International Journal of Mechanical Sciences最新文献_第9页

A meso‑structure based yield stress for fresh concrete

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-20 DOI: 10.1016/j.ijmecsci.2025.109962

Kumar Anjneya , Arghya Deb

Existing empirical relations for predicting the yield stress of concrete are not of general applicability and provide no understanding of the role of meso‑structure. Moreover, experimental yield stress measurements tend to vary with the type of rheometer. The study proposes a discrete element formulation to compute a meso‑structure-based yield stress that is applicable to different meso‑geometries and is valid across diverse flow regimes. The procedure relies on a mesoscale model based on stresses and displacements, which makes it easier to account for the effects of particle shape, size, and orientation. The model incorporates coupling between normal and shear damage in the aggregate-mortar bond, thus enabling reduction in bond shear strength due to excessive stretching in the normal direction. Discrete specimens are generated to simulate well-known flowability tests. The results match experiments for both elongational and shear flow. The validated model is then used to investigate the effect of aggregate angularity and size. The results suggest that viscous forces are largely responsible for the experimentally observed increase in yield stress with reduction in maximum aggregate size. The meso‑structure-based yield stress is seen to be invariant with respect to the type of test and size of the specimen simulated. The predicted yield stress values also compare well with the BML rheometer and two-point test, with the mean percentage error with respect to the BML readings being around 2 %.

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引用次数: 0

A simplified strain energy density approach for multiaxial fatigue predictions

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-17 DOI: 10.1016/j.ijmecsci.2025.109961

Matteo Pedranz , Vigilio Fontanari , Raffaele De Biasi , Filippo Berto , Ciro Santus , Matteo Benedetti

Multiaxial fatigue is a critical challenge in industrial applications, where predicting fatigue life accurately is essential for components with complex geometries and out-of-phase loading conditions. These factors make traditional approaches economically demanding, necessitating simplified yet reliable methods. In this work, a simplified fatigue approach based on strain energy density (SED) is proposed, addressing the need for economically sustainable, accurate, and cautionary fatigue predictions. The proposed model employs a single control radius and an effective SED range, simplifying both the calibration procedure and the required data. This effective SED assigns a sign to the strain energy based on the hydrostatic stress. To validate the approach, multiaxial fatigue tests on aluminum alloy 7075-T6 were performed, investigating various combinations of load ratios, multiaxiality grades, and notch severities. Additionally, previously published fatigue data on ductile cast iron specimens were used for further validation. A comparison is provided between the proposed model and a highly accurate but calibration-intensive predictive model, offering designers a practical evaluation of the method’s capabilities and limitations. The simplified criterion, calibrated using two experimental fatigue curves, yields higher errors than the complete formulation in multiaxial fatigue assessments, with RMS errors on stress amplitudes below 30% for the simplified approach and below 16% for the complete formulation. However, predictions remain generally conservative. This approach is also applicable to complex geometries and loading scenarios where stress components from different modes cannot be distinguished.

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引用次数: 0

Thermo-micro-mechanical modeling of plasticity and damage in single-phase S700 steel 单相S700钢塑性和损伤的热微力学建模

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109909

Karthik Ramalingam , S. Amir H. Motaman , Christian Haase , Ulrich Krupp

In this study, a Thermo-micro-mechanical (TMM) model to describe the viscoplastic flow of polycrystalline metallic materials was extended by integration of micromechanical damage. The original TMM model [1] incorporated the fundamentals of dislocation motions during metal deformation, using microstructural state variables (MSVs) for the statistical quantification of dislocations, represented through the dislocation density. These MSVs track dislocation evolution throughout deformation, allowing for the material behavior and mechanical properties in cold and warm regimes (up to 500 °C) to be derived as functions of these state variables. A key advantage of the TMM model is its ability to transfer MSVs across multi-step process chain simulations, thereby accounting for the deformation history of materials in subsequent processes. However, the previous model was limited to the plastic regime and cannot be applied to processes involving damage and fracture. The primary objective of the current study is to extend the TMM model to predict fracture and damage. Therefore, the Gurson-Tveergard-Needleman (GTN) model, a widely recognized micromechanical damage model, was integrated into the TMM model to describe the material behavior comprising plasticity, damage and fracture (D-TMM model). This integration introduces void fraction from the damage model as an additional state variable alongside the existing MSVs, thus enabling the transfer of both deformation history and damage accumulation across the process chain. The constitutive equations from both models are numerically integrated, and their parameters are calibrated for a commonly used micro-alloyed high strength construction steel – S700. The model is subsequently tested under isothermal conditions up to 500 °C, non-isothermal conditions, and across a range of strain rates.

