【正文】 knowledge of the melting points of the materials involved.（因?yàn)榻饘俚脑俳Y(jié)晶溫度與熔點(diǎn)相關(guān)，比如在退火，熱處理和熱加工操作中需要知道所涉及材料的熔點(diǎn)。）Alloying element have a relatively minor effect on the specific heat of metals.（合金元素在金屬比熱容中有一個(gè)相對(duì)較小的影響。） Temperature rise in a workpiece, if excessive, can decrease product quality by adversely affecting its surface roughness and dimensional accuracy, can cause excessive tool wear, and can result in undesirable metallurgical changes in the material.（工件溫度的上升，假如溫度過(guò)高，將會(huì)以平面粗糙度和尺寸精度的不利影響來(lái)影響產(chǎn)品質(zhì)量，而且會(huì)導(dǎo)致材料中不需要的相變。）Metals generally have high thermal conductivity, while ceramics and plastics have poor conductivity.（金屬通常有高的熱傳導(dǎo)，然而陶瓷和塑料有差的熱傳導(dǎo)。）The main difficulty experienced in machining titanium, for example, is caused by its very low thermal conductivity. （在金屬鈦中主要的問(wèn)題是由于它的差的熱傳導(dǎo)。） Expansion（熱膨脹） The thermal expansion of materials can have several significant effects, particularly the relative expansion or contraction of different materials in assemblies such as moving parts in machinery that require certain clearances for proper functioning.（材料的熱捧場(chǎng)有一些有益的影響，尤其是在裝配中不同材料的熱脹冷縮比如機(jī)械中得活動(dòng)件需要特定的空隙來(lái)完成特定的功能。）For example, a part, such as a flange, is to be installed over a shaft.（比如，一個(gè)零件如法蘭，要安裝穿過(guò)一根軸。） When allowed to cool, the part shrinks and the assembly effectively bees an integral ponent.（當(dāng)冷卻時(shí)，零件收縮而且這個(gè)實(shí)際裝配體變成了一個(gè)整體部件。）The word corrosion itself usually refers to the deterioration of metals and ceramics, while similar phenomena in plastics generally are called degradation. （腐蝕這個(gè)詞本身指的是金屬和陶瓷的退化，然而在塑料中類(lèi)似的現(xiàn)象叫做降解。）Corrosion resistance is an important aspect of material selection for applications in the chemical, food, and petroleum industries, as well as in manufacturing operations. （耐腐蝕性在化學(xué)，食物和石油工業(yè)材料選擇中是一個(gè)重要方面，生產(chǎn)制造中也一樣。）Resistance to corrosion depends on the position of the material and on the particular environment. （耐腐蝕性取決于材料組成和所處的特殊的環(huán)境。） Nonferrous metals, stainless steels, and nonmetallic materials generally have high corrosion resistance, Steels and cast irons usually have poor resistance and must be protected by various coatings and surface treatments..（有色金屬和非金屬材料通常有高的耐腐蝕性，鋼和鑄鐵常有較差的耐腐蝕性而且必須通過(guò)各種膜和表面處理來(lái)防止腐蝕。） Aluminum develops a thin (a few atomic layers), strong, and adherent hardoxide film (Al2O3) that better protects the surface from further environmental corrosion.（鋁形成一層?。◣讉€(gè)原子層）而強(qiáng)的緊貼的Al2O3膜，它能更好地防止平面被進(jìn)一步地腐蝕。） A similar phenomenon occurs in stainless steels, which (because of the chromium present in the alloy) develop a protective film on their surfaces. （不銹鋼應(yīng)用了類(lèi)似的現(xiàn)象，在它表面形成了一層保護(hù)膜（由于合金中鉻的出現(xiàn)）。）12 Spindle Bearings(陳鵬文，有錯(cuò)包含)A machine tool spindle must provide rotational speed, transfer torque and power to the cutting tool, and have reasonable load carrying capacity and life. （機(jī)床主軸必須提供轉(zhuǎn)速、傳遞力矩和公路到切削工具上，而且具有一個(gè)合理的負(fù)載承受能力和壽命。）Highspeed spindle bearing available today include roller, taper roller, and angular contact ball bearings.（當(dāng)今可以用的高速主軸軸承包括滾珠軸承、錐型滾柱軸承和徑向止推滾珠軸承。）Angular contact bearings are the type most monly used in very highspeed spindle design. （徑向止推軸承在超高速主軸設(shè)計(jì)中是用得最普遍的。） Angular contact ball bearings have a number of precision balls fitted into a precision steel race, and provide both axial and radial load carrying capacity when properly preloaded.