Study On The Quality Stability Under The Service Load Of Aluminum Atloy Aerospace Components Trated By Rolling Distortion Correction Processes

Aluminum alloys are widely used in the aviation industry due to their excellent specific strength,specific stiffness and corrosion resistance.During the milling process of aluminum alloy structural parts,a large amount of blank material is removed.Under the coupling effect of multiple factors such as blank stress,processing stress,cutting force,and cutting heat,there is a common problem of processing distortion.The rolling correction process is an important guarantee to ensure the manufacturing accuracy of structural parts and meet the needs of aircraft assembly.The rolling correction process performs double-sided roller rolling on the top of the structure parts such as the flange and rib of the structural part to cause local plastic distortion of the workpiece,and then the coordination of the local distortion leads to the overall distortion,which offsets the processing distortion and achieves the purpose of distortion correction.However,although the rolling correction process improves the distortion tolerance problem of structural parts,it also further increases the complexity of the internal plastic strain,residual stress,microstructure and other states of the structural parts.Under the action of external alternating loads,the workpiece Conditions of service deteriorated.Therefore,it is important to carry out the research on the quality stability of the structural parts after rolling correction treatment under the external mechanical force load,thermal load and deep cooling load respectively,and obtain the influence law of different loads on the quality stability of the structural parts,so as to provide support for the application of the structural parts after rolling correction treatment in the aviation industry.Firstly,in order to carry out the study of the mass stability of the aluminum alloy structural members after rolling correction treatment under different mechanical force loads,a mechanical force load application test device was designed and built in terms of both mechanical structure and control unit according to the motion requirements of the mechanical force loads applied to the structural parts.The device realizes the measurement of the force and distortion of the structural parts,and switches between force control or displacement control modes through the control software.The device was used to conduct a three-point bending test test on a T-shaped specimen,and the error of the test results compared with the theoretical calculation results was within 3.7%,which verified the accuracy and stability of the load control of the device.Then,a study on the mass stability of the roll-corrected treated aluminum alloy 7075-T651 structural parts under different mechanical force loads and loading times was carried out,and the macroscopic dimensions and residual stresses of the samples were characterized.Compared with the rolling correction treatment,the maximum deformation of the sample after loading 1000 times under different mechanical loads is 11.45%,and the maximum deformation after loading different times under 80% F load is 9.76%.With the change of mechanical force load and loading times,the macroscopic dimensions and residual stresses of the T-shaped specimens did not show significant changes,which proved that the structural parts after rolling correction treatment had high quality stability under the mechanical force load.Secondly,the quality stability of the roll-corrected aluminum alloy 7075-T651 structural parts under thermal loading was investigated.The T-shaped samples were selected for thermal insulation treatment with heat loads of 120°C,160°C,230°C and 300°C.Then,the microscopic morphology,physical and mechanical properties and other characteristics of the specimens were characterized,and then the evolution mechanism of the material under thermal loads was analyzed.Compared with the rolling correction treatment,the macroscopic size of the samples treated with different thermal loads changed by a maximum of 10.48%.The residual stress in the rolling area decreases gradually with the increase of thermal load,and the average maximum decreases by 83.13% after treatment at 300 °C,and the microhardness also decreases by about 56%.Under 120℃ and 160℃loads,the microstructure of the material was mainly based on static reversion;under 230℃ and300℃ loads,the material was mainly affected by the static recrystallization effect,and the microstructure was gradually blurred and the hardness decreased significantly.Although the residual stresses introduced by the rolling correction treatment would undergo different degrees of stress relaxation under the action of thermal loading,the microstructure changes caused by the thermal loading treatment failed to cause significant effects on the macroscopic dimensions of the structural parts.Finally,the quality stability of the roll-corrected aluminum alloy 7075-T651 structural parts under deep cooling load was investigated.The T-type samples were subjected to-70°C and-150°C cryogenic load insulation treatments,and the macroscopic size,residual stress,microhardness,and microstructural changes of the samples were characterized and analyzed.The results show that,compared with those after rolling correction,the macroscopic dimensions of samples after cryogenic load treatment at-150℃ and-70℃ have changed by 14.29% and 9.09%,respectively.The microstructural structure of the sample did not change significantly,and the microhardness remained basically stable,indicating that the microscopic plastic distortion accompanied by the residual stress change of the structural parts did not have a significant impact on the macroscopic dimensions,and the structural parts had high quality stability.