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Stress-based dimensional reduction and dual-mixed hp finite elements for elastic plates 弹性板的基于应力的尺寸缩减和双混合hp有限元
IF 3.1 Q2 MECHANICS Pub Date : 2023-01-01 DOI: 10.32973/jcam.2023.001
E. Bertóti
Starting from the linearized weak forms of the kinematic equation and the angular momentum balance equation of three-dimensional non-linear elasticity, a stressbased dimensional reduction procedure is presented for elastic plates. After expanding the three-dimensional non-symmetric stress tensor into power series with respect to the thickness coordinate, the translational equilibrium equations, written in terms of the expanded stress coefficients, are satisfied by introducing first-order stress functions. The symmetry of the stress field is satisfied in a weak sense by applying the material rotations as Lagrangian multipliers. The seven-field plate model developed in this way employs unmodified three-dimensional strain-stress relations. On the basis of the dimensionally reduced plate model derived, a new dual-mixed plate bending finite element model is developed and presented. The numerical performance of the hp-version plate elements is investigated through the solutions of standard plate bending problems. It is shown that the modeling error of the stress-based plate model in the energy norm is better than that of the displacement-based Kirchhoff- and Reissner-Mindlin plate models. The numerical solutions and their comparisons to reference solutions indicate that the dual-mixed hp elements are free from locking problems, in either the energy norm or the stress computations, both for h- and p-extensions, and the results obtained for the stresses are accurate and reliable even for extremely thin plates.
从三维非线性弹性运动方程和角动量平衡方程的线性化弱形式出发,提出了弹性板的应力降维方法。将三维非对称应力张量展开成关于厚度坐标的幂级数后,通过引入一阶应力函数来满足以展开应力系数表示的平移平衡方程。将材料旋转作为拉格朗日乘子,在弱意义上满足应力场的对称性。用这种方法建立的七场板模型采用未经修正的三维应变-应力关系。在已建立的降维板模型的基础上,提出了一种新的双混合板弯曲有限元模型。通过对标准板弯曲问题的求解,研究了hp型板单元的数值性能。结果表明,基于应力的板模型在能量范数下的建模误差优于基于位移的Kirchhoff-和Reissner-Mindlin板模型。数值解及其与参考解的比较表明,无论是能量范数计算还是应力计算,无论是h-扩展还是p-扩展,双混合hp单元都不存在锁紧问题,即使对于极薄板,得到的应力计算结果也是准确可靠的。
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引用次数: 0
Application of the p-version of FEM to hierarchic rod models with reference to mechanical contact problems 考虑机械接触问题的分层杆模型p型有限元法的应用
IF 3.1 Q2 MECHANICS Pub Date : 2023-01-01 DOI: 10.32973/jcam.2023.002
I. Páczelt, B. Szabó, A. Baksa
The formulation of a system of hierarchic models for the simulation of the mechanical response of slender elastic bodies, such as elastic rods, is considered. The present work is concerned with aspects of implementation and numerical examples. We use a finite element formulation based on the principle of minimum potential energy. The displacement fields are represented by the product of one-dimensional field functions and two-dimensional director functions. The field functions are approximated by the p-version of the finite element method. Our objective is to control both the model form errors and the errors of discretization with a view toward the development of advanced engineering applications equipped with autonomous error control procedures. We present numerical examples that illustrate the performance characteristics of the algorithm.
考虑了细长弹性体(如弹性杆)力学响应仿真的层次模型系统的建立。目前的工作是关于实现和数值例子方面。我们使用基于最小势能原理的有限元公式。位移场由一维场函数和二维方向函数的乘积表示。场函数用有限元法的p型逼近。我们的目标是控制模型形式误差和离散化误差,以期开发配备自主误差控制程序的先进工程应用。我们给出了数值例子来说明该算法的性能特征。
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引用次数: 0
Post-extrapolation for specified time-step results without interpolation in MOC-based 1D hydraulic transients and gas release computations 基于模型的一维水力瞬态和气体释放计算中指定时间步结果的后外推,无需插值
IF 3.1 Q2 MECHANICS Pub Date : 2023-01-01 DOI: 10.32973/jcam.2023.003
A. A. Estuti, E. Litvai
The goal of the paper is to present a supplementary step called postextrapolation. When applied to the well-known method of characteristics (MOC), this assures the continuous use of the specified time steps or regular numerical grid without interpolations during computations of transients in 1D 2-phase flow in straight elastic pipes. The new method consists of two steps, the first being a typical MOC step, where the C− and C+ characteristics start from regular nodal points, allowing for the point of intersection to differ from a regular one. After defining the variables there the method transforms it corresponding to the near regular grid point, using the first derivatives contained in the original, nonlinear, governing equations, as evaluated numerically from the variables got earlier in the neighboring nodes. The procedure needs no interpolations; it deals with grid-point values only. Instead of the Courant-type stability conditions, shock-wave catching and smoothing techniques help to assure numerical stability between broad limits of parameters like the closing time of a valve and the initial gas content of the fluid. Comparison by runs with traditional codes under itemized boundary conditions and measurements on a simple TPV (tank-pipe-valve) setup show acceptable scatter.
