Bending Strength of Glass Materials under Strong Dynamic Impact and Its Strain Rate Effects

Based on the structural characteristics of the high-speed loading tester,a four-point bending test device was designed to carry out the four-point bending strength test of glass under the action of static load and different impact velocities,and the formulae for calculating the maximum dynamic stress and strain rate of glass specimens under the action of impact loads were derived.The experimental results show that the bending strength values of the glass under dynamic impact loading are all higher than those under static loading.With the increase of impact speed,the bending strength value of glass specimens generally tends to increase,and the bending strength value increases more obviously when the impact speed exceeds 0.5 m/s or higher.By increasing the impact velocity,higher tensile strain rate of glass specimens can be obtained because the load action time becomes shorter.The bending strength of the glass material increases with its tensile strain rate,and when the tensile strain rate is between 0 and 2 s^(-1),the bending strength of the glass specimen grows more obviously with the strain rate,indicating that the glass bending strength is particularly sensitive to the tensile strain rate in this interval.As the strain rate increases,the number of cracks formed after glass breakage increases significantly,thus requiring more energy to drive the crack formation and expansion,and showing the strain rate effect of bending strength at the macroscopic level.The results of the study can provide a reference for the load bearing and structural design of glass materials under dynamic loading.

Enhanced High-Temperature Energy Storage Performance of All-Organic Composite Dielectric via Constructing Fiber-Re in forced Structure

Optimizing the high-temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems.Selecting a polymer with a higher glass transition temperature(T_(g))as the matrix is one of the effective ways to increase the upper limit of the polymer operating temperature.However,current high-T_(g)polymers have limitations,and it is difficult to meet the demand for high-temperature energy storage dielectrics with only one polymer.For example,polyetherimide has high-energy storage efficiency,but low breakdown strength at high temperatures.Polyimide has high corona resistance,but low high-temperature energy storage efficiency.In this work,combining the advantages of two polymer,a novel high-T_(g)polymer fiber-reinforced microstructure is designed.Polyimide is designed as extremely fine fibers distributed in the composite dielectric,which will facilitate the reduction of high-temperature conductivity loss for polyimide.At the same time,due to the high-temperature resistance and corona resistance of polyimide,the high-temperature breakdown strength of the composite dielectric is enhanced.After the polyimide content with the best high-temperature energy storage characteristics is determined,molecular semiconductors(ITIC)are blended into the polyimide fibers to further improve the high-temperature efficiency.Ultimately,excellent high-temperature energy storage properties are obtained.The 0.25 vol%ITIC-polyimide/polyetherimide composite exhibits high-energy density and high discharge efficiency at 150℃(2.9 J cm^(-3),90%)and 180℃(2.16 J cm^(-3),90%).This work provides a scalable design idea for high-performance all-organic high-temperature energy storage dielectrics.

Interfacial reactions and bending strength of SiC/A356/FeNi50 composite fabricated by gas pressure infiltration

The SiC/A356/FeNi50 composite was fabricated by gas pressure infiltration. The interfacial region of the SiC/A356/FeNi50 composite consisted of FeNi50 reaction layer, A1 reaction layer and A1 alloy matrix. The main intermetallic compounds were （Fe,Ni）a（A1,Sih3 and （Fe,Ni）2（A1,Si）5 at the A1 reaction layer and FeNi50 reaction layer, respectively. The bending behavior versus different infiltration temperatures and holding times was also investigated. The bending strength at 670 ~C was the highest and close to the bending strength of A1 alloy （223 MPa）, and 46% of SIC/A356. The brittle intermetallic compounds existing at the interface induced the decreasing of the bending strength. The pores were reduced by adequate heating time due to the homogeneous temperature of preform, which was beneficial to improve the bending strength of the composite.

Influence of Characteristics on Bending Strength of Layered Steel Fiber Reinforced Concrete

The influence of two main characteristics of steel fiber, the aspect ratio （Df） and volume fraction （ρf）, on the bending strength of Layered Steel Fiber Reinforced Concrete （LSFRC） is investigated by using orthogonal test. Via the variance analysis on the experimental results and trend analysis on the two characteristics, Df is found significantly related to the bending strength of LSFRC. The influence ratio is 63.3%. The bending strength of LSFRC increases if Df increases, makes better when Df reaches 100. ρf has ordinary influence on the bending strength of LSFRC. The influence ratio is 29.2%. Other characteristics, such as the shape of steel fiber and the mix proportion, have less influence. The best ρf contributing to the bending strength of LSFRC is 1.5 %. If ρf is greater than 1.5%, it has negative influence on the bending strength of LSFRC. So, ρf makes a limited contribution to the bending strength of LSFRC.

