International Journal of Mechanics Research

Journal Information
ISSN / EISSN : 2325-498X / 2325-5005
Published by: Hans Publishers (10.12677)
Total articles ≅ 167
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春杜 迎
International Journal of Mechanics Research, Volume 10, pp 294-304; https://doi.org/10.12677/ijm.2021.104029

Abstract:
# 高速磁浮列车通过隧道时会引起剧烈的压力波动,带来乘客耳感舒适性和车体气动疲劳等问题,加大隧道净空面积是显著降低压力波动的基本措施,但也会带来建设成本问题。本文采用一维可压缩非定常不等熵流动模型广义黎曼变量特征线数值模拟压力波的源代码程序,研究了时速600公里速度等级下单列车通过隧道引起的压力波特征,得出了以不同时间间隔舒适性标准为指标的最不利隧道长度,确定了列车动态气密性对最不利隧道长度的影响规律,提出了满足国内外不同舒适性标准的单线隧道净空面积建议值,为补充国内相关技术标准提供了技术依据。 High-speed maglev trains will cause severe pressure fluctuations when passing through tunnels, causing problems such as passenger comfort and car body aerodynamic fatigue. Enlarging the tunnel clearance area is a basic measure to significantly reduce pressure fluctuations, but it will also bring about construction cost issues. In this paper, a one-dimensional compressible unsteady non-isentropic flow model is used to simulate the pressure wave by the source code of the charac-teristic line of the generalized Riemann variable. The characteristics of the pressure wave caused by a single train passing through a tunnel at a speed of 600 kilometers per hour are studied. The critical tunnel length with different time interval comfort standards as indicators is obtained. The influence of the dynamic airtightness of the train on the critical tunnel length is determined. The proposed value of clearance area for single-track tunnels that meets different comfort standards at home and abroad is proposed. This provides a technical basis for supplementing relevant domestic technical standards.
梁 潇
International Journal of Mechanics Research, Volume 10, pp 230-236; https://doi.org/10.12677/ijm.2021.104023

Abstract:
# 本文为了对球阀不同关阀过程下水锤效应产生的影响进行分析,采用fluent软件滑移网格和udf技术模拟球阀关闭时的转动过程,对球阀关阀过程中的流场变化以及水锤压力变化进行了研究分析。研究结果表明:随着阀门的关闭,球阀流速先上升后下降,当球阀流速达到最大值时,流体介质对阀芯产生最大冲击,球阀水锤压力达到最大值。球阀水锤压力的最大值随着关阀时间的增加逐渐减小,且在相同关阀时间下,采用匀加速关阀和匀减速关阀会比匀速关阀产生更大的水锤压力。 In this paper, in order to analyze the influence of water hammer effect in different closing processes of ball valve, the sliding grid of fluent software and udf technology are used to simulate the rotation process of ball valve when it is closed, and the changes of flow field and water hammer pressure during the closing process of ball valve are studied and analyzed. The results show that with the closing of the valve, the flow rate of the ball valve increases first and then decreases. When the flow rate of the ball valve reaches the maximum value, the fluid medium has the maximum impact on the valve core, and the water hammer pressure of the ball valve reaches the maximum value. The maximum water hammer pressure of ball valve gradually decreases with the increase of valve closing time, and under the same valve closing time, uniform acceleration and uniform deceleration will produce greater water hammer pressure than uniform speed.
王 茜
International Journal of Mechanics Research, Volume 10, pp 205-214; https://doi.org/10.12677/ijm.2021.104020

