锅炉受压元件的高温蠕变-疲劳寿命设计计算方法

介绍了锅炉受压元件高温蠕变-疲劳寿命的设计计算方法.该方法建立在线弹性应力分析理论基础上,对我国锅炉制造业长期积累的锅炉受压元件寿命设计计算经验和方法进行了归纳总结,并参照了美国ASME等国际先进标准.它给出了电站锅炉高温受压元件蠕变、低周疲劳及交互作用条件下的寿命损伤计算方法和典型结构及材料的设计计算参数,可供水管锅炉高温受压元件寿命设计使用,在役元件的高温蠕变及高温蠕变-疲劳寿命计算也可借鉴.     

12CrlMoV钢制部件蠕变—疲劳交互作用的特性曲线研制

本文在12CrlMoV钢母材和焊接接头两种材料的疲劳寿命。蠕变寿命和蠕变-疲劳交互作用行为试验研究工作的基础上，重点对12CrlMoV钢在蠕变-疲劳交互作用下的试验结时进行了整理、分析，在国内首次得出了可供工程应用的12CrlMoV钢蠕变-疲劳交互作用寿命评定曲线，并与ASME规范的相关曲线进行了比较。并应用该方法对一实例做了寿命评定。     

P91主蒸汽管道焊接接头的蠕变特性和寿命估算

对P91钢母材和焊接接头进行持久试验,研究P91钢的蠕变特性,采用等温线法和L-M参数法对持久强度进行外推,进而对P91钢制主蒸汽管道的蠕变寿命进行估算.     

汽轮机转子钢疲劳—蠕变交互作用

本文对我国电站汽轮机常用的30Cr2MoV转子钢疲劳—蠕变交互作用进行了试验研究。根据火电厂转子运行工况,选择了不同保载时间,进行裂纹扩展试验。结果表明,这种材料在运行工况下存在疲劳—蠕变交互作用;随着保载时间的增加,裂纹扩展速率增加,寿命大大降低。断口分析发现,断面有沿晶断裂,且呈现“r”型空洞。运用线性累积损伤方法计算该转子钢疲劳—蠕变交互作用系数B=1.47～3.95,提出了交互作用下的裂纹扩展判据。     

蠕变-疲劳交互作用的寿命计算方法

对蠕变疲劳交互作用下的寿命计算方法进行了介绍。这些方法包括单轴和多轴下蠕变疲劳交互作用下的寿命估算模型，交互作用下裂纹扩展计算模型，非零平均应变下的寿命计算模型，以及损伤力学方法等。     

基于应变能密度的X12CrMoWVNbN10-1-1钢的蠕变-疲劳寿命预测模型

根据应力控制下对X12CrMoWVNbN10-1-1钢进行的蠕变-疲劳试验来验证基于应变能密度的蠕变-疲劳寿命预测模型,并对620℃下X12CrMoWVNbN10-1-1钢的弹性应变、塑性应变和蠕变应变进行分析。结果表明:在蠕变-疲劳交互作用下X12CrMoWVNbN10-1-1钢的损伤过程包括3个阶段;一次循环稳定阶段的平均应变能密度与总应变能密度成反比,而总应变能密度与蠕变-疲劳寿命成正比,可选择稳定阶段应变能密度的表达式来预测蠕变-疲劳寿命;在应力控制下X12CrMoWVNbN10-1-1钢的短时保载蠕变-疲劳试验同样可以预测长时保载的蠕变-疲劳寿命,意味着基于应变能密度的蠕变-疲劳寿命预测模型对于X12CrMoWVNbN10-1-1钢也适用。     

高温持久强韧性研究

本文研究了蠕变断裂韧性δ_(cc)对蠕变和蠕变-疲劳交互作用下裂纹开裂和扩展的影响.并进行了在不同δ_(cc)情况下光滑和缺口持久强度试验.文中指出:高过零件断裂寿命取决于缺口尖端处应力场和蠕变断裂韧性两方面的因素,所以在高温零件断裂寿命估算中.则应同时计及持久强度和蠕变断裂韧性.     

