Applied Mechanics and Materials Vol. 421

Abstract: With the rapid development of the wireless communications, the quality of wireless communications services are increasingly improved, which makes people to pay more attention to efficiency and effectiveness of wireless communication system. Recently, some popular portable devices are those defined by 802.11b, 802.11g and 802.11n protocols, such as Wi-Fi card, Wi-Fi card reader and Wi-Fi hard disk. A dual frequency WLAN antenna used for applications of Wi-Fi portable devices is necessary. The reflection loss (Return Loss) of the antenna is a key parameter, therefore, the antenna return loss and bandwidth must meet the conditions of requirements. We use electromagnetic simulation software to simulate and tune the reflection loss of the antenna to more than 10 dB specification. According to the parameters of simulation results, a dual frequency WLAN antenna used for applications of Wi-Fi portable devices is fabricated.

Abstract: A compact prototype of dual band monopole antenna has been fabricated on PCB with small overall size of 36.6 mm×47 mm. By the trial of simulation to tune the dimensions of PCB, an optimum design of antenna can be obtained. Dual resonances excited in 2.4 and 5 GHz bands. For return loss more than 9.6 dB, the achieved bandwidths are 2.41 to 2.77 GHz in 2.4 GHz band and 5.11 to 5.83 GHz in 5 GHz band. The return loss ( ) can keep larger than 9.6dB within the bands of 2.4 and 5 GHz.

Abstract: Rubber CVJ boot is the important part of the car transmission system. Trough crack and surface wear of the CVJ boot are the common failure modes, so the stress distribution simulation of the boot is needed. Acoording to the Mooney-Rivlin model, the definite method of the coefficient for material model was obtained. Based on the software Abaqus, a nonlinear finite element model of CVJ boot was set up. The elements type was hybrid (mixed formulation) C3D4H. The deformation and strength of the boot under working condition were computed. The maximum stress is 11490MPa, located in the first trough and the contact surface of the 3rd and the 2nd crest have more serious wear, which correlate well with the test results. The next work is to optimize boot structure by this simulation model.

Abstract: As the key equipment to ensure the stable operation of containment spray system in nuclear power plant, a RCC-M ejector with safe and credible performance is very important to make sure the containment integrality under lose of coolant accident (LOCA) or pipe broken. However, it was purchased from overseas supplier all along because of its special configuration, nonstandard design, severe safety level and small quantity demand. To implement equipment localization, and referring to practical applications of some nuclear plants, a RCC-M ejector is independently manufactured and tested, all performance could meet the requirement according to the test result. The RCC-M ejector is authenticated by experts by China Nuclear Energy Association, and the localization prototype research of this paper has great application and popularization value.

Abstract: By using dexelization algorithms, the Brep model of artificial bone is transformed to the three direction DEXEL model and VOXEL model. By setting the transparence attributes of VOXELs in this VOXEL model, the artificial porous bone structures are designed. In order to preserve bio-activities of materials when we manufacture the artificial porous bone structure, the low-temperature deposition manufacturingLDM is used. By using the blended materials poly-lactic-coglycolic acid (PLGA) and tricalcium phosphate (TCP), we could manufacture the artificial porous bone structures.

Abstract: In this paper, a novel model combining the microstructure prediction model and a modified constitutive model of the Johnson-Cook (JC) model was developed and embedded into FEM software via the user subroutine. The chip formation and microstructure evolution in high speed cutting of Ti-6Al-4V alloy were simulated based on the presented model. The results indicated that dynamic recrystallization mainly happened in ASBs, where the grain size had a big decline. According to the variation of cutting temperature and grain size of microstructure, the mechanism of the adiabatic shear bands (ASBs) formation was investigated deeply and concluded that dynamic recrystallization was the root cause of the serrated chip formation.

Abstract: In general, firing process in brick manufacturing could affect the properties, colours and appearance of the brick. The main purpose of this study was to evaluate the effect of different heating rates on physical and mechanical properties during the firing of standard bricks and bricks incorporated with cigarette butt (CB). In this investigation, two different heating rates were used: slow heating rate (2oC min^-1) and fast heating rate (5oC min^-1). Samples were fired in solid forms from room temperature to 1050oC. All bricks were tested for their physical and mechanical properties including compressive strength, initial rate of absorption and density. Higher heating rates decrease compressive strength value but slightly increase the initial rate of absorption and density properties respectively. In conclusion, higher heating rates are able to produce adequate physical and mechanical properties especially for CB Brick.

Abstract: To investigate the influence of different roll rotational speeds on tendency of inside bore and lamination defects of large diameter heavy wall seamless P92 (9Cr-0.5Mo-1.8WVNb) steel pipe pierced by two-high rotary piercing process, with the aid of commercial FE code MSC. SuperForm, 3D thermo-mechanical coupled simulations were presented. The damage field of the rolled piece during rotary piercing process, and the tendency of forming inside bore and lamination defects were analyzed using Oyane ductile fracture criterion. The results show that When roll rotational speed increases from 7rpm to 11rpm, the maximal damage characteristic value decreases from 0.4279 to 0.3340 in center area of rolled piece in front of the plug, but which increases from 0.3780 to 0.4858 in a certain depth zone (15~25mm) adjacent to the internal surface of the rolled piece contacting with the front end of the plug. With the increase of roll rotational speed, the tendency of forming inside bore defects of rolled piece reduces, but the tendency of forming lamination defects increases. Therefore, there exists a critical roll rotational speed to make the tendency of both inside bore and lamination defects reduce. This study provides scientific basis for formulating reasonable rotational speed schedule to prevent or reduce inner overlap and lamination defects.

Abstract: Diamond-like carbon (DLC) thin films were deposited on YG6 cemented carbide by an anode-layer linear ion source (LIS). The effect of different temperatures (20°C, 80°C, 115°C and 150°C) on DLC thin films was investigatedby using atomic force microscope (AFM), scanning electron microscope (SEM) and Raman spectroscopy. It was found thatthe surface roughness of the film decreased at first and then increased with the increase of the temperature, and reached the trough at 80°C. The intensity ratio (I_D/I_G) and the adhesion of the film increased at first and then decreased, and both of them reached the peak at 80°C. When the temperature was 80°C, the surface roughness was 6.9nm, the intensity ratio (I_D/I_G) was1.91 and the critical failure load was 107.23N. The results show that the temperatures have a great effect on the surface morphology and mechanism properties of DLC thin films. Consequently, this paperfurther studied the effect mechanism of different temperatures on DLC thin films based on the experiment.

Abstract: Amorphous hydrogenated carbon (α-C:H) thin films were deposited by the linear ion source (LIS)-physical vapor deposition (PVD) at the bias voltages ranging from 0V to-1500V. The characteristics such as surface topography and mechanism properties of the film were investigated under the voltage of 0V, -500V, -1000V and-1500V by using atomic force microscope (AFM), Ball Mills and Rockwell Indentation Tester. The results showed that with the increase of the bias voltage, the surface roughness of the film decreased initially and then increased. The wear resistance and compressive property were continuously improved. When the bias voltage was-1000V, the surface roughness was the lowest of 5.78nm.When the bias voltage went to-1500V, the film had the lowest wear rate of 7.8E-8 and the best compressive property. As a result, deeply understanding the effect mechanism of the bias voltage on α-C:H thin film is meaningful for the future deposition.