Variation of Basic Density and Brinell Hardness Within Mature Finnish <i>Betula Pendula</i> and <i>B. Pubescens</i> Stems


  • Henrik Heräjärvi


Basic density, Brinell hardness, <i>Betula pendula</i>, <i>Betula pubescens</i>, furnishing, parquet, veneer, plywood


The objective of this study was to analyze the variation in basic density between different horizontal and vertical locations within mature Finnish Betula pendula and B. pubescens stems. In addition, the dependence of Brinell hardness in radial direction, which is of importance especially for the parquetry, veneer, and plywood industries, on the basic density was investigated. Furthermore, the sources of error in the Brinell hardness test according to EN 1534 were analyzed. Both basic density and Brinell hardness were measured from small, defect-free specimens. The average basic density of B. pendula and B. pubescens were 512 kg/m3 and 478 kg/m3, respectively. Concerning both birch species, wood material near the pith was clearly less dense than near the surface of the stem. The average Brinell hardness of B. pendula specimens was 23.4 MPa, and that of B. pubescens specimens was 20.5 MPa. Brinell hardness was found to be positively correlated with basic density. Therefore, the assumption that Brinell hardness varies within a birch stem similarly to basic density is confirmed. The test method according to the EN 1534 standard was found to be precise enough but unnecessarily laborious for hardness tests. Finally, an alternative method is suggested for determining Brinell hardness on an industrial scale.


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