Failure Assessment on Tensile Cracked Specimens of Aluminum Alloys

2004 ◽  
Vol 126 (3) ◽  
pp. 404-406 ◽  
Author(s):  
T. Christopher ◽  
K. Sankaranarayanasamy ◽  
B. Nageswara Rao
Keyword(s):  
Aluminum Alloys ◽  
Fracture Criterion ◽  
Pressure Vessels ◽  
Tensile Fracture ◽  
Test Results ◽  
Failure Assessment Diagram ◽  
Cracked Plates ◽  
Failure Assessment ◽  
Cracked Specimens ◽  
Good Agreement

A three-parameter fracture criterion is applied to correlate fracture data from tensile cracked plates made of aluminum alloys. Fracture parameters to generate the failure assessment diagram are determined for the materials considered in the present study. Failure load estimates were found to be in good agreement with test results. The failure assessment diagram of a material generated from tensile fracture plate configurations can also be applied for failure pressure estimations of flawed pressure vessels.

Assessment Procedure for Multiple Cracklike Flaws in Failure Assessment Diagram (FAD)

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Shinji Konosu
Keyword(s):  
Body Force ◽  
Pressure Vessels ◽  
The Body ◽  
Assessment Procedure ◽  
Failure Assessment Diagram ◽  
Reference Stress ◽  
Body Force Method ◽  
Failure Assessment ◽  
Common Problems ◽  
Shielding Effects

Assessment of multiple discrete cracklike flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service (FFS) rules, such as ASME, BS, and so on, multiple cracklike flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between nonaligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction that indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete cracklike flaws in the failure assessment diagram is proposed.

Validation of the Deformation Plasticity Failure Assessment Diagram (DPFAD) Approach—The Case of an Axial Flaw in a Pressurized Cylinder

1990 ◽  
Vol 112 (3) ◽  
pp. 213-217 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Crack Depth ◽  
Pressure Vessels ◽  
Inside Surface ◽  
Failure Assessment Diagram ◽  
Steel Technology ◽  
Failure Assessment ◽  
Deformation Plasticity ◽  
Structural Tests ◽  
Structural Configurations ◽  
Pressurized Cylinder

The validation of the deformation plasticity failure assessment diagram (DPFAD) approach for application to the prediction of failure pressures for pipes or pressure vessels with axial flaws is addressed in this paper. The DPFAD approach has been extensively documented with regard to its validity in open literature for various configurations of test specimens. For actual structural configurations, however, no such comparisons appear in open literature. In particular, the model of a part-through wall axial flaw in a pressurized cylinder has not been validated through comparisons with actual structural tests results. Two sources of test data from structural tests of axially flawed pressurized cylinders were evaluated. • Heavy-Section Steel Technology (HSST) intermediate test vessels. • Eiber/Battelle Columbus Laboratories (BCL) axially cracked pipes. The DPFAD axial flaw model was developed using finite-element results to generate calibration constants as functions of crack depth to wall thickness and crack depth to crack length for an axially oriented semi-elliptical flaw on the inside surface of a pressurized cylinder. The calibration constants were then used to generate failure assessment curves that can be used to assess or predict failure of pipes or vessels with axial flaws under pressure loading. A key assumption in the analysis was the use of the failure assessment curve for the inside surface flaw in the prediction of outside-surface-flawed cylinder failures. Based on the excellent results from the comparisons with predicted failures to actual vessel and pipe failures, this assumption was found to be reasonable. Furthermore, based on predicted test results of the HSST vessel tests and the Eiber/BCL pipe tests, it was concluded that the DPFAD semi-elliptical axial flaw model can be used reliably in assessing part-through flaws in pressurized vessels and pipes.

Extensions of the Failure Assessment Diagram Approach Semi-Elliptical Flaw in Pressurized Cylinder

1985 ◽  
Vol 107 (1) ◽  
pp. 25-29 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Safety Assessment ◽  
Pressure Vessels ◽  
Failure Assessment Diagram ◽  
The United Kingdom ◽  
Safety Margins ◽  
Failure Assessment ◽  
Assessment Approach ◽  
Model Versus ◽  
Pressurized Cylinder ◽  
Diagram Approach

