This is endwise compression, or compression parallel to the grain.In the case of long columns, that is, pieces in which the length is very great compared with their diameter, the failure is by sidewise bending or flexure, instead of by crushing or splitting. of its compressive strength along the grain. The specimens were heated in the chamber for 30 min. Cellulose and hemicelluloses are carbohydrates that are structural components in wood. Compression strength testing. However, the compressive strength of the freshwater ice depended on the crystal size, the strain rate, and the ice temperature. 4(4), 193-201. 2b), the failure occurred between the middle and the end of the specimens, at an angle ranging from 30° to 60°. Table 1. fc0 and Ec0 of Oak wood at a temperature of +23 to -196 ºC, Groups with the same letters in each column are those in which there is no statistical difference (at the 0.05 level) between the samples according to the Duncan’s multiple range tests. cell walls were 125 MPa and 160 MPa, respectively. Zhang, X., Zhao, Q., Wang, S., Trejo, R., Lara-Curzio, E., and Du, G. (2010). Wood Science, China Forestry Publishing House, Beijing. The students observed that during the testing, the wood has shortened. Schaffer, E. L. (1973). The curve of force and deformation. In a range of -130 ºC to -196 ºC (Fig. Oak (Quercus mongolica Fisch et Turcz.) Wood Sci. “Bending strength and toughness of heat-treated wood,” J. A material is strong and tough if it ruptures under high forces and has high strains while materials with limited strain values are not tough. All rights reserved. This is very useful information about Compression testing. Yu, D., and Östman, B. It can be noted that there were two separate temperature ranges, which is the reason for the qualitatively different changes in the strength properties of wood, and those ranges were: Range 1: -196 ºC to +23 ºC. 2004; Shi et al. Wood consists of cellulose, hemicelluloses, and lignin. S means shear strength.. 2d), the specimens were ruptured parallel to the grain, which is a failure pattern known as splitting. Wood is stronger in resisting shear across the grain than it is parallel to the grain. “Accelerated aging: Residual weight and flexural properties of wood heated in atmosphere at 115 ºC to 170 ºC,” Wood Sci. Zhang et al. The present research is unique because the specimens were tested in the climatic chamber while at the desired temperature. In the wood being tested along the grain, the deformation is smaller than the deformation of the wood across the grain; even it has greater loads applied on the wood. The quasiplastic load plateau of the rattan specimens is longer than that of wood, and the slope of stress–strain curves on the descending branch is more gradual than that of wood, which indicates that the toughness of the rattan is higher than that of wood. Figure 3-5- The three principal axes of wood with respect to grain direction and growth rings. (1985). The wooden column can accommodate the given load (1450 kN) because its compressive strength is less than the maximum strength of the wood sample. Five specimens were prepared for each temperature level. 20100307170A1. Hankinson's equation (also called Hankinson's formula or Hankinson's criterion) is a mathematical relationship for predicting the off-axis uniaxial compressive strength of wood. board with dimensions 120 (R) х 30 (T) х 800 (L) mm, air-dry density 0.819g/cm3, and moisture content (MC) 12.18% were sourced from a natural forest. The compression strength and modulus of elasticity were measured at the low end of the temperature range. Moreover, the longitudinal modulus of the oak cell wall was determined to be 18.4 GPa by the method of nanoindentation (Wu et al. Learning Outcomes. The decomposition temperature for hemicelluloses is about +150 to +260 ºC, and the corresponding temperature for cellulose is about +240 to +350 ºC. The ratio between the values perpendicular and parallel to the grain are not the same for different Is Wood stronger in tension or compression? Strength and growth come only through continuous effort and struggle. The specimens were sorted into 19 groups based on their average weights to average the coefficient of variation for each group. If the specimen lies on a flat surface and the load is applied to only a portion of the upper area, the bearing plate indents the wood, crushing the upper fibers without affecting the lower part. Ayrilmis, N., Buyuksari, U., and As, N. (2010). Wu, Y., Wang, S., Zhou, D., Xing, C., and Zhang, Y. An example … When wood is used for columns, props, posts, and spokes, the weight of the load tends to shorten the material endwise. This degradation was probably the reason that the fc0 value was the lowest at +220 ºC. This number is a good indicator of the wood’s strength in applications such as deck posts, chair legs, or other circumstances where the load being applied is parallel rather than perpendicular to the grain. Figure 2: (a) wood sample perpendicular to the grain subjected under compressive load. fc0 = -1.444×Ec02 + 52.104×Ec0 – 250.97, -196 ºC ≤T≤+23 ºC. However, when the temperature was increased from +23 ºC to +220 ºC, the fc0 decreased by 67%, indicating a non-linear relationship. Four patterns of failure were shown by the specimens: pear-shaping, shearing, wedge-splitting, and splitting, all of which are illustrated in Fig. Cao, Y. J., Lu, J. X., Huang, R. F., Zhao, X., and Jiang, J. L. (2012). In this range, the moisture content did not change except for under the liquid nitrogen -196 ºC, but the fc0increased with the decreasing temperature, which was captured by a linear model. 