【正文】 料尤其重要。圖 1 展示了設(shè)置 USM 使用磁致伸縮或壓電換能器釬焊和螺紋加工。相對(duì)于傳統(tǒng)的車削加工，超聲輔助車學(xué)加工聲稱可減少加工時(shí)間、工件的殘余應(yīng)力和加工硬化，提高工件表面質(zhì)量和刀具壽命[12, 36, 42, 45]。燒結(jié)氧化鋁，碳化硅和氮化硅產(chǎn)品一般有大于 1500 HV 的硬度，因此通常金剛石磨削是唯一可行/經(jīng)濟(jì)的加工零件至最終成形的方法，雖然這在加工包括圓柱形元件，平板和彎曲表面零件時(shí)是理想可行且易于接受的，但是當(dāng)被加工表面具有更復(fù)雜的形狀或者其工作特性要求有特定的工件表面完整性時(shí)就會(huì)出現(xiàn)問題。非傳統(tǒng)加工過程也是如此，例如 EDM 或激光加工（LBM）所依賴的熱切削機(jī)制。它們可以也適應(yīng)裝配和刀具磨損的任何微小錯(cuò)誤，給出最小聲波能量損耗和非常小的發(fā)熱性[33]。它不易產(chǎn)生熱損傷，并且更容易適應(yīng)旋轉(zhuǎn)操作[61]并且更容易安裝。但使用開孔刀具進(jìn)行深孔鉆時(shí)，通過變幅桿和刀具的中心進(jìn)給磨料的能力是一個(gè)很大的優(yōu)勢，可以因此減少側(cè)向摩擦力[27]。直接錘擊工件表面的研磨顆粒所導(dǎo)致的機(jī)械磨損[10, 28, 34, 35, 37, 40, 50, 60, 70, 81]。通常的，當(dāng)?shù)毒哒駝?dòng)的幅度增加時(shí) MRR 增加（其他變量不變）[40, 77]，盡管如此，還是存在一個(gè)使 MRR 降低的振幅水平，如圖 7 所示。根據(jù)已有的報(bào)告顯示，切削率跟刀具的形式和形狀系數(shù)（刀具的周長和面積之比）成正比[16, 60, 77, 79]。4 刀具磨損刀具磨損是超聲波加工的一個(gè)重要變量，既影響材料去除率和孔的精度[38, 28, 87, 94,98]，在超聲波加工中，復(fù)合刀具的磨損圖案可分為縱向磨損 WL [71, 87, 94], 橫向，側(cè)向，徑向磨損 WD [99], 有些會(huì)出現(xiàn)氣蝕和吸入磨損現(xiàn)象[38, 71, 75, 100]。提高表面光潔度的方法上面已介紹[16, 23, 27,86, 87]，Koval’chenko[5]和 Kennedy[16]指出在孔底面加工一個(gè)平面是非常困難，因?yàn)樵诩庸て矫嫔蠎腋∫悍植疾痪鶆?，?dǎo)致刀具中心的有效磨粒減少，尤其是工件是硬陶瓷，稍好的表面光潔度可以用硬度和粗糙度較低的材料獲得[2]。然而，在助力器變幅桿，任何降低的情況下在長度必須做到使兩端減小同樣維持其正確共振。它也可以適應(yīng)裝配和刀具磨損的任何微小錯(cuò)誤，給出最小聲波能量損耗和非常小的發(fā)熱性。并且通常較大的磨粒尺寸和更高的懸浮液濃度產(chǎn)生更高的MRR。contour machining。5and a hardness above 40 HRC12, . inorganic glasses, silicon nitride, nickel/titanium alloys, etc.20,829. USM has been variously termed ultrasonic drilling。1,16,33Fig. 1and3445.?There are also nonmachining ultrasonic applications such as cleaning, plastic/metal welding, chemical processing, coating and metal forming.. Contour machining using ultrasonic techniquesMany USM applications are involved in drilling where a tool of either simple or plex cross section penetrates axially into the workpiece, to produce either a through or blind hole of the required dimensions. Where a three dimensional cavity is required (. one in which the depth varies), a process analogous to die sinking is generally employed48, seeSilicon nitride turbine blade countersunk using USM[7].. Ultrasonic machining of ceramic materialsAdvanced ceramics are increasingly being used for applications in the aerospace, automotive and electronics sectors of industry. They offer a number of advantages over metals for automotive valves and cylinder sleevesHv and therefore diamond grinding is usually the only feasible/economic method of machining ponents to final shape. While this may be acceptable and perfectly feasible with ponents that prise cylindrical, flat and curved surfaces, problems can arise where the surface to be machined has a more plex topography or where inservice operating characteristics dictate a particular workpiece surface integrity.The majority of engineering ceramics are electrical insulators and although this can be an advantage in terms of function, it is a significant disadvantage in relation to the machining of ponents such as ceramic or ceramic coated turbine blades. Equivalent metal products rely a great deal on the use of nonconventional processes, such as electrochemical machining (ECM) and EDM. The former is used extensively for the production of aerofoil sections while the latter is used for the machining of blade cooling holes. Unfortunately, both processes rely on the fact that the workpiece material is conductive. In the case of EDM, the workpiece needs to have an electrical resistivity of less than 10048μm can be achievedmm ? ToolGraphite3135and53[61]and more easily constructed.. The ultrasonic horn and tool assemblyThe horn is variously referred to as an acoustic coupler, velocity/mechanical transformer, tool holder, concentrator, stub or sonotrode, seeand65,2770andmm diameter as bending of the tool can occur under too high a load.The slurry is usually pumped across the tool face by jet flow, suction, or a bination of both as shown in25,2724,26andand37,28,10,2870, by fracture (for hard or work hardened material)37ξ, of the ultrasonic tool before machining can be measured by using either an accelerometerand4987have advocated that MRR ∝andRelationship between penetration rate and oscillation amplitudef, of 4007,90. The optimum static load for the maximum machining rate has been found to be dependent on the tool configuration (. crosssectional area and shape), as shown in[92]indicated that the use of a smaller than optimal value (based on MRR) for the static load, is better for reducing abrasive wear and increasing tool life.Fig. 8.and3,16,26,kHz, a linear relationship between frequency and MRR is found. Above an upper threshold value, the MRR falls off rapidly where MRR∝√f6,ξ27,66. Shaw3,3081. Markov[21]and othersand35.Fig. 6.35,37,50,Fig. 6[35], Miller[79], Cook28.Fig. 5.37,75,28. The slurry also provides a good acoustic bond between the tool, abrasive and workpiece, allowing efficient energy transfer. The infeed tube is connected at, or adjacent to, a nodal plane of the horn to avoid damping effects16,and71. Threaded joints are conventionally used because of quick and easy tool changing, however, problems can occur such as selfloosening, loss of acoustic power, fatigue failure, etc64. Tungsten carbide, silver steel, and Monel are monly used tool materials. Polycrystalline diamond (PCD) has recently been detailed for the machining of very hard workpiece material such as hot isostatically pressed silicon nitrideand[65]which should possess a high mechanical Q, good soldering and brazing characteristics, good acoustic transmission properties and high fatigue resistance at high working amplitude. It should also be corrosion resistant and strong enough to take screw attachments. Monel, titanium 64 (IMI 318), AISI 304 stainless steel, aluminium and aluminium bronze are monly usedμm)61consists of two discs of lead zirconatetitanate, or other synthetic ceramic[40]. These losses appear as heat, therefore, the transducer has to be air/water cooled and the size of the transducer is bulky. Also, the transducer is not capable of generating high vibration intensities as pared to piezoelectric types39is used. Because of its lower Q value (Q is a meas