本文選題：釬焊接頭 + 多軸應(yīng)力�。� 參考：《華東理工大學(xué)》2016年博士論文

【摘要】：近年來,釬焊技術(shù)在航空航天、燃?xì)廨啓C(jī)及燃料電池等高溫服役條件下得到了廣泛的應(yīng)用。在高溫下,蠕變及蠕變損傷引起的裂紋擴(kuò)展是導(dǎo)致釬焊接頭失效的主要原因之一。釬焊接頭中存在的釬焊殘余應(yīng)力、熱應(yīng)力與外加載荷疊加使釬焊接頭處于復(fù)雜的多軸應(yīng)力狀態(tài),對(duì)釬焊接頭的蠕變失效產(chǎn)生較大的影響。本文以Inconel625/BNi-2釬焊接頭為研究對(duì)象,對(duì)其多軸應(yīng)力狀態(tài)下的蠕變損傷及裂紋擴(kuò)展性能進(jìn)行研究,探討釬焊接頭的失效規(guī)律,為釬焊接頭在高溫條件下的壽命預(yù)測(cè)提供參考。論文的主要研究工作和相關(guān)結(jié)論如下：(1)對(duì)釬焊接頭中的基體材料Inconel625合金和釬料BNi-2的蠕變性能進(jìn)行了試驗(yàn)研究�？紤]尺寸效應(yīng),特別針對(duì)釬料提出了一種與釬焊接頭中釬料厚度相類比的小試樣。通過高溫單軸拉伸(常規(guī)試樣、小試樣)試驗(yàn)分別獲得了Inconel625合金和釬料BNi-2兩種材料的蠕變應(yīng)變曲線,并基于Norton方程擬合獲得相應(yīng)的蠕變本構(gòu)參數(shù),為蠕變損傷本構(gòu)模型參數(shù)的擬合和有限元分析提供了基礎(chǔ)數(shù)據(jù)。(2)結(jié)合Kachanov-Rabotnov蠕變損傷模型的優(yōu)點(diǎn),通過修正Liu-Murakami模型,建立了描述多軸應(yīng)力狀態(tài)下蠕變?nèi)A段的本構(gòu)模型。基于該模型,利用ABAQUS的CREEP模塊嵌入Fortran子程序,對(duì)Inconel625合金蠕變裂紋擴(kuò)展行為進(jìn)行有限元分析,并通過試驗(yàn)進(jìn)行了驗(yàn)證。結(jié)果表明,修正的蠕變損傷模型可準(zhǔn)確描述Inconel625合金蠕變裂紋的擴(kuò)展情況,解決了Kachanov-Rabotnov模型有限元計(jì)算收斂困難的難題,同時(shí)避免了Liu-Murakami模型因分析過程中σ1/σeq比值過大或比值小于0而出現(xiàn)與實(shí)際情況不符的問題。(3)對(duì)釬焊接頭Inconel625/BNi-2的裂紋擴(kuò)展行為進(jìn)行了研究。根據(jù)微觀金相組織,將釬焊接頭分成母材、擴(kuò)散區(qū)和釬料三個(gè)區(qū)域�？紤]殘余應(yīng)力和熱應(yīng)力的影響,基于上述修正的模型,通過賦予各區(qū)域不同屬性,對(duì)釬焊接頭的蠕變損傷及裂紋擴(kuò)展行為進(jìn)行了有限元分析。進(jìn)而采用緊湊拉伸(CT)試樣對(duì)釬焊接頭進(jìn)行試驗(yàn)研究,獲得了釬焊接頭的失效區(qū)域及蠕變裂紋擴(kuò)展速率,證明了該修正模型可準(zhǔn)確描述釬焊接頭蠕變裂紋擴(kuò)展行為。研究發(fā)現(xiàn)擴(kuò)散區(qū)的性能對(duì)釬焊接頭的蠕變裂紋擴(kuò)展行為具有較大的影響,提高擴(kuò)散區(qū)的蠕變應(yīng)變率有利于延長(zhǎng)釬焊接頭的使用壽命。(4)對(duì)釬焊接頭蠕變裂紋擴(kuò)展行為的影響因素進(jìn)行了參數(shù)化分析。對(duì)不同釬料厚度、試樣尺寸、殘余應(yīng)力和熱應(yīng)力下的釬焊接頭蠕變裂紋擴(kuò)展行為進(jìn)行了有限元分析,結(jié)果表明,適當(dāng)增大釬料厚度和試樣尺寸均有利于提高裂紋擴(kuò)展的孕育期；消除殘余應(yīng)力不但能夠極大地提高釬焊接頭的裂紋擴(kuò)展孕育期,同時(shí)還大大降低了裂紋擴(kuò)展速率,有利于提高釬焊接頭的使用壽命；而釬焊接頭中熱應(yīng)力的存在改變了接頭中的應(yīng)力分布,對(duì)于延長(zhǎng)其使用壽命是有利的。(5)基于上述本構(gòu)模型及研究方法,本文以一航空發(fā)動(dòng)機(jī)回?zé)崞鞯脑O(shè)計(jì)為例,對(duì)回?zé)崞髡w結(jié)構(gòu)在設(shè)計(jì)工況條件下(650℃、3MPa)的蠕變損傷和使用壽命進(jìn)行了模擬分析。結(jié)果顯示,回?zé)崞鹘Y(jié)構(gòu)失效位置位于釬縫區(qū)域,連續(xù)運(yùn)行34,900小時(shí)后,裂紋貫穿整個(gè)釬料區(qū)域,不能達(dá)到連續(xù)工作40,000小時(shí)的設(shè)計(jì)要求。當(dāng)換熱主管的壁厚增加50%,連續(xù)工作40,000小時(shí)后釬料區(qū)域的裂紋長(zhǎng)度為1.1mm,約占管壁壁厚的1/3左右。此時(shí),回?zé)崞髂軌蚶^續(xù)正常工作,滿足航空發(fā)動(dòng)機(jī)安全運(yùn)行的要求。然而壽命的延長(zhǎng)是以重量的增加為代價(jià)的,整個(gè)回?zé)崞鞯闹亓吭黾蛹s10%。所以進(jìn)一步提高釬料的抗蠕變性能是提高航空發(fā)動(dòng)機(jī)回?zé)崞鲝?qiáng)度、降低重量的重要發(fā)展方向。
[Abstract]:In recent years, brazing technology has been widely used in high temperature service conditions such as aeronautics and Astronautics, gas turbine and fuel cell. At high temperature, the crack propagation caused by creep and creep damage is one of the main causes of brazing joint failure. The brazing residual stress, thermal stress and external loading charge are superimposed on the brazing joint to make the brazing filler metal. The welding head is in a complex multi axis stress state, which has a great influence on the creep failure of brazed joint. This paper takes the Inconel625/BNi-2 brazing welding head as the research object, studies the creep damage and crack propagation performance under multi axis stress state, and discusses the failure law of brazing joint, which is the life of brazed joint under high temperature. The main research work and the relevant conclusions of the thesis are as follows: (1) the creep properties of the base material Inconel625 alloy and the solder BNi-2 in the brazed joint are studied. Considering the size effect, a small sample of the brazing joint is presented in particular to the brazing joint in the brazing joint. The creep strain curves of two kinds of Inconel625 alloy and BNi-2 are obtained by the tensile test (conventional and small sample), and the corresponding creep constitutive parameters are obtained based on the Norton equation. It provides the basic data for the fitting of the creep