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Analytical solutions of free vibration for rectangular thin plate and right-angle triangle plate on the Winkler elastic foundation based on the symplectic superposition method 基于辛叠加法的Winkler弹性地基上矩形薄板和直角三角形板自由振动解析解
4区 工程技术 Q3 MECHANICS Pub Date : 2023-11-09 DOI: 10.1093/jom/ufad032
Hao-Jie Jiang, Tong-Bo Chen, Yu-Xiang Ren, Ning-Hua Gao
Abstract Based on the symplectic superposition method, the free vibration models of rectangular and right-angle triangle plates on the Winkler elastic foundation are established in present paper, and the modes and frequencies are studied. In addition, the theoretical calculation model and finite element analysis model of rectangular thin plate and right-angle triangle plate on elastic foundation are established by using Mathematica software and ABAQUS software. It proves that the symplectic superposition method converges very fast and has a good consistency with the finite element simulation results. Analytical results show that foundation stiffness, aspect ratio and boundary condition have great influences on vibration frequency and mode shape for structures. This paper solved the free vibration problem of rectangular plate and right-angle triangle plate on elastic foundation by using symplectic superposition method. Compared with the inverse or semi-inverse method, this method avoids the process of assuming the form about the solution, hence the result of this method is completely rational.
基于辛叠加法,建立了Winkler弹性地基上矩形板和直角三角形板的自由振动模型,并对其振型和频率进行了研究。此外,利用Mathematica软件和ABAQUS软件建立了弹性基础上矩形薄板和直角三角形板的理论计算模型和有限元分析模型。结果表明,辛叠加法收敛速度快,与有限元仿真结果有较好的一致性。分析结果表明,基础刚度、展弦比和边界条件对结构振动频率和振型有较大影响。本文用辛叠加法求解弹性基础上矩形板和直角三角形板的自由振动问题。与逆法或半逆法相比,该方法避免了对解的形式进行假设的过程,因此该方法的结果是完全合理的。
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引用次数: 0
Free vibration analysis of Timoshenko pipes conveying fluid with gravity and different boundary conditions 含重力和不同边界条件下输送流体的Timoshenko管道自由振动分析
4区 工程技术 Q3 MECHANICS Pub Date : 2023-11-09 DOI: 10.1093/jom/ufad031
Bo Shui, Yun-dong Li, Yu-mei Luo, Fei Luo
Abstract In this paper, the free vibration of Timoshenko pipes conveying fluid with gravity and different boundary conditions is analyzed by using the weak form quadrature element method. The dimensionless frequency and critical flow velocity have been calculated considering various parameters such as the mass ratio of pipe to fluid, slenderness ratio, and gravity. The numerical results with different numbers of discrete points are tested, and the results show that the method has a fast convergence speed. Some numerical results are compared with the existing literature, which proves that the weak form quadrature element method has high accuracy and computational efficiency. This paper shows that the weak form quadrature element method is a preferred method for analyzing fluid-conveying pipes with various boundary conditions.
摘要本文采用弱形式正交元法,对具有重力和不同边界条件下输送流体的Timoshenko管道的自由振动进行了分析。考虑管液质量比、长细比、重力等参数,计算了无量纲频率和临界流速。对不同离散点数下的数值结果进行了测试,结果表明该方法具有较快的收敛速度。将一些数值结果与已有文献进行了比较,证明了弱形式正交元法具有较高的精度和计算效率。本文表明,弱形式正交单元法是分析具有各种边界条件的流体输送管道的优选方法。
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引用次数: 0
Growth of force chain network upon non-Bagnold Transition of Inclined Surface Granular Flows via Discrete Element Simulation 斜面颗粒流非bagnold过渡时力链网络的增长及其离散元模拟
4区 工程技术 Q3 MECHANICS Pub Date : 2023-11-09 DOI: 10.1093/jom/ufad030
Cheng-Ting Tsai, Chih-Ying Cheng, F-L Yang
Abstract A steady granular flow down an inclined surface is an important flow configuration to study the dynamic of dry granular flow. This work adopts two-dimensional discrete element simulation to study how inter-grain friction may play a role in momentum transport, in addition to the collision-based transport, to induce the non-Bagnold flow velocity profile reported in the literature. Special efforts were made to apply the knowledge of network science to identify the contact force chain network from particle dynamics information using the graph theory with the Louvain greedy algorithm. We studied how the number of grains born in the force chain network grows when the flow scaled velocity profile degrades from Bagnold to non-Bagnold flows. Concurrently, the stress loading ratio carried by these frictional contacts rises abruptly upon the non-Bagnold flow transition identifies when the flow Froude number falls roughly below 2.15. Both phenomena suggest that the non-local phenomenon of Bagnold velocity profile degradation occurs when sufficient grains are confined in the force chain network to assist the stress transport, replacing the collisional transport. Hence, a refined rheology model is needed in the future to account for this friction-assisted momentum transport at a mesoscopic yet flow-dependent length scale like that of the currently investigated force network.
