經過適當的熱沖壓後，22MnB5錳硼鋼的抗拉強度能提升至1500MPa，適於製作質量更小強度卻更高的零件，這樣的性質使22MnB5在產業界的使用量逐漸提高，22MnB5錳硼鋼板成形極限資訊的需求也跟著提升。在所有用來預估板材成形能力的資訊中，成形極限圖是最重要也是最常被使用的資訊，22MnB5的成形極限圖須在高溫環境下完成，半球形沖頭沖壓實驗為目前最常被用來製作成形極限圖的實驗，然而在此實驗中試片會受到彎曲及摩擦，此兩者都可能影響實驗結果，更重要的是，目前高溫半球形沖頭沖壓實驗無法準確的控制試片的溫度，這也是阻擋其成為標準實驗的主要原因。為了獲得更精確的溫度控制，並排除在半球形沖頭沖壓實驗中試片受到彎曲及摩擦的問題，本研究提出一個新的方法來建立高溫成形極限圖，此方法導入一條將應變路徑納入考量的破壞準則，並搭配兩個使用不同拉伸試片的拉伸實驗來預測材料的成形極限曲線，為獲得精確的溫度控制，此兩組實驗皆以Gleeble 3800物理模擬機進行。本研究利用此法建立22MnB5錳硼鋼板在650oC、三種不同應變率，以及在相近的應變率、三種不同溫度下的成形極限曲線。
有關破壞準則，目前已有許多不同的破壞準則被提出，並都附帶足以驗證其準確性的實驗數據，經觀察，大部分的破壞準則都能準確的預測成形極限圖中第二象限的成形極限曲線，但第一象限的預測則常與實驗結果不同。因此，由於本研究係以破壞準則來建立成形極限曲線，故本研究亦同時建立了一套準確性評估方法來評估所建立的成形極限曲線的準確性。在此方法中，為排除試片彎曲或摩擦等因素，所有的實驗數據都是透過拉伸獲得。透過觀察，雖然成形極限曲線在成形極限圖的第一象限及第二象限常有不同的趨勢，但在兩個象限中都是平滑且接近直線的曲線，故可透過成形極限圖中的三個具代表性的極限應變狀態來評估經預測而得的成形極限曲線的準確性。此三個極限應變的應變狀態為拉壓應變、平面應變、及雙軸拉伸應變。在本研究所提出的準確性評估方法使用兩種不同的拉伸試片來建立拉壓應變狀態及平面應變狀態的極限應變，另一方面，本研究設計了一種十字形試片來取得雙軸拉伸狀態的極限應變，此試片透過厚度變化及疊層的造型使試片中心產生應力集中，進而使試片中心達到雙軸拉伸的應變狀態。
結合以上所提之成形極限建立方法及準確性評估方法，將有機會以Gleeble 3800物理模擬機建立高溫成形極限曲線，此方法的成本遠低於高溫半球形沖頭沖壓實驗，並可在實驗中提供較精確的溫度控制，相較於半球形沖頭沖壓實驗所建立的成形極限曲線，以此法建立的成形極限曲線將更為可靠。

B-Mn steel 22MnB5 is known to have excellent mechanical properties after experiencing a proper hot stamping process. Not surprisingly, 22MnB5 has become an increasingly popular material in industry recently. The need for formability information on 22MnB5 metal sheet is also increasing. A forming limit diagram is one of most important types of formability information. The 22MnB5 forming limit diagram should be made at elevated temperatures. The limiting dome height test is currently the most common experiment used to establish a forming limit diagram, but the specimens are rubbed and bent during the test, both of which influence the experimental results. On the other hand, it is difficult to control the specimen temperature using a high temperature limit dome high test machine, which is the main factor hindering establishing of the standardization of a limiting dome height test for elevated temperatures. In order to obtain experimental data with more accurate temperature control and to exclude the bending and friction that occur in a limiting dome high test, in this study, a new method which includes an experimental analysis and theoretical predictions was developed to investigate the formability of 22MnB5 at elevated temperatures. In this method, two designs for tensile test specimens with laser engraving grids are developed and used to obtain a tension-compression limit strain and a limit strain close to the plane-strain state at elevated temperatures together with the Gleeble 3800 physical simulator. On the other hand, a modified Cockcroft criterion that takes strain path into consideration is employed to predict an entire forming limit curve. A forming limit curve can be established as a result of using the modified Cockcroft criterion together with the limit strains obtained from the tensile tests based on the two novel specimen designs. In this study, forming limit curves at three strain rates and at temperatures ranging from 650oC to 850oC were established.
