Ultimate Tensile Strength Of Samples Research Articles

Piezoelectric core-shell fibrous scaffolds of PVDF-ZnO/PCL for bone regeneration

One promising approach to improve bone regeneration is the use of piezoelectric scaffolds, which can positively affect cell growth and proliferation. PVDF, as a piezoelectric polymer, is an attractive candidate for use as a bone scaffold. However, other components should be added to PVDF to improve wettability, biodegradability, biocompatibility, and other biological properties. In this research, PVDF containing ZnO-PCL core-shell fiber composites were fabricated by coaxial electrospinning. TEM images were used to determine the proper electrospinning parameters that can provide a homogenous core/shell structure. Afterward, the surface of the samples was corona-treated to improve wettability. FTIR spectroscopy was used to estimate the piezoelectric β phase fraction in the core PVDF fibers, which demonstrated that the highest β phase fraction was obtained in the presence of 0.5 wt% ZnO nanoparticles. The tensile test results revealed that by adding ZnO nanoparticles to the scaffolds, the ultimate tensile strength of samples decreased, yet the values were in the acceptable range. The water contact angle measurements showed that the corona treatment could successfully reduce the contact angle from about 130° to 60°. Based on the obtained results, the F-0.5Z sample was chosen as the optimum sample and was used for biological and piezoelectric assessments. It rendered the piezoelectric output of 6.5 pC/N. In vitro assessments showed that this sample is biodegradable and bioactive, could support cell attachment and proliferation and intensified calcium mineralization. The composite containing 0.5 wt% ZnO had the best result and could be used as a scaffold in bone regeneration and repair.

Sustainable Transformation of Waste Soft Plastics into High-Quality Flexible Sheets

Post-consumer soft plastics often face inadequate management practices, posing threats to both human life and the environment while also leading to the loss of valuable recyclable materials when not recycled. Traditional mechanical recycling methods are unsuitable for waste soft plastics due to their thin and flimsy nature. This study presents an effective, user-friendly process for converting waste soft plastics into new products, generating value, and expediting their collection and recycling without the need for pelletization. The outcome of this process was compared with products derived from traditional recycling and commercially available alternatives through various analytical techniques including tensile testing, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The findings suggest that waste soft plastics can be transformed into flexible sheets without significant alterations to their properties. In particular, the ultimate tensile strength of samples recycled using the developed process in this study and traditional recycling were found to be 25.9 ± 0.4 and 25.2 ± 0.8 MPa, respectively, surpassing commercially available products by nearly 15 MPa. Additionally, a life cycle assessment revealed that producing flexible sheets from waste soft plastics using this innovative approach, rather than virgin polymer, could reduce fossil fuel depletion and global warming by 99.4% and 94.6%, respectively. This signifies the potential of the process to mitigate environmental pollution and produce high-quality products exclusively from 100% waste plastics.

The improvement on mechanical anisotropy of AZ31 magnesium alloy sheets by multi cross-rolling process

The rolled AZ31 Mg alloy sheets were manufactured by unidirectional rolling and cross-rolling with two passes and five passes in this study. The improvement of multi cross-rolling on the anisotropy of mechanical properties, microstructure and texture of AZ31 Mg alloys was investigated by tensile fracture experiments, optical microscopy (OM) and electron backscatter diffraction (EBSD). The results indicate that the samples after rolling which were rotated by 90° showed weaker anisotropy than the samples rolled by 0° path. The ultimate tensile strength of the samples after 0° direction rolling increased from 236 MPa to 338 MPa on the transverse direction (TD) compared to as-rolled samples. The ultimate tensile strength of unidirectional rolling samples with two and five passes paralleled to TD is increased by 7% and 14% than that of cross-rolling samples. The enhanced mechanical properties are attributed to fine-grained strengthening, twin strengthening and dislocation strengthening. The {10−12} extension twin, {10−11} contraction twin and {10−12}-{10−11} double twin were investigated in the microstructure of samples by multi cross-rolling. All the samples showed the basal texture on the {0001} < 11–20 > . The basal texture of cross-rolling samples was apparently weakened for comparison to unidirectional rolling samples and the basal texture of five-pass cross-rolling samples was weaker than that of two passes. The improvement of anisotropy after cross-rolling can be attributed to grain refinement, the activation of non-basal slip and the weakening of basal texture.

