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Prestress-mediated damage strength of lattice metamaterials and its optimization 晶格超材料的预应力介导破坏强度及其优化
IF 2.2 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-16 DOI: 10.1007/s10704-023-00743-6
Xinran Li, Jinxing Liu, Ai Kah Soh

Lattice metamaterials have been attracting wide research interests due to their excellent mechanical properties. Most of meta-properties have been implemented by proper geometric designs of microstructures. In this study, we examine another way to obtain outstanding properties, which has been relatively less explored. That is, we aim to adjust the loading bearing capability of lattices by periodically introducing prestress into particular lattice segments. Based on existing related works, we focus on the following two problems deserving further investigations. First, results have been provided based on a single cell with/without taking into account the interactions between each two of neighboring individual cells. Second, it is interesting to search for the optimal distribution of prestress in lattices subjected to a specific load. For the former, we propose a set of constraint equations for implementing periodic boundary conditions (PBC) on a periodic unit cell and validate the method. The significance of PBC related to rotational degrees of freedom is emphasized. We then use the proposed method to calculate the initial damage surface of four kinds of prestressed lattice unit cells under PBC. For the latter, we build a new optimization algorithm with the help of the so-called Symbiotic-Organisms-Search technique (SOS), to calculate the optimal prestress setting corresponding to the requested properties. As an example, the optimal prestress setting is found to almost double the critical load to failure of the lattice in a special direction. This work may be helpful to design lattice metamaterials with programmable strengths.

晶格超材料因其卓越的机械特性而引起了广泛的研究兴趣。大多数超材料特性都是通过适当的微结构几何设计实现的。在本研究中,我们探讨了另一种获得优异性能的方法,而这种方法的探索相对较少。也就是说,我们旨在通过定期向特定晶格片段引入预应力来调整晶格的承载能力。在现有相关工作的基础上,我们重点关注以下两个值得进一步研究的问题。首先,已有的研究结果都是基于单个单元的,没有考虑到相邻单个单元之间的相互作用。其次,在承受特定荷载的晶格中寻找预应力的最佳分布也很有意义。针对前者,我们提出了一套在周期性单元格上实施周期性边界条件(PBC)的约束方程,并对该方法进行了验证。我们强调了与旋转自由度相关的 PBC 的重要性。然后,我们使用所提出的方法计算了四种预应力网格单元在 PBC 条件下的初始损伤面。对于后者,我们借助所谓的共生-有机-搜索技术(SOS)建立了一种新的优化算法,以计算与所要求的特性相对应的最佳预应力设置。举例来说,最佳预应力设置可使晶格在特殊方向上的临界破坏荷载几乎增加一倍。这项工作可能有助于设计具有可编程强度的晶格超材料。
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引用次数: 0
Fracture analysis of pre-cracked graphene layer sheets using peridynamic theory 预裂石墨烯层片断裂的周动力学分析
IF 2.5 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-15 DOI: 10.1007/s10704-023-00744-5
M. A. Torkaman-Asadi, M. A. Kouchakzadeh

The peridynamic (PD) theory is a nonlocal reformulation of mechanics with various advantages over common approaches, mainly local continuum mechanics and molecular dynamics (MD). PD theory can capture phenomena at different dimensions, including nanoscale. However, limited studies have been performed by this theory in nanoscale, which have generally focused on the feasibility and accuracy of using PD in atomic-scale modeling. In the present study, based on the ordinary state-based peridynamic method, we investigate the fracture of pre-cracked single layer graphene sheets (SLGSs) under uniaxial tension. By simulating the exact atomic model of graphene, the failure strain and crack growth pattern in the zigzag and armchair directions in PD are compared with MD. We show that by considering some restrictions, these two methods have a good consistency with each other. Afterward, we study two different coarse-grained PD models and demonstrate this method can simulate the failure of graphene with acceptable accuracy. A significant reduction in simulation cost is an excellent point of the PD compared to the MD simulation model. Under these conditions, a massive atomic model with several million atoms can be easily simulated.

