Research On The Influence Of Scratch On The Inner Surface Of Spring Tube On Its Life And Development Of Testing Device

As an important part of the armature assembly of the electro-hydraulic servo valve,the accuracy of the spring tube directly affects the normal operation of the whole electrohydraulic servo valve.In the processing of spring tube,there are many steps and precise requirements,so both in manufacturing and testing are very strict.During the inspection,it is necessary to carefully observe the inner and outer surfaces of the spring tube to confirm that there are no surface defects such as scratches and cracks on the inner and outer surfaces of the spring tube.At present,the commonly used detection method is naked eye observation,which has low detection efficiency.There is no way to achieve automation,especially the detection of inner surface is more difficult.This paper starts with the influence of scratch on the inner surface of spring tube on its life,analyzes the influence of scratch on its stress distribution,discusses the influence of different initial crack conditions,and develops a set of automatic equipment to automate the detection process.Finally,using the developed equipment,the inner surface of the spring tube is tested to verify the rationality.In order to analyze the stress of the scratched spring tube,firstly,the statistics of the scratched spring tube are made to confirm the distribution of the scratched position in the processing.Confirm the relevant parameters of the material,use ABAQUS software to establish the finite element model of the scratch on the inner surface of the spring tube,and simulate the stress distribution characteristics of the spring tube.By changing the initial crack size and applying different loads,the crack growth of the spring tube is analyzed,and the influence of the crack on the spring tube is studied.After confirming that the scratches and cracks of the spring tube will have a significant impact on the service life of the spring tube,we began to design the detection device for the scratches on the inner surface.Firstly,two schemes of reflection type and oblique type are determined,and then the structure of the device is designed.In order to realize the automation of the device,the electrical system is designed for the device,and a set of control program is developed to realize the automatic control and complete the collection task of the inner surface image of the spring tube.The image collected directly can't completely show the appearance of the inner surface of the spring tube,so it needs to process the image.Because of the segmented shooting,the image is first spliced into a complete image by using the image mosaic algorithm.At the same time,the inner surface of the spring tube is a cylindrical surface,which will produce perspective geometric deformation and distortion geometric deformation during oblique shooting.Therefore,it is necessary to study the causes of optical distortion during shooting.Then the correction algorithm of image distortion is studied to correct the image of the inner surface of the spring tube.Through analysis and experiment,the correction algorithm is developed.The algorithm is applied to the image of the inner surface of the spring tube.The experimental results show that the surface correction algorithm is effective.