Three-dimensional Defect Detection And Repair On The Surface Of Thermal Insulation Layer In Solid Motor

The thermal insulation layer acts as a thermal protection layer for the solid engine.If there are defects,it will aggravate the erosion and ablation of the thermal insulation layer,which will degrade the performance and reliability of the engine,and even lead to catastrophic consequences such as engine failure.Therefore,it is necessary to accurately detect and analyze the defects of the insulation layer and take appropriate methods for repair.At present,the detection of defects in the thermal insulation layer is mainly focused on the internal defect detection of the debonding of the thermal insulation layer,and the detection of the surface defects of the thermal insulation layer is less.In view of the above problems,this thesis takes the thermal insulation layer in the solid engine as the research object,and based on the li ne structure light detection technology and droplet ejection technology,the quantitative detection and repair of the three-dimensional defects on the surface of the thermal insulation layer are studied.In order to obtain the parameters of the mathematical model of the line structure light detection system,the calibration of the internal parameters of the camera and the calibration of the line structure light plane equa tion are completed.In the calibration section of the light plane equation,the measurement error and measurement st ability of the two calibration methods of the checkerboard and the circular array plane target are compared.Finally,the circular array plane target is selected as the calibration method of the light plane.For the line structure light stripe centerline e xtraction algorithm,the gray center of gravity method,Steger algorithm and its improved algorithm are used to compare the extraction precision of the strip center.Considering the detection precision and calculation efficiency,the improved gray center of gravity method is used as the stripe centerline extractio n algorithm.On this basis,the quantitative detection of surface defects of thermal insulation layer is completed.It is proposed to use the point cloud depth color mapping model and the maximum entropy method to realize the identification and location of the surface defects of the thermal insulation layer.And the volume of the surface defect of the thermal insulation layer is approximated by the method of obtaining the cross-sectional area of the defect region on the plurality of scanning lines.On this basis,the feasibility study of droplet ejection technology applied to the repair of thermal insulation defects is also completed.In view of the problem that the liquid ethylene-propylene rubber could not be sprayed normally under normal temperature condition,the optimal heating temperature during the repair of droplet spray is determined to be between 160°C and 180°C through simulation and experimental verification.Then,the surface defect repair experiment of the thermal insulation layer is carried out.Through the tensile test and the ablation test,the performance of the repaired thermal insulation layer is determined to meet the requirements of the engine design.In order to verify the research results,the hardware system and software system required for the experiment are built.And the detection and repair experiments of the circular pit defects and rectangular pit defects are carried out.The experimental results show that the proposed met hod based on line structure light detection can effectively realize the quantitative measureme nt of pit defects.The repair method based on droplet ejection technology can effectively repair the pit defect area.