周动力学(PD)理论是力学的非局部重新表述,与常见方法(主要是局部连续介质力学和分子动力学)相比具有各种优势。PD理论可以捕捉不同维度的现象,包括纳米尺度。然而,该理论在纳米尺度上进行的研究有限,通常集中在原子尺度建模中使用PD的可行性和准确性上。在本研究中,基于基于常态的周动力学方法,我们研究了预裂纹单层石墨烯片(SLGS)在单轴拉伸下的断裂。通过模拟石墨烯的精确原子模型,将PD中Z字形和扶手椅方向的失效应变和裂纹生长模式与MD进行了比较。之后,我们研究了两种不同的粗粒度PD模型,并证明该方法可以以可接受的精度模拟石墨烯的失效。与MD模拟模型相比,模拟成本的显著降低是PD的一个优点。在这些条件下,一个有几百万个原子的大质量原子模型可以很容易地模拟出来。
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引用次数: 0
Rate-dependent fracture behavior of gelatin-based hydrogels 明胶基水凝胶的速率依赖性断裂行为
IF 2.5 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-08 DOI: 10.1007/s10704-023-00738-3
Si Chen, Krishnaswamy Ravi-Chandar

Hydrogels exhibit rate-dependent fracture behavior, due to solvent diffusion, rearrangement of the polymer network, and other mechanisms. To explore rate-dependent fracture behavior, a series of creep fracture experiments were performed on gelatin-based hydrogels under different controlled humidity, and load conditions. The crack tip boundary condition was controlled to non-immersed and fully water-saturated conditions. Additionally, full-field measurements of the displacement field were performed with digital image correlation. From these experiments, we show that humidity influences the crack initiation time but not the growing crack speed, and that water on the crack tip will significantly influence the fracture properties of the failure zone. Schapery’s viscoelastic J-like integral was adopted for analysis of the experimental measurement to distinguish bulk viscoelastic dissipation from the fracture process zone dissipation. We show that viscoelastic J-like integral is path-independent and can serve as a characterizing parameter for quasistatic crack growth, which provides a way to predict crack growth speed in the simulations.

由于溶剂扩散、聚合物网络的重排和其他机制,水凝胶表现出速率依赖性的断裂行为。为了探索速率依赖性断裂行为,在不同的控制湿度和载荷条件下,对明胶基水凝胶进行了一系列蠕变断裂实验。裂纹尖端边界条件被控制为非浸没和完全水饱和条件。此外,位移场的全场测量是用数字图像相关进行的。从这些实验中,我们发现湿度影响裂纹萌生时间,但不影响裂纹扩展速度,并且裂纹尖端的水将显著影响失效区的断裂性能。采用Schapery粘弹性类J积分对实验测量结果进行分析,以区分整体粘弹性耗散和断裂过程区耗散。我们证明了粘弹性类J积分是路径无关的,可以作为准静态裂纹扩展的特征参数,这为在模拟中预测裂纹扩展速度提供了一种方法。
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引用次数: 0
Finite element modeling of the distribution of hydrogen atoms at a dent on pipelines for hydrogen transport under cyclic loading 循环载荷下氢气输送管道凹痕处氢原子分布的有限元模拟
IF 2.2 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-07 DOI: 10.1007/s10704-023-00741-8
Jian Zhao, Y. Frank Cheng

Repurposing existing natural gas pipelines for hydrogen transport requires an accurate assessment of the distribution of hydrogen (H) atoms at defects, such as dents, under frequent pressure fluctuations experienced by gas pipelines. In this work, a 3-dimensional finite element-based model was developed to determine the stress/strain and H atom concentrations at an unconstrained dent on an X52 steel pipe which experienced denting, spring-back and cyclic loading processes. As expected, stress and strain concentrations generate at the dent center. However, the cyclic loading reduces the stress level and shifts the stress concentration zone from the dent center along the circumferential direction. As the dent depth increases, the maximum H atom concentration is further shifted from the dent center to the side. There are no certain relationships among the maximum H atom concentration, von Mises stress, hydrostatic stress, and plastic strain in terms of their distributions and quantities. Pressure fluctuations decrease both the stress and H atom concentrations at the dent, providing a beneficial effect on reduced risk of the dented pipelines to hydrogen embrittlement in high-pressure hydrogen gas environments. The indenter size has little influence on the H atom distribution in the dent area.

