附件 在精鏜中提供穩(wěn)定高頻振動(dòng)的摩擦阻尼器 Evita Edhi, Tetsutaro Hoshi 摘要 在精鏜過(guò)程中防止發(fā)生超過(guò) 10000Hz的高頻振動(dòng)而造成刀具壽命降低問(wèn)題的摩擦阻尼器已研制成功。新阻尼器結(jié)構(gòu)簡(jiǎn)單，它由一個(gè)聯(lián)接在主振動(dòng)結(jié)構(gòu)上的附加質(zhì)量與一小塊永久磁鐵構(gòu)成。 其原理是簡(jiǎn)單的， 利用庫(kù)侖力和粘性摩擦將振動(dòng)能量消散在阻尼器和主振動(dòng)結(jié)構(gòu)的接口之間。阻尼器對(duì)高頻也有效，因此無(wú)需調(diào)諧，本文首先介紹了一種在精鏜中消除高頻顫振的摩擦阻尼器的典型設(shè)計(jì)，其有效性由切削試驗(yàn)得以證明，并保證刀尖的正常 壽命。 對(duì)這種 新型阻尼器基本原理的理解在理論和實(shí)驗(yàn)分析中得以介紹。在鏜削過(guò)程中這種新型阻尼器能夠有效的防止超過(guò) 5000赫茲的 顫振。 關(guān)鍵詞 高頻振動(dòng) 摩擦阻尼器 精鏜 1、引言 先前有研究報(bào)告稱(chēng)精鏜中出現(xiàn)超過(guò) 10000赫茲的高頻顫振。這種頻率首先發(fā)現(xiàn)于留在切削表面的振紋上，然后在切削實(shí)驗(yàn)中直接使用激光位移計(jì)測(cè)量得到進(jìn)一步的證實(shí)。從鏜刀的自然彎曲振動(dòng)以及自我激發(fā)的切削過(guò)程中的動(dòng)力學(xué)再生效果、內(nèi)調(diào)制虛部的影響和 x-y方向的循環(huán)發(fā)現(xiàn)了這種顫振。本研究的目標(biāo)是防止這種顫振振動(dòng)的發(fā)生。 預(yù)防切削顫振的有效措施 可能是通過(guò)提高刀具系統(tǒng)的阻尼能力。阻尼能力是通過(guò)以下方面產(chǎn)生的：（ 1）包含在刀具系統(tǒng)接口處的某些微量滑動(dòng)；（ 2）在晶界滑移內(nèi)部振動(dòng)引起的阻尼損耗（內(nèi)耗）；（ 3）在主振動(dòng)結(jié)構(gòu)和振動(dòng)阻尼器接口處的摩擦。許多研究人員對(duì)不同類(lèi)型的用以防止顫振振動(dòng)，并提高鏜刀或其他切削操作穩(wěn)定性的阻尼器進(jìn)行了研究。 該阻尼器已不是傳統(tǒng)阻尼器的動(dòng)態(tài)特性或沖擊特性了，動(dòng)態(tài)阻尼器包括額外的彈簧質(zhì)量子系統(tǒng)，通過(guò)調(diào)節(jié)系統(tǒng)的固有頻率，使之與主體結(jié)構(gòu)相匹配。一般動(dòng)態(tài)阻尼器設(shè)計(jì)包括任意方向的滑動(dòng)或內(nèi)部摩擦耗能的彈性材料。彈性阻尼器由一個(gè)或多個(gè)的自由 移動(dòng)機(jī)構(gòu)組成，其原理是利用自由移動(dòng)體撞擊主體結(jié)構(gòu)來(lái)耗散顫振能量。阻尼器受一定的速度影響才能有效的發(fā)揮其功能，因此不能適用于抑制低頻振動(dòng)。近來(lái)有報(bào)道一種動(dòng)力與摩擦混合阻尼器，并發(fā)現(xiàn)它能有效地抑制低頻振動(dòng)。 2 本文中所設(shè)計(jì)的阻尼器必須能有效地抑制高達(dá) 10000赫茲的高頻率顫振，而且它的設(shè)計(jì)受到鏜刀本身的工作空間及其自身大小的限制。它最完美的地方就是不需要調(diào)整。該阻尼器在本研究提出一個(gè)大規(guī)模隸屬永磁結(jié)構(gòu)的概念。 本研究的目的是為了分析抑制高頻振顫阻尼器的有效性及其阻尼特性。 為了實(shí)現(xiàn)這一目標(biāo)，已進(jìn)行一個(gè)類(lèi)似于抑制精 鏜中高頻顫振的切削試驗(yàn)以及理論和實(shí)驗(yàn)的能源阻尼耗能分析。 2、鏜刀測(cè)試和阻尼器結(jié)構(gòu)的構(gòu)想 根據(jù)研究，在精鏜中原本有一個(gè)高頻顫振問(wèn)題，鏜刀本身包括一個(gè)直徑分別為 13毫米和 20毫米的長(zhǎng)懸臂桿和法蘭。在桿的一端有一直徑為 5.5毫米的小孔，以適應(yīng) 5毫米或孔徑更小的阻尼器。該孔的位置選擇在徑向方向，因?yàn)槲覀円呀?jīng)知道高頻振動(dòng)在 X-Y方向循環(huán)。當(dāng)鏜刀空轉(zhuǎn)時(shí)，阻尼器被孔壁的離心力推動(dòng)但可以再?gòu)较蚍较蜃杂梢苿?dòng)。上限用以保護(hù)運(yùn)行中的阻尼器。 該阻尼器的有效性已經(jīng)通過(guò)了檢測(cè)并準(zhǔn)備和其他鏜刀做比較。 用作比較的工具之一具有相同直徑 的長(zhǎng)懸臂桿即直徑為 13毫米，但其延伸超出了前沿 10毫米并產(chǎn)生約 5000赫茲的顫振振動(dòng)。其他與之比較是 16毫米直徑懸臂式鏜刀，將以更大的長(zhǎng)徑比產(chǎn)生較低頻率的顫振振動(dòng)。 新型摩擦阻尼器的基本結(jié)構(gòu)是一個(gè)附加質(zhì)量和永久磁鐵的組合，其中質(zhì)量平面平行于主結(jié)構(gòu)的振動(dòng)方向。磁鐵可以是不可分割的或者是可分割的都行。另一部件，墊片，可以插入到永久磁鐵和主要結(jié)構(gòu)之間，其目的是控制電磁力的大小。新型摩擦阻尼器在抑制高頻振動(dòng)的有效性已得到積極評(píng)價(jià)。 3. 實(shí)驗(yàn)方法 為了驗(yàn)證該阻尼器控制顫振的有效性，并保證正常的刀具磨損和表面粗糙度，切削試 驗(yàn)將與其設(shè)計(jì)尺寸一樣，與 13毫米直徑的鉆孔工具配合使用。這樣的話(huà)，鏜刀安裝在一個(gè)臥式加工中心的主軸上，通過(guò)設(shè)置調(diào)整孔直徑以自動(dòng)控制刀尖徑向位置。 將內(nèi)表面是由旋轉(zhuǎn)刀具鏜加工的環(huán)型工件準(zhǔn)備好。工件的材料是 SCM420H合金鋼，淬火至硬度為 313 332HBS，外徑為 25mm，內(nèi)徑為 14.72 0.05mm，長(zhǎng)度為 15mm。工件由專(zhuān)門(mén)設(shè)計(jì)的具有足夠硬度的夾具裝夾。 切削試驗(yàn)是在標(biāo)準(zhǔn)條件下進(jìn)行的，切削速度為 130m/min，進(jìn)給量為 0.03mm/rev,背吃刀量為 0.14mm，切削過(guò)程中不使用任何切削液。