Creep Failure Behavior of Notched Structure in the Simulated Steam Turbine Rotor: Experimental and Damage Analysis

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Tian-Ye Niu ◽  
Cheng Gong ◽  
Jian-Guo Gong ◽  
Fu-Zhen Xuan
Keyword(s):  
Constitutive Equation ◽  
Steam Turbine ◽  
Contact Region ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Failure Behavior ◽  
Creep Failure ◽  
Creep Tests ◽  
Blade Root ◽  
Evolution Behavior

Abstract Notched structures widely exist in steam turbine components in fossil power plant, e.g., the groove of the rotor, etc. Previous studies indicate that creep failures occur at the groove of the rotor or the adjacent regions. Thus, it is essential to study the creep failure behavior of the notched structures for the safe operation of the system. In this work, creep tests of the simulated steam turbine component have been conducted at the temperature of 605 °C, and the creep-damage constitutive equation is used to track the evolution behavior of creep strain and damage of this component. The influence of structural and loading configurations on creep failure behavior of the component is discussed. Results demonstrate that the shearing failure at the contact area between the blade root and the rotor is observed for the tested component, while the cracking at the groove of the rotor is not found. Creep-damage constitutive equation employed in this work could provide an adequate solution of the simulated component. Parametric studies indicate that creep crack initiation and creep failure of the simulated components may occur at the contact region (i.e., between the blade root and the rotor) and the groove of the rotor, which is closely related to structural and loading configurations of the components.

On real-time creep damage prediction for steam turbine

2022 ◽  
pp. 014233122110689
Author(s):  
Yongjian Sun ◽  
Bo Xu
Keyword(s):  
Finite Element ◽  
Steam Turbine ◽  
Real Time ◽  
Creep Damage ◽  
Element Model ◽  
Turbine Rotor ◽  
Theoretical Research ◽  
Element Analysis ◽  
Damage Prediction ◽  
Time Calculation

In this paper, in order to solve the calculation problem of creep damage of steam turbine rotor, a real-time calculation method based on finite element model is proposed. The temperature field and stress field of the turbine rotor are calculated using finite element analysis software. The temperature data and stress data of the crucial positions are extracted. The data of temperature, pressure, rotational speed, and stress relating to creep damage calculation are normalized. A real-time creep stress calculation model is established by multiple regression method. After that, the relation between stress and damage function is analyzed and fitted, and creep damage is calculated in real-time. A creep damage real-time calculation system is constructed for practical turbine engineering. Finally, a numerical simulation experiment is designed and carried out to verify the effectiveness of this novel approach. Contributions of present work are that a practical solution for real-time creep damage prediction of steam turbine is supplied. It relates the real-time creep damage prediction to process parameters of steam turbine, and it bridges the gap between the theoretical research works and practical engineering.

Application of a Creep Damage Constitutive Model for the Rotor of a 1000 MW Ultra-Supercritical Steam Turbine

2015 ◽  
Author(s):  
Jishen Jiang ◽  
Weizhe Wang ◽  
Nailong Zhao ◽  
Peng Wang ◽  
Yingzheng Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Steam Turbine ◽  
Axial Stress ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Creep Analysis ◽  
Wide Range ◽  
Damage Constitutive Model ◽  
Creep Constitutive Model ◽  
Basic Features

A damage-based creep constitutive model for a wide stress range is applied to the creep analysis of a 1000 MW ultra-supercritical steam turbine, the inlet steam of which reaches 600°C and 35 MPa. In this model, the effect of complex multi-axial stress and the nonlinear evolution of damage are considered. To this end, the model was implemented into the commercial software ABAQUS using a user-defined material subroutine code. The temperature dependent material constants were identified from the experimental data of advanced heat resistant steels using curve fitting approaches. A comparison of the simulated and the measured results showed that they reached an acceptable agreement. The results of the creep analysis illustrated that the proposed approach explains the basic features of stress redistribution and the damage evolution in the steam turbine rotor over a wide range of stresses and temperatures.

Prediction of Creep Life on Notched Bar Specimens of Grade 92 Steel

2016 ◽  
Author(s):  
Haruhisa Shigeyama ◽  
Yukio Takahashi ◽  
Jonathan Parker
Keyword(s):  
Finite Element ◽  
Creep Damage ◽  
Creep Data ◽  
Creep Failure ◽  
Creep Tests ◽  
Energy Fraction ◽  
Damage Models ◽  
Finite Element Software ◽  
Notched Specimens ◽  
Life Fraction

Creep tests on two kinds of circumferentially notched round bar specimens as well as plain bar specimen were performed to obtain the multiaxial and uniaxial creep data. Creep damage models of strain fraction and energy fraction rule were developed using these creep data. Then creep damage analyses using a finite element software, MSC Marc, were carried out on notched specimens of both types and creep failure lives were predicted using the creep damage models of classical life fraction rule and developed strain or energy fraction rule. Experimental failure lives of all the conditions of notched specimens were compared with analytical results. As a result, creep failure lives obtained by life fraction rule were underestimated in the short term region and overestimated in the long term region. On the other hands, it is apparent that the majority of creep failure lives obtained by strain and energy fraction rule were predicted with an accuracy within a factor of two. Furthermore, some interrupted creep tests and creep void observations were conducted on the notched specimens of both types. The distributions of creep void number density were in good agreement with the distributions of creep damage calculated by finite element analyses.

