Bending Strength Values Research Articles

Sinthesis and Properties of Marble-Like Glass-Ceramics Using of Ash from Thermal Power Plants

Color marble-like glass-ceramic materials were obtained through thermal treatment of glasses of the system CaO-Al2O3-SiO2 by using natural materials with the introduction of waste materials - ash from thermal power plants (TPP). The melting of the glass batch was in corundum crucibles at 1450oC with an isothermal hold of 60 min. The glasses obtained was fritted in distilled water and dried for 6 hours at 100oC, then completely crushed and divided into fractions with grain size of 0.8 mm, 1.0 mm, 2 mm, 2.5 mm and over 2.5 mm. It was found that the use of ash from TPP lead to higher values of degree of transformation (crystallization) than using base composition. Values of Avramy parameter’s in the range n=1,0 ÷ 1,6 are showed that crystallization of the glass frit is largely heterogeneous and crystal growing starts from the surface. The introduction of ash from TPP to native glasses carry out to significant reduction of energy of crystallization by Ес=289 kJ/mol to Ec=221 kJ/mol. The glass-ceramic materials were obtained through a one stage crystallization - 1050÷1070оС and an isothermal hold of 60 min., colored white, yellow brown to dark brown. The main crystalline phase in glass-ceramics is β-vollastonite with needle habit, size of crystals - ĺ = 40 ÷ 120 μm and d <5 μm in quantities 37 ÷ 42%. As secondary phases depending on the amount of ash have been identified - the anorthite, gehlenite and α-quartz with prismatic habit were appeared. The obtained glass-ceramic materials have a marble-like effect and technical parameters compared with natural granite and marble and have higher values of density, micro hardness, speed grinding, bending strength and chemical resistance. That’s why they can be used in construction such as lining materials.

Analysis of mechanical properties for tea stem using grey relational analysis coupled with multiple linear regression

To improve the picking quality of tea plucking machine, the relationship between mechanical properties of tea stem and their influence factors was studied. Tea variety of Zhongcha 108 was selected as test sample to analyze the grey correlations of stem segment number, stem diameter, stem inter-node distance, moisture content, fracture deflection, moment of inertia, young's modulus, hemicellulose content, cellulose content, lignin content to mechanical properties (bending and shearing strength). Further, multiple parameter optimization and model establishment were performed using partial least squares regression (PLSR), principal component analysis (PCA) + multiple linear regression (MLR), grey relational analysis (GRA) + MLR. The results showed that the cellulose content, bending strength, shearing strength, stem diameter and moment of inertia generally increased with stem segment number. For bending and shearing strength, GRA (0.6) + MLR method was suitable to establish the model. The values of adjusted Rc2 and RMSEC of bending strength were 0.8634 and 3.3264 N, and these values of shearing strength were 0.9730 and 0.2573 N. Besides, adjusted Rp2 values of bending and shearing strength were 0.9443 and 0.9125, RMSEP values were 2.8580 N and 0.7211 N, respectively. The GRA-MLR model is accurate and effective method to investigate the mechanical properties of tea stem for designing a suitable cutting equipment.

Normalized characterization method for fatigue behavior of cement-treated aggregates based on the yield criterion

The objective of this paper is to propose a normalized characterization method based on the yield criterion to eliminate the impacts of different stress models on the fatigue behaviors characterization of cement-treated aggregates. Based on the theory of octahedral shear stress strength and yield surface mode, the yield surface of cement-treated aggregates was established with four-point bending, compression, and indirect tensile strength value under different loading rates. Then, the fatigue stress and corresponding ultimate strength could be characterized by the yield surface, uniformly and uniquely. In the yield surface space (I1, J2), the fatigue stress growth route from initial stress to ultimate strength was identified as fatigue stress path. Based on the fatigue stress path, the fatigue stress ratios related to loading rate and stress model were calculated. With these stress ratios, the conventional S-N fatigue equation was modified, on the basis of which a normalized characterization method of fatigue behavior was proposed to characterize the fatigue behavior of cement-treated aggregates. Compared with the traditional characterized method, the normalized characterization method has considered the influence of loading rate and stress model on strength and fatigue test results. The test results demonstrated that different strength and fatigue test results were obtained under distinct stress model and loading rates. All strength values have been expressed indiscriminately in the yield surface. With the normalized characterization method, a unique fatigue curve was gained for cement-treated aggregates under different loading rates and stress models. Therefore, findings of this work realized the normalization characterization of fatigue behavior of cement-treated aggregates.

