今日更新：International Journal of Solids and Structures 1 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 6 篇International Journal of Solids and StructuresWinding and unwinding a pipe with lüders bands on a reel part I: Analysis of base caseWeihan Zhang, Stelios Kyriakidesdoi:10.1016/j.ijsolstr.2024.112687在卷轴上缠绕和放卷带镏金带的管材 I 部分：基本情况分析Experiments and analyses have demonstrated that under bending tubes with Lüders bands develop localized diamond-shaped patterns of inclined bands of higher strain on both the tensioned and compressed sides. The banding is progressive, accompanied by a sharp change in curvature and ovalization that can lead to collapse. When the pipe is wound onto a large diameter reel, in order for the line to conform to its curvature the bands form clusters separated by elastic zones. The present study uses finite element analysis to study the evolution of these events under repeated reeling/unreeling of pipelines. The analysis is coupled to a custom combined isotropic-kinematic hardening constitutive model; localization associated with Lüders banding is reproduced by partial softening that covers the extent of the instability, and the Bauschinger rounding of unloading/reverse loading by nonlinear kinematic hardening. Part I studies in detail the repeated winding/unwinding of a 12-inch pipeline with diameter-to-thickness ratio of 18 onto a 300 inch radius reel under a low back tension. The analysis demonstrates that the band clustering initiates close to the point of first contact with the reel and leads to localized curvature, wrinkling of the top and bottom surfaces of the pipe, and ovalization. Close to first contact with the reel, the section moment reaches a local maximum and drops to a lower level as it moves further down the reel. This unloading is linked to an uplift of a section of line from the reel adjacent to the point of first contact. During unwinding, the line straightens without sharp changes in curvature, the strain in the clusters is reduced, but new localization patterns nucleate in the elastic zones between the initial clusters. The straightened line ends with residual ovality, axial surface undulations, and residual stresses. During subsequent cycles, the line continues to bend in a smooth manner, but the clusters of bands reappear during winding and the secondary patterns during unwinding. The ovalization accumulates with every cycle, the undulations due to wrinkling remain, and so do the residual stress and strain fields.实验和分析表明，在弯曲条件下，具有l<s:1> ders带的钢管在受拉侧和受压侧都出现了局部菱形的高应变倾斜带。带是渐进的，伴随着曲率和卵形的急剧变化，可能导致塌陷。当管道缠绕在一个大直径的卷轴上时，为了使管线符合其曲率，带形成由弹性区分开的簇。本文采用有限元分析的方法，研究了管道在反复放卷/放卷条件下这些事件的演变。该分析与自定义的各向同性-运动硬化组合本构模型相耦合;与l<s:1>德斯带状带相关的局部化是通过覆盖不稳定程度的部分软化来再现的，而卸载/反向加载的包辛格舍入是通过非线性运动学硬化来再现的。第一部分详细研究了在低背张力下，将直径/厚度比为18的12英寸管道反复缠绕/放绕到半径为300英寸的卷筒上。分析表明，带状聚类始于与卷筒的第一次接触点附近，并导致管道的局部曲率、上下表面起皱和椭圆化。接近第一次接触卷轴时，截面力矩达到局部最大值，并随着它在卷轴上的进一步移动而下降到较低的水平。这种卸料与卷筒上靠近第一次接触点的一段线的隆起有关。在解绕过程中，线变直，但曲率没有急剧变化，团簇中的应变减小，但在初始团簇之间的弹性区形成了新的局部化模式。拉直后的直线末端带有残余的椭圆度、轴向表面波动和残余应力。在随后的循环中，线继续以平滑的方式弯曲，但在缠绕期间再次出现带状簇，在解绕期间再次出现次级图案。每一次循环都有卵化现象的累积，起皱引起的波动仍然存在，残余应力场和应变场也仍然存在。Mechanics of MaterialsProbabilistic modeling of fiber–matrix interface stresses in short-fiber 3D printed composites using effective field methodsE. Polyzos, D. Van Hemelrijck, L. Pyldoi:10.1016/j.mechmat.2024.104934 基于有效场方法的短纤维3D打印复合材料纤维-基体界面应力概率建模This study presents a novel probabilistic modeling approach to investigate the impact of interfacial damage between fibers and the matrix on 3D-printed composites. The approach employs effective field methods (EFM) and Weibull statistics and considers an elastoplastic matrix reinforced with short fibers. A new formulation is developed to compute normal and shear interface stresses using the internal stress of each fiber, which is modeled as an ellipsoid with various aspect ratios. The approach is applied to 3D-printed PLA reinforced with short basalt fibers and compared to literature experiments. The results demonstrate that the proposed approach can aid in understanding interfacial damage and explain the progressive softening of the stress–strain response of composite structures.