今日更新:Mechanics of Materials 1 篇,Thin-Walled Structures 4 篇
A residual stress-dependent mixed-mode phase-field model: Application to assessing the role of tailored residual stresses on the mechanical performance of ceramic laminates
Behera Akash Kumar, Rahaman Mohammad Masiur, Roy Debasish
doi:10.1016/j.mechmat.2023.104867
残余应力相关的混合模相场模型:应用于评估定制残余应力对陶瓷层压板力学性能的作用
Ceramics offer several attractive properties of industrial relevance, e.g. high strength and hardness, low thermal conductivity, and chemical inertness in critical environments. There is thus interest among researchers to improve the fracture toughness of ceramics, which is generally low and considered a major drawback. Numerous experimental studies in the literature report on the enhancement of mechanical performance of ceramic laminates, especially fracture toughness, by tailoring the residual stress, resulting in crack deflection or bifurcation. However, there is a dearth of computational models that can reliably predict the crack path and accurately quantify the improved fracture toughness. In this article, we propose a residual stress-dependent mixed-mode phase-field model within a small deformation set-up. The proposed model is efficient in including any energy dissipation effect in a consistent manner. The model can be exploited as a tool to study the effect of tailored residual stresses on the fracture toughness of ceramic laminates. We have validated our proposal by reproducing the results for a few problems that require the incorporation of residual stresses within the formulation. By conducting a set of four-point bending tests on notched composite beams made of alternating layers of Al2O3 with 5% tetragonal ZrO2 (ATZ) and Al2O3 with 30% monoclinic ZrO2 (AMZ), we demonstrate how tailored residual stresses could indeed influence the mechanical performance of ceramic laminates.
陶瓷具有多种与工业相关的诱人特性,例如高强度和高硬度、低导热性以及在关键环境中的化学惰性。因此,研究人员有兴趣提高陶瓷的断裂韧性,因为陶瓷的断裂韧性通常较低,被认为是一个主要缺点。文献中的大量实验研究报告了如何通过调整残余应力来提高陶瓷层压板的机械性能,尤其是断裂韧性,从而导致裂纹偏转或分叉。然而,能可靠预测裂纹路径并准确量化所改善的断裂韧性的计算模型却十分匮乏。在本文中,我们在小变形设置中提出了一个与残余应力相关的混合模式相场模型。所提出的模型能以一致的方式有效地包含任何能量耗散效应。该模型可用作研究定制残余应力对陶瓷层压板断裂韧性影响的工具。我们对一些需要在公式中加入残余应力的问题重现了结果,从而验证了我们的建议。通过对由含 5%四方氧化锆的 Al2O3(ATZ)和含 30% 单斜氧化锆的 Al2O3(AMZ)交替层组成的缺口复合梁进行一组四点弯曲试验,我们证明了定制残余应力如何影响陶瓷层压板的机械性能。
CFS Lipped Channel Beams Buckling in Distortional Modes at Elevated Temperatures: Behaviour, Failure and DSM Design
das Neves Natan Sian, Landesmann Alexandre, Camotim Dinar
doi:10.1016/j.tws.2023.111366
CFS唇形槽梁在高温下的扭曲模式屈曲:行为,失效和DSM设计
This work reports the findings of a comprehensive numerical investigation on the post-buckling behaviour, failure and Direct Strength Method (DSM) design of cold-formed steel (CFS) single-span simply supported lipped channel beams buckling in distortional modes at elevated temperatures (up to 800 °C) due to fire conditions. It extends the scope of a previous investigation carried out by Landesmann and Camotim [1], by analysing a substantially larger lipped channel beam set, exhibiting various cross-section dimensions and yield stresses, selected to cover wider distortional slenderness ranges. As done before, (i) the beams analysed display two end support conditions, (ii) the Eurocode 3 (part 1.2) model to describe the temperature-dependence of the CFS material properties is adopted and (iii) the results are obtained by means of Abaqus shell finite element GMNIA. After presenting and discussing the main features of the beam distortional post-buckling behaviour, extensive beam failure moment sets are gathered and used to develop and validate DSM-based design approaches. The methodology followed consists of modifying the most performant available DSM-based design curves (developed for beams at ambient temperature [2]), which naturally involves the temperature-dependent reduction factors of the CFS model. A merit assessment procedure shows that the modified DSM-based strength curves predict the lipped channel beam distortional failure moments with remarkable accuracy and reliability, thus constituting an excellent starting point to search for a DSM-based design approach capable of handling arbitrary CFS beams failing in distortional modes at elevated temperatures.
