CN104792868A - Rotary-scanning online ultrasonic detection method for cylinders - Google Patents

Abstract

The invention discloses a rotary-scanning online ultrasonic detection method for cylinders. To-be-detected cylinders are placed in designated positions by a mechanical moving part; positions of transverse and longitudinal detection probes are adjusted, and longitudinal probe detects point-like and transverse surface-like defects, and the transverse probe detects point-like and longitudinal surface-like defects; ultrasonic frequency ranges are selected according to different cylinders; the cylinders are rotated for detection; positions and degrees of the defects are judged according to echo signals. With the adoption of the method, the detection efficiency is improved, and the cylinders made of different materials can be detected through change of acoustic resistance models and positions of sensors.

Description

A kind of Clothoid type scanning cylindrical shell ultrasonic on-line detecting method

Technical field

The invention belongs to based on ultrasound wave online measuring technique field, specifically, relate to a kind of Clothoid type scanning cylindrical shell ultrasonic on-line detecting method.

Background technology

There is the Force research institute of the Krautkramer company of Germany, the Panametrics company of the U.S., ABB AB, Denmark in the foreign vendor being at present in technology and equipment advanced person at automatic ultrasonic detection field; The manufacturer of domestic ultrasonic test equipment also has tens, as Shantou ultrasonic instrument research institute, Shanghai Ultrasonic Instrument Factory etc., but majority belongs to medium-sized and small enterprises, equipment and technical force weaker, lack independent studies and development ability, larger with the gap of external peer enterprises.

Existing " ultrasonic on-line detecting system ", discusses with computer technology composition and the design of the ultrasonic on-line detecting system being core mostly for different workpieces, weld seam etc.Mainly be divided into development three modules of the research of entire system integrated approach, signal processing method research, software platform.Discuss the selection of ultrasonic probe and research principles, signal launch with accept, the principle of design etc. of the research principles of collecting unit, the research principles of control module, the research principles of mechanical system and signal transacting and software systems.It focuses on studying serial communication aspect, Software for Design aspect and signal transacting aspect technology.Aim at cylindrical shell ultrasonic testing system there is not yet.

By Shanghai, Baoying County and relevant Gas Company, the problem of apparatus factory cooperation is thin for civilian tucking in gas cylinder wall, weld width is large, inside and outside strengthen floor height and irregular and the feature such as accurately cannot to detect one by one, through repeatedly verifying, develop and adopt the method for detection of pack parallel shear wave acoustic beam, more desirably solve this ultra-sonic defect detector of Non-Destructive Testing difficult problem ` of steel cylinder cylindrical shell weld seam, detectable two steel cylinders per minute, frequency is 5 hertz, sensitivity and accurate rate high, can up to 99% to steel cylinder weld defect recall rate, when finding excessive defect in the detection, can also with light, sound equipment and the form automatic alarm such as waveform and wave paths line record.Higher economic worth is all had to the guarantee steel cylinder quality of production and safety.Technical design aspect fails to see owing to maintaining secrecy.Ultimate principle utilizes the spin of steel cylinder and work enter to scan, thickness has a definite limitation simultaneously.Cannot detect thinner less cylindrical shell.

For the flaw detection of thin plate, existing multiple detection means, compares and common are: the technology such as ray detection, EDDY CURRENT, magnetic powder inspection and Ultrasonic Detection at present.The irregular fluctuating of common EDDY CURRENT effects on surface and defect are difficult to distinguish, and easily cause erroneous judgement and are difficult to carry out qualitative, quantitative; Magnetic powder inspection be comparatively applicable to beauty defects flaw detection, for this defect be present in thin plate carry out detecting comparatively difficulty, and this mode also difficulty be applied to on-line checkingi environment; For the detection of thin plate internal soundness, what be most widely used is that radio examination detects, simple and clear, for this detected object and testing requirement, cost is high-leveled and difficult in realizing on-line checkingi on the one hand, more importantly double-walled can only be adopted to project because tube structure is less, slightly dark fine crack radio examination cannot detect; Ultrasonic Detection adopts more another kind of detection method, but for this thin-walled (below 1.5mm) tube structure part, detect the micro-crack that the degree of depth is 0.05mm, also do not have a kind of proven technique can for on-line checkingi.

