Applied Mechanics and Materials Vol. 778

Abstract: This paper conducted an experiment to research flexural property of SMA unbounded prestressed box beam ,which applied the Shape Memory Alloy (SMA) at martensite state as externally prestressing tendons, and then through heating the SMA bars fully anchored on the beam with cracks by electrifying motivation, drove SMA to produce the “recovery stress” because of transformation, to study the effects of this stress on the deflection and crack width of concrete box-beam on work ,to study the recovery ability of SMA bars ,and to provide basis for the application of the SMA bars to bridge strengthening.

Abstract: The numerical simulation of a thin-wall aluminum profile was introduced. Then the velocity and temperature of the extrusion process were given. A die design optimization method was proposed by the velocity analysis. After optimization, a profile with uniform exit velocity was gain. Finally, a method for this profile die design was summarized.

Abstract: Ultrasonic shot peening can be used to strengthen mechanical parts. Its equipment structure is compact, which is convenient for incorporated into production line. It is fitting to facilitate operation and high reproducibility without dust pollution and noise. The finite element simulation method of ultrasonic shot peening further contributes to the development of ultrasonic shot peening technology. In the present work, finite element simulation method was adopted to establish a three-dimensional numerical model for analyzing the strengthening mechanism of ultrasonic shot peening. By choosing reasonable material model and different combination of parameters (such as treated material, diameter of shots, peening velocity), the curves of residual stress vs. depth of alloy materials were obtained, including the relationships between the peak value and depth of residual compression stress and peening velocity.

Abstract: To solve the true stress strain of Cr8 steel, a method of cone inversion is used to deal with the high temperature tensile data. Based on the precise determination and description of sample size, the test data is analyzed in the SSC(Stress strain calculator) software developed on MATLAB, and the true stress strain curve of Cr8 is drew. The true stress strain curve calculated by this method is smooth and continuous, and more identical to the principle of metal elastic-plastic deformation process, which shows a good promotion value.

Abstract: The oxidation behavior of photovoltaic ribbon was measured for 48 hours over the temperature range of 300°C to 800°C using thermogravimetric apparatus (TGA). It was found that weigh-gained of both samples was found to be increased with increasing temperature and it was dramatically increased at 800°C for 30 minutes of initial oxidation time. Pure copper with 99.55% purity was successfully recovered from the photovoltaic ribbon of spent solar module using cyclic oxidation method.

Abstract: The effects of reducing the contact resistance of AgNW networks by using TiO₂ and PEDOT:PSS were compared. The AgNW+PEDOT:PSS TCE was able to give a lower sheet resistance of 30~60Ω/□, while the AgNW+TiO₂ gave a relatively higher, but still practical value of 85~125Ω/□. Then the AgNW+PEDOT:PSS TCE was further compared with the SWCNT+PEDOT:PSS TCE, and it was found the SWCNT+PEDOT:PSS TCE had a lower conductivity of 70~110Ω/□ but a superior long-term mechanical stability.

Abstract: Nanocomposite Nd₂Fe₁₄B/α-Fe magnetic material had been prepared by ball milling Nd₈Fe₈₆B₆ as-cast alloy in Argon and subsequent crystallizing. Influence of ball milling on their magnetic properties had been investigated by means of X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) etc. The results show that Nd₂Fe₁₄B grain are refined quickly and grain size of α-Fe decreases while extending milling time. After milling for 25h, grain size of α-Fe reaches about 7nm. Magnetic properties increase with milling time. Milled for 25h and crystallizing at 700°C for 30 minutes, samples have the best comprehensive magnetic properties (remanence, coercivity and magnetic energy product). To obtain nanocomposite permanent materials with high magnetic properties, it is necessary to combine ball milling with crystallizing.

Abstract: The iron oxide anode materials have attracted widespread attention in lithium-ion battery research field. The Fe₂O₃/C composite was synthesized via hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD confirmed that the main crystallization phases of materials were Fe₂O₃. The Fe₂O₃/AC powders showed very uniform cube between 1 and 2 μm. Fe₂O₃/CNTs composites acted as a three-dimensional network wiring to connect Fe₂O₃ spheres. The electrochemical investigation indicated that the electrochemical performance of Fe₂O₃/CNTs materials shows a high specific capacity and an excellent cycling stability. The first reversible capacity of samples is 808.8 mAhg^-1 at the current density of 100 mAg^-1 between 0.01 and 2.5 V vs. Li/Li⁺.

Abstract: ZnMn₂O₄ films were fabricated on p-Si substrate by magnetron sputtering. The effects of annealing temperature on microstructure, resistance switching properties and endurance characteristics of ZnMn₂O₄ films were investigated. The ZnMn₂O₄ films with a structure of Ag/ZnMn₂O₄/p-Si exhibit bipolar resistive switching behavior. The results indicated that the annealing temperature has not changed its spinel structure, the bipolar resistance behavior and endurance characteristics, but the grain become more and more large, arranged closed and distributed evenly with the increase of annealing temperature from 450°C to 750°C. The ZnMn₂O₄ films annealed at 600°C have the biggest R_HRS/R_LRS ratio, the lowest V_ON and V_OFF. The R_HRS/R_LRS ratios of all specimens maintain at about 10³ after successive 1000 switching cycles, which indicated that the Ag/ZnMn₂O₄/p-Si device has better endurance characteristics.

Abstract: Effects of cooling rate on metallographic structure of boron-bearing steel were investigated in present research. The results showed it consists of ferrite and pearlite formed in the initial stage of the transformation in the studied boron-bearing steels cooled at the rate from 1 to 10°C/s. For the higher cooling rate than 15 to 33°C/s, it consisted of bainite formed in the second stage of the transformation. For increasing presently cooling rate than 66°C/s, it consisted of martensite formed in the third stage of the transformation. All the transformation of metallographic structure was proved by CCT diagram.