简介:Thebehaviorofthestressintensityfactoratthetipsofcrackssubjectedtouniaxialtensionσχ^∞=pwithtraction-freeboundaryconditioninhalf-planeelasticityisinvestigated.Theproblemisformulatedintosingularintegralequationswiththedistributiondislocationfunctionasunknown.Intheformulation,wemakeusedofamodifiedcomplexpotential.Basedontheappropriatequadratureformulastogetherwithasuitablechoiceofcollocationpoints,thesingularintegralequationsarereducedtoasystemoflinearequationsfortheunknowncoefficients.Numericalexamplesshowthatthevaluesofthestressintensityfactorareinfluencedbythedistancefromthecrackstotheboundaryofthehalf-planeandtheconfigurationofthecracks.
简介:ItisdifficulttodesignaplatewithwideattenuationzonesinlowfrequencyregionbasedonBraggscatteringmechanism.Aplatewithperiodicrhombusholesisoptimizedanddesigned.Basedonthefiniteelementmethodunderperiodicboundaryconditions,thein-planedispersioncurvesofperiodicallyperforatedplatearecalculatedviaCOMSOL.ThefrequencyresponsesofperiodicallyperforatedplateareinvestigatedviaANSYSsimulation.Theplateswithperiodicholesaresuspendedanddynamicallytestedundersinusoidalexcitations.Theresultsshowthataperiodicallyperforatedplatewithrhombusholeshaswiderattenuationzonesthanplateswithcircularandhexagonalholes.Materialpropertieshaveagreatinfluenceonattenuationzones:nitrile-butadienerubberandsiliconrubbercaneasilyobtainlow-frequencyzones,whileincreasingporositycreateslowerandwiderzones.Thewidthofattenuationzoneincreasesasthehorizontalangleoftherhombusholesincreases.Ananalysisoftheattenuationzones'generationmechanismshowsthattheplatewithperiodicholesexhibitscharacteristicsofBraggscatteringandlocalresonantphononiccrystal,indicatinganinherentrelationshipbetweentwotypesofmechanisms.Theoptimizedplatehasacompleteattenuationzonerangingfrom5281.76-8824.30Hz.Thevibrationsaresignificantlyreducedwhenthenumberofperiodsisnolessthantwo.Theattenuationrangeobtainedviathenumericalmethodisgenerallyconsistentwiththeexperiment.Theresearchshedslightonthenoiseinsulationplateandhasthepotentialtoimprovethesoundenvironmentinvariousapplicationsduetoitssimplemanufacturing.
简介:ThedissipationfunctioninturbulentplanePoiseuilleflows(PPFs)andplaneCouetteflows(PCFs)subjecttospanwiserotationsisanalyzed.Itisfoundthat,inthePCFswithoutsystemrotations,themeanpartisconstantwhilethefluctuationpartfollowsalogarithmiclaw,resultinginasimilarlogarithmicskinfrictionlawasPPFs.However,iftheflowsystemrotatesinthespanwisedirection,noobviousdependenceontherotationnumbercanbeevaluated.InthePPFswithrotations,thedissipationfunctionshowsanincreasewiththerotationnumber,whileinthePCFswithrotations,whentherotationnumberincreases,thedissipationfunctionfirstdecreasesandthenincreases.
简介:摘要状态检修是目前工业发展的一个趋势,如何能够在设备还未出现故障之前对运行状态进行一个正确的评价。并以此为依据,对设备的检修维护做出合理的计划安排。将会对设备运行的安全性和经济性的提高有很大的知道意义。本文将对状态评价模型的建立过程进行一个简要的描述。
简介:摘要:运用二次函数分析和解决简单的实际最值问题,是中考考点,也是难点。要求学生具有分析问题、解决问题的能力和应用数学的意识。本文通过探索实际问题与二次函数的关系的过程,深刻理解二次函数是刻画现实世界的一个有效的数学模型.
简介:摘要采用平面二维数学模型研究长江防洪护岸工程水流条件及通航条件的影响分析。以江安县城河段为例,模型对该河段的实测水面线和流速分布进行了验证,计算结果与天然实测资料较为一致,可正确模拟实际河道的水流运动。分析研究表明,以上边界条件改变对江安县城河段附近水位、流速等水流条件没有明显影响,不会影响上下游的泥沙冲淤能力,基本不会对通航条件造成明显变化。