21-07-2012, 12:25 PM
system for Strength and Rigidity
Design of any product based on strength and rigidity.pptx (Size: 128.37 KB / Downloads: 39)
Strength:
Strength : It is the resistance by which materials oppose the deformation.
It depends on stress and strain in the material.
Stress: A measure of the average amount of force exerted per unit area.
Stress = F/A
Where, F = force acting
A = Area.
Strain: The deformation of materials caused by the action of stress. Strain = DL/L
Where, DL = Change in dimension
L = Original dimension.
Modulus of Rigidity:
The ratio of shear stress to the displacement per unit sample length (shear strain)
Modulus of Rigidity (or Shear Modulus) is the coefficient of elasticity for a shearing force. It is defined as "the ratio of shear stress to the displacement per unit sample length (shear strain)“.
Modulus of Rigidity can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.
Choose provisional dimensions for the Shaft
The shaft's dimensions depend on:
the geometry and function of the system
the position of the shaft's bearings, which should be as close as possible to points where loads apply
When choosing dimensions
look at existing designs
consider the principles of mechanical force transmission
avoid long, slender shafts