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Thin-walled steel material parameters Reverse

Advanced design and manufacture of the State Key Laboratory of auto body Hunan University, Changsha, 4100822.

Hebei new sinda & Steel Co., Ltd., CHN, 201900

Abstract: identify the problem for thin-walled steel material parameters, using a combination of finite element software and the genetic algorithm inverse method to determine the material parameters of steel pipe and verify these parameters.

First, the need to reverse calculation model developed inverse technique program; convergence parameter inverse procedure, the results show that the method has higher convergence precision; Then, set up a test system, test to obtain the material parameters need to reverse;, again, force displacement relationship based on the pilot test, anti-obtained material parameters of the steel pipe; Finally, a test example and its simulation, validation parameters of the reverse engineering applications feasibility. Using this method to determine the parameters of the bumper material, a certain sense, the method can also be used to determine the parameters of other thin-walled pipe material to improve the car's overall simulation accuracy. Keywords: thin-walled steel pipe; material parameters; inverse; finite element method: T G113 25

Article ID: 1004 - 132X (2008) 06 - 0688 - 03

Introduction The development phase of the new models in the car, often using the finite element software specimens, therefore, need a thin tube material parameters in the simulation tensile test method can not be used to determine. Using laser seamless weld metal tubing, by the plate processing Tube outer fiber material after elongated inner fiber shortening, changes in material properties, therefore, before bending the material parameters is also undesirable. The combination of finite element software optimization algorithm inverse method can be used to determine the sheet material parameters, and can improve the accuracy of the material parameters [2, 3].

The key issues of this inverse method first of Reverse chosen simulation model and data converge to the real material parameters, followed by the possibility of establishing a test system to get the test data Reverse Reverse models corresponding Finally, the verification of the parameters Reverse. Diameter 40mm, thickness of 11 6mm thin-walled steel pipe consisting of a car bumper, for example, introduced material parameters inverse method, and these parameters were validated. Car simulation model, in order to make the analysis and evaluation of the car's structural strength and security, laying the foundation for improved vehicle structure, improve the performance of the car. The car in addition to the use of sheet metal stampings, these tubes also car collision deformation mode is not axial compressive deformation, but the weeks to flattening deformation. The collision deformation characteristics can be summarized as "large deformation, small strain. A great influence on the accuracy of the accurate calculation of the the bumper deformation in the force performance simulation of vehicle collisions. Some mechanical parameters of the metal pipe can be used tensile test to use some of the metal pipe, such as the front bumper, door and bumper.

Determined, these mechanical parameters include: the tensile strength, yield strength and elongation of [1], but the determination of the material parameters of the metal pipe of the thin-walled small radius is a practical problem in the works. Metal thin tube is thin, it is difficult to processing to meet the size requirements of the Reverse simulation model Received Date: 2007 - 01 22 Fund: National Outstanding Youth Fund Project (50625519) to shorten the positive the computation time of the problem, according to the simulation object? 688?? 1994-2010 China Teachers College Electronic Publishing House. All rights reserved. reverse http://www.netgms.com/ thin-walled steel material parameters --- Liu Di Hui Wang Chen Lee GHC symmetry, the establishment of a simulation model of the shown in Figure 1 1/4. The model LS - D YNA No. 18 in the material model (mat power of law plasticit y).

Figure 2 material parameters Reverse Reverse simulation model value is less than a certain value, for example, less than 2%, the flow chart of Figure 1 Reverse the accuracy of the parameters meet the engineering requirements of accuracy, you can stop the program calculated. Because each positive time in 3min around, which makes it very necessary to reduce the number of iterations of the genetic algorithm. Pressure pull stroke 28mm, through simulation analysis shows that model the biggest vo n Mises equivalent strain around 0.27, the deformation of the tube is a large deformation, small strain. Since the platen and the pipe is substantially line contact in the entire calculation process, therefore, tubing Z are subject to the influence of friction to the pressure can be negligible. To avoid numerical fluctuations caused by the fluctuations of the pressure curve, the pressure curve fitting, and 20 points calculated as the inverse data.

Reverse the accuracy of the method and its convergence convergence.

