Plastic Analysis of Radial Outlets From Spherical Pressure Vessels

1964 ◽  
Vol 86 (2) ◽  
pp. 193-198 ◽  
Author(s):  
N. C. Lind
Keyword(s):  
Static Loading ◽  
Local Deformation ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Plastic Behavior ◽  
Spherical Vessel ◽  
Rigid Plastic ◽  
Limit Pressure ◽  
Plastic Analysis ◽  
Spherical Pressure

A method is described whereby the limit pressure may be determined for a radial juncture of a cylindrical vessel and a spherical vessel, assuming quasi-rigid plastic behavior. The limit pressure may for mild-steel vessels be interpreted as the pressure causing extensive local deformation at the juncture under static loading conditions.

Blast Adjustment Factors for Elevated Vertical Cylindrical PVBs

2014 ◽  
Author(s):  
Jihui Geng ◽  
Quentin Baker ◽  
Kelly Thomas
Keyword(s):  
Ground Level ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Chemical Processing ◽  
Prior Work ◽  
Spherical Vessel ◽  
Blast Overpressure ◽  
Blast Effect ◽  
Adjustment Factors ◽  
Spherical Pressure

Pressure vessel burst (PVB) is an explosion scenario commonly encountered at chemical processing facilities. PVBs pose both blast and fragmentation hazards. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. The published blast curves were developed for spherical vessel bursts. However, most pressure vessels are cylindrical rather than spherical. The blast wave originating from a cylindrical PVB is not spherical (i.e., as with a spherical vessel). Rather, the blast to the sides of a cylindrical vessel is stronger than on the ends, creating non-spherical pressure contours, particularly near the vessel. The cylindrical vessel directional blast effect has recently been investigated by the authors, resulting in a correlation to account for the directional effects. However, it was assumed in the prior work that the vessel was at ground level. This paper extends the prior work to elevated PVBs. Both elevated spherical and cylindrical PVBs are examined to provide new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions.

A Thermal Stress Mitigation Technique for Local Postweld Heat Treatment of Welds in Pressure Vessels

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Chunge Nie ◽  
Pingsha Dong
Keyword(s):  
Heat Treatment ◽  
Thermal Stresses ◽  
Postweld Heat Treatment ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Spherical Vessel ◽  
Novel Method ◽  
Bull's Eye ◽  
Recommended Guidelines ◽  
Postweld Heat

This paper introduces a novel method for effectively mitigating high thermal stresses caused during local postweld heat treatment (PWHT) of welds in pressure vessels on which traditional heating method such as bull's eye heating arrangement has been proven difficult in meeting Code requirements for avoiding “harmful” temperature gradients. The method involves the use of a secondary heat band (SHB) that strategically positioned at some distance away from primary PWHT heat band (HB) in terms of vessel characteristic length parameter Rt, where R is vessel radius and t wall thickness. The basic principles associated with the SHB based technique are first demonstrated on a simple straight pipe girth weld configuration. Then, applications for treating nozzle welds in more complex spherical vessel, cylindrical vessel, and at end of cylindrical vessel are presented. Finally, a set of recommended guidelines are provided for defining both the SHB size and location for performing local PWHT on welds in three major nozzle/vessel weld configurations.

A Review of Theoretical and Experimental Research on Various Autofrettage Processes

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Rajkumar Shufen ◽  
Uday S. Dixit
Keyword(s):  
Experimental Studies ◽  
Theoretical Models ◽  
Pressure Vessels ◽  
Future Research ◽  
Spherical Vessel ◽  
Considerable Research ◽  
Wide Range ◽  
Set Up ◽  
Compressive Residual Stresses ◽  
Spherical Pressure

Autofrettage is a metal forming technique widely incorporated for strengthening the thick-walled cylindrical and spherical pressure vessels. The technique is based on the principle of initially subjecting the cylindrical or spherical vessel to partial plastic deformation and then unloading it; as a result of which compressive residual stresses are set up. On the basis of the type of the forming load, autofrettage can be classified into hydraulic, swage, explosive, thermal, and rotational. Considerable research studies have been carried out on autofrettage with a variety of theoretical models and experimental methods. This paper presents an extensive review of various types of autofrettage processes. A wide range of theoretical models and experimental studies are described. Optimization of an autofrettage process is also discussed. Based on the review, some challenging issues and key areas for future research are identified.

