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Micro-buckling of carbon fibers in shape memory polymer composites under bending in the glass transition temperature region 形状记忆聚合物复合材料中碳纤维在玻璃化转变温度区弯曲下的微屈曲
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0009
N. Tiwari, A. Shaikh
Abstract The influence of a wide temperature range in the glass transition region of a shape memory polymer (SMP) matrix on micro-buckling of the fiber reinforcements in shape memory polymer composites (SMPC) under large bending deformation is described. Analytical expressions to estimate the strain energy, neutral strain surface, critical buckling surface and half wavelength of the buckled fibers in the SMPC are presented based on the minimum energy method. This study considers the reinforced fibers as three-dimensional elastic bodies and the matrix as a temperature stimulated flat plate. A comprehensive study was performed to understand the dynamic temperature behavior of the micro-buckled fibers and corresponding results were validated by previous works in the literature. The effects of fiber volume fraction and thickness of the SMPC plates on the half wavelength are also discussed along with the simultaneous influence of temperature on the parameters computed in the minimum energy analysis.
摘要研究了形状记忆聚合物(SMP)基体玻璃化过渡区较宽温度范围对形状记忆聚合物复合材料(SMPC)中增强纤维在大弯曲变形下微屈曲的影响。基于最小能量法,给出了SMPC中屈曲纤维的应变能、中性应变面、临界屈曲面和半波长的解析表达式。本研究将增强纤维视为三维弹性体,将基体视为受温度刺激的平板。我们对微屈曲纤维的动态温度行为进行了全面的研究,并对相关结果进行了文献验证。讨论了纤维体积分数和厚度对半波长的影响,以及温度对最小能量分析中计算参数的影响。
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引用次数: 3
Target metric and Shell Shaping 目标度量和壳体成形
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0002
G. R. Argento, S. Gabriele, L. Teresi, V. Varano
Abstract We exploit the possibility of deforming a shell by assigning a target metric, which, for 2D structures, is decomposed into the first and second target fundamental-forms. As well known, an elastic shell may change its shape under two different kinds of actions: one are the loadings, the other one are the distortions, also known as the pre-strains. Actually, the target fundamental forms prescribe a sought shape for the solid, and the metric effectively realized is the one that minimizes the distance, measured through an elastic energy, between the target and the actual fundamental forms. The proposed method is very effective in deforming shells.
摘要我们通过指定目标度量来利用使壳变形的可能性,对于2D结构,目标度量被分解为第一和第二目标基本形式。众所周知,弹性壳在两种不同的作用下可能会改变其形状:一种是载荷,另一种是变形,也称为预应变。事实上,目标基本形状为固体规定了一个所寻求的形状,而有效实现的度量是通过弹性能量测量的目标和实际基本形状之间的距离最小化的度量。所提出的方法在壳体变形方面非常有效。
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引用次数: 1
An overview of the natural force density method and its implementation on an efficient parametric computational framework 概述了自然力密度法及其在高效参数化计算框架上的实现
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0005
Márcio S. de Souza, R. M. Pauletti
Abstract The new paradigms of parametric modelling have been proving promising on the advance of systems for analysis and design of taut (or tensile) structures. With this premise, the presented work consist on the development with a form-finding tool for Computer Aided Design(CAE) and Computer Aided Engineering (CAE) integration using VPL (Visual Programming Language), in the context of parametric modelling. The methods used in the implementation are the Force Density Method (FDM) and the Natural Force Density Method (NFDM), taking advantage of the linear solution approach provided, suitable for fast form-finding computational procedures. The program is implemented as a Grasshopper plug-in and it is named BATS (Basic Analysis of Taut Structures), which enables parametric definition of boundary conditions for the form-finding. The program structure and benchmarks with other available Grasshopper plug-ins for taut structures form-finding are presented, showing considerably superior performance using BATS.
