Outline

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Outline

• Force, vectors
• Units
• Normal, shear components
• Pressure
• Lithostatic Stress
• Stress Tensor
• Resolving stress on a plane

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Dynamic Analysis Stress
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Force is mass acceleration

• Units?
• kg m/s2Newton
• Mass is in kg
• weight is your force on Earth (mass g)

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Force is a vector
Normal
F
Fy F . SinA
Fx F . CosA
Shear
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Does applied force alone control deformation?
LandO Lakes
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Stress

• Stress force / area
• Units Pascals
• mass acceleration
• N/m2
• kg/(m . s2)

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How much is 1 Pascal?

• 1 Pa 0.00014 psi
• Car tire 200,000 Pa
• 1 Megapascal (1 Mpa) 1 million Pa

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Normal and shear components
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Stress Components
z
x
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Principal Stress Components
You always can find an orientation of the
reference cube where there wont be any resolved
shear stresses
z
x
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Magnitude of Normal and Shear Stresses
s1
Normal
s3
Shear
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In Lithostatic Stress, ?1?2?3

• Similar to hydrostatic pressure
• P ? g h
• Units are in MPa
• Be sure to work in meters
• 1 g/cm3 1000 kg/m3

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Mohr Circle of Stress
Mohr Circle of Stress
sn ½ (s1 s3) ½(s1- s3) cos 2Q ss ½(s1- s3)
sin 2Q
Mean Stress
Deviatoric Stress
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Common States of Stress
Triaxial
Biaxial
Hydrostatic
Uniaxial
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World Stress
World Stress Map
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