Thermal, Hoop, and Torsional Stress Flashcards
What is thermal expansion?
When an object experiences length, area and volume changes because of a change in temperature.
What is the magnitude of the thermal expansion changes dependent on?
The coefficient of thermal expansion.
What dimensions are affected by the change in temperature
All dimensions are affected buy the change in temperature.
What does an increase in temperature do in thermal expansion?
Will cause an increase in the dimensions.
What does an decrease in temperature do in thermal expansion?
Will cause a decrease in the dimensions.
How is the thermal strain handled?
The thermal strain is handled in the same manner as strain due to an applied load.
What is the thermal strain equal to?
It is equal to the thermal coefficient of expansion multiplied by the difference in temperature.
How is the thermal strain related to the thermal stress?
Hooke’s Law can be used.
What kind of stress do cylindrical tanks experience under internal pressure?
Circumferential, longitudinal, and radial stresses.
When is the radial stress component negligible for cylindrical thinned walls?
If the wall thickness is small.
When can a tank be considered to be a thin walled tank?
If the ratio of the thickness to internal radius is less than approximately 0.1.
When can a tank be considered to be a thick walled pressure vessel?
A cylindrical tank with a wall thickness to radius ratio greater than 0.1.
How do tanks under external pressure usually fail?
Buckling.
Can thin walled equations be used for tanks under external pressure?
No
What is hoop stress?
Circumferential stress.
Under what conditions is hoop stress under?
For thin walled tanks under internal pressure.
What is the axial stress in cylindrical tanks?
Stress in the direction of its axial or longitudinal dimension.
When is there axial stress in cylindrical tanks?
When the cylindrical tank is closed at the ends..
What are the principal stresses in tanks?
The hoop and axial stresses.
Under what condition are the hoop and axial stresses the principal stresses?
For pressure vessels when internal pressure is the only loading.
When is the stress in the outside surface zero?
It is zero for three dimensional shells.
What is the largest shear stress in three dimensions?
Half the hoop stress.
What is the orientation of the shear stress on three dimensional tanks?
45 degrees to the surface.
Is there a difference with direction in the surface or tangential stress for thin walled spherical tanks?
It is the same in all directions because of symmetry.
What is Lame’s solution?
This method shows that the radial and tangential stresses vary with location within the tank wall.
What are the principal stresses in thick walled pressure vessels?
At every point in the cylinder, the tangential, radial, and longitudinal stresses.
When is it not necessary to use the combined stress equations?
in the absence of an external torsional shear stress.
Where do the maximum radial, tangential and shear stresses occur?
At the inner surface for both internal and external pressurization.
What kind of stresses does thick walled cylinder with internal pressurization experience?
Radial, tangential and axial.
What kind of stresses does thick walled cylinder with external pressurization experience?
Tangential and radial.
What is torsion?
When a shaft experiences shear stress
What is the angle of twist?
If a shaft carries a torque.
What is the angle of twist units?
It is found in radians and must be converted to degrees.
How does the shear stress act due to torsion in thin walled non circular shells?
Around the perimeter of the tube.
Is the shear stress proportional to the distance from the centroid of the cross section for thin walled shells under torsion?
No
What is the shear flow?
Is the shear per unit length of the centerline path.
Is the shear flow around the shell constant?
Yes whether the wall thickness is constant or variable.
