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中原工學(xué)院畢業(yè)設(shè)計(jì)(論文)譯文
3.1.2預(yù)應(yīng)變和前角在銅加工中的影響
在上一節(jié)中，講述的是利用傾角為6度的刀具加工退火金屬。在改變預(yù)應(yīng)變和增加前角的這兩種情況下，顯著的降低了切削力大小和切削溫度，但是對于刀具的影響不大。這些說法可能說明了在加工像銅這樣足夠軟的金屬時(shí)（當(dāng)然鋁也一樣），是容許刀具的切削角最大值為40度的。圖3.6的例子展示的是在室內(nèi)，用前角為6?至35?高速工具鋼刀具，吃刀量為0.12毫米至0.2毫米和剪平面角在8?到32?變化變化時(shí)，來測量退火和深冷銅加工時(shí)的切削力與剪切平面角。當(dāng)切削速度最低時(shí)，切削力的變化超過了6倍。
左圖3.7表示，雖然退火后，預(yù)應(yīng)變明顯比之前大許多，但刀具的接觸應(yīng)力和前角變化不大。右圖表示，前角為6°到35°刀具，溫升的改變是被均分的。這些現(xiàn)象表明，刀具所受的力是由切削材料決定，而切削條件對其影響不大，然而溫度的改變受切削材料和工作條件的影響卻很大。這是個重要的話題 ，它將會在后面的金屬合金的章節(jié)被提及到。
3.1.3銅和鋁合金的加工
人們經(jīng)常發(fā)現(xiàn)合金比單一的金屬材料需要更大剪切面和較低的切削力。其中一個重要的原因由于低價(jià)值的應(yīng)變硬化參數(shù)，其次是由于晶片/工具的摩擦（例如摩擦系數(shù)），但是其影響較小，然后就是那些一點(diǎn)也不明顯，說不清為什么的原因了。但是即使切削力較低，但是刀具受到壓力還是很大的。在這一節(jié)，將用銅和鋁合金的加工的例子來對這一現(xiàn)象進(jìn)行解釋。
圖3.8顯示出銅鎳合金與銅鋅合金的特性。銅鎳合金中含80%的鎳，或許更應(yīng)該被認(rèn)為是鎳合金。然而，這種材料比銅和鎳能承受更高的剪切平面角或較高的切削速度。盡管他們的應(yīng)變硬化特性是相似的，或者說更差些（見附錄4.1）。銅鋅合金是一種廣為人知的一種機(jī)器制造材料，它能承受的剪切平面角是銅的兩倍，盡管它們擁有相同的高強(qiáng)度特性（同樣的見附錄4.1）和明顯的更高的摩擦系數(shù)（被作為評測相對大小及其推力和切削力的標(biāo)準(zhǔn)）。（圖3.8描述的是黃銅的加工。在低溫處理后，就能承載較大剪切平面角和較小的切削力）。這兩個例子都是說明為什么它們在室溫下的低應(yīng)變特性，和單一金屬相比更容易成為機(jī)器制造的首選材料的原因。
圖3.9是鋁合金在機(jī)械制造中的特性與前角的顯示。角和速度的關(guān)系顯示如表3.3。它能承受的剪切平面角為普通材料的5倍，而且它能承受的切削力是純鋁的一半。
在這種其情況下 ，其張力和摩擦系數(shù)和純鋁相比是較小的。銅和鋁合金的例子，它們主要的剪切平面的剪切應(yīng)力和接觸應(yīng)力的平均斜度是相似的，或者說比那些單一金屬大一些。圖3.8僅僅顯示k的影響，但是可以被換算為約等于0.6k。圖3.9顯示的是k和的關(guān)系。它也表明了，在這種情況下，當(dāng)傾斜面溫度不變時(shí)，傾斜角就減小了。這些不同于圖3.7的觀測記錄，也許是鋁合金能承受的最高溫度的限制吧？
圖3.9顯示的是機(jī)械制造的參數(shù)如何隨著前角的變化而變化的，在這種情況下，當(dāng)前角大約為35°時(shí)，驅(qū)動力過零點(diǎn)。結(jié)果表明，這樣一個大的前角在制造機(jī)器的薄壁是可以的，但可能造成驅(qū)動力的失真。
