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楊氏係數測量實驗. Stresses in Solids The level of stress required to obtain a given deformation ※ Tensile stress( 伸長應力 ) , Tensile strain ( 伸長應變 ) and Young’s.

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Presentation on theme: "楊氏係數測量實驗. Stresses in Solids The level of stress required to obtain a given deformation ※ Tensile stress( 伸長應力 ) , Tensile strain ( 伸長應變 ) and Young’s."— Presentation transcript:

1 楊氏係數測量實驗

2 Stresses in Solids The level of stress required to obtain a given deformation ※ Tensile stress( 伸長應力 ) , Tensile strain ( 伸長應變 ) and Young’s modulus ( 楊氏模數 ) ※ Shear stress( 剪應力 ) , Shear strain ( 剪應變 ) and Shear modulus ( 剪力模數 ) ※ Volume stress( 體積應力 ) , Volume strain ( 體積應變 ) and Bulk modulus ( 體積彈性模量 )

3 Tensile stress( 伸長應力 ) , Tensile strain ( 伸長 應變 ) and Young’s modulus ( 楊氏模數 ) F⊥F⊥ F⊥F⊥ F⊥F⊥ F⊥F⊥

4 Stress 應力 -strain 應變 relationship 線性範圍

5 Young’s modulus ( 楊氏模數 ) , Shear modulus ( 剪力模數 ) , Bulk modulus ( 體積彈性模量 )

6 光槓桿系統 (Optical Lever ) 雷射光源 直尺 平面鏡 腳尖 圓柱狀金屬栓 ( 鎖住鋼線 ) 鋼線 L0L0 P AB C A,B C

7 L0L0 ∆d Mg A,B C

8

9 End of Lecture

10 Shear stress( 剪應力 ) , Shear strain ( 剪應變 ) and Shear modulus ( 剪力模數 )

11 Volume stress( 體積應力 ) , Volume strain ( 體積應 變 ) and Bulk modulus ( 體積彈性模量 )

12

13

14 線性範圍

15

16

17 Shear stress( 剪應力 ) , Shear strain ( 剪應變 ) and Shear modulus ( 剪力模數 )

18 血液動力學中的剪力

19 Volume stress( 體積應力 ) , Volume strain ( 體積應 變 ) and Bulk modulus ( 體積彈性模量 )

20 Young’s modulus ( 楊氏模數 ) , Shear modulus ( 剪力模數 ) , Bulk modulus ( 體積彈性模量 )

21 Stresses in Fluids Normal stress ( pressure ) compress or expand the fluid particle without changing its shape ※ Bulk modulus ( 體積彈性模量 ) Tangential or shearing stress shear the fluid particle and deform its shape ※ Viscosity ( 黏滯力 ) The viscosity of a fluid measures its ability to resist a shear stress.

22 The Nature of Fluids The fluids cannot support Tensile stresses and Shear stresses. The fluids flow and deform continuously and permanently under Shear stresses.

23 Young’s modulus ( 楊氏模數 ) , Shear modulus ( 剪力模數 ) , Bulk modulus ( 體積彈性模量 )

24

25

26 Viscosity Shear Stress ≡ Change in momentum in bulk fluids Viscosity Stresses tend to decrease the velocity of the flow on the high speed side of the layer, increase the velocity on the low speed side. 黏滯應力 ( 黏滯應力 ( Viscosity Stress ) Momentum exchange by molecular mixing

27 A shear layer near a solid wall Velocity profile in the region near a solid surface. dudu

28 Growth of a boundary layer along a stationary flat plate. Boundary layers Viscous effects particularly important near solid surfaces.

29 Laminar and Turbulent Flow

30 Figure 1.22 The no-slip condition in water flow past a thin plate. Flow is from left to right. The upper flow is turbulent, and the lower flow is laminar. With permission, Illustrated Experiments in Fluid Mechanics, (The NCMF Book of Film Notes, National Committee for Fluid Mechanics Films, Education Development Center, Inc.,1972).

31 Viscous Internal Flows

32

33 τ (y) of viscous fluids Laminar flow of viscous fluids in a circular pipe d r d x τ, P dr r

34 u

35

36 Flow rate

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38 Figure 1.17 A long flat plate moving at constant speed in a viscous fluid. On the left is shown the velocity distributions as they appear to a stationary observer, and on the right they are shown as they appear to an observer moving with the plate.

39 Surface Tension Cohesive forces≡attractive forces between molecules of the same type F =σ ( 2 l )

40 Surface Tension (a) Drop (b) Bubble Equilibrium (a) drop and (b) bubble, where the excess pressure is balanced by surface tension. ∆p∆p

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42 Capillarity Adhesive forces≡attractive force between molecules of the different type PaPa θ

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44 Figure1.25 Angle of contact. (a) Free surface shape of water and mercury in glass tubes. (b) A wetting, and a non-wetting liquid.

45 Figure 1.26 A drop of liquid squeezed between two glass plates.

46 Home Work 流體力學 chapter 1 Introduction 19, 21, 22, 26, 27, 28, 29, 31 chapter 9 Viscous Internal Flows 35, 36, 38 (a), 39 chapter 29 NMR 24, 25, 27, 29, 30, 31, 32, 33, 34, 35, 37, 39, 40, 41, 42, 43, 44


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