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ŠUMARSKI LIST 5-6/1969 str. 20     <-- 20 -->        PDF

EFFECT OF BLUE STAIN ON THE PHYSICAL AND MECHANICAL PROPERTIES


OF AUSTRIAN PINE WOOD (PINUS NIGRA ARN.)


Summary


Within the framework of the tasks planned and according to the results of the
investigation the following conclusions are to be drawn:


1. The blue stain affects the physical and mechanical properties of Austrian
Pine wood if it has been infected in nature and exposed to conditions ruling
in the logging areas.
2. The blue stain changes the porosity of the attacked wood, which was established
by three different non-destructive methods of testing. The change
in the porosity of bluestained wood is a consequence of the action of fungal
mycelia destroying the nutritive matter in the cell and damaging cell walls.
3. The statistical values for significancy show that the differences in the same
property of sound and bluestained wood for the volume weight of standard
dry wood and the nominal density — are significant. For other physical
properties such as air-dry density of wood, linear and volumetric shrinkage,
hygroscopicity, equilibrium moisture content, water absorption and fibre-
saturation point, the mentioned differences are not statistically significant.
4. The statistical values for significancy show that the differences in the same
property of sound an bluestained wood for the hardness (Janka) in tangential
and radial planes, resistance to wear of the tangential plane (1/dt and
1/dv), compressive strength, bending strength, modulus of elasticity and
shock resistance — are significant,
5. The different durations of infection on relatively large pieces of wood have
no influence on the increase of changes of the physical and mechanical properties
of bluestained Austrian Pine wood.
6. The size of the bluestained surface — irrespective of duration of infection
— affects the physical and mechanical properties of bluestained wood of
Austrian Pine. Significant differences exist in the porosity and density of
standard dry wood, nominal density, radial shrinkage, tangential to radial
shrinkage ratio, hardness (Janka) in the direction across the grain, resistance
to wear of the tangential plane (1/dt and 1/dv), compressive stregth,
bending strength, modulus of elasticity, and in shock resistance.
7. The diminished values of the physical and mechanical properties of bluestained
wood of Austrian Pine may be the consequence of only changes in
the cell-wall structure which are caused by mycelia of bluing fungi.