Advanced Materials Research Vols. 690-693

Abstract: The influence of dimples on the inner surface of big end bearing in internal combustion engine (ICE) on tribological performances of the bearing was investigated based on Navier-Strokes equation and other associated equations. In doing so, the CFD modulus in the software ANSYS12 version is used to analyze the dimple effect on the tribological performances of the bearing using two-way fluid-solid coupling algorithm. Some mechanisms are revealed about the dimple effect on the load-carrying capacity and friction coefficient of oil film, and the deformation and stress for the textured big end bearing.

Abstract: The problem about friction and wear characteristics of piston ring which is directly related to the sealing properties of stirling engine was analyzed. An improved seal structure of piston ring was taken as the research object, the influence of the temperature and the pressure of refrigerant were considered when the friction and wear characteristics of piston ring in stirling engine was studied. The calculation formula about radial weal amount of the piston ring with the change of the temperature and the gas pressure was derived by using the peeling wear theory. Then, the experiment was taken to confirm these formulas. The results show that the formulas were right. Hence, a viable way to analysis the sealing properties and life prediction method of piston rings was got.

Abstract: The riveting is widely used for fitting together two or more components of structure in the same or different materials. And mechanics characteristic is very complex. The paper work focus on study fretting fatigue crack formation with different friction coefficient and fatigue loading, by analyzing the stress field of upper hole edge and outer boundary of contact area. And comparing with the experimental, founding the risk point of single bolt riveted aluminum components.

Abstract: The film temperature of sliding bearing considering the cavitation is studied based on the Rayleigh-Plesset (PRE) model with the computational fluid dynamics (CFD) method. The numerical results show that the maximum film temperature with the cavitation effect becomes smaller than that without the cavitation effect. The larger average vaporization rate of the film, the more decrease in the film temperature.

Abstract: The rock bolt has been widely used as an effective reinforcement in civil and mining engineering for a long time. However, the anchored mechanism of it is not well understood. This paper obtained the expression of the shear stress and axial force of stretched fully grouted rock bolt base on previous working, and detailed analysis the influence parameters of stress distribution. It is considered the anchored effect is influenced by some factors. Augmenting diameter of rock bolt, increasing the pre-stress magnitude and improving the strength of grout may all improve the anchored effect of rock bolt. As the rock character and the grout property are similar, the rock bolt anchored effect is optimal. There is a stress concentrated phenomena at the front of rock bolt. It is shown that the distribution of shear stress and axial force are not even distribution and exponentially attenuated along a fully grouted bolt.

Abstract: Considerable research has been directed towards discovering new engineering materials for various applications. As a superhard material, Cubic Boron Nitride (CBN) has been developed and applied to engineering for several tens of years. Due to its high specific strength and stiffness as well as good creep, fatigue and wear resistance at elevated temperatures, CBN has been widely used as cutting tool material in manufacturing industry. In this paper, the preparation and characteristics of CBN are introduced. As hard turning has been more and more employed in recent years as an advanced metal cutting technique, the application of CBN cutting tools in hard turning is presented based on the literature, and in particular, the main wear mechanisms of CBN tools in hard turning are summarized, owing to the significant influence of tool wear on the tool life and product quality.

Abstract: The demand for surface quality and dimensional accuracy of ferrous metallic components has increased markedly at present. Whereas, it is clear known that diamond tool could not be used for cutting operation of ferrous metals ascribed to excessive tool wear. In this paper, a series of experimental investigations for various stainless steels with ultrasonic vibration assisted turning were proposed. The micro-morphology of rake and flank face of diamond was detected by scanning electron microscopy, in order to discuss the influence law of material composition on tool wear. In addition, the effect of cutting parameters such as depth of cut, feed rate and amplitude on tool wear and surface quality were deeply studied with ultrasonic vibration cutting. The results revealed that this technological measure has enhanced tool life, decreased cutting force and improved surface quality to a large extent.

Abstract: Ti6Al4V alloy is widely used in the aircraft industry, marine and the commercial applications due to its excellent comprehensive properties. However, its poor machinability prevents it from application widely, and the rapid tool wear is one of the key factors. The FEM models of cutting titanium alloy are established. The effect of tool wear on chip morphology, cutting temperature and cutting force are studied. The simulation results show that: the cutting force and cutting temperature will rise with the increase of tool wear. Furthermore, the degree of chip deformation will improve, but the frequency of serrated chip tooth occurred will decrease.

Abstract: An arc-spraying composite coating system for high-temperature oxidation protection is composed of an inner Fe-Cr-Al alloy layer and an Al-Si alloy outer layer. The high-temperature oxidation behavior of the composite coatings on steel substrate was studied during isothermal exposures in air at 900°C. Experiments show that the coatings on steel substrate are not deteriorated and the substrate is protected well, being exposed to high temperatures up to 900°C. Inter diffusion of alloying elements within the protective coatings occur, while the elements, Cr and Al, are also diffusing to the core of the base metal. As test time proceeds, a large number of chromium oxides are generated in situ within the protective coatings, especially close to the coating/substrate interface. The oxides generated increase the bond strength of the coating to the steel substrate, and together with the surface alumina they provide a long-term effective anti-oxidant protection to steel substrate. The results on titanium sponge production site show that the protective coatings on the reactor have provided an effective protection and prolong the lifetime at least forty percent for the reactors.

Abstract: In-situ synthesized two kinds of Fe-Cr-C and Fe-Cr-C-Ti layers were fabricated on the base of Q235 steel by reactive plasma cladding process using composite powder prepared by precursor carbonization-composition process as raw materials. The composite powder is composed of ferrotitanium, chromium, iron and precursor sucrose. Microstructure of the layer was observed by scanning electron microscope (SEM). The phases in the layer were determined by X-ray diffraction (XRD). Results indicate that the Fe-Cr-C layer consists of primary (Cr,Fe)₇C₃ carbide, chrysanthemum-shaped eutectic (Cr,Fe)₇C₃ carbide and eutectic austenite. The cracks in Fe-Cr-C layer might originate at the interface of the layer and the base material as well as at the pores or edges of the layer. These cracks expand along primary (Cr,Fe)₇C₃ grain boundaries in a crystalline form. Because the grains of primary (Cr,Fe)₇C₃ are fiber-shaped and the fiber direction are perpendicular to the surface of the layer, so the cracks expand perpendicularly throughout of the Fe-Cr-C layer. The Ti addition into Fe-Cr-C plays an important role in synthesizing TiC and austenite, reducing primary (Cr,Fe)₇C₃ and improving the microstructure of eutectic (Cr,Fe)₇C₃. Therefore, Fe-Cr-C-Ti has good performance in toughness and crack-resistance.