Plastic Limit Analysis of Modified 9Cr-1Mo Steel Pressure Vessel Containing Volume Defect with Creep Damage Law

2017 ◽  
Vol 09 (02) ◽  
pp. 1750025 ◽  
Author(s):  
Xianhe Du ◽  
Jie Zhang ◽  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
High Temperature ◽  
Service Time ◽  
Pressure Vessel ◽  
Creep Damage ◽  
Limit Load ◽  
Creep Model ◽  
Creep Process ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Volume Defect

A numerical method for evaluating the plastic limit load of modified 9Cr-1Mo steel pressure vessel structures containing volume defect at [Formula: see text]C is proposed based on the plastic limit load concept under high temperature. Firstly, the creep analysis of the defected pressure vessel is conducted with the Liu–Murakami creep model to obtain the creep damage after a prescribed service time. Secondly, the obtained creep damage is introduced into Ramberg–Osgood model through the hardness ratio to characterize the material deterioration during the creep process. Thirdly, the plastic limit load of the defected pressure vessel under high temperature is obtained through the classic zero curvature criterion with the modified Ramberg–Osgood model. The numerical examples for the pressure vessels with different sizes of volume defects are performed, and the failure modes of pressure vessel structures at the limit state are revealed and the fitting formulae between the plastic limit load ratio and the dimensionless defect factor are established based on the numerical results. Results show that the plastic limit load and the service time of pressure vessel structures under high temperature are sensitive to the volume defect ratio and can be determined easily through the fitting formulae which are convenient for engineering applications.

scholarly journals Numerical Limit Load Analysis of 3D Pressure Vessel with Volume Defect Considering Creep Damage Behavior

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Xianhe Du ◽  
Donghuan Liu ◽  
Yinghua Liu
Keyword(s):  
High Temperature ◽  
Pressure Vessel ◽  
Creep Damage ◽  
Limit Load ◽  
Numerical Approach ◽  
Pressure Vessels ◽  
Load Carrying ◽  
Vessel Structure ◽  
Damage Law ◽  
Volume Defect

The limit load of 3D 2.25Cr-1Mo steel pressure vessel structures with volume defect at 873 K is numerically investigated in the present paper, and limit load under high temperature is defined as the load-carrying capacity after the structure serviced for a certain time. The Norton creep behavior with Kachanov-Robotnov damage law is implemented in ABAQUS with CREEP subroutine and USDFLD subroutine. Effect of dwell time to the material degradation of 2.25Cr-1Mo steel has been considered in this paper. 190 examples for the different sizes of volume defects of pressure vessels have been calculated. Numerical results showed the feasibility of the present numerical approach. It is found that the failure mode of the pressure vessel depends on the size of the volume defect and the service life of the pressure vessel structure at high temperature depends on the defect ratio seriously.

Plastic Limit Analysis of Piping with Local Wall-Thinning under Elevated Temperature

2016 ◽  
Vol 725 ◽  
pp. 47-52
Author(s):  
Xian He Du ◽  
Ying Hua Liu
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Limit Analysis ◽  
Limit Load ◽  
Plastic Limit ◽  
Wall Thinning ◽  
Plastic Limit Analysis ◽  
Creep Time ◽  
Plastic Limit Load ◽  
Local Wall Thinning

In order to evaluate the safety and integrity of piping with local wall-thinning at elevated temperature, a numerical method for plastic limit load of modified 9Cr-1Mo steel piping is proposed in the present paper. The limit load of piping at high temperature is defined as the load-carrying capacity after the structure has served for a certain time period. The power law creep behavior with Liu-Murakami damage model is implemented into the commercial software ABAQUS via CREEP for simulation, and the Ramberg-Osgood model is modified to consider the material deterioration effect of modified 9Cr-1Mo steel by introducing the creep damage factor into the elasto-plastic constitutive equation. For covering the wide ranges of defect ratios and service time periods, various 3-D numerical examples for the piping with local wall-thinning defects, and creep time are calculated and analyzed. The limit loads of the defected structures under high temperature are obtained through classic zero curvature criterion with the modified Ramberg-Osgood model, and the typical failure modes of these piping are also discussed. The results show that the plastic limit load of piping containing defect at elevated temperature depends not only on the size of defect, but also on the creep time, which is different from the traditional plastic limit analysis at room temperature without material deterioration.

Use of Limit Load Analysis for Design of Pressure Vessel Cover

2012 ◽  
Author(s):  
Rahul Jain
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Limit Load ◽  
Plastic Limit ◽  
Element Analysis ◽  
Linear Elastic ◽  
Reference Volume ◽  
Plastic Limit Load ◽  
Load Analysis

This paper explores the use of limit load analysis methods for the design of a pressure vessel manway cover as per the ASME boiler and pressure vessel code guidelines. The results of elastic and limit load finite element analysis are discussed for the design. The concept of reference volume consideration along with linear elastic finite element analysis to determine the lower bound limit load has been explored and the results are compared with the non-linear elastic-plastic limit load analysis.

