Bulging in incremental sheet forming of cold bonded multi-layered Cu clad sheet: Influence of forming conditions and bending

Bulge is a defect that causes geometrical inaccuracy and premature failure in the innovative incremental sheet forming (ISF) process. This study has two-fold objectives: (1) knowing the bulging behavior of a Cu clad tri-layered steel sheet as a function of forming conditions, and (2) analyzing the bending effect on bulging in an attempt to identify the associated mechanism. A series of ISF tests and bending analysis are performed to realize these objectives. From the cause-effect analysis, it is found that bulge formation in the layered sheet is sensitive to forming conditions in a way that bulging can be minimized utilizing annealed material and performing ISF with larger tool diameter and step size. The bending under tension analysis reveals that the formation of bulge is an outgrowth of bending moment that the forming tool applies on the sheet during ISF. Furthermore, the magnitude of bending moment depending upon the forming conditions varies from 0.046 to 10.24 N·m/m and causes a corresponding change in the mean bulge height from 0.07 to 0.91 mm. The bending moment governs bulging in layered sheet through a linear law. These findings lead to a conclusion that the bulge defect can be overcome by controlling the bending moment and the formula proposed can be helpful in this regards.     

Effects of Gamma Irradiation on Proteins and Fatty Acids of Soybean

Two hundred grams of soybean seeds (moisture contents of 7.4, 15.3, 22.5, and 30.5%) were irradiated at dose levels of 0, 1, 5, 10, 20, 40, 60, 80 and 100 KGy using Cobalt-60 source. Radiation dose of 100 KGy caused a decrease in the percentage of nitrogen solubility from 80.3 to 67.2, 80.3 to 57.8, and 68.1 to 48.8 when deionized H₂O, 0.6M NaCl, and 0.2M Cacl₂ were used as solvents, respectively. Inhibition of 71% of lipoxygenase activities, 25.4% trypsin inhibitor activities, and 16.7% chymotrypsin inhibitor activities were found when the soybean seeds were irradiated at 100 KGy.     

First-principles study of the double perovskites Sr<Subscript>2</Subscript>XOsO<Subscript>6</Subscript> (X = Li,Na, Ca) for spintronics applications

We investigated double perovskite compounds of the form Sr ₂ XOsO ₆ (X = Li, Na, Ca) using the full-potential linearized augmented plane wave (FP-LAPW) method. For the exchange-correlation energy, Wu and Cohen generalized gradient approximation (WC-GGA), Perdew, Burke and Ernzerhof GGA (PBE-GGA), Engel and Vosko GGA (EV-GGA), and GGA plus Hubbard U-parameter (GGA + U) were used. The calculated structural parameters are in good agreement with the existing experimental results. Calculation of different elastic constants and elastic moduli reveals that these compounds are elastically stable and possess ductile nature. The GGA + U approach yields quite accurate results of the bandgap as compared with the simple GGA schemes. The density of states plot shows that Sr-4d, Os-5d and O-2p states predominantly contribute to the conduction and valence bands. Further, our results regarding to the magnetic properties of these compounds reveal their ferromagnetic nature. In addition, these compounds seem to possess half-metallic properties, making them useful candidates for applications in spintronics devices.     

Influence of pulse electrodeposition parameters on microhardness,grain size and surface morphology of Ni–Co/SiO<Subscript>2</Subscript> nanocomposite coating

Ni–Co/SiO ₂ nanocomposite coatings and Ni–Co alloy coatings were prepared on steel substrate using direct and pulse electrodeposition methods. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray map and energy dispersive X-ray spectroscopy (EDX) were employed to investigate the phase structure, surface morphology, and elemental analysis of coatings, respectively. In high discharge rates, the surface morphology was rough, disordered and gross globular; on the contrary, in the low rates, it was smoother, more ordered and fine globular. Also, effect of electrodeposition parameters such as average current density, pulse frequency and duty cycle on the microhardness and grain size of nanocomposite coatings that produced through the pulse current electrodeposition method have been investigated. By amplifying both duty cycles up to 50% and average current density from 2 to 6 A dm^?2, microhardness increased, while the grain size decreased. But when duty cycle mounted on more than 50% and the average current density went up to 8 A dm^?2, microhardness lessened, while the grain size rose. The optimum value for pulse frequency was about 25 Hz. Results showed that microhardness of nanocomposite coatings which were produced by pulse current method was higher than that of produced by direct current method.     

