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Ohara-Nagakubo Lab
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A lab for non-destructive measurement that uses ultrasound to image invisible defects inside materials.
AboutAbout the lab
Unraveling complex physical phenomena to innovate measurement methods.
The Ohara-Nagakubo Lab conducts cutting-edge research on non-destructive measurement, using ultrasound to examine the inside of materials.
Building on its original technologies in nonlinear ultrasonics, phased arrays, and laser measurement, the lab aims to create measurement techniques that make visible what could not be seen before.
Drawing on international joint research, mainly with partners in Europe and the United States, the lab also aims to realize the industrial metaverse, the "digital twin."
The lab is the Materials System Measurement field of the Department of Materials System Engineering.
Key terms
- Nonlinear ultrasonics
- An ultrasonic measurement method that uses the vibration of crack faces opening and closing. It is attracting attention for measuring closed cracks
- Phased array
- An ultrasonic method that uses an array transducer with multiple piezoelectric elements to image the inside of a material
- Closed crack
- A crack whose faces are in contact, so ultrasound passes through it and conventional methods cannot measure it
NewsLab news
A fourth-year undergraduate student received a Best Poster Presentation Award
Results of joint research with the University of Strathclyde accepted by NDT&E International
A master's student received an Outstanding Presentation Award at the 13th Lecture Meeting of the Tohoku Branch of the Japanese Society for Non-Destructive Inspection
Associate Professor Nagakubo received the 2025 Kawashima Award from the Japanese Society for Non-Destructive Inspection
Paper on effective calibration of nonlinear ultrasonic phased arrays published in the Japanese Journal of Applied Physics (JJAP)
ResearchResearch themes
The lab conducts cutting-edge research on non-destructive measurement using ultrasound, which is essential for a safe, secure, and sustainable society. Building on its original technologies in nonlinear ultrasonics, phased arrays, and laser measurement, the lab aims to create measurement techniques that make visible what could not be seen before, and to realize the industrial metaverse, the "digital twin."
*Illustrative imageNonlinear ultrasonics for imaging closed cracks
In a closed crack, the crack faces are in contact, so ultrasound passes through and conventional methods cannot measure it. The lab is developing a method that combines nonlinear ultrasonics and phased arrays to turn closed cracks into images.
*Illustrative image3D imaging with ultra-multipoint laser scanning
Conventional ultrasonic phased arrays can only produce 2D images. The lab is developing PLUS, a 3D imaging method equivalent to an array of 1,000 to 10,000 elements, which transmits with a single-element transducer and receives with an ultra-multipoint 2D scan by a laser Doppler vibrometer.
*Illustrative image3D analysis of ultrasonic scattering fields
The behavior of ultrasound scattered by a defect is complex. Using the laser scanning technology of PLUS, the lab has built an algorithm that decomposes a defect into many scattering sources and extracts the 3D behavior of the wave scattered by each one.
*Illustrative imageSurface-wave imaging of surface defects
Even ultrasonic phased arrays that can image the interior have a dead zone near the surface and cannot measure it. The lab has developed a phased-array imaging method that uses surface waves instead of longitudinal or transverse waves, and it can visualize defects near the surface in real time.
MembersFaculty
Members of the Ohara-Nagakubo Lab consist of faculty, doctoral, master's, and undergraduate students, and Visiting Scientists.As of 2026
- ProfessorYoshikazu Ohara
- Associate ProfessorAkira Nagakubo
VoicesStudent voices
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “35th MXS Nondestructive Inspection Airmen ensure safety and mission readiness (9240945)” U.S. Air Force photo by Senior Airman Patrick Boyle / Public domain (cropped)
- Nonlinear ultrasonics for imaging closed cracks: “Olympus OmniScan MX2” Boevaya mashina / CC BY-SA 4.0 (cropped)
- 3D imaging with ultra-multipoint laser scanning: “VLT 4LGSF OTA L2 lens measurement on NANOMEFOS (tno kamphues 22)” F. Kamphues/TNO/ESO / CC BY 4.0 (cropped)
- 3D analysis of ultrasonic scattering fields: “TOFD-ManuallyGuidedSensors” CEphoto, Uwe Aranas / CC BY-SA 3.0 (cropped)
- Surface-wave imaging of surface defects: “Ultrasonic pipeline test” w:en:User:Davidmack / Public domain (cropped)
- Related lab (Orimo Lab): “Sodium-borohydride-3D-balls” CCoil (talk) / CC BY-SA 3.0 (cropped)
- Related lab (Narita-Kurita-Wang Lab): “Carbon fiber material” texdata.com / CC BY-SA 4.0 (cropped)
- Related lab (Sato-Suzuki Lab): “Bulkhead & Nosecone Of Orion Spacecraft Joined By Friction Stir Welding” NASA / Public domain (cropped)
- Related lab (Narushima-Ueda Lab): “Root analogue ceramic dental implant vs titanium screw type implant” Logicwhatelse / CC BY-SA 4.0 (cropped)
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