A Damage Assessment of Autofrettaged Tubes Exposed to Decompositions in an LDPE Facility

2015 ◽  
Author(s):  
Jeffrey D. Cochran ◽  
Trace P. Silfies ◽  
Jonathan D. Dobis
Keyword(s):  
Residual Stress ◽  
Damage Assessment ◽  
Damage Parameter ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Remaining Life ◽  
Decomposition Reactions ◽  
Three Samples ◽  
Inner Surface ◽  
Almost All

The manufacture of low density polyethylene (LDPE) by radical polymerization regularly subjects components to extreme pressures exceeding 20 ksi and, possibly, to runaway decomposition reactions with temperatures exceeding 1500 °F and pressures above 30 ksi. Components subject to such extreme conditions are often autofrettaged to induce a beneficial residual stress distribution that retards crack growth and extends fatigue life. Three samples of autofrettaged tubes extracted from these components are examined here. Only one of these samples is known to have been exposed to multiple decompositions while in service. Measurements of the remaining residual stress were taken for each of these tube samples, and a number of other metallurgical tests were performed. The results show that the tube experiencing decompositions lost almost all of the beneficial residual stress induced by autofrettage and actually has a large, detrimental tensile stress at the inner surface. Corresponding to this is a band of embrittled material with a significantly altered microstructure that was most likely caused by thermal excursions. The tubes that experienced no decompositions showed no such alterations, and their residual stress distributions were relatively intact. An FFS assessment of crack-like flaws was performed on these tubes in accordance with API 579-1/ASME FFS-1 in order to determine the effect of this loss of residual stress on remaining life and quantify this loss in terms of a damage parameter.

Effects of Pipe Dimensions and Outer Surface-Buttering Weld Conditions on Residual Stress Distributions

2008 ◽  
Author(s):  
Nobuyoshi Yanagida
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Outer Surface ◽  
Hoop Stress ◽  
Axial Stress ◽  
Butt Joint ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Butt Joints ◽  
Inner Surface

Effects of pipe dimensions and outer surface-buttering weld conditions on residual stress distributions were evaluated using the finite element method. Residual stresses were analyzed for 508–mm-diameter (500A) pipe 38.1 mm thick, 508–mm-diameter (500A) pipe 15.1 mm thick, and 267–mm-diameter (250A) pipe 15.1 mm thick. After the residual stresses at pipe butt joints were analyzed, residual stresses at these joints subjected to the outer surface-buttering welds were analyzed. Residual stresses were determined for various weld widths, thicknesses, and heat inputs. These analyses indicate that tensile axial stress occurred at inner surface of the pipe butt joint and that it decreased with increasing the outer surface buttering-weld width or heat input. They also indicate that compressive hoop stress occurred at inner surface of the joint and that outer surface-buttering weld increased it. The outer surface-buttering weld conditions that generate compressive residual stress at the inner surface of the pipe butt joints were determined.

Important Residual Stress Features in Reactor Nozzle Dissimilar Metal Welds

2011 ◽  
Author(s):  
Jinmiao Zhang ◽  
Shaopin Song ◽  
Pingsha Dong
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Nuclear Reactor ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Weld Overlay ◽  
Dissimilar Metal ◽  
Nozzle Length ◽  
Dissimilar Metal Weld ◽  
Metal Weld

This paper is focused on the study of residual stress distribution at a dissimilar metal weld (DMW) of nuclear reactor nozzle. The paper extends some of the recent research on this subject by investigating the effect of weld sequence and nozzle length design on the residual stress distributions. It also investigates the effect of a partial excavation repair and a weld overlay on the residual stress distribution. As a result, some of the important residual stress features at DMW are revealed and these features are discussed and summarized in the paper.

