Physics and Mechanical Wood
Javad Torkaman; Ramin Naghdi
Abstract
Background and purpose: Dynamic methods (non-destructive) work on the basis of creating tension without failure in the samples and save time and costs for evaluating mechanical properties. Knots or the encapsulated branches are the most important factor in the grading of wood. Therefore, the objectives ...
Read More
Background and purpose: Dynamic methods (non-destructive) work on the basis of creating tension without failure in the samples and save time and costs for evaluating mechanical properties. Knots or the encapsulated branches are the most important factor in the grading of wood. Therefore, the objectives of this research are: detection of knots by non-destructive methods, measuring the dynamic modulus of elasticity of beech log using stress waves, and the effect of knot size on the speed of stress waves Subsequently, the value of dynamic modulus of elasticity.Materials and methods: The studied area of Shafarood series 11, which is located in the southern part of the Shafarood watershed, starts at an altitude of 500 meters and continues up to an altitude of 1650 meters. From this area, Five number of beech trees were cut and divided into three equal parts of three meters by transverse cutting, and according to the size of the knots, the properties of density, stress waves velocity Subsequently, the dynamic modulus of elasticity were measured. From the tangential image of the external indicator and the radial image of the internal indicator by using the Digimizer image4 software, the characteristics of each knot such as the diameter and angle of the knot were measured. For non-destructive detection of beech tree knot, ultrasonic tomography, stress wave velocity and CT scan methods were used. In the stress waves velocity method, a Fakopp microsecond timer device was used to measure the time of stress waves velocity. In the radiographic method as well to prepare CT scan images, A digital ground column device with two detectors made in France belonging to a medical clinic was used. To measure the density, 30 cylindrical stems with knots of small, medium and large classes were used, and according to the relationship between density and stress wave velocity, the value of dynamic elasticity modulus was calculated and evaluated. The diameter of the knot along the length of the stem, the density and the dynamic modulus of elasticity of the beech tree stem were measured. To analyze the data at the 95% confidence level, the one-way Anova test was used, and to determine the normality of the data and the homogeneity of the variance, the Kalmograph Smirnov and Leven tests were used. To compare the means, Tukey's test was used by using Spss software.Results: In the detection of beech tree knot with the three mentioned non-destructive methods, the results show the existence of limitations in each method. As the ultrasonic tomography is not able to detect knots inside the beech tree trunk and the stress wave method also does not detect very small knots. The accuracy of the CT scan method in detecting the knot is high, but the cost of its detection is high. According to the growth stages of the beech tree, factors such as growth speed, branch encapsulation speed and natural pruning are different. The origin of the branch is pith of the stem. As a result, the number and size of the created knots are different along the tree. Therefore, most of the small knots are created in the main trunk of the tree. The diameter of the knot has also increased with the increase in the height of the stem. The knot has increased the density. The density results have shown that the samples with large, medium and small knots have significant differences. Considering that the ultrasonic tomography method is based on the reduction of density, it is not able to detect the knot. But in the radiography method, the parts with higher density are seen in light color and the parts with lower density are seen in darker color. The size of the knot is effective on reducing the speed of stress waves and thus reducing the dynamic modulus of elasticity of wood. In comparison with the samples without knots, the samples with small, medium and large knots reduce the modulus of elasticity by 20%, 50% and 70% respectively.Conclusion: in general, among the non-destructive methods, only the CT scan method is able to detect small knots and evaluate the clear wood and defects. In comparison with the control sample (without knots), with increasing the size of the knot, the value of the density increases and the stress wave velocity decreases Subsequently, the dynamic elasticity modulus of the samples decreases.
Physics and Mechanical Wood
mohammad najafianashrafi; ali Heidari; Hamed Jafarzadeh
Abstract
Background and goal: walnut tree (Juglans regia L.) are cultivated in many countries in Asia, Europe and United States. This tree has high resistance with beautiful pattern and are used in furniture industry, building panels, flooring and covering. Iran are ranked third in the world in the production ...
