Ultimate Bending Strength Research Articles

Study of Distribution of Deformations in Ice Composite Materials Using Integrated Fiber-Optic Sensors

The Arctic region features harsh climatic conditions. The region has underdeveloped industry and infrastructure and it is located far from industrial facilities. This specificity sets forth high requirements for functionality and reliability of materials to be used in the region as well as for various technical devices and structures made from them. In addition, durable structures require assessing the performance status during operations. Optical sensors based on fiber Bragg gratings are promising from the standpoint of monitoring the bulk of construction material. We explored distribution of deformations along the longitudinal axis of a sample in a matrix and in reinforcing filler for ice-based composite materials upon exposing samples to three-point bending. It was demonstrated that unidirectional ice reinforcement using two layers of basalt roving increases the ultimate bending strength by a factor of two. The approach proposed proved to be promising to monitor deformations in reinforced and unreinforced ice materials using integrated fiber-optic sensors by applying external mechanical effects and testing the samples under three-point bending.

Study of the dynamics of stress formation in glass during a thermal hardening

The object of research is the ultimate bending strength of float glass sheet 4 mm thick. The paper confirms that the main factor affecting the increase in glass strength is the dynamics of stress formation in the surface and inner layers of glass. Rapid cooling of float glass with an air flow for 8–10 s at a rate of 25 °C/s leads to the appearance in the glass of an average temperature difference in the surface zone of 30 °C/mm. It was found that during thermal hardening at temperatures exceeding the glass transition temperature limit, there is an abrupt increase in the glass bending strength. A comparative analysis of the results of measuring the bending strength of glass for float glass and heat-strengthened glass indicates that this indicator is significantly improved. The statistical analysis of the results shows that the scatter of the values of the bending strength of annealed glass falls within the range of 30–50 MPa, and the most probable value is 40 MPa. At the same time, the spread in the values of the bending strength of thermally hardened glass is in the range of 100–160 MPa and is 135 MPa. The work proved that thermal hardening of float glass sheets increases its flexural strength by about 3.5 times. The peculiarities of the change in the type of the hardening stress diagram over time have also been studied: thermal hardening causes a more gentle course of the residual stress curve compared to hardening. In this case, the coordinate of the critical tensile stress σcrit can be located on the lower surface of the glass, which will make it possible to fracture at lower loads compared to quenching, but the fracture mechanism will be identical as for annealed glass. In this case, the destruction mechanism will be approximately the same as in the case of annealed glass, but its actual strength will be 2–3 times higher.

Development of effective compositions of composite wood-plastic board materials based on local raw materials and industrial waste

The article presents the results of research aimed at creating of effective compositions of composite wood-plastic board materials based on fillers from cotton stalks and polymer binders. IIt was found that for all the considered plates with a density of 600, 700 and 800 kg/m3, the maximum value of the bending strength of composite wood-plastic materials (14.8–22.9 MPa) is observed when the content of small particles of the crushed mass of cotton stems is from 10 to 20%, and the maximum value of the tensile strength perpendicular to the plate layer (0.58–0.91 MPa) – at the content of a fine fraction from 15 to 25%. The minimum water absorption of plates at three densities of 650, 750 and 850 kg / cm3 was recorded with a fine fraction content of 15–18% in the mass. It was revealed that the high value of the ultimate strength in static bending of composite wood-plastic materials with a density of 650, 750 and 850 kg/cm 3 with a content of the fibrous part of cotton 20- 60% is in the range of 14- 15,5 MPa, 17,5- 19,1 MPa and 20- 22,2 MPa, respectively. The least water absorption and swelling of the slabs is observed when the content of the fibrous part is in the range of 30- 40%.