Shape of creep curves in frozen soils and polycrystalline ice

1987 ◽  
Vol 24 (4) ◽  
pp. 623-629 ◽  
Author(s):  
Anatoly M. Fish
Keyword(s):  
Constitutive Equation ◽  
Creep Strain ◽  
Failure Time ◽  
Frozen Soil ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Creep Tests ◽  
Creep Curves ◽  
Polycrystalline Ice

A new method was developed for determining creep parameters, particularly the time to failure, from a single linear plot in which an individual creep curve forms a straight line for primary and tertiary creep. Secondary creep is considered to be a principal point on this line that predetermines the onset of failure. The times to failure can be predicted even when creep tests are not complete by extrapolating information obtained for primary creep. Based upon T. H. Jacka's test data, prediction of creep strain was evaluated using the constitutive equation of A. M. Fish for entire creep and compared with the modified Sinha equation of M. F. Ashby and P. Duval for attenuating creep as well as with models for primary and secondary creep. It is shown that the shape of the creep curves, and thus the creep parameters, varies with stress, temperature, and other factors. Hence, a family of creep curves cannot be described by a constitutive equation with a single set of creep parameters that do not take into account these variations without loss in the accuracy of the creep strain calculations. Key words: frozen soil, polycrystalline, ice, creep, failure, time to failure, attenuation, constitutive modelling.

Application of a Creep-Damage Constitutive Model for the Rotor of a 1000 MW Ultrasupercritical Steam Turbine

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Jishen Jiang ◽  
Weizhe Wang ◽  
Nailong Zhao ◽  
Peng Wang ◽  
Yingzheng Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Steam Turbine ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Creep Analysis ◽  
Wide Range ◽  
Damage Constitutive Model ◽  
Creep Constitutive Model ◽  
Basic Features ◽  
Heat Resistant Steels

A damage-based creep constitutive model for a wide stress range is applied to the creep analysis of a 1000 MW ultrasupercritical steam turbine, the inlet steam of which reaches 600 °C and 35 MPa. In this model, the effect of complex multiaxial stress and the nonlinear evolution of damage are considered. To this end, the model was implemented into the commercial software abaqus using a user-defined material subroutine code. The temperature-dependent material constants were identified from the experimental data of advanced heat resistant steels using curve fitting approaches. A comparison of the simulated and the measured results showed that they reached an acceptable agreement. The results of the creep analysis illustrated that the proposed approach explains the basic features of stress redistribution and the damage evolution in the steam turbine rotor over a wide range of stresses and temperatures.

Study on Creep Behaviors of T92 Steel under Multiaxial Stress State

2013 ◽  
Vol 860-863 ◽  
pp. 774-779
Author(s):  
Xue Ping Mao ◽  
Yang Yu ◽  
Chao Li ◽  
Sai Dong Huang ◽  
Hong Xu ◽  
...  
Keyword(s):  
Stress State ◽  
Rupture Life ◽  
Creep Damage ◽  
Creep Rupture ◽  
Failure Behavior ◽  
Multiaxial Stress ◽  
Creep Tests ◽  
Creep Ductility ◽  
Notched Specimen ◽  
Multiaxial Stress State

Creep tests for smooth specimens and notched specimens of T92 steel were carried out to study the effect of multiaxial stress state on creep rupture behaviors at 650°C. Creep rupture life was estimated by representative stress at multiaxial state of stress, the failure behavior of multiaxial creep was analyzed, and Kachanov creep damage formula was used to analyze the experimental data. The results show that the notch strengthens rupture life, multiaxial rupture behavior is controlled by mixed parameters, the creep ductility of the smooth and notched specimen decreases with rupture time, and damage factors of the smooth specimen and notched specimen are similar according to Kachanov formula.

scholarly journals Effect of Biaxial Stress Condition on Creep Damage of a Steam Turbine Rotor Material

2009 ◽  
Vol 58 (11) ◽  
pp. 924-929 ◽  
Author(s):  
Masao OKAZAKI ◽  
Kenichi TANAKA ◽  
Toshiyuki OSAWA ◽  
Takashi SATO
Keyword(s):  
Steam Turbine ◽  
Stress Condition ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Biaxial Stress ◽  
Steam Turbine Rotor

ASME 1995 Nadai Lecture—Plasticity of Porous and Particulate Materials

1996 ◽  
Vol 118 (2) ◽  
pp. 145-156 ◽  
Author(s):  
N. D. Cristescu
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Model Prediction ◽  
Creep Damage ◽  
Mining Engineering ◽  
Creep Failure ◽  
Time Effects ◽  
Engineering Problems ◽  
Stationary Creep ◽  
Good Agreement

The paper discusses the formulation of constitutive equation for those materials for which the irreversible changes of the volume is also to be taken into account. These are mainly geomaterials, cement, powders of various kinds, ceramics, etc. Experimental evidence is first presented showing that the time effects on irreversible volumetric changes and failure are very important. The concept of compressibility/dilatancy boundary is further introduced. The general constitutive equation able to describe instantaneous response, transient and stationary creep, dilatancy and/or compressibility during creep, failure, creep damage and creep failure, is presented. Examples formulated for various materials are given. Comparison between model prediction and experimental data shows a very good agreement. A few examples of applications of the model to mining engineering problems are mentioned.

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