ML20207H793

Welds II Residual Stress Analysis of Resistance Heating Stress Improvement Welded Pipes

ML20207H793
Person / Time
Site:	FitzPatrick
Issue date:	08/31/1987
From:	Giannuzzi A, Kuo A, Stonesifer R STRUCTURAL INTEGRITY ASSOCIATES, INC.
To:
Shared Package
ML20207H770	List: JPN-88-043, Forwards Info in Support of Util 880816 Response to Generic Ltr 88-01 Re IGSCC Program at Plant,Including Rev 1 to SIR-87-015, Welds II Residual Stress Analysis of Resistance Heating Stress Improvement Welded Pipes ML20207H793 ML20207H829
References
SIR-87-015, SIR-87-015-R01, SIR-87-15, SIR-87-15-R1, NUDOCS 8808300037
Download: ML20207H793 (53)

Text

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Report No.: SIR-87-015 Project No.: NYPA-14 Rev. 1 August 1987 Ioc.n n /886m -

, 3 c F PAGES - - . :=J

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P WELDS II RESIDUAL STRESS ANALYSIS OF RESISTANCE HEATING STRESS IMPROVEMENT WELDED PIPES t

l l

I l i Prepared by: )

. Structural Integrity Associates, Inc.

Prepared for: i New York Power Authority i

Prepared by: k. h.

Randall B. Stonesiter hMe r [htr!Date: 8/b!S7 l Reviewed by: {A ~ 7 ) Date:

A'h-Yu Ku6) '

Approved by: ,

& Date: AC!['M Anth p J. Giannuzil I

NCTUIULI, 8808300037 880819 M PDR ADOCK 050 3 M3g

. 1

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' Report No. SIR-87-015  !

REVISION CONTROL SHEET SECTION PARAGRAPH DATE REVISION REMARKS All All 6/87 0 Initial Issue j I

2.5 First 8/87 1 Added details of heat transfer analyis in response to customer ,

' request 2.6 & All 8/87 1 Added reference for 5.0 materials properties

in response to customer request l l

3.1 Last 8/87 1 Reworded discussion of I experimental / analytical l comparison in response i to customer request 2.7 & All 8/87 1 Added more detailed l

.t 5.0 description of WELDSII program methodology in l response to customer request i I

1 l l P

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'. TABLE OF CONTENTS

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Section P.A21 1.0 Introduction . . . . . . . . . . . . . 1 2.0 Approach . . . . . . . . . . . . . 3 2.1 Axisymmetric Analysis . . . . . . . . 3 2.2 One-Dimensional Analysis . . . . . . . 4 e.

2.3 Generalized Plane Strain Analysis . . . . 5 2.4 Effect of Initial Residual Stress on RHSI Effectiveness . . . . . . . . . 5 2.5 Heat Transfer Analysis . . . . . . . . 6 2.6 Material Properties . . . . . . . . . 7 2.7 Finite Element Program . . . . . . . . 7 3.0 Results . . . . . . . . . . . . . . . 9 f

3.1 Laboratory Test Pipe RHSI Analysis . . . . 9 3.2 Weld 28-108 RHSI Analyses . . . . . . . 10 3.2.1 One-Dimensional Analyses of the Weld 27-108 RHSI . . . . . . . . . . . 11

.. 3.2.2 Axisymmetric Analyses of the Wald ,28-108 RHSI . . . . . . . . . 12 3.2.3 Generalized Plane Strain (GPS) Analyses of the Wald 28-108 RHSI . . . . . . , 14 3.2.4 Summary and Comparison of Wald 28-108 RHSI Analyses . . . . . . . . . . 17 3.3 Weld 28-50 RHSI Analysis . . . . . . . 18 4.0 Conclusions . . . . . . . . . . . . . . 19 5.0 References . . . . . . . . . . . . . . 20 I i

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LIST OF TABLES l

Table g 1 Temperature Dependent Material Properties for 304 Stainless Steel . . . . . . .', . . . 21 l

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. . l LIST OF FIGURES Ficure F.ASA 1 The Axisymmetric. Finite Element Grid Used for RHSI Analyses Which Assume RHSI Temperature

! Centerline Symmetry (396 nodes, 344 elements) . . 22 2 The Finite Element Grid Used-for Generalized Plane '

Strain RHSI Analyses (819 nodes, 720 elements) . . 23 t

3 The Initial Residual Stresses Which Are Assumed for the Axisymmetric RHSI Models . . . . 24 p 4 The Initial Residual Stresses Which Are Assumed I

for the One-dimensional and Generalized Plane i Strain RESI Models . . . . . . . . . . . 25 5 Laboratory Test Pipe Thermocouple Data and the Axisymmetric Model Input Temperature Distribution . 26 6 Pre- and Post-RHSI Residual Stresses Resulting from the Axisymmetric Analysis of the Laboratory Test Pipe . . . . . . . . . . . . . . 27 f

1 7 Comparison of Predicted Residual Stresses from the Axisymmetric. Analysis and Experimental Stress Data 1

, from the Laboratory Test Pipe . . . . . . . . 28 j 1

8 one-dimensional Analysis Stress Results for l Several Through-wall Temperature Gradients . . . 29 i l

9 Thermocouple Data from Wald 28-108 and Several l Axisymmetric Model Input Temperature Distributions . 30  ;

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10 Pre- and Post-RHSI Residual Stresses Resulting l from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution A7 . . . 31 l

! 11 Pre- and Post-RHSI Residual Stresses Resulting  !

from the Axisymmetric Analysis of Weld 28-100 Using the Input Temperature Distribution Al . . . 32 12 Pre- and Post-RHSI Residual Stresses Resulting )

r. from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution A2 . . . 33 13 Pre- and Post-RHSI Residual Stresses Resulting from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution A3 . . . 34 14 Thermocouple Data from Weld 28-108 and Two Generalized Plane Strain Model Input Temperature Distributions . . . . . . . . . 35 l

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LIST OF FIGUREC (Concluded)

Ficure Pace 15 Inner and Outer Surface Residual Stresses Predicted by the Generalized Plane Strain Analyses of Weld 28-108 . . . . . . . . . . 36 16 Predicted Through Thicknese Residual Stress from the Generalized Plane Strain Analysis of Weld 28-108 Using Temperature Input Distribution G1 . . . . . . . . . . . . 37 Predicted Through Thickness Residuel Stress 17

- from the Generalized Plane Strain Analysis of Weld 28-108 Using Temperature Input Distribution G2 . . . . . . . . . . . . 38 18 Summary of GenerPlized Plane Strain Behavior During RHSI o_ Wald 28-108 . . . . . . . . . 39 19 Comparison of One-dimensional, Axisymmetric, and Generalized Plane Strain Analysis Predictions for Weld 28-108 kHSI Surface Residual Stresses . . 40 20 Comparison of Ona-dimensional, Axisymmetric, and Generalized Flane Strain Analysis Predictions for Weld 28-108 RHSI Through Thickness Axial Residual Stresses . . . . . . . . . . . . 41 21 Comparison of One-dimensional, Axisymmetric, and Generalized Plane Strain Analysis Predictions for Weld 28-108 RHSI Through Thickness Hoop Residual Stresses . . . . . . . . . . . 42 22 thermocouple Data and the Axisymmetric Model Input (Worst case) Temperature Distribution for Weld 28-$0 . . . . . . . . . . . . . 43 o-s INTEGRITY ASSOCIATESINC

1.0 INTRODUCTION

The purpose of this study is to provide ar.alytical verification of a resistance heating stress ibprovement (RHSI) procedure for sensitized stainless steal pipe joints. This study is conducted in parallel with an experimenthi investigation which involves:

1) applying the procedure to a test pipe under laboratory conditions,

2) doing a destructive residual stress determination on the laboratory pipe, and

3) applying the RHSI procedure to two pipe joints in the field.

The analytical verification makes extensive use of temperature l measurements made during all three of the RHSI applications. By using the experimentally determined temperatures, rather than

( temperatures from an analytical temperature model, the number of I

assumptions required in the analysis are significantly reduced; thus improving the reliability of the analytical residual stre.ss predictions.

The analytically predicted residual stresses for the lab weld l

application of the RHSI procedure are compared with the experimentally determined stresses and are found to be in good agreement. Both experimental results and analytical results indicate that the laboratory RHSI application produced inner surface axial and hoop residual stressas which are at or above p

the compressive yield stress of the material.

As might be expected, the field applications resulted in temperature histories which are less favorable than those l obtained in the laboratory application. Typically, the less favorable nature of the temperature histories involve localized regions in which either the through-wall temperature gradient is i 1

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4 smaller than optimum, or the axial lergth of the RMSI temperature zone is smaller than optimum. Analytical simulations are used to show that sufficient margin exists in the procedure that these expected and largely uncontrollable deviations do not result in unacceptable reductions in the effectiveness of the RHSI procedure.