新型耐热钢T91的蠕变断裂寿命估算

T91 /P91钢是国外为提高火力发电机组的效率而研制的一种高合金耐热钢 ,它是完成超临界发电机组主蒸汽参数由 5 66℃向 5 93℃过渡的关键材料。采用受约束蠕变孔洞生长模型计算了不同试验条件下T91钢的蠕变断裂时间 ,计算值与实测值相差不到 2倍。在对模型修正后 ,计算得到的断裂时间与实际值更为接近 ,该模型可以用来估算T91钢高温服役条件下的蠕变断裂寿命     

电站锅炉高温受压元件蠕变和低周疲劳寿命损伤计算及在线监测

高温蠕变和低周疲劳是锅炉高温受压元件寿命损伤的主要机理.采用高温受压元件蠕变和低周疲劳寿命在线监测是提高锅炉安全运行和管理水平的有效途径.给出了电站锅炉高温受压元件蠕变和低周疲劳寿命损伤的计算方法,扼要介绍了寿命损伤在线监测的基本原理、技术关键、使用范围和实际的应用情况.     

304型不锈钢蠕变-疲劳损伤预测和剩余寿命评定

前言最近几年来,火力发电厂延长寿命的紧迫问题是对用于高温、长时的结构材料的损伤预测和剩余寿命评定。高温服役的材料,不仅承受纯蠕变或纯疲劳损伤,而且还承受机械应力和热应力造成的更复杂的蠕变—疲劳交互作用损伤。由于蠕变或疲劳作用下断裂和变形具有不旧样式,所以在蠕变—疲劳交互作用下的剩余寿命及损伤的精确评定相当复杂。为了精确评定蠕变—疲劳损伤,设法使用一些有损和无损试验方法,然而至     

A new high-temperature creep-fatigue damage rule based on the strain range partitioning concept

A new life prediction model based on the strain range partitioned crack growth rate equations is presented which can evaluate the material damage and the residual life under variable creep-fatigue strainings. Two-step sequential creep-fatigue straining tests such as High-Low and Low-High tests were conducted on Mod. 9Cr-1Mo steel and type 316LC stainless steel in order to examine the validity of the proposed model. It was found that the proposed model can be more successfully applied to the creep-fatigue life prediction under variable strainings than the conventional life prediction methods.     

基于材料老化和蠕变疲劳交互作用汽轮机转子寿命预测

根据材料老化和蠕变-疲劳交互作用对致裂寿命的影响，建立了汽轮机转子寿命预测模型和预测方法，以N75MW汽轮机转子为对象进行了寿命损耗分析和预测，指出基于材料老化和蠕变疲劳交互作用，可以有效提高汽轮机转子寿命预测的精度。     

A numerical investigation of creep-fatigue life prediction utilizing hysteresis energy as a damage parameter

This paper explores the hypothesis that there exists an intrinsic material property, hysteresis damage energy at failure, which could be used as a creep-fatigue life prediction parameter. The connection between hysteresis energy and fatigue damage was introduced in the 1920’s by Inglis, but the use of hysteresis energy as a measure of damage was first presented by Morrow and Halford. Hysteresis energy shows promise in bridging the gaps associated with life prediction when the combination of both creep and fatigue scenarios are present. Numerical simulations which replicate experimental test configurations with 9Cr–1Mo steel were performed from which the hysteresis energy failure density (HEFD) could be calculated for each experiment. Taking the average of the HEFD values calculated for all of the experimental data as the parameter for failure (E_Intrinsic), creep-fatigue life predictions were made using a simplistic hysteresis energy based method as well as the time fraction/cycle fraction method endorsed by ASME Code and compared to experimental results. A good correlation with experimental results was obtained for life predictions using hysteresis energy density as a damage parameter. An investigation of the interaction between creep damage and fatigue damage based on the hysteresis energy method was also performed and compared with the damage interaction diagram utilized by the ASME and RCC-MR design codes. The hysteresis energy based method proved easy to implement and gave improved accuracy over the time fraction/cycle fraction method for low cycle creep-fatigue loading.     