然而這部分的要點(diǎn)，在3.2節(jié)工具材料部分廣泛應(yīng)用。這個范圍的估計(jì)值就用k來表示，為0.5~1.0K。
3.1.4加工奧氏體鋼材和高溫鎳鈦合金
奧氏體鋼材，NiCr，和鈦合金與銅和鋁合金是剛好完全相反的。雖然它們的承受的切削力是一樣的，而且剪切平面角更高一點(diǎn)，但是這種材料的壓力和溫度（在給定的切削速度和吃刀量的情況下）會顯著的提高。
圖3.10顯示的是，兩種奧氏體鋼，一種是NiCr,一種是鈦合金。其中一種奧氏體鋼（材料為18Cr8Ni）是一種普通的不銹鋼，而18Mn5Cr這種材料，雖然含碳量也是0.47，但卻是一種結(jié)構(gòu)相當(dāng)穩(wěn)定且耐磨的材料。NiCr合金是一種商業(yè)性的鉻鎳鐵合金，X750。在所有情況下，吃刀量都是0.2mm，除了鈦鋁合金，因?yàn)樗?.1mm。這個角是6度么？除了NiCr合金，因?yàn)樗氖?。切削力的變化范圍大致為2~4個Gpa。驅(qū)動力大小為1~2Gpa。剪切平面角大致大于25°。大多數(shù)情況下，這種晶體結(jié)構(gòu)是不穩(wěn)定的，且有鋸齒葉緣。這種特性顯示在圖3.10中。圖3.11中顯示的是壓力和溫度。較大的壓力和顯著的溫度變化。
3.1.5低碳合金鋼的加工
碳合金鋼是是介于鋁、銅加工性能與奧氏體鋼和高溫合金之間的一種合金材料。這有兩方面，多數(shù)材料的屈服應(yīng)力能夠通過鐵碳合金和其他少量金屬來換算。他們之間的熱交換和擴(kuò)散率導(dǎo)致每次吃刀時(shí)都產(chǎn)生的熱量，當(dāng)然也與切削速度有關(guān)。
圖3.12顯示的是在切削速度不變情況下，棒料旋轉(zhuǎn)時(shí)測量的典型的切削力和切削平面角的變化，這些棒料直接通過熱軋工藝制造沒經(jīng)過任何的熱處理。當(dāng)切削速度達(dá)到100m/min，切削力為2~3Gap時(shí)，純鐵的軟管相似（圖3.3）。但是隨著切削速度的上升，他們之間的差別逐漸減小。對于多數(shù)的合金體系，同樣的方法，鐵合金的剪切角與純鐵相比增大了。
在熱軋的條件下，鋼（除之前提及到奧氏體外）中有一種叫做鐵素體和珠光體的結(jié)構(gòu)（或者擁有較高碳含量的碳鋼材料）。由于珠光體的存在，隨著碳含量提高，材料的的硬度也提高了。右圖3.13顯示的是隨著圖3.12碳含量的提高，k和的變化。另外，結(jié)果已經(jīng)包括，含碳量為0.13C和0.4C鋼材的加工。k和的增長很明顯。右表的數(shù)據(jù)也表明，對于給定的切削速度，如果提高含碳量，切削溫度會隨之提高的。這是由于剪切力的提高。這篇關(guān)于切削力和切削溫度的在不同的合金組織的變化的簡短調(diào)查結(jié)束了。刀具所受的力主要取決于它加工的金屬，與切削條件也有一小部分的關(guān)系（盡管刀具的剪切面傾角，切削速度，吃刀量變化很明顯）。溫度，一方面不僅取決于加工的材料（材料承受的壓力和熱性能），另一方面也與切削速度和吃刀量有關(guān)。
3.1.6機(jī)械加工中的切屑瘤
先前的說法中，取材的數(shù)據(jù)主要是切削速度大于100m/min的。這是由于在稍低的切削速度和吃刀量下，加工中會產(chǎn)生切屑瘤。在第2章中，已經(jīng)有顯示了切屑瘤的產(chǎn)生的圖片。圖3.14顯示，對于含碳量0.15鋼材，專性力和剪切角變化都是與此有關(guān)聯(lián)的。在這個例子中，在切削速度為25m/min時(shí)會產(chǎn)生最大的切屑瘤。這里，專性力通過最低點(diǎn)，而剪切角達(dá)到最大點(diǎn)。從本質(zhì)上講，這或許可以解釋為切屑瘤增大了刀具切削角的有效部分。
