Cleavage fracture modeling of pressure vessels under transient thermo-mechanical loading

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries and oil sands plants. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. In order to better understand the damage mechanisms, an experimental investigation of coke drum material behavior under various thermal-mechanical loading conditions was performed. A thermal-mechanical material testing system is successfully designed and implemented. Six types of various thermal-mechanical cyclic tests were performed: 1. cyclic thermal loading under constant uniaxial stress; 2. in-phase thermal and mechanical stress cycling; 3. out-of-phase thermal and mechanical stress cycling; 4. fully-reversed uniaxial cyclic loading with in-phase thermal cycling; 5. in-phase thermal-axial stress cycling with constant circumferential stress; 6. in-phase thermal-axial stress cycling with mean stress. Some of theses tests are similar to the actual loading scenario experienced by the coke drums. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums such as bulging.

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Experimental Study on the Cleavage Fracture Behavior of an ASTM A285 Grade C Pressure Vessel Steel

Journal of Pressure Vessel Technology ◽

10.1115/1.4028003 ◽

2014 ◽

Vol 137 (2) ◽

Cited By ~ 2

Author(s):

Rafael G. Savioli ◽

Claudio Ruggieri

Keyword(s):

Fracture Toughness ◽

Cleavage Fracture ◽

Pressure Vessel ◽

Fracture Behavior ◽

Pressure Vessels ◽

Experimental Results ◽

Pressure Vessel Steel ◽

Crack Tip Opening Displacement ◽

Opening Displacement ◽

Vessel Steel

This work addresses an experimental investigation on the cleavage fracture behavior of an ASTM A285 Grade C pressure vessel steel. One purpose of this study is to enlarge previously reported work on mechanical and fracture properties for this class of steel to provide a more definite database for use in structural and defect analyses of pressurized components, including pressure vessels and storage tanks. Another purpose is to determine the reference temperature, T0, derived from the Master curve methodology which defines the dependence of fracture toughness with temperature for the tested material. Fracture toughness testing conducted on single edge bend SE(B) specimens in three-point loading extracted from an A285 Grade C pressure vessel steel plate provides the cleavage fracture resistance data in terms of the J-integral and crack tip opening displacement (CTOD) at cleavage instability, Jc and δc. Additional tensile and conventional Charpy tests produce further experimental data which serve to characterize the mechanical behavior of the tested pressure vessel steel. The experimental results reveal a strong effect of specimen geometry on Jc and δc-values associated with large scatter in the measured values of cleavage fracture toughness. Overall, the present investigation, when taken together with previous studies, provides a fairly extensive body of experimental results which describe in detail the fracture behavior of an ASTM A285 Grade C pressure vessel steel.

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Viscoplastic Characterization of A533B Steel at High Strain Rates

Journal of Pressure Vessel Technology ◽

10.1115/1.2928617 ◽

1990 ◽

Vol 112 (3) ◽

pp. 218-224 ◽

Cited By ~ 5

Author(s):

R. J. Dexter ◽

K. S. Chan

Keyword(s):

Dynamic Fracture ◽

Constitutive Equations ◽

Tensile Tests ◽

Pressure Vessels ◽

Strain Rates ◽

Fracture Modeling ◽

Measured Stress ◽

Class 1 ◽

Tensile Data

The yield strength of A533 grade B class 1 steel is relatively low. Dynamic fracture in test specimens and pressure vessels made with this material is generally accompanied by significant plastic flow over a large range of strain rates. Therefore, it is imperative to use viscoplastic constitutive equations in the analysis of dynamic fracture in A533B steel. This paper describes the characterization and modeling of the viscoplastic behavior of A533B steel using the Bodner-Partom model. Tensile tests were performed from −60°C to 175°C at strain rates ranging from 10−3 to 103. The tensile data were used to obtain material constants in the Bodner-Partom constitutive equations over this range of temperatures. Comparison of calculated and measured stress-strain curves showed good agreement, validating the model and the procedures for determining the model constants. The use of the Bodner-Partom model for dynamic fracture modeling is then discussed.

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Cleavage fracture assessment of transient thermo-mechanical loading situations by local approach

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2017.02.012 ◽

2017 ◽

Vol 178 ◽

pp. 512-526 ◽

Cited By ~ 1

Author(s):

Johannes Tlatlik ◽

Dieter Siegele

Keyword(s):

Mechanical Loading ◽

Cleavage Fracture ◽

Local Approach ◽

Fracture Assessment

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Residual Stress Effects on Cleavage Fracture

Volume 6: Materials and Fabrication ◽

10.1115/pvp2007-26035 ◽

2007 ◽

Cited By ~ 1

Author(s):

A. H. Sherry ◽

K. S. Lee ◽

M. R. Goldthorpe ◽

D. W. Beardsmore

Keyword(s):

Fracture Toughness ◽

Residual Stress ◽

Residual Stresses ◽

Cleavage Fracture ◽

Driving Force ◽

Compact Tension ◽

Pressure Vessels ◽

Crack Driving Force ◽

Stress Effects ◽

Definition Of

It is recognised that the driving force for the initiation and propagation of defects in materials may, under some circumstances, include contributions from both externally applied loads such as internal pressure in pressure vessels and piping and secondary stresses such as weld residual stresses. For non stress-relieved welds, residual stresses can provide a significant proportion of the crack driving force. This paper describes the results obtained from an experimental programme aimed at extending the understanding of residual stress effects on cleavage fracture. The paper describes the preparation and testing of standard and preloaded compact-tension specimens of an A533B pressure vessel steel at its Master Curve reference temperature. Standard tests on compact-tension specimens provide fracture toughness data which are broadly consistent with the conventional three-parameter Weibull model, with Kmin = 20 MPa√m and an exponent of about 4. The preloaded compact-tension specimens included a high level of tensile residual stress at the crack location. Fracture toughness data obtained using the test standards from these specimens fall significantly below the standard specimen data, since the contribution from residual stresses is ignored. However, when due account is taken of the residual stress on the crack driving force using a correct definition of the J-integral, the distributions of fracture toughness data from both specimen types are found to overlay each other. The definition of J used in this paper allows residual stress effects on fracture to be accounted for in a single fracture parameter.

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