Evaluation of Creep-Fatigue Damage Interaction in HK40 Alloy

1993 ◽  
Vol 115 (1) ◽  
pp. 41-46 ◽  
Author(s):  
S. Konosu ◽  
T. Koshimizu ◽  
T. Iijima ◽  
K. Maeda
Keyword(s):  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
Strain Range ◽  
Slow Waves ◽  
Design Criteria ◽  
Peak Strain ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fast Waves

In order to establish design criteria for materials which may sustain creep-fatigue damage, the creep rupture and creep-fatigue behavior of a high-carbon centrifugal cast steel was investigated at three different temperatures of 800, 900, and 1000°C, using HK-40 alloy which is a typical furnace tube material for fuel cell plant reformers and so on. The strain waveforms used for the creep-fatigue tests consisted of triangular waveforms—pp waves (fast-fast waves), cc waves (slow-slow waves), pc waves (fast-slow waves), and cp waves (slow-fast waves)—and a trapezoidal waveform holding the peak strain at the tension side. The applicability of various creep-fatigue interaction damage assessment methods were evaluated with particular emphasis on the life fraction rule (LFR) employed in ASME Section III, Boiler & Pressure Vessel Code Case N-47 and the strain range partitioning method (SRP). As it turned out that through the LFR life evaluation of HK-40 alloy subjected to strain cycling with holding at the tension side was well interpreted, design criteria for reformer tubes were established by applying the LFR to creep-fatigue life evaluation.

Evaluation of Creep-Fatigue Damage Interaction in HK40 Alloy

1991 ◽  
Author(s):  
Shinji Konosu ◽  
Tamotsu Koshimizu ◽  
Takahiro Iijima ◽  
Keikichi Maeda
Keyword(s):  
Fatigue Damage ◽  
Fatigue Behavior ◽  
Cast Steel ◽  
Strain Range ◽  
Slow Waves ◽  
Design Criteria ◽  
Peak Strain ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fast Waves

Abstract In order to establish design criteria for materials which may sustain creep-fatigue damage, the creep rupture and creep-fatigue behavior of a high-carbon centrifugal cast steel was investigated at three different temperatures of 800, 900, and 1000°C, using HK-40 alloy which is a typical furnace tube material for fuel cell plant reformers and so on. The strain waveforms used for the creep-fatigue tests consisted of triangular waveforms (pp waves [fast-fast waves], cc waves [slow-slow waves], pc waves [fast-slow waves], and cp waves [slow-fast waves]) and a trapezoidal waveform holding the peak strain at the tension side. The applicability of various creep-fatigue interaction damage assessment methods were evaluated with particular emphasis on the life fraction rule (LFR) employed in ASME Section III, Boiler & Pressure Vessel Code Case N-47 and the strain range partitioning method (SRP). As it turned out that through the LFR life evaluation of HK-40 alloy subjected to strain cycling with holding at the tension side was well interpreted, design criteria for reformer tubes were established by applying the LFR to creep-fatigue life evaluation.

A Direct Method on the Evaluation of Cyclic Steady State of Structures With Creep Effect

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
James Ure
Keyword(s):  
Fatigue Damage ◽  
Mechanical Load ◽  
Direct Method ◽  
Load Condition ◽  
Hysteresis Loops ◽  
Strain Range ◽  
Cyclic Behavior ◽  
Direct Evaluation ◽  
Plastic Strain Range ◽  
Creep Fatigue

This paper describes a new extension of the linear matching method (LMM) for the direct evaluation of cyclic behavior with creep effects of structures subjected to a general load condition in the steady cyclic state, with the new implementation of the cyclic hardening model and time hardening creep constitutive model. A benchmark example of a Bree cylinder and a more complicated three-dimensional (3D) plate with a center hole subjected to cyclic thermal load and constant mechanical load are analyzed to verify the applicability of the new LMM to deal with the creep fatigue damage. For both examples, the stabilized cyclic responses for different loading conditions and dwell time periods are obtained and validated. The effects of creep behavior on the cyclic responses are investigated. The new LMM procedure provides a general purpose technique, which is able to generate both the closed and nonclosed hysteresis loops depending upon the applied load condition, providing details of creep strain and plastic strain range for creep and fatigue damage assessments with creep fatigue interaction.