摘要沿倾斜表面的稳定颗粒流是研究干颗粒流动力学的重要流态。本文采用二维离散元模拟的方法,研究了除了基于碰撞的动量输运之外,晶粒间摩擦如何在动量输运中发挥作用,从而诱发文献中报道的非bagnold流速分布。利用图论和鲁万贪心算法,应用网络科学的知识,从粒子动力学信息中识别接触力链网络。我们研究了当流动比例速度分布从Bagnold流退化到非Bagnold流时,力链网络中出生的晶粒数量是如何增长的。同时,当流动弗劳德数大致低于2.15时,在非bagnold流动过渡阶段,这些摩擦触点所携带的应力加载比急剧上升。这两种现象都表明,当足够的晶粒被限制在力链网络中以辅助应力传递,取代碰撞传递时,就会发生非局部的Bagnold速度剖面退化现象。因此,未来需要一个精细的流变模型来解释这种摩擦辅助动量输运,在介观上,但与流动相关的长度尺度,就像目前研究的力网络一样。
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引用次数: 0
Flow and heat transfer characteristics in fallopian tube with metachronal wave of cilia 纤毛异向波作用下输卵管内流动和换热特性
4区 工程技术 Q3 MECHANICS Pub Date : 2023-10-13 DOI: 10.1093/jom/ufad027
Anum Tanveer, Zain Ul Abidin, Faisal Z Duraihem, S Saleem
Abstract Cilia is an important mechanism for epithelial cells in the respiratory tract, cerebrospinal flow in the brain, hair bundles in the ear and photoreceptor in the retina, etc. Cilia can also be found in human fallopian tube for the transport of the ova, embryos and sperm. In this research, we investigate the combined effects of mixed convection and magnetic field. In the present analysis we describe the flow and heat transfer characteristics of MHD Carreau fluid in fallopian tube with metachronal wave of cilia. The mathematical Eq. of the problem is performed under creeping phenomena and long wavelength approximation. The numerical solution for extra stress tensor, temperature profile and streamline pattern are obtained using the NDSolve method of Mathematica software. The physical and graphical behavior of different value of involved parameter are discussed in the last section. The parametric values are kept small (< 10) in view of cilia walls having very small diameter.
纤毛是呼吸道上皮细胞、脑内脑脊液、耳内毛束、视网膜内光感受器等的重要机制。纤毛也可以在人类的输卵管中找到,用于运送卵子、胚胎和精子。在本研究中,我们研究了混合对流和磁场的联合效应。本文用纤毛的超向波描述了MHD卡罗液在输卵管内的流动和换热特性。在蠕变现象和长波长近似下,给出了问题的数学方程。利用Mathematica软件的NDSolve方法得到了额外应力张量、温度剖面和流线模式的数值解。最后一节讨论了所涉及参数不同值的物理和图形行为。参数值保持较小(<10)鉴于纤毛壁的直径很小。
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引用次数: 0
Jetting and shock wave during oblique hypervelocity impact of spherical projectile 球面弹丸倾斜超高速撞击时的射流与激波
4区 工程技术 Q3 MECHANICS Pub Date : 2023-09-13 DOI: 10.1093/jom/ufad012
Xin Liu, Yongjun Deng, Ken Wen, Yong Yao
Abstract Space debris impacts on whipped shields are dominantly non-vertical. Shock initiation and interaction govern the fragmentation of projectiles and plates, directly determining the features of the produced debris cloud. During the initial impact stage of a projectile on a target, wave propagation and evolution occur in their interior with co-dominant material fragmentation. In this study, the effects of the impact conditions (impact velocity and attack angle) on the critical conditions for jet generation were examined based on the asymmetric jetting theory. In the Geometric Propagation Model (GPM), the effect of the attack angle was considered, and a wave front deflection angle parameter was introduced. The modified GPM could describe the geometric features and position of a wave front during an oblique impact. Combined with smoothed particle hydrodynamics numerical simulations, the interior of projectiles, fragmentation features, and pressure attenuation were studied. It was found that in large attack angle cases, the projectile material is more likely to reach the critical conditions for jet generation, and the jet mass proportion of the projectile material increases with increasing attack angle. The modified GPM is an oblique elliptic Eq. that is a function of the equivalent speed, impact velocity, attack angle, time, and deflection angle. It may be applicable to hypervelocity events involving any monolithic material as long as the equivalent speed and deflection angle can be provided from numerical simulations. The impact conditions exhibit a quantitative relationship with the pressure attenuation in a projectile, among which the impact velocity has a more significant effect. This study established a quantitative analysis method for initial impact stage of the oblique hypervelocity impact of a spherical projectile on a flat plate.
