本文選題：Q345R + 蠕變　； 參考：《東北石油大學(xué)》2016年碩士論文

【摘要】：在實(shí)際工業(yè)生產(chǎn)中,有許多壓力容器長期服役于高溫、高壓的工作環(huán)境中,而這些高溫服役容器的失效大多數(shù)是由于材料蠕變損傷所致。蠕變損傷的出現(xiàn)會使材料的組織及力學(xué)性能發(fā)生劣化,大大降低材料承載能力,給工業(yè)生產(chǎn)帶了極大的安全隱患。因此深入了解容器用鋼的高溫蠕變損傷對高溫、高壓容器的安全使用和事故的預(yù)防具有重要的現(xiàn)實(shí)意義。本文基于材料損傷演化理論,依托承壓系統(tǒng)與安全教育部重點(diǎn)實(shí)驗(yàn)室開放課題基金《耐熱鋼蠕變過程聲發(fā)射特性實(shí)驗(yàn)研究》,采用聲發(fā)射測試技術(shù)對Q345R鋼高溫蠕變過程進(jìn)行監(jiān)測,研究其蠕變損傷特性。本文主要內(nèi)容概括如下:(1)綜述蠕變損傷的國內(nèi)外研究現(xiàn)狀,詳細(xì)探討多種現(xiàn)有的蠕變損傷理論,深入認(rèn)識蠕變損傷產(chǎn)生的內(nèi)在機(jī)理,并結(jié)合聲發(fā)射現(xiàn)象的產(chǎn)生過程,基于現(xiàn)有技術(shù)和方案對論文內(nèi)容進(jìn)行可行性分析,明確本文的研究內(nèi)容,制定合理的研究路線;(2)選擇隱式蠕變法則對Q345R鋼不同溫度、應(yīng)力條件下的蠕變過程進(jìn)行數(shù)值分析,研究溫度、應(yīng)力對Q345R鋼蠕變損傷過程的影響,結(jié)果發(fā)現(xiàn)溫度與應(yīng)力是材料蠕變過程的重要影響因素,隨著溫度的逐漸升高和應(yīng)力的不斷增大,材料蠕變變形也隨之增大,蠕變損傷也愈加嚴(yán)重;(3)分析蠕變過程試件的承載、變形狀況,得到材料蠕變損傷過程的能量釋放模型,結(jié)合應(yīng)力波釋放理論,采取外加激勵的方法模擬試件蠕變過程損傷產(chǎn)生與傳播過程。結(jié)果表明,蠕變損傷源產(chǎn)生后會釋放出瞬態(tài)應(yīng)力波,隨著應(yīng)力波在材料中的傳播,波的能量會產(chǎn)生一定量的衰減,到達(dá)傳感器位置后,得到了類似于典型聲發(fā)射信號波形的位移時程曲線;(4)制定Q345R鋼高溫蠕變聲發(fā)射監(jiān)測實(shí)驗(yàn)方案,并基于實(shí)驗(yàn)方案對試驗(yàn)機(jī)進(jìn)行改裝,借助改裝后的夾具進(jìn)行實(shí)驗(yàn),采用計數(shù)、能量、幅值等聲發(fā)射參數(shù)對Q345R鋼蠕變損傷過程進(jìn)行描述。結(jié)果發(fā)現(xiàn)蠕變初始階段的聲發(fā)射活動相對活躍,但趨于平緩的特征;隨著蠕變的進(jìn)行,聲發(fā)射活動進(jìn)入穩(wěn)定期,信號不斷出現(xiàn),但信號量與幅值相對較低,累積計數(shù)與能量曲線出現(xiàn)了緩慢增加的“臺階”;當(dāng)進(jìn)入蠕變后期,損傷加劇,聲發(fā)射活動隨之更加活躍,進(jìn)而在蠕變斷裂時聲發(fā)射信號能量、幅值達(dá)到極值。對蠕變斷裂后的試件進(jìn)行宏觀、微觀斷口分析,進(jìn)一步認(rèn)識蠕變過程Q345R鋼材料性能的變化,也從另一個角度佐證了聲發(fā)射分析結(jié)果。
[Abstract]:In the actual industrial production, there are many pressure vessels serving in high temperature and high pressure working environment for a long time, and the failure of these high temperature service vessels is mostly caused by creep damage of materials. The appearance of creep damage will make the microstructure and mechanical properties of the material deteriorate, greatly reduce the bearing capacity of the material, and bring great safety hidden trouble to the industrial production. Therefore, it is of great practical significance to understand the creep damage of vessel steel at high temperature and high pressure vessel for safe use and accident prevention. Based on the theory of material damage evolution, this paper uses acoustic emission test technique to monitor high temperature creep process of Q345R steel, based on the open project fund "Experimental study of acoustic emission characteristics of creep process of heat resistant steel", which is based on the stress bearing system and key laboratory of Ministry of Safety of the Ministry of Education. The creep damage characteristics are studied. The main contents of this paper are summarized as follows: (1) the research status of creep damage at home and abroad is summarized, and various existing creep damage theories are discussed in detail, and the inherent mechanism of creep damage is deeply understood, and the process of acoustic emission is combined. Based on the existing techniques and schemes, the feasibility analysis of the content of the paper is carried out, and the research content of this paper is clarified, and a reasonable research route is drawn up. The implicit creep rule is chosen to analyze the creep process of Q345R steel under different temperature and stress conditions. The effect of temperature and stress on the creep damage process of Q345R steel is studied. The results show that temperature and stress are important factors in the creep process of the material. With the increasing of temperature and stress, the creep deformation of the material also increases. The creep damage is more serious than before. (3) analyzing the loading and deformation of the specimens during creep, the energy release model of the creep damage process of materials is obtained, and the stress wave release theory is combined. The damage generation and propagation in creep process of specimens are simulated by means of external excitation. The results show that the transient stress wave will be released when the creep damage source is generated. With the propagation of the stress wave in the material, the energy of the wave will attenuate to a certain extent and reach the sensor position. The displacement time-history curve similar to the typical acoustic emission signal waveform is obtained. The experimental scheme of high temperature creep acoustic emission monitoring for Q345R steel is established. Based on the experimental scheme, the testing machine is refitted, and the experiment is carried out with the help of the modified fixture. The creep damage process of Q345R steel is described by energy and amplitude iso-acoustic emission parameters. The results show that the acoustic emission activity is relatively active in the initial stage of creep, but tends to be gentle. With the creep, the acoustic emission activity enters the stable period, and the signal appears continuously, but the signal quantity and amplitude are relatively low. The cumulative counting and energy curves show a slowly increasing "step", and when the damage increases in the late creep period, the AE activity becomes more active, and the amplitude of the AE signal energy reaches the extreme value when the creep fracture occurs. The macroscopic and microscopic fracture analysis of the specimens after creep fracture is carried out to further understand the change of the properties of Q345R steel during creep, and to support the results of acoustic emission analysis from another point of view.
【學(xué)位授予單位】：東北石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG142.15;TH49

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