Investigating the influence of the scanning rotation angle on the microstructure and properties of LPBFed CuCr0.8 alloy

The fabrication of high-strength and high-conductivity (HSHC) copper alloys by laser powder bed fusion (LPBF) has attracted great interest in recent years. Owing to the excellent strength and high electrical and thermal conductivity of HSHC copper alloy. Moreover, the characteristics of LPBF are suitable for fabricating HSHC. In this paper, the QCr0.8 copper alloy samples with four scanning rotation angles of 0°, 67°, 90°, and 105° were fabricated by LPBF using the high laser power of 2000 W. The results indicate that the scanning rotation angles have no significant influence on the relative density. When the scanning rotation changes to 0°, 67°, 105°, and 90°, the order of the grain size is from large to small. With the 90°scanning rotation angle, the as-built sample has the smallest ultimate tensile strength (UTS) and electrical conductivity. After direct aging, its UTS up to 468.0 Mpa and electrical conductivity is up to 98.3 %IACS. Equally, as a result of precipitation strengthening, the UTS of samples with different scanning rotation angle all increase significantly. This study is to provide theoretical guidance and reference for the selection of scanning rotation angles in the HSHC alloy fabrication process.

Effect of oxygen content of tantalum powders on the characteristics of parts processed by laser powder bed fusion

In this study, spherical tantalum (Ta) powders, having different oxygen contents, were fabricated by a radio frequency plasma spheroidization technique. A laser powder bed fusion (LPBF) technique was then used to consolidate these powders and the effects of different LPBF processing parameters on the densification, microstructure and mechanical properties of parts were investigated. The results indicated that the oxygen content of the used Ta powder has significant influences on the densification, microstructure and the consequent mechanical properties of printed parts. The relative density of the parts printed from the powders with a low oxygen content of ∼150 ppm was insensitive to the applied laser energy density and was higher than the ones prepared from the powders with higher oxygen contents. The grain refinement was observed and the texture in the side-view of the as-built samples changed from {100}∥BD to {111}∥BD with the increase in the oxygen content of the used powders. The microhardness and ultimate tensile strength of samples increased and the ductility of parts decreased with the increase in the oxygen content of the used raw powders. The main fracture mode of the LPBF consolidated Ta samples changed from a typical ductile rupture to the combination of cleavage and ductile rupture modes with the increase of the oxygen content in the processed parts.

Effect of Scanning Strategies on the Microstructure and Mechanical Properties of Inconel 718 Alloy Fabricated by Laser Powder Bed Fusion

The scanning strategy is an essential factor that determines the thermal history and combination of melt tracks within parts in the laser powder bed fusion (LPBF) process, which can significantly influence the microstructure evolution, defect formation, and mechanical properties of parts. Herein, the effect of scanning strategies (i.e., Y‐scan, XY‐scan, Rot‐scan, and Island‐scan) on the microstructure and mechanical properties of Inconel 718 (IN718) parts manufactured by LPBF is investigated. The results show that different scanning strategies can lead to different morphologies of melt tracks, and the Rot‐scan is the most beneficial strategy for improving density of parts. Different scanning strategies change the direction of the temperature gradient within parts, resulting in different morphologies of grain growth. The tensile properties of samples built with four types of scanning strategies show superior mechanical properties compared with the cast. The ultimate tensile strength of samples manufactured by Y‐scan, XY‐scan, and Rot‐scan is equivalent to that of the wrought, while the ductility of them is higher than that of wrought. However, tensile properties of samples manufactured by island scanning are lowest due to defects (e.g., pores, spatters) at the overlap of islands.

