1. PLEASE PASS YOUR HOMEWORK TO THE CENTER ISLE TAKE EVERYTHING OFF YOUR DESKS EXCEPT A PENCIL OR PEN AND CALCULATOR: QUIZ TIME 1

2. 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!!! 2

3. QUIZ ANSWERS 3

4. LESSON 3 STRENGTH OF MATERIALS SECTIONS 1.7

5. TODAY’S LESSON WILL COVER: Shear stress and strain Bearing stress 5

6. 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). 1.Disregard frictional forces and their effects 6

7. SHEAR STRESS, SHEAR STRAIN AND BEARING STRESS To the board… 7

8. SHEAR STRESS (TAU) ACTS PARALLEL TO THE CUT SURFACE A.True B.False

9. 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? RankResponses 110 2100 312.7 418 525.5 6Other Values: 10 Value Matches: 37

10. 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) = σ b = total bearing force divided by bearing area; psi, ksi, Pa, MPa 10

11. 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: 11

12. 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 12

13. QUESTIONS? 13