過程裝備與控制工程專業英語翻譯10-資料下載頁

　　

【正文】 q=r)σr= —POriPiri+(PiPO)（rOririrOr)whpressureσr=radial stressσq=hoop stressPi=internal pressurePO=externalri=inside radiusrO=outside radiusr=radius at any pointThe longitudinal stress in a thick cylinder is obtained by substituting Eqs.(),(),and()into the last expression of Eqs.()to giveσ1=Eε+2μ(PiriPOrO）r2OriThis equation indicates that σ1 is constant throughout a cross section because εis constantand r does not appear in the second the expressionσ1 can be obtained from statics Asσ1=PiriPOrOr2OriWith σ1 known, Eq.()for the deflection of a cylinder can be expressed asw=r(PiriPOrO)(12μ)+(PiPO)rirO(1+μ)Er(rOri)閱讀材料4圓柱殼體的應力源于內部壓力。累積力通過正交于平面ABCD給出：PL ．2r =2σqLtorσqq=Prt說明： P=壓力，L=圓柱體的長度，σ正應變εε=由下面式子決定：_2prr=環繞切應力，r=半徑，t=殼體的壁厚q2p(r+W)2prrrq并且：ε=2prrdWdrorεq=Wr圓柱狀殼體的半徑偏差源于內部壓力。因此，對薄殼體有：W=PrEt說明：W=半徑的偏差值，E=彈性橫量當rt0時，方程式（）和（）給出精確的結果。隨著r的減少，然而，一個更精確的表述是非常必要的，因為厚度的壓力分配并不是均衡的。接著要求助于Lame首先提出來的“厚殼”理論。該理論假定所有的剪切力都為0是由于對稱性和一個正常縱軸的平面，在施壓前仍然是平面壓力。換句話說，?1 是恒在任意橫截面上。σr和σq的關系可以通過一個環dr的自由體示意圖獲得。綜合垂直dσdr方向上的力和不計高階的項，于是我們得到σEq—σr=r第二種關系可以表達為：σq=（1+μ）（12μ）[εq(1μ)+μ（εr+ε）]σr=Eσ1=（1+μ）（12μ）E[εr(1μ)+μ（ε(1μ)+μ（εq+ε+ε）]）]（1+μ）（12μ）[ε1qr.()與及把結果代入Eq.()得：dwdr+1dwrdr—wr=0Br方程的一個值為W=Ar+r=riatσ：w= — μrε1+= —pir= —poatr=roOEr(rri)r2(1μ2μ（）PiriPOrO）+rirO(1+2222μ)（PiPO）］ 當W被求得，σ、圓柱的厚度可以表達為：rirOσq=PiriPOri+(PiPO)（rOr)riσr= —POriPiri+(PiPO)（r2OrirOr)riσr=徑向應力σq=環向應力Pi=內部壓力PO=外部壓力ri=內半徑rO=外半徑r=任意點的半徑、。其為： σ1=Eε+2μ(PiriPOrO）r2O2ri這個表達式說明了σ1是一個橫截面的常數因為ε的表達式可以由靜態值表示:σ1=PiriPOrOr2O2是常數和r不會在第二項出現。因此σri,隨著σ1知道了，表示為：w=r(PiriPOrO)(12μ)+(PiPO)rirO(1+μ)Er(rri)2O22222第五篇：過程裝備與控制工程專業英語翻譯 17Reading Material 17Stress CategoriesThe various possible modes of failure which confront the pressure vessel designer are:(1)Excessive elastic deformation including elastic instability.(2)Excessive plastic deformation.(3)Brittle fracture.(4)Stress rupture/creep deformation(inelastic).(5)Plastic instabilityincremental collapse.(6)High strainlow cycle fatigue.(7)Stress corrosion.(8)Corrosion dealing with these various modes of failure, we assume that the designer has at his disposal a picture of the state of stress within the part in would be obtained either through calculation or measurements of the both mechanical and thermal stresses which could occur throughout the entire vessel during transient and steady state question one must ask is what do these numbers mean in relation to the adequacy of the design? Will they insure safe and satisfactory performance of a ponent? It is against these various failure modes that the pressure vessel designer must pare and interpret stress example, elastic deformation and elastic instability(buckling)cannot be controlled by imposing upper limits to the calculated stress must consider, in addition, the geometry and stiffness of a ponent as well as properties of the plastic deformation mode of failure can, on the other hand, be controlled by imposing limits on calculated stresses, but unlike the fatigue and stress corrosion modes of failure, peak stress does not tell the whole consideration must be given to the consequences of yielding, and therefore the type of loading and the distribution of stress resulting therefrom must be carefully designer must consider, in addition to setting limits for allowable stress, some adequate and proper failure theory in order to define how the various stresses in a ponent react and contribute to the strength of that mentioned previously, different types of stress require different limits, and before establishing these limits it was necessary to choose the stress categories to which limits should be categories and subcategories chosen were as follows: Stress.(a)General primary membrane stress.(b)Local primary membrane stress.(c)Primary bending major stress categories are primary, sec9ondary, and chief characteristics may be described briefly as follows:(a)Primary stress is a stress developed by the imposed loading which is necessary to satisfy the laws of equilibrium between external and internal forces and basic characteristic of a primary stress is that it is not a primary stress exceeds the yield strength of the material through the entire thickness, the prevention of failure is entirely dependenton the strainhardening properties of the material.(b)Secondary stress is a stress developed by the selfconstraint of a must satisfy an imposed strain pattern rather than being in equilibrium with an external basic characteristic of a secondary stress is that it is yielding and minor distortion can satisfy the discontinuity conditions or thermal expansions which cause the stress to occur.(c)Peak stress is the highest stress in the region under basic characteristic of a peak stress is that it causes no significant distortion and is objectionable mostly as a possible source of fatigue need for dividing primary stress into membrane and bending ponents is that, as will be discussed later, limit design theory shows that the calculated value of a primary bending stress may be allowed to go higher than the calculated value of a primary membrane placing in the primary category of local membrane stress produced by mechanical loads, however, requires some explanation because this type of stress really has the basic characteristics of a secondary is selflimiting and when it exceeds yield, the external load will be resisted by other parts of the structure, but this shift may involve intolerable distortion and it was felt that must be limited to a lower value than other secondary stresses, such as discontinuity bending stress and thermal stress could be divided into membrane and bending ponents, just as was done f