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.

Ratchet Boundary for Superimposed Biaxial Membrane Stress States

2018 ◽  
Author(s):  
Wolf Reinhardt
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Analytical Solution ◽  
Pressure Vessels ◽  
Stress Fields ◽  
Design Codes ◽  
Bending Stress ◽  
Membrane Stress ◽  
Asme Code ◽  
Stress States

Thermal membrane and bending stress fields exist where the thermal expansion of pressure vessel components is constrained. When such stress fields interact with pressure stresses in a shell, ratcheting can occur below the ratchet boundary indicated by the Bree diagram that is implemented in the design Codes. The interaction of primary and thermal membrane stress fields with arbitrary biaxiality is not implemented presently in the thermal stress ratchet rules of the ASME Code, and is examined in this paper. An analytical solution for the ratchet boundary is derived based on a non-cyclic method that uses a generalized static shakedown theorem. The solutions for specific applications in pressure vessels are discussed, and a comparison with the interaction diagrams for specific cases that can be found in the literature is performed.

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.

On the Interaction of Thermal Membrane and Thermal Bending Stress in Shakedown Analysis

2008 ◽  
Author(s):  
Wolf Reinhardt
Keyword(s):  
Thermal Stress ◽  
Bending Stress ◽  
Membrane Stress ◽  
Secondary Stress ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Thermal Bending ◽  
Asme Code ◽  
The Impact ◽  
Current Code

When the primary plus secondary stress range exceeds 3 Sm, the current ASME Code rules on simplified elastic-plastic analysis impose two separate requirements to evaluate the potential for ratcheting. The range of primary plus secondary stress excluding thermal bending must be less than 3 Sm, and the thermal stress must satisfy the Bree criterion for thermal stress ratchet. It has been shown previously that this method can be unconservative, i.e. predict shakedown when elastic-plastic analysis shows ratcheting. This paper clarifies the interaction between thermal membrane and bending stress in the presence of a primary membrane stress. An analytical model is used to derive the closed-form ratchet boundary for combined uniform loading of this type. The impact of having stress gradients along the wall that are typical for discontinuities is studied numerically. Simple modifications of the current Code methods are suggested that would achieve a clearer and better-justified set of rules.

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).

Stress Analysis and Structure Optimization for the Opening Flat Cover of Pressure Vessels

2012 ◽  
Vol 538-541 ◽  
pp. 3253-3258 ◽  
Author(s):  
Jun Jian Xiao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Analysis ◽  
Structure Optimization ◽  
Pressure Vessels ◽  
Secondary Stress ◽  
Element Analysis ◽  
Primary Stress ◽  
Flat Cover

According to the results of finite element analysis (FEA), when the diameter of opening of the flat cover is no more than 0.5D (d≤0.5D), there is obvious stress concentration at the edge of opening, but only existed within the region of 2d. Increasing the thickness of flat covers could not relieve the stress concentration at the edge of opening. It is recommended that reinforcing element being installed within the region of 2d should be used. When the diameter of openings is larger than 0.5D (d>0.5D), conical or round angle transitions could be employed at connecting location, with which the edge stress decreased remarkably. However, the primary stress plus the secondary stress would be valued by 3[σ].

Thermal stress state of cryogenic high-pressure vessels during chilling and pressurization. Report no. 1. Method of calculation

1986 ◽  
Vol 18 (1) ◽  
pp. 87-92
Author(s):  
A. S. Tsybenko ◽  
B. A. Kuranov ◽  
A. D. Chepurnoi ◽  
V. A. Shaposhnikov ◽  
N. G. Krishchuk
Keyword(s):  
High Pressure ◽  
Thermal Stress ◽  
Stress State ◽  
Pressure Vessels ◽  
Thermal Stress State ◽  
Method Of Calculation

Design Formulas of Blind End Closures for High Pressure Vessels

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
R. D. Dixon ◽  
E. H. Perez
Keyword(s):  
High Pressure ◽  
Fatigue Life ◽  
Maximum Stress ◽  
Accurate Determination ◽  
Pressure Vessels ◽  
Stress Distributions ◽  
Fatigue And Fracture ◽  
Asme Code ◽  
Section Viii

The available design formulas for flat heads and blind end closures in the ASME Code, Section VIII, Divisions 1 and 2 are based on bending theory and do not apply to the design of thick flat heads used in the design of high pressure vessels. This paper presents new design formulas for thickness requirements and determination of peak stresses and stress distributions for fatigue and fracture mechanics analyses in thick blind ends. The use of these proposed design formulas provide a more accurate determination of the required thickness and fatigue life of blind ends. The proposed design formulas are given in terms of the yield strength of the material and address the fatigue strength at the location of the maximum stress concentration factor. Introduction of these new formulas in a nonmandatory appendix of Section VIII, Division 3 is recommended after committee approval.

Elastic-Plastic Finite Element Simulation and Fatigue Life Prediction for Beam and Elbow Under Cyclic Loading

2007 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Kinematic Hardening ◽  
Kinematic Model ◽  
Cyclic Plastic ◽  
Hardening Models ◽  
Critical Location ◽  
Cyclic Plastic Strain

Work hardening and Bauschinger effects on plastic deformation and fatigue life for a beam and an elbow under cyclic loading are examined using finite element analysis (FEA). Three typical material plastic hardening models, i.e. isotropic, kinematic and combined isotropic/kinematic hardening models are adopted in the FEA calculations. Based on the FEA results of cyclic stress and strain at a critical location and using an energy-based fatigue damage parameter, the fatigue lives are predicted for the beam and elbow. The results show that (1) the three material hardening models determine similar stress at the critical location with small differences during the cyclic loading, (2) the isotropic model underestimates the cyclic plastic strain and overestimates the fatigue life, (3) the kinematic model overestimates the cyclic plastic strain and underestimates the fatigue life, and (4) the combined model predicts the intermediate cyclic plastic strain and reasonable fatigue life.

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