Papers by Keyword: Coupled Thermo-Mechanical

Abstract: The governing equations and the finite element model for the coupled thermo-mechanical multi-pass vertical-horizontal rolling process of a zircaloy strip are established. Considering the temperature-dependent and strain rate-dependent constitutive relation of zircaloy, the numerical simulation of the three-pass V-H rolling process is realized by the coupled thermo-mechanical dynamic explicit finite element method. The computational results such as the plastic deformation, the size variations and the temperature variations in three passes are discussed. The research results indicate that edging by vertical roller benefits improving the sizes of the strip and the temperature variations are rather obvious during the three-pass hot rolling process. The research provides experience and foundations for the FEM simulation of the hot rolling process of composite slabs for nuclear fuel elements.

Abstract: Hot stamping of the ultra high strength steel (UHSS) was studied to meet the requirements of lightweight of automobile. The coupled thermo-mechanical model for hot stamping was established with ABAQUS. Initial temperature of tools (die, punch, blank holder) and stamping speed were studied to insure the impact on the thickness, stress and strain of blank. It shows that punch fillet area is easy to crack. With the temperature of tools increasing, the sheet minimum thickness increases first and then decreases. With the increase of punch velocity, the sheet minimum thickness increases. Compared with the initial temperature of tools, punch velocity has a greater impact on the thickness. The simulation results are in agreement with the experimental results and provide a theoretical basis for the practical stamping process.

Abstract: The hot power backward spinning(HPBS) of the high strength cast aluminums (HSCA) cylinder is a complex metal forming process. To analysis the plastic deformation of HSCA cylinder in HPBS process, a 3D coupled thermo-mechanical FE model of the process was built under the ABAQUS/explicit environment based on the solution of several key techniques, such as heat boundary condition treating, material properties definition, ALE adaptive meshing technology, etc., and verified by theoretical evaluation. Then simulation and analysis of HPBS of the process were carried out. The results show that the strain gradient which leads to the serious inhomogeneous deformation is produced in the thickness direction of the workpiece during the process.

Abstract: Ring parts with small-hole and deep groove such as duplicate gear and double-side flange, are widely used in various engineering machineries. Three-roll cross rolling (TRCR) is a new advanced plastic forming technology for the processing of rings with small-hole and deep groove. In this paper, a 3D coupled thermo-mechanical FE model for TRCR of ring with small-hole and deep groove is established under ABAQUS software environment. By simulation and analysis, the evolution and distribution laws of strain and temperature in the forming process are revealed, and the effects of the key process parameters on the deformation uniformity are explored. The results provide valuable guideline for the technological parameter design and optimization.

Abstract: Hot-stamping molding for ultra-high-strength steel have some similarities with traditional cold-stamping molding in the aspects of molding process and die design. But due to the effect of temperature variation of blank, hot-stamping have some differences in ultra-high-strength products design, material selection and forming process design. Some special forming defects, such as local thinning, cracking and wrinkling, could appear in hot-stamping process due to these differences. In order to obtain uniform phase structure and get high-quality products, it is very important to be able to predict and control the blank temperature and the consistence of blank cooling rate. The thermo-mechanical characteristics of hot-stamping are studied with the material of ADVANCE1500 (22SiMnTiB). Based on the results of simulations and experiments, conclusion are drawn that the complexity of the product and the blank which contacts with die asynchronously causes the uneven distribution of the blank temperature. This is the key factor that leads to the poor mobility of the blank material and local thinning, cracking, wrinkling and other defects in forming process. Proper clearance between punch and die can reduce the probability of defects which could contribute to the improvement of hot-stamping process.

Abstract: Hot stamping is an innovative way to manufacture complex-shaped components of high strength steel (HSS) sheet with a minimum of springback, meanwhile, it can also obviously improve the tensile strength of the formed parts.The coupled thermo-mechanical FE model for hot stamping of HSS sheet for the B pillar was established by commercial software Pam-stamp. Dynamic explicit module was used to simulate the forming processes under different process parameters. The effects of process parameters on thinning of the blank were studied, the maximum thinning zones of the blank in hot stamping were analyzed. The results show that the thinning rates of the blank increase when the blank holder force(BHF) and friction coefficient increase, the maximum thinning zones appear at the straight wall and corner of the B pillar. The causal of blank thinning during hot stamping was analyzed. Experiments had been conducted with the process parameters obtained by simulation. The experimental and simulation results were in good agreement.

Abstract: Defects of pieces rolled by cross wedge rolling (CWR) have great effect on its practical applications. With reference to the center-pressure method used often in the forging, the effects of non-uniform temperature field on defects were studied by using the three-roll CWR tests under different cooling conditions and the coupled thermo-mechanical finite element models. The porous can be reduced or even eliminated when the billets were rolled with a controlled non-uniform temperature filed. The optimal temperature gradient was determined by FEM, which can be used in practical applications.

Abstract: Based on reviewing the applications and machining of the stainless steels, the cutting performance of the austenitic stainless steel 1Cr18Ni9Ti is analyzed through the contrastive experiments. This paper studies drilling minipore mechanics of hard-to-cut material—Austenitic Stainless Steel 1Cr18Ni9Ti by simulation and experiment, analogy results displays the trend that drill thrust, torque and temperature changed with amount of feed, it matches with test result in the same cutting condition well. The research results would be of great benefit for the selection of proper tools and cutting parameters in drilling austenitic stainless steels.

Abstract: Hot ring rolling (HRR) is a 3D unsteady-state and coupled thermo-mechanical process, the metal undergoes complicated unequal deformation and microstructure evolution. In this paper a 3D rigid-plastic and coupled thermo-mechanical FEM model for hot ring rolling was developed based on DEFORM3D platform, taking dynamic recrystallization (DRX) volume fraction, DRX grain size, recystallization volume fraction and average grain size as objects, the mechanism of material microstructure evolution and distributions in HRR process are thoroughly studied. The results show that: with the HRR progressing, the DRX volume fraction, volume fraction, DRX grain size and average grain size have the similar distributing characteristic, and the distribution zones expand from a small local area into the whole ring strip, then diffuse to the mid-layer of ring with small deformation, their distributions become more uniform. Meanwhile with increase of deformation, the values of the DRX volume fraction and recrystallization volume fraction augment, i.e. the degree of recystallization increases. The DRX grain size also augments due to local high temperature, while the average grain size decreases. In general during HRR process the distributions of DRX volume fraction, recrystallization volume fraction, DRX grain size, and average grain size are ununiform due to unequal deforming in HRR process.