An Infrared Detection Method For The Hollowing Defect Of Exterior Wall Decorative Bricks

Exterior wall facing bricks to exterior facades of buildings is a common form of exterior wall decoration in high-rise buildings in cities at present.Before 2000,because of the advantages of facing bricks such as beautiful appearance,low cost and simple attachment technology,the practice of adhering exterior wall facing bricks to exterior facades of buildings in our country was very popular,and the number of them could not be estimated.But when the building has been used for more time,The bonding strength will be greatly reduced,and the probability of falling off will be greatly increased.However,the existing four methods of hollow detection,such as drawing method,acoustic method,visual method and infrared method,have some shortcomings,such as destructiveness,small detection range,low detection efficiency,relying on subjective judgement of the experience of the inspectors to judge the hollow,and lack of objectivity,which make it difficult to guarantee the reliability of the results.It can be expected that in recent years,the number of falling off accidents of building exterior wall decorative tiles will be more and more,and the main cause of endangering social and public safety is the occurrence of falling off of building exterior wall decorative tiles.So this study proposes a new method to detect the abnormal area of exterior wall decorative bricks,The steps of removing noise,calculating temperature gradient,inhibiting gradient non-maxima,threshold segmentation,expanding erosion of contour line,removing texture interference noise and connecting unclosed contour are introduced.Which can detect the abnormal area of decorative bricks in a wide range,accurately,objectively,quickly and noncontact way.Through the prefabricated hollow drum on the experimental wall,the size,threshold and recognition ability of the Gaussian kernel involved in this detection method are experimentally studied.When the thickness of the cavity is 5 mm,according to the evaluation index,the size of gaussian core is 5×5,the threshold value is 0.80.When the temperature difference of drum region is above 0.9 ? and the deviation error of contour position is 11 mm(5 pixels),the drum contour is clear and complete,and the accuracy of drum contour position can reach more than 75%.Through the five indicators of identification process,recognition efficiency,regional temperature difference to determine size,recognition ability and recognition accuracy,it shows that this method has great advantages.An experimental platform is designed and built to study the temperature difference in the hollow area.The experimental results show that when the solar radiation intensity changes abruptly,the change rate of temperature difference in the hollow region is the largest compared with the change rate of light color temperature difference on the wall,and when the solar radiation intensity decreases,only the temperature difference in the hollow region will become negative,as a basis for confirmation of hollow.There is no obvious difference in surface temperature of empty drum due to the unacceptability of direct radiation on the facade of building's shade back.,to be able to detect such small temperature difference,expanding the scope of application of this method.According to the theoretical analysis and experimental results,the time required for the temperature difference change of hollow area to reach 0.9?("the algorithm temperature difference identification limit")under different sudden changes of solar radiation intensity is obtained.Based on this,the strategy of amplifying the temperature difference of empty drum area with the help of plane mirror reflecting sunlight is determined.Finally,using the research results,the actual building empty drum detection is carried out,and the test results are verified,which further illustrates the accuracy and feasibility of the research results.In conclusion,a new infrared detection method for identifying abnormal temperature regions and hollowing of exterior wall decorative tiles is proposed.It provides an effective technical means for the rapid survey of the hollow defects of building exterior wall decorative bricks.