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Performance improvement of the stochastic-resonance-based tri-stable energy harvester under random rotational vibration 随机旋转振动下基于随机共振的三稳定能量采集器性能改进
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-09-01 DOI: 10.1016/j.taml.2022.100365
Tingting Zhang , Yanfei Jin , Yanxia Zhang

In this paper, the stochastic-resonance-based tri-stable energy harvester (TEH) is proposed to enhance harvesting performance under random rotational vibration. An electromechanical coupled system interfaced with a standard rectifier circuit driven by colored noise is considered. The stationary probability density function (SPDF) of the harvester is obtained by the improved stochastic averaging. Then, with the adiabatic approximation theory, the analytical expression of signal-to-noise ratio (SNR) for the TEH is deduced to characterize stochastic resonance (SR). To enhance direct current (DC) power delivery from a rotational TEH, the influences of system parameters on SR is discussed. The obtained results suggest that there are damping-induced resonance and noise-intensity-induced SR in the tri-stable system. The TEH has higher harvesting performance under the optimal SR. That is, the optimal parameter combinations can induce optimal SR and maximize harvesting performance. Thus, the stochastic-resonance-based TEH can be optimized to enhance energy harvesting through choosing the optimal parameter.

为了提高随机旋转振动下的能量采集性能,提出了基于随机共振的三稳定能量采集器(TEH)。考虑了一种以有色噪声驱动的标准整流电路为接口的机电耦合系统。采用改进的随机平均方法,得到了收割机的平稳概率密度函数。然后,利用绝热近似理论,推导了热电偶的信噪比解析表达式,以表征热电偶的随机共振。为了提高旋转TEH的直流输出功率,讨论了系统参数对SR的影响。结果表明,三稳定系统存在阻尼诱发共振和噪声强度诱发SR。在最优SR下,TEH具有更高的收获性能,即最优的参数组合可以诱导最优SR和最大的收获性能。因此,可以通过选择最优参数对基于随机共振的TEH进行优化,以增强能量收集。
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引用次数: 2
Mechanical characteristics of composite honeycomb sandwich structures under oblique impact 复合材料蜂窝夹层结构斜冲击力学特性研究
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-09-01 DOI: 10.1016/j.taml.2022.100379
Yuechen Duan , Zhen Cui , Xin Xie , Ying Tie , Ting Zou , Tingting Wang

Carbon fiber reinforced polymer (CFRP) and CFRP-based composite honeycomb sandwich structures are particularly sensitive to impact. The mechanical characteristics of composite honeycomb sandwich structures under oblique impact are studied by numerical simulation and experiment. The oblique impact model is established, and the reliability of the model is verified by the oblique impact test. To further analyze the influence of structural parameters on energy absorption under oblique impact, the influence of impact angle, face sheet thickness and wall thickness of the honeycomb is numerically studied. The results show that the impact angle has an important effect on energy distribution. The structural parameters also have an effect on the peak contact force, contact time, and energy absorption, and the effect is different from normal impact due to the presence of frictional dissipation energy. Compared with normal impact, the debonding of oblique impact will be reduced, but the buckling range of the honeycomb core will be expanded.

碳纤维增强聚合物(CFRP)和CFRP基复合材料蜂窝夹层结构对冲击尤为敏感。通过数值模拟和实验研究了复合材料蜂窝夹层结构在斜冲击作用下的受力特性。建立了斜冲击模型,并通过斜冲击试验验证了模型的可靠性。为了进一步分析结构参数对斜冲击下吸能的影响,数值研究了冲击角度、面板厚度和壁厚对蜂窝吸能的影响。结果表明,冲击角对能量分布有重要影响。结构参数对峰值接触力、接触时间和能量吸收也有影响,并且由于摩擦耗散能的存在,这种影响与正常冲击不同。与正常撞击相比,斜撞击会减少蜂窝芯的脱粘,但会扩大蜂窝芯的屈曲范围。
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引用次数: 6
A structure-preserving algorithm for time-scale non-shifted Hamiltonian systems 时间尺度非移位哈密顿系统的结构保持算法
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-09-01 DOI: 10.1016/j.taml.2022.100368
Xue Tian , Yi Zhang

