Abstract
The non-destructive testing of structural sawn timber using the resonant frequency methods uses the natural frequency of pieces to assess the quality of test samples. This paper describes the theoretical basis of this non-destructive technique and an investigation into the suitability of this tool. The results of grading 120 pieces of gross cross-section (150 x 200 x 4,060 mm and 200 x 250 x 5,060 mm) structural timber of European black pine, (Pinus nigra subsp. salzmannii (Dunal) Franco) are shown. Furthermore, the specimens were tested for bending according to the UNE-EN 408: 2004 standard, to compare the values of strength and stiffness obtained from this test with the results estimated using the non-destructive method. PLG (the Portable Lumber Grader) developed at the Wood NDT Laboratory of the University of Western Hungary , in Sopron , was used to measure the frequency of the longitudinal stress wave. This equipment determines the frequency and the density of the specimens, and uses them, to evaluate the dynamic modulus of elasticity and to estimate the strength. For gross cross-section European black pine pieces, a strong relationship exists between dynamic modulus obtained by longitudinal vibration frequency and the mechanical properties. Acoustic measurements have become widely acceptable, because they are accurate, portable, cheap and easy to apply.
Highlights
This paper describes the theoretical basis of this non-destructive technique and an investigation into the suitability of this tool
Son de los primero equipos de investigación en desarrollar los métodos de vibración para clasificar especies utilizadas en construcción en nuestro país [8]
Determinación de los valores característicos de las propiedades mecánicas y la densidad
Summary
The non-destructive testing of structural sawn timber using the resonant frequency methods uses the natural frequency of pieces to assess the quality of test samples. PLG (the Portable Lumber Grader) developed at the Wood NDT Laboratory of the University of Western Hungary, in Sopron, was used to measure the frequency of the longitudinal stress wave. This equipment determines the frequency and the density of the specimens, and uses them, to evaluate the dynamic modulus of elasticity and to estimate the strength. Para piezas de gruesa escuadría de pino laricio existe un alto grado de correlación entre el módulo de elasticidad dinámico obtenido a partir de la frecuencia longitudinal de vibración, y las propiedades mecánicas. Palabras clave: clasificación no destructiva; métodos de vibración; frecuencia longitudinal de vibración; madera aserrada estructural de gruesa escuadría; PLG (Portable Lumber Grader). Guillermo Íñiguez González, Francisco Arriaga Martitegui, Miguel Esteban Herrero, Ramón Argüelles Álvarez
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