A numerical prediction of residual stress for a thin-walled part with geometrical features fabricated by GMA-based additive manufacturing

2019 ◽  
Vol 26 (2) ◽  
pp. 299-308
Author(s):  
Rong Li ◽  
Jun Xiong
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Content Type ◽  
Geometrical Features ◽  
Longitudinal Residual Stress ◽  
Thin Walled

Purpose An accurate prediction of process-induced residual stress is necessary to prevent large distortion and cracks in gas metal arc (GMA)-based additive manufactured parts, especially thin-walled parts. The purpose of this study is to present an investigation into predicting the residual stress distributions of a thin-walled component with geometrical features. Design/methodology/approach A coupled thermo-mechanical finite element model considering a general Goldak double ellipsoidal heat source is built for a thin-walled component with geometrical features. To confirm the accuracy of the model, corresponding experiments are performed using a positional deposition method in which the torch is tilted from the normal direction of the substrate. During the experiment, the thermal cycle curves of locations on the substrate are obtained by thermocouples. The residual stresses on the substrate and part are measured using X-ray diffraction. The validated model is used to investigate the thermal stress evolution and residual stress distributions of the substrate and part. Findings Decent agreements are achieved after comparing the experimental and simulated results. It is shown that the geometrical feature of the part gives rise to an asymmetrical transversal residual stress distribution on the substrate surface, while it has a minimal influence on the longitudinal residual stress distribution. The residual stress distributions of the part are spatially uneven. The longitudinal tensile residual stress is the prominent residual stress in the central area of the component. Large wall-growth tensile residual stresses, which may cause delamination, appear at both ends of the component and the substrate–component interfaces. Originality/value The predicted residual stress distributions of the thin-walled part with geometrical features are helpful to understand the influence of geometry on the thermo-mechanical behavior in GMA-based additive manufacturing.

Residual Stress Measurement in 304 Stainless Steel Weld Overlay Pipes

1996 ◽  
Vol 118 (1) ◽  
pp. 135-142 ◽  
Author(s):  
Hung-Ju Yen ◽  
Mark Ching-Cheng Lin ◽  
Lih-Jin Chen
Keyword(s):  
Residual Stress ◽  
Compressive Residual Stress ◽  
Stress Measurement ◽  
Residual Stress Distribution ◽  
304 Stainless Steel ◽  
Steel Weld ◽  
Weld Overlay ◽  
Stainless Steel Weld ◽  
Inner Surface ◽  
Welded Pipe

Welding overlay repair (WOR) is commonly employed to rebuild piping systems suffering from intergranular stress corrosion cracking (IGSCC). To understand the effects of this repair, it is necessary to investigate the distribution of residual stresses in the welded pipe. The overlay welding technique must induce compressive residual stress at the inner surface of the welded pipe to prevent of IGSCC. To understand the bulk residual stress distribution, the stress profile as a function of location within wall is examined. In this study the full destructive residual stress measurement technique—a cutting and sectioning method—is used to determine the residual stress distribution. The sample is type 304 stainless steel weld overlay pipe with an outside diameter of 267 mm. A pipe segment is cut from the circular pipe; then a thin layer is removed axially from the inner to the outer surfaces until further sectioning is impractical. The total residual stress is calculated by adding the stress relieved by cutting the section away to the stress relieved by axially sectioning. The axial and hoop residual stresses are compressive at the inner surface of the weld overlay pipe. Compressive stress exists not only at the surface but is also distributed over most of the pipe’s cross section. On the one hand, the maximum compressive hoop residual stress appears at the pipe’s inner surface. The magnitude approaches the yield strength of the material; the compressive stress exists from the inner surface out to 7.6 mm (0.3 in.) radially. On the other hand, compressive axial residual stress begins at depths greater than 2.5 mm (0.1 in.); its maximum value is located at 10.7 mm (0.42 in.) with magnitude close to four-tenths of yield strength. The thermal-mechanical induced crack closure from significant compressive residual stress is discussed. This crack closure can thus prevent IGSCC very effectively.

