Identification of the Severity and Position of a Single Defect in a Wooden Beam

Abstract

In the present paper changes of validity in Euler-Bernoulli's elementary theory of flexural vibration for homogeneous materials were tested with respect to changing severity and position of a single defect in wood. As an orthotropic material, wood has different material properties or strengths in different orthogonal directions. A set of absolutely clear specimens of oriental beech was chosen and hand drilled in different diameters (severities) at different relative distances from an end oriented in the R direction. A clear specimen showed a steady decrease in evaluated moduli of elasticity related to increasing mode numbers. After creating the defects, this steady decrease line showed some breakages. The slope breakages of modally evaluated elastic moduli in LT and LR vibrations are suggested as potential finger-prints of single hole defects in the specimen by considering the shape and rate of breakages in the decreasing lines. The recognition scenarios of slope breakages for defect severity and position are summarized.

Investigating the acoustical properties of carbon fiber‐, glass fiber‐, and hemp fiber‐reinforced polyester composites

“…It should be noted that acoustic conversion efficiency (ACE) could be considered as a key parameter to evaluate acoustic performance of a material as it comprises of both significant acoustic factors (i.e., acoustic coefficient, K , and sound quality factor, Q ). Roohnia et al used ACE values to rank acoustic performance of wide range of wood spices and expressed an excellent agreement between calculated ACE values and results obtained from practical experiences . As it can be seen from Fig.…”

“…Therefore, if a test specimen possesses a minimum damping factor value (approx. zero), it can vibrate for a long time after disconnecting the vibration source . In other words, damping factor is an indicative of the internal friction coefficient which is desired to be as less as possible for a material which would be used in sound boxes and sound boards of acoustic musical tools.…”

“…According to the ASTM 1548‐02, the dynamic elastic modulus of isotropic materials (this is also acceptable for orthotropic materials like composite samples which have been built in this research) can be calculated from the first mode of vibration which is obtained from the forced vibration test according to the below equation : where E da is the dynamic elastic modulus (Pa), f f is the first resonance frequency obtained from the forced vibration test (Hz), m is the sample weight (kg). b , h , and L are specimen's length, width, and height, respectively.…”

“…One of the promising NDT methods is called resonant vibration method in which the test specimen is mechanically vibrated in a torsional, transverse, or longitudinal vibration mode over a range of frequencies . This method has been used by some authors to investigate and analyze the acoustical performance of various species of wood .…”

Nondestructive Characterization of Dry Heat-Treated Fir (Abies Alba Mill.) Timber in View of Possible Structural Use

“…The latter finding indicates the possible presence and increase of structural inhomogeneity in the heat-treated wood, intensified also by increasing of the heat treatment temperature. The principle of slope breakage of modally evaluated moduli of elasticity was, in the past, already successfully used to recognize the severity of artificially made defects in wooden beams [48], or for the determination of density inhomogeneity along the boards of various wood species [49]. The same methodology has been proposed for detecting concentrated mass due to knottiness in solid wood [50], as well as at the determination of surface-and end-cracks in kiln dried wood [51].…”