發(fā)布時(shí)間：2018-01-21 21:46

  本文關(guān)鍵詞： 蠕變疲勞 孔洞演化 損傷模擬 壽命預(yù)測(cè)　出處：《清華大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：現(xiàn)代工業(yè)正在向著高溫、高壓的方向快速發(fā)展,在石油化工、航空航天、能源動(dòng)力等行業(yè)中,越來(lái)越多的機(jī)械設(shè)備和構(gòu)件,如大型燃?xì)廨啓C(jī)、航空發(fā)動(dòng)機(jī)、核電站設(shè)備、冶金機(jī)械等長(zhǎng)期在高溫高壓條件下工作,承受著越來(lái)越高的溫度和載荷作用,在這樣的條件下,嚴(yán)重威脅其安全的蠕變和疲勞破壞問(wèn)題日益突出,特別是蠕變和疲勞兩者交互作用下的破壞事故不斷發(fā)生,早已引起人們的重視。單純的蠕變或疲勞問(wèn)題是比較傳統(tǒng)的工程問(wèn)題,而蠕變疲勞交互作用下的損傷問(wèn)題更值得我們關(guān)注,也更符合上述實(shí)際工程中的情況。本文從微觀模型、模擬演化和壽命預(yù)測(cè)等幾個(gè)方面對(duì)幾種典型的多晶金屬材料在蠕變疲勞交互作用條件下的損傷問(wèn)題進(jìn)行了分析。從微觀角度出發(fā),改進(jìn)并應(yīng)用孔洞增長(zhǎng)演化方程,利用Voronoi多邊形剖分方法,建立多晶金屬材料的晶粒晶界分布模型,并隨機(jī)生成了晶界中的孔洞萌生點(diǎn),計(jì)算了晶界中孔洞在蠕變疲勞交互作用條件下的演化規(guī)律。同時(shí)定義了孔洞占晶界的百分比為參數(shù)的損傷變量,研究了其隨載荷、溫度、保載時(shí)間、晶粒尺寸等影響因素的變化規(guī)律。為了更準(zhǔn)確和直觀地描述孔洞演化過(guò)程,通過(guò)編制程序,建立了能夠表現(xiàn)微觀孔洞演化的有限元中循環(huán)計(jì)算方法和流程,其中考慮到了每個(gè)載荷循環(huán)中應(yīng)力和孔洞都會(huì)互相影響和隨時(shí)間變化,更符合真實(shí)工況。這種計(jì)算方法和流程可以應(yīng)用于多種典型多晶金屬材料的孔洞演化分析上。在基于Gurson本構(gòu)的研究疲勞問(wèn)題的損傷模型中,孔洞百分比是一個(gè)重要的參量,在此損傷模型中引入由蠕變效應(yīng)導(dǎo)致的孔洞百分比的增加項(xiàng),并將其用于蠕變疲勞交互作用條件下的情況。通過(guò)一個(gè)滾動(dòng)軸承模型的驗(yàn)證,證明改進(jìn)模型較純疲勞條件下的損傷有顯著增加,也實(shí)現(xiàn)了一種通過(guò)孔洞百分比分析蠕變疲勞共同損傷的標(biāo)量方法。最后,對(duì)四種常用的疲勞蠕變交互作用下壽命預(yù)測(cè)方法進(jìn)行了評(píng)估和比較,并選取其中精度較高且更有較明確物理含義的滯回能量法的一個(gè)改進(jìn)模型對(duì)Grade91鋼進(jìn)行了更好的蠕變疲勞壽命預(yù)測(cè)。
[Abstract]:Modern industry is developing rapidly in the direction of high temperature and high pressure. In petrochemical, aerospace, energy power and other industries, more and more mechanical equipment and components, such as large gas turbines, aero-engines. Nuclear power plant equipment, metallurgical machinery and other long-term working under the conditions of high temperature and high pressure, bear more and more high temperature and load, in such conditions, serious threats to its safety of creep and fatigue damage problems become increasingly prominent. Especially, the failure accidents under the interaction of creep and fatigue have been paid more and more attention. Simple creep or fatigue is a traditional engineering problem. The damage problem under the interaction of creep fatigue is more worthy of our attention, but also more in line with the actual engineering situation mentioned above. The damage problems of several typical polycrystalline metal materials under the interaction of creep fatigue are analyzed in the aspects of simulation evolution and life prediction. The grain boundary distribution model of polycrystalline metal materials is established by using the Voronoi polygon method and the evolution equation of pore growth is improved. The pore initiation points in the grain boundary are generated randomly. The evolution law of voids in grain boundaries under the condition of creep fatigue interaction is calculated. At the same time, the percentage of voids in grain boundaries is defined as the damage variable of parameters, and the effect of load, temperature and loading time is studied. In order to describe the evolution process of the pore more accurately and intuitively, the cyclic calculation method and flow chart of finite element which can represent the evolution of the micro pore are established by compiling the program. It is considered that the stress and the hole will affect each other and change with time in each load cycle. This method and process can be applied to the pore evolution analysis of several typical polycrystalline metal materials. In the damage model of fatigue problem based on Gurson constitutive model. The percentage of holes is an important parameter, and the increase of the percentage of holes caused by creep effect is introduced in the damage model. It is used in the case of creep fatigue interaction. Through the verification of a rolling bearing model, it is proved that the damage of the improved model is significantly increased than that of the pure fatigue condition. A scalar method is also implemented to analyze the creep fatigue joint damage through the percentage of voids. Finally, the life prediction methods under the interaction of fatigue and creep are evaluated and compared. An improved model of hysteretic energy method with higher precision and clearer physical meaning is selected to predict the creep fatigue life of Grade91 steel.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG115

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