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Page 1: scanfield/ME 4370 dropbox/notes... · Web viewMechanics of Materials: Hookes Law; σ=eϵ Stress: σ= F A axial τ= F A shear τ= Tr J torsion σ= My I bending Combined Stresses Shear

Mechanical Systems Review for ECE Students:

1) Materials

Metal Specific Gravity

Young's Modulus

(E)

Shear Modulus

(G)Bulk

ModulusPoisson's Ratio

Thermal Conductivi

ty0 deg.C

Linear Expansio

n Coefficie

nt

Melting Point

Proof/Yield

Stress

Ultimate.

Stress

Electrical

Resistivity

20 deg.C

- GPa GPa GPa W / ( m K ) x10-6/ deg C Deg K x 107Pa x 107Pa x10-8

ohm.mAluminium 2,7 68,95 26 75. 0,33 237 25 933 3-14 6-14 2,655Copper 8,96 117,2 46 130 0,36 398. 16,6 1357 4,7-32 20-35 1,673Gold 19,32 74,46 28. 167 0,42 315 14,2 1336 0-21 11-23 2,35

Iridium 22,42 517,1 147 6 2723 5,3

Iron 7,87 196,5 76 0,3 80,3 12 1809 16 35 9,7

Lead 11,35 13,79 6 0,43 35,2 29 600,7 1,5-1,8 20,6

Magnesium 1,74 44,13 0,35 156 25 923 4,45

Manganese 7,34 158,6 22 1517 185

Molybdenum 10,22 275,8 0,32 138 5 2893 5,2

Nickel 8,9 213,7 79. 176 0,31 90,5 13 1726 14-66 48-73 6,85Silver 10,50 72,39 28. 100 0,37 427 19 1234 5,5-30 14-38 1,59

Sodium 0,97 134 70 370,98 4,2

Steel (Mild) 7,8 210 80 0,3 50 12 1630-1750 20-40 30-50 10

Tin 7,31 41,37 17. 52 0,33 67 20 505 0,9-1,4 1,5-20 11,0Titanium 4,54 110,3 41. 110 0,3 22 8,5 1943 2-50 25-70 43

Tungsten 19,3 344,7 140 0,28 178 4,5 3673 100-400 5,65

Table 1: Tensile strength and Young’s modulus for selected materialsmaterial tensile strength MPa modulus of elasticity GPa304 stainless steel 500 200

copper 270 12096% alumina 200 340aluminium 90 70Sn63 solder 35 30epoxy resin 40 3silicone rubber 10 0.003

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Figure 7: The block slip model, showing behaviour of metals under stress

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Mechanics of Materials:

1) Hookes Law; σ=eϵ2) Stress:

a. σ=FA axial

b. τ=FA shear

c. τ=TrJ torsion

d. σ=MyI bending

3) Combined Stresses

4) Shear and Moment

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5) Allowable stress in design

a. σ a=SFS

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Kinematics and Dynamics:

Particle Motion:s=∫ v (t )dt=∬a (t )dt

For constant accelerations

1-D constant Acceleration equations:

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Describing MotionCartesian Coordinates Polar Coordinates:

Motion composed of two components:

Translation Rotation

Kinematics of Multi BodiesLinks Joints

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Degrees of Freedom / Mobility

Linkages:

4-bar Slider-crank

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Notes:

1) Nonlinear2) Toggle positions3) Mulitple solutions4) Forces governed by5)

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Cam systems:Automotive, manufacturing, rocking chairs, garage doors, door latches

Constant-velocity transmissions:Most common:Gear trains, belts & pulleys, gears & sprockets

Governing equation: θ1θ2

=−N 2

N1

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