scholarly journals New Perspectives for LVL Manufacturing from Wood of Heterogeneous Quality—Part 2: Modeling and Manufacturing of Variable Stiffness Beams

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1275
Author(s):  
Robin Duriot ◽  
Guillaume Pot ◽  
Stéphane Girardon ◽  
Louis Denaud
Keyword(s):  
Mechanical Properties ◽  
Analytical Calculation ◽  
Variable Stiffness ◽  
Calculation Model ◽  
Bending Test ◽  
Control Panel ◽  
Optimization Strategy ◽  
Four Point Bending ◽  
Heterogeneous Quality ◽  
Bending Stresses

This paper presents a new strategy in the use of wood of heterogeneous quality for composing LVL products. The idea is to consider veneers representative of the resource variability and retain local stiffness information to control panel manufacturing fully. The placement of veneers is also no longer random as in the first part of this group of papers but optimized for the quality of veneers according to the requirement of bending stresses along the beam. In a four-point bending test arrangement, this means the high-quality veneer is concentrated in the center of the beam in the area between the loading points where the bending moments are the most important, and the low quality is located at the extremities. This initiates the creation of variable stiffness beams. This is driven by an algorithm developed and tested on representative veneer samples from the resource. Four LVL panels were manufactured by positioning the veneers in the same positions as in an analytical calculation model, which allowed the calculation of beam mechanical properties in four-point bending. The proposed optimization of LVL manufacturing from variable quality veneers should help for more efficient usage of forest resources. This optimization strategy showed notable gains for modeled and experimental mechanical properties, whether in terms of stiffness or strength. The analytical calculation of the local modulus of elasticity from modelized beams was satisfactory compared to the tests of the manufactured beams test results, allowing the reliability of the model for this property to be confirmed.

Influence of Fly Ash on the Mechanical Properties of Engineered Cementitious Composites Cured at High Temperature

2010 ◽  
Vol 113-116 ◽  
pp. 1293-1296
Author(s):  
Yu Zhu ◽  
Ying Zi Yang ◽  
Hong Wei Deng ◽  
Yan Yao
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
High Volume ◽  
Bending Test ◽  
Cementitious Composites ◽  
Test Results ◽  
Four Point Bending ◽  
High Volume Fly Ash ◽  
Compressive Strength Test

In order to investigate the mechanical properties of cementitious composites (ECC) cured at 60°C, four-point bending test and compressive strength test are employed to analyze the effect of fly ash on the properties of ECC. The replacement ratio of cement with fly ash is 50%, 70% and 80%, respectively. The test results indicate that ECC with high volume fly ash still remain the characteristic of pseudo-strain hardening and the deflection of ECC increases remarkably by adding more fly ash. The observations of ECC indicate that the crack width is relatively smaller for higher volume fly ash ECC. Meanwhile, compressive strength of ECC specimens with 80% fly ash can reach to 70MPa. This is helpful to produce precast ECC with high volume of fly ash.

High Temperature Mechanical Properties of a Crystallized BaO-B2O3-Al2O3-SiO2 Glass Ceramic for SOFC

2009 ◽  
Author(s):  
Hsiu-Tao Chang ◽  
Chih-Kuang Lin ◽  
Chien-Kuo Liu
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Stress Relaxation ◽  
Flexural Strength ◽  
Glass Ceramic ◽  
Testing Temperature ◽  
Bending Test ◽  
High Temperature Mechanical Properties ◽  
Four Point Bending ◽  
The Given

The high temperature mechanical properties in a glass-ceramic sealant of BaO-B2O3-Al2O3-SiO2 system was studied by four-point bending test at room temperature, 550°C, 600°C, 650°C, and 700°C, to investigate the variation of Young’s modulus, flexural strength, and stress relaxation. Weibull statistic analysis was applied to describe the fracture strength of the given glass ceramic. The crystalline phase was produced by controlled heat treatment and analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the flexural strength was enhanced at high temperatures when the testing temperature was below the glass transition temperature (Tg). This was presumably due to a crack healing effect taking place at high temperature. Significant stress relaxation for the given glass ceramic was observed to generate extremely large deformation without breaking the specimens when the testing temperature was set at 700°C.