damage constitutive model parameters and the finite element analysis. (2) combined with the creep damage model of the creep damage model. By modifying the Liu-Murakami model, a constitutive model describing the three stage of creep in a multiaxial stress state is established. Based on this model, the finite element analysis of the creep crack propagation behavior of the Inconel625 alloy is carried out by using the CREEP module of the ABAQUS to be embedded in the Fortran subprogram. The results show that the modified creep has been carried out. The variable damage model can accurately describe the creep crack growth of Inconel625 alloy and solve the difficult problem of the convergence difficulty of the finite element calculation of the Kachanov-Rabotnov model. At the same time, it avoids the problem that the Liu-Murakami model is too large or the ratio is less than 0 in the analysis process. (3) Inconel625/ for the brazing joint. The crack propagation behavior of BNi-2 was studied. According to micrometallographic microstructure, the brazed joints were divided into three regions: the base material, the diffusion zone and the solder. Considering the influence of the residual stress and thermal stress, the creep damage and the crack propagation behavior of the brazed joint were finite-element based on the modified model. Then the brazed joint was tested by the compact tension (CT) specimen, and the failure region and the creep crack propagation rate of the brazed joint were obtained. It was proved that the modified model can accurately describe the creep crack propagation behavior of the brazed joint. The effect of increasing the creep strain rate of the diffusion zone is beneficial to prolonging the service life of the brazed joint. (4) the factors affecting the creep crack propagation behavior of the brazed joint are parameterized. The finite element analysis of the creep crack propagation behavior of the brazed joints under the thickness of the solder, the size of the sample, the residual stress and the thermal stress is analyzed. The results show that the proper increase of the thickness of the solder and the size of the sample can improve the incubation period of the crack growth, and the elimination of residual stress can not only greatly improve the incubation period of the crack propagation of the brazing joint, but also greatly reduce the rate of crack propagation and improve the service life of the brazing joint. In changing the stress distribution in the joint, it is beneficial to prolong its service life. (5) based on the above constitutive model and research method, this paper takes an aeroengine regenerator design as an example to simulate the creep damage and service life of the regenerator overall structure under the design condition (650 degrees, 3MPa). The results show that The structure failure position of the regenerator is located in the brazing seam area. After 34900 hours of continuous operation, the crack runs through the whole solder area and can not meet the design requirements for continuous work for 40000 hours. When the wall thickness of the heat exchanger is increased by 50%, the length of the crack in the solder area is about 1.1mm after 40000 hours of continuous work, and it is about 1/3 of the wall thickness of the tube. The device can continue to work properly to meet the requirements of the safe operation of the aero engine. However, the prolongation of the life span is at the expense of the increase of the weight. The weight of the whole regenerator increases about 10%., so the further improvement of the creep resistance of the solder is an important direction for improving the strength of the regenerator and reducing the weight of the aero engine.
【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】：2016
【分類號(hào)】：TG454

