外文翻譯---刀具前角對切削加工振動的影響

1、<p>　　Effect of Tool Rake Angle on </p><p>　　Machining Vibration</p><p>　　Abstract：Effect of tool rake angle on cutting vibration by experiments are done at different cutting speed in machi

2、ning operation, and corresponding theoretical analysis is conducted. Result indicates, amplitude of machining vibration gradually decreases with tool rake angle increasing; while rake angle γ0<0°, the biggest uni

3、direction amplitude occurs at V=50~70m/min; While γ0≥0°, it is at V=160~180m/min. Moreover, quarding measures is presented on avoiding the biggest amplitude range so as to g</p><p>　　Keywords: machining

4、,vibration,amplitude,tool rake angle</p><p>　　In machining operation, tool character is not only decided by material, to a certain extent, it depends on resonable geometrical parameters. Tool rake angle is o

5、ne of the specialest geometrical parameters, directly affects cutting zone deformation, chip morphology, chip break effection, cutting force, tool head strength and machined surface, quality it is researched by foreign s

6、cholars. Relative study points out[1]: tool rake angle also has considerable effect on machining vibration. But what is</p><p>　　1 Experimental Material,Equipment and Instrument</p><p>　　1.1 Wo

7、rkpiece Material</p><p>　　Different metal materials have different physical mechanical characters. In this experiment, choose general used workpiece material 45# steel in cylindrical machining.</p>&l

8、t;p>　　1.2 Tool Material</p><p>　　According to piece material, choose YT14 hard alloy tool tip is choosen and drill weld it on to 45# steel tool. Precision and utraprecision machining are strict on qualit

9、y of spare surface, while vibraltion affects is mostly. Therefore, the geometrical parameters and corresponding machining quality of six tools are selected in this experiment rake angle γ0 is made:-20°,-10°,0&#

10、176;,10°,20°and 30°, tool cutting edge anglekris 45°, tool minor cutting edge angle kr′ is 15°, tool orthogonal clearanceα0 i</p><p>　　1.3 Equipment and Instrument</p><p&

11、gt;　　In experiment, choose CA6140 lathe (Shenyang First machine Tool Plant Made), electric eddy-current sensor and riameter WFC-Ⅲ. Electric eddy-current sensor can be used in dynamic untouched survey, survey range is 0~1

12、500μm, resolving power can reach 1μm; Measure range of WFC-Ⅲis 0.2~300μm (Unidirection vibration value), this viameter fairly resists interferance, measured data has quite accurate.</p><p>　　2 Experiment Met

13、hod and Measured Data</p><p>　　Considering up limit of vibration in machining opration, clamp wordpiece on lathe CA6140 with cantilever of three-jaw-chuck. Experiment test device sketch map in Fig.1</p>

14、;<p>　　indicates: Distance from sensor untouched testing point ( its surface roughnessRa=2.2μm)to end surface of chuck is 200mm. Sensor is fixed on lathe tail stock, the measured amplitude (only measure the sensi

15、tive direction of work- piece in machining) is an absolute value of piece relative to lathe guide. Distance between cutting part and outter end of chuck is 50~190mm. Relation between rake angle and amplitute of vibration

16、 measured in machining operation see table 1.</p><p>　　With measured data in table 1, relation curve of tool rake angle and cutting speed</p><p>　　affecting amplitute of vibration is given in Fi

17、g.2.</p><p>　　Fig.2 indicates: The measured amplitudes of vibration differently correspond to dif-</p><p>　　ferent tool rake angle; with rake angle changing, amplitude varies even at same rake a

18、ngle, while γ0< 0°, the biggest amplitute occurs at V=50~70m/min; while γ0≥0°, it</p><p>　　is at V=160-180m/min. To each tool, three repeat experiments are done to verify the</p><p>

19、;　　reliability of above testing data, its trend of vibration is roughly the same, only the amplitude of vibration changes a little all (relative error less 5%).</p><p>　　3 Analysis of Experiment Result</p

20、><p>　　On the base of measured data and experiment curve in Fig.2, analysis is given as</p><p>　　fellows: </p><p>　　3.1 Relation between Ra

21、ke Angle and Biggest Amplitude</p><p>　　In compliance wity table 1, putting data in order, relation between rake angle and biggest amplitude of vibration see table 2. It indicates: With tool rake angle incre

