本文選題：裂紋萌生 + 結(jié)構(gòu)參數(shù)研究　； 參考：《蘭州理工大學(xué)》2015年碩士論文

【摘要】：隨著我國對境外能源依賴度的不斷增加,在陸地建設(shè)一萬公里量級以上的油氣管道及相應(yīng)的集輸壓力容器己變得十分普遍。斜接接管結(jié)構(gòu)作為油氣管網(wǎng)及其附屬集輸壓力容器設(shè)計中不可避免的結(jié)構(gòu)形式,雖在整體管網(wǎng)中所占比例不大,但屬于整體管網(wǎng)中最為薄弱的環(huán)節(jié)之一,常常產(chǎn)生各種形式的失效和破壞。它的安全穩(wěn)定運行不僅涉及到國家能源戰(zhàn)略的安全,更牽扯到管道所經(jīng)地域和國家環(huán)境保護的重要責(zé)任。本文針對內(nèi)壓作用下理想的(沒有初始缺陷的、沒有焊接帶來的不利影響的)斜接接管結(jié)構(gòu)進行裂紋萌生預(yù)測研究,并總結(jié)分析斜接接管結(jié)構(gòu)的結(jié)構(gòu)參數(shù)、應(yīng)力應(yīng)變分布、裂紋萌生預(yù)測結(jié)果之間的關(guān)系,以便在斜接接管設(shè)計的初期提供一些結(jié)構(gòu)優(yōu)化的建議,進而增加其在實際工作中的疲勞壽命。本文采用有限元數(shù)值模擬作為主要的數(shù)據(jù)獲取手段并結(jié)合理論計算對斜接接管結(jié)構(gòu)的裂紋萌生進行預(yù)測,主要包括以下研究內(nèi)容：1.分析了目前普遍使用的缺口構(gòu)件裂紋萌生預(yù)測方法,對比了它們在斜接接管結(jié)構(gòu)裂紋萌生預(yù)測上的步驟和優(yōu)缺點,并對現(xiàn)有條件進行了評估,選擇了一種可行的研究方法。2.針對所選的斜接接管結(jié)構(gòu)裂紋萌生預(yù)測方法的需要,通過有限元模擬的手段,考察了斜接接管結(jié)構(gòu)彈性應(yīng)力集中系數(shù)(理論應(yīng)力集中系數(shù))與無量綱結(jié)構(gòu)參數(shù)之間的關(guān)系。結(jié)果表明,小傾斜角、大開孔率、大的筒體與接管的厚度比、大的筒體徑厚比將加劇斜接接管結(jié)構(gòu)的應(yīng)力集中狀況,對其造成不利影響。其中當(dāng)傾斜角小于45度時彈性應(yīng)力集中系數(shù)大幅增加,在結(jié)構(gòu)設(shè)計時應(yīng)盡量避免。3.考察了斜接接管結(jié)構(gòu)彈性應(yīng)力最大點(危險點)可能出現(xiàn)的部位,并根據(jù)斜接接管結(jié)構(gòu)在應(yīng)力應(yīng)變分布上的特點將考察范圍鎖定在理想的焊縫區(qū)可能出現(xiàn)危險點的內(nèi)相貫線、接管焊趾線、筒體焊趾線這三條危險線上。結(jié)果表明,在理想的斜接接管結(jié)構(gòu)中,裂紋萌生始終發(fā)生在內(nèi)相貫線的銳角側(cè)。4.使用局部缺口應(yīng)力應(yīng)變方法對斜接接管結(jié)構(gòu)的裂紋萌生進行了預(yù)測,得到結(jié)構(gòu)參數(shù)對其的影響規(guī)律。結(jié)果表明,小傾斜角、大開孔率、大的筒體與接管的厚度比、大的筒體徑厚比將減小裂紋萌生預(yù)測結(jié)果,對其造成不利影響。其中當(dāng)傾斜角小于45度時裂紋萌生預(yù)測結(jié)果將大幅減少,在結(jié)構(gòu)設(shè)計時應(yīng)盡量避免。5.從概率分析角度對斜接接管結(jié)構(gòu)的裂紋萌生預(yù)測進行了可靠性分析。并在給定循環(huán)載荷范圍下,對60度斜接結(jié)構(gòu)進行了具有一定可靠度的裂紋萌生預(yù)測。
[Abstract]:With the increasing dependence on overseas energy in China, the construction of oil and gas pipelines and corresponding gathering and transporting pressure vessels over 10,000 kilometers on land has become very common. As an inevitable structural form in the design of oil and gas pipeline network and its affiliated gathering and transporting pressure vessel, the oblique connection structure is one of the weakest links in the whole pipe network, although it occupies a small proportion in the whole pipe network. Often, various forms of failure and destruction occur. Its safe and stable operation involves not only the safety of national energy strategy, but also the important responsibility of the region of pipeline and national environmental protection. In this paper, the crack initiation prediction of the ideal oblique nozzle structure under internal pressure (without initial defects, without the adverse effect of welding) is studied, and the structural parameters, stress and strain distribution of the oblique connection structure are summarized and analyzed. The relationship between the prediction results of crack initiation in order to provide some suggestions for structural optimization in the initial stage of the design of oblique joints and to increase their fatigue life in practical work. In this paper, the finite element numerical simulation is used as the main data acquisition method and the theoretical calculation is used to predict the crack initiation of the oblique nozzle structure, including the following research contents: 1: 1. This paper analyzes the widely used crack initiation prediction methods for notched members, compares their steps, advantages and disadvantages in the prediction of crack initiation of oblique nozzle structures, evaluates the existing conditions, and selects a feasible research method .2. According to the need of the selected prediction method for crack initiation of oblique nozzle structure, the relationship between elastic stress concentration factor (theoretical stress concentration factor) and dimensionless structural parameters of oblique nozzle structure is investigated by means of finite element simulation. The results show that small inclined angle, large opening ratio, large thickness ratio of cylinder to nozzle, and large ratio of diameter to thickness of cylinder will aggravate the stress concentration of the oblique connection structure, which will have a negative effect on it. The elastic stress concentration factor increases greatly when the inclination angle is less than 45 degrees and should be avoided when the structure is designed. The possible position of the maximum elastic stress point (danger point) of the oblique nozzle structure is investigated, and according to the characteristics of the stress and strain distribution of the oblique connection structure, the investigation range is locked in the intersecting line of the danger point which may appear in the ideal weld zone. The pipe welding toe wire, the cylinder body welding toe wire these three dangerous lines. The results show that in an ideal oblique connection structure, the crack initiation always occurs at the acute side of the intersecting line. Local notch stress strain method is used to predict the crack initiation of oblique connection structure, and the influence of structural parameters on the crack initiation is obtained. The results show that the prediction results of crack initiation will be reduced by small inclination angle, large opening ratio, large thickness ratio of tube to nozzle, and large ratio of diameter to thickness, which will have a negative effect on the prediction of crack initiation. The prediction results of crack initiation will be greatly reduced when the inclination angle is less than 45 degrees, and should be avoided as far as possible in structural design. From the point of view of probability analysis, the reliability analysis of crack initiation prediction of oblique connection structure is carried out. At the given cyclic load range, the crack initiation of 60 degree oblique structure is predicted with certain reliability.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TE973

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