Tensile Plastic Instability of Axisymmetric Pressure Vessels

1998 ◽  
Vol 120 (1) ◽  
pp. 6-11 ◽  
Author(s):  
D. P. Updike ◽  
A. Kalnins
Keyword(s):  
Pressure Vessel ◽  
Detrimental Effect ◽  
Cylindrical Shells ◽  
Plastic Instability ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Test Results ◽  
Strength Reduction Factor ◽  
Burst Data ◽  
Longitudinal Welds

This paper examines the calculated pressure at a tensile plastic instability of a pressure vessel and its relationship to burst test results. It is proposed that the instability pressure be accepted as an upper bound to the pressure at which a vessel bursts, and that a strength reduction factor be used to predict the burst. The paper also presents a suitable mathematical model for the calculation of the instability pressures for thin-walled axisymmetric vessels. The proposition is tested by applying the model to a pressurized diaphragm, four cylindrical shells, and two torispherical heads, for which experimental burst data are available. It is found that the ratio of the test burst pressure to the calculated pressure at the tensile plastic instability, expressed in percent, ranges from 71 to 96 percent. The highest ratio occurs for a pressurized diaphragm with no significant defects. The lowest ratios occur for cylindrical shells with longitudinal welds, suggesting that the presence of the welds had a detrimental effect on the burst strength. These results may be useful when designing a pressure vessel with respect to its ultimate strength.

Design of Pressure Vessels for Low-Cycle Fatigue

1962 ◽  
Vol 84 (3) ◽  
pp. 389-399 ◽  
Author(s):  
B. F. Langer
Keyword(s):  
Fatigue Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
The Mean ◽  
Fatigue Evaluation

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.

Elastic-Plastic Stress Analysis of Pressure Vessels

2012 ◽  
Author(s):  
Yang-chun Deng ◽  
Gang Chen
Keyword(s):  
Internal Pressure ◽  
Stress Analysis ◽  
Strain Hardening ◽  
Pressure Vessel ◽  
Plastic Instability ◽  
Pressure Vessels ◽  
Structural Deformation ◽  
Elastic Plastic ◽  
Thin Walled ◽  
Plastic Stress

To save material, the safety factor of pressure vessel design standards is gradually decreased from 5.0 to 2.4 in ASME Boiler and Pressure Vessel Codes. So the design methods of pressure vessel should be more rationalized. Considering effects of material strain hardening and non-linear structural deformation, the elastic-plastic stress analysis is the most suitable for pressure vessels design at present. This paper is based on elastic-plastic theory and considers material strain hardening and structural deformation effects. Elastic-plastic stress analyses of pressure vessels are summarized. Firstly, expressions of load and structural deformation relationship were introduced for thin-walled cylindrical and spherical vessels under internal pressure. Secondly, the plastic instability for thin-walled cylindrical and spherical vessels under internal pressure were analysed. Thirdly, to prevent pressure vessels from local failure, the ductile fracture strain of materials was discussed.

Paris Fatigue Life Modeling of Pressure Vessel Service Simulation Tests

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
John H. Underwood ◽  
John J. Keating ◽  
Edward Troiano ◽  
Gregory N. Vigilante
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Base Alloy ◽  
Pressure Vessels ◽  
Full Scale ◽  
Test Results ◽  
X Ray Diffraction ◽  
Life Model ◽  
Nickel Base

Results from four groups of full-scale pressure vessel service simulation tests are described and analyzed using Paris fatigue life modeling. The objective is to determine how the vessel and initial crack configurations and applied and residual stresses control the as-tested fatigue life of the vessel. The tube inner radii are in the 40–80 mm range; wall thickness varies from 6 to 80 mm; materials are ASTM A723 pressure vessel steel and IN718 nickel-base alloy; applied internal pressure varies from 90 to 700 MPa. The Paris constant, C, and exponent, m, that describe the fatigue crack propagation rate versus stress intensity factor range for the various vessel materials, were measured as part of the investigation. Extensive, previously published fatigue life results from baseline A723 pressure vessels with well characterized autofrettage residual stresses and C and m values are used to demonstrate that a Paris fatigue life model gives a good description of the measured life. The same model is then used to determine the variables with predominant control over life in three types of pressure vessel for which less information and tests results are available. A design life for pressure vessels is calculated for a specified very low probability of fatigue failure using the log(N)-normal distribution statistics often used for fatigue of structures. The results of the work showed: (i) X-ray diffraction measurements of through-wall autofrettage residual stresses are in excellent agreement with prior neutron diffraction measurements from a baseline autofrettaged A723 pressure vessel; these verified autofrettage residual stresses then provide critical input to the baseline Paris life modeling; (ii) comparison of the various full-scale fatigue test results with results from the Paris fatigue life model shows close agreement when autofrettage residual stresses are incorporated into models; (iii) model results for A723 steel vessels with yield strength reduced from the initial 1400 MPa value and degree of autofrettage increased from the initial 40% value indicates a significantly improved resistance to brittle failure with no loss of fatigue life; (iv] comparison of model fatigue life results for IN718 nickel-base alloy vessels with their full-scale test results is improved when near-bore residual stresses measured by X-ray diffraction are included in the model calculations.

