CN110031292A - The online instant measuring system and method for cylindrical structure fatigue growth of surface cracks - Google Patents

Abstract

The invention provides an on-line real-time measurement system for the fatigue propagation of surface cracks of a cylindrical structure, comprising a gantry support device, an adjustment device, a CCD lens and a computer control terminal, wherein: the CCD lens is arranged on the adjustment device, The adjusting device can adjust the position of the CCD lens; the adjusting device is arranged on the stand support device; the computer control terminal is used for collecting the position information and image information obtained by the adjusting device and the CCD lens. The invention can perform real-time measurement and calculation for the surface crack of a cylinder or axisymmetric structure, and can also be used for crack measurement and calculation under a complex crack propagation path after expansion.

Description

On-line real-time measurement system and method for surface crack fatigue propagation of cylindrical structure

technical field

The invention relates to the instant measurement of surface crack fatigue propagation, in particular to an online instant measurement system and method for the surface crack fatigue propagation length of a cylindrical structure.

Background technique

The measurement of crack length is an important part of fatigue crack growth rate testing, and it is also a testing technique of great interest in the field of fatigue fracture. The damage of a large number of practical engineering structures is mainly caused by the crack propagation caused by surface defects under fatigue load. Therefore, accurate surface crack length measurement is of great significance for calculating the crack growth rate and evaluating the remaining life of the actual structure.

Usually, the measurement methods of crack length include direct reading method, replica hair, potential method, flexibility method, etc., of which the direct reading method is the most commonly used method. The so-called direct reading method refers to the direct visual inspection of the crack front and the recording of the crack extension length through a reading microscope or an optical microscope. This method is adopted and recommended by almost all domestic and foreign test standards.

Due to the development of modern industry, the requirements for fatigue fracture performance of various shaft structures have become higher and higher in recent years, such as engine rotors, turbine disks, and steam turbines. In various rotating machines, the surface crack propagation is not on a certain plane, so it is very difficult to measure. Even in laboratory studies, measurements are usually made with an ordinary reading microscope and then converted manually. However, the coordinate scales of the commonly used reading microscopes are all linear. Even if there is a two-dimensional coordinate system, the reading microscope is still a double-linear coordinate system, that is, the X-Y coordinate system. This brings great difficulties and errors to the surface crack measurement of cylindrical or axisymmetric structures.

An invention patent with application number 201510740224.0 discloses a device ridge method for measuring dynamic crack length. Loading a cracked specimen, collecting the opening displacement data of the crack opening through a non-contact crack length measurement and analysis system, using sinusoidal The maximum value of the opening displacement was obtained by curve fitting, and the crack length under the corresponding cycle was obtained by using the relationship between the crack opening displacement and the crack length. It has been verified by experiments that this method is more convenient and faster than the traditional method, and the results are true and reliable. However, the above method cannot realize the surface crack measurement of cylindrical structures or axisymmetric structures.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide an on-line real-time measurement system and method for fatigue propagation of surface cracks of cylindrical structures.

An on-line real-time measurement system for fatigue propagation of surface cracks in a cylindrical structure provided according to the present invention includes a gantry support device, an adjustment device, a CCD lens and a computer control terminal, wherein:

The CCD lens is arranged on the adjusting device, and the adjusting device can adjust the position of the CCD lens;

the adjusting device is arranged on the stand support device;

The computer control terminal is used for collecting the position information and image information obtained by the adjusting device and the CCD lens.

Preferably, the adjustment device includes an angle adjustment device, a height adjustment device and a distance adjustment device, wherein:

The angle adjustment device is arranged on a measuring bracket, and the angle adjustment device is used to adjust the angle position of the CCD lens;

The height adjustment device is installed on the angle adjustment device, and the angle adjustment device is used to adjust the height position of the CCD lens;

The distance adjustment device is arranged on the height adjustment device, and the distance adjustment device is used to adjust the distance between the CCD lens and the sample.

Preferably, the measurement support includes a semicircular track, and the central axis of the semicircular track coincides with the axis on which the sample is located.

Also includes a first step motor and a first connecting shaft, wherein:

The first step motor is connected to the angle adjusting device through the first connecting shaft, and drives the angle adjusting device to move on the measuring bracket.

Preferably, it also includes a second driving motor and a second connecting shaft, wherein:

The second stepping motor is connected to the height adjusting device through a second connecting shaft, and is fixed on the angle adjusting device for adjusting the height position, thereby adjusting the height of the CCD lens.

Preferably, a third driving motor and a third connecting shaft are also included, wherein:

The third stepping motor is connected to the distance adjusting device through a third connecting shaft, and is fixed on the height adjusting device for adjusting the distance between the CCD lens and the sample.

