CN111982005A - A three-dimensional deformation field measurement device - Google Patents

Abstract

A three-dimensional deformation field measurement device, the main structure of the measurement device includes a light splitting path system and a camera system; the light splitting path system is composed of an LED light source, a left plane mirror, a right plane mirror, a double prism, and a light splitting path integrated shell; the camera The system is composed of a camera lens, a CCD camera, a camera casing, and an electrical wire outlet; in the light splitting system, the left plane mirror is located inside the left side of the light splitter integrated shell, the right plane mirror is located inside the right side of the light splitter integrated shell, and the double prism is located in the The LED light source is located between the left plane mirror and the right plane mirror, and the LED light source is located in the middle of the rectangular outer frame of the light splitter integrated shell; the CCD camera in the camera system is located at the rear of the camera shell and is connected to the camera shell through screws; the camera lens is directly connected to the CCD through threads The camera is connected, the wire outlet is located on the outer left side of the camera shell, and the light splitter integrated shell is connected with the camera shell by screws. The present invention can realize the three-dimensional measurement of single-camera binocular vision measurement, and can be realized without the need to be equipped with traditional dual cameras.

Description

A three-dimensional deformation field measurement device

technical field

The invention belongs to the technical field of aircraft structural strength evaluation, and in particular relates to an integrated three-dimensional deformation field measurement device in the mechanical-thermal composite environmental test technology.

Background technique

When the aircraft is flying at hypersonic speed, the temperature of its large-area heat-proof structure can reach 1200 °C, and the temperature of the end, leading edge and other parts is higher, the noise load caused by separation flow and shock wave impact can reach 165dB, and it is also faced with severe vibration environment. In order to adapt to the harsh service environment, a large number of new heat-resistant and load-bearing integrated materials represented by C/C and C/SiC are used in the structure of hypersonic aircraft. Carrying out mechanical and thermal tests such as thermal strength, vibration/thermal vibration, noise/thermal noise, etc. on the aircraft cabin, wing rudder, and the whole system, to evaluate and verify the structural design and bearing capacity, is a key link that must be carried out in the development process of hypersonic aircraft. Radiation heating is often used to simulate the thermal environment in the ground mechanothermal test of aircraft structures. Environments such as high temperature, strong light radiation, vibration and strong noise have brought great difficulties to the test measurement. Parameters such as temperature, displacement, strain, acceleration, etc. need to be measured in the mechanical and thermal test of aircraft structure.

The contact displacement test method represented by the contact displacement meter has problems such as difficulty in thermal protection of equipment and only single-point displacement test. way. Among them, the digital image correlation method is the latest research direction of the non-contact optical measurement method. However, the non-contact measurement of the thermal deformation of the component under the radiation heating method encounters the problem that the radiation heater blocks the optical path of the digital image optical test system. The digital imaging equipment relies on multi-camera and large-angle shooting, and cannot be directly installed in the aircraft cabin to complete the measurement. The establishment of a high-temperature deformation test method that can be placed in a small space such as the aircraft cabin makes it possible to measure the deformation of high-temperature structures from the inside.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a single-camera 3D digital image-related surface deformation field test miniaturization device suitable for local space inside the high temperature composite material structure in response to the ground test environment and the local deformation field test requirements of the high temperature composite material test piece.

The present invention adopts the following technical solutions: a three-dimensional deformation field measurement device, the main structure of the measurement device includes a light splitting path system and a camera system; The camera system is composed of a camera lens, a CCD camera, a camera casing, and a wire outlet; the left plane mirror in the light splitter system is located inside the left side of the light splitter integrated shell, and the right plane mirror is located on the right side of the light splitter integrated shell Inside, the double prism is located between the left plane mirror and the right plane mirror, and the LED light source is located in the middle of the rectangular outer frame of the light splitter integrated shell; the CCD camera in the camera system is located at the rear of the camera shell, and is connected to the camera shell through screws; The camera lens is directly connected with the CCD camera through threads, the wire outlet is located on the left outside of the camera casing, and the optical splitter integrated casing is connected with the camera casing through threads.

