Study on Type-IV Damage Prevention in High-Temperature Welded Structures of Next-Generation Reactor Plants: Part I — Fatigue and Creep-Fatigue Behavior of Welded Joints of Modified 9Cr-1Mo Steel

2006 ◽  
Author(s):  
Yukio Takahashi
Keyword(s):  
Welded Joints ◽  
Power Plants ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Premature Failure ◽  
High Chromium ◽  
Type Iv ◽  
Chromium Steels ◽  
Creep Fatigue ◽  
New Generation

High-chromium ferritic steels, such as modified 9Cr-1Mo steel, are regarded as candidate structural materials for new generation nuclear power plants and reliable design methods need to be developed. Of particular importance is prevention of premature failure, commonly referred to as type-IV failure, in softened regions of the heat-affected zones as several incidents of type IV failures of high-chromium steels in the fossil power plants have been reported. As part of the work aimed at developing design method for high-chromium steels applicable to new generation reactor plants, strain-controlled fatigue and creep-fatigue tests were conducted for welded joints of modified 9Cr-1Mo steel plate mainly at 550°C and 600°C. Failure typically occurred in the base metal in the pure fatigue tests but type-IV failure in the heat-affected zone occurred in most of the creep-fatigue tests where a large life reduction due to strain hold was observed. Life prediction method of the welded joint under creep-fatigue loading condition was studied based on these results.

Component Low Cycle Fatigue Behavior Based on Standard Calculation Procedure and Non-Linear FEA

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Adrian Willuweit ◽  
Steffen Bergholz ◽  
Christian Philippek ◽  
Jevgenij Kobzarev
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hybrid Approach ◽  
Combined Cycle ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Constitutive Material Model ◽  
Standard Design ◽  
Creep Fatigue

Components of conventional power plants are subject to potential damage mechanisms such as creep, fatigue and their combination. These mechanisms have to be considered in the mechanical design process. Against this general background — as an example — the paper focusses on the low cycle fatigue behavior of a main steam shut off valve. The first design check based on standard design rules and linear Finite Element Analysis (FEA) identifies fatigue sensitive locations and potentially high fatigue usage. This will often occur in the context of flexible operational modes of combined cycle power plants which are a characteristic of the current demands of energy supply. In such a case a margin analysis constitutes a logical second step. It may comprise the identification of a more realistic description of the real operational loads and load-time histories and a refinement of the (creep-) fatigue assessment methods. This constitutes the basis of an advanced component design and assessment. In this work, nonlinear FEA is applied based on a nonlinear kinematic constitutive material model, in order to simulate the thermo-mechanical behavior of the high-Cr steel component mentioned above. The required material parameters are identified based on data of the accessible reference literature and data from an own test series. The accompanying testing campaign was successfully concluded by a series of uniaxial thermo-mechanical fatigue (TMF) tests simulating the most critical load case of the component. This detailed and hybrid approach proved to be appropriate for ensuring the required lifetime period of the component.

Creep-Fatigue Damage Evaluation of Grade 91 Steel Using Interrupt Creep Fatigue Test

2018 ◽  
Author(s):  
Uijeong Ro ◽  
Jeong Hwan Kim ◽  
Hoomin Lee ◽  
Seok Jun Kang ◽  
Moon Ki Kim
Keyword(s):  
Fatigue Damage ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Fatigue Behavior ◽  
Fe Model ◽  
Testing Method ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Grade 91 Steel

The Sodium Fast-cooled Reactor (SFR), are generation IV nuclear power plants, have a target operating temperature of 550°C which makes creep-fatigue behavior more critical than a generation III nuclear power plants. So it is important to understand the nature of creep-fatigue behavior of the piping material, Grade 91 steel. The creep-fatigue damage diagram of Grade 91 steel used in ASME-NH was derived using a conventional time-fraction testing method which was originally developed for type 300 stainless steels. Multiple studies indicate that the creep-fatigue damage diagram of Grade 91 steel developed using this testing method has excessive conservatism in it. Therefore, an alternative testing method was suggested by separating creep and fatigue using interrupted creep tests. The suggested method makes it possible to control creep life consumption freely which was difficult with the previous method. It also makes it easier to observe the interaction between creep and fatigue mechanisms and microstructural evolution. In conclusion, an alternative creep-fatigue damage diagram for Grade 91 steel at 550°C was developed using an interrupt creep fatigue testing method and FE model simulation.