Summary of the invention

In order to overcome the defect existed in prior art, the present invention proposes a kind of Clothoid type scanning cylindrical shell ultrasonic on-line detecting method, convolution scan pattern is proposed on an existing basis, rearrange sonac position number, overcome the spin of spiral scan and work to enter to exist and the time consuming procedures found that causes simultaneously, improve detection efficiency.Meanwhile, to the cylindrical shell of different materials, can realize detecting by change acoustic resistance model and sensing station.

Its technical scheme is as follows:

A kind of Clothoid type scanning cylindrical shell ultrasonic on-line detecting method, comprises the following steps:

Cylindrical shell to be measured is transported to detection platform by mechanical moving element by step 1., then is placed in assigned address by built-in machines hand;

Step 2. adjusts and detects probe positions and quantity in length and breadth.Vertical sonde is responsible for detecting point-like and horizontal planar defect, and horizontal probe is responsible for detecting point-like and longitudinal planar defect;

Step 3., according to different cylindrical shell, selects ultrasonic frequency range.Single pass ultrasonic trigger rate is 0.75KHz, and namely the picking rate of the characteristic signal of every passage is 0.75KSPS.Because detected object is cylindrical workpiece, ultrasound wave is swirl type to workpiece track while scan, and the cycle counts the diameter and rotational speed that depend on examined workpiece, is certain to the workpiece of specific model;

Step 4. rotating cylinder, starts to detect.During detection, workpiece rotational frequency is 500 revs/min, and workpiece rotates a circle as 0.12s;

Step 5. ultrasound wave enters cylindrical shell with longitudinal waves from barrel outer surface and forms Lamb wave along cylindrical shell forward direction, defect waves is reflected to form when running into defect, selected in limited time by defect gate, by integrating circuit and peak holding circuit, hardware extraction is carried out to defect characteristic, be converted into digital signal via multichannel collecting card, carry out defect recognition and sorting by Adaptive correlation algorithm.

Beneficial effect of the present invention is: the present invention proposes scan pattern of circling round on an existing basis, rearranges sonac position number, overcomes the spin of spiral scan and work and enters to exist and the time consuming procedures found that causes simultaneously, improve detection efficiency.Meanwhile, to the cylindrical shell of different materials, can realize detecting by change acoustic resistance model and sensing station.

Accompanying drawing explanation

Fig. 1 is the ultrasonic on-line checkingi schematic diagram of thin-wall barrel;

Fig. 2 is ultrasonic probe distribution and Cleaning Principle figure;

Fig. 3 is the graph of a relation of Lamb wave phase velocity and frequency × thickness of slab;

Fig. 4 is f=5MHz d=1.2mm A1 type sound pressure curve;

Fig. 5 is that experimental result outer wall indulges wound figure;

Fig. 6 is the horizontal wound figure of experimental result outer wall;

Fig. 7 is that experimental result inwall indulges wound figure;

Fig. 8 is the horizontal wound figure of experimental result inwall.

Embodiment

Below in conjunction with the drawings and specific embodiments, technical scheme of the present invention is described in more detail.

As shown in Figure 1, control mechanical system motion by Machinery Control System and workpiece for measurement is sent to position to be detected, signal return is given ultrasonic control and data acquisition system (DAS) by ultrasonic probe group by the comformed information of its position, then is judged by information identification and data handling system.Ultrasonic control and data acquisition system (DAS) Triggered ultrasound are launched and are launched ultrasound wave with Echo Processing system through ultrasonic probe, are coupled to workpiece for measurement and detect, and ultrasonic trigger pip is sent to Feature Extraction System simultaneously.The echoed signal detected passes back to Echo Processing system by ultrasonic probe group again, through Feature Extraction System characteristic information extraction uploading data acquisition system, again by information identification and data handling system differentiate product just, secondary, and driving device control system control mechanical system product assortment is deposited.

With reference to Fig. 2, two groups of probe orthogonal distributions, vertical sonde detects point-like and horizontal planar defect, and horizontal probe detects point-like and longitudinal planar defect.