Examining the breaking and bending behaviors of the polymethylmethacrylate composites reinforced with hazelnut shell powder

The objective of the present study is to reveal the toughening effect of the hazelnut shell on the brittle matrices by using the bending and breaking methods. The polymethylmethacrylate composites reinforced with hazelnut shell powder with 50µ particle size at the weight concentrations of 5%, 10%, 15%, and 20% were prepared. The polymer beam samples were exposed to heat cure procedure and the initial notches were created at a/W=0.1, 0.2, 0.3, 0.4, and 0.5. The Mode I breaking behaviors of the notched at single edge and non-notched composite samples were examined by using three-point bending test. The critical stress intensity factor (KIC), J-integral, initial notch depth, and compliance methods were used in calculations. Besides them, the bending module and bending stress values were calculated. The microstructures of HNSP/PMMA composites were determined by using XRD (x-ray diffractometer), FTIR (Fouirer Transform Infrared Spektrofotometre), and SEM (scanning electron microscope) analyses. According to the results obtained, it was determined that the bending strength, elasticity module, and fracture toughness values increased at 10% additive ratio for the HNSP (hasel nut shell flour)/PMMA (polymethylmethacrylate) composites.

DARLING: a device for assessing resistance to lodging in grain crops

BackgroundStalk lodging (breakage of plant stems prior to harvest) is a major problem for both farmers and plant breeders. A limiting factor in addressing this problem is the lack of a reliable method for phenotyping stalk strength. Previous methods of phenotyping stalk strength induce failure patterns different from those observed in natural lodging events. This paper describes a new device for field-based phenotyping of stalk strength called “DARLING” (device for assessing resistance to lodging in grains). The DARLING apparatus consists of a vertical arm which is connected to a horizontal footplate by a hinge. The operator places the device next to a stalk, aligns the stalk with a force sensor, steps on the footplate, and then pushes the vertical arm forward until the stalk breaks. Force and rotation are continuously recorded during the test and these quantities are used to calculate two quantities: stalk flexural stiffness and stalk bending strength.ResultsField testing of DARLING was performed at multiple sites. Validation was based upon several factors. First, the device induces the characteristic “crease” or Brazier buckling failure patterns observed in naturally lodged stalks. Second, in agreement with prior research, flexural rigidity values attained using the DARLING apparatus are strongly correlated with bending strength measurements. Third, flexural stiffness and bending strength values obtained with DARLING are in agreement with laboratory-based stiffness and strength values for corn stalks. Finally, a paired specimen experimental design was used to determine that the flexural data obtained with DARLING is in agreement with laboratory-based flexural testing results of the same specimens. DARLING was also deployed in the field to assess phenotyping throughput (# of stalks phenotyped per hour). Over approximately 5000 tests, the average testing rate was found to be 210 stalks/h.ConclusionsThe DARLING apparatus provides a quantitative assessment of stalk strength in a field setting. It induces the same failure patterns observed in natural lodging events. DARLING can also be used to perform non-destructive flexural tests. This technology has many applications, including breeding, genetic studies on stalk strength, longitudinal studies of stalk flexural stiffness, and risk assessment of lodging propensity.

Enhancement of the Heat Resistance of Polymers and Composites by Curing of Epoxy Resins with Methylendic Anhydride under the Action of Imidazoles

Curing of Bisphenol A diglycidyl ether with methylendic anhydride under the action of imidazole-type catalysts was studied by differential scanning calorimetry and IR spectroscopy. The curing system with the optimum catalyst content was chosen. Heat-resistant polymers and composites with high values of the glass transition point, elastic modulus, and tensile, compression, and bending strength were prepared from epoxy resins of various functionalities.