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,a 2.0 APPROACH This study uses several types ccf analytical stress modeln to examine the RHSI procedure. All model,s are one- or two-dimensional. Three- dimensional modeling was not considered cost effective for this study, and is generally less amenable to sensitivity studies than one- or two- dimensional models.

. 2.1 Axisymmetric Analysis The RHSI procedure is designed to produce an axisymmetric l temperaturo field which, in turn, results in an axioymmetric l residual stress field. Provided, the RHSI temperature field is l

axisymmetric and results in sufficient plastic deformation, l

non-axisymmetry in the original welding induced residual stret ss will not significantly alter the e xisymm'.stry of the post-RHSI l~

residual stresses.

Therefore, axisymmetric analyses are the most I natural means for modeling the RHSI procedure.

l Figure 1 shows the axisymmetric finite element grid used to model

, the RHSI of the 28-inch pipes of this study. This particular grid assumes symmetry about the RHSI temperature band centerline.

A second axisymmetric model is also used which does not assume symmetry about the RHSI temperature band centerline. This second I grid contains twice the number of elements as the grid shown in Figure 1, and is 40 inches in length instead of 20 inches.

The RHSI procedure is designed to produce a temperature gradient r through the pipe wall which is sufficient in magnitude to produce significant plasticity. To generate the required temperature gradient, it is necessary to cool the inner surface of the pipe while heating the outer surface. While the through-wall temperature gradient is a key parameter of the RHSI procedure, a second parameter of importance is the axial length of the RHSI STRUCTURJLL 3 INTEGRITY ASSOCIATESINC

induced temperature band. If the temperature band is not sufficiently long, shell type bending tends to relax the stresses being induced by the through-wall temperature gradient and thus reduces the effectiveness of the procedure. 'Ih e axisymmetric models include the effects of through-wall temperature gradient as well as the effects of the RMSI tamperature band's axial l longth.

s. While the ideal RHSI temperature distribution is axisymmetric, l various practical considerations generally result in the

. temperature distribution having some dependence on circumferential position. The variation can be in terms of peak l outer surface temperature (temperature gradient), or in terms of

. the axial length of the temperature band.

l Inherent in the use of axisymmetric models to examine this temperature band length eff ect is the assumption that localized (i.e., occurring over a small circumferential length) axial 4

shortening of the temperature band will have a less detrimental i

effect on the stress improvement than a similar 360 degree shortening of the temperature band. That is, by modeling the shortest axial length of the temperature band with the axisymmetric model, the predicted residual stress improvement l

will be conservative (i.e., predicted stresses will be less compressive than the actual stresses).

2.2 One-Dimensional Analysis t- For the limiting case in which the axial size of the RHSI temperature band becomes very large, the stresses near the center of the temperature band can be predicted using a one-dimensional model. The residual stresses predicted by this model for a given through-wall temperature distri'bution will be approached i asymptotically by residual stresses obtained from axisymmetric models as the length of the temperature zone is increased. It is t

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because of this bounding relationship and the relacive ease of obtaining the one-dimensional solutions that they are considered in this study.

l 2.3 Generalized Plane Strain Analysis The effect of peak outer surface temperature variations around the circumference of the pipe are examined in this study using A generalized plane strain (GPS) models. Figure 2 shows the finite

! element grid for the GPS model used in this study. This grid

, represents half of the pipe cross-section and reflects the fact

( that the RHSI temperature distributions being examined in this study have a plane of symmetry.

i By generalized plane strain, it is meant that the axial strains i are assumed to result in plane sections remaining plane.

Therefore, in general, the pipe can have an axial expanrion (or I

contraction), and two bending modes. Two types of GPS analyses are considered in this study. In both types, the axial expansion 7, and contraction of the pipe is unrestrained (i.e., the net axial

force is zero). The bending modes, however, are treated

, differently in the two types of GPS analyses. In one, the pipe is forced to remain straight; in the other, the pipe is allowed to bend so as to maintain zero net bending moments.

2.4 Effect of Initial Residual Stress on RHSI Effectiveness This study considers the effect that welding induced residuals p have on thre effectiveness of the RHSI procedure. A conservative approach to the effect of initial residual stresses is taken by assuming a worst case initial stress condition. A worst case condition is assumed to result when the initial residual stresses are as far from the final desired distribution as can be reasonably achieved and still maintain equilibrium and i

compatibility within the models.

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Figure 3 shows the initial residual stresses that are used in the axisymmetric models. The axisymmetric residuals are obtained by applying a temperature cycle which is similar to one that might be used to model a butt veld. However, the welding heat input rate that would be required to achieve the temperatures us6d in this study would be above the range that is commonly used and thus the initial residual stresses are worse that, are commonly found for 28-inch pipe butt welds.

I l Figure 4 shows the initial residual stresses that are used in the one- dimensional and the CTb models. This residual stress pattern is obtained by applying a temperature cycle k.lch is est,entially the inverse of the RHSI cycle. That is, the inside of the pipe is heated while the outside is kept cool. Note that the initial residual stresses for the one- dimensional and GPS models are different from those for the axisymmetric models (particularly in the hoop direction).

i 2.5 Heat Transfer Analytris As noted above, this study relied heavily on thermocouple measurements for determining temperature input to the stress models. Both OD and ID temperature measurements were made in the laboratory application. A one-dimensional heat transfer model was used to predict the shape of the through-wall distribution considering a uniform outside surface heat input and a convective inside surface boundary condition. From this model, it was determined that the through-wall temperature distribution for the e pipe diameter to wall thickness ratio of the subject welds is l l

essentially linear. Thus a linear interpolation scheme was used to interpolate between the measured OD end ID surface temperatures for input to the stress models.

ID temperature measurements wnre not practical for the field applications. Therefore, the one-dimensional heat transfer model l

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< s was also used. to determine inner surface temperatures for the field RHSI simulations. Once the inner surface temperatures were determined in this manner, the same linear interpolation scheme was used for through-wall temperature distributions.

Applying the heat transfer model to the lab test temperature data, the heat transfer coefficient for the inner pipe surface was found to be about 2000 Btu /ft2-hr-F. Since this heat transfer coefficient is believed to be larger than that which can i be achieved in field applications, and since a smaller f coefficient increases the l'.n e r surface temperature, and thus results in a less ef fectivs temperature distribution, the field simulations conservatively assume a heat transfer coefficient of 1000 Btu /ft2-hr-F. A change in the coefficient from 2000 to 1000 )

causes the inner surface temperature to increase by only about 20 F and thus, the effect of this assumed heat transfer coefficient is not expected to have a significant impact on the results and conclusions of this study.

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, 2.6 Material Properties The temperature dependent material properties being used in this study are for 304 stainless steel. These properties are summarized in Table 1 (8).

2.7 Finite Element Program The finite elen.ent program WELDSII is used for all stress I

, analyses of this study (1-6). This methodology for residual stress modeling of welding and heat treatment processes was initially developed at Battelle's Columbus Laboratories (1, 2, 3] l with support from the U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI). As a result of g

numerous complexities associated with modeling such processes and the extreme expense that would be incurred if each aspect of the-7 STRUCTURAL INTEGRITY I ASSOCIATESINC

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. 1 processes were modtled with state of the art analytical tools,  ;

the methodology uses a number of simplifying assumptions. Most of these assumptions are difficult to justify based solely on analytical reasoning and therefore extensive experimental verification of the methodology has resulted. (1-6). While the WELDSII modeling methodology was developed for pipe girth welds, and the bulk of experimental verification has been for girth welds, the methodology has been successfully applied to other

a. geometries and processes (2, 6, 7). Justification of the WELDSII computational methodology for the present RHSI analysis is based

. largely on the extensive analytical and experimental data presented in (7), describing application of this technique to the technically similar IHSI process.

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T 3.0 RESULTS 1

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! This section presents the results of the numerous axisymmetric, l one-dimensional, and GPS analyses which have been made in this l study. While analyses are made for all three RNSI applications, i most of the results being presented are associated with the RHSI l field application to Wald 28- 108. The reason for this is that this application resulted in temperature distributions which

a. deviated more from the RHSI design temperature distribution (both in terms of peak outer surface temperature and in terms of axial length of the temperature band) than did the other two applications. Therefore, this was the natural choice for assessing the sensitivity of the RHSI method to less than optimal temperature distributions.

3.1 Laboratory Test Pipe RHSI Analysis ,,

Figure 5 shows the outer surface thermocouple data at the point in time when power is removed from the resistance heaters. The data from the 0, 120, and 240 degree azimuths are all plotted together so as to be able to determine a lower bound temperature distribution. This distribution is shown on the plot and is the one used in the subsequent axisymmetric stress analysis. The 700 F constant temperature section of this lower bound distribution has a length of 3.18 in. or about 0.75 6 . The curved portions  ;

of the temperature distribution are parabole s. The total width l of the temperature band is 17 in. or about 4M. The inner surface temperature distribution has a similar shape to the outer r- surface with its maximum temperature of 6) F being based on actual thermocouple data. This temperature distribution is named A6 where the A stands for axisymmetric.

l Figure 6 shows the ;esults of 'the axisymmetric RHSI stress analysis for the laboratory test pipe. Two analyses are I

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presented. One analysis simulates the RHSI procedure being applied to a stress-free pipe. The other simulates the application to a pipe with residual stresses. as indicated in ,

Figures 3 and 6. .

