Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2022, 38 (1)   Published: 25 January 2022
Knockdown factor of buckling load for axially compressed cylindrical shells: State of the art and new perspectives
Bo Wang, Peng Hao, Xiangtao Ma, and Kuo Tian
Thin-walled structures are commonly utilized in aerospace and aircraft structures, which are prone to buckling under axial compression and extremely sensitive to geometric imperfections. After decades of efforts, it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections. Up to now, the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures, and this series of kn...
A newly-developed interatomic potential of Nb-Al-Ti ternary systems for high-temperature applications
Henggao Xiang, and Wanlin Guo
Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures, and the underlying mechanism and optimal doping amount remain elusive. Molecular dynamics simulation is helpful to clarify these problems, but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys. Here, an interatomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed. The ternary potential ca...
Evaluating the blast mitigation performance of hard/soft composite structures through field explosion experiment and numerical analysis
Fengyuan Yang, Zhijie Li, Zhuo Zhuang, and Zhanli Liu
The application of hard/soft composite structure in personnel armor for blast mitigation is relatively practical and effective in realistic protection engineering, such as the shell/liner system of the helmet. However, there is still lacking a reliable experimental methodology to effectively evaluate the blast mitigation performance when the structure directly contacts the protected target, which limits the development of protection structures. In this paper, we proposed a new method to evaluate...
Effect of solid particle erosion on fracture strength of low density polyethylene film
Guohua Wang, Shuopeng Xu, Jiaying Ma, and Xi Zhou

In this study, the influence of solid particle erosion on the fracture strength of low density polyethylene (LDPE) film under controlled conditions is investigated through impact experiments. The variations in the residual fracture stress as well as the residual fracture strain of the LDPE film after solid particle impact against the impact angle (α), impact velocity (vp) and impact duration (t) are analysed. The study revealed that the fracture stress and the fracture strain of the LDP...

