【正文】 trictive[35]. Some generators are designed with safety features such as an automatic switch off in cases of horn fracture, horn/tool joint failure, etc.651–2SiC/B4C164224Silicon Oxide33.Workpiece MaterialsHardness HvSurface Roughness Ra (μm)Remended AbrasiveMRR(mm3/min) 5[6], Kremerμm56. This is also true of nonconventional processes, such as EDM or laser beam machining (LBM) which rely on a thermal cutting mechanism. For example, EDM can cause a thermally altered surface zone up to 5055.With any safety critical ponent such as a turbine blade, which is highly stressed during operation, workpiece surface integrity is a key feature and particularly so where the ponent is made of ceramic or employs a ceramic coating. The machining process used should impart as little damage as possible to the finished surface/subsurface. All conventional cutting operations such as turning or grinding will to a lesser or greater degree cause some type of surface damage16,andand and the Erosonic US400/US800 from Erosonic AG (Switzerland).Fig. 3.Fig. 3. Recently, the feasibility of using this technique has bee of interest and has been investigated in a number of countries including the UK, France, Switzerland, Japan, etc.50. The problem with using tools of plex form, however, is that they are not subject to the same machining rate over the whole of their working surface and experience differential wear rates, both of which affect the product shape2,4710,4436.?Ultrasonic assisted conventional/nonconventional machining. USM assisted turning is claimed to reduce machining time, workpiece residual stresses and strain hardening, and improve workpiece surface quality and tool life pared to conventional turning12,20,rpm, but with diamond impregnated tools, rotational speeds can be as high as 500038,Basic elements of USM head . silicon carbide, boron carbide, etc. suspended in water or oil) is pumped around the cutting zone. The vibration of the tool causes the abrasive particles held in the slurry between the tool and the workpiece, to impact the workpiece surface causing material removal by microchipping34. Typical power ratings range from 50–3000kHz) with an amplitude of 5–5018,and ultrasonic abrasive machining and slurry drilling. however, from the early 1950s it was monly known either as ultrasonic impact grinding or USM7,2812.The history of ultrasonic machining (USM) began with a paper by R. W. Wood and A. L. Loomis in 1927μm in diameter can be machined22,18,14,117,4ceramics1. An overview of ultrasonic machining and applicationsUltrasonic machining (USM) is a nonconventional mechanical material removal process generally associated with low material removal rates, however its application is not limited by the electrical or chemical characteristics of the workpiece materials. It is used for machining both conductive and nonmetallic materials。 