英漢雙語材料力學

CHAPTER15FOUNDATIONSOFTHEMechanicsofMaterials材料力學第十五章實驗應(yīng)力分析基礎(chǔ)CHAPTER15FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS

§15–1SUMMARY§15–2PRINCIPLEANDAPPLICATIONOFTHESTRAINOMETEROFTHERESISTANCE§15–3PRINCIPLEANDAPPLICATIONOFTHEPHOTOELASTICITY第十五章實驗應(yīng)力分析基礎(chǔ)§15–1概述§15–2電阻應(yīng)變計法的原理及應(yīng)用§15–3光彈性法的原理及應(yīng)用§15–１

Summary一、Functionofthestressanalysismethodinexperiments：1.

Determinethereasonabledimensionandthestructurealformofamemberaccordingtothetestedstressorstrainofthemodelindesigning.

2.Testthetruestressorstrainofamemberinworkandfindoutthepositionandthevalueofthemaximumstressinordertoevaluatethesaftyandreliabilityoftheengineeringstructureandtoprovidethebasisofimprovingworkingabilityfortheequipment.3.Analyzethedestroyedorfailedmemberandproposethemeasuresofimprovementinordertopreventitfromdestroyingagain.

4.Testthemagnitude,derectionandallkindsofdynamicresponsesoftheexternalload.

5.Explorethenewrulefromtestsandcheckthetheoryofstressanalysisandthecalculationmethod.

FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS§15–１概述一、實驗應(yīng)力分析方法的作用：1.設(shè)計時，測定模型的應(yīng)力或變形，依此來確定構(gòu)件的合理尺

寸和結(jié)構(gòu)形式。2.工作中，測定構(gòu)件的真實應(yīng)力或變形，找出最大應(yīng)力的位置

和數(shù)值，以評價工程結(jié)構(gòu)的安全可靠性，并為提高設(shè)備的

工作能力提供依據(jù)。3.對破壞或失效構(gòu)件進行分析，提出改進措施，防止再次破壞。4.測定外載的大小、方向以及各種動響應(yīng)。5.從試驗中探索新的規(guī)律，并對應(yīng)力分析理論和計算方法進行

校核。實驗應(yīng)力分析基礎(chǔ)二、Briefintroductionofmethodsinthestressanalysisofexperiments

1.Themachinerymeasuringmethod.ThefigureofmeasuringdeformationsinthebookannotatedbyZhengXuan(127-200)intheeastHandynasty.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS二、實驗應(yīng)力分析方法簡介：1.

機

械

量

測

法東漢鄭玄(127—200)注釋的《考工記?弓人》中的測變形圖實驗應(yīng)力分析基礎(chǔ)LeonardoDaVinci(1452-1519).ThispictureisconsideredtoshowtheearliesttestinMechanicsofMaterials.ThetensiletestofanironwiredesignedbyLeonardoDaVinci.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS里奧納多?達?芬奇(1452—1519)此圖被認為是最早的材力試驗實驗應(yīng)力分析基礎(chǔ)里奧納多?達?芬奇設(shè)計的鐵絲受拉試驗tensileFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSGalileo(1564—1642)Fig.14SketchofthetensiletestofGalileoFig.15SketchofthebendingtestofGalileo伽利略(1564—1642)實驗應(yīng)力分析基礎(chǔ)FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSFig.37Tensile-testmachineofMushenbluicFig.38MethodtoclamptwoendsofatensilespecimenMushenbluic(1692—1761)穆申布洛依克(1692—1761)實驗應(yīng)力分析基礎(chǔ)FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSHydraulicverstiletestingmachinecontrolledbythecomputer實驗應(yīng)力分析基礎(chǔ)2.Othermethods：

Sincetheearly20thcentury,thedevelopmentsofelectricity,opticsacousicsandmaterialssciencehaveprovidedconditionsfortheproductionofothermeasurementmethodsofthestressanalysisinexperiments.Thentheresistance-strainmethod,ordinaryphotoelasticitymethod,hologramphotoelasticitymethod,soundlaunchingmethodandsoonaremadefastdevelopmentsandwideapplications.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS2.其它方法：20世紀初至今，電學、光學、聲學和材料科學的發(fā)展，為試驗應(yīng)力分析其它測量方法的產(chǎn)生創(chuàng)造了條件。于是，電阻應(yīng)變法、普通光彈法、全息光彈法、散斑法、聲發(fā)射法等方法都有了快速發(fā)展和廣泛應(yīng)用。實驗應(yīng)力分析基礎(chǔ)§15–2