切屑瘤的出現(xiàn)于較低的切削速度或者說是幾乎所有的金屬加工中，它提供了一種能夠緩解在低速時(shí)隨時(shí)可能發(fā)生較大應(yīng)變 (小剪切平面角)的方法。對于那些產(chǎn)生切屑瘤的合金，當(dāng)在能夠產(chǎn)生最大切屑瘤的切削速度下，提高吃刀量。圖3.15收集的數(shù)據(jù)是關(guān)于三價(jià)鐵合金和結(jié)構(gòu)穩(wěn)定、耐磨的合金（Nimonic 80）。高速加工是指切削速度高于能夠產(chǎn)生切削瘤的速度。這些條件都集中在這本書中。
3.1.7 摘要
3.1節(jié)提到的各種專性力和剪切平面角通常指加工鋁、銅、鐵、鎳鈦合金。人們一直在尋求一種材料，這種材料能夠承受金屬切削時(shí)的剪切流動應(yīng)力、幾乎所有的切削速度和吃刀量及切削前角。3.4表列出各種壓力的范圍，接觸應(yīng)力的峰值可能是表中記錄的平均值的兩到三倍。相反，刀具必須能夠承受由切削速度、吃刀量、切削前角等因素而產(chǎn)生的溫度和材料在加工過程中的性能：擴(kuò)散率，傳導(dǎo)性和熱容。由于溫度和壓力的嚴(yán)格限制，最容易加工的的金屬是鋁合金及銅合金。對于機(jī)器來說，最難加工的是奧氏體鋼、鎳耐熱合金、鈦等合金。鐵素體和珠光體鋼材的溫度與壓力變化、碳含量和硬度居于這兩個極端之間。關(guān)于這些，本部分特別是那些關(guān)于不同合金的剪切平面角的測量的有關(guān)報(bào)告主要是描述性的。這些仍然是力學(xué)預(yù)測的一個重要的話題。補(bǔ)充一點(diǎn)，在下一章節(jié)刀具材料的性能中，將描述刀具的材料性能對于抵抗加工中產(chǎn)生的壓力和溫度的影響。
3.1.2 Effects of pre-strain and rake angle in machining copper
In the previous section, the machining of annealed metals by a 6° rake angle tool was considered. Both pre-strain and an increased rake angle result in reduced specific cutting forces and reduced cutting temperatures, but have little effect on the stressses on the tool. These generalizations may be illustrated by the cutting of copper, a metal sufficiently soft (as also is aluminium) to allow machining by tools of rake angle up to around 40°. Figure 3.6 shows examples of specific forces and shear plane angles measured in turning annealed and heavily cold-worked copper at feeds in the range 0.15 to 0.2 mm, with high speed steel tools of rake angle from 6° to 35°. Specific forces vary over a sixfold range at the lowest cutting speed, with shear plane angles from 8° to 32°.
