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任務(wù)書填寫要求
1．畢業(yè)設(shè)計（論文）任務(wù)書由指導(dǎo)教師根據(jù)各課題的具體情況填寫，經(jīng)學(xué)生所在專業(yè)的負責(zé)人審查、系（院）領(lǐng)導(dǎo)簽字后生效。此任務(wù)書應(yīng)在畢業(yè)設(shè)計（論文）開始前一周內(nèi)填好并發(fā)給學(xué)生。
2．任務(wù)書內(nèi)容必須用黑墨水筆工整書寫，不得涂改或潦草書寫；或者按教務(wù)處統(tǒng)一設(shè)計的電子文檔標準格式（可從教務(wù)處網(wǎng)頁上下載）打印，要求正文小4號宋體，1.5倍行距，禁止打印在其它紙上剪貼。
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畢 業(yè) 設(shè) 計（論 文）任 務(wù) 書
1．本畢業(yè)設(shè)計（論文）課題應(yīng)達到的目的：
? 本課題以機械設(shè)計及制造為主要方向。其目的是使學(xué)生通過了基礎(chǔ)課、專業(yè)基礎(chǔ)課和專業(yè)課的教學(xué)過程后進行一次大型的機械設(shè)備設(shè)計訓(xùn)練，促使學(xué)生綜合運用所學(xué)專業(yè)知識進行機械設(shè)計；查閱各種有關(guān)資料、進行必要的調(diào)查研究和分析;通過成套較為復(fù)雜的模具的設(shè)計，熟練進行中等難度機械結(jié)構(gòu)的設(shè)計，從而獲得獨立自主解決工程技術(shù)問題的能力，使學(xué)生在畢業(yè)后能盡快適應(yīng)所擔(dān)負的工程技術(shù)工作。
2．本畢業(yè)設(shè)計（論文）課題任務(wù)的內(nèi)容和要求（包括原始數(shù)據(jù)、技術(shù)要求、工作要求等）：
? 內(nèi)容：一、按照已有的參數(shù)完成齒輪聯(lián)軸器注塑模的設(shè)計二、完成裝配設(shè)計圖要求： 1. 螺桿轉(zhuǎn)速（r/min）：20——50 2. 模具厚度的校核：模具厚度H必須滿足：Hmin≤Ｈ≤Ｈmax 3. 模具溫度（°C） 60——120 4. 注射壓力（MPa） 80——130 1）、塑件外殼材料的選擇（1）、機械加工性能良好（2）、拋光性能良好（3）、耐磨性和抗疲勞性能好 (4）、具有耐腐蝕性能。 2）、熟悉cad軟件及相關(guān)的注塑模知識開始建模[6-7] 3）、注塑模具的設(shè)計
畢 業(yè) 設(shè) 計（論 文）任 務(wù) 書
3．對本畢業(yè)設(shè)計（論文）課題成果的要求〔包括圖表、實物等硬件要求〕：
1、完成齒輪聯(lián)軸器注塑模的設(shè)計與選擇 2、繪制齒輪聯(lián)軸器注塑模的設(shè)計圖及主要零件圖 3、3000字的英譯漢 4、完成2萬字的畢業(yè)論文
4．主要參考文獻：
1、《塑料成型工藝與模具設(shè)計》 屈華昌：高等教育出版社 2、《塑料模具設(shè)計指導(dǎo)》 伍先明：國防工業(yè)出版社 3、《塑料注塑模結(jié)構(gòu)與設(shè)計》楊占堯：清華大學(xué)出版社 4、《中國模具設(shè)計大典》李志鋼：中國機械工程協(xié)會 5、《機械制圖》李澄 高等教育出版社 6、《塑料模具參考資料匯編》鄒繼強清華大學(xué)出版社 7、胡家秀主編.機械零件設(shè)計實用手冊.北京：機械工業(yè)出版社，1999．10 8、李益民主編.機械制造工藝設(shè)計手冊.北京：機械工業(yè)出版社，1995．10 9、韓森和 主編 《冷沖壓工藝及模具設(shè)計與制造》 高等教育出版社 2005.12 10、馮炳堯 韓泰榮 蔣文森 主編 《模具設(shè)計與制造簡明手冊》（第三版）上?？茖W(xué)技術(shù)出版社 2008.06 11、李云.機械制造工藝及設(shè)備設(shè)計指導(dǎo)手冊.北京.機械工業(yè)出版社. 1996 12、李益民.機械制造工藝設(shè)計簡明手冊. 北京.機械工業(yè)出版社.1993 13、杜林主編 模具加工規(guī)范 江蘇機械工業(yè)出版社 2003 14、黃毅宏主編 模具制造工藝 華南理工大學(xué) 2003 15、《注塑模具設(shè)計要點與圖例》；許鶴峰；化學(xué)工業(yè)出版社
畢 業(yè) 設(shè) 計（論 文）任 務(wù) 書
5．本畢業(yè)設(shè)計（論文）課題工作進度計劃：
20xx.12.16-20xx.1.10 領(lǐng)任務(wù)書、開題
20xx.2.25-2.16.3.9 畢業(yè)實習(xí)調(diào)研，完成開題報告、中英文翻譯、論文大綱
20xx.3.19-20xx.4.25 提交論文草稿，4月中旬中期檢查
20xx.4.26-20xx.5.6 提交論文定稿
20xx.5.6-20xx.5.13 準備答辯
20xx.5.13-20xx.5.26 答辯，成績評定，修改完成最終稿
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Overview of shaft
A shaft is one of the most important components in machines. Shafts are used to support rotating elements and transmit rotational motion and power. It is integral to any mechanical system in which power is transmitted from a prime mover,such as an electric motor or an engine, to other rotating parts of the system. Rotating parts of machines are mounted on shafts which provide for a constant position of the axis of rotation of these parts.