Further, the measurement device further includes a thermal protection system, which is located outside the measurement device and is composed of a water cooling system and an air cooling system. The water cooling system includes a water cooling housing a, a water cooling housing b and a water cooling housing c, and a water cooling cycle. The inlet, the water-cooling circulation outlet, and the guide vane. The water enters the water-cooled casing c, the water-cooled casing b, and the water-cooled casing a in turn from the water-cooled circulation inlet. Including the air-cooled circulation inlet, air inlet pipe, air outlet pipe, and air-cooled circulation outlet. Nitrogen enters the interlayer of the optical splitter integrated casing from the air-cooled circulation inlet through the gas inlet pipe, from the air hole at the other end of the optical splitter integrated casing, and from the gas through the gas outlet pipe. The cold circulation outlet is discharged, and the air cooling system cools the transflective filter; the front end of the light splitter integrated shell and the front end of the water cooling shell a are connected by a circle of screws; the light splitter integrated shell and the camera shell are connected by screws; The rear end of the camera housing is connected with the rear end of the water-cooled housing b by positioning screws; the rear end of the water-cooled housing a and the front end of the water-cooled housing b are connected by a circle of screws; the rear end of the water-cooled housing b and the water-cooled housing c are connected by A circle of screw connections.

Further, the LED light source 1 is a blue light source, and the wavelength of the light source is 450 nm.

Further, the light splitting path system further includes a semi-reflecting and semi-reflecting lens, and the semi-reflecting lens is located outside the LED light source; the camera system further includes a narrow-band filter, and the narrow-band filter is directly installed on the camera lens, The central wavelength is 450nm and the bandwidth is 20nm.

Further, the measuring device uses a network cable to go out from the cable outlet through the wire outlet, and is connected to a graphics workstation for testing, and requires a power supply to work.

Further, the measurement test process of the measurement device includes the following steps:

1) The parameters of the measuring device are calibrated in advance;

2) Check the power supply and thermal protection system of the measuring device, and troubleshoot;

3) Apply a small voltage of 20V to the heater, debug the heating system, and check whether the measuring device is normal;

4) Debug the heater temperature control ability, and determine the PID parameters corresponding to each temperature rise rate;

5) Place the measuring device at a position 10cm from the measured object and fix it through the mounting hole;

6) Debug the measuring device;

7) At the beginning of the test, the temperature is increased at a constant rate, and the measuring device performs image acquisition at a constant acquisition frequency;

8) After the image acquisition at different temperatures ends, the test ends;

9) Calculate the deformation field by passing the collected image through the digital image algorithm.

Further, the step 1 also includes the following specific steps:

①Select the appropriate size of flat checkerboard or flat dot calibration plate;

② Collect a series of images of calibration plate translation, in-plane rotation and out-of-plane rotation;

③The collected picture is divided into left and right parts, and the image containing the left and right parts is divided into two pictures;

④ Carry out the calibration operation on the two pictures to determine the calibration parameters of the measuring device, so as to complete the calibration procedure.

Further, the step 9 also includes the following specific steps:

① Take a collected image of the measured object in the unloaded state as the initial image, and then collect a series of images of the measured object at different temperatures as the deformed image;

② Divide the collected image containing the left and right parts into two pictures, the left image and the right image, and treat the right image part in the left image as none; take the left image part in the right image deemed to be none;

③ According to the calibration parameters, perform image reconstruction operation and displacement field operation on the images imaged by the left image and the right image;

④ Calculate the strain field according to the difference of the displacement field.

The beneficial effects of the present invention are:

1) The optical path construction method of the double prism, the plane mirror and the single camera of the present invention can realize the three-dimensional measurement of the binocular vision measurement of the single camera, and can be realized without being equipped with the traditional dual cameras. This method not only saves the cost, but also reduces the traditional binocular vision. The relative position adjustment of the camera of the imaging system saves the construction and adjustment time of the optical path, and can be used directly without on-site adjustment.

2) In order to avoid the interference of strong stray light and the influence of the thermal radiation of the radiant heater on the quality of the collected images, a narrow-band filter is added in front of the lens and is equipped with an illumination light source of the same wavelength band, and a semi-reflective and semi-transmissive wave plate is equipped in the equipment shell to achieve all The projection of the wavelength light is required, and the reflection of the remaining wavelength light is required.

3) In the present invention, the light source is placed in the middle, and the mirror and the semi-reflective and semi-transmissive mirror are placed on both sides. Compared with the scheme in which the light source is placed around the mirror and the semi-reflective and semi-transparent mirror covers the entire front end of the lens, it is avoided that the light source passes through the semi-reflective and semi-transparent mirrors. The influence of the stray light produced by the perspective lens on the quality of the captured images.

4) After the invention integrates the single-camera three-dimensional deformation measurement system with the light source and the thermal protection system, the final size of the device is only 13cm×12cm×9cm, which can be placed inside the high-temperature composite material test piece to locally deform or damage the key parts. For monitoring, it breaks through the limitation that the traditional digital image correlation method cannot collect images under the surrounding heating of the radiant heater and thus cannot realize the measurement.