要将现有天然气管道重新用于氢气输送,就必须准确评估在天然气管道频繁压力波动的情况下,氢原子在凹痕等缺陷处的分布情况。在这项工作中,开发了一个基于三维有限元的模型,以确定经历了凹陷、回弹和循环加载过程的 X52 钢管上无约束凹痕处的应力/应变和氢原子浓度。不出所料,应力和应变集中在凹痕中心。然而,循环加载降低了应力水平,并将应力集中区从凹痕中心沿圆周方向转移。随着凹痕深度的增加,最大 H 原子浓度进一步从凹痕中心向两侧移动。最大 H 原子浓度、冯-米塞斯应力、静水应力和塑性应变在分布和数量上没有确定的关系。压力波动会降低凹痕处的应力和 H 原子浓度,从而降低凹痕管道在高压氢气环境中发生氢脆的风险。压头尺寸对凹痕区域的氢原子分布影响很小。
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引用次数: 0
Mode-I penny-shaped crack problem in an infinite space of one-dimensional hexagonal piezoelectric quasicrystal: exact solutions 一维六边形压电准晶体无限空间中的i型便士型裂纹问题:精确解
IF 2.2 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-07 DOI: 10.1007/s10704-023-00742-7
Jiaqi Zhang, Xiangyu Li, Guozheng Kang

This paper aims to study the Mode-I penny-shaped crack problem of an infinite body of one-dimensional hexagonal piezoelectric quasicrystal. The problem is transformed into a mixed-boundary value problem in the context of electro-elasticity of quasicrystals, and the corresponding integro-differential equations are analytically solved. Two extreme cases of electrically impermeable and permeable crack surface are considered. By virtue of the generalized potential theory method, the three-dimensional complete analytical solutions of three-dimensional crack problems under symmetric concentrated and uniform loads are expressed in terms of elementary functions. Important parameters in fracture mechanics are explicitly derived, such as crack surface displacements, the distributions of generalized stresses at the crack tip and the corresponding generalized stress intensity factors. The validity of the proposed solutions and the coupling effect of phonon-phason-electric fields are investigagted through numerical examples.

本文旨在研究一维六方压电准晶体无限体的 Mode-I 笔形裂纹问题。将该问题转化为准晶体电弹性背景下的混合边界值问题,并分析求解了相应的积分微分方程。考虑了裂缝表面不透电和透电的两种极端情况。利用广义势理论方法,用初等函数表达了对称集中载荷和均匀载荷下三维裂纹问题的三维完整解析解。明确推导出了断裂力学中的重要参数,如裂纹表面位移、裂纹尖端的广义应力分布以及相应的广义应力强度因子。通过数值示例研究了所提解决方案的有效性以及声-声-电场的耦合效应。
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引用次数: 0
Micromechanical based model for predicting aged rubber fracture properties 基于微观力学的老化橡胶断裂性能预测模型
IF 2.5 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-09-05 DOI: 10.1007/s10704-023-00730-x
R. Kadri, M. Nait Abdelaziz, B. Fayolle, G. Ayoub, M. Ben Hassine, Y. Nziakou

