Applied Mechanics and Materials Vols. 423-426

Abstract: This study investigated the use of nanoscale bilayers assembly for hydrophobic surface modification on stainless steel plate and its effect on condensation. This study first performed nanoscale bilayers assembly method, with the addition of a fluorosilane treatment using chemical vapor deposition (CVD), to modify the surface structure and thereby the wettability of the surface at 15, 20, and 30 bilayers. Experimental results showed 15 bilayers to be the optimal number of bilayers among the samples tested, resulting in the largest contact angle of 150° (compared to 70° on unmodified surface), corresponding to the highest surface hydrophilicity; however, beyond 15 bilayers there seems to be no significant changes or improvements to hydrophobicity. Visualization of the condensation process also indicated later formation of film condensation on superhydrophobic (15 bilayers) surface, and by tilting the condensation surfaces at 90°, the self-cleaning property of the superhydrophobic surface allows water droplets to roll off the surface due to gravity before formation of film condensation, while large water droplets still remain stuck on unmodified surface. Therefore, by allowing the condensation process on the superhydrophobic surface to continuously cycle back to droplet condensation, there is great potential for condensation enhancement on superhydrophobically modified surface.

Abstract: An experimental study on friction and wear properties of carbon strip rubbing against copper contact wire was carried out on a pin-on-disc frictional tester under electric current. The result indicates that the coefficient of friction slowly increases with increasing of electric current. The value of friction coefficient is low, generally not more than 0.125. The wear volume of pin specimen increases with increasing of electric current. The wear volume of pin specimen is very low, generally not more than 0.075g. Through observing the SEM morphology of worn specimens, it can be found that there are obvious pits of arc ablation and traces of melting metal on worn surface. Worn surfaces of the worn specimens are analyzed by an energy dispersive X-ray spectroscopy. It can be observed that the oxidation wear occurs in the frictional process due to arc erosion and significant temperature rise. Therefore the arc erosion and oxidation wear are a main wear mechanism accompanied by materials transferring in the process of electrical sliding friction.

Abstract: This paper provides the details of continuous cutting technology to architectural model made by EPS. To solve the interference problem between outline surface and hot cutting-wire in the cutting process, STL model projection profile method is used. Slicing algorithm based on grouping matrix is proposed to cutting the outline model continuously. Local topological relations in each group are established to improve the efficiency of slicing cutting. In order to apply this algorithm to the actual process better, automatic programming system with Visual C + + 6.0 based on STL model is developed, which used the 5-DOF CNC thermal device to cut the model. The experiment shows that this technology can cut the outline architectural model efficiently and accurately.

Abstract: Mathematical-physical model of powder stream in coaxial powder feeding was established. The concentration fields of powder stream of coaxial nozzle of different size and powder mass flow rate were analyzed. The concentration field and morphology of the powder stream were detected by CCD camera. The results show that the size of coaxial nozzle and powder mass flow rate are major factors affecting the powder stream. The mathematical-physical model and experimental data provide theoretical basis for laser cladding manufacturing.

Abstract: Combined with the pre-test results, homogenization, plastic deformation, aging and other processes of Mg-7.1Gd-4.6Y-1.3Nd-0.5Zr (EW75) magnesium alloy was studied in engineering tests. The results show that in engineering test the large ingots (Φ500×800~900mm) of the EW75 alloy using two-stage homogenization treatment had perfect homogenization effect and no burnt structure. After multi-directional forging and extruded deformation, the homogenized residual second phase particles were fully broken, and the structure was refined and uniform. The peak aged craft was 230°C×6h, with the aging time increasing, the tensile strength and elongation remained unchanged, showing a strong anti-aging ability. The two-stage homogenization treatment + multi-directional forging + direct extrusion deformation + peak aging treatment was used to prepare a high performance EW75 alloy and at longitudinal direction its ultimate tensile strength, yield strength and elongation were 450MPa, 385MPa, 12.0% respectively.

Abstract: This article is based on the analysis of locomotive springs packaging existing situation, combining with spring packaging requirements, giving a spring packaging technology program. The program is by using 0.6mm PE shrink film on the new U type coating machine to achieve reel wrapping package for locomotives inner and outer springs respectively, and then passing the BM-500 thermostatic shrink packaging machine to complete coating process technical solutions .In addition this paper gives a detailed description for the new U type coating machine structure design and working principle to make early program planning for the locomotive springs packaging production line.

Abstract: During the process of radial ring rolling, relative slip or relative slip tendency occurs on the interface between the ring and the rolls. Research on the relative slip or relative slip tendency plays an important role on reducing friction to ensure the ring rolling smoothly. In this paper, the reason of relative slip or relative slip tendency is investigated that there is speed difference between tangential component of the ring and linear velocity of the rolls. According to speed difference, slip types of the interface are classified. Forward slip coefficient and backward slip coefficient are defined and derived and relations between them are studied. Comparison between the new method and the previous one is conducted via case study, which proves the rationality and effectiveness.

Abstract: This work is devoted to research of 30CrMnSiA steel structurally modified surface layers and study of electrolyte-plasma treatment parameters influence on changing peculiarities of structural-phase state and also the increase of constructional 30CrMnSi steel operating ability. The chosen technology leads to the formation of stable ferrite-pearlite structures in 30CrMnSi steel surface layers, provides high mechanical properties. As for the basic experimental methods of research in the work we used metallographic analysis applying optical microscope «NEOPHOT-21» and «AXIOPHOT-2», Х-ray analysis on the diffractometer ХPertPRO in monochromatic CuK_α-radiation, mechanical tests for microhardness on PMT-3М installation. It is established that microstructure of 30CrMnSi steel modified layers samples while different processing modes, consists of α - phase, iron carbides. Using technology of structural steels electrolytic-plasma cementation under arc discharge terms in the electrolyte, we get diffusive surface layer with increased microhardness parameters and wear resistance providing good operating ability for details often subjected to wear.

Abstract: With the diversified market demands, the high precision deep hole processing increased and the difficulty coefficient has been getting greater, Therefore, how to improve the deep hole linearity problem is also imminent. This article studies on the linearity deviation problems in the process of small deep hole processing which diameter is between 3 and 16. From the parameters of gun drill cutting tools, accessoties of machine, and the vibration system of machine tools in the machining process, etc., to discuss the reasons affecting the linearity and put forward corresponding solutions for various influencing factors. Finally through computer analysis software and experimental means to verify the feasibility of the scheme.

Abstract: In this paper the effect of selective laser melting (SLM) input energy density on densification behavior and tensile strengths of commercially pure (CP) titanium was investigated. Fully dense and high strength SLM CP titanium has been obtained. A complex bone-compatible tetrakaidecahedron based porous structure has been successfully SLM-fabricated with optimized laser parameters.