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1.
编织复合材料弹性性能的细观力学模型   总被引:7,自引:0,他引:7  
燕瑛 《力学学报》1997,29(4):429-438
提出了编织复合材料弹性性能分析的细观力学模型,这个力学模型考虑了实际编织结构中的纬向和经向纤维束的曲屈,相邻纤维束之间的间隙和纤维束的横截面尺寸对编织复合材料弹性性能的影响,并探讨了在纤维束间纯树脂区内孔隙的含量和两种叠层结构对材料弹性性能的影响.理论计算结果与实测值的比较,表明所提出的细观力学模型是合理的.根据理论分析的结果,提出了优化单层和叠层编织结构的结构参数选择方法  相似文献   

2.
断裂损伤与细观力学   总被引:7,自引:0,他引:7  
本文从力学发展的角度,对断裂力学、损伤力学与细观力学的主要内容及其发展,作了简要的介绍和评述.指出:固体力学与其它学科的交缘汇合,并深入到细观结构的层次进行研究,这一研究发展的势头已是很明显的了.细观力学、损伤力学与断裂力学构成了从细观尺度直至宏观尺度以描述材料与结构的破坏过程的破环理论的主要内容.它使得作为固体材料的力学的基本内容之一的破坏理论,面临一个新的发展阶段.  相似文献   

3.
基于遗传算法的复合材料细观结构拓扑优化设计   总被引:2,自引:0,他引:2  
利用高精度通用单胞模型将复合材料的细观拓扑结构与宏观力学性能结合起来,采用遗传算法对复合材料的细观结构进行优化,发展了基于遗传算法的复合材料细观结构拓扑优化设计方法.以材料的宏观力学性能为优化目标,从随机的初始细观结构出发,对复合材料纤维体积百分比进行约束,经过迭代获得满足设计要求的代表性体积单元.在优化过程中,对遗传算法的交叉过程作了较大的改进,实现了复合材料细观拓扑结构的任意变化,提高了对可行域的搜索效率.分别以极限剪切模量和泊松比为优化目标,验证了所提出优化方法的正确性和有效性.  相似文献   

4.
含夹杂和微裂纹复合材料的损伤演化和分析   总被引:3,自引:0,他引:3  
利用细观力学的Eshelby和Mori-Tanaka理论,考虑纤维和微裂纹之间的相互作用,研究了定向分布微裂纹的演化规律及其对材料力学性能的影响,分析了纤维体积份数,弹性系数、微裂纹密度,纤维不同取向与基体开裂强度之间的变化关系,并给出了许多有意义的结论。  相似文献   

5.
多向编织复合材料的力学性能研究   总被引:13,自引:0,他引:13  
梁军  陈晓峰 《力学进展》1999,29(2):197-210
综述并评价了关于二维和三维编织复合材料的有效弹性模量研究的代表性工作,并从材料设计的思想出发,宏观与微观相结合,材料科学与力学相结合,对多向编织复合材料的宏观力学性能与细观织物结构、组分性能的关系及编织复合材料非线性行为进行了详细的理论分析和研究  相似文献   

6.
不同热处理条件下45钢柱壳的动态性能   总被引:1,自引:0,他引:1  
以不同热处理条件下的45钢作为研究对象,利用高速摄影和金相分析来研究45钢柱壳在爆轰加载下的膨胀断裂特性,以及不同热处理条件对材料的动态断裂性能的影响。结果表明:随着回火温度的升高,45钢强度减小、静态延伸率增大,爆轰加载时柱壳表面裂纹产生及发生贯穿断裂而导致产物泄漏的时刻逐渐推迟,相应应变逐渐增加,同时回收到的破片尺寸逐渐增大;四种45钢的静态力学性能及动态断裂性能有明显差异,是因为不同热处理条件下,材料细观组织的结构、组成均发生较大变化,即材料的细观组织决定了材料的静态力学性能及动态断裂性能。  相似文献   

7.
本文探讨一种用于材料细观结构与构件宏观响应之间的直接关联分析方法。该方法应用宏现计算,给出细观力学量,并可反映材料细观结构特征,适用于具有细观结构材料制成构件的力学分析。  相似文献   

8.
材料细观结构与构件宏观响应间直接关联关系   总被引:3,自引:0,他引:3  
曹志远  傅志平 《力学季刊》1996,17(4):313-319
本文探讨一种用于材料细观结构与构件宏观响应之间的直接关联分析方法,该方法应用宏观计算,给出细观力学量,并可反映材料细观结构特征,适用于具有细观结构材料制成构件的力学分析。  相似文献   

