Applied Mechanics and Materials Vols. 799-800

Abstract: Thermal properties of Si mechanically alloyed with FeSi₂ and CrSi₂ were characterized for the samples with different volume fraction of the disilicides. An anomalously low thermal conductivity observed in the FeSi₂-doped samples was ascribed to an enhanced porosity of the samples which triggered the size effect on the lattice thermal conductivity reported previously for nanomeshed and “holey” silicon structures. It was also found that alloying of Si with FeSi₂ led to a reduction of thermal conductivity as compared to the reference sample of pure Si prepared under the same conditions. On the other hand, alloying of Si with CrSi₂ resulted in an increase in the thermal conductivity as compared to the reference sample of pure Si. The observed trends in the thermal conductivity were ascribed to the formation of impurity levels in the band gap.

Abstract: The present work has investigated precipitation behavior in an Al-17at%Mg alloy isothermally aged at 373K and 473K, by means of Vickers micro-hardness tests, DSC measurements and TEM observations. The present DSC measurements have revealed that the metastable β′-phase precipitates mainly contributed to precipitation hardening of this alloy in isothermal aging at 373K and 473K. The TEM observations have confirmed that the β ' phase precipitates were formed in the {001} planes of Al matrices in platelet shapes.

Abstract: Although widely used in construction and industrial applications, wood is more prone to defects of different kinds than other materials. These defects are unpredictable and differing randomly from plank to plank. This uncertain nature of the defects complicates establishment of manufacturing plans. In this study, a probabilistic model of wood defects was constructed as a function of three variables which were quantity of defects, position of defects and size of defects. The Kolmogorov-Smirnov hypotheses testing on distributional forms of these variables were carried out. Results showed that Poisson, uniform, and log-normal distributions were suitable to represent the variables statistically. Being knowledgeable of how the defects are distributed on the plank will be of benefit in profitability justification of a cutting plan.

Abstract: Copper-nickel alloys have been used in many applications in marine environments because of excellent corrosion and biofouling resistance. . This investigation is cover a review of many previous studies about the behavior of these alloys in marine environments with different environmental conditions including the effect of sulphur contamination, the effect of CO₂, the effect of chlorine, the effect of flow velocity, the effect of temperature and the effect of adding some alloying elements to the alloy itself. There have been conflicting results in the past about the corrosion rate values and the chemical analysis of the corrosion films in different environmental conditions. More research is needed for studying the behavior of these alloys in marine environments to provide good assessment of the corrosion resisting characteristics.

Abstract: The purpose of this research is to investigate the corrosion rate of low carbon steel in saline environment. The influence of variety of conditions that represent the actual conditions in practice such as the flow velocity and solution composition, particularly Na+, Cl^- and SO₄^-2, content were performed. Weight loss test of low carbon steel in the lab was conducted to determine the corrosion rate data in stagnant and flowing seawater for comparison to investigate the effect of flow velocity of sea water on the corrosion behavior of the low carbon steel. Results show that the corrosion rate of low carbon steel is increased by increasing the flow of seawater, but at very high velocities the corrosion rate was recorded to be decreased. XRD results show that the corrosion products contain both Fe₂O₃ and FeO(OH).

Abstract: An amorphous Ni-Fe-P alloy coated shielding fabric with dense uniform coating was prepared by conducting electrical deposition of amorphous Ni-Fe-P alloy on copper-coated polyethylene terephthalate (PET) fabric. This research investigated the preparation process by using orthogonal test with 8 factors and 3 levels. It analyzed the influences of components of the plating solution on the ohms per square, weight gain rate, and shielding effectiveness of coating. Besides, the morphology, composition, and structure of the coating were analyzed by using Scanning Electron Microscope (SEM), Energy Dispersive Spectrdmeter (EDS), and X-ray Diffraction (XRD). The shielding effectiveness of the alloy fabric was also tested. The results indicated that the processing conditions of the amorphous Ni-Fe-P alloy coated fabric using electrical deposition consisted of 135 g/L of NiSO₄•6H₂O, 105 g/L of FeSO₄•7H₂O, 8 g/L of NaH₂PO₂•H₂O, 24 g/L of C₆H₈O₆, 36 g/L of C₆H₈O₇, 22 g/L of H₃PO₃, 65°C, pH=1.5, and current density =13 A/dm². The fabric obtained in the paper presented compact, smooth, and uniform coating with fine crystal. The coating was the amorphous Ni-Fe-P alloy with 18.67% of P (mass fraction). The shielding effectiveness of this coated fabric reached to 60.82 dB-73.63 dB in a broad frequency range of 300 kHz-1.5 GHz.

