Research On 3D Scanning Detection Technology And Evaluation Method Of Steel Weld

As the skeleton of reinforced concrete structure,steel material is an indispensable part of bridges,houses and other buildings.As a form of steel bar connection,welding seam needs to undergo strict inspection of appearance quality,which is of great significance to the safety of building structure and people's property life.With the continuous improvement of modern welding quality requirements,the traditional manual measurement method is unstable due to subjective factors of inspected personnel in the implementation of national standards on weld appearance quality inspection,and the detection accuracy is difficult to guarantee.Therefore,it is particularly important to research and develop high precision and high efficiency detection device to detect and evaluate the weld quality.Based on the analysis of the traditional three-dimensional measurement principle of weld,a portable scanner for detecting and evaluating the weld formation of steel bar is studied and designed.In this paper,the key technologies such as principle design,hardware circuit selection design,image processing and evaluation algorithm design,system software design and error analysis are studied in the process of high-precision measurement of weld contour dimension parameters,then,design the visual detection system which can realize the detection of weld appearance quality of steel bar,and verify its rationality and effectiveness by the experiment.In the process of researching the appearance inspection of steel weld forming,firstly,based on perspective projection principle,the measurement model of weld visual inspection system is established.Secondly,aiming at the optical imaging system based on optical measurement principle,the structural parameters of the imaging system are designed to obtain the weld structural light image clearly.The calibration of the visual inspection system is realized by using the geometric model of the structured light vision sensor and the mapping relationship between the two-dimensional image coordinates and the world coordinates is obtained.The results show that the accuracy of the calibration method in this paper can reach0.06 mm.Then the embedded image processing hardware,software and core algorithm based on Cortex-A9 are designed for the key technology of image processing.A gray-scale square weighted center of gravity method based on direction field is proposed,which can quickly andaccurately obtain the sub-pixel center of the strip and improve the detection accuracy of the system.Finally,based on the measured parameters of weld contour,FAHP fuzzy comprehensive evaluation algorithm is used to realize intelligent quantitative evaluation of weld forming quality.The accuracy and validity of the evaluation results are verified by comparing with the actual manual test results.