Autofrettaged Spherical Pressure Vessels Design

2007 ◽  
Author(s):  
R. Adibi-Asl
Keyword(s):  
Petrochemical Industry ◽  
Food Industry ◽  
Pressure Vessels ◽  
Stress And Strain ◽  
Optimized Design ◽  
Crack Initiation And Propagation ◽  
Injection Pump ◽  
Initiation And Propagation ◽  
Analytical Expressions ◽  
Spherical Pressure

Autofrettage process, adopted by the pressure vessel industry, enhances the static limit pressure of components. In addition, a significant increase in the fatigue life autofrettage components is also observed due to the inhibition of crack initiation and propagation. The application of autofrettage treated vessels can be extended to the power generation industry (fossil and nuclear), the petrochemical industry, the food industry (bacterial eradication container), and automotive applications (injection pump), among many others. In particular, spherical pressure vessels, due to their inherent stress and strain distributions require thinner walls compared to cylindrical vessels; therefore, they are extensively used in gas-cooled nuclear reactors, gas or liquid containers rather than heads of close-ended cylindrical vessels. In this paper analytical expressions have been derived for stress and strain during autofrettage process of spherical vessels with different material models. These formulas have been applied to evaluate the residual stresses, and optimized design in monotonic and cyclic loading conditions.

Analytical Approach in Autofrettaged Spherical Pressure Vessels Considering the Bauschinger Effect

2006 ◽  
Vol 129 (3) ◽  
pp. 411-419 ◽  
Author(s):  
R. Adibi-Asl ◽  
P. Livieri
Keyword(s):  
Analytical Approach ◽  
Analytical Study ◽  
Bauschinger Effect ◽  
Material Model ◽  
Pressure Vessels ◽  
Stress And Strain ◽  
Material Models ◽  
Loading And Unloading ◽  
Analytical Expressions ◽  
Spherical Pressure

This paper presents an analytical study of spherical autofrettage-treated pressure vessels, considering the Bauschinger effect. A general analytical solution for stress and strain distributions is proposed for both loading and unloading phases. Different material models incorporating the Bauschinger effect depending on the loading phase are considered in the present study. Some practical analytical expressions in explicit form are proposed for a bilinear material model and the modified Ramberg–Osgood model.

scholarly journals Simulation of Crack Initiation and Propagation in the Crystals of a Beam Blank

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 905 ◽  
Author(s):  
Gaiyan Yang ◽  
Liguang Zhu ◽  
Wei Chen ◽  
Gaoxiang Guo ◽  
Baomin He
Keyword(s):  
Crack Initiation ◽  
Tensile Stress ◽  
Damage Mechanics ◽  
Stress And Strain ◽  
Crack Initiation And Propagation ◽  
Surface Cracking ◽  
Initiation And Propagation ◽  
Polycrystalline Model ◽  
Abaqus Software

Surface cracking seriously affects the quality of beam blanks in continuous casting. To study the mechanism of surface crack initiation and propagation under beam blank mesoscopic condition, this study established a polycrystalline model using MATLAB. Based on mesoscopic damage mechanics, a full implicit stress iterative algorithm was used to simulate the crack propagation and the stress and strain of pores and inclusions of the polycrystalline model using ABAQUS software. The results show that the stress at the crystal boundary is much higher than that in the crystal, cracks occur earlier in the former than in the latter, and cracks extend along the direction perpendicular to the force. When a polycrystalline model with pores is subjected to tensile stress, a stress concentration occurs when the end of the pores is perpendicular to the stress direction, and the propagation and aggregation direction of the pores is basically perpendicular to the direction of the tensile stress. When a polycrystalline model with impurities is subjected to force, the stress concentrates around the impurity but the strain here is minimal, which leads to the crack propagating along the impurity direction. This study can provide theoretical guidance for controlling the generation of macroscopic cracks in beam blanks.

Fracture in Spherical Pressure Vessels

1969 ◽  
Vol 11 (5) ◽  
pp. 486-497 ◽  
Author(s):  
F. M. Burdekin ◽  
T. E. Taylor
Keyword(s):  
Shear Fracture ◽  
Fracture Initiation ◽  
Pressure Vessels ◽  
Unstable Fracture ◽  
Critical Crack ◽  
Ductile Materials ◽  
Initiation And Propagation ◽  
Theoretical View ◽  
Spherical Pressure ◽  
Relevant Material

The problem of fracture initiation and propagation from long flaws in spherical pressure vessels is considered from both theoretical and experimental viewpoints. Experimental work has been carried out on vessels of 5 ft diameter and 1/2 in thickness with a range of initial slit lengths from 3-24 in to determine the pressure for rupture by shear fracture. Geometrical variations were further examined by tests on two vessels of 26 in diameter and 1/2 in and 1/4 in thick respectively. The vessel tests were instrumented to give detailed behaviour local to the crack tip and to indicate the gross deformations occurring. The results have been analysed and found consistent with the theoretical view that fracture in vessels of ductile materials may be controlled by the occurrence of a limit mechanism. For less ductile materials it is suggested that fracture mechanics approaches should be used, with allowances for plasticity and bulging. The approach enables the prediction of critical crack lengths for unstable fracture in full size service vessels provided the relevant material properties are known.

