A Re-Autofrettage Procedure for Mitigation of Bauschinger Effect in Thick Cylinders

2004 ◽  
Vol 126 (4) ◽  
pp. 451-454 ◽  
Author(s):  
Anthony P. Parker
Keyword(s):  
Yield Strength ◽  
Residual Stresses ◽  
Fracture Resistance ◽  
Hoop Stress ◽  
Bauschinger Effect ◽  
Pressure Vessels ◽  
Fatigue Lifetime ◽  
Cyclic Pressure ◽  
Manufacturing Procedure ◽  
Tube Geometry

A manufacturing procedure for enhancing residual stresses and thereby improving fatigue lifetime and fracture resistance of pressure vessels is proposed. The procedure involves initial autofrettage; one or more “heat soak plus autofrettage” sequences and an optional final heat soak. Stresses are calculated numerically for traditional, single autofrettage and compared with those created by the new procedure. The loss of bore compressive hoop stress due to Bauschinger effect is predicted to be significantly reduced. Associated fatigue lifetime calculations indicate that life may be improved by a factor of between 2 and 30, depending upon tube geometry and the ratio of cyclic pressure to yield strength. Repeated overload plus heat soak cycles may also be of benefit in other engineering design scenarios.

A Re-Autofrettage Procedure for Mitigation of Bauschinger Effect in Thick Cylinders

2005 ◽  
Author(s):  
Anthony P. Parker
Keyword(s):  
Yield Strength ◽  
Residual Stresses ◽  
Fracture Resistance ◽  
Hoop Stress ◽  
Bauschinger Effect ◽  
Pressure Vessels ◽  
Fatigue Lifetime ◽  
Cyclic Pressure ◽  
Manufacturing Procedure ◽  
Tube Geometry

A manufacturing procedure for enhancing residual stresses and thereby improving fatigue lifetime and fracture resistance of pressure vessels is proposed. The procedure involves initial autofrettage; one or more ‘heat soak plus autofrettage’ sequences and an optional final heat soak. Stresses are calculated numerically for traditional, single autofrettage and compared with those created by the new procedure. The loss of bore compressive hoop stress due to Bauschinger effect is predicted to be significantly reduced. Associated fatigue lifetime calculations indicate that life may be improved by a factor of between 2 and 30, depending upon tube geometry and the ratio of cyclic pressure to yield strength. Repeated overload plus heat soak cycles may also be of benefit in other engineering design scenarios.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

Hydraulic Versus Swage Autofrettage and Implications of the Bauschinger Effect

2003 ◽  
Vol 125 (3) ◽  
pp. 309-314 ◽  
Author(s):  
A. P. Parker ◽  
G. P. O’Hara ◽  
J. H. Underwood
Keyword(s):  
Residual Stresses ◽  
Experimental Evidence ◽  
Hybrid Method ◽  
Bauschinger Effect ◽  
Pressure Level ◽  
Opening Angle ◽  
Fatigue Lifetime ◽  
Analysis Of Results

A hybrid method is presented which permits calculation of residual stresses in a swage autofrettaged tube including Bauschinger effect. The results are generally supported by three types of available experimental evidence by comparing “equivalent” swage and hydraulic autofrettage tubes having the same level of overstrain. Radial slitting of the swaged tube is predicted to show a greater opening angle than its hydraulic equivalent. Fatigue lifetime of the swaged tube is predicted to be significantly higher than the hydraulic case. Re-pressurization of the equivalent tubes is predicted to produce initial re-yielding at the same pressure in both cases. Analysis of results shows that permanent strains in the swaged tube are expected to appear at a pressure level below that for the hydraulic tube.

Finite Element Analysis of Residual Stresses in Threaded End Closures

1991 ◽  
Vol 113 (3) ◽  
pp. 398-401 ◽  
Author(s):  
A. Chaaban ◽  
U. Muzzo
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Bauschinger Effect ◽  
High Stress ◽  
Empirical Method ◽  
Pressure Vessels ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Proof Testing ◽  
Pressure Cycle

Due to the high stress concentration at the root of the first active thread in threaded end closures of high pressure vessels, yielding may occur in this region during the application of the first pressure cycle or proof testing. This overstraining introduces residual stresses that influence the fatigue performance of the vessel. This paper presents a parametric analysis of threaded end closures using elastic and elasto-plastic finite element solutions. The results are used to discuss the influence of these residuals on the estimated fatigue life when the vessel is subjected to repeated internal pressure. A simple empirical method to allow for the Bauschinger effect of the material is also proposed.