1.1 Types of shafts
According to the loads exerted on shafts, the shafts can be classified into three types: shafts , axle, spindle.
1. Shafts
Shafts are members intended for transmitting a torque along their axes and for supporting rotating machine components. Since the transmission of torque is associated with development of forces applied to the shafts ,such as forces acting on the teeth of gear , belt tension etc. , shafts are usually subject to transverse forces and bending moments in addition to the torque.
2. Axle
Axle are members which support rotating components of machines but do not transmit a useful torque. They are commonly subject to bending moments and to torques, not taken into consideration in design ,due to friction forces.
Axles are classified as rotating and fixed , the former providing for better operation of the bearings and better location , and the latter being cheaper but requiring built-in bearing in the rotating members.
3. Spindle
Shafts subject only to torque, just transmit motion from an input source to an output work site , usually called spindle.
With respect to the shape of their geometric axis , shafts are classified as straight shafts ,crankshafts and flexible shafts .
Crankshafts are used to convert reciprocating motion into rotation or vice verse . They combine the functions of ordinary shafts which those of cranks in slider-crank mechanisms. In a separate group are the so-called flexible shafts with a geometric axis of variable shape.
As to their shape , straight shafts are divided into plain shafts and stepped shafts. For the same mass , stepped shafts are more favorable than shafts of constant cross section . Such a shape is convenient in manufacture and assembly ; the shoulders of the stepped shaft can carry large axial forces .
Shafts may be hollow in design . A hollow shaft with a hole to outside diameter ratio of 0.75 is lighter by about 50% than a solid shaft of equal strength and rigidity .
With respect to the shape of their cross section , shafts may be plain , spline , and of special shape.
1.2 Shaft materials
The materials used for shafts are usually carbon steel and its alloy , most of shaft are made of round steel or forging , all kinds of heat treatment and surface strengthening treatment can significantly increase the fatigue strength of axis. Carbon steel are cheaper than its alloy , and the sensitivity to the stress concentration is lower,?so it is applicable to the general requirements of shaft. Alloy steel has higher mechanical properties and better than carbon steel quenching performance. In transmission power and reduce the size and quality, high wear resistance, corrosion and high temperature, low temperature, and alloy steel under the condition of shaft is often adopted.
Under the general working temperature, the elastic modulus of all sorts of carbon steel and alloy steel, so the same size of the carbon steel and alloy steel shaft stiffness.
High strength cast iron and nodular cast iron can be used to make complex shape of the shaft, and has low price, good vibration absorbing resistance and abrasion resistance, and low sensitivity to the stress concentration of advantages, but the quality of a material is brittle.
1.3 Structural design of shafts
The structure of the shaft is affected by many factors , three major problems in the structure design should be considered , functional requirements , technological requirements and the strength of shafts .
1. Functional requirements
In order to ensure the fixed position of elements on the shaft , it is needed to fix each element on the shaft radially and axially . The radial location of elements on the shaft is usually realized by keys . If a shaft has several key ways along its length , it is good practice to align them in a single plane to avoid resetting the shaft in milling the key ways .