Environmental aging induces a slow and irreversible alteration of the rubber material’s macromolecular network. This alteration is triggered by two mechanisms which act at the microscale: crosslinking and chain scission. While crosslinking induces an early hardening of the material, chain scission leads to the occurrence of dangling chains responsible of the damage at the macromolecular scale. Consequently, the mechanical behavior as well as the fracture properties are affected. In this work, the effect of aging on the mechanical behavior up to fracture of elastomeric materials and the evolution of their fracture properties are first experimentally investigated. Further, a modeling attempt using an approach based upon a micro-mechanical but physical description of the aging mechanisms is proposed to predict the mechanical and fracture properties evolution of aged elastomeric materials. The proposed micro-mechanical model incorporates the concepts of residual stretch associated with the crosslinking mechanism and a so-called “healthy” elastic active chain (EAC) density associated with chain scission mechanism. The validity of the proposed approach is assessed using a wide set of experimental data either generated by the authors or available in the literature.

环境老化导致橡胶材料的大分子网络发生缓慢且不可逆的变化。这种改变是由两种微观机制触发的:交联和断链。虽然交联会导致材料的早期硬化,但断链会导致大分子尺度上损伤的悬挂链的出现。因此,力学行为以及断裂性能都会受到影响。在这项工作中,首次通过实验研究了老化对弹性体材料断裂前力学行为的影响及其断裂性能的演变。此外,提出了一种使用基于老化机制的微观力学但物理描述的方法的建模尝试,以预测老化弹性体材料的机械和断裂性能演变。所提出的微观力学模型结合了与交联机制相关的残余拉伸和与断链机制相关的所谓“健康”弹性活性链(EAC)密度的概念。使用作者生成的或文献中可用的大量实验数据来评估所提出方法的有效性。
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引用次数: 1
Micro to macro-cracking mechanism in thermally treated granodiorite followed by different cooling techniques 不同冷却技术热处理花岗闪长岩的微观到宏观裂纹机制
IF 2.2 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-08-29 DOI: 10.1007/s10704-023-00740-9
Mohamed Elgharib Gomah, Guichen Li, Xu Jiahui, Ahmed A. Omar, Hao Haoran, M. M. Zaki

Cooling techniques following thermal treatments and related microcracking are a hot spot in rock mechanics and must be precisely studied. Hence, this research performed systematic experiments on the influences of rapid cooling on the behavior of thermally treated granodiorite at different temperatures. Furthermore, using the optical microscope, a comparison between rapid and slow cooling methods was studied to investigate how the cooling process affected the microstructure of the Egyptian granodiorite. The granodiorite samples were heated to 200, 400, 600, and 800 °C and then cooled slowly by air and rapidly by the water. According to the experimental results, the changes in examined properties occurred in three distinct temperature stages: zone I (25–200 °C), zone II (200–400 °C), and zone III (400–800 °C). Zone II was a conspicuous transition region for the rapid cooling approach, distinguished by a significant increase in porosity, thermal damage, crack density, and a substantial decrease in wave velocities, uniaxial compressive strength, and elastic modulus. Microcrack densities and widths increased with temperature for both cooling methods. According to microscopic analyses of granodiorite samples, boundary cracks were formed at the boundaries of quartz and feldspar first due to their minimal lattice energy, followed by biotite of high lattice energy. However, due to the thermal shock induced, the intragranular microcracks of the rapid cooling technique began to form at lower temperatures (200 °C). The physical and mechanical properties of rapidly cooled granodiorite significantly dropped between 200 and 400 °C, and the failure mode altered from axial splitting to shear modes. Consequently, over 600 °C, longitudinal waves could not penetrate rock samples due to the thermal fusion of inter and transgranular fissures, which turned into macrocracks. Hence, the elastic modulus measurements and wave velocity at 800 °C were challenging with an extremely low UCS and complex failure mode.

