Pulse tomography

from Wikipedia, the free encyclopedia
Sonic tomography on a tree trunk. Line graphics and tomogram. The green areas represent intact, the red areas damaged areas in the trunk of a tree.
Photo and sonic tomogram of a eucalyptus tree with rot. Healthy wood is represented by brown colors. Right: The 3D graphic shows the vertical extent of a rot

In the acoustic or stress wave tomography is a non-destructive measurement method for graphic representation of the mechanical cohesion of solids. It is used, for example, to check the state of preservation of wood or concrete . The term sonic tomography is based on the noises that can be perceived by humans, which are caused by the mechanical impulses used for the measurement. The term pulse tomography, on the other hand, describes the measurement method more precisely.

features

Basis of the process are multiple pulse transit time measurements (engl .: stress wave timing ), which are linked to form a two or three dimensional measurement network. In the case of acoustic pulse tomography of trees ( see also: tree diagnosis ), vibration sensors are attached in one or more levels around the trunk or branch and their position is measured. Impulses are then induced with hammer blows and the transit times between the sensors are recorded.

The impulse speed in solids depends on the density and the modulus of elasticity of the material ( see also: speed of sound ). Internal damage, such as rot and cracks, slow down the impulses or form interfaces that make impulse passage impossible. This leads to an extension of the running times and is evaluated as a reduced speed. With the help of special mathematical algorithms , the matrix of the measured values ​​is converted into a colored or grayscale graphic (tomogram) and thus enables the extent of damage to be assessed. The accuracy of the method is determined by the number of sensors used. However, it is significantly lower than with X-ray-based computed tomography .

Devices of this type are the Arbotom , the PiCUS sonic tomograph and the Arborsonic 3D.

Web links

literature

  • Tomikawa, Y .; Iwase, Y .; Arita, K .; Yamada, H. Nondestructive Inspection of a Wooden Pole Using Ultrasonic Computed Tomography. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 1986, 33, 354-358
  • Tamura, Y .; Adachi, K .; Yanagiya, Y .; Makino, M .; Shioya, K. Ultrasonic Time-of-Flight Computed Tomography for Investigation of Wooden Pillars: Image Reconstruction from Incomplete Time-of-Flight Profiles. Jpn. J. Appl. Phys. 1997, 36, 3278
  • Lewis, CE; Matarese, JR; Turpening, RM; Zhu, Z. Acoustic Tree and Wooden Member Imaging Apparatus International Patent PCT / US99 / 04092 (1999.02.25) 1999.
  • F. Rinn: Device for material investigation. / Device for investigation materials. International patent PCT / DE00 / 01467 (1999-05-11) 1999.
  • S. Rust, L. Gätze: A new tomographic device for the non-destructive testing of standing trees. In: Proceedings of the 12th International Symposium on Nondestructive Testing of Wood. University of Western Hungary, Sopron, 13. – 15. September 2000. pp. 233-238.
  • S. Rust: Tree diagnosis without drilling. In: AFZ-The forest. Volume 56, 2001, pp. 924-925.
  • F. Rinn: Technical basics of pulse tomography. In: Baumzeitung. No. 8, 2003, pp. 29-31.
  • C. Rabe, D. Ferner, S. Fink, F. Schwarze: Detection of decay in trees with stress waves and interpretation of acoustic tomograms. In: Arborcultural Journal. Volume 28, No. 1/2, 2004, pp. 3-19.
  • C. Haaben, C. Sander, F. Hapla: Investigation of the trunk quality of different hardwood species using sound pulse tomography. In: wood technology. Volume 47, No. 6, 2006, pp. 2-5.