Abstract: Cutting fluid is a well-known as one of an important element in machining process. However, the consumption of mineral oils as cutting fluid has been raising concern due to worldwide interest in environmental and health matters. The application of vegetable-oil based lubricant is seen can overcome the problem but requires a research study about the machinability. This research paper represents the machinability of using several possible vegetable oils as cutting fluid in term of chip formation and tool wear during drilling operation on stainless steel, AISI 316. In particular, the performance of the vegetable oils; palm, sesame, olive and coconut oils were compared under minimum quantity lubrication (MQL) technique. The result reported that the coconut oil indicates the best machinability in term of highest and uniform chip thickness and least wear on the drill bit under same condition with others. These performances are followed by palm, olive and sesame oil. In additional, the viscosity measurement indicates that coconut oil has the lowest value which can possesses better fluidity and faster cooling capacity than other oils. Overall, coconut oil is recommended as viable alternative lubricants during drilling of stainless steel.

Abstract: Friction stir welding (FSW) of polymers is relatively a new concept among modern polymer joining techniques. This study demonstrates the applicability of FSW on 16mm thick nylon-6 plates at constant welding rate of 25mm/min and varying rotational speed between 300 to 1000RPM. A special designed tool was fabricated which has double shoulder and right-hand threaded pin profile. It has shown excellent results at relatively lower rotation speeds. Visual inspection and microstructural examination of cross sections showed that the cavities and tunnel defects appeared only at higher rotational speeds. A linear relationship was observed between temperature and rotation speed.

Abstract: This article introduces a methodology for extracting specific cutting force coefficients by performing micro drilling experiments with tool edge radius effect.Tool edge radius mainly affects the effective rake angle that varies according to undeformed chip thickness. Ploughing effect is also considered for undeformed chip thickness lower than the minimum chip thickness. In this work specific normal and frictional cutting coefficients for both ploughing and shearing are determined from mechanistic approach of fitting experimental specific thrust forces of the micro drilling process. The variations of these cutting coefficients with respect to cutting speedand feed are presented. Finally these coefficients have been applied to the mechanistic model to predict thrust force in micro drilling. The predicted thrust force values at different feed show good agreement with the experimental results.

Abstract: Polymer extrusion is one of the most widely utilized manufacturing processes across many industries including automotive, architecture, aerospace etc. However, in order to maintain normal operations, polymer extrusion dies are conventionally designed with large dimensions and thick walls which results in the overweight of them. In this paper, a shape optimization method is proposed to reduce the weight of polymer extrusion dies without sacrificing the required performances of extrudate. Firstly, Finite element simulation of the extrusion process is conducted using the commercial software HyperXtrude to study both the essential flow characteristics of polymer melts and the deformation and stress distribution of extrusion die. Secondly, shape optimization is conducted to find the minimum weight of extrusion die while satisfying the required properties and productivity of polymer product. The extrusion die is then redesigned according to the result of shape optimization and compared with the original one. A Medium-sized polymer profile extrusion die is selected as case study, the result of which shows that the weight of the extrusion die is reduced by 31.6%,though the maximal deformation and stress of the die are increased by 1.7% and 16.1% respectively. The proposed approach is demonstrated to be effective for the lightweight design of polymer extrusion die.