Proposed ASME Code High Cycle Fatigue Design Curves for Austenitic and Ferritic Steels

2017 ◽  
Author(s):  
Sampath Ranganath ◽  
Hardayal S. Mehta ◽  
Nathan A. Palm ◽  
John Hosler
Keyword(s):  
High Cycle Fatigue ◽  
Ferritic Steels ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
The Mean ◽  
Number Of Cycles ◽  
Fatigue Evaluation

The ASME Code fatigue curves (S–N curves) are used in the fatigue evaluation of reactor components. For the assessment of high frequency cyclic loading (such as those produced by flow-induced vibrations), where the number of cycles is expected to be very large and cannot be estimated, the stresses are evaluated by comparison with the fatigue limit1 at 1011 cycles. Other high cycle events of finite time duration (e.g. safety relief loading), where the number of cycles is large but well defined, the fatigue evaluation is performed by comparing the calculated stress with the allowable values defined by the high cycle fatigue design curve. This paper discusses the development of fatigue design curves for austenitic and ferritic steels when the number of cycles is in the range 106 – 1011 cycles. The first part of the paper addresses austenitic stainless steel components which are used for reactor internals. Specifically, the approach described here uses temperature dependent properties (cyclic yield strength, cyclic ultimate strength) for the mean stress correction and the correction for the modulus of elasticity. The high cycle fatigue design curve is developed by applying the mean stress and the E correction on the reversing load mean data curve and applying a factor of 2 on stress. The generic methodology developed for austenitic steel was applied to carbon and low alloy steels also. The proposed fatigue design curves are part of a draft ASME Code Case being considered by the ASME Code Subgroup on Design Methods. This paper describes the technical basis for the proposed ASME Code Case for the high cycle fatigue design curves for austenitic and ferritic steels.

Safety Factor in Fatigue Under Fluctuating Stresses

1987 ◽  
Vol 109 (4) ◽  
pp. 397-401 ◽  
Author(s):  
V. A. Avakov
Keyword(s):  
Safety Factor ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Static Strength ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Safety Factors ◽  
Generalize Expression ◽  
Allowable Stresses ◽  
Number Of Cycles

It is common to assume identical allowable safety factors in static strength [m], defined by mean stress (Sm), and in fatigue [a], defined by stress amplitude (Sa), in order to find the full safety factor (F) under asymmetrical cycles, or to plot any type of the Sm–Sa diagram of allowable stresses. Here additional modification is considered to generalize expression of the full factor of safety in fatigue under asymmetrical stresses, utilizing unequal allowable safety factors in static strength (by mean stress) and in fatigue (by stress amplitude): ([a] ≠ [m]). We assume that loading is stationary, and cumulated number of cycles is large enough to consider high cycle fatigue.

Critical Analysis of the New High Cycle Fatigue Assessment Procedure From ASME B31.3—Appendix W

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Nikola Jaćimović ◽  
Sondre Luca Helgesen
Keyword(s):  
High Cycle Fatigue ◽  
Design Procedure ◽  
Piping System ◽  
Assessment Procedure ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Process Piping ◽  
Piping Systems ◽  
Fatigue Evaluation

Abstract ASME B31.3, the leading process piping system design code, has included in its 2018 edition a new procedure for evaluation of high cycle fatigue in process piping systems. As stated in the Appendix W of ASME B31.3-2018, this new procedure is applicable to any load resulting in the stress range in excess of 20.7 MPa (3.0 ksi) and with the total number of cycles exceeding 100,000. However, this new procedure is based on the stress range calculation typical to ASME B31 codes which underestimates the realistic expansion stress range by a factor of ∼2. While the allowable stress range used typically for fatigue evaluation of piping systems is adjusted to take into consideration this fact, the new fatigue design curves seem not to take it into account. Moreover, the applicability of the new design procedure (i.e., welded joint fatigue design curves) to the components which tend to fail away from the bends is questionable. Two examples are presented at the end of the paper in order to substantiate the indicated inconsistencies in the verification philosophy.

