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Stress Intensity Factor (SIF) analysis on the Pressurized Base Weld Component (PBWC) Materials a Review
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 5430–5437
www.materialstoday.com/proceedings
ICMPC 2017
Stress Intensity Factor (SIF) analysis on the Pressurized Base Weld Component (PBWC) Materials a Review S.K. Dhakad1 , Sourabh Upadhyay2, Pankaj Agrawal3, Rajesh Purohit4 1
Department of Mechanical Engineer,Asstistant . Prof ,S.A.T.I.(Engineering College ), Vidisha,India, 464001 2 Department of Mechanical Engineer M.Tech,Student SATI, Vidisha, India 3 Department of Mechanical Engineer Professor .,S.A.T.I, Vidisha, India 4 Department of Mechanical Engineer, Asso. Proff., MANIT, Bhopal, India
Abstract
This paper presented comprehensive review of literature of past years research work already done in proposed field is presented. The work includes the research work published in various journals and conferences, articles, magazine, available in open literature. The literature review focus on Stress Intensity Factor (SIF) analysis in both surface and depth direction and residual stresses concentration of the Pressurized Base Weld Component (PBWC). Stress intensity is used in fracture mechanics to predict the stress intensity near the crack tip which is caused by residual stresses. In present investigation effect of stress intensity factor over the pressurized weld component has been done on the basis of LEFM, residual stresses and previous studies so far to predict the effect on the crack growth in a pressurized base weld component in any NPP as we know the property of the welded zone of a pipe differs from its parent metal. For a design engineer it is very important to ensure the safety of the nuclear reactor as large amount of energy is transferred when the nuclear reaction takes place. A failure in the piping can be hazardous not only to the environment but also to the human lives and money. . Review work very useful to us find the research gap in the proposed field. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 7th International Conference of Materials Processing and Characterization. Keywords: SIF; Residual Stresses; NPP; LEFM
. * Corresponding author. E-mail address : [email protected]
2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 7th International Conference of Materials Processing and Characterization.
S.K. dhakad et.al./ Materials Today: Proceedings 5 (2018) 5430–5437
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Nomenclature: LEFM Linear Elastic Fracture Mechanism NPP Nuclear Power Plant ASS Austenitic Stainless Steel SIF Stress Intensity Factor FEA Finite Element Analysis IR Infrared FFS Fitness-For-Service SSY Small scale yielding PBWC Pressurised Base Weld Component
1. Introduction Stress intensity factor is used to predict the stress intensity near the tip of crack which is caused by residual stresses. Residual stresses are those stresses which remain on the surface of any object even when no external load is applied over it. Now it is well recognized that pressurized base components like pipe, elbow joints etc. are one of the major challenges for major Nuclear Power Plant. Extensive research has focused on the crack growth initiation of pressurized components of a Nuclear Power Plant to develop empirical relation and assessing the real component and developing safety cases [1,2]. A fatigue resistant cladding concept confirms the compressive residual stresses in a cylinder weld clad [3] as the pressure is applied from the inside of the cylinder. Similarly in any nuclear power plant when the steam or liquid or coolant passes through the cylindrical it can be said that compressive residual stresses also acts on the weld clad of the cylindrical pipe. ASME boiler and pressure vessel code section IX [4] contains rule for analyzing defects in addition to guidance on how to predict their combined effect on the different structure. These procedures are designed to cover various failure mechanisms. However for simplicity, it is based on LEFM [5]. Because of the high end mechanical property of ASS, it is widely used as a nuclear power plant component. But there are many high tensile residual stresses in it,which causes crack [6]. In any NPP it is considered that pressure distribution inside the pipe component is uniformly distributed but we cannot say that it actually happens inside the component. There occur so many stresses and variable load which causes residual stress to grow over there and make a crack tip which is actually caused by the SIF. This crack tip with increasing time propagates the crack formation and from the occurring of the crack to the total fracture in the surface of the component is called as fatigue failure. These fatigue failure are very harmful not only for us human lives but also for the environmental