資源目錄里展示的全都有，所見即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問(wèn)可加】 14 I FORGING I JANUARY / FEBRUARY 2011FLASHLESS FORGINGOF A TWO-CYLINDER CRANKSHAFT WITH SECONDARY FORM ELEMENTSIn recent years flashless precision forging of two-cylinder crank-shafts was developed at the IPH - Institut fr Integrierte Produktion Hannover gemeinntzige GmbH. Compared to conventional forging methods, flashless precision forging permits reduction of raw ma-terial required to complete the part, as well as the omission of the process steps for trimming. Due to the improved quality of the finished parts, flashless forging makes it possible to achieve functional surfaces without extensive additional reworking. To assess the industrial applicability of this forging method, IPH is researching the technology for precision forging a challenging crank-shaft, including the secondary form elements, low end and flange. This report describes the design of the forging sequence and process. The goal of the research is a three-stage forging sequence for flashless precision forging of crankshafts with secondary form elements. Flashless precision forging is conducted in closed dies. With the method described here, die closure is realized temporally separated from the forming. There is no forming until die closure. Only the sub-sequently inserted punch initiates the forming. Precision forging reaches quality levels like tolerance classes IT 8 to IT 10 Doe07, Bro99. A four-stage forging sequence of a simpli-fied two-cylinder crankshaft without any secondary form elements is depicted in Figure 1. This sequence was developed in the special Figure 1: Stage sequence for flashless precision forging of a two-cylinder crankshaft without secondary form elements Mue08.research project, SFB 489.The first and second forming step is done by lateral extrusion in a closed die. The third step consists of multi-directional forming in a semi-open die, and the fourth (and final) step is a flash-less precision forging process, again in a closed die. During the multi-directional forming step, the part is formed in ver-tical and horizontal spatial direction. The redirection of press energy was re-alized by wedges Mue08. Present developmentTo use the precision forging technol-ogy for crankshafts in industrial op-erations, it s first necessary to supple-ment the two-cylinder crankshaft with secondary form elements, low end and flange (see Figure 2), and to redesign the forging process.To reduce production times and tool Researchers seek an industrial-scale, three-stage process for precision parts, with the efficiency and finish-product quality of flashless forging. By DIPL.-ING. MATTHIAS MEYER, DIPL.-ING. (FH) MICHAEL LCKE, DR.-ING. DIPL.-OEC. ROUVEN NICKEL and PROF. DR.-ING. BERND-ARNO BEHRENSWWW.FORGINGMAGAZINE.COM I FORGING I 15costs, opportunities for omitting one or more forming steps were assessed. Tests were conducted to determine whether the staged pro-gression must be forged in four steps (comparable to the two-cylinder crankshaft without secondary form elements), or if it s feasible to scale back to a three-stage forging process. Increased tool-loads due to the omission of one forming step can have negative effects on tool wear, thus can reducing tool life.Regarding the design of the staged sequence for a two-cylinder crankshaft with secondary form elements, marginal conditions must be considered just as for the two-cylinder crankshaft without sec-Figure 2: Two-cylinder crankshaft without (left) and with (right) secondary form elements.Figure 3: Comparison of forming forces in three- and four-stage sequences.ondary form elements. The marginal conditions might be respective presses (maximum ram force and space re-quirements) as well as fold-free and free-form crack formation.Comparison of three- and four-stage sequence The three- and four-stage sequences were designed with the Finite Element Analysis (FEA)-based simulation soft-ware Forge 2009. Before each simula-tion the temperature of the part was set to 1,250C, the tool-temperature to 250C and the forming velocity to 25 mm/s. Subsequent evaluation of the material flow was conducted with re-gard to forming force, deformation de-gree, pressure dwell time, temperature distribution within the part, and the expected tool wear. The aim was a com-parison of both staged sequences. In the intermediate stages of the four-stage forging sequence, the form-ing forces at the end of the forming are similar or higher than those in the three-stage sequence. Since the major-ity of the required deformation energy is introduced during the first three forming steps, the final forming step needs considerably less forming force (see Figure 3)16 I FORGING I JANUARY / FEBRUARY 2011In the three-stage forming sequence, the extended contact times of crankshaft and base tools cause increased cooling in the area around the main bearing and the low-end bearing during the last forming step. In the area of the crank web, a comparison of three- and four-stage forging sequences shows higher temperatures for the three-stage forging sequence due to shorter contact times of work piece and tool (see Figure 6). Due to the increased forming force, tool wear for the three-stage forging sequence is considerably