Prediction of Time to Significant Cracking and Actual Behavior of an Impulsively Loaded Detonation Chamber for Chemical Weapons Destruction

2012 ◽  
Author(s):  
Joseph K. Asahina ◽  
Koichi Akasaka ◽  
Robert E. Nickell ◽  
Toshio Hamada
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Actual Behavior ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
Operation Control ◽  
Fatigue Evaluation ◽  
Estimation Of Time ◽  
Best Fit

For repeated operation of a detonation chamber, evaluation of its fatigue damage and estimation of time to crack initiation are of considerable importance from the aspect of safe operation. This paper proposes the use of a sufficiently conservative operation control fatigue evaluation curve, based upon the ASME Code fatigue design curve and the best fit laboratory air curve upon which the design curve is derived, in order to define operational points for actions to inspect for possible fatigue damage and initiate repairs, as needed. The paper also recommends appropriate actions to verify that any needed repairs maintain structural integrity during subsequent operations.

Environmentally Assisted Fatigue Assessment Considering an Alternative Method to the ASME Code Case N-792

2012 ◽  
Author(s):  
Stéphan Courtin ◽  
André Lefrançois ◽  
Jean-Alain Le Duff ◽  
Anne Le Pécheur
Keyword(s):  
Low Cycle Fatigue ◽  
Assessment Method ◽  
Cycle Fatigue ◽  
Pressurized Water Reactor ◽  
Test Program ◽  
Pressurized Water ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
Experimental Works

The conservatism of the austenitic stainless steel fatigue design curve has been severely questioned since the release of the NUREG/CR-6909 document [1] where a new methodology to assess environmentally assisted fatigue (EAF), including also a new in-air fatigue design curve, have been proposed. In the same way, the ASME Code Case N-792 [2] suggests calculating EAF usage factors via the multiplication of the in-air fatigue usage factors by Fen penalty factors, this resulting in a significant increase of these parameters. In this context, AREVA NP SAS has performed, for several years, its own Pressurized Water Reactor (PWR) Low Cycle Fatigue (LCF) test program to better identify environmental effects in representative industrial conditions [3]. Among others, these experimental works have pointed out the over-conservatism of the NUREG/CR-6909 design approach. From these results, AREVA NP SAS has developed an alternative EAF assessment method which has been approved by the Finnish Nuclear Safety Authority [4]. This paper proposes to give an overview of this approach and to illustrate it on an EAF EPRI sample problem [5].

Statistical Analyses of High Cycle Fatigue French Data for Austenitic SS

2014 ◽  
Author(s):  
Géraud Blatman ◽  
Thomas Métais ◽  
Jean-Christophe Le Roux ◽  
Simon Cambier
Keyword(s):  
Strain Amplitude ◽  
High Cycle Fatigue ◽  
Experimental Testing ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Statistical Analyses ◽  
Starting Point ◽  
The Mean ◽  
Number Of Cycles ◽  
Selection Of

In the 2009 version of the ASME BPV Code, a set of new design fatigue curves were proposed to cover the various steels of the code. These changes occurred in the wake of publications [1] showing that the mean air curve used to build the former ASME fatigue curve did not always represent accurately laboratory results. The starting point for the methodology to build the design curve is the mean air curve obtained through laboratory testing: coefficients are then applied to the mean air curve in order to bridge the gap between experimental testing and reactor conditions. These coefficients on the number of cycles and on the strain amplitude are equal to 12 and 2 respectively in the 2009 ASME BPV code, using the mean air curve proposal from NUREG/CR-6909 [1]. Internationally, with the same mean air curve, other proposals have emerged and especially in France [2]-[3] where a consensus seems to be reached on the reduction of the coefficient on strain amplitude. This paper provides statistical analyses of the experimental data obtained in France at high-cycle for austenitic stainless steels. It enables to bring arguments for the selection of a coefficient on strain amplitude in the French RCC-M code, where less scatter on the data is witnessed due to fewer material grades.

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