| 1. |
- Hu, Min, 1979-, et al.
(författare)
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Comparison of local variation of modulus of elasticity determined on basis of scanned fiber angles and full strain field measurements
- 2013
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Ingår i: The 18th International Nondestructive Testing and Evaluation of Wood Symposium. - Madison, WI, USA.
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Konferensbidrag (refereegranskat)abstract
- Strength grading methods are normally based on relationships between one measured value of modulus of elasticity (MOE), regarded as being valid for the whole board, and bending strength. Studies have shown, however, that with a detailed knowledge of local variation of MOE within boards, a highter coefficient of determination (R2) with respect to bending strength can be obtained. Measurements of fiber angles from laser scanning has shown to be a powerful tool to establish MOE profile along boards in a speed that cooresponds to the production speed at a sawmill. The present study aims at investigating the accuracy of the local MOE profile determined on basis of fiber angles from laser scanning. The study was carried out on a board of Norway spruce of dimension 50 by 150 by 3,900 mm. First the fiber angles on all four surfaces were identified using a WoodEye scanner and on the basis of these measurements, a MOE profile was calculated. Thereafter, the board was subjected to a constant bending moment and suring loading an image correlation system, Aramis, was employed for detection of the strain field with high resolution along the whole board. This strain field was then used to estanlish a 'true' MOE profile along the board. The MOE profiles determined in two different ways were compared and they show a close compliance. However, some difference were found and these were used for calibration of the method for MOE determination on the basis of scanning results. The present research thus contributes further improvement of a newly suggested grading method.
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| 2. |
- Hu, Min, et al.
(författare)
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Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation measurement and scanned fibre orientation
- 2014
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 73:1, s. 17-27
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, the utilization of non-contact deformation measurement systems based on digital image correlation (DIC) has increased in wood related research. By measuring deformations with DIC systems, surface strain fields can be calculated. The first aim of this study concerns the possibility to detect detailed strain fields along the entire length of a wooden board subjected to pure bending and the potential of using such strain fields to determine a bending modulus of elasticity (MOE) profile along a board. Displacements were measured over 12 subareas along a flat surface of the board. For each such area, a separate local coordinate system was defined. After the transformation of locally measured coordinates to a global system, high resolution strain fields and a corresponding bending MOE profile were calculated. A second method in establishing bending MOE profiles is to use fibre angle information obtained from laser scanning and a calculation model based on integration of bending stiffness over board cross sections. Such profiles have recently been utilized for accurate strength grading. A second aim of this study was to investigate the accuracy of the bending MOE profiles determined using the latter method involving fibre angle information. Bending MOE profiles determined using the two described methods agree rather well. However, for some patterns of knot clusters, the local bending MOE, calculated on the basis of fibre angles and integration of bending stiffness, is overestimated. Hence, this research adds knowledge that may be utilized to improve the newly suggested strength grading method.
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| 3. |
- Karlsson, Stefan, 1984-, et al.
(författare)
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Single-Side Ion Exchange Strengthening of Holed Float Glass
- 2012
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Ingår i: Nordic Conference on Ceramic and Glass Technology.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The fracture strength of oxide glasses is to a large degree influenced by other factors than the inherent strength of the bonds in the vitreous network such as surface defects. Due to the brittle nature of glass, mechanical processing decreases the strength substantially. The aim of this study was to investigate ion exchange strengthening also known as chemical strengthening of commercially available mechanically processed soda-lime-silicate float glass and to compare it with as-received float glass by means of flexural fracture load. The dimensions of the samples were 66±2 x 66±2 mm and two series had 7 mm diamond drilled holes in the centre of each sample while one series was as-received. Ion exchange of sodium ions by larger potassium ions were performed by treating the air-side of a series of samples with a KNO3:KCl mixture at 450 °C. The flexural fracture load of both untreated and ion exchanged holed samples was measured by means of the coaxial double ring test. The ion exchanged samples showed an arithmetic mean fracture load increase of approximately 140% compared to untreated holed float glass. The drilled hole decreases the arithmetic mean fracture load to approximately 25% of as-received float glass whilst the strengthening effect of the ion exchange improves it to around 65% of as-received float glass.
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| 4. |
- Karlsson, Stefan, 1984-, et al.
(författare)
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The effect of single-side ion exchange on the flexural strength of plain and holed float glass containing a drilled hole
- 2013
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Ingår i: European Journal of Glass Science and Technology. Part A: Glass Technology. - 1753-3546. ; 54:2, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- The effect of single-side ion exchange (using a KNO3:KCl mixture) on the ring-on-ring flexural strength of float glass has been studied. Two ion exchanged series, treated at 450 and 515°C, were investigated. The ion exchanged samples showed approximately 160 respectively 100% increases in their arithmetic mean strength compared to as-received float glass. Furthermore, a series of samples containing drilled holes were studied in order to investigate the effect of single-side ion exchange on such common construction elements. The samples that contained drilled holes were ion exchanged at 450°C and showed around 140% increase of the fracture load compared to the untreated samples containing drilled holes. As a general observation, the ion exchange treatment induced ~110 MPa compressive stresses (515°C) and ~180 MPa compressive stresses (450°C). The ion exchanged samples showed no significant increase in stiffness.
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| 5. |
- Olsson, Anders, 1973-, et al.
