compressive strength of wood parallel to grain

99(18), 8545-8548. Shi, J. L., Kocaefe, D., and Zhang, J. The compression strength and modulus of elasticity were measured at the low end of the temperature range. Moisture content and seasoning: New wood, that is wood recently cut down, contains a large amount of moisture (this is known as green lumber). In the range from +220 ºC to +50 ºC (Fig. The curve of force and deformation. 2d), the specimens were ruptured parallel to the grain, which is a failure pattern known as splitting. In the temperature range from -50 ºC to -110 ºC (Fig. 2010; Bekhta and Marutzky 2007; Kendra and Cortez 2010), the specimens were placed for several hours in a climatic chamber set at the desired temperature but then tested outside the chamber at room temperature. 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 linear region terminates at what is known as the. Suzuki, S., and Saito, F. (1987). 2c), the boards underwent a wedge-splitting type of failure, in which the direction of the split was either radial or tangential. When the temperature was decreased from +23 ºC to -196 ºC, the average, When the temperature was increased from +23 ºC to +220 ºC, the average. “Effect of steam-heat treatment on mechanical properties of Chinese fir,” BioResources 7(1), 1123-1133. fc0 = -1.444×Ec02 + 52.104×Ec0 – 250.97, -196 ºC ≤T≤+23 ºC. Learning Outcomes. “Temperature dependency of physical properties of wood at low temperature,” Kyoto University Research Information Repository. 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. It was found by Manríquez and Moraes (2010) that the average compression strengths parallel to grain of paricá (Schizolobium amazonicum) were 32 MPa and 11 MPa at +20 ºC and +230 ºC, respectively. This allowed for the determination of the time required for the specimen to reach the desired temperature. When the temperature was decreased from +23 ºC to -196 ºC, the fc0 and Ec0 of wood increased by 283.91% and 146.30%, respectively. However, until this study, the strength and compression modulus of elasticity of kiln-dried wood have not been measured in an ultra-low temperature environment such as that between -100 ºC and -196 ºC. 2b), the failure occurred between the middle and the end of the specimens, at an angle ranging from 30° to 60°. Compression parallel to the grain shortens the fibers in the wood lengthwise. Comparison with the referenced strength. 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. Wood consists of cellulose, hemicelluloses, and lignin. The compression modulus of elasticity (Ec0) values were calculated using the 10% and 40% values of the failure load (fc0max) (Fig. At a temperature of +150 to +250 ºC, major changes in the hemicelluloses occur, which causes them to degrade (Finnish Thermowood Association 2003). Figures 2 and 3 show the normalized ranks of bending strength and compressive strength parallel to the grain. The maximum compressive strength of the wood sample is 20 GPa. 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. “Mechanical properties of ice,” http://ffden-2.phys.uaf.edu/311_fall2004.web.dir/heike_merkel/Intro.htm 2013 (slide 3 and 4). Calculate Compression Strength for Wood. The results were similar to those obtained by previous researchers (Cao et al. All rights reserved. Temperature plays an important role in the mechanical strength of wood. COMPRESSION PARALLEL TO THE GRAIN(“Fc”). Moreover, the longitudinal modulus of the oak cell wall was determined to be 18.4 GPa by the method of nanoindentation (Wu et al. Fig. where fc0max is max load, a is width of cross section, and b is thickness of cross section. “Cryogenically treated wooden baseball bat,” USA Patent No. The relationships between fc0 and temperature and between Ec0 and temperature could be described by a linear and a polynomial model, respectively. Moraes, P. D., Rogaume, Y., and Triboulot, P. (2004). The present research is unique because the specimens were tested in the climatic chamber while at the desired temperature. 2000; Manríquez and Moraes 2010; Millett and Gerhards 1972; Moraes et al. The determined values for fc0 and Ec0 parallel to the grain of the wood at ultra-low temperatures are presented in Table 1. “Influence of temperature on the modulus of elasticity (MOE) of Pinus sylvestrisL.,” Holzforschung 58(2), 143-147. Manríquez, M. J., and Moraes, P. D. (2010). Compression strength testing. However, in those previous studies, the specimens were placed into a climatic chamber at the desired temperature for several hours and then tested in a separate room temperature environment. From Fig. Compressive strength tells you how much of a load a wood species can withstand parallel to the grain. Several researchers also reported similar increases in the fc0 of wood with decreasing temperatures (Chang 1985; Green et al. The results indicated that there were four different failure patterns, depending on the temperature range. Compressive stress perpendicular to grain—Reported as stress at proportional limit. ure of the combined strength and toughness of wood under bending stresses. Test Eval. The results indicated that there were four different failure patterns, depending on the temperature range. 