Principleandapplicationofthestrainometeroftheresistance

1、Resistancelaw:Resisanceofaconductor

2、Elasticlaw:

LandAwillchangeafterthecinductorissubjectedtoforcesorchangesintemperatures.

3、StrainfoilofresistanceＫ—Sensitivecoefficient12345Wire-coiledstrainfoil1—Overburden2—Fundus3—Drawnline4—Binder5—SensitivebarFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS§15–2

電阻應(yīng)變計法的原理及應(yīng)用

一、電阻定律：導體電阻

二、彈性定律：導體受力或變溫后，L、A都將發(fā)生改變。

三、電阻應(yīng)變片：Ｋ—靈敏系數(shù)：實驗應(yīng)力分析基礎(chǔ)12345絲繞式應(yīng)變片1—覆蓋層2—基底3—引出線4—粘結(jié)劑5—敏感柵

4、BalanceprincipleoftheelectricbridgeAftertheresistancechanges：UR1R2R4I1,2I3,4ABCDBridgewiththeoutputvoltageR3FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS四、電橋平衡原理電阻變化后：實驗應(yīng)力分析基礎(chǔ)UR1R2R4I1,2I3,4ABCD電壓輸出橋R3

5、StrainometerofresistanceTransformtooutputvoltageintothemagnitudeofstrain.

FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS五、電阻應(yīng)變儀將輸出電壓轉(zhuǎn)變?yōu)閼?yīng)變讀數(shù)。實驗應(yīng)力分析基礎(chǔ)6、Arrangefoils：Makethedirectionsoffoilscoincidewiththoseofprincipalstressesasmuchaspossible.

Whenthedirectionsofprincipalstressesareun-known,thestressstateofapointmustbedeterminedbythreeindependentquantities.

Threestrainfoilsof45°0°45°90°Threestrainfoilsof60°0°60°120°FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS六、布片：盡可能使片子的方向與主應(yīng)力方向一致。主應(yīng)力方向未知時，必須由三個獨立量才能確定一點的應(yīng)力狀態(tài)。實驗應(yīng)力分析基礎(chǔ)三片45°應(yīng)變花0°45°90°三片60°應(yīng)變花0°60°120°7、Relationsbetweentheprincipalstrainsandthemeasuredstrains.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS七、主應(yīng)變與測量應(yīng)變之間的關(guān)系：實驗應(yīng)力分析基礎(chǔ)Example1

Threelinearstrainsofapointaretestedbythestrainfoil45°.Trytodeterminetheprincipalstrainofthispoint.0max45°xyuFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS[例1

]用45°應(yīng)變花測得一點的三個線應(yīng)變后，求該點的主應(yīng)變。0max實驗應(yīng)力分析基礎(chǔ)45°xyuExample2Trytodeterminetheprincipalstrainofapointafterthethreelinearstrainsofthispointaretestedbythestrainfoilof60°。Threestrainfoilsof60°0°60°120°FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS[例2

]

用60°應(yīng)變花測得一點的三個線應(yīng)變后，求該點的主應(yīng)變。實驗應(yīng)力分析基礎(chǔ)三片60°應(yīng)變花0°60°120°8、Connectthebridge：

Makethestressdistributealternately;makethetotalbridgehaveahighprecisionandthehalfbridgealowprecision.Thehalfbridhewithtwoarmsisoftenused.9、Temperaturecompensation：Itisbettertorealizethecompensationbyitself;otherwiseweshouldusethetemperaturecompensatorthatiswithoutanyforces.Wemustmaketheworkingfoilandthecompensationfoilinthesametemperaturefield.

FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS八、接橋：要使應(yīng)力正負相間；全橋精度高，半橋精度低。常用半橋雙臂式橋路。九、溫度補償：最好能在橋路中自補償；否則，要用絕對不受力的溫度補償片。工作片與補償片要始終處于同一溫度場中。實驗應(yīng)力分析基礎(chǔ)§15－3Principleandapplicationofthephotoelasticity1、Principleofthephotoelasticity:①.Permanentdoublerefraction：②.Temporary(artificial)doublerefraction:DoublerefractionintheanisotropicbodyduetotheenteringoflighteoFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS§15－3

光彈性法的原理及應(yīng)用一、光測原理：1.永久雙折射：2.暫時（人工）雙折射：實驗應(yīng)力分析基礎(chǔ)光射入各向異性體產(chǎn)生的雙折射eo

2、Planestress--opticslaw：①.Refractiveindex：C——Stressopticalcoefficientofthemodelmaterial

Ds1s1s2s2PlanepolarizedlightTheplanepolarizedlightpassesthroughthemodelsubjectedtoforces.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSSo

二、平面應(yīng)力——光學定律：1.折射率：C——模型材料的應(yīng)力光學系數(shù)。實驗應(yīng)力分析基礎(chǔ)Ds1s1s2s2平面偏振光平面偏振光通過受力模型②.Opticalpathdifference：③.Thelightintensityintheplanepolarizationfield:Themodelsubjectedtoforcesisinthecrossplanepolarizationfield.Ps1s2AOfLightsourceModelAnalyzerPolarizerFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS2.光程差：3.平面偏振場中的光強：實驗應(yīng)力分析基礎(chǔ)受力模型在正交平面偏振布置中Ps1s2AOf光源模型檢偏鏡起偏鏡①EqualinclinationlinesFOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSAsablackpointoccursbehindtheanalyzer.Theinterferencefringesformedinthelocusoftheblackpointsarecalledequalinclinationlines.Ontheequalinclinationlines,thedirectionsofthepricipalstressesaresameandtheycoincidewiththepolarizationaxle.Picturesoftheplanepolarizationfieldtakenevery150.Thepositionofthecoloredequalcolorlinesisnotchanged,butthepositionoftheblackequalinclinnationlinesischangedwhenthepolaroidrotatessynchronously.①等傾線引起的黑點的跡線形成的干涉條紋——等傾線等傾線上，主應(yīng)力方向相同且與偏振軸重合。實驗應(yīng)力分析基礎(chǔ)②Equaldifferencelines.Theformedinterferencefringes--equaldifferencelines.

Thewhitelightisconsideredtobethelightsourceandtheequaldifferencelinesaarecolouredfringes,sotheequaldifferencelinesarealsocalledequalcolourlines.FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSAsN=0,theyarecalledtheNo.0equaldifferencelines(black);asN=1,theyarecalledtheNo.1equaldifferencelines.Simulatingtheplaepartconnectedbyscrewsandscrewcaps(methodofpastingfoils)②等差線形成的干涉條紋——等差線以白光為光源,等差線為彩色條紋,故等差線又稱等色線實驗應(yīng)力分析基礎(chǔ)

f——Thevalueofthefringeofamaterial

a、Undertherepeatedloading,theequalinclinationlinesarenotchanged,buttheequaldifferencelinesarechanged③Distinguishequalinclinationlinesandequaldifferencelinesb、Ifwerotatesynchronouslythepolarizerandtheanalyzer,theequalinclinationlinesarechangedandtheequaldifferencelinesarenotchanged.c、Accordingtoexperiences,theequalinclinationlinesarethick(alltheblack)andequaldifferencelinesarethin(aline).FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTS

f——材料的條紋值。a、反復加載，等傾線不變，等差線改變。③區(qū)分等傾線與等差線b、同步旋轉(zhuǎn)起偏鏡與檢偏鏡，等傾線改變，等差線不變。c、憑經(jīng)驗，等傾線較粗（一片黑），等差線較細（一條線）。實驗應(yīng)力分析基礎(chǔ)Therearenoequalinclinationlinesinthecrosscircularpolarizationfield.Sotheequaldifferencelinesareclear.

FOUNDATIONSOFTHESTRESSANALYSISINEXPERIMENTSLightintensity:as