condition apart from that it also causes loss of money and lives of the employee and people living around the plant. In any NPP it is very important to ensure the safety of the employee of that plant and also the environment that’s why every component of the nuclear power plant should be checked on the regular basis because components of the NPP often undergoes various type of load which causes residual stresses on the surface of the pipes. These pipes are often welded at certain cross sections. Now the properties welded part differs from the parent metal to certain extent. Here we are trying to elaborate a review regarding the effect of residual stresses and SIF on the pressurised weld base component. Recent researches has said that because of thermal ageing embrittlement it tend to lose toughness [7,8,9]. Now from time to time these component must be checked and inspected but this takes a lot of time, resources, workers and more importantly money. However due to the inherent complexity of the welding there is a significant difference between the reading by analyst and FFS codes the effect of residual stresses on the weld should be evaluated rigorously before thermal ageing take place. Apart from previous reasons because of the stress concentration life of the welded joint decreases [10]. This stress concentration is maximum at weld toes and weld root because of the variation of the shape of weld. Hence for finding the fatigue life of such structures evaluation of stress intensity factor is very important. For measuring the fatigue life it is really important to understand the linear elastic fatigue mechanism because it actually helps us in measuring the fatigue life of an y component. For doing that we need to find many constraint like residual stresses which eventually lead us to stress intensity factor. We also
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need to find fracture toughness which is ability of a material containing a crack to resist a failure. Paris law creates a relationship between crack growth rate and SIF. Nowadays notch stress intensity factor which also is an extension of the stress intensity factor which allow us to know the stress intensity feild at the surface of the component. 1.1. Residual stresses In most of the ductile substances residual stresses often causes plasticity. But it is known that residual stresses do contribute in influence of fracture in the welded structures[11]. In any NPP it is well known that at many cross sections pipes are welded and because of the localized heating and cooling distortion occur near the welded region. This also causes the change in the metallurgical properties of the welded joint from the parent metal. Hence for accurate prediction of residual stresses and distortion in the weld joint one must control the microstructure. Residual stresses may be desirable or undesirable for example compressive residual stresses actually helps in making of scratch resistant glass for mobile phones. Residual stresses can occur through various methods like: • Plastic deformation • Thermal cycles • Structural change Recently there has been many researches regarding the heat transfer analysis and multi physics of the welding [12]. Another researched emphasized challenges in residual stresses prediction using 3D FEA modeling [13]. Another analytical approach focused on predicting temperature field produced by moving heat sources [14]. While some predicted on the basis of the weld pool[15]. Also the weld process parameters and material properties were significant in the weld pool shape prediction has been published before [16]. Some researches have also predicted that residual stresses also depends upon the kind of heat source. Further it also concluded that there is a need of heat transfer model as it was the driving force of the microstructure model [17,18].Some researches showed the effect on it via analytical solution for thermal field from a 3D double ellipsoidal power density heat source [19]. Also some researchers also discussed about specific material properties especially thermal conductivity and yield stress which was sensitive to the process and other properties could be considered in the room temperature [20]. Similarly Barosso used simplified material model to reduce the solver time and perform the semi destructive stress measurement [21]. Numerical distortion analysis has also been done to calculate the residual stresses [22]. Also most recently [23] numerically predicted thermal cycles and temperature distribution were validated using IR Thermography was also performed for the measurement of the residual thermal stresses. But none of them were able to specify the solution for the problem of measuring residual stresses in a pressurised base weld component. Below figure1 and Fig 2. Shows the basic residual distribution in a pipe component.