Binder jetting additive manufacturing of 316L stainless-steel green parts with high strength and low binder content: Binder preparation and process optimization

• A self-developed binder with A-stage phenolic resin as a key agent was prepared. • High strength 316 L green part with low binder saturation was fabricated by BJAM. • The uneven distribution of binder hinders the strength of green parts. Recently, binder jetting additive manufacturing (BJAM) was used to manufacture complex metal parts in an economical and large-scale way. However, the usage of resin to bond metal powder renders as-printed green parts with low strength, which is potential to cause the structural damages of final parts during post treatments. To overcome the intractable problem, a self-developed binder mainly consisting of A-stage phenolic resin was explored for BJAM to achieve relatively high-strength as-printed green parts. The binder can be cured as a C-stage phenolic resin with 190 ℃ and then provide a high strength for the green parts. The effect of layer thickness and binder saturation on the strength, dimensional accuracy, and surface roughness of the BJAM-printed 316 L stainless-steel green samples using the developed binder was investigated systematically. With the optimized parameters (a layer thickness of 100 μm and a binder saturation of 30.2 %), green samples can possess the ultimate bending strength (UBS) of 10.08 MPa and the ultimate compressive strength (UCS) of 25.56 MPa, which are beneficial for the structural stability of the printed samples during subsequent treatments. A reduction in strength and an increase in roughness are observed with increasing the layer thickness for the as-printed green samples. An increment in binder saturation results in the improvement in strength and surface roughness of the green samples. The relationships between the binder and the mechanical performance of the green samples were discussed from the viewpoint of the uneven distribution of binder in depth. This work explored a promising binder with a low saturation for BJAM to fabricate 316 L green parts with desirable mechanical strength and acceptable surface roughness.

Nanostructured strain-hardened aluminum-magnesium alloys modified by C60 fullerene obtained by powder metallurgy Part 2. The effect of magnesium concentration on physical and mechanical properties

This paper is intended to continue the studies of magnesium effects on the structural phase composition, physical and mechanical properties of the nanostructured strain-hardened aluminum-magnesium alloys modified with C60 fullerene [1]. Previously obtained mechanically alloyed composite powders [1] were consolidated by direct hot extrusion method. Consolidation parameters were chosen based on previous studies of the structure and phase composition formation during mechanical alloying and heat treatment. It was found that an increase in magnesium concentration improves mechanical properties of extruded nanosructured composite materials, and additives modified by C60 fullerene stabilize the grain structure and slow down decomposition of α solid solution of magnesium in aluminum to 300 °C. Under similar thermobaric treatment Al82Mg18 (AMg18) not modified with C60 demonstrates a reduced α solid solution lattice constant and an increased average crystallite size. These processes are accompanied by sequential formation of γ, β′, and β phases, while γ and β′ are intermediate phases. The grain structure of extruded samples is typical for materials obtained in this way – grains are closely packed, elongated and oriented along the extrusion axis. The grain structure of extruded samples inherits the morphology of mechanically alloyed powders. Thus, mechanical alloying methods followed by intense plastic deformation (extrusion) improved mechanical properties significantly. Materials with ultimate tensile strength of 880 MPa; ultimate bending strength of 1100 MPa; microhardness up to 3300 MPa; and with the same density of 2.4–2.6 g/cm3 were obtained. This result demonstrates the prospects for using powder metallurgy techniques in the production of new nanostructured composite materials modified by C60 fullerene with improved physical and mechanical properties.

Comparison of Bending Strength among Plate, Steinmann Pin, and Headless Compression Screw Fixations for Proximal Ulnar Shaft Fracture in Sawbones

