Applied Mechanics and Materials Vols. 446-447

Abstract: The high temperature tensile experiments were carried out to investigate the superplasticity of Inconel 718 alloy by using the strain-reduced superplasticity deformation process based maximum m value method. The results indicate the fine and homogeneous grain structure of Inconel 718 alloy is obtained by hot forging, δ phase precipitation and recrystallization heat treatment process. The Inconel 718 alloy exhibits good superplasticity at a wide range of temperature from 950°C to 1020°C, and the best elongation of 566% appears at 950°C. It shows the excellent superplasticity of Inconel 718 alloy can be obtained with the strain-reduced superplasticity deformation process based maximum m value method.

Abstract: Constitutive equation for metal plastic forming reflects the relationships among the parameters of stress, strain and strain rate. The accuracy of constitutive equation is a key factor in the research of material mechanism, finite element simulation accuracy and forming failure. The commonly used establishment methods of constitutive equation are summarized. Those methods include experiment method, theory analysis method, neural network method, regression method and inverse finite element method. The advantages and disadvantages of those methods are discussed, and application scope of those methods is summarized simultaneously.

Abstract: Planar flow melt spinning (PFMS) is a rapid solidification process to produce amorphous ribbons for transformer core applications. The present study deals with the development of 3dimensional time-dependent model, for the numerical simulation of ribbon formation during the PFMS process. Space between nozzle wall and the rotating wheel is considered as the computational domain. Volume of fluid technique is applied along with energy and momentum equations to simulate the two phase flow in the domain. Effect of ejection temperature of the melt is investigated during ribbon formation. Ribbon patterns like dimple and continuous are obtained for different ejection temperatures. Phenomenon of air entrainment which leads to dimple pattern is discussed. Vacuum conditions are suggested to avoid air entrainment.

Abstract: It is one of the keys that determining reasonable damping block geometry in the process of designing the extrusion dies. In this paper, the finite element software POLYFLOW was used to simulate the flow process of tread rubber in the head channel. In addition, the orthogonal experiment method was adopted for the optimum design of the damping block in the head channel. After optimum design, the flow velocity of rubber melt becomes more uniform in the full width at the head outlet. Consequently, the warping deformation of the rubber, which flow through the head channel, is also significantly reduced.

Abstract: Eco-friendly films have been prepared using various biopolymers and their properties have been improved in order to meet the requirements for appropriate applications. However, the frequently encountered weakness of the properties of most biopolymer film is its water solubility. In this study, the polyvinyl alcohol/rice starch/silk fibroin (PVA/RS/SF) films were modified by the addition of glycerol aiming to increase the hydrophobicity of the films. Some properties of the modified films including water contact angle, degree of swelling and water solubility were compared with the unmodified PVA/RS/SF film. Results from the contact angle measurement showed that the films with glycerol could be transformed to be hydrophobic after soaking in ethanol medium. The increase in soaking time tends to increase the hydrophobicity of the films. However, at about 60 min soaking, the water contact angles on the films were quite constant with the values of about 107.9±5.2º comparing with 65.3±2.4º of the ethanol-untreated PVA/RS/SF films. In addition, the ethanol-treated glycerol-modified films also show higher degree of swelling with constant solubility and better mechanical properties.

Abstract: Silk fibroin (SF) and rice starch (RS) are both biopolymers being non-toxic, biocompatible and biodegradable which can be utilized as hydrogels. The aim of this study was to prepare the SF–RS hydrogels modified with trisodium trimetaphosphate (STMP) and determine its crosslinking density for providing a guideline for preparing better quality absorbable hydrogels. The SF–RS hydrogels modified with various percentages of STMP were prepared by solution casting at pH 12 then neutralized to pH 7. The functional groups and molecular linkages of the hydrogels were investigated by Fourier transform infrared spectrometry (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectrometry, respectively. Finally, the crosslinking density of the hydrogels was determined by UV/Vis spectrophotometry via the measurement of the relative amount of methylene blue (RMB) bound to the hydrogels. Results from the FTIR and ¹H NMR spectra revealed that linkages within the hydrogels occurred mainly between the O–H groups of RS and the triphosphate groups of STMP. From the MB adsorption study, the crosslinking density of the SF–RS hydrogel with 1.0 %w/w STMP at the 60 min saturation time was approximately 63 %.

Abstract: The spontaneous emission spectrum of a two-level atom in a one-dimensional (1D) anisotropic photonic crystal with symmetry of double helix is investigated using Laplace transform. Properties of spectrum of the radiation modes are discussed in detail under different values of detuning of atomic resonant frequency from a band-edge. Since spontaneous emission is proportional to the density of states (DOS), it is suppressed within the reflection band, corresponding to vanishing of the DOS. However, it is enhanced at the band edge. Therefore, spontaneous emission spectrum of the system is influenced at the edge of the stop band rather than at its centre.

Abstract: In order to develope the eri-silk/bamboo fiber blended yarn for knitting, the authors analyze the main qualities of eri-silk and bamboo pulp, explain the method of pre-processing the eri-silk stapes in detail and the spinning technique of the eri-silki staple and bamboo pulp fiber blended yarn. Various measures are taken to deal with the problems such as the smooth surface, weak cohesive force, too much yarn hairness. This kind of new yarn has a good prospect. It can further improve the technique, improve the yarn strength and production effectiveness, lower the cost and better satisfy the consumers.

Abstract: Study the influence of eri-silk degumming process for degumming results of 2709 alkaline protease; combined with the orthogonal experimental analysis of high degumming rate and breaking strength of the best eri-silk degumming process, and then compare the optimized extracted eri-silk with mulberry silk, virgin silk, cotton, wool and ramie fibers for their fineness, mechanical properties, and friction performance comparison. The results show that the 2709 alkaline protease can effectively remove silkgum, and that the amount of enzyme is the main factor affecting degumming rate; pH value is the main factors for the breaking strength. Comparing with other fibers, eri-silks average fineness is smaller, breaking strength and initial modulus tend to be larger, but their coefficient of variation also tend to be larger. Besides, eri-silkis breaking elongation is not as good as wool and silk, but better than other fibers. Natural silks dynamic and static coefficient of tangential impedance is lower in comparison with other natural fibers. Ramie has the largest tangential resistance factor. Among the natural silks, the eri-silks tangential impedance coefficient is greater than tussah and smaller than mulberry silk.

Abstract: The hydrochloric acid pickling process which is widely applied in carbon steel pickling ensures high speeds with little pollution. In this research, hydrochloric acid pickling process was introduced into stainless steel pickling to improve the surface integrity. Research indicated that the impedance spectrum obtained from 430SS in HCl solution consisted of a capacitive loop at high frequencies and an inductive loop at low frequencies. As the concentration of hydrochloric acid rose, the radiuses of the capacitive loop decreased.And the corrosion potential of 430SS in hydrochloric acid solution moved to positive direction with band to a narrow 0.1V.And high HCl concentration more markedly influenced the charge-transfer resistance.