簡易檢索 / 詳目顯示

回結果列表
研究生： 羅方韋
Luo, Fang-Wei
論文名稱： 鋁合金板件於電磁成形時之高應變率成形極限預測
Prediction of High-strain-rate Forming Limit of Aluminum Alloy under Electromagnetic Forming Process
指導教授： 李榮顯
Lee, Rong-Shean
學位類別： 碩士
Master
系所名稱： 工學院 - 機械工程學系
Department of Mechanical Engineering
論文出版年： 2010
畢業學年度： 98
語文別： 英文
論文頁數： 82
中文關鍵詞： 高應變率 、鋁合金板材 、成形極限 、電磁成形 、延性破壞準則
外文關鍵詞： high strain-rate, aluminum alloy sheet, forming limit, electromagnetic forming, ductile fracture criterion
相關次數： 點閱：99  下載：1 
分享至:
查詢本校圖書館目錄 查詢臺灣博碩士論文知識加值系統 勘誤回報

    • 現今已有許多研究探討金屬板件的破壞行為，工程師可藉由對材料破壞行為的瞭解來預測並防止板件破壞的發生。近年，隨著高應變率成形製程的發展，準靜態之可成形性理論以及Cockcroft-Latham (CL) 破壞準則曾被應用於高達1000 (1/s) 之高應變率情況。本文利用電磁成形製程高速變形的特點，對板材在高應變速率下之成形極限進行研究，其應變率可高達5000 (1/s)。在電磁成形實驗中，本文利用蚊香型線圈將電磁力作用於厚度0.5釐米的鋁合金Al5052-H32薄板上，使之撞擊衝頭而變形或破壞。本文利用不同幾何外形的板材撞擊衝頭，以獲得不同應變路徑下的成形極限資料。而為了求得材料的塑流應力，本文先將板材撞擊不同尺寸的衝頭以獲得不同的應變量，並以疊代分析建立撞擊過程之應力應變曲線，再利用此應力應變曲線建立材料在高速下之塑流應力。此塑流應力可用以建立高速變形行為下適用的CL破壞準則。本文最後得到材料在高速變形下的破壞預測結果，並比較實驗與模擬的結果，證實本文所提出之實驗設計可適用於建立高達5000 (1/s) 高應變率下之板材成形極限資料。

    A great deal of effort has been made on investigating fracture behaviors of metal sheets. With knowing the fracture behaviors, engineers are able to predict the occurrence of fracture and to prevent the sheet from fracture. With the development of high speed forming, formability theory and Cockcroft-Latham (CL) fracture criterion, which have been developed in quasi-static state, have been applied to predict fracture at high strain rate up to 1000 (1/s). In this work, the EMF experiment, which can deform a sheet at high strain-rates, was used for investigating the forming limit. The EMF experiment was performed by electromagnetically launching an aluminum alloy Al5052-H32 sheet of 0.5 mm thickness at a punch with a flat spiral electromagnetic coil. The punch was impacted by the sheets of different shapes in order to obtain forming limits at different strain paths. On the other hand, the punch radius was varied to generate various strain values of the sheet. Then, with the help of iteration analysis, the iterated effective stress – effective strain curve (ESESC) of the sheet was obtained. The obtained ESESC can be used to construct Johnson-Cook flow stress model. To predict the forming limit at high strain-rates, Cockcroft-Latham criterion was constructed using the obtained flow stress model. The results of simulation and fracture prediction at high strain-rates were both compared with the experimental results. The proposed experimental design was confirmed to be suitable for constructing the forming limit data of sheet at high strain rate up to 5000 (1/s).