Effects of oxygen content on microstructure and mechanical properties of 18Ni300 maraging steel manufactured by laser directed energy deposition

Compared to conventional material processing technologies, laser directed energy deposition (LDED) belonging to additive manufacturing (AM) has many advantages and enormous commercial potential. However, the effect of external factors on the deposition process has not been completely revealed such as the oxygen content in the manufacturing environment. 18Ni300 as maraging steel has excellent mechanical performance, but oxidation inside parts could induce metallurgical defects like inclusion or cracks and impair the service life of parts. Therefore, this paper focuses on the microstructure and mechanical properties of 18Ni300 maraging steel fabricated by LDED under different oxygen contents. The control of oxygen content in the environment was achieved by changing the argon content. Experimental results indicated that the forming accuracy of specimens and process stability were effectively improved at both 500 ppm and 50 ppm oxygen contents. The width of equiaxed grain region, grain growth orientation and primary dendritic arm spacing were significantly affected by gaseous environment. In the low oxygen content group, higher microhardness values were obtained due to the effect that similar to heat treatment. The ultimate tensile strength of samples reached to 908 MPa under 50 ppm oxygen content, which exceeded the tensile strength of wrought components.

Strengthening mechanisms and tensile properties of 20Cr2Mn2Mo processed by laser shock peening and vacuum carbonitriding

The effects of laser shock peening and vacuum carbonitriding on strength and plasticity of 20Cr2Mn2Mo were investigated. Uniaxial tension tests were carried out and the microstructures were analyzed by optical microscope, scanning electron microscope, electron backscatter diffraction, and transmission electron microscope. The phase composition was characterized by X-ray diffraction. The results revealed that the yield strength and ultimate tensile strength of samples were increased by 10.63% and 4.15%, respectively, after compound treatment due to the formation of large volume fraction of grain boundaries, high-density dislocations, and second-phase particles. However, the plasticity was only decreased by 0.99%, which was benefited from gradient structures induced by laser shock peening. The improvement of strength was mainly attributed to Orowan strengthening and dislocation strengthening. The grain refinement had little influence on the improvement of strength.

Influence of multi-pass friction stir processing on the formation of microstructure and mechanical properties of Ti6Al4V alloy

Friction stir processing (FSP) is an advanced technology for altering the surface microstructure of metals and alloys to improve mechanical and performance properties. Previous research on titanium alloy processing showed that varying the FSP process parameters (such as rotational speed, movement speed and tool contact force) significantly affects the Ti–6Al–4V microstructure evolution and mechanical properties. However, the effect of multipass FSP on the Ti–6Al–4V alloy was not studied. Therefore, this paper studies the effect of four-pass FSP of the Ti–6Al–4V titanium alloy on the microstructure evolution, mechanical properties and wear resistance of this alloy. Microstructure analysis showed that the stirring zone forms heterogeneous microstructure with dynamically recrystallized equiaxed α grains, β grains and β areas with α phase of needle and laminar type, which is associated with the stirring zone temperature gradient during FSP. It was found that an increase in the number of FSP passes up to 3 times improves the ultimate tensile strength (up to 1173 MPa) and wear resistance (by 33 %). The improved ultimate tensile strength of samples after 3 FSP passes is caused by grain size reduction in the stirring zone by 88 % compared to the initial Ti–6Al–4V alloy. It was shown that after 4 FSP passes the grain size increases and the ultimate tensile strength decreases to 686 MPa in the stirring zone, which is associated with large defects formed along the contour of metal flows. At the same time the Ti–6Al–4V wear resistance after 4 FSP passes increases by 39 % compared to the raw material.