Enhanced Thermal Conductivity and Bending Strength of Graphite Flakes/aluminum Composites Via Graphite Surface Modification

The effect of graphite surface modification on the thermal conductivity(TC) and bending strength of graphite flakes/Al composites(Gf/Al) prepared by gas pressure infiltration were investigated. Al3 Ni and Al4C3 phase may form at the interface in Ni-coated Gf/Al and uncoated Gf/Al composites, respectively, while the Al-Cu compound cannot be observed in Cu-coated Gf/Al composites. The Cu and Ni coatings enhance TC and the bending strength of the composites in the meantime. TC of Cu-coated Gf/Al composites reach 515 Wm^-1·K^-1 with 75 vol% Gf, which are higher than that of Ni-coated Gf/Al. Meanwhile, due to Al3 Ni at the interface, the bending strength of Ni-coated Gf/Al composites are far more than those of the uncoated and Cu-coated Gf/Al with the same content of Gf. The results indicate that metal-coated Gf can effectively improve the interfacial bonding between Gf and Al.

Relationships among Preparative Technique,Phase Composition and Bending Strength of Bauxite Porcelain

Bauxite porcelain can be sintered to make its bending strength reach 179Mpa by using sintered bauxite, clay and potash feldspar and albite as the main raw materials in oxidation atmosphere under the normal pressure. XRD, SEM and so on are utilized to study the relationships between factors like the composition of ingot, reduction particle size and heat insulating time at sintering temperature and the phase composition, microstructure and bending strength of ceramic body. The results show that the main phases in bauxite porcelain are corundum, mullite and glass, and the mullite is composed of two parts： primary mullite formed by clay conversion and secondary mullite whiskers precipitating from high temperature melt. The bending strength of ceramic body can be improved by enhancing the content of sintered bauxite in the formula： the smaller the particle size of the ceramic body is, the higher the bending strength will be. The high-temperature heat insulating technique is beneficial to the precipitation of certain quantitative secondary mullite whiskers so as to remarkably improve the strength of glass phase and ceramic body.

Effect of RE addition on solidification process and high-temperature strength of Al-12%Si-4%Cu-1.6%Mn heat-resistant alloy

The effect of RE addition on solidification process and high-temperature strength of Al-12%Si-4%Cu-1.6%Mn(in wt.%)heat-resistant alloy was investigated by microstructure observation and tensile test.A great number of fine needle-like RE-rich phases are observed in the alloys with RE addition. Solutionizing treatment does not change their morphologies and sizes, indicating that they have good thermal stability. The addition of RE totally alters the solidification process of eutectic CruAl2 phase, from network-like phase in the form of segregation at the final eutectic grain boundaries to discretely blocky phase growing on the hair-filamentous RE-rich needles. In the alloys with Ce addition, blocky CuAl2, particulate Al15Mn3Si2 and needle-like RE-rich needle phases grow together, but they did not occur in the alloy with only La addition. The addition of RE does not considerably improve the strength of the alloy at high temperatures. The formation of RE-rich phases also does not significantly alter the originating and propagating of micro-cracks in the alloy during tensile test.

Effect of nano TiO_(2) and SiO_(2) on gelation performance of HPAM/PEI gels for high-temperature reservoir conformance improvement

Nanoparticles have been widely used in polymer gel systems in recent years to improve gelation performance under high-temperature reservoir conditions. However, different types of nanoparticles have different effects on their gelation performance, which has been little researched. In this study, the high-temperature gelation performance, chemical structure, and microstructure of polymer gels prepared from two nanomaterials (i.e., nano-SiO_(2) and nano-TiO_(2)) were measured. The conventional HPAM/PEI polymer gel system was employed as the control sample. Results showed that the addition of nano-TiO_(2) could significantly enhance the gel strength of HPAM/PEI gel at 80 ℃. The gel strength of the enhanced HPAM/PEI gel with 0.1 wt% nano-TiO_(2) could reach grade I. The system also had excellent high-temperature stability at 150 ℃. The enhanced HPAM/PEI gel with 0.02 wt% nano-TiO_(2) reached the maximum gel strength at 150 ℃ with a storage modulus (G′) of 15 Pa, which can meet the need for efficient plugging. However, the nano-SiO_(2) enhanced HPAM/PEI polymer gel system showed weaker gel strength than that with nano-TiO_(2) at both 80 and 150 ℃ with G′ lower than 5 Pa. Microstructures showed that the nano-TiO_(2) enhanced HPAM/PEI gel had denser three-dimensional (3D) mesh structures, which makes the nano-TiO_(2) enhanced HPAM/PEI gel more firmly bound to water. The FT-IR results also confirmed that the chemical structure of the nano-TiO_(2) enhanced HPAM/PEI gel was more thermally stable than nano-SiO_(2) since there was a large amount of –OH groups on the structure surface. Therefore, nano-TiO_(2) was more suitable as the reinforcing material for HPAM/PEI gels for high-temperature petroleum reservoir conformance improvement.

