Ke Lu Wang

Calculation of the Pull-Out Force of Ni47Ti44Nb9 Shape Memory Ally Pipe Coupling

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.

Effects of Annealing on Microstructure and Phase Transformation Temperature of NiTiNb Shape Memory Alloy after Equal Channel Angular Pressing

The effect of annealing temperature（300-600°C）on the microstructure and transformation temperature of NiTiNb shape memory alloy rods deformed with equal channel angular pressing（ECAP） method was analyzed. The results show that the hard brittle phase （Ti,Nb）2Ni was decreased after ECAP. With the rising of annealing temperature, the number of β-Nb phase increase while eutectic declines. The DSC analysis shows that the martensite and reverse transformation temperature increase with annealing temperature. After annealing with 500°C, the martensite/austenite transformation starting temperatures rise to -64.6°C and -30.1°C, respectively.

Effect of Boosting Velocity on Forming Quality of High-Strength TA18 Titanium Alloy Tubes in Numerical Control Bending

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.

Study on Hot Deformation Behavior of a New Titanium Alloy

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.

Intermediate Slabs and Optimization in Forging Process of Balance Elbow by FEM

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.

Influence of Predeformation Temperature on Recovery Performance of Ni47Ti44Nb9 Alloy Φ16mm Pipe Joint

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.

Effect of Tempering Temperature on Mechanical Properties and Microstructures of 800MPa Microalloy Low Carbon Bainitic Steel

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.

Study on Dynamic Recrystallization Behavior in Deformed Austenite of 52100 Steel by Using JMAK-Model

A Johnson-Mehl-Avrami-Kolmogorov (JMAK)-model was established for dynamic recrystallization in hot deformation process of 52100 steel. The effects of hot deformation temperature, true strain and strain rate on the microstructural evolution of the steel were physically studied by using Gleeble-1500 thermo-mechanical simulator and the experimental results were used for validation of the JMAK-model. Through simulation and experiment, it is found that the predicted results of DRX volume fraction, DRX grain size and average grain size are in good agreement with the experimental ones.

The Microstructure Evolution and Twinning Characterization of AZ31 Mg Alloy Sheet in Low-Temperature Bending Process

The relationship among stress, cavities and twinning in the room-temperature bending process of hot-rolled AZ31 Mg alloy sheet was researched. It can be seen that the mount of twins which was tightly affected by stress value increases with the distance to press point. Otherwise, the cavities and twinning which seem totally independent, in fact affect with each other. Some cavities were hindered by twins and can not further grow up. Then, the relationship between slip and twinning was also roughly discussed. The dislocation lines in twins can be thought to release the stress focus and were beneficial for deformation.

Simulation of Dynamic Recrystallization for Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy in β Processed Using Cellular Automaton

The cellular automaton (CA) method coupling fundamental metallurgical principles was used to simulate the dynamic recrystallization (DRX) behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy in β processed. Using physically based rules for the simulation of nucleation and growth phenomena of dynamically recrystallized grains. The effects of hot deformation temperature and true strain on the DRX characteristic of the alloy during β processed was studied, and the results compared with experiments. The predictions show very good agreement with the experimental results for the alloy.