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Vortex-induced vibration of a square cylinder in wind tunnel 风洞中方形圆柱体的涡流诱导振动
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2024-01-09 DOI: 10.1016/j.crme.2009.12.00
X. Amandolese, P. Hémon
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引用次数: 60
The Meyer’s estimate of solutions to Zaremba problem for second-order elliptic equations in divergent form 二阶发散型椭圆方程Zaremba问题解的Meyer估计
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-06-07 DOI: 10.5802/CRMECA.87
Yu. A. Alkhutov, G. Chechkin
In this paper we obtain an estimate for the increased integrability of the gradient of the solution to the Zaremba problem for divergent elliptic operator in a bounded domain with nontrivial capacity of the Dirichlet boundary conditions. Résumé. Dans cet article, nous obtenons une estimation de l’intégrabilité accrue du gradient de la solution du problème de Zaremba pour un opérateur elliptique divergent dans un domaine borné avec une capacité non triviale des conditions aux limites de Dirichlet. ∗Corresponding author. ISSN (electronic) : 1873-7234 https://comptes-rendus.academie-sciences.fr/mecanique/ 300 Yurij A. Alkhutov and Gregory A. Chechkin
In this paper》(we estimate for the您每年会圣母圣母解决梯度to the Zaremba integrability elliptic运营商In a . for不一bounded domain with the nontrivial容量由Dirichlet边界条件。摘要。在本文中,我们估计了在具有非平凡狄利克雷边界条件的有界域上发散椭圆算子的Zaremba问题解的梯度可积性的增加。∗对应着作者。他的父亲是一名律师,母亲是一名律师,父亲是一名律师,母亲是一名律师。
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引用次数: 4
2D model simulating the hydro-rheological behavior of leather during convective drying 模拟皮革在对流干燥过程中流体流变特性的二维模型
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-06-07 DOI: 10.5802/CRMECA.86
Naima Benmakhlouf, S. Azzouz, L. Hassini, A. Cafsi
An experimental and numerical study of a two-dimensional spatio-temporal variation of the temperature, moisture content, and mechanical stress during the convective drying process of unsaturated and deformable products (leather) were conducted. The bovine leather sample response under convective drying is described by a mathematical model. The leather sample was modeled by an elastic medium, and the mass, heat, and momentum transfer principles are applied. The numerical results agreed well with the corresponding experimental data. The variation of the internal temperature and moisture content was simulated for different drying conditions. A reduction by 15 °C was noted in the optimum temperature for best product quality when the drying air relative humidity was 20%. The cost to achieve a better quality product was found to be minimized due to the decrease in the optimum temperature. The presented simulation results of the elastic material could be applied to the leather, which will reduce the needed time of exposure for predetermined final water content. The damage of the sample is more likely to occur at the beginning of the drying in the time interval of 300–400 s. According to these simulations, the sample’s face, which is exposed to the drying air, has the highest stress; therefore, the sample’s face is at a high risk of cracking. It is also observed that the risk of damage to the sample corresponding to the maximum level of the stress is higher for the highest drying temperature of 60 °C. The peak of the three thicknesses of leather can be achieved for normal stresses in the interval of 60,000 to 140,000 MPa at around 10,000 s.
