Average Bending Strength Research Articles

A study into the scale effect on the strength properties of polymer composite materials

Polymer composite materials (PCM) are used extensively and are viewed as candidates for application in various industries, including nuclear power. Despite a variety of methods and procedures employed to investigate the mechanical characteristics of PCMs, the use of the laboratory sample mechanical test results to design and model large-sized structures is not always fully correct and reasonable. In particular, one of the problems is concerned with taking into account the scale parameter effects on the PCM strength and elastic characteristics immediately in the product. The purpose of the study is to investigate the scale effects on the mechanical characteristics of glass reinforced plastics using phenolformaldehyde and silicon-organic binders and a fabric quartz filler. Samples of four different standard sizes under GOST 25604-82 and GOST 4648-2014 were tested for three-point bending using an LFM-100 test machine to estimate the scale effect. The thicknesses of the model samples were chosen with regard for the wall thicknesses of full-scale products under development or manufactured commercially and the test machine features, and varied in the limits of 1.6 to 7.5 mm. The tests showed that strength decreased as the sample thickness was increased to 3 mm and more both at room and elevated (200 to 500 °C) temperatures, which can be described by an exponential function based on the Weibull statistical model. The values of the Weibull modulus that characterizes the extent of the scale effect on the strength of the tested materials were 4.6 to 6.7. The average bend strength in the sample thickness range of 3 mm and less does not vary notably or tends to increase slightly as the thickness is increased. This fact makes it possible to conclude that estimation of allowable stresses in a thin-wall product requires the use of test results for samples with a thickness that is equal to the product wall thickness since standard samples may yield overestimated allowable stress values and lead, accordingly, to incorrect calculations of the strength factor. The results obtained shall be taken into account when defining the allowable levels of operation for full-scale products and structures of polymer composites based on the laboratory sample strength data as well as when estimating their robustness as a characteristic of the product’s fail-safe operation.

A study into the scale effect on the strength properties of polymer composite materials

Polymer composite materials (PCM) are used extensively and are viewed as candidates for application in various industries, including nuclear power. Despite a variety of methods and procedures employed to investigate the mechanical characteristics of PCMs, the use of the laboratory sample mechanical test results to design and model large-sized structures is not always fully correct and reasonable. In particular, one of the problems is concerned with taking into account the scale parameter effects on the PCM strength and elastic characteristics immediately in the product. The purpose of the study is to investigate the scale effects on the mechanical characteristics of glass reinforced plastics using phenolformaldehyde and silicon-organic binders and a fabric quartz filler. Samples of four different standard sizes under GOST 25604-82 and GOST 4648-2014 were tested for three-point bending using an LFM-100 test machine to estimate the scale effect. The thicknesses of the model samples were chosen with regard for the wall thicknesses of full-scale products under development or manufactured commercially and the test machine features, and varied in the limits of 1.6 to 7.5 mm. The tests showed that strength decreased as the sample thickness was increased to 3 mm and more both at room and elevated (200 to 500 °C) temperatures, which can be described by an exponential function based on the Weibull statistical model. The values of the Weibull modulus that characterizes the extent of the scale effect on the strength of the tested materials were 4.6 to 6.7. The average bend strength in the sample thickness range of 3 mm and less does not vary notably or tends to increase slightly as the thickness is increased. This fact makes it possible to conclude that estimation of allowable stresses in a thin-wall product requires the use of test results for samples with a thickness that is equal to the product wall thickness since standard samples may yield overestimated allowable stress values and lead, accordingly, to incorrect calculations of the strength factor. The results obtained shall be taken into account when defining the allowable levels of operation for full-scale products and structures of polymer composites based on the laboratory sample strength data as well as when estimating their robustness as a characteristic of the product’s fail-safe operation.

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.