Bending Strength and Fracture Behavior of Ni50Mn29Ga21 Alloy with Terbium

The bending strength and fracture behaviors of Ni50Mn29Ga21 alloy with terbium were investigated.The results show that the bending strength of the alloy is increased dramatically with the increase of terbium content.The fracture appearance of the sample without terbium is dominated by grain boundary fracture,while that with terbium is dominated by cleavage fracture with the increase of terbium content.Moreover,the grains are refined obviously and the oxygen content is decreased after adding terbium.

Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of f ibers in specimens of the f iber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

Improvement of high-temperature strength of 6061 Al matrix composite reinforced by dual-phased nano-AlN and submicron-Al_(2)O_(3)particles

Nano-AlN and submicron-Al_(2)O_(3) particles were simultaneously utilized in a 6061 Al matrix composite to improve the high-temperature strength.According to the SEM and TEM characterization,nano-AlN and submicron-Al_(2)O_(3) particles are uniformly distributed in the Al matrix.Brinell hardness results indicate that different from the traditional 6061 Al matrix alloy,the aging kinetics of the composite is obviously accelerated by the reinforcement particles.The T6-treated composite exhibits excellent tensile properties at both room temperature and elevated temperature.Especially at 350℃,the T6-treated composite not only has a high yield strength of 121 MPa and ultimate tensile strength of 128 MPa,but also exhibits a large elongation of 11.6%.Different strengthening mechanisms of nano-AlN and submicron-Al_(2)O_(3) particles were also discussed in detail.

SIZE EFFECT ON THE BENDING AND TENSILE STRENGTH OF MICROMACHINED POLYSILICON FILMS FOR MEMS

The bending strength of microfabricated polysilicon beams was measured by beam bending using a nanoindenter. Also, the tensile strength of microfabricated polysilicon thin ?lms was measured by tensile testing with a new microtensile test device. It was found that the bending strength and tensile strength of polysilicon microstructures exerts size e?ect on the size of the specimens. In such cases, the size e?ect can be traced back to the ratio of surface area to volume as the governing parameter. A statistical analysis of the bending strength for various specimen sizes shows that the average bending strength of polysilicon microcantilever beams is 2.885 ± 0.408 GPa. The measured average value of Young’s modulus, 164 ± 1.2 GPa, falls within the theoretical bounds. The average fracture tensile strength is 1.36 GPa with a standard deviation of 0.14 GPa, and the Weibull modulus is 10.4 -11.7, respectively. The tensile testing of 40 specimens on failure results in a recommendation for design that the nominal strain be maintained below 0.0057.

The Influence of Mineral Admixtures on Bending Strength of Mortar on the Premise of Equal Compressive Strength

The influence of mineral admixtures on bending strength of mortar on the premise of equal compressive strength was investigated. Three mineral admixtures （fly ash, ground granulated blast-furnace slag and steel slag） were used. The adding amount of mineral admixture in this study ranges from 22.5% to 60%, and the water-to-binder ratio ranges from 0.34 to 0.50. With equal compressive strength, different mortars can be arranged in such a descending order with their bending strength： cement-fly ash mortar, cement mortar, cement-GGBS mortar, and cement-steel slag mortar. With the same compressive strength, the higher the steel slag content and water-to-binder ratio, the lower the bending strength of mortars. However, the effect of mineral mixture content and water-to-binder ratio on the bending strength of cement-fly ash mortar and cement-GGBS mortar is far inconspicuous.

Numerical Simulation on Dynamic Bending Strength of Three-Graded Concrete Beam Based on Meso-Mechanics

To study the bending strength of mass concrete under dynamic loading, the pure bending zone of three-graded concrete beam is considered as a three-phase composite composed of matrix, aggregate and interface between them on meso-level. Dynamic constitutive model considering strain-rate strengthening effect and damage softening effect is adopted to describe the cocrete and meso-element's damage. The failure mechanisms of beam under impact loading, triagle wave load, dynamic load coupling with initial static loading were simulated by using displacement-controlled FEM. Furthermore, stress-strain curve of the specimens and their dynamic bending strength were obtained. The results obtained from numerical simulation agreed well with experimental data.