热处理后的冷却技术和相关的微裂纹是岩石力学的一个热点,必须加以精确研究。因此,本研究就快速冷却对不同温度下热处理花岗闪长岩行为的影响进行了系统实验。此外,还利用光学显微镜对快速冷却法和缓慢冷却法进行了比较研究,以了解冷却过程如何影响埃及花岗闪长岩的微观结构。将花岗闪长岩样品加热至 200、400、600 和 800 ℃,然后用空气缓慢冷却和用水快速冷却。根据实验结果,所检测的特性变化发生在三个不同的温度阶段:I 区(25-200 ℃)、II 区(200-400 ℃)和 III 区(400-800 ℃)。II 区是快速冷却方法的明显过渡区,其特点是孔隙率、热损伤、裂纹密度显著增加,波速、单轴抗压强度和弹性模量大幅降低。两种冷却方法的微裂缝密度和宽度都随温度升高而增加。根据花岗闪长岩样品的显微分析,边界裂缝首先在石英和长石的边界形成,因为它们的晶格能最小,其次是晶格能较高的斜长石。然而,由于受到热冲击,快速冷却技术的晶内微裂缝在较低温度(200 °C)下开始形成。快速冷却花岗闪长岩的物理和机械性能在 200 至 400 °C之间显著下降,破坏模式从轴向劈裂转变为剪切模式。因此,当温度超过 600 ℃ 时,纵波无法穿透岩石样本,原因是粒间和跨粒间裂隙的热熔,并转化为大裂缝。因此,800 °C时的弹性模量测量和波速测量在极低的UCS和复杂的破坏模式下具有挑战性。
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引用次数: 0
Modelling fracture due to corrosion and mechanical loading in reinforced concrete 钢筋混凝土中腐蚀和机械载荷引起的断裂建模
IF 2.5 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-08-24 DOI: 10.1007/s10704-023-00733-8
J. Alfaiate, L. J. Sluys, A. Costa

Corrosion in reinforced concrete is an important feature which can lead to increased deformation and cracking, as well as to premature failure. In the present work, macro-mechanical modelling of corrosion is performed, namely the degradation of bond–slip between concrete and steel. A mixed-mode damage model is adopted, in which the interaction between the bond–slip law and the stress acting in the neighbourhood of the concrete–steel bar interface is taken into account. Bond–slip degradation is modelled using an evolutionary bond–slip relationship, which depends on the level of corrosion. Different relevant loading cases are studied. Special attention is given to the evolution of corrosion in time, under constant load. This is done by adopting a Total Iterative Approach, in which the structure is reevaluated each time step, upon damage increase due to corrosion. Pullout tests are presented to illustrate the performance of the model. Bending tests are also performed to evaluate the influence of corrosion at structural level.

钢筋混凝土中的腐蚀是一个重要特征,它会导致变形和开裂增加,以及过早失效。在目前的工作中,对腐蚀进行了宏观力学建模,即混凝土和钢之间的粘结滑移退化。采用混合模式损伤模型,其中考虑了粘结-滑移定律和作用在混凝土-钢筋界面附近的应力之间的相互作用。粘结-滑移退化是使用演化粘结-滑移关系建模的,该关系取决于腐蚀水平。研究了不同的相关荷载情况。特别注意在恒定载荷下腐蚀随时间的演变。这是通过采用全迭代方法来实现的,在腐蚀导致损伤增加时,每个时间步长都对结构进行重新评估。为了说明模型的性能,进行了拉拔试验。还进行了弯曲试验,以评估结构层面的腐蚀影响。
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引用次数: 0
Interfaces in dynamic brittle fracture of PMMA: a peridynamic analysis PMMA动态脆性断裂界面的周动力学分析
IF 2.2 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-08-19 DOI: 10.1007/s10704-023-00731-w
Longzhen Wang, Javad Mehrmashhadi, Florin Bobaru

