| As an advanced solid phase welding technology,inertial friction welding has high connection quality and has become a typical and reliable manufacturing process in the aerospace field.However,in the welding process and service process,the occurrence of defects such as unbonding and kiss-bonding will affect the safety and reliability of the workpiece,which is a major safety hazard.In order to ensure that the product is safe and reliable during service,it is of great significance for the quality inspection of inertial friction welding joints.In this paper,the linear and nonlinear ultrasonic testing research is carried out for the quality inspection of inertial friction welding of titanium alloys.First,by changing the welding process parameters,to prepare a test sample of inertial friction welding of titanium alloy,including natural defect samples prepared by adjusting the welding process,and friction welding comparative samples prepared manually,analyze the macro and micro morphology of inertial friction welded joints by metallography and scanning electron microscope.The sensitivity of the ultrasonic C-scan test was determined by comparing the samples,and the ultrasonic imaging test of the friction welding samples was carried out,and the defects were verified and analyzed in conjunction with the metallographic results.The self-built nonlinear ultrasonic testing system was used to detect the kissing bond defects in the friction welding joint of titanium alloy,the effect of excitation signal and excitation power on the nonlinear ultrasonic of the kissing bond of friction welding joint is analyzed.Simulated and verified the accuracy of non-linear ultrasonic testing of friction welding rods in three ways:vertical incidence on the end face,vertical incidence on the circumferential face and oblique incidence on the circumferential face.And comparative analysis of the advantages and disadvantages of conventional nonlinear ultrasonic testing and pulse reversal method for the detection of friction welding defects.Finally,combined with EBSD technology,the microstructure and texture evolution of titanium alloy joints were studied.By analyzing the correlation of sound velocity,attenuation coefficient and nonlinear coefficient with each area of the joint,the relationship between nonlinear coefficient and EBSD-KAM is established,which provides new ideas for characterizing the performance of the joint.Experimental results show that:(1)Ultrasonic C-scan can detect unbonding defects of inertial friction welded joints of titanium alloy,and defects with a minimum of?0.4 mm flat bottom hole can be detected.(2)The non-linear ultrasonic detection system can detect the kissing bond defects inside the joint,which is about 2?m wide and 100?m long.By testing the comparative samples,it is found that the?0.2 mm flat bottom hole defect has the strongest nonlinear effect,and the nonlinear effect rapidly attenuates with the increase of the aperture.The flat bottom hole is regarded as a closed plane defect,and the maximum detection area is about 0.28 mm~2.(3)The vertical incident method of circular plane has high precision,short detection distance and good adaptability of workpiece detection.(4)Compared with the conventional linear parameters such as sound velocity and attenuation coefficient,the nonlinear coefficient has higher sensitivity to each region of the joint,and the maximum relative variation is 69.4%.(5)Through the EBSD-KAM analysis of each region of the joint,it is found that the KAM value has a similar trend with the nonlinear coefficient,which can be used to characterize the dislocation density of the inertial friction welding joint,and to establish the relationship between the nonlinear ultrasonic coefficient,the dislocation density and the mechanical properties of the friction welded joint. |
PDF Full Text Request