外文翻譯--非圓柱齒輪壓力機的數(shù)字設(shè)計

1、<p>　　Numerical design of a new forging press drive incorporating non-circular gears</p><p>　　Abstract: Manufacturing processes as well as products have to be improved continually to meet all the requir

2、ements of international competition. Along with economic demands，changing consumer and environmental legislation lead to increased pressure for new and advanced products and processes. Consequently，the forging industry

3、continually tries to improve hot forging processes. Precision hot forging technology，used for the production of connecting rods，bevel gears，straight planet gears，helical ge</p><p>　　Keywords: metal forming;

4、finite element simulation; thermal die loading; drive mechanism; non-circular gears .</p><p>　　NOTATION : </p><p>　　1. PRECIDION FORGIN</p><p>　　Owing to its working principle and t

5、he higher accuracy of parts-die hot forging calls for higher requirements on process parameters and tool technology. Figure 1 shows the concept of the closed-die forging of a helical gear wheel. Closed-die forging is mos

6、tly used for the manufacturing of near net shape or additional closing elements close the die during the deformation, to operate the closing elements, multi-acting presses, spring assemblies or separate closing devices a

7、re needed to provide the</p><p>　　Divided dies or additional closing elements are needed if the punch is not able to close the die because of radial form elements such as helical gearings. Horizontally divid

8、ed dies have the advantage that the closing load can easily be provided by the ram movement combined with spring assemblies. Vertically divided dies, which are necessary for the ejection of parts with undercuts such as c

9、lutch gearings or constant velocity joints, need special devices for the transformation of vertical press l</p><p>　　The quality of the precision forged arts reaches the ISO standard IT 7-9. Typical forging

10、temperatures are between 1100 and 1280 for steel materials.</p><p>　　2. NEW PRESS CONCEPT IN PRECISION FORGING</p><p>　　An increasing number of precision forging applications of conventional for

11、ging machines particularly for requirements such as reliable closing of the dies, short pressure dwell, constantly energy distribution, overload protection and process integrated quality control. New concepts in hot fo

12、rging machines are being developed continually. Based on the technological requirements for economic precision hot forging processes, IFUM has developed an innovative press concept [5,6]. The concept is bas</p>&l

13、t;p>　　2.1 Optimization of the ram kinematics for the precision forging press</p><p>　　Figure 2 shows the calculated optimized kinematics of a precision forging press in comparison with a conventional cran

14、k drive. The cycle time of both press drives is 1.0s, whereas every second stroke is an idle one in order to prolong the cooling time. With a forming section of 20mm, the resulting pressure dwell time of the conventional

15、 drive is 75ms. By using non-circular gears, it is decreased to 39ms.</p><p>　　The varying transmission ratio, , of the non-circular gears [5] causes a non-uniform angular velocity, , of the crankshaft, a de

16、creased ram velocity, within the upper stroke area and an increased one within the forming area. The variable pitch curve radii, and , of the non-circular gears are determined by the required course of the transmission

17、 ratio i and therefore the ram kinematics:</p><p>　　with a given constant center distance:</p><p>　　a = constant = </p><p>　　the transmission function describes the relation betw

18、een the pitch curves of the non-circular gears.</p><p>　　In order to fulfill the requested demands on the ram kinematics, (Fig.2), the transmission function of the non-circular gears has to be suitably adapt

19、ed. This function is determined as a Fourier series with a limited number, M, of harmonic waves:</p><p>　　In order to determine the Fourier coefficient record so that the resulting ram kinematics fits the d

20、emands, an iterative genetic algorithm has been realized(Fig.3) .</p><p>　　Firstly, an initial coefficient record is estimated from the given kinematics demands by regression of s fifth-degree polynomial ov

21、er all demands and subsequent determination of its Fourier coefficients. By randomized change of single coefficients am and bm and interchange of coefficients, the next generation of N coefficient records ,n = 1,……N is

22、generated. Then, the resulting ram stroke functions, , are determined by means of integration of and the following consideration of the crank driv</p><p>　　The quality,, of the transmission functions gener

