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History
Magnetic particle inspection
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Magnetic particle inspection (MPI) is a nondestructive testing process where a magnetic field is used for detecting surface, and shallow subsurface, discontinuities in ferromagnetic materials. Examples of ferromagnetic materials include iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current, which may be either alternating current (AC) or some form of direct current (DC).
A technician performs MPI on a pipeline to check for stress corrosion cracking using what is known as the "black on white" method. No indications of c
A technician performs MPI on a pipeline to check for stress corrosion cracking using what is known as the "black on white" method. No indications of cracking appear in this picture; the only marks are the "footprints" of the magnetic yoke and drip marks.
A close-up of the surface of a (different) pipeline showing indications of stress corrosion cracking (two clusters of small black lines) revealed by M
A close-up of the surface of a (different) pipeline showing indications of stress corrosion cracking (two clusters of small black lines) revealed by MPI. Cracks that would normally have been invisible are detectable due to the magnetic particles clustering at the crack openings. The scale at the bottom is numbered in centimetres.
A wet horizontal MPI machine with a 36 in (910 mm) coil
A wet horizontal MPI machine with a 36 in (910 mm) coil
Using a similar machine, a U.S. Navy technician sprays magnetic particles on a test part under ultraviolet light.
Using a similar machine, a U.S. Navy technician sprays magnetic particles on a test part under ultraviolet light.
Nondestructive testing
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Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing. NDT is commonly used in forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art. Innovations in the field of nondestructive testing have had a profound impact on medical imaging, including on echocardiography, medical ultrasonography, and digital radiography.
X-ray vault used in Radiography
X-ray vault used in Radiography
Chest radiography indicating a peripheral bronchial carcinoma.
Chest radiography indicating a peripheral bronchial carcinoma.
An example of a 3D replicating technique. The flexible high-resolution replicas allow surfaces to be examined and measured under laboratory conditions
An example of a 3D replicating technique. The flexible high-resolution replicas allow surfaces to be examined and measured under laboratory conditions. A replica can be taken from all solid materials.