Study On Ultrasonic Feature Scan Of Defective Base And Dynamic Properties Of Aluminum Alloy FSW Welding

Friction stir welding is a new type of solid phase welding technology.Compared with traditional connection methods,this technology has the advantages of high efficiency,high quality,low energy consumption,low pollution,small welding distortion,etc.Therefore,it has a wide range of application in aerospace and shipbuilding and other key areas.However,due to the improper selection of welding parameters,welding defects such as large textures,grooves,incomplete penetration,and non-fusion are also generated,which reduces the use performance of the material.Therefore,the variety of friction stir welding defects becomes a difficult detection point.At present,the detection of the friction stir welding head mainly adopts the ultrasonic method because the ultrasonic detection has the advantages of wide range of detection materials,strong penetration,high sensitivity,low detection cost,high speed,and no harm to the human body and the environment.This article through the non-destructive testing of ultrasonic features scanning aluminum alloy friction stir welding defects and real-time dynamic fatigue crack propagation,the main research content is as follows.1 ?In view of the characteristics of typical defects in aluminum alloy friction stir welding,two kinds of flat holes are designed parallel to the weld.One is a flat hole with the same depth and different size,and the other is a flat hole with the same size and different depth.There are two kinds of flat holes in the vertical direction to the weld,one is a flat hole with the same height and different size,and the other is a flat hole with the same size and different height.Studies have shown that: Ultrasonic method can accurately identify the defects of each leveling hole,and give a positioning.2 ?Ultrasonic feature scanning is also performed on the surface of 6mm thick aluminum alloy friction stir welding joints with large arc lines,grooves,incomplete penetration,low density impurities,and low density impurities + loose tissue defects.,extracting feature information of different defects,establishing a vector correspondence table,and performing imaging processing to achieve accuraterecognition of five kinds of defects.Studies have shown that: Ultrasonic feature scanning imaging is a feasible method to detect surface roughness textures,grooves and incomplete penetration defects in friction stir welding;echo is obtained by extracting and analyzing interface wave,intermediate layer wave,and bottom wave.Amplitude imaging can effectively determine the size and nature of defects;combined with echo amplitude and depth amplitude imaging to achieve automatic identification of defects,the results are more intuitive and can effectively solve the phenomenon of missed detection.3 ?The ultrasonic feature scanning imaging technology is applied to the fatigue test of friction stir welding,and the surface textures,grooves,low-density impurities and low-density impurities(tissue loosening)in the friction stir welding head are processed into fatigue test requirements,and To ensure that each type of defect can be cut out of 3 samples,a total of 12 defects in four kinds of defects,each defect at60 Mpa,70Mp,80 Mp 15min fatigue test about 82000 fatigue,remove the sample,At the same time,using ultrasonic feature scanning imaging technology,the image is processed and the proportion of defects is counted.According to such a cycle,until the sample breaks,it cannot be tested.Studies have shown that in the friction stir welding surface texture,grooves,low density impurities and low density + loose tissue four typical defects,surface texture and groove is the best anti-fatigue,low-density impurities and low-density impurities The loosening and fatigue resistance of the reinforcements are all relatively poor,and the low density impurities plus the loosening of the microstructures are the worst for fatigue resistance;when the surface macrosynthetic defects are 70 MPa,the expansion of the defects is the slowest,and is below 70 MPa or higher than 70 MPa.The expansion of surface defects is rapid;trenches,low-density and low-density impurities + loose-tissue defects are fatigued under repeated repeated different loads,and the defects are expanded.With the increase of continuous repetitive loads,the defect propagation speed increases.Also increase,the greater the continuous repeated load,the faster the defect expansion speed.