Research On Joggle Warm Forming Of 7A09-T6 Aluminium Alloy By Resistance Heating

With the increasingly prominent environmental problems,the aerospace industry is facing increasingly severe challenges in energy conservation and emission reduction.7A09-T6 aluminum alloy is an important lightweight structural material with high specific strength in the aerospace industry.In order to improve the existing production efficiency of the 7A09-T6 aluminum alloy stringer parts,reduce energy waste,and improve the surface quality of the stringer parts,the subject uses the craft of resistance heating and warm forming to achieve the joggle forming of the stringer parts.In the research process of joggle warm forming by resistance heating,the deformation amount of the joggle forming was estimated by theoretical calculation and finite element simulation.The heating temperature,strain rate and holding time were studied by resistance heating uniaxial tensile test.The mechanical properties of the material was compared at room temperature which material sufferd heat treatment and at high temperature by stretching.The law of uniaxial tensile test was verified from the microstructure evolution law,and the process window of the joggle forming was determined.Secondly,the resistance heating experiment was carried out to study the influence of the contact area between the electrode and the material,the contact pressure and the current density on the temperature field distribution of the heated part,and the key electrothermal parameters of the joggle forming of the stringer parts were determined.When the profile is formed by sinking,the temperature of the deformation zone is stable and uniform to reach the forming temperature.Finally,the preparation of the test piece was carried out based on the forming process window determined by the uniaxial tensile test and the microstructure analysis and the electrothermal parameters determined by the resistance heating temperature test.The shape precision of the test piece and the mechanical properties were comprehensively evaluated.The quality verified the rationality of the forming process.Research indicates:(1)Temperature is the main factor affecting the material’s deformability.The plasticity of the material increases with the increase of temperature.(2)The strain rate is another important factor affecting the material’s deformability.The strain rate has no effect on the deformation ability of the material at room temperature.As the temperature increases,the influence of strain rate increases.(3)After the heat is formed at a temperature of 200 ° C or less for a short time,the second phase of the microstructure of the material does not change,and the strength of the material naturally cooled to room temperature can be restored to the T6 state strength level.Compared with the forming quality of the molded articles at 150 ° C and 200 ° C,the forming quality of the formed part is better at 200 ° C,which not only ensures the strength level of the formed parts,but also improves the shape accuracy of the formed parts.(4)The temperature field distribution of the stringer parts which is heated by resistance heating is related to the current density,the macro contact area of the electrode and the material,and the contact pressure.When the current density of the profile formed by the subject is 9-12.5 A/mm2,the contact pressure is set to 30 MPa,and the nip width is set to 20 mm,the deformation zone can be stably and uniformly reached the forming temperature under the experimental conditions.It is convenient to stably control the temperature of the deformation forming zone and ensure the forming temperature.