Janka hardness test
The Janka hardness test is a method for determining and classifying the hardness of wood ( wood hardness test method ). The Janka hardness test was developed by the Austrian wood technologist Gabriel Janka (1864–1932), whose life work focused on the problems of elasticity and strength of timber from 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 into the material to be tested was measured at certain pressures.
The hardness value is based on the resistance that wood opposes to the penetration of a harder body. The force measured is the force required to press a steel ball with a diameter of 11.28 mm into the wood up to half of its own diameter. The unit of measure for the degree of hardness is not uniform internationally; either Newton , Pond, or lb f is used. In the USA the hardness of wood is often given in janka , 1 janka corresponds to 1 lb f .
It should be noted that the hardness represents an average value for the respective type of wood and the variation is usually not specified. In addition, the value determined depends on whether the measurement was made in the direction of the grain or across it. Therefore, tables of Janka hardness are more suitable for comparing different types of wood with one another than for determining an absolute value.
In Germany, however, the hardness of wood is usually specified in Brinell in accordance with the ISO 3350 standard, namely in two values: across the grain (H BI) and along the grain (H BII). The unit of Brinell hardness is N / mm².
| Wood species | Latin name | Hardness in Janka | Hardness in Newtons |
|---|---|---|---|
| Pockwood | Guaiac sp. | 4500 | 20000 |
| Tabebuia | Tabebuia sp. | 3684 | 16387 |
| Lapacho | Handroanthus sp. | 3640 | 16192 |
| Ebony | Diospyros sp. | 3220 | 14323 |
| Fiber bamboo | Bamboo beach sp. | 3000 | 14002 |
| Logwood | Haematoxylum campechianum | 2900 | 12900 |
| Eucalyptus resinifera | Eucalyptus resinifera | 2697 | 12000 |
| Jatoba | Hymenaea sp. | 2350 | 10453 |
| Mesquite | Prosopis sp. | 2345 | 10431 |
| Cordie | Cordia sp. | 2200 | 9786 |
| Bubinga | Guibourtia sp. | 1980 | 8807 |
| Merbau | Intsia sp. | 1925 | 8563 |
| Jarrah | Eucalyptus marginata | 1910 | 8496 |
| Pecan | Carya illinoinensis | 1820 | 8096 |
| Afzelia | Afzelia sp. | 1810 | 8051 |
| Bangkirai | Shorea sp. | 1798 | 7998 |
| Rosewood | Dalbergia sp. | 1780 | 7918 |
| Black locust | Robinia pseudoacacia | 1700 | 7512 |
| Wenge | Millettia laurentii | 1630 | 7251 |
| Sapeli | Entandrophragma cylindricum | 1510 | 6717 |
| Swamp oak | Quercus palustris | 1510 | 6717 |
| Sugar maple | Acer saccharum | 1450 | 6450 |
| bamboo | Bambuseae | 1380 | 6139 |
| Ornamental cypress | Callitris sp. | 1375 | 6116 |
| American white oak | Quercus alba | 1360 | 6050 |
| White ash | Fraxinus americana | 1320 | 5872 |
| Red oak | Quercus rubra | 1290 | 5738 |
| Yellow birch | Betula alleghaniensis | 1260 | 5605 |
| teak | Tectona grandis | 1155 | 5138 |
| Cocobolo | Dalbergia retusa | 1136 | 5053 |
| Siberian larch | Larix sibirica | 1100 | 4893 |
| Black walnut | Juglans nigra | 1010 | 4493 |
| Paper birch | Betula papyrifera | 910 | 4048 |
| cedar | Cedrus sp. | 900 | 4003 |
| American plane tree | Platanus occidentalis | 840 | 3737 |
| African mahogany | Khaya sp. | 830 | 3692 |
| Brazilian araucaria | Araucaria angustifolia | 780 | 3470 |
| Monterey pine | Pinus radiata | 750 (625-792) | 3336 |
| Frankincense Pine | Pinus taeda | 690 | 3069 |
| Douglas fir | Pseudotsuga menziesii | 660 | 2936 |
| Red alder | Alnus rubra | 590 | 2624 |
| chestnut | Aesculus sp. | 540 | 2402 |
| Black spruce | Picea mariana | 520 | 2313 |
| hemlock | Tsuga sp. | 500 | 2224 |
| Coastal fir | Abies grandis | 490 | 2180 |
| Coast redwood | Sequoia sempervirens | 480 | 2135 |
| Linden tree | Tilia sp. | 410 | 1824 |
| White pine | Pinus strobus | 380 | 1690 |
| Balsa | Ochroma pyramidale | 100 | 445 |
Web links
- 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)