【參考文獻(xiàn)】

相關(guān)期刊論文 前4條

1 徐鴻;袁軍;倪永中;;基于Norton-Bailey模型的P92鋼初期蠕變過程分析[J];材料科學(xué)與工程學(xué)報(bào);2013年04期

2 耿魯陽;劉建杰;鞏建鳴;姜勇;尹基奉;沈利民;;基于修正θ投影法的爐管用Cr25Ni35Nb鋼蠕變壽命預(yù)測(cè)[J];機(jī)械工程材料;2011年12期

3 陳建鈞;史進(jìn);涂善東;軒福貞;王正東;;BNi-2/0Cr18Ni9釬焊接頭高溫蠕變行為的試驗(yàn)研究及數(shù)值模擬[J];焊接學(xué)報(bào);2006年03期

4 藍(lán)仕偉;釬焊工藝在航空發(fā)動(dòng)機(jī)制造中的應(yīng)用和進(jìn)展[J];航空科學(xué)技術(shù);1994年04期

相關(guān)博士學(xué)位論文 前2條

1 談建平;納入拘束效應(yīng)的含裂紋結(jié)構(gòu)蠕變壽命評(píng)價(jià)方法研究[D];華東理工大學(xué);2014年

2 莊法坤;基于梁彎曲理論的小試樣蠕變?cè)囼?yàn)方法研究[D];華東理工大學(xué);2014年

相關(guān)碩士學(xué)位論文 前1條

1 史進(jìn);不銹鋼釬焊接頭高溫強(qiáng)度的研究[D];南京工業(yè)大學(xué);2004年

，

本文編號(hào)：2033290