Papers by Author: Shi Hong Zhang

Abstract: Ultra-thin Cu/Al clad strip with 0.12 mm thickness was successfully fabricated by accumulative roll bonding and the interfacial structure of Cu/Al clad strip has been characterized by means of optical microscope (OM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and also X-ray diffraction (XRD). The intermetallic phases and their formation sequence at the interface was experimentally verified. And the growth kinetics of each phase was also modeled considering the diffusion controlled reaction mechanism. The effect of interfacial compounds on tensile fracture of ultra-thin Cu/Al clad strip was also studied. The obtained results indicate that, intermetallic compounds formed in the interface region of ultra-thin Cu/Al clad strip within the experimental condition are confirmed to be Al₂Cu, Al4Cu9 and AlCu in sequence. The calculated activation energies for the growth of Al₄Cu₉, AlCu and Al₂Cu are 101.45、114.30 and 95.15 kJ/mol, respectively. The major cracks propagate through the AlCu intermetallic layer and the Al₂Cu / AlCu interface.

Abstract: A fast optimization approach is demonstrated for design optimization of the multi-pass wire drawing process with the multi-objective genetic algorithm, and with the aims at minimizing both power consumption and temperature, via optimizing the process parameters involving pass number, pass schedule, die angle, bearing length and loops on capstan etc. A jump fitness function and a penalty fitness function are proposed for the survival of good designs and killing the bad designs which temperature, die wear factor, delta factor, or ratio of drawing stress to yield stress exceed the limits during optimization. The numerical examples show that the optimizer with the penalty fitness function, when its parameter n ranges from 1 to 2, presents the best performance in finding the minimum power consumption with a limit in temperature. Compared with a reference design, a significant reduction in the total power consumption about 300W, with the well control in temperature, delta factor and die life, has been achieved by the optimization. The penalty fitness function presents the better performance in the reduction of the iteration generations and computational cost to the jump fitness function.

Abstract: The effects of key process parameters including initial lengths of tube blank, forming velocity and loading paths on hydroformability of stainless steel tubular components with rectangular section were systematically investigated. The results showed that sufficient axial feed must be given before the tube contacting the surface of die in order to prevent the excessive thickness thinning, especially for longer tube blank. The lower loading velocity led to enhanced formability. It is more important that pulsating loading path observably improved the formability of 304 stainless steel.

Abstract: It had been studied that thermal deformation properties of super-alloy Inconel690(IN690) by thermal simulation on Gleeble 3800 Simulator, which the ranges of temperature was 1000～1200°Cand strain rates was 1.0～80/s. According to the experiment data, the critical conditions of super-alloy Inconel690 had been researched by strain hardening rate. Zener-Hollomn parameters (Z) had been introduced into establish the critical conditions of dynamic recrystallization, such as critical strain and critical stress and peak strain. The results showed that the critical strain model which established using strain hardening rate was in good agreement with that of Sellar’s model.

Abstract: The effect of δ phase content on the hot deformation behavior of alloy IN718 has been investigated using isothermal compression tests. The results indicated that the δ phase has a significant effect on the deformation behavior of alloy IN718 during hot working. After the peak stress, the decreasing speed of the stress raises as the increase in the δ phase content. The deformation activation energy for alloy IN718 increases with the raise of the δ phase content. And the peak strain for the alloy decreases with the increase of the δ phase content, which indicates that the δ phase can stimulate the occurrence of dynamic recrystallization during hot working.

Abstract: It had been studied that thermal deformation properties of AerMet100 steel (AMT100) by thermal simulation on Gleeble 3500 Simulator, which the ranges of temperature and strain rates were 900～1100°C and 0.01～10/s. According the experiment data, the parameters of thermal deformation was calculated, in which the activation energy is 261.2KJ/mol. The strain-rate sensitivity coefficient is m=0.0998, and temperature sensitivity coefficient is s=7912. The relationship among peak stress and deformation temperature and strain rate was established. And the ranges of temperature and strain rates were 900～1100°C and 0.01～10/s, and the relative errors of calculation results by the stress-strain model were less than 11.3%.

Abstract: Deep drawing of square boxes of tailor-welded blanks (TWBs) was studied by experiment and simulation in this paper. When the tailor-welded square boxes with different thickness was drawn to square boxes, the weld seam moved towards the thick part on the bottom and towards the thin part on the wall of square boxes. If the blank-holder force was very small, the wrinkling will happen on the thin part. If the blank-holder was very large, fracture will occur on thin part. Draw beads and non-uniform blank-holder force were investigated to control the deformation of the TWBs workpieces in this paper. When using the draw beads during TWBs drawing, using draw beads in both sides was better measures to control the movement of the weld seam. When non-uniform blank-holder force was used to control the movement of weld seam of tailor-welded blanks, it should be choice that the non-uniform blank-holder force on thick part was a half of that on thin part. It was shown that draw beads give better effects on the control of TWBs drawing than other methods. The variation of thickness was little in the bottom, and the variation of thickness was obviously in the corner of bottom. The maximal variation of thickness of TWBs workpieces on different area was both about 90.1%.