本研究提出了一种新的概率建模方法来研究纤维和基体之间的界面损伤对3d打印复合材料的影响。该方法采用有效场法(EFM)和威布尔统计，并考虑了短纤维增强弹塑性基体。提出了一种新的计算法向和剪切界面应力的公式，利用每根纤维的内应力，将其建模为具有不同纵横比的椭球体。将该方法应用于短玄武岩纤维增强PLA的3d打印，并与文献实验进行了对比。结果表明，该方法有助于理解复合材料结构的界面损伤，解释复合材料结构应力-应变响应的逐渐软化。International Journal of PlasticityOptimization of crystal plasticity parameters with proxy materials data for alloy single crystalsShahram Dindarlou, Gustavo M. Castellucciodoi:10.1016/j.ijplas.2024.103894用替代材料数据优化合金单晶的晶体塑性参数Multiscale modelling approaches have demonstrated ample value in understanding, predicting, and engineering materials response. While increasing computational power has aided in modelling atomic behaviour from first principles, mesoscale mechanisms such as intergranular failure or crack initiation still rely strongly on correlative models. Crystal Plasticity models have been extensively used to relate process-property-structure in metallic materials including mesoscale effects such as texture, microplasticity, and failure variability. However, models still suffer from low predictive power at the grain scale, which leads to poor damage prognosis outside the experimental calibration set. In addition to model form error, mesoscale uncertainty is dominated by an inadequate model parameterization that arises from calibration exclusively to macroscopic experimental data. This work explores parameter uncertainty in Crystal Plasticity models and proposes a hybrid physic-based and numerical optimization approach to identify parameters associated to mesoscale strengthening in FCC metals and alloys. The strength and novelty of the approach rely on calibrating parameters independently using single-crystal and polycrystal stress–strain curves. We further demonstrate that multiple materials can be incorporated into a single optimization algorithm to robustly quantify mesoscale material-invariant parameters. These values are then used to blindly predict the response of single- and poly-crystals engineering alloys. As a result, our approach mitigates modelling uncertainty by augmenting the data for calibration with single crystal experiments from different materials with similar dislocation structures (i.e., proxy materials). The results provide the basis for a robust parameterization of crystal plasticity models that can predict single- and poly-crystal responses for engineering alloys even in the absence of direct experimental data.多尺度建模方法在理解、预测和工程材料响应方面已经证明了足够的价值。虽然不断提高的计算能力有助于从第一性原理模拟原子行为，但中尺度机制(如晶间破坏或裂纹起裂)仍然强烈依赖于相关模型。晶体塑性模型已广泛用于金属材料的工艺-性能-结构，包括中尺度效应，如纹理、微塑性和失效变异性。然而，模型在颗粒尺度上的预测能力仍然较低，导致实验校准集之外的损伤预测较差。除了模式形式误差外，中尺度的不确定性主要是由于模式参数化不充分，这种不充分源于对宏观实验数据的校准。本研究探讨了晶体塑性模型中参数的不确定性，并提出了一种基于物理和数值的混合优化方法来识别FCC金属和合金中尺度强化相关参数。该方法的强度和新颖性依赖于使用单晶和多晶应力-应变曲线独立校准参数。我们进一步证明，多种材料可以合并到一个单一的优化算法，以稳健地量化中尺度材料不变参数。然后用这些值盲目地预测单晶和多晶工程合金的响应。因此，我们的方法通过增加来自具有相似位错结构的不同材料(即代理材料)的单晶实验的校准数据来减轻建模的不确定性。这些结果为晶体塑性模型的鲁棒参数化提供了基础，即使在没有直接实验数据的情况下，也可以预测工程合金的单晶和多晶响应。