The multiscale model based on micro-mechanics failure theory is modified to consider complex internal structures, including a fiber random arrangement pattern and interface with the clustering method. Then, a feed-forward-neural-network (FFNN)-based damage evolution method is developed to evaluate the macroscale property degradation. The progressive damage analysis of open-hole laminates under compression is conducted to validate the modified multiscale method. The predicted results reveal that the interface results in the premature initiation of damage, and the fiber random arrangement pattern contributes to the decrease in the predicted compression responses. The developed FFNN-based method aimed at degradation results in an increase in the predicted compression strength. For the fiber random distribution pattern, the increase in percentage of predicted compressive strength is 6.0%, which is much larger than the value for the fiber diamond distribution pattern.

The nonlinear characteristics of bolted connections are of significant importance for analyzing the mechanical performance of structures. The Iwan model is well-known and has been widely applied; its limitation is that it is not convenient for complex structures with multiple bolted connections. To simplify the modeling process, a material with the force-displacement characteristics of the Iwan model is proposed and applied to the bolted connection region, which can convert the nonlinearity of the bolted connection into the nonlinearity of the material. The constitutive relation of the proposed Iwan-based material is determined by the force-displacement equation of the bolted connection under load and the elastic-plastic hypothesis. The proposed Iwan-based material is implemented using the UMAT subroutine of ABAQUS, and the properties of the Iwan-based material are assigned to a solid finite element for an equivalent modeling of bolted connections. Through comparisons with the s imul ation results of the AIBE, the feasibility of the equivalent modeling method for the force-displacement relationship of the original Iwan model is verified, and through comparisons with the simulation results and experimental results of a detailed 3D FE model of the bolted connection, the universality of the equivalent modeling method is verified. The results show that the equivalent modeling method can well restore the statics characteristics of bolted structures under cyclic loading and can be applied to complex combined structures. The method is more convenient for establishing the finite element model of bolted connections and has more flexibility in adjusting parameters than traditional methods.

Numerical simulations employing the dynamic mesh method were performed to investigate the unsteady aerodynamics of variable-sweep wings during morphing. Quasi-steady and unsteady aerodynamic characteristics were compared, and the effects of key operating conditions (freestream velocity, angle of attack, morphing period, wingspan, chord length) on unsteady aerodynamics were analyzed. To enable the rapid prediction of unsteady aerodynamics, a Kriging surrogate model was established and validated against high-fidelity CFD results. The results indicate that unsteady effects manifest as hysteresis loops in aerodynamic coefficients within the morphing cycle. The wing morphing period, angle of attack, freestream velocity, and wingspan have a pronounced impact on the unsteady aerodynamic characteristics, whereas the effect of chord length is negligible. Reduced morphing periods, increased angles of attack, and increased wingspans amplify the hysteresis loop size and enhance the unsteady effects. An increase in the freestream velocity intensifies unsteady effects in the subsonic flow, while it attenuates unsteady effects in the supersonic flow. Compared to direct CFD simulations, the Kriging model for unsteady aerodynamic characteristics prediction achieves a 97% improvement in overall computational efficiency, while its predicted hysteresis loops are in good agreement with CFD results in both trend and magnitude, with an average prediction error below 4% and a maximum error of less than 6%. The Kriging surrogate model developed in this study offers substantial practical value for engineering applications by meeting the demand for rapid aerodynamic computation in the concept design phase for morphing aircraft.

To overcome the low accuracy and inefficiency of the conventional influence coefficient method for micromotor rotor balancing, this paper proposes a rotor unbalance identification approach based on a long short-term memory (LSTM) neural network. Synthetic vibration responses generated from the rotor-support dynamic model are used to pre-train the network, which is then fine-tuned with measured data, so that the knowledge learned from the idealized model is adapted to real measurement conditions. After min–max normalization, the data are fed into a multi-layer LSTM network that directly predicts the unbalance masses and phases on both correction planes from a single constant-speed vibration measurement. Simulation results show that the identification error remains below 5% for unbalance masses above 40 mg and within 4 mg for smaller masses. Experimental validation on three-slot and five-slot micromotor rotors demonstrates that the residual unbalance after correction is reduced by 10.8–17.4% depending on rotor type and correction plane, corresponding to an overall reduction of 15.4% in total residual unbalance mass. The proposed method eliminates repeated start–stop and trial-weight operations, significantly improving balancing efficiency. This work provides an effective approach for high-precision and rapid balancing of micromotor rotors.

The frequency-domain flutter analysis method requires a linear model as input; however, when a telescopic actuator is applied to morphing aircraft, traditional frequency-domain flutter analysis methods face challenges in addressing issues involving contact nonlinearity. To enable classical frequency-domain methods to handle this type of nonlinearity, this paper presents an equivalent linearization modeling method for morphing aircraft wing structures. The proposed modeling method uses rod elements as the equivalent linearization elements and avoids the need to handle node correspondence issues. The model is parameterized by the rod element’s elastic modulus, contact surface distance, and element length coefficient. Upon completion of the equivalent modeling, flutter analysis can be performed by the PK method. The proposed modeling method increases modeling efficiency while maintaining the accuracy of the model. A simulation study of a typical hypersonic telescopic wing structure is conducted. The effects of angle of attack and altitude on flutter characteristics are analyzed. The proposed modeling method effectively captures both the static and dynamic characteristics of the original structure. The flutter Mach number decreases with increasing extension length, and it increases with altitude and angle of attack. The flutter frequency decreases with increasing extension length, angle of attack, and altitude.