It is seen that the predicted inner surface stresses near the weld are 1) highly compressive, 11) largely independent of the initial residual stress state, and lii) extend for a distance of F several inches to either side of the weld centerline. Near the pipe midwall, the effect of the initial residual stresses is more

'i pronounced. This effect is due to the RHSI process creating a bending type of stress field which has a neutral axis near the midwall and thus producing the largest plastic strains at the inner and outer pipe surfaces.

Figure 7 compares the predicted residual stresses wita those obtained from the destructive experimental residual stress determination of the laboratory test pipe. It is seen that the experimentally determined stresses range from a low value near the compressive yield point of the material to a high of three to four times the compressive yield point. The analytical model

, thus conservatively underpredicts the experimentally observed residual stress benefits of the RHSI process. This is believed to be due to the use of lower, base metal tensile properties j throughout the model, and the fact that strain hardening of the weldment during the welding process was not modeled. This comparison is very similar to that presented between IHSI analyses and experiments 1.1 (7), and demonstrates that the

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WELDSII analysis provides a conservative basis for the evaluations of field RHSI applications which follow.

3.2 Weld 28-108 RHSI Analyses i As mentioned previously, analyses for Weld 28-108 are more extensive than for the other RHSI applications due the RHSI STRUCTURM.

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temperatures being judged least favorable of the three cases being considered.

3.2.1 One-Dimensional Analyses of the Walo 24-108 RHSI 1

1 The one-dimensional model consists of a single stack of eight I i

axisymmetric elements through the pipe wall thickness. Boundary l conditions are imposed which require that plane sections remain plane. The one-dimensional model serves to illustrate the best residual stress improvement that a given axisymmetric through thickness temperature distribution is capable of providing.

Figure 8 compares the residual stress improvement associated with four maximum outer surface temperatures. The inner surface temperature is determined by a steady-state one-dimensional thermal analysis which assumes an inner surface heat transfer coefficient of 1000 Btu /ft2-hr-F. The lowest outer surface temperature that is considered is 400 F (Figurie 8a). It is seen that this temperature tosults in very small residual stresses for l the case in which the pipe is initially stress-frem. Despite the small effect this distribution has on the stress-free pipe, it does significantly reduce the tensile residua $ stresses for the pipe with initial tensile residual stresses. However, highly compressive residual stresses cannot be attained with this level l

I of temperature.

Figure 8b s, hows the residual stress improvement from a 550 F outer surface temperature. This temperature produces significant

" compressive stresses at the inner surface for both the 1 l

stress-free and the initial residual stress condition. The reversal in the slope of the final stress distributions near the midwall, however, indicate that the RHSI induced plasticity is largely limited to the pipe surfaces.

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e Figures 8c and 8d are representative of the outer sur. face temperatures which are generally obtained with the RHSI procedure. It is seen that the difference between the stress-free and initial stress results become progressively smaller, and that the tendency for a reversal in the slope of the curves near midwall decrease as the outer scrface temperature (and thus temperature gradient) is increased. Temperatures above 300 F would not significantly improve the distribution obtained

s. with 900 F.

3.2.2 Axisymmetric Analyses of the Weld 28-108 RHSI Figure 9 summarizes the thermocouple data from three azimuths of the Weld 28-108 RHSI application. Figure 9a and 9b both show the data from the 240 degree azimuth. Figure 93 shows a fit to the data which does not assume that the RHSI temperaturas have a plane of symmetry. The fit shown in Figure 9b assumes a plane of symmetry.

The temperature fit of Figure 9b has a total temperature band I

width of 13.28 in. or about 3 6 . The temperature fits of 9c and i 9d have a total band width of 17.71 or about 4 6 . The central I constant temperature region of both 9c and 9d is 4.42 in. or about 1.0 6 .

I It can be seen in Figure 9 that all of the temperature fits are shifted relative to the weld centerline. For the temperature distributions of 9c and 9d, the shift is fairly small compared to e the overall temperature cand width. However, the distributions for the 240 degree azimuth shov a fairly large shift compared to the temperature band width. Due to this large shift, and due to the fairly poor fit of the data in 9b, two axisymmetric analyses of the 240 degree azimuth temperatures are made.

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f The axisymmetric analysis using the temperature distribution of Figure 9a does not assume a symmatry plane. That is, both sides of the veld and RHSI temperature field are modeled. The results of this analysis are shown in Figure 10. It can be seen that the final inner surface residual stresses are compressive. However, in the case of initial residual stresses, the axial stress is only compressive by a small amount (10 ksi), and there remains a tensile stress zone at about 0.2 inches below the surface.

As discussed previously, the stress results obtained from an axisymmetric analysis of a temperature distribution which represents a localized cool spot are expected to be conservative.

That is, if a cool spot is relatively small, then neighboring material which is outside the cool spot is expected to offset the effect of the cool spot and result in stresses which are more favorable than would be predicted by . an axisymmetric analysis,

( which assumes the cool spot to be 360 degrees. This type of behavior can be seen from the GPS analyses to be discussed below.

The results from a second analysis of the 240 degree azimuth are i

presented in Figure 11. These results are from using the

. symmetrical temperature distribution of Figure 9b. This analysis addresses 1) the effect of assuming the symmetry plane of the initial residual stresses coincides with the symmetry plane of l the RHSI temperature field, and 11) the effect of using a temperature fit which fell below the thermocouple data points at one side of the temperature band. It is seen that the results are not significantly different from those of Figure 10. This similarity serves as a justification for assuming that the symmetry plane of the initial residual stresses coincides with the symmetry plane of the RHSI temperature distribution for the remaining axisymmetric analyses. .

( .Igures 12 and 13 show the stresses resulting from the axisymmetric analyses using the temperature distributions of STRUCTURAL

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Figures 9c and 9d, respectively. Both analyses result in strongly compressive axial and hoop stresses at the inner pipe surface as well as for a significant distance below the surface. l l

It is seen that the higher temperature case (Figure 9d and Figure l l

13) results in noticeably stronger compression at points beneath '

the surface but results in very similar stresses at the surface.

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3.2.3 Generalized Plane Strain (GPS) Analyses of the Wald 28-108 RHSI The above axisymmetric analyses illustrate the residual stress improvement that results from RHSI temperature distributions which do not. vary with circumferential position. For the

. distributions which are generally representative of RHSI temperatures (i.e., Figure 9c and 9d), these analyses give results which are expected to be representative . of the actual

stress improvement. For the distributions which represent localized cool spots (Figure 9a and 9b), these analyses give results which are indicative of the worst case (i.e., when the cool spot approaches 360 degrees).

The purpose of the GPS analyses is to further examine the effect

! of localized cool spots on the effectiveness of RHSI. This is done by considering two circunferential temperature profiles based on the thermocouple data from the RHSI of Weld 28-108.

These two temperature profiles are designated G1 and G2 and are shown in Figure 14. Both profiles are symmetrical about the 0/180 degree plane as requirsd by the finite element model of Figure 2.

As a result of the GPS temperature distributions not being axisymmetric, one side of the pipe tends to expand more than the other thus creating a tendency for bending of the pipe. The I effect of bending restraint is addressed by considering the two limiting cases of no bending restraint and total bending i

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constraint. Axial expansion and contraction is permitted to occur freely in all GPS analyses as well as in all of the previously discussed axisymmetric and one-dimensional analyses.

Since it has been demonstrated that analyses which assume worst case initial residual stresses result in less favorable RMSI results than analyses which assume an initially stress-free condition, the GPS results are presented only for the case of initial stress.

Figure 15 shows the results of the GPS analyses in terms of inner and outer surface stresses. It is seen that the entire inner surface is predicted to have axial and hoop stresses which are in the neighborhood of the compressive yield stress. While the locations of the cool spots are readily discernible from the outer surface stresses, the inner surface stresses give no clue to as to their location.

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l Figures 16 and 17 show the through thickness stresses from the i GPS analyses. Generally, the residual stresses are quite similar to'those obtained from the axisymmetric analyses of typical RHSI l temperature distributions (Figures 9c, 9d, 12, and 13) despite l the existence of regions where the maximum outer surface j temperature is less than 600*F. j The GPS analj ses are similar to the one-dimensional analyses in that they inherently assume the axial width of the temperature band is very large. For this reason, the GPS results may be overly optimistic at locations for which the width of the RHSI temperature band is less than the design width. However, it can be seen from Figures 16 and 17, that the least favorable (least compressive) stress distributions tend to be for circumferential i locations which have the highest temperatures rather than the l lowest. For example, Figures 16a and 17a both show the least

.I faverable axial stress profile occurring at angular position E which corresponds to the position of the hottest outer surface i

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temperature. Position C, which corresponds to the sectien with the coolest temperatures has the most favorable stresses.

