Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber

The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.

Prediction of uniaxial compressive strength and modulus of elasticity for Travertine samples using regression and artificial neural networks

Uniaxial Compressive Strength (UCS) and modulus of elasticity (E) are the most important rock parameters required and determined for rock mechanical studies in most civil and mining projects. In this study, two mathematical methods, regression analysis and Artificial Neural Networks (ANNs), were used to predict the uniaxial compressive strength and modulus of elasticity. The P-wave velocity, the point load index, the Schmidt hammer rebound number and porosity were used as inputs for both meth-ods. The regression equations show that the relationship between P-wave velocity, point load index, Schmidt hammer rebound number and the porosity input sets with uniaxial compressive strength and modulus of elasticity under conditions of linear rela-tions obtained coefficients of determination of (R2) of 0.64 and 0.56, respectively. ANNs were used to improve the regression re-sults. The generalized regression and feed forward neural networks with two outputs (UCS and E) improved the coefficients of determination to more acceptable levels of 0.86 and 0.92 for UCS and to 0.77 and 0.82 for E. The results show that the proposed ANN methods could be applied as a new acceptable method for the prediction of uniaxial compressive strength and modulus of elasticity of intact rocks.

DEPENDENCE OF MODULUS OF ELASTICITY AND THERMAL CONDUCTIVITY ON REFERENCE TEMPERATURE IN GENERALIZED THERMOELASTICITY FOR AN INFINITE MATERIAL WITH A SPHERICAL CAVITY

The equations of generalized thermoelasticity with one relaxation time with variable modulus of elasticity and the thermal conductivity were used to solve a problem of an infinite material with a spherical cavity.The inner surface of the cavity was taken to be traction free and acted upon by a thermal shock to the surface. Laplace transforms techniques were used to obtain the solution by a direct approach.The inverse Laplace transforms was obtained numerically.The temperature,displacement and stress distributions are represented graphically.

A Statistical Analysis of the Modulus of Elasticity and Compressive Strength of Concrete C45/55 for Pre-stressed Precast Beams

Random behavior of concrete C45/55 XF2 used for prefabricated pre-stressed bridge beams is described on the basis of evaluating a vast set of measurements. A detailed statistical analysis is carried out on 133 test results of cylinders 150 ~ 300 mm in size. The tests have been running in laboratories of the Klokner Institute. A single worker took all specimens throughout the period, and the subsequent measurements of the static modulus of elasticity and the compressive strength of the concrete were performed. The measurements were made at the age of 28 days after specimens casting, and only one testing machine with the same capping method was used. Suitable theoretical models of division are determined on the basis of tests in good congruence, with the use of Z2 and the Bernstein criterion. A set of concrete compressive strength （carried out on 133 test results of cylinders 150 ~ 300 mm after test of static modulus of elasticity） shows relatively high skewness in this specific case. This cause that limited beta distribution is better than generally recommended theoretical distribution for strength the normal or lognormal. The modulus of elasticity is not significantly affected due to skewness because the design value is based on mean value.

Relation between Modulus of Elasticity and Compressive Strength of Ultrahigh-Strength Mortar with Mixed Silicon Carbide as Fine Aggregate

Ultrahigh-strength mortar mixed surface-oxidized silicon carbide as a fine aggregate was prepared by means of press-casting followed by curing in an autoclave. The relation between modulus of elssticity up to 111 GPa and compressive strength up to 360 MPa of mortar mixed silicon carbide was discussed and it was revealed that the contributions of the aggregate hardness and of the interfacial strength between the aggregate and the cement paste on the elasticity of mortar were imporant.