A simple, viable engineering method for assessing the integrity of nuclear pressure vessels has been developed at Babcock & Wilcox. The method uses results given in a plastic fracture handbook developed by General Electric and which are in the format of the Central Electricity Generation Board of the United Kingdom R-6 failure assessment diagram. The method is currently limited to two-dimensional/axisymmetric structural models with continuous flaws. Failure assessment of nuclear pressure vessels with assumed continuous flaws result in the calculation of overly conservative safety margins. This paper presents the extension of the existing failure assessment approach to include semi-elliptical flaw models, as well as example problems which demonstrate increased safety margins over the continuous flaw assumptions. In particular, failure assessment diagram curves and the corresponding failure assessment point expressions for an axially cracked pressurized cylinder with an ASME Section III, Appendix G semi-elliptical flaw are presented. The results of the example problems considering the less conservative semi-elliptical flaw model versus the continuous flaw model dramatically illustrate increased safety margins of 50 percent when more realistic semi-elliptical flaws are postulated. The results given in this paper are particularly valuable in the safety assessment of PWR vessels which have low toughness welds in their beltline regions.

Critical Crack Sizes of Pressure Vessels Based on Failure Assessment Diagram Under Design Requirements

2019 ◽  
Author(s):  
Yuebing Li ◽  
Weiya Jin ◽  
Mingjue Zhou ◽  
Zengliang Gao
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessels ◽  
Design Standards ◽  
Critical Crack ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Section Viii ◽  
Design Requirements ◽  
Assessment Standards ◽  
Material Fracture

Abstract Standards or codes for defects assessment usually accompany their own design standards, such as, ASME BPVC section VIII and API 579-1/ASME FFS-1, GB 150 and GB/T 19624. The development of defects assessment standards should be adapted to the design requirements of pressure vessels. The consistency between fitness-for-service (FFS) procedures and design requirements of pressure vessels is discussed in this work. As a key link between FFS procedures and design standards, the required material fracture toughness not only depends on the methods of FFS procedures such as failure assessment diagram, but also on the design requirements. A procedure based on failure assessment diagram under design requirements is proposed to calculate critical crack sizes. The result can give some meaningful suggestions for the development of standards or codes.

Evaluation of Bending Limit of 9Cr-1Mo-V Steel by Master Curve and Failure Assessment Diagram Method: Evaluation of Base Metal

2018 ◽  
Author(s):  
Kazuo Oda ◽  
Mitsuyoshi Nakatani ◽  
Tomohiro Tanaka ◽  
Masamitsu Abe ◽  
Yasuhito Takashima ◽  
...  
Keyword(s):  
Brittle Fracture ◽  
Master Curve ◽  
Steel Plate ◽  
Fracture Probability ◽  
Pressure Vessels ◽  
Unstable Fracture ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Bending Process ◽  
Loading Tests

We investigated the bending and rolling limit of 9Cr-1Mo-V steel plate used in pressure vessels for the purpose of improving its manufacturing efficiency. Hereafter in this report, the bending limit refers to bending by press or by roller. It includes acceptable crack size, temperature, introduced plastic strain and other factors. When fracture toughness tests of 9Cr-1Mo-V steel plate were performed at bending temperature in production, unstable fracture rarely occurred. Since fracture probability during the bending process seems to be low, it was not possible to evaluate aspects of the degree of safety factor for brittle fracture. To estimate the bending limit at high temperature where unstable fracture rarely occurs, a method was proposed for estimating fracture probability using master curve and failure assessment diagram (FAD). In order to verify the proposed method, loading tests simulating the bending process were performed. The bending limits obtained from the loading tests were in good agreement with the values predicted by the proposed method. In this study, guidelines such as required toughness value and bending temperature for preventing brittle fracture during the bending process of 9Cr-1Mo-V steel plate were investigated.

scholarly journals Failure Assessment Diagram (FAD) analysis of fatigue test results for X65 welded joints

2018 ◽  
Vol 165 ◽  
pp. 21011
Author(s):  
Hsin Jen Hoh ◽  
John Hock Lye Pang ◽  
Kin Shun Tsang
Keyword(s):  
Welded Joints ◽  
Oil And Gas ◽  
Fatigue Cracks ◽  
Local Limit ◽  
Limit Load ◽  
Test Results ◽  
Offshore Pipelines ◽  
Failure Assessment Diagram ◽  
Four Point Bending ◽  
Failure Assessment

Offshore pipelines transfer oil and gas from seabed to production facility on the surface. The long pipelines are formed by welding of pipe segments, where these welded joints are a source of stress concentration and defects from which fatigue cracks can grow. This work aims to study the behaviour of deep fatigue cracks. In this current work, finite-element based on a parametric study of four-point bending is used to assess the stress intensity factors (SIFs) of deep surface cracks in X65 specimens, while considering local limit load the remaining load bearing ligament. These deep cracks take on a non-regular shape and have widths that exceed that of the specimen. They will be compared to empirical expressions from derived standards such as British Standards BS7910, which may be more conservative. The existing large flaw is also assessed via the failure assessment diagram (FAD). The effects of limit load solutions and reference stresses used to determine the FAD diagram will be discussed.

