X-ray inspection

Question 1

How are material inhomogenity identified by radiography?

Answer 1

They are identified due to the different absorption of the incident radiation

Question 2

How does the wavelength of X-rays influence the penetration?

Answer 2

Short wavelength means higher frequency and higher energy, therefore higher penetration depth.

Question 3

What are the two types of emission spectra?

Answer 3

• Continuous radiation: where the incident electrons are stopped by interaction with the anode and dissipate energy in the form of X-rays
• Line sprectrum: where the incident electrons provide energy to the electros, that pass to higher energies. The electrons then decay to the fundemental energy levels by emitting X-rays of energy equal to the energy jump.

Question 4

What happens when a beam of x-rays passes through an object?

Answer 4

It is absorbed in the object, with an exponential function of the thickness and density of the material

Question 5

What are the applications of radiography in NDT?

Answer 5

• Examinations of welds for detection of discontinuties
• Detection of porosity and shrinkage cracks in foundry products
• Survey of the positioning of incorporated elements, f.ex inside castings
• Searching for internal corrosion or corrosion under coatings

Question 6

What is backscattered radiation?

Answer 6

a secondary radiation that is generated by multiple reflections of the primary X-ray beam against walls and objects, even behind the analyzed sample

Question 7

What is a focal spot for X-rays?

Answer 7

It is the projection of the actual size of the beam from X-ray tube anode on the plane perpendicular to the direction of propagation of X-rays

Question 8

What is sensitivity in radiography?

Answer 8

It is defined ad the minimun detectable difference in thickness of the test material

Question 9

What are wire-type penetrameters?

Answer 9

Normally consists in a series with 16 wires with descending diameters. The radiographic image quality is indicated by the number of the minimum diameter of the wire that is visible on the radiograph

Question 10

What are plaque-type penetrameters?

Answer 10

Series of plates with increasing thickness T, each with 3 holes with d=1T, 2T, 4T. Sensitivity is based on which of the three holes is better visible on the radiographic image.

Question 11

What are X-ray tomography?

Answer 11

Reconstruction of the observed 3D item through the analysis of several projections taken from different directions, so that the location og the internal defects become possible-