首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 125 毫秒
1.
IntroductionMethodofcharacteristics (MOC)hasstillbeenthepowerfultooltoanalyzehydraulictransientofpipelineflowsincethe 1 960s.Seldomhasthethermaltransientbeentakenintoaccount.Heatduetofrictionvarieswhenflowratechangedbecauseofvariouskindsofreasons,whichcaus…  相似文献   

2.
IntroductionInthe1980’s,nanocrystalinematerials(NCM)havebeenproposedbyprofesorH.GleiterinGerman.Theacademicworldwasinterested...  相似文献   

3.
IntroductionConsideringthestabilitybehaviourinthenumericalsolutionofgeneralizedneutraldelaydifferentialequationsy′(t) =Ly(t) My(tτ) Ny′(tτ)   (t≥ 0 ) ,( 1 )y(t) =(t)   (t≤ 0 ) ,( 2 )whereL ,MandN∈Cd×dareconstantcomplexmatrices,(t) ∈Cdisagivenvector_valuedinitialfunction ,a…  相似文献   

4.
ANOMALOUS DYNAMICS RESPONSE OF NONLINEAR ELASTIC BAR   总被引:1,自引:0,他引:1  
IntroductionInresentyears,thechaoticbehaviorofbeamssubjectedtoperiodicloadbringsmoreandmorescholars’interests.In 1 983 ,FCMoonetal.[1]studiedthechaoticmotionsofbeamsinnonlinearboundaryconditions.In 1 994 ,S .AnanthaRamuandTSSankaretal.[2 ]analyzedbifurcationandCata…  相似文献   

5.
ONGRAMMATICALCOMPLEXITYOFACLASSOFATTRACTORSLuQinhe(卢钦和)(DepartmentofMathematics.SuzhouUniversit}'.Suzhou215006.P.R.China)Abst...  相似文献   

6.
IntroductionMoreandmoreproblemsinscienceandengineeringhaveconcernedthestabilityanalysisoftheviscoelasticstructuresduetotheirbroadapplications .In [1]CederbaumandMondappliedthemultiple_scalesmethodtotreatstabilityofaviscoelasticcolumnunderaperiodicaxiall…  相似文献   

7.
IntroductionLetΓ0 beasmoothconnectedhypersurfaceanditistheboundaryofaboundedopensetU Rn.Supposethatt0 isatime ,M =M(x) ∈C3withM( 0 ) =0 ,M′(x) >0 ,andl1,l2 ,… ,lnarepositiverealnumbers.{Γt} 0 ≤t≤t0 isaclassicalsmoothsurface,anditistheboundaryofaboundedopensetUt,whichisdiff…  相似文献   

8.
COMPUTERSIMULATIONOFTHEMOTIONOFTHEBULLETBELTOFAIRPLANEGUNZhangDingguo(章定国)(ReceivedMarch17,1995;CommunicatedbyWuRuifeng)Abstr...  相似文献   

9.
ONUNILATERALLYCONSTRAINEDMOTIONSOFRIGIDBODIESSYSTEMSLiHongbo(李洪波)(MMRC,InstituteofSystemsScience,AcademiaSinica,Beijing100080...  相似文献   

10.
IntroductionConsidertheindirectcontrolsystem x =Ax Bφ(σ) , σ =CTx ρφ(σ) ,(1 )wherex∈Rn,σ ∈R ,Aisn×nstablematrix ,BandCarendimensionalvectors,thesymbolTstandsfortransposition ,ρisaconstant,function φ(σ) :R →Riscontinuousandsatisfiesconditionσφ(σ) >0   ( σ∈R ,σ≠ 0 ) . (2 )Manyspe…  相似文献   

11.
界面特性对短纤维金属基复合材料蠕变行为的影响   总被引:1,自引:0,他引:1  
基于短纤维增强金属基复合材料(MMC)的单纤维三维模型(三相),利用粘弹性有限元分析方法对影响金属基复合材料的蠕变行为的因素进行了较为系统的分析。研究中主要讨论了界面特性和纤维取向角对金属基复合材料的蠕变性能的影响。研究结果发现,界面特性诸如厚度、模量和应力指数都对纤维最大轴应力和稳定蠕变率产生影响:稳态蠕变率随界面模量的增大而逐渐减小,当高于基体模量时基本保持不变;纤维轴应力的变化与蠕变率正好相反。稳态蠕变率随界面厚度、应力指数的增加而增大;而轴应力则随之减小。同时不同的纤维取向也影响金属基复合材料蠕变时的轴应力分布和稳态蠕变率。  相似文献   