对非饱和可变形制品(皮革)对流干燥过程中温度、含水率和机械应力的二维时空变化进行了实验和数值研究。用数学模型描述了牛皮革样品在对流干燥条件下的响应。采用弹性介质对皮革样品进行建模,并应用了质量、热量和动量传递原理。数值计算结果与相应的实验数据吻合较好。模拟了不同干燥条件下内部温度和水分含量的变化。当干燥空气相对湿度为20%时,在最佳产品质量的最佳温度下减少了15°C。由于最佳温度的降低,获得更好质量产品的成本被最小化。所提出的弹性材料的模拟结果可以应用于皮革,这将减少所需的暴露时间为预定的最终含水量。在300 - 400s的干燥时间间隔内,试样更容易发生损伤。根据这些模拟,暴露在干燥空气中的样品表面具有最大的应力;因此,试样的表面有很高的开裂风险。我们还观察到,当最高干燥温度为60℃时,与最大应力水平相对应的样品损伤风险更高。三种皮革厚度的峰值可以在6万到14万MPa的正常应力范围内,在10000秒左右达到。
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引用次数: 0
Large-scale smooth plastic topology optimization using domain decomposition 基于域分解的大规模光滑塑性拓扑优化
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-06-07 DOI: 10.5802/CRMECA.88
M. Fourati, Z. Kammoun, J. Néji, H. Smaoui
A domain decomposition procedure based on overlapping partitions of the design domain is proposed for solving large problems of smooth topology optimization of plastic continua. The procedure enables the solution of problems with sizes exceeding the available computational and storage capacities. It takes advantage of the favorable features of the integrated limit analysis and design formulation of the smooth topology design problem. The integrated approach preserves the mathematical structure and properties of the underlying static, lower bound problem of limit analysis. In particular, the formulation is characterized by weak coupling between subproblems because it does not involve a stress–strain relationship. The decomposition strategy begins by solving a reduced design problem, using a coarse finite element mesh, followed by an iterative process using a fine discretization. At each iteration, an independent topology optimization subproblem is associated with each subdomain, considered as a substructure. The traction vectors acting on the subdomain boundaries are updated at each iteration as the overlapping partitions are switched. The numerical tests showed that as early as the first iteration, the decomposition process generates a feasible, near optimal design with a weight less than 0.1% above the direct solution.
针对塑性连续体的光滑拓扑优化问题,提出了一种基于设计域重叠分区的区域分解方法。该过程能够解决超出可用计算和存储容量的问题。它利用了光滑拓扑设计问题的综合极限分析和设计公式的优点。这种综合方法保留了极限分析的静态下界问题的数学结构和性质。特别地,该公式的特点是子问题之间的弱耦合,因为它不涉及应力-应变关系。分解策略首先通过使用粗糙的有限元网格解决简化的设计问题,然后使用精细离散化进行迭代过程。在每次迭代中,每个子域关联一个独立的拓扑优化子问题,将其视为子结构。作用于子域边界的牵引向量在每次迭代中随着重叠分区的切换而更新。数值试验表明,早在第一次迭代中,分解过程就产生了一个可行的、接近最优的设计,其权重比直接解高出小于0.1%。
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引用次数: 0
Modal energetic analysis and dynamic response of worm gear drives with a new developed dynamic model 基于新建立的蜗轮传动动力学模型的模态能量分析与动态响应
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-05-03 DOI: 10.5802/CRMECA.80
Ala Eddin Chakroun, A. Hammami, A. De-Juan, F. Chaari, Alfonso Fernández, F. Viadero, M. Haddar
In order to investigate the behaviour of worm drives, a new dynamic model, composed of two blocks, is established and used to extract numerical results. The tooth deflection of the worm drive, bearings, and wheels inertias are taken into consideration. Newmark solving method is applied to solve motion equations. The state of contact of teeth is what enables these signals to manifest themselves. Modal analysis is developed to investigate the different natural modes of the model. Furthermore, modal energetic analysis is used to understand the distribution of strain and kinetic energies. It is also applied to classify natural models into “teeth modes” and “bearing modes”. These two modes constitute two different frequency bands. The dynamic coefficient is measured simultaneously with the gradual increase of the turning speed of the motor. This allows for the evaluation of the overload of the system.
