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A note on the MHD flow in a porous channel 关于多孔通道中MHD流动的说明
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam220103004m
E. Marušić‐Paloka, Igor Pažanin
In this paper we study the flow of a viscous incompressible conducting fluid through a corrugated channel filled with a porous medium. The fluid flow in the channel is under the action of the transverse magnetic field and driven by the pressure drop between the channel?s edges. Using boundary-layer analysis, we derive a higher-order asymptotic model taking into account the inertia and roughness-induced effects on the filtration velocity.
本文研究了粘性不可压缩导电流体在多孔介质填充的波纹沟道中的流动。流体在通道内的流动是在横向磁场的作用下,由通道间的压降驱动的。年代的边缘。利用边界层分析,我们导出了考虑惯性和粗糙度对过滤速度影响的高阶渐近模型。
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引用次数: 1
An efficient algorithm for biomechanical problems based on a fully implicit nested Newton solver 基于全隐式嵌套牛顿求解器的生物力学问题求解算法
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam221115012k
Markus M. Knodel, Stefano Di, A. Nägel, A. Grillo
Numerical simulations of the dynamics of soft biological tissues are highly non-trivial because tissues generally exhibit complex biological response to external and internal actions, including large deformations and remodeling. Combining the advantages of globally implicit approach (GIA) solvers with the general applicability of the semi-implicit General Plasticity Algorithm (GPA), introduced by some of us some years ago, we present a new, efficient plasticity algorithm, which we call Bio Mechanics Basis Plasticity Algorithm (BMBPA). This is fully implicit, based on a nested Newton solver, and naturally suited for massively parallel computations. The Bilby-Kr?ner-Lee (BKL) multiplicative decomposition of the deformation gradient tensor is employed to introduce the unknowns of our model. We distinguish between global and local unknowns, associated with local and global equations, which are connected by means of a resolution function. The BMBPA asks for very few conditions to be applied and thus can be easily employed to solve several types of biological and biomechanical problems. We demonstrate the efficacy of BMBPA by performing two numerical experiments of a monophasic model of fiber-reinforced tissues. In one case, we consider the shear-compression test of a cubic specimen of tissue, while, in the other case, we focus on the unconfined compression test of a cylinder. The BMBPA is capable of solving the deformation and the remodeling of anisotropic biological tissues by employing a computation time of hours, while the GPA, applied to the same problems as the BMBPA, needs a substantially longer amount of time. All computations were performed in parallel and, within all tests, the performance of the BMBPA displayed substantially higher than the one of the GPA. The results of our simulations permit to study the overall mechanical behavior of the considered tissue and enable further investigations in the field of tissue biomechanics.
软体生物组织动力学的数值模拟是非常重要的,因为组织通常对外部和内部的作用表现出复杂的生物反应,包括大的变形和重塑。结合全局隐式方法(GIA)的优点和半隐式广义塑性算法(GPA)的通用性,我们提出了一种新的、高效的塑性算法,我们称之为生物力学基础塑性算法(BMBPA)。这是完全隐式的,基于嵌套牛顿求解器,自然适合大规模并行计算。Bilby-Kr吗?采用变形梯度张量的ner-Lee (BKL)乘法分解引入模型的未知量。我们区分全局和局部未知数,与局部方程和全局方程相关联,它们通过解析函数连接。BMBPA要求的应用条件很少,因此可以很容易地用于解决几种类型的生物学和生物力学问题。我们通过对纤维增强组织的单相模型进行两个数值实验来证明BMBPA的有效性。在一种情况下,我们考虑剪切压缩试验的一个立方的组织标本,而在另一种情况下,我们集中在一个圆柱体的无侧限压缩试验。BMBPA计算各向异性生物组织的变形和重塑只需几个小时,而GPA计算相同问题所需的时间要长得多。所有计算都是并行进行的,在所有测试中,BMBPA的性能明显高于GPA的性能。我们的模拟结果允许研究所考虑组织的整体力学行为,并使组织生物力学领域的进一步研究成为可能。
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引用次数: 0
Auxetic metamaterials subjected to dynamic loadings 受动态载荷作用的形变超材料
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam211103002t
Georgios K. Tairidis, I. Ntintakis, G. Drosopoulos, Panagiotis Koutsianitis, G. Stavroulakis
Materials with negative Poisson?s ratio are called auxetics and they present enhanced properties (e.g. damping, indentation resistance, fracture toughness and impact resistance) under external loadings. The auxetic properties are derived from peculiar-shaped microstructures, such as starshaped frames. In the present investigation, several applications are studied using auxetic microstructures. Finite element models are developed for dynamic analysis. First, an application related to auxetic microstructures, for the core of structural panels, is presented. Next, the use of auxetic materials in armor plates in dynamic bullet penetration problems is considered. Finally, a numerical simulation for wind turbines blades, with aluminum foam, polymeric foam and the proposed auxetic material is carried out. The numerical results demonstrate that the use of auxetic microstructures results in improved dynamic response of the system in comparison to conventional materials.
