Papers by Author: Zhong Tang Wang

Abstract: The curves of true stress-strain of AZ80 Magnesium alloy had been tested with thermal simulation experiment, at the conditions of the experimental temperature being 260°C~ 410°C, and strain-rate being 0.001~ 10s-1, and the deformation degree being 50％. According the Arrhenius equation, a kind of constitutive equation of AZ80 Magnesium alloy which considered the strain had been put forward, and the relative errors between calculation results by the stress-strain model and experiment results are less than 10.5%.

Abstract: Effects of hot extrusion processes on grain size of ZK60 alloy tubes was researched by combining numerical simulation with experimental research. The results show that grain size varies inversely as extrusion ratio and extrusion speed, with extrusion temperature being constant. In order to get the finer and homogeneous microstructure, higher extrusion ratio, higher extrusion speed and lower billet temperature should be chosen in the equipment's rated load. Isothermal extrusion is conducive to tube forming , and the smallest grain size and the better microstructure can be obtained at temperature of 300°C when other deformation conditions are constant.

Abstract: ] Theoretical calculation formula of punch force during tube extrusion has been proposed by means of slab method. On the basis of theoretical and experimental study, it is found that theoretical results of extrusion force given by the calculating formula approached to that of the experiment, and the relative errors are less than 20％. It is also found that the extrusion force is closely related to deformation temperature, lubricant and the ratio of extrusion. The calculating formula of extrusion force is given by considering the factors which are the conical angle of die, and the friction coefficient between the deformation zone and the extrusion container, and the friction coefficient between the undeformed zone and the mandrel. Key Words: Tube, Extrusion, Force, Physical model

Abstract: Abstract: It had been put forward that a new method to establish material constitutive model based on extrusion test, which was that the material constitutive model was determined with the Arrhenius equation according to the extrusion test data. The tube extruding test of supper-alloy Inconel625(IN625) had been done on 16300kN extrusion machine. According to the extrusion test data and the Arrhenius equation, it had been determined that the constitutive model of supper-alloy IN625 based on extrusion test, and the relative errors between calculation results of the model and experiment results are less than 7.8%. The suitable conditions of the constitutive model of supper-alloy IN625 are that the temperature being 1150°C～1200°C, and extrusion speed being 15～60mm/s, and strain-rate being 1.86～7.44.

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%.

Abstract: Magnesium alloy tailor-welded blanks(MTWBs) of AZ31 and AZ80 sheet had been manufactured by gas tungsten arc welded(GTAW), which the thickness were 0.8mm. The welding properties of Magnesium alloy sheet had been analyzed, and the technology parameters of GTAW were determined by experiment study, which was that welding thread being Φ2.0mm, welding electricity 50A, welding voltage 9V, welding rate 12—13cm/min. The research results presented that the grain in welded seam was isometric crystal, and the grains were branching crystal in heat-affected zone (HAZ). For MTWBs of AZ31and AZ80 sheet which the thickness was 0.8mm, the forming parameters were that the forming temperature of AZ31 being 190-220°C, and forming temperature of AZ80 being 310°C-350°C, and the temperature of tools is 180°C~200°C.

Abstract: The constitutive equation of Ti-6Al-3.5Mo titanium alloy had been researched with thermal simulation experiment. The experimental temperature was between 1030°C and 1120°C, and strain-rate was between 0.001 and 1.0, and the deformation degree was 50％. According to Arrhenius　equation, a kind of constitutive equation of Ti-6Al-3.5Mo titanium alloy had been put forward. Compared the calculation results by constitutive equation with experiment results, the relative errors were less than 12%. For Ti-6Al-3.5Mo titanium alloy, strain-rate sensitivity coefficient being m=0.1688, and temperature sensitivity coefficient being s=10233.

Abstract: Recently, physical simulation has played a more and more important role in modeling hot forming process. However, difficulty still existed in simulating real hot forming process using physical simulation results directly for obvious difference in deformation history between physical simulation condition and real hot forming process. In this work, difference between physical simulation and real hot forming process was discussed and a mathmatical approach was proposed to model real hot forming process using physical simulation results. The main consideration of the method was to put physical simulation results into differential forms in order to take count in the contribution of deformation history (temperature and strain rate) at each incremental step. For the application of the approach, modeling of material flow stress, dynamical recrystallization including critical condition and recrystallziaton fraction, damage evolution and fracture criteria during real hot forming process were presented as examples, although experimental support was still needed for validation and further application.

Abstract: Press forging of magnesium alloy AZ31 sheets was investigated in this paper. The typical component, a rectangular box with bosses at the bottom was formed. The experimental results show that the magnesium alloy sheets are suitable for press forging. The bosses and the rectangular box can be formed synchronously for 2 mm or 3 mm thick sheets when the punch temperature is 250 °C. By experimentation and numerical simulation, the effects of process parameters on material flow were analyzed, including the temperature, the die shape, the blank size, the lubrication manners and the friction condition.