Abstract:
本文利用基面力单元法,建立了二维再生混凝土随机骨料细观模型,该模型采用了与界面对齐的Delaunay三角形剖分,模型中的各相材料均采用多折线损伤本构模型,并运用Kupfer双轴强度破坏准则作为双压区损伤的判定依据。其中采用零厚度界面单元考虑了再生混凝土试件与加载垫板之间的摩擦,并讨论了端部摩擦对再生混凝土试件峰值强度和破坏模式的影响。数值结果与前人试验结果吻合较好,证明了本文建立的模型能较好地模拟再生混凝土试件的宏观力学行为。此外,数值结果表明:端部摩擦会显著影响再生混凝土的峰值强度和破坏模式,并且随着高宽比减小,影响程度增大;端部摩擦的影响范围有限,距离端部越远,受到的影响越小。 In this paper, a two-dimensional random aggregate mesoscopic model of recycled concrete is de-veloped using the base force element method, which employs Delaunay triangular dissection aligned with the interface, and the constitutive relation of multi-line damage evolution is used for each phase material in the model, and the Kupfer criterion is applied as the basis for determining damage in the biaxial compression zone. The friction between the recycled concrete specimens and the loading plate was considered using the zero-thickness interface element, and the influence of end friction on the peak strength and failure mode of the recycled concrete specimen was discussed. The numerical results are compared well with experimental results. It is proven that the model established in this paper can simulate the macroscopic mechanical behavior of recycled concrete specimens. In addition, the numerical results show that: End friction significantly affects the peak strength and damage mode of recycled concrete, and the degree of influence increases as the aspect ratio decreases; the influence range of end friction is limited, and the farther away from the end, the smaller the influence is.
锐陈 葛
International Journal of Mechanics Research, Volume 10, pp 143-152; https://doi.org/10.12677/ijm.2021.102014

Abstract:
电动力学教材一般仅仅在附录部分给出曲线正交坐标系下标量的梯度∇→Ψ、矢量的散度∇→•A→和旋度∇→×A→,以及标量的拉普拉斯算符∇2Ψ的一般表达式。在教学中我们发现,∇→ A→和∇2 A→在曲线正交坐标系下的表达式也是很重要的。本文从微分几何的角度推导出三维欧氏空间中曲线正交坐标系下∇→ A→和∇2 A→的一般表达式,以及它们在直角坐标系、柱坐标系和球坐标系的具体表达式,供感兴趣的学生和教师参考。 In textbooks of electrodynamics, the formulas of the gradient ∇→Ψ, divergence ∇→•A→, curl ∇→×A→,and Laplace operator ∇2Ψ in curvilinear orthogonal coordinates are often given in the appendix. However, in the teaching process, we find that the expressions of ∇→ A→ and ∇2 A→ in curvilinear orthogonal coordinates are also very important. In this paper, the general expressions of ∇→ A→ and ∇2 A→ in curvilinear orthogonal coordinates in three-dimensional Euclidean space are derived based on the method of differential geometry. And the formulas of ∇→ A→ and ∇2 A→ in the Cartesian coordinates, cylindrical coordinates and spherical coordinates are also given for convenience of interested students and teachers.
龙光 子
International Journal of Mechanics Research, Volume 10, pp 215-221; https://doi.org/10.12677/ijm.2021.104021

Abstract:
以大跨桥梁中常用的近流线型箱梁断面为研究对象,通过计算流体力学(computational fluid dynamics, CFD)数值模拟方法,对断面流场特性进行分析。并利用Fluent软件对近流线型主梁断面绕流进行数值模拟,得到−6˚~+6˚风攻角范围内风轴坐标下的静力三分力系数,并经后处理软件处理得到±5˚风攻角下桥梁断面的流场分布示意图(包括压强分布图、流速分布图及流线图)。分析结果表明:风攻角为主梁断面三分力系数的影响因素,且随着风攻角的增大,阻力系数先减小后增加,升力系数逐渐增加,扭矩系数逐渐减小。 Taking the nearly streamlined box girder section commonly used in long-span bridges as the re-search object, the flow field characteristics of the section are analyzed through the numerical si-mulation method of computational fluid dynamics (CFD). And use the Fluent software to numeri-cally simulate the flow around the cross-section of the nearly streamlined main girder, and obtain the static mean aerodynamic force coefficient under the wind axis coordinate within the range of −6˚~+6˚ wind attack angle, and the post-processing software processes to obtain ±5˚ Schematic diagram of flow field distribution of bridge section under wind attack angle (including pressure distribution diagram, velocity distribution diagram and streamline diagram). The analysis results show that the wind attack angle is the main factor affecting the mean aerodynamic force coefficient of the beam section, and as the wind attack angle increases, the drag coefficient first decreases and then increases, the lift coefficient gradually increases, and the torque coefficient gradually decreases.
刘 奎
International Journal of Mechanics Research, Volume 10, pp 52-61; https://doi.org/10.12677/ijm.2021.101005