负泊松?S比率被称为助剂,它们在外部载荷下表现出增强的性能(例如阻尼、抗压痕、断裂韧性和抗冲击性)。这种减振特性来自于特殊形状的微观结构,如星形框架。在本研究中,研究了几种利用形变显微组织的应用。建立了有限元模型进行动力分析。首先,介绍了一种与结构板芯的生长性微结构相关的应用。其次,考虑了弹丸动态侵彻问题中装甲板中增氧材料的应用。最后,对采用泡沫铝、聚合物泡沫和所提出的增塑剂的风力发电机叶片进行了数值模拟。数值计算结果表明,与常规材料相比,采用形变微结构可以改善系统的动态响应。
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引用次数: 0
Symmetries and stability of motions in the Newtonian and the Hookean potentials 牛顿势和胡克势中运动的对称性和稳定性
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam220213005c
C. Carimalo
A new way of looking at symmetries is proposed, especially regarding their role in the stability of two-body motions in the Newtonian and the Hookean potentials, the two selected by Bertrand?s theorem. The role of the number of spatial dimensions is also addressed.
提出了一种观察对称性的新方法,特别是关于它们在牛顿势和胡克势中两体运动稳定性中的作用,这两种势由伯特兰?年代定理。还讨论了空间维度数量的作用。
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引用次数: 0
On inelasticity of damaged quasi-rate-independent orthotropic materials 损伤准速率无关正交各向异性材料的非弹性
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam211007001m
M. Mićunović, L. Kudrjavceva
The paper deals with a body having a random 3D-distribution of two-phase inclusions: spheroidal mutually parallel voids as well as differently oriented reinforcing parallel stiff spheroidal short fibers. By the effective field approach the effective stiffness fourth-order tensor is formulated and found numerically. Simultaneous and sequential embeddings of inclusions are compared. Damage evolution is described by modified Vakulenko?s approach to endochronic thermodynamics. A brief account of the problem of effective elastic symmetry is given. The results of the theory are applied to the damage-elasto-viscoplastic strain of reactor stainless steel AISI 316H.
本文研究了具有三维随机分布的两相夹杂体:球体相互平行的空洞和不同取向的增强平行刚性球体短纤维。利用有效场法,给出了有效刚度四阶张量的数值表达式。比较了夹杂体的同时嵌入和顺序嵌入。损伤演化由修改后的Vakulenko?内时热力学的S方法。对有效弹性对称问题作了简要说明。将理论结果应用于反应器不锈钢AISI 316H的损伤弹粘塑性应变。
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引用次数: 0
Gradient-dependent transport coefficients in the Navier-Stokes-Fourier system Navier-Stokes-Fourier系统中梯度相关输运系数
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam221005009s
Mátyás Szücs, R. Kovács
In the engineering praxis, Newton?s law of viscosity and Fourier?s heat conduction law are applied to describe thermomechanical processes of fluids. Despite several successful applications, there are some obscure and unexplored details, which are partly answered in this paper using the methodology of irreversible thermodynamics. Liu?s procedure is applied to derive the entropy production rate density, in which positive definiteness is ensured via linear Onsagerian equations; these equations are exactly Newton?s law of viscosity and Fourier?s heat conduction law. The calculations point out that, theoretically, the transport coefficients (thermal conductivity and viscosity) can also depend on the gradient of the state variables in addition to the wellknown dependence of the state variables. This gradient dependency of the transport coefficients can have a significant impact on the modeling of such phenomena as welding, piston effect or shock waves.
