Papers by Author: Ke Lu Wang

Abstract: In order to reveal the effect laws of boosting velocity on forming quality of tube bending. A three dimensional (3D) elastic plastic finite element (FE) model of whole process of high-strength TA18 tubes in numerical control (NC) bending was established based on the FE code of ABAQUS, and its reliability was validated by using the experimental results in literature. Then, the effect laws of boosting velocity on deformation behaviors of high-strength TA18 tubes in NC bending were explored with respect to multiple defects such as wall thinning, wall thickening, cross section deformation and springback. The results show that wall thinning ratio decreases with the increasing of boosting velocity; wall thickening ratio increases with the increasing of boosting velocity; cross section deformation ratio decreases with the increasing of boosting velocity; springback decreases slightly with the increasing of boosting velocity.

Abstract: Using the method of expanding diameter in low temperature and water bath heating, this paper studied the effect of pre-deformation strain on shape memory recovery characteristics of Ni₄₇Ti₄₄Nb₉ alloy Φ8 mm pipe joint. The results showed that the transformation hysteresis was relative stable along with the pre-deformation strain more than 12.1%, which was 130°C. And the radial recoverable strain got maximum value 8.4% when the pre-deformation strain was in 10.8%~12.5%. But the radial recovery rate of inside diameter declined smoothly with the pre-deformation strain. Systems considering the three parameters of transformation hysteresis, recoverable strain and strain recovery rate, it seemed the excellent predeformed strain for Ni₄₇Ti₄₄Nb₉ alloy Φ8 mm pipe joint was just in 12%~17%.

Abstract: Cr/NbCr₂ alloy containing with 91at.%Cr and 9at.% Nb was prepared by mechanical alloying and hot pressing .Then it was annealing at 1200°C for10h, 30h,50h,100h ,respectively in vacuum condition. The results show that the relative density of Cr/NbCr₂ alloy increases slightly with the annealing time. Meanwhile, Vickers hardness of Cr/NbCr₂ alloy decreases with the annealing time. After annealing at 1200 °C for 100 h, the relative density and Vickers hardness of Cr/NbCr₂ alloy vary from 98.9% to 99.7% and 5.6 GPa to 3.78 GPa, respectively. Due to the good plasticity of chromium solid solution, obvious plastic deformation appears during room temperature compression tests. After annealing at 1200°C for 10h, the compression properties of Cr/NbCr₂ alloy, such as compressive strength, yield strength and strain, get the maximum value.

Abstract: Based on Deform-3D software, a 3D rigid-plastic FE model of forging forming process was established, then simulation analysis effective strain distribution, temperature distribution and load-stroke curve of three kinds of intermediate slabs (S1,S2,S3) in forging process. The results show that the optimized intermediate slab (S3) of effective strain distribution and temperature distribution is most homogeneous. And the maximum load force is minimum, the Shapes and dimensions of forging reach the preset value.

Abstract: Investigation of mechanical state of shape memory alloy pipe-coupling had an important significance in engineering field. Theory of plastic deformation was used to analyze the coupling force in the tube connecting process of NiTiNb shape memory alloy, in this paper. Based on the analyzed results a mechanical modeling and formula calculation were carried out, the radial pressure of the SMA tube was calculated, in this paper. The results show that, when the temperature doesn’t reach to contact temperature, the pipe coupling of TiNiNb shape memory alloy has no radial pressure; when the temperature reaches to inverse martensite phase transformation temperature, the radial pressure increases; with the decreasing of temperature, the radial pressure increases a little. The radial pressure and push-out force increase with the increasing of the wall thickness. Thus, to improve the strength of connection, the wall thickness of pipe coupling can be properly increased.

Abstract: Two-phase titanium alloy sample which initial microstructure is equiaxed have been tested by the Gleeble-3500 thermo-analogue machine with the isothermal and constant strain rate, the constitutive relationship of the titanium alloy was constructed by analyzing true stress-strain curve under different hot deformation conditions and considering the effect of the strain rate, deformation temperature and strain on flow stress synthetically. Error analysis shows that the constructed constitutive relationship has good accuracy, in the range of 900 ~ 1150 °C the error is less than 10% of the data points are accounted for 97.4% of all data points, can conform the requirements of plastic processing.

Abstract: Based on the nonlinear FE platform ABAQUS, an elastic plastic 3D-FE model of 0Cr21Ni6Mn9N stainless steel tube was established to simulate the whole process, and its reliability was validated by experiment. Using the model, the effect of bending speed on forming quality was studied and the influence laws of bending speed on wrinkling wave ratio, wall thinning, cross section deformation and springback angle were revealed. The results show that the wrinkling wave ratio and springback angle decrease with the increasing of bending speed, while the effect of bending speed on wall thinning and cross section deformation are not significant. The maximum cross section deformation degree presents in the vicinity of the bending angle 30° along the bending direction and its position is almost unchanged with the variation of bending speed.

Abstract: Using the method of expanding diameter in low temperature and water bath heating, this paper studied the effect of pre-deformation temperature on shape memory recovery characteristics of Ni₄₇Ti₄₄Nb₉ alloy Φ16 mm pipe joint. The results showed that the transformation hysteresis and the radial recoverable strain were relative stable along with the addition of pre-deformation temperature, which were 122°C±4°C and 7.1%±0.3% respectively. Moreover the radial recovery rate of inner diameter declined smoothly with the addition of pre-deformation temperature. Systems considering the three parameters of transformation hysteresis, recoverable strain and strain recovery rate, it seemed the excellent predeformed temperature for Ni₄₇Ti₄₄Nb₉ alloy Φ16 mm pipe joint was in-65~-70°C.

Abstract: The effect of tempering temperature on the microstructures and mechanical properties of a microalloy low carbon bainitic steel was investigated by microscopic analysis and testing of mechanical properties. The results show that the microstructures of the tested steel primarily consists of lath bainite, granular bainite, quasipolygonal ferrite and little acicular ferrite at different tempering temperatures. With the tempering temperature increasing, the proportion of lath bainitie decreases, while the volume of granular bainite and quasipolygonal ferrite increases. At the tempering temperatures of 550-650°C and tempering time of 1 hour, the steel was mostly composed of granular bainite, quasipolygonal ferrite and a little lath bainite, which a good combination of strength and toughness can be obtained.

Abstract: Optimization and design for shape and size of pre-forging with numerical simulation have some advantages compared with the conventional methods. The optimization object is the pre-forgings of an aircraft wheel hub. A commercially available software DEFORM 3D is used for the finite element method (FEM) simulation of the forging process of the aircraft wheel hub. The pre-forgings with three different shapes and sizes were used for numerical simulation. The effects of shape and size of the pre-forging on mould filling, forging load, effective strain and effective stress were analyzed. Finally, the suitable shape and size of the pre-forging were obtained based on the numerical simulation results.