22、asing, the biggest amplitude value progrssively decreases. It is because rake angle increasing lessens press of rake face to chip, plastic defrmation of chip reduced, then coefficient of chip frictiona force on tool rake

23、 face decreases, therefore, it lessens cutting force, results in amplitude of viberation in machining operation d</p><p>　　3.2 Effect of Rake Angle and Clearanec Angle Dynamic Changing on Amplitude of Vibra

24、tion</p><p>　　From machining principle, tool work angle changes with tool movement properties, and it affects cutting force. Variation of work angle is decided by the situation of cutting edge plane in machi

25、ning operation[2,3].Variation of tool rake angle and clearance angle in machining operation is list in Fig.3. In cutting process, tool vibrates at the direction of main vibration, formes vibrating , relative velocity

26、 </p><p>　　changes not only at value, but also at direction. Namely, because of changes with time, it changes the situation of tool cutting edge plane, results in both tool working rake angleγoeand

27、working clearance angleαoechanging cyclically, then form an alternating force. Variation of cutting force is decided by change quantity (strictly speaking, it also includes the change of clearance angle).</p><

28、p>　　Variation of rake angle can be get from Fig.3:</p><p>　　Thus, variation of level compont of force Py can be discribed as</p><p>　　Where Kγ is the effect coefficient of rake angle on level

29、 component of force. As mentioned above,Py decreases with γ0 increasing, thus Kγ< 0 .</p><p>　　Analysying force state in Fig.3, motion equation is</p><p>　　Straigten out as fellows, </p&g

30、t;<p>　　There upon, condition of causing self driving vibration is : (C+Kγ/v0) < 0 </p><p>　　Thus it can see: 1) While γ0= 0°, due to change of working angle, it makes γoe>0°, Namely,

31、at this time, change rate of Kγ is fairly big, it causes considerable amplitude of vibration in machining opration.</p><p>　　2) While γ0>0°, though working angle also changes, but γoe increases relat

32、ively less than γ0(change rate of Kγ if small), thus Py changes a little, just small amplitude of vibration forms.</p><p>　　3.3 Effect of Tool Head Dynamic Stiffness on Amplitude </p><p>　　In

33、the condition of fixing others tool geometrical paramenters, just change rake angle, it will cause tool head dynmic stiffness changing, thus the intrinsic frequency of tool and compund rest is affected, when it approache

34、s technological system frequency, considerable amplitude forms (even resonance forms). Relation of biggest amplitude caused by tool rake angle and corresponded cutting speed see table 3.</p><p>　　Table 3 ind

35、icates:</p><p>　　While γ0<0°, the corresponding cutting speed range of largest vibrating amplitude is V=50~70m/min; </p><p>　　While γ0≥0°, the range is V=160~180m/min.</p>&l

36、t;p>　　Thus it can see, it is necessary to solve the problem of vibration to get high precision and high quality spares at high speed (over 120m/min). Otherwise, it is difficult to ensure machining high precision, high

37、 quality spares with high efficiency. According to equation (3): Amplitude of vibration can be decreased by increasing coefficient of damper C. Namely, adopt dead pressure compound rest or set up auxiliary damper to incr

38、ease C, or increase section of tool, reduce suspend quantity, polish </p><p>　　4 Conclusion</p><p>　　1) With tool rake angle increasing, amplitude of machining vibration progressively reduces;&l

39、t;/p><p>　　2) At fixed rake angle, with cutting speed changing, amplitude of machining vibration changes continuonsly;</p><p>　　3) At same cutting speed, with rake angle changing, amplitude of mach

40、ining vibration also changes;</p><p>　　4) In the choosen condition of this experiment, while γ0<0°, the largest amplitude occurs at V=50~70m/min; while γ0≥0°, it is at V=160~180m/min;</p>

41、<p>　　5) It must solve the problem of vibrating in high speed zone in precision machining (select γ0> 0°), namely, adopt damp and siffness etc.</p><p>　　References</p><p>　　1 Zho

42、u Zehua. Metal cutting principles. Shanghai: Shanghai Science and Technology Press, 1984,139</p><p>　　2 Yangdi. Machine tool dynamics. Beijing: Engineering Industry Press, 1993</p><p>　　3 Zhen

43、g Weizhong. machine tool vibration and prevention. Beijing: Science Press, 1981</p><p>　　From: JOURNAL OF BASIC SCIENCE AND ENGINEERING Vol.7,No.2June 1999</p><p>　　刀具前角對切削加工振動的影響</p>&

