Search Results (3)

Large aluminum alloy ring forgings are the core components of heavy-duty rocket fuel storage tanks, and the large residual stress inside the rings leads to poor shape accuracy of large thin-walled parts. The initial stress of the 2219 aluminum alloy ring blank was tested using the drilling method, and the creep constitutive coefficient of the 2219 aluminum alloy was determined through stress relaxation tests. The numerical simulation processes of thermal stress relief (TSR), vibration stress relief (VSR), and thermal–vibration stress relief (TVSR) were compared and established. Through the correlation analysis between the actual measurement results of residual stress and the simulation results, it can be seen that the strong correlation in three directions at each measurement point accounts for over 37.5%, and the moderate correlation accounts for over 62.5%. This indicates that the numerical simulation model of 2219 aluminum alloy ring containing initial residual stress can accurately reflect the size and distribution of residual stress inside the actual ring. The simulation results show that the derived constitutive model can describe the stress relaxation process of TVSR by combining a single thermal time effect stress relaxation constitutive theory with a VSR plastic deformation material model. The simulation models established above were used to calculate the residual stress homogenization ability of three types of aging. The results showed that VSR, TSR, and TVSR can homogenize and reduce the residual stress field inside the ring, improve the distribution of residual stress inside the ring, and have a better overall homogenization ability of TVSR. The VSR control has a certain effect on reducing and homogenizing residual stress, but compared with TSR and TVSR, the reduction and homogenization ability of residual stress control is limited. The homogenization control effect TVSR > TSR > VSR, and the maximum equivalent stress homogenization rates of VSR, TSR, and TVSR are 52.8%, 80.6%, and 82.2%, respectively. Then, numerical simulation technology was used to study how the initial residual stress in the blank causes the deformation of the ring during the thin-walled machining process. The roundness error theory of the minimum containment area method was applied to evaluate the deformation degree during the thin-walled numerical machining process, and the TVSR method was used for stress regulation. The deformation law of the thin-walled machining of the ring under different aging parameters was studied. Full article

2219 aluminum–copper alloy is a major material in launch vehicles transition rings. The study of dynamic recrystallization during its rolling and forming process is beneficial to improving the performance enhancement of 2219 aluminum alloy ring parts. In this paper, a multi-scale simulation of grain refinement and distribution of dynamic recrystallization (DRX) grains during the rolling of 2219 aluminum alloy rings is carried out using the finite element method and cellular automata method. On the basis of the JMK DRX model, an ABAQUS subroutine was written to simulate the ring-rolling of 2219 aluminum alloy, and the distribution of DRX percentage and average grain size was analysed from a macroscopic point of view, with a maximum DRX level of 12% and an average grain size distribution from 247 μm to 235 μm from the inside of the aluminum alloy ring towards the surface. A cellular automaton model of DRX during rolling of large aluminum alloys was developed to effectively simulate DRX nucleation, growth, and grain compression deformation during rolling. The DRX nucleation occurs at the grain boundaries and then grows, resulting in a homogeneous organisation and a refinement of grain size, with both the original and DRX grains being compressively deformed as the rolling process progresses and the grains being gradually elongated tangentially. Finally, a comparison of the experimental results with the simulations to obtain grain size and morphology demonstrates consistent results, indicating that the combination of FE and CA methods is an effective approach for a more comprehensive understanding of the microstructural evolution during rolling. Full article

Aerospace thin-walled rings are vulnerable to machining distortion during the manufacturing process. Various research results show that the main factor causing machining deformation is initial residual stress inside the blank. In this study, the residual stress of a 2219 aluminum alloy ultra-large rolling ring was measured by using the indentation strain-gauge method. Results showed the maximum residual maximum principal stress was +265 MPa and stress distribution was uneven. To homogenize the initial residual stress of the ring, an expansion method is proposed based on the principle of pre-stretching plate, and the feasibility of the expansion method was analyzed by establishing a simplified theoretical model of ring. A FE (Finite Element) model was established to investigate residual-stress evolution during the rolling ring and the expanding ring process. The expansion simulation results show that the reduction rates of residual stress were greater than 40% and the maximum residual stress was only 65 MPa. Full article