This unexpected behavior of the GPS model is believed to be the result of ovalization of the cross-section due to the form of the circumferential temperature variation being considered. The ovalization tends to reduce the RHSI induced plasticity at the hot sections (which occur at the major axes of the oval) and

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tends to increase the plasticity at the cooler sections. While )

this pronounced of an effect is not to be expected in general, it is clear that the detrimental effects of localized outer surface cool spots will generally be reduced as a result of neighboring regions which have higher outer surface temperatures.

Figures 16 and 17 show that the presence or absence of bending restraint is of secondary importance compared to the temperature t distribution. Typically, the difference between the two extreme bending restraint conditions is less than 10 kai for the G1 and G2 temperature cases considered here. The more axisymmetric the

RHSI temperature distribution becomes, the smaller the effect of I

bending restraint will become.

l Figure 18 illustrates the degree of bending which the G1 and G2 temperature distributions induce. Figure 18a and 18b are for the l

case in which bending is unrestrained while 18c and 18d are for the totally restrained case. The curvature and moment information can be converted into equivalent elastic bending stresses using simple beam theory with the following results.

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The final curvatures for the unrestrained G1 and G2 cases are equivalent to 5.9 and 0.4 ksi, respectively. The final moments for the totally restrained G1 and G2 cases are equivalent to 9.9 and 5.4 ksi, respectively. The axial contractions for the four cases are equivalent to an average axial stress between 14.6 and

' 17.9 ksi. These results are consistent with the GPS results for this weld presented in Figures 16 and 17.

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! 16 DfFE@ TIT AShMINC .

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3.2.4 Summary and comparison of Weld 28-108 RHSI Analyses The results from the axisymmetric, one-dimensional, and GPS models of the Wald 28-108 RHSI are compared in Figures 19, 20, and 21. Figure 19 compares the inner surf ace axial and hoop stresses. The tendency for the axisymmetric analyses to produce a worst case behavior for axial stresses is readily apparent.

6 The differences between the axisymmetric results and the P one-dimensional results are primarily due to the finite axial I

width of the temperature band in the axisymmetric analyses, but may also be due in part to the slightly different initial residual stress states. The tendency for the GPS model to smooth

, or average the stresses is also apparent.

The differences between the one-dimensional results and the GPS results in Figure 19 are due entirely to the smoothing / averaging 4

ef fect of the GPS model. The same smoothing / averaging behavior would be expected to improve the localized behavior of the l:

axisymmetric model (i.e., the -12.5 kai value at 240 degrees l would become more compressive) if a three-dimensional model was to be employed. I 8

Figures 20 and 21 compare the through thickness stress results from the various types of analyses. It can be seen that these various analyses generally result in similar stress predictions over the inner half vall thickness at the 0 and 120 degree locations. However, at the 240 degree location there is a sizable spread in predicted stresses. It has been argued that

" the axisymmetric analysis produces a worst case result. On the other hand it can also be argued that the GPS analysis results are overly optimistic due to the inherent assumption of a large I axial length for the RHSI temperature band. Therefore, it is l reasonable to conclude that the actual stresses lie somewhere

, between the axisymmetric and GPS analysis predictions.

I I

STRUCTURAL 17 .

N ASSOCIATESINC

i

. . l 4

3.3 Wald 28-50 RHSI Analysis Figure 22 compares the outer surface thermocouple data from the RHSI of Weld 28-50 with the axisymmetric temperature distribution called A2. This A2 temperature profile is one that was used to represent the o degree azimuth data of Wald 28-108 (Figure 9c).

This temperature profile is seen to represent a lower bound temperature distribution for this RHSI application. Since an

• axisymmetric analysis of this temperature distribution has already been made, no additional analysis is required. The residual stresses resulting from this temperature distribution are given in Figure 12. It can be seen from this figure that a highly compressive state of stress is predicted at the inner surface of the pipe.

I i

i F*

1

. 1 I

l E

18 'm4TIMR1T/

ASSOCIATESINC l

O, e e

e

(

4.0 C011CLUSIOllS It has been shown through analytical and experimental results that the RHSI procedure creates significant compressive axial and hoop residual stresses over a significant portion of the inner pipe surface.

It has further been shown that when the design temperature gradient and temperature band size are achieved, the results are not significantly affected by initial residual stresses.

Finally, it has been shown that the procedure is reasonably tolerant of deviations from the optimal design temperature distribution if the deviations are of a local nature.

(

i .

l r-l

(

l FTRUCTURAL i

! 19 MfEGRITY As h M INO

'l

5.0 REFERENCES

(1) Rybicki, E. F., et. al., "Residual Stresses at Girth-Butt Welds in Pipes and Pressure Vessels", Final Report to U.S.

Nuclear Regulatory Commission, Division of Reactor Safety, Research under contract No. AT (49-24)-0293, HUREG-0376, published November, 1977.

(2) Rybicki, E. F., et. al., "Residual Stresses Due to Wald Repairs, Cladding and F.lectron Beam Welds and Effect of Residual Stresses on Fracture Behavior", Final Report to U.S. Nuclear Regulatory Commission, Division of Reactor Safety, Research under Contract No. AT (49-24)-0293, NUREG-0559, published December, 1978.

(3) Brust, F. W. and Stonesifer, R. B., "Effect of Weld Parameters on Residual Stresses in BWR Piping Systems", Final Report to Electric Power Research Institute, NP-1743, Research Project 1174-1, March 1981.

(4) Rybicki, E. F., et. al . _ "A Finite Element Model for l Residual Stresses and Deflections in Girth Butt Walded Pipes",

Journal of Pressure Vessel Technology, Vol. 100, No. 3, August I 1978, pp. 256-262.

[5] Rybicki, E. F. and Stonesifer, R. B., "Computation of Residual Stresses Due to Multipass Welds in Piping Systems",

i Journal of Pressure Vessel Technology, Vol. 101, No. 2, May 1979, pp. 149-154.

(6) Rybicki, E. F. and Stonesifer, R. B., "An Analysis Procedure

- for Predicting Weld Repair Residual Stresses in Thick-Walled Vessels", Journal of Pressure Vessel Technology, Vol. 102, No. 3, 1980, pp. 323-331.

[7] Rybicki, E. F. et. al., "Computational Residual Stress Analysis for Induction Heating of Welded BWR Pipes", Final Report to Electric Power Research Institute, NP-2662-LD, Research Project T113-6, December, 1982.

- [8] International Nickel Company, Inc., "Mechanical and Physical Properties of Austenitic Chrome-Nickel-Stainless Steels at Elevated Temperatures", Chrome-Nickel Stainless Steel Data, Section 1, Bulletin B.

s I

i STRUCTURAL l 20 DCTEQtT]T

. mmDC

Table 1 Temperature Dependent Hechanical Properties of 304 Stainless Steel (8)

Temperature Elastic Poisson Hardening Thermal Yield (F) Modulus Ratio Modulus Expansion Stress p (ksi) (ksi) (1/F) (ksi) i 50 2s700 0.26 539.7 8.16E-06 36.0 300 27100 0.28 452.0 8.94E-06 31.1 550 25800 0.31 364.8 9.60E-06 25.9 750 24200 0.32 296.3 10.03E-06 22.3 1000 22500 0.30 217.9 10.56E-06 18.5 1300 20200 0.28 139.0 11.41E-06 14.9 1600 16000 0.24 79.6 12.63E-06 10.2 2100 10 0.22 1.0 14.8BE-06 1.0 l

F n .

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i i

STRUCTURAL 21 WrR3 RIM ASSOCIAmilNC

. _. ~ . , . .

3 _. .

T

1. =

20 w g ,

~

t

! . __l_.

t WELD 28-108 s.'fo~

WELD 28-50 f.10" .