Process evaluation, tensile properties, mathematical models, and fracture behavior of 3D printed continuous fiber reinforced thermoplastic composites

Continuous fiber reinforced thermoplastic composites with advantages of high strength, long life, corrosion resistance, and green recyclability have been widely used in aerospace, transportation and high-precision processing equipment, etc. 3D printing is an advanced additive manufacturing technology that enables the rapid manufacture of complex structures and high-performance composites. The aim of this study is to evaluate the precision and stability of 3D printed continuous fiber reinforced thermoplastic composite structures and construct suitable mathematical models to predict tensile properties. Samples evaluated in this study were produced by varying the volume fraction and distribution mode (average and central mode) of fibers within the printed structures. The measured data proved the continuous fiber reduced the printing precision on width and thickness and the printing stability on thickness, while it improved the width stability in the XY horizontal plane. The printing precision and stability of samples with an average mode were slightly better than those of samples with a central mode. The tensile results of 3D printed continuous fiber reinforced thermoplastic composites demonstrated that an increasing volume of fiber reinforcement resulted in the increasing stiffness and ultimate strength of tested samples. The average elastic modulus and ultimate tensile strength of samples with the average mode were higher than those of samples with the central mode, while the average strain at break was quite the opposite. Mathematical models of elastic modulus were established to achieve the relative errors 0.06% and 2.14% for checked samples, while relative errors of the mixing rule were up to 76.15% and 81.71%, respectively. Some typical defects affecting the surface quality and the fracture behavior of 3D printed samples were researched by the analysis of micromorphology.

Investigation of Friction Stir Welding of AA2024-T4 Thin Sheets for Industrial Applications

The welding of aluminum alloys thin sheets is a complicated process no matter what the technology used. A 2024-T4 AL sheets of 1.2mm thickness were welded using stir welding method and then examined for their mechanical and microstructure characteristics. The process included the use of specifically designed fixture along with cylindrical tool. Thin sheets welding of aluminum alloy is a complicated process either in conventional or newly developed methods. In this approach the friction stirs welding (FSW) is used. Tensile test and microstructure test were conducted to analyze final product properties. The cylindrical rotating tool was used to create a joint which is specifically useful in the welding of aluminum alloys in particular. It was found that All tested samples were defects free. Mechanical properties show that ultimate tensile strength of samples is below the base metal. Two rotational speed were applied (900 and 1400) rpm with welding feed rate of (20, 40 and 80) mm/min respectively. The tool has a 1.2mm diameter pin of 1 mm height and 8mm shoulder diameter. A rotation speed of (900) rpm and feed rate of (40) mm/min gave the best quality product in which an increase of (72%) in ultimate tensile strength was observed.

Physicochemical and Antibacterial Characterization of Nanofibrous Wound Dressing from Silk Fibroin-polyvinyl Alcohol- Elaeagnus Angustifolia Extract

The herbal drug incorporated nanofibers with potential accelerating wound healing has become a promising wound dressing to treat wounds. The present research aimed to study the effects of adding different amounts of Elaeagnus Angustifolia (EA) extract on physical, mechanical, and biological properties of silk fibroin-polyvinyl alcohol (SF-PVA) nanofibers. Thus, different electrospun mats were made by changing the SF to the EA ratio. The successful incorporation of EA in SF-PVA nanofibers was confirmed by Fourier transform infrared spectroscopy (FTIR). No obvious change was observed in the mean fiber diameter except for EA/SF ratio 1:3. Also, mechanical properties results showed that the ultimate tensile strength of samples dropped from 9±0.8 MPa to 2.50±0.03 MPa with decreasing SF amount. The in vitro release studies indicated that the fickian diffusion controlled the EA release profile and it was faster in the nanofibers containing more EA. Furthermore, the addition of EA into the nanofibrous dressings improved their antioxidant activity as well as antibacterial activity against both gram-positive (S. aureus) and gram- negative (E. coli) bacteria. Cell viability was also measured using fibroblast cells cultured on prepared dressings and results proved that the higher amounts of EA have a significant impact on cell viability. These findings suggest the advantages of EA as an additive to regulate cell behavior and for skin tissue regeneration.