Fig 1. Residual stress distribution in a cylindrical component
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Fig 2. Residual stresses at the surface of the weld component Lee and Chang also performed many test experiment on the cylindrical pipe component and analyzed the structural behaviour of it using finite element analysis which leads them to observe non axi-symmetric buckling in the specimen because of the non symmetrical residual stress distribution. Another research by Wang et al. Who did the experiment on the mechanical properties of dissimilar metal realised that the variation in the local mechanical property at the interface because of the non uniform temperature between the interface of the two different metal surfaces in contact. Same thing was further analysed by the Lee and Chung only to come up with the same result. So this can be said about the residual stresses that because of the unevenness of the temperature the basic structure of the metal similar or dissimilar get distorted and shows a different nature with regard to the residual stresses, SIF and even the fatigue life. Due to the non symmetric distribution of the temperature and the residual stresses difference in the thermal properties of the metal was observed which further leads to the strain hardening. Also residual stresses in the metal forming processes such as joining of the two different metal can be reduced by preheating the interface cross section [27, 28]. Often it is considered as residual stresses are local in range of yield stresses and hence for evaluating the welding induced residual stress welding simulation is considered as the simulation method. Recent works reveal that residual stresses in the similar metal affects the joining metal according to the length of the welded specimen [29]. But prior to the fracture it shows the ductile deformation and improving the reliability of the welded structure is the basic need of any design engineer in any NPP as the bearing capacity of the welded joint are weaker as compared to the base or parent metal because of the phase transformation. 1.2. Stress Intensity Factor (S.I.F) As one can perceive through many mechanical failures occurring nowadays it can be said that these failure occurs because of the propagation of fatigue crack frequently in many structures and component. For instance Chernobyl Disaster in 1986. Prediction of fatigue life is very important for supporting frame of wind turbines, offshore machineries, nuclear reactor where high cycle major fatigue is concern. Welding is very convenient and inexpensive way of joining two or more different components in such kind of facility. With the rapid development in the industry and our never ending hunger for energy nuclear power plants have came into existence. These plant though very efficient in terms of producing electricity carries risk of failing which has been explained earlier. Therefore taking full care of the power plant and its component has to be a main concern of any design engineer and with rapid development of the latter, its components are now given more and more attention. Now as we have discussed earlier about the effect on the welded joint in a nuclear power plant we can say that at many cross sections there is a chance of welding of two dissimilar metal which causes us to show different material properties in the Heat Affected Zone. In this heat affected zone because of non linear temperature distribution and coefficient of thermal expansion there occur some residual stresses in heat affected zone. These residual stresses actually propagates the crack propagation and stresses at the crack tip is called as Stress Intensity Factors. For problems related to crack, Paris law is actually used for evaluating crak growth. However Paris law is actually based upon LEFM approach which helps in evaluating the crack growth and fatigue life does not contributes in the
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evaluation of SIF accurately [24]. Hence use of FEA has been introduced nowadays. As 2-dimensional modeling in FEA is easier and hence less accurate that’s why use of 2D modeling for a pressurized base weld component (PBWC) is restricted. 3-Dimensional modeling is used for the PBWC because of the kind of the structure PBWC possess. A pipe is a 3D model of a cylinder. We are not making analysis on a 2D projection of a cylindrical pipe. Though 3D modeling is tough and time taking, it gives accurate and best result according to the problem formulated. FEM requires special techniques and nowadays for saving time people are using the hybrid between between 2D and 3D model. Though conditioned based maintenance system are in trend in any nuclear power plant but still a more accurate working systems and software are still needed as it does not tell us the information regarding the fatigue failure and crack propagation accurately. Apart from that these softwares are the kind of software which works according to the specific set of plan, the do not self analyze the condition and tell the operator the assessment of the situation regarding the components in the nuclear power plant or in any thermal power plant. Also crack propagation actually takes place at the surface of the pipes as the fluid flows through it at very high speed and temperature which causes repetitive fluctuating loads over the surface of the pipe. Thus pipe after some time start showing the sign of fracture. It is same as when gunshot is fired through a barrel though the fluid does not flows through It as fast as a bullet but then again it actually flows through it with some speed at very high temperature leaving the pipe in a very bad position. Hence it was proposed to increase