Axial loads acting on shafts or on components mounted on the shafts are transmitted as follows:
(1) light loads and as a safety measure to prevent displacement by chance forces ——by means of a locating ring or setscrews holding the component ；
(2) Medium loads —— by means of shoulder and nuts , fixed locating rings , or cone and nut;
(3) Heavy loads —— by having the loaded components bear against shoulders of the shaft , or mounting the components with dual-nuts or an interference fit .
Two-way axial securing of a shaft is not compulsory if it is held in place by a constant force which prevents displacement .
2. Technological requirements
(1) Manufacturability
In practice shafts are of stepped design , and steps should as little as possible for cutting down the cost . Narrow thrust collars are inexpedient on shafts as they increase the size of the bar stock required to make the shaft and lead to the conversation of a considerable amount of metal into chips .
The transition between two shaft steps of different diameters may be one of the following types .
①With necks for grinding wheel clearance . Usually on the 10 ~ 50 mm diameter shaft, to 3 mm wide, deep 0.25 mm slot ; In a diameter of 50 ~ 100 axis, to 5 mm wide, deep 0.5 mm slot . Slot radius should be as large as possible . The more routine groove greatly improve the wear ability of grinding wheel in machining, but also caused great stress concentration and reduce the strength of the shaft under varying stress.
The slot diameter used the stiffness terms and conditions to determine the axis, such as transmission shaft, also used for shaft end part of the bending moment is not big. Shaft screw thread section at the end of the also need these groove, in order to exit the thread cutting tool.
②With a fillet of a single radius for a transition surface . The radius r of the fillet is to be taken smaller than that of the edge round or radial dimension of the chamfer of the components to be mounted on the shaft step against the shoulder .
Journal of rolling bearing installation, we recommend the following values: = 3 h/r and r/d = 0.02 to 0.04, where d for two adjacent smaller diameter shaft segment, h to shoulder height.
On the stress of shaft, it is better to make the shoulder fillet radius is greater than or equal to 0.1 d. But not only to comply with this condition. For overloading axis, but also will on the part orientation on the surface of the shaft shoulder fillet, but that would make the manufacturing is very complex. Parts on the shaft on the hub on the edge of the hole radius is limited the shaft shoulder radius cases, installing a spacer ring is better
③With special shape of shoulder fillet. Usually, the circular arc line shaft shoulder fillet transition to a smaller diameter shaft section is the danger zone. So under the appearance of a given size, change the radius of curvature of the rounded corners, in the period of transition to smaller diameter shaft radius increases gradually, this is good. Sometimes using elliptic rounded corners, but more commonly used in two different curvature radius to draw the rounded corners. With variable radius of curvature of the rounded, can make the axial bearing capacity increased by 10%. With heavy cutting slots or grooves shoulder fillet increase the length of the transition area, but there are polishing the rounded corners is difficult.
By designing fillets of optimal shape that extend over a considerable length of the shaft , it is possible to practically eliminate stress concentration .
An effective method for increasing the strength of shafts in their transition zones is the removal of low-stressed material by providing load-relief grooves or by drilling an axial hole in the larger step . These measures provide for a more uniform stress distribution and reduce stress concentration .
Strain hardening of shaft fillets can raise the load-carrying capacity of shafts by 50% to 100% .
（2）Design for assembly
The diameters of the seating surfaces are selected from a standard series of fit diameters , the diameters for anti-friction bearings are selected from a standard series of ball and roller bearing bores . The differences in diameter of the steps are determined by the standard diameters of the fit surfaces for hubs and bearings , by the requirement of sufficient thrust surface to carry the axial forces ,taking into account the given corner radial and size of the champers ,and , finally, by the conditions of assembly of the shaft and its mounted components . The difference in diameter of steps having straight keys should be such that the mounted components can be taken off the shaft without removing the keys from the shaft . The difference in diameter should always be the minimum feasible values .
Seating surfaces for the hubs of components that are to be mounted on a shaft are either cylindrical or tapered . Cylindrical surfaces are chiefly used because they are simpler to manufacture . Tapered surfaces are employed to facilitate the mounting and removal of heavy components , to obtain the required tightness for changeable parts such as change gears and for improving the accuracy with which the components are centered on the shaft . In late years , tapered joints with a large interference are being widely applied .
3. Improving the strength of shafts
(1) In practice , the maximum shear stress would be decreased if the location of each rotating elements arranged in the optimum way .
(2) If the width of spool is much bigger , then the bending moment exerted to the shaft is also bigger than the short element .
(3) The endurance of shafts is determined by relatively small volumes of metal located in zones of considerable stress concentration . For this reason , special design and processing measures to raise the endurance of shafts prove highly effectively .
