Thermal Stress: READ SEC 317

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Thermal Stress READ SEC 3-17
Thermal Strain consider free expansion of a bar
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Constrain so that it cannot expand in the
x-direction but it can expand freely in the y-and
z-directions
no friction
thermal expansion or thermal-mechanical stress
Another example would be two different materials
bonded together that have different coefficients
of thermal expansion (thermal expansion mismatch).
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Thermal Stress Constraint also occurs due to a
non-uniform temperature field in the component
under consideration. Different locations expand
different amounts, causing stress due to the
constraining effect.

• welding
• heat treatment
• operating temperature distributions and thermal
  cycling

e.g. thermal stress distribution in large slab
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Contact Stresses READ SECTION 3-19
When elements having curved surfaces or limited
contacting surfaces are pressed together,
subsurface stresses occur. Generally, there is a
tri-axial stress state under the contact and the
stresses die off far away from the contact.
Significant shear stress often occurs if there is
a tractive force between the contacting elements.
Examples rail wheel/rail contact, cam/follower
contact, roller bearings, gear teeth, etc.
High stress under contact
Analytical solutions for special geometries due
to Hertz and others (Hertzian contact stress).
Some are presented in the text.