共查询到20条相似文献,搜索用时 71 毫秒
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进行严寒地区碾压混凝土坝越冬层面温控防裂研究,为越冬层面温控防裂设计提供理论依据。针对严寒地区某碾压混凝土重力坝,考虑碾压混凝土热力学参数随龄期的变化、碾压混凝土浇筑进度对温度应力的影响,对碾压混凝土重力坝施工期和运行期全过程进行三维有限元仿真计算分析,着重分析越冬层面应力分布特征。结果表明:约束区和非约束区的越冬层面温度应力分布特征相似,但约束区越冬层面温度应力较大;未采取温控措施时,越冬层面上、下游侧铅直方向温度应力较大,致使越冬层面上、下游侧易出现水平裂缝;越冬层面中部顺水流方向温度应力也较大,因此中部易出现沿坝轴线方向裂缝。提出了采取表面保温、升温水管、微膨胀混凝土、设置水平人工短缝四种措施改善越冬层面的温度应力。采用表面保温和微膨胀混凝土可有效减小越冬层面上、下游侧和中部各个方向的温度应力;采用升温水管和设置水平人工短缝可有效减小越冬层面上、下游侧铅直方向应力。 相似文献
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混凝土变形与损伤的分析 总被引:16,自引:1,他引:16
本文首先对材料本构理论尤其是混凝土材料本构理论的研究现状进行丁评述,然后分析了混凝土的变形与损伤的物理机理及混凝土的几个重要而且特殊的本构现象,讨论了混凝土损伤、单侧受力特性、剪胀效应等的描述方法,最后介绍了几种混凝土损伤本构模型。 相似文献
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有限弹塑性变形的三维组集式本构模型 总被引:2,自引:1,他引:2
本文将文[1]中提出的三维组集式弹塑性本构模型推广应用于有限变形分析,导出了全量型和增量型本构关系在初始构形上的拉格朗日(Total Lagrange)形式和瞬时构形上的拉格朗日(Updated Lagrange)形式。文中对晶体单轴拉伸中的宏观剪切带进行了分析。预测结果与实验吻合。从而说明这种本构模型能够模拟有限变形中的几何非线性效应和晶体材料塑性变形中的宏观力学行为。 相似文献
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基于脆性岩石变形力学特征,将脆性岩石视为由岩石颗粒骨架等硬物质以及裂隙和孔隙等软物质组成;考虑软硬物质变形特点,分别建立了软物质与硬物质的本构关系以及软硬物质与RVE之间的关系。然后,基于几何损伤理论,建立了考虑软硬物质双变形特征的脆性岩石变形破坏模拟方法,根据软硬物质及其与脆性岩石宏观变形关系以及峰值点法,分别提出了力学参数和统计参数的合理确定方法。最后,通过实例分析对本文模型和方法进行验证,结果表明本文模型能够对脆性岩石变形破坏过程进行模拟,脆性岩石宏观变形被视为由软物质变形和硬物质变形两部分组成具有可行性与合理性。 相似文献
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本文着重探讨了生长变形体连续介质理论中的本构模型。首先列出了描述生长变形体能量平衡的微分方程以及熵不等式;以此为基础,通过将密度演化的历史作为独立的本构变量扩展了理性力学的因果性公理与决定性公理,具体而详细地推导了简单材料的生长弹性本构方程,给出了这些本构方程中的相关本构变量之间的约束不等式,得到了“生长变形体的自由能与其密度成反比”的结论,并从热力学上对这一结果进行了定性的解释。最后,文中对几个尚待解决的问题进行了说明,并指出了今后的发展方向。 相似文献
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The construction interfaces of RCCD have a distinct influence on the deformation of dams. The characters and rules on deformation of construction interfaces are studied. The methods simulating the deformation of the interfaces at different stages are proposed. A thickness analytic model and a no-thickness analytic model of construction interfaces are built. These models can reflect the elastic deformation, the attenuation creep deformation, the irreversible creep deformation and the accelerating creep defor- mation of interfaces. The example shows that these proposed models can simulate the deformation of the dam structure objectively. Especially, the results of the thickness analytic model which simulates the gradual changing regularities of interfaces can tally with those of monitoring in situ preferably. The methods proposed and the analytic models can be generalized and applied to general concrete dams, especially to the analysis on deformation rules of fault and interlayer in dam base. 相似文献
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The differences between finite deformation and infinitesimal deformation are discussed. They are exercised on elasto-viscoplastic constitutive relations of concrete. Then, a rate-dependent mechanics model was presented on the basis of Ottosen‘ s fourparameter yield criterion, where different loading surface transferring laws were taken into account, when material was in hardening stage or in softening stage, respectively. The model is well established, so that it can be applied to simulate the response of concrete subject to impact loading. Green-Naghdi stress rate was introduced as objective stress rate. Appropriate hypothesis was postulated in accordance with many experimental results, which could reflect the mechanical behaviour of concrete with large deformation. Available thoughts as well as effective methods are also provided for the research on related engineering problems. 相似文献
