Magnetic particle testing history

YEAR

IMPORTANT STEPS

Ancient Greece

Several millenniums B.C. Greeks discovered magnetism in a mineral they called magnetite. The name ‘‘magnetite’’ comes from MAGNETOS ("the big mountain"), a Greek mountain rich in this mineral.

Ca 1000

Chinese discover the Earth magnetism and the compass.

XVIth Century

William GILBERT, a doctor of ELISABETH I of England, shows that a uniformly magnetized globe can produce a magnetic field in two poles.

XIXth Century

BERGMANN (?-?), BECQUEREL (1788-1870) and FARADAY (1791-1867) discovered that any material, including liquids and gasses react to magnetism, but that only few do so to a noticeable extent.

1800

VOLTA finds the electric battery and for the first time, sees the properties of the electric current that AMPÈRE will call "magnetic emanations".

1868

S.M SAXBY, an Englishman, describes in a paper the detection of longitudinal cracks in tubes using a magnetized needle, thus without magnetic particles.

Putting the tube in the East-West direction and making it turn while maintaining the needle at a constant distance, he saw that a crack produces a distortion of the magnetic field induced in the part by the Earth magnetic field, and as a result, a deviation of the compass needle. This very weak effect was probably improved using a permanent magnet. He called this process "damage-free inspection".

The earliest known use of magnetism to check a part: flaws were found on magnetized gun barrels by moving a compass along the length of the barrel.

1879

The American HERING uses this technique on railroad rails.

The probe invented by the North American physicist E.H. HALL (1855-1938), has been widely used in cracks detection.

End of the XIXth Century

The magnetometer, a magnetic field meter, is invented.

1906

C.W BURROWS, an American consultant of the American Bureau of Standards, is said to be the first one to use a solenoid to detect magnetic field leaks.

World War I and later

Major William E. HOKE discovers the magnetic particle crack-finding method during World War I.

William HOKE understood that magnetic particles (coloured metal chips) could be used along with magnetism as a means to locate defects.

W. HOKE is the first people to have understood and described the principle of magnetic particle testing: he noticed that tiny magnetic particles from steel part grinding had sometimes a tendency to form very clear patterns.

W.HOKE discovered that a surface or subsurface flaw in a magnetized material induced a distortion of the magnetic field that went beyond the surface of the part. In the machining area of a plant, he noticed that the metallic grindings from a hard steel part (held by a magnetic jaw while being ground) formed patterns on the face of the parts which matched to the cracks on the surface. Applying a fine ferromagnetic powder to the parts caused a build-up of powder on top of the flaw and formed a visible indication.

In the USA, HOKE noticed that fine magnetic particles produced during steel parts grinding accumulated in the metal losses due to machining when magnetic jaws were used.

Later, DE FOREST, again in the USA, made a thorough review of the data from HOKE: his most important idea has been to use a high amperage electric current to produce the magnetic field, so far produced only through permanent magnets. He also noticed that the detection of cracks in a given direction was far better if the magnetic field lines are more or less perpendicular to the cracks' plan.

Using an electric current makes it easier to match this requirement as it is sometimes possible then to choose the direction of the magnetic field lines. Further, a current flow through the part, after a DE FOREST's idea, produces a circular magnetisation almost impossible to get from a magnet.

Early '30s

MT quickly replaced the oil-and-whiting method (an early way to perform liquid penetrant inspection) as the method of choice for the railroad industry to inspect steam engine boilers, wheels, axles, and tracks.

1934

C.E. BETZ invented the TOOL STEEL RING, forerunner of the KETOS RING (Aerospace Standard AS5282).

1934 and 1935

DE FOREST: first patents for: particles of different dimensions and magnetic characteristics; particles individually coated with lubricating material; and particles coated with non-magnetic material.

1935

C.E. BETZ: formulation and manufacture improvement of the powders and pastes used in the wet method.

1937

Probe of the German physicist Friedrich FÖRSTER (1908-1999) for the detection of very weak modifications of magnetic fields due to cracks.

AC portable MPI unit for railroad parts inspection.

From 1938

During World War II, the process was massively used in the aircraft industry.

1940

Hand-held (UV-A) lamp fitted with a separate Woods glass filter.

1941

Portable HWDC unit and powder blower.

Fluorescent magnetic particles.

1942

TOOL STEEL RING, forerunner of the KETOS RING (Aerospace Standard AS5282) used in the industry.

From 1950

Spray cans for MT materials.

Ca 1950

Berthold penetrameter.

Pie gage (ASME).

1953

First MPI unit designed in France.

1960

MPI bench, output power manually set using transformers with preselected contacts. Needled ammeters.

Ca 1960

FLUXA test block.

MTU N°3 test block, listed much later as reference test pièce type 1 in ISO 9934-2:2002 standard.

Ca 1970

Moving-coil tangential magnetic field meter. (The FÖRSTER 1580 has been the reference in MT measurement for a long time).

1972

Swinging field technique on magnetic bench.

1975

Output power control of the current generator by thyristors dimmer replacing transformers.

From October 1978

Total halogens (chlorine, fluorine, then bromine) content and sulphur content checked in MT materials, according to the French Electricity Board (EDF) RCC-M code.

Ca 1980

BURMAH CASTROL™ flux strips.

Combined digital radiometer/luxmeter.

1985

Magnetic bench comprising a thyristor-controlled infinitely variable current and digital display and timers.

KETOS RING (Aerospace Standard AS5282)

1988

Michel TOITOT, a French Engineer invents the ‘‘Témoin C’’, later listed as reference test piece Type 2 in ISO 9934-2: 2002 standard.

1990

Digital tangential magnetic field meter and analyser. These meters such as the ADC3 were finally able to measure TRMS" (True Root Mean Square) magnetic fields given by thyristor-controlled magnetic benches.

By mid ‘90

Swinging field produced through AC magnetic heads on magnetic bench.

1993

Non-contact MPI technique by swinging field in 2D or 3D chamber.

1995

First AC magnetic heads in France (they have been in service for several years especially in Germany) and increased use of swinging-field benches.

Fan cooled hand-held (UV-A) lamp fitted with a separate Woods glass filter.

1996

Card with magnetic stripe for testing magnetic inspection particle material

1997

First magnetic bench comprising a computer-controlled process (better reliability and repeatability).

1999

Xenon gas discharge UV lamp.

Magnetic bench fitted with a switchboard with ‘‘prerecorded parameters’’ and automatic programmable logic controller (PLC).

February 11, 2002

Non-contact MPI technique by induced current flow.

2003

Pocket-size tangential magnetic field meter (ANALYSSE^®). Miniaturized and user-friendly meter.

2004

• Fully computerized control of MT benches.

• Friendly and easy-to-use touch screens.

• Setting and recording of preadjusted parameters.

• Automatic adjustment of current flow.

From 2006

Non-contact MPI technique by induced current flow.