Localized Autofrettage as a Design Tool for the Fatigue Improvement of Cross-Bored Cylinders

1998 ◽  
Vol 120 (4) ◽  
pp. 393-397 ◽  
Author(s):  
A. E. Segall ◽  
C. Tricou ◽  
M. Evanko ◽  
J. C. Conway
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
High Stress ◽  
Circular Crack ◽  
Design Tool ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Significant Extension ◽  
The Cross ◽  
Machining Operations

An investigation was launched into the feasibility of improving the fatigue life of thick-walled cylinders with cross-bores by using a localized autofrettage technique. This technique utilized the high stress concentration at the cross-bore to induce localized residual stresses using relatively low internal pressures. An elastic-plastic finite-element analysis indicated that the resulting residual stresses in the vicinity of the cross-bore were predominately compressive and not sufficient in magnitude to induce reverse plasticity. When the resulting residual stresses were used with an elastic fracture-mechanics assessment of a quarter-circular crack at the intersection of the cylinder and cross-bore inner diameter, a significant extension of fatigue life was shown to be possible. In addition to prolonging the useful life of the cylinder, the localized residual stresses were shown to be possible at pressures below the yield threshold for the thick-walled cylinder. Thus, reverse plasticity, permanent deformations, and the need for post-autofrettage machining operations that could inadvertently lessen the beneficial results of a traditional autofrettage were avoided.

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.

Development of Design Curve for Sweepolet Subjected to Acoustic Induced Vibration

2016 ◽  
Author(s):  
Yuqing Liu ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Ismat Eljaouhari ◽  
Ajay Prakash
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Fatigue Failure ◽  
High Stress ◽  
Peak Stress ◽  
Acoustic Energy ◽  
Piping System ◽  
Element Analysis ◽  
Design Curve ◽  
High Stress Concentration

High acoustic energy has the potential to cause severe Acoustic Induced Vibration (AIV) that leads to fatigue failure at high stress concentration regions such as fittings in a piping system. Sweepolet fittings have been extensively used as mitigation to counteract the risk of fatigue failure caused by AIV. The advantages of a sweepolet are its integrally reinforced contoured body and low stress concentration. However, there are inconsistencies in published standards and regarding the design limits for sweepolet subjected to AIV. In this paper, Finite Element Analysis is conducted to simulate high frequency pipe shell wall vibration caused by acoustic energy inside the pipe. Peak stress and the associated minimum fatigue life are calculated for sweepolet and sockolet under the same acoustic excitation. By comparing the stress level to that of a sockolet whose design limit to AIV had been published, the design curve and fatigue life equation for sweepolet are developed.

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

Design of Oil Injection Quills for Hypercompressors Cylinders

2011 ◽  
Author(s):  
Guido Volterrani ◽  
Carmelo Maggi ◽  
Marco Manetti
Keyword(s):  
Finite Element Analysis ◽  
Fracture Mechanics ◽  
Residual Stresses ◽  
High Stress ◽  
Element Analysis ◽  
Threaded Connection ◽  
Advanced Technologies ◽  
Inner Diameter ◽  
Oil Injection ◽  
Autofrettage Pressure

Fatigue impacts the life of all components subject to alternating loads, including lube oil injection quills. These occurrences are more frequent if a defect (initial flaw) nucleates in the component due to corrosion, high stress, machining imperfections, etc. The design of components undergoing high fluctuating pressures needs advanced technologies, like autofrettage, and design methods, like FEM or fracture mechanics. This component can be identified as a cylinder with different outside diameters and notches deriving from the geometry variation and threaded connection. The inner diameter is the most stressed area and will require an adequate stress analysis. A sensitivity analysis of the autofrettage pressure can be performed to identify the most appropriate residual stresses on the inner diameter and to obtain a threshold defect larger than the minimum detectable. Fracture mechanics allows the analysis the propagation of an initial defect with materials having different properties and considering different autofrettage pressures. Finite Element Analysis is used to validate the residual stresses predicted by calculation for each autofrettage pressure. An optimized solution of the hypercompressor injection quill can be designed.

scholarly journals Validation of Welding Simulations Using Thermal Strains Measured with DIC

2011 ◽  
Vol 70 ◽  
pp. 129-134 ◽  
Author(s):  
Maarten De Strycker ◽  
Pascal Lava ◽  
Wim Van Paepegem ◽  
Luc Schueremans ◽  
Dimitri Debruyne
Keyword(s):  
Residual Stresses ◽  
Cross Section ◽  
Circular Cross Section ◽  
Welding Process ◽  
Weld Bead ◽  
Image Correlation ◽  
Steel Tubes ◽  
Element Analysis ◽  
Strain Evolution ◽  
The Cross

