Method for Selecting Stress States for Use in an NB-3200 Fatigue Analysis

2010 ◽  
Author(s):  
Thomas L. Meikle V ◽  
E. Lyles Cranford ◽  
Mark A. Gray
Keyword(s):  
Time History ◽  
Stress Range ◽  
Total Stress ◽  
Secondary Stress ◽  
Transient Stress ◽  
Automated Method ◽  
Relative Minimum ◽  
Asme Code ◽  
Time Histories ◽  
Stress States

In ASME Code Section III NB-3222.4 fatigue evaluations, selecting stress states to determine the stress cycles according to Section NB-3216.2, Varying Principal Stress Direction, can become a challenging and complex task if the transient stress conditions are the result of multiple independent time varying stressors. This paper will describe an automated method that identifies the relative minimum and maximum stress states in a component’s transient stress time history and fulfills the criteria of NB-3216.2 and NB-3222.4. Utilization of the method described ensures that all meaningful stress states are identified in each transient’s stress time history. The method is very effective in identifying the maximum total stress range that can occur between any real or postulated transient stress time histories. In addition, the method ensures that the maximum primary plus secondary stress range is also identified, even if it is out of phase with the total stress maxima and minima. The method includes a process to determine if a primary plus secondary stress relative minimum or maximum should be considered in addition to those stress states identified in the total stress time history. The method is suitable for use in design analysis applications as well as in on-line stress and fatigue monitoring.

Straight Pipe Cyclic Analyses for Shakedown Verification Code Criteria

2003 ◽  
Author(s):  
Tehemton Bhagwagar ◽  
Robert Gurdal
Keyword(s):  
Cross Section ◽  
Plastic Material ◽  
Temperature Cycling ◽  
Stress Range ◽  
Secondary Stress ◽  
Straight Pipe ◽  
Linear Temperature ◽  
Pipe Cross Section ◽  
Primary Stress ◽  
Asme Code

The analyses performed in this paper are exclusively for a straight pipe subject to a constant primary stress and a cyclic secondary stress, as a result of a bending moment on the pipe cross-section. The constant primary stress is, in each analysis, from a CONSTANT dead-weight load and a CONSTANT internal pressure. The cyclic secondary stress is due to cyclic thermal expansion in the pipe, which is the result of a cyclic top-to-bottom linear temperature difference on the pipe cross-section. This temperature cycling produces a secondary stress range C2 ΔM Do / 2 I. This secondary stress range is either higher, or lower than the 3 * Sm stress limit from the ASME-Code. Twenty-four different cyclic elasto-plastic analyses have been performed for this paper. The same elastic perfectly-plastic material model is used for all twenty-four analyses. An attempt has been made to compare the results from the cyclic elasto-plastic analyses with the ASME-Code NB-3600 Rules and with the Efficiency Diagram developed in France for their Code. The main advantage of the Efficiency Diagram is that the decision whether shakedown occurs, or not, is not only a function of the secondary stress RANGE, but also of the CONSTANT primary stress that exists at that time. A relief to the current ASME-Code rules is suggested for the case of a low constant primary stress (less than Sy / 2).

A Proposal to Consider Cycle Counting Methods for Fatigue Analysis of Nuclear and Conventional Power Plant Components

2016 ◽  
Author(s):  
Felippe M. S. Costa ◽  
José Luiz F. Freire ◽  
Jürgen Rudolph ◽  
José Eduardo Maneschy
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Time History ◽  
Peak Stress ◽  
Fatigue Analysis ◽  
Transient Temperature ◽  
Stress Range ◽  
Structural Components ◽  
Finite Element Software ◽  
Asme Code

This paper points out some relevant aspects of the simplified elasto-plastic fatigue analysis as addressed in the ASME Code Section III Subsection NB and its application to two structural components that are subjected to a slow or to a fast thermal transient. The structural components considered are a thick-walled pipe and a nozzle-to-vessel junction. For the case of the thick-walled pipe, a closed form analytical solution proposed by Albrecht for pipes subjected transient temperature loading was implemented and its results were compared to coupled thermal and mechanical finite element analyses using a commercial finite element software. The application of the analytical solution allows for an optimization of the time consumed to obtain the stresses that occur across the thickness of the pipe as a function of time, i.e. the membrane plus bending plus peak stress range, Sp. The analytical solution equally allows for the linearization of the stress components actuating along the pipe thickness for all time steps considered within the thermal stress solution. This yields the membrane plus bending stress range, Sn, and allows for a design code conforming plasticity correction by means of Ke factors. In the considered case of the nozzle-to-vessel junction, a finite element solution was used. It was one aim of the study to point out, that under fast transients loading situations the relevant stresses Sp and Sn do not necessarily coincide with each other. In the ASME Code the alternating stress Sa is a function of the factor Ke and of the range of Sp, with Ke being a function of the range of Sn and of the material properties. Consequently, a non-conservative fatigue analysis may result in the case of performing cycle counting only based on the time history of the critical Sp values and simply assigning the corresponding Sn and Ke values. This paper exemplifies one of those cases and proposes a method to overcome this problem.

