Mechanical Properties Of Specimens Research Articles

MECHANICAL PROPERTIES OF POLYPROPYLENE PLASTELIZED BY CHLOROPHYLL

There are many of industrial plasticizers materials used to improve mechanical properties of polypropylene. In this study chlorophyll, natural pigment is used. Its eco – friend and not toxic material, extracted from plants. The chlorophyll, natural pigment is extracted and mixed with polypropylene with following weight percentages (0.0, 0.1, 0.25, 0.5, 0.75, and 1.0), then extruded as a sheet by screw extrusion machine. The mechanical properties of specimens are examined by mechanical testing, such as (Tensile test, Impact test). The results showed improvements in mechanical properties of polypropylene plasticized by chlorophyll. Where it gives ultimate tensile strength of (32.64, 33.972, 44.63, 40.633, 33.306, and 45.962) Mpa, the modulus of elasticity of (439.27, 1040, 1195.63, 700, 1785, and1525) Mpa, the maximum elongation % at fracture of (24.46, 16.182, 19.632, 61.584, 17.587, and 12.121) mm/mm %, and impact strength of (0.1, 0.2, 0.25, 0.355, 0.24, and 0.2) Joule, respectively with each chlorophyll addition weight percent wt%. The polypropylene blend consisting chlorophyll of 0.5 wt % presents significant improvements of mechanical properties, high ductility, and impact strength, suitable ultimate strength, and modulus of elasticity.Â

An investigation in to the mechanical properties of CP Ti/TiO2 nanocomposite manufactured by the accumulative roll bonding (ARB) process

In this study, a commercially pure titanium (CP Ti) sheet was produced by the ARB process. Then, the mechanical properties of monolithic and nanocomposites specimens manufactured using 0.1, 0.3, and 0.5wt% TiO2 nanoparticles as the reinforcement were investigated at different ARB cycles. The results showed improvement in the mechanical properties of specimens with the addition of TiO2 nanoparticles, as their yield strength and ultimate tensile strength were increased by increasing the TiO2 nanoparticles percent. In this regard, the ultimate tensile strength of the monolithic specimen reached to 810MPa, while it was 980MPa, 1040MPa, and 1085MPa after applying 8 ARB cycles for 0.1wt%, 0.3wt% and 0.5wt% nanocomposite specimens, respectively. However, the ultimate tensile strength of the as-received CP Ti sheet was 285MPa. Moreover, the yield strength and the ultimate tensile strength were increased by increasing the number of ARB cycles and the total elongation; on the other hand, in the monolithic and nanocomposite specimens, it was decreased by increasing the number of ARB cycles. Grain refinements due to severe strain, work hardening and TiO2 nanoparticles reinforcements were the main causes accounting for the improved mechanical properties. Recovery and dynamic recrystallization were two phenomena observed via TEM studies in the ARB process, leading to the development of equiaxed grains in the final ARB cycles.

Influence of Nb content on grain size and mechanical properties of 18 wt% Cr ferritic stainless steel

The influence of Nb contents between 0.20 and 1.20wt% on the grain size and mechanical properties of 18wt% Cr ferritic stainless steel produced by investment casting was investigated. The average grain sizes of the three steels decreased apparently with increasing Nb content mainly due to the increasing number of pre-existing oxides formed at higher temperature, which were more likely to be the nuclei of heterogeneous nucleation. The thermodynamic analysis of Nb(C,N) formation was in conformity to the experimental result that the Nb(C,N) precipitates became larger with increasing Nb content. The as-cast specimen with the smallest grain size of steel C had the worse tensile strength and elongation in comparison with the as-cast specimens of steels A and B, mostly owing to the catenarian and dendritic Nb(C,N) particles distributed densely at the grain boundaries. The mechanical properties of specimens were not improved remarkably through high temperature solid-solution, whereas the mechanical properties of normalized specimens in the three steels were improved to different degrees. The coalescence and sparse distribution of smaller precipitates at grain boundaries after normalizing effectively weakened the local stress concentration arising from the reticular distribution of particles. The normalized specimen of steel A with 0.24wt% Nb still showed good mechanical properties. Normalizing at 850°C for 2h is the appropriate heat treatment for the 18wt% Cr ferritic stainless steel. The comparatively rational Nb content of the ferritic stainless steel is between 0.20 and 0.40wt% for investment casting production.