一種新的 尖端技術(shù)在加工過(guò)程中不斷調(diào)整加工條件。每個(gè)試驗(yàn)重復(fù)兩次，其中一次在鏜刀系統(tǒng)中安裝阻尼器，而另一次不安裝。刀具材料用的是非涂層 TiC金屬陶瓷，其軸向前角為 -50，徑向前角為 -150，刀尖圓弧半徑為 0.4mm。 對(duì)于直徑為 16毫米的工件振動(dòng)的測(cè)量，準(zhǔn)備用另一個(gè)安裝程序?qū)h(huán)行工件的外表面固定。這樣的話(huà)，工件被夾緊使測(cè)試在一對(duì)立式加工中心機(jī)床基板上舉行。環(huán)行工件和機(jī)床主軸一同旋轉(zhuǎn)。 3 4.摩擦阻尼器的機(jī)理分析 4.1 理論分析 振動(dòng)的產(chǎn)生，一旦達(dá)到一定的振動(dòng)幅度，阻尼器將開(kāi)始滑動(dòng)，由此引起阻尼器的主體結(jié)構(gòu)和界面的 摩擦，從而耗散振動(dòng)能量，并防止振幅不斷增大甚至超出極值振幅。 實(shí)驗(yàn)分析 為了確定該假設(shè)庫(kù)侖力和粘性摩擦的區(qū)別，一個(gè)主體結(jié)構(gòu)模型振動(dòng)的兩個(gè)理論模型的有效性監(jiān)測(cè)了二者的不同狀況，并激發(fā)了電動(dòng)式激振器外部。用作主體結(jié)構(gòu)的是一直徑為 16毫米的懸臂鋼梁，它和原長(zhǎng)為 170mm的鏜刀具有相似的設(shè)計(jì)，其二階彎曲頻約能達(dá)到 5700Hz。在檢測(cè)梁的端部振動(dòng)時(shí)將使用微型加速度測(cè)量計(jì)。阻尼器主體結(jié)構(gòu)的頂部有一磁鐵，并通過(guò)此處與油管口相接。 首先采用隨機(jī)激勵(lì)確定主體結(jié)構(gòu)的固有頻率。然后是應(yīng)用在正弦激勵(lì)變幅的動(dòng)力輸入 f至 z微調(diào)周?chē)S機(jī) 激勵(lì)確定固有頻率。與此同時(shí)，用 FFT分析儀分析振幅在主體結(jié)構(gòu)出的響應(yīng)差異。 激發(fā)各周期能源供應(yīng)量的正弦振動(dòng)是從測(cè)量 f時(shí)開(kāi)始的，計(jì)算如下 當(dāng) x是降低阻尼器或與供油接口相連接時(shí)，主體結(jié)構(gòu)的振幅也降低了。當(dāng)使用阻尼器時(shí)，激勵(lì)由 0.3N增至 0.6N時(shí)，振幅 x將不會(huì)增大。對(duì)于較低的頻率，雖然也能有一定大的抗振效應(yīng)，但效果并不明顯。 5、結(jié)論 為了控制頻率高達(dá) 10000Hz的高頻顫振，正如以前報(bào)道的精鏜過(guò)程一樣，利用一種新的阻尼器與主體結(jié)構(gòu)之間的摩擦效應(yīng)，削弱振動(dòng)能量而達(dá)到減振目的。 新的阻尼器 由一個(gè)聯(lián)接在主振動(dòng) 結(jié)構(gòu)上的附加質(zhì)量與一小塊永久磁鐵構(gòu)成。 據(jù)目前的研究已證實(shí)了庫(kù)侖力和粘性摩擦在滑動(dòng)界面的產(chǎn)生。由于庫(kù)倫摩擦力，發(fā)生在主體結(jié)構(gòu)處的滑移就能抵消一部分顫振能量，而且它們之間大致是呈線(xiàn)性關(guān)系的。如果在此條件下能夠充分的消耗顫振能量，則就可以抑制顫振了。 在抑制高頻顫振時(shí)，該阻尼器顯得更為有效。由于受到阻尼器主體結(jié)構(gòu)自身?xiàng)l件的限制，在精鏜中該阻尼器能抑制的最高顫振頻率只能略高于 5000Hz。 由于簡(jiǎn)單的結(jié)構(gòu)設(shè)計(jì)，也無(wú)需經(jīng)常調(diào)整，使用擬阻尼器抑制連續(xù)切削高頻率顫振（如精鏜等）是一種可行性方法。 致謝 本研究得到了 NT工 程公司的大力支持。他們提供了大量的研究材料和工具，得到了 4 Y. Komai先生和 M. Nakagawa先生 的大力支持和幫助。 附件 II 英文文獻(xiàn)原文 Stabilization of high frequency chatter vibration in fine boring by friction damper Evita Edhi*, Tetsutaro Hoshi Abstract Friction damper has been found successful to prevent high frequency chatter occurring at more than 10,000Hz, and causing problem of reduced tool life in fine boring operation. The new damper is characterized by simple structure that consists of an additional mass attached to the main vibrating structure with small piece of permanent magnet. The principle is straightforward in which Coulomb and viscous frictions dissipate vibration energy at the interface between the damper and main vibrating structure. The damper needs no tuning, and is effective at high frequency. The paper first introduces a typical design of the friction damper with experimental proof by cutting tests of its effectiveness in eliminating the high frequency chatter in fine boring, and assuring normal tool life of the cutting edge. Theoretical and experimental analyses are introduced for understanding the fundamental principle and characteristics of the new damper. The new