Ultrasonic Residual Stress Detection Of GH4169 Alloy Ring Forgings

GH4169 alloy is widely used in aero-engine turbine discs,compressor drums,casings and other key components.These components are usually forged into blanks,which are mechanical processing shaped.In the forging process of GH4169,due to the uneven forging temperature and pressure.,it is easy to leave residual stress in the forging,resulting in subsequent machining deformation,even reduce the fatigue life of the component,so the non-destructive method to measure the residual stress in the forging can guide the improvement of the forging process and improve the quality of the forging.Based on the comprehensive analysis of the residual stress measurement method of forgings,this paper selects the ultrasonic critical refracting longitudinal wave(LCR wave)stress measurement method suitable for industrial field testing.A set of LCR wave residual stress measurement system and corresponding data acquisition and analysis software were built.Combined with CIVA simulation and specific experimental research,the detection parameters such as critical refraction angle,detection frequency and probe spacing of LCR wave detection were determined.Through the mechanical properties test of materials and LCR wave detection,the ultrasonic stress coefficient of GH4169 material is obtained,which is verified by comparative test of LCR wave detection,X-ray diffraction and blind hole residual stress measurement of the self-designed C-ring specimen.The stress distribution after the forging of the four-stage disc of the actual GH4169 compressor and the stress change before and after shot peening are evaluated by the ultrasonic stress coefficient.The GH4169 forging LCR wave stress detection probe designed in this paper has an optimum incident angle of 28°,the detection frequency is optimally 10 MHz,and the detection distance is optimally 10 mm.When the distance of detection is 10 mm,the relational expression of the stress and ultrasonic travel time is ?(35)(28)(35)25.3t,the ultrasonic stress coefficient is 25.3(MPa/ns),and the ensile stress coefficient is the same as the compressive stress coefficient,and the direction is opposite;the LCR wave stress detection result of the C-ring sample and the X-ray diffraction method and the blind hole method test results are basically consistent,and all conform to the stress distribution law of C-ring;the results of ultrasonic LCR wave stress detection testing the stress distribution of the four-stage disc forging of GH4169 alloy compressor are agree with the results of simulation of after forging.Shot peening effectively reduces the circumferential tensile stress of the aero-engine four-stage disc forging and improves the residual stress distribution of the forging.The GH4169 ultrasonic LCR wave stress detection system established in this test has high accuracy and reliability.It can be directly used in the stress detection of GH4169 ring forgings,providing a new means for the quality control of GH4169 forgings.The reliability of aeroengine is improved to provide protection.