Advanced Materials Research Vol. 628

Abstract: Through methods, such as microscope analysis, metallography examination, the causes resulting in tee joint crack of subcritical power station boiler platen superheater header have been analyzed. The result indicates the tee joint crack originated in the original defects, expanded to connect with reheat cracking and leaked finally. In repair crack, the measures of reducing residual stress, such as lower welding heat input, reducing thickness of welding layer, hammer blowing, assigning reasonably heat treatment power ,lengthening holding time and so on, were taken. The welding repair succeeded greatly.

Abstract: This work is focused to evaluate heat removal simulation on the continuous casting process of stell, which is the most used method to produce big mounts of steel.The understanding of steel thermal behavior is very important in order to control the industrial processing and guarantee steel quality, here different mechanism are involved such as radiation,forced convection and conduction.A finite difference method easy to program is used to solve the simulation.This calculation is also coupled a with virtual kinematics model in order to create a more realistic simulation.Finally computer tools were programmed to save and display graphically the steel thermal behavior.

Abstract: Recently, laser welding has been in its infancy primarily used for exotic applications where no other welding process would be suitable. In recent era, industrial product parts and components are produced at a minute-scale for sustainable manufacturing, creating a growing need for micro-welding applications. In this regards, laser processing is more likely considered to be the method of choice as it allows precise heat control compared with other parallel methods. This paper presents the operating principle of laser device. In line with this it puts forth a review on advancement of Laser welding/Laser Micro-Welding. At the end, it concludes with description of benefits manufacturing engineers would obtain.

Abstract: The present article prepared tungsten wire using doped Co, sintering and stretching. By metallographic analysis and mechanical performance test, it discussed the effect of Co on the performance of the seismic tungsten filament. This article studied the effect of additive Cobalt on the ductility, recrystallization temperature and performance of organization on the aseismatic tungsten filament preparation process. It shows that, Co can purify tungsten matrix. Adding Cobalt in doped tungsten can improve the tungsten second recrystallization temperature, and reduce the temperature of plastic-brittle transition. It had a large L/W and small cold-brittleness after annealing, and its seismic performance at high temperature was effectively improved.

Abstract: The new generation of high power fiber lasers presents several benefits for industrial application. Nevertheless, due to the small spot size of the laser, the fiber laser has difficulties in some welding applications. These shortcomings can be overcome by laser-arc hybrid welding technique such as laser-gas metal arc welding or laser-gas tungsten arc welding. In this work, a high power fiber laser was coupled to an arc welder and the AA5754-H111 magnesium aluminum alloy was welded. The trials were carried out using laser leading configuration. A new generation of high power fiber laser was used. The experimental trials included process parameters such as laser power, welding speed and arc current. Microstructure, microhardness and weld appearance were analyzed. The experimental results showed that laser leading configuration produces full penetration for some welding parameters. The obtained results worth a larger investigation based on the experimental design technique.

Abstract: Friction Stir welding has been attempted to study the feasibility of FSW between aluminium sheet (AA 6061) of 2 mm thick and Zinc coated steel (HIF-GA) sheet of 1 mm thick in lap joint configuration. The interfacial area of dissimilar welds has been analyzed by XRD, EPMA,TEM with EDS and nano indentation technique to identify the IMC distribution pattern depending on the combined effect of rotational speed and travel speed as well as the effect of energy and thermal cycle. The average joint strength is significantly influenced by the thermal cycle, respective torque and combined effect of rotational speed and travel speed as well as energy input. Improved joint strength between Al and coated steel could be obtained within a combination of rotational speed and travel speed as well as energy input. Force and torque response during FSW have been analyzed in terms of parameter optimization and joint performance.

Abstract: Friction stir welding processes involve many variables. Engineers and operators often find it difficult to effectively design or control it. The objective of this work is to develop a friction stir welding platform of thin plates to improve welding quality and to increase production efficiency. The study is conducted by using finite element modeling and temperature field analysis technology to obtain optimization parameters, and using virtual instrument, multi-sensor data fusion to monitor the force of the stirring spindle. Experiment results show that the developed platform can reach the requirements of processing quality and is cost-effective.

Abstract: Laser molten cutting silicon wafer was focused more recently, but this method has the material loss disadvantage. So this paper indicates the finite element simulation and experiments of cutting silicon wafer with YAG laser induced thermal-crack propagation. A theoretical model of a thermal laser shock method for separation of the silicon wafer is developed, and the fracture propagation mechanism is studied by the stress fields using finite element software ABAQUS. Optical microscope and laser scan confocal microscope (LSCM) photographs of the separation surface and path are obtained to examine the cutting quality. The impact of technological parameters on the cutting quality is studied and the optimum processing parameters are presented in the paper.

Abstract: In present paper, sensitivity study on parameters for fatigue-creep model of stainless steel materials has been carried out. An analytical model has been established to predict fatigue-creep life of AISI347 stainless steel. Manson’s Universal Slopes equation has been used as an empirical correlation which relates fatigue endurance to tensile properties. Different creep prediction models have been studied in order to correlate the results of shout-time elevated temperature tests with long-term service performance at more moderate temperatures. Comparison between the different creep prediction models and experimental results were carried out for a range of stresses and temperatures. A linear damage summation method has been used to combined fatigue and creep. The results of sensitivity analysis indicate that strain range and temperature have very significant influence on creep-fatigue life estimation.

Abstract: The box body drawing process is prone to breakage defect. Using finite element analysis software Dynaform5.7, the box part in deep drawing process was simulated. The friction coefficient was observed to change between sheet metal and die. Analysis of sheet metal forming limit and wall thickness distribution，therefore came out with the following conclusion：box deep drawing is affected by the lubrication , when the friction coefficient is lower than 0.17, Lubrication can effectively prevent the box shaped parts from cracks. At the same time, the research still is developing a new drawing.