Fundamental Evaluation of Thermal Crack Resistance for Wheel Fracture Prevention

2002 ◽  
Author(s):  
Haruo Sakamoto
Keyword(s):  
Crack Resistance ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Railroad Wheel ◽  
Special Device ◽  
Cycle Fatigue ◽  
Thermal Crack ◽  
Critical Crack Length ◽  
New Device ◽  
Railroad Wheels

This paper presents a method for the thermal crack evaluation of railroad wheel materials and the results. The research investigated the basic thermal crack resistance as a low cycle fatigue behavior in terms of Δεt-Ni and da/dN-ΔK. In order to be able to evaluate such material characteristics in service by experimentation, reproducible conditions such as similar stress-strain, temperature rise, and damage morphology are required. The methods proposed in the past for high temperature low cycle fatigue or thermal shock such as Coffin’s and Manson’s methods do not provide the above conditions at the same time for thermal cracks in railroad wheels. The material design to avoid such thermal damages has not yet been established. Therefore, a simple brake tester with a special device for measuring radial deflection converted into strain was designed and manufactured. The relations of Δεt-Ni and da/dN-ΔK, which have not been clarified for thermal crack behavior in railroad wheels, were obtained for wheel materials by experiment using this new device. To predict the life of a wheel, one must know the real service conditions from field measurements. Once the histogram of the initial brake speed, intensity of brake application, and number of brakings from the initial speed is obtained, the histogram can be converted into the relation of strain range and number of cycles. The calculation of cycles for crack origination and propagation is possible based on the experimental results on Δεt-Ni and da/dN-ΔK. From the material data of fracture toughness and possible residual stress value in the field, the critical crack length for wheel fracture can be then estimated, and the life from the cycles to the critical length is estimated. This method will provide the appropriate maintenance schedule to prevent wheel fracture.

Effects of Surface Finish and Loading Conditions on the Low Cycle Fatigue Behavior of Austenitic Stainless Steel in PWR Environment for Various Strain Amplitude Levels

2009 ◽  
Author(s):  
Jean Alain Le Duff ◽  
Andre´ Lefranc¸ois ◽  
Jean Philippe Vernot
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Strain Amplitude ◽  
Surface Finish ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Complex Loading ◽  
Loading Conditions ◽  
Test Results ◽  
Cycle Fatigue

In February/March 2007, The NRC issued Regulatory Guide “RG1.207” and Argonne National Laboratory issued NUREG/CR-6909 that is now applicable in the US for evaluations of PWR environmental effects in fatigue analyses of new reactor components. In order to assess the conservativeness of the application of this NUREG report, Low Cycle Fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in air environment a fatigue behavior consistent with the ANL reference “air” mean curve, as published in NUREG/CR-6909. LCF tests in a PWR environment were performed at various strain amplitude levels (± 0.6% or ± 0.3%) for two loading conditions corresponding to a simple or to a complex strain rate history. The simple loading condition is a fully reverse triangle signal (for comparison purposes with tests performed by other laboratories with the same loading conditions) and the complex signal simulates the strain variation for an actual typical PWR thermal transient. In addition, two various surface finish conditions were tested: polished and ground. This paper presents the comparisons of penalty factors, as observed experimentally, with penalty factors evaluated using ANL formulations (considering the strain integral method for complex loading), and on the other, the comparison of the actual fatigue life of the specimen with the fatigue life predicted through the NUREG report application. For the two strain amplitudes of ± 0.6% and ± 0.3%, LCF tests results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates give “Fen” penalty factors close to those estimated using the ANL formulation (NUREG/6909). However, for the lower strain amplitude level and a triangle loading signal, the ANL formulation is pessimistic compared to the AREVA NP test results obtained for polished specimens. Finally, it was observed that constant amplitude LCF test results obtained on ground specimens under complex loading simulating an actual sequence of a cold and hot thermal shock exhibits lower combined environmental and surface finish effects when compared to the penalty factors estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins, whereas the current ASME approach seems sufficient to cover significant environmental effects for representative loadings and surface finish conditions of reactor components.

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.

LOW CYCLE FATIGUE BEHAVIOR AND LIFE PREDICTION OF A CAST COBALT-BASED SUPERALLOY

2012 ◽  
Vol 06 ◽  
pp. 251-256
Author(s):  
HO-YOUNG YANG ◽  
JAE-HOON KIM ◽  
KEUN-BONG YOO
Keyword(s):  
Fatigue Life ◽  
Strain Energy ◽  
Life Prediction ◽  
Prediction Models ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Different Temperatures

Co -base superalloys have been applied in the stationary components of gas turbine owing to their excellent high temperature properties. Low cycle fatigue data on ECY-768 reported in a companion paper were used to evaluate fatigue life prediction models. In this study, low cycle fatigue tests are performed as the variables of total strain range and temperatures. The relations between plastic and total strain energy densities and number of cycles to failure are examined in order to predict the low cycle fatigue life of Cobalt-based super alloy at different temperatures. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

scholarly journals Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

2012 ◽  
pp. 853-862 ◽  
Author(s):  
J. Telesman ◽  
T.P. Gabb ◽  
Y. Yamada ◽  
L.J. Ghosn ◽  
D. Hornbach ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Disk Alloy

scholarly journals On the Low Cycle Fatigue Behavior in the Longitudinally Butt Welded Joints between High Strength Steel and Mild Steel

1977 ◽  
Vol 1977 (142) ◽  
pp. 236-244
Author(s):  
Kinichi Nagai ◽  
Mitsumasa Iwata ◽  
Kenhichiro Kurihara ◽  
Junkichi Yagi ◽  
Yasumitsu Tomita
Keyword(s):  
Mild Steel ◽  
Welded Joints ◽  
High Strength Steel ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
High Strength ◽  
Cycle Fatigue
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