Abstract:
有限元法在学术界和工程界都取得了巨大的成功,然而有限元法也存在一些问题。例如,为了避免网格畸变,需要花费大量的时间进行有限元计算的前处理。目前已经开发了一些不匹配网格方法来解决这个问题。近年来,宽边界法(Fat Boundary Method)被提出并应用于弹性力学领域,而双宽边界法(Dual Fat Boundary Method)是宽边界法的一种改进。这些方法都需要通过迭代法进行求解。本文研究了宽边界法与迭代相关的算法参数对迭代的影响,并提出了一种基于双宽边界法的插值方法,以降低计算成本。 Finite Element Method (FEM) has achieved a great success both in the field of academic and engi-neering. However, there are some problems for FEM. For example, the mesh generation procedure consumes a lot of time for an engineering problem to avoid mesh distortion. Some fictitious domain methods have been developed to tackle this problem. Recently, the Fat Boundary Method (FBM) has been proposed and applied to elasticity and as an improvement of FBM, the Dual Fat Boundary Method (DFBM) is proposed. These methods need an iteration procedure. In this article, the algorithmic parameters related to the iteration of FBM are studied and an interpolation method based on DFBM is proposed to reduce computational costs.
曾 成
International Journal of Mechanics Research, Volume 10, pp 62-69; https://doi.org/10.12677/ijm.2021.101006

Abstract:
考虑功能梯度材料物性参数的温度依赖性研究变化的温度场中陶瓷-金属功能梯度Timoshenko梁的弹塑性屈曲特性,其中功能梯度材料的弹塑性材料参数由TTO模型模拟、弹塑性本构方程应用线性强化模型建立。研究中利用Hamilton系统中的辛方法将问题转换为求解正则方程,临界载荷和屈曲模态对应于正则方程的辛本征值和辛本征解。精确解析求解正则方程得到梁的临界载荷和屈曲模态,并结合屈服条件获得弹塑性分界面。最后进行参数研究分析了梯度参数、几何参数和边界条件对该复合材料梁的屈曲载荷和屈曲时弹塑性变形分界面的影响。 The elastoplastic buckling characteristics of functionally graded Timoshenko beams in varying temperature field are studied by considering the temperature dependence of material parameters. The elastoplastic material parameters of functionally graded materials are simulated by TTO model and the elastoplastic constitutive equation is established by linear strengthening model. By using the symplectic method in Hamilton system, the problem is transformed into solving canonical equations. The critical load and buckling mode correspond to the symplectic eigenvalue and eigen solution of the canonical equations, and are obtained by accurate analytical solution. At the same time, the elastoplastic interface is obtained by combining the yield condition. Finally, the influence of gradient parameters, geometric parameters and boundary conditions on the buckling load and elastoplastic deformation interface of the beam is analyzed.
如范 学
International Journal of Mechanics Research, Volume 10, pp 29-51; https://doi.org/10.12677/ijm.2021.101004