The Influence of Molecular Weight and Tacticity on Thermal, Morphological and Mechanical Properties of Ziegler–Natta Catalyzed Isotactic and Syndiotactic Polypropylene Blends

The thermal, morphological and mechanical properties of polypropylene blends as influenced by the molecular weight and tacticity were investigated. Polypropylene sample blends (50/50 wt.%) were injection moulded into standard disks for morphological and mechanical tests. The thermal properties of the polypropylene blends were measured by differential scanning calorimetry (DSC), while the morphological and mechanical properties of specimens were investigated by means of optical microscope (OM), scanning electron microscopy (SEM), microhardness (MH) and dynamic mechanical analysis (DMA). DSC results of the bulk crystallization of the various isotactic polypropylene blends showed one melting peak, which indicates that cocrystallization of the blends occurred. However, the crystallization behavior of the polymer blends was strongly affected by the configuration (tacticity) and molecular weight of the polypropylene polymers. In addition, the MH and DMA measurements showed that blends of two different isotactic polypropylenes presented MH and storage modulus values between the values of the respective two MH and storage modulus values of the homopolymer samples, which in turn, depended on the type and degree of the crystallinity of the blends. However, the presence of syndiotactic polypropylene in a blend with isotactic polypropylene leads to a decrease in the MH value of the isotactic polypropylene samples. Normal 0 19 false false false LT X-NONE X-NONE DOI: http://dx.doi.org/10.5755/j01.ms.22.3.9056

Use of silica fume and recycled steel fibers in self-compacting concrete (SCC)

This paper aims to investigate the effects of replacing cement with silica fume in the reinforced self-compacting concrete with recycled steel fiber and study its mechanical properties and impact resistance. To characterize mechanical properties and impact resistance, 144 specimens with different fiber volume fractions of 0.25%, 0.5%, and 0.75% were experimentally tested. Mechanical properties of specimens were characterized with regard of compressive, splitting tensile, and flexural strengths. Concerning the obtained large experimental database, an analytical analysis was performed by using regression analysis to investigate the correlate between the impact and mechanical properties of self-compacting concrete reinforced with recycled steel fibers. In addition, the correlation between the mechanical properties of specimens and the content of the replaced cement with silica fume was also examined.The results revealed that the combined effects of silica fume and recycled steel fiber improved the mechanical properties and impact resistance of specimens. Moreover, linear equations were also developed to correlate mechanical properties and impact resistance of specimens with a high coefficient of determination.

Fatigue crack growth analysis of plasma nitrided AISI 4140 low-alloy steel: Part 1-constant amplitude loading

The compact tension (CT) specimens manufactured from AISI 4140 steel were plasma nitrided at 400°C, 500°C and 600°C for 1 and 4h in a gas mixture of 50% N2 and 50% H2. CT specimens were subjected to fatigue crack growth under constant amplitude loading in order to analyze the effect of plasma nitriding on fatigue crack growth (FCG). The crack sizes of specimens were correctly detected by a digital image monitoring system. Also, the structural and mechanical properties of specimens were characterized by XRD, SEM, optical microscopy and 3D profilometer and microhardness tester. The structural and mechanical examinations showed that the surface hardness, layer thicknesses and surface residual stresses continuously increased with increasing plasma nitriding time and temperature. It was found that plasma nitriding improved the FCG life of the material due to the formation of compressive residual stresses and nitride layers in surface and near-surface regions. Additionally, the highest FCG increase rate was obtained from 500°C to 4h plasma nitrided specimen with respect to untreated specimen. The formation of compound layer and braunite layer constrained the continuous increase of FCG life because of increasing embrittlement and cracking tendency of nitride layers.

Effect of Dendritic Segregation on the Structure and Mechanical Properties of Hot-Deformed Pipes from Steel 38KhN3MFA

The effect of dendritic segregation on mechanical properties of specimens cut from templates of two different batches of hot-deformed pipes from steel 38KhN3MFAis investigated. Comparative analysis of the results of mechanical tests and metallographic and x-ray spectrum studies of specimens with satisfactory and unsatisfactory macrostructures are performed, and the results are used to estimate the influence of intracrystalline inhomogeneity on the mechanical properties of ready articles from steel 38KhN3MFA.