Purpose: Although plate osteosynthesis is commonly used to treat proximal ulna fracture, its treatment method is controversial because of complications such as large incision, long operation time, and soft tissue injury. Therefore, intramedullary headless compression screw (HCS) and Steinmann pin are considered as alternative treatment options. In this study, we aim to compare bending strength of plate and cortical screws, HCS, and Steinmann pin for proximal ulnar shaft fracture with sawbone. Methods: Transverse type fractures were made intentionally at the distal 7 cm from the proximal end of ulna sawbones and fixated with plate, HCS, and Steinmann pin after reduction. Three-point bending tests were performed with total of 21 sawbones, seven pieces for each group. Results: Average ultimate bending strength for each group was as follows; 521.7N for plate fixation group, 706.4N for HCS fixation group, and 812.6N for Steinmann pin fixation group. Statistically significant results were observed among the three groups (p<0.01). When two groups were compared separately, Steinmann pin fixation and plate fixation (p<0.01), Steinmann pin and HCS fixation (p=0.047) showed statistical significance. There was a significant trend between HCS and plate fixation group (p=0.064).Conclusion: HCS and Steinmann pin fixation showed higher bending strength when compared to plate fixation for proximal ulnar shaft fracture in sawbone. Although further studies are needed, HCS and Steinmann pin fixation are promising fixation methods that may be used as an alternative to plate fixation.

Experimental study on mechanical behavior of double-layer toughened sandwich glass with two-side simple support

To study the mechanical behavior of double-layer toughened sandwich glass with two-side simple support under out-of-plane bending, a total of sixty-four specimens with different test parameters were experimentally investigated in this paper. The main parameters of specimens include thickness of single layer, supporting width, and loading length. It was demonstrated that the specimens failed with all pieces of cracks combined together as an entire unit rather than to separate into a large number of glass fragments. What's more, the cracks appeared only in the lower layer of the toughened sandwich glass, extending in a way similar to the spider web. The ultimate bending strength and bending stiffness of the toughened sandwich glass are enhanced with the increase of the thickness of single layer, the supporting width, and the loading length. Among the above parameters, the thickness of single layer plays a leading role in enhancing the ultimate bending strength and bending stiffness of the toughened sandwich glass. Nevertheless, the supporting width only has a slight effect on improving the ultimate bending strength and bending stiffness. Based on the bending theory of thin plates, the simplified design formulas were presented to evaluate the ultimate bending strength of double-layer toughened sandwich glass with two-side simple support under out-of-plane bending, which was verified to be reasonable and accurate.

Problems of the use of lightweight cement in oil and gas well fixing and possible solutions

The article presents the results of the selection of the grouting mortar made out of the cement that does not comply with the state standard (GOST) for cementing the upper part of the column during the construction of an oil well. The object of study was the cement grade PСT III-ob 5-50 GOST 1581-96. The study used the additives that, according to the literary sources, are able to enhance the cement technological parameters. The additives were calcium chloride (CaСl2), sodium chloride, magnesium chloride (MgCl2), gypsum (CaSO4·2H2O), marble chips (MK-100), silica fume (МК-65, МК-85), caustic soda (NaOH) and calcined soda (Na2CO3), as well as high and low viscosity polyanionic cellulose. The following technological parameters were determined: the mortar density, the mortar paste spreadability, water separation, the thickening of the mortar, the ultimate bending and ultimate compression strength of the cement stone. The study was conducted taking into account the domestic and international standards. The test results show that the use of the agents such as NaCl, MgCl2, CaСl2, Easy SET, МК-100, and CaSO4·2H2O enhances the water separation of the mortar and the strength properties of the cement stone. However, the agents used to improve water separation (low viscosity polyanionic cellulose, high viscosity polyanionic cellulose, Na2CO3, МК-65, and МК-85) significantly reduce the strength properties of the cement stone. The columns can be fixed with the above mentioned cement using agents such as CaCl2 (2 % of the cement mass), NaCl (1.2 %), MgCl2 (1 %), and the hardening agent Easy SET (1 % of the cement mass).

Development of Heat Resistant Aluminum Composite with Minor Addition of Alumina Nanofibers (Nafen™)

This article describes development of an aluminum composite with a matrix of mixed powdered aluminum, nickel, copper, and boron hardened by 0.01–0.1 wt % alumina nanofibers (Nafen™). The composite samples have been produced by conventional powder metallurgy including pressing and sintering in vacuum furnace. The microstructure and fine structure of aluminum composites, average grain diameter, density, phase composition, Vickers microhardness, and ultimate bending strength at ambient temperature and at 300°C have been analyzed. According to X-ray diffractometry, the samples contain the phases of Al, Al3Ni, CuAl2, Al7Cu23Ni, and Ni4B3. The microhardness increases monotonically with concentration of alumina nanofibers. It has been established that, at ambient temperature, the strength of the samples with 0.01–0.1 wt % of alumina nanofibers is higher by 30% on average than that of the matrix. During tests at 300°C, the best result has been shown by the sample with 0.01 wt % of nanoparticles; its strength was by 14% higher than that of the matrix.

