Acoustic measurement differences on trees and logs from hardwoods in wet and dry condition

peer-reviewedAcoustic velocities measured on standing trees using time-of-flight (TOF) devices have been found to be between 7% and 36% higher for softwoods than those in logs using resonance techniques based on longitudinal frequencies. This effect was explained in three different ways: (1) TOF devices on standing trees measure outerwood containing more mature wood while resonance methods assess the whole crosssection, (2) the variation in the velocity is due to loading conditions in standing trees, while logs are free of loads and (3) the acoustic waves are dilatational waves in the case of TOF measurements on standing trees and one-dimensional longitudinal waves in the case of resonance on logs. This is an important topic considering the fact that resonance methods are considered more accurate for predicting mechanical properties and it has been proposed that correction factors should be applied on TOF measurements. In the present work, four hardwoods from Irish forests were studied and, on average, TOF velocities measured in the forest above fibre saturation point (FSP) were 19.8% higher than those from resonance measurements taken on logs immediately after felling. However, this difference reduced to 5.4% when the measurements were repeated at a moisture content (MC) of about 18% in the laboratory. Therefore, there is a MC effect on the velocity differences. Furthermore, higher differences were systematically found in older specimens in wet condition. However, this age effect was small in most cases

Nondestructive testing used on timber in spain: A literature review

Nondestructive testing (NDT) includes several highly efficient techniques for the estimation of the physical and mechanical properties of structural timber. Apart from visual grading, scientific research using Nondestructive testing on timber has been used in Spain since the 1990s. Nondestructive testing can be used for two different purposes: timber grading and the assessment of existing timber structures. The most common devices used in Spain are portable ones based on ultrasound, stress waves, vibration and probing techniques. Many statistical linear models for estimating the mechanical properties of new sawn timber and timber from existing structures have been proposed. Furthermore, several factors that affect Nondestructive testing measurements have been studied (moisture content, temperature, specimen dimensions, sensors position-grain angle…) and adjustment factors have also been proposed. Species have been characterized for visual grading standards from the 1980s to date. The large number of research works using different species, devices and procedures shows the need of homogenization and standardization of Nondestructive testing use. This paper presents a review of research works using Nondestructive testing on timber in Spain, in order to add to knowledge, elucidate the concepts to unify Nondestructive testing used and promote research group collaboration in the near future

Use of non-destructive test methods on Irish hardwood standing trees and small-diameter round timber for prediction of mechanical properties

peer-reviewedKey message Mechanical properties of small-diameter round timber from hardwood thinnings of common alder ( Alnus glutinosa (L.) Gaertn.), European ash ( Fraxinus excelsior L.), European birch ( Betula pendula Roth. and Betula pubescens Ehrh.), and sycamore ( Acer pseudoplatanus L.) can be evaluated by non-destructive testing on either standing trees or green logs without wood density determination. Velocity differences between acoustic and resonance methods are influenced by tree species and age. Tree diameter improves the estimation of bending strength but not of stiffness. Context There is a need for a reliable, fast, and inexpensive evaluation method to better sort hardwood thinnings according to mechanical properties for use in potential added-value applications. Aims The estimation by non-destructive testing of mechanical properties of round small-diameter timber of four hardwood species (common alder, European ash, European birch, and sycamore). Methods Acoustic velocity was measured in 38 standing trees and resonance velocity was recorded in green logs from these trees. The logs were then dried and tested in bending. Estimation models to predict mechanical properties from non-destructive testing measurements were developed. Results Large differences between velocities from acoustic and resonance techniques were found. Models based on both non-destructive testing velocities together with a species factor are well correlated with bending modulus of elasticity while models including tree diameter are moderately well correlated with bending strength. Inclusion of density in the models does not improve the estimation. Conclusion Models based on acoustic measurements on standing trees or resonance on green logs together with tree species and diameter provide reliable estimates of mechanical properties of round timber from hardwood thinnings. This methodology can be easily used for pre-sorting material in the forest

A Note on Twistor Gravity Amplitudes

In a recent paper, Witten proposed a surprising connection between perturbative gauge theory and a certain topological model in twistor space. In particular, he showed that gluon amplitudes are localized on holomorphic curves. In this note we present some preliminary considerations on the possibility of having a similar localization for gravity amplitudes.Comment: 14 pages, 6 figures. v2: minor changes, added referenc

Mechanical properties estimation by non-destructive testing of Irish hardwood round timber from thinnings for construction purposes