Read More
Background and goal: walnut tree (Juglans regia L.) are cultivated in many countries in Asia, Europe and United States. This tree has high resistance with beautiful pattern and are used in furniture industry, building panels, flooring and covering. Iran are ranked third in the world in the production of walnut fruit after China and US. Thus, with considering high production of this tree in Iran and its diverse application in different industries, a comprehensive studding for physical and mechanical properties of this species in different regions of Iran seems necessary.Materials and methods: Walnut tree (Juglands regia L.) from two different regions, one from northeast (Mashhad) and the other from northwest (Maku) of Iran was selected for this study. Three trees from each region were selected randomly and cut with almost with the same diameter for physical and mechanical experiments. Samples also were cut from 2-4 meter from the ground. ISO 3129 and ASTM (D143-14) were used for doing physical and mechanical experiments respectively and at the humidity of 12%. Statistical analysis of data was performed using Graphpad prism version 8 and t-Test was performed for significant difference of data.Results: The average dry density of both Mashhad and Mako walnut wood was 0.625 and 0.579 g/cm3 respectively. There were a significant difference for both tangential shrinkage with values of 9.77 and 8.78 and volumetric shrinkage with measurement of 16.26 and 15.42 in Mashhad and Mako respectively. However, there was no significant difference for longitudinal and radial shrinkage in both walnut wood of the two regions. Walnut wood cut from Mashhad region showed higher physical and mechanical properties. The results of the mechanical characteristics of walnuts from two regions showed bending strength 100.54 and 87.61N/mm2 and elasticity modulus 10049.59 and 7504.21 N/ mm2 for Mashhad and Mako regions respectively which were significant. Results also showed not significant difference for compression parallel to the grain with values of 37.91 and 33.88N/mm2, for shear parallel to the grain with values of 9.15 and 8.95N/mm2, for Tensile strength parallel to the grain with 127.97 and 125.83 N/mm2, for Screw withdrawal strength in tangential values of 4031.01 and 3685.97N and Screw withdrawal strength in radial values of 4218.63 and 3915.03N and impact strength with the values of 27.81 and 25.24KJ/m2 for Mashhad and Maku regions respectively. Results also showed that the density of walnut wood in the two regions of Iran was similar to the those in Italy and eastern Europe but the mechanical properties of walnut tree such as bending strength and elasticity modules measured from Mashhad region was similar to the wone in turkey.Conclusion: The results showed that the physical and mechanical resistance of walnut wood located in Mashhad is higher than Maku wood, which was attributed to the higher dry density and the difference in weather conditions. Considering the appropriate mechanical resistance of walnut wood from both regions of Iran, this wood can be used in coating and furniture industries, building panels and flooring.
Physics and Mechanical Wood
Ebrahim Khosravi; Amir Lashgari; Mehran Roohnia; Ahmad Jahan latibari; Ajang Tajdini
Abstract
Background and objectives: From the limitations of detecting the amount of useful life remaining in the components of the structures in the conditions of use with acoustic methods is the impossibility of calculating the modulus of elasticity due to the impossibility of removing the part from the structure. ...
Read More
Background and objectives: From the limitations of detecting the amount of useful life remaining in the components of the structures in the conditions of use with acoustic methods is the impossibility of calculating the modulus of elasticity due to the impossibility of removing the part from the structure. Therefore, most of the classifications during use in the components of structures such as historical buildings are based on measuring the speed of sound. In this research, to calculate the local and global density with the method of pin penetration rate in wooden tie in order to calculate the amount of their remaining useful life by combining stress wave and free longitudinal vibration methods has been studied. There was no significant difference between the values of global sound velocity and global modulus of elasticity with the local results of these factors at the five tested points in each of the wooden tie.Methodology: The number of three saturated wooden tie from Iran Railway Company and with the dimensions of 15x25x260 cm, which are made of beech species (Fagus orientalis) and the density was measured by pin penetration method at 5 points of each wooden tie (50 cm distance between each point) and the average results of 5 points were compared with the results of ISO 13910 standard method. The stress wave test was carried out at the same 5 points of density determination by pin penetration rate method to determine the local modulus of elasticity and the results of each point were compared with the global modulus of elasticity of the beam. Longitudinal vibration test was also performed to calculate the damping factor values of the samples.Results: The results showed that there was no significant difference at the 95% level between the values calculated with both the ISO 13910 standard methods and the pin penetration rate method, and there was a favorable linear correlation between the results of the two methods. According to the results, there was no significant difference between the global sound speed of the beams and their local sound speed in any of the five measured points at the 95% level and there was a linear correlation between the values of the global sound speed and each of the five local points. There was no significant difference at the 95% level between the values of the global modulus of elasticity and the values of the local modulus of elasticity calculated in each of the five points. Also, there was a linear correlation between the values of the global modulus of elasticity and the results of the local modulus of elasticity in each of the five points. There was an exponential correlation between the values obtained from the global modulus of elasticity and the damping factor of each of the wooden tie.Conclusion: The equality of density according to the ISO 13910 standard method and the nail penetration method, as well as the equality of the modulus of elasticity calculated by the stress wave method and the free longitudinal vibration method, make it possible to obtain all the data required for calculations without removing the part from the structure. The remaining strength of wooden components should be provided according to EN338 standard.
Physics and Mechanical Wood
Mohammad Najafian ashrafi; Mohammad Ghorbanian Far; Esmail Rastbod; Mohammad Salehi; Mahdi Shamshiri
Abstract
The walnut tree is one of the most important species in Europe, Asia and Iran, which is used in various industries such as furniture, veneer, and construction due to its high resistance and beauty. In this research, walnut trees from two different geographic locations, one from the forests in the north ...