The Effect of Loading Frequency on Fatigue Life of Green onyx under Fully Reversed Loading

Rock structures, in reality, may be subjected to reversed tension-compression loading conditions due to blasting, earthquake, and traffic or injection-recovery process. In this case, loading frequency may have a great influence on fatigue life and behavior of rocks. The effect of loading frequency on fatigue life of a crystalline rock sample under fully reversed loading condition was examined. A new apparatus, based on the R. R. Moore fatigue test machine, was used to assess the fully reversed loading condition. The experimental tests were conducted with five sets of loading frequency and five levels of stress based on the ultimate tensile strength of samples. The test results showed that the variation of ultimate fatigue stress versus loading cycle number (S-N curve) of crystalline rock samples were in accordance with the observed results in other materials such as metals and ceramics. The results showed that fatigue life of a component is positively correlated with the frequency level. The fatigue life improves with increasing the loading frequency, but the improvement was more tangible at lower stress levels than at higher stress levels. The effect of loading frequency in an ordinary S-N equation was also formulated. The results also showed that the loading frequency does not influence the fatigue limit.

Effect of SPD Processing Technique on Grain Refinement and Properties of an Austenitic Stainless Steel

The formation of nanocrystalline structures and mechanical properties were studied in a nitrogen-bearing 304-type stainless steel subjected to severe plastic deformation (SPD). The steel samples were processed at ambient temperature using three different methods, i.e., caliber rolling, multidirectional forging and high pressure torsion. All these techniques resulted in pronounced grain refinement. The microstructures consisting of austenite/ferrite crystallites with transverse dimensions of 50 and 30 nm evolved in the rolled and forged samples, respectively. The austenite fractions comprised approximately 0.4. In contrast, the microstructure consisted mainly of austenite with an average grain size of about 25 nm evolved after high pressure torsion. All samples of the stainless steel subjected to severe plastic deformation demonstrated significant strengthening. The ultimate tensile strengths of 2065 MPa and 1950 MPa, were obtained after rolling and high pressure torsion, respectively. The ultimate tensile strength of samples subjected to multidirectional forging was 1540 MPa.

Investigation of mechanical properties and fatigue life of ECARed AA5083 aluminium alloy

AbstractEqual‐channel angular rolling (ECAR) is a continuous severe plastic deformation process. In this process, severe shear strains apply to the sheet. This strain increases the yield or ultimate strength of sheet without significant change in sheet dimension. In this paper, the effect of ECAR process on mechanical properties and fatigue life of manufactured sheets will be studied. Four AA5083 samples have been prepared and annealed for obtaining stress‐free samples. Three samples have been rolled by the ECAR process with one, two and three passes of rolling, respectively. Mechanical tests including tensile test, hardness and axial fatigue tests have been carried out on prepared samples. Fatigue tests have been implemented according to a strain‐based approach with a constant strain ratio equal to 0.75 and 0.5 Hz frequency of loading. All of the tests have been carried out in controlled laboratory conditions. Results show that the ultimate tensile strength of samples increases with increasing the pass of rolling. Also, the maximum elongation of samples decreases. Maximum elongation was 17% in annealed samples, while it decreases to 10% in samples with three passes of rolling. The hardness of samples has been measured, and the results show an increase in hardness for a higher pass of the ECAR process. Fatigue test results show that fatigue life of AA5083 samples decreases in manufactured sheets of the ECAR process. Also, cyclic softening has been observed in the ECARed sample. The fracture surfaces of samples after fatigue test have been observed with a scanning electron microscope. A comparison of fracture surfaces confirms that the crack growth was intergranular in annealed samples while it changes in ECARed samples to transgranular.

