PSI - Issue 72

Sviatoslav Homon et al. / Procedia Structural Integrity 72 (2025) 301–307

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Fig. 3. Complete ‘stress σ с - strain u c ’ diagrams for glued coniferous wood

In Section I, the following strength values were recorded: birch σ c1 = 9.0 MPa; alder σ c1 = 7.2 MPa; ash σ c1 = 9.1 MPa; larch σ c1 = 9.6 MPa; pine σ c1 = 8.1 MPa; and spruce σ c1 = 7.4 MPa. The corresponding deformability characteristics were as follows: for birch laminated wood u с1 = 0.00071; alder u с1 = 0.00067; ash u с1 = 0.00062; larch u с1 = 0.00073; pine u с1 = 0.00064; and spruce u с1 = 0.00057. Now, let’s delve deeper into the second Section. For the prisms constructed from glued wood, the ultimate strength values measured at the upper maximum point of the diagram were: birch f c,0,d = 55.0 MPa, alder f c,0,d = 50.9 MPa, ash f c,0,d = 66.6 MPa, larch f c,0,d = 68.8 MPa, pine f c,0,d = 51.2 MPa, and spruce f c,0,d = 53.7 MPa. The critical deformations observed for birch wood were u c,0,d,exp = 0.00493; for alder u c,0,d,exp = 0.00450; for ash u c,0,d,exp = 0.00597; for larch u c,0,d,exp = 0.00672; for pine u c,0,d,exp = 0.00521; and for spruce u c,0,d,exp = 0.00453. Additionally, we calculated the critical deformations of the examined wood species using formula (2), with the results presented in Table 2.

Table 1. Experimental and theoretical values of the average critical deformations of glued wood

Wood species

f c,0,d , MPa

E 0 , MPa

u c,o,d,exp , mm/mm u c,el,th , mm/mm u c,pl,th , mm/mm u c,o,d,th , mm/mm

Birch Alder Ash Larch

55.0 50.9 66.6 63.8 52.2 53.7

15600 15800 18300 16900 14800 16200

0.00493 0.00435 0.00590 0.00672 0.00516 0.00453

0.00362 0.00322 0.00363 0.00378 0.00353 0.00322

0.00180 0.00154 0.00265 0.00242 0.00162 0.00171

0.00542 0.00476 0.00628 0.00619 0.00515 0.00503

Pine

Spruce

The differences between the experimental values of critical deformations and the theoretical values derived from the author's formula (2) for both glued hardwood and coniferous wood are illustrated in Fig. 4. In the third Section, we determined the ultimate deformations of glued hardwood and coniferous wood using formulas (3-8). The ultimate deformations at the end of this section were as follows: for birch laminated wood u c,u = 0.00802; for alder u c,u = 0.00671; for ash u c,u = 0.01036; for larch u c,u = 0.00848; for pine u c,u = 0.00711; and for spruce u c,u =0.00704. In the fourth Section, we present only the final deformations at the stresses σ с,fin = 0.1f c,0,d , as the samples were subsequently destroyed and fully unloaded. The relative residual deformations of the glued wood were as follows: for birch u c,fin =0.3349; for alder u c,fin = 0.2796; for ash u c,fin =0.4793; for larch u c,fin =0.4589; for pine u c,fin =0.3526; and for spruce u c,fin =0.3042.