scholarly journals Residual Stresses in Weld-Deposited Clad Pressure Vessels and Nozzles

1999 ◽  
Vol 121 (4) ◽  
pp. 423-429 ◽  
Author(s):  
D. P. Jones ◽  
W. R. Mabe ◽  
J. R. Shadley ◽  
E. F. Rybicki
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Pressure Vessel ◽  
Fatigue Testing ◽  
Pressure Vessels ◽  
Flat Plates ◽  
Spherical Head ◽  
Layer Removal Method ◽  
Ring Segment ◽  
Cladding Material

Results of through-thickness residual stress measurements are provided for a variety of samples of weld-deposited 308/309L stainless steel and Alloy 600 cladding on low-alloy pressure vessel ferritic steels. Clad thicknesses between 5 and 9 mm on samples that vary in thickness from 45 to 200 mm were studied. The samples were taken from flat plates, from a spherical head of a pressure vessel, from a ring-segment of a nozzle bore, and from the transition radius between a nozzle and a pressure vessel shell. A layer removal method was used to measure the residual stresses. The effects of uncertainties in elastic constants (Young’s modulus and Poisson’s ratio) as well as experimental error are assessed. All measurements were done at room temperature. The results of this work indicate that curvature plays a significant role in cladding residual stress and that tensile residual stresses as high as the yield stress can be measured in the cladding material. Since the vessel from which the spherical and nozzle corner samples were taken was hydrotested, and the flat plate specimens were taken from specimens used in mechanical fatigue testing, these results suggest that rather high tensile residual stresses can be retained in the cladding material, even after some mechanical loading associated with hydrotesting.

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.

Surface Modification Analysis after Shot Peening of AA 7075 in Different States

2013 ◽  
Vol 768-769 ◽  
pp. 519-525 ◽  
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Aluminium Alloy ◽  
Shot Peening ◽  
Fatigue Testing ◽  
Stress Profile ◽  
Treatment Conditions ◽  
Stress Profiles ◽  
Compressive Residual Stresses

The paper deals with the effect of different shot peening (SP) treatment conditions on the ENAW 7075-T651 aluminium alloy. Suitable residual stress profile increases the applicability and life cycle of mechanical parts, treated by shot peening. The objective of the research was to establish the optimal parameters of the shot peening treatment of the aluminium alloy in different precipitation hardened states with regard to residual stress profiles in dynamic loading. Main deformations and main residual stresses were calculated on the basis of electrical resistance. The resulting residual stress profiles reveal that stresses throughout the thin surface layer of all shot peened specimens are of compressive nature. The differences can be observed in the depth of shot peening and the profile of compressive residual stresses. Under all treatment conditions, the obtained maximum value of compressive residual stress ranges between -200 MPa and -300 MPa at a depth between 250 μm and 300 μm. Comparison of different temperature-hardened aluminium alloys shows that changes in the Almen intensity values have greater effect than coverage in the depth and profile of compressive residual stresses. Positive stress ratio of R=0.1 was selected. Wöhler curves were determined in the areas of maximum bending loads between 30 - 65 % of material's tensile strength, measured at thinner cross-sections of individual specimens. The results of material fatigue testing differ from the level of shot peening on the surface layer.

Development of Residual Stress Improvement for Nuclear Pressure Vessel Instrumentation Nozzle Weld Joint (P-43+P-8) by Means of Induction Heating

2006 ◽  
Author(s):  
Takuro Terajima ◽  
Takashi Hirano
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Residual Stresses ◽  
Induction Heating ◽  
Weld Joint ◽  
Thermal Stresses ◽  
Pressure Vessels ◽  
Weld Joints

As a counter measurement of intergranular stress corrosion cracking (IGSCC) in boiling water reactors, the induction heating stress improvement (IHSI) has been developed as a method to improve the stress factor, especially residual stresses in affected areas of pipe joint welds. In this method, a pipe is heated from the outside by an induction coil and cooled from the inside with water simultaneously. By thermal stresses to produce a temperature differential between the inner and outer pipe surfaces, the residual stress inside the pipe is improved compression. IHSI had been applied to weld joints of austenitic stainless steel pipes (P-8+P-8). However IHSI had not been applied to weld joints of nickel-chromium-iron alloy (P-43) and austenitic stainless steel (P-8). This weld joint (P-43+P-8) is used for instrumentation nozzles in nuclear power plants’ reactor pressure vessels. Therefore for the purpose of applying IHSI to this one, we studied the following. i) Investigation of IHSI conditions (Essential Variables); ii) Residual stresses after IHSI; iii) Mechanical properties after IHSI. This paper explains that IHSI is sufficiently effective in improvement of the residual stresses for this weld joint (P-43+P-8), and that IHSI does not cause negative effects by results of mechanical properties, and IHSI is verified concerning applying it to this kind of weld joint.

