Influence of moisture content on the wave velocity to estimate the mechanical properties of large cross-section pieces for structural use of Scots pine from Spain

Montero, M.J; Mata, J de la; Esteban, Miguel; Hermoso, Eva

doi:10.4067/s0718-221x2015005000038

Cited by 18 publications

(12 citation statements)

References 14 publications

(14 reference statements)

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“…This difference in level of E a between dynamic test methods is in line with the literature, which reports that axial dynamic stiffness in timber is typically overestimated 10-20% by Tof [25,74], and previous test results on 100 control and 100 TM boards tested 'directly' [22]. Levels of mean E a and MC of control and TM boards were inversely related (Figure 8a), and are consistent with established E a -MC relationships for unmodified timber [33,75,76]. Significant differences in mean values of E a,tof and E a,res were found between measurement intervals for control boards (one-way ANOVA, p < 0.001), but not for TM boards (one-way ANOVA, p > 0.05) (Figure 8b).…”

Section: Non-destructive Testssupporting

confidence: 89%

Performance of Thermally Modified Spruce Timber in Outdoor Above-Ground Conditions: Checking, Dynamic Stiffness and Static Bending Properties

2020

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Previous studies have shown that thermally modified wood (TMW) performs well in outdoor, above-ground conditions in terms of resistance to wood-decaying fungi. Yet, little is known about the development of defects such as checks and the corresponding mechanical properties of TMW in this condition. This experiment focused on the effect of 30 months outdoor above-ground exposure (weathering) on the degree of checking, dynamic stiffness and static bending properties of thermally modified timber (TMT) of Norway spruce. Two board pairs per log were cut from 190 logs; one board of each pair was thermally modified and the other used as control. Then, 90 board pairs were exposed to the weather in south Sweden. Surface checking and axial stiffness were monitored at six-month intervals by using digital photography and non-destructive tests (time-of-flight and resonance method) to monitor changes in the material upon weathering. Finally, all boards were tested destructively in a 4-point static bending test following EN 408 standard. Results showed that weathering had no significance influence on static bending properties of TMT even though the degree of checking was considerably higher in TMT than unmodified timber after weathering. In particular, checks along growth rings were deeper, longer and more common in TMT after weathering, especially on the pith side of boards. The maximum depth of these checks did not depend on board orientation (i.e., which side was exposed) and exceeded limits given in strength grading standards for 7% of the modified boards included. Axial dynamic stiffness determined at 6-month intervals was less influenced by fluctuations in moisture content for TMT compared to unmodified timber, but did not confirm the increase in the degree of checking of TMT. The presence of checks from weathering did influence failure modes in TMT; horizontal shear failure became more frequent and some boards failed in compression.

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Section: Non-destructive Testssupporting

confidence: 89%

Performance of Thermally Modified Spruce Timber in Outdoor Above-Ground Conditions: Checking, Dynamic Stiffness and Static Bending Properties

2020

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“…For wood we can assume that with a decrease in moisture content within 0 -FSP will increase the speed of ultrasonic (Mishiro 1995;Montero et al 2015), what was confirmed for Douglas fir, black locust, maple, poplar and alder. Thus, for these kinds of wood, the ultrasonic cannot clearly detect the initial stages of damage.…”

Section: Discussionmentioning

confidence: 82%

Ultrasonic technique for evaluation of initial stadium of wood degradation in exterior conditions without ground contact

Pánek¹,

Trgala²

2016

Forestry Journal

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The experiment evaluate the possibility of using non-destructive measure techniques of the mechanical properties of wood using ultrasonic to determine the initial stages of degradation by biotic and abiotic factors in the outdoors without ground contact. Nine tree species were tested: spruce, pine, Douglas fir, larch, oak, black locust, maple, poplar and alder. Test specimens were exposed to the exterior according to EN 927-3, Prague-Suchdol in the Czech Republic. Measuring changes in velocity of ultrasonic using the apparatus Ultrasonic Timer and moisture content change were measured after 1, 2, 3, 4 and 6 months. Certain ways of detecting the initial stages of damage have been demonstrated to trees oak, larch and spruce. The initial stages of damage by molds at non-durable maple, alder and poplar had not a clear impact on the decrease in the speed of ultrasonic, as well as hairline surface cracks at the Douglas fir.

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“…Specifically, estimating the MOE from the dynamic MOE (MOE d ) obtained from the measured ultrasonic wave velocity has been studied by many researchers. [27][28][29] However, the viscoelastic nature of wood, which leads to an increase in MOE d with frequency, causes the MOE d to overestimate the static MOE. [29][30][31][32] Thus, the accurate nondestructive estimation of the elastic properties of wood materials has remained challenging.…”

Section: Introductionmentioning

confidence: 99%

Combined machine learning–wave propagation approach for monitoring timber mechanical properties under UV aging

Nasir

Fathi

Kazemirad

2021

Structural Health Monitoring

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This study proposes a combined machine learning–wave propagation approach for nondestructive prediction of the modulus of elasticity (MOE) and rupture (MOR) of timber subjected to ultraviolet (UV) radiation. Fir, poplar, alder, and oak wood specimens were subjected to artificial UV aging and assessed using the Lamb wave propagation. Different features including the wave characteristics and the viscoelastic properties of the specimens were obtained from the Lamb wave propagation tests. The extracted features trained a decision tree model for MOE and MOR prediction. The UV radiation caused a decrease in the elastic properties of wood but increased its viscoelasticity. The results also showed a decrease in the wave velocity and an increase in the wave amplitude decay with the UV exposure time. It was revealed that compared with the wave velocity, the wave amplitude decay was better correlated to the MOE of MOR of UV-degraded wood. The MOE and MOR of UV-degraded wood were accurately predicted by the machine learning models fed by the features extracted from the Lamb wave propagation tests, where the shear storage modulus was found as the most important feature for training the models. It was concluded that the proposed approach offers a great tool for in-situ monitoring of wood structures under weathering and photodegradation conditions.

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Influence of moisture content on the wave velocity to estimate the mechanical properties of large cross-section pieces for structural use of Scots pine from Spain

Cited by 18 publications

References 14 publications

Performance of Thermally Modified Spruce Timber in Outdoor Above-Ground Conditions: Checking, Dynamic Stiffness and Static Bending Properties

Performance of Thermally Modified Spruce Timber in Outdoor Above-Ground Conditions: Checking, Dynamic Stiffness and Static Bending Properties

Ultrasonic technique for evaluation of initial stadium of wood degradation in exterior conditions without ground contact

Combined machine learning–wave propagation approach for monitoring timber mechanical properties under UV aging

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