Maximum Bending Strength Research Articles

Rotary friction welded C45 to 16NiCr6 steel rods: statistical optimization coupled to mechanical and microstructure approaches

In the present work, the dissimilar joints between C45 carbon steel and nickel-chromium 16NiCr6 steel rods were produced using rotary friction welding process. Statistical analysis based on response surface methodology (RSM), microstructural examination using scanning electron microscopy with backscattered electron diffraction (EBSD) and mechanical tests were performed to investigate the friction weld joints. The results showed that friction time and rotation speed were the most effective parameters on the weld joint quality with the highest t-ration of − 4.27, where the maximum bending strength of 1406.9 MPa was obtained at 2000 rpm for 13 s friction time. Increasing friction time to 13 s resulted in remarkable decrease in grain size (about 35%) at the weld interface, which increased the hardness (350HV0.1) and elastic modulus (260 GPa).Graphical abstract

Reduced fracture load of dental implants after implantoplasty with different instrumentation sequences. An in vitro study.

To assess the mechanical stability of implants after implantoplasty and thermocyclic loading, the residual thickness of the instrumented areas and neighbouring tooth injury due to implantoplasty. Using a phantom head simulator and maxillary model implants were subjected to an implantoplasty procedure. Thirty implants were randomly assigned to receive one of three instrumentation sequences. After instrumentation, injury on neighbouring teeth was assessed. Instrumented implants and non-instrumented controls were subjected to 1.2 million cycles of thermo-mechanical loading in a chewing machine. Afterwards, maximum fracture load for all implants and an additional five pristine control implants was tested. Generally, damage of neighbour teeth was a frequent finding (33±56% of all cases) with considerable inter-group differences. No considerable inter-group difference for the residual implant thickness was found for different areas assessed. No implant fractured during cyclic loading. Fracture load was reduced after cyclic loading of uninstrumented implants from 2,724±70N to 2,299±127N, and after implantoplasty to 1,737±165N, while no effect by the instrumentation sequence could be observed. Both implantoplasty and cyclic loading were shown to reduce the implants' maximum bending strength. Cyclic loading in a laboratory masticator, simulating a five-year equivalent of chewing, did not result in fractured implants. Since neighbouring tooth injury was assessed often, care should be taken with the selection of suitable instruments.

Characterization of in-situ zirconia/mullite composites prepared by sol-gel technique

ABSTRACT The main objective of this study was to investigate the role of zirconia addition to mullite through an in-situ reaction aimed at improving both the mechanical properties and the sinterability behavior. In this work, mullite–zirconia composites were produced using a sol-gel technique. Different amounts of zirconia (0, 10, 15, and 20 wt.%) were added to the mullite, and the calcined gels were sintered at 1550–1700°C for 1 h. The apparent porosity and bulk density of the blank and zirconia/mullite composites were estimated in accordance with ASTM C-20. The phase composition and sample morphology were evaluated via X-ray diffraction (XRD) and scanning electron microscopy analysis (SEM), respectively. Furthermore, the mechanical properties and thermal expansion coefficient (TEC) were also evaluated. The results revealed that the apparent porosity decreased and the density of the zirconia/mullite composites increased when the sintering temperature was increased from 1550 to 1700°C. However, the mechanical properties improved with increasing zirconia content and MZ20 sintered at 1700°C exhibited the maximum bending strength. The TEC results reflected the influence of the composition on the sample TEC. Samples with higher ZrO2 content yielded higher TEC figures than those with lower content.

Fabrication of Hydroxyapatite/Tantalum Composites by Pressureless Sintering in Different Atmosphere.