5) The integrated design scheme of the thermal protection and the main body of the device designed by the present invention further reduces the final size of the device than the separate design of the device and the thermal protection. The thin semi-reflector and semi-mirror are cooled by nitrogen gas, so that the semi-reflector and semi-lens can withstand high temperature. Compared with no air-cooling protection, only by increasing the thickness of the semi-reflector and semi-lens, the size of the device direction is reduced and the occurrence of excessive thickness of the lens is reduced. stray light interference and image distortion.

6) After integrating the traditional dual-camera digital image correlation test system, the present invention does not need to perform work such as camera calibration before each measurement. On the basis of a fixed focal length, one calibration and multiple measurements are realized, which solves the problem of the narrow internal space of the material structure. Problems that cannot be calibrated.

7) The application scope of the present invention is not limited to the measurement of the local deformation field inside the test piece in the environment surrounded by the radiant heater, but also can be placed in any small space under normal temperature and high temperature environment for local measurement.

Description of drawings

1 is a side view of the main structure of a three-dimensional deformation field measurement device;

2 is a top view of the main structure of a three-dimensional deformation field measurement device;

3 is a side view of a thermal protection structure of a three-dimensional deformation field measurement device;

4 is a top view of a thermal protection structure of a three-dimensional deformation field measurement device;

Fig. 5 The strain field distribution along the beam length direction of the standard test piece of four-point bending beam at room temperature;

Figure 6. Comparison of the measurement results of a three-dimensional deformation field measurement device with the normal temperature strain gauge;

Among them, 1-LED light source, 2-semi-mirror mirror, 3-left plane mirror, 4-right plane mirror, 5-biprism, 6-light splitter integrated shell, 7-lens, 8-CCD camera, 9-wire outlet, 10-Narrowband filter, 11-Camera housing, 12-Water cooling housing a, 13-Water cooling housing b, 14-Water cooling housing c, 15-Water cooling circulation inlet, 16-Water cooling circulation outlet, 17-Air cooling circulation inlet, 18- Air-cooled circulation inlet and outlet, 19-cable outlet, 20- guide vane, 21-air inlet pipe, 22-air outlet pipe.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Aiming at the requirement of local deformation field test inside the high temperature composite material test piece under the surrounding heating of the radiant heater, the present invention proposes a three-dimensional deformation prevention and heat insulation integration based on the binocular vision principle and the digital image correlation method using a single camera and a beam splitter. Field test miniaturized devices.

A three-dimensional deformation field measurement device, as shown in Figure 1 and Figure 2, includes a thermal protection structure and a main body structure; wherein the main body structure includes a light splitting path system and a camera system, and the light splitting path system consists of an LED light source 1, a half mirror and a half mirror 2. The left plane mirror 3, the right plane mirror 4, the double prism 5, and the light splitter integrated shell 6 are composed; the camera system is composed of a camera lens 7, a CCD camera 8, a narrowband filter 10, a camera shell 11, and a wire outlet 9; the light splitter path is composed of In the system, the left plane mirror 3 is located inside the left side of the beam splitter integrated shell 6, the right plane mirror 4 is located inside the right side of the beam splitter integrated shell 6, the biprism 5 is located between the left plane mirror 3 and the right plane mirror 4, and the LED light source 1 is located in the beam splitter integrated shell 6. The middle position of the rectangular outer frame of the shell 6 (the rectangular grid area in the top view), the half mirror 2 is in the outer position of the LED light source 1 (the rectangular light gray area in the top view); in the camera system, the CCD camera 8 is located in the camera casing The rear part of 11 is connected with the camera shell by screws; the camera lens 7 is directly connected with the CCD camera 8 through threads, the narrow-band filter 10 is directly installed on the camera lens 7, and the wire outlet 9 is located on the left side of the camera shell 11. The integrated housing 6 is connected with the camera housing 11 by screws.