本文的目的是提出一个补充步骤,称为后外推。当应用于众所周知的特征方法(MOC)时,这保证了在计算直弹性管道中一维两相流瞬态时连续使用指定的时间步长或规则的数值网格而不需要插值。新方法包括两个步骤,第一步是典型的MOC步骤,其中C -和C+特征从规则节点开始,允许交点与规则节点不同。在定义了那里的变量之后,该方法使用原始的非线性控制方程中包含的一阶导数,将其转换为对应于附近规则网格点的一阶导数,并根据先前在相邻节点中得到的变量进行数值计算。这个过程不需要插值;它只处理网格点值。与courant稳定性条件不同的是,冲击波捕捉和平滑技术有助于确保广泛的参数范围(如阀门关闭时间和流体的初始气体含量)之间的数值稳定性。在分项边界条件下与传统规范的运行比较以及在一个简单的TPV(罐-管-阀)装置上的测量显示出可接受的分散。
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引用次数: 0
Investigation of micro-shock waves in a planar magnetogasdynamic flow using the discontinuous Galerkin finite element method 用不连续伽辽金有限元法研究平面磁气动力流中的微激波
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.006
Alberto Gallottini, L. Könözsy
The present work focuses on the numerical investigation of micro-shock wave propagation in a two-dimensional magnetogasdynamic flow in the framework of the Dis- continuous Galerkin-Finite Element Method (DG-FEM). The Lorentz force has been im- plemented in the compressible, viscous Navier–Stokes equations as a source term using first-order spatial and fourth-order temporal Runge–Kutta discretization schemes. To in- vestigate the effect of the electrical conductivity on the micro-shock wave propagation, a two-dimensional micro-shock channel problem with hydraulic diameter of 2.5 mm, length of 82 mm, and no-slip boundary conditions at the left and at the right wall is considered as a benchmark problem. In this case, acoustic waves are generated behind after the rupture of the membrane that separates two states of the same gas originally at different pressure and density and both initially at rest. The magnetic field is taken into account as uniform and stationary throughout the microchannel, and the numerical simulations are performed in a short physical time, before the reflection of the waves on the lateral wall. A detailed parametric study of the temperature, density, pressure, and u-velocity is carried out by a variation of the electrical conductivity of the magnetogasdynamic flow, under the assumption of low magnetic Reynolds numbers. It has been found that the jumps of the acoustic waves become significantly intensified when the electrical conductivity of the gas is increased. It has also been observed that the presence of the Lorentz force causes an acceleration in the gasflow towards the outlet section of the microchannel at the low Knudsen number of 0.05. The outcome of this research work could be relevant to biomedical applications where the ability to control the flow in a microchannel has a significant impact on the development of small devices aimed to deliver pharmaceutical drugs in specific locations.
本文采用非连续伽辽金有限元法(DG-FEM)对二维磁气动力学流中微激波的传播进行了数值研究。采用一阶空间和四阶时间龙格-库塔离散格式,将洛伦兹力作为源项引入可压缩粘性Navier-Stokes方程中。为了研究电导率对微激波传播的影响,以一个水力直径为2.5 mm、长度为82 mm、左右壁面无滑移边界条件的二维微激波通道问题为基准问题。在这种情况下,声波是在分离同一气体的两种状态的膜破裂后产生的,这两种状态最初处于不同的压力和密度,最初都处于静止状态。考虑磁场在整个微通道中是均匀和平稳的,并在较短的物理时间内进行了数值模拟,然后将波反射到侧壁上。在低磁雷诺数的假设下,通过磁气动力学流的电导率变化,对温度、密度、压力和u型速度进行了详细的参数研究。研究发现,当气体的电导率增加时,声波的跳变明显增强。还观察到,在低克努森数为0.05时,洛伦兹力的存在导致气体流向微通道出口段的加速。这项研究工作的结果可能与生物医学应用有关,在生物医学应用中,控制微通道流量的能力对旨在在特定位置输送药物的小型设备的开发具有重大影响。
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引用次数: 0
Evaluation of the SU2 Open-Source Code for a Hypersonic Flow at Mach Number 5 5马赫数高超声速流的SU2开源代码评估
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.004
Jia-Ming Yeap, Z. Rana, L. Könözsy, K. Jenkins
This paper presents the evaluation of the Stanford University Unstructured (SU2) open-source computational software package for a high Mach number 5 flow. The test case selected is an impinging shock wave turbulent boundary layer interaction (SWTBLI) on a flat plate where the experimental data of Sch¨ulein et al. [27] is used for validation purposes. Two turbulence models, the Spalart–Allmaras (SA) and the k-ω Shear Stress Transport (SST) within the SU2 code are evaluated in this study. Flow parameters, such as skin friction, wall pressure distribution and boundary layer profiles are compared with experimental values. The results demonstrate the performance of the SU2 code at a high Mach number flow and highlight its limitations in predicting fluid flow physics. At higher shock generator angles, the discrepancy between experimental and CFD data is more significant. Within the interaction and flow separation zones, a smaller separation bubble and delayed separation are predicted by the SA model while the k-ω SST model predicts early separation. Both models are able to predict wall pressure distribution correctly within the experimental values. However, discrepancies were observed in the prediction of skin friction due to the inability of the models to capture the boundary layer recovery after shock impingement.