在本研究中，通过整合微机械损伤，扩展了用于描述多晶金属材料粘塑性流动的热-微-机械（TMM）模型。最初的 TMM 模型[1]结合了金属变形过程中位错运动的基本原理，使用微结构状态变量（MSV）对位错进行统计量化，并通过位错密度来表示。这些 MSVs 跟踪整个变形过程中的位错演变，从而可以根据这些状态变量的函数推导出冷态和热态（最高 500 °C）的材料行为和机械性能。TMM 模型的一个关键优势是能够在多步骤过程链模拟中转移 MSV，从而考虑材料在后续过程中的变形历史。然而，之前的模型仅限于塑性体系，无法应用于涉及损伤和断裂的过程。当前研究的主要目标是扩展 TMM 模型，以预测断裂和损伤。因此，Gurson-Tveergard-Needleman（GTN）模型（一种广受认可的微机械损伤模型）被集成到 TMM 模型中，以描述包括塑性、损伤和断裂在内的材料行为（D-TMM 模型）。这种集成将损伤模型中的空隙率作为附加状态变量与现有的 MSVs 一起引入，从而实现了变形历史和损伤累积在整个工艺链中的转移。对这两个模型的构成方程进行了数值积分，并对常用的微合金高强度建筑钢材 S700 的参数进行了校准。随后，在高达 500 °C 的等温条件、非等温条件和各种应变速率下对模型进行了测试。

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引用次数: 0

Multi-level alterable transportation of a two-dimensional near-field acoustic levitation platform

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109851

Pengfei Zhang , Wenjun Li , Shenling Cai , Qi Chen , Shuai Huang , Kai Feng

Near-field acoustic levitation (NFAL) is an innovative contactless handling technology with broad applications in precision manufacturing equipment and micro-electrical mechanical systems. The study systematically investigates the multi-level alterable transportation characteristics of a novel two-dimensional non-contact platform based on NFAL technology. The thrust forces in the x- and y-directions provided by the two-dimensional platform on the levitation plate are primarily influenced and adjusted by the amplitudes of the holed and bumped rails, respectively. Therefore, the levitation plate enables multi-level alterable transportation under different operation conditions by adjusting the vibration characteristics of two rails and the physical parameters. The theoretical model, including the governing equation of the squeeze film and the motion equation of the levitation plate, is established to analyze the mechanical and transportation performances. An experimental testbed is constructed to verify the numerical analysis solved by the theoretical model. Both numerical and experimental results demonstrate that the levitation plate can be moved along various angles from a stationary state, termed static multi-angle motion, by adjusting the relative amplitudes of the two rails. Additionally, the experimental results confirm that the levitation plate can perform dynamic turning motion from an initial running state under various operational conditions. The validated multi-level alterable transportation capability highlights the potential of the two-dimensional non-contact platform in precision manufacturing equipment and micro-electromechanical systems.

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引用次数: 0

Effective strength estimation of metal matrix composites by stress compensation method

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109908

Zerui Chen , Heng Peng , Yinghua Liu

Shakedown theory has been widely used to evaluate the load-bearing capacity of elastic-plastic structures under cyclic load. The stress compensation method (SCM) shows good performance in the shakedown analysis of homogeneous materials in previous work. In this paper, the numerical procedure of the SCM is extended for shakedown analysis of metal matrix composites (MMCs) made of heterogeneous materials. To validate the applicability and accuracy of the extended SCM, the calculated results of the method are compared with those available in the literature and the results of step-by-step analyses. Based on the computational homogenization method, the effective strength of MMCs is determined through shakedown analysis on representative volume elements (RVEs). Two kinds of RVEs individually from periodic particle-reinforced metal matrix composite and continuous fiber-reinforced aluminum matrix composite are investigated. The shakedown boundaries under various combinations of thermal and mechanical loads are given. Both the ratchetting mechanism and reverse plasticity mechanism to determine the different regimes of the shakedown boundary are revealed. Additionally, we illustrate that both stress approach and strain approach are feasible for the shakedown analysis of MMCs. The boundary conditions for constructing the self-equilibrium stress fields for stress-controlled and strain-controlled shakedown problems are formulated. The corresponding shakedown boundaries are determined and compared. A discrepancy exists in the shakedown boundaries obtained under the two loading approaches. The discrepancy is strongly correlated with the macroscopic residual strain and macroscopic residual stress.

