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CN-121994786-A - Double-light path nuclear graphite damage evolution and crack propagation whole-process deformation field measurement method

CN121994786ACN 121994786 ACN121994786 ACN 121994786ACN-121994786-A

Abstract

A dual-light path nuclear graphite damage evolution and crack propagation whole-process deformation field measurement method comprises the steps of setting a fracture trigger mechanism, setting a low-speed high-resolution camera to continuously collect full cycles, capturing crack images through the high-speed low-resolution camera when trigger conditions are met, solving a global high-precision deformation field of the surface of a test piece in the full cycles through a digital image correlation method (PINN-DIC) based on a physical information neural network, identifying a damage characteristic area, solving a displacement field of the high-speed fracture process of the surface of the test piece through the PINN-DIC, extracting crack core parameters, combining strain distribution evolution characteristics and crack initiation positions, mapping high-speed fracture information to a main coordinate system, and building a cross-scale correlation mechanism. According to the method, the accurate measurement and trans-scale data penetration of the nuclear graphite damage evolution-fracture failure full-period deformation field are realized, the deformation field measurement precision of a boundary area and a crack neighborhood is remarkably improved, and a key technical support is provided for analysis of a nuclear graphite fracture mechanism.

Inventors

  • LI XIAOHAO
  • YI YANAN
  • MA SHAOPENG
  • ZHOU SHICHAO

Assignees

  • 上海交通大学
  • 中核能源科技有限公司

Dates

Publication Date
20260508
Application Date
20260116

Claims (10)

