Applied Mechanics and Materials Vol. 680

Abstract: The evaluation of material cutting performance is a complicated and comprehensive process. Only by using the fuzzy comprehensive evaluation way can we get a satisfactory result. This essay, on the basis of fuzzy theory, illustrates the steps of fuzzy comprehensive evaluation, introduces the factors influencing 18Cr2NiWA's cutting processing performance, gives a fuzzy evaluation of the factors, and thereby successfully solves the problems regarding these multi-factors' decision and evaluation.

Abstract: Aluminium metal matrix composites are being widely investigated with Carbon Nanotubes (CNTs) as one of their reinforcing agents. This is done in order to improve the mechanical strength of the composite. Various studies on this concept have already been recorded. In this study, Aluminium has been reinforced with CNTs using powder metallurgy technique. The powders of aluminium and CNT are ball milled, compacted in a die made up of die steel, and then sintered. The specimens thus obtained were subjected to hardness, compression and chemical tests and the values were compared with pure aluminium specimen fabricated by same technique. The study indicated that there was no improvement in hardness of the composite on addition of CNT. The compressive strength of the composite was increased by 143.58 MPa. The microstructure of pure aluminium and Al-CNT composite had fine grains of pure aluminium particles and Al-Si eutectic particles throughout the matrix phase.

Abstract: In this study, semi-solid Al-Mg-Si alloy (AC4C) was produced by using the Gas Induced Semi-Solid (GISS) die casting process. The tensile strength and ductility of the semi-solid die cast Al alloy (GISS-DC) after T6 heat treatment were investigated and compared with those of the conventional liquid die casting (CLDC). The microstructures of GISS-DC and CLDC observed by an optical microscopy were presented. The ultimate tensile strength (UTS) and yield strength (0.2% YS) of GISS-DC are compatible with those of the CLDC. However, the GISS-DC has better ductility than the CLDC, this may be due to the smaller and more globular primary α-Al phase and rounder shaped-Si particle microstructures presented in the GISS-DC. Common shrinkage pores and defects were also observed by SEM from the fracture surfaces of both alloys.

Abstract: The deformation behaviors of as-cast Mg-11Gd-2Y-Zn-Zr magnesium alloy were investigated by compression test with Gleeble-1500 thermal simulator at temperature of 623-753K and strain rate of 0.01-0.5 s^-1. The flow stress behaviors of the magnesium alloy were carried out at a strain of 0.7. The strain rate and deformation temperature had great influence on the flow stress behaviors. The flow stress increases with increasing strain rate and decreasing temperature. The flow stress has more than one peak stress at a strain rate of 0.5s^-1 showing continuous dynamic recrystallization (DRX) mechanism, while other flow stresses exhibited only one peak stress indicating discontinuous dynamic recrystallization (DDRX) mechanism. It was also found that the flow stress behavior could be described by the hyperbolic sine constitutive equation, in which the determined average activation energy is 273.426 kJ·mol^-1. The maximum error value between calculated value and experimental value is 5.5%. The deformation map was also established, and the best parameter for hot working was found to be 0.1s^-1/753k approximately.

Abstract: Nowadays composite materials play a vital role in automotive and aerospace industries due to their important properties like high strength to weight ratio, biodegradability and ease of production. In this paper, compression and hardness properties of a hybrid composite made of manila and abaca fibers are evaluated. Hand layup process is used in this work. The result shows that hybrid composite possesses very high strength and hardness as compared to mono fibre composite.

Abstract: Development of new natural fiber composite for a good characteristic is the focus of many studies, because of their cellulose contents make their properties more potential. However, the main challenge in the research on natural fiber/ polymer composites is their poor compatibility. Based on that, the comparison study by chemical treatment of sodium hydroxide (NaOH) method and adding wax has been explored in two different processes to improve the compatibility of the natural fiber surface. The sodium hydroxide (NaOH) treated sugarcane bagasse (SCB) and coconut coir wax (CCW) in low density polyethylene (LDPE) as a reinforced matrix in fact, will enhance the mechanical properties of the resulting composites. In this study, four different compositions of (90/2, 90/4, 90/6, 90/8), with additional of 2% of NaOH and 2-8 % wax with sugarcane bagasse (SCB) / coconut coir respectively were tested. The specimens were analyzed by different techniques such as tensile test, hardness test, impact test and scanning electron microscopy (SEM) according to ASTM standard. This research has shown that the presence of NaOH indicates higher tensile strength and impact strength compared to coconut coir wax (CCW). While for the young modulus and hardness test value shows coconut coir wax (CCW) has increased and improved. The morphological analysis was conducted to determine the effects of natural fiber bonding between the matrix materials for broken specimens after mechanical testing.

Abstract: Utilization of ascorbic acid as corrosion inhibitor has several weaknesses. These weaknesses are easy to oxidize in solution form and reduction of its antioxidant properties due to heat, light, oxidizing agent, dissolve oxygen, and heavy metals. Purple sweet potato extract is an alternative green corrosion inhibitor with major contains of anthocyanin compound. Anthocyanin will withstand enzymatic reaction and oxidation process of ascorbic acid. Addition of purple sweet potato extract in ascorbic acid will enhance inhibition efficiency of steel compare to the used of ascorbic acid alone. Interaction of purple sweet potato extract with 0.01M ascorbic acid in 0.1M FeCl₃ environment was analyzed using FTIR spectroscopy. The result shows that interaction of purple sweet potato extract with ascorbic acid in 0.1M FeCl₃ build ability to form iron chelate.

Abstract: We studied the effect of time and temperature for preparation of SnO₂ nanostructures by chemical vapor deposit methods. SnO₂ nanostructures were synthesized using Sn powder with carbon charcoal as starting materials. The source materials and Si substrates were heated with various times, temperatures under atmosphere of nitrogen and oxygen. The synthesized products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) techniques. The results showed the nanostructures of prepared products were very uniformly of SnO₂ nanowires with diameter about 100-300 nm and length around more 1-2 μm depending on times and temperatures.

Abstract: Diabetes mellitus, following cancer and cardiovascular disease, become one of the most serious diseases that threat to human health. The treatment of diabetes is imminent for the health of people. Thus, the developments of efficient insulin administration exhibit great practical significance. The glucose-responsive insulin delivery system (GRIDS) is developing rapidly which is expected to be a promising therapy approach to replace the frequent insulin injection administration. A novel glucose-responsive nanogel was conveniently prepared through one-pot copolymerization of pentaerythritol tetra (3-mercaptopropionate), poly (ethylene glycol) diacrylate, methoxyl poly (ethylene glycol) acrylate and N-acryloyl-3-aminophenylboronic acid. The successful incorporation of phenylboronic acid (PBA) in the nanogel endowed the nanogel high glucose sensitivity in phosphate buffer saline (PBS). Therefore, the PBA incorporated nanogel with high glucose-responsiveness and good biocompatibility may have great potential for self-regulated drug release