Influence of External Loads on Pressure-Carrying Capacity of Outlet Connections

1973 ◽  
Vol 95 (1) ◽  
pp. 113-120 ◽  
Author(s):  
S. Palusamy ◽  
N. C. Lind
Keyword(s):  
Carrying Capacity ◽  
Pressure Vessels ◽  
Plastic Limit ◽  
Rigid Plastic ◽  
Upper Bound Analysis ◽  
Theoretical Predictions ◽  
Plastic Limit Pressure ◽  
External Loads ◽  
Spherical Pressure ◽  
Bound Analysis

Six experiments were performed on mild steel models which confirm that the presence of external loads (axial force, coplanar moment, and shearing force) lowers the plastic limit pressure-carrying capacity of outlet connections from spherical pressure vessels. Excellent agreement is observed between experimental results and theoretical predictions obtained from lower-bound rigid plastic analysis. Similar agreement with upper bound analysis is obtained in the case of axisymmetric loading.

Three-Dimensional Stress Intensity Factors for Ring Cracks and Arrays of Coplanar Cracks Emanating From the Inner Surface of a Spherical Pressure Vessel

2013 ◽  
Author(s):  
M. Perl ◽  
V. Berenshtein
Keyword(s):  
Crack Depth ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Intensity Factors ◽  
Spherical Vessel ◽  
Wide Range ◽  
Inner Surface ◽  
Ring Crack ◽  
Spherical Pressure ◽  
Coplanar Cracks

Certain spherical pressure vessels are composed of two hemispheres joined together by a girth weld. These vessels are susceptible to multiple cracking along the weld resulting in one or more cracks developing from the inner surface of the vessel and creating either a ring (circumferential) crack, or an array of coplanar cracks on the equatorial-weld plane. In order to assess the fracture endurance and the fatigue life of such vessels it is necessary to evaluate the Stress Intensity Factors (SIF) distribution along the fronts of these cracks. However, to date, only two solutions for the SIF for an internal ring crack as well as two 3-D solutions for a single internal semi-elliptical crack prevailing in various spherical pressure vessels are available. In the present analysis, mode I SIF distributions for a wide range of ring, lunular, and crescentic cracks are evaluated. The 3-D analysis is performed, via the FE method employing singular elements along the crack front. SIFs for numerous ring cracks of different depths prevailing in thin, moderately thick, and thick spherical vessels are evaluated first. Subsequently, Three-dimensional Mode I SIF distributions along the crack fronts of a variety of lunular and crescentic crack array configurations are calculated for three spherical vessel geometries, with outer to inner radii ratios of R0/Ri = 1.01, 1.1, and 1.7 representing thin, moderately thick, and thick spherical vessels. SIFs are evaluated for arrays of density δ = 0 to 0.99; for a wide range of crack-depth to wall-thickness ratios, a/t, from 0.025 to 0.95; and for various lunular and crescentic cracks with ellipticities, i.e., the ratio of crack-depth to semi-length, a/c, from 0.2 to 1.5. The obtained results clearly indicate that the SIFs are considerably affected by the three-dimensionality of the problem and by the following parameters: the crack density of the array – δ, the relative crack depth – a/t, crack ellipticity – a/c, and the geometry of the spherical vessel – η. Furthermore, it is shown that in some cases the commonly accepted approach that the SIF for a ring crack of any given depth is the upper bound to the maximum SIF occurring in an array of coplanar cracks, of the same depth, is not universal.

Elastic-Plastic Analysis of Functionally Graded Spherical Pressure Vessels Using Strain Gradient Plasticity

2017 ◽  
Vol 09 (08) ◽  
pp. 1750118 ◽  
Author(s):  
Hassan Shokrollahi
Keyword(s):  
Internal Pressure ◽  
Strain Gradient ◽  
Plastic Region ◽  
Pressure Vessels ◽  
Functionally Graded ◽  
Strain Gradient Plasticity ◽  
Gradient Plasticity ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Spherical Pressure

In this paper, formulation of elastic-plastic analysis of functionally graded (FG) spherical pressure vessels under internal pressure based on strain gradient plasticity is presented. The material properties are assumed to vary in a power law manner in the radial direction. A linear hardening rule for the material behavior in the plastic region is assumed. After deriving the governing differential equations, a closed form solution is obtained. At the first step, the obtained results were validated against other available results in the literature. Then the effects of changing the inner radius from a few micro-meters to one meter, FG power index and strain gradient coefficient on stress and plastic region size are studied based on classical and strain gradient theories. Also, the effect of internal pressure on the size of plastic region is studied.