Today, many different fracture criteria have been developed. All studies on this topic have presented experimental data that can justify the criterion they presented. However, the experimental results and predictions in the first quadrant of the forming limit diagrams often diverge. Therefore, due to the fact that the forming limit curves established in this study were predicted using a fracture criterion, an accuracy identification method was developed. In this method, all the experimental data are obtained through pure stretching, which can avoid the problems that occur in a limiting dome height test. In respect to the second quadrant of a forming limit diagram, two different tensile test specimens are applied to obtain the fracture strains in the second quadrant of a forming limit diagram. On the other hand, for the first quadrant of the forming limit diagram, a cruciform biaxial tensile specimen was developed, while a biaxial tensile apparatus was adopted. The proposed specimen has the feature of thickness reduction and a contour design to ensure the fracture position is in the central region of the specimen so that a biaxial tensile state can be obtained. By combining the forming limit curve establishing method and the accuracy identification method, there is an opportunity to obtain an entire forming limit curve at an elevated temperature using the Gleeble 3800 physical simulator, which is a low-cost and more reliable alternative compared with a high temperature limiting dome height test.

ASAME Technology LLC. The automated strain analysis and measurement environment (ASAME) reference manual. ver. 4.12, 253-257. (2010)
Atkins, A. G. Possible explanation for unexpected departures in hydrostatic tension-fracture strain relations. Metal Science. 15, 81-83. (1981)
Banabic, D. Sheet metal forming processes. Springer-Verlag Berlin Heidelberg. (2009)
Bariani, P. F., Bruschi, S., Ghiotti, A., and Turetta, A. Testing formability in the hot stamping of HSS. CIRP Annals-Manufacturing Technology, 57(1), 265-268. (2008)
Carvelli, V., Corazza, C., Poggi, C. Mechanical modelling of monofilament technical textiles. Computational Materials Science, 42(4), 679-691. (2008)
Chen, C. H., Lee, R. S., and Gau, J. T. Size effect and forming-limit strain prediction for microscale sheet metal forming of stainless steel 304. The Journal of Strain Analysis for Engineering Design, 45(4), 283-299. (2010)
Chen, Y. J. Formability evaluation in cold forming processes by energy criteria. Dissertation for doctor of philosophy. Department of mechanical engineering, National Cheng Kung University, Taiwan. (2012)
Chen, G. H. Perform design and analysis of multi-stage tube hydroforming. Master thesis, Department of mechanical engineering, National Cheng Kung University, Taiwan. (2013)
China steel corporation. Product manual: Hot rolled steel. China steel corporation, Taiwan. http://www.csc.com.tw/csc/pd/table/hr_2014.pdf, 2014/7/9. (2014)
Chiu, H. Y. Formability analysis of HA-188 cobalt-base super alloy in tube hydroforming. Master thesis, Department of mechanical engineering, National Cheng Kung University, Taiwan. (2011)
Cockcroft, M. G. and Latham, D. J. A simple criterion of fracture for ductile metals. National Engineering Laboratory. (1966)
Dahan, Y., Chastel, Y., Duroux, P., Wilsius, J., Hein, P., Massoni, E. Procedure for the experimental determination of a forming limit curve for USIBOR 1500 P. In IDDRG 2007 International Conference Proceedings. (2007)
Freudenthal, A. M. The inelastic behavior of engineering materials and structures. John Wiley & Sons. (1950)
Garcia Aranda, L., Chastel, Y., Fernández Pascual, J., Dal Negro, T. Experiments and simulation of hot stamping of quenchable steels. Advanced Technology of Plasticity 2, 1135–1140. (2002)
Gensamer, M. Strength and ductility. Transactions of the American Society for Metals 36:30–60. (1946)
Goodwin GM (1968) Application of strain analysis to sheet metal forming problems in the press shop. Society of Automotive Engineers No. 680093, 380–387
Hannon, A., and Tiernan, P. A review of planar biaxial tensile test systems for sheet metal. Journal of materials processing technology, 198(1), 1-13. (2008)
Karbasian, H. and Tekkaya, A. E. "A review on hot stamping." Journal of Materials Processing Technology 210 (15), 2103-2118. (2010)
Keeler, S. P., and Backofen, W. A. Plastic instability and fracture in sheets stretched over rigid punches. Transactions of American Society of Metals (ASM TRANS Q), 56(1), 25-48. (1963)
Kuan, J. J. The design and implementation of biaxial tensile apparatus for uniaxial tensile machine. Undergraduate student project, Department of mechanical engineering, National Cheng Kung University, Taiwan. (2010)
Lechler, J., and Merklein, M. Hot stamping of ultra strength steels as a key technology for lightweight construction. Materials science and technology (MS&T), Pittsburgh, Pennsylvania, 1698-1709. (2008)