the allowable pressure of the cylindrical pipe component so as to increase the pipe’s life cycle. This phenomenon is same as a autofrettage which tends to take place in the gun barrel. It was first discovered by the Jacob of the French artillery in 1907. He said that the allowable pressure of the gun barrel must be increased so that shot can be fired to a great distance. Here our aim is not to fire the fluid to great distance but to minimize the residual stresses at the surface of the pipe. And this is the normal ASS pipe we are talking about not the welded joint between the cross section of a pipe. Where because of the coefficient of expansion residual stress emerge. And it has been proved before that these residual stresses actually influence the crack propagation. Beside even if we increase the size of the cylindrical pipe component or any other component it will take more space which is not useful and not ideal already. For design engineer using of the floor space area efficiently is very important as it reduces the cost of the transportation. Nowadays autofrettage has been developed further for producing better result not only in the field of weaponry but also in the field of cylindrical pressure vessel. We know pressure vessels is also a kind of a cylinder but a close one from both of the ends. Cylindrical pipes however are open in both the direction to facilitate the flow of fluid in a nuclear power plant. Therefore these cylindrical structures are called as thin walled structures. Therefore crack initiation actually takes place in the radial direction or axial direction because of the hoop stresses being larger in magnitude in that direction. The structural integrity is actually based upon the Stress Intensity Factor in order to bring out the crack growth and its life cycle hence it is really important to perform the proper FEA test on it in order to get the accurate result. In the calculation of stress intensity factor various parameters should be calculated like S.Suresh et al.[25] explained the need of calculating the geometry correction factor for the purpose of better accuracy in result. However most of the results are limited to the Mode-I of the failure which is the tensile stresses normal to the surface of the specimen. Mode II and Mode III of the failure have been neglected by most of the researches because of the hard and time taking calculation of the FEA experiment. Calculation of Stress intensity factor works best under high constraints because if not this may lead to the deviation of the crack tip from the SSY solution hence a high constraint SIF would lead to a better and accurate result for the purpose of evaluating of the fatigue crack life[26]. 2. Summary of work From the studies so far it is clear that the researches so far have been done on many specimen for example similar metal, dissimilar metal, joining of two metal of different geometry and also in various cylindrical component of the nuclear power plant or in any thermal power plant or in the day to day welding methods. Every studies have shown that the residual stresses has the influence over the stress intensity factor which actually leads to the initiation of the crack formation. Hence for the evaluating of the fatigue crack growth calculation related to the stress intensity factor and the residual stresses is very important. Also stress intensity factor without proper constraints function will not lead to a good result which is undesirable. The review work is summarized in table 1.
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Table- 1 Summary of the work S.No. 1.
2.
3.
4.
5. 6.
7. 8.
9. 10.
Effective of SIF & Residual stress and Methodology used in the analysis The effect of residual stress on the Preferential Intergranular Oxidation of Alloy600 Determination of mixed-mode stress intensity factors, fracture toughness, and crack turning angle for anisotropic foam material material and residual stress consideration associated with the weld clad component
Materials/ Component shape Alloy600
Stress intensity interaction between dissimilar semi-elliptical surface Cracks H.E. Coules Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes Modified Stress Intensity Factor Equations for Semi-Elliptical Surface Cracks in Finite Thickness and width Plates Influence of Residual Stress on Stress Intensity Factor Estimation of Multiple Cracks in a Dissimilar Welded Joint Modeling, Prediction and Validation of Thermal Cycles, Residual Stresses and Distortion in type 316 LN Stainless Steel Weld Joint made by TIG Welding Process
Dissimilar semielliptical surface
Estimation of residual stresses influence on oscillation modes of welded housing part Experimental determination of residual stresses in the hard-faced layers after hard-facing and tempering of hot work steels
Anisotropic material
foam
Weld component
clad
Welded Stainless Steel Pipes Finite Thickness and width Plates
Authors /Journal G.Bertali,et al. International Journal of Corrosion Science Nagaraj K. Arakere a, Erik C. Knudsen et al International Journal of Solids and Structures G Benghalia, J Wood et alInternational Journal of Pressure Vessels and Piping H.ECoules, International Journal of Pressure Vessels and Piping Chang-Gi Han a, et al..Nuclear Engineering and Tec hnology Yang PENGa et al, Procedia Engineering
Year 2016
2008
2014
2016
2016 2011
Dissimilar Welded Joint
S. Suresh Kumar,
2014
316 LN Stainless Steel Weld Joint made by TIG Welding Process
K.C. Ganesh et al. Procedia Engineering 86 ( 2014 ) 767 – 774
2014
Welded housing part
2015
Hard-faced layers after hardfacing
Yaushev A.A et al, Procedia Engineering 129 ( 2015 ) 75 – 80 Vuki Lazic et al, Procedia Engineering 153 ( 2016 ) 392 – 399
2016
11.
