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

2. Dynamic Analysis Stress

3. Force is mass * acceleration
Units?
kg m/s2=Newton
Mass is in kg
“weight” is your force on Earth (mass * g)

4. Force is a vector y x
Normal F
Fy= F . SinA A
Fx= F . CosA
Shear

5. Does applied force alone control deformation?
Land’O Lakes

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

7. How much is 1 Pascal? 1 Pa= 0.00014 psi Car tire ~200,000 Pa
1 Megapascal (1 Mpa) = 1 million Pa

8. Normal and shear components

9. Stress Components
sxx
szz
sxz
szx z x

10. Principal Stress Components
You always can find an orientation of the reference cube where there won’t be any resolved shear stresses s1 s3
Most compressive
Least compressive z x

11. Magnitude of Normal and Shear Stresses

12. 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

14. 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

15. Common States of Stress
Triaxial
Biaxial
Hydrostatic
Uniaxial

17. World Stress Map
World Stress