Read More
The walnut tree is one of the most important species in Europe, Asia and Iran, which is used in various industries such as furniture, veneer, and construction due to its high resistance and beauty. In this research, walnut trees from two different geographic locations, one from the forests in the north of Iran (Noor) and the other in the west of Iran (Shahrkord), were selected. We studied physical properties including dry density, basic density, shrinkage, and mechanical properties including bending strength, modulus of elasticity, compression parallel to the grain, shear, tensile parallel and perpendicular to the grain, tangential and radial screw withdrawal strength and toughness. In this research, standards 3129 and ASTM D143-14 were used to perform physical and mechanical tests, respectively. The moisture content of all samples during mechanical tests was 12%. The average dry density of Noor and Shahrekord walnuts was 0.61 and 0.57 (g/cm3) respectively. The results of variance analysis showed that the characteristics and physical resistances of these two species were not significantly different except for dry density, radial, tangential and volumetric shrinkages. However, due to the higher density of Noor species, it showed higher mechanical resistance compared to the Shahrekord species.
Physics and Mechanical Wood
Saeed Mahdavi
Abstract
The use of renewable energies, such as biomass, is becoming increasingly important as countries realize that bioenergy present an approach to their international commitments to reduce greenhouse gas emissions. Biomass with higher thermal energy value and optimal composition is more desirable for the ...
Read More
The use of renewable energies, such as biomass, is becoming increasingly important as countries realize that bioenergy present an approach to their international commitments to reduce greenhouse gas emissions. Biomass with higher thermal energy value and optimal composition is more desirable for the thermal conversion systems. In present investigation, properties of ten type's wood biomass relevant to combustion were evaluated. Important characteristics requiring analysis for the biomass were moisture and ash content, volatile matter, elemental composition (C, H, N, S, and O), and high and low heating values (HHV and LHV). The heating value has been determined based on experimental and computational methods by colorimeter bomb and elemental content, respectively. The results showed that eldarica pine biomass had the highest content of biomass sulfur, which is undesirable environmental factor in the bioenergy system. Regarding to the fixed carbon to volatile matter ratio, Citrus sinensis var. thomson has the lowest ratio, so it is the best biomass for the gasification process. The highest and lowest heating values were determined for the poplar pruning residues (group a) and apple (group b and c), respectively. The highest and lowest of HHV and LHV were measured for P. deltoides and Malus spp., respectively.
Physics and Mechanical Wood
Hadi Dashti; Kambiz Pourtahmasi; asghar tarmian
Abstract
In this research, the effect of preheating in nitrogen medium on acoustic properties of walnut and white mulberry’s boards was studied. Sapwood boards of 300×20×20 mm with the green moisture content were prepared. Heat treatments were applied at 140 and 160 oC under pressure of 2 pascal ...
Read More
In this research, the effect of preheating in nitrogen medium on acoustic properties of walnut and white mulberry’s boards was studied. Sapwood boards of 300×20×20 mm with the green moisture content were prepared. Heat treatments were applied at 140 and 160 oC under pressure of 2 pascal for 30 and 60 minutes. Following the heat treatment, the samples were dried in a convectional laboratory kiln of 8% at 50 oC, relative humidity of 50%, and air velocity of 1 m/s to the average final moisture content of 8%. Using the free vibration method on free- free bar, the dynamic modulus of elasticity and damping factor were evaluated. Results revealed that the heat-treatment at 140 oC for 30 minutes did not have a significant effect on vibration properties of the wood samples. On the other hand, the heat-treatment at 160 oC caused a significant increase in dynamic modulus of elasticity and also a reduction in the damping factor of walnut and white mulberry samples. The FTIR spectroscopy and X-ray studies showed that the degradation of cell-wall polymers and increase in the crystallinity of the walnut wood specimens occurred due to heat treatment at 160 0C.
Physics and Mechanical Wood
Faezeh Farhadi; Seyed Majid Zabihzadeh; foroogh dastoorian
Abstract
Extensive application of heat treated wood in exterior uses with high relative humidity and high temperature circumstances, necessitates the study of mechanical and creep behavior of them at such situations. The general objective of the present study was investigating the effect of test temperature on ...
Read More
Extensive application of heat treated wood in exterior uses with high relative humidity and high temperature circumstances, necessitates the study of mechanical and creep behavior of them at such situations. The general objective of the present study was investigating the effect of test temperature on creep behavior of heat treated velvet maple wood. Heat treatment was conducted on oven dried maple wood samples at three temperature levels of 160, 175 and 190oC. Four-point static flexural test was conducted for determination of the required load level for creep test in three replications at each treatment temperature levels. For conducting creep tests, three levels of test temperature of 21, 40 and 60oC and duration of 65 hours were considered. Results of flexural test showed that heat treatment led to decreasing the rupture modulus compared to the control one; however, the elastic modulus did not change significantly. Results of creep test showed that with increasing test temperature, instantaneous and creep compliance values increased. With increasing treatment temperature, creep compliance was increased as well. Anti-creep efficiency ratio for evaluating the effect of test temperature on creep value at different levels of treatment showed that generally heat treatment led to decreasing the creep strength compared to the control ones. Heat treatment at temperature of 160oC led to in improvement in creep behavior at higher test temperature, in which the reason was attributed to increase of cellulose crystallinity and lignin condensation reaction, in turn led to lower plasticization of wood at higher test temperature.