Preferably, the angle adjustment device further includes an angle displacement meter, and the angle displacement meter is used to measure the rotation angle of the angle adjustment device and send it to the computer control terminal.

Preferably, it also includes a testing machine upright, and the adjusting device is arranged on the testing machine upright by connecting a hoop.

The present invention also provides a measurement method of an online real-time measurement system for the fatigue propagation of a surface crack of a cylindrical structure, comprising the following steps:

Assembly steps: Assemble the adjustment device, install the sample on the bench support device, and clear the parameter information at the computer terminal;

Test steps: Adjust the position of the CCD lens through the adjustment device to ensure that the crack tip of the sample is just in the center area of the CCD lens;

Collection and calculation steps: collect position information and image information to the computer terminal, and the computer terminal calculates the crack length of the sample according to the position information and the image information.

Preferably, the location information includes angle information, altitude and distance information.

Compared with the prior art, the present invention has the following beneficial effects:

1. In the present invention, the test bracket device can be installed on the columns of different testing machines, and has universality;

2. The angle adjustment device, the height adjustment device, the distance adjustment device and the CCD lens in the present invention can be set as an integrated system, which can be fixed on the test bench device, and can conduct online real-time online real-time analysis for surface cracks of different cylinders or surface cracks of axisymmetric structures. Observed;

3. The computer terminal in the present invention is used for the acquisition of angle information, height information, distance information and crack front image during the crack propagation process; the software program can calculate and directly give the actual result of the crack length according to the acquired parameters.

4. The present invention can degenerate into a length measurement system in a common rectangular coordinate system by changing the angle adjustment device on the measurement bracket, or expand into a surface crack measurement system with other anomalous structures.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram of an on-line measurement system for cylinder surface cracks of the present invention.

Figure 2a is a schematic diagram of the cylinder structure with surface cracks; Figure 2b is a schematic diagram of the cross-sectional morphology and geometric parameters of the surface cracks under the action of fatigue loading.

Figure 3 is a schematic diagram of the crack measurement and calculation when the surface crack propagates in the cross-sectional direction of the cylinder.

Figure 4 is a schematic diagram of the crack length measurement and calculation when the surface crack propagates in any direction.

The figure shows:

11- Test machine column;

12- the chuck of the testing machine;

13- sample;

21-Connect the hoop;

22-Angle coordinate system measuring bracket;

23-Angle adjustment device;

24 is the height adjustment device;

25 - distance adjustment device;

26-CCD lens;

31 - Computer terminal.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

As shown in Figures 1 to 4, the on-line real-time measurement system for surface cracks of cylindrical structures provided according to the present invention includes a gantry support device, an angle adjustment device, a height adjustment device, a distance adjustment device, a CCD lens and a computer control terminal and calculation program;

Among them, the angle adjustment device, height adjustment device, distance adjustment device, and CCD lens can be integrated and fixed on the bench support; the bench support device is fixed with the column of the testing machine, and its distance and position can be adjusted;

The angle adjustment device is arranged at the center of the stand support device and is used to adjust the angle position of the CCD lens. The angle adjustment device is designed with an angle scale. angle;

The height adjustment device is installed on the slider of the angle adjustment device, and can move along the arc track together with the angle slider, and the height adjustment device can independently adjust the height of the CCD lens installed on the device at any angle position, and can adjust the height of the CCD lens. Real-time record altitude information;

The distance adjustment device is installed on the slider of the height adjustment device, which can arbitrarily adjust the front and rear positions of the CCD lens installed on it, and can record the front and rear distance information in real time;

The CCD lens is installed on the distance adjustment device to capture the image information of the surface crack and directly observe the leading edge position of the crack propagation;

The angle adjustment device, the height adjustment device, the distance adjustment device, and the angle information, height information, distance information and surface crack front edge image recorded by the CCD lens are connected to the computer control terminal and can be collected in real time;

The on-line real-time measurement system for surface cracks provided by the present invention further includes a first stepping motor and a first connecting shaft;

The first step motor is connected to the angle adjustment device through the first connection shaft; it is used to adjust the angle of the CCD lens mounted on the bracket by adjusting the angle adjustment device, so that the CCD lens can be adjusted between -90° and 90°. Crack observation in the ° range.

The angle adjustment device is driven by a stepping motor to rotate and is positioned by an angle displacement meter.

More specifically, the angle adjustment device 23 is installed and fixed on the angle coordinate system measurement bracket 22 together with the slider. The measuring bracket 22 is fixed between the two uprights 11 according to different types of testing machines. The angle adjustment device 23 generates a certain rotation through a stepping motor, and drives the height adjustment device 24 connected to the device through the connecting shaft to produce a precise angle of movement; and through the angle displacement meter connected to it, the instant angle information is determined and transmitted to the computer. Terminal 31.

