To effectively reduce the recoil force generated by pyrotechnic launching devices during operation, this study applies a knitted stainless steel metal wire mesh damper (MWMD) to pyrotechnic launching systems and analyzes its mechanical behavior and buffering performance. Through quasi-static cyclic compression tests and numerical simulations, the effects of wire diameter (d) and relative density (ρ) of MWMD on its mechanical and rebound characteristics were investigated, along with its impact on recoil force in shock tests. The results demonstrate that MWMDs with smaller wire diameters (d) and lower relative densities (ρ) exhibit more cyclic loading cycles and superior rebound performance. Simulation data reveal that MWMDs with smaller wire diameters and higher relative densities display stronger resistance to repeated impacts under multiple cyclic shocks, demonstrating excellent energy absorption capability with an efficiency of up to 37.59
The demand for noise and vibration control in aerospace and vehicle manufacturing is increasing, but reliable design strategies are still lacking. Here, an integrated acousto-mechanical metastructure is proposed to realize broadband low-frequency sound absorption and vibration isolation simultaneously. Due to the introduction of bistable substructures, the proposed metastructure achieves quasi-zero stiffness vibration isolation and sound energy dissipation without external loads. Rapid customized design of the optimized metastructure is achieved by the proposed optimization algorithm. An average sound absorption coefficient of 0.8 is realized by optimization design within the frequency range of 350 Hz to 800 Hz. In addition, the proposed acousto-mechanical metastructure exhibits ultra-low broadband vibration isolation performance, with an initial isolation frequency of 40.4 Hz. Theoretical calculations, numerical simulations, and experimental results show that the acoustic performance of the metastructure benefits from the intensive mode density brought by multiple geometric degrees of freedom, while its vibration isolation performance originates from the quasi-zero stiffness beams. Overall, a multi-objective optimization method under a given structural design domain is proposed to optimize the multifunctional metastructure.
High-temperature dynamic seals are the structures used to seal movable clearances in high-temperature environments. The essential components of these seals are the fiber-braided seal strips. When it is working, the strip is subjected to a transverse preload, decreasing its porosity and restricting gas flow to achieve sealing. To implement seal design, efficient numerical analysis is essential, which is supposed to involve the deformation, heat transfer, seepage, and the interactions among these physical processes. In this paper, a nonlinear thermal-mechanics-seepage coupled contact model is used to describe the seal strips with circular sections. An element differential scheme is proposed to solve the coupled governing equations, and an iterative procedure based on the element differential method (EDM) tracks the contact interfaces, which further determines the range of boundary conditions of other physical fields. The proposed method simplifies the computation by avoiding integral evaluations and reducing matrix density. Two examples are implemented to verify the correctness of the proposed scheme and to predict the variations in physical variables of the seal structures. Furthermore, a comparison between the EDM and finite element method results indicates that the EDM is more efficient because of fewer contact iterations and a sparser coefficient matrix.
To address the critical challenge of end-effector stabilization in bipedal robots while enhancing upper-body motion flexibility, this study introduces a novel bionic fully-elastically-connected tensegrity robot (BFEC-TR) inspired by the biomechanics of avian cervical construction. The proposed design transcends conventional approaches by implementing a multi-nodes bionic tensegrity structure that enables superior spatial deformation capabilities, complemented by an innovative elastic muscle control strategy for dynamic stabilization across multiple locomotion gaits: swing, walking, and running. The study encompasses three key technical contributions. First, we establish a comprehensive dynamic model of the BFEC-TR through kinematic geometric analysis. Second, we develop a feedforward control strategy that explicitly addresses the dynamic requirements of various gaits by establishing the relationship between gait parameters and control parameters, thereby ensuring segmental coordination for head stabilization. Within this control framework, we derive an optimal configuration that maintains bionic posture under energy-efficient driving criteria. Finally, extensive experimental validation demonstrates the efficacy of the proposed control strategy across different locomotion gaits. This work provides biologically-inspired design paradigm and control methodology to achieve spatial dynamic stabilization for bipedal robot end-effectors. The integration of tensegrity principles with biological inspiration from avian neck mechanics presents a novel direction for enhancing the performance and adaptability of robotic systems in dynamic environments.
This paper investigates the size-dependent axisymmetric frictionless contact problem between a rigid spherical indenter and a one-dimensional (1D) hexagonal quasicrystal (QC) half-space within the context of couple stress elasticity. By introducing the characteristic material length parameter and employing the Hankel integral transformation, the governing equations for the axisymmetric contact problem of 1D hexagonal QC under the theory of couple stress are derived and solved analytically. The least-squares integral method is also employed to obtain the expression for the contact pressure distribution with size effect. Through numerical examples, the effects of the characteristic material length parameter on the contact radius, contact pressure, and indentation depth are analyzed. The results incorporating the size effects lead to notable departures from classical elasticity predictions. The presence of the phason field leads to a reduction in peak contact pressure with the size effect.