Fuzzy linear programming approach for solving transportation problems with interval-valued trapezoidal fuzzy numbers

Transportation problem (TP) is an important network structured linear programming problem that arises in several contexts and has deservedly received a great deal of attention in the literature. The central concept in this problem is to find the least total transportation cost of a commodity in order to satisfy demands at destinations using available supplies at origins in a crisp environment. In real life situations, the decision maker may not be sure about the precise values of the coefficients belonging to the transportation problem. The aim of this paper is to introduce a formulation of TP involving interval-valued trapezoidal fuzzy numbers for the transportation costs and values of supplies and demands. We propose a fuzzy linear programming approach for solving interval-valued trapezoidal fuzzy numbers transportation problem based on comparison of interval-valued fuzzy numbers by the help of signed distance ranking. To illustrate the proposed approach an application example is solved. It is demonstrated that study of interval-valued trapezoidal fuzzy numbers transportation problem gives rise to the same expected results as those obtained for TP with trapezoidal fuzzy numbers.     

Cu<Superscript>2+</Superscript> and Al<Superscript>3+</Superscript> co-substituted cobalt ferrite: structural analysis,morphology and magnetic properties

Cu–Al substituted Co ferrite nanopowders, Co_1?x Cu _x Fe_2?x Al _x O₄ (0.0 ≤ x ≤ 0.8) were synthesized by the co-precipitation method. The effect of Cu–Al substitution on the structural and magnetic properties have been investigated. X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) are used for studying the effect of variation in the Cu–Al substitution and its impact on particle size, magnetic properties such as M _s and H _c . Cu–Al substitution occurs and produce a secondary phase, α-Fe ₂ O ₃. The crystallite size of the powder calcined at 800 ^°C was in the range of 19–26 nm. The lattice parameter decreases with increasing Cu–Al content. The nanostructural features were examined by FESEM images. Infrared absorption (IR) spectra shows two vibrational bands; at around 600 (v ₁) and 400 cm ^?1 (v ₂). They are attributed to the tetrahedral and octahedral group complexes of the spinel lattice, respectively. It was found that the physical and magnetic properties have changed with Cu–Al contents. The saturation magnetization decreases with the increase in Cu–Al substitution. The reduction of coercive force, saturation magnetization and magnetic moments are may be due to dilution of the magnetic interaction.     

Effect of water removal on the textural properties of resorcinol/formaldehyde gels by azeotropic distillation

The resorcinol/formaldehyde gels containing 5% (w/v) of reactants have been prepared. After curing for seven days, the gel is treated with trifluoroacetic acid to initiate the condensation of hydroxymethyl groups. Drying of the prepared gels is done by removing water with the help of vacuum heterogeneous azeotropic distillation using amyl acetate and n-butanol. The textural properties of the gels thus obtained are compared with the properties of the gel obtained from exchange of water by acetone (control experiment). The pore volume and average pore diameter of the gel obtained from the azeotropic distillation of water with amyl acetate are 0.7663 × 10–3 m3/kg and 0.0145 m, respectively. These values are 1.5 times higher than the values obtained by vacuum heterogeneous azeotropic distillation with n-butanol and about twice than the values obtained in the control experiment. The surface areas in all the three gels are almost constant.     

声音与震动阵列的分析、实现与应用

In this paper, we consider the analysis, implementation, and application of wideband sources using both seismic and acoustic sensors. We use the approximate maximum likelihood (AML) algorithm to perform acoustic direction of arrival (DOA). For non-uniform noise spectra, whitening filtering was applied to the received acoustic signals before the AML operation. For short-range seismic DOA applications, one method was based on eigen-decomposition of the covariance matrix and a second method was based on surface wave analysis. Two well-known optimization schemes were used to estimate the source locations from the estimated DOAs at sensors of known locations. Experimental estimation of the DOAs and resulting localizations using the acoustic and seismic signals generated by striking a heavy metal plate by a hammer were reported.     

Recent Advances in Disordered and Nanostructured Carbon Coatings for Superl Ubricity and Wearless Sliding

Increasingly more demanding and very stringent operating conditions envisioned for future mechanical and tribological systems will certainly require new materials and coatings that are superhard and at the same time self-lubricating.For example, dry machining is a much desired practice in manufacturing sector, but it is currently very difficult to realize mainly because of high friction and severe wear losses. However, recent advances in surface engineering and coating technologies may enable design and production of novel coatings architectures that can combine superhardness with self-lubricating properties in both the disordered or nanostructured forms. Recently developed nearly frictionless carbon films, ultrananocrystalline diamond and carbide derived carbon films can dramatically lower friction and at the same time reduce wear under very harsh sliding conditions. These coatings can be formulated in such a way that they can substantially increase the load-bearing capacity of sliding surfaces and hence improve their resistance to scuffing. It is also possible to design nano-composite coatings that can form self-replenishing and-lubricating tribofilms on their sliding surfaces and thus help increase the overall lubricity of these surfaces. In this paper, an overview of recent advances in disordered and nanostructured carbon films will be presented. Specific examples will be given to demonstrate the superior performance and durability of such novel coatings under a very wide range of tribological conditions. The major emphasis is placed on super low friction carbon films. The fundamental tribological mechanisms that control their exceptional friction and wear behaviors are also discussed.