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MER200: Theory of Elasticity Lecture 13. 2D Problems in Polar Coordinates. 2D Problems in Polar Coordinates. Polar coordinates or cylindrical coordinates are special cases of curvilinear orthogonal coordingates. Equations of Equilibrium. Radial Circumferential.
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MER200: Theory of Elasticity Lecture 13 2D Problems in Polar Coordinates MER200: Theory of Elasticity
2D Problems in Polar Coordinates • Polar coordinates or cylindrical coordinates are special cases of curvilinear orthogonal coordingates MER200: Theory of Elasticity
Equations of Equilibrium • Radial • Circumferential MER200: Theory of Elasticity
Strain-Displacement Relations • Radial • Circumferential • Shear Strain MER200: Theory of Elasticity
Hooke’s Law - Plane Stress MER200: Theory of Elasticity
Hooke’s Law – Plane Strain MER200: Theory of Elasticity
Rotation about the z-axis MER200: Theory of Elasticity
Compatibility Equations in terms of Stress Function • BiHarmonic Equation • Stress Components MER200: Theory of Elasticity
Axisymmetric Problems • Body is symmetrical about z-axis • Applied forces and/or displacements are symmetrical about z-axis • Stress and displacement independent of θ • Derivatives with respect to θ vanish • Stress functions independent of θ MER200: Theory of Elasticity
Axisymmetric Plane Problems • Bi-Harmonic Equation • Substitution reduces equation to a DE with Constant Coefficients MER200: Theory of Elasticity
Solution and Stresses • General Solution • Resulting Stresses MER200: Theory of Elasticity
CASE 1: Simply Connected Region • In order that the stresses remain FINITE at the origin • The stresses reduce to MER200: Theory of Elasticity
CASE 2: Multiply Connected • A circular cylinder with a concentric circular hole • Compatibility Equations are not sufficient to guarantee single valued displacements MER200: Theory of Elasticity
Example 1 • Consider a hollow cylinder which is subjected to the prescribed radial displacements • ur(a)=u0 • ur(b)=0 • Determine an expression for the displacements and stresses MER200: Theory of Elasticity