Physics and Mechanical Wood
shahrzad omrani ghahjaverstani; amir lashgari; mahran roohnia
Abstract
Non-destructive tests today play a vital role in human life. Non-destructive evaluation technology is widely used in industries, especially wood based industries and wood based products and has led to advances in Strength grading lumber, determine the disadvantages of wooden materials, Inspection of ...
Read More
Non-destructive tests today play a vital role in human life. Non-destructive evaluation technology is widely used in industries, especially wood based industries and wood based products and has led to advances in Strength grading lumber, determine the disadvantages of wooden materials, Inspection of timber and wooden structures. The purpose of this research was to estimate the flexural strength of dynamic tests and compare them with the results of static standard tests in two Forest Pine species (Pinus sylvestris) and Rush (Fagus orientalis). The results of the comparison of the estimation of the modulus of elasticity and the estimated modulus of rupture by a non-destructive free vibration method in a free supported beam with similar results from the static test showed a very good correlation So, according to calculations done by applying a safety coefficient of 18% for beech species and 11% for pine species, a non-destructive vibration test can be substituted by a static destructive standard test for estimating the factors mentioned in these two species.
Physics and Mechanical Wood
Parastoo Majdabadifarahani; Mehran Roohnia; amir lashgari
Abstract
DOR:98.1000/1735-0913.1398.34.87.66.1.1585.1588 This study deals with the possibility of evaluation and estimating the wood density in Quercus castaneifolia and Fagus orientalis. Wood samples were prepared and cut firstly in 4×20×30 cm (thickness×width×length). Then their density ...
Read More
DOR:98.1000/1735-0913.1398.34.87.66.1.1585.1588 This study deals with the possibility of evaluation and estimating the wood density in Quercus castaneifolia and Fagus orientalis. Wood samples were prepared and cut firstly in 4×20×30 cm (thickness×width×length). Then their density was calculated after 72 hours of conditioning in an oven at 60°C temperature. In thermography process, the temporal temperature was monitored in 1st, 5th, 10, 20, 30, 45 and 60th minutes of cooling (monitoring steps). Investigating the effects of shape factor and dimension on thermographic density evaluation errors, the specimens were cut down in two more steps to 3×20×30 cm and 2×15×20 cm and the course of thermography experiments was repeated. The relationships of shape factor, density and the ratio of density to the shape factor with the logarithmic cooling rate were evaluated separately. Results showed that density without considering the shape factor variations was not sufficiently correlated to the cooling rate. But the ratios of the density to their proper shape factors were promising for the density evaluations from the cooling rates. However, it is suggested to revise this non-destructive method using a larger variety of the wood specimens and species.
Physics and Mechanical Wood
Abdolrahman Hosseinzadeh; Fardad Golbabaei
Abstract
In this investigation physical and mechanical properties of oak (Quercus castaneaefolia C.A. Mey) in Sangdeh region of Caspian Forests were measured according to the ASTM Standard D-143-83 for small samples. Statistical analysis included the performing of factorial design and Duncan's multiple- range ...
Read More
In this investigation physical and mechanical properties of oak (Quercus castaneaefolia C.A. Mey) in Sangdeh region of Caspian Forests were measured according to the ASTM Standard D-143-83 for small samples. Statistical analysis included the performing of factorial design and Duncan's multiple- range test.The results indicated that geographical direction on the stems were not significant sources of differences for physical and mechanical properties, but the effects of height of stems were great and statistically significant and in most cases properties decreased with increasing height.
Physics and Mechanical Wood
Fardad Golbabaei; Hossein Hosseinkhani; Amir Nourbakhsh; Abolfazl Kargarfard; Abas Fakhryan
Abstract
Most industrial production processes need cooling water to operate efficiently and safely. Refineries، steel mills، petrochemical manufacturing plants، electric utilities and paper mills all rely heavily on equipment or processes that require efficient temperature control. Cooling water system control ...
Read More
Most industrial production processes need cooling water to operate efficiently and safely. Refineries، steel mills، petrochemical manufacturing plants، electric utilities and paper mills all rely heavily on equipment or processes that require efficient temperature control. Cooling water system control these temperatures by transferring heat from hot process fluids into cooling water. As this happens، the cooling water itself gets hot before it can be used again it must either be cooled or replaced by a fresh supply of cold water. The aim of this study was utilizing domestic wood in cooling towers structure. For this purpose، five wood spices included: Hornbeam، Oak، Alder،Populus and Tehran pine (Eldarica pine) and also five different regions with different climate، included: electric plant Montazer ghaem from Karaj near of Tehran، electric plant Loshan from north of Iran، electric plant Dorcheh Esfahan from center of Iran and petrochemical manufacturing plants Bandar emam from south of Iran، have been chosen. Sampling have been done and treated with CCA. All samples were put in the cooling towers and were tested during the study period. (Mechanical tests such as specific gravity، static bending، compression parallel to grain and hardness). Based on this study، the mechanical properties of these spices during last four years were done. At the fifth year of study، virtual damages have not seen where as significant difference have been achieved in aspect of mechanical properties. Among of theses wood spices، Populous and Pinus eldarica had minimum mechanical degrade and it should be noted that Pinus eldarica spices had better quality than populous spices.