A Procedure for the Assessment of the Structural Integrity of Nuclear Pressure Vessels

1983 ◽  
Vol 105 (1) ◽  
pp. 28-34 ◽  
Author(s):  
J. M. Bloom
Keyword(s):  
Structural Integrity ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Plastic Collapse ◽  
Failure Assessment Diagram ◽  
Linear Elastic ◽  
Failure Assessment ◽  
Deformation Plasticity ◽  
Margin Of Safety ◽  
Two Parameters

This paper presents a simple engineering procedure that the utility industry can use to assess the integrity of typical nuclear-grade pressure vessels. The procedure recognizes both brittle fracture and plastic collapse and is based on a set of proposed failure assessment curves which make up a safety/failure plane. The plane is defined by the stress intensity factor/fracture toughness ratio as the ordinate and the applied stress/reference plastic collapse stress ratio as the abscissa. The failure assessment procedure is based in part on the British Central Electricity Generating Board’s R-6 failure assessment diagram and the deformation plasticity solutions of the General Electric Company. Two parameters, a plastic collapse parameter (Sr′) and linear elastic fracture mechanics parameter (Kr′) are calculated by the user. The point (Sr′, Kr′) is plotted on the appropriate failure assessment diagram. If the point lies inside the respective curve, the structure is safe from failure. Moreover, for a given pressure and a postulated or actual flaw size, the margin of safety of the structure can be simply determined. Consistent with Appendix A of Section XI, (Division 1) of the ASME Boiler and Pressure Vessel Code the procedure presented in this paper is limited to ferritic materials 4 in. (102 mm) and greater in thickness. Details of the derivation of the proposed set of failure assessment curves are provided along with a sample problem illustrating the use of these curves.

Integrity Assessment of Defected Structure at High Temperature With a Material Database

2010 ◽  
Author(s):  
Zhengdong Wang ◽  
Fu-Zhen Xuan ◽  
Shan-Tung Tu
Keyword(s):  
High Temperature ◽  
Crack Size ◽  
Pressure Vessels ◽  
Time Dependent ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Base Materials ◽  
Axial Tension ◽  
Failure Assessment ◽  
Dependent Failure

The basic theory of Time Dependent Failure Assessment Diagram (TDFAD) is introduced in this paper to be modified for cracks in mismatched welds at high temperature. A time-dependent failure assessment curve is constructed using the method of R6 Option 2. This curve depends not only on the geometry and crack size but also on the mechanical properties of both weld and base materials. The application of such an approach is given to an internal circumferentially defected welded-cylinder under axial tension. An engineering tool of integrity assessment for defected structure at high temperature has been developed for a decade based on the Time Dependent Failure Assessment Diagram (TDFAD) technology for pressure vessels. The software is illustrated in this paper by framework and interfaces and some industrial cases are introduced to show the procedure of the assessment by using the software. A high temperature material database (HTMD) of main properties for typical high temperature steels and alloys is constructed to meet the needs of the safety assessment of the pressure vessels and other structures. The structure of the database is shown in the paper with some tables and charts.

A Comparison of Notch Failure Assessment Diagram Methods for Assessing the Fracture Resistance of Structures Containing Non-Sharp Defects

2014 ◽  
Author(s):  
Anthony J. Horn ◽  
Peter J. Budden
Keyword(s):  
Failure Mechanism ◽  
Fracture Resistance ◽  
Failure Criteria ◽  
Test Results ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Different Types ◽  
Definition Of ◽  
Made In

This paper analyses and compares a range of Notch Failure Assessment Diagram (NFAD) methods for assessing the fracture resistance of structures and components that contain defects with non-sharp tips. As micromechanistic failure criteria for predicting fracture from notch tips have developed, several forms of NFADs have been proposed over the last 20 years with notable developments having been made in the last 10 years. This paper quantifies the differences between four different types of NFAD approach and uses test results from test specimens containing notches of varying acuities to evaluate each approach. The results highlight significant differences in fracture predictions between the different NFAD approaches due to differences in the definition of the NFAD axes, the failure loci, the assumed failure mechanism and the corresponding micromechanistic failure criteria employed by each method.

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