Advanced Materials Research Vols. 602-604

Abstract: The paper presents some metallurgical and mechanical examinations of the joint between dissimilar metals viz. copper and alloy steel obtained by Shielded Metal Arc Welding (SMAW) using consumable nickel based superalloy electrode as the weld filler. Material microstructures at all the important zones of the weldment are examined with the help of Optical and Scanning Electron Microscopes (SEM). Examinations reveal corrugated weld interfaces with good fusion between the metals and the filler. The weld joints are subjected to tensile and impact tests in ambient conditions. In both the tests, the weldments fracture on copper side with all the weld interfaces remaining intact confirming a strong joint.

Abstract: Alumina spinel is widely used as a refractory material in metallurgy industries. Arc furnace melting method is suitable to produce high quality alumina spinel. However, the high melting temperature (> 2200 °C) and high electric energy consumption limit the application of this method. There exists huge opportunity for energy saving through process optimization. A newly designed 2400 kVA electric arc furnace is used as melting facility to produce alumina spinal in this study. It shows from the experiments and analysis that melting voltage has much effect on electric power input and electric efficiency. At voltages higher than 150V, stable electric power input and adequate efficiency can be maintained. Stable melting voltage is difficult to maintain at 100-150V range and power efficiency are also apparently lower. For voltage less than100V, the process is very difficult to control and energy efficiency are very poor. Too high voltage on the other hand can lead the electric arc expose directly to the surroundings and increase the energy loss. In practical melting process, controlling the melting voltage at 140-160V range is suitable for high quality alumina spinel production.

Abstract: As a reference to some minibus,establishing the Vehicle FEM Model including Body and Frame,and discussing the effect of joint simulation on vehicle modal analysis result;using the method based on environment incentive operational modal parameter identification to obtain vehicle modal,and compare test result with simulation result,it proves that the method of weld joint simulation is more accurate;At last, the FEM Model of Interior cavity is established and the NVH problems of the minibus are found and the improvements are Put forward.

Abstract: In this paper, the distribution law of residual stress normal to the welding joint in LY12 aluminum alloy was measured by the combination use of hole drilling and electrical-measurement method. The experimental results indicated that it was an effective way to measure the residual stress of LY12 aluminum alloy with thickness of 6 mm by applying hole drilling. The distribution of residual stress vertical to welding joint is quite obvious. The residual stress increases as the distance away from the welding joint decreases. The value of the longitudinal residual stress is higher than that of the transverse residual stress. But they are all smaller than the value of ultimate stress in LY12 aluminum alloy. The heat treatment after welding can greatly improve the tensile strength of the weldment.

Abstract: Assembled camshaft has used gradually in engines for automotive, ship etc. The camshaft bearing a great deal of impact loads and dynamic torque when the engine is high-speed rotation.Its quality directly determines engine combustion and dynamic characteristics. Hence, how to improve the joint strength economically between the shaft and the cam lobes is one of the key technologies needed to be solved. Main methods offered to the designers which can be used for assembled camshaft are: expanding technologies, interference-fits technologies and bonding technologies. It can be divided into joining by mechanical expanding, hydroforming, electromagnetic forming, knurling, welding sintering, injection molding. The advantage and disadvantage of joint techniques are analyzed, the current state of researches are summarized at home and abroad. Then followed are its new approaches in the future development.

Abstract: In this study, effects of welding time and elements Mg, Si and Cu in aluminum alloys on hardness and tensile shear strength of aluminum alloys/steel joints in resistance spot welding have been investigated. The welding current was kept a constant 10.5kA and electrode force was 1kN. Welding time was increased from 0.067s up to 0.2s with a rise of 0.033s. Two intermetallic compound layers were generated at weld interfacial zones between aluminum alloys and steel during welding process, and the major phases were FeAl3 adjacent and directing to aluminum alloy and Fe2Al5 adjacent and directing to the steel. Diffusion of Si in aluminum alloy occurred at the interface, whereas the diffusion of Mg and Cu was not observed at the interface according to the EPMA analysis results. Hardness of intermetallic compound layers was 13.8GPa, which was about 12 times as much as that of the aluminum alloy. The largest tensile-shear strength was obtained on the condition of 0.134 and 0.167s welding time.

Abstract: Solidification behavior and phase relation of LaFe13-xSix alloys was investigated using arc melting. Phase formation and structure in arc melted LaFe13-xSix alloys has been investigated by means of power X-ray diffraction analysis and scanning electron microscopy. The results have shown that La(Fe,Si)13 (1:13) phase is a peritectic phase and the solidification behavior and phase relations of LaFe13-xSix alloys are different with Si contents. Under arc melting condition, composition with low Si contents (x=0.5 to 1.5) consist mainly of α-(Fe,Si) phase the same as induction melting. Composition with high Si contents (x=2.0 to 3.0) consists mainly of 1:13 phase. The results were discussed with respect to the effect of cooling rate.

Abstract: 2519A/7A52 aluminum alloys were welded by using ER4043 and ER2319 welding wires with the method of MIG. The mechanical properties, microstructures as well as fracture of welded joints were studied. The results show that the welding wire of ER2319 is favorable for grain refinement of welding structures, and the strength and elongation of the joint are better than that welded by ER4043 welding wire. While for the use of ER4043, the strength and ductility of joint decline due to the generation of Si-rich brittle phase, and the fracture of weldment is mostly brittle type.

Abstract: The finite element method was used to study the stress distribution of strip joints under different elastic modulus and crack length. The results show that with the elastic modulus increases, the crack tip of the peak stress also increases, which provide maximum load continue to expand on the joint crack is SY stress, while little impact to the continued crack expansion on joints is SXY stress. I-type crack perpendicular the surface Crack under the stress of characteristics; With the initial crack length increases, I-stress intensity factor present weak tendency to increase, II-stress intensity factor is still almost zero, so that even after a longer crack length, strip adhesive joints under load the fracture is still mainly based on I-type crack, which is also consistent with the strip load characteristics: external stress perpendicular to crack surface. Another I-type stress intensity factor slight increasing trend.

Abstract: To study the structural performance of resin mineral composites part with metal embedded, a series of finite element analysis for mechanical parts made of different materials such as cast iron, resin mineral composites (RMC), and metal embedded resin mineral composites (MRMC) are conducted respectively in this article. Different performances of these three kinds of materials are acquired by static and modal analysis. It is proved that mechanical part made of MRMC has advantages of static and dynamic performance, to meet the requirement of vibration reduction.