Papers by Keyword: Mechanical Strength

Abstract: Metal matrix composites attain a significant position in Industrial, defense, structural and automobile applications. To amplify that strategy there is a need to find out the conditional behavior of the composites and enhancing the properties will be mandatory. The present work mainly investigates on the effect of processing parameters like densification rates, sintering temperature, reinforcement content on the microstructure, mechanical properties of the Al7175/B4C composite material fabricated by mechanical milling and powder metallurgy techniques. Results show there is a grain size reduction and refinement in the composite material through ball milling operations and along with that increasing B4C content in the composite powders make milling conditions very effective. Increasing the sintering temperature results in a consistent grain growth along with that porosity level decreases up to a limit and then attain a steady state, the strength of the composites increases with compaction pressures but reinforcements content effects the strength of the material by losing its ductility making it brittle.

Abstract: Rapid expansion of technologies poses higher requirements to structural materials and items made of them. Conventional materials are being replaced by composite materials (composites). Different additives enhancing the properties of initial materials are used as reinforcement fibers of composites. Utilization of micro-and nanosize particles for production of present-day materials is paid much attention to. Whiskers are among such materials. These crystals have high strength, high chemical and temperature resistance. But for rational utilization of whickers of different chemical composition in composite materials one should know their physical and chemical properties. Objectives of the paper: to study physical and chemical properties of whiskers in different compounds, their composition and structure; to prove experimentally the feasibility of utilizing whiskers as a reinforcement fiber of composite materials. Object of study: specimens of whiskers of silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), aluminum nitride (AlN), and mullite (Al₆Si₂O₁₃). Methods of investigation: thermal study of specimens, study of mechanical properties and chemical strength, and IR-spectroscopy. Results of study: specimens of whiskers have been studied and their mechanical properties have been tabulated for comparison. Extensive thermal investigation was followed by deduction of regularities and identification of chemical properties of whiskers. IR-spectra of whiskers have been studied and conclusions on molecular composition and on presence of impurities in some whiskers have been made.

Abstract: Geopolymers can effectively deal with construction waste disposal problems, achieving resource recycling and higher strength than normal cement concrete. However, natural defects make geopolymer concrete difficult to apply in actual construction. This paper aims to make up for the natural defects of geopolymers while maintaining environmentally friendly materials. The low-calcium fly ash and blast furnace refining slag powder are used as raw materials, sodium silicate and sodium hydroxide are used as alkali activators, and chopped natural fibers are added as reinforcing materials to prepare natural fiber reinforced low-calcium fly ash and blast furnace refining slag base. Polymeric composites were used to investigate the effects of different natural fibers on the workability, compressive strength, tensile strength, water absorption, shrinkage and microstructure of geopolymer composites.

Abstract: This study focused on the feasibility of utilizing waste rubber tyre as coarse aggregate in concrete as a partial replacement of brick aggregate (BA). Within this context, fresh and hardened properties were investigated on concrete made with three different percentage replacements (0, 10 and 20% by volume) of BA by waste rubber tyre aggregate (WRTA). The WRTA was washed with tap water (H₂O) and treated with 20% sodium hydroxide (NaOH) for 2 hours. It was found that the workability and dry density of concrete decrease with an increasing percentage of WRTA. In case of mechanical properties, the compressive strength decreases with the increasing content of both treated and untreated WRTA. The maximum decrease was observed for 20% of both treated and untreated WRTA, which was 41-46% for treated and 47-54% for untreated lower than the reference concrete for all curing ages. It was observed that the concrete made with tyre treated with NaOH provides better strength than untreated tyre aggregate. This behavior could be attributed to the better bonding between cement paste and rubber aggregates as a result of the increased surface roughness by NaOH.

Abstract: This study presents a step towards exploring the possibility of using silicon materials as a surrogate to produce a multi-material 3D printed soft silicone brain model to be used in the investigation of Traumatic Brain Injury (TBI) in paediatric populations. Silicone represents a popular choice of material due to its viscoelastic properties, 3D printability, and capability to be tuned to possess different properties. Dynamic oscillatory shear tests were carried out for seven types of silicon materials at three different speeds against a different range of frequencies. The mechanical parameters response has been ranked on, which is the most appropriate to try. It also agrees with the range of reported paediatric brain tissue imitating grey and white matter as a surrogate brain material. Utilising of silicone for 3D printing represents a new approach to fabricate surrogate models that closely mimic biofidelic features and advance the medical engineering discipline.

