Lecture
2Mechanics Review
1
S
TRESS
A
NALYSIS
(
Mechanics
Review)
1.
Detailed sketch of problem including dimensions and loads
Identify a righthanded coordinate system
2.
Draw freebody diagram of problem cut from supports
Include appropriate (unknown) reaction forces and moments from supports
E.g.
Roller
⇒
1 force
Pin joint
⇒
2 forces
Clamped (“builtin”)
⇒
3 forces, 2 moments & 1 torque
3.
If statically determinate, use equilibrium to determine unknown reaction forces /
moments / torques
4.
Draw freebody diagram with beam sectioned at point of interest
Include all appropriate internal forces / moments / torques
In general, there will be:
1 normal force
2 shear forces
2 moments
1 torque
But, some of these may be obviously zero and can be neglected
Sign convention:
Forces, moments and torques are positive if they act in a
positive direction on a positive face
5.
Use equilibrium to determine internal forces / moments / torques
6.
Use these forces /moments / torques to calculate all six stress components acting
at the point of interest.
Imagine cutting a cube of material from around the material
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 Fall '08
 YALISOVE
 Force, Shear Stress, Stress, zz

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