One of the oldest nondestructive testing method of radiography start with invention of x-ray by Wilhelm Conrad Roentgen in 1895. Initialy it is used in medical applications. US army used radiography as an nondestructive testing method to inspect welds in 1930. After World War II, gamma rays and end of 1960s the neutron radiography expanded the capacity of Industrial radiography
In radiography, gamma rays and x-rays travel directly inversely proportional the square of distance. X rays and gamma rays pass the material being tested. These rays attenuates due to thickness, density and composition of the material. It is seen that thick and more dense places are light, thin and less dence places are dark in the recording media that is called film. For this feature, defects and discontiniuties seen on the film more dense than material density to identify the location.
It can be applied to iron and steel products, alloys, ceramics, plactics. It is preferred and commonly used nondestructive testing nethod in aerospace sector, shipyards, defense industry, pipelines and industrial plants. Gas voids, cracks, porosities, slag inclusions, lack of fusions, undercuts, misalignments etc are mainly production defects can be find by radiography. Sensitivity of radiography testing is depend on wavelength of radiation source, material thickness and densities and the type of film.