Effects of Tension and Compression Stresses on the Quasistatic and Dynamic Elastic Moduli of Pine Lumber

This study investigates the effects of tension and compression stresses on the quasistatic and dynamic elastic moduli of pine lumber. Utilizing prismatic specimens of Uruguayan-sourced Pinus elliottii, the research incorporates a dual-mode load frame to apply controlled tension and compression forces to the same specimens, while measuring deformation and ultrasonic pulse velocities to explore acoustoelastic effects. The results reveal that the tension quasistatic elastic modulus is statistically 4.3% higher than its compression counterpart, with the dynamic modulus showing a 0.4% increase under tension compared to compression. Additionally, aside from initial loading cycles, further tests demonstrate a positive, nearly linear relationship between dynamic modulus and stress, leading to softening under greater compression and stiffening under tension. In contrast to concrete, which exhibits more pronounced nonlinear behaviors and a hardening in compression, Pinus elliottii shares more similarities with metals like steel and aluminum in its acoustoelastic behavior. Although the sample size was limited, the methodology allowed meaningful comparisons and conceptually robust conclusions; future studies with larger data sets are encouraged to refine the quantitative estimates. Understanding these characteristics is crucial for the development of sustainable wood technology.