Cross-scale indentation scaling relationships of strain gradient plastic solids: influence of inclusions near the indenter tip
Zhijie Yu, and Yueguang Wei
The indentation test is a localized testing technique; therefore, the role of the material size-effect and local non-uniformity is of much importance. The influence of the heterogeneity in size-independent materials has been studied previously. The present work detailedly investigated the influence of the material size-effect and heterogeneity (inclusions near the indenter tip) on the indentation hardness using a size-dependent strain gradient plastic theory. And it was found that when consideri...
On the extinction route of a stochastic population model under heteroclinic bifurcation
Qing Yu, Yang Li, and Xianbin Liu
The noise-induced transition of the augmented Lotka-Volterra system is investigated under vanishingly small noise. Populations will ultimately go extinct because of intrinsic noise, and different extinction routes may occur due to the Freidlin-Wentzell large deviation theory. The relation between the most probable extinction route (MPER) and heteroclinic bifurcation is studied in this paper. The MPERs and the quasi-potentials in different regimes of parameters are analyzed in detail. Before the ...
Numerical investigation of efficient synthetic jets generated by multiple-frequency actuating signals
Yiran Lu, Jiangsheng Wang, and Jinjun Wang
The synthetic jets generated by multiple-frequency actuating signals composed of a basic sinusoidal wave and a superposed high-frequency signal is investigated by two-dimensional simulation in the present study. The effect of the frequency and amplitude of the high-frequency signal on the synthetic jet in the quiescent flow is investigated in detail with stroke length ratio and Reynolds number kept as constant. It is found that, with the high-frequency signal superposed, the vortex pairs induced...
Exact mathematical formulas for wall-heat flux in compressible turbulent channel flows
Peng Zhang, Yubin Song, and Zhenhua Xia
In this paper, several exact expressions for the mean heat flux at the wall () for the compressible turbulent channel flows are derived by using the internal energy equation or the total energy equation. Two different routes, including the FIK method and the RD method, can be applied. The direct numerical simulation data of compressible channel flows at different Reynolds and Mach numbers verify the correctness of the derived formulas. Discussions related to the different energy equations, and d...
Lagrangian-based spatial-temporal topological study on the evolution and migration of coherent structures in wall turbulence
Haiping Tian, Xingrui Yi, Fang Xu, Fen Li, and Nan Jiang
In this work, we study the development, evolution, and migration of turbulent coherent structures in the turbulent boundary layer at = 630 using time-resolved particle image velocimetry (TR-PIV). Multiple techniques, including multi-scale analysis, conditional averaging, cross-correlation, and spatial-temporal topological analysis are applied to extract the evolution principle, migration trajectory, and convection velocity vector of the targeted coherent structures from a Lagrangian perspective....
New method for the determination of convective heat transfer coefficient in fully-developed laminar pipe flow
Ji Lin, Yongxing Hong, and Jun Lu
Convective heat transfer coefficient is one of the most vital parameters which reveals the thermal efficiency of a pipe flow. To obtain such coefficients for problems with variable pipe wall temperature, numerical iterative methods should be used which could be time-consuming and less accurate. In this paper, thermophysical properties of fluids are assumed to be constant. We define a variable related to the temperature gradient of the pipe wall and study the varying law of the local coefficient....
Compressive properties and energy absorption of BCC lattice structures with bio-inspired gradient design
Fuchao Gao, Qinglei Zeng, Jing Wang, Zengfei Liu, and Jun Liang
Inspired by the gradient structure of the nature, two gradient lattice structures, i.e., unidirectional gradient lattice (UGL) and bidirectional gradient lattice (BGL), are proposed based on the body-centered cubic (BCC) lattice to obtain specially designed mechanical behaviors, such as load-bearing and energy absorption capacities. First, a theoretical model is proposed to predict the initial stiffness of the gradient lattice structure under compressive loading, and validated against quasi-stat...
Numerical study on crack propagation under explosive loads
Chuanjin Pu, Xin Yang, Han Zhao, Zhenlin Chen, Dingjun Xiao, Changlin Zhou, and Bing Xue
Dynamic crack propagation in brittle materials plays an important role in understanding the fracture mechanism. Numerical simulations on crack propagation in the polymethyle methacrylate (PMMA) under explosive loads were carried out through Autodyn 3D code. Although the Johnson-Holmquist (JH-2) constitutive model has been widely treated as an acceptable scheme, it cannot improve the description in the post-failure response of material and reduce the mesh dependency, so the crack softening failur...
Multi-parameter joint optimization for double-strip high-speed pantographs to improve pantograph-catenary interaction quality
Mengzhen Wu, Xianghong Xu, Yongzhao Yan, Yi Luo, Sijun Huang, and Jianshan Wang
The significant increase in speed of high-speed train will cause the dynamic contact force of the pantograph-catenary system to fluctuate more severely, which poses a challenge to the study of the pantograph-catenary relationship and the design of high-speed pantographs. Good pantograph-catenary coupling quality is the essential condition to ensure safe and efficient operation of high-speed train, stable and reliable current collection, and reduction in the wear of contact wires and pantograph c...
Signal-to-noise ratio gain of an adaptive neuron model with Gamma renewal synaptic input
Yanmei Kang, Yuxuan Fu, and Yaqian Chen
We take an adaptive leaky integrate-and-fire neuron model to explore the effect of non-Poisson neurotransmitter on stochastic resonance and its signal-to-noise ratio (SNR) gain. Event triggered algorithm is adopted to speed up the simulating process. It is revealed that both the output SNR and the SNR gain can be monotonically improved when increasing the shape parameter for Gamma distribution. Particularly, for large signal coupling strength, the 1:1 stochastic phase locking induced by Gamma no...
Patient-specific modeling of left ventricle mechanics
J. I. Colorado-Cervantes, P. Nardinocchi, P. Piras, V. Sansalone, L. Teresi, C. Torromeo, and P. E. Puddu

We present a computational framework for the study of cardiac motion. The bio-mechanical model captures the passive and active properties of the cardiac tissue as well as the fiber architecture. We focus on the analysis of deformations of a beating left ventricle (LV), confronting numerical simulations with real data acquired by echocardiography. The goal is to determine the clinical relevance of the LV strains pattern and to investigate the relationships between that pattern and the arrangem...

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