Analysis of Multi-Axial Creep–Fatigue Damage on an Outer Cylinder of a 1000 MW Supercritical Steam Turbine

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Weizhe Wang
Keyword(s):  
Steam Turbine ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Hydrostatic Stress ◽  
Fatigue Behavior ◽  
Axial Stress ◽  
Outer Cylinder ◽  
Continuum Damage Mechanics ◽  
Transfer Coefficients ◽  
Creep Fatigue

A multi-axial continuum damage mechanics (CDM) model was proposed to calculate the multi-axial creep–fatigue damage of a high temperature component. A specific outer cylinder of a 1000 MW supercritical steam turbine was used in this study, and the interaction of the creep and fatigue behavior of the outer cylinder was numerically investigated under a startup–running–shutdown process. To this end, the multi-axial stress–strain behavior of the outer cylinder was numerically studied using Abaqus. The in-site measured temperatures were provided to validate the heat transfer coefficients, which were used to calculate the temperature field of the outer cylinder. The multi-axial mechanics behavior of the outer cylinder was investigated in detail, with regard to the temperature, Mises stress, hydrostatic stress, multi-axial toughness factor, multi-axial creep strain, and damage. The results demonstrated that multi-axial mechanics behavior reduced the total damage.

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.

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 Damage and Life Evaluation for Boiler Header Stub Weldment.

2003 ◽  
Vol 52 (2) ◽  
pp. 162-166 ◽  
Author(s):  
Takuya ITO ◽  
Isamu NONAKA ◽  
Hideo UMAKI ◽  
Hidetaka NISHIDA ◽  
Shizuma SHINTANI
Keyword(s):  
Fatigue Damage ◽  
Life Evaluation ◽  
Creep Fatigue

The Creep-Fatigue Evaluation Method for Intermediate Hold Conditions: Proposal and Validation

2011 ◽  
Author(s):  
Satoshi Okajima ◽  
Nobuchika Kawasaki ◽  
Shoichi Kato ◽  
Naoto Kasahara
Keyword(s):  
Initial Stress ◽  
Fatigue Damage ◽  
Evaluation Method ◽  
Strain Range ◽  
Creep Damage ◽  
Fatigue Tests ◽  
Reactor Vessel ◽  
Liquid Sodium ◽  
Improved Method ◽  
Creep Fatigue

In this paper, for the application to the Japan Sodium-cooled Fast Reactor, JSFR, the creep-fatigue damage evaluation method is improved to consider the intermediate holding condition. The improved method is validated through both of the uni-axial and the structure model creep-fatigue tests. In these validations, the target material is 316FR steel, which is planned to use for the reactor vessel. The reactor vessel portion near the liquid sodium surface is one of the most probable points where the creep-fatigue damage is considerable. Because of the relaxation of the temperature gradient, the steady operation stress on the portion near the liquid sodium surface is less than the maximum stress in the transient. In the conventional method, in order to evaluate the creep damage conservatively, the maximum tensile value in the thermal stress transient cycle is used as the initial stress. The improved method evaluates the creep damage using the lower initial stress than the conventional method, while it has the rational margin. For the validation of the improved method, uni-axial creep-fatigue tests and structure model tests are carried out. A series of uni-axial creep-fatigue tests was carried out in the following conditions: 600 degree C testing temperature, 1% total strain range, 1 hour holding time, vacuum or air environments, and the various holding position. While the test environment affects the fatigue damage, it didn’t have significant effect on the creep damage. In the cases with high holding position, the creep damages were evaluated based on the given initial stress with high precision. In the other cases, by the assumption of the steady-stress existence, the rational margin is given for the evaluation. Furthermore, in the design stage, the evaluated creep-fatigue damage has enough margins derived from the conservative evaluation of the initial stress. The structural tests modeled the movement of the liquid sodium surface in the start-up and the shut-down stages, and the relaxation of the temperature gradient in the operation stage. In these tests, the temperature distribution was given by coolant water and an external high-frequency heating coil for the cylindrical specimen, and moved in the axial direction. In addition, the primary stress, which was caused by the weight of the reactor vessel, was given by the screw jack. As a result, using the strain range evaluated by the elastic analysis, the improved method evaluated the crack initiation life due to the creep-fatigue damage with the sufficient safety margin. In the case when the strain range was evaluated by the elastic-plastic analysis, the method predicted the crack initiation life with the good precision. While the evaluation of the crack penetration life was possible, further examination was desired for the precision improvement.

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