英汉双语材料力学

五、电阻应变仪 将输出电压转变为应变读数。
读 数 1234
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 quantities.
3. Analyze the destroyed or failed member and propose the measures of improvement in order to prevent it from destroying again.
4. Test the magnitude,derection and all kinds of dynamic responses of the external load.
四、电桥平衡原理
B
R1
百度文库R2
A
I1,2
CU
R4 I3,4 R3 D
电压输出桥
R1 R4 时: R2 R3
U0
电阻变化后：
UE(R1R2R3R4) 4 R1 R2 R3 R4
K4E(1234)
5、Strainometer of resistance
Transform to output voltage into the magnitude of strain. meas1 ur2 ed3 4
xy x y
Example 1
Three linear strains of a point are tested by the strain foil 45°.Try to determine the principal strain of this point.
y
u
m a 1 2(x x y)2 （ [x u ） 2 （ u y ） 2]
90°
45° 0°
60°
120°
0°
Three strain foils of 45°
Three strain foils of 60 °
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。
90°
45° 0°
60°
120°
0°
三片45°应变花
三片60°应变花
1、Resistance law :Resisance of a conductor 2、Elastic law:
R L A
Land A will change after the cinductor is subjected to forces or changes in
temperatures. T
2. Test the true stress or strain of a member in work and find 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.
§15–2 电阻应变计法的原理及应用
一、电阻定律：导体电阻
R L A
二、弹性定律：导体受力或变温后，L、A都将发生改变。
T
E
1 2 3
三、电阻应变片：
RKLK
RL Ｋ— 灵敏系数：
5
4
丝绕式应变片
1—覆盖层 2—基底 3—引出线
4—粘结剂 5—敏感栅
4、Balance principle of the electric bridge
Fig.15 Sketch of the bending test of Galileo
伽利略 (1564—1642)
Mushenbluic (1692—1761)
Fig.37 Tensile-test machine of Mushenbluic
Fig.38 Method to clamp two ends of a tensile specimen
1. 机 械 量 测 法
东汉郑玄(127—200)注释的《考工记•弓人》中的测变形图
Leonardo Da Vinci( 14521519).This picture is considered to show the earliest test in Mechanics of Materials.
穆申布洛依克 (1692—1761)
Hydraulic verstile testing machine controlled by the computer
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 stress analysis in experiments.Then the resistancestrain method,ordinary photoelasticity method,hologram photoelasticity method,sound launching method and so on are made fast developments and wide applications.
45° max
0
x
m 1 2 in (x y)2 （ [x u ） 2 （ u y ） 2]
tg202uxxyy
Example 2 Try to determine the principal
strain of a point after the three linear strains of this point are tested by the strain foil of 60°。
45° 0
max m 1 2 in (xy)2 （ [xu ） 2 （ uy ） 2]
x
tg202uxxyy
[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。
y
u
m a 1 2(x x y)2 （ [x u ） 2 （ u y ） 2]
tg20230(660011220)0
60°
120°
0°
Three strain foils of 60 °
The tensile test of an iron wire designed by Leonardo Da Vinci.
里奥纳多•达•芬奇(1452—1519) 此图被认为是最早的材力试验
里奥纳多•达•芬奇设计的铁丝受 拉试验
Galileo (1564—1642)
tensile
Fig.14 Sketch of the tensile test of Galileo
Mechanics of Materials
CHAPTER15 FOUNDATIONS OF THE STRESS ANALYSIS IN EXPERIMENTS
§15–1 SUMMARY §15–2 PRINCIPLE AND APPLICATION OF THE STRAINOMETER OF THE RESISTANCE §15–3 PRINCIPLE AND APPLICATION OF THE PHOTOELASTICITY
B
whenR1 R4 R2 R3
R1
R2
A
I1,2
CU
R4 I3,4 R3 D
U0
After the resistance changes：
UE(R1R2R3R4) 4 R1 R2 R3 R4
K4E(1234)
Bridge with the output voltage
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。
§15–2 Principle and application of the strainometer of the resistance
1.The machinery measuring method.
The figure of measuring deformations in the book annotated by Zheng Xuan(127-200)in the east Han dynasty.
二、实验应力分析方法简介：
第十五章 实验应力分析基础
§15–1 概 述 §15–2 电阻应变计法的原理及应用 §15–3 光弹性法的原理及应用
§15–１ 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.
5. Explore the new rule from tests and check the theory of stress analysis and the calculation method.
§15–１ 概 述
一、实验应力分析方法的作用： 1.设计时，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。
E
1 2 3
3、Strain foil of resistance
RKLK
RL Ｋ— Sensitive coefficient
5
4
Wire-coiled strain foil 1—Overburden 2—Fundus
3—Drawn line 4—Binder 5—Sensitive bar
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。
二、Brief introduction of methods in the stress analysis of experiments
tg20
xy x y
七、主应变与测量应变之间的关系：
x2yx2yco2s12xysin2

2
x2ysin212xyco2s
m m a inx 1 2(xy)(xy)2x 2y
tg20
7、Relations between the principal strains and the measured strains.
x2yx2yco2s12xysin2

2
x2ysin212xyco2s
m m a inx 1 2(xy)(xy)2x 2y