Probabilistic Parameter Sensitivity Study on Design Fatigue Curve for Carbon and Low-Alloy Steels

2012 ◽  
Author(s):  
Masahiro Takanashi ◽  
Jyunki Maeda ◽  
Shinsuke Sakai
Keyword(s):  
Surface Roughness ◽  
Size Effect ◽  
Limit State ◽  
Fatigue Curve ◽  
Sensitivity Study ◽  
Parameter Sensitivity ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Partial Safety Factors ◽  
State Functions

In a previous paper[1], we discussed the margins of the design fatigue curve in ASME Boiler and Pressure Vessel Codes Section III using a probabilistic approach. Limit state functions of the design fatigue curve for carbon and low-alloy steels were proposed in order to investigate the physical implication of the design margin. In the limit state functions, four parameters, namely, fatigue data scatter, size effect, surface roughness, and applied stress were taken into consideration as random variables. Based on the limit state functions, reliability index contours of the design fatigue curve were obtained together with the partial safety factors (PSFs). Among these partial safety factors, the fatigue strength (or life) and the applied stress were predominant. The other parameters, the PSFs for the size effect and the surface roughness were small enough and almost constant. The parameter sensitivity, however, remains unknown and whether these parameters should be treated as constants or as random variables is also not clear. In this study, a probabilistic parameter sensitivity study on the design fatigue curve was conducted to discuss how the design fatigue curve should be. Two sensitivities were computed. One is the rate sensitivity indicating the contribution of the mean value of the parameter in the probability of failure. The other is the probabilistic sensitivity to parameter dispersion. The parameters for the size effect and the surface roughness showed lower probabilistic sensitivities. This result suggests that the parameters can be considered as constants. In general, a higher number of parameters in a probabilistic model leads to more uncertainty and the design concept tends to be more conservative. We, therefore, proposed to deal with the parameters of the size effect and the surface roughness separately in the design fatigue curve to eliminate conservativeness.

Fatigue Design Margin Evaluation for Carbon and Low-Alloy Steels by Reliability-Based Load and Resistance Factor Method

2011 ◽  
Author(s):  
Masahiro Takanashi ◽  
Makoto Higuchi ◽  
Junki Maeda ◽  
Shinsuke Sakai
Keyword(s):  
Applied Stress ◽  
Limit State ◽  
State Function ◽  
Low Alloy Steels ◽  
Limit State Function ◽  
Safety Factors ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Partial Safety Factors ◽  
Two Parameters

This paper discusses the margins of the design fatigue curve in the ASME Boiler and Pressure Vessel Codes Section III from a reliability analysis point of view. It is reported that these margins were developed so as to cover uncertainties of fatigue data scatter, size effect, and surface condition[1], but the reasons for them remain unclear. In order to investigate the physical implications of the design margin, a probabilistic approach is taken for the collected fatigue data of carbon and low-alloy steels. In this approach, these three parameters are treated as random variables, and an applied stress is also taken into consideration as a random variable. For the analysis, to begin with, a limit state function for fatigue is proposed. Next, reliability index contours of the design fatigue curves for carbon and low-alloy steels are obtained based on the proposed limit state function. The contours indicate that the margins 2 on stress and 20 on life do not provide equal reliability. The margin 20 on life is more conservative and the margin became a minimum near intersections of the design curves with margins 2 on stress and 20 on life. For practical applications, the partial safety factors (PSF) for the target reliability are computed for all materials and several levels of coefficients of variation (COV) of the applied stress. A sensitivity analysis of the PSFs clarifies that only two parameters, the strength (or the life) and the applied stress, are predominant. Thus, the partial safety factors for these two parameters are proposed in a tabular form.

Proposal of Surface Finish Factor on Fatigue Strength in Design Fatigue Curve

2014 ◽  
Author(s):  
Yuichi Fukuta ◽  
Hiroshi Kanasaki ◽  
Seiji Asada ◽  
Takehiko Sera
Keyword(s):  
Surface Roughness ◽  
Tensile Strength ◽  
Stainless Steel ◽  
Fatigue Strength ◽  
Surface Finish ◽  
Fatigue Curve ◽  
Low Alloy Steels ◽  
Mean Stress ◽  
Alloy Steels ◽  
Surface Finish Effect

The published papers related to the effects of surface finish on fatigue strength are reviewed in order to formulate its factor in the design fatigue curve in air environment. Firstly, some of regulations and literatures were examined to verify the surface finish effect on fatigue strength and formulation of that in design fatigue curve. The fatigue strength of carbon and low alloy steels is decreased with an increase of its surface roughness and tensile strength but that of stainless steel is not decreased except for special conditions. After screening the data of carbon and low alloy steels, a surface finish factor is formulated with these data which is a function of tensile strength, surface roughness and mean stress.

Study on Mean Stress Effects for Design Fatigue Curves

2016 ◽  
Author(s):  
Seiji Asada ◽  
Takeshi Ogawa ◽  
Makoto Higuchi ◽  
Hiroshi Kanasaki ◽  
Yasukazu Takada
Keyword(s):  
Evaluation Method ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Mean Stress ◽  
Research Committee ◽  
Stress Effects ◽  
Alloy Steels ◽  
Design Factors

In order to develop new design fatigue curves for austenitic stainless steels, carbon steels and low alloy steels and a new design fatigue evaluation method that are rational and have a clear design basis, the Design Fatigue Curve (DFC) subcommittee was established in the Atomic Energy Research Committee in the Japan Welding Engineering Society. Mean stress effects for design fatigue curves are to be considered in the development of design fatigue curves. The Modified Goodman approach for mean stress effects is used in the design fatigue curves of the ASME B&PV Code. Tentative design fatigue curves were developed and studies on the effect of mean stress and design factors are on-going. Development of design fatigue curves, effect of mean stress and design factors is needed to establish a new fatigue design evaluation method. The DFC subcommittee has studied correction approaches for mean stress effects and the approaches of modified Goodman, Gerber, Peterson and Smith-Watson-Topper were compared using test data in literature. An appropriate approach for mean stress effects are discussed in this paper.

