CN-121981935-A - Nondestructive testing method and system for performance of vacuum heat insulation composite heat preservation material

CN121981935ACN 121981935 ACN121981935 ACN 121981935ACN-121981935-A

Abstract

The invention relates to the technical field of nondestructive testing, in particular to a nondestructive testing method and a nondestructive testing system for the performance of a vacuum heat-insulating composite heat-insulating material, comprising the steps of heating the surface of the vacuum heat-insulating composite heat-insulating material to be tested and collecting time sequence infrared image data; the method comprises the steps of carrying out statistical analysis on an image sequence before heating in time sequence infrared image data by adopting a dynamic multi-baseline background suppression method to obtain a temperature differential sequence after background suppression, carrying out feature extraction on the temperature differential sequence after background suppression to obtain a heating rate feature image, a cooling rate feature image, a lifting asymmetry feature image and a time domain feature image, fusing the images to obtain an enhanced defect feature image, carrying out segmentation processing on the enhanced defect feature image, and outputting a nondestructive detection report. The invention can keep higher detection sensitivity under different temperature difference conditions, and realizes reliable identification of defects under the condition of low signal-to-noise ratio.

Inventors

WANG ZHONGNAN
CAO JINGKAI
LIU JIN
HU BAI
SHENG LUYAO
WANG ZHIHAO
FAN WENGUANG
WANG HAORAN
WANG YUCHEN

Assignees

中电建路桥集团有限公司

Dates

Publication Date: 20260505
Application Date: 20251127

Claims (10)