23、ated by the records is determined by calculation of the difference to the predetermined kinematic demands and several other conditions such as minimization of the ram acceleration. The records with the best quality ar

24、e selected in order to generate the next generation , of coefficient records by randomized modification. The iteration is stopped when the accuracy of the solution is sufficient, which is indicated by the quality,, of a

25、 solution f</p><p>　　Figure 4 shows the pair of non-circular gears calculated for the kinematic demands shown in Fig. 2. Since the angular velocity is variable owing to the changing transmission ratio. The

26、course of the slide velocity as an important parameter for the wear of the gears is different for every pair of teeth. In order to obtain a sufficient load-carrying capacity, a module of 20m and a teeth number of 72 have

27、 been chosen.</p><p>　　2.2 Optimization of the shape of the non-circular gears </p><p>　　Since the shape of the driving gear is very similar to a circle, it is possible to obtain similar ram ki

28、nematics with an eccentrically mounted circular driving gear combined with a driven </p><p>　　gear with a non-circular pitch curve. Such a pair of gears may be more economically manufactured than two gears w

29、ith non-circular shapes.</p><p>　　The radius, , of an eccentrically mounted circular gear is: </p><p>　　where , R is the radius and e is distance between the center and the pivot of the circle

30、(Fig.5). </p><p>　　The transmission ratio is: </p><p>　　In order to achieve an average transmission ratio of 1 and therefore closed pitch curves with identical circumferences, the condition:<

31、/p><p>　　has to be fulfilled [8]. For a given ratio, the center distance has to be determined by solving this nonlinear equation.</p><p>　　Figure 5 shows a pair of gears with an eccentrically mount

32、ed driving gear, which realizes similar ram kinematics as the first pair of gears. The ram velocity as well as the acceleration only shows a negligible difference to the original course. Owing to the changed shape and th

33、erefore changed circumference of the gears, the center distance for an identical number of teeth and an identical module has changed to 1503.62mm.</p><p>　　In order to simplify the design of non-circular gea

34、rs for press manufacturers, a PC program has been developed at IFUM. For a given set of kinematics it offers the possibility of calculating the shape of the pitch curves and teeth as well as other parameters including lo

35、ad-carrying capacity and slide velocity.</p><p>　　3 FINITE ELEMENT SINMULATION OF THE THERMAL DIE LOADING</p><p>　　After the design of the press drive, the effects the optimized kinematics on th

36、e thermal die loading should be examined. Therefore, finite element simulations have been performed in order to compare the different forming velocities and pressure dwells of a conventional crank drive and this newly pr

37、oposed press drive.</p><p>　　A survey of the developments in metal forming simulation is given in the literature [9-11], for the prediction or optimization of the material flow; an FE simulation with rigid d

38、ies is often sufficient. For estimation of process safety, knowledge of the die loading is required. In this case meshing of the dies with finite elements is also necessary. Some FE packages allow the simulation of formi

39、ng processes with deformable dies and workpiece. The contact processor couples the boundary and transi</p><p>　　3.1 Strategy of an uncoupled FE simulation </p><p>　　At LFUM, helical gear wheels

40、 have been formed in s precision forging process. Characteristics for this process are the high local stresses in the die. For this reason, the thermal die loading due to the forging process was investigated by the uncou

41、pled method (fig.6). Firstly, an FE simulation of the forging process was performed with rigid dies. This simulation was performed with the commercial FE package FORGE3. The thermal fluxes into the rigid dies were then d

42、etermined during this simulation</p><p>　　3.2 FE simulation of the forging process and the thermal die loading</p><p>　　To collect information about the thermal die loading as a result of the h

43、ot forging process for both press kinematics, uncoupled FE simulations were executed for the example of a helical gear wheel. In the first step, simulations with rigid dies were performed with FORGE3 for the non-circular

44、 and the conventional press kinematics (see fig.2). For both cases, the billet temperature was 1200. The heat transfer coefficient for contact between the two surfaces was constant .</p><p>　　To reduce the