TEST PIPE f.28"

~

IT" z =

Figure 1. The Axisymnetric Finite Element Grid Used for RHS! Analyses Which

. lig Assume Ril51 Temperature Centerline Symmetry (396 nodes, 344 elements)

~

~

E _

E. ;9 -

s 1

~

I 4 0 r

5 + =,

p , --

4. _

= I4 Figure 2. The Finite Element Grid Used for Generalized Plane Strain RH5I Analyses (8t9 nodes, 720 elements) b

i

,o 0, Out - surroce go .

ytcQ Cenlerloc Ie Inner- Surface _

40 - 40 -

M -

g E -

g j 20 - j 20 -

\.

g 10 -

^ - - -

C' e 10

' O

^

\ - - ^

O b b * -10 -

" -10 -

3x -20 -0 "3 -20 -

,N x

< _3o - < _30 -

-40 - -40 -

"^' * ' - ' ^ ' ^ ' * *

-50

- ' ' ^' ' ' '

-50 O 2 4 8 8 10 12 14 IS 19 20 0 0. 2 0. 4 0. 8 0. 9 1. 0 1. 2 1. 4 Oletance from Temperature Centerline (In) Oletance from Inner Surface (In)

InitIof Ax!eyametric Reeidual Stree. Initial AxseyemetrIc Reeidual Strsee E 50 O e Outer Swho 50 -

40 - 40 - NcN b MC'E"C 2 0 2 6 6 N i N. . Am-  : . . . . . . .

b >I $

m -10 - m -10 -

-20 - -20 -

) -30 - -30 -

y

-40 - -40 -

^ ' " ^' *^' ' "

- ' - ' ^'^' '^' '^

-50

-50 9 10 12 14 18 IS 20 0 0. 2 0. 4 0. 8 0. 8 1. 0 1. 2 1. 4 0 2 4 8 Oletece from Temperature Centerline (In) Distance from Inner Surfoce (in)

Initial AxisymmetrIc ReeIdual Strese InitIof Ax1eyametr5c ReeIdual Strese II h Figure 3. The Initial Residual Stresses Which Are Assumed for the One-dimensional and Generalized Plane Strain RH51 Models

~ 4

. e 0 51 0 5 1 6 7 2 A 3 3 2 2 .

/ / / /

0 5 0 5 0 )

4 9 3 9 1 1 e 2 n 3 I

(

e e e e e . s e

c e e l A B C D E a

. e 0 a 1 f t r o n

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6 I R

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- ~ - - - - . - - s 0 A 0

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- - - - _ re Ad O.6 :,bn g2 o i hM i!

c

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s en si sa er rt tS S

4 e

. l n 0 51 & ]5 t aa

- 6 2 1 ul

- 3 3 2 2 . dP

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. n 2 n I ee 1

( Rz e e e e e . s i A B C D E e c e e ll aa

. . t 1

0 a f t r ir t e r S in u ne S l IG 8 e ed

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h n

. n l T a 1 I n ee

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.\ . . r a e f i r 4 t u g

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n I a

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- ~ . - - - - - -

0 0

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0 o 0 o 0 0 g 1 1 2 3 4 O.6 ,bu g1<

,* l l

!, l

_ 3 - _

Weid

• s 0 0 T. C. Data 900 - Center 1ine s Model Input A6 800 -

700 -

Outer Surface a 600 -

b _

E 500 -

?, _

o y 400 -

~

?

s 5-- 300 -

200 -

100 -

Inner Surface 35 F 0 0 5 10

-10 -5 Distance from RHSI Temperature Symmetry Pione (in)

Axial temperature profile for the RHSI lab test Figure 5. Laboratory Test Pipe Thermocouple Data and the Axisymmetric Model Input Temperature Distribution

3

• * '"9 ~ ' * ~ "

Ve Welding residual otrese 50 -

Ae m 61 on a etress-free pipe 50 -

Ae m61 on a etrese-free pipe * "' '" " * "**

1. U ~ #0 ~

8e M61 with initial residemi stresses

, 30 -

o 30 -

• W

$ 20

. .a e

10 -

t

^ -

-

• O O

-10 - -10 -

3 -20 - 2 -20 M

M

< -30 -

< -30 -

A

-40 -

g -40 -

- * - ' '- * ' ' - * ^ ' - ' -50

-50 0 0. 2 0. 4 0. 6 0. 8 I. 0 I. 2 1. 4 O 2 4 6 9 10 12 14 IS 10 20 Osetonce froe RHSI Teeperature Center 11ne (in) 0Ietance from Inner Surfoce (in)

c. Inner surface axial strees (AS) b. Axtof stresses at the weld (A67

% Ve Velding residual etrese Ve Valding reeldual etreee 5g p , ggg an a ,ge,,,-gre,pgpe 40 Ae M61 on a etrese-free plP* g . 8e M 61 with initial ressdval beoes Be M61 with Initial reeldval stresses

~

N -

, M -

e 20 -

• 20 -

6 6 10 , 10 e y ^

e 0 e O -

b b -

- en -10 in -10

• - E-20 o

}-2030 -

I

_30 -

40 g -40 Ti01stancefroeRHS!TemperatureCenterline- '

> 4- * * - ' '

50

-50 3. 2 1. 4 10 32 14 16 19 20 0 0. 2 0. 4 0. 6 0. 9 1. 0 O 2 4 6 8 (in) Oletance from Inner Surfw e (s n)

Inner surface hoop etrees (A6) d. Hoop stresome at the weld (A6) haea c.

H.

3 Figure 6. Pre- and Post-RH5! Residual Stresses Resulting from the Axisynenetric

• Analysis of the Laboratory Test Pipe

3 m *- ..

~

Ae RMSI analyste on o etreee-free pipe (A6) Ae RMS! analyese on a etreee-free pipe (A6)

Be RHS1 analyese with Instsal reeldvol streseen ,g ,

Be M 1 m iyose en m Instsal reet k i etreeeen ee RMS! Roosdual Streee Data e e RHS! Reesdual ,Streee Data,

-10

- 2 11 b

A -2D -

-30 - #

-30 -

y'

-40 -

• j -40 -

[

-so -

8  : -so -

3 $ -so -

f-so E

5 -70 -

• -70 -

1 -so .

< -go .

-90 - -90 -

-100 - .

-100 -

-110 - * -110 -

. . . ,, e . .,. . e . , . e . e ,,3

. e . , ... + . e e . e . .' e . . e

,,3 -4 O 2 4 8 8 10 8 4 -2 0 2 4 6 8 10 8 -6 1?

Dsetance trom Weld smd RH51 Centerline (s n) Dsetance From WeLeand RH51 Centerline (in)

e. WH51 Inner Surroce Aesal Reeldual Streee Doto erwl Analyste k RH51 inner Surface Hoop R mldual Strees Date erwl Analyets C Figure 7. Comparison of Predicted Residual Stresses from the Axisywinetric Analysis and Experimental Stress Data from the Laboratory Test Pipe E

o

1 I . .

- n ...

Vs Valding reeldual streen Ve Valding reeldval etrese 50 Ae M61 on a etrene-free pipe 50 Ae RHS! on a etrese-free pipe 8s M61 with Insttal resI6 sal /g streneen 40 40 -

8s M 61 with initial residual otraseos o 30 - 30 -

j 20 -

j 20 -

-A M

!' i m

-10 -10 -

3x -20 -

3X -20 -

< -30 - < -30 /

-40 - -40 -

' - ' - ' ^ ' ' '

-50

-50 0 0. 2 0. 4 0. 6 0. 9 1. 0 1. 2 1. 4 O 0. 2 0. 4 0. 5 0. 8 1. 0 1. 2 1. 4 01 stance from Inner Surface (in) Oletance from Inner Surface (in)

a. Maximum 00 Temperature of 400 F b. Maximum 00 Temperature of 550 F ro V ,e Velding reeldual etreee Ve Valding reeldval streee 50 -

Ae RHS! on a streee-free pipe 50 -

Ae M 61 on a streee-free pipe 40 - 8s RHS! with initial reeldual dreseos 40 Be M61 with initial reeldn al e reeees o 30 - m 30 -

, j 20 -

j 20 -

l s

b e

"o O

^x / ^

b

• $a O

^x ^

! " -10 - M -10 -

_, -20 -

3X -20 -

X

< -30 - < -30 -

• • -4D -40 -

.E * ' ' " - ' ' - " "

• " ^' '

CJ -50

-50 O D. 2 0. 4 0. 6 0. 0 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 5 0. 0 1. 0 1. 2 1. 4 l 01 stance from Inner Surface (in) Oletance frosi inner Surface (in)

c. Hoximum 00 1separature of 700 F J Maximum 00 Temperature of 900 F l Figure 8. One-dimensional Analysis Stress Results for Several Through-Wall l Teciperature Gradients -

1 I

~

% 1

~

_ _ . _ _ 7 _

e s 0 0 T. C. Data *a 00 T. C. Dato l 800 - -e Model loput A7 B00 -

f*ffaeline e Model input Al l

700 - l 700 -

Outer Surface Outer Surface .

l

@ 600

@ 600 ,

(500 (500 g 400

"(400 -

e e g 300 -

J 300 -

• Inner Surface 200 - fnner Surface 200 130 F W 130 F

/~

100 100

-5 0 5 10 IS -10 -5 0 5 10

-10 i Distance from Wald Centerline Ga) Oletance from RHSI Temperature Symmetry Plane fin)

a. Weld 28-108 at the 240 degree azimuth b. Wald 28-100 at the 240 degree azimuth o"

• s 00 T.C. Data *s DD T.C. Data 800 -

f*fferigne e Model Irput '2 1000 -

f*ff,eggn, a Model Input A3 Duter Surface 900 -

.N

^

700 -

. Outer Surfahe 800 -

C 600 - C 700 -

e e 500

• h 600 3 o e -

(400

{ 500 E I* 400 -

,8 300 300 -

200 -

Inner Surfoce I""*" 8""I***

l 200 -

130 F 30 F

' ^ ' ' -8 100

• ' ^ ' - '

100

-5 0 5 10 -10 -5 0 5 10

-10 Dietance from RHSI Temperature Symmetry Plane Ge) Oletance from RHSI Temperature Symetry Plane Un)

c. Weld 20-100 at the O degree azimuth d. Weld 28-108 at the 120 degree azimuth a

g i U ..