Assessment of the Influence of Central and Lateral Feed Injection Systems on the Remaining Life of Coke Drums

2017 ◽  
Author(s):  
Gabriel A. Vivas ◽  
Armando J. Moret ◽  
Roberto E. Bello ◽  
Luis M. Melian ◽  
Jose R. Carmona
Keyword(s):  
Axial Stress ◽  
New Technology ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Strain Gauges ◽  
Feeding System ◽  
Remaining Life ◽  
Thermal Cycles ◽  
Strength Reduction Factor ◽  
Cyclic Operation

Coke drums are thin walled pressure vessels that are subjected to severe thermal cyclic operation, which causes low cycle thermal fatigue. Because of that, they are considered as the vessels with the highest failure rate in a refinery according to API survey conducted in1996. In the last decade, a new technology in bottom blocking valve systems for coke drums has been introduced which induces a change in the traditional center feeding system to lateral feeding system; basically with the main goal to increase operators safety. Taking into account the mechanical integrity and remaining life of coke drums, the central feeding system has traditionally been considered as the best option, however; this hypothesis has not been fully demonstrated. Two central fed coke drums were heavily instrumented with strain gauges and thermocouples in bulged zones identified after performing a bulge severity analysis (BSA). Thermocouple arrays and several strain gauges were installed in eight specific locations of the drums. This instrumentation was installed three months before installing bottom blocking valves in the drums, and consequently, changing their feeding system to lateral. A statistical analysis was performed using 40 thermal cycles of the two coke drums with central feeding system and 120 thermal cycles of the same coke drums after changing to lateral feeding system. The usage factor was estimated for each cycle considering the axial stress amplitude and a fatigue strength reduction factor of 2 for the ASME S-N design curve Fig. KD-320.2. Finally, the remaining life was estimated for each instrumented zone taking into consideration that the coke drums would have the same cumulative damage in the future. The results show that average remaining life at instrumented zones (considering all locations) of one coke drum increased when the lateral feeding system was introduced; while the average remaining life at instrumented zones for the second coke drum remained practically unchanged after the lateral feeding system was put in to service.

Stiffness Reduction for Flat Plate Systems due to Cracking

2007 ◽  
Vol 348-349 ◽  
pp. 781-784
Author(s):  
Young Mi Park ◽  
Sang Whan Han ◽  
Ja Ock Cho
Keyword(s):  
Flat Plate ◽  
Beam Width ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Deformation Curve ◽  
Test Results ◽  
Lateral Loads ◽  
Strength Reduction Factor ◽  
Stiffness Reduction ◽  
Current Design

The purpose of this study is to propose a stiffness reduction factor for flat plate systems under lateral loads. According to current design provisions, slab stiffness under lateral loads should account for stiffness reduction due to the effects of cracks. Several researchers have conducted for evaluating the stiffness reduction in flat plate slab systems under lateral loads. However, no research is found for establishing strength reduction factor with respect to the level of applied moment. This study attempted to propose equations for calculating stiffness reduction factor with respect to the level of applied moment (Ma) represented by the ratio of Ma to the cracking moment of the slab (Mcr). For this purpose, test results of 20 interior slab-column connections were collected. For each specimen, stiffness reduction was measured with respect to Ma/Mcr. To verify the proposed factor, this study conducted the experimental test of interior connection under quasistatic cyclic loading, from which load-deformation curve was obtained. The curve was compared with that obtained from the effective beam width method with the proposed stiffness reduction factor. It shows that the proposed factor accurately predicts stiffness reduction in flat plate systems.

The Control Technology of Pressure Vessel In-Service Quality Inspection

2013 ◽  
Vol 437 ◽  
pp. 700-704
Author(s):  
Xue Rong Ma
Keyword(s):  
Service Quality ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Control Technology ◽  
Quality Inspection ◽  
Test Results ◽  
Optimization Scheme ◽  
Test Tank ◽  
Comprehensive Test ◽  
The Cost

Aiming at the comprehensive inspection of pressure vessels in service, put forward the original test results as the basis, realize the optimization scheme of comprehensive test, the possibility is to a minimum missing caused in pressure vessel that the crack (defects) are greater than the critical, so as to ensure the safety of the structure at the same time, the workload and the cost is reduced to the lowest. Through the test tank group, this method is proved to be feasible.