Abstract: In the Metal Market, it has been important to understand the structure of steels, so that it is possible to develop new cutting materials at lower costs and more resistant to high temperatures and wear. This is possible by raising the mechanical strength for solid solution in fast steels, ie, addition of alloying elements to the steel in its solid state, the alloys fundamental to this process were: cobalt, manganese, silicon, tungsten and vanadium. Among the thermal treatments, tempering and quenching were used to raise the degree of hardness and strength of the steel. The samples studied were high speed steels HS6-5-3, HS6-5-3-5, K190 e K390. Hardness and metallographic tests were carried out on the samples and with the results generated, it was possible to draw a comparison and understand which alloying elements provide the least oxidation, corrosion and greater impact strength of fast steel.

Abstract: The generation of waste batteries is increasing yearly, and it is more prone to improper disposal resulting in environmental and health concerns. Treatment and handling of this waste are often costly and complex. Hence, an upcycling route to turn such waste into valuable material, specifically the production of graphene from graphite rods of waste batteries, was explored. Graphene dispersions were prepared by the solvent exfoliation of powdered graphite rods. A significant increase in the surface area was observed from 3.75 m² g^-1 (graphite rod powder) to 239.05 m² g^-1 (graphene powder) with a transparent sheet-like appearance. Then, the graphene dispersed in the solvent used for dip-coating of paper, cardboard, and composite plyboard. The tearing strength of paper and cardboard was improved by 70.6% and 31.0%, respectively. The compressive and shear strength of the composite plyboard increased by 14.8% and 72.0%, respectively. These results demonstrate the feasibility of utilizing the graphene solvent from graphite rods of spent primary batteries for the fabrication of composite samples with significantly augmented mechanical properties for various applications.

Abstract: This study also investigates the effectiveness of multiple surface modification of recycled concrete aggregate (RCA) with respect to mechanical properties of the resultant recycled aggregate concrete (RAC) when exposed to various curing conditions, namely, normal water (N_w) and seawater (S_w). The properties included compressive and flexural strength and impact resistance. Findings show that effect inclusion of the treated coarse RCA is significant in enhancing the mechanical properties of RAC. The exposure to S_w appears to affect the degradation of the compressive strength of RAC remarkably in a marine environment. In this case, however, using of treated RCA is found beneficial in decreasing the deterioration in the compressive strength of RAC.

Abstract: Repair mortar (RM) with dense texture and high anti-crack is cost-effective for application onto the surface of concrete structure to effectively delay the detachment of concrete protective layer and the corrosion of steel bars. Here, the effects of ductile fiber and polymer latex on the flexural strength (f_t), compressive strength (f_c), bond strength (f_b), and shrinkage rate (δ_r) of fiber-reinforced polymer repair mortar (FP-RM) were comprehensively studied. Results show, the individual doping of polymer latex can improve the f_t, f_b, and the toughness (the f_t/f_c ratio) of P-RM, and the f_b is increased by 75.78% with respect to the plain mortar, which imply polymer ingredient is essential to P-RM. Some ductile fibers individual dosage also can enhance the f_t, f_c, and δ_r of F-RM, respectively; When the polymer latex and ductile fiber are simultaneously doped into the FP-RM mortar together, the f_t and f_b of FP-RM can be increased up to 9.4MPa, and 2.52MPa, respectively, in tandem with 40.54% reduction of δ_r, showing superior synergy effect.

Abstract: In the research, the mechanical behavior of duplex stainless steels SAF 2205 and 2507 subjected to Normalized thermal treatments at temperatures at temperatures of 900, 950 and 1000oC for a time of 7 minutes for SAF 2205 and 15 minutes for SAF 2507 were evaluated. It was determined that the mechanical strength increased considerably the higher value was found at 900 °C. It was determined that the K_IC values for the normalized conditions of 900 oC and 950oC, reduce strongly in both steels with respect to the original condition. However, it is clearly reflected that for the normalized condition at 1000 °C the K_IC is fully recovered, and for the temperature range of 700 °C to 900 °C, the values of impact toughness suffer a drastic decrease, caused by the appearance of intermetallic phases.