Investigating the effects of traveling speeds and post-weld heat treatment on mechanical properties of nano-Al2O3-fortified AA6061-T6 friction stir welds

In this study, 6 mm thick AA6061-T6 plates were friction stir welded (FSWed) at different traveling speeds while Al2O3 nano-particles were incorporated between adjoining plates. The solution heat treatment was applied on samples for one hour at 540 ℃ and subsequently aged for 18 h at 180 ℃ to investigate the effect of post-weld heat treatment on mechanical properties of specimens. All joints were investigated macro- and micro-structurally. The microstructural characterization of the FSWed samples was carried out using scanning electron microscopy (SEM) and light microscopy techniques. Distribution of Al2O3 nano-particles in the stir zone was studied by SEM. The specimen FSWed at 40 mm/min exhibited the most homogeneous particles distribution. Tensile properties including ultimate tensile strength, elongation, and fracture surfaces were studied. Microhardness of specimens was also investigated. Surprisingly, all specimens exhibited inferior hardness compared to the as-received AA6061-T6 alloy. This phenomenon was attributed to the dissolution of precipitates during FSW process.

The impact resistance and mechanical properties of fiber reinforced self-compacting concrete (SCC) containing nano-SiO2 and silica fume

In this study, an extensive study including an experimental and analytical approach describes the effects of presence 1% nano-SiO2 and 7% silica fume on the key mechanical properties (compressive, tensile and flexural strength) and impact resistance of such compositions with inclusion of different fibre volume fractions of Polypropylene (PP) (.25, .5, .75 and 1%) and water-to-cement ratios (.27, .34, .41). The experimental tests have been implemented on two hundred and seventy specimens. Experimental results indicated that using both silica fume and nano-SiO2 instead of cement into the plain self-compacting concrete (SCC) leads to improved impact resistance and mechanical properties. This improvement was higher in terms of impact resistance compared to mechanical properties. Moreover, it was observed that using nano-SiO2 particles consequences to reduce the wall effect between PP fibre and its surrounding matrix. Reduction of this effect enhanced the impact resistance and mechanical properties of fibre-reinforced SCC. Moreover, a statistical/ analytical study was carried out on the executed large experimental database and it was observed that the impact resistance and mechanical properties of specimens containing silica fume and nano-SiO2 follow a normal distribution. Furthermore, the highest rate of gaining the number of post initial crack blows to failure for the fibre-reinforced specimens registered for specimens with water-to-cement ratio of .41.

Pre-aging time dependence of microstructure and mechanical properties in nanostructured Al-2wt%Cu alloy

This work is focused on the effect of pre-aging time on the properties of Al-2wt%Cu alloy processed by accumulative roll bonding (ARB) process. Following aged at 190 °C for 10 or 30 min, the samples were deformed up to a strain of 4.8 by the ARB process. The microstructure evolution was investigated by transmission electron microscope and electron backscattering diffraction analyzes. The results showed that the Al2Cu precipitates were formed with different sizes due to the different pre-aging times and the finer precipitates were more effective on the formation of high angle grain boundaries during the ARB process. The grain size of Aged-10 min and Aged-30 min specimens decreased to 400 nm and 420 nm, respectively, after 6 cycles of the ARB process. Also, the final texture after 6 cycles of the ARB process, shown in the {111} pole figure, were different depending on the starting microstructures. The mechanical properties of specimens were investigated by the Vickers microhardness measurements and the tensile tests. The results showed that the mechanical properties are affected by the starting microstructure. The mechanical properties of Aged-10 min specimen were different compared to Aged-30 min specimen due to the different size of the pre-existing precipitates. Although by continuing process, the precipitates were probably dissolved due to the heavy deformation.

Low thermal cycling effects on mechanical properties of laminated composite materials

Degradation of mechanical properties by thermal cycling can be an important reason which accelerates failure of polymer matrix composites (PMCs). Different parameters affect the mechanical properties of the PMCs during the thermal cycling. So, a comprehensive experimental analysis to find main effective factors and contribution of the factors is essential. In this article, Taguchi method is used to design experiment and find contributions of four effective parameters on glass/epoxy composite components subjected to the thermal cycling. These parameters are temperature difference, composite layups, fiber volume fraction and number of thermal cycles that are selected among the different parameters. For thermal cycling tests, an apparatus is developed to subject samples on different temperature cycle profiles. The mechanical properties of specimens are obtained using the tensile test after the thermal cycling load. Statistical analysis of the experimental results showed the stacking sequence and the fiber volume fraction were the main factors to control the thermal cycling effects. Also, a regression analysis was developed for modeling the mechanical properties using the effective factors. Finally, sensitivity analysis of the effective factors was studied to describe the relationship between these parameters.

