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NDT by Radiography in Civil Engineering

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Radiography Technique and it's application in Civil and Structural Engineering along with safety aspects.

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NDT by Radiography in Civil Engineering

  1. 1. Danish Khan 000CE11DD07 Ayush Bhardwaj 000CE11DD05 RAJIV GANDHI PROUDYOGIKI VISHWAVIDYALAYA DUAL DEGREE PG PROGRAM
  2. 2. OUTLINE  Principle  Gamma Ray Radiography  Application in Structural Engineering  X Ray Radiography  Safety Measures  Conclusion
  3. 3. INTRODUCTION Radiography Gamma Ray Radiography X-Ray Radiography Neutron Radiography Micro Radiography
  4. 4. PRINCIPLE  When radiographic rays are directed into an object, some of the photons interact with the particles of the matter and their energy can be absorbed or scattered. This absorption and scattering is called “Attenuation”.
  5. 5. ATTENUATION  The relationship between the intensity of photons incident and transmitted is: where I is transmitted photon intensity, I0is incident photon intensity, µ is attenuation coefficient, x is thickness of object
  6. 6. EFFECT OF ATTENUATION  As the radiation passes through the member its intensity is reduced according to the thickness, density and absorption characteristics of the materials within the member.  The quantity of radiation passing through the member is recorded on a film.
  7. 7. GAMMA RAY RADIOGRAPHY  Gamma rays are types of electromagnetic radiation of shorter wavelengths than visible light  Shorter wavelengths permit penetration through materials  High energy levels break chemical bonds  allows “looking” inside structures with photographic fidelity
  8. 8. ELECTROMAGNETIC SPECTRUM
  9. 9. GAMMA RAYS  Gamma radiation is the product of radioactive atoms. Depending upon the ratio of neutrons to protons within its nucleus, an isotope of a particular element may be stable or unstable.  Over time, the nuclei of unstable isotopes spontaneously disintegrate, or transform, in a process known as “radioactive decay” and such material is called “radioactive material”.
  10. 10. RADIOACTIVE DECAY
  11. 11. GAMMA RAY SOURCES USED  Two of the most common industrial gamma-ray sources for industrial radiography are Iridium-192 and Cobalt-60  Iridium 192 –  Energy : 0.317 to 0.468 MeV  upto 25 to 250 mm thick concrete  Cobalt 60 –  Energy : 1.332 to 1.173 MeV  upto 125 to 500 mm thick concrete
  12. 12. RADIOGRAM AND ITS INTERPOLATION
  13. 13. SETUP FOR CONCRETE TEST
  14. 14. APPLICATION IN STRUCTURAL ENGINEERING  Moisture Content  Detection of reinforcement location  Detection of Voids and Cracks  Detection of quality of grouted post-tensioned tendons  Measurement of bar depth and flaw depth  The failure of cables  Discontinuities of the ducts  Broken wires or cables in some cases
  15. 15. MOISTURE CONTENT  For materials with uniform thickness and porosity, the transmitted intensity of gamma rays is dependent only on the moisture content of the pores.  Find Gamma ray intensity transmitted by that same material when it is dry.
  16. 16. DETECTION OF REINFORCEMENT  Reinforcing bars absorb more energy than the surrounding concrete and show up as light areas on the exposed film.
  17. 17. DETERMINATION OF CRACKS  Cracks and voids, on the other hand, absorb less radiation and show up as dark zones on the film.  Crack planes parallel to the radiation direction are detected more readily than cracks perpendicular to the radiation direction.
  18. 18. QUALITY OF POST TENSIONED MEMBER Gammagraphy at 3 different location of bridge, Observe the marked void in upper duct of Plate 1 (dark band)  In Argentina’s largest bridge complex, Zárate-Brazo Largo,
  19. 19. MEASURING DEPTH  Depth of bar and depth of flaw can be measured by many ways :  Rigid formula Method  Single Marker Method  Double Marker Method
  20. 20. RIGID BAR METHOD B D BT , D A T D A B H D K       T - D D H K FILM PLANE FLAWCONCRETE SPECIMEN SHADOWS
  21. 21. MARKER METHOD MARKER T H K SOURCE PLANE FILM PLANE FLAW CONCRETE SPECIMEN SHADOWS B1 A B2 IF B2 = 2 B1 FLAW IS AT CENTRE