Microwave hot press sintering: New attempt for the fabrication of Fe–Cu pre-alloyed matrix in super-hard material

Super-hard diamond drill bits were prepared with microwave hot press sintering (MHPS) method at low sintering temperature. The micro-structures were analyzed using SEM. The samples were characterized for their properties such as bending strength, hardness, relative density and compression and tensile test. The purity of the diamond in samples was investigated by Raman spectroscopy. The results display that when MHPS method is applied to the manufacture of diamond drill bits, it has prominent advantages such as shorter sintering time, lower sintering temperature et al. And the samples prepared with MHPS at 860 °C show excellent performance. The values of hardness, relative density and bending strength are 106.6 HRB, 97.6% and 895.8 MPa respectively. Thus, a reaction kinetic study was performed to analyze reaction mechanism. And a potential sintering mechanism of MHPS is discussed. This work will provide a theoretical basis for the preparation of diamond tools through MHPS process.

Effects of moisture content on mechanical properties of micro-size oak wood

Effects of moisture content (MC) were investigated for the mechanical properties of oak wood (Quercus petraea Liebl.) using micro-size test specimens. The micro-size specimens for bending, tensile, and compression tests were prepared and divided into five groups. Each group was conditioned at a different relative humidity and temperature to achieve MC values of 8%, 12%, 16%, 20%, and above-fiber-saturation-point MCs. After conditioning, the bending strength, modulus of elasticity (MOE) in bending, tensile strength, and compression strength values were determined. The results showed that MC had statistically significant effects on all the measured mechanical properties in the micro-size oak wood samples. The greatest decrease was observed for the compression strength, while the lowest decrease was observed for the tensile strength, when MC increased. The changing rates induced by 1% MC were calculated as 3% for bending strength, 2.5% for the MOE, 2.0% for the tensile strength, and 3.1% for the compression strength.

Effects of alkaline earth oxides on the densification and microwave properties of low-temperature fired BaO–Al2O3–SiO2 glass–ceramic/Al2O3 composites

The effects of alkaline-earth oxides (SrO, CaO, MgO) on the densification and microwave properties of low-temperature fired BaO–Al2O3–SiO2 (BAS) glass–ceramic/Al2O3 composites have been investigated. By adding alkaline-earth oxides, the softening and crystallization behaviors of BAS-based glass–ceramics, which determine the densification of composites, are sequentially weakened in the order of BAS, SrO–BaO–Al2O3–SiO2 (SBAS), CaO–BaO–Al2O3–SiO2 (CBAS) and MgO–BaO–Al2O3–SiO2 (MBAS). It is also found in the above BAS-based glass–ceramics that the addition of alkaline-earth oxides plays a more profound role on crystallization behavior than on softening behavior, leading to the expansion of the interval between crystallization and softening temperatures (i.e., densification temperature range) to different degrees depending on the type of oxides added. As a result, the microstructures of oxides-modified glass–ceramic/Al2O3 composites (SBAS/Al2O3, CBAS/Al2O3, MBAS/Al2O3) are much denser than those of BAS/Al2O3. The properties of such composites are determined by the interplay among density of microstructure, amount and relative ratio of crystalline and residual glass phases related to the crystallization behavior and interfacial reaction. Detailed analyses suggest that CBAS/Al2O3 achieves optimal properties among all the four composites. Specifically, for CBAS/Al2O3 the dielectric constant, dielectric loss, bending strength and CTE value are 5.81 ± 0.12 (at ~ 10 GHz), (2.04 ± 0.12) × 10−3 (at ~ 10 GHz), 155 ± 7 MPa and 6.58 ± 0.11 ppm/°C, respectively. Our findings may provide a new avenue to design LTCC substrate materials as feasible candidates for microwave devices.