Figure 9. Thermocouple Data from Weld 28-108 and Several Axisymmetric Model Input Temperature Distributions

g ., . .

m 7 - .~ .-

i Ve Valding reeldval atrese Ve Valding residual strese 50 - Ae RHS! on a stress-free pipe So -

8s M61 with nitial residual stresses As M61 on a stress-free pipe 8e M61 with initial residual etresses 30 - o 30 -

a.

F j 20 y 20 e 10 -

e 10 -

I

' e - '-

) O

-10 - 8 -10

, 3 -20 - 3x -20 x *

< -30 - < -30 -

-40 - -40 -

' ^ " '

-50

^ ' ' ' '

-50 -

0 4 8 12 I6 r, 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4

~16 -12 -8 -4 Otetonce from Veld CenterInne (In) Otetance from Inner Surface (in)

. a. Inner surface oxial strees (A7) b. Axial stressee at the weld (A7)

U l

,Ve Valding residual etreen Ve Valding residual streee 50 - As RHS! on a stress-free pipe 50 - A s RHS! on a stress-free pipe

} 8s RHS! with initial residual streeeee

_ 40 8o RHS! with initial realdual stresees

30 -

30 -

xe 20

e 20 -

5 # 10 10 i .

0 s A ---

0 . . g- -

{

i m -10 - m -10 -

f-20 f-20 1

• * -30

-30 -

-40 - -40 -

j ' * ' * ' '

- ' ' ^ ' ' ' ' ' '

-50 -50

-16 -12 -8 -4 0 4 8 12 16 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 Oletance from Weld Centerline (in) Otetance from Inner Surroce (in)

c. Inner surface hoop stress (A7) d. Hoop stresses o the weld (A7) i Figure 10. Pre- and Post-RHSI Residual Stresses Resulting from the Axisymmetric Analysis f of Weld 28-108 Using the Input Temperature Distribution A7 i

l l

- 3 e . . . .

_ -~

"' * ** * * ' "9 " * ' ' * ~ * *

• * '"9 ~

• 50 -

$ 50 -

Ae RHS! on a stress-free pipe Ae RHSt on a etress-free pipe "O

^

AU ^

Be RHSE with initial residual streseos 8e RHSE with initial residual stressas 30 - o 30 -

a 20 - F j 20 -

, 5 m i

10 - 20 -

e 0 0 --

4 (

" -10 8 " -10 3x -20 - 3X -20 -

< -30 - < -30 -

-40 - -40 -

^ ' ' ' ' ' ' '

-50

• ' * ^ " ' ' ' '

-50 5 0 10 12 14 16 18 20 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 O 2 4 O! stance from Temperature Centerline (In) Oletance from Inner Surface (In)

a. Inner surface exto; otrees (AI) b. Axtol stresses at the weld (AI)

U Ve Welding reeldval strese V's Valding residual stress 5 Ae RHS1 on a strees-free pipe Ae RHSI on a strese-free pipe 40 - 8e RHS! with initial reeldval str ses AU

~ 8s RHS! with initial reeldval stresses j 30 -

30 -

e 20 - e 20 -

5 5 10 tV 10

-\ - -  : .

/

5* "J 5*

rn -10 -

f en -10 -

E-20 - E -20 -

E .x- E

-w -

A B -40 -

_,o . . . . . .. . . . .

_,o l 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 10 12 14 16 18 20 ll 0 2 4 6 8 Oletance from Temperature Centerline (in) 01 stance from Inner Surface (In) l

c. Inner surfoco hoop ste ese (AI) d. Hoop stresees at the weld (AI) en b Figure 11. Pre- and Post-RHSI Residual Stresses Resulting from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution Al -

l i

l o

l __ _ __

i Ve Valding reeldval streen 50 -

Ve Valding reeldval streme 50 Ae RHSI on a stre.re-free pipe As RHS! on a stress-free pipe * #"# '" # *****

1. O "O ~

Bs RHS! wIth inttIal restdual stressee

~

30 - o 30 -

t o,,,

1 20 - V . 5 20 v

v e to - e 10 -

- I .

5 - U 5

" -10 -

A

" -10 -

\

O -20 - 0 -20

< 8 < -30

7. -40 -

~40 -

-50

- * ' * ' ' ' ^ * *

-50' ' '

0. 4

0. 8

1. 0

1. 4 O 2 4 6 8 10 12 14 16 18 20 0 0. 2 0. 8 1. 2 Distance fross Temperature Centerline (in) Distance from Inner Surface (in)

a. Inner surface axlal strees (A2) b. Axlal stresses at the weld (A2)

U V 'e Valding reeldval streen Ve Valding reeldval streen 5 Ae RHS! on a streen-free pipe Ao RHS! on a strene-free pipe 40 -Be RHS! with initial reeldval stre en AU ~ 8e RHS! with Initial reeldval streeeen 30 -

30 -

• 20 - e 20 -

6 6 10 -V 9 10 I I O O -

b b m -10 - m -10 -

g E -20 - E-20 -

2 -30 -

-30 -

-40 - -40 -

p g

' ' ' ^' ' ' '

-50 lle

-50 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 O 2 4 6 8 10 12 14 16 18 20 Otetonce from Temperature Centerline '(in) Distance fra.a inner Surface (in)

c. Inner surfaces hoop strees (A2) d. Haap stresses at the weld (A2)

Figure 12. Pre- and Post-RH51 Residual Stresses Resulting from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution A2

-~~

• 7

~~ ~ ~ ~ ~ . .

l , ,

Ve Valding residual otreen Ve Velding residual stress 50 -

Ae RHS! on a strese-free pipe Ae RHS! on a stres**fr** PIP

• 4g . 8s RHS1 with initial residual stresses

. 40 ~

8s RHSt with initial residual stresses n 30 - o 30 -

V j 20 -

j 20 -

e 10 -

ee 10 -

e * ^

e ^

O l b O

\ b - '\ U

" -10 -

1 m -10 -

\ A "3 -20 -

) B y "3 -20 -

x .

7

< B < -30 -

T N l -40 - -40 -

-50

, O 2 4 6 8 10 12 14 16 18 20 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 01;.1va from temperature Centerline (In) Diet.ance from Inner Surface (In)

a. Innee ourface axial stress (A3) b. Axlal stresses at the weld (A3)

U y, Valding reeldvat streen go

• • M % ~ " ""

gg _

Ae RHSI on a streme-free pipe Ao RHS1 on a streen-free pipe AU 40 - 8e RHS! with initial reeldval e e

~ Be RHSE with initial residual streseen 30 -

30 -

• 20 -

• 20 -

5 5 10 -V , 10 s 0 -

e 0 b b -

m -10 - m -10 -

E -20 - E-20 -

-30 -30 -

A

" -40 -

' ^'^' * ' ' ' ' ' '

I'01stancefromTemperatureCenter

-50

-50 0 2 4 6 8 10 12 14 16 18 20 0 0. 2 0. 4 0. 6 0. 9 1. 0 1. 2 1. 4 .

DIetance from Inner Surface (in)

(In)

c. Inner surface hoop stress (A3) d. Hoop stresses at the weld (A3)

Figure 13. Pre- and Post-RHSI Residual Stresses Resulting from the Axisymmetric Analysis of Weld 28-108 Using the Input Temperature Distribution A3 l

_ j

.___3 -

t-a Temper-atur-se at veld Concer-12ne Temper etur-se at veld Contarline 2

1000 - 1000 -

I 900 -

! 900 -

t e Se face 900 -

800 -

700 Outer- Sur-face 700 G G 8 800 -

e 600 -

5 *

,h e

'" 500 - 3 500 -

W

• *e T. C. Data s

• *e T.C. Data e _

-e Nadel input e ..ade! Input 300 - 300 -

i inner- Sur-face g .

Inner- Surface e x / N j

200 100 0 45 90 135 180 225 270 315 360

O 45 90 135 180 225 270 315 360 i

Azimuth (deg) Azimuth (deg) l

a. Temperature Casa C1 (Veld 29-106) b. Temperature Come C2 (Weld 29-108)

Figure 14. Thermocouple Data from Weld 28-108 and Two Generalized Plane Strain Model Input Temperature Distributions

~~

~

~~

l  ! .. ." -

Outer- Surfoco Outer Surface

• O A g _n

- 8 30 -

. 30l- ,

20

- e 20 -

A (a,th ,nst,al res,dva, streee)

'

• in th snit,al res, dual stress)

gg .

g gy .

e r .

