简介：Phononicmaterialswithspecificband-gapcharacteristicsatdesiredfrequencyrangesareingreatdemandforvibrationandnoiseisolation,elasticwavefilters,andacousticdevices.Theattenuationcoefficientcurvedepictsboththefrequencyrangeofbandgapandtheattenuationofelasticwave,wherethefrequencyrangescorrespondingtothenone-zeroattenuationcoefficientsarebandgaps.Therefore,theband-gapcharacteristicscanbeachievedthroughmaximizingtheattenuationcoefficientatthecorrespondingfrequencyorwithinthecorrespondingfrequencyrange.Becausetheattenuationcoefficientcurveisnotsmoothinthefrequencydomain,thegradient-basedoptimizationmethodscannotbedirectlyusedinthedesignoptimizationofphononicband-gapmaterialstoachievethemaximumattenuationwithinthedesiredfrequencyrange.Toovercomethisdifficulty,theobjectiveofmaximizingtheattenuationcoefficientistransformedintomaximizingitsCosine,andinthisway,theobjectivefunctionissmoothedandbecomesdifferentiable.Basedonthisobjectivefunction,anovelgradient-basedoptimizationapproachisproposedtoopenthebandgapataprescribedfrequencyrangeandtofurthermaximizetheattenuationefficiencyoftheelasticwaveataspecificfrequencyorwithinaprescribedfrequencyrange.Numericalresultsdemonstratetheeffectivenessoftheproposedgradient-basedoptimizationmethodforenhancingthewaveattenuationproperties.

简介：ThenonlinearvibrationsofviscoelasticEuler–BernoullinanobeamsarestudiedusingthefractionalcalculusandtheGurtin–Murdochtheory.EmployingHamilton'sprinciple,thegoverningequationconsideringsurfaceeffectsisderived.Thefractionalintegro-partialdifferentialgoverningequationisfirstconvertedintoafractional–ordinarydifferentialequationinthetimedomainusingtheGalerkinscheme.Thereafter,thesetofnonlinearfractionaltime-dependentequationsexpressedinastate-spaceformissolvedusingthepredictor–correctormethod.Finally,theeffectsofinitialdisplacement,fractionalderivativeorder,viscoelasticitycoefficient,surfaceparametersandthickness-to-lengthratioonthenonlineartimeresponseofsimply-supportedandclamped-freesiliconviscoelasticnanobeamsareinvestigated.

简介：基于镍的单个水晶superalloy与的低周期的疲劳(LCF)行为[001]取向在T0掳C的中间的温度和T0+的更高的温度被学习在10的经常的低紧张率下面的250掳C?3s?1在周围的空气。superalloy展出了依赖于温度并且使用紧张振幅的周期的紧张压缩不对称现象。破裂表面上的分析证明表面和表面下的扔micropores是主要裂缝开始地点。内部Ta富有的碳化物经常在所有标本被观察。骨折的二种不同类型被frac-togaphy建议。一种类型被模式描绘--我与一台用显微镜裂开在T0+的不平的表面250掳C。而在更低的温度T0C的另外的类型赞成了中的一个或几八面{111}飞机，与正常模式相对照--我生长模式典型地在低装载观察了频率(几Hz)。为二个裂开的模式的失败机制纬鈥?正在砍在T0+在矩阵和纬/纬鈥?接口在T0掳C和裂开的反对ned和矩阵猛抛250掳C。

简介：Anewcomputationschemeproposedtotacklecommensurateproblemsisdevelopedbymodifyingthesemi-analyticapproachforminimizingcomputationalcomplexity.Usingtheproposedscheme,thelimitstateequations,usuallyreferredtoasthefailuresurface,areobtainedfromtransformationofanintervalvariabletoanormalizedone.Inordertominimizethecomputationalcost,twoalgorithmsforoptimizingthecalculationstepshavebeenproposed.Themonotonicityoftheobjectivefunctioncanbedeterminedfromnarrowingthescopeofintervalvariablesinnormalizedinfinitespacebyincorporatingthealgorithmsintothecomputationalscheme.Twoexamplesareusedtoillustratetheoperationandcomputationalefficiencyoftheapproach.Theresultsoftheseexamplesshowthattheproposedalgorithmscangreatlyreducethecomputationcomplexitywithoutsacrificingthecomputationalaccuracy.Theadvantageoftheproposedschemecanbeevenmoreefficientforanalyzingsophisticstructures.

