Materials Science Forum Vols. 575-578

Abstract: The bulge test has many advantages such as large deformation range and facility of loading. But the curvature and thickness of specimens are varied at different positions of meridian, and changed with the loading, so it's quite difficult to acquire the true stresses and true strains. Fixed attention on the crown of specimens, this paper put forward an improved method of bulge test. 3D coordinates of grid points on the surface of specimens are measured on each sub-step of loading by universal toolmaker’s microscope, and then the curvatures and in-plane strains at the crown can be acquired. The influence of springback on the curvatures at the crown is taken into account using finite element methods based on MITC4 (mixed interpolation of tensorial components) shell element. Thus the relationships between equivalent stresses and strains may be established, which integrally represents the work hardening characteristics of sheet metals. Bulge tests had been done on 316L austenite stainless steel.

Abstract: The meshless methods effectively deal with large material distortion simulation. Based on the rigid (visco)plastic material model, the element-free Galerkin method (EFGM) is introduced to simulate the metal forming processes. Aiming at the volume locking and pressure oscillation during EFGM analysis, a volumetric strain rate mapping method is proposed based on pressure projection method. The releasing algorithm is established by modifying the volumetric strain rate in the functional equation. The volumetric strain rate calculated according to velocity field is mapped onto a lower-order space to reduce the number of independent discrete constrain equations. The numerical example shows that the releasing algorithm can effectively eliminate the volumetric locking and pressure oscillation without the expense of employing large support size in the rigid-plastic meshless method.

Abstract: Nowadays, 3D-FE Modeling and simulation is an indispensable method for the optimum design and precise control of radial-axial ring rolling process for its complexities. In this paper, the unique forming characteristics of radial-axial ring rolling have first been summarized, and then some key technologies for 3D-FE modeling of the process have been presented and their solution schemes have been given out, lastly the modeling and simulation of radial-axial ring rolling process have been realized using elastic-plastic dynamic explicit procedure under ABAQUS environment. The work provides an important basis and platform for the future investigations, such as forming mechanism and laws, process optimum design and precise control.

Abstract: By using 6061-T6 Aluminum alloy plate, the micro-plastic flow process of surface material induced by LSP was analyzed with FEM code ABAQUS/CAE, the change of residual stress distribution and micro-topography was shown dynamically. Based on the results of numerical simulation, factorial model of MINITAB was used to carry out response optimizer design to gain the optimum strengthening effects. After the creation and analysis of factorial design, contour plots and surface plots were output, the optimum strengthening effects were obtained by statistic results of response optimizer, and the influencing factors of correspondence were achieved. Finally, LSP experiments were carried out with the optimized laser parameters on 6061-T6 plate, good agreement was found between numerical and experiment results.

Abstract: High-speed automated systems of management and control which include mathematical models of technological processes nowadays serve as a basis in the manufacture of competitive products in different fields, including metallurgy. A reliability of such systems and reproducibility of results finally provide for the stability of complicated metallurgical processes. To secure the stability of the technological process of manufacture of high quality products and introduction of new product ranges, the issues of revamping of a Hot Rolling Mill are still one of the priorities of modernization of the JSC «NLMK» (NLMK). Commissioned at the end of the 60s, 2000 Mill during the last years was subject to fundamental modernization when new equipment and automated systems were installed to measure parameters, collect and process information. However, these means are sometimes used for a local control based on the disturbance principle to return the process parameters to the set range, while the information systems exist only for the operative registration of the production flow. This is in fact necessary, but nowadays it is evidently not enough. Especially, at introduction of end-to-end technologies of metal production. To effectively manage the quality of metal production at all stages of end-to-end technology, we witness at present a shortage not of technical means, but of artificial intelligence, that is, a set of algorithms and monitoring programs which can solve the following basic tasks: − forecasting the structure and qualities of the ready products based on the actual parameters of treatment at each process stage; − preventing adverse results of disturbances by correcting the further technological operations (regimes); − designing technologies during expansion of production range. The Lipetsk State Technical University (LSTU) jointly with the NLMK Information Technologies Department has developed a number of PC applications which have been successfully introduced at 2000 Wide Strip Continuous Mill [1]. Within the frameworks of this publication, we analyze two main systems which determine the factors of the consumer qualities of the rolled stock, namely, «Hot Rolled Stock Structure and Qualities Forecast System» and «Strip Surface Quality Control System». The applications realized in these systems have a set of their own program modules.

Abstract: The realizability for spatial structure of suspended bio-carriers should be considered in the process of structure designing. Injection molding analysis could obtain the injection performance of spatial structure, and provide the references for economic benefit of structure realization and structure optimization, so it become an important tool for structure designing and optimization. In oder to apply the injection molding analysis to the process of bio-carriers designing, three structures, multi-plane spherical structure, straight chip columnar structure, wing panel structure are designed. Their injection performances, such as best location of injection, fill time, and injection pressure are be compared, the results show that the multi-plane spherical structure has the best injection economic benefit.

Abstract: The environment and energy related problem has become one of the most important global issues in recent years. One of the most effective ways of improving the fuel efficiency of automobiles is the weight reduction. In order to obtain this goal the hydroforming technology is adapting for the high strength steel and its application is being widened. In present study, the whole process chain of chassis components (cross members) simulation and development by hydroforming technology to apply high strength steel having tensile strength of 440 MPa grade is covered. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydroformability in details. Overall possibility of hydroformable chassis parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydroforming. At the die design stage, all the components of prototyping tool are designed and interference with press is investigated from the point of geometry and thinning.

Abstract: In the environment of visual programming DELPHI there is developed the program complex enabling to make express-analysis of the picture of metal flow while forming of workpieces and to offer technological receptions for elimination of non-uniformity of shaping separate parts of workpiece, and also for decrease in the forces necessary for workpiece forming.

Abstract: This paper advances a new optimization method about material constitutive equation on the basis of physical simulation and numerical simulation results which basic thinking can be described as the following: through comparing the results of the material deformation process under actual experimental conditions and virtually simulated by the finite element numerical simulation method with the constitutive equation established on the basis of the physical simulation, the constitutive equation established by the experimental data is optimized in turn. Based on it, this paper advances a visco/plastic constitutive equation to depict the semi-solid thixo-forming and the constitutive equation is analyzed and optimized through coupling of the physical simulation and numerical simulation. It is observed that this method can effectively eliminate the influence of the factor outside material itself on the constitutive equation. So, it can exactly depict the deformation behavior of the materials and improve the accuracy and reliability of the numerical simulation.

Abstract: There are many factors, such as the laser and geometrical parameters, which influence greatly on the laser bending process. So it is of great importance to determine these variables properly. Considering the relationship of material properties and temperature, a 3-D thermal-mechanical finite element analysis model for laser micro-bending of stainless steel foil is developed based on the software MSC.Marc, and the laser micro-bending process of 0.1mm thick stainless steel foil is implemented. The finite element method simulation process is integrated with the optimization software package iSIGHT through secondary development. The objective function is to realize the maximum bending angle after single laser scan, and laser power, beam diameter and scanning velocity are regarded as the design variables. The forming process is optimized by using genetic algorithm. The optimal result shows the bending angle can be got to the maximum 1.0332°when the laser power, beam diameter and scanning velocity are 32W, 0.17mm and 132mm/s respectively. The experiment results are in good agreement with optimal results.