英汉双语材料力学.ppt

1、,CHAPTER 15 FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,材料力学,第十五章 实验应力分析基础,CHAPTER15 FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,151 SUMMARY 152 PRINCIPLE AND APPLICATION OF THE STRAINOMETER OF THE RESISTANCE 153 PRINCIPLE AND APPLICATION OF THE PHOTOELASTICITY,第十五章 实验应力分析基础,151 概 述 152

2、电阻应变计法的原理及应用 153 光弹性法的原理及应用,15 Summary,一、Function of the stress analysis method in experiments ：,1. Determine the reasonable dimension and the structureal form of a memberaccording to the tested stress or strain of the model in designing.,2. Test the true stress or strain of a member in work and fin

3、d out the position and the value of the maximum stress in order to evaluate the safty and reliability of the engineering structure and to provide the basis of improving working ability for the equipment.,3. Analyze the destroyed or failed member and propose the measures of improvement in order to pr

4、event it from destroying again.,4. Test the magnitude,derection and all kinds of dynamic responses of the external load.,5. Explore the new rule from tests and check the theory of stress analysis and the calculation method.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,15 概 述,一、实验应力分析方法的作用：,1.设计

5、时，测定模型的应力或变形，依此来确定构件的合理尺 寸和结构形式。,2.工作中，测定构件的真实应力或变形，找出最大应力的位置 和数值，以评价工程结构的安全可靠性，并为提高设备的 工作能力提供依据。,3.对破坏或失效构件进行分析，提出改进措施，防止再次破坏。,4.测定外载的大小、方向以及各种动响应。,5.从试验中探索新的规律，并对应力分析理论和计算方法进行 校核。,实验应力分析基础,二、Brief introduction of methods in the stress analysis of experiments,1.The machinery measuring method.,The f

6、igure of measuring deformations in the book annotated by Zheng Xuan(127-200)in the east Han dynasty.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,二、实验应力分析方法简介：,1.机械量测法,东汉郑玄(127200)注释的考工记弓人中的测变形图,实验应力分析基础,Leonardo Da Vinci( 1452-1519).This picture is considered to show the earliest test in Mecha

7、nics of Materials.,The tensile test of an iron wire designed by Leonardo Da Vinci.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,里奥纳多达芬奇(14521519) 此图被认为是最早的材力试验,实验应力分析基础,里奥纳多达芬奇设计的铁丝受拉试验,tensile,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,Galileo (15641642),Fig.14 Sketch of the tensile tes

8、t of Galileo,Fig.15 Sketch of the bending test of Galileo,伽利略 (15641642),实验应力分析基础,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,Fig.37 Tensile-test machine of Mushenbluic,Fig.38 Method to clamp two ends of a tensile specimen,Mushenbluic (16921761),穆申布洛依克 (16921761),实验应力分析基础,FOUNDATIONS OF THE ST

9、RESS ANALYSIS IN EXPERIMENTS,Hydraulic verstile testing machine controlled by the computer,实验应力分析基础,2. Other methods：,Since the early 20th century,the developments of electricity,optics acousics and materials science have provided conditions for the productionof other measurement methods of the stre

10、ss analysis in experiments.Then the resistance-strain method,ordinary photoelasticity method,hologram photoelasticity method,sound launching method and so on are made fast developments and wide applications.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,2.其它方法：,20世纪初至今，电学、光学、声学和材料科学的发展，为试验应力分析其它

11、测量方法的产生创造了条件。于是，电阻应变法、普通光弹法、全息光弹法、散斑法、声发射法等方法都有了快速发展和广泛应用。,实验应力分析基础,152 Principle and application of the strainometer of the resistance,1、Resistance law :Resisance of a conductor,2、Elastic law: Land A will change after the cinductor is subjected to forces or changes in temperatures.,3、Strain foil of

12、 resistance, Sensitive coefficient,Wire-coiled strain foil,1Overburden 2Fundus 3Drawn line 4Binder 5Sensitive bar,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,152 电阻应变计法的原理及应用,一、电阻定律：导体电阻,二、弹性定律：导体受力或变温后，L、A都将发生改变。,三、电阻应变片：, 灵敏系数：,实验应力分析基础,4、Balance principle of the electric bridge,After the re

13、sistance changes：,U,R1,R2,R4,I1,2,I3,4,A,B,C,D,Bridge with the output voltage,R3,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,四、电桥平衡原理,电阻变化后：,实验应力分析基础,U,R1,R2,R4,I1,2,I3,4,A,B,C,D,电压输出桥,R3,5、Strainometer of resistance,Transform to output voltage into the magnitude of strain.,FOUNDATIONS OF THE

