Research On Digital Metrology For Inspecting The Shape Of Aerial Welded Tube

The aerial welded tube is composed of various sizes and shapes of parts such as the main tube,branch tube,flange,sleeve,nozzle and so on.It can be used to transport gas,liquid and other things to the engine,landing gear,cockpit,and other products.At present,in most aviation companies in China,the fixture is usually used to inspect welded tubes.This method has the disadvantages of low detection accuracy,high cost,and limited help in improving the quality of the aerial welded tube's shape.To solve the above problems,this paper studied the digital measurement solution,registration method and method of deviation evaluation related to the digital inspection of the aerial welded tube's shape and developed the shape inspection software.The specific research contents are as follows:(1)This paper analyzed the structure of the aerial welded tube and the disadvantages of the traditional inspection solution.To choose a suitable digital measurement solution,this paper compared some representative digital measurement solutions.After analyzing the ROMER and ATOS Triple Scan two comprehensive measurement solutions and considering the price,measurement accuracy and measurement conditions and so on,the ROMER measurement solution was considered more suitable for the welded tube.(2)To fulfill the registration demands of the measurement data and the CAD model,this paper solved the coordinate transformation based on the correspondence between the datum of the measurement data and the datum of the CAD model.According to different types of welded tubes,this paper proposed IP reference registration,3-2-1 reference registration,and multi-reference weighted registration.The weighted multi-reference registration was suitable for inspecting the welded tube with many references,a certain degree of flexibility and adjustable quantities.This method made the error evaluation of the welded tube more consistent with engineering reality.(3)After analyzing the main sources of error while measuring the aerial welded tube and classifying the measurement error,this paper proposed some methods for reducing measurement error.To analyze the error between the measurement data and the CAD model quickly,the error was classified into linear error and angular error.The linear error and angular error of the welded tube measurement element were defined in this paper and used a sample welded tube to explain how to evaluate the error between the measurement data and the CAD model.(4)After studying the digital inspection techniques about the shape of the aerial welded tube,this paper developed the shape inspection software.The software proved to be practical by inspecting the sample of aerial welded tubes successfully.