Design measures for raising the endurance of shafts at the seating surfaces by reducing edge pressure are followed , such as shaft enlargement for seating hub ; rounding of the corners on the hub ; making the hub thinner ; load relief grooves ; bushing or in a hub of material with low modulus of elasticity , etc.
The endurance limit of shafts can be increased by 80% to 100% by strengthening the surfaces for seating hubs by work hardening . This measure proves effective foe shafts up to 500 mm or 600 mm in diameter . Such hardening procedures are widely used at presented .
1.4 Strength calculation of shafts
The main loads acting on shafts are forces due to power transmission .
Forces constant in magnitude and direction cause constant stresses in fixed axles , and stresses that vary in an alternating symmetrical cycle in rotating axles and in shafts . Constant loads rotating together with the axles and shafts , due , for instance , to unbalanced rotating components , cause constant stresses .
In many shaft design and analysis projects , calculations must be done at several points to account completely for the variety of loading and geometry conditions that exist .
For the main calculations of the strength of shafts and axles it is necessary to determine the bending moment and torque in all the dangerous cross sections . In calculations for shafts subject to complex loads , bending and torsional moment diagrams are constructed . If the shaft is subject to loads in different planes , the loads are usually projected onto two perpendicular planes . If the forces act in planes located at an angle up 30° to one another , they can be assumed to be in a single plane . If the forces act in planes up to 15° from the coordinate planes they can be assumed to coincide with the latter .
1.5 Fatigue strength calculation of shafts
Fatigue strength calculation should taken into consideration the character of stress variation , static and fatigue characteristic of materials , stress concentration , the scale factor , surface conditions and surface hardening . These calculations are usually in the form of a check of the safety factor . To know the values of calculations , firstly , the mean stress and stress amplitude must be determined . The checking principle is that the safety factor of the designed shaft must be higher than permissible safety factor .