1. A nondestructive testing method for the performance of a vacuum heat insulation composite heat preservation material is characterized by comprising the following steps: s1, heating the surface of a vacuum heat insulation composite heat preservation material to be detected, and acquiring infrared thermal image sequences before heating, in a heating process and in a cooling process by using an infrared thermal imager to obtain time sequence infrared image data; S2, carrying out statistical analysis on an image sequence before heating in the time sequence infrared image data by adopting a dynamic multi-baseline background suppression method, calculating a background baseline according to the time domain stability of the pixel points, and carrying out differential processing on images in a heating process and a cooling process by utilizing the background baseline to obtain a temperature differential sequence after background suppression; S3, extracting features of the temperature differential sequence after background suppression, extracting a heating rate feature image, a cooling rate feature image and a lifting asymmetry feature image by adopting a normalization processing method, and extracting a time domain feature image by adopting a time sequence weighted principal component analysis method; s4, fusing the heating rate characteristic image, the cooling rate characteristic image, the lifting asymmetry characteristic image and the time domain characteristic image to obtain an enhanced defect characteristic image; s5, segmentation processing is carried out on the enhanced defect characteristic image, a defect area is extracted, defect characteristic parameters are calculated, and a nondestructive testing report is output.
2. The nondestructive testing method for the performance of the vacuum insulation composite thermal insulation material according to claim 1, wherein the step S2 comprises the following steps: s21, extracting an image sequence of a pre-heating stage from time sequence infrared image data; s22, calculating the time domain standard deviation of the temperature value of each pixel point in the image sequence of the pre-heating stage; s23, comparing the time domain standard deviation of each pixel point with a stability threshold value, and judging the pixel point as a stable pixel point or an unstable pixel point according to a comparison result; S24, adopting a time domain mean value as a background baseline for the stable pixel points, and adopting a time domain median value as a background baseline for the unstable pixel points; and S25, differentiating each frame of image in the heating stage and the cooling stage with the corresponding background baseline to obtain a temperature differential sequence after background inhibition.
3. The method for non-destructive testing of vacuum insulation composite thermal insulation material performance according to claim 1, wherein in step S3, the normalization processing method comprises the steps of extracting a temperature-time curve for each pixel point in a temperature differential sequence after background inhibition, identifying peak characteristic parameters and shape characteristic parameters from the temperature-time curve, calculating heating rate characteristics, cooling rate characteristics and lifting asymmetry characteristics according to the peak characteristic parameters, correcting the heating rate characteristics and the cooling rate characteristics according to the shape characteristic parameters, and respectively forming a heating rate characteristic image, a cooling rate characteristic image and a lifting asymmetry characteristic image by corrected characteristic values of all the pixel points.
4. A nondestructive testing method for vacuum insulation composite thermal insulation material performance according to claim 3, wherein the peak characteristic parameters comprise a maximum temperature difference value, a peak time for reaching the maximum temperature difference value and a half-width time for decreasing from the peak time temperature to half the maximum temperature difference value, and the shape characteristic parameters comprise a skewness coefficient and a kurtosis coefficient of a temperature-time curve, wherein the skewness coefficient reflects symmetry of the curve relative to a peak point, and the kurtosis coefficient reflects sharpness of a peak of the curve.
5. The method for nondestructively testing the performance of a vacuum thermal insulation composite thermal insulation material as set forth in claim 3, wherein the heating rate is characterized by The calculation formula of (2) is as follows: the cooling rate characteristics The calculation formula of (2) is as follows: Wherein, the In order for the peak time to be the same, Is the half-width time of the half-height, In order to prevent a small constant of zero removal, Is the skewness coefficient of the temperature-time curve, As the coefficient of kurtosis, And For the reference normalization constant, And Is a shape weight coefficient.
6. The method for non-destructive testing of vacuum insulation composite thermal insulation material performance according to claim 1, wherein in step S3, the time sequence weighted principal component analysis method comprises the steps of calculating spatial variance of each frame of image in a temperature differential sequence after background suppression, distributing time sequence weights to each frame of image according to the spatial variance, weighting each frame of image according to the time sequence weights to construct a weighted data matrix, performing principal component analysis on the weighted data matrix, and extracting principal component images as time domain feature images.
7. The method for nondestructively testing the performance of a vacuum thermal insulation composite thermal insulation material according to claim 1, wherein the step S4 comprises: s41, calculating the global temperature contrast of the time domain feature image; s42, calculating time domain feature weights and space domain feature weights according to the global temperature contrast; S43, weighting and synthesizing the heating rate characteristic image, the cooling rate characteristic image and the lifting asymmetry characteristic image to obtain a airspace characteristic image; And S44, carrying out weighted fusion on the time domain feature image and the space domain feature image according to the time domain feature weight and the space domain feature weight to obtain the enhanced defect feature image.
8. The method for non-destructive testing of vacuum insulation composite thermal insulation material performance according to claim 1, wherein in step S44, the enhanced defect feature image has a calculation formula as follows: Wherein, the Is the global temperature contrast of the temporal feature image, As a temperature contrast threshold value, In order to smooth the parameters of the image, As an image of the temporal feature, Is a spatial domain feature image.
9. The method for non-destructive testing of vacuum insulation composite thermal insulation material performance according to claim 1, wherein in step S5, the enhanced defect feature image is segmented by Otsu automatic thresholding, the segmentation result is processed by morphological operation, the extracted defect region calculation defect feature parameters comprise area, center position coordinates, perimeter, equivalent diameter, roundness, average temperature difference and maximum temperature difference, and a non-destructive testing result is output, wherein the non-destructive testing result comprises defect region area, defect position distribution and defect type.
10. A nondestructive testing system for the performance of a vacuum insulation composite thermal insulation material is characterized in that the system is used for executing the nondestructive testing method according to any one of claims 1-9, and comprises the following steps: The excitation unit is used for carrying out pulse heating excitation on the surface of the material to be detected; the infrared thermal imaging unit is matched with the excitation unit and is used for acquiring time sequence infrared image data of the surface of the material to be detected in real time in a pre-heating stage, a heating stage and a cooling stage; The image preprocessing unit is connected with the infrared thermal imaging unit and is used for carrying out background suppression processing on the time series infrared image data to obtain a temperature differential sequence after background suppression; the nondestructive testing unit is connected with the image preprocessing unit and is used for carrying out feature extraction and defect identification on the temperature difference sequence after background suppression and outputting a nondestructive testing result; the storage unit is connected with the infrared thermal imaging unit, the image preprocessing unit and the nondestructive testing unit and is used for storing time series infrared image data, intermediate results in the processing process and final defect detection results.