空间碎片对鞭笞护盾的冲击主要是非垂直的。激波的起爆和相互作用决定了弹丸和弹片的破碎,直接决定了产生的碎片云的特征。在弹丸撞击目标的初始阶段,波的传播和演化发生在弹丸内部,材料破片共占主导地位。基于非对称射流理论,研究了冲击条件(冲击速度和攻角)对射流产生临界条件的影响。在几何传播模型(GPM)中,考虑了攻角的影响,引入了波前偏转角参数。修正后的GPM可以描述斜碰撞时波前的几何特征和位置。结合光滑颗粒流体力学数值模拟,对弹丸内部、破片特征和压力衰减进行了研究。研究发现,在大攻角情况下,弹体材料更容易达到产生射流的临界条件,且弹体材料的射流质量比例随攻角的增大而增大。修正后的GPM是一个斜椭圆方程,它是等效速度、冲击速度、攻角、时间和偏转角的函数。只要能从数值模拟中得到等效速度和等效偏转角,就可以适用于涉及任何单片材料的超高速事件。冲击条件与弹丸内压力衰减呈定量关系,其中冲击速度的影响更为显著。本研究建立了球形弹丸斜向超高速撞击平板初始冲击阶段的定量分析方法。
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引用次数: 0
Temperature-Dependence Mechanical Characteristics Investigation of Cu Wire and Corresponding High Strain Rate Plasticity Behaviors Enabled by Johnson-Cook Constitutive Model 基于Johnson-Cook本构模型的铜丝温度依赖力学特性及高应变率塑性行为研究
IF 1.7 4区 工程技术 Q3 MECHANICS Pub Date : 2023-08-11 DOI: 10.1093/jom/ufad020
De-Shin Liu, Po-Chun Wen, Z. Zhuang, Y. Chao, Pei-Chen Huang
The temperature dependence mechanical characteristics of 4N Cu wire with 25, 30, and 38 μm diameters are investigated via the utilization of micro-tensile tests. Measured data revealed that the concerned mechanical characteristics, Young's modulus and yield stresses, are significantly degraded under high testing temperature, and the variation of aforementioned characteristics degradation are almost linear proportional to the temperature increment. Trapezoidal and standard triangle loop formation of Cu wire is simulated based on the finite element method, the simulated looping profiles of Cu wires is compared to the Au wires and the Cu wire is regarded as the improved solution for the high loop height wire formation. Moreover, the Johnson-Cook constitutive model is utilized to describe the plasticity of Cu wire in accordance with the experimental data under different temperature level consideration. Accordingly, the comprehensive mechanical characteristics investigation of 4N Cu wire is systemically demonstrated and explored.
