Advanced Materials Research Vols. 139-141

Abstract: As tailor-welded blank having two or more sheet metal welded together, with different mechanical properties, coating and thicknesses, its yield strength and tensile strength are higher, but hardening exponent and elongation are lower than a single sheet. The different mechanical properties of substrates and weld movement have significant effects on TWB’s formability, different materials or thicknesses easily lead to uneven deformation and forming defects such as cracking, wrinkle and springback. This paper takes tailor-welded box-shaped part for example; the forming process and weld movement were simulated and analyzed. In this process, the weld type was ignored, only considering the weld-line position, using segmented blank holder to control the size of the blank holder force on both sides respectively. Three cases of sheet metal matching were carried out including: different thicknesses with same material, same thickness with different materials, and different thicknesses with different materials. Finally, some meaningful results were obtained.

Abstract: The cracking tendency of large-scale high-chromium cast iron impeller was large, and its casting production was a problem in slurry pump industry. The casting process of the largest high-Chromium cast iron impeller in China was presented in this paper. Through casting process design and alloy composition design, the produced impellers met the quality demands, such as no crack, surface smoothness and high hardness. Huazhu CAE was used to simulate the casting process and the parameters used in the simulation were introduced. The STL document used in Huazhu CAE was converted from the 3D molding of the casting process using the Solidwork software. The simulation result showed that the casting process was feasible. They have been successfully used in the dredge, New Sea lion.

Abstract: In this paper, a new precision forging technique composite processing of the moving-die forging and divided flow forging process to form the spur gear is introduced. A systematic investigation of the floating-relief method process is performed by using finite element numerical simulation. The stress distributions on the workpieces were obtained. The closer the die teeth corner is, the higher stress value results can be acquired. And the effective stress is concentrated in spur gears forging die cavity corner. It was found that the floating-relief method forging process with upper and lower convex punches control the material flow effectively and the tooth cavity is filled successfully during the performing forging and final forging. The proposed method can serve as preconditions to analyze the abrasion and fatigue of spur gears forging die. The obtained results can offer valuable guidelines for gear precision forging experiments and practical process planning.

Abstract: The process of sintering material from the powder to the liquid with high temperature and then to the continuous solid are simulated, considering the effects of heat conduction, thermal radiation, thermal convection and thermal physical parameters on temperature. The results show that the temperature gradient is larger in the front of pool, and the end of which is smaller due to the fast-moving laser beam and uneven distribution of laser energy. With the increase of scanning time, the overall temperature of substrate and powder particles is gradually rising, the heat-affected zone is increasing and the asymmetric temperature distribution has become more obvious for the heat conduction. As the pool depth is larger than the powder thickness and the pool width is larger than the scanning spacing at the current process parameters, the bond strength of layers and scanning lines is enough.

Abstract: To meet the increasing application requirements of stainless steel fibers with rough surface morphology, a self-made multi-tooth tool which can bifurcate chip during the cutting process was utilized to manufacture stainless steel fibers. The novel cutting method can achieve efficient processing of continuous stainless steel fibers with complex surface morphology. The influence of cutting parameters (back engagement ap and feed rate f ) on forming process of fibers’ surface morphology was studied. The cutting experiments were carried out under the condition of selected tool and fixed workpiece rotating speed. The results show that: the surface morphology of stainless steel fiber is simultaneously effected by ap,and feed rate f .Between them, ap has more significant effect on it. In order to obtain stainless steel continuous fibers with coarse surface morphology, the optimum cutting parameters were recommended as follows: ap∈(0.1-0.2) mm, f ∈(0.1 -0.17) mm/r.

Abstract: In the present work, the ductile fracture process of hydropiercing is simulated using Rice and Tracey ductile fracture criterion by means of the user subroutine VUMAT of ABAQUS. The simulations at different loading pressures coincide well with the experiments. Based on this criterion, the processes of hydropiercing at different technical conditions are simulated with orthogonal design and the sensitivity analysis of parameters is conducted. The sensitivity analysis shows that internal pressure plays the most important role in controlling quality of the hydropierced products, namely the sheared zone length, roll-over depth and whole coefficient Y. High pressure and better lubricant are better for all the three indexes. Large punch corner radius is better for sheared zone length and Y but worse for roll-over depth. Additionally, it is found that internal pressure and punch corner radius could be intensified each other at conditions of both larger values.

Abstract: Relationship among equilibrium moisture content (EMC), temperature and pressure was established under vacuum condition, and EMC regression equation was constructed based on experimental data, with Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) as Experimental material, and MC was measured by oven-drying method. The experimental temperature range was from 40 to 90°C at the interval of 10°C, and pressure range was from 0.02 to 0.08 MPa at the interval of 0.02 MPa. EMC Comparison of Chinese fir and paper wafer sensor showed: EMC of paper wafer sensor changed in the same trend of solid wood. A regression equation was presented and the calculated EMC value was highly correlated with experimental data. This regression equation can be used to predict EMC under vacuum, especially for automatic control system of wood drying under vacuum.

Abstract: In order to improve the flame resistance and reduce the formaldehyde emission of plywood, a multifunctional formaldehyde scavenger with flame resistance (FSFR) was prepared and used to treat plywoods bonded with high molar ratio urea-formaldehyde (UF) resin. The weight percent gain (WPG), formaldehyde emission, oxygen index (OI), and bonding strength of plywoods after FSFR treated were measured to evaluated properties of FSFR. The results showed that the formaldehyde emission of the treated plywood was 0.1-0.32 mg/L, which could meet the E0 grade requirement (<0.5 mg/L ). The flame resistance of treated plywood increased significantly and the bonding strength changed little. The formaldehyde emission decreased 96.8 % and OI increased 47.2 % and the bonding strength kept unchanged when FSFR reached 8.87 % compared with that of untreated plywood.

Abstract: Semi-solid A356 slurry was prepared by compound process, and the fractal characteristic of primary phase morphology was researched. The fractal dimensions of primary phase morphology in semi-solid A356 alloy were calculated by the calculating program written to calculate the fractal dimensions of box-counting in the imagine of morphology of semi-solid primary phase in A356 alloy. The results indicated that the primary phase morphology in semi-solid A356 prepared by compound process is characterized by fractal dimension, and the primary phase morphology prepared by the different technology parameters had different fractal dimensions. The primary phase morphology at the different position of ingot had the different fractal dimensions, which reflected the effect of solidified conditions at different position in the same ingot on the morphology of semi-solid primary phase

Abstract: Effects of different technological parameters such as stirring temperature, stirring speed and stirring time on the microstructure of semi-solid Y112 alloy were investigated using a self-developed mechanical stirring device in this paper. The results show that the higher of stirring temperature and stirring speed, the finer and more homogeneous the spherical grains, the higher the tensile strength and elongation. If the temperature is too high, the solid grains will be melted, the tensile strength and elongation will be reduced. With the increasing of stirring time, the grains firstly become fine, uniform and round, and then grow up. The tensile strength and elongation firstly increase, and then reduce.