SIMULATION AND STUDY OF THE MODULUS OF ELASTICITY OF NANOCRYSTALLINE MATERIALS

In this paper, a molecular dynamics simulations are provided for atomic structure of nanocrystals(1～3nm)by which t he lattice parameter of X_ray diffraction, cohesive energy and modulus of elas ticity were computed. The results show that the structure of grain and grain bou ndaries in the same in both nanocrystal and coarse grain materials. The decrease of grain size and the increase volume fraction of grain boundaries lead to a se ries of different features, the modulus of elasticity of nanocrystalline materia ls have been found to be much reduced.

Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.

Use of the pilodyn for assessing wood properties in standing trees of Eucalyptus clones

The effectiveness of pilodyn was tested in evaluating wood basic density, outer wood density, heartwood density, and modulus of elasticity （MoE） at 22 four-year-old eucalyptus clones in Guangxi, China. Results indicated that the mean value ranged from 9.44 to 15.41 mm for Pilodyn penetration, 0.3514 to 0.4913 g.cm^-3 for wood basic density, and 3.94 to 7.53 Giga Pascal （GPa） for MoE, respectively. There were significant differences （1% level） in pilodyn penetration between different treatments, different directions and among the clones. Generally strongly negative correlations were found between pilodyn penetration and wood properties, and the coefficients ranged from -0,433 to -0,755. Our results, together with other studies, suggest that the use of pilodyn for assessing wood density and MoE was confirmed as a possibility.

MECHANICAL PROPERTIES AND SIZE EFFECTS OF SINGLE CRYSTAL SILICON

Six kinds of micro bridge-beam specimens with different sizes are fabricated using photolithography technology for bending test. Beam specimens with trapezoidal section could be representatives of those with rectangle and square section, which are usually applied in MEMS. Nano indentation method used in bending test can be applied to both elastic and plastic materials. Also, some mechanical properties parameters such as the modulus of elasticity, hardness and the bending strength are obtained. The average modulus of elasticity of SCS is 170.295 0±2.485 0 GPa, showing no size effects, but the bending strength ranges from 3.24 GPa to 10.15 GPa, displaying strong size effects, and the average hardness is 9.496 7±1.753 3 GPa,in which no obvious size effects are observed.

Selection of regression models for predicting strength and deformability properties of rocks using GA

Recently,many regression models have been presented for prediction of mechanical parameters of rocks regarding to rock index properties.Although statistical analysis is a common method for developing regression models,but still selection of suitable transformation of the independent variables in a regression model is diffcult.In this paper,a genetic algorithm(GA)has been employed as a heuristic search method for selection of best transformation of the independent variables(some index properties of rocks)in regression models for prediction of uniaxial compressive strength(UCS)and modulus of elasticity(E).Firstly,multiple linear regression(MLR)analysis was performed on a data set to establish predictive models.Then,two GA models were developed in which root mean squared error(RMSE)was defned as ftness function.Results have shown that GA models are more precise than MLR models and are able to explain the relation between the intrinsic strength/elasticity properties and index properties of rocks by simple formulation and accepted accuracy.

Effect of the amount of lignin on tensile properties of single wood fibers

Chemical components are the main factors affecting the mechanical properties of wood fibers. Lignin is one of the main components of wood cell walls and has a critical effect on the mechanical properties of paper pulp and wood fiber based composites. In this study, we carried out tensile tests on single mature latewood tracheids of Chi- nese fir （Cunninghamia lanciolata （Lamb.） Hook.）, using three different delignified treatment methods to obtain different amounts of lignin. We applied single fiber tests to study the effect of the amount of lignin on mechanical tensile proper- ties of single wood fibers at the cellular level. The results show that in their dry state, the modulus of elasticity of single fi- bers decreased with the reduction in the amount of Iignin; even their absolute values were not high. The amount of lignin affects the tensile strength and elongation of single fibers considerably. Tensile strength and elongation of single fibers increase with a reduction in the amount of lignin.