Weld Residual Stress and Fracture Behavior of NASA Layered Pressure Vessels

2019 ◽  
Author(s):  
F. W. Brust ◽  
R. H. Dodds ◽  
J. Hobbs ◽  
B. Stoltz ◽  
D. Wells
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Fracture Behavior ◽  
Service Evaluation ◽  
Pressure Vessels ◽  
Weld Residual Stress ◽  
Proof Testing ◽  
Fracture Assessment ◽  
High Level ◽  
Initial Results

Abstract NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. The number of thinner layers required depends on the thickness required for the complete vessel with most tanks having between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents some initial results which consider weld residual stress and fracture assessment of some layered pressure vessels and is a small part of the much larger fitness for service evaluation of these tanks. This effort considers the effect of weld residual stresses on fracture for an inner layer longitudinal weld. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Finally, cracks are introduced, and service loading applied to determine the effects of WRS on fracture.

Assessment of a Stress-Free Temperature Model for Residual Stresses in Surface Cladding of a Reactor Pressure Vessel

2017 ◽  
Author(s):  
B. Richard Bass ◽  
Paul T. Williams ◽  
Terry L. Dickson ◽  
Hilda B. Klasky
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Base Metal ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Normal Operation ◽  
Inner Surface ◽  
Reactor Pressure

This paper describes further results from an ongoing study of a simplified engineering model that is intended to account for effects of clad residual stresses on the propensity for initiation of preexisting inner-surface flaws in a commercial nuclear reactor pressure vessel (RPV). The deposition of stainless steel cladding during fabrication of an RPV generates residual stresses in the cladding and the heat affected zone of the under-lying base metal. In addition to residual stress, thermal strains are generated by the differential thermal expansion (DTE) of the cladding and base material due to temperature changes during normal operation. A simplified model used in the ORNL-developed FAVOR probabilistic fracture mechanics (PFM) code accounts for the clad residual stress by incorporating a stress-free temperature (SFT) approach. At the stress-free temperature (Ts-free), the model assumes there is no thermal strain, i.e., the thermal expansion stresses and clad residual stresses offset each other. For normal cool-down transients applied to the RPV, interactions of the latter stresses generate additional crack driving forces on shallow, internal surface-breaking flaws near the clad/base metal interface; those flaws tend to dominate the RPV failure probability computed by FAVOR. In a previous report from this study (PVP2015-45086), finite element analysis was used to compare the stresses and stress-intensity factors (SIF) during a cool-down transient for two cases: (1) the existing SFT model of FAVOR, and (2) directly applied RPV clad residual stress (CRS) distribution obtained from empirical (hole-drilling) measurements made at room temperature on an RPV that was never put into service. However, those analyses were limited in scope and focused on a single flaw orientation. In this updated study, effects of CRS on the SIF histories computed for both circumferential and axial flaw orientations subjected to a cool-down transient were determined from an extended set of finite element analyses. Specifically, comparisons were made between results from applying CRS experimental data to ABAQUS two-dimensional, inner-surface flaw models and those generated by the FAVOR SFT model. It is demonstrated that the FAVOR-recommended SFT value of 488 °F produces conservatively high values of SIF relative to the use of CRS profiles in the ABAQUS models. For the vessel and flaw geometry and transient under study, the circumferential flaw (360° continuous) required a decrease of SFT down to 390 °F to match the CRS SIF histories. For the infinite axial flaw model, a decrease down to 300 °F matched the CRS SIF histories. Future plans are described to develop more general conclusions regarding the FAVOR model.

Feasibility Studies on the Modeling and Evaluation of Residual Stresses in Arc Welded Butt Joints

2006 ◽  
Author(s):  
K. Satyambabu ◽  
N. Ramachandran
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Arc Welding ◽  
Thermal Loading ◽  
Submerged Arc Welding ◽  
Pressure Vessels ◽  
Welding Parameters ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding ◽  
Submerged Arc

Many important engineering applications such as nuclear reactors, ships, pipes and pressure vessels are shell-like structures made with weldments. For such a structure, a major problem is the development of residual stress and distortion due to welding. Residual stresses in weldments significantly affect stress corrosion cracking, hydrogen-induced cracking and fatigue strength in welded structures. As-welded components generally have certain amount of residual stresses caused by the application of intense heat or thermal loading at the weld joint, formed due to non-uniform cooling rates at different points in the weld metal and heat affected zones. Presence of residual stresses in a component is detrimental as they may lead to failure below the design stress value and also affect many important properties including the life of a welded component. Welding induced residual stresses can significantly increase the fracture driving force in a weldment and also contribute to brittle fracture. The thermal cycle imposed on any welded object causes thermal expansions and contractions which are not uniform. Quantitative measurement of residual stresses is essential to take remedial measures such as change in the welding technique, optimizing welding parameters (heat input, electrode diameter etc,), change in the weld groove design and post-weld heat treatment for minimizing the residual stresses. Residual stress measurements after post-weld treatment would also ensure the adequacy of stress relief treatment. To have an investigation into these aspects, residual stresses due to Manual Metal Arc Welding and Submerged Arc Welding were measured nondestructively with Ultrasonic technique. Residual stress distribution for Shielded Metal Arc Welding and Submerged Arc Welding were compared and the present studies emphasized, that Shielded Metal Arc Welding gave higher compressive stresses than Submerged Arc Welding. Further, to substantiate the studies, commercial finite element analysis software ANSYS 5.6 was used for modeling of manual metal arc welded joint. The results obtained by ANSYS were compared with those by Ultrasonic method.