Residual stresses can affect the performance of steel tubes in many ways and as a result their magnitude and distribution is of particular interest to many applications. Residual stresses in cold-rolled steel tubes mainly originate from the rolling of a flat plate into a circular cross section (involving plastic deformations) and the weld bead that closes the cross section (involving non-uniform heating and cooling). Focus in this contribution is on the longitudinal weld bead that closes the cross section. To reveal the residual stresses in the tubes under consideration, a finite element analysis (FEA) of the welding step in the production process is made. The FEA of the welding process is validated with the temperature evolution of the thermal simulation and the strain evolution for the mechanical part of the analysis. Several methods for measuring the strain evolution are available and in this contribution it is investigated if the Digital Image Correlation (DIC) technique can record the strain evolution during welding. It is shown that the strain evolution obtained with DIC is in agreement with that found by electrical resistance strain gauges. The results of these experimental measuring methods are compared with numerical results from a FEA of the welding process.

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.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

The Weight Reduction Design of the Regenerator CA Nozzle in FCC Unit Using the FEA

2013 ◽  
Vol 658 ◽  
pp. 345-349
Author(s):  
Il Taek Lee ◽  
Hyun Sik Kim ◽  
Namr Young Choi ◽  
Dong Pyo Hong
Keyword(s):  
Weight Reduction ◽  
Catalytic Cracking ◽  
Equivalent Stress ◽  
High Stress ◽  
Fluid Catalytic Cracking ◽  
Code Design ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Unit Energy ◽  
Asme Code

Recently, due to the rising of oil prices, interest in FCC Unit (Fluid Catalytic Cracking Unit) energy recycling is increasing. FCC Unit (Fluid Catalytic Cracking Unit) is a mechanical used to convert bunker C oil into high quality gasoline. Pressure vessel of FCC Unit is that refining the crude oil when is operating in high-temperature and high-pressure environment. So it needs analysis of structure carefully. In this paper, FEA (Finite element analysis) of the FCC unit was performed to evaluate its structural stability and weight reduction. The equivalent stress of the FCC unit was investigated and compared against the ASME code design specifications. The area of high stress concentration with maximum stress higher than the prescribed value was analyzed locally to carefully evaluate the stress. Finally, we were reduces the thickness of the CA nozzle in FCC unit, and it was satisfied structural stress.

Residual Stress Evaluation and Its Effects on the Fatigue Life of an Autofrettaged Tube

2006 ◽  
Vol 321-323 ◽  
pp. 699-702 ◽  
Author(s):  
Seung Kee Koh
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Crack Growth ◽  
Bauschinger Effect ◽  
Theoretical Calculations ◽  
Superposition Principle ◽  
Tube Steel ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
Element Analysis

The theoretical residual stresses in the autofrettaged tube were calculated, considering Bauschinger effect caused by the reverse yielding while removing autofrettage pressure. Actual residual stresses were measured by using X-ray diffraction analysis, and compared with the theoretical calculations. From the tension-compression tests, however, the tube steel showed a significant Bauschinger effect, depending on the plastic strain prior to unloading. Fatigue crack growth life of the tube was evaluated by integrating the crack growth rate equation. Stress intensity factor of an inside crack at the tube due to pressure and residual stresses was determined from finite element analysis and superposition principle. Compared to the unautofrettaged tube, the extended fatigue life of the autofrettaged thick-walled tube was obtained depending on the autofrettage level and the Bauschinger effect.

Effect of Clearance on Rotary Rock Bit Journal Bearing Contact Stress

1986 ◽  
Vol 108 (1) ◽  
pp. 1-7 ◽  
Author(s):  
K. M. Marshek ◽  
H. H. Chen
Keyword(s):  
Numerical Method ◽  
Large Scale ◽  
High Stress ◽  
Design Tool ◽  
Linear System Of Equations ◽  
High Stress Concentration ◽  
Pressure Area ◽  
Bit Life ◽  
Rock Bit ◽  
Conformal Contact

This paper presents a numerical method for analyzing the effect of clearance on closely conforming rotary rock bit journal bearings. The modified Boussinesq point-force displacement influence function and the modified profile function are introduced in conjunction with the discretization of the integral equation. Automatic mesh generation is employed to redefine a new pressure area boundary and therefore round-off errors normally found while solving a large-scale linear system of equations can be avoided. The numerical method has been implemented in a computer program and has been applied to the problems of misaligned and perfectly aligned conformal contact. There is a close agreement with the Persson’s analytical solution at the center of the aligned bearing length. However, owing to a high stress concentration at the bearing edge, the edge pressure distribution will differ significantly from the Persson’s plane stress model. The conformal contact will have a comparatively higher peak pressure and lower contact-angle than the Hertzian line contact prediction. The results of the analysis provides a design tool for improving drill bit life.

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