Study on the Tangential Tensile Mechanical Properties of Moso Bamboo

In this work,we used tensile tests to analyze the tangential failure forms of raw bamboo and determine a relationship between tangential tensile strength,elastic modulus,position,density,and moisture content.We found that the tangential mechanical properties of the culm wall were mainly dependent on the mechanical properties of the basic structure of the thin wall.Formulas for calculating the tangential tensile strength of moso bamboo and adjusting the moisture content were also determined.The tangential tensile strength and the tangential tensile modulus of elasticity(TTMOE)followed:outer>middle>inner,and diaphragm>bamboo node>culm wall.Below the fiber saturation point,the tangential tensile strength and TTMOE values of the bamboo gradually decreased with increasing moisture content.When the moisture content was 15%,the tangential tensile strengths of the inner,middle,outer,culm wall,bamboo node,and diaphragm samples of the five-year-old moso bamboo were 3.17,3.29,3.31,3.24,3.67,and 8.85 MPa,respectively.Furthermore,their TTMOE values were 215.09,227.98,238.45,224.04,267.21,and 559.27 MPa,respectively.Hence,this study provides a theoretical basis for future research on bamboo cracking.

Study on the Effect of Two-Step Saturated Steam Heat Treatment Process on the Properties of Reconstituted Bamboo

With the aim of utilizing reconstituted bamboo as a carbon cycle oriented material,the improvement of physical and mechanical properties has been actively studied to solve using problems The saturated steam heat treatment process has been widely used in worldwide.With the development and exploration of this technology,two step satu-rated steam heat treatment process appears in some practical production,that is,affer a period of saturated steam heat treatment at a lower temperature,the bamboo bundles are taken out and seasoned for a period of time,and then put back into the heat tank again,and heated at a higher temperature for another period of time.During the two-step saturated steam heat treatment,the physical and mechanical properties of bamboo changed.However,the mechanism of two step saturated steam heat treatment has not been thoroughly discussed.For purpose that this paper all discuss and find out the mechanism of two step saturated steam heat treatment on the change of physical and mechanical properties of reconstituted bamboo.In this work,the one and two step saturated steam heat treat-ments were carried out according to the actual production parameters,and the physical and mechanical properties of the reconstituted bamboo board made of treated bamboo bundles were analyzed,including the color change,the thickness swelling(TS),modulus of elasticity(MOE),modulus of rupture(MOR)and shear strength.The results indicate that two-step saturated steam heat treatment is better than one step.Based on the detailed study of the chemical composition,crytalinity and micro morphologial characteristics of the heated bamboo bundles,it is further revealed that during two-step saturated steam heat treatment,oxygen air is added to the reaction system between the two heat treatment processes to further catalyze the oxidation of hemicellulose and enhance the crystal-linity of cellulose,so as to improve the properties of the final products.Our work has optimized the saturated steam heat treatment process which is widely used in industry,pointing out a new idea in the experimental and theoretical basis for the development of recombinant bamboo manufacturing industry.

A Comparative Study into the Engineering Properties of Neem Wood from Ghana

A study into the mechanical properties of Neem wood was done to explore the possibility of its usage as a structural material. This paper presents the results of some investigations into the strength properties of Neem (Azadirachta indica A. Juss.) and compares them with those of Odum (Milicia excelsa) and European Oak (Quercus spp.) which are well known structural wood species in Ghana and Europe, respectively. The properties were determined using British (BS 373, 1957) and American timber testing specifications (ASTM D143, 1983) using testing methods for small, clear specimens of wood. The results showed that at 12% moisture content the wood has a density of 740 kg/m3 with a mean modulus of rupture of 8317 N/mm2, compressive strength parallel to the grain of 318.8 N/mm2, modulus of elasticity of 8644 N/mm2, and shear strength parallel to the grain of 17 N/mm2. The bending strength (MOR) of Neem is about 30% lower than that of Odum and about 2% higher than Oak. The modulus of elasticity of Neem is about 39% lower than Odum and 43% lower than Oak. The strength properties in the present work suggest that the wood of Neem has a potential for utilisation in structural applications.

