Determining moisture-dependent elastic characteristics of beech wood by means of ultrasonic waves

Abstract

The present study investigates the influence of moisture content on the elastic characteristics of beech wood (Fagus sylvatica L.) by means of ultrasonic waves. A set of elastic engineering parameters (i.e. three Young's moduli, three shear moduli and six Poisson's ratios) is determined at four specific moisture contents. The results reveal the significant influence of the moisture content on the elastic behaviour of beech wood. With the exception of some Poisson's ratios, the engineering parameters decrease with increasing moisture content, indicating a decline in stiffness at higher moisture contents. At the same time, wood anisotropy, displayed by the two-dimensional representation of the velocity surface, remains almost unchanged. The results prove that the ultrasonic technique is suitable for determining the elastic moduli. However, non-diagonal terms of the stiffness matrix must be considered when calculating the Young's moduli. This is shown experimentally by comparing the ultrasonic Young's moduli calculated without, and allowing for, the non-diagonal terms. While the ultrasonic technique is found to be reliable to measure the elastic moduli, based on the measured values, its eligibility to measure the Poisson's ratios remains uncertain.

Módulos de rigidez dinámicos de siete maderas mexicanas determinados por vibraciones en torsión

“…Por otra parte, Kránitz et al (2014) emplearon ultrasonido para la determinación del módulo de elasticidad en madera de P. abies con densidad de 465 kg·m -3 y 12 % de humedad, y obtuvieron G LR = 926 MPa, G LT = 863 MPa y G RT = 107 MPa. moduli of rigidity for the longitudinal-tangential plane determined by the authors: Naruse (2003), Keunecke et al (2007), Yoshihara (2012b), Ozyhar et al (2013), Kránitz et al (2014), Nadir et al (2014) and Sotomayor (2015), for woods with densities and humidity contents similar to the ones determined in this study. Figure 3 presents a graphic comparison between the G LT determined in these studies.…”

“…La frecuencia natural es un predictor del módulo de rigidez dinámico con una correlación de G LT = 3.41ρ -7,288 y R 2 = 0.81. Los valores del G LT de las siete especies mexicanas son similares a los módulos de rigidez para el plano longitudinal-tangencial determinados por los autores Naruse (2003), Keunecke et al (2007), Yoshihara (2012b), Ozyhar et al (2013), Kránitz et al (2014), Nadir et al (2014) y Sotomayor (2015, para maderas con densidades y contenidos de humedad similares a los determinados en el presente estudio. La Figura 3 presenta una comparación gráfica entre los G LT determinados en dichos estudios.…”

“…Los resultados obtenidos en la madera de T. baccata fueron: G LR = 1,740 MPa, G LT = 1,650 MPa, G RT = 368 MPa; y en el caso de P. abies: G LR = 617 MPa, G LT = 587 MPa y G RT = 53 MPa. También Ozyhar et al (2013) utilizaron ondas de ultrasonido y determinaron el módulo de rigidez de madera Fagus sylvatica L. con densidad de 689 kg·m -3 y 9.6 % de humedad. Los módulos de rigidez obtenidos fueron: G LR = 1,370 MPa, G LT = 1,010 MPa y G RT = 430 MPa.…”

“…Regarding the modulus of rigidity, some authors such as Naruse (2003); Keunecke et al (2007); Yoshihara (2012b); Ozyhar, Hering, Sanabria, and Niemz (2013); Kránitz, Deublein, and Niemz (2014) ;Nadir, Nagarajan, and Midhun (2014) and Sotomayor (2015) have reported data from several types of wood. The information on the modulus of elasticity determined through non-destructive methods and quality indexes of Mexican wood is lacking, with the exception of Sotomayor-Castellanos, GuridiGómez, and García-Moreno (2010).…”

Comparative Analysis of the Elastic Constants Measured via Conventional, Ultrasound, and 3-D Digital Image Correlation Methods in Eucalyptus globulus Labill.

“…The reason for this is because the rest of the elastic properties of the body affect wave propagation along one direction. Ozyhar et al (2013) concluded that obtaining the stiffness matrix when taking into account only the terms along the main diagonal of the matrix led to an over-estimation of the longitudinal and transversal elastic moduli.…”