    摘要 I ABSTRACT II ACKNOWLEDGEMENTS III CONTENTS V LIST OF FIGURES VIII LIST OF TABLES XII CHAPTER 1 INTRODUCTION 1 1.1 Motivation 1 1.2 Electromagnetic Forming Process (EMFP) 2 1.2.1 Tubular Electromagnetic Forming Process 3 1.2.2 Sheet Electromagnetic Forming Process 3 1.3 Forming Limit Diagram (FLD) and Fracture Criteria 7 1.3.1 Forming Limit Diagram (FLD) 8 1.3.2 Necking and Fracture Criteria 9 1.4 Fracture Prediction at High-strain-rate Level 12 1.4.1 Material Behavior under High Strain Rate 13 1.4.2 Forming Limit Prediction under High Strain Rate 15 1.5 Objective and Methodology 16 1.6 Outline of the Study 17 CHAPTER 2 THEORETICAL METHODS 19 2.1 Ductile Fracture Criteria 19 2.2 Some Experimental and Numerical Methods Used in the Study 21 2.2.1 Strain Measurement on a Square Grid 21 2.2.2 Estimation of Impact Velocity 24 2.2.3 Iteration Analysis for ESESC Construction 27 CHAPTER 3 DESIGN FOR EMF EXPERIMENT 29 3.1 Outline of the EMF Experiment 29 3.2 Design for the Experiment 32 3.2.1 Punch Design 33 3.2.2 Strain Path Design 34 3.2.3 Control over Strain Rates 40 3.3 EMF Experiment 44 3.3.1 Preparation for EMF Experiment 44 3.3.2 EMF Experiments 47 CHAPTER 4 RESULTS AND DISCUSSIONS 51 4.1 FLD Construction 52 4.2 Flow Stress Construction 55 4.2.1 Iterated Effective Stress – Effective Strain Curve 55 4.2.2 Johnson-Cook Flow Stress Model Construction 59 4.3 Strain Path Simulation 62 4.4 Forming Limits Predicted by Fracture criteria 66 CHAPTER 5 CONCLUSIONS AND SUGGESTIONS 72 5.1 Conclusions 72 5.2 Suggestions 74 REFERENCES 75 ABOUT AUTHOR 82

    [1] Dey, S., T. Børvik, O. S. Hopperstad, and M. Langseth, 2006, On the influence of fracture criterion in projectile impact of steel plates, Computational Materials Science 38, p. 176-191.
    [2] Walling, H.C. and M.J. Forrestal, 1973, Elastic-plastic expansion of 6061-T6 aluminium rings, AIAA Journal 11, p. 1196.
    [3] Cheng, T. C., 2008, The situations of EMF joining / forming development in Taiwan, International electromagnetic forming / forming technology and application conference, Metal Industries Research and Development Centre, Taiwan.
    [4] Lee, R. S., 1986, Plastic Working (塑性加工學 In Chinese), Sam Min Book Co., p. 446.
    [5] Manish Kamal, M. S., 2005, A uniform pressure electromagnetic actuator for forming flat sheets, Ph. D. Thesis, The Ohio State University, US.
    [6] Chen, C. H., 2010, Forming limit prediction of micro sheet metal forming due to grain size effect, Ph. D. Thesis, Department of Mechanical Engineering, National Cheng Kung University.
    [7] Keeler, S. P. and W. A. Backofen, 1963, Plastic instability and fracture in sheets stretched over rigid punches, Trans. ASM, 56(1), 25-48.
    [8] Goodwin, G. M., 1968, Application of strain analysis on sheet metal forming problems in the press shop, SAE paper, No. 680093.
    [9] Hiam, J. and A. Lee, 1978, Factors influencing the forming-limit curves of sheet steel, Sheet Metal Industries, 55(5), p. 631-641.
    [10] Swift, H. W., 1952, Plastic instability under plane stress, Journal of the Mechanics and Physics of Solids, 1, p.p. 1-18.
    [11] Hill, R., 1952, On discontinuous plastic states with special reference of localized necking in thin sheets, Journal of the Mechanics and Physics of Solids, 1, 19-30.
    [12] Venter, R., W. Johnson, and de M. C. Malherbe, 1971, The limit strains of inhomogeneous sheet metal in biaxial tension, International Journal of Mechanical Sciences, 13, 299-308.
    [13] Marciniak, E. and K. Kuczynsky, 1967, Limit strains in the processes of stretch forming sheet metal, International Journal of Mechanical Sciences, 9, 609-620.