（徑向止推軸承有許多安裝在精確鋼槽里的精確滾珠，在正確安裝下提供軸向和徑向的負(fù)載承受能力。）However, tapered roller bearings do not allow the high speeds required by many spindles.（然而，錐型滾柱軸承不能保證許多主軸需要的高的速度。） Light preloaded bearings allow maximum speed and less stiffness. These bearings are often used for very highspeed applications, where cutting loads are light.（輕載型軸承能保證最大速度和較小的剛度。）Heavy preloading allows less speed, but higher stiffness.（重載型軸承可以保證較低速度，較高剛度。）In this way, the bearings share the loads, and increase overall spindle stiffness.（用這種方法，軸承分擔(dān)負(fù)載，而且提高了整個(gè)主軸的剛度。） The ceramic balls, when used in an angularcontact ball bearing, offer distinct advantages over typical bearingsteel balls（應(yīng)用于徑向止推滾珠軸承中的陶瓷滾珠提供了較鋼珠軸承中鋼珠明顯的優(yōu)點(diǎn)。） This is significant because as a ball bearing is operating, particularly at high rotational speeds, shape of the ball. （這是有意義的，因?yàn)橐粋€(gè)轉(zhuǎn)動(dòng)的滾珠軸承尤其是在高速旋轉(zhuǎn)中，滾珠的形狀會(huì)發(fā)生變化。）Ceramic balls, with less mass, will not be affected as much at the same speed. （陶瓷滾珠具有較小的質(zhì)量，在相同速度下陶瓷滾珠受到影響不如鋼珠大。） Due to the nearly perfect roundness of the ceramic balls, hybrid ceramic bearings operate at much lower temperatures than steel ball bearings, which results in longer life for the bearing lubricant. （由于幾近完美圓度的陶瓷滾珠，混合的陶瓷軸承工作在較鋼珠軸承低得溫度，這些導(dǎo)致在軸承潤(rùn)滑中有較長(zhǎng)的壽命。）Bearing lubricant is necessary for angular contact ball bearing to operate properly.（軸承潤(rùn)滑在徑向止推軸承正確工作中是必要的。）In addition, it protects surfaces from corrosion, and protects the contact area from particle contamination.（另外，它還防止平面腐蝕，保護(hù)接觸平面受磨粒影響。） It is injected into the space between the balls and the races, and is permanent. （它被注射到滾珠和滾槽之間的縫隙中，是永久的。） Generally, highspeed spindles utilizing grease lubrication do not allow replacement of the grease between bearing replacements. （通常情況下，高速主軸應(yīng)用油脂潤(rùn)滑不能保證潤(rùn)滑油脂在軸承替換件中的替換。）Often at high rotational speeds, lubrication with grease is not sufficient. （通常在高轉(zhuǎn)速中，油脂潤(rùn)滑是不夠的。） Maintenance of the lubrication system is vital, and must be closely monitored to ensure that proper bearing conditions are maintained. （潤(rùn)滑維護(hù)系統(tǒng)式非常重要的，而且必須嚴(yán)密檢測(cè)來(lái)保證維護(hù)中正確的軸承維護(hù)條件。How much life can be expected?（預(yù)測(cè)壽命是多長(zhǎng)呢？） All bearings will have a useful life, defined as operation time until the bearing specifications are lost, or a plete failure of the bearing occurs. （所有的軸承都將有一個(gè)使用壽命，被定義為從工作開(kāi)始時(shí)間到軸承規(guī)格破壞時(shí)間或者到軸承完全地實(shí)效。）Bearing life, in general, is affected by axial and radial bearing loads, vibration levels, lubrication quality and quantity, maximum speed, and average bearing temperature. （通常情況下，軸承的壽命受軸向和徑向的負(fù)載、振動(dòng)程度、潤(rùn)滑質(zhì)量、最高速度和平均軸承溫度影響。）Today, puter models are often used to forecast bearing life.（現(xiàn)在，計(jì)算機(jī)模型經(jīng)常用于預(yù)測(cè)軸承壽命。一個(gè)機(jī)構(gòu)是一個(gè)由兩個(gè)以上的部分裝配成的機(jī)器的一個(gè)組件以實(shí)現(xiàn)一個(gè)部件的運(yùn)動(dòng)帶動(dòng)其他部分運(yùn)動(dòng)。動(dòng)力學(xué)是研究運(yùn)動(dòng)的部分和受力和力矩影響的機(jī)構(gòu)。 綜合分析是設(shè)計(jì)產(chǎn)品以滿(mǎn)足一定的性能需求的一個(gè)步驟，如果一個(gè)產(chǎn)品配置先初步指定，然后檢查產(chǎn)品以確定是否他的性能規(guī)格是否能滿(mǎn)足需要。機(jī)器的設(shè)計(jì)包括綜合和分析兩個(gè)方面。這個(gè)設(shè)計(jì)步驟可能包括了重新設(shè)計(jì)那些影響速度、加速度、力和力矩的部件。增加生產(chǎn)率，升級(jí)產(chǎn)品功能，重新設(shè)計(jì)使造價(jià)和重量降低是常常需要的，成功可能取決于這個(gè)運(yùn)動(dòng)學(xué)和動(dòng)力學(xué)