The variational calculus of time-scale non-shifted systems includes both the traditional continuous and traditional significant discrete variational calculus. Not only can the combination of Δ and derivatives be beneficial to obtaining higher convergence order in numerical analysis, but also it prompts the time-scale numerical computational scheme to have good properties, for instance, structure-preserving. In this letter, a structure-preserving algorithm for time-scale non-shifted Hamiltonian systems is proposed. By using the time-scale discrete variational method and calculus theory, and taking a discrete time scale in the variational principle of non-shifted Hamiltonian systems, the corresponding discrete Hamiltonian principle can be obtained. Furthermore, the time-scale discrete Hamilton difference equations, Noether theorem, and the symplectic scheme of discrete Hamiltonian systems are obtained. Finally, taking the Kepler problem and damped oscillator for time-scale non-shifted Hamiltonian systems as examples, they show that the time-scale discrete variational method is a structure-preserving algorithm. The new algorithm not only provides a numerical method for solving time-scale non-shifted dynamic equations but can be calculated with variable step sizes to improve the computational speed.

时标非移系统的变分演算包括传统的连续变分演算和传统的显著离散变分演算。Δ和∇导数的结合不仅有利于在数值分析中获得更高的收敛阶,而且使时尺度数值计算方案具有良好的结构保持性。本文提出了一种时间尺度非位移哈密顿系统的结构保持算法。利用时间尺度离散变分方法和微积分理论,在非移位哈密顿系统的变分原理中取一个离散时间尺度,可以得到相应的离散哈密顿原理。进一步得到了离散哈密顿系统的时间尺度离散哈密顿差分方程、Noether定理和辛格式。最后,以时间尺度非位移哈密顿系统的开普勒问题和阻尼振子为例,证明了时间尺度离散变分方法是一种结构保持算法。该算法不仅为求解时尺度非位移动力学方程提供了一种数值方法,而且可以采用可变步长进行计算,提高了计算速度。
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引用次数: 0
Optimization for vibro-impact nonlinear energy sink under random excitation 随机激励下振动冲击非线性能量汇优化
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-09-01 DOI: 10.1016/j.taml.2022.100364
Jiamin Qian , Lincong Chen

As a promising vibration control device, the vibro-impact nonlinear energy sink (VI-NES) gathered extensively attention in recent years. However, general optimization procedures have not been available for the design of VI-NES subjected to random excitations. To this end, this paper constitutes a research effort to address this gap. Specifically, the approximate analytical solution of the system stochastic response is obtained in conjunction with non-smooth conversion and stochastic averaging methodology. Taking advantages of this approximate solution, the variance of the system is defined and easily minimized to calculate the optimal parameters for VI-NES. In addition, the results computed by this way fairly correlate with direct numeric simulations.

振动冲击非线性能量阱作为一种很有前途的振动控制装置,近年来受到了广泛的关注。然而,对于受随机激励的VI-NES的设计,还没有通用的优化程序。为此,本文构成了解决这一差距的研究努力。具体地,结合非光滑转换和随机平均方法,得到了系统随机响应的近似解析解。利用这一近似解,系统的方差被定义并易于最小化,从而计算出VI-NES的最优参数。此外,用这种方法计算的结果与直接数值模拟结果相当吻合。
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引用次数: 1
An alternative form of energy density demonstrating the severe strain-stiffening in thin spherical and cylindrical shells 能量密度的另一种形式表明在薄球形和圆柱形壳体中严重的应变硬化
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100361
Md. Moonim Lateefi , Deepak Kumar , Somnath Sarangi

The present article investigates an elastic instability phenomenon for internally pressurized spherical thin balloons and thin cylindrical tubes composed of incompressible hyperelastic material. A mathematical model is formulated by proposing a new strain energy density function. In the family of limited elastic materials, many material models exhibit strain-stiffening. However, they fail to predict severe strain-stiffening in a moderate range of deformations in the stress-strain relations. The proposed energy function contains three material parameters and shows substantially improved stain stiffening properties than the limited elastic material models. The model is further applied to explore the elastic instability phenomenon in spherical and cylindrical shells. The findings are compared with other existing models and validated with experimental results. The model shows better agreement with experimental results and exhibits a substantial strain-stiffening effect than the current models.