The on-line measurement system for surface cracks provided by the present invention further includes a second driving motor and a second connecting shaft;

The second stepping motor is connected to the height adjusting device through the second connecting shaft, and is fixed on the angle adjusting device for adjusting the height device, and then adjusting the height of the CCD lens mounted on the bracket, so that the CCD lens can be adjusted at a certain level. Crack observation within the range such as 0 ~ 100mm;

More specifically, the height adjustment device 24 is fixed on the angle adjustment device 23, and can slide arbitrarily in the height direction through the slider, and the adjustment of its height position is driven by the second stepper motor and accurately positioned by the height displacement sensor to achieve The relative height position between the CCD lens 26 and the sample crack ensures that the surface crack is in the central area in the image of the CCD camera lens. The obtained altitude position information is immediately transmitted to the computer terminal 31 .

The on-line measurement system for surface cracks provided by the present invention further includes a third driving motor and a third connecting shaft;

The third stepping motor is connected to the distance adjusting device through a third connecting shaft, and is fixed on the height adjusting device; it is used to adjust the distance between the CCD lens and the sample to ensure that the image is focused clearly.

More specifically, the distance adjusting device 25 is fixed on the height adjusting device 24, and adjusts the distance between the CCD lens 26 and the sample 13 with surface cracks through the slider, so as to achieve the effect of clearly observing the crack front. The crack photo obtained by the CCD lens 26 can be immediately transmitted to the computer terminal 31 .

The driving of the first, second and third motors can be realized by the computer control terminal 31 connected with the driving motor through program software, so as to control parameters such as the angle position, height position and distance position of the CCD lens. The computer terminal 31 can also obtain the angle information, height information, distance information and picture information of the crack front in real time through the connected angle adjustment device 23, height adjustment device 24, distance adjustment device 25, and related sensors of the CCD camera 26.

The computer terminal 31 includes a program software system, which can instantly obtain the angle, height, distance and picture information of the crack front edge of the surface crack, and can also obtain the actual crack length and curve and other results in real time through the software program according to the above parameters.

When conducting an experiment in the on-line real-time measurement system for surface cracks of a cylindrical structure provided by the present invention, firstly, the measurement system provided by the present invention is connected with the test machine column connecting hoop 21 and the two end columns 11 of the test machine itself. The measuring bracket 22 is then mounted on the hoop and positioned. The angle adjustment device 23 , the height adjustment device 24 , the distance adjustment device 25 , and the CCD camera 26 can be integrated systems, which have been connected in advance and are directly fixed on the angle coordinate system measuring bracket 22 .

Before starting the experiment, the angle adjustment device 23 was used to adjust the angle position of the CCD lens 26, the height adjustment device 24 was used to adjust the height position of the CCD lens 26, and the distance adjustment device 25 was used to adjust the distance between the CCD lens 26 and the sample crack, Make sure that the crack tip of the specimen is exactly in the center area of the CCD lens 26 . Then, on the software program of the computer terminal 31, the parameter information such as angle, height, distance, etc. is cleared to zero.

Start the fatigue test program of the testing machine. After loading a certain number of fatigue times, the crack will expand forward for a certain distance. The position of the CCD camera 26 can be adjusted through the angle adjustment device 23, the height adjustment device 24, and the distance adjustment device 25 to ensure that the crack image is clear. The crack image is then saved in a computer software program, along with the associated angle, height and distance information. And use the software program provided by the present invention to automatically calculate the crack length.

The on-line real-time measurement system for the surface crack of the cylindrical structure provided by the invention can accurately measure the expansion path and expansion length of the surface crack of the circular section or the surface crack of the axisymmetric structure in any direction. And the relevant angle, height, distance information at any time, and the image of the crack front are collected and saved through the program software installed in the computer terminal. The software program provided by the present invention can also automatically calculate the surface crack length, draw a crack propagation curve, and the like.

In addition, the on-line real-time measurement system for surface cracks provided by the present invention is not limited to the measurement of surface cracks on cylinders. By modifying the angle adjustment device 23, it is possible to measure the surface cracks of any product and structure within the allowable size specification and load application conditions range of the test system of the present invention. It is also possible to convert the angle adjustment device 23 of the present invention into a rectangular coordinate adjustment device to degenerate into a general three-coordinate tool measurement microscope device.

The actual crack length calculation of the surface crack online real-time measurement system of the present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

Figure 2 presents the geometric parameter characteristics of the circular section specimen model with surface cracks. Under the action of fatigue load, the surface crack will continue to propagate until fracture. The simplest form of propagation is that the crack propagates in the direction of the cross section, as shown in Figure 2a. Usually, the cracks are in the form of symmetrical expansion, so only the length of one side needs to be measured when measuring the crack length. It can be seen from Fig. 2b that the initial crack length is the arc length L _OA0 , and when the fatigue loading reaches a certain number of times, the crack length is the arc length L _OA1 , and the crack length increases the arc length L _A0A1 .