^

• O

( 0 E -10 - m -10 -

f-20

$-20 x

. z A ~0 ~

Imor Surface A

< -30 -

g ,,,. Surface 8 5

-50 - 0 f -40 -

^" ' ' ' - ' ' ' ' ' J -50

-50 40 60 80 100 120 140 ISO 180 O 20 40 60 80 100 120 140 160 180 0 20

. Azimuth (deg) Azimuth (deg)

a. G1 and C2 with Bending Roetroint b. G1 md G2 with Bending Restraint M

Outer Surfaco 50 -

g

, 50 -

^

8 A 40 -

v 40 -

8 30 -

30 -

n

-=

• 20 -

s 20  :: g >: g c.,th ,nsts., .. su., .tr...) i c.,th ,n,t ., r..,+., .t . )

e 3 ^

• e O O

b b

" -10 - m -10 -

f-20 3-20 -

• A

-30 -

Imoe Surface N -30 -

y Imer surface A

-40 - N " o -40 6

-50

-50 40 80 100 120 140 ISO 180 0 20 40 60 80 100 120 140 160 180 O 20 60 IIC Azimuth (dog) Azimuth (dog)

C. C1 and C2 without Bending Restraint d. C1 and G2 without Bending Reetraint Figure 15. Inner and Outer Surface Residual Stresses Predicted by the Generalized h Plane Strain Analyses of Weld 28-108

~~

_ 3 m e n

Ae 0/360 Ae 0/360

]

j 8* 45/315 50 - 8* 45/315 50 -

n Ce 90/270 Ce 90/270 .

40 ~ De 13S/225 40 ' De 13S/225 1 '

Ea 180 30 - Ee 180 39 .

n ^

j s # 20 - -

20 -

- 10 -

/

i l 10 . ///. 3 . /

f

/ 8-0

• -30 E -30 -

, /

1

-40 - -40 I -50

-50

0. 2 0. 4 0. 5 0. 3 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 8 0. 8 1. 0 1. 2 1. 4 O

Distance from Inner Surface (in) Dietonce from Inner Surface (in)

a. G1 with Bending Restraint b. C1 with Bending Restraint U

Ae 0/360 Ae 0/363 B's 45/315 5g - Be 45/315 50 -

Ce 90/270 Ce 90/270 40

• De 135/225

^0 ~ De 135/225

- Ee 100 30 . Ee 180 3g l n 7 20 - 20 -

, 10 - 10 -

['

, I .A / . .

-10 -

. \ w -1 -

3 -20 - E-20 -

l E -30 -30 ts /

-40 -40

^ ' ' ' ^ ' ' ' '

-50

' - ' ' ' ^ ' '

-50 1. 2 1. 4 i

0. 8 0. 8 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 6 0. 8 1. 0 O 0. 2 0. 4 Ic i 01 stance from Inner Surface (in) Oletance from Inner Surface (in) 01 without Bending Restraint J. G1 withou', Bending Reetraint h Q.

Figure 16. Predicted Through thicknest Residual Stress from '.he Generalized Plane h Strain Analysis of Weld 28-108 Using Temperaturr. Input Distribution G1

^

.- ~

Ae 0/360 Ae 0/360 Be 4S/31S 50 Be 45/315 50

• Ce 90/270 l Ce 90/270

~

40 ' De 135/22S 40 ^ De 135/225 0 e 30 . Ee 180 .s 39 . Ee 180 g, a

-1 - -1 8 -20 - -20 -

q ,

< -30 - ,// -30 jf

-40 -40

' ' ' ' ' ' ' ^ '

' ' ^

-50

^ ' ^ ' ' ' ' ^

-50 O 0. 2 0. 4 0. 6 0. 9 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 01 stance from Inner Surface (In) 01 stance from Inner Surface (in)

a. C2 with Bending Restraint b. C2 with Bending Restraint l

Ae 0/360 Ae 0/360 B'* 45/315 50 - B* 45/315 50 -

+ Ce 90/270 AD ~ 0e 13S/225 Ce 40

• Oe 13S/225 90/270 l

n

-e 30 . Ee 190 /

l '

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,E ^

3g . Ee 180 .s f_

e 20 s.".

f 20 s

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< / / -30  ;

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' - ' ' ' ^ ' * *

• ' - ' ' ' ' ^ '

-50

^

C -50 O 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 Otetance from Inner Surface (In) Otetance from Inner Surface (in)

C. C2 without Bending Restrotnt d. C2 without Bending Restraint Figure 17. Predicted Through Thickness Residual Stress from the Generalized Plane Strain Analysis of Weld 28-108 Using Temperature Input Distribution G2.

o

~

n ] . -- .- 2 .-

U

• lihs form Strain

• 1000 Ue ()htform Strain

• 1000 3- Te Curvature

• 10.000 3- Te Curvature

• 10.000 7 c U 2

/ 'g U 2 -

e 51 11 / '

c, 0 A V" c 0 3 a

O b b un us ..

_3 5 6 7 8 9 10 0 1 2 3 4 5 6 7 9 9 10 0 1 2 3 4 RHS! Increment RHSI Increment

a. CIR9 CPS Parametere b. C2RB CPS Parametere U Ue ()ht form Strain

• 2000 Us Uniform Strain

• 1000 3- Me Moment / 1.0E7 3- 'M e Moment / 1.0E7 3 3 I2 v

v f2 -

o o E h

$1 -

z

$1 -

x c ./ .

y j "

=

3 ll;"y;y. . . . . . . . . . . . . . . . .

i . . . . . . .. . . .. _g 7 8 10 0 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 9 1 RHSI Increment RHS! Increment C. GIR CPS Poromotore d. C2R GPS Parametore Figure 18. Summary of Generalized-Plane Strain Behavior During RHSI of Weld 28-108 h

- ' - o I  !

a

..~

4 1

1 Ce CPS with Bending Reetraint Ca GPS with Bending Reetraint D~ 0~ Ae Axleymmetric Analysee Ae Axleymmetric Analysee ie 10 Analyees ie 10 Analysee

-10 - -10 -

0 O.

e -

6 -20 -

6 -20 Ie .I A h n us in j -30 - . -30 -

j

~

Cl z f

GI j

-40 -

gp -40 -

-50

-50 0 45 90 135 180 225 270 315 360 0 45 90 135 ISO 225 270 315 360 3

Aztesuth (deg) Azimuth (deg)

a. Veld 28-109 ID Surface Strees Analyste Summaary b. Veld 29-109 ID Surface Strees Analyste Summary Figure 19. Comparison of One-dimensional. Axisymmetric, and Generalized Plane Strain l Analysis Predictions for Weld 28-108 RilSI Surface Residual Stresses

- 3 - P Ce CPS with bending reetraint Ce CPS with banding restraint (90 t 135 deg) 50 - 8e GPS without bending restraint $g - 8e GPS without bending restraint (90 E 135 deg)

Ae Axisymmetric analyste Ae Axleynenetric analyste .

40 '

AD

'f

~ ~

2e ID analyste le ID analyete 30 -

30 -

3 3 j 20 -

j 20 -

e 10 -

. 10 -

A  : -

-10 -

-10 -

$-20 -

$-20 -

E -30 E -30 -

/

-40 -

-40 7

-50' ' ' '

0. 6 0. 9

1. 0

1. 2

^ '

-50 0

0. 2

0. 4

0. 6

0. 8 I. 0

1. 2

1. 4 O 0. 2 0. 4 1. 4 Distance from Inner Surface (in) Oletance from Inner Surface (in)

a. Wald 28-108 Strese Analyste Summary (0 dog) b. Veld 29-100 Strees Analynle Summary (120 deg)

Ce CPS with bending reetraint (90 t 135 deg) 50 - Bs GPS without bending restraint (90 8 135 dag)

Ae Axleymmetric analyele - -

40 ~

1a 3D analyste 3 30 -

,E 20 -

i '" ~

/2 /

-I

-20 -

30 -

40

\\<50 O 0. 2 0. 4 0. 6 0. 0 1. 0 1. 2 1. 4 Otetance from Inner Surface (in)

c. Wald 28-100 Strese Analyste Summary (240 deg)

Figure 20. Comparison of One-dimensional, Axisymmetric, and Generalized Plane Strain Analysis Predictions for Weld 28-108 RilSI Through Thickr.e:s Axial Residual Stresses

~

T ~

r Cs CPS with bondtng reetraint Ge CPS with bending rentraint (90 E 135 deg)

- 8e CPS without bending restr-: Int $g - 8e GPS without bending reetraint (90 L 135 do.;)

50 Ae Axisynunotric onalysis Ae Axleymmetric analyste 40

• 40 -

Ie 10 analyele - Ie 10 onalysis 30 -

30 -

e 20 e 20 -

6 6 10 -

/

10 -

I e 0

/ ^

e 0 - -a

-10 - -10 -

]

E-20 - o -20 -

o o

• I -30

-30 -

-40

-40 '

-50

-50' 1.' 2 1. 4 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 0 0. 2 0. 4 0. 6 0. 9 1. 0 Distance fron: Inner Surface (In) b1 stance from Inner Surface (In)

a. Veld 20-100 Strese Analyste Summary (0 deg)

b. Wald 28-100 Strese Analyste Summary (120 deg)

Cs CPS with bending restraint (90 t 135 deg) 50 - 8's CPS without bending restraint (90 8 135 dag)

Ae Axleynumetric analysis '

40 -

1e 10 analysse 30 -

e 20 -

6 10 -

I e 0 4 y b -

.; us -10 k-20 -

1 -go

-40 -

O O. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 1 Ic. Wald 28-108 Strees Analyste Summary (240 deg)

Distance from Inner Surface (in)

Figure 21. Comparison of One-dimensional. Axisymmetric, and Generalized Plane Strain Analysis Predictions for Weld 28-108 RHSI Through Thickness Hoop Residual Stresses

y .