本文研究了由不可压缩超弹性材料组成的内压球形薄气球和薄圆柱管的弹性失稳现象。提出了一种新的应变能密度函数,建立了数学模型。在有限弹性材料族中,许多材料模型都表现出应变硬化。然而,它们不能预测在中等变形范围内的应力-应变关系中的严重应变硬化。所提出的能量函数包含三个材料参数,与有限弹性材料模型相比,具有明显改善的硬化性能。将该模型进一步应用于探讨球壳和圆柱壳的弹性失稳现象。将所得结果与已有模型进行了比较,并与实验结果进行了验证。该模型与试验结果吻合较好,具有较强的应变加劲效应。
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引用次数: 2
Independent component analysis of streamwise velocity fluctuations in turbulent channel flows 紊流河道中沿流速度波动的独立分量分析
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100349
Ting Wu , Guowei He

Independent component analysis (ICA) is used to study the multiscale localised modes of streamwise velocity fluctuations in turbulent channel flows. ICA aims to decompose signals into independent modes, which may induce spatially localised objects. The height and size are defined to quantify the spatial position and extension of these ICA modes, respectively. In contrast to spatially extended proper orthogonal decomposition (POD) modes, ICA modes are typically localised in space, and the energy of some modes is distributed across the near-wall region. The sizes of ICA modes are multiscale and are approximately proportional to their heights. ICA modes can also help to reconstruct the statistics of turbulence, particularly the third-order moment of velocity fluctuations, which is related to the strongest Reynolds shear-stress-producing events. The results reported in this paper indicate that the ICA method may connect statistical descriptions and structural descriptions of turbulence.

采用独立分量分析(ICA)研究了紊流沟道中顺流速度波动的多尺度局域模态。ICA的目的是将信号分解成独立的模式,这些模式可能会诱导出空间局部化的对象。定义高度和大小分别用于量化这些ICA模式的空间位置和扩展。与空间扩展固有正交分解(POD)模态相比,ICA模态通常在空间上是局域化的,某些模态的能量分布在近壁区域。ICA模态的大小是多尺度的,并且与它们的高度近似成正比。ICA模式还可以帮助重建湍流的统计数据,特别是速度波动的三阶矩,这与最强的雷诺兹剪切应力产生事件有关。本文的结果表明,ICA方法可以将湍流的统计描述和结构描述结合起来。
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引用次数: 3
On the number of fractured segments of spaghetti breaking dynamics 意大利面断裂动力学中断裂段数的研究
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100347
Yi Zhang, Xiang Li, Yuanfan Dai, Bo-Hua Sun

Why are pieces of spaghetti generally broken into three to ten segments instead of two as one thinks? How can one obtain the desired number of fracture segments? To answer those questions, the fracture dynamics of a strand of spaghetti is modelled by elastic rod and numerically investigated by using finite-element software ABAQUS. By data fitting, two relations are obtained: the number of fracture segments in terms of rod diameter-length ratio and fracture limit curvature with the rod diameter. Results reveal that when the length is constant, the larger the diameter and/or the smaller the diameter-length ratio D/L, the smaller the limit curvature; and the larger the diameter-length ratio D/L, the fewer the number of fractured segments. The relevant formulations can be used to obtain the desired number of broken segments of spaghetti by changing the diameter-to-length ratio.

为什么意大利面通常被分成三到十段,而不是像人们想象的那样分成两段?如何获得所需的骨折段数?为了回答这些问题,采用弹性杆模拟了一股意大利面条的断裂动力学,并利用有限元软件ABAQUS进行了数值研究。通过数据拟合得到两种关系:裂缝段数与杆径长比的关系和裂缝极限曲率与杆径的关系。结果表明:当长度一定时,直径越大和/或径长比D/L越小,极限曲率越小;径长比D/L越大,裂缝段数越少。相关的公式可以通过改变意大利面条的直径与长度比来获得所需的破碎段数。
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引用次数: 0
Motion of a sphere and the suspending low-Reynolds-number fluid confined in a cubic cavity 球体的运动和限制在立方腔内的低雷诺数悬浮流体
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100352
Gaofeng Chen , Xikai Jiang

Dynamics of a spherical particle and the suspending low-Reynolds-number fluid confined by a cubic cavity were studied numerically. We calculated the particle’s hydrodynamic mobilities along x-, y-, and z-directions at various locations in the cavity. The mobility is largest in the cavity center and decays as the particle becomes closer to no-slip walls. It was found that mobilities in the entire cubic cavity can be determined by a minimal set in a unit tetrahedron therein. Fluid vortices in the cavity induced by the particle motion were observed and analyzed. We also found that the particle can exhibit a drift motion perpendicular to the external force. Magnitude of the drift velocity normalized by the velocity along the direction of the external force depends on particle location and particle-to-cavity sizes ratio. This work forms the basis to understand more complex dynamics in microfluidic applications such as intracellular transport and encapsulation technologies.

