Photoelasticity

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Photoelasticity

  1. 1. Photoelasticity Submitted By Abhimanyu Kumar B.Tech(ASE-6 Sem) r180208001
  2. 2. Content• Theory of Photoelasticity• The application of photoelasticity• Limitations Conclusions
  3. 3. Theory of Photoelasticity• Photoelasticity applying a given stress state to model utilising the induced birefringence of the transparent material by polarized light examining the stress distribution Natural and polarized light Light Vector (Amplitude, Direction, Phase Angle), mixed of rays of different frequency
  4. 4. Theory of Photoelasticity • Birefringence A transparent material is birefringent if a ray of light passing through it experiences two refractive indices. The effect of this is to change the polarization state of the transmitted light to form interference fringes e Transparent Double Refraction ni sin θ = nt sin θ material i t no ≠ ne ni sin θ λt = t = o nt sin θi λi Different Optic Mechanics :” the refractive refractive indices are depended on the indices existing stress state in transparent material”Phase Angle is φ 2π = λ nl V
  5. 5. Theory of Photoelasticity Isochromatic fringes are lines of constant principal stress difference, (σ P – σ Q). Isoclinic fringes happens when principal stress direction coincides with the axis of polarisation of the polariser. “Photoelasticity can provide both magnitude and direction of principal stress and strain”
  6. 6. Theory of Photoelasticity• Basic Instrumentation Simplest , but no light pass through The analyzer
  7. 7. Theory of Photoelasticity• Circular Polariscope for Stress Opticon Specimen induced stressed Light Circular Analyzer Polarizer Circular source Polarizer Polarizer Colors
  8. 8. The application of photoelasticity Non-contact optical method for determining stresses and load paths in components or structures coating 2D investigation 3D investigation  Impact Testing  Assembly Stress Analysis  Glass Inspection  Flaw Detection  Residual Stress Analysis  FEA Model Verification Residual Stress in Glass
  9. 9. Limitations• Data Acquisition for principal stress magnitude and direction• Coating material and process for damp concrete- problem from bond failure and unknown shrinkage stress effects in concrete• The difference between thermal coefficient in coating material and concrete leads to errors to field investigation• Too sensitive to the Young Modulus and poisson’s ratio ( local effect from coating process)
  10. 10. ConclusionPhotoelasticity theory and its application are given. The examples of products from venders are described. The most practical use of photoelasticity is to qualitatively investigate the stress-strain pattern in complex specimen. The limitations of this technology is to measure the direction and magnitude of principal stress of a number of interesting locations is impractical due to the data acquisition process. The unreliability in applying the coating material in the field investigation of reinforced concrete structures due to shrinkage, thermal effect, bond, and local effect of material properties.

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