Investigation on Method of Elasto-Plastic Analysis for Piping System Made of Stainless Steel: Secondary Benchmark Analysis

2017 ◽  
Author(s):  
Masashi Arai ◽  
Nobuyuki Kojima ◽  
Takuro Kabaya ◽  
Satoru Hirouchi ◽  
Masatsugu Bando
Keyword(s):  
Stainless Steel ◽  
Piping System ◽  
Maximum Strain ◽  
Benchmark Analysis ◽  
Draft Code ◽  
Plastic Analysis ◽  
Piping Systems ◽  
Tee Joints ◽  
Possible Cause ◽  
Shape Data

This paper provides investigation on method of elasto-plastic analysis for practical seismic design of nuclear piping system made of austenitic stainless steel. Our policy for the evaluation is that material properties used in the benchmark analyses are based on Japanese standard in nuclear design. The result of the first phase of this benchmark analysis intended for carbon steel piping systems has been provided in ASME PVP2016-63186[1]. In secondary benchmark analysis, analytical investigations focused on austenitic stainless steel piping were conducted. These analysis objects are two vibrating tests (model 1: piping containing an elbow, model 2:piping containing a tee). The elasto-plastic characteristic based on bilinear plasticity model based on the draft code case of JSME (Japan Society of Mechanical Engineers) was used in analyses. Additionally, analyses using the elasto-plastic characteristic which made yield point and 2nd modulus as a parameter were also carried out. For the model 1, the maximum strain estimated by elasto-plastic analysis using the elasto-plastic characteristics of stainless steel material determined as proposed by the draft code case of JSME agreed well, but on the safe side, with the experiment. However, this is not the case for the model 2: the maximum strain estimated using the same elasto-plastic characteristics was underestimated compared with the experiment. However, for both the models 1 and 2, the elasto-plastic behavior of the piping systems estimated by this analysis was approximately the same between the analysis with the material’s elasto-plastic characteristics approximated by bilinear plasticity modeling proposed by the draft code case of JSME and that approximated by the same bilinear plasticity modeling but with different setting of yield point and 2nd modulus values of the material. A possible cause of the underestimate that occurred in the model 2 is, according to the shape data of the tee, that the wall thickness of the tee is so large that its connection with the main and branch pipes has a large, step-like change in thickness, as opposed to the model that was designed without referencing the shape data. Another possible cause of this underestimate is coarse meshes of elements of the model. In order to improve analytical accuracy, it is necessary to add a method for modeling tee joints to the draft code case. To this end, a database of the shape of tee joints should be developed in cooperation with the manufacturers so that an optimum modeling method can be developed. As mentioned above, according to the result of elasto-plastic analyses for the model 1 (piping containing an elbow) and model 2 (piping containing a tee), it is necessary to develop a modeling method for tee joints. It is likely possible to directly use the elasto-plastic characteristics of carbon steel for the purpose of analyzing a piping of stainless steel.

Investigation on Method of Elasto-Plastic Analysis for Piping System (Benchmark Analysis)

2016 ◽  
Author(s):  
Masashi Arai ◽  
Nobuyuki Kojima ◽  
Takuro Kabaya ◽  
Satoru Hirouchi ◽  
Masatsugu Bando
Keyword(s):  
Yield Point ◽  
Kinematic Hardening ◽  
Strain Range ◽  
Fatigue Curve ◽  
Piping System ◽  
Analysis Method ◽  
Benchmark Analysis ◽  
Hardening Law ◽  
Plastic Analysis ◽  
Piping Systems

This report proposes an elasto-plastic analysis method to be used for practical aseismic designing of nuclear piping systems. JSME (the Japan Society of Mechanical Engineers) initiated a task to establish an elasto-plastic analysis method for nuclear piping systems. During this task, benchmark analysis was conducted in order to examine the elastic-plasticity analytical method, in which our company decided to participate. Our policy for evaluation was that the material characteristics to be used in benchmark analysis were based on the standards for nuclear designs in Japan. As a consequence, we prepared a method to accurately simulate the vibration test on piping systems. The recommended elasto-plastic analysis method is thus specified as follows: 1) The elasto-plastic analysis method comprised of dynamic analysis on piping system modeled using beam elements and static analysis of the deforming elbow which was modeled using shell elements. 2) Bi-linear was applied as the elasto-plastic characteristics. The yield point was the standardized yield point times 1.2, and the second gradient was 1/100 the Young’s modulus. Kinematic hardening law was used as the hardening law. 3) Rain flow method and fatigue curve of an existing research were used to evaluate the fatigue life for the strain range obtained by elasto-plastic analysis.