45、 CPU time further, only a segment of the helical gear was modeled. Figure 7 shows the material flow and the temperature distribution of the thermomechanical simulation with OFRGE3. Significant differences in temperature

46、 can be seen at the top of the tools and at the reliefs. The surface temperature of the conventionally forged part at the end of the forging process is 100-150K lower than for the part that is forged with a non-circular

47、gear drive unit. This effect becomes important </p><p><b>　　where </b></p><p>　　Q = quantity of heat ;</p><p>　　A = surface area of the die;</p><p>　　During

48、 the FE simulation with rigid tools, the fluxes, have to be determined at the surface. In the second step, the calculated heat flow into the lower die is transferred to an FE model with meshed dies. To determine the evo

49、lution of heat into the die of more than one forging:</p><p><b>　　where</b></p><p><b>　　;</b></p><p>　　= local surface temperature of the workpirce;</p>

50、;<p>　　= local temperature of the tool;</p><p>　　= heat transission coeffient;</p><p>　　= cycle time;</p><p>　　n = number;</p><p>　　In this manner it is possible

51、 to simulate the temperature field and include the thermal dilatation of the dies for many forging cycles.</p><p>　　The heat flow into the upper and lower die and from there into the matrix was neglected. Th

52、e different pressure dwell times of both drive units wee taken into account. The calculated heat flow from the forging simulation was transferred for a total of 36 strokes on to the die.</p><p>　　The simulat

53、ions were accomplished using the commercial FE package MSC.MARD. The starting temperature pf the die was 100C. Figure 8 shows the simulated temperature distribution of both drive units. Already after 18 forging strokes

54、 (36 strokes). Significant differences can be seen between the drive units. In the case of the non-circular gear drive unit, the maximum temperature reached approximately 460C.</p><p>　　The highest temperatu

55、re for the conventional drive unit was 780C. owing to the shorter pressure dwell time of the non-circular gear drive unit, the amount of heat flow during the forging process was significantly lower than for the conventio

56、nal drive unit. Further more , heat was conducted away more efficiently as a result of the longer cooling time.</p><p>　　4. CONCLUSION</p><p>　　This article describes how to optimize the design

57、 of non-circular gears used in press drives. The required symmetrical ram kinematics means that an eccentrically mounted circular driving gear can be used. Since this gear may be manufactured conventionally, a reduction

58、in manufacturing costs may be possible in comparison with two non-circular gears. </p><p>　　The evolution of the temperature of the workpiece during the forging time can be simulated very easily with the unc

59、oupled simulation tool described. This simulation tool is optimized to reduce the FE simulation time of complex three –dimensional that the workpiece is hotter after the forging process using a press with non-circular ge

60、ars. This can be very important for the integrated heat treatment. Nevertheless, the thermal die loading of this press is much lower than for the conventional press.</p><p>　　In contrast to the conventional

61、press drive unit, the non-circular gear drive4 unit has the following advantages:</p><p>　　（1）The pressure dwell time is reduced significantly;</p><p>　?。?）The time for cooling and handling is l

62、onger;</p><p>　　（3）The thermal die loading is lower;</p><p>　?。?）The heat transfer from the workpiece into the dies is lower.</p><p>　　非圓柱齒輪壓力機的數(shù)字設(shè)計</p><p>　　摘要：加工工藝如同產(chǎn)

63、品一樣，必須不斷改進去適應(yīng)激烈的國際競爭，隨著經(jīng)濟的需求，消費者的改變，環(huán)境的立法，新產(chǎn)品和生產(chǎn)工藝的需求日益強烈。因此，鍛造業(yè)又努力去改進熱鍛工藝。曾被用以生產(chǎn)連桿、斜齒輪、直齒輪、螺旋齒輪傳動裝置和恒速結(jié)的熱鍛工藝已經(jīng)多次改進，為了保證工件的連續(xù)和產(chǎn)品不被剪、拉破壞，封閉模具在精密鍛造中被廣泛應(yīng)用，使精密鍛的技術(shù)又向前推進了一步。很多因素影響產(chǎn)品的質(zhì)量和工藝的經(jīng)濟性，特別是工件溫度，模具溫度和工作時間。高溫條件導(dǎo)致模具溫度升高。因此