The Case for MACA: The Optimization of Corrosion Allowance

2016 ◽  
Author(s):  
Jaan Taagepera
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Pressure Vessel ◽  
Cylindrical Shells ◽  
Pressure Vessels ◽  
Degradation Mechanisms ◽  
Working Pressure ◽  
Exothermic Reactions ◽  
Allowable Compressive Stress ◽  
Original Edition

Engineers are taught to optimize. In the case of pressure vessel design, one means of optimizing the steel which is used is to increase the rated pressure capacity of the vessel beyond the design needs. This optimized pressure is formally known by the term MAWP or Maximum Allowable Working Pressure. Of historical interest, this concept has existed for over 100 years, with the MAWP formula for cylindrical shells being tracable back to the original edition of the Boiler Code. However, other variables in vessel design can also be optimized. In addition to pressure, consideration can be given to temperature or corrosion allowance. Increasing the temperature has the effect of reducing the basic allowable tensile stress as well as the allowable compressive stress and flange ratings. In the case of some specialty vessels such as reactors with exothermic reactions adding a few degrees to the design temperature may be very beneficial. But virtually all vessels degrade in some manner, most often corrosion but sometimes via erosion or other degradation mechanisms. Significant amounts of time and effort are spent with unnecessary shutdowns, repairs, and / or fitness for service (FFS) evaluations all of which might have been avoided or deferred for years had the vessel originally been optimized for corrosion allowance. The term Maximum Allowable Corrosion Allowance or MACA is used to describe this approach. This paper presents some arguments in favor of optimizing the corrosion allowance of pressure vessels, using a MACA based optimization for the design of new vessels rather than a pressure optimization or MAWP philosophy.

Finite Element Investigation of Bauschinger Effect in High-Strength A723 Pressure Vessel Steel

2006 ◽  
Vol 128 (2) ◽  
pp. 185-189 ◽  
Author(s):  
Edward Troiano ◽  
John H. Underwood ◽  
Anthony P. Parker
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Bauschinger Effect ◽  
High Strength ◽  
Pressure Vessels ◽  
Pressure Vessel Steel ◽  
Test Results ◽  
Vessel Steel ◽  
Reverse Yielding ◽  
The Difference

The Bauschinger effect has been evaluated in high-strength pressure vessels. A simple initial test suggested that a biaxial Bauschinger effect was present and that it was different from previously published uniaxial Bauschinger results. The difference was believed to be significant, so further investigation was undertaken. Several full-size A723 steel gun sections were heavily overstrained and subjected to slit tests in order to measure opening angles and displacements. These geometries were then modeled with finite element (FE) analysis using both ideal autofrettage stresses and Bauschinger modified stresses, which were based on previously published uniaxial Bauschinger test results. Because techniques available for predicting reverse yielding for overstrained pressure vessels were limited, a simple methodology for predicting the yield surface upon reverse yielding from a series of uniaxial Bauschinger test data was developed and is presented. This methodology, when used in the FE predictions, compares favorably with analytical predictions made previously. Comparisons of slit-opening results measured from pressure vessel sections with FE calculations using uniaxial Bauschinger data are made. The opening displacements comparison between the uniaxial predictions and those measured from the heavily overstrained sections with biaxial stresses are so subtle (<1mm) that the tests appear to be inconclusive.

Numerical Study on Buckling Strength of Vertical Vessel Skirts With Access Opening

2018 ◽  
Author(s):  
Takuma Takahashi ◽  
Toshikazu Miyashita ◽  
Shunji Kataoka ◽  
Yoshiaki Uno ◽  
Takuya Sato
Keyword(s):  
Cylindrical Shell ◽  
Numerical Study ◽  
Design Method ◽  
Cylindrical Shells ◽  
Reduction Factor ◽  
Finite Element Analyses ◽  
Strength Reduction Factor ◽  
Design Factor ◽  
Buckling Strength ◽  
Present Design

Vertical vessel skirts generally have access openings. The evaluation for buckling of vertical vessel skirts shall consider the effect of the opening. On the other hand, evaluation methods of buckling in present design codes are established based on the theory for a cylindrical shell without any opening. There is no method to assess effects of openings on buckling strength. The purpose of this paper is to establish a new design method of vertical vessel skirts with access openings, by evaluating the effects of openings on buckling strength of cylindrical shells. The finite element analyses of buckling strength for cylindrical shells with and without openings were conducted by an eigenvalue analysis. A study was conducted on the effects of geometric parameters, such as skirt diameter, thickness, opening shape and application of reinforcements. The effects of openings on buckling strength were revealed by comparing the analysis results. Based on these results, the new design factor, Buckling Strength Reduction Factor (BSRF), was proposed for evaluating buckling strength. BSRF is the ratio of buckling strength of a cylindrical shell with an opening to that of a cylindrical shell without an opening. BSRF provides a practical simplified method to evaluate how an access opening affects skirt buckling strength.

Analysis of Burst Pressure of Damaged Tubes Using Plastic Instability Analysis

2007 ◽  
Vol 120 ◽  
pp. 187-192
Author(s):  
Kyu In Shin ◽  
Jai Hak Park
Keyword(s):  
Steam Generator ◽  
Plastic Instability ◽  
Reduction Factor ◽  
Burst Pressure ◽  
The Finite Element Method ◽  
Strength Reduction Factor ◽  
Experiment Data ◽  
Instability Analysis ◽  
Steam Generator Tubes ◽  
Good Agreement

Generally rupture of steam generator tubes occurs accompanying significant plastic deformation. In this study, the burst pressure of a damaged steam generator tube is calculated from the plastic instability analysis using the finite element method. Two wear types, flat and circumferential types are considered. An equation for the burst pressure is proposed by using the concept of strength reduction factor and the Svensson equation. The analysis results are also compared with the experiment data from published references and they show a good agreement with the experiment data.

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