Effect of length in rotational autofrettage of long cylinders with free ends

2021 ◽  
pp. 095440622110342
Author(s):  
Rajkumar Shufen ◽  
Uday Shanker Dixit
Keyword(s):  
Plastic Deformation ◽  
Residual Stresses ◽  
Axial Stress ◽  
Fem Analysis ◽  
Longitudinal Axis ◽  
Pressure Vessels ◽  
Stress Changes ◽  
Different Types ◽  
Compressive Residual Stresses ◽  
Spherical Pressure

Thick-walled cylindrical and spherical pressure vessels are often subjected to autofrettage, a process in which the vessel is loaded at the inner wall to cause a partial or complete plastic deformation emanating from the inner wall, followed by unloading. This introduces the beneficial compressive residual stresses in the vicinity of the inner wall. Depending on the type of the loading, there are five different types of autofrettage processes— hydraulic, swage, explosive, thermal and rotational. This article analyzes the rotational autofrettage, in which the cylinder to be autofrettaged is loaded by rotating it about its longitudinal axis. The centrifugal forces cause the required plastic deformation in the cylinder. Hence, when the cylinder is unloaded by bringing it to rest, compressive hoop residual stresses are introduced in the vicinity of its inner wall. When long cylinders are rotated about their axes, the distribution of axial stress changes with length of the cylinder and affects the generation of the residual stresses in the autofrettaged cylinder. This effect is investigated here by a finite element method (FEM) analysis of rotational autofrettage of cylinder made up of A723 gun steel. The FEM analysis using ABAQUS® package reveals the presence of tensile axial residual stresses in the vicinity of the inner wall of the cylinder, which increase with length. The tensile residual stresses can be mitigated by constraining the ends of the cylinder during the rotational autofrettage.

The Effect of Several Finishing Processes on the Fatigue Resistance of Hole Surfaces

1989 ◽  
Vol 111 (1) ◽  
pp. 71-73 ◽  
Author(s):  
M. O. Lai ◽  
A. Y. C. Nee
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Radial Direction ◽  
Fatigue Loading ◽  
Steel Plates ◽  
Finishing Processes ◽  
Compressive Residual Stresses

This investigation examines the effects of different finishing processes on the fatigue life of premachined holes in Assab 760 steel plates. The finishing processes studied were reaming, ballizing, and emery polishing. A general decrease in fatigue life with increase in surface roughness is observed for all the processes employed. In comparing the different processes, for a constant surface roughness, polishing is generally found to give the longest fatigue life while ballizing, in spite of the greater compressive residual stresses induced on the surface of the finished hole, the shortest. The surprising phenomenon was found to be attributed to the amount of plastic deformation occurred before fatigue loading. For Assab 760 steel, a prestrain in the radial direction of less than about 2.5 percent appeared to reduce the fatigue resistance of the material.

Investigation of Residual Stress Development During Swage Autofrettage, Using Finite Element Analysis

2009 ◽  
Author(s):  
Michael C. Gibson ◽  
Amer Hameed ◽  
John G. Hetherington
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Axial Stress ◽  
Slope Angle ◽  
Subsequent Development ◽  
Element Model ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Reverse Yielding

Swaging is one method of autofrettage, a means of pre-stressing high-pressure vessels to increase their fatigue lives and load bearing capacity. Swaging achieves the required deformation through physical interference between an oversized mandrel and the bore diameter of the tube, as it is pushed through the tube. A Finite Element model of the swaging process was developed, in ANSYS, and systematically refined, to investigate the mechanism of deformation and subsequent development of residual stresses. A parametric study was undertaken, of various properties such as mandrel slope angle, parallel section length and friction coefficient. It is observed that the axial stress plays a crucial role in the determination of the residual hoop stress and reverse yielding. The model, and results obtained from it, provides a means of understanding the swaging process and how it responds to different parameters. This understanding, coupled with future improvements to the model, potentially allows the swaging process to be refined, in terms of residual stresses development and mandrel driving force.

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.

Characterization of the Residual Stresses in Plastically Deformed Ferrite-Martensite Steels Using Barkhausen Noise Measurements

2005 ◽  
Vol 500-501 ◽  
pp. 655-662 ◽  
Author(s):  
Xavier Kleber ◽  
Aurélie Hug-Amalric ◽  
Jacques Merlin
Keyword(s):  
Plastic Deformation ◽  
Tensile Stress ◽  
Residual Stresses ◽  
Barkhausen Noise ◽  
Opposite Behavior ◽  
Noise Measurements ◽  
Two Phases ◽  
Noise Signature ◽  
Compressive Residual Stresses