本文对斯坦福大学非结构化(SU2)开源高马赫数流计算软件包进行了评价。本文选择的测试用例是平板上的撞击激波湍流边界层相互作用(SWTBLI),其中采用Sch¨ulein等[27]的实验数据进行验证。本文对SU2规范中的两个湍流模型Spalart-Allmaras (SA)和k-ω剪切应力输运(SST)进行了评估。将表面摩擦、壁面压力分布和边界层轮廓等流动参数与实验值进行了比较。结果证明了SU2程序在高马赫数流动中的性能,并突出了其在预测流体流动物理方面的局限性。当激波发生器角度较大时,实验数据与CFD数据的差异更大。在相互作用和流动分离区内,SA模型预测分离泡较小,分离延迟,而k-ω SST模型预测分离提前。两种模型均能在实验值范围内准确预测壁面压力分布。然而,由于模型无法捕捉冲击后的边界层恢复,因此在皮肤摩擦的预测中观察到差异。
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引用次数: 0
Modeling Rapid Solidification and Melting Processes for Multiphase Flows in a Welding Technology Application 多相流快速凝固和熔化过程建模在焊接技术中的应用
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.002
Xin Xiong, L. Könözsy
This article presents unsteady simulations of laser welding based on a rapid solidification/melting model using the ANSYS-FLUENT software package with the implementation of a UDF (User Defined Function) C code. It assumes a flat interface of liquid and gas without plasma plume, evaporation and reflection and absorption effect. In the simulations, a variety of parameters are considered with different welding speeds and laser powers. The results show that with the increase of laser power, liquid fraction and velocity, penetration depth and bead width all increase. In contrary, with the increase of welding speed, the temperature, liquid fraction, penetration depth, and bead width all decrease, while the velocity magnitude is an exception. It has also been found that the increase of welding speed distorts the pool shape and forms a long tail in temperature, liquid fraction and velocity contour. The buoyancy force did not have a significant impact on the results, while the convective term makes the velocity, temperature and liquid fraction smaller. Furthermore, the negative Marangoni shear stress makes the velocity along the height and the width direction smaller in the middle of the workpiece and larger on the edges. The simulation results show a similar tendency to that obtained by other authors. The reason for the possible differences is due to the unsteadiness of the fluid flow field and the slightly different boundary conditions imposed in the model presented here. The novelties of this work are unsteady simulations, new boundary conditions and parametric studies relevant to industrial applications.
本文介绍了基于快速凝固/熔化模型的激光焊接非定常仿真,并使用ANSYS-FLUENT软件包实现了UDF(用户定义函数)C代码。它假定液体和气体的界面是平坦的,没有等离子体羽流、蒸发和反射吸收效应。仿真中考虑了不同焊接速度和激光功率下的各种参数。结果表明:随着激光功率的增大,液体分数、速度、穿透深度和熔头宽度均增大;相反,随着焊接速度的增加,焊接温度、焊液分数、焊深和焊头宽度均减小,但速度大小不同。焊接速度的增加使熔池形状发生扭曲,并在温度、液率和速度曲线上形成长尾。浮力对结果的影响不显著,而对流项对速度、温度和液率的影响较小。负马兰戈尼剪切应力使工件沿高度和宽度方向的速度在工件中部较小,而在工件边缘较大。仿真结果与其他作者的结论有相似的趋势。可能存在差异的原因是由于流体流场的非定常以及此处模型中施加的边界条件略有不同。这项工作的新颖之处在于非定常模拟、新的边界条件和与工业应用相关的参数研究。
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引用次数: 0
Mathematical aspects of non-Fourier heat equations 非傅立叶热方程的数学方面
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.001
R. Kovács
Due to technological advancement, as materials with complex structures (e.g., metamaterials and foams) appear in practice there is a need to develop advanced thermal models. These are called non-Fourier equations, and all have particular mathematical properties differing from the conventional attributes of Fourier's law. The present paper discusses the thermodynamic origin of non-Fourier equations and their consequences. The second law of thermodynamics influences the relations among the material parameters, and therefore, it restricts how the temperature-dependent properties can be included in the model. Furthermore, we present the properties of initial and boundary conditions, since these are crucial in solving any practical problems and are different from the usual interpretation used for the Fourier equation.