Mechanical and Physical Properties of Particleboard from Untreated and Treated Kenaf Particles

Composite panels were manufactured from kenaf particles and treated with two different alkali treatments using 2% NaOH and 2% KOH with resin contents of 8% and 10% of phenol formaldehyde (PF) at medium density of 650kg/m3. The objectives of this study were to determine the mechanical properties in terms of its modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB), and physical properties namely thickness swelling (TS) and water absorption (WA) of treated kenaf board. The mechanical and physical tests were performed according to the Malaysian Standard (MS1787:2004). The minimum requirements value for MOE, MOR and IB were 2000 MPa, 14 MPa and 0.45 MPa respectively for furniture grade particleboards for use in humid conditions (PF2). According to Malaysian specifications for physical properties, the maximum requirement for thickness swell is 15%. Results indicated that both treated boards with NaOH and KOH showed an increase in strength properties compared to untreated particleboard. Particleboard treated with KOH exhibited the highest MOR and MOE values, while board with NaOH treatment gave the highest IB value. The boards with treated particles gave better performance in terms of physical properties. There were no significant differences in mechanical properties (MOR, MOE and IB) and physical properties for the different alkali treatment. The values of bending strength and IB strength increased with an increase in resin content, while TS and WA increased with a decrease in resin content. In conclusion, NaOH and KOH treated kenaf particles improved board performance and could be considered as an alternative material for particleboard production.

Influence of in-situ Al2O3 content on mechanical properties of Al2O3 reinforced Fe–Cr–Ni alloys

AbstractIn-situ Al2O3 (14.8–31.3 wt.%) reinforced Fe–Cr–Ni alloys were prepared using reactive hot pressing at a temperature of 700°C and pressure of 30 MPa for 2 h. X-ray diffraction showed that the obtained metal matrix composites (MMCs) mainly comprised Al2O3, Fe–Cr and Cr0.7Fe0.36Ni2.9 phases. Vickers hardness values of the composites with varying Al2O3 contents were all around 4.28 GPa. Scanning electron microscopy images showed that the Al2O3 particles in the MMCs (with Al2O3 content of 14.8 wt.%) were ultrafine and uniformly distributed. Moreover, the metal matrix composite with 14.8 wt.% Al2O3 exhibited the highest values of fracture toughness and bending strength, which were 15.2 MPa · m1/2 and 529 MPa, respectively.

Effect of blowing agent concentration on rigid polyurethane foam and the properties of foam-core particleboard

ABSTRACT In this research, a sandwich panel with particleboard as surface layers and rigid polyurethane (PU) foam as core layers (foam-core particleboard) was produced with a one-step in situ foaming process. The effects of hydrofluorocarbon concentration as the blowing agent (BA) on the foam features and physical and mechanical properties of the produced panels were investigated. Typical micrograph of the rigid PU foam showed well-defined closed cells of spherical and polyhedral shapes. It was shown that the number of fractured cells in the foam structure was increased with the addition of BA in the amount of more than 4.5%. The results showed that the bending strength and internal bond values significantly raised with increasing BA concentration up to 6%. Screw withdrawal resistance from the face and thickness swelling were not significantly changed while the BA concentration varied. Edge screw withdrawal resistance and water absorption were drastically decreased when the blowing agent concentration was raised in the whole studied range. ABBREVIATIONS: PU: polyurethane; OH: hydroxyl; PO: polyol; ISO: isocyanate; BA: blowing agent; PMDI: polymeric methylene diphenyl diisocyanate; BS: bending strength; IB: internal bond; SWR: screw withdrawal resistance; TS: thickness swelling; WA: water absorption

Structural properties and mechanical behavior of SWCNTs and MWCNTs reinforced Al2O3 fabricated by spark plasma sintering

Abstract Carbon nanotubes due to their structural and mechanical properties are good candidates as the second phase to improve the mechanical properties of alumina-based ceramics. In the present study, the effects of single wall and multi-wall carbon nanotubes on structural and mechanical properties of alumina were investigated. SWCNTs and MWCNTs were dispersed in alumina powder via a conventional method using 1 wt % PVA water solution as media. Sintering process for two different composite powders, alumina-2 wt. % SWCNTs and alumina 2 wt % MWCNTs was performed by spark plasma sintering technique at 1500 °C and 20 MPa for 10 min. Results showed that the presence of CNTs in alumina caused a considerable amount of porosity in final bodies. SEM images of fracture surfaces revealed the agglomeration of SWCNTs which played a dominant role in the deterioration of mechanical properties. MWCNTs reinforced alumina obtained higher Vickers hardness and bending strength values (12.91 GPa and 291 MPa, respectively) compared to that of SWCNTs (9.18 GPa and 276 MPa, respectively), due to sever agglomerate of SWCNTs throughout sintered composites. Typical load-displacement (P/h) curves were obtained from bending strength test and discussed. It was concluded that the addition of MWCNTs to alumina represented better densification and mechanical properties compared to SWCNTs.