3 .. . .

• s 00 T. C. Data 1200 -

s Model Input A2

- Weld 1100 -

Center 11ne y

• 1000 -

900 -

m S 800 -

. m  :

• 0 700 -

o .

3 - Outer Surface

, g ,

" L 600 -

G -

ct

$ 500 -

F- .

400 -

300 -

• 200 - Inner Surface 339 g 100 0 5 10

-10 -5 Distance fron. RHSI Temperature Symmetry Plane (in)

Worst case axial temperatu.e profile for Weld 28-50 I Figure 22. Thermocouple Data and the Axisymmetric Model Input (Worst Case)

Temperature Distribution for Weld 28-50

, e. ,.. ena \

c OSR Lji/i 9JYo R

%,.n .. uf y 0F PAGM y- 1 wa nn, s.as < 43 y -

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Ma mann, et ena a st so, 1 87 PCR=t?-136 t Mr. David Sancio New York Power Authority 123 Main Street White Plains, NY 10601 I SUILTECT: Transmittal of Resistance Beatlag Stresa r= % ,

Report 81R-87-015, Revision 1 ,

1 Dear Davos Enclosed please find' three copies of a revised version of our .

I RHSI report reflecting comunants math during our 4 telecon with you and H. Y. Chang. The specifice of the .*

' hd are summarised in the document revision control sheet. To avoid

• confusion we have bound up all three documents which comprise the complete RMSI ' justification (Tony's letter report &3G-47=047,.SI _

w report SIR-87-015, and the 8vRI report on the experimental work)

.7 into a single package for your use. .

2.7 . .

jjp'j Also .as requested in the telecce, we'ere enclosing arcerpts from EPRI report NP-3414 which details the method of residual stress >

measurement used in the experimental part of the werkt'and copies of References 4, 5, and 4 in the 81 report are being transmitted by Randy Stonesif r undar separate cover. .

We hope that this transmittal resolves any outstanding questions 4 ,

on the RHSI application at J. A.F. As always, it has been e

,J pleasure working with you and the NYPA staff on this pro act.

, Y? ' f

~ j i/

Peter C. Riccardd'11a a I=

Enclosures .T Z cet A. J. Giannuzzi .D D 71 R. B. Stonesifer * ! !!,' ,--

• ".)

, . * . =>  ;

i,. t .,. g Te .i.. ' ~'.,

- , 5. :

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3130 AD4ADEN D0%2SSWAY SUITE BB e SAN 10St. CALECENIA $$118 e (423764200 a ftLIX IMal? STEDC

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ASSOCIATESINC I na.nca c.p.taa Ph.n A,% r. o.edos. Pr June 12, 1987 h",IoME3 AJG-87-047 Anthony N. Macenarch, Ph.D. t UEDE[Psn -

l Mr. David Sancic L New York Power Authority I 123 Main Street I White Plains, NY 10601

Subject:

Final Letter Report on Effectiveness Of Resistance Heating Stress I=provement (RMSI) As A Residual Stress L

Remedy For Austenitic Stainless Steel Pipe Welds At J. A. Fitzpatrick l

Dear Dave:

This final letter report and the attached experimental measurement and analyses reports present the results of the recent NYPA, Structural Integrity Associates (SI) and Southwest Research Institute (SWRI) joint program designed to qualify the Resistance Heating Stress Improvement Process (RHSI) as a l residual stress remedy for austenitic stainless steel pipes used 1 in boiling water reactors (BWRs) and to demonstrate the RHSI j

,. effectiveness on actual plant pipe welds. The approach used for l n the efficacy demonstration was to collect temperature data on the l pipes while resistance heating coils were used to heat the pipe i exterior, much as Induction Heating coils have been used to heat l treat other stainless steel joints for residual stress ,

_ improvement. The demonstration of RMSI effectiveness is, by )

analogy to IHSI, the residual stress benefit resulting from the 1 hes: treatment. l l

An earlier phase of this program demonstrated "proof of principle" of the RHSI process, that is, the ability of RHSI to

[ produce compressive inside surface residual stresses in a large diameter austenitic stainless steel welded pipe (SIR-86-003, and SIR-86-035, and letter report AJG-84-053). This phase of the program presents data in addition to and supporting the earlier RMSI residual stress data and analyses. In this phase, however, the actual process parameters and the actual resistance heating coils which were subsequently used in the field heat treatments I at James A. Fitzpatrick were used in the 28-inch pipe laboratory test. This 28-inch diameter schedule 80 pipe was subsequently destructively examined for the post RHSI residual stress

. N

/ ,*

3150 ALMADEN EXPRESSWAY SUITE 226 e SAN JOSE, CAIFORNIA 95118 e (406) 978-8200 e TELEX 184817 STRUCT

.2 __ _ . - . _ . _ . . __ _ _ _ _ . _ . _ . _ _ _ _ _ _ _ . __. _ ___ _ ._

Mr. David Sancic Page 2 .

June 12, 1987 AJG-87-047 distribution at Southwest Research Institute (SWRI), Attachment 1, and an elastic-plastic finite element analysis was performed modelling the temperature data and the RHSI parameters for the joint (Attachment 2). The finite element model results, validated by the laboratory pipe test residual' stress measurements, were then used to demonstrate the effective residual stress benefit resulting from the RHSI treatment on the L field welds. The following paragraphs of this report highlight the measurement and analysis results for the three 28-inch pipe welds. Detailed measurement and analyses data are presented in Attach =ents 1 and 2 to this report.

T

1. Laboratory Pipe Test Results q

J A 28-inch diameter schedule 80 welded pipe was heat treated at JAF using the process parameters and resistance heat treat =ent coils which were to be used subsequently on two actual plant pipe welds at JAF. Subsequent to the RHSI treatment, the pipe was sent to SWRI for destructive residual stress measurement and the

- temperature data and coil width information were sent to SI as

{ input to the finite element analysis. The destructive residual stress data illustrated that very compressive post RHSI residual stresses were introduced on the pipe inside surface at the three azimuths examined and remained compressive well into the pipe

[- thickness for the single azi=uth for which through thickness measurements were made (see Attachment 1 for details) . These

~

results compared quite favorably to those obtained on IHSI L treated pipes of the same diameter. Elastic plastic finite element analyses were performed on this weld using the RHSI parameters obtained from NYPA personnel. The results of the finite ele =ent analyses agreed very well with the residual stress h measurement results, thus validating the analysis for the in-plant pipe measurements (see Attachment 2 for details of analysis). It should be noted that this finite element analysis using the Welds II program has been used routinely to verify the efficacy of the IHSI treatment for welded stainless steel pipes.

( 2. In-Plant RHSI Pipe R>=M ts Two 28-inch diameter recirculation system pipe welds, welds f 28-108 and 28-50, were RHSI treated using the NYPA procedure and the RMSI coils which had been used in the laboratory pipe demonstration. The RHSI temperature data were supplied to SI by NYPA and elastic-plastic finite element analyses were performed I using the Welds II procram as validated by the SWRI laboratory pipe test results. The results of the analyses, presented in detail in Attachment 2, illustrate that the PRSI process was able I to create significant compressive axial and circumferential residual stresses over a significant portion of the inner pipe l STRUCTURAL INTEGRITY ASSOCIATES INC

l. . ,

1 1 Mr. David Sancic Page 3 June 12, 1987 AJG-87-047 .

l surface. In addition, it was shown that the RHSI process is reasonably tolerant to deviations from the opti=al temperature distributions as long as the deviations are of a locil nature.

Finally, it is shown that the residual stresses produced in these pipes are expected to be compressive at the inside surface and I well through the wall thickness for both welds.

i If you have any questions regarding this report and the f attachments, or if you require further detail, please do not hesitate to call. As always, it is a pleasure having the I

f

.; opportunity to work with you. )

very truly yours, A9

l A. J. Giannuzzi Enclosures

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I I STRUCTURAL INTEGRITY ASSOCIATES INC l