The effect of sintering atmosphere (air and Ar) and temperature (1100, 1200, 1300 °C) on the microstructure, mechanical properties, and bioactivity of hydroxyapatite/tantalum (HA/Ta) composites were systematically investigated by pressureless sintering of the mixture of HA and Ta powders. It shows that the sintering atmosphere greatly impacts the phase composition and microstructure of the HA/Ta composites. The higher diffusion of atoms promotes shrinkage and causes deeper reaction fusion between the HA matrix and Ta, which improved the interfacial binding of the HA/Ta composites. The refined grain structure and improved interfacial binding obtained within the Ar atmosphere compared to the air atmosphere benefit the mechanical properties. The maximum bending strength and shrinkage observed for the composites sintered at 1300 °C in the Ar atmosphere are 27.24 MPa and 6.65%, respectively. The cell counting kit-8 (CCK-8) method was used to investigate the in vitro cytocompatibility of HA/Ta composites. The results revealed that the HA/Ta composites sintered with different conditions have no cytotoxicity. The simulated body fluid (SBF) soaking results showed that all of the studied composites possess desirable bioactivity, as demonstrated by their ability to form calcium-deficient carbonate apatite layer on the surfaces. For composites sintered at 1300 °C, the surface apatite layer coverage of the composites obtained in the Ar atmosphere was increased by 139.7% than the ones obtained in air, which confirmed an enhanced bioactive mineralization ability. The results indicated that the HA/Ta composites sintered at 1300 °C in Ar possess desirable mechanical properties and bioactivity. This work opens up the new possibility for preparing HA-based composites and is of great value in biomedical applications.

Influence of Age on the Strength of Different Species of Timber

Timbers are used as structural members in various areas of construction works. Hence the knowledge of properties of wood especially strength and factors affecting the strength of timber is very important. This study was conducted to determine the effect of age on the structural strength of timber. The wood species studied are Iroko (Chlorophora excelsa), Nigerian Mahogany (Khaya anthotheca) and Ita (Celtis mildbraedii). The age of timber were determined by counting the number of annual growth rings, which is the combination of early wood and late wood and samples of different ages of timber, were obtained by personal visit to the forest where fresh timber was cut. The samples obtained were machined and trimmed to standard size with respect to BS 373 1957 (imprint 1999), 20mm X 20mm X 60mm for the determination of maximum compressive strength parallel to grain (MCS//), 20mm X 20mm X 20mm for static shear strength and 20mm X 20mm X 300mm to determine the bending strength. The samples obtained were carried to the laboratory at Forestry Research Institutes of Nigeria (FRIN) in Ibadan for testing using Instron Tensiometer machine. SPSS was used to analyze the relationship between strength and age of timber. The result obtained showed that the maximum compressive and Shear strength for Iroko, were at 120years, whereas it has maximum bending strength at 70years. Nigeria Mahogany and Ita has maximum compressive, bending and shear strength at 80 years, and 70 years respectively and among the three timber samples Ita is better in compression and shear strength and iroko is better in bending strength. It was concluded that age of timber has significant influence on timber strength

Extreme Modelling of Concrete Optimal Composition and Content of the Components

The optimal compositions of fine-grained concrete (FGC) with two-level reinforcement with fiber are determined via the extreme modelling of experimental data based on the Scilab engineering and scientific computing environment. At the macro level brass plated fibre of the wave profile FSW LV 15/0.3 made of steel grade 70-85 with the fiber length of 15 mm and the diameter of 0.3 mm was used for reinforcement. At the micro-level the halloysite nanotubes NN-RTE 200 with the particle sizes from 0.05 to 5 microns were applied. Having calculated the models the designed program Extr.sce determined the extrema of the required characteristics of fine-grained concrete Max_z and their coordinates max_x and max_y, corresponding to the contents of the brass plated fiber (x) and halloysite nanotubes additive (y). The graphic dependences of the compressive strength, bending strength and water absorption of fine-grained fiber concrete on the content of brass plated fibre and halloysite nanotubes additive with minimum, average and maximum cement content in it in the form of contour and 3d graphs of the interpolation surface are obtained. Two-level reinforcement of FGC, optimized by the program Extr.sce, proved that fine-grained concrete with 10% of brass plated fibre, 20% of halloysite nanotubes additives, and cement content of 600 kg had the maximum compressive strength of 70.26 MPa. In order to obtain FGC with maximum bending strength (17.43 MPa), there should be 5% of brass plated fibre, 10% of halloysite nanotubes additives, and 600 kg of cement in it. The fine-grained concrete without any reinforcement additives will have the minimum water absorption (3%).

Synthesis and Properties of Mg-Mn-Zn Alloys for Medical Applications.