The left panel of Figure 3.7 shows that the estimated tool contact stresses change little with rake angle, although they are clearly larger for the annealed than the pre-strained material. The right-hand panel shows that the temperature rises are halved on changing from a 6° to 35° rake angle tool. These observations, that tool stresses are determined bythe material being cut and do not vary much with the cutting conditions, while temperatures depend strongly on both the material being cut and the cutting conditions, is a continuing theme that will be developed for metal alloys in the following sections.
3.1.3 Machining copper and aluminium alloys
It is often found that alloys of metals machine with larger shear plane angles and hence lower specific forces than the elemental metals themselves. Sometimes a strong reason is a lower value of the strain hardening parameter Dk/kmax, at other times the chip/tool friction (as indicated by the friction coefficient) is less; and at others again it is not at all obvious why this should be so. But even when the specific forces are lower, the tool contact stress can be higher. In this section, examples of machining two copper and one aluminium alloy are taken to illustrate this.
Figure 3.8 records the behaviours of a CuNi and a CuZn alloy. The CuNi alloy, with 80%Ni, might better be considered as a Ni alloy. However, it machines at a higher shear plane angle at a given cutting speed than either copper or nickel, despite its strain-hardening characteristic being similar to or more severe than either of these (Appendix 4.1). The CuZn alloy (an a-brass) is a well-known very easy material to machine. Its shear plane angle is twice as large as that of Cu, despite having a similar strain-hardening characteristic (Appendix 4.1 again) and an apparently higher friction interaction with the tool (as judged by the relative sizes of its specific thrust and cutting forces). (Figure 3.8 describes the machining of an annealed brass. After cold-working, even higher shear plane angles, and lower specific forces are obtained.) These two examples are ones where the reason for the easier machining of the alloys compared with the elemental metals is not obvious from their room temperature, low strain rate mechanical behaviours.
Figure 3.9 shows machining data for an aluminium alloy. In this case the variation of behaviour with rake angle is shown. At a rake angle and speed comparable to that shown in Figure 3.3, the shear plane angle is five times as large and the specific cutting force is half as large for the alloy as for pure Al. In this case both the strain-hardening and friction factors are less for the alloy than for pure Al.
For both the copper and aluminium alloy examples, the primary shear plane shear stress and the average rake contact stresses are similar to, or slightly larger than, those for theelemental metals. Figure 3.8 shows only the values of k, but (sn)av may be calculated to be ≈ 0.6k. Figure 3.9 shows both k and (sn)av. It also shows that, in this case, the estimated rake face temperature does not change as the rake angle is reduced. This is different fromthe observations recorded in Figure 3.7: perhaps the maximum temperature is limited bymelting of the aluminium alloy?
The choice in Figure 3.9 of showing how machining parameters vary with rake angle has been made to introduce the observation that, in this case, at a rake angle of around 35° the thrust force passes through zero. Consequently, such a high rake angle is appropriate for machining thin walled structures, for which thrust forces might cause distortions in the finished part.
However, the main point of this section, to be carried forward to Section 3.2 on tool materials, is that the range of values estimated for k follows the range expected from Figure 3.1 and the estimated values of (sn)av range from 0.5 to 1.0k. This is summarized in Table 3.4 which also contains data for the other alloy systems to be considered next.
3.1.4 Machining austenitic steels and temperature resistant nickel and
titanium alloys
The austenitic steels, NiCr, and Ti alloys are at the opposite extreme of severity to the aluminium and copper alloys. Although their specific forces are in the same range and their shear plane angles are higher, the tool stresses and temperatures (for a given speed and feed) that they generate are significantly higher. Figure 3.10 presents observations for two austenitic steels, a NiCr and a Ti alloy. One of the austenitic steels (the 18Cr8Ni material) is a common stainless steel. The 18Mn5Cr material, which also contains 0.47C, is an extremly difficult to machine creep and abrasion resistant material. The NiCr alloy is a commercial Inconel alloy, X750. In all cases the feed was 0.2 mm except for the Ti alloy, for which it was 0.1 mm. The rake angle was 6° except for the NiCr alloy, for which it was 0°. Specific cutting forces are in the range 2 to 4 GPa. Thrust forces are mainly between 1 and 2 GPa. Shear plane angles are mainly greater than 25°. In most cases, the chip formation is not steady but serrated. The values shown in Figure 3.10 are average values. Figure 3.11 shows stresses and temperatures estimated from these. The larger stresses and temperatures are clear.