The thermal protection system is located outside the measuring device and is used to protect the measuring device from working in a high temperature environment, as shown in Figure 3 and Figure 4; the thermal protection system is composed of a water cooling system and an air cooling system, and the water cooling system It consists of a water-cooled casing a12, a water-cooled casing b13, a water-cooled casing c14, a water-cooled circulation inlet 15, a water-cooled circulation outlet 16, and a guide plate 20. The water-cooling system mainly cools the main structure by using the guide vane 20 to divide the water into two parts: the inlet and the outlet. , Nitrogen enters the interlayer of the optical splitter integrated casing 6 from the air-cooled circulation inlet 17 through the gas inlet pipe 21, from the air hole at the other end of the optical splitter integrated casing 6, and is discharged from the air-cooled circulation outlet 18 through the gas outlet pipe 22, and the air-cooled system is half Anti-transflective filter 2 for cooling;

The front end of the light splitter integrated shell 6 is connected with the front end of the water cooling shell a12 by a circle of screws; the light splitter integrated shell 6 is connected with the camera shell 11 by screws; the rear end of the camera shell 11 is connected with the water cooling shell b13 The rear end Connected by positioning screws; the rear end of the water-cooled housing a12 and the front end of the water-cooled housing b13 are connected by a circle of screws; the rear end of the water-cooled housing b13 and the water-cooled housing c14 are connected by a circle of screws.

The LED light source 1 is a blue light source with a wavelength of 450 nm.

Further, in order to avoid the influence of thermal radiation on the quality of the collected images, a half-reflection lens 2 is added to the measuring device, and a narrow-band filter 10 is added in front of the camera lens 7, with a central wavelength of 450 nm and a bandwidth of 20 nm.

The light on the surface of the object to be measured is reflected on the left plane mirror 3 and the right plane mirror 4, and the light reflected by the left plane mirror 3 and the right plane mirror 4 is reflected on the left and right sides of the double prism 5 respectively; The light reflected by the plane mirror 3 and the right plane mirror 4 are respectively imaged on the sensor plane after passing through the photosensitive lens. In reality, there are two images presented by the image sensor. The light reflected by the left plane mirror 3 becomes a "left image". The light reflected by the object through the right plane mirror 4 becomes a "right image".

The test principle of the single-camera three-dimensional deformation field test device based on the digital correlation method is to directly create high-temperature random speckle on the surface of the object to be tested, and the image sensor collects images with speckle information, and uses techniques such as filtering and image reconstruction. Then, the three-dimensional digital image correlation algorithm is used to calculate the surface deformation field of the test piece.

The measuring device uses a network cable to go out from the cable outlet 19 through the wire outlet 9, and is connected to a graphics workstation for testing, and requires a power supply to work.

The specific implementation steps are as follows:

1) Pre-calibration of measuring device parameters:

①Choose a flat checkerboard or flat dot calibration board of the appropriate size; ②Collect a series of images of the calibration board translation, in-plane rotation and out-of-plane rotation; ③The collected picture is divided into two parts: The images of the two parts are divided into two pictures; 4. Carry out the calibration operation on the pictures that are divided into "left" and "right" to determine the calibration parameters of the measuring device, so as to complete the calibration procedure;

2) Check the power supply and thermal protection system of the measuring device, and troubleshoot;

3) Apply a small voltage of 20V to the heater, debug the heating system, and check whether the measuring device is normal;

4) Debug the heater temperature control ability, and determine the PID parameters corresponding to each temperature rise rate;

5) Place the measuring device at a position 10cm from the measured object and fix it through the mounting hole;

6) Debug the measuring device;

7) At the beginning of the formal test, the temperature is increased at a constant rate, and the device invented in this paper is used to perform image acquisition at a constant acquisition frequency;

8) After the image acquisition at different temperatures ends, the test ends;

9) Calculate the deformation field of the collected image through the digital image correlation algorithm. The specific steps are as follows: 1. Take the collected image of the unloaded object as the initial image, and then collect a series of different measured objects. A series of images under the temperature are regarded as deformed images; ② The collected images containing the left and right parts are divided into two pictures, that is, the right image part in the "left image" is regarded as none; The left part of the image is regarded as none; ③According to the calibration parameters, perform image reconstruction operation and displacement field operation on the images imaged by "left" and "right"; ④ Calculate the strain field according to the difference of the displacement field.