Time History Broadening

2011 ◽  
Author(s):  
Andrzej T. Strzelczyk
Keyword(s):  
Time History ◽  
Support Point ◽  
Frequency Variation ◽  
Simple Modification ◽  
A Value ◽  
History Analysis ◽  
Point Motion ◽  
Asme Code ◽  
Time Histories ◽  
Frequency Variations

Section 6.5.2 of N283.3-10 of the CSA Standard [1] describes analytical methods for seismic qualification of nuclear components. Clause 6.5.2.2 of this Section instructs how to prepare seismic input for the time history method, specifically it states: “Time-histories of support point motion (displacement, velocity, or acceleration) may be used as dynamic inputs to components. To take into account the effects of possible frequency variations of component and structure, the analysis shall be carried out using three different time-history excitations. These time-histories shall be obtained by varying time scale of the original support point time-history by (a) 1.0; (b) 1 - Δfj/fj; and (c) 1 + Δfj/fj, where fj = the dominant structural frequency; Δfj = a parameter defining the frequency variation due to uncertainties in structural soil properties. The most severe effects obtained from these three time history analyses shall be considered in the design of the components. Notes: (1) A value of 15% for Δfj/fj may be used for the time-history analysis specified in this Clause; (2) For structures directly on bedrock, a value of Δfj/fj = 0% may be used”. This paper identifies some ambiguities in the approach described above. It shows, by theory and examples, that significantly different responses are obtained depending on which form of excitation is used (acceleration, velocity or displacement). In a typical acceleration excitation approach, the response may be over or under estimated. To remove this ambiguity, the paper proposes a simple modification of the broadening procedure described in [1]. The problem discussed in this paper may also be meaningful for the broadening time history described in Appendix N of ASME Code [2].

Distinguishing Ratcheting and Shakedown Conditions in Pressure Vessels

2003 ◽  
Author(s):  
W. Reinhardt
Keyword(s):  
Thermal Stress ◽  
Kinematic Hardening ◽  
Pressure Vessels ◽  
Stress Range ◽  
Secondary Stress ◽  
Hardening Models ◽  
Asme Code ◽  
Elastic Shakedown

The nature of the boundary between stable cycling and ratcheting is discussed using several illustrative example scenarios. The examples are analyzed in the context of the elastic methods currently in the ASME Code to demonstrate the conservatism of the existing approach that exists in some cases, and the unconservative estimation that exists in others. It is shown that the limit on the linearized primary plus secondary stress range can be related to conditions for elastic shakedown in certain kinematic hardening models of plasticity, while the limits on thermal stress ratchet address only scenarios similar to the Bree problem.

Separation of Primary Stress in Finite Element Analysis of Pressure Vessel with the Principle of Superposition

2007 ◽  
Vol 353-358 ◽  
pp. 373-376 ◽  
Author(s):  
Bing Jun Gao ◽  
Xiao Ping Shi ◽  
Hong Yan Liu ◽  
Jin Hong Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Engineering Application ◽  
Total Stress ◽  
Principle Of Superposition ◽  
Element Analysis ◽  
Primary Stress ◽  
The Finite Element Analysis ◽  
Asme Code ◽  
Allowable Load

A key problem in engineering application of “design by analysis” approach is how to decompose a total stress field obtained by the finite element analysis into different stress categories defined in the ASME Code III and VIII-2. In this paper, we suggested an approach to separate primary stress with the principle of superposition, in which the structure does not need to be cut into primary structure but analyzed as a whole only with decomposed load. Taking pressurized cylindrical vessel with plate head as example, the approach is demonstrated and discussed in detail. The allowable load determined by the supposed method is a little conservative than that determined by limited load analysis.

CO and H2O Time-Histories in Shock-Heated Blends of Methane and Ethane for Assessment of a Chemical Kinetics Model

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
O. Mathieu ◽  
C. R. Mulvihill ◽  
E. L. Petersen ◽  
Y. Zhang ◽  
H. J. Curran
Keyword(s):  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Time History ◽  
Good Marker ◽  
Ignition Delay Times ◽  
Depletion Rate ◽  
Time Histories ◽  
Main Components ◽  
Detailed Kinetics

Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4/10% C2H6 diluted in 99% Ar was studied at fuel lean (equiv. ratio = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from combustion, and its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules were compared to a state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the CO profiles typically increase rapidly after an induction time, reach a maximum, and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated for pressures above 1 atm.