Calculation of stress intensity factors KI, KII and KIII of cracked components submitted to flexural and torsional loads
KI, KII and KIII of cracked components
J. Isidoro et al, Procedia Engineering 160 (2016 ) 131 – 136
2016
12.
Analytical Stress Intensity Factors for cracks at blunted V-notches
blunted V-notches
2014
13.
Prediction of welding residual stress profile in dissimilar metal nozzle butt weld of nuclear power plant
Dissimilar metal nozzle butt weld of nuclear power plant
Alberto Sapora et al, Procedia Materials Science 3 ( 2014 ) 738 – 743 Tae-Kwang Song et al., Procedia Materials Science 3 ( 2014 ) 784 – 789
2014
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14.
Simulations of a large-scale four point bending experiment; influence of residual stresses from a repair weld
Weld material
Son Do et al., Volume 3, 2014, Pages 1599–1605
2014
15.
3D simulation of residual stress developed during TIG welding of stainless steel pipes
TIG welding of stainless steel pipes
Varma Prasad V.M. et al., Procedia Technology 24 ( 2016 ) 364 – 371
2016
16.
Automated ultrasonic system residual stresses in the welded joints of the circulation pipe NPP Nonlinear stress intensity factors in fracture mechanics and their application
Welded joints of the circulation pipe NPP
S.I. Minin et al.,
2016
V. shllyanikov, Structural Integrity Procedia 00 (2016) 000–000
2016
16.
3. Conclusion: The summery of the work it is clear that the all the studies which have been done over the similar topic is however incomplete and there are variety of tests which are needed to be done over the estimation of the stress intensity factor at the welded cross section of the pipe component containing pressurized fluid which will eventually lead us to further evaluate the fatigue life of the pressurized based weld component. Further the effect of the residual stresses over the weld component in which some fluid is flowing at high temperature is needed to be analyzed and elaborated in the future studies. 4. References: [1] G. Bertali , F.Scenini ,M.G.Burke The effect of residual stress on the Preferential Intergranular Oxidation of
Alloy600 ; Corrosion
Science 111 (2016) 494–507 [2] P.L. Andresen, F.P. Ford, Life prediction by mechanistic modeling and system monitoring of environmental cracking of iron and nickel alloys in aqueous systems, Mater Sci Eng A A103 (1988) 167–184 [3] G Benghalia, J Wood etal material and residual stress consideration associated with the weld clad component; International Journal of Pressure Vessels and Piping 139-140 (2016) 146-158 [4] Fujimitsu Masuyama, John P. Shingledecker, 2013 ASME boilers and pressure vessel code section XI, New York, Procedia Engineering, Volume 55, 2013, Pages 314-325 [5] H.E. Coules , stress intensity interaction between similar and dissimilar semi elliptical surface cracks; International Journal of Pressure Vessels and Piping 146 (2016) 55-64 [6] Chang-Gi Han a, Yoon-Suk Chang a,*, Jong-Sung Kim b, and Maan-Won Kim, Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes; Nuclear Engineering and Tec hnology 48 (2016 ) 1412 -1422 [7] Chang-Gi Han a, Yoon-Suk Chang a,*, Jong-Sung Kim b, and Maan-Won Kim, Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes; Nuclear Engineering and Tec hnology 48 (2016 ) 1412 -1422 [8] K Chandra,V K Jain, V Bhutani, VS Raj et al. Low temperature thermal ageing of the austenitic stainless steel; Mater. Sci. Eng. A 534 (2012) 163-175 [9] P.K. Singh et al, thermal ageing in the austenitic stainless steel weld; Trans. Struct. Mech. Reactor Technol. 23 (2015) 305. [10] Yang et al, Modified stress intensity factor equation semi elliptical surface crack in finite thickness, Procedia Engineering 14 (2011) 2601– 2608 [11] Son do et al simulation of large point bending experiment influence on the residual stresses, Volume 3, 2014, Pages 1599–1605 [12] Joy Varghese V M, Suresh M R and Siva Kumar D, Int. J. Adv. Man. Tech., (2012) [13] De A and DebRoy T, Sci. Tech. Wel. Jo., (2011), 16. [14] Eagar T W and Tsai N S, AWS Conv., (1983). [15] Tsai N S and Eagar T W, Mod. Cast. Weld. Pro., (1984). [16] Goldak J A, Chakravarti A and Bibby M, Meta. Tran. B, (1984), 15B. [17] Goldak J A, Oddy A, Gu M, Ma W, Mashaie A and Hughes E, IUTAM Symp., (1992). [18] Nguyen N T, Ohta A, Matsuoka K, Suzuki N and Maeda Y, Weld. Res. Sup., (1999). [19] Zhu X K and Chao Y J, Comp. Stru., (2002), 80. [20] Asserin O, Loredo A, Petelet M and Iooss B, Fini. Ele. Anal. Des., (2011), 47.
