Advanced Materials Research Vol. 820

Abstract: Cadmin sulfate nanoparticles, hollow sphere (CdS-HS) and rode (CdS-NR) were synthesized by ultrasonic and solvothermal process, respectively. The effect of the two kinds of nanoparticles on flammability of polystyrene was investigated using cone calorimeter (Cone) and microscale combustion calorimeter (MCC). Cone data indicate that the incorporation of 1% CdS nanoparticles leads to a about 20% reduction in the peak heat release rate (PHRR) compared to the pure PS; CdS-NR is more efficient in reducing the PHRR proved by both Cone and MCC results. The TG results show that the addition of the nanoparticles mainly increases thermal stability of PS at high temepratures.

Abstract: Stopping power of test ions in magnetized plasmas is investigated by means of linearized Vlasov Poisson theory. The influences of the magnetized field, the angle between the test particle velocity and magnetized field, and certain plasma densities and temperatures on the stopping power are studied. Simulation results show that the stopping power emerges a peak around the plasma thermal velocity due to the electron excitation. When the magnetized field is strong, the stopping power is strengthened; while when the magnetized field is weak, the stopping power is weakened.

Abstract: The surface morphology of the Al₂O₃ powder was observed by SEM and the composition content was analyzed by EDS spectrum under different vacuum level condition. The effects of the atmosphere pressure on the SEM image quality and EDS analysis were explored systematically. The platinum sputtering treatment on the materials surface in high vacuum mode is beneficial to the observation of the images but has negtive effects on the analysis of O and Al elements. The decrease of vacuum degree in low vacuum mode can result in the drop of the image resolution and EDS spectrum accuracy. However, clear SEM image and EDS composition analysis result near to the real element kinds and contents of sample can be obtained in the low vacuum mode of 1Pa~50Pa.

Abstract: In ultrasonic testing of coarse-grain materials, signal to noise ratio (SNR) is so poor because of the serious structure noise, and reflected wave from defects is difficult to be identified. In order to improve SNR and increase the reliability of ultrasonic testing for coarse grain materials, Hilbert-Huang Transform (HHT) is introduced to analyze and process the testing signal here. Firstly, detected signals from the coarse grain material can be collected by using ultrasonic test system; And then many Intrinsic Mode Function (IMF) can be obtained according to Empirical Mode Decomposition (EMD), and marginal spectrum of different mode can be gotten by Hilbert transform; And finally, the noise should be removed after analyzing the time-frequency information, and SNR is able to be enhanced and the reflection wave from defect is being more obvious. It was shown from the experimental result that the ineffective structure noise could be removed after HHT, and SNR could be improved and the defect reflection is more outstanding.

Abstract: The fusion power is considered an ideal energy for the future due to abundant, green and safety. Wetting properties between the liquid metal and the structural materials in the liquid blanket of the fusion reactor related to the heat exchange efficiency and the irradiated plasma resistance, and directly related to the service life of the reactor structural materials. This article describes the wetting angle measurement experimental procedure of liquid lead-bismuth (PbBi) at reduced activation ferritic/martensitic steel (RAFM steel) surface based on the high-temperature static sessile drop method under the protection of high purity argon, including the images enhancement processing obtained by CCD camera, using ellipse fitting method to calculate the wetting angle, and were measured at 350-600°C. The experimental results show that the wetting angles of liquid PbBi and RAFM steel are greater than 140°, non-wetting.

Abstract: The extreme hardness of Polycrystalline Diamond (PCD) makes it an ideal choice for the machining of hard materials as a cutting tool. Due to the high hardness, fabrication of PCD tools relies on conventional abrasive grinding which suffers from low machining efficiency. Electrical discharge machining (EDM) is an advanced machining process and can be utilised to fabricate complicated PCD tools. High temperature of sintering and EDM processes creates residual stress inside PCD and can result in unmatured failure of PCD tools. This paper analyses the distribution of residual stress in PCD after electrical discharge machining process.

Abstract: The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.

Abstract: A mechanical transmission equipment of traditional straightening machine for plates are driven by worm gear and worm, which causes small straightening force, slow pressing speed and low control precision. However, screwdown control system of straightening machine can be driven by hydraulic system, which will lead to large straightening force, rapid pressing speed and high control precision. This system was designed for straightening machine with nine rolls for plates, its transfer function was deduced, and the analysis on its stability and time response was conducted. A BP neural network PID controller was utilized in the system for improving dynamic characteristics. It can be concluded that the system responds rapidly, and stability and control precision are high if BP neural network PID controller is used in the system.

Abstract: In this study, technological difficulties of machining titanium alloy impeller were analyzed. Furthermore, machining process of a certain impeller was illustrated as an example. Firstly, the impeller model was built through UG software. Secondly, the virtual simulation software was utilized to achieve simulating machining of the titanium alloy impeller, simulate cutting trajectory of cutters, motion of the machine tool, and so on. Finally, all machining parameters were optimized.

Abstract: A new Online Detection Simulation Technology for 5-Axis Linked-Blade Grinder was presented, Using the modeling of virtual inspection environment, the obtaining of inspection information and the driving of the virtual machine. The experimental results show that the simulation technology provides high precision and can be used in wide fields.