fracturemechanics断裂力学英文版.ppt

1,6/9/2023,The strength theory which have crack in body,紧凭阶鸦霍怂琴果涛早此受歉偿捉即热盼露壶熄窄怎玛吉汉至畜根桐秒畸fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,2,6/9/2023,GOAL:recount conventional strength theory of nonindividual body.Fundamental assumption of elastic and plastic theory.Basic approach and equation to solve the stress.Description and analysis of one points stress state.,APPLY：strength designCalculate external force；Count one points stress state（theory of elasticity and plasticity）；Verdict a points stress is critical state(yield or destroy)or not according to the strength condition.ATTENTION：Generally used for checking.,Brief summary of first four chapters,峭询辨奈更驻挠锑霞汪玻购冗貉帽笼宵攀簿椭情饼鹃距抚汲才诱缸排漫哎fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,3,6/9/2023,Uncertainties during stress analysisIndeterminacy of external load.Indeterminacy during stress analysis.Indeterminacy of material characteristics.,Practical application:Security coefficient which bigger than one.,Designs basic ideanonindividual body never damage,Problems and solves during strength design,毗褂赘忍票患赘燥回蝗曳掌楚刮温迟巍旅蓬塌吗审迟弃抒丑套芳诧漫杯檀fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,4,6/9/2023,Reality of engineering damage,斥劈杏纪永郑钎嘉篮笑旱圆询坚锯跃瞪衅藏淡口琢券刷劈崎驾镇侠缔观闯fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,5,6/9/2023,Who is responsible for the air crash?In1979,there was a largest disaster event in American history,more than 270 people died.Reason:Connection which connect engines and wings had fractured.Review of the historyRailway：England，wheel、track、orbital fractureBridge：Belgium，14 accidents in 4 yearsSteamship：World War Two，American freighter、tanker，weldAirplane：British“comet”Missile：American“Polaris”Pressure vessel：Aerospace plane、,In the 1950s,American“Polaris”solid fuel engine was fractured when launch.The material was high-strength steel,yield strength s=1400MPa，working stress 900MPa。,Accident case,赁影滚李掂兽褂凄禄镀淡淄鸣清廖蚤年整河羡奇赊坠晒瓮跟骡布誓式坚枯fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,6,6/9/2023,When it damage,working stress is much less than materials yield limit；The primary cause of damage is that there are all kinds of defects or cracks in the actual structural materials.The existence of these cracks significantly reduce actual strength of structural materials.The important reason why it cause damage is defects in the structure.,Common features of the accidents,Where do cracks come from？Material defect；Fatigue initiation；Damages in machining、manufacture、assemble and so on.,昔凳勤厉挠雅昧牡祭贮机柬梯剪椅俭尽营挡石不馒裔芯沂坐糖绢抢旺家玻fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,7,6/9/2023,After 1950s,Crack-containing body strength theory was been researched and developed：,Fracture Mechanics,How to solve it?,果拔氯超熟浴媚郑妖吧每耳搔碾落矣干唆示宜津荐昧酱裤淳能碰效亚越竖fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,8,6/9/2023,5.1 Introduction5.2 The crack-tips stress-strain field5.3 Stress intensity factor and its solution5.4 Brittle ruptures K-factors5.5 The popularization of linear elastic fracture mechanics in small scale yielding5.6 Elastic-plastic fracture mechanics5.7 Fatigue crack growth rate,5.Crack-containing body strength theory,彰惜甩疽抵驰案陆途犁扔必娱池盟钮嘎脂乒目局辐器诱扔素憎角匠扶卒贬fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,9,6/9/2023,5.1.1 Development process of fracture mechanics5.1.2 Research contents of fracture mechanics5.1.3 Several basic conception of fracture mechanicsBrittle rupture and ductile fractureTrans-granular fracture and inter-granular fractureThe division of length and break related disciplines5.1.4 Fracture analysisMacro-fracture analysisMicro-fracture analysis,5.1 Introduction,堡肋豢屯熄骏精秉友柞晰祷罢厦迟截判友亩患洗项募倍党碧烯渊迎慑琶砍fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,10,6/9/2023,15 century，Vinci：Iron wire breaking load and length are in reverse proportion.In 1919，Russia coB：The stress concentration problem when the infinity plate contains an oval hole stress.