Autofrettaged Cylindrical Vessels and Bauschinger Effect: An Analytical Frame for Evaluating Residual Stress Distributions

2001 ◽  
Vol 124 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Paolo Livieri ◽  
Paolo Lazzarin
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Explicit Form ◽  
Analytical Solutions ◽  
Bauschinger Effect ◽  
Superposition Principle ◽  
Pressure Vessels ◽  
Material Behavior ◽  
Stress Distributions ◽  
Hardening Law

The paper reports analytical solutions valid for residual stresses in cylindrical pressure vessels subjected to autofrettage. The material behavior is thought of as obeying a generic monotonic σ−ε curve and exhibiting the Bauschinger effect during the unloading phase. Under linear and power-hardening conditions, the solution is given in an explicit form. The circumstances under which it is possible to apply the superposition principle also in the presence of localized plasticity are clearly identified. When possible, the final stresses can be obtained by using in an appropriate manner the stress expressions related to the loading phase. Finally, the influence on residual stresses, both of the hardening law and of the shape of the unloading σ−ε curve, is discussed.

Bauschinger Effect Design Procedures for Autofrettaged Tubes Including Material Removal and Sachs’ Method

1999 ◽  
Vol 121 (4) ◽  
pp. 430-437 ◽  
Author(s):  
A. P. Parker ◽  
J. H. Underwood ◽  
D. P. Kendall
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Material Removal ◽  
Bauschinger Effect ◽  
Numerical Procedure ◽  
Pressure Vessels ◽  
Material Behavior ◽  
Stress Fields ◽  
Complete Analysis ◽  
Elastic Plastic

Autofrettage is used to introduce advantageous residual stresses into pressure vessels and to enhance their fatigue lifetimes. The Bauschinger effect serves to reduce the yield strength in compression as a result of prior tensile plastic overload and can produce lower compressive residual hoop stresses near the bore than are predicted by “ideal” autofrettage solutions (elastic/perfectly plastic without Bauschinger effect). A complete analysis procedure is presented which encompasses representation of elastic-plastic uniaxial loading material behavior and of reverse-loading material behavior as a function of plastic strain during loading. Such data are then combined with some yield criterion to accurately predict elastic-plastic residual stress fields within an autofrettaged thick cylinder. Pressure for subsequent reyielding of the tube is calculated. The numerical procedure is further used to determine residual stress fields after removal of material from inside diameter (i.d.) and/or outside diameter (o.d.), including the effects of any further plasticity. A specific material removal sequence is recommended. It is shown that Sachs’ experimental method, which involves removing material from the i.d., may very significantly overestimate autofrettage residual stresses near the bore. Stress ranges and stress intensity factors for cracks within such stress fields are calculated together with the associated fatigue lifetimes as such cracks propagate under cyclic pressurization. The loss of fatigue lifetime resulting from the Bauschinger effect is shown to be extremely significant.

Residual Stresses and Lifetimes of Tubes Subjected to Shrink Fit Prior to Autofrettage

2003 ◽  
Vol 125 (3) ◽  
pp. 282-286 ◽  
Author(s):  
Anthony P. Parker ◽  
David P. Kendall
Keyword(s):  
Material Removal ◽  
Hoop Stress ◽  
Bauschinger Effect ◽  
External Pressure ◽  
Fatigue Lifetime ◽  
Shrink Fitting ◽  
Plain Tube ◽  
Specific Geometry ◽  
Shrink Fit ◽  
Summary Data

There is increasing interest in the use of compound cylinders that combine shrink fit and autofrettage, taking account of Bauschinger effect. Previous work has analyzed material removal from a plain, autofrettaged cylinder and the application of an external pressure or shrink to a previously autofrettaged plain tube. In this paper a different design philosophy is examined, namely the shrink fitting of two tubes prior to autofrettage. Such a process is shown to be beneficial in inhibiting loss of near-bore compressive residual hoop stress due to Bauschinger effect and thereby increasing calculated fatigue lifetime. These effects are described in detail for a specific geometry, and summary data suitable for use by designers are presented for a large range of configurations.

The Influence of Bauschinger Effect on the Stability of Residual Stresses in Autofrettaged High Pressure Tubes

2018 ◽  
Author(s):  
Hermann Maderbacher ◽  
Manfred Pölzl
Keyword(s):  
High Pressure ◽  
Yield Strength ◽  
Residual Stresses ◽  
Bauschinger Effect ◽  
High Strength ◽  
Quantitative Character ◽  
Compressive Stresses ◽  
Pressure Tubes ◽  
The Stability ◽  
Fatigue Endurance