In this work, we show that the measurement of the Barkhausen noise allows the residual stresses in each of the two phases of ferrite-martensite steels to be characterized. We have first studied the effect of a tensile and a compressive stress on the Barkhausen noise signature. We observed that for a ferrite-martensite steel, the application of a tensile stress increases the Barkhausen activity of the martensite and ferrite phases, whereas a compressive one reduces it. In a second time, we induced residual stresses by applying a plastic deformation to ferrite-martensite steels. After a tensile plastic deformation, we observed that (i) compressive residual stresses appear in ferrite, and (ii) tensile residual stresses appear in martensite. An opposite behavior is observed after a compressive plastic deformation. These results show that the Barkhausen noise measurement makes it possible to highlight in a nondestructive way the distribution of the stresses in each of the two phases of a ferrite-martensite steel. This result could be used to characterize industrial Dual- Phases steels that are plastically deformed during mechanical processes.

Analysis of Residual Stress in the Rotational Autofrettage of Thick-Walled Disks

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
S. M. Kamal
Keyword(s):  
Plastic Deformation ◽  
Residual Stresses ◽  
Yield Criterion ◽  
Three Dimensional ◽  
Circular Disk ◽  
Flow Rule ◽  
Plane Stress Condition ◽  
Radial Temperature ◽  
Fem Validation ◽  
Compressive Residual Stresses

Autofrettage is a means of generating compressive residual stresses at the inner side of a thick-walled cylinder or hollow disk by causing nonhomogeneous plastic deformation of the material at the inner side. The presence of residual compressive stresses at the inner region of the cylinder/disk enhance the pressure withstanding capacity, fatigue life and the resistance to stress corrosion cracking of the component. Despite the hydraulic and swage autofrettage are the widely practiced processes in industries, there are certain disadvantages associated with these processes. In view of this, in the recent years, researchers have proposed new methods of achieving autofrettage. Rotational autofrettage is such a recently proposed autofrettage method for achieving the beneficial compressive residual stresses in the cylinders. In the present work, the rotational autofrettage is studied for a thick-walled hollow circular disk. A theoretical analysis of the residual stresses produced in the disk after unloading are obtained assuming plane stress condition, Tresca yield criterion and its associated flow rule. The analysis takes into account the effect of strain hardening during plastic deformation. Further, the effect of residual stresses in the typical SS304 and aluminum disk is studied by subjecting them into three different types of loads viz., internal pressure, radial temperature difference, and rotational speed individually. A three-dimensional (3D) finite element method (FEM) validation of the theoretical stresses during rotational autofrettage of a disk is also presented.

Post Autofrettage Thermal Treatment and Its Effect on Re-Yielding of High Strength Pressure Vessel Steels

2009 ◽  
Author(s):  
E. Troiano ◽  
J. H. Underwood ◽  
A. P. Parker ◽  
C. Mossey
Keyword(s):  
Thermal Treatment ◽  
Low Temperature ◽  
Plastic Strain ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Lower Amount ◽  
Isotropic Hardening ◽  
Maximum Pressure ◽  
Compressive Residual Stresses

The autofrettage process of a thick walled pressure vessel involves applying tensile plastic strain at the bore of the vessel which reverses during unloading and results in favorable compressive residual stresses at the bore and prolongs the fatigue life of the component. In thick walled pressure vessels this process can be accomplished with either a hydraulic or mechanical overloading process. The Bauschinger effect, which is observed in many of the materials used in thick walled pressure vessels, is a phenomenon which results in lower compressive residual stresses than those predicted with classic ideal isotropic hardening. The phenomenon is a strong function of the amount of prior tensile plastic strain. A novel idea which involves a multiple autofrettage process has been proposed by the present authors. This process requires a low temperature post autofrettage thermal treatment which effectively returns the material to its original yield conditions without affecting its residual stress state. Details of this low temperature thermal treatment are proprietary. A subsequent second autofrettage process generates a significantly lower amount of plastic strain during the tensile re-loading and results in higher compressive residual stresses. This paper reports the details of exploratory tests involving tensile and compressive loading of a test coupon, followed by a low temperature post plastic straining thermal treatment, and subsequent re-loading in tension and compression. Finally results of a full scale Safe Maximum Pressure (SMP) test of pressure vessels are presented; these tests indicate a significant increase (11%) in SMP.

Investigation of Residual Stress Development During Swage Autofrettage, Using Finite Element Analysis

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Michael C. Gibson ◽  
Amer Hameed ◽  
John G. Hetherington
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Axial Stress ◽  
Slope Angle ◽  
Subsequent Development ◽  
Element Model ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Reverse Yielding

Swaging is one method of autofrettage, a means of prestressing high-pressure vessels to increase their fatigue lives and load bearing capacity. Swaging achieves the required deformation through physical interference between an oversized mandrel and the bore diameter of the tube, as it is pushed through the tube. A finite element model of the swaging process was developed, in ansys, and systematically refined, to investigate the mechanism of deformation and subsequent development of residual stresses. A parametric study was undertaken, of various properties such as mandrel slope angle, parallel section length, and friction coefficient. It is observed that the axial stress plays a crucial role in the determination of the residual hoop stress and reverse yielding. The model, and results obtained from it, provides a means of understanding the swaging process and how it responds to different parameters. This understanding, coupled with future improvements to the model, potentially allows the swaging process to be refined, in terms of residual stresses development and mandrel driving force.