    [14] Hutchinson, J. W. and K. W. Neale, 1978, Sheet necking-II time-independent behavior, Mechanics of Sheet Metal Forming, edited by D.R. Koistinen and N.M. Wang, New York: Plenum Press, 127-150.
    [15] Storen, S. and J. R. Rice, 1975, Localized necking in thin sheets, Journal of the Mechanics and Physics of Solids, 23, p.p. 421-441.
    [16] Freudenthal, A. M., 1950, The inelastic behavior of engineering materials and structures. New York: John Wiley & Sons.
    [17] Cockcroft, M. G. and D. J. Latham, 1968, Ductility and workability of metals, Journal of the Institute of Metals, 96, 33-39.
    [18] Brozzo, P., de B. Luka, and R. Rendina, 1972, A new method for the prediction of formability in metal sheets, Proc. 7th Biennial Conference on Sheet Metal Forming and Formability. International Deep Drawing Research Group, 9-13.
    [19] Norris, D. M., J. E. Reaugh, B. Moran, and D. F. Quinones, 1978, A plastic strain mean-stress criterion for ductile fracture, Journal of Engineering Materials and Technology, Trans. ASME, 100, pp 279-286.
    [20] Atkins, A. G., 1981, Possible explanation for unexpected departures in hydrostatic tension-fracture strain relations, Metal Science, 15, 81-83.
    [21] Oh, S., C. C. Chen, and S. Kobayashi, 1979, Ductile failure in axisymmetric extrusion and drawing, Part 2, Workability in extrusion and drawing, Journal of Engineering for Industry, Trans. ASME, 101, pp 36-44.
    [22] McClintock, F. A., 1968, A criterion of ductile fracture by growth of holes, Journal of Applied Mechanics, Trans. ASME, 35, 363-371.
    [23] Rice, J. R., and D. M. Tracey, 1969, On the ductile enlargement of voids in triaxial stress fields, Journal of the Mechanics and Physics of Solids, 17, p.p. 201-217.
    [24] Oyane, M., 1972, Criteria of ductile fracture strain, Japan Society Mechanical Engineering, 15, p.p. 1507-1513.
    [25] Smerd, R., S. Winkler, C. Salisbury, M. Worswick, D. Lloyd, and M. Finn, 2005, High strain rate tensile testing of automotive aluminum alloy sheet, International Journal of Impact Engineering, 32, p.p. 541-560.
    [26] Kleiner, M., and A. Brosius , 2006, Determination of Flow Curves at High Strain Rates using the Electromagnetic Forming Process and an Iterative Finite Element Simulation Scheme, Annals of the CIRP, vol. 55/1/2006, p. 267
    [27] Gourdin, W., 1989, Analysis and assessment of electromagnetic ring expansion at a high-strain-rate test , Journal of Applied Physics. 65, 411.
    [28] Ismael, Henchi, Pierre L'eplattenier, Glenn Daehn, Yuan Zhang, Anupam Vivek, and Nielen Stander, 2008, Material Constitutive Parameter Identification using an Electromagnetic Ring Expansion Experiment Coupled with LS-DYNA and LS-OPT, 10th International LS-DYNA Users Conference, June 08-10.
    [29] Kajberg, J., Sundin, K.G., Melin, L.G., Stahle, P., 2004, High strain-rate tensile testing and viscoplastic parameter identification using microscopic high-speed photography, Int. J. Plasticity 20, 561–575.
    [30] Chiou, Su-Tang, Wei-chun Cheng, and Woei-Shyan Lee, 2005, Strain rate effects on the mechanical properties of a Fe-Mn-Al alloy under dynamic impact deformations, Materials Science and Engineering A 392, p.156-162.
    [31] Balanethiram, V. S., and G. S. Daehn, 1992, Enhanced formability of interstitial free iron at high strain rates, Scripta Mater. 27, 1783.
    [32] Balanethiram, V. S., and G. S. Daehn, 1994, Hyperplasticity: increased forming limits at high workpiece velocity, Scripta Mater. 30, 515.