in final form 30 April 1997)AbstractUltrasonic machining is of particular interest for the cutting of nonconductive, brittle workpiece materials such as engineering ceramics. Unlike other nontraditional processes such as laser beam, and electrical discharge machining, etc., ultrasonic machining does not thermally damage the workpiece or appear to introduce significant levels of residual stress, which is important for the survival of brittle materials in service. The fundamental principles of ultrasonic machining, the material removal mechanisms involved and the effect of operating parameters on material removal rate, tool wear rate and workpiece accuracy are reviewed, with particular emphasis on the machining of engineering ceramics. The problems of producing plex 3D shapes in ceramics are outlined.KeywordsUltrasonic machining。 超過標(biāo)準(zhǔn) USM 鏡頭的優(yōu)異性能可以通過解釋工件表面的壓痕的聯(lián)合作用，之間的滑動(dòng)接觸上的游離磨粒/工件之間的刀具/工件和滾動(dòng)接觸嵌入式粒。，良好的濕潤(rùn)性，較好和較高的熱導(dǎo)率，高效的高溫冷卻性。 Q 值，良好的焊接和釬焊的特點(diǎn)，良好的聲學(xué)傳播特性和高工作幅度高耐疲勞性。 被認(rèn)為是一個(gè)應(yīng)力和損壞自由的過程。圖 17 在 USMamp。5 μm 可以在很多材料中獲得[36]，如圖 16 所示，更細(xì)的磨粒能得到更低的表面粗糙度[40]。Shaw [35]和其他研究者[3,23,40, 73, 83]研究表明通過降低磨粒大小，并抑制刀具的橫向震動(dòng)能增加靜態(tài)載荷，從而減少了表面粗糙度，因此也能提高圓柱度和錐度，如圖 15 所示，Adithan [73]等人發(fā)現(xiàn)得到的矩形孔的精度明顯比用鉆得到的高，如圖 16 表明具有高楊氏模量的材料更容易受非圓柱度影響。5 超聲波加工對(duì)工件表面光潔度和粗糙度的影響超聲波加工不會(huì)明顯的發(fā)熱，這樣可以避免局部發(fā)生熱損傷和殘余應(yīng)力，磨粒粒度大小會(huì)顯著影響工件精度和工件表面粗糙度[4, 23, 26, 36, 40, 73, 82, 94]，在超聲波加工中，降低粒度的大小能得到較低的表面粗糙度如圖 14 所示，加工孔的精度也會(huì)提高，孔的底部的精度會(huì)比孔內(nèi)壁高[2, 5, 7, 60, 86, 102]。硬質(zhì)磨粒如碳化硼和軟質(zhì)材料如碳化硅相比，前者會(huì)導(dǎo)致更加嚴(yán)重的刀具磨損，刀具磨損也會(huì)受工件的硬度影響，也會(huì)被工件的韌性影響，那種性能變得堅(jiān)韌的陶瓷不太合適用超聲波加工，它會(huì)導(dǎo)致很高的刀具磨損量，它比常規(guī)陶瓷需要更高的加工速率[6, 101]。圖 8 在不同截面下靜負(fù)載和穿透速度的對(duì)比圖9影響陶瓷斷裂韌度的USM MRR和相對(duì)磨損（55）圖10 不同材料在USM amp。對(duì)于較小截面積的刀具而言，如何在靜載荷下調(diào)整出最佳加工狀態(tài)變得非常重要，這會(huì)使得在相同條件下，切削率會(huì)更好（見圖 8）。就 MRR 而言，水的性能通常優(yōu)于其他油類如苯和甘油水溶液，Pentland 等地和其他國(guó)家發(fā)現(xiàn)提高懸浮液循環(huán)，氣穴現(xiàn)象，污染物和堵塞效應(yīng)能被減少甚至克服。在更高的頻率（直到 5kHz），頻率和 MRR 被發(fā)現(xiàn)存在線性關(guān)系，超過一個(gè)上限值后，MRR 迅速下降，Rozenberg 等人[7]和 Kainth 等人[22]認(rèn)為，在實(shí)際操作中，其他參數(shù)不變，靜態(tài)負(fù)載從零增加，MRR 和靜態(tài)負(fù)載存在近似線性關(guān)系。多孔材料如石墨與硬化鋼和陶瓷相反，對(duì)于材料去除來(lái)說(shuō)，氣蝕具有重大的貢獻(xiàn)[10, 23,28, 35, 37, 81]，Markov [21]等人[27, 35]認(rèn)為氣蝕和化學(xué)效應(yīng)是第二大重要性，多數(shù)工件材料作用本質(zhì)上是削弱工件表面，協(xié)助磨料循環(huán)利用和排除碎屑，在 RUM 中，Komaraiahetal.[83] 和 Enomoto [84] 發(fā)現(xiàn)在脆性材料中赫茲裂縫的形成所要求的靜負(fù)載要小于滑動(dòng)縮進(jìn)。沖擊自由移動(dòng)研磨顆粒所產(chǎn)生的微小碎屑[28, 35, 37, 50, 70,81, 82]。最普通的磨料材料常用氧化鋁，碳化硅，碳化硼，等等[4, 12, 24, 27, 37, 75–78]，磨料輸送媒介應(yīng)控制低粘度并且接近磨料密度，良好的濕潤(rùn)性，較好和較高的熱導(dǎo)率，高效的高溫冷卻性，親水性，盡量滿足這些要求[3, 26, 28]。施加的力必須仔細(xì)選擇，因?yàn)槿粼O(shè)置太低就無(wú)法達(dá)到最大的切削速度，若設(shè)置太高則會(huì)導(dǎo)致刀具和磨料之間的干擾[3, 70]。多晶金剛石（PCD）近來(lái)被用于加工非常堅(jiān)硬的工件材料，例如熱等靜壓氮化硅[68]。換能器表面的振幅過?。ǎ┒鵁o(wú)法達(dá)到合適的切削率，因此，變幅桿可作為放大設(shè)備。磁致伸縮換能器主要的缺點(diǎn)是其高電力損失（例如電渦流損失）和低能量效率（約等于 55%）[40]，這些損失以熱的形式出現(xiàn)，換能器必須空冷/水冷而且換能器的體積龐大笨重，而且，相比于壓電型，該換能器不適于產(chǎn)生高強(qiáng)度振動(dòng) [59, 60]，典型的壓電換能器 [26, 42, 53, 61]由兩盤鋯鈦酸鉛或其他合成陶瓷組成[62]，其厚度通常不到超聲波換能器總長(zhǎng)的 10%[63]。有些超聲發(fā)生器的設(shè)計(jì)帶有安全特性，如在變幅桿斷裂，變幅桿/刀具接頭故障等[17，31，33]情況的自動(dòng)開關(guān)。對(duì)石墨，碳化硅和一系列陶瓷材料的 USM數(shù)據(jù)來(lái)由 Gilmore[6]，Kremer[33]總結(jié)于表 1 中。與此相反，超聲波加工（USM）是一種不依賴于導(dǎo)電工件并且適合于陶瓷材料加工的非熱過程。加工過程中應(yīng)盡可能減少最終成型表面/亞表面的損傷。相當(dāng)多數(shù)量的金屬依靠于大量使用非傳統(tǒng)加工，例如電化學(xué)加工（ECM）和 EDM，前者被廣泛用于生產(chǎn)翼型型材，后者則用于葉片冷卻孔的加工。 圖 3 利用 USM 加工碳纖維復(fù)合材料的加速桿、孔和外輪廓 超聲波加工陶瓷材料高性能陶瓷越來(lái)越多地被用于航空航天，工業(yè)和汽車電子行業(yè)的應(yīng)用。非加工超聲波應(yīng)用，例如清潔、塑料/金屬焊接、化學(xué)制品加工、涂層和金屬成形。旋轉(zhuǎn)超聲波加工。這導(dǎo)致刀具沿著其縱向軸線以振幅 050μm 高頻率振動(dòng)（通?！?0KH