Advanced Materials Research Vols. 217-218

Abstract: We report on the effect of anode-cathode spacing on the fabrication of TiO2 nanotube arrays by using a facile two-electrode anodization system. The experimental results show that the formation of nanotubes is affected by the anode-cathode spacing and the possible mechanism is also discussed. The as-formed TiO2 nanotube arrays were mainly examined by using a field emission scanning electron microscope. The present results are believed to be generalized to fabricate self-organized oxide nanotube arrays in other anodizing systems.

Abstract: Radial ball bearings made of metal, ceramics and plastics are commonly used as important components in industrial machinery. Usage of high performance engineering plastic polymers is increasing progressively as a replacement for metal components due to the latest markets demands. Poly-ether-ether-ketone (PEEK) is a promising material for precision-machined custom bearings, products that are expected to suit special market needs. In the present study, PEEK radial ball bearings were manufactured by lathe machining under different parameters and their rolling contact fatigue (RCF) resistance under water lubricated conditions was investigated. We observed the surface of the bearings prior and after testing by laser confocal microscope. The wear loss was measured by weighing the bearings before and after test. Cracks and/or flaking failures were identified on the bearing surface after testing. From the RCF tests results, we found that, at water lubricated conditions, crack initiation occurred later in the material that was machined at slower feed rate while at dry condition, the feed rate had little influence on the wear loss and cracking. Wear loss in the case of bearings tested under water was much less severe than that of bearings tested at dry conditions.

Abstract: Martensitic high carbon high strength SAE 52100 bearing steel is one of the main alloys used for rolling contact applications when high wear and fatigue resistance are required. Refining the microstructure of steel improves its mechanical properties (e.g. toughness). In this work SAE 52100 specimens were exposed to repeated induction heating process and rotation bending tests were performed using single- and repeatedly heat-treated material in order to investigate the influence of this cyclic heat treatment on the mechanical properties of SAE 52100. In an attempt to determine the effect of the repeated induction heating and quenching on the material, we focused our observations on the internal fatigue “fisheye" cracks. It was noted that crack propagation was successfully halted by the refined microstructure in heat affected zone, therefore it can be concluded that repeated induction heating and quenching processes help to slow down the propagation of fisheye cracks in SAE52100 steel bars.

Abstract: The PPS needle nonwoven filter were treated by singeing, calendaring, dipping and covering with PTFE membrane. Their structure and property were studied. The results showed that the thickness of filter was decreased and their weight was increased by finishing. Their surface structure became denser after being treated. The pore diameter and filtration resistance of the filter were increased by finishing. The filtration efficiency of the filter was largely improved by finishing, especially covering with the PTFE membrane.

Abstract: Ti-15V-3Cr-3Al-3Sn, β-phase titanium alloy, is subjected to study the temperature effects on microstructure and mechanical behavior by using different aging temperature (426 ∼ 600 oC) and high temperature (450oC) notched tensile test. It follows that the highest hardness of Ti-15V-3Cr-3Al-3Sn would be got up to 420 Hv after 426 oC aging. Afterward, the hardness is decreasing with increasing aging temperature. By means of microstructure analyses, it reveals that the narrow and intragranular α-phase precipitates with lamella-shape in the grains at 426 oC aging treatment caused the age hardening of the titanium alloy. Subsequently, the α-phase precipitates were coarsening with increasing the aging temperature and showed the thick morphologies distributed along grain boundaries, which results in overaging. In the notched tensile test at 450oC, the highest notched tensile strength (1160 MPa) is also obtained after 426oC aging treatment, and then decreasing with increasing aging temperature. Its mechanical behavior is different from the room temperature notched tensile test, which demonstrates the lowest notched tensile strength (813 MPa) after 426 oC aging treatment due to the notched embrittlement effect. According to microstructure study, it suggests that the environment temperature effect enhanced the toughness of the alloy and terminated the notched embrittlement effect resulted from the 426oC aging treatment.

Abstract: The effect of starting notch machining methods on fracture splitting of connecting rod was studied by axial tensile tests with single edge notch. The axial tensile specimens were made of the high carbon microalloyed steel (C70S6) which is now most widely used by the connecting rod of fracture splitting. The single edge notch of axial tensile specimens were respectively machined by laser notch、wire cut electrical discharge and broaching. The notch tip plastic deformation of specimens was compared by the fractography. The experimental results indicate that the specimens with laser notch can be fractured by the smallest axial tensile load which is respectively about 20% and 30% smaller than the fracture load of the specimens by wire cut electrical discharge and broaching. Considering the rich micro-local crack transformation hardened zones around the notch by laser the paper present the equivalent critical stress intensity factor KIcL which can be used to calculate the fracture load with laser notch.

Abstract: There is a general consensus that the movement of electricity price is crucial for electricity market. As a practical tool to estimate the future prices, electricity price forecast is of great importance and use for the operations of market participants. So a hybrid forecast model is proposed in this paper that integrates independent component analysis (ICA) with least squares support vector machines (LS-SVM). First, a novel feature extraction method of price influence factors is proposed based on ICA, which aims at mining the latent source-features by using the higher-ordered statistical characteristics. After that, nonlinear regression modeling of electricity price and its extracted features is accomplished by LS-SVM with more efficient training and forecasting. Finally, Californian market data are employed to test the proposed approach.

Abstract: This article describes an intelligent simulation method for measuring price risk, which is still one of the important problems for various risk managements and need to be studied profoundly. To solve this problem, risk measured in terms of Value at Risk on electricity price is proposed by intelligent simulation. In this work, prices under various market scenarios are produced by intelligent model using fuzzy neural network (FNN). After that, the quantitative model for price risk analysis is built in the form of a function of the estimated probability distribution of price, where price VAR is determined from the distribution according to parameter set, i.e. confidence level. The proposed method is more realistic and effective than variance approach to provide the assessment of the potential loss of electricity price over some period of time.

Abstract: Fatigue failure of steel occurs when cracks form and grow in the material’s stress concentration area. In order to understand the relation between stress concentration and crack propagation phenomena, non-destructive evaluation methods that can be related to in-situ measurements around the stress concentration area are necessary. In the present work, we developed a scanning Hall probe microscope (SHPM) equipped in a GaAs film sensor and observed three dimensional magnetic fields at room temperature in air. Medium carbon low alloy steels specimens (JIS, S45C) were used in the experiments. Only the area around the artificial slit had been magnetized and the effect of the magnetization area on the artificial slit was observed.

Abstract: The present paper gives a detailed inferential reasoning to a new mathematical model for structural strength indicator of soil under dynamic load, which is established on the base of law of conservation of energy and strain energy transformed principle. Through dynamic triaxial test, it points out that the relation of principal stress difference and accumulation subsidence quantity exists threshold value and calculates the structural strength indicator change rule. According to the analysis of structural strength indicator variation rule, it lays emphasis on uniformity of structural strength indicator variation rule under different vibration times and draws the conclusion which is the increasing of the structural strength indicator.