对球形颗粒和受立方腔约束的低雷诺数悬浮流体的动力学进行了数值研究。我们计算了粒子在腔内不同位置沿x、y和z方向的流体动力学移动。迁移率在腔中心最大,并且随着粒子靠近无滑移壁而衰减。发现整个立方腔内的迁移率可以用其中的单位四面体的极小集来确定。观察并分析了粒子运动引起的腔内流体涡流。我们还发现,粒子可以表现出垂直于外力的漂移运动。由沿外力方向的速度归一化的漂移速度的大小取决于颗粒位置和颗粒与腔的尺寸比。这项工作形成了理解微流体应用中更复杂动力学的基础,如细胞内运输和封装技术。
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引用次数: 1
Design of elliptical underwater acoustic cloak with truss-latticed pentamode materials 桁架五模材料椭圆水声斗篷的设计
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100346
Yuanyuan Ge, Xiaoning Liu, Gengkai Hu

Pentamode acoustic cloak is promising for underwater sound control due to its solid nature and broadband efficiency, however its realization is only limited to simple cylindrical shape. In this work, we established a set of techniques for the microstructure design of elliptical pentamode acoustic cloak based on truss lattice model, including the inverse design of unit cell and algorithms for latticed cloak assembly. The designed cloak was numerically validated by the well wave concealing performance. The work proves that more general pentamode acoustic wave devices beyond simple cylindrical geometry are theoretically feasible, and sheds light on more practical design for waterborne sound manipulation.

五模声斗篷由于其固体性质和宽带效率,在水声控制方面有很大的应用前景,但其实现仅限于简单的圆柱形。本文建立了一套基于桁架晶格模型的椭圆五模声斗篷微观结构设计技术,包括单元胞的反设计和晶格斗篷装配算法。仿真结果表明,所设计的隐身衣具有良好的井波掩蔽性能。这项工作证明了超越简单圆柱几何的更一般的五模声波装置在理论上是可行的,并为更实际的水声操纵设计提供了启示。
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引用次数: 2
Mathematical modeling of fractional derivatives for magnetohydrodynamic fluid flow between two parallel plates by the radial basis function method 用径向基函数法建立两平行板间磁流体流动的分数阶导数数学模型
IF 3.4 3区 工程技术 Q2 MECHANICS Pub Date : 2022-05-01 DOI: 10.1016/j.taml.2022.100350
Saman Hosseinzadeh, Seyed Mahdi Emadi, Seyed Mostafa Mousavi, Davood Domairry Ganji

Investigations into the magnetohydrodynamics of viscous fluids have become more important in recent years, owing to their practical significance and numerous applications in astro-physical and geo-physical phenomena. In this paper, the radial base function was utilized to answer fractional equation associated with fluid flow passing through two parallel flat plates with a magnetic field. The magnetohydrodynamics coupled stress fluid flows between two parallel plates, with the bottom plate being stationary and the top plate moving at a persistent velocity. We compared the radial basis function approach to the numerical method (fourth-order Range-Kutta) in order to verify its validity. The findings demonstrated that the discrepancy between these two techniques is quite negligible, indicating that this method is very reliable. The impact of the magnetic field parameter and Reynolds number on the velocity distribution perpendicular to the fluid flow direction is illustrated. Eventually, the velocity parameter is compared for diverse conditions α, Reynolds and position (y), the maximum of which occurs at α = 0.4. Also, the maximum velocity values occur in α=0.4 and Re=1000 and the concavity of the graph is less for α=0.8.

近年来,粘性流体的磁流体动力学研究由于其实际意义和在天体物理和地球物理现象中的许多应用而变得越来越重要。本文利用径向基函数求解流体在磁场作用下通过两个平行平板的分数阶方程。磁流体力学耦合应力流体在两个平行板之间流动,底板静止,顶板以恒定速度运动。将径向基函数方法与数值方法(四阶Range-Kutta)进行了比较,以验证其有效性。结果表明,这两种技术之间的差异是相当微不足道的,表明该方法是非常可靠的。说明了磁场参数和雷诺数对垂直于流体流动方向的速度分布的影响。最后,比较了不同条件α、雷诺数和位置(y)下的速度参数,其中最大值出现在α = 0.4时。最大速度值出现在α=0.4和Re=1000时,α=0.8时曲线的凹凸度较小。
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引用次数: 2
期刊
Theoretical and Applied Mechanics Letters
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