【摘要】：在電力、石化、核能及航空航天等工業(yè)領(lǐng)域中,廣泛采用高溫工藝。在高溫下長(zhǎng)期服役的結(jié)構(gòu)部件中,不可避免地產(chǎn)生蠕變損傷。加之在制造和服役過程中常常產(chǎn)生夾渣、凹坑、減薄等體積型缺陷,削弱了結(jié)構(gòu)的極限承載力。傳統(tǒng)的安全評(píng)定規(guī)范不考慮結(jié)構(gòu)中蠕變損傷的累積對(duì)結(jié)構(gòu)極限承載力的影響,可能導(dǎo)致不合理的評(píng)定結(jié)果。本文針對(duì)這一問題,考慮蠕變損傷對(duì)極限載荷的影響,基于“合乎使用”的原則,通過理論計(jì)算與數(shù)值模擬相結(jié)合的方法,構(gòu)建了耦合材料蠕變損傷的彈塑性本構(gòu)模型,系統(tǒng)地研究了含體積型缺陷高溫結(jié)構(gòu)的極限載荷,提出了考慮結(jié)構(gòu)中蠕變損傷累積的安全評(píng)定方法。論文的主要研究工作及結(jié)論如下： (1)基于冪律強(qiáng)化材料本構(gòu)模型,推導(dǎo)了無缺陷厚壁及薄壁圓筒的內(nèi)壓極限載荷的解析解。用有限元計(jì)算了結(jié)構(gòu)尺寸及材料參數(shù)對(duì)無缺陷圓筒的內(nèi)壓極限載荷的影響規(guī)律,并驗(yàn)證了解析解。 (2)通過實(shí)驗(yàn)觀察,分析了2.25Cr1Mo鋼蠕變損傷的物理機(jī)制和影響因素,并將這些因素耦合到彈塑性本構(gòu)方程中；構(gòu)建了基于Ramberg-Osgood方程的耦合蠕變損傷的彈塑性本構(gòu)模型,可以預(yù)測(cè)含蠕變損傷的高溫結(jié)構(gòu)的彈塑性響應(yīng),為計(jì)算含蠕變損傷高溫結(jié)構(gòu)的極限載荷奠定基礎(chǔ)。 (3)基于該彈塑性本構(gòu)模型,運(yùn)用有限元計(jì)算分析了各種形狀尺寸的凹坑及局部減薄缺陷的圓筒形容器在內(nèi)壓或彎矩的作用下,塑性區(qū)域的擴(kuò)展過程和失效模式。著重分析了缺陷尺寸和蠕變損傷累積對(duì)結(jié)構(gòu)塑性極限載荷的影響規(guī)律。 (4)考慮了結(jié)構(gòu)中的蠕變損傷累積,建立了基于歸一化的蠕變時(shí)間和歸一化的缺陷尺寸為參量的安全評(píng)定方法。可以簡(jiǎn)便地進(jìn)行含體積型缺陷高溫結(jié)構(gòu)的安全評(píng)定。
[Abstract]:High-temperature technology is widely used in the fields of electric power, petrochemical, nuclear energy, aerospace and so on. Creep damage is inevitable in structural components in long service at high temperature. In addition, volume defects such as slag, pits and thinning are often produced in the process of manufacture and service, which weaken the ultimate bearing capacity of the structure. Traditional safety assessment codes do not consider the effect of creep damage accumulation on the ultimate bearing capacity of structures, which may lead to unreasonable assessment results. In this paper, considering the effect of creep damage on the limit load, an elastic-plastic constitutive model of coupled material creep damage is established by combining theoretical calculation with numerical simulation based on the principle of "fit for use". The limit loads of high-temperature structures with volumetric defects are systematically studied, and a safety assessment method considering creep damage accumulation in structures is proposed. The main research work and conclusions are as follows: (1) based on the constitutive model of power-law strengthened materials, the analytical solution of the internal pressure limit load of the thin-walled and non-defective thick wall is derived. The influence of the structure size and material parameters on the internal pressure limit load of the non-defective cylinder is calculated by finite element method, and the analytical solution is verified. (2) through experimental observation, the physical mechanism and influencing factors of creep damage of 2.25Cr1Mo steel are analyzed, and these factors are coupled to the elastoplastic constitutive equation; The elastoplastic constitutive model of coupled creep damage based on Ramberg-Osgood equation is constructed, which can predict the elastoplastic response of high temperature structures with creep damage, which lays a foundation for calculating the ultimate loads of high temperature structures with creep damage. (3) based on the elastoplastic constitutive model, the expansion process and failure mode of plastic region under the action of internal pressure or bending moment of various shapes and sizes of pits and cylindrical vessels with local thinning defects are calculated and analyzed by using the elastoplastic constitutive model. The influence of defect size and creep damage accumulation on the plastic limit load of the structure is analyzed. (4) considering creep damage accumulation in structure, a safety assessment method based on normalized creep time and normalized defect size is established. It is easy to evaluate the safety of high temperature structures with volume defects.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TB302.3;TH49

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