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粘弹塑性统一本构模型理论 总被引:6,自引:1,他引:5
文章在已有的统一本构模型的基础上,将粘弹性变形引入到统一本构模型之中,成功地改善了材料过渡段的变形模拟情况。通过Hastelloy-X的变形模拟及与其它统一本构模型的变形模拟比较,证明了粘弹塑性统一本构模型的合理性。 相似文献
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对取自玉龙铜矿边坡的花岗斑岩进行相关物理和静力学实验,获得岩石的密度、弹性模量、泊松比、单轴抗压强度以及抗拉强度等参数。通过花岗斑岩SHPB实验得到试样的典型冲击动载应力-应变曲线。利用相关实验结果,借助显式动力有限元软件LS-DYNA,得到花岗斑岩的HJC(Holmquist-Johnson-Cook)本构模型参数,分析岩石动载强度对HJC模型参数的敏感性,总结出一套HJC模型参数的取值方法。岩石动载强度对HJC模型的A,B,N和fc参数最为敏感,该参数变化幅度在-30%~30%时,强度变化率大于11%。HJC模型参数的取值过程中,将岩石物理和力学实验数据与数值模拟进行结合,即可体现HJC模型基本理论,又可均衡实验和数值模拟的工作量,并能获得可靠的模型参数,为岩石动载数值模拟计算提供帮助。 相似文献
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《International Journal of Solids and Structures》2014,51(15-16):2777-2790
Shape memory polymers (SMPs) have gained strong research interests recently due to their mechanical action that exploits their capability to fix temporary shapes and recover their permanent shape in response to an environmental stimulus such as heat, electricity, irradiation, moisture or magnetic field, among others. Along with interests in conventional “dual-shape” SMPs that can recover from one temporary shape to the permanent shape, multi-shape SMPs that can fix more than one temporary shapes and recover sequentially from one temporary shape to another and eventually to the permanent shape, have started to attract increasing attention. Two approaches have been used to achieve multi-shape shape memory effects (m-SMEs). The first approach uses polymers with a wide thermal transition temperature whilst the second method employs multiple thermal transition temperatures, most notably, uses two distinct thermal transition temperatures to obtain triple-shape memory effects (t-SMEs). Recently, one of the authors’ group reported a triple-shape polymeric composite (TSPC), which is composed of an amorphous SMP matrix (epoxy), providing the system the rubber-glass transition to fix one temporary shape, and an interpenetrating crystallizable fiber network (PCL) providing the system the melt-crystal transition to fix the other temporary shape. A one-dimensional (1D) material model developed by the authors revealed the underlying shape memory mechanism of shape memory behaviors due to dual thermal transitions. In this paper, a three-dimension (3D) finite deformation thermomechanical constitutive model is presented to enable the simulations of t-SME under more complicated deformation conditions. Simple experiments, such as uniaxial tensions, thermal expansions and stress relaxation tests were carried out to identify parameters used in the model. Using an implemented user material subroutine (UMAT), the constitutive model successfully reproduced different types of shape memory behaviors exhibited in experiments designed for shape memory behaviors. Stress distribution analyses were performed to analyze the stress distribution during those different shape memory behaviors. The model was also able to simulate complicated applications, such as a twisted sheet and a folded stick, to demonstrate t-SME. 相似文献
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STUDY ON COUPLING MODEL OF SEEPAGE-FIELD AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM 总被引:1,自引:1,他引:1