Microstructures and mechanical properties of a modified high-C–Cr bearing steel with nano-scaled bainite

The microstructures and mechanical properties of a novel bainitic bearing steel subjected to austenitizing at 950°C for 40min followed by low-temperature austempering at 200°C for 2h, 6h, 12h and 72h were studied. Nano-bainite microstructure with bainitic ferrite plate thickness about 50±15nm was obtained by austempering at 200°C for 6h, 12h and 72h. Besides nano-scaled bainitic ferrite plates, there were small amount of retained austenite and undissolved carbides in the microstructure. The volume fraction of retained austenite is 7.2% in the samples austempered at 200°C for 72h. The ultimate tensile strength of samples austempered at 200°C for 72h reaches 2373MPa, which is superior to the sample austempered at 200°C for 2h, whose microstructure is almost full martensite. The weight loss values are 0.0100g and 0.0273g for samples austempered for 72h and 2h respectively and the wear resistance of the sample austempered for 72h is about 1.7 times higher than that for 2h. Because of the excellent strength and wear resistance of the low-temperature bainite, this low-temperature austempering could be a potential technology for manufacturing bearings.

Influence of Structural Parameters on Tensile Property of Gasar Porous Copper

Abstract Gasar porous copper with various structural parameters was made by metal-gas eutectic unidirectional solidification process. The effects of structure parameters on the uniaxial tensile properties of the porous copper were investigated. The fracture morphologies of tensile samples were studied by scanning electron microscope (SEM). Math models and numerical simulation were performed and confirmed by experimental data. Results show that the tensile properties of porous copper depend on porosity and tensile direction. Ultimate tensile strength of samples with the same porosity whose pore axes are parallel to tensile direction is better than that whose pore axes are perpendicular to tensile direction. For the porous copper whose pore axes are parallel to tensile direction, the ultimate tensile strength decreases linearly with increasing of the porosity, indicating that pores have no stress concentration on matrix. While for the porous copper whose pore axes are perpendicular to tensile direction, the ultimate tensile strength decreases significantly as porosity increases. Ultimate tensile strengths from experiments, models and numerical simulations of two kinds of specimens are consistent well.

Spark Plasma Sintering of Mechanically Activated Ni and Al Nanopowders

The structure and mechanical properties of materials fabricated by spark plasma sintering of mechanically activated mixture of nickel and aluminum nanopowders were investigated. On account of the elemental powders ratio formation of Ni3Al compound was expected. Relative density of sintered samples was equal to ~ 95 %, microhardness of materials was 6540 MPa. Ultimate tensile strength of samples tested according to three-point bending scheme exceed 1100 MPa.

Optimization of quenching process in hot press forming of 22MnB5 steel for high strength properties for publication in

This paper presents hot press forming of 22MnB5 steel blanks for high strength automotive components. The hot press forming was performed using Schenck press PEZ0673 machine with maximum press force of 1000 kN. Samples were square 22MnB5 blanks, of 50 × 60 mm dimension. A high temperature furnace was used to heat up the blanks to austenite temperature of 950°C. Samples were held at the austenite temperature prior to forming and quenching process. Three independent controlled parameters were cooling water temperature, press holding time and flow rate of water. Pressed samples were characterized for metallographic study, hardness properties and tensile properties. Metallographic study was conducted using Meiji optical microscope. Hardness was measured using Vickers indenter with load 1000gf. From metallographic study, the hot pressed 22MnB5 boron steel samples produced lath martensitic microstructure. Hardness of hot pressed samples increased with decreasing cooling time. The yield strength and the ultimate tensile strength of samples after hot forming were between 1546 and 1923 N/mm2. These findings were important to design tailored ultra-high strength in automotive components at different process parameter settings.

Al-Li Surface Alloying in the Electrolytic Method

Surface alloying is a new method of surface treatment by which an element is diffused into the surface of another element causing the formation of a solid solution on its surface. Using this method, the problems of casting methods have been eliminated. In this method, the sample is sunk into an aqueous solution and is connected to the cathode. Applying enough voltage, lithium separated from lithium sulphat-sulfuric acid solution diffuses into the aluminum surface. The depth of diffusion into the aluminum is measured to be 50 to 500μm according to the diffusion time which is selected to be 1 to 24 hours. Experiments showed that the formed layer is very uniform. It was also concluded from the experiments that hardness is increased extensively, with the maximum value of 98HV, and fatigue life is increased by the factor 4. It was also shown that the toughness, yield stress and ultimate tensile strength of samples are the same as those of pure aluminum.