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Navier-Stokes Equation for Solid Deformation

Analogy between Solid Deformation and Fluid Flow

Example solutions in solid mechanics and strength of material, equivalence of Structural and Fluid Mechanics: At the fundamental level, the governing equations of fluid mechanics ("relatively LARGER" deformation and kinematics of fluids particles) and structural mechanics ("relatively SMALLER") deformation and kinematics of solid particles) are equivalent.

Navier-Stokes Equation for Solid Mechanics

Navier-Stokes Equation for Solid Mechanics

Navier-Stokes Equation for Solid Mechanics


Stress-strain formula

Stress-strain formula in algebraic form

Stress-strain formula in matrix form


Deflection of Beams

The layout of a general beam with varying cross-section is shown below.

Beam Deflection Schematic

Differential equation of deflection curve:

Beam Deflection Equation

Deflection by Area-Moment Method: distance of point B on a beam from tangent at point A on the beam is equal to the moment with respect to the vertical through B of the area of the bending moment diagram between A and B divided by flexural rigidity EIZ.

Beam Area Moment

Bending of a trapezoidal plate or tapered beam subject to uniform pressure 'p':

Tapered Beam Bending

No analytical expression exists for these integrals. However, it can be integrated analytically if the tapered beam ends at zero widths (sharp edge) and is shifted to the tip instead of the base. In this case, BZ(x) = BL × (x/L).
For bending of circular disk supported at one of its diameter and under uniform pressure 'p', H = thickess of the plate and symmetric half is shown below:

Circular Plate Layout

The deflection at any location x is given by:

Circular Plate Bending Equation


Bolted Joints

  • Pre-load = tension in bolt (due to tightening) as net elongation of bolt which is difference of change in length of the bolt and compression of the clamped member.
  • Service Load = external force acting on the clamped member.
  • Bolted-joint Diagram: this is a "external force" vs. "bolt elongation" curve used to describe variation in clamping force with respect to applied force.
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