Embodiment

1. model selection: when utilizing Lamb wave to detect, for ease of defect recognition and detecting, should ensure that the acoustic wave mode propagated in plate is single, velocity-stabilization as far as possible.Such as: when frequency, thickness of slab amass and be greater than 4MHz mm, the Lamb wave group velocity of A0, S0 pattern trends towards a constant, and therefore adopt 5MHz probe to detect thickness of slab when the sheet material of about 0.8mm, Lamb wave group velocity does not have large change.When A0, S0 template ripple is propagated in even thin plate, waveform will be a regular unimodal pulse, is conducive to waveform recognition when detecting.By Lamb wave equation:

$4\mathrm{pq}\tan \left(\frac{\mathrm{\πfdq}}{\mathrm{Cp}}\right)+{(p^2-1)}^2\tan \left(\frac{\mathrm{\πfdp}}{\mathrm{Cp}}\right)=0$

$4\mathrm{pq}\tan \left(\frac{\mathrm{\πfdp}}{\mathrm{Cp}}\right)+{(p^2-1)}^2\tan \left(\frac{\mathrm{\πfdq}}{\mathrm{Cp}}\right)=0$

d is thickness of slab; F is ultrasonic frequency; Cp is transverse wave speed; Cl is longitudinal wave velocity.

For the elastic medium of given thickness of slab d, give timing at ultrasonic frequency f, infinitely multiple Lamb wave type corresponding with it can be produced.Meet the Displacements Distribution symmetrically type of the Lamb wave type of the first formula, in the upper and lower surface of i.e. plate, the phase place of particle vibration is contrary, the similar compressional wave of the mode of vibration of particle on central plane, these patterns are named as: S0, S1, S2 ... the Displacements Distribution meeting the Lamb wave type of the second formula is skew symmetry, and in its communication process, in the upper and lower surface of plate, the phase place of particle vibration is identical, the similar shear wave of the mode of vibration of particle on central plane, these patterns are named as: A0, A1, A2 ...

The relation of f, d, Cp can be obtained as shown in Figure 3 according to frequency equation.

2. acoustic energy distribution optimization: more various Lamb wave pattern, in the effect of actual signal Treatment Analysis, selects different Lamb wave pattern.Such as, with reference to Fig. 4, A1 Lamb wave pattern acoustic pressure distribution curve: A1 template ripple is when frequency, thickness of slab amass as 4MHzmm, although it is not very straight that group velocity frequency thickness of slab amasss curve, the acoustic pressure of sound pressure curve near upper and lower surface place is less, increases gradually to center.

3. signal transacting: because defect presents good periodicity, the method that employing data sectional and autocorrelation function combine, as defect estimation foundation, when auto-correlation function value is greater than a certain threshold value, has then been judged to be wounding signal:

(1) count to the signal subsection gathered by corresponding with model, like this burst is divided into several cycles;

(2) average, the variance in n-th and n+1 cycle is obtained;

(3) autocovariance and the autocorrelation function in adjacent two cycles is asked;

(4) auto-correlation function value is greater than a certain threshold value, is determined as wound.Until all signal transacting are complete, in whole detection, the auto-correlation function value of all adjacent periods is all less than the threshold value of specifying, then workpiece is certified products, otherwise is unacceptable product.The amplitude of echo reflects the degree of depth of defect, and the periodicity of echo reflects the length of defect.

4. experiment effect: as shown in Figure 5-Figure 8.

Experiment shows: loss is 0, and different cylindrical shell detection time, False Rate was less than 0.2%, and precision can reach 0.05 millimeter between 5-10 second.Detection time and cost can be saved.

The above; be only the present invention's preferably embodiment; protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses, the simple change of the technical scheme that can obtain apparently or equivalence are replaced and are all fallen within the scope of protection of the present invention.

Claims (1)

1. a Clothoid type scanning cylindrical shell ultrasonic on-line detecting method, is characterized in that, comprise the following steps:

Cylindrical shell to be measured is transported to detection platform by mechanical moving element by step 1., then is placed in assigned address by built-in machines hand;

Step 2. adjusts and detects probe positions and quantity in length and breadth, and vertical sonde is responsible for detecting point-like and horizontal planar defect, and horizontal probe is responsible for detecting point-like and longitudinal planar defect;

Step 3. is according to different cylindrical shell, and select ultrasonic frequency range, single pass ultrasonic trigger rate is 0.75KHz, and the picking rate of the characteristic signal of every passage is 0.75KSPS;

Step 4. rotating cylinder, start to detect, during detection, workpiece rotational frequency is 500 revs/min, and workpiece rotates a circle as 0.12s;

Step 5. ultrasound wave enters cylindrical shell with longitudinal waves from barrel outer surface and forms Lamb wave along cylindrical shell forward direction, defect waves is reflected to form when running into defect, selected in limited time by defect gate, by integrating circuit and peak holding circuit, hardware extraction is carried out to defect characteristic, be converted into digital signal via multichannel collecting card, carry out defect recognition and sorting by Adaptive correlation algorithm.