国际机械系统动力学学报(英文)最新文献

A passive approach is developed to quench excess vibration along a harmonically driven, arbitrarily supported, nonuniform Euler–Bernoulli beam with constant thickness (height) and varying width. Vibration suppression is achieved by attaching properly tuned vibration absorbers to enforce nodes, or points of zero vibration, along the beam. An efficient hybrid method is proposed whereby the finite element method is used to model the nonuniform beams, and a formulation based on the assumed modes method is used to determine the required attachment force supplied by each absorber to induce the desired nodes. Knowing the attachment forces needed to induce nodes, design plots are generated for the absorber parameters as a function of the tolerable vibration amplitude for each absorber mass. When the node locations are judiciously chosen, it is possible to dramatically suppress the vibration along a selected region of the beam. As such, sensitive instruments can be placed in this region and will remain nearly stationary. Numerical studies illustrate the application to several systems with various types of nonuniformity, boundary conditions, and attachment and node locations; these examples validate the proposed method to passively control excess vibration by inducing nodes on nonuniform beams subjected to harmonic excitations.

Hexagonal boron nitride (h-BN) is a semiconductor material with a wide band gap, holding promising potential for applications in thermal conductivity devices and nanoresonators in the field of microelectronics. Here, molecular dynamics is simulated to investigate the tensile and vibrational behaviors of bilayer h-BN under five different stacking modes across varying temperatures. The mechanical properties of five different stacking modes of h-BN at various temperatures are focused on, including Young's modulus, the ultimate stress, and the ultimate strain. Results indicate that bilayer h-BN nanosheets exhibit anisotropic characteristics, with their tensile properties decreasing as temperature increases. Additionally, we explore the influence of temperature on the natural frequency of bilayer h-BN under five different stacking modes. These results establish a fundamental understanding of the mechanical and vibrational characteristics of bilayer h-BN nanosheets under different stacking modes, contributing to their potential applications in advanced nanodevices operating in extremely high-temperature environments.

A bolted joint may be in a state of continuous fretting friction and wear under random oscillatory loading, which makes the bolted joint prone to loosening. Therefore, it is essential to find a way to monitor the contact state of a bolted joint on time and handle it adeptly. Acoustic emission (AE) signals will be generated during the reciprocating friction of the bolted joint interface. Exploring the relationship between the frictional slip features and the acoustic emission characteristics under different bolt preloads can lay the foundation for using the acoustic emission techniques to monitor the pretightening state of bolted joints. This paper experimentally investigates the acoustic emission signals of a bolted joint structure during friction under different preloads, three repeated tests are implemented. The relationship between friction behavior and acoustic emission characteristics under different preloads is studied. The evolution of classical acoustic emission parameters and kinematic parameters with bolt preload levels is also analyzed. The 3-D topography of the specimens after parametric tests is analyzed. The results show that the characteristics of both burst-type and continuous-type acoustic emission can reflect different friction behavior under different bolt preloads. The evolution curves of acoustic emission parameters changed under the interaction of both frictional kinematic parameters and bolt preload levels. For the 3-D surface topography, the reciprocating friction shears the peaks and fills the surface valleys, and the topography of the scratched surface areas is redistributed.

The First General Assembly and the First Session of the First Executive Board Meeting of International Society of Mechanical System Dynamics (ISMSD), the ISMSD Launching Ceremony, the Second International Conference on Mechanical System Dynamics (ICMSD), the Second ICMSD Standing Steering Committee Meeting, the Third Editorial Board Meeting of the International Journal of Mechanical System Dynamics (IJMSD), and the IJMSD Expert Symposium 2023 were held as a series of international activities on mechanical system dynamics, during the period from August 31 to September 4, 2023, at the Wyndham Beijing North, Beijing, China. More than 1000 scientists, engineers, and scholars from nearly 30 countries of six continents, including China, the United States, Canada, Russia, the United Kingdom, Germany, Portugal, Spain, Romania, the Netherlands, Poland, Finland, Italy, Denmark, Australia, Sri Lanka, Israel, Saudi Arabia, Pakistan, Singapore, India, and Japan, attended these meetings. These meetings were attended by 37 members of the National Academy of Sciences/Engineering, seven Presidents/Vice Presidents of international societies, and 18 Editors-in-Chief/Associate Editors of international journals, as well as the Leaders of Jiangsu Provincial People's Government, China Association for Science and Technology, and China National Space Administration. Focusing on the theme of “improving the research and development capability of science, technology, and industry and the mechanical system performance by using mechanical system dynamics.” These meetings and conferences defined new chapters for the future development of the field of mechanical system dynamics.

