Advanced Materials Research Vols. 97-101

Abstract: Piston ring-cylinder is one of the most important friction pair of internal combustion engine，the lubricating state between them has decided internal combustion engine lubrication quality. So the theoretical research to the lubricating characteristics of the piston-ring group, especially the calculation of the lubricating oil film thickness is very important. The oil film thickness between piston-ring and cylinder is studied by calculation method. The calculation program is developed with average Reynolds equation taken the surface topography, viscosity-temperature effect, viscosity-pressure effect, extrusion effect and other factors into account. The position of oil outlet point is preinstalled, the full lubrication is assumed, and the Reynolds equation is solved by full pivot element gausses elimination approach, so the iterative course and calculation workload are reduced, and a great lot of the calculating time is saved, the oil film thickness of full period can be more accurately predicted by the ordinary PC within 30 minutes, which can supply quick effective evidence for next calculation and analysis.

Abstract: Amorphous silicon carbide nitride (SiCN) films have been deposited in a dual ion beam sputtering deposition (DIBSD) using a SiC target. Films with various compositions were obtained by changing the nitrogen and argon gas ratio in the assisted ion source. Mechanical properties of the SiCN films were evaluated by Nano-indentation in N2 ambient. Surface morphology of the films was characterized by an Atomic Force Microscope (AFM). The microstructure and chemical bonding correlating with behavior of the films were studied by a Fourier transform infrared spectroscopy (FTIR) and a laser Raman spectroscopy. The results show that N2 proportion in the assisted ion source has a great effect on the structure and properties of the films and the mechanism was discussed in brief.

Abstract: A thermo-mechanical coupling model for the rough surface is established. The model considers friction contact between a rigid flat plane and a rough surface based on 3D fractal theory and allows the analysis of the effects of elastic-plastic deformation of rough body and the interplay among asperities. The contact pressure distribution for the static state beneath different loading mode and for the dynamic state in the presence of the frictional heat flux is found. The results show the fluctuation of the average contact pressure during the process of loading is related to the velocity of loading. The synthetical function of multiple factors such as the thermal deformation, the rising temperature, the interaction between asperities makes the complicated relationships among the maximum temperature, the maximum contact pressure and the real contact area.

Abstract: Hot-dip aluminizing panels of Q235 steels were produced in laboratory. Then the hot-dip aluminizing samples were executed diffusion at elevated temperatures protecting with flowing argon gas. Metallographic microscope, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed for compositional analyses and graphical analyses of coating. The diffusion process was researched and the phase’s microstructure after diffusion was analyzed and discussed. The hot-dip aluminizing diffusion mathematical model was established with the finite element method. The results show that after diffusion in hot-dip aluminizing, the aluminum of the coating disappeared. The thickness of diffusion layer increased and the dentate frame disappeared. There are some iron-rich phases such as Fe2Al5, FeAl and Fe3Al in the diffusion layer. The phase Fe2Al5 decreases and the phase FeAl increases. The mathematical model corresponds with the actual situation. The diffusion coefficients of Al atoms diffusing in intermetallic compounds were calculated at 950°C, which were 0.29×10-12 m2/s for Fe2Al5, 0.7×10-12 m2/s for FeAl, and 0.27×10-12 m2/s for Fe3Al, respectively.

Abstract: 69111-stainless steel has wide applications in aerospace industry due to its comprehensive performance. However, its machining properties are not well studied due to the short using history in product components. In this study, a series of end milling experiments were conducted to characterize surface integrity at various milling conditions. The experimental results have shown that the milled surface roughness value increases with increased feed and cutting speed, while decrease with axial depth-of-cut (DoC) , and presents an inflexion with the radial DoC, with a rang of 0.7~1.7μm. Residual stress determined by the coupling effect of mechanical and thermal deformations varies differently with the increased cutting parameters.

Abstract: The effects of high speed steel substrate roughness on adhesion and wear behavior of reactive sputtered chromium oxide coatings was investigated using scratch and tribological tests. While coating adhesion slightly increased, its wear rate deceased with substrate roughness increase from 2 to 38 nm.

Abstract: Due to the relatively high surface-to-volume ratio, the surface effect can be significant for nanoscale materials. A numerical method, which combines surface energy and three-dimensional (3-D) finite element analysis, is proposed to simulate the elastic and plastic deformation of materials and structures at nanoscale. To demonstrate the method is valid and efficient, the free relaxation of single crystalline Cu nanowires is investigated and the numerical results are compared to the atomic simulation results.

Abstract: This paper presents the results of an experimental investigation of fretting wear characteristics on the contact surface of press-fitted shaft subjected to a cyclic bending load. A series of interrupted fretting wear tests with press-fitted specimens were carried out by using a rotating bending fatigue test machine. The evolution of contact surface profile of press-fitted shaft due to fretting wear were measured with a profilometer. The local wear coefficient during the running-in period is discussed from experimental results and FE analysis. It is found that the maximum depth of fretting wear by repeated slip between shaft and boss occurred at the close of contact edge at the early stage of fatigue life and the regions of worn surface are expanded to the inner side of contact edge as increasing number of fatigue cycles. The initial fretting wear rate at the early stage of fatigue life increased rapidly at all loading condition. After steep increasing, the increase of wear rate is nearly constant in the low bending load condition. The local wear coefficient in running-in period decrease dramatically at the early stage of fretting wear.

Abstract: Texture classification is a necessary task in a wider variety of application areas such as manufacturing, textiles, and medicine. In this paper, we propose a novel wavelet-based feature extraction method for robust, scale invariant and rotation invariant texture classification. The method divides the 2-D wavelet coefficient matrices into 2-D clusters and then computes features from the energies inherent in these clusters. The features that contain the information effective for classifying texture images are computed from the energy content of the clusters, and these feature vectors are input to a neural network for texture classification. The results show that the discrimination performance obtained with the proposed cluster-based feature extraction method is superior to that obtained using conventional feature extraction methods, and robust to the rotation and scale invariant texture classification.

Abstract: Four-point bending tests are conducted on fiber reinforced cementitious composites (FRCC) overlaid concrete beams with a “T” notch. The objective is to evaluate the fracture behavior of the interface between the FRCC and the concrete substrates. Two types of FRCC overlays are prepared including a traditional steel fiber reinforced concrete (SFRC) composite and an ultra high toughness cementitious composite (UHTCC), which has a very high tensile strain capacity. All two types of FRCC are prepared in two forms: cast on-situ and prefabricated. Test results indicate that, in comparison with others, the prefabricated UHTCC overlay system has exhibited most desirable behavior in terms of the energy absorption in the interface as well as the crack distributions in the overlay, and therefore has a great potential for use in repair of concrete structures.