利用微拉伸试验研究了直径为25、30和38 μm的4N铜丝的温度随温度变化的力学特性。实验数据表明,在高温下,杨氏模量和屈服应力等力学特性显著退化,且上述特性退化的变化几乎与温度的升高成线性关系。基于有限元法对铜丝梯形和标准三角形环形成形进行了模拟,将模拟的铜丝环形轮廓与金丝进行了比较,并将铜丝视为高环形高度成线的改进方案。根据不同温度水平下的实验数据,采用Johnson-Cook本构模型来描述铜丝的塑性。据此,对4N铜线的综合力学特性研究进行了系统的论证和探讨。
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引用次数: 0
Nonlinear Ultrasonic Characterization of Joint Structures Using Backscatter Guided Waves 基于后向散射导波的关节结构非线性超声表征
IF 1.7 4区 工程技术 Q3 MECHANICS Pub Date : 2023-08-10 DOI: 10.1093/jom/ufad022
Wenqiu Wu, C. Yin
Joint structures made from plates or shells are frequently used in large constructions, such as oil storage tanks in petrochemical industries. The corrosion-induced metal loss often appears on the back side of the bottom plate supported by ground or sand. The welding residual stress and weight of shell walls accelerate the corrosion. Determining the severity of metal loss under the joint is challenging. This work uses the mode pair technique for nondestructive inspection of inaccessible regions in joint structures. A finite element analysis model simulates the transient responses of the incident and mode-converted fundamental and second harmonic plate waves. The second harmonic s0 plate wave satisfying the phase velocity matching condition accompanies the transmitted fundamental SH0 plate wave. A directional filter identifies every mode-converted plate wave by comparing the frequency spectra with the dispersion curves. Linear ultrasonic guided waves can detect inaccessible regions using mode-converted reflections. The symmetry of the linear mode-converted fundamental plate waves depends on the defect position and geometry, not the size. The mode-converted second harmonic guided wave can achieve better spatial resolution for defect sizing. The nonlinear parameter shows a proportional trend with an increasing thickness reduction. Experimental and numerical evidence reveals nonlinear ultrasonic guided wave technique has the potential for defect detection in joint structures.
由板或壳制成的接头结构经常用于大型建筑中,例如石化工业中的储油罐。腐蚀引起的金属损失通常出现在由地面或沙子支撑的底板背面。焊接残余应力和壳壁重量加速了腐蚀。确定接头下金属损失的严重程度具有挑战性。本工作使用模式对技术对接头结构中的不可接近区域进行无损检测。有限元分析模型模拟入射和模式转换的基波和二次谐波板波的瞬态响应。满足相速度匹配条件的二次谐波s0板波伴随着传输的基波SH0板波。定向滤波器通过将频谱与色散曲线进行比较来识别每个模式转换的板波。线性超声导波可以使用模式转换反射来检测不可到达的区域。线性模式转换的基波的对称性取决于缺陷的位置和几何形状,而不是尺寸。模转换后的二次谐波导波可以获得更好的缺陷尺寸空间分辨率。非线性参数显示出随着厚度减小的增加而成比例的趋势。实验和数值证据表明,非线性超声导波技术具有检测接头结构缺陷的潜力。
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引用次数: 0
The numerical investigation of aerodynamics and aeroacoustics effects in a full-scale True Wireless headphone 全尺寸真无线耳机中空气动力学和空气声学效应的数值研究
IF 1.7 4区 工程技术 Q3 MECHANICS Pub Date : 2023-08-10 DOI: 10.1093/jom/ufad021
Wei-Hsiang Wang, Hua-Ching Chang, Ta-Yuan Cheng, Yu-Chien Chen
This study investigates the flow characteristics and aeroacoustic effects in a True Wireless (TWS) headphone using Computational Fluid Dynamics (CFD) simulations. A low-speed compressible flow solver is employed to analyze the flow fields and pressure variations associated with fluid-induced noise. The accuracy of the simulations is validated through comparisons with experimental and numerical data, demonstrating good consistency. The analysis reveals the presence of asymmetric vortex shedding patterns, attributed to the angle of airflow and the irregular surface of the headphones. The examination of the microphone chamber highlights the significance of design parameters in shaping flow patterns and acoustics. Optimized designs have the potential to achieve noise reductions of up to 10.62% or amplifications of up to 24.95%. These findings contribute to the development of improved Active Noise Cancellation (ANC) systems and the enhancement of TWS headphone technology, aiming to reduce external noise and enhance sound quality.