Assessment of reliability of natural limestone cladding material

The goal of research was identifying possible application of natural limestone samples as a cladding material for facades by means of evaluation of physical and chemical properties and inclusive of external aggressive factors. As the object of research, there were used the samples of naturally occurring limestone, of Afanasyevskiy deposit, Moscow region, designated for face slabs manufacturing of ventilated facades. In compliance with the All-Union Standard (GOST) 30629-2011, the samples have been exposed to the following testing, namely determination of mean density and true specific gravity, kg/m3, pore-saturation coefficient with water; ultimate compressive strength, MPa, water fastness (lowering of compressive strength in the water-saturated state, %); ultimate bending strength, MPa; freeze-thaw resistance, cycles, acid fastness. Chemical (elemental) analysis was carried out by the method of scanning electron microscope investigation. The tests were implemented on the electronic microscope FEI Quanta 200. The microscope is equipped by X-ray spectrometer that is designated for elemental analysis (EDAX). Both masonry units have satisfactory freeze-thaw resistance. As far as acid fastness is concerned, only marmorized limestone has demonstrated satisfactory performance. Thus, only the second group of samples presented by marmorized limestone could be recommended as a reliable material for façade cladding.

Study on Effect of Aerodynamic Sound Hardening for Wear of Coated Carbide Metal Plates

To increase the durability of metal-cutting carbide plates operating during in harsh technological conditions with impact load, an aerodynamic sound hardening method has been developed that can increase a life of carbide tools up to 3.7 times with a small added cost. The wear of plates hardened by the aerodynamic sound method, after 100 min of cutting, is 1.12–1.7 times less than their un-strengthened analogues. A coating on metal carbide plates does not have a prevailing value when a tool is working with impact loads. While working with impact loads viscosity of an internal plate structure occurs the greatest influence on increasing resistance. For metal-cutting carbide plates during interrupted cutting with significant impact loads, a method of aerodynamic sound hardening is more effective than a coating method, not only in terms of tool performance, but also in the cost of completion itself. Empirical dependences of wear on the rear surface of carbide plates hardened by a aerodynamic sound method and plates with PVD coatings have been obtained in the form of approximation by polynomials of the 5thand 2nddegrees, which are convenient to use in a production environment. It has been revealed the higher carbide plate strength in bending leads to less influence of the method of aerodynamic sound hardening on the increase in wear resistance. So, taking into account the fact that for ВК8-base the ultimate bending strength is 1666 MPa, and for T5K10 it is 1421 MPa, wear reduction after hardening by the aerodynamic sound method for ВП3115-plates with ВК base is 11.5 %, while for ВП3225 – plates with ТК-base – 27.1 %.

Research on mechanical behavior of three-layer toughened sandwich glass with trilateral simple support

This paper presents the results of an experimental investigation on the mechanical behavior of three-layer toughened sandwich glass with trilateral simple support under uniform lateral loads. A total of sixty-four specimens with different test parameters are designed and tested to consider the effects of the thickness of single layer, supporting width and loading length. It was observed that the specimens failed with all pieces of cracks combined together as an entire unit rather than to separate into a large number of glass fragments. The cracks occurred only at the lower layer of toughened sandwich glass and extended in a way similar to the spider web. The ultimate bending strength and bending rigidity of the toughened sandwich glass are enhanced as the thickness of single layer, the supporting width, and the loading length increase. Among the above parameters, the thickness of single layer plays a leading role in improving the ultimate bending strength and bending rigidity of toughened sandwich glass. However, the enhancement effect of supporting width on the ultimate bending strength and bending rigidity of toughened sandwich glass is quite limited. Based on elastic thin plate theory, the derived mechanical formulae were presented to evaluate the ultimate bending strength of three-layer toughened sandwich glass with trilateral simple support under uniform lateral load, which was verified to be reasonable and accurate.

