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Explore stress functions, polynomial solutions, Airy’s stress function, and polynomial examples in elasticity theory for biharmonic equations and associated stresses in various degrees. Dive into compatibility equations and examples for practical applications.
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MER200: Theory of Elasticity Lecture 8 TWO DIMENSIONAL PROBLEMS Stress Functions Examples MER200: Theory of Elasticity
Polynomial Solution • Linear combinations of POLYNOMIALS • In X and Y • Undetermined coefficients of the stress function φ • Must satisfy biharmonic equation • Must be 2nd degree or higher • In order to yield non-zero stress function • Finding polynomials may be laborious MER200: Theory of Elasticity
Body Force is Conservative • Potential Function V exists • V causes compatibility equations to reduce to one equation with one dependent variable MER200: Theory of Elasticity
Airy’s Stress Function φ • Definitions • Φ implies that equilibrium equations are identically satisfied MER200: Theory of Elasticity
Compatibility equations can now be written • For Plane Stress • Biharmonic operator • Biharmonic equation MER200: Theory of Elasticity
Polynomial of the 2nd Degree • Form • Associated stresses • For a rectangular plate • Simple tension: c2≠0 • Double Tension: c2≠0, a2≠0 • Pure Shear: b2≠0 MER200: Theory of Elasticity
Polynomial of the 3nd Degree • Form • Associated stresses • For a rectangular plate • Pure Bending • a3=b3=c3≠0 MER200: Theory of Elasticity
Polynomial of the 4nd Degree • Form • Associated stresses • The Biharmonic Equation is satisfied if MER200: Theory of Elasticity
Polynomial of the 5nd Degree • Form • Associated stresses • The Biharmonic Equation is satisfied if MER200: Theory of Elasticity
Example 1 • Consider the beam shown. Using polynomials, determine expressions for the stresses in the beam MER200: Theory of Elasticity
Polynomial of Order 5 MER200: Theory of Elasticity
Polynomial of Degree 2 MER200: Theory of Elasticity
Polynomial of Order 3 MER200: Theory of Elasticity
Pure Bending MER200: Theory of Elasticity