9.
近年来,混凝土3D打印技术在土木建筑等领域取得了快速的发展和应用。与模板浇筑工艺不同,3D打印在逐行逐层堆叠的建造过程中引入了一定量的层间弱面和空隙,造成了细观非均质性;而且3D打印过程无法自动嵌入钢筋,制备纤维混凝土作为打印材料可有效改善力学性能。本文首先制备了一种适用于挤出型3D打印工艺的玄武岩纤维增强陶砂混凝土,将水平打印层作为XY平面,然后从三个正交方向加载,实验测试了3D打印混凝土的抗压、抗弯等力学性能,提出了各向异性系数及其评估方法。研究结果表明,对于单轴压缩,X方向强度最高,而对于抗弯性能,Y方向强度最高。纤维对挤出型3D打印材料的各向异性影响较大,纤维掺量越大,各向异性越大。  相似文献   

10.
混凝土静态力学性能的细观力学方法述评   总被引:2,自引:0,他引:2  
杜修力  金浏 《力学进展》2011,41(4):411-426
混凝土力学特性是大坝、海洋平台等工程结构抗震设计及仿真分析的前提条件之一,也是目前研究的薄弱环节.混凝土是一种典型的非均质材料,其宏观力学特性由细观组成来决定.本文总结了目前研究混凝土宏观力学特性的细观力学分析方法,细观有限元法及理论分析法;阐述了界面过渡区(ITZ)对混凝土性能的影响,简单介绍了混凝土界面过渡区问题的...  相似文献   

11.
本文基于Cosserat近场动力学发展了一种纤维混凝土的近场动力学模型,对纤维混凝土的破坏现象进行研究。该模型考察了物质点独立的转动自由度和物质点间的力偶作用,而且有表征微结构尺寸的内禀长度,相比于传统的近场动力学模型,更适合描述纤维混凝土这类胶结颗粒材料的力学行为。本文采用完全离散的方式对纤维进行建模,引入了纤维拔出实验中拔出位移和切应力的关系,并且采用组构张量描述纤维的局部分布。数值算例部分模拟了单纤维拔出实验、带预制裂纹的平板拉伸实验和三点弯曲梁实验。数值结果和已有的数值模型以及实验进行了对比,验证了所提出模型的正确性。此外,本文还调查了微结构对纤维混凝土破坏的影响,数值结果显示Cosserat剪切模量和内禀长度会影响裂纹的局部分布,但是不会改变裂纹的主方向。  相似文献   

12.
This paper presents a proposal of test setup and methodology for testing the flexural creep behaviour of pre-cracked Fibre Reinforced Concrete (FRC) specimens, aimed at providing a basis for standardization. The design criteria used to define the equipment and methodology are presented. A test results sheet and a curve are established to present the results of creep tests, and some experimental results are shown so that the test can be validated. The equipment and methodology proposed make it possible to research the influence of factors such as concrete type, fibres type and content, applied load, and crack opening value.  相似文献   

13.
许震宇  张若京  何伟 《力学季刊》2003,24(2):191-197
在某些纤维增强复合材料(FRC)中使用金属或高分子聚合物作为基体材料。在高温等情况下,这类材料具有明显的粘弹性特性。本文采用Riemann—Liouville形式的分数阶导数模型描述基体的粘弹性特性。通过渐近均匀化方法给出了预测FRC整体三维本构关系的解析表达式。给出了应用于基体具有Makris粘弹性关系的具体形式。以圆截面纤维正方形排列的情形为例,给出了等效模量随纤维体积比的变化曲线。结果说明,这类复合材料仍具有粘弹性特性,其整体粘弹性本构关系的弹性部分综合了纤维弹性和基体弹性的贡献,粘性部分来自基体粘性的贡献,复合材料具有和基体相同的粘性系数和分数阶。为分析微结构特征对整体特性的贡献,须求解两类局部问题。可以看出,在整体的等效模量中包含了局部变形的贡献,局部变形增加了复合材料的耦合刚度。  相似文献   

14.
滞后细观模型在岩石力学中的应用   总被引:4,自引:0,他引:4  
对以砂岩为代表的所谓``NME材料'的力学行为研究方面的一些新的 概念和模型进行了评介.首先介绍了一种基于所谓``滞后单元'的描述滞后现象 的物理模型------Preisach-Mayergoyz(P-M)模型,然后详细阐述了P-M模型应用 于模拟岩石的非线性滞后应力应变关系的过程和结果.这种唯象模型很好地描述 了宏观上的滞后表现和``离散记忆'效应.接着本文对应变能耗散的力学机制进 行了简单分析. 最后,介绍了一种描述弹性波在``NME材料'中传播规律的数 学方法, 该方法从一般的弹性波传播规律出发,分析了``NME材料'特殊的力 学性质给弹性波传播带来的影响,揭示了产生特殊的弹性波传播规律的原因.  相似文献   

15.
Summary From the continuum mechanics points of view, most of commercial fibre-reinforced composites (FRCs) can be considered to be anisotropic materials with one of the five material symmetries: transverse isotropy, orthotropy, tetratropy, hexatropy and octotropy, as illustrated in the preceding paper (Part I) [1]. No properly general formulation of constitutive equations for tetratropic, hexatropic and octoctropic types of FRC has been found in the literature. In this paper, the restriction to the admissible deformation of a FRC imposed by the failure strains of the fibres is investigated. The complete and irreducible two-dimensional tensor function representations regarding tetratropy, hexatropy and octotropy derived in Part I are applied to formulate constitutive equations for FRCs in plane problems of elasticity, yielding and failure in the present work, and of heat conduction, continuum damage and asymmetric elasticity in a continued work (Part III, forthcoming).The supports from the Alexander von Humboldt Foundation, Germany and the Research Foundation of Tsinghua University, P. R. China are acknowledged by the first author.  相似文献   