scholarly journals Comparison of ICEPEL Predictions With Single-Elbow Flexible Piping System Experiment

1979 ◽  
Vol 101 (2) ◽  
pp. 142-148 ◽  
Author(s):  
M. T. A-Moneim ◽  
Y. W. Chang
Keyword(s):  
Stainless Steel ◽  
Circumferential Strain ◽  
Structural Response ◽  
Response Analysis ◽  
Piping System ◽  
System Experiment ◽  
Stainless Steel Pipe ◽  
Piping Systems ◽  
In Series ◽  
Nickel 200

The ICEPEL Code for coupled hydrodynamic-structural response analysis of piping systems is used to analyze an experiment on the response of flexible piping systems to internal pressure pulses. The piping system consisted of two flexible Nickel-200 pipes connected in series through a 90-deg thick-walled stainless steel elbow. A tailored pressure pulse generated by a calibrated pulse gun is stabilized in a long thick-walled stainless steel pipe leading to the flexible piping system which ended with a heavy blind flange. The analytical results of pressure and circumferential strain histories are discussed and compared against the experimental data obtained by SRI International.

Findings From the Benchmark Analyses on an Elbow In-Plane Bending Test and a Piping System Test

2016 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Tadahiro Shibutani ◽  
Masaki Morishita ◽  
Masaki Shiratori
Keyword(s):  
Bending Test ◽  
Piping System ◽  
Seismic Safety ◽  
Benchmark Analysis ◽  
Elastic Plastic ◽  
Strain Behavior ◽  
Analytical Results ◽  
Piping Systems ◽  
Plane Bending ◽  
Safety Estimation

For introducing the elastic-plastic behavior effect in the seismic safety estimation of nuclear piping systems, benchmark analyses on a static in-plane bending test on an elbow (the pipe element test) and a piping system test under one-directional excitation (the piping system test) were conducted. As for the benchmark analyses on the pipe element test, 14 groups participated in the benchmark analysis. The variation of the elastic-plastic analyses and the factors which affect the analytical results are examined by comparing the analytical results with the experimental results. From the examination of analytical results, it is shown that the decision of the yield stress for the analysis rather than the secondary gradient affects a lot on the load deflection curve or the strain behavior, when the stress-strain relationship is simulated by bi-linear approximation. The strain ranges are well simulated by the analyses, though the residual strains scatter a lot. The failure mode in the experiment was the fatigue failure at the flank of the elbow, and it was well predicted by the participants’ analyses. As for the benchmark analyses on the piping system test, ten groups participated in the benchmark analysis. The eigenvalue analyses are well estimated by the all participants, but the dynamic response and strain behavior of pipes under random input waves vary widely. The findings from the benchmark analyses would be reflected to the inelastic analysis guideline for the seismic safety estimation of nuclear piping systems under beyond design seismic input.

Investigation of Method of Elasto-Plastic Analysis for Piping System Excited by Multi-Direction Input

2018 ◽  
Author(s):  
Takuro Kabaya ◽  
Nobuyuki Kojima ◽  
Masashi Arai ◽  
Satoru Hirouchi ◽  
Masatsugu Bando
Keyword(s):  
Ultimate Strength ◽  
Seismic Design ◽  
Strain Range ◽  
Plastic Behavior ◽  
Piping System ◽  
Japan Society ◽  
Analysis Method ◽  
The Past ◽  
Plastic Analysis ◽  
Piping Systems