  1. 1. The method for measuring the deformation field in the whole process of dual-light path nuclear graphite damage evolution and crack propagation is characterized by comprising the following steps of: step 1, adjusting the working distance of a camera, selecting the focal length of a lens, and using cross laser to assist in calibrating the spatial position of a double light path; step 2, calibrating through a checkerboard calibration plate, and solving a transformation matrix of the two-camera coordinate system; Step 3, establishing a background gray level reference, calibrating a trigger threshold value and constructing a fracture trigger mechanism; step 4, continuously acquiring full cycles through a low-speed high-resolution camera, and capturing crack images through the high-speed low-resolution camera when the triggering condition is met; Step 5, solving a global high-precision deformation field of the surface of the test piece in the whole loading period through a digital image correlation method (PINN-DIC) based on a physical information neural network, identifying a damage characteristic region, and simultaneously solving a displacement field of the high-speed fracture process of the surface of the test piece through PINN-DIC to extract crack core parameters; And 6, combining strain distribution evolution characteristics and crack initiation positions, mapping high-speed crack information to a main coordinate system, and establishing a cross-scale correlation mechanism.
  2. 2. The method for measuring the deformation field in the whole process of the damage evolution and crack propagation of the double-light-path nuclear graphite is characterized by comprising the following steps of 1, constructing a double-light-path imaging module, namely sequentially placing a cube light-splitting prism and a low-speed high-resolution camera in front of a nuclear graphite test piece to be observed to form a first light path, and simultaneously placing a high-speed low-resolution camera in the direction perpendicular to the first light path on the cube light-splitting prism to form a second light path.
  3. 3. The method for measuring the deformation field of the dual-light path nuclear graphite damage evolution and crack propagation overall process according to claim 2, wherein the surface target observation Area (AOI) size of the nuclear graphite test piece to be observed is as follows Target surface size of two cameras The method meets the following conditions: Obtaining the magnification Then, the working distance of the camera Image distance And lens focal length The relation of (a), i.e.) Obtaining 。
  4. 4. The method for measuring the deformation field in the whole process of dual-light-path nuclear graphite damage evolution and crack propagation as claimed in claim 2 is characterized in that when the spatial positions of the two cameras and the cubic beam splitter prism are adjusted, cross laser is respectively emitted to a preset light path in three directions by using a laser level meter, the spatial postures of the cameras and the cubic beam splitter prism are assisted to be calibrated, the coaxiality and the verticality of the dual light paths are ensured, a black reinforced carbon fiber material is selected to process a packaging container and a shading cylinder of the cubic beam splitter prism, and reserved holes adapting to the aperture of the lenses are respectively formed on the side faces of the two cameras and extend outwards to form a light path channel, so that the invasion of ambient stray light is effectively blocked, and the imaging signal-to-noise ratio and the gray signal stability are ensured.
  5. 5. The method for measuring the deformation field in the whole process of the damage evolution and the crack propagation of the double-light path nuclear graphite according to claim 1, wherein the step 2 is characterized in that a low-speed high-resolution camera image pixel coordinate system is used as a main coordinate system ) The high-speed low-resolution camera image pixel coordinate system is a secondary coordinate system ) Placing a checkerboard calibration plate (or a mark point array) in a common effective observation view field of a double camera, and extracting angular point coordinates in a main coordinate system image and a secondary coordinate system image by utilizing a Harris angular point detection algorithm, wherein the method specifically comprises the following steps of: wherein the coordinates of the corner points of the main coordinate system are% ) The coordinates of the corresponding angular points of the auxiliary coordinate system are% ), 、 、 、 For the amount related to rotation and scaling, 、 Is the translation amount.
  6. 6. The method for measuring the deformation field of the whole process of the dual-light path nuclear graphite damage evolution and crack propagation according to claim 1, wherein the step 3 specifically comprises the following steps: 3.1 based on static image before loading nuclear graphite, establishing background gray scale reference matrix by multiple time sequence average method, specifically, collecting before loading Frame static image, background gray scale reference matrix is constructed by point-by-point pixel time sequence averaging method Wherein: Is the first The gray matrix of the frame still image, Corresponding to the pixel row and column coordinates of the image, In a reference matrix Gray values of the position pixels; 3.2 generating a real-time gray level difference matrix by pixel-by-pixel differential operation in the experiment process Wherein: is a low-speed high-resolution camera The gray moment of the image acquired in real time by the frame, the nuclear graphite only generates tiny displacement on the surface at the initial loading stage, no obvious morphological change on the surface, the gray distribution gently fluctuates, The absolute values are smaller and are all in a low-level threshold range, and the high-speed low-resolution camera maintains a state to be triggered; 3.3 after the crack is initiated and expanded, the gray scale of the surface of the test piece is suddenly changed, and the crack area presents gray scale characteristics close to a pure black background, so that Is obviously negative, and the absolute value greatly exceeds the low level threshold value, so as to form a characteristic trigger signal representing the breaking behavior, when continuously In the difference matrix of the frame, the pixel duty ratio exceeding the preset high level threshold value Monitoring the effective duty cycle of an area The trigger path is switched to a stable high level, and the high-speed low-resolution camera immediately starts acquisition.
  7. 7. The method for measuring a deformation field in the whole process of dual-light path nuclear graphite damage evolution and crack propagation as claimed in claim 1, wherein said step 4, when the gray level change satisfies the trigger condition in S3, starts the high-speed low-resolution camera at the frame rate The continuous acquisition time length meets the following conditions: And Wherein: In order to estimate the maximum crack length, In order to estimate the maximum crack growth rate, The minimum number of effective image frames required to characterize the crack growth overall process.
  8. 8. The method for measuring a deformation field in the whole process of dual-light path nuclear graphite damage evolution and crack propagation as set forth in claim 1, wherein the global deformation field measurement and damage characteristic identification means that an image coordinate domain is input based on a Physical Information Neural Network (PINN), a displacement field is obtained by prediction, and the PINN is used for predicting a deformed image And actual deformed image As a loss function, specifically: iterative optimization of parameters through a fully connected network, minimizing a loss function, and realizing training, wherein: To calculate the total number of pixels, the process solves the problem of calculation distortion of the traditional DIC at the boundary of the test piece, and outputs the global displacement field to PINN by means of the automatic differentiation function of the deep learning frame Performing differential operation without additional numerical differential processing to obtain direct deduction 、 Positive strain in direction Shear strain The components, through the spatial distribution and the time evolution characteristics, define the strain concentration area as the damage characteristic area of the nuclear graphite, and define the accumulated spatial position and the development trend of the damage; The PINN-DIC performs fine analysis, namely, inputting a coordinate domain of a high-speed low-resolution image into a full-connection network, predicting to obtain a local displacement field corresponding to the high-speed low-resolution image, wherein the full-connection network adopts a gray consistency hypothesis as a loss function, training is realized by iteratively optimizing parameters to the convergence of the loss function, the problem of information deletion of a traditional DIC in a crack area is effectively avoided, core fracture parameters such as crack tip positions, expansion tracks, local deformation characteristics and the like are accurately extracted, and instantaneous fracture characteristic data is provided for subsequent association mechanism analysis.
  9. 9. The dual-light path nuclear graphite damage evolution and crack propagation whole-process deformation field measurement method according to claim 1 is characterized in that step 6 is based on a main-auxiliary coordinate system conversion matrix established in step 2, crack initiation coordinates and propagation tracks extracted by carrying out refined analysis on PINN-DIC are accurately mapped to a strain field coordinate system for global deformation field measurement and calculation and damage characteristic identification, spatial alignment of dual-light path data is achieved, the correspondence between crack initiation and propagation positions and an early strain concentration region in a low-speed high-resolution image is clarified, and finally the correlation characteristic of 'strain concentration accumulation-crack initiation and propagation' is established, so that experimental basis is provided for cross-scale mechanism analysis of nuclear graphite 'long-term damage evolution-instant fracture failure'.
  10. 10. A deformation field measurement system for realizing the dual-light path nuclear graphite damage evolution and crack propagation whole process of the method in any one of claims 1-9 is characterized by comprising a light splitting imaging module, a trigger adaptation module, a calibration module and a deformation analysis module, wherein the light splitting imaging module is used for realizing the spatial matching of an instantaneous fracture area captured by the high-speed low-resolution camera and a long-time deformation field recorded by the low-speed high-resolution camera through long-time global deformation observation to completely record the damage evolution and strain concentration process of a test piece from loading to before fracture, and is used for precisely recording the instantaneous dynamic behavior of crack initiation and propagation through short-time high-dynamic capture by the high-speed low-resolution camera; The light splitting imaging module comprises a low-speed high-resolution camera, a high-speed low-resolution camera and a cubic light splitting prism, wherein the cubic light splitting prism is arranged right in front of the nuclear graphite test piece, uniformly divides reflected light on the surface of the nuclear graphite test piece into two beams and guides the two beams to the low-speed high-resolution camera and the high-speed low-resolution camera respectively; The deformation analysis module comprises a control unit and a digital image correlation unit, wherein the control unit respectively constructs a data transmission link with a low-speed high-resolution camera and a high-speed low-resolution camera to synchronously control acquisition parameters of the two cameras, stores acquired full-period deformation images and instantaneous crack images in a classified mode according to time stamps and outputs the acquired full-period deformation images and instantaneous crack images to the digital image correlation unit, and the digital image correlation unit respectively carries out global high-precision strain field analysis and damage characteristic region identification on the loaded full-period images acquired by the low-speed high-resolution camera to quantify a nuclear graphite damage accumulation process, and carries out local displacement field solving and crack core parameter extraction on the instantaneous crack images acquired by the high-speed low-resolution camera to characterize failure fracture dynamic behaviors.

