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Outline. Force, vectors Units Normal, shear components Pressure Lithostatic Stress Stress Tensor Resolving stress on a plane. Dynamic Analysis Stress. Force is mass * acceleration. Units? kg m/s 2 =Newton Mass is in kg “weight” is your force on Earth (mass * g). y. A. x.
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Outline • Force, vectors • Units • Normal, shear components • Pressure • Lithostatic Stress • Stress Tensor • Resolving stress on a plane
Force is mass * acceleration • Units? kg m/s2=Newton Mass is in kg “weight” is your force on Earth (mass * g)
y A x Force is a vector Normal F Fy= F . SinA Fx= F . CosA Shear
F F Does applied force alone control deformation? Land’O Lakes
Stress Stress = force / area Units = Pascals = mass * acceleration = N/m2 =kg/(m . s2)
How much is 1 Pascal? • 1 Pa= 0.00014 psi • Car tire ~200,000 Pa • 1 Megapascal (1 Mpa) = 1 million Pa
szz szx sxz sxz sxx sxx szx szz Stress Components z x
s1 Most compressive s3 s3 Least compressive s1 Principal Stress Components You always can find an orientation of the reference cube where there won’t be any resolved shear stresses z x
s1 Magnitude of Normal and Shear Stresses Normal s3 Shear
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
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
Common States of Stress Triaxial Biaxial Hydrostatic Uniaxial
World Stress Map World Stress