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简介：在铝合金的测量粒子地以内的空成核被调查开发哪个的一个连续统成核模型在单个粒子规模的reects成核。为异构的粒子分布的一个成核模型用平均成核紧张与Chu和裁缝的连续统模型一起被同步。在连续统模型的参数从粒子域被识别并且在在表金属形成观察的压力状态的范围上被评估。同步连续统成核模型在单轴的紧张，飞机紧张，和equal-biaxial紧张为三测量粒子域与成核趋势完成很好的同意。

简介：Theeffectivethermalconductivityofmatrix-inclusion-microcrackthree-phaseheterogeneousmaterialsisinvestigatedwithaself-consistentmicromechanicalmethod（SCM）andarandommicrostructurefiniteelementmethod（RMFEM）,IntheSCM,microcracksareassumedtoberandomlydistributedandpen-ny-shapedandinclusionstobespherical,thecrackeffectisaccountedforbyintroducingacrackdensitypa-rameter,theeffectivethermalconductivityisderivedwhichrelatesthemacroscopicbehaviortothecrackdensityparameter.IntheRMFEM,thehighlyirregularmicrostructureoftheheterogeneousmediaisaccu-ratelydescribed,theinteractionamongthematrix-inclusion-microcracksisexactlytreated,theinclusionshapeeffectandcracksizeeffectareconsidered.ANi/ZrO2particulatecompositematerialcontainingran-domlydistributed,penny-shapedcracksisexaminedasanexample.Themainresultsobtainedare:（1）theeffectivethermalconductivityissensitivetothecrackdensityandexhibitsessentiallyalinearrelationshipwiththedensityparameter;（2）theinclusionshapehasasignificanteffectontheeffectivethermalconductiv-ityandapolygon-shapedinclusionismoreeffectiveinincreasingordecreasingtheeffectivethermalconduc-tivitythanasphere-shapedone;and（3）theSCMandRMFEMarecomparedandthetwomethodsgivethesameeffectivepropertyinthecaseinwhichthematrixthermalconductivityλ,isgreaterthantheinclusiononeλ2.Intheinversecaseofλ1<λ2,thetwomethodsagreeastheinclusionvolumefractionandcrackdensityarelowanddifferastheyarehigh.Areasonableexplanationfortheagreementanddeviationbetweenthetwomethodsinthecaseofλ1<λ2ismade.

简介：这篇论文介绍各向异性的损坏理论的应用程序给形成A12024T3铝合金表的限制图的学习。在限制铝板结构的紧张的预言，一个有限元素房间模型被构造了。房间模型由二个阶段，铝合金矩阵和金属间化合的簇组成。铝合金矩阵的材料行为与充分联合的elasto塑料的损坏被描述组成的方程。金属间化合的簇被假定有弹性、易碎。由改变拉长的比率，在二轴的拉长下面的表的限制紧张被使用建议的necking标准预言了。预言在对试验性的调查结果的好同意。而且，有限元素房间模型能为理解铝合金的显微镜的损坏机制提供信息。如果材料损坏的效果在形成学习的表金属被忽略，限制紧张的在评价上可以结果。

简介：Anewadaptivetechniqueofr-andh-versionforvibrationproblemsutilizingthematrixper-turbationtheoryandelementenergyratioisproposed.Instructuralvibrationanalysis,throughther-conver-genceadaptivefiniteelementprocess,meshoptimizationcanberealized.Inthelightofthejudgementonthechangesinthemagnitudeoftheelementenergyratio,localrefinementcanbeachievedintheprocessofh-convergenceadaptivefiniteelementsothatmoreaccuratefiniteelementsolutionscanbeobtainedwithasfewmeshesaspossible.Manynumericalexamplesaregivenandtheproposedapproachisshowntobefeasibleandeffective.