【正文】 。The analysis of the membrane stresses induced in shells of revolution by internal pressure gives a basis for determining the minimum wall thickness required for vessel shells. The actual thickness required will also depend on the stresses arising from the other loads to which the vessel is subjected.對(duì)受內(nèi)壓回轉(zhuǎn)體的薄膜應(yīng)力分析為確定容器殼體最小壁厚奠定了基礎(chǔ)。實(shí)際所需壁厚也依賴于容器上所受其他載荷引起的應(yīng)力。Consider the shell of revolution of general shape shown in under a loading that is rotationally symmetric。 that is, the load per unit area (pressure) on the shell is constant round the circumference, but not necessarily the same from top to bottom.，研究的是回轉(zhuǎn)殼一般模型在旋轉(zhuǎn)軸對(duì)稱的載荷作用下的情行；也就是，單位圓周面積上的載荷是一定的，但不都是從上到下。Let P=pressure, 令：P=壓力 t=thickness of shell, t=壁厚 =the meridional (longitudinal) stress, the stress acting along a meridian, =經(jīng)向應(yīng)力 =the circumferential or tangential stress, the stress acting along parallel circles (often called the hoop stress), =周向應(yīng)力 =the meridional radius of curvature,r1=經(jīng)向曲率半徑 =circumferential radius of =環(huán)向曲率半徑Note: the vessel has a double curvature。 the values of and are determined by the shape.注意：容器有兩個(gè)曲率；r1 和r2值由模型決定。Consider the forces acting on the element defined by the points a. b c, d. Then the normal ponent (ponent acting at right angels to the surface) of the force on the element 假設(shè)作用在元件上的力由a、b、c、d四點(diǎn)確定。那么元件上的法向力（垂直于表面的分力）This force is resisted by the normal ponent of the forces associated with the membrane stresses in the walls of vessel （given by, force=stressarea） 通過與容器器壁的薄膜應(yīng)力聯(lián)系的法向力來抵抗這個(gè)力（即，力=應(yīng)力*面積）Equating these forces and simplifying, and noting that in the limit , and , gives:假設(shè)這些力是相等的并簡(jiǎn)化，取極限, 和，有 ()An expression for the meridional stress can be obtained by considering the equilibrium of the forces acting about any circumferential line, Fig . The vertical ponent of the pressure force經(jīng)向應(yīng)力的一個(gè)表達(dá)式可由作用在周向線上力的平衡得到，This is balanced by the vertical ponent of the force due to the meridional stress acting in the ring of the wall of the vessel=2σ1tл(r2sinθ) sinθ這與作用在容器壁上的經(jīng)向力的垂直分力是平衡的 =2σ1tл(r2sinθ) sinθEquating these forces gives:令這兩個(gè)力相等有： ()Equations () and () are pletely general for any shell of revolution.方程（）和（）對(duì)所有的回轉(zhuǎn)殼都適用。Cylinder()圓柱體（）A cylinder is swpet out by the rotation of a line parallel to the axis of revolution, so:圓柱體是由一條平行于軸的直線繞著軸旋轉(zhuǎn)形成的，于是：where D is the cylinder 。Substitution in equations () and () gives: 代入方程（）和（）得： ()Sphere()球（） hence:于是: ()Cone()圓錐（）A cone is swept put by a straight line included at an angle to the axis.圓錐是由一條直線以一定的角度繞軸旋轉(zhuǎn)而成的。Substitution in equations () and () gives: 代入方程（）和（）得： ()The maximum values will occur at 。當(dāng)時(shí)取得最大值。 (Select from: , Chemical Engineering, , and Edition, Pergamon Press,1996.) Word and Expressions1. membrane n. 薄膜，隔膜，隔板2. revolution n. 