Effect of genetic sources on anatomical, morphological,and mechanical properties of 14-year-old genetically improved loblolly pine families from two sites in the southern United States

Tree improvement programs on loblolly pine(Pinus taeda) in the southeastern USA has focused primarily on improving growth, form, and disease tolerance.However, due to the recent reduction of design values for visually graded southern yellow pine lumber(including loblolly pine), attention has been drawn to the material quality of genetically improved loblolly pine. In this study,we used the time-of-flight(TOF) acoustic tool to assess the effect of genetic families on diameter, slenderness, fiber length, microfibril angle(MFA), velocity and dynamic stiffness estimated using green density(DMOEG) and basic density(DMOEB) of 14-year-old loblolly pine stands selected from two sites. All the 184 and 204 trees of the selected eight half-sib genetic families on sites 1 and 2 respectively were tested using TOF acoustic tool, and two 5 mm core samples taken at breast height level(1.3 m)used to for the anatomical and physical properties analysis.The results indicated a significant positive linear relationship between dynamic MOEs(DMOEGand DMOEB)versus tree diameter, slenderness, and fiber length while dynamic MOEs negatively but nonsignificant correlated with MFA. While there was no significant difference in DMOEBbetween sites; velocity 2 for site 1 was significantly higher than site 2 but DMOEGwas higher for site 2 than site 1. Again, the mean DMOEGand DMOEBreported in the present study presents a snapshot of the expected static MOE for green and 12% moisture conditions respectively for loblolly pine. Furthermore, there were significant differences between families for most of the traits measured and this suggests that forest managers have the opportunity to select families that exhibit the desired fiber morphology for final product performance. Lastly,since the dynamic MOE based on green density(DMOEG),basic density(DMOEB) and velocity 2 present difference conclusions, practitioners of this type of acoustic technique should take care when extrapolating results across the sites.

Natural durability of wood of ten native species from northeastern Mexico

Thorn scrub vegetation in Mexico is distributed over 50 million ha, where native tree species are the source of forage, timber, firewood and charcoal. Research describing wood durability of species from this vegetation type has not been fully determined, nor classified according to international standards. Thus, the aim of this study was to determine and classify the natural durability of ten woody species. Their natural durability was determined according to the European Pre-Norm 807, the loss of dynamic modulus of elasticity （MOEdyo） （MPa） was determined and wood mass loss （g） after being exposed to Trametes versicolor and Coniophora puteana fungi. Wood durability was classified accord- ing to the European Norm 350-1. Highly significant differences （p 〈 0.001） were found between the durability of woody species. The more durable species with lower MOEdyn lost were Condalia hooked （57.5% ± 0.6%）, Havardia pallens （58.2% ± 0.4%） and Acacia schaffneri （58.9% ±6.3%）. Species with lower mass loss after exposed to Coniophora puteana were Ebenopsis ebano （6.3% ±1.9%）, Condalia hooked （8.6% ±2.3%） and Cordia boissieri （11.8% ±2.3%）. E. ebano （7.1% ±2.4%）, Condalia hooked （8.2% ± 2.5%） and Cordia boissieri （11.5% ± 3.1%） showed the lower mass lost after exposed to T. versicolor. According to European Norm 350-1, three woody species were classified as very durable and durable species.

Tangential stress analysis of myocardial wall by finite element method

A novel method is presented to build the triangular surface model and calculate the tangential stress and strain of myocardial wall ,which can be further used to reflect the left ventricle twisting—a sensitive index to assess the systolic and diastolic function of heart. Firstly, a point distribution model is used to obtain the feature points of the ventricular surface in medical images. Secondly, the surface model is constructed by triangular mesh, and then the subdivision strategy is introduced to refine the model. Thirdly, plane projection and finite element method(FEM) are applied to calculate the tangential stress and strain.Finally, the distribution of tangential modulus of elasticity is discussed. The stimulation results show that the proposed method can be used to compute the tangential stress and strain of myocardial wall effectively and the computing result is consistent with the results mentioned in the literatures.

