The Results of Experimental Studies of the Apparent Density of Wood

The article presents the results of experimental studies of the apparent density of wood obtained under various operating modes of the pneumatic measurement system. A new technique and experimental unit have been used for the research to determine the apparent volume of porous bodies in an atmospheric air environment. For the experiments, samples of aspen, spruce, birch, pine and oak wood taken from the sapwood of tree stems have been used. The functional stability of the developed method for determining the apparent volume of porous bodies has been experimentally confirmed. Using the developed experimental unit, the apparent volumes have been measured and apparent densities of wood samples of various species have been calculated under conditions of overpressure and underpressure of the system operation. In the overpressure mode, the pneumatic system has operated at +70 and +90 kPa, and in the underpressure one at –70 and –90 kPa, respectively. It has been experimentally established that when operating the measurement system in the underpressure mode, the apparent density of wood is higher than in the overpressure mode. The values of apparent densities determined in the underpressure mode vary within the range of 1.361 to 1.434 g/cm3 for aspen, 1.151 to 1.348 g/cm3 for spruce, 1.356 to 1.402 g/cm3 for birch, 1.298 to 1.444 g/cm3 for pine and 0.99 to 1.147 g/cm3 for oak. The corresponding values of apparent densities determined in the overpressure mode have been 1.316 to 1.372 g/cm3 for aspen, 1.106 to 1.274 g/cm3 for spruce, 1.292 to 1.356 g/cm3 for birch, 1.285 to 1.412 g/cm3 for pine and 0.904 to 1.138 g/cm3 for oak. Thus, the hypothesis about the priority of applying the underpressure mode when determining the apparent volume of porous bodies in the atmospheric air environment has been confirmed. The magnitude of the largest deviation in the results between the highest and lowest values of apparent density when determined in different modes has been, respectively: for aspen – 6.83 %, for spruce – 8.54 %, for birch – 6.35 %, for pine – 6.82 % and for oak – 3.91 %. The magnitude of the largest deviation between the maximum values of apparent density and the generally accepted value of 1.46 g/cm3 have been, respectively: for aspen – 1.78 %, for spruce – 7.67 %, for birch – 3.97 %, for pine – 1.1 % and for oak – 21.44 %.

wood, apparent density, measurement system, measurement modes, overpressure, underpressure