Properties of Microporous Composite Ceramics Based on Zirconium and Aluminum Oxides

Processes for preparing ceramic microporous diaphragms based on aluminum and zirconium oxides are studied. Diaphragm test results for long-term corrosion resistance are presented. It is shown that ceramic material based on zirconium and aluminum oxides prepared at 1350°C with linear shrinkage of 75% has open porosity of 49% and ultimate strength in bending of 48 MPa. Diaphragms prepared from this material can withstand pressure up to 1.0 MPa and operate under aqueous chloride solution electrolysis conditions for at least 40,000 hours.

The effects of interface and matrix reinforcements on fracture toughness of E-Glass/epoxy laminate

In this study, the effects of low amount (0.1 wt%) multi-walled carbon nanotube (MWCNTs) distributed homogenously in epoxy via cationic surfactant (cetyl pyridiniumchloride-CPC), polyacrylonitrile nanofiber (in the range of 240–570 nm diameter) mats between each lamina, main fiber-matrix interface improvement using γ-Glycidoxypropyltrimethoxysilane and intermediate combinations were investigated on the fracture toughness of E-Glass/epoxy laminate. Considering the data obtained from three-point bending test samples with a single edge crack, it was found that the ultimate bending strength, modulus and fracture toughness of the silane-treated samples increased by 25.6%, 4.9 and 16.6% respectively, with respect to the reference sample. When MWCNTs was added to the silane treated sample, it was observed that it did not enhance the fracture toughness and decreased the strength and modulus slightly (1%) with the effect of CPC. The effect of 128 μm thick nanofiber mats on the silane-treated sample did not occur as expected and was found to cause delamination by working as a separate layer between the laminae.

Suitability of paulownia wood from Malaysia for furniture application

Imported wood resources, especially yellow poplar and Chinese poplar, are increasingly evident in the Malaysian furniture sector due to declining supply of domestic wood materials. In order to reverse this trend, paulownia, a fast-growing forest plantation tree species, is emerging as an alternative wood material source. This study evaluated the mechanical strength, including fatigue life, machining, adhesive bond, screw withdrawal, and finishing properties of paulownia against the imported wood of yellow poplar and Chinese poplar. The results revealed that paulownia has better properties than Chinese poplar, but it is inferior to yellow poplar due to its lower density. In terms of fatigue strength, all the wood species performed comparably equal, with the allowable design stress set at 40% of the wood species’ respective ultimate bending strength. Against these findings, paulownia is a promising alternative wood resource for furniture manufacturing in Malaysia, and it could possibly replace the imported yellow poplar and Chinese poplar. Nevertheless, the successful application of paulownia for furniture manufacturing will depend on its supply volume and economics in the future.

The Influence of Heat Treatment on the Quality of Vehicle Component Parts Made of Rigid Polyurethane Foam

The paper provides the results of the investigation in the influence of heat treatment on the quality of vehicle component parts made of rigid polyurethane integral foam. The temperature of heat treatment was based on the exo-peak of the first heat cycle in DSC curve, and was equal to 135 °С. At that temperature, the samples were treated for 2-8 hours, and, as a result, they experienced an abnormal exo-effect in the glass transition region, which was indicative of thermal relaxation. The paper shows that the additional heat treatment stage for parts made of rigid polyurethane integral foam results in an increase in molecular mass of polymer, due to a smaller quantity of end groups, and, thus, in an increase in glass transition temperature from 169 °С to 176 °С. An increase in heat treatment time to 6 hours at 135 °С leads to a higher ultimate bending strength, which reaches its maximum, while further heat treatment (up to 8 hours) lowers this value. Therefore, with a higher degree of cross-linking the fracture toughness increases and passes its maximum, after that it starts to decrease, and the material becomes brittle.