16.
Some refractory linings of metallurgical vessels consist of masonry without mortar. To describe the mechanical behaviour of these large-sized structures, it is necessary to use an equivalent material instead of a model that comprises all the bricks and joints involved. The properties of the equivalent material depend on the opening and closure mechanism of joints. In this paper, four joint states which are the combination of open/closed states of bed and head joints are identified, and the corresponding equivalent elastic properties are determined accordingly using homogenisation techniques. The transition criterion between these joint states is based on the unilateral contact conditions written in terms of macroscopic strain. The developed model is then compared to an in-plane biaxial compression test. The numerical and experimental results are in good agreement.  相似文献   

17.
In the present contribution, a phenomenological material model is presented describing the viscoelastic behaviour of polyurethane bonds under finite deformations. The model includes the temperature dependency of the material behaviour close to the glass transition temperature. Experimentally observed size effects can also be described. It is known from previous investigations that the bonds show an effective behaviour that is influenced by the layer thickness. The physical reason for this behaviour can be found in the formation of boundary layers in the polymer which are located close to the substrate. In these boundary layers, the material behaviour differs from the bulk behaviour. The effective properties of bonds of different thickness are experimentally investigated in isothermal shear tests performed at different temperatures. In order to model the observed effects, a previously developed approach of viscoelasticity is extended including the temperature dependency. Furthermore, a supplementary parameter field is introduced, taking the formation of the boundary layers into account. This field is determined by a partial differential equation in form of a reaction–diffusion equation containing the boundary conditions. The local properties of the polymer are linked to the distribution of this additional field. It is shown that the model parameters can be identified and that the model is able to describe the complex experimentally observed behaviour.  相似文献   

18.
Filler-reinforced elastomers are extremely complicated materials with pronounced deformation and temperature history-dependent material properties. In the current paper, the dynamic material behaviour is investigated and modelled. To this end, a carbon black-filled rubber compound is loaded with harmonic deformations under different frequencies and amplitudes and the stationary stress response is evaluated in terms of the storage and the loss modulus or, equivalently, in terms of the dynamic modulus and the loss angle. In this essay, detailed experimental investigations of the dynamic material properties of carbon black-filled elastomers are provided and a new three-dimensional constitutive approach of finite nonlinear viscoelasticity to represent the observed material behaviour is developed.  相似文献   

19.
Domain switching in piezoelectric materials is caused by external loads such as electric field and stress that leads to non-linear behaviour. A study is carried out to compare the non-linear behaviour of 1–3 piezocomposites with different volume fractions and bulk piezoceramics. Experiments are conducted to measure the electrical displacement and strain on piezocomposites and bulk ceramics under high cyclic electrical loading and constant compressive prestress. A thermodynamically consistent uni-axial framework is developed to predict the nonlinear behaviour by combining the phenomenological and micromechanical techniques. Volume fractions of three distinct uni-axial variants (instead of six variants) are used as internal variables to describe the microscopic state of the material. In this model, the grain boundary effects are taken into account by introducing the back fields (electric field and stress) as non-linear kinematic hardening functions. An analytical model based on equivalent layered approach is used to calculate effective properties such as elastic, piezoelectric, and dielectric constants for different volume fractions of piezocomposites. The predicted effective properties are incorporated in the proposed uni-axial model and the dielectric hysteresis (electrical displacement versus electric field) as well as butterfly curves (strain versus electric field) are simulated. Comparison between the experiments and simulations show that this model can reproduce the characteristics of non-linear response. It is observed that the variation in fiber volume fraction and compressive stress has a significant influence on the response of the 1–3 piezocomposites.  相似文献   

20.
In this work, a self-consistent constitutive framework is proposed to describe the behaviour of a generic three-layered system containing a functionally graded material (FGM) layer subjected to thermal loading. Analytical and semi-analytical solutions are obtained to describe the thermo-elastic and thermo-elastoplastic behaviour of a three-layered system consisting of a metallic and a ceramic layer joined together by an FGM layer of arbitrary composition profile. Solutions for the stress distributions in a generic FGM system subjected to arbitrary temperature transient conditions are presented. The homogenisation of the local elastoplastic FGM behaviour in terms of the properties of its individual phases is performed using a self-consistent approach. In this work, power-law strain hardening behaviour is assumed for the FGM metallic phase. The stress distributions within the FGM systems are compared with accurate numerical solutions obtained from finite element analyses and good agreement is found throughout. Solutions are also given for the critical temperature transients required for the onset of plastic deformation within the three-layered systems.  相似文献   

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