The study on composites formation from HDPE and sawdust/rice husk as raw materials

In this study, composites were prepared using compression molding method from cheap raw materials of high-density polyethylene (HDPE) as matrix and mixture of rice husk and sawdust as filler. The small amount of coupling agent was added during preparation of composites and for comparison composite without addition of coupling agent was also prepared. The coupling agent used in this study was maleic anhydride (MA). The aim of this study is to form composites with and without addition of coupling agent and to know the effect of coupling agent addition and different ratio of matrix and filler toward mechanical properties of produced composites. Composites that contained different ratio of matrix and filler were pressed and heated at temperature of 170°C. The composites were tested its mechanical properties (bending strength and tensile strength) and water absorption capacity. The results indicated that the bending strength of the composite increased with addition of 4 wt% of maleic anhydride and with increased the percentage of filler until 50%. As for the tensile strength, the addition of 4 wt% of maleic anhydride as coupling agent increased the tensile strength significantly. The highest bending strength value of 12.8 MPa was obtained from composite prepared from raw materials contained same amount of matrix and filler and addition of 4 wt% of maleic anhydride. While the highest tensile strength value of 6.1 MPa was obtained from composite prepared from raw materials contained ratio percentage of matrix and filler (40:60 of wt%) and addition of 4 wt% of maleic anhydride.

Technological and physical properties of dry pressed red mud bodies containing chamotte

Each clay has its own distinct makeup, resulting in a different handling quality, color, temperature range and plasticity, or workability. The choice of clays is wide and you can also combine them which will increase the possibilities further. In this study, dry pressed red mud bodies containing chamotte were used for increasing mechanical properties. Five, 10, and 15 wt% chamottes were added to red mud bodies, separately. Prepared granules were dry pressed with suitable pressing pressure. Dry pressed granules were sintered at 900, 950, and 1000 °C for 2 h. Physical and technological properties were determined by measuring pore diameter, density, shrinkage, and water absorption. Structural characterization was carried out with XRD and scanning electron microscopy (SEM) studies. Vickers microhardness and bending strength test were done to determine mechanical properties. Optimum chamotte addition to red mud bodies and optimum sintering temperature with high mechanical properties were determined with this study. The best density, water absorption, firing shrinkage and bending strength values were obtained with RM15C sample sintered at 1000 °C as 2.94 g/cm3, 6.6%, 10.9%, and 107 MPa, respectively.

PENGARUH VARIASI JUMLAH LAPISAN FIBERGLASS DAN ANYAMAN BAMBU TERHADAP KEKUATAN BENDING KOMPOSIT DENGAN METODE VACUUM ASSISTED RESIN INFUSSION (VARI)

The objective of this research is to obtain the bending properties of composite material produced by VARI method, and to get analysis of polyester resin distribution time on the layer of fiberglass composite and bamboo woven strip.The process of making composites varies, but the process of making this research is the process of Vacuum Assisted Resin Infusion (VARI). In the VARI process, dry fiber is placed between the fixmold and plactic bag, then the resin is injected after the chamber inside the low- pressure plastic bag and the process continues until all parts of the fiber are wetted by the resin.From the results of research, testing and discussion of bending test results that have been done then can be drawn conclusions include: Variation of the number of reinforcement layer on VARI method will affect the value of bending strength of composite. By using the VARI method The highest average value of bending stress occurs in variation 4 (206,69 MPa), while the lowest occurs in variation 1 (42,83 MPa), and the time required for the distribution of resin varies in time variation 1 which takes 5 minutes 02 seconds, while for variation 4 takes 8 minutes 3 seconds.Keywords: composites, VARI method, glass fiber, bending test

Mechanical Properties of Superconducting (Gd,Y)BaCuO Large Single-Grain Material Fabricated by RE Compositional Gradient Technique