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[21] Barroso A, Canas J, Picon R, Paris F, Mendez C and Unanue I, Mat. Des (2010), 31. [22] Aarbogh H M, Hamide M, Fjaer H G, Mo A and Bellet M, J. Mat. Pro. Tech., (2010), 210 [23] Suresh Kumar, influence of residual stresses on stresses on the stress intensity factor, Volume 86, 2014, Pages 234–24 [24] Zenhua wu et al., prediction of the pavement cracking , Expert Systems with Applications, Volume 41, Issue 4, Part 1, March 2014, Pages 1021-1030 [25] S Suresh et al , influence of the residual stress intensity estimation; Volume 86, 2014, Pages 234–241 [26] Lee and Chang, influence of the residual stresses distortion on the structural behaviour; Construction and Building Materials, Volume 41, April 2013, Pages 766-776 [27] Albrecht, P and Yamada K. Rapid calculation of stress intensity factors. Journal of the Structural Division, ASCE. 103(2), 1977, pp. 377-389 [28] Newman J. A review and assessment of the stress intensity factors for surface cracks. Part-Through Crack Fatigue Life Prediction, ASTM STP 687, 1979, pp. 16-42. [29] Newman J and Raju I. An empirical stress-intensity factor equation for the surface crack. Engineering Fracture Mechanics, 1981, 15(1-2), pp. 185-192 [30] Experimental determination of residual stresses in the hard-faced layers after hard-facing and tempering of hot work steels Vuki Lazia, Dušan Arsia , Ružica R. Nikoli, Branislav Hadzimab; Procedia Engineering 153 ( 2016 ) 392 – 399
ScienceDirect Materials Today: Proceedings 5 (2018) 5430–5437
www.materialstoday.com/proceedings
ICMPC 2017
Stress Intensity Factor (SIF) analysis on the Pressurized Base Weld Component (PBWC) Materials a Review S.K. Dhakad1 , Sourabh Upadhyay2, Pankaj Agrawal3, Rajesh Purohit4 1
Department of Mechanical Engineer,Asstistant . Prof ,S.A.T.I.(Engineering College ), Vidisha,India, 464001 2 Department of Mechanical Engineer M.Tech,Student SATI, Vidisha, India 3 Department of Mechanical Engineer Professor .,S.A.T.I, Vidisha, India 4 Department of Mechanical Engineer, Asso. Proff., MANIT, Bhopal, India
Abstract
This paper presented comprehensive review of literature of past years research work already done in proposed field is presented. The work includes the research work published in various journals and conferences, articles, magazine, available in open literature. The literature review focus on Stress Intensity Factor (SIF) analysis in both surface and depth direction and residual stresses concentration of the Pressurized Base Weld Component (PBWC). Stress intensity is used in fracture mechanics to predict the stress intensity near the crack tip which is caused by residual stresses. In present investigation effect of stress intensity factor over the pressurized weld component has been done on the basis of LEFM, residual stresses and previous studies so far to predict the effect on the crack growth in a pressurized base weld component in any NPP as we know the property of the welded zone of a pipe differs from its parent metal. For a design engineer it is very important to ensure the safety of the nuclear reactor as large amount of energy is transferred when the nuclear reaction takes place. A failure in the piping can be hazardous not only to the environment but also to the human lives and money. . Review work very useful to us find the research gap in the proposed field. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 7th International Conference of Materials Processing and Characterization. Keywords: SIF; Residual Stresses; NPP; LEFM
. * Corresponding author. E-mail address : [email protected]
2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 7th International Conference of Materials Processing and Characterization.