3.1.5 Machining carbon and low alloy steels
Carbon and alloy steels span the range of machinability between aluminium and copper alloys on the one hand and austentic steels and temperature resistant alloys on the other. There are two aspects to this. The wide range of materials’ yield stresses that can be achieved by alloying iron with carbon and small amounts of other metals, results in their spanning the range as far as tool stressing is concerned. Their intermediate thermal conductivities and diffusivities result in their spanning the range with respect to temperature rise per unit feed and also cutting speed.
Figure 3.12 shows typical specific force and shear plane angle variations with cutting speed measured in turning steel bars that have received no particular heat treatment other than the hot rolling process used to manufacture them. At cutting speeds around 100 m/min the specific forces of 2 to 3 GPa are smaller than those for pure iron (Figure 3.3), but as speed increases, the differences between the steels and pure iron reduce. In the same way as for many other alloy systems, the shear plane angles of the ferrous alloys are larger than for the machining of pure iron. In the hot rolled condition, steels (other than the austenitic steels considered in the previous section) have a structure of ferrite and pearlite (or, at high carbon levels, pearlite and cementite). For equal coarsenesses of pearlite, the steels’ hardness increases with carbon content. The left panel of Figure 3.13 shows how the estimated k and (sn)av values from the data of Figure 3.12 increase with carbon content. Additional results have been included, for the machining of a 0.13C and a 0.4C steel. An increase of both k and (sn)av with %C is clear. The right panel of the figure likewise shows that the increasing carbon content gives rise to increasing temperatures for a given cutting speed. This comes from the increasing shear stress levels.
This completes this brief survey of the stresses and temperatures generated by different alloy groups in machining. Tool stresses are mainly controlled by the metal being machined and vary little with cutting conditions (although the tool rake face area over which they act changes with speed and, obviously, also with feed). Temperatures, on the other hand, depend not only on the material being machined (both through stress levels and thermal properties) but also on the speeds and feeds used.
3.1.6 Machining with built-up edge formation
In the previous section, data were presented mainly for cutting speeds greater than 100 m/min. This is because, at slightly lower cutting speeds, at the feeds considered, those steels machine with a built-up edge (BUE). In Chapter 2, photographs were shown of BUE formation. Figure 3.14 shows, for a 0.15C steel, what changes in specific force and shear plane angle are typically associated with this. In this example, the largest BUE occurred at a cutting speed close to 25 m/min. There, the specific forces passed through a minimum and the shear plane angle through a maximum. Qualitatively, this may be explained by the BUE increasing the effective rake angle of the cutting tool. Built-up edge formation occurs at some low speed or other for almost all metal alloys. It offers a way of relieving the large strains (small shear plane angles) that can occur at low speeds, but at the expense of worsening the cut surface finish. For those alloys that do show BUE formation, the cutting speed at which the BUE is largest reduces as the feed increases. Figure 3.15 gathers data for three ferrous alloys and one Ni-Cr creep resistant alloy (Nimonic 80). One definition of high speed machining is machining at speeds above those of built-up-edge formation. These are the conditions mostly focused on in this book.