Shakedown and Limit Analysis of Kinematic Hardening Piping Elbows Under Internal Pressure and Bending Moments

2021 ◽  
Author(s):  
Heng Peng ◽  
Yinghua Liu
Keyword(s):  
Yield Strength ◽  
Internal Pressure ◽  
Limit Analysis ◽  
Kinematic Hardening ◽  
Limit Load ◽  
Bending Moments ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Interaction Curves ◽  
Shakedown Limit

Abstract In this paper, the Stress Compensation Method (SCM) adopting an elastic-perfectly-plastic (EPP) material is further extended to account for limited kinematic hardening (KH) material model based on the extended Melan's static shakedown theorem using a two-surface model defined by two hardening parameters, namely the initial yield strength and the ultimate yield strength. Numerical analysis of a cylindrical pipe is performed to validate the outcomes of the extended SCM. The results agree well with ones from literature. Then the extended SCM is applied to the shakedown and limit analysis of KH piping elbows subjected to internal pressure and cyclic bending moments. Various loading combinations are investigated to generate the shakedown limit and the plastic limit load interaction curves. The effects of material hardening, elbow angle and loading conditions on the shakedown limit and the plastic limit load interaction curves are presented and analysed. The present method is incorporated in the commercial finite element simulation software and can be considered as a general computational tool for shakedown analysis of KH engineering structures. The obtained results provide a useful information for the structural design and integrity assessment of practical piping elbows.

The Effects of Classification of Misalignment-Induced Stresses in Engineering Critical Assessments of Welded Joints With Some Misalignment

2010 ◽  
Author(s):  
Liwu Wei
Keyword(s):  
Welded Joints ◽  
Driving Force ◽  
Limit Load ◽  
Surface Cracks ◽  
Plastic Limit ◽  
Secondary Stress ◽  
Butt Weld ◽  
Crack Driving Force ◽  
Plastic Limit Load

In the ECA of a structure or component such as a pipeline girth weld, the bending stress component arising from misalignment across the weld is often classified as primary, partly because standards such as BS 7910 and API 579-1/ASME FFS-1 do not give definitive guidance on this subject. This approach may be over-conservative as the σmis is localised. In order to obtain a more realistic assessment of the structural integrity of structures containing misalignment, it is necessary to understand the conservatism or non-conservatism in an ECA associated with the classification of σmis. To address the above concerns, systematic investigations were carried out of surface cracks in a plate butt-weld including some misalignment, external circumferential surface cracks and external fully circumferential cracks in a misaligned pipe connection. FEA of these cracked welded joints with some misalignment (typically from 1mm to 2mm) was performed to calculate crack driving force and plastic limit load. The results from FEA were compared with the existing solutions of KI and σref in BS 7910 generated by assuming three options of treating the σmis. The three options were: (1) classification of σmis wholly as primary stress; (2) 15% of σmis as primary and 85% of σmis as secondary stress; and (3) classification of σmis wholly as secondary stress. Variations in parameters (eg misalignment, crack size, loading, weld overmatch and base material properties) were taken into account in order to determine the effects of these parameters on plastic limit load and crack driving force. The implication of different classifications of σmis in terms of ECAs of misaligned welded joints was revealed by conducting BS 7910 Level 2B assessments with the use of a FAD. It was found in this work that for the cases examined, use of the σmis as entirely primary bending in an ECA was over-conservative, and even treatment of σmis as entirely secondary bending was generally shown to be still conservative, when compared with the assessments based on FEA solutions. Furthermore, caution should be exercised in using the solutions of KI and σref given in the existing BS 7910 for crack-containing structures subjected to a bi-axial or tri-axial stress state. A non-conservative estimate may result from the use of these solutions which have been derived based on a uniaxial stress condition.

Developments in Cyclic Analysis and High Temperature Design

2005 ◽  
Author(s):  
Peter Carter ◽  
Douglas L. Marriott
Keyword(s):  
High Temperature ◽  
Power Systems ◽  
Creep Damage ◽  
Limit Load ◽  
Cyclic Stress ◽  
Research Literature ◽  
Stress Classification ◽  
Analysis Technique ◽  
Recent Developments

Design for cyclic loading is emerging as a key question for next generation power systems. Recent developments in techniques for cyclic stress analysis have significant implications for high temperature design. In the same way that limit load analysis is now being used to overcome the difficulties and guesswork of stress classification for steady primary loads, so shakedown and ratcheting analysis can eliminate the more difficult problems of stress classification for cyclic loads. The paper shows how reference stresses defined for shakedown and ratcheting provide rapid and conservative information for design against rupture and creep damage, deformation and strain accumulation, and ratcheting. These techniques will provide additional insights to designers and are likely to augment rather than replace, existing options. These ideas have existed in the research literature for some time, but have now become more accessible by the general industry with a new analysis technique in a commercial finite element code. Examples are given which demonstrate the methodology for nozzles having non-thermal secondary stresses, and prediction of long-term distortion in thermal shock problems.

Anwendung der Plastischen Grenzlast / Application of the Plastic Limit Load

1991 ◽  
Vol 33 (1-2) ◽  
pp. 31-35
Author(s):  
G. Vazoukis ◽  
W. Brocks
Keyword(s):  
Limit Load ◽  
Plastic Limit ◽  
Plastic Limit Load

Plastic Limit Load Solutions for Surface Crack in the Steam Generator Tubes

2005 ◽  
pp. 1704-1712
Author(s):  
Ouk Sub Lee ◽  
Hyun Su Kim ◽  
Jong Sung Kim ◽  
Tae Eun Jin ◽  
Hong Deok Kim ◽  
...  
Keyword(s):  
Steam Generator ◽  
Surface Crack ◽  
Limit Load ◽  
Plastic Limit ◽  
Plastic Limit Load ◽  
Steam Generator Tubes
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