12.
高温环境下纤维复合材料蠕变损伤的细观机理研究   总被引:1,自引:0,他引:1  
姜云鹏  岳珠峰 《力学季刊》2004,25(4):523-527
首先利用复合材料纤维断裂单胞模型,编制蠕变损伤子程序,对单胞模型进行蠕变损伤分析。分析了纤维/基体弹性模量比对蠕变变形、蠕变损伤以及应力场的影响。从计算结果发现,蠕变损伤首先在纤维断裂尖端起始,然后沿着一定的角度向基体外围延伸,直至完全损伤,而且纤维/基体模量比对高温环境下的复合材料蠕变损伤产生很大的影响;纤维与基体的模量相差越大,复合材料越容易变形,抵抗蠕变变形的能力就越小,蠕变损伤越严重。经过对不同韧性的基体材料进行研究,发现基体韧性低的复合材料蠕变损伤明显高于高韧性基体复合材料,表明低韧性基体复合材料抵抗蠕变破坏的能力较低。  相似文献   

13.
苑忠慧  仲政 《力学季刊》2022,43(3):482-489
皮肤组织作为富含纤维的非均匀材料,具有复杂的力学特性.皮肤组织在循环加载作用下,随着循环次数的增加,加载过程的应力响应逐渐降低,并最终达到不随循环次数增加而改变的稳定状态,这种现象被称为应力软化行为.本文对加载过程中纤维的延展机制对宏观力学响应的影响进行研究,认为在外界载荷较小时该机制主导了宏观层次上的应力软化行为,随着外界载荷的增大,拉伸过程中微观结构损伤的演化开始产生影响,而且此时内部微观结构的演化由两种机制共同影响,据此建立了连续介质模型,将宏观尺度上应力软化行为和微观结构的演化相关联.将所获得的应力响应理论结果与猪离体头部皮肤在循环加载作用下的实验结果进行对比分析,证明了该模型能够合理地描述皮肤组织在循环加载作用下的应力软化行为.  相似文献   

14.
A numerical simulation for predicting the axial creep-rupture lifetime of continuous fiber-reinforced metal matrix composites is proposed, based on the finite element method. The simulation model is composed of line elements representing the fibers and four-node isoparametric plane elements representing the matrix. While the fibers behave as an elastic body at all times, the matrix behaves as an elasto-plastic body at the loading process and an elasto-plastic creep body at the creep process. It is further assumed in the simulation that the fibers are fractured not only in stress criterion but time-dependently with random nature. Simulation results were compared with the creep-rupture lifetime data of a boron-aluminum composite with 10% fiber volume fraction experimentally obtained. The simulated creep-rupture lifetimes agreed well with the averages of the experimental data. The proposed simulation is further carried out to predict a possibility of creep-rupture for the composite without time-dependent fiber breakage. It is finally concluded that the creep-rupture of a boron-aluminum composite is closely related with the shear stress relaxation occurring in the matrix as well as time-dependent fiber breakage.  相似文献   

15.
高温下金属基复合材料的蠕变主要由基体蠕变和界面扩散蠕变两部分构成,以往的研究中常常只考虑其中一种蠕变机理,从而导致得到的规律具有较大的局限性.本文提出了一种可预测金属基复合材料整体蠕变性能的细观力学方法,同时考虑了基体蠕变和界面扩散蠕变两种蠕变机理,导出了具有张量形式并满足不可压缩性的界面扩散蠕变应变表达式.采用Mori-Tanaka法和自洽法二者结果的平均以便更准确地计算纤维中的应力,揭示了两种蠕变机理相互影响的竞争关系.研究了恒定双轴荷载下的总体蠕变和固定位移约束下的应力松弛这两种常见蠕变问题,探究了基体蠕变与界面扩散蠕变两种蠕变机理在总蠕变中发挥的作用,考察了不同加载条件和不同纤维体积分数对复合材料整体蠕变行为的影响.  相似文献   