Experimental Study on the Properties of Concrete Mixed with Iron Ore Tailings

The objective of this study is to evaluate the modified performance of concrete with mixing of iron ore tailings in order to solve the shortage of natural sand and make full use of industrial waste. Firstly, the raw materials of mixing were analyzed, and the test ratio was determined. Secondly, the workability and mechanical property of concrete specimens with different amounts of iron ore tailings as replacement were tested. Results show that 35% replacement of natural aggregate by iron ore tailings is optimal. Finally, tests of impermeability, frost resistance, and carbonation resistance were further performed for the concrete specimens with optimal amount of iron ore tailings. The compression performance of the specimens after a durability test was determined. The change in the mechanical properties of the specimens was obtained after seepage, freezing-thawing, and carbonation. Findings showed that the performance of the concrete with 35% replacement of iron ore tailings is basically equivalent to that of natural sand concrete. Hence, it can be utilized in engineering applications.

Flexural and Compressive Properties of Hybrid Kenaf/Silica Nanoparticles in Epoxy Composite

Kenaf fiber like other natural fibers is used as a sustainable form of material to fabricate composite. But natural fibers are generally weaker than synthetic fibers due to the porosity of the fibers making them grow weaker mechanically and physically as time passes. To improve the quality of kenaf reinforced composite, silica nanoparticles was introduced as a filler material. Silica nanoparticle is a material with high surface area contributing to its high interfacial interaction with the matrix resulting in the improvement of the matrix. In this work, the composites were fabricated via vacuum infusion process by creating a system in which the compressed randomly orientated kenaf mat are laid in. The silica nanoparticles are dispersed into the epoxy using a homogenizer at 3000rpm for 10minutes before being infused into the fibers. The results shows that generally the inclusion of hydrophobic silica nanoparticles had a detrimental effect on the mechanical properties. However, composites with 2 vol% silica had the best mechanical properties of specimens with silica nanoparticles included at 43.8MPa and 3.05GPa for flexural strength and flexural modulus, and 40.0MPa and 1.15GPa for compressive strength and compressive modulus, respectively.

Lubricating ability of albumin and globulin on artificial joint implants: a tribological perspective

Albumin and globulin proteins are dominant protein components in synovial fluid, and play important roles in the lubrication mechanism of joint prostheses. The present study investigated the lubricating ability of albumin and globulin on ceramic-on-polyethylene joint implants. A pin-on-disk tribometer was used for friction tests where the experimental condition was replicated with a simulated hip joint condition. The experiment was conducted under three lubricating conditions: bovine synovial fluid (BSF), albumin and globulin. Mechanical properties of specimens and physical properties of lubricant were measured before and after the tests. The experimental results show that albumin yielded a lower friction coefficient as compared to globulin. However, both exhibited a higher friction coefficient and wear rate than that of bovine synovial fluid. This study suggests that further tribological investigations on major biological components of synovial fluid should be carried out, which will help optimise implant design.

Molecular weight and tacticity effect on morphological and mechanical properties of Ziegler–Natta catalyzed isotactic polypropylenes

The morphological and mechanical properties of Ziegler–Natta catalyzed isotactic polypropylenes as influenced by the molecular weight and tacticity was investigated. Polypropylene samples were injection moulded into standard disks with a HAAKE MiniJet II injection moulder at 190 °C and 200 bar for morphological and mechanical tests. The morphological and mechanical properties of specimens were investigated by means of optical microscope (OM), scanning electron microscopy (SEM), microhardness (MH) and dynamic mechanical analysis (DMA). The samples exhibited a typical α-modification spherulite structure of isotactic polypropylenes crystallized from the melt. It was found that the most important factor affecting the structure and properties of these polymers is the isotacticity content. A clear molecular weight effect was also found for samples with low molecular weights. The microhardness and storage modulus values increased as crystallinity did. Accordingly, isotacticity degree is considered as the main parameter affecting the crystallinity of samples.