(stress)Conclusion：Elements with crack unable load bearing.In 1921，Griffith research brittle materials fracture problem.(energy)After world war II，Irwin and Orowan supplemented the Griffith theory respectively and independently,so that it can be applicable to metallic material.Link the concept of energy release rate and stress intensity factor.Lay the foundations of linear elastic fracture mechanics.,5.1.1 Development process of fracture mechanics,挽鸟敢棉贯吨毒五闹阁启惺穷让钦紊胸充纬佰湍釜樟宰诀更笛娠皑号元册fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,11,6/9/2023,In 1958，Irwin,with amendments to broaden the scope of application of linear elastic fracture mechanics；Wells propose COD;In 1968，Rice and Hutchinson et al.work，provided a theoretical basis for j-integral method.Since then gradually established a system of main parameters of elastic-plastic fracture mechanics;In 1961，Paris proposed famous formula that is the relationship between stress intensity factor and crack growth rate;Study on quantitative analysis of dynamic fracture is in the ascendant,5.1.1 Development process of fracture mechanics,珍沃弗志刨恫抒母婴斑疥唤止题折疼家洞锹究瞩烙舅都啤皿雌蒋了鳃胶亏fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,12,6/9/2023,Research the power and resistance of material or structures crack growth(initiation).Fracture criterion and its scope of application and applicable conditions.Apply to the analysis of multiple structure：Process of crack from initiation,extending to unstability.Estimation the life of structure with cracks：Fatigue problems.,The goal of fracture mechanics is quantificationally research on the conditions of fracture which caused by he reason that the main crack in the supporting body extend(including static load and the expansion under fatigue load).,5.1.2 Research contents of fracture mechanics,右赢偶试梳淌剧招橙戴碉啮发袭腿邹男曙脾位菌溉琐相莫姻堤膝胞忠难戏fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,13,6/9/2023,5.1.2 Research contents of fracture mechanics,Engineering applicationUnder the action of known external load,how much is the crack length in the structure allowing(i.e.critical crack length)?When structure exist(or assumed)an initial crack length,how long does it need to expand to the critical crack length(or number of load cycles)?-Remaining lifeWhat function relations between residual strengths of structure and crack lengths?,耍择唱炸署撇泉购躬奢譬纽藤掩捕物迭瓦左乔蛾菇淤刘歪磺盈寿民迪嚎笆fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,14,6/9/2023,Issues relate to material selectWhat kinds of material are not easy germination crack?What kinds of material can allow relatively long cracks exist but not break?What material have better performance in resist crack growth?How can melting,processing and treatment get the best results?,5.1.2 Research contents of fracture mechanics,叉陛局唤诺秒曳东拂颐彰政棘翻熄碉坞汞脐疟俐余梭畏耍剂罗你膝礁刊氖fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,15,6/9/2023,Fracture mechanics involve many problems of mechanics,materials science and engineering application,it can be used to process：When structure has been set,cracking is know,how about this structures bearing capacity(residual intensity)?When structure has been set,external load is know,how much is the allowing maximum crack(Damage tolerance)?Knowing of damage tolerance and external load of structure,how to make each component of structure meet dimensional requirement(damage tolerance design)?Life time calculation.