The magnesium alloys Mg-0.5Mn-2Zn, Mg-1.0Mn-2Zn, and Mg-1.5Mn-2Zn (wt.%) with potential biomedical applications, synthesized by powder metallurgy, were investigated to evaluate the influence of manganese content on their microstructure, mechanical properties, and corrosion resistance. The results show that Mg-Mn-Zn alloys prepared by powder metallurgy reached the maximum compressive stress of 316 MPa and the maximum bending strength of 186 MPa, showing their good resistance to compression and bending, and meeting the mechanical properties required for the human bone plate. With an increase in manganese content, the corrosion resistance improved. In the polarization curve, the maximum positive shift of corrosion potential was 92 mV and the maximum decrease of corrosion current density was 10.2%. It was concluded that, of the alloys tested, Mg-1.0Mn-2.0Zn (wt.%) had the best overall performance, and its maximum compressive stress force and corrosion current density reached 232.42 MPa and 1.32 × 10−5 A·cm−2, respectively, being more suitable for service in human body fluids.

Mechanical Testing and Modeling of the Time-Temperature Superposition Response in Hybrid Fiber Reinforced Composites.

The purpose of this study was to manufacture hybrid composites from fabrics with superior ballistic performance, and to analyze their viscoelastic and mechanical response. Therefore, composites in hybrid lay-up modes were manufactured from Vectran, Kevlar and aluminum fiber-woven fabrics through a vacuum assisted resin transfer molding. The specimens were consequently analyzed using static three-point bending, as well as by dynamic mechanical analysis (DMA). Apart from DMA, time–temperature superposition (TTS) analysis was performed by all available models. It was possible to study the intrinsic viscoelastic behavior of hybrid ballistic laminates, with TTS analysis gained from creep testing. A polynomic mathematical function was proposed to provide a high accuracy for TTS curves, when shifting out of the linearity regimes is required. The usual Williams–Landel–Ferry and Arrhenius models proved not useful in order to describe and model the shift factors of the acquired curves. In terms of static results, the highly nonlinear stress–strain curve of both composites was obvious, whereas the differential mechanism of failure in relation to stress absorption, at each stage of deformation, was studied. SEM fractography revealed that hybrid specimens with Kevlar plies are prone to tensile side failure, whereas the hybrid specimens with Vectran plies exhibited high performance on the tensile side of the specimens in three-point bending, leading to compressive failure owing to the high stress retained at higher strains after the maximum bending strength was reached.

Mechanical Properties of Al Matrix Composite Enhanced by In Situ Formed SiC, MgAl2O4, and MgO via Casting Process.

Al matrix composite, reinforced with the in situ synthesized 3C–SiC, MgAl2O4, and MgO grains, was produced via the casting process using phenolic resin pyrolysis products in flash mode. The contents and microstructure of the composites’ fracture characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were tested by universal testing machine. Owing to the strong propulsion formed in turbulent flow in the pyrolysis process, nano-ceramic grains were formed in the resin pyrolysis process and simultaneously were homogeneously scattered in the alloy matrix. Thermodynamic calculation supported that the gas products, as carbon and oxygen sources, had a different chemical activity on in situ growth. In addition, ceramic (3C–SiC, MgAl2O4, and MgO) grains have discrepant contents. Resin pyrolysis in the molten alloy decreased oxide slag but increased pores in the alloy matrix. Tensile strength (142.6 ± 3.5 MPa) had no change due to the cooperative action of increased pores and fine grains; the bending and compression strength was increasing under increased contents of ceramic grains; the maximum bending strength was 378.2 MPa in 1.5% resin-added samples; and the maximum compression strength was 299.4 MPa. Lath-shaped Si was the primary effect factor of mechanical properties. The failure mechanism was controlled by transcrystalline rupture mechanism. We explain that the effects of the ceramic grains formed in the hot process at the condition of the resin exist in mold or other accessory materials. Meanwhile, a novel ceramic-reinforced Al matrix was provided. The organic gas was an excellent source of carbon, nitrogen, and oxygen to in situ ceramic grains in Al alloy.