Abstract:
本构理论描述的是宏观和细观微观尺度下材料或结构在外载荷作用下的响应,是力学研究中不可忽视的研究方向,是材料力学中经久不息的研究课题。本文重点以非均匀介质如岩石或者岩土体、混凝土等准脆性材料为研究对象,针对采动和强动载环境过程中的关键科学问题,系统的阐述国内外关于准脆性材料的动态本构关系的繁衍历程、构建起源、发展适用范畴及基本原理。同时,对常用的几类表征准脆性材料动态力学响应的本构模型进行了系统的理论推导。最后,针对准脆性材料的动态本构进行了细化分类,并研究了其相互关系的演化过程。 Constitutive theory describes the response of material or structure under external load at macro and micro scales. It is a research direction that cannot be ignored in mechanical research and a long-standing research topic in material mechanics. This paper focuses on non-uniform medium such as rock or rock mass, concrete and other quasi brittle materials as the research object, aiming at the key scientific problems in the process of mining and strong dynamic load environment. The development history, origin, application scope and basic principle of dynamic constitutive relation of quasi brittle materials at home and abroad are systematically described. Meanwhile, several kinds of constitutive models which are commonly used to characterize the dynamic mechanical response of quasi brittle materials are systematically deduced. Finally, the dynamic constitutive models of quasi brittle materials are classified and the evolution process of their relationship is studied.
宇张 兴
International Journal of Mechanics Research, Volume 10, pp 1-9; https://doi.org/10.12677/ijm.2021.102008

Abstract:
本文提出基于有限元功率流的三维轴承座能量分布及传递特性的研究方法。首先介绍了有限元功率流的理论和相关表达式;然后以轴承座为研究对象,比较分析了简谐力作用下有无裂纹轴承座的能量分布和振动传递,实现了载荷冲击下有无裂纹轴承座的功率流可视化研究;最后讨论了裂纹对轴承座功率流的影响。应力云图、功率流云图和功率流矢量图分别用来呈现轴承座应力分布、能量分布和能量传递路径。结果表明简谐载荷下轴承座的应力集中区域和能量集中区域是不同,裂纹影响轴承座的应力分布、能量分布和能量传递,裂纹轴承座含有的能量更大。有限元功率流的可视化分析方法可为结构设计及安全运行提供依据。 The characteristics of energy distribution and transfer in three dimensional bearing block were investigated by finite element power flow technique. Firstly, the calculation process of power flow introduced. The energy distribution and vibration transmission of the bearing block with or without cracks under the action of the harmonic force are compared and analyzed, and the visualization of the power flow of the bearing housings is realized. Finally, the influence of the crack on the power flow of the bearing block is discussed. The stress distribution, energy distribution and energy transfer path are shown by stress nephogram, power flow nephogram and power flow vector diagram, respectively. The results show that the stress and energy distribution is different, the crack impact stress distribution, energy distribution and energy transfer of the bearing housing. The visual analysis method of power flow of finite element can provide the basis for structural design and safe operation.
Safwan Fouad Al-Sayed
International Journal of Mechanics Research, Volume 10, pp 153-161; https://doi.org/10.12677/ijm.2021.102015

Abstract:
本文针对再生混凝土材料,利用均质化分析方法,建立了串联均质化模型,采用新型有限元法——基于余能原理的基面力单元法对再生混凝土进行细观层次的损伤研究,利用所编非线性损伤基面力单元法分析程序,分析了再生混凝土在单轴压缩荷载情况下的应力应变软化曲线和破坏机理,并将计算结果与试验和细观随机骨料模型分析方法的结果进行对比分析。研究结果表明:这种串联均质化分析方法可以用于分析再生混凝土材料的非线性损伤分析,可以得到再生混凝土材料的抗压强度、应力应变软化曲线和裂纹扩展的过程。 The homogenization analysis method was used to establish a series homogenization model for recycled concrete materials in the paper. A new type of finite element method—Base Force Element Method based on complementary energy principle is used to conduct meso-level damage research on recycled concrete. The stress-strain softening curve and failure mechanism of recycled concrete under uniaxial compression load are analyzed using the nonlinear damage analysis program of base force element method. The calculation results are compared with the results of experiments and meso-level random aggregate model analysis methods. The research results show that this series homogenization analysis method can be used to analyze the nonlinear damage analysis of recycled concrete materials. The compressive strength, stress-strain softening curve and crack propagation process of recycled concrete materials can be obtained using the present method.
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