为了研究蜗杆传动的动态特性,建立了一种新的由两个块组成的动力学模型,并利用该模型提取了数值结果。考虑了蜗杆传动的齿挠度、轴承和车轮惯性。应用Newmark解法求解运动方程。牙齿接触的状态使这些信号能够表现出来。模态分析用于研究模型的不同自然模态。此外,采用模态能分析来了解应变和动能的分布。它也被用于将自然模型分类为“齿模式”和“轴承模式”。这两种模式构成了两个不同的频段。动态系数随电机转速的逐渐增大而同步测量。这允许对系统的过载进行评估。
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引用次数: 5
Indicator kriging for damage position prediction by the use of electromechanical impedance-based structural health monitoring 基于机电阻抗的结构健康监测损伤位置预测指标克里格法
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-04-27 DOI: 10.5802/CRMECA.81
Daniel Resende Gonçalves, Jose dos Reis Vieira de Moura, Paulo Pereira, Marcos Vinícius Agapito Mendes, Henrique Senna Diniz-Pinto
Some nondestructive techniques of the Structural Health Monitoring (SHM) have improved their analysis in the past decades. Among them, the electromechanical impedance-based SHM technique (EMISHM) has been tested in several fields and associated to different statistical methodologies. Considering the nature of the spatial variation of the damage metric data along structures, herein is proposed the use of the indicator kriging method for predicting the existence of a known damage located in the center of an aluminum plate. Maps showing the probability of the damage metric to fall in several value ranges were capable of outlining the areas affected by the damage and predict its location. Comparisons between scenarios with different spacing between PZT patches showed a reduction in the reliability of the model with the increasing of such spacing. Also, for the structure under study, it demonstrates that it is not possible to obtain results by the methodology for distance between sensors/actuators greater than 16.67 cm. However, the results show that this approach can be a viable alternative for using damage metrics to map regions affected by damage and its location.
在过去的几十年里,一些结构健康监测(SHM)的无损技术已经改进了它们的分析方法。其中,基于机电阻抗的SHM技术(EMISHM)已经在几个领域进行了测试,并与不同的统计方法相关联。考虑到损伤度量数据沿结构方向空间变化的性质,提出了用指示克里格法预测铝板中心是否存在已知损伤的方法。地图显示了损失指标在几个值范围内的概率,能够勾勒出受损害影响的区域并预测其位置。不同PZT斑块间距的情景比较表明,随着PZT斑块间距的增加,模型的可靠性降低。此外,对于所研究的结构,它表明不可能通过传感器/致动器之间的距离大于16.67 cm的方法获得结果。然而,结果表明,这种方法可以作为一种可行的替代方法,使用损伤度量来绘制受损伤影响的区域及其位置。
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引用次数: 1
Impact of the fracture contact area on macro-dispersion in single rough fractures 裂缝接触面积对单个粗裂缝宏观弥散的影响
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-04-27 DOI: 10.5802/CRMECA.82
A. Beaudoin, M. Farhat
In the scientific literature, the study of the impact of the fracture contact area on macro-dispersion in single rough fractures is still an open question. In this work, we study numerically the combined effects of the fracture roughness and the fracture contact area on the non-Fickian transport in single rough fractures. In particular, we quantify the contribution of the fracture contact area on macro-dispersion. These objectives are achieved by estimating the macro-dispersion coefficient from Monte Carlo parallel numerical simulations in pure advection and advection–diffusion cases. When the fractional void SO is equal to 1 (i.e., for σlnb < 0.25), the Monte Carlo simulations show that macro-dispersion results of two contributions, dispersion caused by the heterogeneity of fracture apertures that induces a channelization of flow paths and molecular diffusion, as shown by the analytical solution proposed by Gelhar in 1993. When the fraction void SO is different from 1 (i.e., forσlnb > 0.25), a third mechanism plays in macro-dispersion. The presence of contacts or obstacles causes a disruption of flow paths. This mechanism is identical to that induced by the fracture roughness with a lower amplitude. Its amplitude is the function of the fractional void SO .