（Fatigue crack growths life）Selecting material.,5.1.2 Research contents of fracture mechanics,草宝埃破库著煤忌均羚坞揩阂狙粱细檬趣意惯明珠素秆王沂涕驶瑚衔胜斋fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,16,6/9/2023,Brittle fracture and ductile fracture,Toughness：Ability of materials absorb energy during the elastic-plastic deformation which before material break.,5.1.3 Several basic conception of fracture mechanics,糟隶驶轻剃吼掩类拣显懒陪尉硒渔笆逐引当咽汲枉念罗默缝骨陶舵宦妮宵fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,17,6/9/2023,Brittle fracture and ductile fracture,When breaking,there is not obvious plastic deformation,it is a sudden break and without warning before breaking;The fracture surface is quite smooth,and it is basically perpendicular to the axial；The fracture is abreast and luminous,and it is perpendicular to the normal stress.On the fracture often follow a zig-zag or radiation pattern.,The root of cut which before breaking occur plastic deformation,and the area of surplus section will reduce(i.e.necking)；Fracture may be jagged；With the observation of naked eye and low time microscope,the fracture is dark grey and fibrous.,Brittle fracture：,Ductile fracture,Notice：The relativity of concept（Influence by temperature,stress and environment）,5.1.3 Several basic conception of fracture mechanics,巷隐蜕努傲傅熔根耀陵瞥分到亚酉锗犁颠痔渊千婿肺沼帕闷浮霖山沂乾寡fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,18,6/9/2023,Trans-granular fracture and inter-granular fracture,Cleavage forms(Simple abruption of atomic binding)Brittle fracture,Slip and empty aggregationDuctile fracture,Fracture arouse by temper brittleness or crystal boundary has brittle phase,hydrogen embrittlement and any other reasons,it always belongs to the brittle fracture.,5.1.3 Several basic conception of fracture mechanics,涝序糜着嘎肺炕哭炯以坝虑皆陛忍猛鸭密栓猖鲸佛轩仿猿辰灌尿称砒睦湘fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,19,6/9/2023,The division of length dimension and break related discipline(Subject),5.1.3 Several basic conception of fracture mechanics,鱼湿乡只贵拂沮桥距颓勘汞宪苹努茫凰知华瓢闺裁米奶携秋扰俱孟集羔同fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,20,6/9/2023,The division of length dimension and break related discipline(Fissure)Static cracking(Stress analysis)Subcritical crack growth(fracture criterion)Unstable extensionsCrack arrest,5.1.3 Several basic conception of fracture mechanics,堪甚晌掣凑敦瘩蚀胆屡泡栗彻入先衷柄拙遮锌部庭搁溶血爆嘎擎玩信医箩fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,21,6/9/2023,5.1.4 Fracture analysis(concept),Metal fracture:After metal components break,the general terms of damaged parts outward appearance.Recording the process of cracks generation,propagation and fracture.Fracture analysis：Using methods of macroscope and microscope to analyse and research to fracture morphology.Purpose：Analyze the material organization and the characteristics and essence of defect,so that it can accurately determine steel quanlity,improvement smelting and heat treatment technology;Studing the micro-mechanism of metal fracture process,as the foundation of exposition fracture process elementary theory;Exploration the cause of accident.Method:Macro-fracture analysis,micro-fracture ananlysis.,芹暖依貉函降悦丝数轴筐结痉浅猩络谣仑顾蜗研姚奥涯参腕介荤火宪艇田fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,22,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Macro-fracture analysisThrough macroscopic fracture analysis,we can determine the nature of the metal fracture(brittle,ductile or fatigue);Can analyze the crack source location and the direction of crack propagation；Can judge the quality of the material.Distinguish between the static load fracture and fatigue fracture,素掘冤炒雇殷缀盛赖悼俗扩吴寂虱丸息旧胞蔓恳神郧牺烽赣耘但泛吹香弄fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,23,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Static load fracture：three elements,Fiber area,Radiation area,Shear lip area,Non-gap tensile specimen and impact test sample fracture chart,酮滁苑疤尾瞻赵读站铬源亚痈哄逊丰籽奠诫躇午湘曼粉抽惶密费亨尺缀妊fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,24,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Radiation area shapeCounter directional crack source,胺赌烂隘购蛋俩睁槽扫咒访沮泡饲胀倒投徐稿维付芒潮筒敲视苹察绊衙骂fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,25,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Three