回轉(zhuǎn)，旋轉(zhuǎn)（運(yùn)動(dòng)）3. cylindrical （體型）的，（圓）圓筒的4. conical ，橢球的5. hemispherical （形，狀）6. ellipsoidal ，橢球的7. torispherical 8. include ，導(dǎo)致，誘發(fā)9. symmetric ，勻稱的，平均的10. curvature ，曲率11. resist ，耐（得?。?2. equate ，使等于13. meridional ，經(jīng)向的14. substitution Metals金屬About threequarters of the elements available can be classified as metals, and about half of these are of at least some industrial or mercial importance. Although the word metal, by strict definition, is limited to the pure metal elements, mon usage gives it wider scope to include metal alloys. While pure metallic elements have a broad range of properties, they are quite limited in mercial use. Metal alloys, which are binations of two or more elements, are far more versatile and for this reason are the form in which most metals are used by industry. 大約現(xiàn)有元素中的四分之三可歸類為金屬；而大約一半金屬元素都有一定的工業(yè)或商業(yè)上的重要性。盡管嚴(yán)格定義的金屬只局限于純金屬，但是普遍的用法是把它擴(kuò)展到更廣范圍的金屬合金。盡管純金屬有很多特性，他們?cè)谏虡I(yè)中的應(yīng)用也很局限。金屬合金由兩種或兩種以上的元素組成，用途非常廣泛，正是由于這種結(jié)構(gòu)上的原因，很多金屬被用于工業(yè)上。 Metallic materials are crystalline solids. Individual crystals are posed of unit cells repeated in a regular pattern to form a threedimensional crystallattice structure. A piece of metal is an aggregate of many thousands of interlocking crystals (grains) immersed in a cloud of negative valence electrons detached from the crystals’ atoms. These loose electrons serve to hold the crystal structures together because of their electrostatic attraction to the positively charged metal atoms (ions). The bonding forces, being large because of the closepacked nature of metallic crystal structures, account for the generally good mechanical properties of metals. Also, the electron cloud makes most metals good conductors of heat and electricity. 金屬材料是晶狀固體。單個(gè)晶體是由單元晶粒按有規(guī)則模式重復(fù)而形成的三維晶格。一塊金屬則是成千上萬相聯(lián)晶體的集合體，而這些晶粒都沉浸在從晶體原子中脫離出來的帶負(fù)電的價(jià)電子云中。由于這些自由電子對(duì)帶正電的金屬原子或離子有靜電吸引力，因此可以將晶體結(jié)構(gòu)緊湊的結(jié)合在一起。而由于金屬結(jié)晶結(jié)構(gòu)致密本質(zhì)導(dǎo)致的這種很大的結(jié)合力是造成金屬一般都具有良好機(jī)械性質(zhì)的原因。同樣，電子云使大多數(shù)金屬有很好的導(dǎo)電性和導(dǎo)熱性。 Metals are often identified by the method used to produce the forms in which they are used. When a metal has been formed or shaped in the solid, plastic state, it is referred to as a wrought metal. Metal shapes that have been produced by pouring liquid metal into a mold are referred to as cast metals. 在大多數(shù)情況下，根據(jù)生產(chǎn)金屬的模板來辨認(rèn)金屬。當(dāng)金屬已經(jīng)以固體的形式存在或形成時(shí)，并且是塑性的，被稱為可鍛金屬。將液體金屬傾倒入模型形成的金屬稱為澆鑄金屬。 There are two families of metallic materials: ferrous and nonferrous. The basic ingredient of all ferrous metals is the element iron. These metals range from cast irons and carbon steels, which 90% iron, to specialty iron alloys, containing a variety of other elements that add up to nearly half the total position. 金屬材料分為兩類：黑色金屬和有色金屬。所有黑色金屬的基本成分都是鐵元素。這些金屬涉及的范圍從含碳90%以上的鑄鐵和碳鋼到特種鐵合金，在這些鐵合金中，各種其他元素的總和幾乎占總成分一半。 Except for mercially pure iron, all ferrous materials, both irons and steels, are considered to be primarily ironscarbon alloy systems. Although the carbon content is small (less