Effects of vanadium and titanium addition on the densification, microstructure and mechanical properties of WC-Co cermets

WC-Co cermets containing Ti and V metallic powders were prepared by ultra-fast microwave heating process. The mixing of WC-5wt%Co containing 5 wt% concentrations of Ti and V was performed by a high-energy mixer mill in ethanol media for 10 min. A fast microwave sintering process was carried out at temperatures of 1400, 1500 and 1600 °C with an average heating rate of 40 °C/min in a graphite bed without any soaking time. The XRD patterns showed WC, TiC and VC crystalline phases as reaction products. The FESEM images demonstrated uniform distribution of formed carbides in the microstructure of WC based cermet. By increasing the sintering temperature to 1600 °C, almost fully dense samples were obtained in both series of composites containing Ti and V. The maximum bending strength (981 ± 10 MPa), hardness (24.7 ± 0.1 GPa) and fracture toughness (8.6 ± 0.1) were measured for WC-Co-Ti hard metal at sintering temperature of 1600 °C.

Fiber deformation behavior of discontinuous CFRTP in gear forging

The purpose of the study is to elucidate fiber deformation behavior during the forging of a spur gear by using a carbon fiber reinforced thermoplastic billet. The billet was composed of PA6/UD chips with a fiber length of 30 mm and fiber volume fraction of 50%. A gear forging mold was developed to deform the billet into a gear shape without cutting the fibers. Three types of billets were prepared: a horizontal billet with fibers orientated in the X and the Y directions, a vertical billet with fibers orientated in the Z and the X directions, and a random billet with fibers randomly orientated in the X–Y plane. The fibers along the tooth profile were formed using the horizontal and vertical billets. The adjacent teeth were connected by the fibers. A maximum tooth bending strength was 500 MPa. The delamination occurred under the tooth valley. The orientation of fibers in the teeth using the random billet was also random. The fracture occurred in the middle of the tooth. The results indicated that the fiber orientation in the billet is strongly correlated to the fiber orientation in the gear teeth and the tooth strength. The fiber orientation in the billet proposed in the study can form a tooth with fibers along its profile and with high strength.

Temperature effect on mechanical and tribological properties of WNiCoFe alloy powder for cutting tools

In order to improve the wear resistance of WNiCoFe alloy for cutting tools, WNiCoFe alloy powder is prepared by multiple metals electrolysis, alloy powder and its sintered morphology is observed and phase is analyzed using X-ray diffractometer and scanning electron microscope (SEM), the effect of sintering temperature on its physical mechanics and friction properties was studied. The results show that the prepared WNiCoFe alloy powder is alloyed to some extent, irregular and finer particle size, the diffraction peaks of Co3Fe7 and Fe19Ni are formed in addition to the elemental Fe; the maximum hardness of the sintered is 107.6HRB, the maximum bending strength at three points is 1638.3 mpa, the maximum density is 96.2%, and wear loss is 0.498–0.555 g when WNiCoFe alloy powder is sintered at 800∘C. Diamond tools are made with WNiCoFe alloy powder as the main matrix composition, and cut hard stone, cutting velocity is 8.6 m2/h and life is 11.3 m2/m, which has a good comprehensive performance.

Microstructural and Mechanical Behaviors of Friction Stir Welded Dissimilar AA6082‐AA7075 Joints

In this research, microstructural events and mechanical behaviors in dissimilar friction stir welding (FSW) of aluminium (Al) alloy AA6082‐AA7075 joints have been evaluated to apply aerospace, defense, and military sectors. FSW parametric effects have a more significant impact on the mechanical performances and microstructure of produced joints. FSW tool rotational speed, welding speed, and tool plunge speed were chosen to make the weld joints. The rotational tool speeds of 1600 rpm and 2300 rpm, welding speeds of 40 mm/min and 60 mm/min, and tool plunge speeds of 20 mm/min and 30 mm/min were set as the upper and lower limits. A constant axial force of 5 kN was maintained throughout the joint fabrication process. A taper pin‐profiled tool was utilized to produce the butt welded joints. Mechanical properties of microhardness, tensile strength, yield strength, elongation, and bending strength of the joints were analyzed. The response of the stir zone microstructure to processing parameters was evaluated using optical microscopy (OM) and fractographic analysis of a tensile specimen shown by scanning electron microscope (SEM). The weld joints produced at 2300 rpm, tool traveling rate of 40 mm/min, and tool plunge speed of 30 mm/min showed the greatest tensile strength of the 191 MPa hardness of 145 Hv at the weld center and also the maximum bending strength of 114.23 N/mm2 was achieved. The lowest bending strength of 25.38 N/mm2 was obtained at 1600 rpm with 60 mm/min due to inappropriate mixing of the base metals and poor joint quality. Furthermore, this study revealed that a higher tool plunge speed facilitates the formation of equiaxed grains in the thermomechanically affected zone (TMAZ) on the advancing side (AS). Additionally, the increment in tool rotational speed significantly improved the tensile strength, weld joint quality, and joint efficiency.