In order to investigate the mechanical properties of a (Gd,Y)BaCuO large single-grain bulk material, bending tests were carried out at room temperature for the specimens cut from the bulk material. A precursor, which consisted of three regions with different Gd and Y contents, was used for the fabrication of the large single-grain bulk material in order to overcome the undesirable nucleation apart from the seed crystal. The precursor was prepared such that Y content increased with increase in the distance from the center, where the seed crystal was placed, to decrease the peritectic decomposition temperature. Two types of bending test specimens were cut from the bulk material—the specimens that included the interface between two regions with different Gd and Y contents and the specimens that did not include the interface. Although the bending strength data of the specimens that did not include the interface scattered widely in comparison with the specimens that included the interface, the average bending strength values of these specimens were similar to each other. This result demonstrates that the interface does not cause the deterioration of the mechanical properties of the whole bulk material.

Determination of modulus of elasticity and bending strength of wood material impregnated with nanoparticle silicon dioxide (SiO2)

The purpose of this study is to determine the effects of the nano-particulate silicon dioxide (SiO2) material on the bending strength and modulus of elasticity in bending of some wood species. Oriental beech (Fagus orientalis L.) and sessile oak (Quercus petrea L.) woods species which are commonly used in the furniture industry were used in this study. Impregnation was carried out with the preparation of SiO2 at concentrations of 1% and 3% according to ASTM-D 1413-76 (1976) standards. According to the results, while solution concentration was increasing in both wood species, total retention (kg/m3) and percentage retention (%) values increased; air dry density (12%), bending strength and modulus of elasticity in bending decreased. The maximum mean values of bending strength and modulus of elasticity was in control samples of oriental beech and the minimum were in sessile oak wood with 3% concentration. These results can be related to the fact that the higher density of oriental beech wood (0.630-0.685 g/cm³). In both species of wood, impregnation with SiO2 resulted loss of about 3-5% in bending strength and 0.6-9% in modulus of elasticity.

Mechanical and tribological assessments of high-vanadium high-speed steel by the conventional powder metallurgy process

This paper reported the facile fabrication of high-vanadium high-speed steel (HVHSS) by the conventional powder metallurgy process for the wear-resistant applications. The effect of compaction pressure and of subsequent sintering temperatures on the formability and structural evolution of HVHSS was assessed by scanning electron microscopy (SEM) with electron-dispersive spectra (EDS), and X-ray diffraction (XRD) analysis. The results well revealed the primary constitution composed of mixed hardening phases MC and M6C existing within the α-ferrite matrix after hot solidification, and the association of microstructural alteration with the sintering temperatures was discussed for as-obtained HVHSS specimens. The HVHSS attained the desirable values of mechanical hardness and bending strength and thereby delivered the capability of friction reduction and wear inhibition, closely depending on the sintering temperature. The optimal sintering condition was determined on the basis of bulk density, shrinkage, and capability assessments. A well-established fabricating route for producing high-quality HVHSS was explored through the combined process of cold compaction and subsequent sintering on the conceptual design of chemical composition and alloying design of commercial M2 steel.

Prediction of Bending Strength of Self-Leveling Glass Fiber Reinforced Concrete

Many studies have been conducted on the prediction of fiber reinforced concrete strength; however, there are very rare data concerning the prediction of bending strength values of self-leveling glass fiber reinforced concrete. And there is no study for prediction of bending strength of self-leveling glass fiber reinforced concrete from mixture ingredients and slump values. In the present study, relationships between the bending strength and the mixture proportions are explored. An artificial neural network model (ANN) is designed with an extensive experimental data including 395 four-point bending tests, and input parameters as white cement amount, maximum aggregate size, glass fiber content, water cement ratio, superplasticizer and metakaolin content and slump test results. Effect of each parameter on the bending strength is investigated with the developed model. An empirical and user-friendly formula was obtained with the generalization capabilities of the ANN. Results showed that the prediction results are in good agreement with the field data. And these numerical results with high efficiency can make it possible to use the neural design for real-life self-leveling glass fiber reinforced concrete applications.