44、lt;p>　　摘 要 對機械加工中刀具前角對切削加工振動的影響進行系統(tǒng)的實驗研究和相應的理論分析,結(jié)果表明:隨著刀具前角增加切削加工振動的振幅逐漸減小，當?shù)毒咔敖铅?<0°時,最大振幅產(chǎn)生在V=50-70m/min;而當γ0≥0°時,最大振幅產(chǎn)生在V=160-180m/min。這一結(jié)果為精密和超精密加工中有效地抑制或避免切削振動提供了理論與實驗依據(jù)。</p><p>　　關鍵詞

45、 機械加工 振動 振幅 刀具前角</p><p>　　機械加工中，刀具的性能除了受材料的影響，在一定程度上取決于刀具集合參數(shù)的合理性。刀具前角是一種最特別的集合參數(shù)，它直接影響切削帶形變，切屑形狀，切屑強度，刀具頭強度和加工表面質(zhì)量，這些情況已經(jīng)經(jīng)過一些國外學者的調(diào)查研究。相關研究表明[1]：刀具前角對加工振動也有明顯的影響。但刀具前角對切削加工中振動的影響的研究結(jié)果怎么樣呢？在不同的切削速度下，刀具前角與振動

46、振幅有什么關系？規(guī)律是什么呢？這些以及一些其它問題沒有經(jīng)過整理且沒有確切的數(shù)據(jù)。由于這方面的原因，在不同的切削速度下對刀具前角與加工振動相互關系的經(jīng)驗調(diào)查和理論分析與結(jié)果的產(chǎn)生中進行一般的刀具選擇和合理的使用工件與刀具材料，目的是試圖得到相關數(shù)據(jù)和相應材料。這個調(diào)查為實際中采用合理的刀具前角提供了理論依據(jù)。</p><p>　　1. 實驗材料.設備和儀器</p><p><b>

47、　　1.1 工件材料</b></p><p>　　不同的金屬材料有不同的物理機械性能。在這個實驗中選擇在柱面加工中用過的45#鋼工件材料。</p><p><b>　　1.2 刀具材料</b></p><p>　　通過一部分材料，選擇YT14硬質(zhì)合金刀頭并把它焊接于45#刀柄上。在大多數(shù)時候，精密和半精密機器對配件表面有嚴格要求。因

48、此，實驗中選擇六種相應刀具集合參數(shù)和加工質(zhì)量。它們前角γ0分別為：-20°,-10°,0°,10°,20°和30°，刀具主偏角kr為45°,刀具副偏角kr′為15°。刀具后角α0為8°，刃傾角λ0為 0°，刀具圓角半徑為1.5—2.0mm，切削速度V為20—30m/min，進給量為0.2mm/r，嚙合量間隙為0.5mm。</p>

49、;<p><b>　　1.3 設備與儀表</b></p><p>　　實驗中，選擇CA6140型車床，電氣渦流傳感器和WFC-Ⅲ振。電器渦流傳感器可用于動態(tài)非接觸測量，它的測量范圍為0—1500μm，分辨率可達到1μm；WFC-Ⅲ的測量范圍為0.2—300μm（單行振動值），此振抗干擾能力很強，測量數(shù)據(jù)比較準確。</p><p>　　2. 實驗方法與測量

50、數(shù)據(jù)</p><p>　　考慮極限振動加工運行中，CA6140車床工件夾具與懸臂三爪卡盤。實驗裝置示意圖如圖1</p><p>　　圖1 實驗裝置示意圖</p><p>　　說明：真空傳感器測試點距離卡盤表面為200mm（表面粗糙度為Ra=2.2μm），傳感器固定于車床尾部，切削部分與卡盤外部底端的距離為50—190mm。在機械加工中，前角與振動的關系如表1所示。&

51、lt;/p><p>　　表1 前角與振幅的關系</p><p>　　如表1中的測量數(shù)據(jù)，刀具前角和切削速度對振動振幅的影響關系曲線如圖2.</p><p>　　圖2.前角.速度與振幅之間的關系</p><p>　　圖2表明：不同的刀具前角對應不同的振幅：當前角γ0< 0°時，隨著刀具前角的變化，即使前角相同，最大振幅會發(fā)生在V=5

52、0—70m/min；當γ0≥0°時，最大振幅發(fā)生在V=160—180m/min。對每個刀具都做了3次重復實驗以驗證測量數(shù)據(jù)的可靠性，它的趨勢大致相同，只是振幅均有所變化（相對誤差小于5%）。</p><p><b>　　3.實驗結(jié)果分析</b></p><p>　　以實驗數(shù)據(jù)和實驗曲線為依據(jù)，研究員分析如下：</p><p>　　3.