IntroductionRCCDisbuiltwithconcreterolledandcompactedlayeruponlayer.Therefore,thereisonehorizontalconstructioninterfacebetweentwoconterminouslayers.Iftheconterminouslayersarenotcementedclosely ,theconstructioninterfaceswillbecomeweakpartsofRCCDthatinfluencethestrengthandstabilityofRCCD .Ontheotherhand ,theanti_seepageabilityofconstructioninterfacesisthedeterminantofanti_seepagecharacteristicsofthewholeRCCD .Whenadamisconstructedandfilledbywater,seepage_fieldcomesintobeinginthedambody ,w… 相似文献
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The stress response of amorphous polymers exhibits tremendous change during the glass transition region, from soft viscoelastic response to stiff viscoplastic response. In order to describe the temperature-dependent and rate-dependent stress response of amorphous polymers, we extend the one-dimensional small strain fractional Zener model to the three-dimensional finite deformation model. The Eyring model is adopted to represent the stress-activated viscous flow. A phenomenological evolution equation of yield strength is used to describe the strain softening behaviors. We demonstrate that the stress response predicted by the three-dimensional model is consistent with that of one-dimensional model under uniaxial deformation, which confirms the validity of the extension. The model is then applied to describe the stress response of an amorphous thermoset at various temperatures and strain rates, which shows good agreement between experiments and simulation. We further perform a parameter study to investigate the influence of the model parameters on the stress response. The results show that a smaller fractional order results in a larger yield strain while has little effect on the yield stress when the temperature is below the glass transition temperature. For the stress relaxation tests, a smaller fractional order leads to a slower relaxation rate. 相似文献
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为探究根土复合体的应力-应变关系,将其视为两相体,根系采用线弹性模型,土体采用邓肯-张模型,并考虑根系与土体之间的相对滑移关系,基于混合物法则建立根土复合体本构模型。通过素土与不同含根量的根土复合体三轴压缩试验,得到其应力-应变关系,通过单根拉伸试验得到根系的弹性模量。结果发现,(1)根土复合体的极限主应力差随含根量的增加先增加后减小,含根量0.3%为最优含根量。(2)单根的直径与抗拉力、抗拉强度符合幂函数关系,与弹性模量符合多项式关系。(3)通过反分析的方法,建立滑移关系,得到模型计算值的应力-应变关系,发现模型计算值与试验值的拟合度(R2)为0.96。该研究为根土复合体本构模型的建立提供新思路,并为根土复合体的数值分析提供参数。 相似文献
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Flexible insect wings deform passively under the periodic loading during napping flight. The wing flexibility is considered as one of the specific mechanisms on improving insect flight performance. The constitutive relation of the insect wing material plays a key role on the wing deformation, but has not been clearly understood yet. A viscoelastic constitutive relation model was established based on the stress relaxation experiment of a dragonfly wing (in vitro). This model was examined by the finite element analysis of the dynamic deformation response for a model insect wing under the action of the periodical inertial force in flapping. It is revealed that the viscoelastic constitutive relation is rational to characterize the biomaterial property of insect wings in contrast to the elastic one. The amplitude and form of the passive viscoelastic deformation of the wing is evidently dependent on the viscous parameters in the constitutive relation. 相似文献