Rui Yang

In engineering, viscoelastic materials are commonly attached to mechanical or engineering structures to form a damping layer. With the rapid development of additive manufacturing, lattice structure design is frequently integrated into the manufacturing process to attain optimal performance. In this study, high-damping materials are incorporated into the design and manufacturing of bi-material lattice structure to further enhance vibration suppression capability. This study proposed a multi-scale topology optimization method to concurrently optimize both the macroscale and microscale structures. Both single-material and bi-material lattices are considered, enabling the optimization of damping material layouts at both the macroscale and microscale. At the macroscale, the level set optimization method is employed to optimize the macro distribution of each type of lattices. To ensure manufacturability, uniform coated structures are introduced via an interpolation model based on multi-level set functions, serving to isolate infill regions of single-material and bi-material lattices. At the microscale, the configurations of both single-material and bi-material lattice are optimized simultaneously by using Solid Isotropic Material with Penalization (SIMP) method. The effective complex properties of the lattices are derived via the frequency-domain homogenization method. Subsequently, the sensitivity analysis for relative vibration amplitude with respect to the design variables at both scales is carried. Finally, the effectiveness of the proposed method is verified by several numerical examples, and experimental test on manufactured specimens are conducted to validate the numerical results.

Needled ceramic composites have great application prospects for high-temperature structural components. However, due to the manufacturing defects, the properties of the composite show significant dispersion, which poses great challenges for predicting the service life. Firstly, X-ray computed tomography was used to determine the pores in the composites, and multiscale models considering the pores were established. Combined with the multiscale method, the elastic modulus was predicted, and the relationship between porosity and elastic modulus was established. Secondly, the thermal diffusion coefficient was predicted. The relationship between porosity and thermal diffusion coefficient was determined. The accuracy of the multiscale method was verified by comparative analysis with the tensile experiment and the thermal diffusion experiment, respectively. Finally, based on the results of the model analysis, the correlation equations between thermal diffusion coefficient, porosity and elastic modulus were established. Thereby, new ideas are provided for the assessment of porosity and elastic properties of the composites.

Aiming to address the issue that folding wing research lacks robust modeling methods suitable for rapid analysis of structural dynamic characteristics and integrated research for experimental model verification, this paper deduces a rapid structural dynamic modeling method for folding wings based on the fixed interface substructure modal synthesis method. Following the principles of structural and functional similarity, a low-speed flutter experimental model of the folding wing with a continuous variable folding angle is designed and manufactured. For the folding wing model, the former main mode frequencies of the structure are obtained by the method of dynamic formula and ground percussion experiment, respectively. The experimental results show that the derived dynamic model is reliable. The P-k method and low-speed wind tunnel model experiment method are employed to study flutter characteristics of folding wing models. The results indicate that the critical flutter velocity is determined by the coupling of the first bending mode and the first torsional mode. The modal coupling trend is the same under different folding angles, but the critical flutter velocity is different. In addition, the damping coefficient has a significant effect on the critical flutter velocity, and the modal damping of the experimental model of the mechanically manufactured folding wing in this study ranges between 0.01 and 0.02.