本研究使用计算流体动力学(CFD)模拟研究了True Wireless(TWS)耳机中的流动特性和空气声学效应。采用低速可压缩流求解器来分析与流体诱导噪声相关的流场和压力变化。通过与实验和数值数据的比较验证了模拟的准确性,证明了良好的一致性。分析揭示了不对称涡流脱落模式的存在,这归因于气流的角度和耳机的不规则表面。麦克风室的检查突出了设计参数在形成流型和声学方面的重要性。优化设计有可能实现高达10.62%的降噪或高达24.95%的放大。这些发现有助于开发改进的有源噪声消除(ANC)系统和增强TWS耳机技术,旨在降低外部噪声并提高音质。
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引用次数: 0
Thermal Performance of Open Microchannel Heat Sink with NACA Airfoil Shaped PIN Fins NACA翼型PIN翅片开放式微通道散热器的热性能
IF 1.7 4区 工程技术 Q3 MECHANICS Pub Date : 2023-08-10 DOI: 10.1093/jom/ufad019
Kun-Da Wu, H. Weng
The main purpose of this study is to numerically investigate the effect of pin-fin NACA airfoil on the heat transfer performance of a single open microchannel heat sink with a fixed surface area and a constant wall heat flux. It was found that the helical flow within the microchannel and the converging-diverging flow near the two sides of the microchannel, caused by the periodically arranged NACA airfoil shaped pin fins with an attack angle, dominate the overall heat dissipation ability of the heat sink. The heat dissipation ability can be further improved by increasing the attack angle and Reynolds number. Of the airfoils considered, the symmetrical airfoil NACA0012 in no attack angle case presents the smallest pressure drop, but also the smallest thermal performance value, which can still achieve a Nusselt number improvement of 35.15% and a thermal performance factor (TPF) improvement of 1.38%, compared to the no-fin case. The NACA airfoil effect can be improved when asymmetric airfoils are considered. In terms of overall thermal performance, the NACA6412 would be the best choice. Its percentage increases in the Nusselt number and TPF can be further enhanced by up to 57.62% and 35.43%, respectively, compared to the no-attack-angle NACA0012 case.
本研究的主要目的是数值研究针翅NACA翼型对具有固定表面积和恒定壁面热通量的单个开放微通道散热器传热性能的影响。研究发现,微通道内的螺旋流和微通道两侧附近的会聚-发散流,由具有迎角的周期性布置的NACA翼型销片引起,主导着散热器的整体散热能力。增加攻角和雷诺数可以进一步提高散热能力。在所考虑的翼型中,对称翼型NACA0012在无迎角情况下的压降最小,但热性能值也最小,与无翅片情况相比,其仍能实现35.15%的努塞尔数改进和1.38%的热性能因子(TPF)改进。当考虑不对称翼型时,NACA翼型效果可以得到改善。就整体热性能而言,NACA6412将是最佳选择。与无迎角NACA0012情况相比,其努塞尔数和TPF的百分比增加可分别进一步提高57.62%和35.43%。
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引用次数: 0
Flow and Heat Transfer Characteristics of Staggered Cylinders 交错圆柱的流动和传热特性
IF 1.7 4区 工程技术 Q3 MECHANICS Pub Date : 2023-07-28 DOI: 10.1093/jom/ufad014
L. Hsu, P. Chou
Determining how the flow structure affects the heat transfer of a staggered cylindrical array was one of the objectives of this numerical study. The major flow patterns and the corresponding characteristics of heat transfer were investigated, including Shear Layer Reattachment (SLR), Induced Separation (IS), Vortex Pairing and Enveloping (VPE), Vortex Impingement (VI), and Synchronized Vortex Shedding (SVS). As the stagger angle is larger than 35°, the mean Nusselt numbers of array systems are larger than that of a single cylinder. The magnitude of Nu/Cd is suggested as a parameter to measure the efficiency of the heat transfer for an array system.
确定流动结构如何影响交错圆柱阵列的传热是本数值研究的目标之一。研究了剪切层再附着(SLR)、诱导分离(IS)、涡对包络(VPE)、涡撞击(VI)和同步涡脱落(SVS)等主要流动模式及其传热特性。当交错角大于35°时,阵列系统的平均努塞尔数大于单个圆柱体的平均努塞尔数。建议用Nu/Cd的大小作为衡量阵列系统传热效率的参数。
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引用次数: 0
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