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. 4, the relationships between Ec0 and temperature (T), and Ec0and fc0 were established using a polynomial model with the following form: Ec0= 2.0×10-4×T2 – 0.005×T + 8.199, -196 ºC≤T≤+23 ºC, R² = 0.924 (F<0.001)   (6). Moisture content influence compressive (parallel to grain) strength of Red Spruce, Longleaf Pine and Douglas Fir: Indicated strengths are relative to wood containing 2% moisture. The mean modulus elasticity of wood across the grain is smaller by a factor of about 30 than when parallel … However, the compressive strength of the freshwater ice depended on the crystal size, the strain rate, and the ice temperature. So, better take any challenges as your stepping stone to become a better person. Table 2. fc0 of Oak Wood at a Temperature of +23 to +220 ºC. The compressive strength of the material would correspond to the stress at the red point shown on the graph. 1999; Yamada 1971). 3, the relationships between fc0 and temperature (T) were obtained as follows: fc0 = -0.813×T + 70.649, -196 ºC ≤T≤+23 ºC, R2=0.974 (F<0.001) (4). Have fun, explore and make a lot of memories.n8fan.net www.n8fan.net. “Bending strength and modulus of elasticity of particleboards at various temperatures,” Holz als Roh- und Werkstoff 65(2), 163-165. Moreover, the Ec0 could be used to predict fc0 using a polynomial model. Kendra, G. D., and Cortez, J. Wood is 30% stronger in compression than in tension. Red Spruce - air dried : 14% moisture content, kiln dried : 6% moisture content; Longleaf Pine - green wood : 20 % moisture content The specimen-clamping head of the universal mechanical testing machine was pre-set in an adjustable-temperature chamber. Abstract. The results revealed that a 5 % parametric tolerance limit of bending and compressive strength parallel to the grain satisfied the referenced strength, even when using green round timber. “Bending strength and toughness of heat-treated wood,” J. I: Solid Wood, Springer Verlag, Berlin. 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. 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. Cellulose constitutes 40 to 50%, and hemicelluloses 25 to 35%, of wood. 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 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. f 1 and f 2 are compression strengths of wood parallel and perpendicular to the grain. This video shows the compression failure of a Class CL28 softwood timber block loaded parallel to the grain. This is very useful information about Compression testing. Jiang (2013) observed that when the temperature was increased to +140 ºC, the hemicellulose content began to decrease, the α-cellulose content began to increase, and the cellulose crystallinity, which was higher than it had been at +23 ºC, increased. The fc0 and Ec0 values of the wood increased with decreasing temperature, which was mainly attributed to the formation of ice crystals in the wood cell walls at ultra-low temperatures, especially at the liquid nitrogen temperature (-196 ºC). It has been reported that the MOE values of Swedish pine (Pinus sylvestris) wood having a moisture content of 12% were 14.2 GPa and 11.6 GPa at -20 ºC and +20 ºC, respectively (Kollmann and Cote 1968). where σ 1 and σ 2 are compressive stresses parallel and perpendicular to the grain. For example; knots, slope of grain, juvenile wood, reaction wood [2]. When wood is heated, its mechanical properties generally decrease. Explain briefly why the compressive strength of wood loaded "parallel" to its grain is higher than the compressive strength of the same wood loaded "perpendicular" to the grain? It was concluded that at low moisture contents such as 12.18%, the presence of frozen water molecules between the cellulose fibrils improved fc0 and Ec0 of the wood due to the fact that the water molecules stiffened the cellulose fibrils in the same manner as an adhesive. With increase in temperature, the fc0 values were initially reduced, then increased, and finally reduced again. A 3 mm diameter end-perforation was made in each specimen of size 20 (R) х 20 (T) х 50 (L) mm. In this study, the fc0 value at +110 ºC was lower than that at +140 ºC. 