Advanced Materials Research Vols. 418-420

Abstract: The microstructure and carbide precipitate of simulated coarse grain heat affected zone(CGHAZ) in modified high Cr ferritic heat-resistant steel at different cooling rates have been investigated by means of thermal simulator, optical microscope, SEM and TEM . It was found that the microstructure of CGHAZ of testing steel was mainly lath martensite and δ-ferrite under the different welding thermal cycles. However, the prior austenite grain size reduced with increasing the cooling rate. Furthermore, with increasing the cooling rate, the amount of carbide precipitate inside laths of martensite increased, and the size and morphology of precipitates have changed from elongated and coarse to needlelike and fine.

Abstract: In upsetting forging process of the crank of crankshaft the defects such as lap and caving probably occurs since the bending and upsetting is not in good coordination. In this paper, aiming at 305 crankshaft for marine engine, the coordinative relation between bending and upsetting was thoroughly studied based on 3-step crank upsetting forging approach, i.e. bending-upsetting, upsetting and finish forming. Numerical simulation was carried out to find the reasonable stroke matches of bending and upsetting and physical experiment of using lead sample reduced at the ratio 1:6 in size was conducted to verify the match scheme gained from numerical simulation. The result found from numerical simulation is in good accordance with the one gained through experiment. The work in this paper provides theoretical basis for practice of upsetting forging technique of crank.

Abstract: Silicon is widely used as substrate material for the fabrication of micro-electro and micromechanical components. Since silicon is very brittle, how to cut it into complex shapes remains a hot topic. Thanks to the small spot diameter, laser cutting is a promising alternative. However, during laser cutting, different kinds of defects can be generated depending on the beam-material interaction phenomena (ablation, melting, etc). Molecular Dynamics simulation is an effective way to study the beam-material interaction phenomena. Lots of work has been done to develop MD models of laser ablation of silicon. However, due to lack of support from high performance parallel simulation platform, the scale of the molecular systems is limited. This paper presents a component-based parallel simulation platform Sensing-VISICOM, for large scale molecular dynamics simulation. To test its runtime performance, a molecular system of femtosecond laser ablation of silicon is designed and implemented under Sensing-VISICOM. The results of the simulation show the platform can scales well to millions of atoms.

Abstract: The response surface model is established through application of surface response method, then the main impact factors of ceramic machining are determined, and the process parameters are optimized. The mechanical machining technology of ceramic materials is analyzed, and the corresponding optimal parameters are proposed by cutting tool material, rake angle, clearance angle and edge angle, and three cutting elements as cutting speed, cutting depth and feed. Accord to the optimal parameters, high efficiency, good quality and low cost results can be achieved to machine ceramic parts.

Abstract: Chilled cast iron is a typical hard and brittle material, often be used to make all kinds of roller. According to chilled cast iron machining characteristics, cutting tool material should has high red hardness, good impact resistance and wear resistance, high bending strength and large thermal conductivity coefficient. For determination of the suitable cutting parameters in machining chilled cast iron by PcBN cutting tools dry turning, the samples which are prepared to be used in the experiment, 200 mm in length and 120 mm in diameter, are machined in lathe. During experiments, cutting tool parameters and dry turning parameters, such as edge chamfer width and angle, feed rate, cutting speed and cut depth are investigated. The suitable edge chamfer width and angle, cutting speed and feed rate are determined according to cutting tool life and cutting tools flank wear. Finally, edge chamfer width of 0.2 mm, edge chamfer angle of -15 degree, cutting speed of 90 m/min, feed rate of 0.15 to 0.2 mm/rev and cut depth of 0.3 mm gave the satisfied results.

Abstract: In the present study, AA3003, AA6061 were selected as the object to investigate the mixing condition and mechanical property of the dissimilar Friction Stir Butt Welding joint. Experimental results showed the two Al alloys of the joint were interwoven together in the river shape with an obvious gradient. When ω/v was moderate, the two kinds of materials can be better mixed together and improved the mechanical property. Meanwhile the bonding was complete under all the welding conditions. The joint coefficients could all achieve more than half of those of the base material and the best was 96% (ω=1541rad/min, v=142 mm/min).

Abstract: The exploitation of Tube Hydro-forming (THF) experimental device plays an important role on the development of THF technology. In this paper, some representative experimental devices are introduced, including device with outside pressure source and device with internal pressure source. The working principle, technical characteristics, sealing mode and pressurization way are compared and analyzed. Meanwhile, the development trend in exploitation of the test device is envisioned.

Abstract: Based on the engine lathe, the vibratory turning experiment system was built up with low frequency of the mechanical vibratory device. Orthogonal experiment was carried out for the findings of the chip configuration, chip breakage, and the surface roughness with relationship of the cutting engagement especially the combination of the vibratory frequency, amplitude, and the feed and cutting velocity. Regressive analysis was done for the empirical formula of the roughness with parameters of vibratory turning engagement. From the experiment it has been shown that the higher the frequency is in vibratory turning, the smoother the machined surface is, other conditions being equal. The surface roughness increases with the feed, at the same frequency. The cutting tool was still smooth on the rake and flank and along the cutting edges all the time in vibratory turning. Because of the vibration and the lubrication the BUE can hardly be built up, being good for the surface integrity.

Abstract: The experimental investigations on resistance spot welding of 201 stainless steel are presented. Experiments are carried out to study the influence of spot welding parameters (electrode force, welding current and welding time) on the tensile shear load and the diameter of nugget, based on an orthogonal test and analysis method. The optimum parameters are as follows: electrode force is 3600N, welding current is 6400A and welding time is 8 cycles. The maximum tensile shear force is up to 8920N.The microstructure of spot weld is columnar crystals in the nugget and equiaxed grains around periphery induced by non-equilibrium freezing. And the heat input has great influence on the welding defects which can cause joint quality degradation.

Abstract: The influence of hardening index n value at different holding forces on LDR of cylinder cup was simulated by the finite element software PAM-STAMP 2G. The results showed that the limit drawing ratio of the sheet metal decreased with the increase of the blank holder force. There was little influence of hardening index n value on the limit drawing ratio at smaller blank holder force. The influence of hardening index n value on the limit drawing ratio increased with the increase of the blank holder force. The hardening index n value could be increased to increase the limit drawing ratio when the blank holder force is large.