INVESTIGATION OF SOME MECHANICAL PROPERTIES OF PINE WOOD UNDER A RIGID TEST MODE
Keywords:
wood, compression, deformation diagrams, maximum stresses, critical and residual deformationsAbstract
Domestic and foreign works on the study of physical and mechanical properties of deciduous and coniferous wood by axial compression along the fibers are analyzed in detail.
A method of experimental studies of pine wood with a single short-term compressive load along the fibers is proposed. It allows to test such materials under a rigid mode (by increasing displacements). It is established that such experimental researches should be carried out on modern servohydraulic or electromechanical testing machines and presses.
Experimental studies of pine wood materials with a cross section of 30×30×120 mm with a standard humidity of 12 % under a rigid test mode (by increasing displacements) by axial compression along the fibers on a modern servo-hydraulic test machine STM-100. Based on the experiment, complete diagrams of the deformation “stress σс – relative deformations uc” of pine wood were constructed.
The average relative critical deformations of pine wood uc, 0, d and their corresponding maximum stresses fc, 0, d were experimentally established. The residual relative deformations of such materials uc, fin and their corresponding stresses are also determined.
The average values of the obtained indicators were established, in particular the average value of critical deformations was uc, 0, d = 0,00342; maximum stresses fc, 0, d = 39.5 MPa; residual relative deformations uc, fin = 0,301
It is confirmed that the diagrams of wood deformation «stress σc – relative deformations uc» have ascending and descending branches, as well as have characteristic points in certain areas.
With the help of such complete mechanical characteristics it is possible to determine the actual stress-strain state of reinforced and non-reinforced wooden elements and structures and to perform appropriate calculations.
References
Beliankin F. P., Yatsenko V F. Deformability and resistance of wood as an elastic-viscous-plastic body: monograph. Kyiv: Ed. AN Ukrainian SSR, 1957. 200 p.
Bykov V. V. Experimental studies of the strength and deformability of Siberian larch wood under compression and tension along the fibers, taking into account the long-term load: Izvestiya vuzov. Construction and architecture. 1967. No 8.
Da Silva A., Kyriakides S. Compressive response and failure of balsa wood. International Journal of Solids and Structures. Volume 44. Issues 25–26. P. 8685–8717.
DSTU 3129:2015. Wood. Sampling methods and general requirements for physical and mechanical testing of small defect-free samples. Kyiv: Ministry of Regions of Ukraine, 2016. 9 p.
DSTU EN 380-2008. Structural lumber. General guidelines for static load test methods. Kyiv: Ministry of Regional Construction of Ukraine, 2010. 8 p.
Gomon S. S., Savchuck V. O., Melnyk Yu. A., Vereshko O. V. Modern testing machines for investigation of wood and timber-based composite materials. Modern technologies and calculation methods in construction. Lutsk, 2020. Issue 14. P. 73–80.
Homon P. S. Approximation of the «moment-curvature» diagram of wooden reinforced and unreinforced beams of rectangular section. Urban planning and territorial planning. Kyiv: KNUBA, 2021. No 78. P. 157–165.
Homon S. S. Mathematical model for determining the limiting deformations of hardwood and coniferous species. Science and Education a New Dimension. Natural and Technical Sciences. Budapest, 2020. Sep. VIII (29), Issue 238. P. 46–50.
Homon S. S., Homon P. S. Construction of valid diagrams of the mechanical state of wood «σ-u» of a solid section of spruce and birch under a strict test regime. Resource-saving materials, constructions, buildings and structures. Rivne: NUVHP, 2020. Issue 38. P. 321–330.
Homon S. S., Homon P. S., Vereshko O. V. On determination of the critical deformations of coniferous and deciduous wood species. Urban planning and territorial planning. Kyiv: KNUBA, 2020. Issue 73. P. 78–87.
Homon S., Homon P., Karavan V. Experimental studies of coniferous and deciduous wood species with a one-time short-term compressive load along the fibers under a rigid test regime. Bulletin of the Lviv Agrarian University. Architecture and agricultural construction. 2020. No 21. P. 34–40.
Zhou A., Bian Y., Shen Y., Huang D., Zhou M. Inelastic bending performances of laminated bamboo beams: experimental investigation and analytical study. Bio Resources, 2018. 13 (1). P. 131–146.