Post-Autofrettage Thermal Treatment and Its Effect on Reyielding of High Strength Pressure Vessel Steels

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
E. Troiano ◽  
J. H. Underwood ◽  
A. P. Parker ◽  
C. Mossey
Keyword(s):  
Thermal Treatment ◽  
Low Temperature ◽  
Plastic Strain ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Lower Amount ◽  
Isotropic Hardening ◽  
Maximum Pressure ◽  
Compressive Residual Stresses

The autofrettage process of a thick walled pressure vessel involves applying tensile plastic strain at the bore of the vessel, which reverses during unloading and results in favorable compressive residual stresses at the bore and prolongs the fatigue life of the component. In thick walled pressure vessels this process can be accomplished with either a hydraulic or mechanical overloading process. The Bauschinger effect, which is observed in many of the materials used in thick walled pressure vessels, is a phenomenon, which results in lower compressive residual stresses than those predicted with classic ideal isotropic hardening. The phenomenon is a strong function of the amount of prior tensile plastic strain. A novel idea, which involves a multiple autofrettage processes, has been proposed by the present authors. This process requires a low temperature post-autofrettage thermal treatment, which effectively returns the material to its original yield conditions with minimal effect on its residual stress state. Details of this low temperature thermal treatment are proprietary. A subsequent second autofrettage process generates a significantly lower amount of plastic strain during the tensile reloading and results in higher compressive residual stresses. This paper reports the details of the exploratory tests involving tensile and compressive loading of a test coupon, followed by a low temperature post-plastic straining thermal treatment, and subsequent reloading in tension and compression. Finally results of a full scale safe maximum pressure (SMP) test of pressure vessels are presented; these tests indicate a significant increase (11%) in SMP.

scholarly journals Experiments on Rocks Under High Pressure Conditions in GTA 20-32 Triaxial Press / Experimenty Na Horninách Ve Vysokotlakém Triaxiálním Lisu GTA 20-32

2012 ◽  
Vol 58 (1) ◽  
pp. 9-16
Author(s):  
Josef Poláček ◽  
Alena Kožušníková
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Brittle Failure ◽  
Axial Stress ◽  
Deformation Behaviour ◽  
Confining Pressure ◽  
Strength Properties ◽  
Experimental Results ◽  
State Of Stress ◽  
Different Types

Abstract The paper describes the methodology of measurements in the GTA 20-32 triaxial press. The deformation behaviour of two different types of rocks was compared: - gypsum with plastic deformation even at lower confining pressure, - Carboniferous sandstone with brittle failure even at the highest confining pressure. The influence of gypsum layering was studied as well. The experimental results show that the deformation and strength properties of the gypsum in the triaxial state of stress do not significantly depend on the orientation of axial stress to the observed layering.

Development of a Residual Stress Evaluation Technique by the Combined Use of Surface Strain Measurements Under the Spherical Indentation Method

2013 ◽  
Author(s):  
Norihiko Ozawa ◽  
Tomoaki Yoshizawa ◽  
Yutaka Watanabe ◽  
Tetsuo Shoji
Keyword(s):  
Residual Stresses ◽  
Elastic Strain ◽  
Fem Analysis ◽  
Indentation Load ◽  
Surface Strain ◽  
Spherical Indentation ◽  
Maximum Pressure ◽  
Strain Measurements ◽  
Combined Use ◽  
Compressive Residual Stresses

In this research, a technique was developed for quantitatively evaluating the amount and distribution of tensile and compressive residual stresses by the combined use of strain measurements under the spherical indentation loading together with the finite element method (FEM). When the spherical indentation is applied to the top surface of a welded plate, the elastic strain at an optimized position near the indentation is measured by strain gauges, where the residual and applied indentation stresses are largely superposed. In order to analyze the residual stresses, FEM analysis was conducted to establish the relationship between the elastic strain adjacent to the indentation and the indentation pressure for plates subjected to various uniform tensile and compressive stresses. The critical indentation load was identified, which maximizes the difference between the tensile and compressive residual stresses. A strain energy term (U*) is newly introduced by integrating along the trajectory between the indentation pressure and the elastic strain in a range from 0 to maximum pressure. The application of this technique could contribute to improved reliability in welded parts.

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