Thinning involves the removal of competitors of high quality trees, and trees for extraction racks, all to favour the growth of the selected trees. Many felled trees are small-diameter and in Ireland hardwood thinnings are mainly used for energy production (DORAN 2012; MOCKLER 2013) or for wood-based panels or in the pulp industry (CAMPION AND SHORT 2016). Since the 1990's the Irish Government has been encouraging private owners to combine agricultural and forest commercial activities. Grant aid was initially provided each year for the first 20 years (nowadays 15) in order to compensate the loss of agricultural land use. Furthermore, the first and second hardwood thinning is also grant aided. There is commercial value in seeking to use hardwood thinnings in higher value-added end uses as structural components within the construction industry and to develop its volume use in local rural industry (WOLFE AND MOSELEY 2000; CUMBO ET AL. 2004; GORMAN ET AL. 2016). The Exploitation And Realisation of Thinnings from Hardwoods (EARTH) project aims to investigate potential added-value uses of hardwood thinnings and develop a grading system for sorting into different classes, estimating mechanical properties using non-destructive testing (NDT).EARTH project has been funded by the Department of Agriculture, Food and Marine’s Competitive Research Funding Programmes (COFORD). Project reference: 15C666.peer-reviewe

Recovered wood as raw material for structural timber products. Characteristics, situation and study cases: Ireland and Spain

The circular economy is an efficient system to reuse materials reducing the amount of waste generated. In order to implement it in the timber sector, the InFutUReWood (Innovative Design for the Future Use and Reuse of Wood (Building) Components) is a European project studying the possibilities for reuse and recycling of timber from demolition for structural applications. Nowadays in Ireland and Spain, most of the wood waste is reduced to chips. In Ireland, chips are mainly used for energy production, pallet blocks, and composting, while in Spain are used for energy production and particleboard manufacture. Possible structural applications depend on the amount, dimensions, and condition of recovered timber. Most of the recovered timber in Ireland has medium size cross-sections, while in Spain it is mainly large cross-section. Cross laminated timber (CLT) is a good option for reuse and experimental tests are ongoing in Ireland on CLT manufactured from old timber trusses. However, for large cross-sections, direct reuse for rehabilitation works will be a more efficient use of the material.ProjectInFutUReWood is funded in Spain by the Ministerio de Ciencia, Innovación y Universidades (MICIU). Project reference PCI2019-103544. Diseño innovador para el futuro – uso y reutilización de componentes de edificación de madera. Project InFutUReWood is funded in Ireland by the Department of Agriculture, Food and the Marine under the DAFM research funding program. Project reference 18CENForestValue1. Project InFutUReWood is supported under the umbrella of ERA-NET Cofund Forest Value by Vinnova – Sweden´s Innovation Agency, Formas– Swedish Research Council for Sustainable Development, Swedish Energy Agency, the Forestry Commissioners for the UK, the Department of Agriculture, Food and the Marine for Ireland, the Ministry of the Environment for Finland, the Federal Ministry of Food and Agriculture through the Agency for Renewable Resources for Germany, the Ministry of Science, Innovation and Universities for Spain, the Ministry of Education, Science and Sport for Slovenia. Forest Value has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement N° 773324. The authors would like to thank Mr. Paul Hogan from Hegarty Demolition (InFutUReWood Irish industrial partner), and demolition and waste management companies from Ireland and Spain for kindly supplying information.non-peer-reviewe

Acoustic wave velocity in long pieces of Salzmann pine for in-situ structural assessment

9 Pág. Instituto de Ciencias Forestales (ICIFOR)In-situ assessment of timber members by acoustic measurement usually requires specific procedures (indirect and semidirect measurement) compared with those used in the laboratory (direct) and over longer distances. This research aims to determine which procedure is the most suitable. Acoustic Non-Destructive Testing measurements were taken in 21 150 × 200 mm2 nominal cross-section Salzmann pine structural timber pieces from 9.5 to 11.0 m long from a 1768 structure. Wave velocity was obtained from ToF measured with different sensor arrangements (direct, indirect and semidirect) in different lengths using stress wave and ultrasound. The direct velocity value was very close to non-direct measurements (0.4% higher), while previous research works with shorter pieces (3–4 m) showed larger differences (3.3–5.4%). There were no significant differences between indirect and semidirect measurements when using the same device or between devices, although a steady ratio was observed in the last case. The most predictive velocity procedure was determined by the correlation between static and dynamic modulus of elasticity. The most reliable stiffness prediction was obtained with the global velocity method, taking ToF measurements at distances from 1 to 10 m. A second method was proposed, consisting of taking only 2 measurements, and it achieved practically the same predictive capacity.Ministerio de Economía y Competitividad [Spanish Ministry of Economy and Competitiveness]. Plan Nacional I + D 2013-2016.Proj.: BIA 2014-55089-P. Mr. Antonio Arce from Intrama S.A. for the free supply of timber. Partial financial support 2020 by Timber Construction Research Group, Universidad Politécnica de Madrid, SpainPeer reviewe