  22. 22. X-RAYS  XRAY EQUIPMENT  Three basic requirements must be met to produce X rays, namely, (a)source of electrons as a heated filament, (b)means of directing and accelerating the electrons as a high voltage supply, (c)target which the electrons can bombard, normally in the form of heavy metal
  23. 23. PRINCIPLE  The specimen absorbs radiation but where it is thin or, where there is a void, less absorption takes place. Since more radiation passes through the specimen in the thin or void areas, the corresponding areas of the film are darker.
  24. 24. X RAY TUBE
  25. 25. REQUIREMENT FOR OPERATION • the X ray tube must be powered by a stable electrical supply. Power variations in the filament and the high voltage circuit alter the spectrum and intensity of the generated X ray. • the target anode and its connecting support structure must be cooled and be designed to facilitate heat dissipation. A large rotating anode, which spreads the heat produced over a larger area of the anode, is often used to extend the serviceable life of the anode and provide a stable emission of spectra. • the electron beam emitted from the cathode and the X ray beam emitted from the anode be focused so that a narrow, high intensity beam of X rays is produced.
  26. 26. GENERAL CAUTIONS IN RADIOGRAPHY  Specifically trained and accredited persons for implementing the technique  Define a protection area around structure  Move away all the persons during the entire test
  27. 27. RADIATION PRECAUTIONS AND SAFETY  No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment that it causes.  In relation to any particular source, the magnitude of individual doses, the number of people exposed and the likelihood of incurring exposure where these are not certain to be received shall be kept as low as reasonably achievable economic and social factors taken into account  The exposure of individuals resulting from the combination of all the relevant practices should be subject to dose limits. These are aimed at ensuring that no individual is exposed to radiation risks that are judged to be unacceptable in normal circumstance
  28. 28.  The most important aspect of radiation protection, assuming that the practice is justified, is to keep radiation doses as low as reasonably achievable.
  29. 29. REQUIREMENTS  Role of Authorities  Inspection and enforcement  Safety culture  Local rules and supervision  Quality assurance
  30. 30. PRACTICAL PROTECTION  Time  Distance  Shielding  Prevention of access
  31. 31. ADVANTAGES  Both surface and internal discontinuities can be detected.  Significant variations in composition can be detected.  It has a very few material limitations.  Can be used for inspecting hidden areas (direct access to surface is not required)  Very minimal or no part preparation is required.  Permanent test record is obtained.  Good portability.
  32. 32. DISADVANTAGES  Hazardous to operators and other nearby personnel.  High degree of skill and experience is required for exposure and interpretation.  The process is generally slow.  Highly directional (sensitive to flaw orientation).  Depth of discontinuity is not indicated.  It requires a two-sided access to the component.
  33. 33. DISADVANTAGES  For application in Bridges with long span, the power required will be very high  Several hundred metres of area will need to be cleared so that no possibility of accidental exposure.  Not feasible in densely populated area
  34. 34. CONCLUSION  Gamma Ray Radiography is a powerful technique as it enables us to look inside the structure literally  possible to study concrete reinforcements with unprecedented detail and accuracy  Applications fall outside the scope of the routine inspections of reinforced concrete beams columns and slabs  Safety issues are there which needs to be taken care of properly
  35. 35. REFERENCES  Guideline on Non Destructive Testing, Ministy of Railway, Government of India  Non-Destructive Assessment of Concrete Structures: Reliability and Limits of Single and Combined Techniques - RILEM STATE- OF-THE-ART REPORTS  Guidebook on NDT, Department of Atomic Energy  Investigations With Reinforced Concrete Tomography M. A.J. Mariscotti, P. Thieberger, T. Frigerio, F. Mariscotti And M. Ruffolo Thasa

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