Thin-Walled StructuresA novel spectral element method with a higher-order coarse quad meshing approach to design laminated composite panels with arbitrarily shaped cutoutsPeiman Khandar Shahabad, Salih Alan, M. Erden Yildizdag, Bekir Bedizdoi:10.1016/j.tws.2024.111636采用高阶粗四边形网格的谱元法设计任意形状切割的复合材料层合板Laminated panels are widely used in various industries due to their distinct advantages. The design of laminated composites requires efficient methodologies due to the vast design space. This study proposes a new spectral element modeling approach for accurate and computationally efficient analysis of laminated composites with arbitrarily shaped cutouts. The method employs a coarse quad meshing approach and a spectral Chebyshev method to determine the element matrices. The presented method enables obtaining high-fidelity models by applying h- and p-refinements following a non-dimensional approach, aiming to yield a model with the fewest degrees of freedom to achieve a desired convergence level. Benefiting from the advantages of both meshless methods (in terms of computational efficiency) and finite element methods (in terms of geometric capabilities), we performed several case studies for laminated panels with cutouts and it is shown that the presented spectral element method (SEM) enables calculating the natural frequencies and the mode shapes as accurate as FEM, yet decreases the analysis duration by 13 folds. Furthermore, the developed approach was employed with a gradient-based optimizer or genetic algorithm to demonstrate the design of (sandwich) laminated composites for obtaining optimal lamination parameters and 2D Pareto fronts.层压板因其独特的优势被广泛应用于各行各业。由于设计空间巨大，层压复合材料的设计需要高效的方法。本研究提出了一种新的谱元建模方法，用于对具有任意形状切口的层压复合材料进行精确且计算效率高的分析。该方法采用粗四网格划分法和切比雪夫光谱法来确定元素矩阵。所提出的方法通过采用无维度方法进行 h- 和 p- 细分来获得高保真模型，旨在以最少的自由度生成模型，从而达到理想的收敛水平。得益于无网格方法（在计算效率方面）和有限元方法（在几何能力方面）的优势，我们对带有切口的层压板进行了几项案例研究，结果表明，所提出的谱元方法（SEM）能够计算出与有限元方法同样精确的固有频率和模态振型，同时将分析时间缩短了 13 倍。此外，所开发的方法还与基于梯度的优化器或遗传算法相结合，用于演示（三明治）层压复合材料的设计，以获得最佳层压参数和二维帕累托前沿。Pull-out capacities of screw connections in thin steel battens exposed to bushfire conditions.Gopikrishna Athmarajah, Mahen Mahendran, Anthony Ariyanayagamdoi:10.1016/j.tws.2024.111650暴露在森林火灾条件下的薄钢板条螺钉连接的拉出能力。External building envelopes made of cold-formed steel (CFS) claddings are commonly used in bushfire prone areas due to their non-combustible properties. However, their designs should ensure safety under the combined action of enhanced wind suction loading and elevated temperatures experienced during bushfires. Although numerous studies have investigated the critical pull-out failures in CFS batten screw connections under wind suction loading at ambient temperature, the pull-out failure behaviour of batten screw connections under bushfire conditions has not been investigated. The main objective of this study is to examine the pull-out failure mechanisms and capacities of screw connections in CFS battens under wind suction loading at elevated temperatures. Two hundred and sixteen small-scale tests were conducted on CFS battens made of three commonly used thicknesses and both high (G550) and low (G300) strength steels. Tests were conducted at six different temperatures using three types of screw fasteners to investigate the critical localised pull-out failures of batten screw connections. The results of these tests were utilised to develop applicable design equations and capacity reduction factors for the pull-out capacities of batten screw connections under the combined action of wind suction loading and elevated temperatures. The findings of this study will help design and build structures safely in bushfire-prone regions.由冷弯型钢(CFS)包层制成的外部建筑围护结构由于其不可燃特性，通常用于森林火灾易发地区。然而，它们的设计应确保在增强的风吸力载荷和森林火灾期间经历的高温共同作用下的安全。尽管已有大量研究对室温下风吸力载荷作用下CFS板条螺钉连接的临界拔出失效进行了研究，但尚未对林火条件下板条螺钉连接的拔出失效行为进行研究。本研究的主要目的是研究高温风吸力作用下CFS板条螺钉连接的拔出破坏机制和能力。对三种常用厚度的高强度钢(G550)和低强度钢(G300)制成的CFS板条进行了216次小规模试验。在六种不同的温度下，使用三种类型的螺钉紧固件进行了测试，以研究板条螺钉连接的关键局部拔出故障。这些试验的结果被用来建立适用的设计方程和能力降低系数的板条螺钉连接在风吸载荷和高温共同作用下的拉拔能力。这项研究的结果将有助于在森林火灾易发地区安全地设计和建造建筑物。