这项工作报告了一项全面的数值研究结果,研究了冷弯钢(CFS)单跨简支唇形槽钢梁在高温(高达800°C)火灾条件下以扭曲模式屈曲的后屈曲行为、破坏和直接强度法(DSM)设计。它扩展了Landesmann和Camotim[1]之前进行的调查的范围,通过分析一个更大的唇形通道梁组,显示出各种截面尺寸和屈服应力,选择覆盖更宽的扭曲长细比范围。如前所述,(i)所分析的梁显示两种端支条件,(ii)采用欧洲规范3(第1.2部分)模型来描述CFS材料特性的温度依赖性,(iii)通过Abaqus壳有限元GMNIA获得结果。在介绍和讨论了梁变形后屈曲行为的主要特征之后,收集了大量的梁破坏矩集,并用于开发和验证基于dsm的设计方法。接下来的方法包括修改最高性能的基于dsm的设计曲线(为环境温度下的梁开发),这自然涉及到CFS模型的温度相关折减因子。一个优点评估程序表明,改进的基于dsm的强度曲线预测唇形通道梁的畸变破坏矩具有显著的准确性和可靠性,从而为寻找一种能够处理任意CFS梁在高温下畸变模式失效的基于dsm的设计方法提供了一个很好的起点。
Comprehensive investigation into the thermal rheological behaviour and relaxation characteristic of single/composite polymers in laminated glass
Xie Dongdong, Yang Jian, Zhao Chenjun, Wang Xing-er
doi:10.1016/j.tws.2023.111369
夹层玻璃中单一/复合聚合物热流变行为和弛豫特性的综合研究
Polymeric interlayers are of significance for the structural capability of thin-walled laminated glass members both before and after glass fracture. Polymers present evident temperature and time dependence, which should be carefully assessed in the design process. To improve mechanical properties dependent on the temperature and time, novel interlayers including modified ethylene-vinyl acetate (PVE®) and composite PVE/PC (SGE®), have been developed along with the sound resistance of the interfacial adhesion to aging. In this work, dynamic mechanical thermal analysis tests were carried out to investigate the thermal rheological behaviour and relaxation characteristic of polyvinyl butyral (PVB), ionomer (SentryGlas®, SG), PVE, PC and SGE. The results show that PVE and SGE follow the complex thermal rheological behaviour as a result of the existence of two different types of relaxation transitions, whilst PVB, SG, and PC are thermorheologically simple materials. The arctangent function was introduced to describe the temperature dependence of PVB and SG. The relaxation modulus of polymers was subsequently derived based on the approximation equation and inverse Fourier transform. The results of the inverse Fourier transform indicate that vertical shift might need to be considered for PVE and SGE. The application of the approximation equation was assessed and its limitation was discussed. Finally, the relaxation characteristics of five polymers were described using the generalized Maxwell model based on the weighted least squares method.
聚合物夹层对薄壁夹层玻璃构件断裂前后的结构性能都有重要影响。聚合物表现出明显的温度和时间依赖性,在设计过程中应仔细评估。为了改善随温度和时间变化的机械性能,新型夹层包括改性乙烯-醋酸乙烯酯(PVE®)和复合PVE/PC (SGE®),并具有良好的界面粘附抗老化性能。在这项工作中,进行了动态机械热分析测试,以研究聚乙烯醇丁醛(PVB),离聚物(SentryGlas®,SG), PVE, PC和SGE的热流变行为和弛缓特性。结果表明,由于存在两种不同类型的弛豫转变,PVE和SGE遵循复杂的热流变行为,而PVB, SG和PC是热流变简单的材料。引入反正切函数来描述PVB和SG的温度依赖性。基于近似方程和傅里叶反变换,推导了聚合物的弛豫模量。傅里叶反变换的结果表明,垂直位移可能需要考虑PVE和SGE。评价了近似方程的应用,讨论了它的局限性。最后,利用基于加权最小二乘法的广义Maxwell模型描述了五种聚合物的弛缓特性。
Nonlinear Two-Dimensional Transient Thermoelastic Analysis of Functionally Graded Composite Plates Subjected to Localised Cooling Loads
Babaee Alireza, Jelovica Jasmin
doi:10.1016/j.tws.2023.111370
局部冷却载荷作用下功能梯度复合材料板的非线性二维瞬态热弹性分析
In this study, for the first time, localized thermal cooling is considered for the transient thermoelastic response of an axisymmetric plate, addressing the underexplored area of localized low-temperature thermoelasticity. Functionally graded composite plates are analyzed which consist of a mixture of stainless steel (SUS304) and low-carbon steel (AISI1020). A two-dimensional transient heat conduction equation is employed to capture localized cooling effects, featuring various adaptive time-dependent thermal boundary conditions which mirror both loading and unloading scenarios, effectively simulating real-world phenomena. Novel parameters are introduced to facilitate a comprehensive understanding of various aspects of thermal load handling and their impact on thermoelastic responses. The heat conduction equations are solved using the Generalized Differential Quadrature Method (GDQM) and the Crank-Nicolson scheme. The nonlinear governing equations, incorporating geometrical nonlinearity through the von Kármán assumption within the First Shear Deformation Theory (FSDT) framework, are solved using the GDQM and the Picard's technique. The model is validated using Finite Element Method (FEM) through Abaqus. A comprehensive analysis is provided that considers influence of the ratio of thermally affected and unaffected plate surface, thermal load magnitude, rapidity of thermal loading and unloading, duration of the cooling load, geometrical nonlinearity, and temperature dependence of material. The study shows that the maximum von Mises stress within the structure remains consistent regardless of the duration of the cooling load, as long as the rate at which the cooling load is applied stays the same. Additionally, the findings reveal that even minor localized thermal loads can produce substantial stress, especially at the intersection of thermally affected and non-affected zones on the exposed surface in some situations.