64、，模具的溫度與工作時間有直接關(guān)系。過高溫度不可避免的導(dǎo)致模具的破壞。這篇文章介紹了一種利用非圓柱齒輪嚙合這一全新概念在壓力機機械上的數(shù)字化研究。這種運動原理同傳統(tǒng)的運動學(xué)相比減少了壓力機工作時間。</p><p>　　關(guān)鍵詞： 金屬組織、有限元仿真、模具熱裝載、驅(qū)動機械、非圓周齒輪。</p><p><b>　　符號說明：</b></p><p&g

65、t;　　a 中心距</p><p>　　am, bm 傅立葉級數(shù)的系數(shù)</p><p>　　A 模具的表面積</p><p>　　C 補償系數(shù)</p><p>　　e .偏心距</p><p>　　i(φ) .

66、壓力角的轉(zhuǎn)換率函數(shù)</p><p>　　n .轉(zhuǎn)數(shù)</p><p>　　q .溶劑</p><p>　　Q ..熱量</p><p>　　r1(φ) .主動輪漸開線關(guān)于壓力角的極坐標函數(shù)</p><p>　　r2(φ) .從動輪漸開線

67、關(guān)于壓力角的極坐標函數(shù)</p><p>　　R 齒輪分度圓半徑</p><p>　　s .滑塊行程</p><p>　　Tdie ..工具的局部溫度</p><p>　　Twp .工件的局部溫度</p><p>　　υs ..滑動速

68、度</p><p>　　x 傅立葉系數(shù)的記錄</p><p>　　αtr .熱傳導(dǎo)系數(shù)</p><p>　　T 周期</p><p>　　φ 主動輪壓力角</p><p>　　ψ 從動輪壓力角</p><p

69、><b>　　精密鍛</b></p><p>　　由于精密鍛的工作原理和分模鍛的較高精度，對工藝參數(shù)和模具參數(shù)有較高要求。圖1顯示了用封閉模鍛斜齒輪的工作原理。封閉模大部分用來加工網(wǎng)狀或者在主變形過程中的一些附屬特征。為了形成封閉模的多壓力，必須有彈性裝配或者有操作封閉設(shè)備來提供封閉壓力。</p><p>　　如果壓力機象在加工斜齒輪時由于徑向變形不能閉合，必須

70、有多?；蛘哂懈郊拥姆忾]部件。水平分模的優(yōu)點是壓力好提供，而且滑塊運動同彈性裝配部件的組合很容易實現(xiàn)。垂直分模對有彈射部件的下切很有必有。像離合齒輪和恒速結(jié)就是這樣的。當單步壓時同時需要水平和垂直壓力。一個替換物是鑄件壓力機。即使滑塊的速度在熱鍛工藝中不是足夠的快，這已在有些加工中被使用。</p><p>　　精密鍛的精度已達到國際標準IT7~9, 對金屬材料典型的鍛溫在1100度到1280度之間。</p&

71、gt;<p><b>　　精密鍛中的新概念</b></p><p>　　在傳統(tǒng)的壓力機上進行精鍛的應(yīng)用迅速增長。尤其象模具的完全封閉，短的工作時間，恒定的能量散失，過載保護和集中工藝質(zhì)量控制的需求。關(guān)于熱鍛的新技術(shù)不斷被發(fā)展。對經(jīng)濟型熱鍛壓力機基于技術(shù)上的需求，IFUM創(chuàng)造了一種全新的概念。這種技術(shù)主要基于用非圓柱齒輪嚙合來保證最小的工作時間和由此而來的最小的熱載荷。</

72、p><p>　　精鍛壓力機滑塊的運動優(yōu)化</p><p>　　圖2表示了精鍛同傳統(tǒng)的壓力機相比的優(yōu)良特性。兩者的周期都是1秒。然而，在一秒鐘中壓塊并不工作，都是在延長冷卻時間。對截面為20 mm的變形，傳統(tǒng)壓力機需要75ms, 而新型壓力機可減少到39ms。</p><p>　　傳導(dǎo)率的變化，是由非圓柱齒輪的非常規(guī)的角速度的變化引起的。在變形面積較大，滑塊速度增長，節(jié)線