摘要参数建模的新范式在拉紧(或拉伸)结构的分析和设计系统的发展中被证明是有前景的。在这一前提下,所提出的工作包括在参数化建模的背景下,使用VPL(可视化编程语言)开发用于计算机辅助设计(CAE)和计算机辅助工程(CAE)集成的形式设计工具。在实现中使用的方法是力密度法(FDM)和自然力密度方法(NFDM),利用所提供的线性求解方法,适用于快速找形计算程序。该程序是作为Grasshopper插件实现的,它被命名为BATS(Taut结构的基本分析),它可以为形状查找定义边界条件的参数。介绍了用于张紧结构找形的程序结构和其他可用Grasshopper插件的基准测试,表明使用BATS具有相当优越的性能。
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引用次数: 3
Patterns for gridshells with negligible geometrical torsion at nodes 节点几何扭转可忽略的网格壳图形
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0014
X. Tellier, Romane Boutillier, C. Douthe, O. Baverel
Abstract Curved envelope structural building envelopes have been quite popular in architecture in the past decades, and pose many challenges in their design, manufacturing and planning. In gridshells, a popular structural morphology for curved structure, designers will often strive to orient beams such that their top face is parallel to the envelope surface. However, this tends to induce geometrical torsion along the beam centerline, which complexifies significantly the manufacturing of the connection nodes or of the beams themselves. It is well known that such issue can be avoided by aligning beams with principal curvature directions of the envelope surface, thus yielding a quadrangular paneling. In this article, we study how other types of patterns (non-quadrangular) can be used to design torsion-free grid-shells. Based on asymptotic considerations, we derive a set of geometrical rules which, if fulfilled by a pattern, insure that a surface can be covered by this pattern with negligible torsion and limited deviation of beams from surface normals. A wide variety of patterns fulfill these rules, offering interesting possibilities for the design of curved architectural envelopes (Figure 1) is shown. As these rules are based on first order asymptotic analysis, we perform global validation on case studies. One main application is for structures in which face planarity is not necessary, for example ones cladded with ETFE cushions.
摘要在过去的几十年里,曲面围护结构在建筑中非常流行,并在其设计、制造和规划中提出了许多挑战。在网格壳(弯曲结构的一种流行结构形态)中,设计师通常会努力确定梁的方向,使其顶面与包络面平行。然而,这往往会引起沿梁中心线的几何扭转,这会使连接节点或梁本身的制造变得非常复杂。众所周知,通过将梁与包络面的主曲率方向对齐,从而形成四边形镶板,可以避免这种问题。在本文中,我们研究了如何使用其他类型的图案(非四边形)来设计无扭转网格壳。基于渐近考虑,我们导出了一组几何规则,如果由图案来满足,则确保曲面可以被该图案覆盖,并且具有可忽略的扭曲和光束与曲面法线的有限偏差。各种各样的图案都符合这些规则,为弯曲的建筑围护结构的设计提供了有趣的可能性(图1)。由于这些规则是基于一阶渐近分析的,我们对案例研究进行了全局验证。一个主要应用是不需要表面平面性的结构,例如用ETFE衬垫包覆的结构。
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引用次数: 1
Design of a modular exhibition structure with additive manufacturing of eco-sustainable materials 采用生态可持续材料增材制造的模块化展览结构设计
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0019
S. Invernizzi, A. Bertetto, Federico Ciaccio, Paolo Nicola
Abstract In this paper the mechanical characteristics of an innovative bioplastic material, the HBP® -HempBioPlastic® filament, is investigated. HBP® was recently patented by an Italian company Kanésis that focused its activity on nature-derived materials. The filaments are the upshot of an original process allowing to reuse the surplus of the agricultural supply chains and transform it into new sustainable materials. At first, the 3D printed HBP® samples were tested in tensile tests according to the ASTMD638 standard and monitored in term of deformations by the Digital Image Correlation techniques (DIC) in order to evaluate the stress-strain behavior of different HBP® textures under loading. In addition, using the HBP® and the results coming from the experimental campaign, the design of an exhibition pavilion was proposed. The pavilion was modelled starting from the geometric construction of the fullerene. The supporting modular structure is combined by HBP® modular elements, that can be produced by 3D printing or moulding. Finally, in order to demonstrate the feasibility of the proposed pavilion, a linear finite element analysis is presented on the base of the experimentally determined mechanical properties of HBP® elements, under the effects of wind and seismic environmental actions.
摘要本文研究了一种新型生物塑料材料HBP®-HempBioPlastic®长丝的力学特性。HBP®最近获得了一家意大利公司的专利,该公司专注于自然衍生材料。细丝是一个原始过程的结果,允许重新利用农业供应链的剩余,并将其转化为新的可持续材料。首先,根据ASTMD638标准对3D打印的HBP®样品进行拉伸测试,并通过数字图像相关技术(DIC)对变形进行监测,以评估不同HBP®纹理在加载下的应力-应变行为。此外,利用HBP®和实验活动的结果,提出了一个展览馆的设计。展馆的模型是从富勒烯的几何结构开始的。支撑模块化结构由HBP®模块化元素组合而成,可以通过3D打印或模塑生产。最后,为了证明所提议的展馆的可行性,在实验确定的HBP®元素的力学性能的基础上,在风和地震环境作用的影响下,提出了线性有限元分析。
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引用次数: 1
Out-of-plane local mechanism analysis with finite element method 平面外局部机构的有限元分析
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0012
R. Spagnuolo
Abstract The stability check of masonry structures is a debated problem in Italy that poses serious problems for its extensive use. Indeed, the danger of out of plane collapse of masonry walls, which is one of the more challenging to evaluate, is traditionally addressed not using finite element models (FEM). The power of FEM is not properly used and some simplified method are preferred. In this paper the use of the thrust surface is suggested. This concept allows to to evaluate the eccentricity of the membrane stresses using the FEM method. For this purpose a sophisticated, layered, finite element with a no-tension material is used. To model a no-tension material we used the smeared crack method as it is not mesh-dependent and it is well known since the early ’80 in an ASCE Report [1]. The described element has been implemented by the author in the program Nòlian by Softing.