    [33] Balanethiram, V. S., 1996, Hyperplasticity: enhanced formability of sheet metals at high velocity, Ph.D. Thesis, The Ohio State University, US .
    [34] Hu, X., and G. S. Daehn, 1996, Effect of velocity on localization in uni-axial tension, Acta Mater. 44, 1021.
    [35] Altynova, M., 1995, The improved ductility of aluminum and copper by electromagnetic forming technique, MS Thesis, The Ohio State University.
    [36] Tamhane, A., M. Padmanabhan, G. K. Fenton, V. J. Vohnout, V. S. Balanethiram, M. Altynova, and G. S. Daehn, Impulsive Forming of Sheet Al: Cost Effective Technology for Complex Component Manufacturing.
    [37] Tamhane, A., M. Altynova, and G. S. Daehn, 1996, Effect of sample size on ductility in electromagnetic ring expansion, Scripta Mater. 34 (8), p. 1345.
    [38] Thomas, J. D., M. Seth, G. S. Daehn, J.R. Bradley, and N. Triantafyllidis, 2007, Forming limits for electromagnetically expanded aluminum alloy tubes: Theory and experiment, Acta Materialia 55, p.p. 2863-2873.
    [39] Oliveira, D. A., M. J. Worswick, M. Finn, and D. Newman, Electromagnetic forming of aluminum alloy sheet: Free-form and cavity fill experiments and model, Journal of Materials Processing Technology 170, p.p. 350-362.
    [40] Seth, Mala, Vincent J. Vohnout, and Glenn S. Daehn, 2005, Formability of steel sheet in high velocity impact, Journal of Materials Processing Technology 168, p.p. 390-400.
    [41] Hancock, J. W. and A. C. Mackenzie, 1976, On the mechanisms of ductile failure in high –strength steels subjected to multi-axial stress-states, J Mech Phys Solids 24, p. 147-69.
    [42] El-Magd, E. and M. Brodmann, 2001, Influence of precipitates on ductile fracture of aluminum alloy AA7075 at high strain rates, Materials Science and Engineering A307, p. 143-150.
    [43] El-Magd, E. and M. Abouridouane, 2005, Characterization, modeling and simulation of deformation and fracture behaviour of the light-weight wrought alloys under high strain rate loading, International Journal of Impact Engineering 32, p. 741-758.
    [44] Johnson, G. R. and W. H. Cook, 1983, A constitutive model and data for metals subjected to large strains, high strain rates, and high temperatures, Proceedings of the 7th international symposium on ballistics, The Hague, Netherlands, p. 541-7.
    [45] Arias, A., J. A. Rodríguez-Martínez, and A. Rusinek, 2008, Numerical simulations of impact behaviour of thin steel plates subjected to cylindrical, conical and hemispherical non-deformable projectiles, Engineering Fracture Mechanics, 75, p. 1635-1656.
    [46] Chuang, W. L., 1990, Master Thesis, Department of Mechanical Engineering, National Cheng Kung University, Taiwan.
    [47] Daehn, G. S., M. Altynova, V. S. Balanethiram, G. Fenton, M. Padmanabhan, A. Tamhane, and E. Winnard, 1995, High-velocity metal forming – an old technology addresses new problems, JOM 47 (7) 42.
    [48] Daehn, G. S., V. J. Vohnout, and S. Datta, 2000, Hyperplastic forming: process potential and factors affecting formability, Mater. Res. Soc. Symp. Proc. 601, 247.
    [49] Macdougall, D. A. S. and J. Harding, 1999, A constitutive relation and failure criterion for Ti6Al4V alloy at impact rates of strain, Journal of the Mechanics and Physics of Solid, 47, p. 1157-1185.
    [50] Mercier, S. and A. Molinari, 2004, Analysis of multiple necking in rings under rapid radial expansion, International Journal of Impact Engineering 30, p. 403-419.
    [51] Shenoy, V. B. and L. B. Freund, 1999, Necking bifurcations during high strain rate extension, Journal of the Mechanics and Physics of Solids 47, p. 2209.

    下載圖示 校內：2012-08-25公開
    校外：2012-08-25公開
    QR CODE