在工程实践中,牛顿?s粘度定律和傅里叶定律?应用S热传导定律来描述流体的热力过程。尽管有一些成功的应用,但仍有一些模糊和未探索的细节,这些细节在本文中使用不可逆热力学的方法得到了部分回答。刘吗?采用s程序推导出熵产率密度,其中通过线性Onsagerian方程保证了熵产率密度的正确定性;这些方程就是牛顿方程吗?s粘度定律和傅里叶定律?S热传导定律。计算指出,理论上,除了众所周知的状态变量的依赖性之外,输运系数(导热系数和粘度)也可以依赖于状态变量的梯度。这种输运系数的梯度依赖性对焊接、活塞效应或激波等现象的建模具有重要影响。
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引用次数: 1
Inverse dynamics in rigid body mechanics 刚体力学中的逆动力学
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam221109011f
S. Federico, Mawafag F. Alhasadi
Inverse Dynamics is used to calculate the forces and moments in the joints of multibody systems investigated in fields such as Biomechanics or Robotics. In a didactic spirit, this paper begins with an overview of the derivations of the kinematical and dynamical equations of rigid bodies from the point of view of modern Continuum Mechanics. Then, it introduces a matrix formulation for the solution of Inverse Dynamics problems and, finally, reports a simple two-dimensional example of application to a problem in Biomechanics.
逆动力学用于计算多体系统关节中的力和力矩,在生物力学或机器人等领域进行了研究。本着教学的精神,本文首先概述了从现代连续介质力学的角度推导刚体的运动学方程和动力学方程。然后介绍了求解逆动力学问题的矩阵公式,最后给出了一个简单的二维应用实例。
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引用次数: 1
Modelling and stability analysis of the nonlinear system 非线性系统的建模与稳定性分析
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam211101003v
Mitra Vesović, R. Radulović
The production industries have repeatedly combated the problem of system modelling. Successful control of a system depends mainly on the exactness of the mathematical model that predicts its dynamic. Different types of studies are very common in the complicated challenges involving the estimations and approximations in describing nonlinear machines are based on a variety of studies. This article examines the behaviour and stability of holonomic mechanical system in the arbitrary parameter sets and functional configuration of forces. Differential equations of the behaviour are obtained for the proposed system on the ground of general mechanical theorems, kinetic and potential energies of the system. Lagrange?s equations of the first and second kind are introduced, as well as the representation of the system in the generalized coordinates and in Hamilton?s equations. In addition to the numerical calculations applied the system, the theoretical structures and clarifications on which all of the methods rely on are also presented. Furthermore, static equilibriums are found via two different approaches: graphical and numerical. Above all, stability of motion of undisturbed system and, later, the system that works under the action of an external disturbance was inspected. Finally, the stability of motion is reviewed through Lagrange-Dirichlet theorem, and Routh and Hurwitz criteria. Linearized equations are obtained from the nonlinear ones, and previous conclusions for the stability were proved.