In order to adapt to the rapid development of global mechanical systems and mechanical system dynamics, nearly 100 well-known scientists and experts from 34 countries of six continents jointly initiated and established IJMSD, ICMSD, and ISMSD, including 46 members of the National Academy of Sciences/Engineering, 34 Presidents/Chairmen of international societies, and 17 Editors-in-Chief of international journals. On the afternoon of September 1, 2023, at the Wyndham Beijing North, Beijing, China, the First General Assembly and the First Session of the First Executive Board Meeting of the ISMSD marked the beginning of the series of international activities (Figure 1A,B). The 67 members of the ISMSD Preparatory Committee from nearly 30 countries of six continents attended the meeting. Among them, 36 members participated in the meeting offline, including 12 members of the National Academy of Sciences/Engineering, six Presidents/Vice Presidents of international societies, and 12 Editors-in-Chief/Associate Editors of international journals; 31 members participated in the meeting online; and four members of the National Academy of Sciences/Engineering attended in person. Prof. Xiaoting Rui, Member of the Chinese Academy of Sciences and the President of the ISMSD Preparatory

In modern warfare, fortifications are being placed deeper underground and with increased mechanical strength, placing higher demands on the target speed of the penetrating munitions that attack them. In such practical scenarios, penetrating fuze inevitably experience extreme mechanical loads with long pulse durations and high shock strengths. Experimental results indicate that their shock accelerations can even exceed those of the projectile by several times. However, due to the unclear understanding of the dynamic transfer mechanism of the penetrating fuze system under such extreme mechanical conditions, there is still a lack of effective methods to accurately estimate and design protection against the impact loads on the penetrating fuze. This paper focuses on the dynamic response of penetrating munitions and fuzes under high impact, establishing a nonlinear dynamic transfer model for penetrating fuze systems, which can calculate the sensor overload signal of the fuze location. The results show that the relative error between the peak acceleration obtained by the proposed multibody dynamic transfer model and that obtained by experimental tests is only 15.7%, which is much lower than the 26.4% error between finite element simulations and experimental tests. The computational burden of the proposed method mainly lies in the parameter calibration process, which needs to be performed only once for a specific projectile-fuze system. Once calibrated, the model can rapidly conduct parameter scanning simulations for the projectile mass, target plate strength, and impact velocity with an extremely low computational cost to obtain the response characteristics of the projectile-fuze system under various operating conditions. This greatly facilitates the practical engineering design of penetrating ammunition fuze.

Molecular dynamics (MD) simulation and orthotropic continuum model that considers interlayer shear are used to investigate the transverse deformation and free transverse vibration of multilayered rectangular molybdenum disulfide (MoS₂). The interlayer shear effect is considered in the continuum model by considering the multilayered MoS₂ as a continuous uniform orthotropic material. A method for obtaining mode shapes using a single thermal vibration MD simulation is proposed. The frequencies and mode shapes predicted using the orthotropic continuum model and MD simulation agree well. The mechanical problem of multilayered two-dimensional material plate resonator can be solved easily and efficiently by using the finite element method for the orthotropic continuum model.