First, by moving the position of the CCD camera through the angle adjustment device, the angles θ ₀ and θ ₁ can be accurately measured, as shown in FIG. 3 . At the initial time t ₀ of crack propagation, the crack length, that is, the arc length L _OA0 , can be obtained as:

When reaching t ₁ , the crack length L _OA1 can be obtained as:

Then the increase in crack length is the arc length L _A0A1 :

Then the total crack length extension is:

The crack propagation direction and length measurements for irregular arbitrary paths, as shown in Figure 4, can be calculated by reducing the time step and increasing the measurement frequency.

The increment of the crack length in the cross-sectional direction was first measured by reducing the time step, and its parameters are shown in Fig. 3. Since the length is small, it can be approximated as a chord length measurement, which is calculated by the following formula:

Δc ₀ =OA ₀ =Dsin(θ ₀ /2) (5)

Δc ₁ =A ₀ A ₁ =Dsin(θ ₁ /2) (6)

Then the increment of each crack propagation in the height direction can be directly measured by the height adjustment device, and the length of the first actual crack propagation can be calculated as:

Subsequent crack length calculation and so on, the total crack propagation length is calculated as:

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essential content of the present invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily, provided that there is no conflict.

Claims (10)

1. an on-line instant measurement system for the fatigue expansion of a cylindrical structure surface crack, is characterized in that, comprises a gantry support device, an adjustment device, a CCD lens and a computer control terminal, wherein: The CCD lens is arranged on the adjusting device, and the adjusting device can adjust the position of the CCD lens; the adjusting device is arranged on the stand support device; The computer control terminal is used for collecting the position information and image information obtained by the adjusting device and the CCD lens. 2. The on-line real-time measurement system for fatigue propagation of surface cracks on cylindrical structures according to claim 1, wherein the adjusting device comprises an angle adjusting device, a height adjusting device and a distance adjusting device, wherein: The angle adjustment device is arranged on a measuring bracket, and the angle adjustment device is used to adjust the angle position of the CCD lens; The height adjustment device is installed on the angle adjustment device, and the angle adjustment device is used to adjust the height position of the CCD lens; The distance adjustment device is arranged on the height adjustment device, and the distance adjustment device is used to adjust the distance between the CCD lens and the sample. 3. The on-line real-time measurement system for fatigue propagation of surface cracks in cylindrical structures according to claim 2, wherein the measurement support comprises a semicircular track, the central axis of the semicircular track and the position where the sample is located. Axes coincide. 4. The on-line instant measurement system for fatigue propagation of surface cracks of cylindrical structure according to claim 2, characterized in that, further comprising a first stepping motor and a first connecting shaft, wherein: The first step motor is connected to the angle adjusting device through the first connecting shaft, and drives the angle adjusting device to move on the measuring bracket. 5. The on-line instant measurement system for fatigue propagation of surface cracks in cylindrical structures according to claim 2, characterized in that, further comprising a second driving motor and a second connecting shaft, wherein: The second stepping motor is connected to the height adjusting device through a second connecting shaft, and is fixed on the angle adjusting device for adjusting the height position, thereby adjusting the height of the CCD lens. 6. The on-line instant measurement system for fatigue propagation of surface cracks in cylindrical structures according to claim 2, characterized in that, further comprising a third driving motor and a third connecting shaft, wherein: The third stepping motor is connected to the distance adjusting device through a third connecting shaft, and is fixed on the height adjusting device for adjusting the distance between the CCD lens and the sample. 7. The on-line real-time measurement system for fatigue propagation of surface cracks in cylindrical structures according to claim 2, wherein the angle adjustment device further comprises an angle displacement meter, and the angle displacement meter is used to measure the rotation of the angle adjustment device. angle and send it to the computer to control the terminal. 8 . The on-line instant measurement system for fatigue propagation of surface cracks in cylindrical structures according to claim 1 , further comprising a test machine column, and the adjustment device is arranged on the test machine column through a connecting hoop. 9 . 9. A measurement method based on the on-line instant measurement system of the fatigue propagation of cylinder structure surface cracks described in any one of claims 1-8, is characterized in that, comprises the steps: Assembly steps: Assemble the adjustment device, install the sample on the bench support device, and clear the parameter information at the computer terminal; Test steps: Adjust the position of the CCD lens through the adjustment device to ensure that the crack tip of the sample is just in the center area of the CCD lens; Collection and calculation steps: collect position information and image information to the computer terminal, and the computer terminal calculates the crack length of the sample according to the position information and image information. 10 . The on-line instant measurement method for fatigue propagation of surface cracks on cylindrical structures according to claim 9 , wherein the position information includes angle information, height and distance information. 11 .