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  • Experiment reports


Title of the invention Ultrasonic flaw-detection method and flaw detector
Patent number No. 4672441
Registration date January 28, 2011

●The phase of reflected normal incident wave

The phase of the reflective wave is depending on the sign (plus or minus) of reflectivity obtained by the acoustic impedance of ultrasonic propagating medium and reflector.

●The setting of color display by the phase of echo

This is the setting that display the ratio of waveform in a θ coordinate (polar coordinate) using color charts, which based on a forward waveform of a probe used in the test.
It can be discriminated what kind of reflector with accuracy by the color of the phase of reflected wave.

The setting of color display by the phase of echo

We scanned an epoxy resin test piece containing a piece of metal and paper by X-Y scanning.

The phase of the reflected wave from Alumina containing steel is generally inversion, but it changes to normal inversion at the test using a spherical probe which has an adequate angle of incidence, and it can be discriminated between Alumina and void.

Title of the invention The method of a matrix crack detection in a CFRP laminate
Patent number No. 4583550
Registration date September 10, 2010

The testing of cruciform specimen

The testing of cylindrical specimen

・What is Matrix crack?

A matrix crack, also known as a transverse crack, is an internal defect of a laminate sheet which runs vertically or horizontally along the surface of medium layer which constitutes a laminate sheet.The defects are progressed by transverse crack and delamination alternately.

・Detecting method

  • 1、The conventionally method injects a contrast medium into the laminate sheet used as a test sample, applies X-ray, and looks at the shade.
  • 2、There is a problem that they need the end face for injecting a contrast medium, cannot test the sample which has no end face like a tank or a container.
  • 3、This method is able to verify the presence or absence of cracks by comparison of testing results, before and after fatigue test.

Experiment report

Report 1:Size of detectable defects by Air-coupled(Non-contact) ultrasonic Testing

Ultrasonic testing required couplant (water, oil, glycerin, etc.) to propagate ultrasonic waves to the test piece. However, this flaw detection method propagates ultrasonic waves in the air without requiring a couplant. Therefore, it is possible to use test specimens that cannot be applied to water, oil, etc.

  • Propagation of ultrasonic waves
    by transmission technique

  • System block diagram

Compared with the water immersion technique, the Air-coupled ultrasonic technique is advantageous in that a couplant unnecessary. In this report, we checked the size of defects that can be detected by Air-coupled(Non-contact) ultrasonic Testing.

A test piece of a resin plate pasting paper artificial defects of 9mm, 7mm, 5mm, 3mm in diameter was prepared. Then, the transmitter / receiver probes were placed opposite to each other, flaw detection was performed, and checked the detection situation.

Blue = Healthy part
Yellow/Red = artificial defest part

  • Test piece of a resin plate

  • Result of flaw detection

    Transmitted pulse height graph

For artificial defects up to φ3mm, since the height of the transmitted pulse was decreases, it was possible to distinguish it from the healthy parts.

Report 2:Air-coupled(Non-contact) ultrasonic Testing of 「PLYWOOD」

Bonding failure (peeling between laminations) that occurs in the bonding process of the plywood is a problem. The experiment was made to detect it by confirming state of the adhesive bonding part by Air-coupled ultrasonic flaw detection.

●In case of flaw detection of materials which is low density and has rough surface like the wood・Since wood is not suitable for water, oil, etc. as a couplant, it is necessary to conduct the test by non-couplant.
・The transmission technique is suited for the materials that ultrasonic waves are attenuated by material structures,or the direction of flaw is uneven.

Because transmission pulse height decreased in the part having poor joining (detachment between the laminates), in the flaw detection result of the photograph (lower), it was possible to distinguish the joint part (blue) from the poor joint part (yellow / red).

In addition, since the bonding part of the plywood has little influence of material noise, and the transmittance is good, a reduction of the transmission pulse height of the defective bonding portion was particularly notable.

(yellow/red) = artificial defect part

In the experiment, prepare plywood (length 450mm × width 150mm ×thickness 18mm), arrange the transmitting probe and the receiving probe in opposition, insert a plywood between them.
The transmitted ultrasonic wave passes through the plywood and receives by the receiving probe. Part or all of the ultrasonic waves are intercepted in the defective bonding portion. Therefore, received pulse heights are lower than in the healthy part.

  • The plywood used for the test

  • Peeling of adhesive part

  • Experiment situation

Report 3:Defect detection of "crack" of building materials (fireproof material)

Until now, because the transfer loss to the specimen is large, thick objects with high attenuation could not be detect flaws, but highly sensitive flaw detection became possible.

In this experiment, we prepared fireproof material (length 300mm ×width 300mm ×thickness 75mm) and affixed paper detection artificial defects φ18mm and φ15mm which simulated cracks, and confirmed the detection situation.

  • Fireproof material

  • Thickness

In the artificial defects with φ18mm and φ15mm, the transmitted pulse height decreased, and hence it was possible to discriminate from the healthy part.

(blue) = healthy part
(yellow/red) = artificial defect part

  • Surface of specimen

  • Detection result

    Transmitted pulse
    height graph