73、r1,r2的變化是由傳導(dǎo)率的需求而定的：</p><p><b>　　。</b></p><p><b>　　中心距為定值：</b></p><p>　　a = constant = r1(φ) + r2(φ)</p><p>　　轉(zhuǎn)換函數(shù)描述了圓周齒輪節(jié)線和非圓柱齒輪節(jié)線的關(guān)系。</p>

74、;<p>　　為了滿足滑塊運動學(xué)的要求，這函數(shù)必須進行一些適應(yīng)性修改。函數(shù)值是由m個代數(shù)式的傅立葉級數(shù)決定的：</p><p>　　為了確定傅立葉系數(shù)滿足滑塊的運動學(xué)需求，須使用迭代，如圖3，首先，由滑塊運動學(xué)要求估計出傅立葉系數(shù)的初值。根據(jù)公式推出級數(shù)為1到15的傅立葉系數(shù)，其值為和隨機相乘之和。函數(shù)由和曲軸的驅(qū)動決定。</p><p>　　質(zhì)量因數(shù), 由預(yù)先確定運動條件以

75、及滑塊最小加速度的產(chǎn)生出來的記錄決定。系數(shù)和決定了下一個因數(shù)，并可被隨機修改。當精度達到要求時，計算值低于預(yù)期值，并在超過一定步數(shù)后對結(jié)果改進不大就停止計算。</p><p>　　圖4顯示兩個非圓柱齒輪嚙合計算。用角速度的變化去改變傳動因數(shù)?；瑒铀俣茸鳛辇X輪磨損的一個重要因數(shù)，在每對嚙合齒出并不相同。根據(jù)傳動負載計算并取模數(shù)m為20mm, 齒數(shù)72。</p><p>　　2.2 非圓柱

76、齒輪的形狀的優(yōu)化</p><p>　　因為主動輪同圓是非常相似的，因此，很容易按照圓柱齒輪的運動學(xué)原理去驅(qū)動從動輪。這樣比造兩個非圓柱齒輪更經(jīng)濟。</p><p>　　圓齒輪的偏心半徑為：</p><p><b>　　式中 ：</b></p><p>　　ε= e/R , R是齒輪分度圓半徑，e為偏心距。如圖5。<

77、;/p><p><b>　　轉(zhuǎn)換率為：</b></p><p>　　為了獲得平均轉(zhuǎn)換率，對節(jié)線進行積分：</p><p>　　ξ為已知，中心距由非線性公式?jīng)Q定。</p><p>　　圖5顯示了一對偏心齒輪實現(xiàn)了非圓柱齒輪的相似運動。在整個工作過程中速度和加速度只有很小的差異，可以忽略。由于圓周形狀的改變，在相同模數(shù)和齒數(shù)的情

78、況下，中心距變?yōu)?503.62mm。</p><p>　　為了簡化設(shè)計,IFUM開發(fā)了一種程序，只要給出滑塊速度，公稱壓力，節(jié)線長，程序能自動進行計算。</p><p>　　3. 模具載荷的有限元仿真</p><p>　　壓力機設(shè)計好后，應(yīng)該檢驗一下在熱負載方面的效果。用有限元模擬新壓力機同傳統(tǒng)壓力機在速度和工作時間上的不同表現(xiàn)。</p><p&

79、gt;　　[9－11]給出了有關(guān)金屬組織有限元模擬發(fā)展的調(diào)查報告。由于預(yù)計或者材料變形比較理想，往往一次PE模擬就夠了，處于安全考慮，模具安全的知識是必須的。在分析中模具同有限元的嚙合也是必要的。一些有限元分析程序包可進行工作狀態(tài)下的模具與工件的變形分析，接觸處理器連接工件和模具的邊界和瞬態(tài)條件，模具的機械變形和他們在材料流動性方面的影響，可以用接觸模擬器進行分析。今天，可變形的三維模型與二維網(wǎng)格模型進行分析相比需要耗費CPU更長的時間