In the embodiment, the strain field distribution of the four-point bending beam standard test piece at room temperature along the beam length direction is shown in Figure 5, and Figure 6 is the comparison between the measured results of the measuring device and the normal temperature strain gauge, and the data collected at different temperatures were collected. The digital image is subjected to digital image correlation calculation, and the deformation field at different temperatures can be obtained.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or some or all of the technical features thereof are equivalently replaced; these modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. A three-dimensional deformation field measurement device, characterized in that the main structure of the measurement device comprises a light splitting system and a camera system; the light splitting system is integrated by an LED light source, a left plane mirror, a right plane mirror, a double prism, and a split light path. The camera system is composed of a camera lens, a CCD camera, a camera casing, and a wire outlet; the left plane mirror in the light splitter system is located inside the left side of the light splitter integrated shell, and the right plane mirror is located inside the right side of the light splitter integrated shell , the double prism is located between the left plane mirror and the right plane mirror, and the LED light source is located in the middle of the rectangular outer frame of the light splitter integrated shell; the CCD camera in the camera system is located at the rear of the camera shell and is connected with the camera shell through screws; The lens is directly connected with the CCD camera through threads, the wire outlet is located on the left outside of the camera casing, and the optical splitter integrated casing is connected with the camera casing through threads. 2 . The measuring device according to claim 1 , wherein the measuring device further comprises a thermal protection system, the thermal protection system is located outside the measuring device, and is composed of a water cooling system and an air cooling system, and the water cooling system includes a water cooling system. 3 . Shell a, water-cooled shell b, water-cooled shell c, water-cooled circulation inlet, water-cooled circulation outlet, and guide vanes. The inlet and outlet are circulated; the air cooling system includes an air cooling circulation inlet, an air inlet pipe, an air outlet pipe, and an air cooling circulation outlet. Nitrogen enters the interlayer of the optical splitter integrated shell from the air cooling circulation inlet through the gas inlet pipe. The air hole at the other end of the optical splitter integrated shell is discharged from the air-cooling circulation outlet through the air outlet pipe, and the air-cooling system cools the transflective and semi-permeable filter; the front end of the optical splitter integrated shell and the front end of the water-cooled shell a are connected by a circle of screws; The optical splitter integrated shell is connected with the camera shell through threads; the rear end of the camera shell is connected with the rear end of the water-cooled shell b through positioning screws; the rear end of the water-cooled shell a and the front end of the water-cooled shell b are connected by a circle of screws; The rear end of the water-cooled housing b is connected with the water-cooled housing c through a circle of screws. 3 . The measuring device according to claim 1 , wherein the LED light source 1 is a blue light source, and the wavelength of the light source is 450 nm. 4 . 4 . The measuring device according to claim 1 , wherein the optical splitting path system further comprises a semi-reflecting and semi-reflecting lens, and the semi-reflecting and semi-reflecting lens is located outside the LED light source; and the camera system further includes a narrow-band filter. 5 . , the narrow-band filter is directly installed on the camera lens, the center wavelength is 450nm, and the bandwidth is 20nm. 5 . The measuring device according to claim 1 , wherein the measuring device uses a network cable to go out from the cable outlet through the wire outlet, and is connected to a graphics workstation for testing, and requires power supply to work. 6 . 6. The measurement device according to claim 1, wherein the measurement test process of the measurement device comprises the following steps: 1) The parameters of the measuring device are calibrated in advance; 2) Check the power supply and thermal protection system of the measuring device, and troubleshoot; 3) Apply a small voltage of 20V to the heater, debug the heating system, and check whether the measuring device is normal; 4) Debug the heater temperature control ability, and determine the PID parameters corresponding to each temperature rise rate; 5) Place the measuring device at a position 10cm from the measured object and fix it through the mounting hole; 6) Debug the measuring device; 7) At the beginning of the test, the temperature is increased at a constant rate, and the measuring device performs image acquisition at a constant acquisition frequency; 8) After the image acquisition at different temperatures ends, the test ends; 9) Calculate the deformation field by passing the collected image through the digital image algorithm. 7. The measuring device according to claim 6, wherein the step 1 further comprises the following specific steps: ①Select the appropriate size of flat checkerboard or flat dot calibration plate; ② Collect a series of images of calibration plate translation, in-plane rotation and out-of-plane rotation; ③The collected picture is divided into left and right parts, and the image containing the left and right parts is divided into two pictures; ④ Carry out the calibration operation on the two pictures to determine the calibration parameters of the measuring device, so as to complete the calibration procedure. 8. The measuring device according to claim 6, wherein the step 9 further comprises the following specific steps: ① Take a collected image of the measured object in the unloaded state as the initial image, and then collect a series of images of the measured object at different temperatures as the deformed image; ② Divide the collected image containing the left and right parts into two pictures, the left image and the right image, and treat the right image part in the left image as none; take the left image part in the right image deemed to be none; ③ According to the calibration parameters, perform image reconstruction operation and displacement field operation on the images imaged by the left image and the right image; ④ Calculate the strain field according to the difference of the displacement field.

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