Janka hardness test

The Janka hardness test is a method for determining and classifying the hardness of wood (wood hardness test ). Developed the Janka hardness test of the Austrian wood technologists Gabriel Janka (1864 - 1932), whose life work was the problems of the elasticity and strength of timbers of various Austrian growth areas. The method he developed was a modification of the Brinell hardness test, in which the depth of penetration of steel balls in the material under test was measured at certain pressures.

The hardness value may vary depending upon the resistance, the wood opposes the penetration of a harder body. Measuring the force required to depress a steel sphere having a diameter of 11.28 mm up to half of its own diameter in the wood. The unit of measurement of the degree of hardness is not internationally standardized; it is needed either Newton, Pond or pound -force ( lbf ). In the U.S., the hardness of wood is often expressed in Janka, Janka 1 corresponds to 1 lbf.

Note that the hardness is an average value for the particular type of wood and the dispersion is usually not given. Also from the determined value is dependent on whether measured in the fiber direction or transversely thereto. Therefore tables of the Janka hardness are more suitable for comparing different types of wood with each other for the determination of an absolute value.

In Germany, the hardness of wood, however, is usually given according to the standard ISO 3350 in Brinell, in two levels: cross -machine direction (H BI) and along the grain (H BII ). The unit of Brinell hardness is N / mm ².

Websites

  • New methods of wood and tree-ring analysis and applications in environmental research by Rupert Wimmer
  • Janka hardness scale ( English)
  • Janka Hardness Scale for Wood ( English)
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