Mechanical and Magnetic Properties of Hot-Deformed Nd-Fe-B Magnets Doped with SiC Whiskers

To improve the mechanical properties of hot-deformed Nd-Fe-B magnets, anisotropic Nd-Fe-B magnets doped with SiC whiskers were fabricated by hot-pressing and hot-deformation processes. The influence of the SiC whiskers on the microstructure and magnetic and mechanical properties of the Nd-Fe-B magnets was investigated. The bending strength of the hot-deformed Nd-Fe-B magnets reinforced with SiC whiskers first increased and then decreased with increasing SiC whisker content from 0 wt.% to 1.0 wt.%. The composite magnet with 0.5 wt.% SiC whiskers exhibited the highest average bending strength and still retained the maximum energy product of approximately 45.8 MGOe. The morphology of the fracture surface of the magnets revealed that the majority of the SiC whiskers were distributed at intergranular boundaries. The phenomenon of SiC whisker pullout from the matrix was observed, which results in increased bending strength. The improvement of the mechanical properties can be attributed to the high strength of the SiC whiskers, the whisker pullout phenomenon, and crack deflection.

A investigation and analysis of characteristics of solid furniture boards made of post-consumer wood

It is substantiated that post-consumer wood (PCW) is an additional timber resource for the woodworking industry. It is established that the physical and mechanical parameters of all furniture boards, regardless of their design, satisfy the requirements of regulatory documents. It has been found that the ratio of thickness to the width of the strips is most influenced by the physical and mechanical properties of the furniture boards. The highest physical and mechanical parameters are characterized by a solid furniture boards with a strips cross section of 22×20 mm. The average static bending strength across the strips of such a solid furniture boards is 27.03MPa. The lowest physical and mechanical indicators are characterized by a solid furniture boards with a strips section of 22×80 mm. The average static flexural strength across the strips of such a solid furniture boards is 16.10MPa. The physical-mechanical parameters of a traditional solid furniture boards made of primary wood are slightly higher than the physical-mechanical parameters of a similar solid furniture boards design made of PCW. Thus, the static flexural strength across the strips of a traditional solid furniture boards is 22.05MPa, and the strength of a solid furniture boards made of PCW is 19.88MPa. According to the results of experimental researches it is established that in order to achieve the shape resistance and sufficient strength of the solid furniture boards on a static bend across the strips, it is recommended that the width of the rail for gluing the furniture board should be no more than triple its thickness.
 It is recommended to use radial cross-section wooden strips when making solid furniture boards to ensure high resistance. Remodeling the iron on the furniture boards will bring financial and environmental benefits. The financial advantage of the manufacturer is to reduce the material costs of making solid furniture boards made of PCW of iron from the traditional furniture boards. Yes, our calculations show that the cost of solid furniture boards made of PCW is 43.57% depending on the design of the furniture boards. The social and ecological and economic benefit is that by using used wood we reduce by 3 4% the landfill area, reduce deforestation by 0.29 hectares each year, thereby improving the environment.

Effect of Sintering Atmosphere on the Synthesis Process, Electrical and Mechanical Properties of NiFe2O4/Nano-TiN Ceramics

NiFe2O4/nano-TiN ceramics were fabricated by a two-step cold-pressing sintering process. Effect of sintering atmosphere (air, nitrogen, argon) on the synthesis process of NiFe2O4/nano-TiN ceramics was investigated. The DSC-TG and XRD analysis results indicated that besides principal phases of NiO and NiFe2O4, new-phase Ni3TiO5 formed in the sintered ceramics under the three sintering atmospheres, and metallic phase including iron and nickel appeared in the sintered samples with inert gas (nitrogen, argon) sintering condition. Microstructure analysis results showed that considerable quantity of micropores appeared in the ceramic samples sintered under inert gases (argon, nitrogen), but lower porosity (3.0, 3.6%) and higher densities (4.78 g/cm3, 4.51 g/cm3) can be obtained, comparing to the both values (14.4%, 4.17 g/cm3) for the ceramic samples sintered under air atmosphere. Besides, the average bending strength and elastic modulus of the samples sintered under argon is 113.75 MPa and 7.13GPa, which is higher than that of 75.12 MPa, 5.42GPa and 91.96 MPa, 6.26GPa for the samples synthesized under air and nitrogen, separately. When changing sintering atmosphere from air to inert gases (argon, nitrogen), the fracture model of the 4 wt.%nano-TiN/NiFe2O4 ceramics synthesized at 1400 °C for 4 h transformed from intergranular fracture to intergranular-transgranular fracture.