由于技术的进步,随着结构复杂的材料(如超材料和泡沫)在实践中出现,需要开发先进的热模型。这些被称为非傅立叶方程,它们都有不同于传统傅立叶定律的特殊数学性质。本文讨论了非傅立叶方程的热力学起源及其结果。热力学第二定律影响了材料参数之间的关系,因此,它限制了如何将温度相关性质包含在模型中。此外,我们提出了初始条件和边界条件的性质,因为它们在解决任何实际问题中都是至关重要的,并且与傅里叶方程的通常解释不同。
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引用次数: 2
Two Theorems on the Torsional Rigidity of Piezoelectric Beams 压电梁扭转刚度的两个定理
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.003
I. Ecsedi, Á. Lengyel
In this paper two inequalities are presented for the torsional rigidity of homogeneous monoclinic piezoelectric beams. All results of the paper are based on the Saint-Venant theory of uniform torsion. The cross section of the considered elastic and piezoelectric beams may be simply connected or multiply connected two-dimensional bounded plane domain. Examples illustrate the proven inequality relations.
本文给出了均匀单斜压电梁扭转刚度的两个不等式。本文的所有结果都是基于均匀扭转的圣维南理论。所考虑的弹性梁和压电梁的截面可以是单连通或多连通的二维有界平面域。举例说明已证明的不等式关系。
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引用次数: 0
Solutions for the vibration and stability problems of heterogenous beams with three supports using Green functions 用格林函数求解三支承非均质梁的振动和稳定性问题
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.007
L. Kiss, Messaudi Abderrazek, G. Szeidl
The goal of this study is to calculate the eigenvalues that provide the eigenfre- quencies and the critical loads for two heterogeneous beams with three supports: the (first) [second] beam is (fixed)[pinned] at the left end, the intermediate support is a roller while the right end of the beams can move vertically but the rotation is prevented there. The beams are referred to as FrsRp and PrsRp beams. Determination of the (eigenfrequencies) [critical loads] leads to three point eigenvalue problems associated with homogeneous boundary con- ditions. With the Green functions that belong to these eigenvalue problems we can transform them into eigenvalue problems governed by homogeneous Fredholm integral equations. The eigenvalue problems can then be reduced to algebraic eigenvalue problems that are solvable numerically by utilizing effective solution algorithms.
本研究的目的是计算具有三个支撑点的两个非均质梁的特征值,这些特征值提供了特征频率和临界载荷:(第一)[第二]梁(固定)[固定]在左端,中间支撑点是滚轮,而梁的右端可以垂直移动,但旋转在那里被阻止。这些光束被称为FrsRp和PrsRp光束。临界载荷(特征频率)的确定导致了与齐次边界条件相关的三点特征值问题。对于属于这些特征值问题的格林函数我们可以将它们转化为由齐次Fredholm积分方程控制的特征值问题。然后,特征值问题可以简化为代数特征值问题,这些问题可以通过利用有效的求解算法在数值上求解。
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引用次数: 0
Fundamental solutions in the theory of thermoelastic diffusive materials with microtemperatures and microconcentrations 微温度微浓度热弹性扩散材料理论中的基本解
IF 3.1 Q2 MECHANICS Pub Date : 2022-01-01 DOI: 10.32973/jcam.2022.005
T. Kansal
The main aim of this paper is to construct the fundamental solutions of a system of equations for isotropic thermoelastic diffusive materials with microtemperatures and microconcentrations in the case of steady oscillations in terms of elementary functions. In addition to this, the fundamental solutions of the system of equations of equilibrium theory of isotropic thermoelastic diffusivity materials with microtemperatures and microconcentrations are also established.
本文的主要目的是用初等函数构造具有微温度和微浓度的各向同性热弹性扩散材料在稳定振荡情况下的方程组的基本解。此外,还建立了各向同性热弹性扩散材料的微温度微浓度平衡理论方程组的基本解。
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引用次数: 0
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Journal of Applied and Computational Mechanics
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