Lee, R. S., Chiu, H. Y., Chen, Y. J., Lo, Y. C., Wang, C. C. Evaluation of Facture Criteria Considering Complex Loading Paths in Cobalt Alloy Tube Hydroforming. Materials Transactions, 53(5), 807-811. (2012)
Lee, R. S., Lin, Y. K., Chen, Y. J., Chien, T. W. Determination of the forming limit curve of high strength steel sheet based on fracture criterion. Chinese Mechanical Engineering Society Symposium, 29 no. 1439. (2012)
Lee, R. S. and Chien, T. W. Formability Evaluation using Modified Cockcroft Criterion with strain paths for Sheet Metal Forming. Asia-Pacific Conference on Engineering Plasticity and Its Applications (AEPA). (2014)
Li, J. Y., Min, J. Y., Qin, K. Y., Lin, J. P., Liu, F. Q., Liu, L. C. Investigation on the effects of sheet thickness and deformation temperature on the forming limits of boron steel 22MnB5. Key Engineering Materials, 474, 993-997. (2011)
Li, F. F., Fu, M. W., Lin, J. P., Wang, X. N. Experimental and theoretical study on the hot forming limit of 22MnB5 steel. The International Journal of Advanced Manufacturing Technology, 1-10. (2013)
Lin, Q. F. Fracture energy and strain path simulations for sheet metal forming using the finite element method. Master thesis, Department of mechanical engineering, National Cheng Kung University, Taiwan. (1991)
Luo, F. W. Prediction of High-strain-rate Forming Limit of Aluminum Alloy under Electromagnetic Forming Process. Master thesis, Department of mechanical engineering, National Cheng Kung University, Taiwan. (2010)
Makinde, A., Thibodeau, L., and Neale, K. W. Development of an apparatus for biaxial testing using cruciform specimens. Experimental mechanics, 32(2), 138-144. (1992)
Merklein, M., Lechler, J., and Geiger, M. Characterisation of the flow properties of the quenchenable ultra high strength steel 22MnB5. CIRP Annals-Manufacturing Technology, 55(1), 229-232. (2006)
Merklein, M., Lechler, J., Stoehr, T. Characterization of Tribological and Thermal Properties of Metallic Coatings for Hot Stamping Boron Manganese Steels. In Proceedings of the Seventh International Conference on Coatings in Manufacturing Engineering, 1-3. (2008)
Min, J., Lin, J., Li, J., and Bao, W. Investigation on hot forming limits of high strength steel 22MnB5. Computational Materials Science, 49(2), 326-332. (2010)
Naderi, M. Hot stamping of ultra high strength steels (Doctoral dissertation, Universitätsbibliothek). (2007)
Nakazima, K., Kimuta T., and Asuka, K. Study on the formability of steel sheet. Yawata Technical Report. 284, 678-680. (1968)
Norris, D. M., Reaugh, J. E., Moran, B., and Quinones, D. F. A plastic-strain, mean stress criterion for ductile fracture. Journal of Engineering Materials and Technology. 100, 279-286. (1978)
Ohtake, Y., Rokugawa, S., and Masumoto, H. Geometry determination of cruciform-type specimen and biaxial tensile test of C/C composites. Key Engineering Materials, 164, 151-154. (1998)
Oyane, M., Sato, T., Okimoto, K., and Shima, S. Criteria for ductile fracture and their applications. Journal of Mechanical Working Technology. 4(1), 65-81. (1980)
Pellegrini, D., Lechler, J., Ghiotti, A., Bruschi, S., and Merklein, M. Interlaboratory comparison of forming limit curves for hot stamping of high strength steels. Key Engineering Materials, 410, 297-304. (2009)
Solid mechanics lecture notes. Lecture Notes in Solid Mechanics Part III: Foundations of Continuum Solid Mechanics, 212, 215. Department of Engineering Science, University of Auckland
http://homepages.engineering.auckland.ac.nz/~pkel015/SolidMechanicsBooks/index.html, 2014/7/9. (2013)
Somani, M. C., Karjalainen, L. P., Eriksson, M., Oldenburg, M. Dimensional changes and microstructural evolution in a B-bearing steel in the simulated forming and quenching process. ISIJ international, 41(4), 361-367. (2001)
Teaca, M., Charpentier, I., Martiny, M., Ferron, G. Identification of sheet metal plastic anisotropy using heterogeneous biaxial tensile tests. International Journal of Mechanical Sciences, 52(4), 572-580. (2010)
Turetta, A., Bruschi, S., and Ghiotti, A. Investigation of 22MnB5 formability in hot stamping operations. Journal of Materials Processing Technology, 177(1), 396-400. (2006)
Vogel, J. H., and Lee, D. An automated two-view method for determining strain distributions on deformed surfaces. Journal of Materials Shaping Technology, 6(4), 205-216. (1988)
William Riley, Leroy Sturges, Don Morris. Mechanics of materials, Jon Wiley & Sons (Asia) Pte Ltd. Wiley Asia student edition, 6th ed. (2006)
Zhuang, W. L. Forming limit simulation for sheet metal using the finite element method. Master thesis, Department of mechanical engineering, National Cheng Kung University, Taiwan. (1990)
Zidane, I., Guines, D., Léotoing, L., and Ragneau, E. Development of an in-plane biaxial test for forming limit curve (FLC) characterization of metallic sheets. Measurement Science and Technology, 21(5), 055701. (2010)