Physics and Mechanical Wood
Mehran Roohnia; Ahmad Jahanlatibari; Behzad Behnam; Jamshid Zarrinmehr; Mostafa Kohantorabi; Negin Manouchehri; Ajang Tajdini
Abstract
Reaching to the technology of acoustical Tomography and imaging, this project was ordered for facilitating the work for green space researchers and managers in urban standing trees. Comparing the sensors and micro-second timers with those of a certified European device in radial to tangential and longitudinal ...
Read More
Reaching to the technology of acoustical Tomography and imaging, this project was ordered for facilitating the work for green space researchers and managers in urban standing trees. Comparing the sensors and micro-second timers with those of a certified European device in radial to tangential and longitudinal directions showed a good agreement for the Iranian made device. So, a new horizon was opened for the researchers of this approach supported by the local scientific knowledge and technology. Holding this technology, the selected trees concerning the collar defect symptoms were firstly inspected visually, then the visual accuracy was monitored by sonic tomography. Some trees were extremely defected internally, while the visual inspection showed their intactness (9 from 23). Meanwhile some trees holding visually defect signs were proved to be intact after carrying the tomography images (up to 10 from 53). It is concluded that the visual tree defect inspection is not satisfactory for saving or omitting the individual and these kinds of decision makings must be supported by the methods showing the hidden discontinuities.
Physics and Mechanical Wood
Mohamad ali Sadatnia; noshin sattari; mehran roohnia; mohsen bahmani
Abstract
The goal of this study was to determine the modulus of elasticity and modulus of rapture of two kinds of date palm (Khasi and Hajmohammadi) using static bending and dynamic (flexural vibration) techniques. To reduce the difference between static and dynamic stiffness values, the static bending modulus ...
Read More
The goal of this study was to determine the modulus of elasticity and modulus of rapture of two kinds of date palm (Khasi and Hajmohammadi) using static bending and dynamic (flexural vibration) techniques. To reduce the difference between static and dynamic stiffness values, the static bending modulus of elasticity was modified by taking into account the value of the shear deflection. In addition to, for better understanding of the mechanical properties of date palm, values were compared with those measured for poplar samples. The results showed that, in Khasi the mean values of the modulus of elasticity obtained by flexural vibration, the static modulus of elasticity, the modified static modulus of elasticity and as well as the modulus of rapture were 47, 67,68 and 38% less than those measured for Hajmohammadi respectively. In comparing with date palm, values measured for poplar samples were more pronounced. The difference between dynamic and static values of modulus recorded for Khasi, Hajmohammadi and poplar samples were 63, 40 and 19% respectively. After modification of the static values, the difference was reduced in to 3% for Khasi, 6% for Hajmohammadi and 7 % for poplar experimental samples. Finally the significant correlation coefficients were found between the static and the dynamic modulus of elasticity for both two kinds of date palm.
Physics and Mechanical Wood
mostafa kohantorabi; Mehran Roohnia; Shadabeh Fathi
Abstract
In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture ...
Read More
In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture content conditions (moisture content in conditions of: saturated with water (EMC=35±5%), equilibrium moisture content exposed to air (EMC=19±5%), and conditioning moisture content in a climatic chamber (EMC=12±2%), they underwent free flexural vibration test in two longitudinal-tangential and longitudinal-radial planes, and some of the physical, mechanical, and acoustical properties in both planes were investigated. The results showed that the correlation coefficient of the first three modes of flexural vibration in both planes under climatic chamber had a similar situation, but when the samples were in the water-saturated condition, they showed an adverse behavior in each plane. The effect of increasing the temperature above 100°C caused stresses resulting from shrinkage leading to the development of micro-cracks and reduction in the modulus of elasticity of cell walls and ultimately reduction in wave propagation ability of wood, thus increase in the damping vibration values in both longitudinal-tangential and longitudinal-radial planes of the samples. Also, the concurrent changes in modulus of elasticity and damping vibration in both vibration planes are a desirable indicator for monitoring the process from the primary logging process stages to processes such as wood drying and heat treatment.
Physics and Mechanical Wood
foroogh dastoorian; Mohammad Layeghi; Ghanbar Ebrahimi; Mehdi Tajvidi; Seid Majid Zabihzadeh
Abstract
In the present study, creep rupture behavior of a bagasse fiber- polypropylene composite was investigated. Two accumulated damage model (EDRM and Wood) and an energy based failure model (R-W) were adopted to describe the load duration influence on the studied composite. Results have shown that at very ...