摘要砌体结构的稳定性验算在意大利是一个有争议的问题,它的广泛使用带来了严重的问题。事实上,砌体墙平面外倒塌的危险是评估更具挑战性的危险之一,传统上不使用有限元模型(FEM)来解决。有限元法的威力没有得到适当的利用,因此优选一些简化的方法。本文建议使用推力面。这一概念允许使用FEM方法来评估膜应力的偏心度。为此,使用了一种复杂的、分层的、无张力材料的有限元。为了对无张力材料进行建模,我们使用了涂抹裂纹法,因为它不依赖于网格,并且自80年代初ASCE报告[1]中就已经为人所知。所描述的元素已由作者通过Softing在程序Nålian中实现。
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引用次数: 0
Form-finding of pierced vaults and digital fabrication of scaled prototype 穿孔拱顶的寻形及比例样机的数字化制作
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0020
A. Bertetto, Federico Riberi
Abstract The new serious consideration to masonry and non-metallic structures evidenced their direct prospective to be, even in the present days, advanced architectural and engineering solutions. In the present paper, a form finding for a cement based tessellated pierced vault is studied. The multi-body rope approach (MRA) was used to define compression-only vault optimal shapes. Successively, the thrust network analysis (TNA) was implemented by Rhino-vault for a further validation of the shape and the definition of different tessellation meshes of the surfaces, according to different hole pattern configuration. Different piercing percentage of the vaults were considered and compared for the best solution identification. In addition, the geometrical solutions were analyzed by means of global stability analysis, taking into account the different positions of the holes. Furthermore, 3D printing with a Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material (completely eco-friendly) is used for the construction of the formworks of the cement based blocks (dowels) useful for the assembly of a vault scaled prototype. The prototype of the vault, characterized by a certain piercing percentage was subjected to different loading conditions and monitored by a non-contact device based on the Digital Image Correlation (DIC) technique. The 3D-DIC was performed to recognize the structural behavior during the loading process of the model (prototype). DIC measurements were used to recognize in advance the critical condition of the vault under loading and the displacement measurements were correlated to the different loading phases up to the collapse condition.
对砖石和非金属结构的新的认真考虑证明了它们的直接前景,即使在今天,也是先进的建筑和工程解决方案。本文研究了水泥基镶嵌穿孔拱顶的寻形问题。采用多体绳法(MRA)确定纯压缩拱顶的最佳形状。随后,利用Rhino-vault进行推力网络分析(TNA),进一步验证不同孔网配置下的曲面形状和不同曲面细分网格的定义。考虑并比较了不同孔洞的穿孔率,以确定最佳溶液。此外,考虑孔的不同位置,采用全局稳定性分析方法对几何解进行了分析。此外,在聚乳酸(PLA)材料(完全环保)中使用熔丝沉积建模(FDM)技术的3D打印用于构建用于组装拱顶比例原型的水泥基块(销子)的模板。采用基于数字图像相关(DIC)技术的非接触式装置对具有一定穿透率的拱顶原型进行了不同加载条件下的监测。采用3D-DIC对模型(原型)加载过程中的结构行为进行识别。利用DIC测量提前识别拱顶在荷载作用下的临界状态,并将位移测量与不同加载阶段直至坍塌状态相关联。
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引用次数: 4
Stress analysis of infinite laminated composite plate with elliptical cutout under different in plane loadings in hygrothermal environment 水热环境下不同平面载荷下椭圆切口无限层合复合材料板的应力分析
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0001
A. Magar, A. Lal
Abstract This paper presents the solution of stress distribution around elliptical cutout in an infinite laminated composite plate. Analysis is done for in plane loading under hygrothermal environment. The formulation to obtain stresses around elliptical hole is based on Muskhelishvili’s complex variable method. The effect of fibre angle, type of in plane loading, volume fraction of fibre, change in temperature, fibre materials, stacking sequence and environmental conditions on stress distribution around elliptical hole is presented. The study revealed, these factors have significant effect on stress concentration in hygrothermal environment and stress concentration changes are significant with change in temperature.