regions of the fracture surface exist or not,size,location,scale and shape,etc.will have great change along with the difference of material intensity levels,stress conditions,size dimensions,geometric forms,inside and outside flaws and positions,temperature,external environment and so on.The toughness of material is good,the area that textile fiber area occupies is big,even has not radiation area,is full of fiber area and shear lip.Material with big brittleness,the radiation area increases,fiber area reduces,even will not have fiber area and shear lip,and the pattern of emission area is very tiny,becomes less obvious and presents other characteristics.,监北句垂栗硷铭衣拿匝凶匈烫二吓耘势皂遵校忱砧镐溪辙惶蛮版疑敏奴陇fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,26,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Fatigue fracture,佐丢宝沮鹏镣搔魁栓伯呈珍堪衷柳命遇位培斌秽罩挠措蚕柑笨赵八腆愁焚fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,27,6/9/2023,5.1.4 Fracture analysis(Macroscopic),Macroscopic fracture analysis methodObserving whether there have radiation pattern or herringbone pattern on fracture surface,we can find the crack source position according to the trace;Meanwhile,according to the relative scale of radiation area and fiber area we can roughly estimated fracture properties.The bigger the proportion that the radiation area accounts is,then the brittleness is bigger.Observing whether there is shell pattern on the fracture surface,if it is,it indicates that the component is fatigue fracture,and we can find the fatigue initiation according to the trace.Observing to the rough degree,gloss and color of fracture.The fracture is rougher,the color is gloomier,indicated that in the fracture growth process the plastic deformation is bigger,the degree of ductile fracture is bigger;Otherwise,fracture is thin and flat,multi-gloss,it means that the proportion of brittle fracture is significant.,捞清华痢辈仪穆葛脖螟挞照值憨职纤每顶彰您泊榴掠鞭跪绪礁悠钮围崖瘪fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,28,6/9/2023,5.1.4 Fracture analysis(Microscopic),Micro-fracture analysisIn addition to being able to understand the cause of the fracture,but can also study mechanisms of fracture occurred.Method：transmission electron microscope（TEM）and scanning electron microscopeMicro fracture morphology：Cleavage fractureToughness nest fractureFatigue fracture,狼圆腐遭视友僻成汾雪抉捶羚孽巧碘蹲力瑞陋肢弘久烟樟拥您迷秽退伞捶fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,29,6/9/2023,5.1.4 Fracture analysis(Microscopic),Cleavage fracture is a kind of transgranular fracture,on a specific crystal surface,occur due to the simple breakdown of atomic key fracture.Within a grain,cleavage crack has relatively flat.It must change direction at the grain boundary,so cleavage fracture is composed of many small smooth planes which orientation is slightly different,each group of small plane represents a grain;The most important character of cleavage fracture is rivers pattern。,Cleavage fracture:A kind of the crispest fracture form which occurs in the crystallization material.,辣浸嗓辛舵蹈瓤舀咋崭砌返初晰场满阿砍帮仰乓查懈整线淖柴诵赚藻厚函fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,30,6/9/2023,5.1.4 Fracture analysis(Microscopic),Toughness nest fracture：Toughness nest fracture is a main type of ductile fracture,it also belongs to transgranular fracture;The chief feature of the fracture surface of toughness nest fracture is to have dimple;According to the different force,it will form different shapes of dimple,there are isometric toughness nest,parabolic toughness nest and elongation toughness nest and so on.Fracture surface presents rough and irregular shape.,槐贺锗博袱蹋胰里猪渡敏赢紧隔元舌货幂桌矮巧劲缔芍通咸填伺邯亥帽冬fracturemechanics断裂力学英文版fracturemechanics断裂力学英文版,31,6/9/2023,5.1.4 Fracture analysis(Microscopic),Isometric toughness nest,Parabolic toughness