Read More
In the present study, creep rupture behavior of a bagasse fiber- polypropylene composite was investigated. Two accumulated damage model (EDRM and Wood) and an energy based failure model (R-W) were adopted to describe the load duration influence on the studied composite. Results have shown that at very high stress levels, the EDRM and Wood models underestimated and overestimated the time to failure than static value respectively. This was attributed to the difference between application of static loading and creep loading. Findings indicated that the all three models were able to describe the creep rupture behavior of the studied composite and among this; the Wood model has shown a better fitting with experimental data, statistically. Based on findings in the present research, it can be concluded that the R-W model was more conservative in predicting time to failure in comparison with the two other models, and the reason can be attributed to the difference between failure criteria in energy based models and accumulated damage models. Results also showed that with increasing stress levels, the secondary stage of creep will shorten and at high stress level, the tertiary stage of creep will be more dominant
Physics and Mechanical Wood
Hamid Reza Koohkan; Ali Maleki; Shahin Besharati
Abstract
In this research the effects of moisture content and cutting speed on the specific shearing energy and shearing stress for four variety of almond tree (Mamayy, Rabi, Sefid and Shahrodi12) was investigated and results the each any the varieties were compared with each other. Shear properties of almond ...
Read More
In this research the effects of moisture content and cutting speed on the specific shearing energy and shearing stress for four variety of almond tree (Mamayy, Rabi, Sefid and Shahrodi12) was investigated and results the each any the varieties were compared with each other. Shear properties of almond wood varieties in this study, using a universal testing machine manufactured STM20 Sntam was determined. Knife bevel form of one-sided and edge angle is 40 degree.The characteristics at three moisture levels of 18, 25 and 45% (w.b.) wet basis, three cutting speed levels of 20, 30 and 40 mm/min and in three size 6, 9 and 12 mm were determined. The results of analysis of variance (ANOVA) showed specific shearing energy and shearing stress to all test factors were response significant (P<0.01). The results showed that Both specific shearing energy and shearing stress increased with an increase in moisture content. While increasing cutting speed of 20 to 40 mm per minute, these values are reduced. Based on the results of the study the average specific shearing energy were determined for varieties Mamayy, Rabi, Sefid and Shahrodi12 59.41, 56.088, 54.38 and 77.57 J/ mm2 respectively and for shearing stress, 16.01, 14.34, 13.73 and 19.35 MPa, respectively. Also, the study effect of test factor in the shear test results can be explained factors moisture content and variety most effect and relatively less effect in cutting speed factor.
Physics and Mechanical Wood
Aysoda Talaei; Mohammad saleh Zare; Hamideh Abdolzadeh
Abstract
The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high ...
Read More
The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high (fir 38% and beech 65%) levels were prepared and evaluated in comparison with untreated specimens. The furfurylation was performed after impregnating the specimens by furfuryl alcohol under vacuum condition followed by heating duration to complete polymerization and crosslinking. Specimens were prepared according to standard ASTM D 905 in order to assess shear strength of bond line formed with three different types of adhesives, single-component polyurethane, polyvinyl acetate as well as urea-formaldehyde. Also screw withdrawal resistance of wood polymer specimens was measured perpendicular to grain and parallel to grain. The results indicated that the shear strength of the bond line decreased and screw withdrawal resistance increased by furfurylation level. Examination of adhesion mechanism demonstrated that formation of an appropriate interface between water-soluble adhesives and wood-polymer involves effective penetration of adhesive into cell wall. Hence, the interface of adhesives and material would be the determining factor in developing strength of adhesive joints. Since the wood-furfuryl alcohol is a cell-wall wood-polymer, the possibility of creating an appropriate interface by increasing of furfurylation level was impaired. On the other hand, the adhesion mechanism of polyurethane glue compared to water-soluble adhesives such as polyvinyl acetate and urea-formaldehyde is significantly different, therefore exhibited more strength. The withdrawal screw resistance of furfurylated wood was increased by furfurylation level due to changing nature of wood and increasing shear strength of wood-polymer. This gain was also more evident in fir than beech. The results showed that screw withdrawal resistance perpendicular to grain was higher than parallel to grain.
Physics and Mechanical Wood
Ali Kazemi tabrizi; Amir Nourbakhsh; Javad Sepidehdam
Abstract
In this study, the effect of fish waste powder, base material polyethylene , and also the quantity of coupling agent (MAPE) on physical and mechanical properties of wood-plastic composite were studied. For this purpose, wood powder at 40% was mixed with 60% of HDPE. Fish waste in three levels (5, 10 ...