Description

Double-light path nuclear graphite damage evolution and crack propagation whole-process deformation field measurement method Technical Field The invention relates to a technology in the field of optical damage fracture test, in particular to a method for measuring a deformation field in the whole process of dual-light path nuclear graphite damage evolution and crack propagation. Background The nuclear graphite is used as a key structural material of an advanced nuclear energy system, and the damage evolution and fracture failure are directly related to the operation safety of the reactor. To ensure the long-term stable operation of the reactor, the full-period behavior rule of nuclear graphite from the initiation and accumulation of damage to fracture failure needs to be accurately mastered, and the analysis of the rule is highly dependent on the support of a reliable observation technology. However, the prior art has the remarkable limitation that the full-period observation capability of a cross-time scale is lacking, and key data of progressive damage and instantaneous fracture of a material are difficult to penetrate. Deep analysis of a nuclear graphite damage-fracture association mechanism is restricted, and an observation system which combines full-period coverage and high-precision measurement is needed. Disclosure of Invention Aiming at the problems that the prior art lacks collaborative analysis association of double-time data sources, cannot simultaneously cover the complete observation requirement of long-time damage evolution and instantaneous crack propagation, the inconsistent reference of image data collected by different cameras and the insufficient measurement resolution and spatial resolution of deformation fields in the damage evolution and crack propagation, the invention provides a deformation field measurement method in the whole process of double-light-path nuclear graphite damage evolution and crack propagation, and the deformation field measurement precision of boundary areas and crack neighborhood is obviously improved. The invention is realized by the following technical scheme: The invention relates to a method for measuring a deformation field in the whole process of dual-light path nuclear graphite damage evolution and crack propagation, which comprises the following steps: step 1, adjusting the working distance of a camera, selecting the focal length of a lens, and using cross laser to assist in calibrating the spatial position of a double light path; step 2, calibrating through a checkerboard calibration plate, and solving a transformation matrix of the two-camera coordinate system; step3, establishing a background gray level reference, calibrating a trigger threshold value, and constructing a high-speed low-resolution camera fracture trigger mechanism; step 4, continuously acquiring full cycles through a low-speed high-resolution camera, and capturing crack images through the high-speed low-resolution camera when the triggering condition is met; Step 5, solving a global high-precision deformation field of the surface of the test piece in the whole loading period through a digital image correlation method (PINN-DIC) based on a physical information neural network, identifying a damage characteristic region, and simultaneously solving a displacement field of the high-speed fracture process of the surface of the test piece through PINN-DIC to extract crack core parameters; And 6, combining strain distribution evolution characteristics and crack initiation positions, mapping high-speed crack information to a main coordinate system, and establishing a cross-scale correlation mechanism. The invention relates to a dual-light path nuclear graphite damage evolution and crack propagation whole-process deformation field measurement system for realizing the method, which comprises a beam-splitting imaging module, a trigger adaptation module, a space calibration module and a deformation analysis module, wherein the beam-splitting imaging module is used for completely recording the damage evolution and strain concentration process from loading to fracture by long-time global deformation observation of a low-speed high-resolution camera, is used for precisely recording the instantaneous dynamic behavior of crack initiation and propagation by short-time high-dynamic capture of the high-speed low-resolution camera, the trigger adaptation module is used for monitoring the characteristic gray scale mutation and the form change of a connected domain caused by fracture of the test piece, the high-speed low-resolution camera of the beam-splitting imaging module is used for starting the image acquisition by adopting a post-trigger mode, the space calibration module is used for achieving the space matching of the instantaneous fracture region captured by the high-speed low-resolution camera and the long-time deformation field recorded by the low-speed high-resolution camera by a space coordinate con