Microstructure, formation mechanism and property characterization of Ti + SiC laser cladded coatings on Ti6Al4V alloy

Surface modification of Ti6Al4V alloy was conducted by additive manufacturing using ball-milling treated mixture of Ti and SiC powder particles. Two laser cladded layers of 90%Ti + 10%SiC and 80%Ti + 20%SiC were deposited onto the Ti6Al4V substrate by single channel feeding system. This single channel feeding process using the ball-milled Ti+SiC powder mixture could offer a more homogeneous SiC distribution and thus cause a better fluidity during the laser cladding process. The microstructures of the cladded layers were analyzed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). An X-ray diffraction (XRD) and a transmission electron microscope (TEM) were used for the determination of the phase products. The Vickers hardness of the cladded coatings was measured by H450-SVDH microhardness tester. Chemical reactions took place between the Ti and SiC particles in the composite layers, and the reaction products consisted of TiC and Ti5Si3. The average three-point bending strength of the sample from the Ti6Al4V substrate to the 80%Ti + 20%SiC coating was 515 MPa at room temperature. The 80%Ti + 20%SiC cladded layer increased the hardness of the Ti6Al4V matrix from 339.1 HV to 932.2 HV. As a consequence, the wear resistance was improved remarkably.

Effects of SPS pressure on the mechanical properties of high packing ratio bulk MgB2 superconductor

In order to investigate the effects of SPS pressure on the mechanical properties of MgB2 bulk, MgB2 bulk samples were processed by SPS under different pressures. Mechanical properties of these bulk samples were evaluated at room temperature through the bending tests for specimens cut from the bulk samples. Stress-strain behaviours of these bulk samples were almost linear until the fracture. No significant difference was observed for the Young’s modulus values among the bulk samples. The average bending strength values of these bulk samples were also similar to each other. However, the bending strength data of the samples processed under higher pressure scattered widely in comparison with those of the sample processed under lower pressure. The bending strength values were related with the pore sizes observed on the tensile side fracture surfaces.

Preparation of W–TiC alloys from core–shell structure powders synthesized by an improved wet chemical method

In order to improve the homogeneous distribution of the TiC particles and facilitate the TiC particles to distribute in the tungsten grain interiors, two kinds of TiC-doped tungsten precursors with a core–shell structure were prepared by an improved wet chemical method at different reaction temperature conditions. Consequently, fine plate-like precursor (200–400 nm) and flower-like precursor (approximately 1.25 μm) are obtained. After reduction and sintering, the microstructures of the samples were characterized by scanning electron microscopy and transmission electron microscopy. In the sample sintered from the plate-like precursor, TiC particles with sizes in the range of 40–300 nm and an average size of approximately 80 nm were uniformly distributed in the tungsten matrix with a high share in the grain interiors. However, in the sample sintered from the flower-like precursor, the TiC particles with sizes in the range of 50–700 nm are significantly aggregated and non-uniformly distributed in the tungsten matrix. As a result, the sample sintered from the plate-like precursor achieves higher mechanical properties and a much narrower range of bending strength values than that sintered from the flower-like precursor. The average bending strength of the sample sintered from the plate-like precursor is 655 MPa, which is higher than that of the sample sintered from the flower-like precursor (524 MPa). Different reaction mechanisms and dispersing stabilities of the TiC particles at different temperature conditions should be accounted for the differences between the two samples.

Torsion Strength Measurement of Engineering Ceramics

This paper discusses the relationship between torsion strength and bending strength of Al2O3 and Si3N4 ceramics. Measurement of the torsion strength was carried out by a simplified torsion test method proposed by Yasuda and Tsutsumi. In this experiment, the average torsion strength was approximately 2/3 of its average bending strength for both ceramics. By estimating the characteristic strength σ0 in Weibull distribution from the strength data, σ0 in torsion is almost the same as that in bending, which agrees to the basic discussion in mechanics of materials. The characteristic strength σ0 is one of the normalized strength by eliminating the effects of specimen shape, dimensions and also its stress distribution, and therefore the apparent difference between torsion and bending strengths can be explained by the difference in effective surface area (Conversely, the measured torsion strength data by the simplified method must be reasonable). It reveals that biaxial fracture in tension/compression during torsion test is equivalent to uniaxial tensile fracture by this experiment.