Read More
In this study, the effect of fish waste powder, base material polyethylene , and also the quantity of coupling agent (MAPE) on physical and mechanical properties of wood-plastic composite were studied. For this purpose, wood powder at 40% was mixed with 60% of HDPE. Fish waste in three levels (5, 10 and 15%) mixed into wood powder and coupling agent on three levels (0, 2 and 4) of HDPE in a blender at 180 °C and a speed rotating of 50 rpm, and samples were made with using of injection molding for standard tests. The mechanical properties: tensile and bending strength, bending and tensile modulus were investigated according of ASTM standards. This result suggests that increasing the amount of fish powder waste to 10%, increased bending strength while other strengths diminished. The amounts of all strengths were increased by increasing in percentage of coupling agent to 4%.The results shows that fish waste was suitable as a new material for wood plastics composites.
Physics and Mechanical Wood
Saeid asmaeili moghadam; Mohammad Shamsian; Ali Bayat Kashkoli; Behzad Kord
Abstract
This study with aim of investigation the effect of Nano SiO2 on the physical, mechanical and morphological properties of hybrid Nano composite from polypropylene-wood flour was done. For this purpose, wood flour at 60% weight ratio with polypropylene in extrusion were mixed and Nano SiO2 with 0, 1, 3 ...
Read More
This study with aim of investigation the effect of Nano SiO2 on the physical, mechanical and morphological properties of hybrid Nano composite from polypropylene-wood flour was done. For this purpose, wood flour at 60% weight ratio with polypropylene in extrusion were mixed and Nano SiO2 with 0, 1, 3 and 5% as variable agent were used. Also 4% of MAPP in all compounds as a coupling agent was used. Then Nano composites were manufactured by using injection molding techniques. Then mechanical tests such as tensile and bending and physical tests such as water absorption and thickness swelling in short time according to the ASTM standard was done on the samples. Also To determine how to dispersion of nanoparticles in polymeric matrix was used of Scanning Electron Microscope (SEM). Results showed that increase of SiO2 Nano particles, has positive effect on the mechanical properties and caused the improve them. With Increase in the amount of SiO2 Nano particles the water absorption in Nano composites were increased, but this process for thickness swelling was decrease.
Physics and Mechanical Wood
Ardlan Doreemam; Vahidreza Safdari; Abolfazl Kargarfard; Ajang Tajdini
Abstract
In this study, the effect of using waste of Alnus subcordata and Poplar wood in manufacturing particle board was investigated. The particle boards were produced by adding (0-25-50-75-100)% alder branches with poplar wood and two press temperatures 170°C and 180 °C. In total, 30 particleboards ...
Read More
In this study, the effect of using waste of Alnus subcordata and Poplar wood in manufacturing particle board was investigated. The particle boards were produced by adding (0-25-50-75-100)% alder branches with poplar wood and two press temperatures 170°C and 180 °C. In total, 30 particleboards (10 treatments with 3 replications) were made and data was analyzed with complete randomized design. Results showed that particleboards which were made of 75% alder branches and 25% poplar wood with press temperature of 180 °C had the most flexural strength. In addition, this study manifests that the increase of alder branches up to 25% led to the enhancement of modulus of elasticity of particle boards while adding more than 25% caused in the decrease of the modulus of elasticity. The increase of alder branches would augment the internal bounding and thickness swelling of particleboards. Therefore, the particleboards of 100% alder branches had the best internal bonding. However, this research concluded that the press temperature would not any significant effects on mechanical and physical characteristics.
Physics and Mechanical Wood
Ehsan Haji rafiriha; Mehran Roohnia; Ahmad Jahan latibari; Ajang Tajidini
Abstract
The effect of lamination and adhesive coverage rate in layered products made from Poplar wood was studied The effect of lamination and adhesive coverage rate in layered products made from Poplar wood was studied by non-destructive free vibration test. 120 samples with nominal dimensions of 2.5×2.5×45 ...
Read More
The effect of lamination and adhesive coverage rate in layered products made from Poplar wood was studied The effect of lamination and adhesive coverage rate in layered products made from Poplar wood was studied by non-destructive free vibration test. 120 samples with nominal dimensions of 2.5×2.5×45 cm without any obvious deficiencies were selected and free flexural vibration in free-free bars were performed for testing them. Samples were longitudinal cut in three thinner tangential layers and jointed together again using Poly Vinyl Acetate glue. The specimens were divided into four groups according to adhesive coverage rates, which one group was fully glued and 3 groups were carrying some glue deficiencies in different rates. Manipulated samples were tried again in above mentioned test. Results indicated that shear moduli compare to modulus of elasticity is a more sensitive parameter to evaluate glue efficiency in laminated beams but concerns remained due to blind points in flexural vibration nondestructive method.
Physics and Mechanical Wood
Hamideh Abdolzadeh; Ghanbar Ebrahimi; Mohammad Layeghi; Mehdi Ghasemieh; Seiad Ahmad Mirshokraei
Abstract
In this study, characteristics of wood-polymer fracture under mode I were investigated by double cantilever beam. In this regard, the properties of furfurylated specimens with three different levels of furfurylation (20%, 30% and 65%) were evaluated in both RL and TL systems. Results indicated that load-displacement ...