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Nomenclature: LEFM Linear Elastic Fracture Mechanism NPP Nuclear Power Plant ASS Austenitic Stainless Steel SIF Stress Intensity Factor FEA Finite Element Analysis IR Infrared FFS Fitness-For-Service SSY Small scale yielding PBWC Pressurised Base Weld Component
1. Introduction Stress intensity factor is used to predict the stress intensity near the tip of crack which is caused by residual stresses. Residual stresses are those stresses which remain on the surface of any object even when no external load is applied over it. Now it is well recognized that pressurized base components like pipe, elbow joints etc. are one of the major challenges for major Nuclear Power Plant. Extensive research has focused on the crack growth initiation of pressurized components of a Nuclear Power Plant to develop empirical relation and assessing the real component and developing safety cases [1,2]. A fatigue resistant cladding concept confirms the compressive residual stresses in a cylinder weld clad [3] as the pressure is applied from the inside of the cylinder. Similarly in any nuclear power plant when the steam or liquid or coolant passes through the cylindrical it can be said that compressive residual stresses also acts on the weld clad of the cylindrical pipe. ASME boiler and pressure vessel code section IX [4] contains rule for analyzing defects in addition to guidance on how to predict their combined effect on the different structure. These procedures are designed to cover various failure mechanisms. However for simplicity, it is based on LEFM [5]. Because of the high end mechanical property of ASS, it is widely used as a nuclear power plant component. But there are many high tensile residual stresses in it,which causes crack [6]. In any NPP it is considered that pressure distribution inside the pipe component is uniformly distributed but we cannot say that it actually happens inside the component. There occur so many stresses and variable load which causes residual stress to grow over there and make a crack tip which is actually caused by the SIF. This crack tip with increasing time propagates the crack formation and from the occurring of the crack to the total fracture in the surface of the component is called as fatigue failure. These fatigue failure are very harmful not only for us human lives but also for the environmental condition apart from that it also causes loss of money and lives of the employee and people living around the plant. In any NPP it is very important to ensure the safety of the employee of that plant and also the environment that’s why every component of the nuclear power plant should be checked on the regular basis because components of the NPP often undergoes various type of load which causes residual stresses on the surface of the pipes. These pipes are often welded at certain cross sections. Now the properties welded part differs from the parent metal to certain extent. Here we are trying to elaborate a review regarding the effect of residual stresses and SIF on the pressurised weld base component. Recent researches has said that because of thermal ageing embrittlement it tend to lose toughness [7,8,9]. Now from time to time these component must be checked and inspected but this takes a lot of time, resources, workers and more importantly money. However due to the inherent complexity of the welding there is a significant difference between the reading by analyst and FFS codes the effect of residual stresses on the weld should be evaluated rigorously before thermal ageing take place. Apart from previous reasons because of the stress concentration life of the welded joint decreases [10]. This stress concentration is maximum at weld toes and weld root because of the variation of the shape of weld. Hence for finding the fatigue life of such structures evaluation of stress intensity factor is very important. For measuring the fatigue life it is really important to understand the linear elastic fatigue mechanism because it actually helps us in measuring the fatigue life of an y component. For doing that we need to find many constraint like residual stresses which eventually lead us to stress intensity factor. We also
5432
S.K. dhakad et.al./ Materials Today: Proceedings 5 (2018) 5430–5437