軸的概述
軸是機械中的重要零件之一。軸通常用于支承旋轉(zhuǎn)件、傳遞運動和動力。在任一將動力從原件，如電機或發(fā)動機，傳遞到系統(tǒng)中其它旋轉(zhuǎn)零件的機械系統(tǒng)中，軸都是必不可少的。旋轉(zhuǎn)的機械零件安裝在軸上，以保持定軸轉(zhuǎn)動。
1.1軸的分類
根據(jù)軸的承載情況不同，軸可分為轉(zhuǎn)軸、心軸和傳動軸三類。
1.轉(zhuǎn)軸
轉(zhuǎn)軸用來沿著它的軸線傳遞轉(zhuǎn)矩并支持旋轉(zhuǎn)的機械零件。因為傳遞轉(zhuǎn)矩時要連帶發(fā)生傳到軸上的力，例如齒輪輪齒上的力、帶的拉力等，所以通常轉(zhuǎn)軸除受轉(zhuǎn)矩外，還受有橫向力和彎矩。
2.心軸
心軸只是用來設(shè)計支持旋轉(zhuǎn)的機械零件而不傳遞有效轉(zhuǎn)矩。心軸上通常作用著彎矩和因摩擦力產(chǎn)生的轉(zhuǎn)矩。
心軸分為轉(zhuǎn)動心軸和固定心軸，前者為軸承提供較好的運轉(zhuǎn)，并且安裝方便，后者比較便宜但需在旋轉(zhuǎn)零件中裝設(shè)軸承。
3.傳動軸
只承受轉(zhuǎn)矩，并將運動從輸入端傳遞到工作端的軸，通常稱為傳動軸。
按其幾何形狀，軸可分為直軸、曲軸和撓性軸。
曲軸用于將往復(fù)運動轉(zhuǎn)變?yōu)樾D(zhuǎn)運動或作相反轉(zhuǎn)變的場合，它兼有通常轉(zhuǎn)軸的功用和曲柄滑塊機構(gòu)中曲柄的功用。轉(zhuǎn)軸中還有一種特殊的類型就是所謂的撓性軸。這種軸的軸線形狀可以改變。
直軸按形狀不同可分為：直徑不變的光軸和階梯型轉(zhuǎn)軸。當(dāng)質(zhì)量相同時，階梯軸比等截面軸更為有利，這種形狀便于制造和裝配，階梯軸的軸肩可承受大的軸向力。
轉(zhuǎn)軸課設(shè)計成空心的。內(nèi)外直徑之比為0.75的空心軸，較之強度相等和剛度相等的實心軸約輕50%。
轉(zhuǎn)軸按其截面形狀不同可分為光軸、花鍵軸以及特殊形狀的軸。
1.2軸的材料
軸通常由碳鋼及其合金組成，剛軸的毛坯多數(shù)用圓鋼或鍛件，各種熱處理和便面強化處理可以顯著提高軸的抗疲勞強度。
碳鋼比合金鋼價廉，對應(yīng)力集中的敏感性比較低，適用于一般要求的軸。
合金鋼比碳鋼有更高的力學(xué)性能和更好的淬火性能，在傳遞大功率并要求減小尺寸和質(zhì)量、要求高的耐磨性，以及處于高溫、低溫和腐蝕條件下的軸常采用合金鋼。
在一般工作溫度下，各種碳鋼和合金鋼的彈性模量都差不多，因此相同尺寸的碳鋼和合金鋼軸的剛度差不多。
高強度鑄鐵和球墨鑄鐵可用于制造外形復(fù)雜的軸，且具有價廉、良好的吸振性和耐磨性，以及對應(yīng)力集中的敏感性較低等優(yōu)點，但是質(zhì)地較脆。
1.3軸結(jié)構(gòu)的設(shè)計
軸的結(jié)構(gòu)受多方面的影響，在結(jié)構(gòu)設(shè)計時主要考慮三個主要問題，即使用要求，工藝性要求及提高軸的強度。
1.使用要求
為了確定軸上零部件的位置，需要對軸上的每一個零件在周向和軸向進行固定。零件的周向定位通常利用鍵來實現(xiàn)。如果軸上沿長度方向有著幾個鍵槽，則為了避免銑鍵槽時軸要重新裝夾起見，這些鍵槽最好開在同一個平面內(nèi)。
作用在軸及軸上零件的軸向載荷可用以下方法傳遞：
（1）輕載和用作防止因偶然受力而移動的安全措施——用彈性擋圈或緊定螺釘固定零件。
（2）中載——用軸肩和螺母、用固定定位環(huán)或用圓錐面和螺母連接。
（3）重載——將零件支撐在軸肩上，將零件用雙螺母或過盈配合裝到軸上。
如果存在所謂力鎖合的話，即經(jīng)常作用著阻止零件軸向移動的力，零件不必雙向軸向固定。
2.工藝性要求
（1）加工工藝性
實際設(shè)計階梯軸時，為降低成本，階梯應(yīng)盡可能少。在軸上不易做出狹窄的推力凸肩，因為這會加大毛坯直徑，并把大量金屬變?yōu)榍行肌?
軸上直徑不同的兩段之間的過渡部分可制成下列形式：
①帶有砂輪越程槽。通常在直徑為10~50mm的軸上，做出寬3mm、深0.25mm的槽；在直徑為50~100的軸上，做出寬5mm、深0.5mm的槽，槽的圓角半徑應(yīng)盡可能大些。這種越程槽在加工時大大提高了砂輪的耐磨性，但同時也引起了大的應(yīng)力集中和降低軸在變應(yīng)力下的強度。