The Relationship of Microstructure, Density and Bending Strength Properties of Blighia sapida

Wood anatomical structures of various tree species help identify the wood. The characteristics and composition of these structures affect their utilisation. In this work, the microstructure of Blighia sapida a lesser-known Ghanaian hardwood species using light microscope and scanning electron microscope (SEM) was studied. The relationship between the microstructure and some physical properties such as density, and bending strength were also studied. The anatomical features studied were fibre length, double fibre wall thickness, fibre proportion, vessel diameter and proportion, rays and axial parenchyma proportions. It was observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gives a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida are reported in the work. The study also established that Blighia sapida had a low water uptake even though it had vessel distribution of 12 vessels/mm2. Having not very distinct axial parenchyma may have accounted for the low water uptake. The presence of occluded pits could also account for the low water uptake and the fibre wall thickness may also account for a medium bending strength of 62.8 N/mm2 at 12% moisture content.

Experimental study on the causes of cracking of high-strength steel during bending

This paper studies the chemical composition, tensile properties, inclusions, metallogrophic structure, and other such parameters to identify the causes of cracking during the bending of high-strength steel. The results show that the major causes of cracking are the original transverse cracks or holes on the surface of the slab and the presence of scales rolled into the cracks or holes. Cold fracturing from such defects is rare, and can be eleminated by enhancing the control of the steelmaking process and by mechanical clean-up of the surface cracks and holes in the slab.

Three-point bending performance of a new aluminum foam composite structure

A new composite structure based on aluminum foam sandwich and fiber metal laminate was proposed. A layer of glass fiber was provided at the interface between the metal panel and the aluminum foam core in this composite structure, using adhesive technology to bond the materials together by organic glue in the sequence of metal panel, glass fiber, aluminum foam core, glass fiber and metal panel. The experimental results show that the new composite structure has an improved comprehensive performance compared with the traditional aluminum foam sandwiches. The optimized parameters for the fabrication of the new aluminum foam composite structure with best bending strength were obtained. The epoxy resin and low porosity aluminum foams are preferred, the thickness of aluminum sheets should be at least 1.5 mm, and the type of glass fiber has little effect on the bending strength. The main failure modes of the new composite structures with two types of glues were discussed.

Molecular dynamics analysis on bending mechanical behavior of alumina nanowires at different loading rates

The molecular dynamics(MD)model ofα-Al_(2)O_(3) nanowires in bending is established by using LAMMPS to calculate the atomic stress and strain at different loading rates in order to study the effect of loading rate on the bending mechanical behaviors of theα-Al_(2)O_(3) nanowires.Research results show that the maximum surface stress−rotation angle curves ofα-Al_(2)O_(3) nanowires at different loading rates are all divided into three stages of elastic deformation,plastic deformation and failure,where the elastic limit point can be determined by the curve symmetry during loading and unloading cycle.The loading rate has great influence on the plastic deformation but little on the elastic modulus ofα-Al_(2)O_(3) nanowires.When the loading rate is increased,the plastic deformation stage is shortened and the material is easier to fail in brittle fracture.Therefore,the elastic limit and the strength limit(determined by the direct and indirect MD simulation methods)are closer to each other.The MD simulation result ofα-Al_(2)O_(3) nanowires is verified to be valid by the good agreement with the improved loop test results.The direct MD method becomes an effective way to determine the elastic limit and the strength limit of nanoscale whiskers failed in brittle or ductile fracture at arbitrary loading rate.

Nodes Effect on the Bending Performance of Laminated Bamboo Lumber Unit

This research studied the ultimate bearing capacity of laminated bamboo lumber(LBL)unit and thereby calculated the maximum bending moment.The load-displacement chart for all specimens was obtained.Then the flexural capacity of members with and without bamboo nodes in the middle section was coMPared.The bending experiment phenomenon of LBL unit was concluded.Different failure modes of bending components were analysed and concluded.Finally,the bending behaviour of LBL units is coMPared with other bamboo and timber products.It is shown that the average ultimate load of BS members is 866.1 N,the average flexural strength is 101 MPa,the average modulus of elasticity is 8.3 GPa,and the average maximum displacement is 17.02 mm.The average ultimate load of BNS members is 1008.1 N,the average flexural strength is 118.02 MPa,the average modulus of elasticity is 9.9 GPa,and the average maximum displacement is 18.26 mm.Laminated bamboo lumber(LBL)unit without bamboo nodes(BNS)has relatively higher flexural strength coMPared with LBL unit with bamboo nodes(BS).The presence of bamboo nodes reduces the strength of the entire structure.Three failure modes were concluded for BS members,and two failure modes were observed for BNS members during the experimental process.According to a coMParison between the LBL unit and other products,the flexural strength and bending modulus of elasticity of the LBL unit are similar as bamboo scrimber and raw bamboo components,which is much higher than timber components.