higher than for the four-stage sequence. It is par-ticularly notable in the area around the main bearing and the low-end bearing (see Figure 7). This is due to increased cooling of the part due to extended con-tact times. This increased locally the flow stress, and hence heightened tri-bological load, between the parts and the tool.ConclusionBased on the deliverables, it is evi-dent, that both staged progressions are feasible since critical parameter levels, like the deformation degree X = 4 are not exceeded. Due to a lower forming force and reduced tool wear, a compari-son of FEA-results indicated benefits from the four-stage forging sequence. In order to realize the three-stage se-quence the re-design of the second in-termediate stage might be necessary in an additional loop. To reduce the forming force within the three-stage forging sequence, the material distribu-tion for the second intermediate stage should be less around the main bearing and the low end bearing and deepen in the crank web. This could reduce the contact time around the main bearing and the low-end bearing and hence the cooling effect. In addition, an increased forming velocity (at present 25 mm/s) can accelerate the forming, shorten the contact time and thus reduce the ef-fort for the realization of the final form-ing stage of the three-stage forging se-quence.Summary and outlookIn continuing research it will be necessary to explore possible applica-Figure 4: Comparison of degrees of deformation.Figure 5: Comparison between the contact times.COMPARISONS BETWEEN THREE- AND FOUR-STAGE SEQUENCES:Regarding the forming force, the analysis showed an estimated 40% higher forming force in the three-stage forming sequence com-pared to the four-stage forging sequence. The predominant forming of the four-stage forging sequence within the first three forming steps is illustrated in the comparison of deformation degrees (see Figure 4). Due to the extended forming path in the last forming step, the con-tact time of tool and work piece in the three-stage forming sequence is considerably longer than in the four-stage sequence. In particulary, the difference occurs in the area around the main bearing and the low-end bearing, where contact times are between 1.0 and 1.7 seconds for the three-stage forging sequence, and between 0.7 to 1.0 second for the four-stage forming sequences. With the three-stage forging sequence, the gravure area of the crank web is not filled before the end of the forming process. Hence, the contact period in this area is short, while the four-stage forming sequence shows longer contact times between 1.0 s and 1.3 seconds (see Figure 5). WWW.FORGINGMAGAZINE.COM I FORGING I 17Figure 6: Comparison of forming temperatures.Figure 7: Comparison of tool wear.The authors are affiliated with the Institute of Integrated Production Hannover (IPH), in Hanover, Germany; visit www.iph-hannover.de. Dipl.-Ing. Matthias Meyer studied mechanical engineering at the Leibniz University of Hanover. Since June 2008 he has worked as scientific assistant at the IPH .Dipl.-Ing. (FH) Michael Lcke studied mechanical engineering at the University of Applied Science Stralsund. Since July 2007 he has worked as scientific assistant at the IPH.Dr.-Ing. Dipl.-Oec. Rouven Nickel studied economics, focusing on production management, manufacturing technology and performance measurement at the Leibniz Universitt Hannover. Subsequently, he worked as research associate at the Institute of Production Systems and Logistics (IFA). Since 2007 he has been the managing director of the IPH. In 2008 he received his doctorate in mechanical engineering at the Universitt Bremen.Prof. Dr.-Ing. Bernd-Arno Behrens studied mechanical engineering at the University of Hanover and, subsequently, worked as research associate at the Institute of Metal Forming and Metal-Forming Machines (IFUM) at the Leibniz Universitt Hannover. After receiving his doctorate in mechanical engineering he headed the Department of Application Technology at Salzgitter AG, Salzgitter, Germany. Since 2003 he has headed the IFUM at the Leibniz Universitt Hannover, and in 2005 became a member of the management board of the IPH. The authors express their thanks to the German Research Foundation (DFG) for its financial support of the SFB 489 project described here.REFERENCESBro99 Bro, G.: Entwicklung eines Verfahrens zum Przisionsschmieden von PKW-Pleueln. Dissertation, Universitt Hannover, Fortschritt-Berichte VDI, Reihe 2, Nr. 508, VDI-Verlag, Dsseldorf 1999.Doe07 Doege, E.; Behrens, B.-A.: Handbuch Umformtechnik Grundlagen, Technologien, Maschinen. Springer-Verlag, Berlin Heidelberg 2007.Mue08 Mller, S.; Mller, K.: Parameterstudie eines mehrdirektional wirkenden Werkzeugs zum gratlosen Przisionsschmieden einer Zwei-zylinderkurbelwelle. In: STAHL, Verlag Stahleisen, o. Jg. (2008), H. 3, S.38-39.tions of cross wedge rolling for the production of the first pre-form. For the two-cylinder crankshaft with secondary form elements, the first pre-form can be realized with mass concentrations in differ-ent locations. Based on this, the design of the cross wedge rolling process will be adjusted to determine the potential for rolling with multiple wedges. 2011 Penton Media, Inc. All rights reserved.