Characterization and Simulation of Bending Properties of Continuous Fiber Reinforced C/C-SiC Sandwich Structures

2017 ◽  
Vol 742 ◽  
pp. 215-222 ◽  
Author(s):  
Yuan Shi ◽  
Bernhard Heidenreich ◽  
Pranav Kumar Dileep ◽  
Dietmar Koch
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structures ◽  
Analytical Calculation ◽  
Fiber Reinforced ◽  
Continuous Fiber ◽  
Four Point Bending ◽  
Versatile Tool ◽  
Numerical Finite Element ◽  
German Aerospace ◽  
Skin Panels

At the Institute of Structures and Design of German Aerospace Center (DLR) in Stuttgart, C/C-SiC sandwich structures based on continuous fiber reinforced folded cores and skin panels have been developed via Liquid Silicon Infiltration (LSI) and in situ joining method. The resulting lightweight structures offer a high potential in various application areas such as optical benches of satellites or charging racks for high temperature furnaces.A major impediment for the new development and practical application of ceramic sandwich structures is the lack of know-how of characterization and simulation of their mechanical properties. In this study, several types of C/C-SiC sandwich structures with folded cores with different fiber orientations (0°/90° and ±45°) in the core structure were manufactured and mechanically tested in four point bending. The mechanical properties of the different sandwich structures were correlated to analytical calculation and numerical (finite element) simulation. The comparison showed good correlation. The proposed evaluation methods are suitable to determine and simulate the mechanical properties of C/C-SiC sandwich structures and are a versatile tool for further product development.

Strength and Toughness of Graphite Materials for Solid Rocket Motor

2004 ◽  
Vol 449-452 ◽  
pp. 709-712
Author(s):  
Shoichi Nambu ◽  
Manabu Enoki
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Crack Propagation ◽  
Fracture Probability ◽  
Bending Test ◽  
Fracture Toughness Test ◽  
Solid Rocket Motor ◽  
Four Point Bending ◽  
Toughness Test ◽  
Solid Rocket

It was pointed out that one of the causes of recent failure to launch rocket was due to the fracture of nozzle throat insert made of graphite materials. The relationship between mechanical properties and microfracture process in graphite was not enough analyzed. To ensure the reliability of such aerospace equipment, we considered the necessity of assurance by non-destructive evaluation, evaluation of mechanical property for graphite material and design based on fracture probability. In this study, four-point bending test and fracture toughness test were used to evaluate mechanical properties. Mean strength, Weibull parameters, and R-curve for crack propagation were estimated. AE measurement during tests was performed in order to obtain location and stress of microfracture. AE results were analyzed by stochastic process theory. The result of AE demonstrates that microfracture process during bending test is divided into three stages. AE behavior in fracture toughness test was also closely related to crack propagation.

Effects of Sintering Temperature and Excess Zr on Mechanical Properties of Reactive Hot-Pressed ZrB2-ZrCx-Zr Cermets

2016 ◽  
Vol 697 ◽  
pp. 633-638 ◽  
Author(s):  
S.Q. Guo
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Sintering Temperature ◽  
Bending Test ◽  
Cracking Behavior ◽  
Propagation Behavior ◽  
Four Point Bending ◽  
Different Temperatures ◽  
Four Point Bending Test ◽  
Reactive Hot Pressing

In this study, a series of ZrB2-ZrCx-Zr cermets were prepared by reactive hot-pressing of Zr + B4C powder mixtures at different temperatures between 1400°C and 1900°C. The microstructure of the resulting cermets was characterized by field emission scanning electron microscopy. The strength and fracture toughness of the cermets were measured by four-point bending test at room temperature. The results showed that the strength and fracture toughness dependend on the amount of excess Zr and sintering temperature as well. In addition, the crack propagation behavior of the cermets was examined under indent cracking. The cracks induced by indenter directly propagated in the samples with less than 16 vol% Zr. For comparison, the multiple cracking behavior was observed for the samples with equal to or greater than 16% Zr. Furthermore, the effects of compositions and sintering temperatures on the microstructure and the mechanical properties of the cermets were discussed.

scholarly journals Determination of Strength Classes of Selected Nigerian Timbers in Accordance with EN338 (2009)

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Idayat O Sholadoye ◽  
Idris Abubakar
Keyword(s):  
Mechanical Properties ◽  
Limit State ◽  
Physical And Mechanical Properties ◽  
Tectona Grandis ◽  
Bending Test ◽  
Timber Species ◽  
Gmelina Arborea ◽  
Permissible Stress ◽  
Four Point Bending ◽  
Four Point Bending Test

Wood has several unique, independent properties. The physical and mechanical properties of wood do vary from species to species and even within species due to environmental conditions during growth. In Nigeria, timber is been grade based on permissible stress (NCP) an upgrade to the limit state is required. A laboratory test was carried out to develop the physical and mechanical properties (four-point bending test) of the timber species in accordance with EN 13153-1, ASTM D143 and EN 408. The strength classification of selected timber was performed according to EN 338 using characteristic value of the material properties in accordance with EN384 from the generated physical and mechanical properties, after being adjusted to 12% (Eurocodes reference moisture content). The timber species considered were Tectona grandis and Gmelina arborea. The result showed Tectona grandis had a higher property than Gmelina arborea and the species were assigned to strength classes of D50 and D35 (hardwoods) respectively. The study shows that the selected timber species are suitable for structural purposes.Keywords: Strength classes, Nigerian timber, Four-point bending test, Tectona grandis, Gmelina arborea

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