Reaction Process and Influence of WC Content on Microstructure and Mechanical Properties of Ti(C, N)-Based Cermets

The incorporation of WC promotes the sintering and grain refinement of Ti(C, N)-based cermets, leading to superior mechanical and functional properties. Herein, we present the reaction process of Co–Ti–C–BN–WC system and influence of WC content on microstructure and mechanical properties of Ti(C, N)-based cermets. The results reveal that Ti(C, N) is produced due to the combination of C/TiN or TiN/TiC, whereas TiB2 is formed due to the reaction between B/TiB or Ti/B. Moreover, (W, Ti)(C, N) solid-solution is synthesized due to the reaction of W and C with TiN in the liquid state. In addition, XRD analysis indicates the presence of a small amount of CoW2B2 and Co3C phases with WC content of 15 and 20 mass%. Furthermore, the content of core-ring structure gradually increases with the increase of WC content from 5 to 20 mass%. Also, the grain size increases from 0.364 µm to 0.484 µm with increasing WC content from 5 to 20 mass%. On the other hand, the porosity initially decreases with increasing WC content, followed by a gradual increase. Consequently, the microhardness, fracture toughness and bending strength initially increase with increasing WC content, followed by a decrease. The maximum microhardness, fracture toughness and bending strength are found to be 2010 HV10, 7.21 MPa·m1/2, and 725 MPa, respectively.

Effect of the Production Conditions on the Structure and Strength of the AMg6 Alloy–12Kh18N10T Steel Bimetallic Joint

The structure and the strength properties of the AMg6 aluminum alloy–12Kh18N10T steel bimetal formed by hot isostatic pressing under various conditions of preparing the contact surfaces of the materials to be joined and various connection media have been investigated. The maximum tensile strength (196 MPa) is reached upon scraping the aluminum components and the presence of a steel surface relief. The maximum bending strength (329 MPa) is reached upon scraping the aluminum components and the absence of steel surface relief.

Effects of Composition on the Physical Properties of Water-Soluble Salt Cores

The demand for producing essential cast parts and the design requirements for superior engineering performance have increased in recent years. Sand cores used in conventional aluminum cast parts are harmful to the environment, which limits their application. Utilizing water-soluble cores in the aluminum casting industry is expected to be an environmentally friendly approach due to recyclability of the salt cores. In this study, water-soluble salt cores were made from chloride- and/or carbonate-containing salts in various amounts. The salts were melted and cast into steel molds to obtain salt cores. The salt cores were subjected to three-point bending tests to determine their mechanical strength, the melting points were determined with thermal analyses, and the water solubility was measured at room temperature and 50 °C. A maximum bending strength of 17.19 MPa, a maximum melting point of 776 °C and a maximum water solubility of 89 g salt/100 ml water were obtained for the samples with compositions of 75% KCl–25% K2CO3 and 25% Na2CO3–75% K2CO3, respectively. Fractographs of the samples used in bending tests were taken by a still camera in macro mode, and from these fractured surfaces, scanning electron microscopy studies were performed. The X-ray diffraction pattern of the sample exhibiting optimal properties (28.3% Na2CO3 and 71.7% K2CO3) also showed that K2CO3, NaKCO3 and KNaCO3 phases were present in the structure, as expected. An actual casting process with aluminum die casting of an automotive part was also performed. The diecast aluminum part was subjected to a leak-proof test, and X-ray images were used to check for porosity in the part.