Predicting Welding Residual Stress Distributions in P92 Steel Joints Considering the Influence of Solid-State Phase Transformation

2016 ◽  
Author(s):  
Dean Deng ◽  
Hidekazu Murakawa
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Solid State ◽  
Computational Approach ◽  
Residual Stress Distribution ◽  
Welding Residual Stress ◽  
Stress Distributions ◽  
P92 Steel ◽  
Solid State Phase Transformation ◽  
Steel Joints

In this study, an advanced computational approach based on SYSWELD software was developed to simulate welding residual stress distributions in P92 steel joints with the consideration of solid-state phase transformation. Using the developed numerical method, we calculated the welding residual stress distribution in a single-pass weld joint, and clarified the influences of volume change, variation of yield strength and phase transformation induced plasticity on the formation of residual stress. Meanwhile, experiment was carried out to measure the welding residual stress distributions in the single-pass joint. The effectiveness of the developed computational approach was verified by the experimental results. In addition, the features of welding residual stress distribution in multi-pass P92 steel joint were discussed based on the results obtained by numerical simulation, and some new viewpoints on welding residual stress in multi-pass P92 steel joints were obtained.

Effect of the interpass temperature on the predicted residual stress distributions in a multipass welded piping branch junction

2008 ◽  
Vol 43 (2) ◽  
pp. 109-119 ◽  
Author(s):  
W Jiang ◽  
K Yahiaoui
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cross Sections ◽  
Branch Pipe ◽  
Three Dimensional ◽  
Weld Line ◽  
Element Model ◽  
Stress Distributions ◽  
Inner Surface ◽  
Interpass Temperature

A sequentially coupled three‐dimensional thermomechanical finite element model has been developed to predict residual stress distributions in a multipass welded piping branch junction. The residual stresses at the branch and run pipe cross‐sections, as well as along the circumferential weldlines on the outer surfaces of both the run and the branch pipes and on the inner surface of the branch pipe, are predicted. Three levels of interpass temperature have been selected to investigate their effect on the peak residual stresses. It is revealed that the interpass temperature has a significant effect on the residual stresses. As the interpass temperature is increased, both the peak hoop and the axial residual stresses at the run and branch cross‐sections decrease. The peak normal stresses along the circumferential weldline on the outer surface of the run pipes are also reduced. However, increasing the interpass temperature had a negligible effect on the peak tangential residual stresses along the circumferential weld line on the inner surface of the branch pipe. The results presented and the modelling technique described in the current study can be used towards formulating a recommendation to optimize residual stress profiles in multipass welded complex geometries through better interpass temperature control.

scholarly journals Residual Stress Distribution in Water Jet Peened Type 304 Stainless Steel

2020 ◽  
Vol 4 (2) ◽  
pp. 18 ◽  
Author(s):  
Makoto Hayashi ◽  
Shinobu Okido ◽  
Hiroshi Suzuki
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Stress Distribution ◽  
Stress Gradient ◽  
Diffraction Method ◽  
Peak Shift ◽  
Residual Stress Distribution ◽  
304 Stainless Steel ◽  
Stress Distributions ◽  
Gauge Volume

In materials with a surface treatment such as shot peening, the residual stress gradient in the surface layer is severe. When measuring the residual stress distribution near the surface with a severe stress gradient by the neutron diffraction method, the gauge volume must be removed from the measurement sample. However, when the gauge volume deviates from the sample, a pseudo peak shift occurs and accurate stress distribution cannot be evaluated. Therefore, it is necessary to evaluate the pseudo peak shift in advance under the same conditions, as in the case of actual residual stress measurement, using a sample in an unstressed state. In this study, the stress distributions in the surface layer of a type 304 stainless steel plate and bar with simulated stress-corrosion cracks which were subjected to water jet peening—giving a surface layer residual stress equivalent better than that of normal shot peening—were evaluated considering the pseudo peak shift. As a result, the residual stress distributions in the surface layer were measured in good agreement with the measurement result obtained by the sequential polishing X-ray diffraction method. It was clarified that the residual stress distribution in the near surface with steep stress gradient can be evaluated by the neutron diffraction method.