Mechanical property and quality aspects of rice dried in industrial dryers.

The influence of drying methods on selected mechanical properties and qualities of MR219 rice variety has been investigated. The results showed significant effects of drying methods on bending strength and head rice yields while the average bending strength of paddy were 28.6-31.8MPa. The effect of drying methods on apparent modulus of elasticity of rice was not significant (204.5-222.4MPa). The fracture energy of rice varied significantly under control drying but not with industrial drying methods. Higher temperature in drying by IBD contributed in making the grains tougher, where the effect of FBD temperature was positive toward the development of fracture energy inside rice kernel. IBD at temperature above 40°C resulted in lower bending strength in rice kernels which affected head rice yield. Two stage paddy drying practices with FBD using temperature of 115-125°C as first stage is still acceptable, and inclined bed dryer either as single stage or as second stage after FBD should be operated at temperature of <40°C to maintain head rice yield. The whiteness and milling recovery of rice achieved from different drying methods were comparable.

Mechanical bending strength of (Bi0.5Na0.5) TiO3-based lead-Free piezoelectric ceramics

(Bi0.5Na0.5)TiO3 [BNT] is expected as one of candidate lead-free materials because these ceramics show relatively good high-power piezoelectric properties. In this study, we tried to understand the bending strength and fracture behavior of the BNT-based ceramics. To measure the bending strength, a three-point bending test on the basis of JIS was conducted using 12.0 × 4.0 × 1.0 mm3 specimens. An average bending strength, σA, of pure BNT ceramics sintered at 1100 °C for 2, 12 and 24 h were 217, 195 and 187 MPa, respectively. It is cleared that the σA increased with decreasing the sintering time, (grain size and pore size). We also investigated the bending strength of Nb2O5 doped BNT ceramics [BNT-Nb x, x = 0.05 ∼ 1.5 wt%] and MnCO3 doped BNT ceramics [BNT-Mn x, x = 0.5 and 1.0 wt%]. Values of the σA of BNT-Nb 0.5 and BNT-Mn 0.5 were 222, and 188 MPa, respectively. It is clarified that soft dopants (Nb) can improve the bending strength of BNT-based ceramics. Additionally, hot-pressed BNT [HP-BNT] were sintered at 1050 °C for 5 h, and the σA of HP-BNT was 245 MPa.

Study on the Preparation of SiC Coating by Chemical Vapor Phase and the Mechanical Properties of Ceramic Matrix Composites

In view of the oxidization-prone feature of C/C composites at high temperature, the effect of SiC ceramic coating on the structure and performance of the composites and the oxidation resistance of new nano-carbon particles/ silicon carbide ceramics are explored. The results show that the chemical vapor phase method applied in preparing SiC coated C/C composites can produce good coatings, which is large in coating thickness, uniform in distribution and good in combination with the matrix. The average bending strength of the SiC coated material is 40.4% higher than that of the original material, and the average maximum fracture displacement is increased by 9.26%. The vapor permeation and the enhanced interaction between SiC particles during the preparation of the SiC coating lead to the improvement of strength of the coated samples. After the coating, the fracture mode of the original material does not change fundamentally with the phenomena including interlayer debonding and fiber removal still occurring at the time of fracture, showing good damage resistance and pseudoplastic fracture characteristics. The oxidation process of the new Cp/SiC composite ceramics at 400-700°C is mainly controlled by C-O2 reaction, where the apparent porosity of Cp/SiC increases and the bending strength decreases. At 700-1100 °C, the SiC on the surface of the material is oxidized into SiO2 protective film with the apparent porosity decreased and the bending strength increased. The content of nano-carbon is the key factor affecting the strength and the complexity of oxidation of Cp/SiC composite ceramics. The SiC composite ceramics with 15% of nano-carbon has excellent oxidation resistance.

