Applied Mechanics and Materials Vols. 80-81

Abstract: A 3-D modeling based on the numerical resolution of fluid flow and heat transfer for laser-cladding processes of In718 Superalloy is proposed. The implementation of developed procedures allowed us to treat the problem with specific and complex boundary conditions. The applied loading is a moving heat source that depends on process parameters such as power density, laser beam diameter and scanning speed. The effects of process parameters on the melt pool are quantitatively discussed by numerical analysis. The computational results present good coincidences with the corresponding experiments of laser cladding process.

Abstract: The cyclic oxidation behaviour of Ni 5.5Al 2.6Ti 4.8Co 3.9Mo 5.0W 11.0Cr superalloy at 900 °C in air has been investigated by means of measuring the kinetics curves of the oxidation and analysis method of XRD and SEM/EDAX. The results show that the mass gain rapidly increases in the initial stage, and the weight loss and mass gain occurs alternately during the cyclic oxidation. An obvious oxidation and internal oxidation occurs during cyclic oxidation. Ti in the alloy oxidized, diffusing through the Al2O3 and Cr2O3 scales to form faceted TiO2 particle on the surface of the alloy. Al2O3 formed discontinuousness inner oxides in the alloy.

Abstract: The 0.05%Gd³⁺ /0.4%Eu³⁺ co-doped TiO₂ composite nanopowders have been prepared by sol-gel method and characterized by the techniques such as XRD, SEM/EDAX. The photocatalytic degradation of Methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activity. The results show that the 0.05%Gd³⁺ /0.4%Eu³⁺ co-doped TiO₂ are only structuresd by anatase phase with grain sizes of about 16nm at 540 °C for 4 h. The photocatalutic degradation of Methylene blue was 96.7% in 120 min of irradiation when the pH value was 9.

Abstract: Incorporation of metallic elements, titanium and copper, into carbonaceous mesophase (CM) was performed through mechanical alloying in a ball mill apparatus. The structures of the raw CM as well as the Ti/Cu-added CM were characterized by X-ray diffraction. The tribological behavior of the Ti/Cu-added CM used as lubricating additives was investigated by using a high temperature friction and wear tester. The results show that, compared with the raw CM, the Ti/Cu-added CM exhibits a drop in the crystallinity and a transition to the amorphous. The Ti/Cu-added CM used as lubricating additive displays an obvious high temperature anti-friction and wear resistance effect, and the lager the applied load, the lower the friction coefficient and the wear severity.

Abstract: The application of thermoelastic stress analysis in compound structure is particularly complicated because of the different material components, which determines the different thermoelastic effect to be depended on the different material property and mechanical performance. This paper describes a theoretical and experimental analysis on full-filed stress distribution from thermoelastic measurements and its application to determination of stress concentration for compound Steel-Foam-GFRP structure. A finite element modeling is proposed to calculate the sum of the principal stress under the condition of dynamic cyclic load. The sum of the principal stress can be measured by means of thermal stress analysis (TSA). Lock-in thermography has been applied to measure the sum of principal stress distribution of component by its high thermal resolution. In this study, Experiments were carried out with Steel-Foam-GFRP compound structure under dynamic periodic load. The thermoelastic constant is calibrated for different component of compound structure, respectively. An artificial neural network (ANN) is proposed to identify the different component stress distribution on whole compound structure. The experimental result shows that the stress distribution of compound structure can be measured and analyzed using lock-in thermography. It is found that the stress distribution of compound structure can be evaluated with good accuracies by lock-in thermography.

Abstract: As an important metallic powder, aluminum powders are used widely in coating, inks and plastic industry. However, it is necessary to treat the aluminum powders first to improve the properties of weather-resistance, anti-corrosion in acidic or basic media and compatibility with resin. The methods of surface treatment of aluminum powders including encapsulation and using corrosive inhibitors are summarized. The kinds of corrosive inhibitors used in the method of corrosion inhibition and their mechanisms are also reviewed. The processes and technologies of inorganic passivation, encapsulation by polymer absorption and by in situ polymerization are introduced. The research directions of aluminum powders are also presented.

Abstract: For flat plate of Q-235 Carbon Steel whose thickness is 4, 5 and 6mm, with the small hole that diameter is 3, 5 and 7 mm in the center and the load of 9, 18 and 27 KN at the both ends, the magnetic signal on the surface of the plate under the state of static tension conditions was detected by using CMT5305 and TSC-1M-4 test instruments. It is found that the magnetic signal on the surface of the sample is interrelated with stress concentration around the hole and diameter of the hole, while independent to thickness and load of the plate.

Abstract: In order to more accurate simulation the solidification of billet continuous casting. The measured shell thickness and surface temperature have been used to revise the heat transfer model. The calculated results of the model are in excellent agreement with the experimental ones based on an actual casting machine. The revised model can excellent to simulate the billet solidification process. So it provides the possibility for better simulation the dynamic solidification process and optimizing of the secondary cooling water.

Abstract: Pipeline system is the main form of transportation for oil and natural gas. High grade pipeline steel can effectively improve the security of long-distance transportation and to reduce costs, will become the main steel for gas pipeline project. A highly selective and sensitive spectrophotometric method for the determination of molybdenum in high grade pipeline steel has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient (e) is 1.75´10⁴L·mol^-1·cm^-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.11%~0.89% (mass fraction), and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in X80 pipeline steel and X70 pipeline steel samples with the improved accuracy and precision.

Abstract: Continuous extrusion under the large expansion ratio is an advanced forming process for manufacturing copper strip, preventing mould structure, die structure, expansion chamber structure and the shape of the billet section is important process paraments of deformation. Based on the characteristic of the forming process, the model of rigid-plastic FEM on DEFORM-3D is established and the numerical simulation of continuous extrusion forming process of the copper strip is carried. The metal flow regularity and the mean-square deviation of velocity with the different process paraments is analyzed. As the result, when using the drum form of preventing mould with promote flow angle and the die with variable calibrating strap, the mean-square deviation of velocity is 0.58. When the second extending angle is 134°, the mean-square deviation of velocity is 0.23. When size of billet is 30 x 1.64 mm2, the mean-square deviation of velocity is only 0.19.