生产行业一再与系统建模问题作斗争。系统的成功控制主要取决于预测其动态的数学模型的准确性。在涉及到描述非线性机器的估计和近似的复杂挑战中,不同类型的研究是非常常见的,这些研究是基于各种各样的研究。本文研究了在任意参数集和力的功能配置下完整机械系统的行为和稳定性。根据系统的一般力学定理和系统的动能和势能,得到了系统的微分方程。拉格朗日吗?介绍了第一类和第二类方程,以及系统在广义坐标系和Hamilton坐标系中的表示。s方程。除了应用该系统的数值计算外,还介绍了所有方法所依赖的理论结构和说明。此外,静态平衡是通过两种不同的方法:图形和数值。首先考察了未受扰动系统的运动稳定性,然后考察了在外部扰动作用下工作的系统。最后,通过拉格朗日-狄利克雷定理、劳斯准则和赫维茨准则对运动的稳定性进行了评述。由非线性方程得到了线性化方程,并证明了先前关于稳定性的结论。
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引用次数: 0
Stability of solution for Rao-Nakra sandwich beam model with Kelvin-Voigt damping and time delay 具有Kelvin-Voigt阻尼和时滞的Rao-Nakra夹层梁模型解的稳定性
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam210502006c
V. Cabanillas, C. Raposo, L. Potenciano-Machado
This paper deals with stability of solution for a one-dimensional model of Rao-Nakra sandwich beam with Kelvin-Voigt damping and time delay given by ?1h1utt ? E1h1uxx ? k(?u + v + awx) ? auxxt ? ?uxxt( ? , t ? ?) = 0, ?3h3vtt ? E3h3vxx + k(?u + v + ?wx) ? bwxxt = 0, ? hwtt + EIwxxxx ? k?(?u + v + ?wx)x ? cwxxt = 0. A sandwich beam is an engineering model that consists of three layers: two stiff outer layers, bottom and top faces, and a more compliant inner layer called ?core layer?. Rao-Nakra system consists of three layers and the assumption is that there is no slip at the interface between contacts. The top and bottom layers are wave equations for the longitudinal displacements under Euler-Bernoulli beam assumptions. The core layer is one equation that describes the transverse displacement under Timoshenko beam assumptions. By using the semigroup theory, the well-posedness is given by applying the Lumer-Phillips Theorem. Exponential stability is proved by employing the Gearhart-Huang-Pr?ss? Theorem.
本文研究具有Kelvin-Voigt阻尼和时滞的Rao-Nakra夹层梁一维模型解的稳定性。E1h1uxx吗?k (?U + v + awx) ?auxxt吗?uxxt (???) = 0, ?3h3vtt ?x + x + kU + v + ?wx ?BWXXT = 0, ?hwtt + EIwxxxx ?k ? (?U + v + ?wx)x ?CWXXT = 0。夹层梁是一种由三层组成的工程模型:两个坚硬的外层,底部和顶部,以及一个更柔顺的内层,称为“核心层”。Rao-Nakra系统由三层组成,假设触点之间的界面没有滑移。顶层和底层是欧拉-伯努利梁假设下纵向位移的波动方程。核心层是在Timoshenko梁假设下描述横向位移的一个方程。利用半群理论,利用Lumer-Phillips定理给出了半群的适定性。利用Gearhart-Huang-Pr?ss?定理。
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引用次数: 1
Parametrically excited unidirectional wave propagation in thin beam phononics 细束声子中参数激发的单向波传播
IF 0.7 Q4 MECHANICS Pub Date : 2022-01-01 DOI: 10.2298/tam221030010r
Nevena Rosic, Danilo Karličić, Milan Cajić, M. Lazarevic
Wave attenuation, filtering and guiding is an ongoing topic of scientific research, as there are many opportunities for improvement of existing solutions in modern industry. One of the recent advancements has been made with the use of non-reciprocal metamaterials. Certain properties of metamaterials have made them suitable for use in various engineering fields. In this study, we investigate non-reciprocal wave propagation behavior in coupled thin beams phononics, due to time-modulation of material properties and axial loads. We compare the results for the beams which are interconnected with Winkler?s type of elastic layers and elastic or viscoelastic Pasternak layers. An analytic approach is used to discover directional band gaps and investigate wave propagation through these systems of beams, at relevant excitation frequencies. The proposed framework can be exploited in further analysis of phononic systems based on multiple beams coupled through different mediums and structural elements modeled with higher-order beam theories.
波的衰减、滤波和导波是一个不断发展的科学研究课题,因为在现代工业中存在许多改进现有解决方案的机会。最近的一项进展是使用非互易超材料。超材料的某些特性使其适用于各种工程领域。在这项研究中,我们研究了由于材料特性和轴向载荷的时间调制而导致的耦合薄束声子中的非互反波传播行为。我们比较了与Winkler?s型弹性层和弹性或粘弹性帕斯捷尔纳克层。用解析的方法来发现定向带隙,并研究波在相关激励频率下通过这些光束系统的传播。所提出的框架可用于进一步分析基于不同介质和高阶梁理论建模的结构单元耦合的多光束声子系统。
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引用次数: 1
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Theoretical and Applied Mechanics
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