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引用次数: 0

Enhanced high-frequency continualization scheme for inertial beam-lattice metamaterials

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109794

Andrea Bacigalupo, Paolo Badino, Vito Diana, Luigi Gambarotta

A multifield continualization technique is introduced that offers a thermodynamically consistent description of the constitutive and dispersive properties of beam-lattice inertial metamaterials with periodic microstructures. The balance equations governing the mechanics of the discrete Lagrangian system are appropriately handled using an innovative continualization scheme to derive an equivalent integral-type continuum model. Based on formal Taylor series expansion of the integral kernels or the corresponding pseudo-differential functions incorporating shift operators and appropriate pseudo-differential downscaling laws, the proposed multifield enhanced continualization scheme allows the derivation of a gradient-type continuum model of given rank and equivalent to lattices. Two different resolution techniques are proposed. Firstly, the corresponding infinite-order average differential equations are tackled using a perturbative approach to describe the forced Bloch wave propagation in the metamaterial. Secondly, higher-order continuum models are employed through proper differential equation truncation to characterize the dispersive properties of the metamaterial in both high- and low-frequency regimes. Moreover, an energetically consistent generalized equivalent Micropolar continua, with non-local inertial terms, are here identified. The multifield continualization procedure is applied to two-dimensional periodic microstructures with tetrachiral, hexachiral, and hexa-tetrachiral topologies. Illustrative examples highlight the ability of the equivalent continuum model to accurately describe the effective constitutive properties of inertial metamaterials with periodic microstructures and to define a dynamic response consistent with the discrete Lagrangian model, validated and tested through virtual experimental verification under free and forced wave conditions.

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引用次数: 0

All-dielectric bifocal metalens with diffraction-limited focusing and polarization-dependent characteristics 具有衍射限制聚焦和偏振依赖特性的全介质双焦超透镜

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2025.109916

Xuyang Gao , Yuxin Liu , Hao Chen , Yu-Sheng Lin , Xuequan Chen

Terahertz (THz) metalenses have attracted significant attention due to their potentials in advanced imaging, sensing, and communication applications, offering compact, lightweight designs and superior focusing capabilities compared to the conventional lenses. However, few studies have focused on polarization-independent bifocal metalenses in this frequency range. In this work, we design and demonstrate a transmissive all-dielectric bifocal metalens (ADBM), studied through simulation, optimization, fabrication, testing, and imaging methods. The metalens, composed of cross-shaped microrod phase elements made of high-resistivity silicon (Si), features low absorption, high transmission, and a simplified fabrication process. It generates distinct focal lengths for incident waves in transverse electric (TE) and transverse magnetic (TM) polarization states. They are 19.93 mm and 37.98 mm in TE and TM modes, respectively, enabling bifocal functionality. To enhance focusing performances, an error evaluation function is introduced to reduce phase errors during polarization multiplexing. The impact of different parameters in the error evaluation function on focusing performances is also discussed. ADBM achieves high Strehl ratios of 0.87 and 0.92 in TE and TM modes, respectively, indicating diffraction-limited focusing performances. Additionally, ADBM exhibits broadband focusing performances across the 0.70 THz to 1.10 THz spectra range for both polarizations. The fabricated ADBM exhibits high-resolution imaging capabilities, whihc are in agreement with simulations. This innovative design provides a new strategy for controlling orthogonal polarization states, promising broad applications in advanced optical imaging and communication.

太赫兹（THz）超透镜由于其在先进成像、传感和通信应用方面的潜力而引起了极大的关注，与传统透镜相比，它提供了紧凑、轻便的设计和卓越的聚焦能力。然而，很少有研究集中在这个频率范围内的不依赖偏振的双焦点超透镜。在这项工作中，我们设计并展示了一种透射式全介电双焦超透镜（ADBM），通过模拟、优化、制造、测试和成像方法进行了研究。该超构透镜由高电阻率硅（Si）制成的十字形微棒相元件组成，具有低吸收、高透射、制造工艺简化等特点。在横向电（TE）和横向磁（TM）极化状态下，入射波产生不同的焦距。它们在TE和TM模式下分别为19.93 mm和37.98 mm，可实现双焦点功能。为了提高对焦性能，引入了误差评估函数来减小偏振复用过程中的相位误差。讨论了误差评价函数中不同参数对聚焦性能的影响。ADBM在TE和TM模式下分别达到了0.87和0.92的高Strehl比率，表明其具有衍射受限聚焦性能。此外，ADBM在0.70太赫兹到1.10太赫兹的光谱范围内都具有宽带聚焦性能。制备的ADBM具有高分辨率成像能力，与模拟结果一致。这种创新的设计为控制正交偏振态提供了新的策略，在先进的光学成像和通信中有广泛的应用前景。