Recent experiments in bonded PMMA layers have shown dramatic changes in dynamic crack growth characteristics depending on the interface location and its toughness. We present a peridynamic (PD) analysis of the problem and identify three necessary elements in a model aimed at reproducing the observed dynamic fracture behavior at an interface in PMMA: (1) softening near the crack tip to account for changes in PMMA properties due to heat-generation induced by the high strain rates reached around the crack tip in dynamic fracture, (2) independence of extension (mode I) and shear (mode II) modes of fracture, and (3) a two-parameter bond-failure model, that can match both strength and fracture toughness for any horizon size. The PD model with these elements captures the experimentally observed dynamic fracture characteristics in bi-layer PMMA: the presence/absence of crack branching at the interface, depending on the interface location; cracks running along the interface for a while before punching through the second PMMA layer; slight crack path oscillations as the cracks approach the free surface. The computed crack speed profiles are close to those measured experimentally. The simulations help explain the observed behavior of dynamic crack growth through an interface. The model shows an enlargement of the fracture process zone when the cracks running along the interface penetrate into the second PMMA layer, as observed experimentally. This is where nonlocality of the PD model becomes relevant and critical.

最近在粘合 PMMA 层中进行的实验表明,动态裂纹生长特性会因界面位置及其韧性而发生巨大变化。我们对这一问题进行了周动态 (PD) 分析,并确定了模型中的三个必要元素,以重现在 PMMA 接口处观察到的动态断裂行为:(1) 裂纹尖端附近的软化,以解释由于动态断裂中裂纹尖端周围达到的高应变率所引起的热量产生而导致的 PMMA 性能变化;(2) 拉伸(模式 I)和剪切(模式 II)断裂模式的独立性;以及 (3) 双参数粘结-断裂模型,该模型可与任何水平面尺寸的强度和断裂韧性相匹配。包含这些元素的 PD 模型捕捉到了实验观察到的双层 PMMA 的动态断裂特征:根据界面位置的不同,在界面上存在/不存在裂纹分支;裂纹在冲破第二层 PMMA 之前沿界面运行一段时间;裂纹接近自由表面时出现轻微的裂纹路径振荡。计算得出的裂纹速度曲线与实验测量结果接近。模拟结果有助于解释观察到的穿过界面的动态裂纹生长行为。模型显示,当沿着界面的裂纹穿透第二层 PMMA 时,断裂过程区会扩大,这与实验观察到的情况相同。这正是 PD 模型的非局部性变得重要和关键的地方。
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引用次数: 0
Investigation on the dynamic fracture behavior of A508-III steel based on Johnson–Cook model 基于Johnson-Cook模型的A508-III钢动态断裂行为研究
IF 2.5 3区 工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY Pub Date : 2023-08-19 DOI: 10.1007/s10704-023-00735-6
Jianhua Sun, Guangshun Cui, Yilei Li, Chen Bao

In this study, the Johnson–Cook constitutive and failure model parameters of A508-III steel are determined through quasi-static and dynamic tensile and fracture tests. The reliability of model parameters is then verified by dynamic fracture tests at different loading rates. Using the Johnson–Cook model, the dynamic fracture behavior of the SEB specimen of A508-III steel under various loading rates and geometric configurations has been simulated. The effect of loading rate and specimen geometric configuration on the dynamic fracture toughness of A508-III steel is investigated. The results reveal that the critical fracture force and impact absorbed energy increase with the increase of loading rate. The dynamic fracture behavior of deep-cracked specimens is more sensitive to the loading rate than that of shallow-cracked specimens. Moreover, the critical fracture force and impact absorbed energy increase linearly with increasing specimen thickness while the initial crack size remains constant.

本研究通过准静态和动态拉伸和断裂试验,确定了A508-III钢的Johnson-Cook本构和失效模型参数。通过不同加载速率下的动态断裂试验,验证了模型参数的可靠性。采用Johnson-Cook模型,模拟了A508-III钢SEB试样在不同加载速率和几何形态下的动态断裂行为。研究了加载速率和试样几何形态对A508-III钢动态断裂韧性的影响。结果表明:临界断裂力和冲击吸收能随加载速率的增加而增大;与浅裂纹试件相比,深裂纹试件的动态断裂行为对加载速率更为敏感。临界断裂力和冲击吸收能随试样厚度的增加而线性增加,而初始裂纹尺寸保持不变。
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引用次数: 0
期刊
International Journal of Fracture
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