CO and H2O Time-Histories in Shock-Heated Blends of Methane and Ethane for Assessment of a Chemical Kinetics Model

2017 ◽  
Author(s):  
O. Mathieu ◽  
C. Mulvihill ◽  
E. L. Petersen ◽  
Y. Zhang ◽  
H. J. Curran
Keyword(s):  
Gas Turbine ◽  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Practical Interest ◽  
Time History ◽  
Good Marker ◽  
Ignition Delay Times ◽  
Time Histories ◽  
Detailed Kinetics

Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4 /10% C2H6 diluted in 99% Ar was studied at fuel lean (ϕ = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from hydrocarbon combustion, and following its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules measured herein were compared to a modern, state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the measured CO profiles typically increase rapidly after an induction time, reach a maximum and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated by the models for pressures above 1 atm. This study demonstrates the need to improve on the accuracy of the HCCO reactions involved in CO formation for pressures of practical interest for the gas turbine industry.

Damage Detection in Rods Using Wave Propagation and Regression Analysis

1999 ◽  
Author(s):  
K. T. Feroz ◽  
S. O. Oyadiji
Keyword(s):  
Wave Propagation ◽  
Regression Analysis ◽  
Damage Detection ◽  
Numerical Study ◽  
Time History ◽  
Ball Impact ◽  
Spherical Ball ◽  
Time Histories ◽  
Measured Strain ◽  
Force Time

Abstract The phenomena of wave propagation in rods was studied both numerically and experimentally. The finite element (FE) code ABAQUS was used for the numerical study while PZT (lead zirconium titanate) sensors and a 50 MHz transient recorder were used experimentally to monitor and to capture the propagation of stress pulses. For the study of damage detection in the rods the analyses and the experiments were repeated by introducing slots in a fixed axial location of the rod. A longitudinal wave was induced in the rod via collinear impact which was modelled in the FE analyses using the force-time history computed from the classical Hertz contact theory. In the experimental measurements this was achieved by a spherical ball impact at one plane end of the rods. It is shown that the predicted and measured strain-time histories for the defect-free rod and for the rods with defect correlate quite well. These results also show that defects can be located using the wave propagation phenomena. A regression analysis technique of the predicted and measured strain histories of the defect free rod and of the rod with defect was also performed. The results show that this technique is more efficient for smaller defects. In particular, it is shown that the area enclosed by the regression curve increases as the defect size increases.

Selection and Scaling Time History Records for Performance-Based Design

2017 ◽  
pp. 1-35
Author(s):  
Yasin M. Fahjan ◽  
F. İlknur Kara ◽  
Aydın Mert
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Time History ◽  
Design Code ◽  
Uniform Hazard Spectra ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Recent Developments ◽  
Time Histories ◽  
Strong Ground

Recent developments in performance-based analyses and the high performance of computational facilities have led to an increased trend for utilizing nonlinear time-history analysis in seismic evaluation of the performance of structures. One of the crucial issues of such analysis is the selection of appropriate acceleration time histories set that satisfy design code requirements at a specific site. In literature, there are three sources of acceleration time histories: 1) recorded accelerograms in real earthquakes scaled to match design code spectrum/uniform hazard spectra/conditional mean spectrum, 2) artificial records generated from white noise spectra to satisfy design code spectrum, and 3) synthetic records obtained from seismological models. Due to the increase of available strong ground motion database, using and scaling real recorded accelerograms is becoming one of the most contemporary research issues in this field. In this study, basic methodologies and criteria for selecting strong ground motion time histories are discussed. Design code requirements for scaling are summarized for ASCE/SEI-7-10, EC8 and Turkish Seismic Codes. Examples for scaling earthquake records to uniform hazard spectra are provided.

An Adaptive Multiscaling Approach for Reducing Computation Time in Simulations of Articulated Biopolymers

2019 ◽  
Vol 14 (5) ◽  
Author(s):  
Ashley Guy ◽  
Alan Bowling
Keyword(s):  
Computational Cost ◽  
Time History ◽  
Computation Time ◽  
Coarse Graining ◽  
Integration Time ◽  
Dynamic Simulations ◽  
Equivalent Time ◽  
Time Histories ◽  
Time Required ◽  
Computational Resources

Microscale dynamic simulations can require significant computational resources to generate desired time evolutions. Microscale phenomena are often driven by even smaller scale dynamics, requiring multiscale system definitions to combine these effects. At the smallest scale, large active forces lead to large resultant accelerations, requiring small integration time steps to fully capture the motion and dictating the integration time for the entire model. Multiscale modeling techniques aim to reduce this computational cost, often by separating the system into subsystems or coarse graining to simplify calculations. A multiscale method has been previously shown to greatly reduce the time required to simulate systems in the continuum regime while generating equivalent time histories. This method identifies a portion of the active and dissipative forces that cancel and contribute little to the overall motion. The forces are then scaled to eliminate these noncontributing portions. This work extends that method to include an adaptive scaling method for forces that have large changes in magnitude across the time history. Results show that the adaptive formulation generates time histories similar to those of the unscaled truth model. Computation time reduction is consistent with the existing method.

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