FEA of Residual Stresses in Butt Welded Type Low Carbon Steel Using MMAW Technique

2011 ◽  
Vol 110-116 ◽  
pp. 2686-2692
Author(s):  
Gurinder Singh Brar ◽  
Gurdeep Singh
Keyword(s):  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Carbon Steel ◽  
Residual Stresses ◽  
Low Carbon Steel ◽  
Pressure Vessels ◽  
Transient Temperature ◽  
Low Carbon ◽  
Element Method

Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is widely employed in diverse structures such as ships, aircraft, marine structures, bridges, ground vehicles, pipelines and pressure vessels. When two dissimilar plates are joined by welding process, a very complex thermal cycle is applied to the weldment, which further causes inhomogeneous plastic deformation and residual stress in and around fusion zone and heat affected zone (HAZ). Presence of residual stresses may be beneficial or harmful for the structural components depending on the nature and magnitude of residual stresses. In this study, a finite element analysis has been carried out to analyze the thermo-mechanical behaviour and effect of residual stress state in butt-welded in low carbon steel plates. A coupled thermal mechanical three dimension finite element model was developed. Finite element method based software SolidWorks Simulation, was then used to evaluate transient temperature and residual stress during butt welding of two plates. Plate thickness of 8 mm were used which are normally joined by multi-pass operation by Manual Metal Arc Welding (MMAW) process. During each pass, attained peak temperature and variation of residual stresses in plates has also been studied. The results obtained by finite element method agree well with those from X-ray diffraction method as published by Murugan et al. for the prediction of residual stresses.

Experimental Investigation on Residual Stress of Model S1100 of Crankshaft Chamfer Based on XRD

2007 ◽  
Vol 353-358 ◽  
pp. 2301-2304
Author(s):  
Yong Kang Zhang ◽  
De Jun Kong ◽  
Jin Zhon Lu ◽  
Ai Xin Feng ◽  
Xu Dong Ren ◽  
...  
Keyword(s):  
Residual Stress ◽  
Experimental Investigation ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Service Life ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Residual Stress Distribution ◽  
Isothermal Quenching ◽  
Main Factors

Residual stresses of model S1100 of crankshaft chamfer were measured by the technology of XRD. The distributions of residual stresses under mechanical peening, mechanical rolling and isothermal quenching are measured, and the tests of fatigue life were conducted. The results showed that the distribution of residual stress by machining in the crankshaft chamfer is complicated, which is at the tensile-compressive status, and it is one of the main factors to affect fatigue life of the crankshaft; isothermal quenching improves the distribution of residual stress, and tensile stress of the crankshaft chamfer is changed into the compressive stress, which may satisfy the requests of fatigue testing for 5 × 106 cycles. Although the mechanical rolling improved the residual stress distribution in the chamfer linked with the crank, tensile stresses in the chamfer connected with the linkage also increase, which influences the service life of the crankshaft.

scholarly journals Development of Residual Stress Simulation and Experimental Measurement Tools for Stainless Steel Pressure Vessels

2015 ◽  
Author(s):  
Thomas B. Reynolds ◽  
Arthur A. Brown ◽  
Lauren L. Beghini ◽  
Timothy D. Kostka ◽  
Chris W. San Marchi
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Pressure Vessels ◽  
Contour Method ◽  
Residual Stress State ◽  
Measurement Tools ◽  
Fatigue And Fracture ◽  
Evolution Of Microstructure ◽  
Stress Simulation

In forged, welded, and machined components, residual stresses can form during the fabrication process. These residual stresses can significantly alter the fatigue and fracture properties compared to an equivalent component containing no residual stress. When performing lifetime assessment, the residual stress state must be incorporated into the analysis to most accurately reflect the initial condition of the component. The focus of this work is to present the computational and experimental tools that we are developing to predict and measure the residual stresses in stainless steel for use in pressure vessels. The contour method was used to measure the residual stress in stainless steel forgings. These results are compared to the residual stresses predicted using coupled thermo-mechanical simulations that track the evolution of microstructure, strength and residual stress during processing.

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