Study on Characteristics of Green Parts of Birch Flour/Polyester Composite by Selective Laser Sintering

In this paper, the birch flour was the raw material with its particle size less than 100μm and the polyester hot-melt adhesive was used as binder with its particle size less than 60μm. The birch flour was dried using high speed mixer with heating function. The birch flour/polyester composite were prepared using the physical mixing method. The surface of the specimen and fracture surface of specimen were analyzed through the micrographs of scanning electron microscopy. In order to study the characteristics of laser sintering, the preheating temperature of the powder bed of laser sintering machine and the processing parameters of the birch flour/polyester composite were determined using single layer sintering method and empirical method. The tensile, flexural and impact specimens were built in the two scanning laser ways of subarea scan and progressive scan. The testing results show that the mechanical properties using subarea scan method are superior to those of progressive scan method and the mechanical properties of the specimens increase as the laser scan speed decreases. The best mechanical properties of SLS specimens of brich flour/polyester composite powder were obtained with the following parameters: the laser power was 11W, layer scan speed was 1800mm/s; layer thickness was 0.1mm; laser scan spacing was 0.1mm and the average tensile, flexural and impact strength of specimens were 1.35MPa, 3.69Mpa and 0.73KJ/m2 respectively.

The Effects of Grain Size and Lubrication on Micro Curl Forming Process of Metallic Thin Sheet

This article aims at the discussion of deformation behavior considering size effect on curl forming process of sheet metal. In this study, the test specimens were made by phosphor bronze sheets for curl forming test. The specimens with different thickness were firstly heated at different temperatures for obtaining the objective grain sizes. And the mechanical properties of specimen were acquired by using tensile test. Through the curl forming test with a curl forming machine, the curled angles, springback and curling load were measured and analyzed for investigating the grain size effect of the chamfer and carbon lubricant during the curl forming process.

Microstructure and Mechanical Properties of Ti-6Al-4V Manufactured by SLM

The article presents results of a study of phase composition and microstructure of initial material and samples obtained by selective laser melting of titanium-based alloy, as well as samples after heat treatment. The effect of heat treatment on microstructure and mechanical properties of specimens was shown. It was studied mechanical behavior of manufactured specimens before and after heat treatment at room and elevated temperatures as well. The heat treatment allows obtaining sufficient mechanical properties of material at room and elevated temperatures such as increase in ductility of material. The fractography of samples showed that they feature ductile fracture with brittle elements.

Damage detection of SFRC concrete beams subjected to pure torsion by integrating acoustic emission and Weibull damage function

In some cases, torsion is the dominant or critical factor contributing to the failure of a concrete member. This research proposes a novel damage detection method for fiber-reinforced concrete beams subjected to pure torsion loading by statistical analysis of acoustic emission (AE) data. Concrete beams with varying water/cement ratios and different fiber volume fractions were subjected to pure torsion during AE monitoring. It was found that the cumulative AE event with respect to the twist angle correlated well to the mechanical loading. A Weibull rupture probability distribution is introduced to quantitatively predict the mechanical damage behavior under pure torsion. A bi-logarithmic regression analysis is carried out to calibrate the Weibull damage distribution function with the detected AE data in order to characterize the torsion fracture process. Moreover, a quantitative approach by means of b-value results is presented in this article to further analyze damage and fracture process. Torsion fracture properties were correlated to the AE parameters, and it was shown that the magnitudes of AE parameters were influenced significantly by mechanical properties of specimens. Therefore, AE would be suitable to describe the fracture of concrete specimens subjected to torsion. Copyright © 2015 John Wiley & Sons, Ltd.

Achieving ultrafine grained and homogeneous AA1050/ZnO nanocomposite with well-developed high angle grain boundaries through accumulative press bonding

Aluminum matrix nanocomposites with 2vol% ZnO nanoparticles were produced using accumulative press bonding (APB) as a very effective and novel severe plastic deformation process. Microstructural evaluation and mechanical properties of specimens were characterized by field-emission scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), electron backscatter diffraction (EBSD) and tensile test. Microstructure of AA1050/ZnO nanocomposite showed a uniform distribution of ZnO nanoparticles throughout the aluminum matrix. STEM and EBSD observations revealed that ultrafine-grained Al/ZnO nanocomposite with the average grain size of <500nm and well-developed high angle grain boundaries (80% high angle boundaries and 37° average misorientation angle) was successfully obtained by performing 14 cycles of the APB process. When the number of APB cycles increased the tensile strength of Al/ZnO nanocomposite improved and reached 228MPa after 14 cycles, which was 2.6 and 1.3 times greater than the obtained values for annealed (raw material, 88MPa) and monolithic aluminum (180MPa), respectively.