53、1 前角與最大振幅的關系</p><p>　　按表1對數(shù)據(jù)進行有規(guī)律的排列，前角與最大振幅關系如表2所示。它表明：隨著刀具前角的增大，最大振動幅度會逐步減小。這是因為刀具前角的增大會使前表面對切屑及切屑塑性變形減小從而使刀具表面摩擦系數(shù)降低，因此，它可以減小切削強度，從而使切削加工振動降低。</p><p>　　表2 前角與最大振幅的關系</p><p>　　3.2

54、 前角和后角對振幅動態(tài)變化的影響</p><p>　　通過加工原理，刀具工作角度隨刀具運動性能而變化并影響切削強度。工作角度的變化情況取決于前角的加工操作[2，3]。刀具前角和后角的變化在機械加工中如圖3所示。在切削進程中，刀具振動在主振動方向形成振動速度y.，相對速度</p><p>　　不僅數(shù)值變化，方向也變化。即由于y·隨時間變化而變化，它改變了刀具切削前刀面的情況，結(jié)果使

55、刀具前角γo 和后角αo周期性變化，從而形成強度的交替變化。切削強度的變化取決于角度的變化量（嚴格的說，它也包括后角的變化），前角的變化可以通過圖3得出：</p><p>　　圖3 前角與后角動態(tài)變化</p><p>　　因此，構(gòu)件強度變化變化程度Py可表示為：</p><p>　　其中Kγ是影響組件強度的前角因素。如上所述，Py隨前角的增大而減小，因此Kγ<

56、0。</p><p>　　如圖3進行強度分析，相關方程為：</p><p>　　變形為： </p><p>　　通過以上可以得出引起自激振動的條件是：(C+Kγ/v0) < 0</p><p><b>　　可以看出：</b></p><p>　　1）當γ0= 0°時，應

57、該改變工作時的角度，它可以引起γoe>0°, 即如果這樣，Kγ的改變量比較大，它會在機械加工中帶來不可預測的振動幅度。</p><p>　　2）當γ0>0°時，即便刀具工作角度變化，但是由于γ∝的增加幅度小于γ0（假設Kγ改變量較?。?，因此Py改變量較小，形成的振動幅度也較小。</p><p>　　3.3 刀具頭動態(tài)剛度對振動幅值的影響</p>

58、<p>　　在刀具其它集合參數(shù)固定的情況下，僅改變刀具前角就會使刀具頭動態(tài)剛度發(fā)生變化，刀具前角與切削速度引起對應最大振幅的關系如表3所示。</p><p>　　表3 刀具前角與切削速度引起的最大振幅的關系</p><p><b>　　表3表明：</b></p><p>　　當γ0<0°，最大振動幅度時相應的切削速度

59、范圍為V=50—70m/min；</p><p>　　當γ0≥0°，最大振動幅度時相應的切削速度范圍為V=160—180m/min。</p><p>　　由此可以看出，在高速（V>120m/min）切削下，為了得到高精度和高質(zhì)量的備件，這些問題都必須要決，否則很難保證機械加工中的高精度，高質(zhì)量和高效率。通過方程3可以看出：振動振幅的減小可以通過增加減振系數(shù)C來實現(xiàn)。也就是通

60、過采用設置助減振系統(tǒng)來增加系數(shù)C或者暫時減少數(shù)量，這樣就可以在高速切削情況下得到高的精度和高的質(zhì)量。</p><p><b>　　4. 結(jié)論</b></p><p>　　1)隨著刀具前角的增大，加工中的振動幅度會逐步減??；</p><p>　　2)當前角一定時，隨著切削速度的變化，加工中的幅度會持續(xù)變化；</p><p>

61、;　　3)切削速度相同時，隨著刀具前角的變化，加工中的振動幅度也變化；</p><p>　　4)在實驗所分析的幾種情況下，當前角γ0<0°時，最大振幅出現(xiàn)在V=50—70m/min；當γ0≥0°時，最大振幅出現(xiàn)在V=160—180m/min；</p><p>　　5)必須解決在精密加工中高速切削區(qū)中的振動問題（假設γ0>0°），即采用合適的剛度和濕