Elastic-Plastic Behaviour of Flush Nozzles in Spherical Pressure Vessels

1967 ◽  
Vol 9 (3) ◽  
pp. 182-189 ◽  
Author(s):  
P. V. Marcal ◽  
C. E. Turner
Keyword(s):  
Computer Program ◽  
Shell Theory ◽  
Pressure Vessels ◽  
Finite Width ◽  
Test Results ◽  
Shells Of Revolution ◽  
Elastic Plastic ◽  
Plastic Behaviour ◽  
Plastic Analysis ◽  
Spherical Pressure

A computer program for the elasto-plastic analysis of axially symmetrical shells of revolution has been modified to allow interaction loads at nozzle junctions to be distributed over bands of finite width, rather than the conventional concentrated lines of loading at the intersection of the shell centre-lines. Comparison with previously published test results for displacements, yield and collapse loads of flush nozzles shows that this modification greatly improves the predictions from those of conventional shell theory so that realistic behaviour of nozzle junctions can be forecast.

scholarly journals Thermo-Mechanical Autofrettage Process of Spherical Vessel

2020 ◽  
Vol 9 (3) ◽  
pp. 1109-1114
Keyword(s):  
Stress Distribution ◽  
Pressure Vessel ◽  
Mechanical Load ◽  
Pressure Vessels ◽  
Stress Distributions ◽  
Spherical Vessel ◽  
Yield Criteria ◽  
Elastic Plastic ◽  
Spherical Pressure ◽  
Plastic Stress

In this analysis results of Elastic-plastic stress distributions in a spherical pressure vessel with ThermoMechanical loads are discussed. Results of study are obtained with Finite element (FE) analysis. A quarter of pressure vessel is considered and modeled with all realistic details. In addition to presenting the stress distribution of the pressure vessel, in this work the effects thermo-Mechanical autofrettage on different limit strength for spherical pressure vessels are investigated. The effect of changing the load and various geometric parameters is investigated. Consequently, it can be observed that to be the significant differences between the present thermo-Mechanical autofrettage and earlier (Mechanical autofrettage and Thermal autofrettage) method of autofrettage for the predictions of Elastic-plastic stress distributions of spherical pressure vessels. Some realistic examples are considered and results are obtained for the whole vessel by applying thermal load and mechanical load. The actual material curve is used for loading, unloading and residual stress behavior of spherical pressure vessel. Kinematic hardening material is considered and effect of Bauschinger effect factors are studied with thermo-mechanical load. Equivalent Von -Mises yield criteria is used for yield criteria. Behavior of elastic-perfectly plastic is also studied and compared. Influence of Thermo-Mechanical autofrettage over stress distribution and load bearing capacity of spherical vessel is examined. The question of whether Thermo-mechanical autofrettage gives more favorable residual compressive stress distribution and therefore extension of pressure vessel life is investigated in this analysis.

Pressure Vessel Burst Directional Effects

2011 ◽  
Author(s):  
Jihui Geng ◽  
Quentin Baker ◽  
Kelly Thomas
Keyword(s):  
Pressure Vessel ◽  
High Explosive ◽  
Spherical Shape ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Chemical Processing ◽  
Spherical Vessel ◽  
Pressure Transducers ◽  
Blast Overpressure ◽  
Blast Effects

Pressure vessel burst (PVB) is a class of explosion for which there are hazards at virtually all chemical processing facilities. PVBs present both airblast and fragmentation hazards. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. The published blast curves were developed for spherical vessel bursts, whereas most pressure vessels in use in industry are cylindrical. Blast effects around a bursting cylindrical vessel are not uniform as with a spherical vessel. The blast to the side of a cylindrical vessel is stronger than off the ends, creating non-circular pressure contours. The directional effects diminish with distance as the expanding shock wave approaches a spherical shape. A correlation was developed in the 1970s to account for directional effects using high explosive test data, the best available resource at the time. Like all test programs, pressure transducers extended to limited distances from the explosive charge, yet the data are often extrapolated to a far greater distance. This paper presents the results of recent work on directional effects specific to bursting cylindrical pressure vessels and provides new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions. The results can be used to predict the airblast hazards from cylindrical PVBs over the range of standoff distances for which directional effects exist.

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