General Principles of Radiography :
The part is placed between the radiation source and a piece of film. The part will stop some of the radiation. Thicker and more dense area will stop more of the radiation.
The film darkness (density) will vary with the amount of radiation reaching the film through the test object.
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What Is Radiation:
X and Gamma Rays are a family of waves that are called electromagnetic waves. X-rays and gamma rays differ only in their source of origin. X-rays are produced by an x-ray generator and gamma radiation is the product of radioactive atoms. They are both part of the electromagnetic spectrum. They are waveform, as are light rays, microwaves, and radio waves. X-rays and gamma rays cannot been seen, felt, or heard. They possess no charge and no mass and, therefore, are not influenced by electrical and magnetic fields and will generally travel in straight lines. However, they can be diffracted (bent) in a manner similar to light.
General Principal Of Radiography:
1. The energy of the radiation affects its penetrating power. Higher energy radiation can penetrate thicker and more dense materials.
2. The radiation energy and/or exposure time must be controlled to properly image the region of interest.
Properties of X Ray & Gamma Rays:
Each photon contains a certain amount (or bundle) of energy, and all electromagnetic radiation consists of these photons. The only difference between the various types of electromagnetic radiation is the amount of energy found in the photons. Due to their short wavelength they have more energy to pass through matter than do the other forms of energy in the electromagnetic spectrum. As they pass through matter, they are scattered and absorbed and the degree of penetration depends on the kind of matter and the energy of the rays.
What is Radiation :
X and Gamma Rays are a family of waves that are called electromagnetic waves. X-rays and gamma rays differ only in their source of origin. X-rays are produced by an x-ray generator and gamma radiation is the product of radioactive atoms. They are both part of the electromagnetic spectrum. They are wave forms, as are light rays, microwaves, and radio waves. X-rays and gamma rays cannot been seen, felt, or heard. They possess no charge and no mass and, therefore, are not influenced by electrical and magnetic fields and will generally travel in straight lines. However, they can be diffracted (bent) in a manner similar to light.
The film darkness (density) will vary with the amount of radiation reaching the film through the test object.
The part is placed between the radiation source and a piece of film. The part will stop some of the radiation. Thicker and more dense area will stop more of the radiation.
Limitation of RT:
- Impracticable to use on specimens of complex geometry.
- Accessibility from both side required.
- Laminar type of discontinuity are often undetected by RT.
- Safety consideration imposed by X and Gamma Rays must be considered.
- It is relatively expensive & time consuming mean for NDT.
Basic Operation of RT ( Radiography Testing) :
The basic principle of radiographic inspection of welds is Penetrating radiation is passed through a solid object, like weld or casting onto a photographic film, resulting in an image of the object’s internal structure being deposited on the film. The amount of energy absorbed by the object depends on its thickness and density. Energy not absorbed by the object will cause exposure of the radiographic film. These areas will be dark when the film is developed. Areas of the film exposed to less energy remain lighter. Therefore, areas of the object where the thickness has been changed by discontinuities, such as porosity or cracks, will appear as dark outlines on the film.
What is Industrial Radiography?
Industrial radiography is a form of nondestructive testing of products, utilizing different techniques, on the foundation of x-ray technology. X-ray and Gamma radiography are similar.
Production of X-Rays: X-rays are produced due to sudden deceleration of fast-moving electrons when they collide and interact with the target Tungsten anode. In this process of deceleration, more than 99% of the electron energy is converted into heat and less than 1% of energy is converted into x-rays. X- Ray generation is very inefficient process.
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