damper is effective for boring tools, which vibrate at frequency more than 5,000Hz. Keywords: High frequency chatter； Friction damper； Fine boring. Introduction A previous study reported fine boring tools exhibiting chatter at high frequency, more than 10,000Hz . The frequency was first identified from the chatter mark left on the surface, then further confirmed in cutting test by direct measurement using the laser displacement meter. The chatter was found attributable to bending natural vibration of the boring tool, self-excited by cutting process dynamics that include the regenerative effect, the imaginary part effect of inner modulation, and X-Y Looping. Prevention of such chatter vibration is the target of the present study. Effective chatter prevention during cutting operations may be achieved by increasing the damping capacity of cutting tool system. Damping capacity is generated through (i) micro-slip 5 at certain interfaces included in the tool system, (ii) slip at the grain boundary within a vibrating body by material damping (internal friction), (iii) friction at an interface between the main vibrating body and the damper structure . Studies on various kind of damper to prevent chatter vibration, and to improve stability of boring tools or other cutting operation have been carried out by many researchers. Practical types of damper have been conventionally either dynamic or impact damper . Dynamic damper consists of additional spring-mass sub-system, and needs tuning of natural frequency of the sub-system to match that of the main structure. The dynamic damper is usually designed to include energy dissipation by either sliding or internal friction of the spring material. Impact damper consists of one or more of free moving bodies, and the principle mechanism is to dissipate energy by the impact of free moving body with the main structure. Impact damper needs certain velocity to effectively function, thus cannot be applied to suppress vibration at low frequency. A hybrid design of dynamic and impact dampers has been reported recently, and found to be effective to suppress the low frequency vibration . In the present study, the damper is required to be effective at frequencies as high as 10,000Hz, and it should be designed within size limitation of the boring tool to accommodate space for seating the tool insert, chip pocket and the damper itself. It is also preferable that the damper needs no tuning. The damper proposed in the present study consists of a piece of mass attached to the main structure by permanent magnet. The objective of the present study is to analyze the effectiveness and characteristics of the proposed damper in preventing chatter vibration that occurs at high frequency. To achieve the objective, cutting tests have been conducted in boring operation analogues to the one having high frequency chatter problem in the