Advanced Materials Research Vols. 189-193

Abstract: Friction stir welding (FSW) is a novel solid-state welding process and has been employed in several industries such as aerospace and automotive. Several parameters such as rotational speed, welding speed, axial force and attack angle play critical roles in FSW process in order to analyze the weld quality. The aim of this study is to investigate the effects of different rotational speeds and attack angles on the weld quality of high density polyethylene (HDPE). In the optimum welding condition, 75% of the base material strength is achieved. SEM micrographs show the changes of the weld microstructure which result in the reduction of the strength and the percent of elongation.

Abstract: Two grafting starch was obtained by grafting copolymerization of two synthetical vinyl monomers using HRP/H2O2 as catalyst. The structure of vinyl monomers was verified by 1H-NMR.The grafting polymer was proof by structures were verified by FTIR. The effect of mass ratio of starch and vinyl monomer on the grafting efficiency (GE) and grafting percentage (GP) was studied. The highest GE and GP of the first grafting starch was 35% and 32%, 59% and 50% for the second grafting starch when the vinyl monomer ratio was 9%. The molecular mass tested by GPC for the two kinds grafting starch with highest GE and GP were 54 600 and 63 970. The two mostly grafted starches were used as retanning agent. The increase ratios in thickness were 18.1% and 18.6% respectively and the tanned leather has excellent softness and flexibility.

Abstract: The maximum nonmetallic inclusion size and type of bearing steel has been analyzed using statistics of extreme values (SEV) in this study, and the influence of reduction in area on the maximum nonmetallic inclusion size and the fatigue life of bearing steel have been discussed as well. Scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) are used to measure the inclusion size and identify the inclusion type respectively. By adopting the criterion of return period (T) at 200, a serial analysis shows that with increasing the reduction in area of steel, the predicted inclusion size for √area max is decreasing, and the fatigue life is prolonging. This results from the defragment of hard inclusion during rolling process, and the decrease of concentration of stress around the inclusion.

Abstract: Resistance microwelding of Au/Ni-plated phosphor bronze sheet to insulated Cu wire have been investigated using mechanical testing, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that mechanisms of joint formation involve solid-state bonding with Au and Cu atoms diffusion at low welding current, a combination of brazing and solid-state bonding at high welding current. Due to the hindrance of Ni plating which has a higher melting temperature and hardness, the joint breaking force is smaller than that without plating.

Abstract: Friction stir processing (FSP) was applied to modify the surface of a hypereutectic alloy Al-30wt.%Si, the influence of FSP passes on the size and morphology of Si particles, the mechanical properties of the materials in the stir zone was investigated. In the nugget by FSP, the silicon particles were intensely refined to several micrometers and spheroidized, and the refinement and spheroidization degree increased with FSP passes. The tensile behavior of the alloy by FSP has typically plastic feature. With FSP passes increasing, the tensile strength and the elongation increased gradually, and the improvement ratio of the elongation is more obvious. The improvement is attributed to the spheroidization and refinement of silicon particles by FSP.

Abstract: To meet the needs of video monitoring applications, the paper researches and designs of Hi3510-based embedded wireless video monitoring systems.The systems uses H.264 for video data encoding, combining Hi3510 encoding API to adjust H.264 rate control dynamically. Based on real-time transmission control RTP / RTCP protocol, in order to achieve adaptability and guarantee the QoS of the real-time transmission, this paper presents variable constant growth and change constant reduction method to adjust the transmission speed dynamically. In addition, this paper processes the packet loss during transmission processing, trying to ensure the I-frame reliable transmission. To transplant DWL-G122 wireless network card, it can realize communication.

Abstract: In this paper, the different applications of piezoelectric material (PZT) are surveyed such as: actuators, motors, transformers, sensors, and benders. The operation concept, advantages and disadvantages of these types are explained, that drive the suitable application of them. Moreover, the electrical and mechanical features of piezoelectric material are presented. These features are dynamic behavior, operation voltage, maximum force, and temperature effect. There are different piezoelectric material types such as ferroelectric materials and ferroelectric polymers that are presented and a comparison between them is achieved.

Abstract: Various joining methods (i.e., spot welding, arc welding, laser beam welding) have been used for vehicle body assembly. However it is unclear for the equivalent conversion of various joints which has the equivalent joint strength for the vehicle body, such as weld-bonded joint, SPR joint, which have been considered likely to replace RSW in the area of high strength steel’s joining. In order for the flexible design in the auto line of vehicles body’s joining, the equivalent (strength) weld pitch design method for various joints, including the joining of similar and dissimilar materials, is presented in this work. And some primary simulating results are presented and discussed. It is shown that the conversion method for various joints can be established based on the joint’s shear failure criteria. And the conversion results can be influenced by the sheet gage obviously. The failure criteria of various joint still need further investigation based on the simulating and experimental results.

Abstract: This paper presents the test of ultrasonic impact for reducing the welding residual stress. Three full-scale specimens according to the anchor connection plate of main girder with cable of the Jiangjin Yangtze River Bridge are made and the ultrasonic impact test are taken in laboratory to study the effectiveness of reducing welding residual stress. The comparison of welding residual stress before ultrasonic impact with the stress after ultrasonic impact is conducted and the results from test show that the welding residual stress can significantly be reduced over 50% by ultrasonic impact method and even some stress in weld could be changed form tensile stress into compressive stress after ultrasonic impact.

Abstract: In order to study the load-bearing properties of butt-welded connection of steel structure post fire, the strength design value of weld connection post-fire is proposed based on the experimental data and theoretical analysis. Considering the influence of different high temperatures and cooling patterns on strength damage of the weld, a revised checking method for strength of butt-welded connection of steel structure after high temperature is established on the basis of the analysis method for strength of butt-welded connection of steel structure at room temperature. The method can be used for damage assessment and strengthening technique of steel structure post fire.