Abstract: The growth mechanism of ECCS was investigated by means of metallurgical microscope, SEM and XPS. The results show that the different modes of annealing and rolling have a remarkably effects on the surface morphology and grain size of TFS products. Compact surface Cr-coating of BA material with low porosity the grains are larger and coarser in comparison with that of CA material, while the evident microcracks are found in the surface Cr-coating of DR material. The chemical compositions of ECCS oxide film on steel mainly consist of CrOOH or Cr(OH)3 as the main composition, plus Cr2O3 in definite proportion and a small amount of H2O. Cr(OH)3 is mainly formed from cathodic films generated in the electroplating process. CrOOH as the intermediate resultant was formed in process of Cr(OH)3 loss water to generate Cr2O3.
Abstract: Loading path is one of importance factors that influence the formability of sheet forming process. In this study, the effect of punching speed loading paths (PSLP) on forming and spring-back processes of TRIP (transformation induced plasticity) steel has been investigated. Four kinds of loading paths with three punch speeds are introduced to verify the cup drawing and U-channel spring-back processes based on a constitutive model accompanying the strain-induced martensite transformation. The results show that higher punch speed results in the thickness uniformity of drawing cup and the spring-back angle of stamping U-channel increased with the same loading path. Furthermore, a given loading path (C4) not only increases the minimum thickness of cup but also decreases the spring-back angle of U-channel.
Abstract: The Reduced Modulus value for the bonded Au ball bond that have undergone three different time intervals of high temperature storage (HTS) have been obtained by using nanoindentation test. Twelve indentations have been made at three different locations (Au, IMC and Si area) across the bonded ball bonds to evaluate the variation of Reduced Modulus with the location of indentation. It was shown that the Reduced Modulus value for the indentations at IMC area is increased with the increment of HTS time interval. It was also observed that the Reduced Modulus at the Au area was increased with the increment of the HTS exposure time. No particular pattern was noted to describe the changes of Reduced Modulus with the location of the indentations that have been made. It was also found that the average Reduced Modulus for Au obtained through nanoindentation with value of 107 GPa has higher value compared to that of the Young’s modulus value obtained through actual tensile test with value of 79 GPa.
Abstract: Firstly, the geometry condition of useful wrinkles during the hydroforming of double-cone tube was given. Then the stress condition of useful wrinkles was given by formula between the parameters of wrinkles shape at the end of axial feeding and internal pressure, hoop stress and axial stress. The analytical results were compared with the FEM analysis and experiments results. The results show that the useful wrinkles must meet both the geometry condition and the stress condition. The geometry condition of useful wrinkles is that the area of arbitrary length of wrinkles is a little smaller than the area of corresponding die cavity. The stress condition of useful wrinkles is that shape parameter G is not smaller than the radius R at the top of middle wrinkle. That means the increment of thickness strain dεt is positive and no thickness thinning will occur during the calibration. When the wrinkles didn’t match geometry condition, the dead wrinkles or bursting will take place. And when the wrinkles didn’t match stress condition, the bursting at top of middle wrinkle will occur during the calibration.
Abstract: The Nd:YAG laser welding experiments of Hastelloy C-276 was presented and the results of experiments were discussed which reflect the rise of electric resistivity of the sample. In addition, a mathematic model of 2-D nonlinear eddy current field for motor of the nuclear reactor coolant pump with the Hastelloy C-276 can was simulated which provides the concrete effect of electric resistivity change on the eddy current losses of cans. It was found that the eddy current losses of the motor can were decreased as the increase of electric resistivity of can. Then, the advantage of laser welding on the molding of motor can was discussed which not only does not destroy the electric performance of Hastelloy C-276 but enhances it and declines the eddy current losses of can forming with it.
Abstract: A new constitutive model for semi-solid composites forming was derived with analyzing constitutive relationships of semi-solid metal and composites forming. Parameters in the constitutive model were determined by the multiple nonlinear regression method. A constitutive relationship of semi-solid SiCp/AZ61 composites thixotropic plastic forming was proposed. The calculated results were good agreement with the experimental ones. The proposed constitutive model has the higher forecast precision and practical significance. The construction of constitutive model provides references for the thixotropic forming theory, simulation and technology.
Abstract: The objective of this paper is to study the cutting forces in hard turning T250 steel with CBN tools. Experiments based on the Box-Behnken design were conducted to develop the cutting forces models by response surface methodology (RSM). Significance tests of the model are performed by the analysis of variance (ANOVA). It is also discussed the effects of cutting parameters (cutting speed, feed rate and depth of cut) on the cutting force components. The results show that the models can fit experimental data via analysis of variance. The most important cutting parameter is depth of cut, followed by feed rate, while the effect of cutting speed can be neglected. Compared to cutting force and feed force, thrust force is the largest. In addition, the cutting forces generated by the uncoated tool are smaller than by the coated one due to tool wear.
Abstract: Energy saving in manufacturing is the key to reduce energy consumption of unit GDP. Forming equipments are one of the biggest energy consumers. The basic reason of high energy consumption and low efficiency for current forming equipments is the mismatch between uncontrollable driving characteristics and the variable loads in forming processes. Complex transmission and control mechanisms are needed, wasting a lot of energy. The basic principles of driving were put forward to realize energy saving for forming equipments: faster in virtual strokes, slower in working strokes, stop when idling and recycling excessive energy. The servo driving based on large AC servo motors can make the driving and forming loads match each other well, realizing not only high automation and intelligence, but energy saving greatly as well. Theoretical analysis and experiments showed that by adopting AC servo driving the crank presses, hydraulic presses and screw presses could get the energy saving results of 25-70%.
Abstract: Powder metallurgy (PM) nickel-based superalloy is regarded as one of the most important aerospace industry materials. A series of turning tests in a wide range of speeds with different inserts were carried out to select the proper tool material. Then, the effect of cutting parameters on the cutting force, cutting temperature and tool wear was investigated for the selected insert. The effect of cutting parameters on the tool wear was examined through SEM and TEM micrographs. The experiential functions of tool life, cutting force and cutting temperature were developed. Finally, the cutting parameters in PM nickel-based superalloy dry turning were optimized based on tool life-efficiency contour analysis. The present approach and results will be helpful for understanding the machinability of PM nickel-based superalloy during dry turning for the manufacturing engineers.
Abstract: Setting up an adaptable and flexible simulation model for steel-making process is very important to improve production system design and manufacture automation. To assist the decision-makers in steel-making plants, the Logistical simulator for steel-making has been developed using em-Plant software. The Simulator can be used to rapidly model any steel plant, including the movement of the operation equipments and the changes of production parameters. With the help of Simulator, the influences of lay-out changes, process parameters, and changes in planning could be revealed vividly, and the realistic production planning could be created. Results include production Gantt charts, display of cranes track, utilization figures and production statistics. Simulation cases show that the simulator is valid for simulating different steel-making processes, and production states on different conditions can be investigated by using this model.