plant, as well as theoretical and experimental analyses of energy dissipation of the proposed damper. Boring tools tested and the proposed damper structure The boring tool under study that originally had a problem of high frequency chatter consists of a 13mm diameter and 20mm long cantilevered steel bar integral with a base flange. A small diameter hole, 5.5 mm, is prepared at the end of the bar to accommodate the damper mass of which diameter may be 5mm or less. The position of the hole is selected in radial orientation om1, because the high frequency vibration due to X-Y looping has been known to occur dominantly in the orientation om2 as depicted. When the tool is rotated in boring operation, the damper is pushed to the wall of the hole by the centrifugal force, but is free to move in the orientation of the vibration om2. A cap is provided to protect the damper from chips removed during the operation. The effectiveness of the damper has been tested for the tool as shown in the figure, as well 6 as other boring tools that have been prepared for comparison. One of the comparison tools has the same diameter 13mm, but extended 10mm beyond the cutting edge, and generates chatter vibration at about 5,000Hz. Other comparisons are 16mm diameter cantilever type boring tools, designed with greater length (L) to diameter (D) ratios that exhibit chatter at lower frequencies. Basic structure of the new friction damper is the combination of a mass and permanent magnet, which anchors the mass to the main structure on a flat surface parallel to the direction of vibration. The magnet may be either integral or separated with the mass. A third member, a spacer, may be inserted between the permanent magnet and the main structure whose purpose is to control magnitude of magnetic force. Effectiveness of the friction dampers in suppressing high frequency chatter has been evaluated. 3. Method of experiment To validate the effectiveness of the damper in view of controlling the chatter, and to assure normal tool wear and surface roughness generated, cutting tests have been performed with the 13mm diameter boring tool rotated as it is in production site. In this case,the boring tool is mounted on the main spindle of a horizontal machining center via a setting head whose function is to adjust the radial position of the tool tip for automatic control of the hole diameter in production. Ring type workpieces have been prepared whose inner surface is to be machined by the rotating boring tool. Rings are made of SCM420H alloy steel, hardened to 313 to 332 Brinnell hardness with 25mm outer diameter, 14.720.05mm inner diameter, and 15mm length. A milling chuck clamps the ring on a specially designed fixture with sufficient stiffness. The standard condition for cutting test is set to 130m/min cutting speed, 0.03mm/rev feed rate, 0.14mm depth of cut, and using no cutting