這種槽用于直徑按剛度條件來確定的軸上，例如變速箱的軸，還用于彎矩不大的軸端部分。軸上螺紋段的末尾也需要這些槽，以便退出切螺紋的刀具。
②帶有半徑不變的軸肩圓角。軸肩圓角的半徑r應(yīng)小于所裝零件的圓角半徑或者倒角的徑向尺寸。
對安裝滾動軸承的軸頸，推薦采用以下值：h/r=3和r/d=0.02~0.04，其中d為兩相鄰軸段中較小的直徑，h為軸肩高度。
在應(yīng)力嚴重的軸上，最好使軸肩圓角的半徑大于或等于0.1d?？墒遣⒉恢皇悄軌蜃袷剡@個條件的。對于重載軸，也可將所裝的零件定位于軸肩圓角的表面上，但這會使制造極為復(fù)雜。在軸上所裝零件轂孔邊緣的圓角半徑使軸肩圓角半徑受到很大限制情況下，裝設(shè)間隔環(huán)是比較好的。
③帶有特殊形狀的軸肩圓角。通常，圓弧行軸肩圓角向直徑較小的軸段過渡之處是危險區(qū)域。因此在給定的外形尺寸下，使圓角的曲率半徑改變，在向直徑較小的軸段過渡時半徑逐漸增大，這是有利的。有時采用橢圓形的圓角，然而更常用的是以兩個不同曲率半徑畫出的圓角。用變曲率半徑的圓角，可使軸的承載能力提高10%。帶沉割槽或凹槽的軸肩圓角增大過渡區(qū)的長度，但是拋光這種圓角是有困難的。
設(shè)計出過渡曲線在軸上延伸較長的形狀最佳的圓角，能夠在實際上消除應(yīng)力集中。
提高軸上的過渡區(qū)強度的有效方法，是去掉一些應(yīng)力低的材料，即做成卸載槽或在直徑大的軸段上鉆出軸向孔。這些措施保證應(yīng)力在軸體內(nèi)分布的更加均勻，降低了應(yīng)力集中。
將圓角處進行變形硬化，可將軸的承載能力提高50%~100%。
（2） 可裝配工藝性
軸上配合表面的直徑由標準的配合直徑系列中選?。貉b滾動軸承處的直徑則由標準的滾動軸承內(nèi)徑尺寸系列中選取。軸上兩個軸段直徑之差決定于輪轂或軸承配合表面的標準直徑，在邊緣處圓角半徑和倒角尺寸給定情況下能有充分的支承表面以承受軸向力，以及軸和其上所裝零件的裝配條件。有平鍵的軸段間直徑之差，最好根據(jù)不從軸上去下平鍵即能拆卸所裝零件的條件來選取。直徑之差應(yīng)盡可能小。
軸上所裝零件輪轂的配合表面可做成圓柱形或圓錐形的。主要采用圓柱形的表面，因為這種表面制造簡單。采用圓錐形表面是為了使軸上的重型零件裝拆方便，使得像變速齒輪這樣的零件有足夠的緊密性以及提高軸上零件的對中精度。近年來，正在廣泛地應(yīng)用大過盈的錐形連接。
3. 提高軸的強度
（1) 工程應(yīng)用中，如果合理安排旋轉(zhuǎn)零件的位置，可減小最大剪切應(yīng)力的值。
（2) 如果輪轂的寬度較大，則作用在軸上的彎曲力矩也會比零件寬度小的情況要大。
（3) 軸的疲勞強度取決于應(yīng)力集中嚴重區(qū)域內(nèi)相當(dāng)小的金屬體積。所以采用特殊的結(jié)構(gòu)和加工方法對提高軸的疲勞強度是特別有效的。
由降低邊緣壓力來提高軸上配合表面的疲勞強度，在結(jié)構(gòu)上采取的措施有：將軸上裝入輪轂中的部分加粗、輪轂邊做成的外圓角、減薄輪轂壁、使用卸載槽、將彈性模量低的材料制成套筒或澆注入輪轂內(nèi)等方法。
用冷作硬化來強化軸上與輪轂配合的表面，可將軸的疲勞極限提高80%~100%，這種措施對于直徑500~600mm一下的軸證明是有效的。這種強化法目前正廣泛運用。
1.4軸的強度計算
軸上的基本載荷是由傳遞功率而來的力。
大小和方向不變的力在不轉(zhuǎn)的心軸中引起不變的應(yīng)力，而在旋轉(zhuǎn)的心軸和轉(zhuǎn)軸中則引起對稱循環(huán)的交變應(yīng)力。與心軸及轉(zhuǎn)軸一起轉(zhuǎn)動的不變的力，例如來自旋轉(zhuǎn)零件的不平衡力，引起不變的應(yīng)力。
在許多軸的設(shè)計和分析中，必須在幾個位置進行計算以全面考慮載荷和幾何條件變化的影響。
在轉(zhuǎn)軸和心軸的主要強度計算中，必須確定所有危險截面上的彎矩和轉(zhuǎn)矩。在計算收復(fù)雜載荷的軸時，應(yīng)作出彎矩和轉(zhuǎn)矩圖。當(dāng)作用在軸上的載荷位于不同的平面中時，通常將這些力分解到相互垂直的兩個平面中，此時可取諸力中之一的作用平面作為一個分解平面。如果作用力系位于夾角在30°以內(nèi)的平面中，可假設(shè)將它們合并在一個平面中。當(dāng)力對坐標平面的傾斜角小于15°時，可將其并到該平面中。
1.5軸的疲勞強度計算
計算疲勞強度時，對應(yīng)力變化的特性、材料的靜強度和疲勞強度性能、應(yīng)力集中、尺寸系數(shù)、表面狀況和表層強化都加以考慮。這種計算通常以校核安全系數(shù)的方式進行。要校核安全系數(shù)，首先必須知道平均應(yīng)力和應(yīng)立幅。校核準則為：軸的安全系數(shù)必須大于許用安全系數(shù)。