Predicted life of P91 steel for cyclic high temperature service

The P91 steel is widely used in high temperature components of power plants, and it is a candidate material for Gen-IV reactors. The P91 steel has relatively attractive mechanical and physical properties combined with resistance to stress corrosion cracking in water–steam environments. This study aimed to explore the combined cyclic, creep and relaxation behaviour of P91 material. Uniaxial specimens were subjected to cyclic loadings with periodic forward creep or relaxation at peak stress. The results indicate that prior creep or intermediate relaxation periods up to 72 h will influence the subsequent cyclic softening of P91, but do not significantly reduce the cyclic life. In contrast, prior cycling has a detrimental effect on the subsequent creep life. A simplified creep-fatigue model is shown to predict life better than usual code-based approaches. Improved verification of all models would benefit from the availability of more extensive long-term data on P91 steel.     

长期运行后汽轮机转子裂纹扩展行为的研究

对运行16年的30Cr1Mo1V亚临界汽轮机高中压转子进行解剖试验,采用直流电位法对材料在538℃下的蠕变裂纹、蠕变-疲劳裂纹萌生与扩展行为进行了研究,分析了不同初始应力强度因子对蠕变裂纹扩展孕育时间和蠕变裂纹扩展速率的影响,并对高温段和低温段的相关性能进行了比较,研究了不同保持时间对蠕变-疲劳裂纹扩展行为的影响,同时还分析了不同条件下裂纹扩展行为的时间或循环相关性．结果表明：疲劳缩短了蠕变-疲劳裂纹的扩展孕育期,加速了裂纹的扩展;载荷保持时间较短情况下,蠕变-疲劳裂纹扩展行为与循环相关;栽荷保持时间较长情况下,裂纹扩展行为与时间相关．     

Study on creep-fatigue evaluation procedures for high chromium steels—Part II: Sensitivity to calculated deformation

High-chromium steels containing 9–12% chromium such as ASME SA-213 Grade 91 or Grade 122 are widely used in conventional and combined cycle fossil power plants and are also regarded as candidate structural materials for future nuclear power plants aiming at operation in the creep range. Evaluation of failure life under creep-fatigue conditions constitutes an important part of assessing the structural integrity of these plants. The author has been conducting a series of creep-fatigue tests for three types of high-chromium steels and the validity of life prediction methods has been evaluated using the measured deformation data. Here an additional exercise was carried out in order to evaluate the adequacy of the total life prediction procedure, including the process of predicting stress and strain. After making comparisons of the test data with various existing equations developed for describing deformation and failure behaviour of Grade 91 and Grade 122, prediction of creep-fatigue life was attempted using deformation behaviour analytically estimated by these equations. Many calculations revealed that failure lives predicted by the time fraction approach showed a strong dependency on stress relaxation behaviour, whereas those based on the modified ductility exhaustion method showed a much smaller sensitivity, and therefore some error or uncertainty in stress and strain would be tolerated.     

Lifetime estimates of cracked high temperature components

Cracked high temperature components subjected to creep-fatigue loading can fail by crack growth, net-section rupture or some combination of both processes. Models for describing this behaviour are presented. The influence of build up of damage in a process zone at the crack tip, material deterioration in the uncracked ligament and the importance of tertiary creep on the mode of failure are each considered. It is shown how the models can be employed to predict crack growth and for making residual life assessments in high temperature equipment. Finally a simple cumulative damage law is outlined for describing creep-fatigue interaction.     

Assessment of a creep-fatigue crack initiation and crack propagation for a welded cylindrical shell

An assessment of the creep-fatigue crack bahaviour for a cylindrical structure with weldments has been carried out by using a structural test and an evaluation with an assessment procedure. The structural specimen with a diameter of 600 mm and thickness of 7 mm is a welded cylindrical shell made of 316L stainless steel (SS) for one half of the cylinder and 304 SS for the other half. Eight artificial defects were machined and the defect behaviours were examined. In the creep-fatigue test, the hold time was 1 h at 600 °C and the primary nominal stress was 45 MPa. The evaluation results for the creep-fatigue crack initiation and crack propagation were compared with those of the observation images from the structural test. The assessment results for the creep-fatigue crack behaviour by using the French A16 procedure showed that the A16 guide is reasonably conservative but overly conservative for the creep-fatigue crack propagation in the case of a short hold time. It was shown that the crack initiation and propagation were dominated by a creep.