80、。因此，IFUW開發(fā)了一種非連續(xù)計算的軟件，用他的FORGE模塊對模具和工件進行建模，用他的MSCMARC模塊進行有限元分析。</p><p>　　3.1 分解的有限元分析策略</p><p>　　在IFUM 中，螺旋狀斜齒輪已被用精密鍛工藝進行制造。他的特點是模具的局部表面有較高的壓力。因此，非接觸分析對這種現(xiàn)象進行了分析。如圖6。首先，鍛壓的有限元模擬是用網(wǎng)格模型進行的，用的是商業(yè)有限

81、元分析軟件FORGE3.仿真中熱量大量傳到網(wǎng)格模具并進行了計算。節(jié)點是模型單元的邊界條件，這種方法減少了CPU的花費。據(jù)調(diào)查顯示，這種模擬比連續(xù)的有限元分析少用一半的時間。</p><p>　　3.2 鍛造的有限元模擬和模具的熱負載</p><p>　　為了收集壓力機工作后模具熱負載的信息，用非連續(xù)的有限元模擬對斜齒輪進行了模擬。第一步，用傳統(tǒng)動力學(xué)對網(wǎng)格模型進行分析，見圖2。這種情況下局

82、部溫度高達1200度。兩接觸面之間的傳導(dǎo)率為定值。</p><p>　　為了進一步減少CPU的開銷，僅對斜齒輪的一部分進行分析。圖7顯示了用FORGE3 對材料流動和和溫度的分布模擬。可以看出在模具上溫度有很大不同。用傳統(tǒng)壓力機工作后表面的溫度是100到150度比用非圓柱齒輪壓力機低。這種現(xiàn)象對加工熱的綜合利用很重要。熱流量由下式?jīng)Q定：</p><p>　　式中：Q表示熱量；A 表示模具

83、表面積。</p><p>　　在用有限元對網(wǎng)格模型進行分析時，熱流量主要由表面決定。在第二步中，計算流入溫度較低的模具的熱量。為了確定熱量的流量，用了一下公式進行計算： </p><p><b>　　式中：</b></p><p>　　q0 =αtr(Twp - Tdie );</p><p>　　上式中先計算一段時間

84、中的熱量，然后求其平均值。</p><p>　　熱量從模具高溫部分流到低溫部分過程中的熱損失被忽略。兩種壓力機的不同工作時間的不同熱量被分別統(tǒng)計?；瑝K的能量的百分之36被轉(zhuǎn)化到模具上。</p><p>　　這中模擬應(yīng)用了商業(yè)分析軟件MSC.MARD。開始溫度是100度。圖8顯示了兩種壓力機的溫度擴散情況。工作18個周期后，溫度出新明顯差異，非圓柱齒輪壓力機模具的溫度最高可達460度。<

85、;/p><p>　　而傳統(tǒng)壓力機的最高溫度為780度。由于工作時間短，非圓柱齒輪的模具的傳入熱量明顯比傳統(tǒng)壓力機低。更重要的是熱量被更加有效的控制。</p><p><b>　　結(jié)論</b></p><p>　　這篇文章描述了如何進行非圓柱齒輪壓力機的優(yōu)化設(shè)計。這意味著利用圓柱齒輪傳動原理的非圓柱齒輪能被應(yīng)用。相比之下，用圓柱齒輪傳動是用非圓周齒輪

86、傳動加工成本的兩倍。</p><p>　　在加工過程中溫度的變化可被分解仿真工具很容易的模擬。這種仿真工具用來減少三維仿真的時間。這種仿真表明工件鍛造后溫度較高。這對完全熱量處理是很重要的。然而模具的溫度同傳統(tǒng)壓力機相比比較低，因此，熱載荷對模具的影響減小。</p><p>　　同傳統(tǒng)的壓力機相比，非圓柱齒輪有已下優(yōu)點：</p><p>　?。?）工作時間顯著減少；