Table Figure 3 parameters convergence process Reverse the essence of the method is optimized through the optimization algorithm parameters, so the simulation results of the model using these parameters approximation test results [2Ο5. The objective function for Nt Table 1 lists strengthen convergence results and convergence precision range after the the convergence results after 30 iterations and inverse parameter coefficient k (GPa) [00, 20] F = i = 1 Σ Si m (i) - Ex p (i) Ex p (i) convergence value of 1.1120 set value the 1.15 convergence accuracy (%) 95.96, N t is the total number of test data; Ex p (i ; Si m (i)) for the test measurement data for the simulation calculation data. (GA), the material parameters for function optimization using genetic algorithms [6] inverse process shown in Figure 2. The material parameters using the inverse method to strike the material parameters using the modified the Levenberg Marguart of optimization algorithms Reverse [7]. The number of individuals per generation value 5. The individuals selected initial value is a random number generated within the specified range, to calculate the objective function value for each individual call LSD YNA software. The entire calculation, target enhancement index n [0, 05, 0 20] 0 0904 0 10 90 40 minimum function corresponding to the parameters is the method the demand parameter. Material models need to enter the stress - strain curve data, ε true stress - strain relation σ = kn, the hardening coefficient k and hardening exponent n as the parameters of the reverse. Reverse convergence of the method, it is assumed that a set of material parameters, simulation model in order to study the parameters calculated a set of data as the test data, compare the calculated parameters, and assumptions of material parameters through inverse procedure, calculate its convergence precision. Fitness function value of the change process is shown in Figure 3, where the fitness function value is the reciprocal of the objective function value, as long as the objective function? 1994-2010 China Teachers College Electronic Publishing, House All rights reserved. Convergence of the parameters in Table 1 accuracy is not ideal, but is used in the simulation represented by these two parameters, the stress - strain curve, in the range of strain of less than 0127, the deviation of these two sets of parameters represented by the stress - strain curve at 211 % range, as shown in Figure 4. As can be seen from Figure 4, the material parameters using the inverse method can find the wall of the pipe material, and high precision of convergence. If you increase the number of iterations in the above analysis, but also further improve the accuracy of the inverse parameter convergence. Two sets of parameters in Figure 4 represents the stress - pipe flattening test in the second half of March 2008, of the Chinese Mechanical Engineering force - displacement curve. Figure 7. As can be seen from Figure 7, the reverse parameters able to describe the mechanical properties of the material, this simulation to accurately calculate the acceleration of the vehicle in a collision is very important. Tests on the Hunan University automobile laboratory sheet metal testing machine, the test apparatus is shown in Figure 5.

The test system includes a hydraulic cylinder, the platen supporting plate, the force sensor and the displacement sensor and the like. Platen decline in the effect of the hydraulic cylinder, pressure is applied to the steel pipe, steel pipe is deformed under the pressure generated. The platen force and stroke respectively measured by the force sensor and displacement sensor, the time can be calculated based on the collection of data points and sampling frequency. Test is controlled by the computer, to record sensor to measure the force and displacement data. Interception of a section from a car bumper as a test piece, sizes are as follows: the outer diameter of 40mm, a wall thickness of 11 6mm, a length of 100mm. The test device Figure 7 with the experimental results contrast Reverse inverse parameter validation in order to observe whether the reverse calculation parameters can be used for other model calculations, the special configuration of a cylindrical punch car in Hunan University laboratory sheet gold testing machine for a length of 120mm in the same kind of steel pipe to do the test, measuring got the punch force and the stroke curve. After the test, the shape of the tube shown in Figure 8. The deformation of the steel pipe after the test shown in Figure 6. Sheet convex concave on both sides of the portion of the sheet thinning greatest. Test test platen pressure and stroke curve. Figure 8 Inverse deformation of the steel pipe in the parameter validation test inverse parameters of the simulation model of the verification test as shown in Figure 9, the model used in the front anti-determined material parameters. The punch time - stroke curve using the data obtained in the tests. Simulation and test results of the comparison are shown in Figure 10. From its junction Figure 6 Reverse steel pipe deformation experiments bumper material parameters first spreadsheet few set of parameters, selected a set of test results very close parameters to determine the range of parameters, and then run the reverse process to strike materials parameters. 2 Reverse the range of parameters and convergence results. Exemplar the inverse parameter range and convergence results range [0.80, 1.00] [0. 00, 0.10] inverse simulation model parameter validation test convergence results in Figure 9 0.908 strengthening coefficient k (GPa index n 1. 33 × 10 - 3) strengthen

Round tube after bending deformation, and at Figure 10 verification test results and simulation results contrast (the 724), changed management, material parameters, so the inverse parameters and tablet tensile test Parameters are some differences. Reverse parameters to calculate the force - displacement curve and test

(2) these two six-DOF parallel manipulator topology composition and structural properties (including institutions of degrees of freedom of movement of the motor output characteristics, kinematics and dynamics of complexity, input - output motion control decoupling , the drive can be configured, etc.) made a detailed analysis of its kinematics.