Effects of Increasing Chitosan Nanofibre Volume Fraction on the Mechanical Property of Hydroxyapatite

This work attempted to synthesize chitosan (CH) nanofibre from crab shell and hydroxyapatite, HA, from limestone with the objective of studying the effects of increasing volume fraction of chitosan nanofibre on the mechanical properties of HA. Mechanical characterization of different fraction composite was carried out to study the effects of increasing volume fraction of chitosan nano fibre on the mechanical properties of HA. In addition, surface characterization of the composite was carried out using Fourier Transform Infrared Spectrometry, FT-IR. Results obtained indicated that the optimum mechanical properties were obtained at a volume fractions of 30: 70, CH: HA respectively; average compressive strength of 10.12 MPa; average tensile strength of 173.9 MPa; average hardness value of 420.80 HV; average fracture toughness of 14.72 MPa.m1/2; average elastic modulus of 0.1583 GPa and average bending strength of 157.96 MPa were obtained for this optimum volume fractions. Increasing volume fractions of chitosan nanofibre was therefore found to result in decrease in compressive strength, hardness and elastic modulus of HA while its tensile strength, bending strength and fracture toughness increased. The FTIR revealed that possible interaction between the NH2 group and the primary and secondary –OH group of CH with Ca2+ (metal coordination interaction) of HA might be responsible for the higher mechanical property of HA. In conclusion, it was found that increasing chitosan volume fraction in chitosan/HA composite results in increasing strength of hydroxyapatite, consequently enhancing its load bearing ability.

Effects of Nodes on the Properties of Laminated Bamboo Lumber

The objective of this study was to determine the effects of node on the properties of laminated bamboo lumber (LBL) glued with water based polymer-isocyanate adhesive. Bamboo strips for LBL fabrication were prepared from andong bamboo (Gigantochloa pseudoarundinacea) collected from private gardens in West Java. Each bamboo strip has dimension of 40 cm x 2 cm x 0.5 cm. The bamboo strips were assigned into 3 groups by the node positions: without node, with node position of 10 cm from one end of the bamboo strip, and with node position in the centre of the bamboo strip. Prior LBL fabrication, the bamboo strips were treated by cold soaking in 7% boron solution for 2 h. The laboratory scale 3-layer laminated bamboo lumbers were manufactured with 5 different layer compositions: all layers made of bamboo strips without node, inner layer made of bamboo strips with nodes at 10 cm from one end of the strip, inner layer made of bamboo strips with nodes at the centre of the strip, all layers made of bamboo strips with nodes at 10 cm from one end of the strip, and all layers made of bamboo strips with nodes at the centre of the strip. The glue spread and cold pressing time applied were 250 g/m2 and 1 h, respectively.The results showed that the average density, moisture content, thickness swelling, bending strength and compression strength of laminated bamboo lumbers were 0.74 g/cm3, 11.3%, 2.9%, 1090 kg/cm2,and560 kg/ cm2, respectively. No delamination occurred in all samples, indicating high bonding quality. The average bonding strength (dry test) of laminated bamboo lumbers was 70.3 kg/cm2. Several properties of laminated bamboo lumber were not significantly affected by the present of nodes in the bamboo strips except the thickness swelling and compression strength.

Fractography of self-glazed zirconia with improved reliability

The fractography of a new grade of zirconia ceramics, known as self-glazed zirconia, was investigated. The as-sintered intact top surface was made with superior smoothness that mimicked the optical appearances of the natural teeth enamel. The beneath surface opposite to this was made hierarchically rough with microscopic pits of the size up to 60μm together with grain-level roughness of about 2μm. The three-point bending test of the samples made with the hierarchically rough surface being tensile one demonstrated an average bending strength of 1120±70MPa and a Weibull modulus of as high as 18 ascribed to the improved structural homogeneity. Surface topography was found the main origins of crack initiation leading to fracture. The observed unusually predominant transgranular fracture mode of submicron-sized grains disclosed a possible toughening mechanism of disassembling of mesocrystalline grains that differs significantly from the commonly quoted phase transformation toughening of this category of ceramics.