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引用次数: 0

Microstructural, interfacial, and frictional properties of TixCy /Ni composites

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109883

Phu-Cuong Le , Tan-Tai Do , Te-Hua Fang , Chun-I Lee

This study examines the variation of Ti_xC_y/Ni composite properties during the polishing process using molecular dynamics simulation. Various material parameters and testing conditions, including abrasion depth, abrasion velocity, reinforcement particle derivatives, and reinforcement particle size, are examined, revealing both advantageous and disadvantageous impacts on feedstock characteristics such as supply force, friction coefficient, dislocation distribution, von Mises stress, and displacement vector. The findings indicate that increasing the velocity of the abrasive ball reduces the friction coefficient up to a certain threshold, beyond which it no longer improves and instead increases the density of dislocation distribution within the structure. Strong covalent bonding of TiC aids in reducing the friction coefficient and absorbing the force transmitted from the Ni matrix. Changes in the TiC reinforcement particle radius had minimal impact on polishing and normal force, as larger particles exhibited elastic deformation. However, TiC particles with 12 Å and 15 Å radii formed locked dislocations, significantly hardening the TiC/Ni matrix. This research offers key insights for optimizing TiC/Ni friction characteristics of composites and machining parameters for high-value product fabrication.

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引用次数: 0

Influence of strain rate and temperature on the multiaxial failure stress locus of a polyamide syntactic foam

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109864

Yue Chen , Yuan Xu , Antonio Pellegrino

This study introduces a comprehensive experimental methodology allowing for the direct measurement of the rate dependent multiaxial response of polymer syntactic foams under combined direct-shear loading. The combined tension-torsion behaviour of a syntactic foam and its rate dependence are investigated for the first time.

Dynamic tension-torsion experiments were conducted using a newly developed Tension-Torsion Hopkinson Bar (TTHB) enabling the measurement of the combined tensile-shear response of engineering materials at high rates of strain.

The response and multiaxial failure envelope of a polyamide syntactic foam were experimentally measured and analysed to determine the combined influences of stress state, strain rate, and temperature. The multiaxial failure stress locus was defined in both the normal versus shear stress space and the principal stress space, providing a comprehensive characterisation of the behaviour of the material under various loading and environmental conditions.

The suitability of existing pressure dependent failure criteria to represent the measured experimental data was also assessed. The Drucker-Prager pressure dependent criterion proved to be effective in capturing the measured quasi-static and dynamic multi-axial stress loci at different temperatures.

The effects of temperature, loading rate and stress state on the deformation and failure modes were analysed by means of SEM micrographs of the tested samples.

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引用次数: 0

Implementing multiple biaxial-tension proportional loading paths using double elliptical dies

IF 7.1 1区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Mechanical Sciences

Pub Date : 2025-01-15 DOI: 10.1016/j.ijmecsci.2024.109897

Zhubin He , Xinyu Hu , Xiujian Yu , Yanli Lin , Kelin Chen

When sheet metals are integrally formed into complex thin-walled components, to determine the forming scheme, establishing an accurate material model is essential. Traditional biaxial loading experiments are used to test the properties of sheet metals. However, a single test can only obtain the deformation behavior under one stress state. Multiple experiments are required to realize different loading paths to fully test the mechanical properties of the sheet under various stress states. To simplify test procedure and obtain multiple loading paths on a specimen by one single test, a bulge test method for sheet metal using a double elliptical die is proposed. The study is carried out on a cold-rolled 304 stainless steel sheet. To assess the stress state at various points along the symmetry line of the bulging zone, a mechanical analysis model is established. The feasibility of the double elliptical die bulge test method for achieving multiple loading paths by both simulations and experiments. Furthermore, the effect of variations in the elliptical ratios of the double elliptical die on the bulging results is analyzed. The findings suggest that during the single bulging process with double elliptical die, the stress path of points on symmetry line of the bulging zone follows a linear trajectory. The relationship between the upper and lower limits of the stress ratio (α_max and α_min) on the symmetry line of the bulging zone and the first elliptical ratio of the double elliptical die (λ₁) is found to be: α_max=0.56λ₁+0.82, α_max−α_min=0.5λ₁. The stress ratio α is defined as a numerical result: the ratio of the in-plane principal stresses σ_RD and σ_TD. By adjusting the value of λ₁, biaxial loading experiments within a specific stress ratio range can be realized based on this principle.

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引用次数: 0