With the increase in car ownership, traffic noise pollution has increased considerably and is one of the most severe types of noise pollution that affects living standards. Noise reduction by sound barriers is a common protective measure used in this country and abroad. The acoustic performance of a sound barrier is highly dependent on its shape and material. In this paper, a semianalytical meshless Burton–Miller-type singular boundary method is proposed to analyze the acoustic performance of various shapes of sound barriers, and the distribution of sound-absorbing materials on the surface of sound barriers is optimized by combining a solid isotropic material with a penalization method. The acoustic effect of the sound-absorbing material is simplified as the acoustical impedance boundary condition. The objective of optimization is to minimize the sound pressure in a given reference plane. The volume of the sound-absorbing material is used as a constraint. The density of the nodes covered with the sound-absorbing material is used as the design variable. The method of moving asymptotes was used to update the design variables. This model completely avoids the mesh discretization process in the finite element method and requires only boundary nodes. In addition, the approach also does not require the singular integral calculation in the boundary element method. The method is illustrated and validated using numerical examples to demonstrate its accuracy and efficiency.

In this paper, according to the fractional factor derivative method, we study the Lie symmetry theory of fractional nonconservative singular Lagrange systems in a configuration space. First, fractional calculus is calculated by using the fractional factor, and the fractional equations of motion are derived by using the differential variational principle. Second, the determining equations and the limiting equations of Lie symmetry under an infinitesimal group transformation are obtained. Furthermore, the fractional conserved quantity form of singular Lagrange systems caused by Lie symmetry is obtained by constructing a gauge-generating function that fulfills the structural equation, which conforms to the Noether criterion equation. Finally, we present an example of a calculation. The results show that the Lie symmetry condition of nonconservative singular Lagrange systems is more strict than conservative singular systems, but because of increased invariance restriction, the nonconservative forces do not change the form of conserved quantity; meanwhile, the fractional factor method has high natural consistency with the integral calculus, so the theory of integer-order singular systems can be easily extended to fractional singular Lagrange systems.

Fiber-reinforced composites are a popular lightweight materials used in a variety of engineering applications, such as aerospace, architecture, automotive, and marine construction, due to their attractive mechanical properties. Constructing lattice materials from fiber-reinforced composites is an efficient approach for developing ultra-lightweight structural systems with superior mechanical properties and multifunctional benefits. In contrast to corrugated, foam, and honeycomb core materials, composite lattice materials can be manufactured with various architectural designs, such as woven, grid, and truss cores. Moreover, lattice materials with open-cell topology provide multifunctional advantages over conventional closed-cell honeycomb and foam structures and are thus highly desirable for developing aerospace systems, hypersonic vehicles, long-range rockets and missiles, ship and naval structures, and protective systems. The objective of this study is to review and analyze dynamic mechanical behavior performed by different researchers in the area of composite lattice materials and to highlight topics for future research.

Displacement is a critical indicator for mechanical systems and civil structures. Conventional vision-based displacement recognition methods mainly focus on the sparse identification of limited measurement points, and the motion representation of an entire structure is very challenging. This study proposes a novel Nodes2STRNet for structural dense displacement recognition using a handful of structural control nodes based on a deformable structural three-dimensional mesh model, which consists of control node estimation subnetwork (NodesEstimate) and pose parameter recognition subnetwork (Nodes2PoseNet). NodesEstimate calculates the dense optical flow field based on FlowNet 2.0 and generates structural control node coordinates. Nodes2PoseNet uses structural control node coordinates as input and regresses structural pose parameters by a multilayer perceptron. A self-supervised learning strategy is designed with a mean square error loss and L₂ regularization to train Nodes2PoseNet. The effectiveness and accuracy of dense displacement recognition and robustness to light condition variations are validated by seismic shaking table tests of a four-story-building model. Comparative studies with image-segmentation-based Structure-PoseNet show that the proposed Nodes2STRNet can achieve higher accuracy and better robustness against light condition variations. In addition, NodesEstimate does not require retraining when faced with new scenarios, and Nodes2PoseNet has high self-supervised training efficiency with only a few control nodes instead of fully supervised pixel-level segmentation.