PSI - Issue 81

Mykola Polishchuk et al. / Procedia Structural Integrity 81 (2026) 282–286

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The expected linear dependence was confirmed by the high degree of agreement between the correlation and experimental relative strain values. Table 2 presents the main parameters of the correlation equations for the E′ – η relationship and their statistical characteristics. Table 2. Main parameters of the correlation equations for the E′ – η relationship and their statistics for all series Series Correlation equation r m r r/m r V,% І(P -0) E'=14.121(1- 0.068∙η) 0.998 0.001 734 0.27 ІІ(P -0.5) E'=12.580(1- 0.055∙η) 0.893 0.072 13 1.35 ІІІ(P -1) E'=13.111(1- 0.080∙η) 0.915 0.058 16 1.65 ІV(P -24) E'=10.603(1- 0.072∙η) 0.835 0.115 7 2.30 V(P-120) E'=11.518(1- 0.070∙η) 0.955 0.033 29 1.00 Based on the experimental studies (Fig. 3, Table 2), it was established that both the modulus of elasticity and the secant modulus of deformation decrease after water exposure compared to the untreated specimens. Specifically, the modulus of elasticity decreased by 12.2% for Series II (P-0.5) compared to Series I (P-0); by 7.7% for Series III (P-1); by 33.2% for Series IV (P-24); and by 22.6% for Series V (P-120). With increasing humidity, the main mechanical properties deteriorate, including the elastic modulus and secant modulus of deformation (Homon et al. (2023); Janiak et al. (2023)). 4. Conclusions 1. Experimental studies of pine wood specimens under single short-term axial compression along the grain with varying water exposure durations were conducted. 2. Using the experimental results and equation (1), graphs of the secant modulus of deformation versus load level after water exposure were constructed for each series. 3. Mathematical and statistical analysis confirmed a linear dependence of the secant modulus of deformation E′ on the load le vel η. 4. 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