Study on Creep-Fatigue Damage Evaluation for Boiler Weldment Parts

2000 ◽  
Vol 123 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Takashi Ogata ◽  
Masatsugu Yaguchi
Keyword(s):  
Weld Joint ◽  
Creep Damage ◽  
Fem Analysis ◽  
Fatigue Tests ◽  
Type Iv ◽  
Fine Grain ◽  
Creep Fatigue ◽  
Damage Accumulation Model ◽  
Type Iv Cracking ◽  
Failure Life

Creep-fatigue tests on the heat-affected zone(HAZ) simulated materials, base metal, weld metal and weld joint of 2.25Cr-1Mo steel, and elastic-plastic and creep FEM analysis for the weld joint were conducted. It was found from the comparison between experimental evidences and the analytical results that “Type IV” cracking was caused by two major reasons. One is accumulation of creep strain during strain hold in the fine-grain region is larger than that in other regions, suggesting progress of creep damage in the fine-grain region prior to other regions. The other is existence of triaxial tensile stress field within the fine-grain region caused reduction of failure ductility. Crack initiation portion and failure life under the creep-fatigue test could be well predicted by the nonlinear damage accumulation model based on the FEM analysis results.

Fatigue Strength Assessment for High Strength Steel Welded Joints

2010 ◽  
Author(s):  
Ho Jung Kim ◽  
Sung Won Kang ◽  
Jae Myung Lee ◽  
Myung Hyun Kim
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fatigue Behavior ◽  
High Strength ◽  
Fatigue Tests ◽  
Cold Metal Transfer ◽  
Strength Assessment ◽  
Back Plate ◽  
Cold Metal

The aim of the present paper is to investigate and to compare the fatigue characteristics of butt welded joints made of high strength steel with tensile strength 700MPa. The influence of different back plate materials and the groove shapes of copper backing are investigated. Various backing methods have been used in the steel construction industries, but steel backing, which is the most frequently used, sometimes is not capable of providing sufficient fatigue strengths for welded joint, particularly for high strength steel. Therefore, alternative backing methods have been investigated in order to improve the fatigue strength by employing ceramic backing, CMT (Cold Metal Transfer) [1] and copper backing. The main objective of the work is to estimate the fatigue test results for improving fatigue strength by comparing different backing materials and groove shapes. A series of fatigue tests with different types of backings has been carried out to obtain the fatigue life of butt welded joints. It was observed that the fatigue behavior of welded joints can be substantially improved by changing back bead shapes. The result has shown that the back bead shape of copper backing is better than others except for that of CMT, accompanied by improved fatigue strength.

scholarly journals Microstructure and Fatigue Behavior of 2205/316L Stainless Steel Dissimilar Welded Joints

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 93
Author(s):  
Saúl Leonardo Hernández-Trujillo ◽  
Victor Hugo Lopez-Morelos ◽  
Marco Arturo García-Rentería ◽  
Rafael García-Hernández ◽  
Alberto Ruiz ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Welded Joints ◽  
316L Stainless Steel ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Base Material ◽  
Fatigue Tests ◽  
Solidification Mode ◽  
Tension And Compression ◽  
Weld Toe