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 When the temperature was reduced from +23 ºC to -196 ºC, the average fc0 and Ec0 values were increased by 283.91% and 146.30%, respectively. Above this point the material behaves plastically and will not return to its original length once the load is removed. In the previous studies (Ayrilmis et al. The test was considered completed when the specimen failed. Kollmann, F. F. P., and Cote, W. A. cell walls were 125 MPa and 160 MPa, respectively. A 200 T universal testing machine YAW–2000 and the corresponding analysis system were used for groups B, C, D, and E. 2010). Bekhta, P., and Niemz, P. (2003). The analysis of variance showed that there were statistically significant differences between the fc0 at +23 ºC and those at other temperature levels. ANALYSIS AND INTERPRETATION OF DATA AND RESULT. Kendra and Cortez (2010) found that the MOR of a wooden baseball bat increased by 26% when it was subjected to a temperature of -190 ºC for 24 h. Kollmann and Cote (1968) observed a straight-line relationship between crushing strength of oven-dry wood and temperature in the range of temperature between -191 ºC and +200 ºC. Millett, M. A., and Gerhards, G. C. (1972). “Tensile strength properties of particle boards at different temperatures and moisture contents,” Holz als Roh- und Werkstoff 41(7), 281-286. Article submitted: December 23, 2013; Peer review completed: March 19, 2014; Revised version received and accepted: April 28, 2014; Published: April 30, 2014. Fig. structural applications are given only for directions parallel to grain (longitudinal) and perpendicular to grain (radial and tangential). 95 1. This degradation was probably the reason that the fc0 value was the lowest at +220 ºC. Wood Science, China Forestry Publishing House, Beijing. Is Wood stronger in tension or compression? A reduction in moisture content causes an increase in wood strength, while an increase in temperature produces a decrease in strength. “Mechanical behavior of Québec wood species heat-treated using ThermoWood process,” Holz als Roh- und Werkstoff 65(4), 255-259. Pulp and Paper Fundamental Research Symposia Proceedings. 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. The specimens were kept at each temperature level for 30 min before a mechanical test was performed in an adjustable-temperature chamber. It is highest parallel to the grain and lowest perpendicular to the grain, and for other angles has intermediate values. Since the tensile strength of wood parallel to the grain is greater than the compressive strength, and exceedingly greater than the shearing strength, it is very difficult to make satisfactory tension tests, as the head and shoulders of the test specimen (which is subjected to both compression and shear) must be stronger than the portion subjected to a pure tensile stress. The following is for calculating the adjusted compression capacity of wood member. wood in the range of -196 ºC to +23 ºC were studied. 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. The first effect of compression across the grain is to compact the fibers, the load is irregularly increasing as the. Figure 2: (a) wood sample perpendicular to the grain subjected under compressive load. 2012BAD24B02). The compression load was applied at a speed of 1.0 mm/min during a period of 1 to 5 min. wood in the range of -196 ºC to +23 ºC were studied.Five specimens were prepared for each temperature level. ... Fc - Reference design value for compression parallel to grain A - Cross section area of member Cd - Load duration factor Cm - Wet service factor Ct - Temperature factor Ci - … The compressive-strength test method refers to a test method for the compressive strength of longitudinal wood fiber (GB/T1935-2009) in China. The moisture content of the specimens decreased with the increasing temperature and was near to zero by +170 ºC (Table 2). Five specimens were prepared for each temperature level. 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. Yamada, T. (1971). The specimens were cryogenically treated with liquid nitrogen for 2 h in an adjustable-temperature chamber of a universal mechanical testing machine. The coefficients of determination for linear and nonlinear modes were 0.974 and 0.942, respectively, at a significance level of 0.01. 