14、STRESS ANALYSIS IN EXPERIMENTS,五、电阻应变仪,将输出电压转变为应变读数。,实验应力分析基础,6、Arrange foils ：Make the directions of foils coincide with those of principal stresses as much as possible.,When the directions of principal stresses are un-known, the stress state of a point must be determined by three independent quant

15、ities.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,六、布片：,尽可能使片子的方向与主应力方向一致。,主应力方向未知时，必须由三个独立量才能确定一点的应力状态。,实验应力分析基础,7、Relations between the principal strains and the measured strains.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,七、主应变与测量应变之间的关系：,实验应力分析基础,Example 1 Three linear strains of a

16、 point are tested by the strain foil 45.Try to determine the principal strain of this point.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,例1 用45应变花测得一点的三个线应变后，求该点的主应变。,实验应力分析基础,45,x,y,u,Example 2 Try to determine the principal strain of a point after the three linear strains of this point are t

17、ested by the strain foil of 60。,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,例2 用60应变花测得一点的三个线应变后，求该点的主应变。,实验应力分析基础,8、Connect the bridge：,Make the stress distribute alternately;make the total bridge have a high precision and the half bridge a low precision .The half bridhe with two arms is ofte

18、n used.,9、Temperature compensation：,It is better to realize the compensation by itself; otherwise we should use the temperature compensator that is without any forces.We must make the working foil and the compensation foil in the same temperature field.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIME

19、NTS,八、接桥：,要使应力正负相间；全桥精度高，半桥精度低。常用半桥双臂式桥路。,九、温度补偿：,最好能在桥路中自补偿；否则，要用绝对不受力的温度补偿片。,工作片与补偿片要始终处于同一温度场中。,实验应力分析基础,153 Principle and application of the photoelasticity,1、Principle of the photoelasticity:,. Permanent double refraction：,. Temporary(artificial)double refraction:,FOUNDATIONS OF THE STRESS ANAL

20、YSIS IN EXPERIMENTS,153 光弹性法的原理及应用,一、光测原理：,1.永久双折射：,2.暂时（人工）双折射：,实验应力分析基础,2、Plane stress -optics law：,.Refractive index：,CStress optical coefficient of the model material,Plane polarized light,The plane polarized light passes through the model subjected to forces.,FOUNDATIONS OF THE STRESS ANALYSIS

21、IN EXPERIMENTS,So,二、平面应力光学定律：,1.折射率：,C模型材料的应力光学系数。,实验应力分析基础,平面偏振光,平面偏振光通过受力模型,. Optical path difference：,.The light intensity in the plane polarization field:,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,2.光程差：,3.平面偏振场中的光强：,实验应力分析基础,Equal inclination lines,FOUNDATIONS OF THE STRESS ANALYSIS IN

22、EXPERIMENTS,As,a black point occurs behind the analyzer.,The interference fringes formed in the locus of the black points are called equal inclination lines.,On the equal inclination lines,the directions of the pricipal stresses are same and they coincide with the polarization axle.,Pictures of the

23、plane polarization field taken every 150.The position of the colored equal color lines is not changed, but the position of the black equal inclinnation lines is changed when the polaroid rotates synchronously.,等倾线,引起的黑点的迹线形成的干涉条纹等倾线,等倾线上，主应力方向相同且与偏振轴重合。,实验应力分析基础,Equal difference lines.,The formed in

24、terference fringes-equal difference lines.,The white light is considered to be the light source and the equal difference lines aare coloured fringes, so the equal difference lines are also called equal colour lines.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,As N=0,they are called the No.0 eq

25、ual difference lines(black); as N=1,they are called the No.1 equal difference lines.,Simulating the plae part connected by screws and screw caps (method of pasting foils),等差线,形成的干涉条纹等差线,以白光为光源,等差线为彩色条纹,故等差线又称等色线,实验应力分析基础,fThe value of the fringe of a material,a、Under the repeated loading, the equal

26、inclination lines are not changed, but the equal difference lines are changed,Distinguish equal inclination lines and equal difference lines,b、If we rotate synchronously the polarizer and the analyzer, the equal inclination lines are changed and the equal difference lines are not changed.,c、Accordin

27、g to experiences,the equal inclination lines are thick(all the black) and equal difference lines are thin(a line).,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,f材料的条纹值。,a、反复加载，等倾线不变，等差线改变。,区分等倾线与等差线,b、同步旋转起偏镜与检偏镜，等倾线改变，等差线不变。,c、凭经验，等倾线较粗（一片黑），等差线较细（一条线）。,实验应力分析基础,There are no equal inclination lines in the cross circular polarization field.So the equal difference lines are clear.,FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS,Light intensity:,as,B