Read More
In this study, characteristics of wood-polymer fracture under mode I were investigated by double cantilever beam. In this regard, the properties of furfurylated specimens with three different levels of furfurylation (20%, 30% and 65%) were evaluated in both RL and TL systems. Results indicated that load-displacement curves from mode I fracture specimens were changed by furfurylation so that it was much clear on curves of TL system. These changes not only included curve slope in elastic and proportional limit zones, but also fracture zone and initiation of crack growth were included . Furthermore furfurylation and raising its content on both systems and especially on TL one, caused to change in stress intensity factor, KIC , and critical energy release rate , GIC. In both systems GIC were highly increased by increasing of furfurylation contents. This criterion demonstrated that the wood- polymer showed much toughness under mode I fracture. Moreover, variation of KIC values due to furfurylation at both systems was different with that of GIC. At the RL system, ascending trend was observed at KIC and GIC values by increasing furfurylation levels. But at TL system, KIC was decreased by furfurylation and this criterion enhanced by increasing of furan polymer in the cell wall. Generally, results of this research show that fracture toughness of wood is highly affected by furfurylation process
Physics and anatomy
Majid Kiaei
Abstract
This study examined the effects of altitude and soil characteristics on wood properties of Eldar pine and soil characteristics in western of Mazandran forest. For this purpose, nine normal pine trees was selected from three classes of altitude 500, 1200, and 1400 m, which located in Chaloos region. Disks ...
Read More
This study examined the effects of altitude and soil characteristics on wood properties of Eldar pine and soil characteristics in western of Mazandran forest. For this purpose, nine normal pine trees was selected from three classes of altitude 500, 1200, and 1400 m, which located in Chaloos region. Disks were cut at breast height for each of trees. Testing samples were taken in radial position from the pith to the bark to determine wood properties such as oven dry density, wood basic density, and annual ring width. For each of tress in three different altitudes, four soil profiles of 20-40cm depth was taken to examine soil physical and chemical properties include clay, silt, sand, pH, Mn, fe, cu, zn, P, and K. Then relationship between the soil and wood properties were investigated with Pearson correlation and multiple correlations. Results of soil and wood properties indicated that by increasing altitude, the amount of annual ring width was increased, and the wood density was decreased, while the clay, Mn, fe, and Cu content in altitude 1200m, silt, Zn and K in lower altitude and P and sand in higher altitude is higher than other altitudes. Among of above variables, only the effect of clay, sand, P and Fe of soils on the wood different properties by Pearson correlation. The relationship between soil and wood properties by forward stepwise regression indicated that
Physics and Mechanical Wood
parisa azari; mohammad talaeipour; noorodin nazarnezhad; behzad bazyar
Abstract
In this study the effect of surface oxidation of wood particles in order to reducing amount of adhesive for making single layer particleboard was investigated. Oxidation of wood particles cause to form carboxylic groups and free phenolic radicals that lead to activate the surface of wood particles for ...
Read More
In this study the effect of surface oxidation of wood particles in order to reducing amount of adhesive for making single layer particleboard was investigated. Oxidation of wood particles cause to form carboxylic groups and free phenolic radicals that lead to activate the surface of wood particles for adhesion. This search was conducted on Populus nigra wood particles that they were oxidized by nitric acid (40%) including 0, 2, 4 and 6 percent (based on OD weight of wood). These wood particles were adhered by phenol formaldehyde resin in three amounts of 3, 5 and 7 percent (based on OD weight of wood) then wood particle cakes pressed in 180 degree of centigrade, 5 min and 30 kg/cm2. The results indicate that maximum MOR, MOE and minimum water absorption and swelling thickness was observed in boards with 7% adhesive and 4% acid. Using 5% adhesive and 4% acid had the best performance on shearing strength.
Physics and anatomy
Neda Sakhavati; Moslem Akbari nia; Hoshangh Zanganeh
Abstract
Cerasus mahaleb (L.) Mill is among the important broad-leaved trees in Zagros forests. Good bending property and the pleasant aroma helped the tree species to find a long history of rural and local uses. Wood consumption is closely influenced by the physical, biometric and other engineering properties. ...
Read More
Cerasus mahaleb (L.) Mill is among the important broad-leaved trees in Zagros forests. Good bending property and the pleasant aroma helped the tree species to find a long history of rural and local uses. Wood consumption is closely influenced by the physical, biometric and other engineering properties. Three sound trees were harvested and tested according to ASTM-D143 standards testing procedures. Results showed that Cerasus mahaleb (L.) Mill has semi-heavy wood with high bending ability. Its compression strength parallel strain was measured as 48.45 MPa. The average fiber length and fiber diameter was 0.71 mm and 19.85 m respectively. Mean volume shrinkage and swelling was measured as 6.09% and 6.69% respectively. The radiant and tangent shrinkage and swelling after 2 and 24 hour immersion in water was 19.65%, 19.74%, 19.9%, 19.89%, 20.62% and 21.16% respectively. Mean annual diameter growth as well as mean height growth were 4.96 mm and 0.31 m respectively.