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 Duncan’s multiple comparison tests were performed with IBM SPSS Statistics 17.0 software. Five specimens were prepared for each temperature level. The Ec0 values could be estimated based on temperature, which could be used for predicting the fc0 of the wood. Compression Testing Equipment Manufacturer. P-123. “Effects of environmental factors on the properties of particleboard,” Mokuzai Gakkaishi 33(4), 298-303. The strength parallel to the fiber ... Often such characteristics can cause a reduction of the wood strength. #strengthwww.ufgop.org, Life is a battle, if you don't know how to defend yourself then you'll end up being a loser. The relationships between Ec0 and temperature (a), and fc0 and Ec0 (b). The fc0 values of the specimens were calculated as follows. As the temperature continuously increased, the hemicelluloses and cellulose were degraded, resulting in the loss of mass and the reduction in wood strength. According to the Duncan’s multiple comparison tests that were run, significant differences (p<0.05) were observed in both the fc0 and Ec0 by SPSS statistics 17.0 software. In a range of -130 ºC to -196 ºC (Fig. Range 2: +23 ºC to +220 ºC. Ayrilmis, N., Buyuksari, U., and As, N. (2010). 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. 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. The graph is also one of the proofs where in parallel, has lesser value of strains than in the perpendicular. Zhang, X., Zhao, Q., Wang, S., Trejo, R., Lara-Curzio, E., and Du, G. (2010). (2010), who reported that the increase in temperature from -30 ºC to +30 ºC adversely influenced the flexural properties of plywood, medium density fiberboard, and oriented strand board. Several researchers reported similar increases in the MOE and MOR of wood-based panels with decreasing temperatures (Ayrilmis et al. 2a), the boards showed a pear-shaped pattern of failure. (2007). 4. 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. The table shows that the fc0 and Ec0 increased as the temperature was reduced. The objective of the study was to determine the effects of temperature on the compression strength parallel to grain of oak in the temperature range from -196 ºC to +220 ºC. In Fig. (b) Wood sample parallel to the grain subjected under compressive load. However, when the temperature was increased from +23 ºC to +220 ºC, the fc0 decreased by 67%, indicating a non-linear relationship. The decomposition temperature for hemicelluloses is about +150 to +260 ºC, and the corresponding temperature for cellulose is about +240 to +350 ºC. “Studies on the mechanism and properties of superheated steam heat-treated oak wood,” Ph.D. dissertation, Chinese Academy of Forestry. In this range, the fc0 values initially decreased in correspondence with the increase in temperature, increased, and then decreased again. The compression strength was measured at the high end of the temperature range. The students conclude that the strength of wood parallel to the grain subjected under compressive load is greater than that of the strength of wood perpendicular to the grain subjected under compressive load. Moisture content and seasoning: New wood, that is wood recently cut down, contains a large amount of moisture (this is known as green lumber). The specimens were sorted into 19 groups based on their average weights to average the coefficient of variation for each group. 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. Water is in contact with hydrophilic hydroxyl groups on the cellulose chains. 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. QUESTION: 1. 2820 Faucette Dr., Campus Box 8001Raleigh, NC 27695. Several researchers have reported that moisture content and temperature are important factors affecting the strength of wood. © 2020 NC State University. Although wood has nominally the same capacity in tension and compression parallel to the grain, bending members invariably fail in tension. “Use of nanoindentation and silviscan to determine the mechanical properties of 10 hardwood species,” Wood and Fiber Science 41(1), 64-73. The average fc0 and Ec0 values at +23 ºC were 57.17 MPa and 7.83 GPa, respectively, while the average fc0 and Ec0 values at -196 ºC were 219.49 MPa and 19.28 GPa, respectively. A similar result was obtained by Ayrilmis et al. Four failure patterns, known as pear-shaping, shearing, wedge-splitting, and splitting, were observed within the temperature ranges +220 to +50 ºC, +23 to -30 ºC, -50 to -110 ºC, and -130 to -196 ºC, respectively. The mechanical tests were performed with a MTS-SANS CMT5000 universal testing machine (Shenzhen, China) with a max load of 100 kN and a temperature-controlled chamber. The mass of lignin starts to decrease only when the temperature exceeds +200 ºC. “Effect of high temperature on the change in color, dimensional stability and mechanical properties of spruce wood,” Holzforschung 57(5), 539-546. In one of the test set-ups a uniform compression over the complete square face of the specimen was used - Cellulose and hemicelluloses are carbohydrates that are structural components in wood. Principles of Wood Science and Technology. See the link below for more info. The compressive strength of wood depends on the direction of the grain with respect to the direction of the applied force. The relationships between fc0 and temperature and between Ec0 and temperature could be described by a linear and a polynomial model, respectively. 