Zhenchao Qi’s research while affiliated with Nanjing University of Aeronautics and Astronautics and other places

The bidirectional thermo-mechanical coupling effect during CF/PEEK drilling significantly impacts the hole quality and component safety, presenting a current challenge in relevant research. To tackle this issue, this paper establishes a constitutive model that incorporates temperature effects, based on quasi-static tensile tests and theoretical analyses of the elastic response, damage criterion, and stiffness reduction of CF/PEEK materials. A drilling thermo-mechanical monitoring platform is set up, and a bidirectional thermo-mechanical coupling model for drilling thermoplastic composites is established using the VUMAT subroutine. A simulation analysis method is proposed, and the reliability of the finite element model is verified. The results indicate that the average absolute errors of the maximum drilling axis force and the highest temperature obtained from the simulation and experiments for all process parameters are 5.255 and 4.34%, respectively. Notably, when the spindle speed reaches or exceeds 5000 r/min, the simulated hole temperature reaches the melting point, and resin melting and coating phenomena are observed in the microscopic morphology images.

Wing-fuselage docking is one of the most crucial stages in the aircraft assembly process. In China, the process of wing-fuselage docking for large aircraft relies on experience and on-the-spot error detection during the docking process currently. However, the inefficiency of the approach makes it difficult to meet the demands of efficient production. Moreover, aircraft wings are susceptible to deformation, and various manufacturing errors can lead to different types of deformations. To address this problem, an inverse planning method for wing docking paths was developed, leveraging measured data and an enhanced PSO-RRT* algorithm. Firstly, a part model was reconstructed using measured point cloud data to depict manufacturing errors accurately. Then, the deformation occurring during the wing positioning process was simulated based on this model. Finally, improved PSO-RRT* algorithm was proposed and the inverse planning of wing docking path was executed. The experiment showed that the average absolute error between wing deformation simulation and measured values is 0.0015 mm. The maximum absolute error is 0.03182 mm. Finally, to ensure that the generated path can be used for the actual assembly process. A path smoothing method based on cubic spline interpolation was proposed, and the path was segmented.

The durability of bolted composite joints has long been a significant concern within the field. However, the specific influence of transverse vibration relaxation on bolted composite joints has not been extensively studied. This study aims to investigate the effects of transverse vibration relaxation on bolted composite joints. A series of transverse vibration experiments were conducted to investigate the effect of initial preload, displacement load, and lubrication position on bolt preload relaxation. Additionally, tensile tests were performed on composite joints after relaxation and without relaxation to evaluate mechanical properties quantitatively. A finite element model was established to reveal the mechanism of damage evolution. The results indicate that displacement load and thread lubrication have the most significant influence on bolt preload relaxation. The clamping force of the composite structure generated by the smaller preload force has a limited effect on damage suppression during the tensile process. The relaxation of bolt preload can be effectively reduced by increasing the initial preload properly. The tensile strength of composite laminated structures with 10%, 22%, and 32% relaxation (10.4 kN initial preload) decreased by 5%, 6%, and 11%, respectively. Transverse vibration relaxation affects the tensile strength of composite structures, which is caused by the decay of preload. In contrast, the damage to the hole wall of the connection domain caused by transverse vibration almost does not affect the bearing capacity of the composite joints. Overall, this research contributes to the understanding of bolted composite joints’ durability by uncovering the novel effects of transverse vibration relaxation and providing valuable insights for design and optimization strategies in composite joint applications.

Large size is one of the typical characteristics of aircraft panel components. These characteristics are prone to deformation during assembly process, which affects the assembly quality of aircraft panel seriously. Therefore, to solve this problem, a combined prediction model is proposed for predicting panel assembly deformation. Firstly, the prediction model of skin assembly deformation based on Adam optimized BP neural network algorithm is proposed to solve the normal deformation of key characteristics in skin assembly stage. Then, a panel assembly deformation prediction model based on substructure is established. The prediction results derived from the skin assembly stage are taken as the input of the prediction model of stringer assembly stage. Thereby, the combined prediction model is established. Finally, a panel assembly experiment is conducted to validate the combined model. By comparing the predicted results coming from the model and the results from assembly experiment, it can be found out that the average absolute error of aircraft panel assembly deformation is 0.155 mm. Therefore, this study provides a reliable and efficient new approach for the assembly deformation prediction of aircraft panel.

With the advancement of space technology, satellites are assuming an increasingly pivotal role in various fields. Currently, satellite structures incorporate a growing number of thin-walled parts. During the assembly process, the movement and connection of these parts are prone to generating assembly deviations, which seriously affects the overall assembly quality of the satellites. In order to accurately predict assembly deviations before assembly, this paper introduced an assembly deviation analysis model which took rigid and flexible properties into account. Starting from the attitude adjustment of satellite assembly, the transmission law of manufacturing error was established. Then, the assembly deviation analysis model integrating rigid and flexible properties was established. Finally, the assembly experiment was carried out to verify the effectiveness of the proposed model. The results showed that the average absolute error between the measurement results and calculation results was only 0.032 mm and the maximum absolute error was 0.074 mm. The average solving accuracy of the assembly deviation was 94%. The result fully proved the effectiveness of the proposed model.

The composite structure composed of carbon fiber reinforced composite and titanium alloy is widely used in aviation and aerospace fields. Due to the different physical properties of these two materials, in the process of lamination, it is easy to appear the pore in the direction of thickness is inconsistent, which is called double-step pore defects (DSPD). The existence of DSPD will undoubtedly have an impact on the connection performance of components, but there is no clear conclusion on the extent of its impact on the connection performance, which restricts the improvement of the pore quality evaluation system, and may cause a waste of resources or leave a safety hazard for aircraft. To solve this problem, the finite element model was established to analyze the initial damage phenomenon of the component with DSPD during bolt tightening. The influence of DSPD on the static strength and fatigue properties of the component was studied by designing experiments, and the failure mechanism was revealed from the perspectives of failure form and damage evolution. The purpose of this study is to provide guidance for the improvement of the evaluation standard and the high quality and stability of the lamination component.

Countersink bolts are extensively utilized in aircraft connection structures due to their excellent connectivity performance. However, the occurrence of countersink depth errors is inevitable during the production of CFRP components. Therefore, research on the effects of countersunk hole depth mistakes on structural connection performance becomes imperative. This research aims to offer recommendations for repairing countersunk hole errors and assessing the effectiveness of hole connections. In this study, fatigue tests were conducted for CFRP single-lap joints with different countersunk hole sizes, the analysis focused on examining the effects of countersunk hole depth errors on the fatigue life, and structural stiffness of CFRP single-lap joints. Additionally, the failure forms of CFRP single-lap joints under different countersunk hole depth errors were revealed. A mechanical analysis model of the contact between the bolt taper and the hole wall was established to analyze the bearing performance of the structure under different countersunk hole head sizes and elucidate the failure behavior of the bolt. The results show that the fatigue life and structural stiffness of CFRP component exhibit an increasing trend with the deepening of countersunk holes. Furthermore, the bending moment at the bolt taper surface initially increases and subsequently decreases, reaching its peak when the bolt head is flush with the upper surface of the connecting plate. Compared with the case where the bolt protrudes from the plate, the compressive stress borne by the tapered surface of the bolt is reduced by about 47.5% when the tapered surface achieves full contact with the hole wall. Conversely, when the depth of the countersunk hole is shallow, the bolt is prone to compression collapse damage.