本研究首次考虑了轴对称板材瞬态热弹性响应的局部热冷却,解决了局部低温热弹性这一尚未充分开发的领域。分析了由不锈钢(SUS304)和低碳钢(AISI1020)混合组成的功能分级复合板。采用二维瞬态热传导方程来捕捉局部冷却效应,并采用各种自适应的随时间变化的热边界条件来反映加载和卸载情况,从而有效地模拟真实世界的现象。引入的新参数有助于全面了解热负荷处理的各个方面及其对热弹性响应的影响。热传导方程采用广义微分正交法(GDQM)和 Crank-Nicolson 方案求解。通过第一剪切变形理论(FSDT)框架内的 von Kármán 假设,将几何非线性纳入非线性控制方程,并使用 GDQM 和 Picard 技术进行求解。通过 Abaqus 使用有限元法 (FEM) 对模型进行了验证。综合分析考虑了受热影响和未受热影响板面的比例、热载荷大小、热加载和卸载速度、冷却载荷持续时间、几何非线性以及材料的温度依赖性等因素的影响。研究表明,无论冷却载荷持续时间长短,只要施加冷却载荷的速度保持不变,结构内的最大 von Mises 应力就会保持一致。此外,研究结果还表明,即使是轻微的局部热负荷也会产生很大的应力,特别是在某些情况下,在暴露表面的热影响区和非影响区的交汇处。
Free-damped vibration analysis of viscoelastic foam-filled FGM anisogrid lattice cylindrical shells
Dai Zuocai, Shi Yan, Kiani Yaser
doi:10.1016/j.tws.2023.111373
粘弹性泡沫填充FGM等网格点阵圆柱壳的自由阻尼振动分析
Our aim with this paper is to model and investigate the vibration and damping of a new hybrid composite shell. The considered composite cylindrical shell includes an FGM anisogrid lattice shell perfectly filled with viscoelastic foams. The modeling of the lattice part composed of spiral and hoop ribs is accomplished according to a global continuous standard based on orthotropic deep shells. The distribution pattern of the metal and ceramic constituents along the lattice ribs is specified by a power law. The homogenizations between ceramic and metal phases within the ribs, as well as between the FGM lattice structure and foam, are governed by the rule of mixtures. Based on the transferred Kelvin-Voigt viscoelastic scheme, the dynamic moduli of the foam portion are acquired. Because viscoelastic foam is a soft material, the higher-order shear deformation shell theory is used to estimate the system's displacement components. After emanating the dynamic equations by Hamilton's principle, the Chebyshev collocation-based semi-numerical method is implemented to detect the system's frequencies and loss factors. The comprehensive results show the role of each composite characteristic in the vibration and damping behavior of the defined structure.
本文的目的是对一种新型复合材料壳体的振动和阻尼进行建模和研究。所考虑的复合圆柱壳包括一个完美填充粘弹性泡沫的FGM等网格晶格壳。根据基于正交各向异性深壳的全局连续标准,对螺旋肋和环肋组成的点阵部件进行了建模。金属和陶瓷成分沿晶格肋的分布模式由幂律指定。肋内陶瓷相和金属相之间以及FGM晶格结构和泡沫之间的均质化受混合规律支配。基于传递的Kelvin-Voigt粘弹性格式,得到了泡沫部分的动力模量。由于粘弹性泡沫是一种软质材料,因此采用高阶剪切变形壳理论来估计系统的位移分量。在Hamilton原理推导出系统的动力学方程后,采用基于切比雪夫配置的半数值方法检测系统的频率和损耗因子。综合计算结果表明了各复合材料特性对结构振动和阻尼性能的影响。