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PLEASE PASS YOUR HOMEWORK TO THE CENTER ISLE

TAKE EVERYTHING OFF YOUR DESKS EXCEPT A PENCIL OR PEN AND CALCULATOR: QUIZ TIME

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QUIZ

You’ll have 10 minutes to complete

Make sure your mark your answers clearly.

Put your names on the front page!

DON’T PANIC!!!

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QUIZ ANSWERS

LESSON 3

STRENGTH OF MATERIALS

SECTIONS 1.7

TODAY’S LESSON WILL COVER:

Shear stress and strain

Bearing stress

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FIRST, A COUPLE OF ASSUMPTIONS FOR THIS COURSE

Unless stated otherwise:

1. All materials are assumed to be linearly elastic, homogeneous, and isotropic (same properties in all directions).

2. Disregard frictional forces and their effects

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SHEAR STRESS, SHEAR STRAIN AND BEARING STRESS

To the board…

True

False

17%

83%

SHEAR STRESS (TAU) ACTS PARALLEL TO THE CUT SURFACEA. True

B. False

10 100

12.7 18 25

.5

90%

2% 2%2%2%

IF THE BEARING FORCE IS 10 KIP, THE BOLT DIAMETER IS 0.5 INCHES, AND THE PLATE THICKNESS IS 2 INCHES, WHAT IS THE BEARING STRESS ON THE BOLT IN KSI?

Rank Responses

1 10

2 100

3 12.7

4 18

5 25.5

6 Other

Values: 10

Value Matches: 37

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KEY TERMS, SYMBOLS, CONSTANTS, ETC.

Average Shear Stress = τ (Greek lowercase tau): total shear force divided by the area of the cross section over which it acts; parallel to surface; psi, ksi, Pa, Mpa

Shear Strain = γ (Greek lowercase gamma): distortion or change in shape of material due to shear stress; this is an angle, not a length!

Bearing Stress (or pressure) = σb = total bearing force divided by bearing area; psi, ksi, Pa, MPa

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KEY TERMS, SYMBOLS, CONSTANTS, ETC.

G = Shear Modulus of Elasticity: shear stress over shear strain; another property of a material

Hooke’s Law in Shear = τ= Gγ

Shear Modulus, Poisson’s Ratio and Modulus of Elasticity are all related:

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EG

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TAKE AWAYS

Wednesday: finish chapter 1, begin chapter 2 (read 2.1 and 2.2)

HW#2 will be posted on the wiki space by Wednesday. I’ll be due a week from Wednesday

Solutions to HW#1 will be posted this afternoon.

Register you clickers for this class

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QUESTIONS?