Three-dimensional printing of porous load-bearing bioceramic scaffolds

This article reports on the use of the binder jetting three-dimensional printing process combined with sintering to process bioceramic materials to form micro- and macroporous three-dimensional structures. Three different glass-ceramic formulations, apatite-wollastonite and two silicate-based glasses, have been processed using this route to create porous structures which have Young's modulus equivalent to cortical bone and average bending strengths in the range 24-36 MPa. It is demonstrated that a range of macroporous geometries can be created with accuracies of ±0.25 mm over length scales up to 40 mm. Hot-stage microscopy is a valuable tool in the definition of processing parameters for the sintering step of the process. Overall, it is concluded that binder jetting followed by sintering offers a versatile process for the manufacture of load-bearing bioceramic components for bone replacement applications.

A novel method for joining aluminum foil and alumina by polysiloxane coating

This paper describes the joining of aluminum and alumina by using polymethylphenylsiloxane, which is a type of polysiloxane. The polymethylphenylsiloxane that was coated on alumina formed an interlayer through a heat reaction involving aluminum, alumina, and polymethylphenylsiloxane. Scanning electronic microscopy and transmission electronic microscopy showed that the alumina and aluminum were joined together through the interlayer without any cracks or exfoliation, and the thickness of the interlayer was approximately 100 nm. The interlayer formed at temperatures of 873 K and higher. The X-ray diffraction pattern and energy dispersive X-ray spectroscopy suggested that the interlayer consisted of aluminum silicate. The average bending strength of the joined samples was 232 MPa. Although the strength of the samples decreased during a thermal cycling test under conditions of alternating exposure to heating at 423 K and cooling at 233 K, the strength maintained a value of at least 160 MPa, despite the number of thermal cycles exceeding 100 times.

Synthesis, pyrolysis of a novel liquid SiBCN ceramic precursor and its application in ceramic matrix composites

SiBCN ceramic precursor, polyborosilazane, was synthesized through a novel method which used sodium borohydride as boron source. Vinyl silazane with SiCl was converted to vinyl silazane with SiH structure, followed by hydroboration reaction and subsequent high-temperature reaction to form soluble polyborosilazane liquid. The process of precursor-to-ceramic conversion was almost completed before 800°C and the cross-linked polyborosilazane precursor exhibited higher ceramic yield 75.6% at 1200°C. The SiBCN ceramic annealed at 1400°C contained BN, SiN and SiC bonds with smooth and dense surface and still retained principally amorphous structure up to 1600°C. In addition, the viscosity of the polyborosilazane was 65mPa.s, which can efficiently prepare ceramic matrix composite by means of precursor infiltration and pyrolysis (PIP). The density of as-obtained ceramic matrix composite (CMC) was 1.82g/cm3, and the average bending strength, bending modulus and tensile strength were 265.2MPa, 37.5GPa and 158.6MPa, respectively.

Comparison of Micro- and Standard-Size Specimens in Evaluating the Flexural Properties of Scots Pine Wood

The aim of this study was to investigate the flexural properties (bending strength and modulus of elasticity) of Scots pine wood (Pinus sylvestris L.) using micro- and standard-size test specimens. In the standard- and micro-size specimens, the average bending strengths were evaluated as 72.8 and 62.4 MPa, and the bending modulus of elasticity was 9917 and 2884 MPa, respectively. These results showed that the bending strength and modulus of elasticity values of the micro-size specimens were lower than those of the standard-size specimens. The statistically significant effects included the specimen size, individual trees, and the interactions of the specimen size and trees on the bending strength and modulus of elasticity. Furthermore, regression analyses indicated a positive linear regression between the flexural properties of the micro- and standard-size specimens. The results indicated that micro-size specimens can be used to estimate the flexural properties of Scots pine wood when obtaining standard-size specimens is not possible.