This paper provides investigation on method of an elasto-plastic analysis for practical seismic design of nuclear piping systems, which are excited by multi-direction input. The Japan Society of Mechanical Engineers (JSME) established a task group to develop an elasto-plastic analysis method for nuclear piping systems, and prepared a case example code proposal for JSME.[1],[2] Our studies in past (ASME PVP2016-63186[3] and ASME PVP2017-65341[4]) were implemented on tests with unidirectional excitation using simple piping systems. In order to examine the applicability of the proposed case example code for JSME in piping of actual systems, it is necessary to examine cases in which there is multidirectional input excitation in piping systems in scales comparable to those of the piping in actual systems. We therefore conducted an analytical examination on demonstration of “the ultimate strength of piping system,” which was implemented at NUPEC. [5] We confirmed in the results of analytical examination that the strain range could be calculated at precision nearly equivalent to our examinations in the past, and that the draft code case was applicable. However, we also found a problem which needs to be solved. In addition, we were able to confirm that the local damping increase caused by the elasto-plastic behavior of the elbow which was subject to examination in this study was 1% or larger.

Fracture Estimation Method for Pipe With Multiple Circumferential Surface Flaws

2009 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Kunio Onizawa ◽  
Masayoshi Shimomoto
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Numerical Solutions ◽  
Estimation Method ◽  
Arbitrary Distribution ◽  
Piping System ◽  
Piping Systems ◽  
Asme Code ◽  
As Stress ◽  
Steel Piping

When a flaw is detected in a stainless steel piping system of a nuclear power plant during in-service inspection, the fracture estimation method provided in the codes such as the ASME Code Section XI or the JSME S NA-1-2004 can be applied to evaluate the integrity of the pipe. However, in these current codes, the fracture estimation method is only provided for the pipe containing a single flaw, although independent multiple flaws such as stress corrosion cracks have actually been detected in the same circumference of stainless steel piping systems. In this paper, a fracture estimation method is proposed by formula for multiple independent circumferential flaws with any number and arbitrary distribution in the same circumference of the pipe. Using the proposed method, the numerical solutions are compared with the experimental results to verify its validity, and several numerical examples are provided to show its effectiveness.

The Role of Displacement-Controlled Stresses in Critical Flaw Size Determination for Piping Systems

2008 ◽  
Author(s):  
Peter C. Riccardella ◽  
Paul Hirschberg ◽  
Ted Anderson ◽  
Greg Thorwald ◽  
Eric Scheibler
Keyword(s):  
Stainless Steel ◽  
Thermal Expansion ◽  
Nuclear Power ◽  
Power Plants ◽  
Bending Moment ◽  
Flaw Size ◽  
Piping System ◽  
Nuclear Plants ◽  
Piping Systems ◽  
Critical Flaw

A debate has long ensued in ASME Subcommittee XI regarding the need to include displacement-controlled (secondary) stresses in critical flaw size calculations for austenitic weldments. There is general agreement that inclusion of secondary stresses is not necessary for highly ductile piping materials such as wrought stainless steel and high nickel alloys. However, some stainless steel weldments are classified as “low-toughness” because, although not considered brittle, they exhibit lower toughness than wrought stainless steel. The Code requires the inclusion of global secondary stresses, such as piping thermal expansion loads, in critical flaw size calculations for such weldments, albeit at reduced safety factors. The Code requirements are less clear for dissimilar metal weldments, such as Alloy 82/182, which were often used for ferritic nozzle to safe-end welds in nuclear power plants, and which have proven in service to be susceptible to a form of stress corrosion cracking. Analyses are presented in this paper that shed additional light on the subject. Finite element analyses (FEA) of a straight pipe with a through-thickness crack were used to determine the effect on bending moment and crack driving force due to an imposed end rotation. Moment and J-integral knock-down factors are computed for a range of crack sizes for two different pipe lengths. Piping analyses are also presented for two typical PWR surge lines, which are among the highest secondary stress locations in U.S. nuclear plants. These analyses predict the maximum rotation at the surge nozzle that could be produced by the secondary loads (anchor movement + thermal expansion + stratification), and compare that to rotations that were sustained in full scale pipe tests containing large complex cracks. The analyses demonstrate that secondary loads would be substantially reduced prior to fracture of a cracked weldment, and that they are therefore of reduced significance in critical flaw size calculations. A general method for estimating the effect of secondary loads on pipe fracture as a function of relative piping system and crack section stiffness is suggested.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

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