Comparison of Crack Width and Space between SCC and Conventional Concrete Beams

Concrete is a material which is in wide use in engineering especially in construction engineering and road infrastructure facilities. Development trends for high rise constructions, modern skyscrapers indicate that building such constructions with normal concretes and low consistency is impossible, therefore there is a need for concrete with high processes because of great amount of reinforcement in cross-section of concrete elements. Solution for such construction is self-compacting concrete because of its ability to fill good formworks without compaction and vibration. Considering this fact, researches for cracks, mechanical characteristics of concrete and deformations have been conducted worldwide. In this paper, we conducted an experimental research to determine the cracks on beams of self-compacting concrete and compared it with conventional concrete. The experimentally-obtained results will be presented for both types of concrete for： module of elasticity, compression strength, crack with and cracks spacing for duration failure testing time t = 400 days.

Effects of Incorporating Expanded Polystyrene in Concrete Construction

Polystyrene is a highly popular plastic packaging material. It is essentially non-biodegradable and takes hundreds of years to decompose in case of land filling while other disposal methods or treatments methods create hazardous effects on the environment. However, this material is known to possess properties such as sound insulation, high thermal conductivity, and lightweight, thereby making it a great additive in concrete. Haven incorporated this material into a concrete matrix;in various percentages which served as partial replacement for coarse aggregates, the concretes’ properties were tested and compared with the properties of the conventional concrete. The experimental data was obtained based on the replacement coarse aggregate by EPS volume ratio of 0%, 4%, 8%, 12% and 16%. The concretes’ properties such as its slump, density, compressive strength, flexural strength and split tensile strength were experimentally determined. These results were then used to determine the influence of polystyrene as partial replacement for coarse aggregate was analyzed and the results compared with that of a concrete mix containing no polystyrene. The results obtained from this analysis indicate that the addition of polystyrene in a concrete mix implies smaller densities as the densities of concrete containing 0%, 4%, 8%, 12% and 16% are 2536, 2443, 2363, 2339 and 2316 Kg/m3 respectively. It was also observed that the compressive strength of the concrete decreased with an increase in the percentage of polystyrene incorporated. This is clearly shown using in the 28th day strength of the concrete samples (21.68, 17.25, 15.87, 14.53 and 13.92 mpa for replacements at 0%, 4%, 8%, 12% and 16% respectively). Similarly, the flexural strength of the concrete decreased with an increase in the percentage of polystyrene incorporated. Whereas, the variations in the split tensile strengths were inconsistent as they were notable increments and decrease in the 28th day strength of the various concrete matrixes.

Mechanical Properties of Terminalia catappa from Ghana

Ghana is rich in forest resources, of whichTerminalia catappa, a wood species of common occurrence is one. Even though sometimes it is used for decorative purposes, however, it grows in the wild. It grows in almost all the regions of the country and does well in the tropics. The parts of the tree such as the leaves, fruits and seeds have been known to be very useful for medicinal and other uses. Some work on the strength properties of the leaves and other parts has also been done, however, strength properties of the wood are yet to be explored. In this study, its mechanical properties such as bending strength, compression parallel to the grain, and shear parallel to the grain properties were determined. The British (BS 373, 1957) and American Society of Testing Materials’ specifications (ASTM D143, 1983) using testing methods for small, clear specimens of wood were used in determining the properties. The results showed that at 18% moisture content the wood has a density of 520 kg/m3 with a mean modulus of rupture of 86.04 Mpa, compressive strength parallel to the grain of 42.02 Mpa, modulus of elasticity of 10,500 Mpa, and shear strength parallel to the grain of 16.42 N/mm2. These strength properties are comparable to that of Strombosia glaucescens. Therefore, T. catappa can be used in applications where this species is used.