Crack Initiation and Propagation Under Hydrogen-Enhanced Fatigue of a Cr-Mo Steel for Gaseous Hydrogen Storage

2014 ◽  
Author(s):  
Laurent Briottet ◽  
Marielle Escot ◽  
Isabelle Moro ◽  
Gian Marco Tamponi ◽  
Jader Furtado ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Hydrogen Storage ◽  
Crack Growth ◽  
Hydrogen Pressure ◽  
Pressure Vessels ◽  
Gaseous Hydrogen ◽  
Crack Initiation And Propagation ◽  
High Hydrogen ◽  
Initiation And Propagation

The current international standards and codes dedicated to the design of pressure vessels do not properly ensure fitness for service of such vessel used for gaseous hydrogen storage and subjected to hydrogen enhanced fatigue. Yet, hydrogen can reduce the fatigue life in two ways: by decreasing the crack initiation period and by increasing the fatigue crack growth rate. The European project MATHRYCE aims are to propose an easy to implement vessel design methodology based on lab-scale tests and taking into account hydrogen enhanced fatigue. The study is focused on a low alloy Cr-Mo steel, exhibiting a tempered bainitic and martensitic microstructure, and classically used to store hydrogen gas up to 45 MPa. Due to hydrogen diffusion at room temperature in such steel, tests have to be performed under hydrogen pressure to avoid outgassing. In the present work, experimental procedures have been developed to study both crack initiation and crack growth. The specimens and tests instrumentation have been specifically designed to quantitatively measure in-situ these two stages under high hydrogen pressure. We developed and tested crack gages located close to a small drilled notch. This notch simulates the presence of steel nonmetallic inclusions and other microstructural features that can affect fatigue crack initiation and propagation. The experimental results addressing the effects of the testing conditions, such as stress ratio, frequency and hydrogen pressure will be compared to the local strain and stress fields obtained by Finite Element Method and correlated to the possible hydrogen enhanced fatigue mechanisms involved.

Numerical Stress Intensity Factors Determination for Fabrication Defects in Coronary Stents

2011 ◽  
Vol 488-489 ◽  
pp. 718-721 ◽  
Author(s):  
Cristian Sorin Nes ◽  
Angelica Enkelhardt ◽  
Nicolae Faur ◽  
Adrian Birlan
Keyword(s):  
Stress Intensity ◽  
Crack Initiation ◽  
Stress Intensity Factors ◽  
Coronary Stents ◽  
Large Strains ◽  
Stress And Strain ◽  
Crack Initiation And Propagation ◽  
Intensity Factors ◽  
Hexahedral Elements ◽  
Initiation And Propagation

Objectives: Numerical stress intensity factors (SIFs) computation for several fabrication defect geometries in coronary stents. XFEM crack initiation and propagation was also performed. Methods: The model represents a self-expandable coronary stent, made from a shape memory alloy (L-605). Several flaw shapes are considered. The analysis was performed using the ABAQUS code. The loads and boundary conditions simulate the interaction between the blood vessels and stents, immediately after the angioplasty was performed. The mesh contains 3d stress hexahedral elements. For global stress and strain distributions, the model of a complete stent was used. For crack propagation analysis and SIF determination, the model represented a single segment of the stent. The stress intensity factors were computed using the contour integral method. Results and conclusions: The stress and strain fields highlight the negative effects of crack initiation and propagation on the residual life of the stent. Furthermore, by compromising the structural integrity of the stent, large strains may occur, thus increasing the risk of restenosis and further stenosis-related complications. The stress intensity factors indicate the most dangerous locations for the flaws (cracks), as well as the most dangerous geometries.

Fatigue Crack Initiation and Propagation in Cr-Mo Steel Hydrogen Storage Vessels: Research on Design for Safe Life

2016 ◽  
Author(s):  
Jussi Solin ◽  
Laurent Briottet ◽  
Beatriz Acosta ◽  
Paolo Bortot ◽  
Jader Furtado ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Design Procedure ◽  
Pressure Vessels ◽  
International Standards ◽  
Crack Initiation And Propagation ◽  
Joint Research ◽  
Initiation And Propagation

International standards and codes dedicated to design of pressure vessels are still unable to competitively ensure safe design and fitness for service of steel vessels for high pressure gaseous hydrogen. Emptying and shallow pressure cycles subject the material to hydrogen enhanced fatigue. A pre-normative project, MATHRYCE under the EU joint research program focused in this subject through material and component testing, analytical work, review of design methodologies and international collaboration. An easy to implement, safe and economically competitive vessel design methodology is targeted. Steps towards this goal were taken by deepening our understanding on hydrogen enhanced fatigue in different kinds of laboratory specimens and real vessels designed for hydrogen service at maximum 45 MPa pressure. This included cyclic pressure testing of artificially notched vessels both in hydrogen and inert environment. The effect of hydrogen pressure, frequency and mechanical loading parameters (ΔK, Sa) on fatigue crack initiation and propagation was analyzed. Attention was paid on the definition of “initiation” and influence of hydrogen on the relative parts of initiation and propagation on the fatigue life of a component. A good correlation between results with various test types was found. Particularly promising was the match between the measured — and estimated — crack growth rates in laboratory specimens and vessels. This supports our proposal for a safe design procedure based on crack growth and defect tolerant approach. Recommendations for implementation in a new international standard, on how to properly address hydrogen enhanced fatigue based on laboratory tests, were given and will be summarized in this presentation. Our results indicate that crack initiation from inclusions or other small microstructural features is not necessarily affected by hydrogen to a similar extent as crack growth, but when initiated, the remaining life may be short due to fast growth. This is challenging for design and inspection rules to allow economically competitive construction of hydrogen equipment without compromising safety.

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