金屬疲勞斷口分形和裂紋尖端塑性區(qū)研究.pdf

1、天津大學(xué)碩士學(xué)位論文金屬疲勞斷口分形和裂紋尖端塑性區(qū)研究姓名：徐蓮云申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：固體力學(xué)指導(dǎo)教師：侯振德2001.12.1!鯊叁蘭塑i蘭絲堡蘭——————!里翌蘭!!旦ABSTRACTManganesesteelisthematerialusedinofthetanktrack，SOtoinvestigateitsfracturequalityisveryimportantInthispaperwestudytherelat

2、ionshipbetweenfractaldimensionoffracturesurfaceandplastic—zoneofthecracktipInthispaperfirstwefollowthecracktipofthefatigueextensionofthemanganesesteelmaterial，andthenrecordthepictureofcracktipforthemaximumloadingstateand

3、minimumloadingstaterespectivelyAfterthatweusefractalcorrelationmethodtocalculatethedisplacementfieldsofthecracktipbeforeandafterdistortion，fromwhichdisplacementfieldsinthesectionofcracktipCanbeobtainedThenwecandeterminet

4、heformanddimensionoftheplastic—zoneofthefatiguefracturesurfacebycalculatingandcountingupthestrainvalueatthesectionofcracktipAtlastthetendencyoftheplastic—zonedimensionofcracktipwithrespecttofractureextensionisanalyzedInt

5、hispaperweuseSEMtotakephotosforthefatiguefractureandwriteprogrambyCBuildertodealwiththephotosAfterobtainingthecrackprofilewecalculatethefractaldimensionbyusingtheFractureProfileMethodanddetermineitschangetrendalongthecra

6、ckextensionThecalculatedfractaldimensionisverysmall，whichindicatesthedistortionoffractureprofileisverysmall，Therefore，thefractaldimensioncanbeusedasaquantitativeparametertoexpressthecharacteristicsoffractureWeobtainedthe

7、relationshipbetweenfractaldimensionandplastic—zoneofthefatiguefracturesurfaceTheexperimentsshowthattheplastic—zoneislargeintheareawherethefractaldimensionislargeWiththeincreasementofplastic—zone，theextensionspeedoffractu

8、reisdecreased，whichleadtotheincreasementoffractaldimensionBecausetheplastic—zoneisrelatedtotenacityofthematerialandthedimensionofplastic—zoneinfluencetheprofileoffatiguefracturesurface，thefractaldimensionmethodisveryimpo

9、rtanttoinvestigatethemetalfracturesurfaceInthispaperwehaveinvestigatedtherelationshipbetweenthefractaldimensionandmaterialtenacity，whichprovideaneffectivemethodforthefracturetheoryofmetalmaterialKeywords：Plastic。zone，F(xiàn)ra