Physical and mechanical properties of composite materials in the MoSia2-SiC-TiB2 system

In this work, we obtained ceramic materials based on MoSi2, hardened by SiC and TiB2 particles, which makes it possible to increase the heat resistance of the composite and increase the level of its physical and mechanical properties (at a relative density of more than 99, 0 %, tensile strength in bending 520 ± 10 MPa). The shrinkage, density, porosity and weight loss of composite materials during sintering were studied. The value of the ultimate strength in bending of materials at the optimum sintering temperature is determined. The maximum values of physical and mechanical properties are achieved for a material composition of 50, 0 vol. % MoSi2 + 15, 0 vol. % SiC + 35, 0 vol. % TiB2: E = 471 ± 10 GPa; σb = 520 ± 10 MPa, K1C = 4, 4 ± 0.1 MPa • m1/2; HV = 22.1 ± 0.1 GPa obtained at a sintering temperature of 1950 ° C.

Reinforcing of Composite Materials on the Basis of Fresh Ice and Natural Origin Additives

Possibility of application fibrous additives of a natural origin in an ice matrix as the reinforcing additives is investigated. As a matrix, fresh ice water was used, reinforcing additives — hay fiber 10 mm long and 0.5–1 mm thick and basalt fiber produced by Plant of Basalt Materials LLC (Pokrovsk, Sakha Republic (Yakutia)) with a thickness of 9–12 µm and 40 mm long. The volume content of hay fibers was 10, 20, 30%. The density of chaotic styling of basalt fiber in a single layer was about 3 mm / mm2. Magnitude of breaking load was determined experimentally when tested according to three-point bending pattern. It is shown, that introduction fibrous additives a natural origin leads two - to triple increase of ultimate bending strength of fresh ice. During the tests, unreinforced ice samples fractured brittle along the loading force, and reinforced samples showed viscous fracture and an increase in breaking load due to the mechanical adhesion of reinforcing fibers to ice matrix.

Поливинил спирті мен крахмал негізіндегі гидрофильді қоспалардың жылу оқшаулағыш материалдардың физика-механикалық қасиеттеріне әсері

Thermal insulating materials based on diatomite with burnable and reinforcing additives modified with synthetic and natural polymers have been developed. A mixture of polyvinyl alcohol and starch was used as modifying polymers. The parameters of linear shrinkage, density, tensile strengths in compression and bending, as well as the coefficient of thermal conductivity of the material were determined depending on the concentration and ratio of polymers. It was established that polymer additives had a positive effect on almost all specified characteristics of thermal insulating materials. For example, when adding polymers up to 1 mass.%, the linear shrinkage coefficients decrease from 14.5 to 4.5%, the ultimate compression strengths increase from 0.22 to 2.51 MPa, the ultimate bending strengths increase from 0.2 to 1.26 MPa, the coefficients of thermal conductivity decrease from 0.068 to 0.049 W/m∙K. The densities of materials are in the range of 0.592-0.491 g/cm3. The results of the work showed that the obtained heat-insulating materials can be used as plasticizers in the field of thermal energy.

Improving four-point bending performance of marine composite sandwich beams by core modification

The aim of this study was to improve four-point bending performance of foam core sandwich composite beams by applying various core machining configurations. Sandwich composites have been manufactured using perforated and grooved foam cores by vacuum-assisted resin transfer moulding method with vinyl-ester resin system. The influence of grooves and perforations on the mechanical performance of marine sandwich composite beams was investigated under four-point bending test considering the weight gain. Bending strength and effective bending stiffness increased up to 34% and 61%, respectively, in comparison to a control beam without core modification. Analytical equations were utilised for calculating the mid-span deflection, equivalent bending stiffness and ultimate bending strength of the sandwich beams. Finite element analysis was also performed to analyse the flexural response of the specimens taking into account the combined effect of orthotropic linear elasticity of the face sheet and the non-linear behaviour of the foam core.