A fracture mechanics study of stress resultant intensity factors in stiffened panels employing RKPM meshfree FSDT modelingSatoyuki Tanaka, Akihiro Takata, Naoki Matsuoka, Shota Sadamotodoi:10.1016/j.tws.2024.111634采用RKPM无网格FSDT模型对加筋板应力合成强度因子的断裂力学研究Panel cracking for stiffened panels is investigated based on linear elastic fracture mechanics. Meshfree flat shell formulation and fracture modeling are employed. After investigating stress distribution of the intact stiffened panel, the mode-I and mixed-mode crackings are studied using the stress resultant intensity factors (SRIFs). When the crack tip approaches to the stiffener, deformation around the crack is suppressed due to presence of the stiffeners. The mechanical behaviors are carefully examined by changing crack length, loading conditions and thickness of the main panel and stiffeners. Quantitative evaluation of the SRIFs is addressed by comparing with the reference solutions. An in-depth discussion is provided for the meshfree modeling of the panel cracking in the stiffened panels. This series studies are useful for examining crack arrest effect of the stiffened panel due to presence of the stiffeners.基于线弹性断裂力学对加筋板的开裂问题进行了研究。采用无网格平壳公式和裂缝建模。在研究了完整加筋板应力分布的基础上，利用应力合成强度因子(SRIFs)对ⅰ型裂纹和混合型裂纹进行了研究。当裂纹尖端靠近加强筋时，由于加强筋的存在，裂纹周围的变形受到抑制。通过改变裂纹长度、加载条件和主板和加强筋的厚度，仔细研究了其力学行为。通过与参考解决方案的比较，解决了srif的定量评估。对加筋板开裂的无网格建模进行了深入的讨论。这一系列的研究有助于检验加筋板由于加筋的存在而产生的止裂效果。Flexural response of additively manufactured honeycomb sandwich structures with continuous density-gradient variationsJiayun Zhao, Zhuang Cui, Shilong Wang, Zhengping Sun, Yuanyuan Dingdoi:10.1016/j.tws.2024.111642具有连续密度梯度变化的增材制造蜂窝夹层结构的弯曲响应Sandwich structures with graded cellular cores exhibit promising flexural performances, but their reliance on gradient continuity and distribution warrants further exploration. In this study, seven honeycomb sandwich structures with diverse continuous density gradients, encompassing horizontal, uniform and vertical variations, were designed based on the Voronoi technique and fabricated via 3D printing. Quasi-static three-point bending tests and numerical simulations were conducted to comprehensively analyze the flexural response of density-graded honeycomb sandwich structures. The results reveal a significant influence of the honeycomb core's density distribution on flexural performance, with pronounced sensitivity to horizontal distribution (perpendicular to the loading direction) and less sensitivity to vertical distribution. A favorable flexural resistance is achieved by strategically assigning higher relative density cells to the mid-span of a honeycomb core layer, gradually diminishing towards the ends, which was further optimized into an arched density distribution along the horizontal direction. The influences of cover plate and honeycomb thicknesses on the deformation mechanisms and energy absorption were also investigated, and indicate that thin cover plates and honeycomb layer have a detrimental effect on the bending load-bearing and energy absorption of the sandwich structure.具有梯度蜂窝芯的夹层结构具有良好的抗弯性能，但其对梯度连续性和分布的依赖有待进一步探索。在本研究中，基于Voronoi技术设计了七个具有不同连续密度梯度的蜂窝夹层结构，包括水平、均匀和垂直变化，并通过3D打印制造。通过准静态三点弯曲试验和数值模拟，全面分析了密度梯度蜂窝夹层结构的弯曲响应。结果表明，蜂窝芯密度分布对弯曲性能的影响显著，对水平分布(垂直于加载方向)的敏感性显著，对垂直分布的敏感性较低。通过将相对密度较高的单元战略性地分配到蜂窝核心层的跨中，向两端逐渐减小，从而实现良好的抗弯性能，并进一步优化为沿水平方向的拱形密度分布。研究了盖板和蜂窝厚度对夹层结构变形机理和能量吸收的影响，表明薄盖板和蜂窝层对夹层结构的弯曲承载和能量吸收有不利影响。Wrinkle, Fold, and Ridge Patterns of Thin Films Attached to a Compliant Substrate: Direct Numerical Simulations Involving Plastic YieldingSiavash Nikravesh, Yu-Lin Shendoi:10.1016/j.tws.2024.111649薄膜附着在柔顺基底上的皱折、褶皱和脊纹:涉及塑性屈服的直接数值模拟Surface wrinkling is a frequently observed form of deformation instability when a thin film bonded to a compliant substrate is under in-plane compression. In this study, a recently developed computational approach is applied to study the formation and transformation of wrinkles involving plastic yielding of the thin film. The two-dimensional (2D) finite element models contain an