(författare)
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Förfarande och anordning för utvärdering av en bräda av trä
- 2014
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Patent (populärvet., debatt m.m.)abstract
- Föreliggande redogörelse avser en metod och en anordning för utvärdering av en bräda av trä med en ländriktning. Data som indikerar fiberorienteringen över brädans yta inhämtas och för ett antal underpartier hos brädan bestäms en nominell, lokal elasticitetsmodul, MOE, på basis av nämnda fiberorienteringsdata och en nominell materialparameter. En nominell global MOE i längdriktningen för träbrädan i sin helhet genereras och jämförs med en sekundär global MOE. På basis av nämnda fiberorienteringsdata och denna jämförelse genereras en uppskattad lokal elasticitetsmodul, MOE, i nämnda längdriktning för ett flertal underpartier. Dessa data kan användas för exempelvis tillförlitlig hållfasthetsgradering av träbrädor.
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| 6. |
- Olsson, Anders, 1973-, et al.
(författare)
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Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:3, s. 319-333
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Tidskriftsartikel (refereegranskat)abstract
- Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.
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| 7. |
- Oscarsson, Jan, 1958-, et al.
(författare)
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Determination of tensile strain fields in Norway spruce side boards using two master-slave connected contact-free measurement systems based on digital image correlation.
- 2011
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Ingår i: Proceedings (Poster session) of the 17th International Nondestructive Testing and Evaluation of Wood Symposium, Sopron, Hungary, September 14-16, 2011..
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Konferensbidrag (refereegranskat)abstract
- A sample of nine Norway spruce side boards of narrow dimensions were tested in tension according to the standard EN 408. Strain fields were simultaneously measured using two master-slave connected measurement systems based on digital image correlation (DIC). Each system performed a separate measurement project measuring about 50% of the measurable length of each board and the results were combined, visualized and evaluated as one project using specific DIC software. The objectives were to investigate the possibility of measuring strain fields by use of multi-system measurements, to analyze the strain field distribution and to investigate the possibility of determining local modulus of elasticity (MOE) using strain field measurements. The results show that longitudinal strain fields were useful for identification of areas with reduced stiffness, that lateral board displacements, measured by the DIC systems, can be applied for identification of local defects, and that strain fields can be used for local MOE determination.
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| 8. |
- Oscarsson, Jan, 1958-, et al.
(författare)
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Determining tensile strain fields in Norway spruce side boards using two master-slave connected digital image correlation systems
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Machine strength grading of structural timber is in general based upon statistical relationships between bending strength and other timber properties (so called indicating properties). The overall aim of the research presented in this report was to investigate the possibility of obtaining a better understanding of such relationships using a contact-free deformation measurement technique based on digital image correlation (DIC). A sample of nine Norway spruce (Picea abies) side boards of narrow dimensions was tested in tension according to the European Standard EN 408. Deformations and strain fields along flatwise board surfaces were simultaneously determined using two master-slave connected DIC measurement systems. Each system performed a separate measurement project measuring slightly more than 50 % of the measurable length of each board and the results were combined, visualized and evaluated as one project using specific DIC software. The objectives were to investigate the possibility of identifying strain fields on timber pieces of narrow dimensions by use of multi-system measurements, to analyze the strain field distribution, and to investigate the possibility of determining local modulus of elasticity (MOE) using deformations and strain fields occurring on board surfaces. The results show that longitudinal strain fields can be useful for identification of areas with reduced stiffness and that lateral board displacements, measured by the DIC systems, can be applied for identification of local defects. Promising results were also achieved as regards local MOE determination on the basis of strain field measurements.
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| 9. |
- Oscarsson, Jan, et al.
(författare)
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Strength grading of narrow dimension Norway spruce side boards in the wet state using first axial resonance frequency
- 2011
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Ingår i: International Wood Products Journal. - Leeds/London United Kingdom : Maney Publishing. - 2042-6445. ; 2:2, s. 108-114
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Tidskriftsartikel (refereegranskat)abstract
- Strength grading of Norway spruce (Picea abies (L.) Karst.) side boards in the wet state was investigated. For a sample of 58 boards, density and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Finally, tensile strength of the split boards was measured and its relationship to MOEdyn for both wet and dried split boards determined. The investigation also included an evaluation of a so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts. The results show that strength grading of split boards in the wet state can give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.
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| 10. |
- Oscarsson, Jan, 1958-, et al.
(författare)
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Strength grading of wet Norway spruce side boards by use of axial dynamic excitation
- 2010
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Ingår i: Proceedings of the 11th World Conference on Timber Engineering 2010, WCTE 2010, Riva del Garda, Trento, Italy, June 20-24. - : Curran Associates, Inc.. - 9781622761753 ; , s. 1601-1606
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Konferensbidrag (refereegranskat)abstract
- Strength grading of Norway spruce side boards in the wet state was investigated. For a batch of 58 boards, densities and dynamic modulus of elasticity in the axial direction, MOEdyn, were determined in the wet state. The boards were then split into two parts and the procedure of determining MOEdyn was repeated both before and after the boards were dried to a target moisture content of 12 %. Tensile strength of the split boards was measured and its relation to MOEdyn for both split and unsplit boards determined. A so called reversed lamination effect on the stiffness caused by the splitting of boards into two parts was also evaluated. The results show that strength grading of split boards in the wet state could give just as good results as grading performed after drying. The reversed lamination effect on the stiffness of split boards was found to be of lower order.
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