fluid. A new cutting edge is prepared for each set of cutting tests in which workpieces are continuously machined. The cutting test is repeated twice for each boring tool system with and without the damper. Tool insert material used for the boring tool is TiC Cermet non-coated, with axial rake angle -5, radial rake angle -15, and nose radius 0.4mm. For measuring vibration of the 16mm diameter tool, another setup was prepared with the tool held stationary, and used to machine outer surface of the rotating ring workpiece. In this setup, the tool is clamped by a milling chuck staged on a baseplate on the machine table of vertical machining center. The ring workpiece is mounted and rotated by the machine spindle. 4. Analysis of friction damper mechanism 7 4.1 Theoretical analysis During the development of chatter, once the vibration reaches certain threshold amplitude, the damper will start sliding, therefore introducing friction at the interface between the damper mass and the main structure. The friction dissipates the vibration energy, and prevents the chatter from growing beyond the threshold amplitude. 4.2 Experimental analysis In order to ascertain validity of the two theoretical models assuming Coulomb and viscous friction respectively, vibration of a main structure model has been monitored with and without the damper mass attached, and excited externally by an electro-dynamic exciter. A cantilevered steel beam 16mm diameter, having similar cutting edge design with the original boring tool and 170mm length, has been used as the main structure whose second order bending mode was excited around 5,700Hz frequency. The vibration at the end of the beam is detected by micro size accelerometer pickup. A damper with an integral magnet is attached on top of the main structure via cleaned and dried interface as well as oiled interface. Random excitation is first applied to identify the natural frequency of the main structure. Then sinusoidal excitation is applied at variable amplitude f of the input dynamic force F at frequency Z finely tuned around the natural frequency identified by random excitation. At the same time, amplitude x of response vibration X of the main structure, and the phase difference between input dynamic force and response vibration , are measured by the FFT Analyzer. Amount of energy supplied Es per vibration cycle by the sinusoidal excitation is computed from the measured f,as follows: vibration amplitude x of the main structure is reduced when the damper is attached on either dried or oiled interface. When the damper is used, the amplitude x exhibits a stagnant step during the excitation force increment from 0.3 to 0.6N. 5. Conclusion To control chatter vibration occuring at frequencies as high as 10,000Hz, as previously reported in fine boring operation, performance of a new damper mechanism utilizing friction between a