Drilling resistance measurement
The drilling resistance is a test tree and wood by measuring the required torque in the drilling path thin bore . The measured torque results in a measurement curve that is linearly correlated to the density.
The method is used for tree examinations , tree care and control , play equipment and wooden mast controls , timber-framed and structural timber examinations such as the wooden bridge control. Drilling resistance measuring devices are used on sawn timber as well as on living trees.
functionality
A long, thin needle (shaft diameter usually 1.5 and head diameter 3 mm) is drilled into the wood. The electrical power of one or both of the motors driving the needle is measured, recorded, stored and printed out. With a suitable choice of motors and electronic control, this power consumption corresponds to the torque at the needle, which in turn corresponds primarily to the mechanical penetration resistance at the wider needle tip. The measured values obtained in this way correlate with the density of the drilled wood (r²> 0.9), both in dry and in green wood. The measurement profiles therefore reflect the course of the gross density of the wood along the drilling path. The resulting drilling profiles reflect the relative density distribution of the wood.
After appropriate training, u. a. In wood anatomy and biomechanics , statements about the internal condition of the wood can be made from the measurement curves, among other things. a. About pressure wood , rot , cavities, cracks and other internal defects as well as about the growth of the annual rings.
Drilling resistance measurements by means of appropriate measuring devices are carried out by materials testing institutes and special companies.
disadvantage
As with all drilling examination methods, the material to be examined is damaged. In addition, a single measurement is a random sample, precise statements require (depending on the wooden body) a large number of holes in different places. Significant damage to the wooden body must therefore be accepted.
development
The method was developed by Frank Rinn in the 1980s and trademarked in the 1990s.
literature
- F. Rinn: A new method for determining tree ring parameters. Thesis. University of Heidelberg 1988.
- F. Rinn: A new drilling method for examining wood. In: Holz-Zentralblatt. 115, 34, 1989, pp. 529-530.
- F. Rinn: Device for material testing, especially wood testing by drilling or penetration resistance measurement. Patent DE4122494B4. Priority date September 3, 1990.
- D. Eckstein and U. Saß: Wood anatomical studies on drilling resistance measurements on hardwoods Wood as raw material. In: wood research. 52, 1994, pp. 279-286.
- F. Rinn, FH Schweingruber, E. Schär: Resistograph and X-ray density charts of wood comparative evaluation of drill resistance profiles and X-ray density charts of different wood species. In: wood research. 50, 4, 1996, pp. 303-311.
- Contributions by Kowohl, Kehr, Wohlers, Dujesiefken, Jaskula, Blatt, Kersten, Stobbe, Rhesa, Eckstein: Drilling processes, what happens in the tree? In: Yearbook of Tree Care. 2001, pp. 186-217.
Web links
- Wood experts association Brandenburg-Berlin: Practical comparison of examination methods for assessing tree damage . 2004 (PDF file; 576 kB)
- Hans-Joachim Schulz (2005): VTA and its technically reliable basics . Valuation forum (PDF file for download; 422 kB)
Footnotes
- ↑ Register information Register number: 2067216 at the German Patent and Trademark Office
- ↑ LG Mannheim Az. 7-O-126/99