indicator, the preamplifier output is connected to the input of a band-pass filter, the output of which connected to the first input of the amplitude discriminator, the output of the low-pass filter is connected to the input of the amplifier, the output of the latter is connected to the first input the compiler and the second inputs of the amplitude discriminator and the two-channel recorder, the second input of the comparator is connected to the output of the reference voltage block, and the output of the comparator is connected to the input of the indicator.