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). Conventional compressive strength parallel to the grain and mechanical resistance of wood against pin penetration and microdrilling established by in-situ semidestructive devices The material has in general a high strength to weight ratio, it is a renewable resource and it is also by many considered to be aesthetically appealing. 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. 2010; Bekhta and Marutzky 2007; Suzuki and Saito 1987; Yu and Östman 1983). 2007). End view of failures in compression across the grain, showing splitting of the ends of the test specimens. is increased. The letters in Table 1 show the results of Duncan’s multiple range tests. Parallel to Grain "F t " Horizontal Shear "F v " Compression Perpendicular to Grain. 46(1), 8-15. Compression parallel to the grain shortens the fibers in the wood lengthwise. Kendra and Cortez (2010) found that the MOR of a wooden baseball bat was increased by 26% at -190 ºC. However, a significant difference in Ec0 was observed between -170 ºC and the liquid nitrogen temperature of -196 ºC. In one study, when the specimens were treated under the ultra-low temperatures, the water in the specimens turned into ice. (1985). Contact information: State Key Laboratory of Tree Genetics and Breeding, Research Institute of Wood Industry of Chinese Academy of Forestry, Beijing, 100091, China; * Corresponding authors: jianxiong@caf.ac.cn; youke_zhao@hotmail.com. A thermocouple was inserted in the hole to attain a measurement of the temperature at the geometrical center of the specimen. wood in the range of -196 ºC to +23 ºC were studied. Wood Sci. Cao, Y. J., Lu, J. X., Huang, R. F., Zhao, X., and Jiang, J. L. (2012). Compression parallel to the grain shortens the fibers in the wood lengthwise. Wu, Y., Wang, S., Zhou, D., Xing, C., and Zhang, Y. 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. The decrease in wood strength as a result of heat treatment is mostly due to the degradation of the hemicelluloses (Brito et al. 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). 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. When wood is used for columns, props, posts, and spokes, the weight of the load tends to shorten the material endwise. The gathered data on the table show that the compressive strength of the wood being tested along the grain is greater than the compressive strength of the wood being tested across the grain. Compression parallel to the grain shortens the fibers in the wood lengthwise. (2009). Bekhta, P., and Marutzky, R. (2007). This video shows the compression failure of a Class GL28 glulam timber block loaded perpendicular to the grain. The present research is unique because the specimens were tested in the climatic chamber while at the desired temperature. Jiang, J. H. (2013). Tables 1 and 2 list the results of the bending test and compressive test parallel to the grain, respectively. Green, D. W., Winandy, J. E., and Kretschmann, D. E. (1999). Yu, D., and Östman, B. Five specimens were prepared for each temperature level. Four patterns of failure were shown by the specimens: pear-shaping, shearing, wedge-splitting, and splitting, all of which are illustrated in Fig. “Effect of pyrolysis temperatures on the longitudinal strength of dry Douglas fir,” J. The strength of adhesion of ice to substrate surfaces, such as wood and concrete, may exceed the strength of the substrate material and cause the substrate to break or spall (Ayrilmis et al. 2008). No significant differences in Ec0 were found between +23 ºC and -50 ºC, or between -70 ºC and -150 ºC. In the experiment, testing the compressive strength of wood, which is the measurement of the largest compression force the material can withstand before it loses its shape or fails, the students used two samples (wood parallel and perpendicular to the grain). Figure 3-5- The three principal axes of wood with respect to grain direction and growth rings. S means shear strength.. Zhang et al. in compression across the grain, showing crushing of blocks under bearing plate. 1) from the load and deformation curve under proportional limits using the following formula. Compressive strength parallel to grain—Maximum stress sustained by a compression parallel-to-grain speci-men having a ratio of length to least dimension of less than 11.

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