Grain Growth Simulation of Precipitated Phase on Surface and Evaluation of the Residual Stress Distribution

2012 ◽  
Vol 538-541 ◽  
pp. 322-325
Author(s):  
Takuya Uehara
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Grain Growth ◽  
Phase Field Model ◽  
Residual Stress Distribution ◽  
Stress Generation ◽  
Slight Variation ◽  
Stress Distributions ◽  
Precipitated Phase ◽  
Multi Phase

Grain growth simulations considering heat treatment process were carried and the change in microstructure on the surface was regenerated. Stress-dependency of the phase transformation from original phase to precipitate was introduced into the conventional multi-phase-field model, and stress distributions were calculated. Volumetric dilatation was considered as a source of the stress generation, and a slight variation in the dilatation coefficient was applied for each grain. As a result, a mosaic pattern in the stress distribution correlated to the polycrystalline microstructure was obtained. The residual stress distribution was also calculated under three different conditions, and revealed to vary depending on the microstructure obtained.

Cyclic Torsion of a Circular Cylinder and Its Residual Stress Distribution

1985 ◽  
Vol 107 (1) ◽  
pp. 48-52 ◽  
Author(s):  
Han C. Wu ◽  
M. R. Aboutorabi ◽  
Peter C. T. Chen
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Circular Cross Section ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Numerical Techniques ◽  
Torsional Loading ◽  
Endochronic Theory ◽  
Solid Specimen ◽  
Versus Strain

The endochronic theory of plasticity is applied to discuss the cyclic full-reversed torsional loading of a solid bar with circular cross section. Numerical techniques are employed to obtain the solution. The parameters of the constitutive equations are determined from the test data of thin-walled specimens. These parameters are then used without alteration to compute stress distributions within the solid specimen. Special attention is given to the residual stress distribution. It is shown that reasonable results are obtained. The relation of torque versus strain at the outermost fiber of the solid specimen provides an ultimate check of the theory as applied to this case.

Inherent-Strain-Based Theory of Measurement of Three-Dimensional Residual Stress Distribution and Its Application to a Welded Joint in a Reactor Vessel

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Keiji Nakacho ◽  
Naoki Ogawa ◽  
Takahiro Ohta ◽  
Michisuke Nayama
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Strain Distribution ◽  
Measurement Method ◽  
Welded Joint ◽  
Three Dimensional ◽  
Reactor Vessel ◽  
Residual Stress Distribution ◽  
Stress Distributions ◽  
Inherent Strain

The stress that exists in a body under no external force is called the inherent stress. The strain that is the cause (source) of this stress is called the inherent strain. This study proposes a general theory of an inherent-strain-based measurement method for the residual stress distributions in arbitrary three-dimensional bodies and applies the method to measure the welding residual stress distribution of a welded joint in a reactor vessel. The inherent-strain-based method is based on the inherent strain and the finite element method. It uses part of the released strains and solves an inverse problem by a least squares method. Thus, the method gives the most probable value and deviation of the residual stress. First, the basic theory is explained in detail, and then a concrete measurement method for a welded joint in a reactor vessel is developed. In the method, the inherent strains are unknowns. In this study, the inherent strain distribution was expressed with an appropriate function, significantly decreasing the number of unknowns. Five types of inherent strain distribution functions were applied to estimate the residual stress distribution of the joint. The applicability of each function was evaluated. The accuracy and reliability of the analyzed results were assessed in terms of the residuals, the unbiased estimate of the error variance, and the welding mechanics. The most suitable function, which yields the most reliable result, was identified. The most reliable residual stress distributions of the joint are shown, indicating the characteristics of distributions with especially large tensile stress that may produce a crack.

Sign in / Sign up

Export Citation Format

Share Document