Hierarchical composites of B4C–TiB2 eutectic particles reinforced with Ti

Eutectic particles of B4C–TiB2 were reinforced with Ti by spark plasma sintering (SPS) or infiltration. The SPSed samples with 20, 30 and 40 wt. % Ti consisted of ceramic phases, and had a bicontinuous macrostructure formed by the Ti-rich region and the eutectic particles region, while the infiltrated sample was a complex composite comprised of a 3D Ti-rich continuous network, composite in nature, that contained Ti-metal and in which are embedded isolated ceramic (eutectic) particles. The SPSed samples are brittle with the maximum bending strength of 300 MPa for the 30 wt. % Ti, higher than for a reference sample produced by SPS from directionally solidified eutectic particles. A higher amount of added Ti results in a higher displacement in the bending test suggesting a higher fracture toughness. Simultaneous strengthening and toughening of the composite was realized. The infiltrated sample was ductile, while its bending strength (220 MPa) was comparable to the values measured for the brittle as-introduced reference sample and the sample with 20 wt. % Ti, both produced by SPS. In the SPSed and infiltrated samples at the interface between the Ti-rich region and B4C–TiB2 eutectic particles, a local ‘pull-out’ intergranular fracturing mechanism mainly involving Ti–B 1D-grains was observed. This local micromechanism together with a ‘pull out’ macromechanism of the eutectic grains from the Ti-rich component are considered important for the bridging/anchoring behavior responsible for the strengthening and toughening processes in our novel hierarchical composites.

Optimization of pretreating poplar wood shavings with cellulase to produce binderless fiberboard using response surface methodology

Wood processing waste, poplar wood shavings, were used for fiberboard production, and the pretreatment conditions using cellulase were studied using response surface methodology (RSM). After single factors optimization, central level of temperature, dosage, and liquid/solid ratio (LSR) of cellulase pretreatment conditions were obtained. Further optimization to study the influence of the factors was carried out using Box-Behnken design of experiments. A second-order polynomial equation was obtained, and the low p-value (<0.007) implied that the model was highly significant by analysis of variance (ANOVA). The optimized cellulase pretreatment conditions for maximum bending strength (BS) of the fiberboard were determined by ridge analysis as 44.4 °C of temperature, 1.23 U/g of dosage, 4.2 of LSR, and 5 h of pretreatment time. Under the optimized conditions, the BS of the fiberboard reached 25.12 ± 0.35 MPa by validation experiment, which was twice that of the fiberboard without pretreatment. Thus, the cellulase pretreatment should be a good choice to produce high-strength binderless fiberboard.

Fabrication and bend testing of DHAK fiber composites

In the current work, composite specimens were fabricated using DHAK fiber up to a maximum volume fraction of about 0.188. The retting and manual processes have been used to extract the fibers. Density of DHAK is found to be 1098.5 Kg/m3. The bend properties of the composites were examined as a function of fiber content. It is found that the bend strength of the composite increases with an increase in fiber content up to 0.15 vol fraction and thereafter decreases. It has been observed that the maximum mean bend strength of the composite is 223.54 MPa for the volume fraction 0.15 which is about 3.15 times greater than that of resin. The maximum mean flexural modulus of the composite is calculated as 3.88 GPa for volume fraction 0.15, which is about 2.62 times higher than that of a base resin. These results show that there could exist a strong solid bond between the fiber and resin at the volume fraction of 0.15. It has been concluded that incorporating DHAK fiber in a base resin leads to higher bend strength as well as modulus of a new formulated composite material.

Fabrication of Silk Resin with High Bending Properties by Hot-Pressing and Subsequent Hot-Rolling.

This research reports the processability and mechanical properties of silk resins prepared by hot-pressing followed by hot-rolling and then analyzes their thermal and structural properties. The results show that regenerated silk (RS) resins are better suited for hot-rolling than Eri and Bombyx mori silk resins (untreated silk). When hot-rolling at 160 °C with a 50% of reduction ratio, maximum bending strength and Young’s modulus of RS resin reaches 192 MPa and 10.2 GPa, respectively, after pretreatment by immersion in 40 vol% ethanol, and 229 MPa and 12.5 GPa, respectively, after pretreatment by immersion in boiling water. Increased strength of the material is attributed to the increased content of aggregated strands and intramolecular linking of β sheets (attenuated total reflectance Fourier-transform infrared spectroscopy) and higher crystallinity (X-ray diffraction analysis). After hot-pressing and hot-rolling, RS resins have a stable decomposition temperature (297 °C).