The relation among microstructure and fatigue behavior of 2205/316L stainless steel dissimilar welded joints was investigated. Plates of 6.35 mm in thickness with a single-V joint configuration were gas metal arc welded (GMAW) in a single pass by feeding at 6 m/min an ER2209 filler wire with a heat input of 1.2 kJ/mm. Grain growth in the high temperature-heat affected zone (HT-HAZ) occurred mostly at the mid-height of the plates, delimiting the width of this region up to ~1.28 and ~0.73 mm of the 2205 and 316L plates, respectively. Dilution of the 316L plate with the ER2209 filler altered the solidification mode in this side of the weld and led to a significant content of austenite along the fusion line. Fatigue tests were performed using sinusoidal waveform at room temperature applying uniaxial cyclic loading, between constant stress limits within the elastic deformation of tension and compression (Δσ) with stress ratio R = −0.3. With stress ranges of 98% and 95% the fatigue specimens rapidly failed in much less than 106 cycles. The failure crack initiated at the surface of the 316L in the HT-HAZ near the weld toe. Surface analyses of unbroken specimens before and after fatigue testing revealed a significant increment in roughness of the 316L base material owing to the formation of intrusions and extrusions.

A STUDY ON THE FRETTING FATIGUE LIFE OF ZIRCALOY ALLOYS

2008 ◽  
Vol 22 (11) ◽  
pp. 851-856
Author(s):  
JAE-DO KWON ◽  
DAE-KYU PARK ◽  
SEUNG-WAN WOO ◽  
YOUNG-SUCK CHAI
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Fatigue Behavior ◽  
Fretting Fatigue ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Cyclic Damage

Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr , and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

Evaluation of Creep-Fatigue Life Using Backscattering of Rayleigh Surface Wave

2005 ◽  
Vol 297-300 ◽  
pp. 415-420 ◽  
Author(s):  
Byeong Soo Lim ◽  
Bum Joon Kim ◽  
Sung Jin Song ◽  
Young H. Kim
Keyword(s):  
Fatigue Life ◽  
Surface Wave ◽  
Fatigue Damage ◽  
Power Plants ◽  
Fatigue Behavior ◽  
Hold Time ◽  
Rayleigh Surface Wave ◽  
P92 Steel ◽  
Creep Fatigue ◽  
Main Steam

The application of nondestructive evaluation to creep-fatigue damage was examined in this paper. Generally, as the hold time of static load increases, the degradation of material becomes more rapid and the creep-fatigue life decreases. Therefore, in the evaluation of creep-fatigue strength and life of high-pressure vessel such as main steam pipe at high temperature is very important in power plants. In this study, the creep-fatigue behavior of P92 steel was evaluated nondestructively by the backscattered ultrasound using the creep-fatigue specimens. The results obtained by Rayleigh surface wave of backscattered ultrasound were compared and analyzed with the experimental parameters. Also, the relation between the SDA (slope of degraded area) and creep-fatigue life was examined. From the result of nondestructive test, we suggest that SDA would be used as the new parameter for the evaluation of creep-fatigue damage. As the degradation increased, the SDA decreased and also the creep-fatigue life decreased.

scholarly journals Creep-fatigue behavior of a new generation Ni-base superalloy for aeroengine usage

2010 ◽  
Vol 2 (1) ◽  
pp. 1865-1875 ◽  
Author(s):  
J.M. Silva ◽  
R.A. Cláudio ◽  
C. Moura Branco ◽  
J. Martins Ferreira
Keyword(s):  
Fatigue Behavior ◽  
Creep Fatigue ◽  
New Generation ◽  
Base Superalloy

Type IV Creep Damage Analysis for Full Size Component Test on Welded P91 Boiler Hot Reheat Piping

2004 ◽  
Author(s):  
Fumio Takemasa ◽  
Isamu Nonaka ◽  
Takuya Ito ◽  
Kensuke Saitou ◽  
Yoshikazu Miyachi ◽  
...  
Keyword(s):  
Welded Joints ◽  
Power Plants ◽  
Creep Damage ◽  
Assessment Method ◽  
Life Assessment ◽  
Creep Tests ◽  
Full Size ◽  
Type Iv ◽  
Component Test ◽  
Creep Life Assessment

In order to establish the creep life assessment method for modified 9Cr-1Mo steel welded joints on hot reheat piping of generating power plants, internal pressure creep tests conducted with full size components are analysed using the finite element method (FEM). As a result, it is shown that the creep damage distribution in weld heat affected zone (HAZ) can be predicted by stress distribution in HAZ, and that average stress in HAZ can be a representative value for creep strength of welded joints.

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