Grain size effect of austenite on the kinetics of pearlite transformation in low- and medium-carbon low-alloy steels

2015 ◽  
Vol 6 (1) ◽  
pp. 41-44 ◽  
Author(s):  
A. E. Gvozdev ◽  
A. G. Kolmakov ◽  
D. A. Provotorov ◽  
I. V. Minaev ◽  
N. N. Sergeev ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Low Alloy Steels ◽  
Grain Size Effect ◽  
Medium Carbon ◽  
Alloy Steels ◽  
Kinetics Of

Effect of stress concentrations of size effect in the fatigue of medium-carbon and low-alloy steels

1980 ◽  
Vol 12 (3) ◽  
pp. 285-290 ◽  
Author(s):  
M. M. Matseiko ◽  
V. I. Pokhmurskii ◽  
G. N. Filimonov
Keyword(s):  
Size Effect ◽  
Low Alloy Steels ◽  
Stress Concentrations ◽  
Medium Carbon ◽  
Alloy Steels

Proposal for the Implementation of Elevated Temperature Design Fatigue Curve for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V Steels

2004 ◽  
Author(s):  
Tatsumi Takehana ◽  
Takeru Sano ◽  
Susumu Terada ◽  
Hideo Kobayashi
Keyword(s):  
Elevated Temperature ◽  
Fatigue Strength ◽  
High Strength ◽  
Fatigue Curve ◽  
Temperature Limit ◽  
Fatigue Tests ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Elevated Temperature Design

2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels have been used extensively as materials for elevated temperature and high-pressure hydro-processing reactors. These steels have both of high strength at elevated temperature and high resistance against elevated temperature hydrogen attack due to the addition of vanadium. The operating temperature of these reactors is between 800 and 900deg.F. The fatigue evaluations of these reactors per ASME Sec. VIII Div.2 and Div.3 can’t be performed in spite of demand for fatigue analysis because the temperature limit of design fatigue curve in ASME Sec. VIII Div.2 and Div.3 for carbon and low alloy steels is 700deg.F. Results of load and strain controlled fatigue tests conducted over the temperature range from room temperature to 932deg.F (500deg.C) are reported for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels. These data were compared with data for 2-1/4Cr-1Mo steels available from the literatures. The fatigue strength for a 2-1/4Cr-1Mo-V steel in high cycle region is higher than that for 2-1/4Cr-1Mo steels and in low cycle region is lower. The fatigue strength for a 3Cr-1Mo-V steel is almost same as that for 2-1/4Cr-1Mo-V steels. Therefore an elevated temperature design fatigue curve for 2-1/4Cr-1Mo-V and 3Cr-1Mo-V steels is newly proposed. It is found from the case study that the different fatigue life can be predicted by using different mean stress correction procedure.

A Consideration of Margin on Fatigue Design Curves for Carbon and Low-Alloy Steels

2011 ◽  
Author(s):  
Makoto Higuchi ◽  
Masahiro Takanashi ◽  
Ichiro Tamura ◽  
Toshiaki Takada
Keyword(s):  
Stainless Steels ◽  
Fatigue Curve ◽  
Light Water Reactor ◽  
Ferritic Steels ◽  
Low Alloy Steels ◽  
Light Water ◽  
Fatigue Design ◽  
The Us ◽  
Asme Code ◽  
Alloy Steels

In 2007, the US NRC issued Regulatory Guide 1.207[1] and NUREG/CR-6909[2] for evaluating fatigue incorporating the life reduction due to the effects of light-water reactor environment for new reactors. NUREG/CR-6909 provides new design fatigue curves (DFC) for carbon, low-alloy and stainless steels which are different from those in the ASME Boiler and Pressure Vessel Code Section III[3] (2007 Edition). The design fatigue curves for carbon and low-alloy steels in NUREG/CR-6909 are higher than that for ferritic steels of which specified minimum tensile strength is 552 MPa (80 ksi) or less in the ASME Code Section III. The design fatigue curve for stainless steel in the ASME Code Section III was changed to the same curve as NUREG/CR-6909 in the 2009 Addenda. However, those for carbon and low-alloy steels are still different from the NUREG curves.

Plan and Status of Development of Design Fatigue Curves: Phase 1

2013 ◽  
Author(s):  
Seiji Asada ◽  
Akihiko Hirano ◽  
Masao Itatani ◽  
Munehiro Yasuda ◽  
Takehiko Sera ◽  
...  
Keyword(s):  
Stainless Steels ◽  
Phase 1 ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Energy Research ◽  
Research Committee ◽  
Engineering Society ◽  
Alloy Steels

In order to develop and propose new design fatigue curves for austenitic stainless steels, carbon steels and low alloy steels that are rational and have clear design basis, Design Fatigue Curve (DFC) subcommittee has been established in the Atomic Energy Research Committee in the Japan Welding Engineering Society and the study on design fatigue curves are going on. This paper introduces the plan and status of the activities of the DFC subcommittee.

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