Description

Nondestructive testing method and system for performance of vacuum heat insulation composite heat preservation material Technical Field The invention relates to the technical field of nondestructive testing, in particular to a nondestructive testing method and a nondestructive testing system for the performance of a vacuum insulation composite thermal insulation material. Background The vacuum heat insulation composite heat preservation material is a novel material applied to a building external wall heat preservation system. The material is formed by compounding a vacuum heat insulation core material and an inorganic fireproof protective layer, and has ultralow heat conductivity coefficient and A-level fireproof performance. Compared with the traditional heat insulation material, the heat conductivity coefficient of the vacuum heat insulation composite board is one order of magnitude lower, the heat insulation effect is obvious, and the vacuum heat insulation composite board has wide application prospect in the field of building energy conservation. However, the materials are easy to have quality defects such as empty bonding layer, cracking plastering layer, core material breakage and the like in the construction, installation and use processes. Particularly, once the vacuum core material is damaged and leaked, the internal vacuum degree is reduced, the heat conductivity coefficient is rapidly increased, and the heat preservation performance is greatly reduced. Therefore, nondestructive inspection techniques must be employed to identify defects without touching or damaging them. The infrared thermal imaging nondestructive testing technology is one of the main methods for testing the quality of the building exterior wall insulation system at present. The technology is based on the difference of heat conduction characteristics of a defect area and a normal area, the temperature distribution of the surface is acquired through a thermal infrared imager, and the defect position and the defect range are identified according to the abnormality of a temperature field. The active infrared detection adopts an artificial heat source to apply thermal excitation to the detected object, and the thermal infrared imager is used for collecting the dynamic change process of the surface temperature field, so that all-weather and all-dimensional detection can be realized. The typical active detection process comprises the steps of collecting a background temperature field before heating, applying pulse thermal excitation, and continuously observing a cooling process after heating, wherein the whole collection process obtains a thermal image sequence comprising tens to hundreds of frames. The processing method for the thermal image sequence mainly comprises a temperature signal reconstruction method, a principal component analysis method, a pulse phase method, an independent component analysis method and the like. However, for vacuum heat insulation materials with ultra-low heat conductivity, as the heat resistance is far greater than that of conventional composite materials, the surface temperature difference between a defect area and a normal area is small, the temperature contrast is weak, and the feature extraction and enhancement capability of the conventional image processing method under the condition of weak temperature contrast is insufficient, so that the accuracy and sensitivity of defect identification are limited. Chinese patent CN202211070855.2 discloses a method for extracting characteristics of composite impact damage by infrared thermal imaging, which comprises detecting a test block by a thermal imaging detector, collecting a thermal imaging information graph sequence, selecting a thermal imaging information graph of an impact damage region from the beginning to the gradually disappearing process to form a maximum thermal imaging information graph sequence, obtaining a temperature difference and forming a temperature difference time history curve, generating a maximum gradient value according to the temperature difference time history curve, taking a thermal graph with the maximum gradient value corresponding to the frame number as an optimal thermal graph, performing gray level transformation, histogram equalization processing and high-pass filtering processing on the thermal graph to improve image contrast, and finally processing the edge of a defect region by passivation masking and extracting defect characteristic parameters. The patent proposes to select the quantization index of the optimal heat map through the gradient value of the temperature difference time history curve, and to improve the contrast by adopting the traditional image enhancement methods such as histogram equalization, high-pass filtering and the like. However, the method mainly relies on a single-frame optimal heat map for feature extraction, and for defects with weaker temperature contrast, the traditional image processing method ha