Kinetic analysis and design of the mechanical structure and its potential for industrial applications and lay the foundation. References: [1] Hunt K H. St ruct ure Kinematic of In - parallel act uated Robot - arms [J]. ASM EJ. Of Mecha2 nisms, Transmissio ns and Auto mation Design, 1983, 105: 705Ο 712. 14Ο 19 . [J]. Mechanical Engineering, 1991, 27 (2): 30. T228 26Ο - 2002 materials at ambient temperature tensile test methods [S] North [6] Ting-Li Yang. robot mechanism topology learning [M] Beijing: six degrees of freedom parallel mechanism: Mechanical Industry Press, 2004. [7] Hui-Ping Shen, Yang, horse shoe. the virtual axis CNC machine tools and measuring machines, ZL03113048 8 [8] Hui-Ping Shen, Yang, horse shoe used the virtual axis CNC machine tools and machine [P], 02 11. mechanical measurement machine 2004Ο Ο six DOF parallel mechanism: China ZL03113115 [9] Shen HP, Yang, TL, Ma L Z. Synt hesis, and St. ruc2 t ure Analysis of Kinematic St ruct-ures of 6 - dof Machine Theo ry, 2005, 40 (10): 118Ο 1194. Parallel Ro botic Mechanisms [J]. Mechanism and [10] Yang Ting basic theory of mechanical systems - Anatomically, kinematic, dynamic 8 [P]. 2003Ο Ο 10 01. mechanics [M]. Beijing: Mechanical Industry Press, 1996 [2] Liang lofty, Wing Fai. a Stewart platform-type mechanical hand displacement is solution [3] Huang Zhen, KONG Ling-fu, Fang Yue law parallel robot mechanism theory and control (edit HE Cheng root) About the author: Hui-Ping Shen, male, born in 1965. Professor, Department of Mechanical Engineering of Jiangsu Polytechnic University, Ph.D. The main research direction for the agency, mechanical design, parallel movement of machinery. A provincial and ministerial level scientific and technological progress second prize, third prize 2 by 8 patents. Issued a statement more than 70 papers. Ting-Li Yang, male, born in 1940. Of Sinopec Jinling Petrochemical Company of China Association for Science and Technology, Senior Engineer. Horse shoe, male, born in 1939. Professor of Mechanical Engineering, University of Jiangsu. System [M] Beijing: China Machine Press, 1997., 2003. [4]

Hui-Ping Shen, Yang, horse shoe in six degrees of freedom model design and methods of weakly coupled parallel mechanism [J]. Mechanical Engineering, 2004, 40 (7): (690 pages) [3] Gao Hui, Han Lifen Lee Kuan Yew, etc. Based on the Micro GA and finite element 16 (16): 1681. 1996 1678Ο, 136: 225Ο 258 11 (1): 21Ο 25. thin plastic material parameter identification [J]. Mechanical Engineering of China, 2005 the fruit contrast can be seen, the calculated and experimental results is relatively close. Model calculation error and experimental error, calculated and experimental results, there are still some errors. From the above study, inverse material parameter can be applied to actual projects, also applies to other pipe materials parameters strike.

6 Conclusions finite element software optimization algorithm combined inverse method, as well as the article describes the test system, anti-calculated car bumper material parameters, the inverse parameters accuracy, to achieve the requirements of engineering applications. The ways to obtain the material parameters of thin-walled steel car, a certain significance to improve the precision of the automotive vehicle collision. Reverse the strain of the test specimen is relatively small, so only when the pipe circumferential the flattening deformation mode to using this method to get the parameters in the simulation. References: About the author: Liu Di Hui, male, born in 1975. Advanced Design and Manufacturing, associate professor of the State Key Laboratory of Hunan University of auto body. The main research direction of vehicle body, Dr. Wang, male, born in 1968. Baoshan Iron & Steel Co., Ltd. Research Institute senior engineering Morning division. Lee Kuan Yew, male, born in 1963. Auto Body of Hunan University State Key Laboratory of Advanced Design and Manufacturing Director, professor and doctoral tutor. [1] National Quality Supervision, Inspection and Quarantine of the People's Republic of China. GB / materials, automotive crash safety CA E and stamping forming process CA E. 6 papers.

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