在科学文献中,裂缝接触面积对单个粗裂缝宏观弥散的影响研究仍然是一个悬而未决的问题。在本文中,我们数值研究了裂缝粗糙度和裂缝接触面积对单一粗糙裂缝非菲克输运的综合影响。特别是,我们量化了断裂接触面积对宏观弥散的贡献。这些目标是通过蒙特卡罗平行数值模拟在纯平流和平流扩散情况下估计宏观色散系数来实现的。当分数孔隙SO = 1(即σlnb < 0.25)时,Monte Carlo模拟结果表明,宏观弥散有两种贡献,即由裂缝的非均匀性引起的流道通道化和分子扩散,如Gelhar(1993)提出的解析解所示。当分数孔隙SO > 1(即σlnb > 0.25)时,宏观色散发生第三种机制。触点或障碍物的存在会导致流动路径的中断。该机理与较低振幅断裂粗糙度引起的机理相同。它的振幅是分数空SO的函数。
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引用次数: 1
CFD analysis of operating condition effects on optimum nozzle exit position of a supersonic ejector using the refrigerant R134a 采用R134a制冷剂的超声速引射器工况对喷口最佳出口位置影响的CFD分析
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-04-14 DOI: 10.5802/crmeca.60
A. Hadj, M. Boulenouar
In this work, the computational fluid dynamics technique is employed to study operating condition effects on the optimum value of an important parameter called the nozzle exit position (NXP) for an ejector design. This ejector uses the gas R134a as the working fluid. Numerical tests are carried out using a combination of the REFPROP 7.0 database state equation and the high-Reynolds version of the SST k–ω model. Good agreement in terms of entrainment ratio and critical temperature is obtained between computed values and measurements. In addition, numerical results indicate that the optimum NXP maximizes ejector performance and is highly dependent on operating conditions.
本文采用计算流体力学方法研究了工况对喷射器出口位置(NXP)最优值的影响。该喷射器使用气体R134a作为工作流体。采用REFPROP 7.0数据库状态方程和高雷诺数版本的SST k -ω模型进行了数值试验。在夹带比和临界温度方面,计算值与测量值很好地吻合。此外,数值结果表明,最优的NXP使喷射器性能最大化,并且高度依赖于操作条件。
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引用次数: 1
Correlation between the toroidal modes of an elastic sphere and the viscosity of liquids 弹性球的环面模态与液体粘度的关系
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-03-26 DOI: 10.5802/CRMECA.79
J. L. Pommellec, A. E. Baroudi
Vibration characteristics of elastic nanostructures embedded in fluid medium have been used for biological and mechanical sensing and also to investigate materials and mechanical properties. An analytical approach has been developed in this paper to accurately predict toroidal vibrations of an elastic nanosphere in water–glycerol mixture. The Maxwell and Kelvin–Voigt models are used to describe the viscoelasticity of this fluid. The influence of key parameters such as glycerol mass fraction, sphere radius, and angular mode number are studied. We demonstrate that the sphere radius plays a significant role on the quality factor. Results also highlight three behavior zones: viscous fluid, transition, and elastic solid. In addition, these investigations can serve as benchmark solution in design of liquid sensors.
弹性纳米结构在流体介质中的振动特性已被用于生物和机械传感,以及材料和力学性能的研究。本文提出了一种准确预测弹性纳米球在水-甘油混合物中的环面振动的分析方法。麦克斯韦和开尔文-沃伊特模型被用来描述这种流体的粘弹性。研究了甘油质量分数、球半径、角模数等关键参数对反应的影响。我们证明了球半径对质量因子有重要的影响。结果还突出了三个行为区域:粘性流体,过渡和弹性固体。此外,这些研究可以作为液体传感器设计的基准解决方案。
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引用次数: 0
Fractional stress-dilatancy equation based on critical state lines with arbitrary form 基于任意形式临界状态线的分数阶应力-剪胀方程
IF 0.8 4区 工程技术 Q4 MECHANICS Pub Date : 2021-03-17 DOI: 10.5802/CRMECA.78
Yifei Sun, Jiancheng Zhang
The original state-dependent fractional stress-dilatancy (FSD) equation for soils is developed based on the critical state lines (CSLs) with linear form. However, experimental evidences showed that the CSLs of soil in the p ′–q and e–p ′ planes could be both nonlinear as well due to significant material degradation. This note aims to propose a unified FSD equation for soils with arbitrary types of CSLs. Detailed derivations are provided. To validate the proposed FSD equation, a series of triaxial test results of ballast and rockfill are simulated.
基于线性形式的临界状态线(CSLs),建立了土的初始状态相关分数应力-剪胀方程。然而,实验证据表明,由于材料的显著降解,p ' -q和e-p '面土壤的csl也可能是非线性的。本文旨在提出具有任意类型csl的土壤的统一FSD方程。给出了详细的推导。为了验证所提出的FSD方程,模拟了一系列压舱物和堆石料的三轴试验结果。
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引用次数: 1
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Comptes Rendus Mecanique
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