3.1.7 Summary
Section 3.1 mentioned the variety of specific forces and shear plane angles that are commonly observed in machining aluminium, copper, ferrous, nickel and titanium alloys. It has sought to establish that the average contact stresses that a tool must withstand depend mainly on the material being machined, through the level of that material’s shear flow stress and hardly at all on the cutting speed and feed nor on the tool rake angle. Table 3.4 lists the range of these stresses. Peak contact stresses may be two to three times as large as the average values recorded in the table. In contrast, the temperatures that a tool must withstand do depend on cutting speed and feed and rake angle, and on the work material’s 96 Work and tool materials Fig. 3.17 Machining characterisitcs of a low alloy (?) and a semi-free-cutting low alloy (o) steel (f = 0.25 mm, α = 6o) thermal properties: diffusivity, conductivity and heat capacity. By both thermal and stress severity criteria, the easiest metals to machine are alumimium alloys and copper alloys.The most difficult to machine are austenitic steels, nickel heat resistant alloys and titanium alloys. Ferritic and pearlitic steels lie between these extremes, with stresses and temperatures increasing with carbon content and hardness. Beyond that, this section has been mainly descriptive, particularly with respect to reporting what shear plane angles have been measured for the different alloys. This remains the main task of predictive mechanics. The next section, on tool material properties, complements this one, in describing the properties of tool materials that influence and enable the tools to withstand the machininggenerated stresses and temperature .
中 原 工 學(xué) 院
畢業(yè)設(shè)計(jì)（論文）任務(wù)書
姓 名
王孟孟
機(jī)電 學(xué)院 機(jī)自 專業(yè) 063 班
題 目
成品軸承自動清洗生產(chǎn)線上料裝置設(shè)計(jì)
設(shè)
計(jì)
任
務(wù)
1、外文翻譯，并且按學(xué)院規(guī)定的統(tǒng)一規(guī)范化要求用譯文紙撰寫或打印。
2、畢業(yè)設(shè)計(jì)調(diào)研，并且按學(xué)院規(guī)定的統(tǒng)一規(guī)范化要求撰寫調(diào)研報(bào)告、開題報(bào)告；
3、查閱資料確定成品軸承自動上料裝置方案設(shè)計(jì);
4、參數(shù)選擇及驗(yàn)算;
5、繪制總體裝配圖及主要零件圖；
6、按學(xué)院規(guī)定的統(tǒng)一規(guī)范化要求撰寫設(shè)計(jì)說明書
時(shí)
間
進(jìn)
度
3.8～3.21 畢業(yè)實(shí)習(xí)；
3.22～4.4 方案論證，確定方案，完成調(diào)研報(bào)告、開題報(bào)告及外文翻譯；
4.5～4.25 進(jìn)行成品軸承自動上料裝置體結(jié)構(gòu)方案設(shè)計(jì)；
4.26～5.31 主要零部件設(shè)計(jì)，繪制成品軸承自動上料裝置總體結(jié)構(gòu)圖及零件圖，按學(xué)院規(guī)定的統(tǒng)一規(guī)范化要求撰寫設(shè)計(jì)說明書（完成初稿）；
6.1～6.6 審查設(shè)計(jì) 準(zhǔn)備答辯；
6.7～6.13 答辯資格評審；
6.14～6.20 畢業(yè)答辯；
6.21～6.27 修改畢業(yè)設(shè)計(jì)。
原 要
始 參
資 考
料 文
和 獻(xiàn)
主
[1] 黃大宇 梅瑛主編. 機(jī)械設(shè)計(jì)課程設(shè)計(jì).吉林大學(xué)出版社,2007
[2] 徐灝主編. 機(jī)械設(shè)計(jì)手冊[第二版].北京：機(jī)械工業(yè)出版社,2000
[3] 彭文生等主編.機(jī)械設(shè)計(jì).北京：高等教育出版社，2002
[4] 黃玉美等主編.機(jī)械制造裝備設(shè)計(jì). 高等教育出版社，2006
[5] 劉德忠 費(fèi)仁元主編.裝配自動化. 高等教育出版社，2003
[6] Kuehnle M R. Toroidal Drive Combines Concepts.Product Enfineering. Aug. 1979
院長（系主任）簽名： 指導(dǎo)教師 胡敏