16.
纤维沥青混凝土FRA(Fiber reinforced asphalt concrete)的力学行为取决于沥青混合料和纤维的物理属性及几何特征。通过三参数固体模型,考虑纤维的几何特性,构造了一种预测FRA黏弹性行为模型,推导出该模型的本构方程、蠕变柔量和松弛模量表达式。采用该模型研究了纤维体积分、比半径和弹性模量等对FRA松弛模量和蠕变柔量的影响。结果表明,纤维掺入量和比半径对FRA的松弛模量和蠕变柔量影响较大,而弹性模量影响较小。通过试验,验证了FRA预测模型具有较高的精度。在研究试验范围内,SMA-13沥青混凝土的聚丙烯腈纤维(PAN)最佳掺入量和长径比分别为0.3%~0.4%和600~900。  相似文献   

17.
This work presents a homogenization-based constitutive model for the mechanical behavior of elastomers reinforced with aligned cylindrical fibers subjected to finite deformations. The proposed model is derived by making use of the second-order homogenization method [Lopez-Pamies, O., Ponte Castañeda, P., 2006a. On the overall behavior, microstructure evolution, and macroscopic stability in reinforced rubbers at large deformations: I—theory. J. Mech. Phys. Solids 54, 807–830], which is based on suitably designed variational principles utilizing the idea of a “linear comparison composite.” Specific results are generated for the case when the matrix and fiber materials are characterized by generalized Neo-Hookean solids, and the distribution of fibers is periodic. In particular, model predictions are provided and analyzed for fiber-reinforced elastomers with Gent phases and square and hexagonal fiber distributions, subjected to a wide variety of three-dimensional loading conditions. It is found that for compressive loadings in the fiber direction, the derived constitutive model may lose strong ellipticity, indicating the possible development of macroscopic instabilities that may lead to kink band formation. The onset of shear band-type instabilities is also detected for certain in-plane modes of deformation. Furthermore, the subtle influence of the distribution, volume fraction, and stiffness of the fibers on the effective behavior and onset of macroscopic instabilities in these materials is investigated thoroughly.  相似文献   

18.
Many natural materials like cotton, wool, or wood consist of short, stiff, discontinuous fibers embedded in a softer matrix. In recent times, synthetic materials have been produced by incorporating short metal fibers in a relatively malleable polymeric base. Here, we propose a mathematical model for describing the macroscopic behavior of these materials that is able to incorporate both the stress singularity that arises at the tips of each individual fiber and the ensuing partial detachment. Received July 29, 2002 / Accepted February 4, 2003/ Published online May 9, 2003 / H. Struchtrup For Ingo Müller on his 65th birthday. Correspondence to: J. Jenkins (e-mail: jtj2@tam.cornell.edu)  相似文献   

19.
Lots of work had been reported in the experimental investigation and modeling of the debonding and pullout behavior for straight crack-bridging fibers in brittle matrix composites, but few of them involving in the dynamic and/or non-straight fiber case. In this paper, a dynamic meso-scale model for non-straight fiber was proposed on the work of Chanvillard. The model was time-dependent and related to the impact loading through the interfacial shearing stress along the embedded part of the steel fiber, and properly setting the thresholds, the dynamic meso-damage model of the fiber's debonding and pullout process was eventually constructed. The model prediction fitted the experimental data of Chanvillard for non-straight steel fiber under static condition quite well and could demonstrate the rate sensitivity of the reinforcing effects of fibers. Then, a 3-D discrete meso-element method (DEM3) was used to simulate the dynamic pullout behavior of such fiber configurations as wiredrawn fibers from cementitious matrix with pores. Comparing to afro-mentioned model, DEM3 was more effective in simulating the complete procedures of matrix dynamic failure and fiber pullout and would be more helpful in the analyses of complicated configurations of fiber.  相似文献   

20.
Metal matrix composites (MMCs) generally do not follow the classical plasticity theory, even though the matrix metals do deform plastically. A tension-compression yield asymmetry is typically observed in MMCs. For particulate-reinforced MMCs, this non-classical response is mainly due to the variation of damage evolution with loading modes. In this paper, a viscoplastic multi-axial constitutive model for plastic deformation of MMCs is constructed using the Mises-Schleicher yield criterion. The subsequent plastic flow is characterized by an associated and decomposed flow rule considering effects from both deviatoric and hydrostatic stresses. This model is capable of describing the multi-axial yield and flow behavior of MMCs by using simulated or measured asymmetric tensile and compressive stress-strain responses as input. As an example, the influence of damage evolution in terms of interfacial debonding in MMCs (obtained from FEM simulations) is incorporated through the different tensile and compressive stress-strain behaviors. Applying this model to predict the torsion and the pressure-dependant tensile responses of some commonly used MMCs provides good agreement with experimental data.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号