In the petrochemical industry, in particular for LDPE (Low-Density-Poly-Ethylene) and EVA-processes (Ethylene-Vinyl-Acetate), high strength quenched and tempered steels are used for seamless tubes subjected to ultra-high pressure. The high safety demands at pressures up to 4000bar require besides high fracture toughness and static strength also high fatigue endurance. The fatigue performance can be significantly impoved by the use of autofrettage. In this case residual compressive stresses are generated with simultaneous material work-hardening by targeted plastic deformation in the area of the inner wall of the tube. The positive effect of autofrettage mainly depends on the level of residual compressive stress. The maximum magnitude of these compressive stresses is always smaller than the yield strength of the material in tensile direction, even if the autofrettage level is increased. The amount by what this stress is smaller than the material yield strength depends on the characteristic of the so-called Bauschinger-effect, or on the kinematic hardening behavior of the material. The target of the present work is to investigate the stability of residual stresses from autofrettage and their influence on the service life of high pressure tubes under cyclic internal pressure loading. For this purpose, in the first part, the quantitative character of the Bauschinger effect for a high strength quenched and tempered steel is determined by means of specimen tests. In the next step, the influence of the Bauschinger-effect on the resulting residual compressive stresses in a tube-like specimen is investigated. Autofrettage tests are performed on these specimens equipped with strain gages. In the second part of the work, the results of fatigue tests of the mentioned tube-like specimen are compared with the calculated fatigue endurance according to Division 3, Section VIII of the ASME Pressure Vessel Code (BPVC). Calculations are performed, which once use the residual stress correction for reverse yielding according to ASME Code and once consider the actual residual stresses from tests and simulation.

Prediction of Residual Stress Distribution for RPV CRDM Penetration Nozzles

2012 ◽  
Author(s):  
Hong-Yeol Bae ◽  
Yun-Jae Kim ◽  
Ju-Hee Kim ◽  
Sung-Ho Lee ◽  
Kyoungsoo Lee
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Alloy 600 ◽  
Tube Radius ◽  
Pressurized Water ◽  
Tube Geometry ◽  
Reactor Pressure

In nuclear power plants, RPV (Reactor Pressure Vessel) upper head CRDM (Control Rod Drive Mechanism) penetration tubes has been fabricated J-groove weld geometry. Recently, the incidences of cracking in Alloy 600 CRDM tubes and their associated welds have increased significantly. The cracking mechanism has been attributed to PWSCC (Pressurized Water Stress Corrosion Cracking) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. Weld induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operating. In this point, we have been conducting detailed welding simulation analyses for Korea Nuclear Reactor Pressure Vessel to predict the magnitude of weld residual stresses in penetration tubes. In the present work, the FE (Finite Element) simulations were conducted to investigate the effects of tube geometry (location and ro/t) and material properties on the residual stresses in the J-groove weld for a different location of CRDM tubes. The variables of tube location included three (center-hole, intermediate and steepest side hill tube) inclination angles (Ψ). And this comparison was performed for different tube geometry (ro/t = 2, 3, 4), different yield strength (σo) of tube. In CRDM tube, when increases in tube inclination angle (Ψ), axial residual stress are gradually increased, but hoop residual stresses are decreased at the nearby weld root. In effect of tube radius and thickness, when the thickness of CRDM tubes increases the residual stresses are gradually decreased at the inner surface of tube. And there is no effect of CRDM tube radius (ro). In effect of plastic properties of Alloy 600 material in CRDM, when yield strength of the tube increases the axial residual stresses decreases but hoop residual stress increases.

Influence and Modeling of Residual Stresses in Thick Walled Pressure Vessels With Through Holes

2012 ◽  
Author(s):  
E. Troiano ◽  
A. P. Parker ◽  
J. H. Izzo
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Bauschinger Effect ◽  
Pressure Vessels ◽  
Paris Law ◽  
Lower Confidence ◽  
Lower Confidence Bound ◽  
Log Normal ◽  
Log Normal Distribution ◽  
Compressive Residual Stresses

Thick walled pressure vessels are often autofrettaged in order to impart favorable near bore compressive residual stresses which can significantly increase the life of the vessels. These stresses can be imparted via a thermal shrink process in which there is no loss of residual stresses due to the Bauschinger Effect, or more economically with a mechanical swage or hydraulic overload process in which the Bauschinger Effect is present. In some cases these vessels have holes bored through the wall in order to take advantage of the escaping gasses for actuation of external peripherals associated with the vessel. These through holes, which can be angled or perpendicular to the centerline of the pressure vessel can significantly reduce the fatigue life of the vessel depending on the wall ratio of the vessel as well as the, angle of inclination of the hole to the centerline of the vessel. This study utilizes the classic stress based Paris Law fatigue life approach which takes into account the residual stresses as a function of radial location to assess the life of the vessel in the region of both configurations of through holes. It quantifies the concentration of stresses associated with the perpendicular and angled through wall holes, and the amount of pressure that actually enters the hole. The analysis is employed to ensure that the life within these through holes meets or exceeds the safe life of the vessel without holes which has been determined by assuming a log normal distribution from of a sample size of six with the 90% lower confidence bound on the 0.1th percentile of the population.

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