embedded imperfection with perturbed material properties at the film-substrate interface, which serves to activate the bifurcation modes. The extension of this technique to allow for film plasticity is demonstrated, including the evolution of surface patterns and its correlation with the overall load-displacement and amplitude responses. More localized forms of wrinkles are revealed by the simulations, including the transition of periodic wrinkles to more isolated folds and how it can be influenced by the elastoplastic properties of the film material. A through-thickness variation of material properties is shown to significantly alter the wrinkle morphology. Plastic folding can be suppressed by only a very thin elastic sub-layer, and the waveform can become ridge-like. We also present a preliminary analysis by applying the same numerical methodology to three-dimensional (3D) models, which generates consistent results compared to the 2D counterpart.表面起皱是一种经常观察到的变形不稳定的形式，当薄膜结合到一个柔性的基材是在平面内压缩。在本研究中，采用了一种新发展的计算方法来研究薄膜塑性屈服过程中褶皱的形成和转变。二维(2D)有限元模型在薄膜-衬底界面处包含一个具有扰动材料特性的嵌入缺陷，该缺陷用于激活分岔模式。该技术的扩展允许薄膜塑性被证明，包括表面图案的演变及其与整体载荷-位移和振幅响应的相关性。模拟揭示了更多局部形式的褶皱，包括周期性褶皱向更孤立的褶皱的转变，以及它如何受到薄膜材料弹塑性特性的影响。通过厚度变化的材料性能显示显着改变皱纹形态。仅通过极薄的弹性子层就可以抑制塑性折叠，并且波形可以变成脊状。我们还通过将相同的数值方法应用于三维(3D)模型进行了初步分析，与2D模型相比，该模型产生了一致的结果。Nonlinear web crippling analysis and design of cold-formed high strength steel channel sections having different stiffened flangesJun He, Ehab Ellobodydoi:10.1016/j.tws.2024.111651不同加筋法兰冷弯高强钢槽钢截面的非线性腹板破坏分析与设计Web crippling analysis and design of cold-formed high strength steel channel sections having different stiffened flanges are presented in this paper. 3D finite element models were developed for the analysis of sections with unstiffened flanges, stiffened flanges with simple lips, stiffened flanges with inward return lips and outward return lips loaded under End-Two-Flange (ETF) and Interior-Two-Flange (ITF) loading conditions. The models were verified against tests recently reported by the authors on cold-formed high strength channel sections having different stiffened flanges. The web crippling strengths, load-displacement relationships and failure modes were predicted numerically and compared well against that measured experimentally. Extensive parametric studies were performed using the validated models on 280 channel sections having different web slenderness, ratios of bearing length to web thickness, cross-section geometries and shapes of flange lips. The web crippling numerical strengths were compared with the web crippling design strengths specified in North American Specification, Australian/New Zealand Standards and Eurocode as well as with other proposed design equations in the literature. In addition, a reliability analysis was performed to assess the reliability of the design rules. It is found that the design strengths were either unconservative or conservative, and generally unreliable for the cold-formed channels with unstiffened and stiffened flanges investigated. Therefore, a modification for the North American Specification design equation was proposed. The modified proposed design equation provided more accurate and reliable web crippling strengths compared with specified and available in the literature web crippling design strength predictions.本文对不同加筋法兰的冷弯高强钢槽钢截面进行了腹板破坏分析和设计。建立了三维有限元模型，分析了端部双法兰(ETF)和端部双法兰(ITF)加载条件下的非加筋法兰、加筋带简唇的法兰、加筋带内回唇的法兰和加筋带外回唇的法兰。这些模型与作者最近报道的具有不同刚度法兰的冷弯高强度通道截面的试验进行了验证。对腹板的破坏强度、荷载-位移关系和破坏模式进行了数值预测，并与实验测量结果进行了比较。使用验证模型对280个具有不同腹板长细比、轴承长度与腹板厚度之比、截面几何形状和法兰唇形的通道截面进行了广泛的参数研究。将网损数值强度与北美规范、澳大利亚/新西兰标准和欧洲规范中规定的网损设计强度以及文献中提出的其他设计方程进行比较。此外，还进行了可靠性分析，以评估设计规则的可靠性。研究发现，对于带加筋和未加筋法兰的冷弯通道，其设计强度要么是非保守的，要么是保守的，而且通常不可靠。为此，对北美规范设计方程进行了修正。修正后的设计方程与现有文献中规定的腹板折弯设计强度预测相比，提供了更准确可靠的腹板折弯设计强度。来源：复合材料力学仿真Composites FEM