摘要本文给出了无限层合复合材料板椭圆切口周围应力分布的求解方法。对湿热环境下的平面载荷进行了分析。椭圆孔周围应力的计算公式基于Muskhelishvili的复变量法。讨论了纤维角度、平面载荷类型、纤维体积分数、温度变化、纤维材料、堆积顺序和环境条件对椭圆孔周围应力分布的影响。研究表明,这些因素对湿热环境下的应力集中有显著影响,且应力集中随温度变化显著。
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引用次数: 2
Folded surface elements coupled with planar scissor linkages: A novel hybrid type of deployable structures 折叠面单元与平面剪刀连杆耦合:一种新型混合可展开结构
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0013
Evangelia Vlachaki, K. Liapi
Abstract Origami folding structures can find significant applications in the general area of building design, as they can be lightweight and deployable. An inherent property of folded surfaces, which is related to the degrees of freedom of each origami crease pattern, is form flexibility. Therefore, when building-scale applications are considered, in many instances, the folded surfaces, in order to become stiff and load-bearing, need to be constrained. A study of different types of deployable structures has led to the observation that in planar scissor linkages, hinges and pivots follow the same deployment path in space, as sets of vertices in certain origami structures. Due to the similarities in their kinematic behavior, selected origami patterns and scissor linkages can function as effective kinematic pairs, leading to structures able to transform in a controlled manner through a wide range of possible spatial configurations. A few examples of combining these two types of structures already exist [1–3]. In this paper a systematic approach for coupling origami crease patterns characterized by biaxial and rotational symmetry, with translational, polar and angulated scissor linkages, towards the development of novel forms of deployable structures, has been attempted. For the design and evaluation of the kinematic performance of the developed new structures, existing geometric modeling and calculation methods, parametric and simulation processes, as well as testing with physical models have been used. It is anticipated that research in this direction will lead to promising novel hybrid types of deployable structures.
折纸结构在建筑设计的一般领域可以找到重要的应用,因为它们可以是轻量级的和可展开的。折叠表面的一个固有特性是形式的灵活性,这与每个折纸折痕图的自由度有关。因此,当考虑到建筑规模的应用时,在许多情况下,为了变得坚硬和承重,折叠表面需要受到约束。对不同类型的可展开结构的研究表明,在平面剪刀式连杆中,铰链和枢轴在空间中遵循相同的展开路径,就像某些折纸结构中的一组顶点一样。由于其运动行为的相似性,选择的折纸图案和剪刀连杆可以作为有效的运动对,导致结构能够通过广泛的可能的空间配置以可控的方式转换。结合这两种结构的例子已经存在[1-3]。在本文中,一个系统的方法耦合折纸折痕模式的特点是双轴和旋转对称,与平移,极性和成角剪刀连杆,朝着新的形式的可展开结构的发展,已经尝试。为了设计和评估所开发的新结构的运动性能,使用了现有的几何建模和计算方法、参数化和仿真过程以及物理模型测试。预计在这个方向上的研究将导致有前途的新型混合类型的可展开结构。
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引用次数: 3
Influence of pattern anisotropy on the structural behaviour of free-edge single-layer gridshells 模式各向异性对自由边单层网壳结构性能的影响
IF 1.5 Q4 MECHANICS Pub Date : 2021-01-01 DOI: 10.1515/cls-2021-0011
F. Venuti
Abstract Free-edge gridshells represent the majority of built gridshells. Indeed, the gridshell reference geometry usually needs to be trimmed in order to provide building access or to insert the gridshell within an existing building, giving rise to one or more elastic boundaries. Despite the current design practice, so far a very limited number of scientific studies has been devoted to investigate the influence of elastic boundaries on the overall structural behaviour of gridshells. This paper focuses on the effects of the orientation of the boundary structure with respect to the grid direction. This is done by studying the buckling behaviour of an ideal single-layer steel gridshell, for different grid layout (quadrangular, hybrid, triangular) and orientation. The results of the parametric study demonstrate that the sensitivity of free-edge single-layer gridshells to the free-edge orientation strongly depends on the grid pattern. In particular, isotropic gridshells have shown an almost negligible influence of the free-edge orientation in terms of buckling load, in opposition to orthotropic gridshells. Moreover, the change in free-edge orientation induces significant variations of the global structural stiffness for all the layouts, resulting in possibly unacceptable displacements in service conditions.
摘要自由边格壳代表了大多数已建成的格壳。事实上,通常需要修剪格构参考几何图形,以便提供建筑通道或将格构插入现有建筑中,从而产生一个或多个弹性边界。尽管目前有设计实践,但到目前为止,用于研究弹性边界对格栅壳体整体结构性能的影响的科学研究数量非常有限。本文重点研究了边界结构相对于网格方向的方向的影响。这是通过研究不同网格布局(四边形、混合型、三角形)和方向的理想单层钢网架的屈曲行为来完成的。参数研究结果表明,自由边单层网格壳体对自由边方向的敏感性在很大程度上取决于网格模式。特别是,与正交各向异性网格壳相反,各向同性网格壳在屈曲载荷方面显示出几乎可以忽略的自由边缘方向的影响。此外,自由边缘方向的变化会导致所有布局的整体结构刚度发生显著变化,导致在使用条件下可能出现不可接受的位移。
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引用次数: 6
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