Q345R钢蠕变过程声发射特性实验研究

发布时间：2018-05-11 14:45

本文选题：Q345R + 蠕变　；参考：《东北石油大学》2016年硕士论文

【摘要】：在实际工业生产中,有许多压力容器长期服役于高温、高压的工作环境中,而这些高温服役容器的失效大多数是由于材料蠕变损伤所致。蠕变损伤的出现会使材料的组织及力学性能发生劣化,大大降低材料承载能力,给工业生产带了极大的安全隐患。因此深入了解容器用钢的高温蠕变损伤对高温、高压容器的安全使用和事故的预防具有重要的现实意义。本文基于材料损伤演化理论,依托承压系统与安全教育部重点实验室开放课题基金《耐热钢蠕变过程声发射特性实验研究》,采用声发射测试技术对Q345R钢高温蠕变过程进行监测,研究其蠕变损伤特性。本文主要内容概括如下:(1)综述蠕变损伤的国内外研究现状,详细探讨多种现有的蠕变损伤理论,深入认识蠕变损伤产生的内在机理,并结合声发射现象的产生过程,基于现有技术和方案对论文内容进行可行性分析,明确本文的研究内容,制定合理的研究路线;(2)选择隐式蠕变法则对Q345R钢不同温度、应力条件下的蠕变过程进行数值分析,研究温度、应力对Q345R钢蠕变损伤过程的影响,结果发现温度与应力是材料蠕变过程的重要影响因素,随着温度的逐渐升高和应力的不断增大,材料蠕变变形也随之增大,蠕变损伤也愈加严重;(3)分析蠕变过程试件的承载、变形状况,得到材料蠕变损伤过程的能量释放模型,结合应力波释放理论,采取外加激励的方法模拟试件蠕变过程损伤产生与传播过程。结果表明,蠕变损伤源产生后会释放出瞬态应力波,随着应力波在材料中的传播,波的能量会产生一定量的衰减,到达传感器位置后,得到了类似于典型声发射信号波形的位移时程曲线;(4)制定Q345R钢高温蠕变声发射监测实验方案,并基于实验方案对试验机进行改装,借助改装后的夹具进行实验,采用计数、能量、幅值等声发射参数对Q345R钢蠕变损伤过程进行描述。结果发现蠕变初始阶段的声发射活动相对活跃,但趋于平缓的特征;随着蠕变的进行,声发射活动进入稳定期,信号不断出现,但信号量与幅值相对较低,累积计数与能量曲线出现了缓慢增加的“台阶”;当进入蠕变后期,损伤加剧,声发射活动随之更加活跃,进而在蠕变断裂时声发射信号能量、幅值达到极值。对蠕变断裂后的试件进行宏观、微观断口分析,进一步认识蠕变过程Q345R钢材料性能的变化,也从另一个角度佐证了声发射分析结果。
[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.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG142.15;TH49

【相似文献】