2012BAD24B02). Abstract. Technol. Five strength properties that are commonly measured for design purposes include bending, compression parallel and perpendicular to the grain, tension par­ allel to the grain, and shear parallel to the grain. The influence of temperature on the compression strength (fc0) in the range of -196 ºC to +220 ºC, and compression modulus of elasticity (Ec0) parallel to the grain of oak (Quercus mongolica Fisch et Turcz.) In the case of off-axis compression, stresses must be transformed using a transformation equation for the principal directions (1 and 2 directions) of materials. “Cryogenically treated wooden baseball bat,” USA Patent No. Moraes, P. D., Rogaume, Y., and Triboulot, P. (2004). The Ec0 values could be estimated based on temperature, which could be used for predicting the fc0 of the wood. The findings may help to explain the behavior of wood contractures during fires as well as to expand the application range of wood in ultra-low temperature environments, such as under liquid natural gas or liquid nitrogen conditions. The moisture content of the specimens decreased with the increasing temperature and was near to zero by +170 ºC (Table 2). Compression Strength and Modulus of Elasticity Parallel to the Grain of Oak Wood at Ultra-low and High Temperatures, Jinghui Jiang, Jianxiong Lu,* Yongdong Zhou, Youke Zhao,* and Liyuan Zhao. Compressive strength of wood is measured by loading a block of wood parallel to the grain until it breaks, and the bending strength is measured by loading a block perpendicular to the grain. Because the water in the specimens forms ice at the freezing point, Merkel (2004) established the following relationship between compression strength (σ) and temperature (T): As temperature decreases, the ice increases in strength, which may partially explain the increase in wood strength (Michael 1978). Test Eval. The values in parentheses are standard deviations. wood in the range of -196 ºC to +23 ºC were studied. A reduction in moisture content causes an increase in wood strength, while an increase in temperature produces a decrease in strength. Several researchers have reported that moisture content and temperature are important factors affecting the strength of wood. The determined values for fc0 and Ec0 parallel to the grain of the wood at ultra-low temperatures are presented in Table 1. 2009). The previous study reported that the MOE of Swedish pine was 14.2 GPa at -20 ºC and 11.6 GPa at +20 ºC (Kollmann and Cote 1968). The analysis of variance showed that there were statistically significant differences between the fc0 at +23 ºC and those at other temperature levels. The results were similar to those obtained by previous researchers (Cao et al. ure of the combined strength and toughness of wood under bending stresses. The research aimed to derive substantiated reduction factors for compressive strength and modulus of elasticity parallel to the fiber for structural sized spruce and fir (round) wood with moisture contents at and beyond fiber saturation. The compression strength was measured at the high end of the temperature range. 2820 Faucette Dr., Campus Box 8001Raleigh, NC 27695. Moreover, the Ec0 could be used to predict fc0 using a polynomial model. In one of the test set-ups a uniform compression over the complete square face of the specimen was used - With increase in temperature, the fc0 values were initially reduced, then increased, and finally reduced again. Kollmann, F. F. P., and Cote, W. A. The compressive strength of the material would correspond to the stress at the red point shown on the graph. This video shows the compression failure of a Class GL28 glulam timber block loaded perpendicular to the grain. (2007). Bekhta and Marutzky (2007) found that the relationships between the MOR/MOE and temperature from -40 ºC to +40 ºC were described by a linear model. Work to maximum load is a measure of the combined strength and toughness of wood under bending stresses. In the range from +220 ºC to +50 ºC (Fig. In the temperature range from -50 ºC to -110 ºC (Fig. ThermoWood Handbook, www.thermowood.fi. The compression modulus of elasticity (Ec0) values were calculated using the 10% and 40% values of the failure load (fc0max) (Fig. The influence of temperature on the compression strength (fc0) in the range of -196 ºC to +220 ºC, and compression modulus of elasticity (Ec0) parallel to the grain of oak (Quercus mongolica Fisch et Turcz.) This video shows the compression failure of a Class CL28 softwood timber block loaded parallel to the grain. Brito, J. O., Silva, F. G., Leão, M. M., and Almeida, G. (2008). The specimen-clamping head of the universal mechanical testing machine was pre-set in an adjustable-temperature chamber. Thus, the values that were determined using the previous methods did not report the exact properties of the specimens at those chamber temperatures because the specimens were exposed to room temperature in the few seconds following. Cellulose constitutes 40 to 50%, and hemicelluloses 25 to 35%, of wood. 99(18), 8545-8548. Kendra and Cortez (2010) found that the MOR of a wooden baseball bat was increased by 26% at -190 ºC. Discuss if the wooden column can accommodate the given load. The relationships between Ec0 and temperature (a), and fc0 and Ec0 (b). The liquid nitrogen condition gave rise to the maximum fc0 and Ec0, which was attributed to the 10% increase in weight that the specimen incurred as a result of having absorbed and frozen some extra moisture. However, when the temperature was increased from +23 ºC to +220 ºC, the fc0 decreased by 67%, indicating a non-linear relationship. 4. From Fig. Range 2: +23 ºC to +220 ºC. 1999; Yamada 1971). fc0 = -3.0×10-5×T3 + 0.011×T2 – 1.264×T + 81.529, +23 ºC ≤T≤+220 ºC. “Mechanical behavior of Québec wood species heat-treated using ThermoWood process,” Holz als Roh- und Werkstoff 65(4), 255-259. Determine the axial force P that can be safely applied to the block if the compressive stress in wood is limited to 20 MN/m 2 and the shearing stress parallel to the grain is limited to 5MN/m 2.The grain makes an angle of 20° with the horizontal, as shown. Moisture content and seasoning: New wood, that is wood recently cut down, contains a large amount of moisture (this is known as green lumber). This study evaluated the influence of temperature, in the range of -196 to +220 ºC, on the fc0 and Ec0 parallel to the grain of oak wood. 46(1), 8-15. 2007). (2010). The experimental device was placed inside the chamber. Table 2. fc0 of Oak Wood at a Temperature of +23 to +220 ºC. The coefficients of determination for linear and nonlinear modes were 0.974 and 0.942, respectively, at a significance level of 0.01. In terms of heat-treated wood, it has been reported that the modulus of rupture (MOR) of spruce (Picea abies) decreased by 44 to 50% when the treatment temperature was raised from +100 ºC to +200 ºC, while the modulus of elasticity (MOE) decreased by only 4 to 9% (Bekhta and Niemz 2003).