need to find fracture toughness which is ability of a material containing a crack to resist a failure. Paris law creates a relationship between crack growth rate and SIF. Nowadays notch stress intensity factor which also is an extension of the stress intensity factor which allow us to know the stress intensity feild at the surface of the component. 1.1. Residual stresses In most of the ductile substances residual stresses often causes plasticity. But it is known that residual stresses do contribute in influence of fracture in the welded structures[11]. In any NPP it is well known that at many cross sections pipes are welded and because of the localized heating and cooling distortion occur near the welded region. This also causes the change in the metallurgical properties of the welded joint from the parent metal. Hence for accurate prediction of residual stresses and distortion in the weld joint one must control the microstructure. Residual stresses may be desirable or undesirable for example compressive residual stresses actually helps in making of scratch resistant glass for mobile phones. Residual stresses can occur through various methods like: • Plastic deformation • Thermal cycles • Structural change Recently there has been many researches regarding the heat transfer analysis and multi physics of the welding [12]. Another researched emphasized challenges in residual stresses prediction using 3D FEA modeling [13]. Another analytical approach focused on predicting temperature field produced by moving heat sources [14]. While some predicted on the basis of the weld pool[15]. Also the weld process parameters and material properties were significant in the weld pool shape prediction has been published before [16]. Some researches have also predicted that residual stresses also depends upon the kind of heat source. Further it also concluded that there is a need of heat transfer model as it was the driving force of the microstructure model [17,18].Some researches showed the effect on it via analytical solution for thermal field from a 3D double ellipsoidal power density heat source [19]. Also some researchers also discussed about specific material properties especially thermal conductivity and yield stress which was sensitive to the process and other properties could be considered in the room temperature [20]. Similarly Barosso used simplified material model to reduce the solver time and perform the semi destructive stress measurement [21]. Numerical distortion analysis has also been done to calculate the residual stresses [22]. Also most recently [23] numerically predicted thermal cycles and temperature distribution were validated using IR Thermography was also performed for the measurement of the residual thermal stresses. But none of them were able to specify the solution for the problem of measuring residual stresses in a pressurised base weld component. Below figure1 and Fig 2. Shows the basic residual distribution in a pipe component.
Fig 1. Residual stress distribution in a cylindrical component
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Fig 2. Residual stresses at the surface of the weld component Lee and Chang also performed many test experiment on the cylindrical pipe component and analyzed the structural behaviour of it using finite element analysis which leads them to observe non axi-symmetric buckling in the specimen because of the non symmetrical residual stress distribution. Another research by Wang et al. Who did the experiment on the mechanical properties of dissimilar metal realised that the variation in the local mechanical property at the interface because of the non uniform temperature between the interface of the two different metal surfaces in contact. Same thing was further analysed by the Lee and Chung only to come up with the same result. So this can be said about the residual stresses that because of the unevenness of the temperature the basic structure of the metal similar or dissimilar get distorted and shows a different nature with regard to the residual stresses, SIF and even the fatigue life. Due to the non symmetric distribution of the temperature and the residual stresses difference in the thermal properties of the metal was observed which further leads to the strain hardening. Also residual stresses in the metal forming processes such as joining of the two different metal can be reduced by preheating the interface cross section [27, 28]. Often it is considered as residual stresses are local in range of yield stresses and hence for evaluating the welding induced residual stress welding simulation is considered as the simulation method. Recent works reveal that residual stresses in the similar metal affects the joining metal according to the length of the welded specimen [29]. But prior to the fracture it shows the ductile deformation and improving the reliability of the welded structure is the basic need of any design engineer in any NPP as the bearing capacity of the welded joint are weaker as compared to the base or parent metal because of the phase transformation. 1.2. Stress Intensity Factor (S.I.F) As one can perceive through many mechanical failures occurring nowadays it can be said that these failure occurs because of the propagation of fatigue crack frequently in many structures and component. For instance Chernobyl Disaster in 1986. Prediction of fatigue life is very important for supporting frame of wind turbines, offshore machineries, nuclear reactor where high cycle major fatigue is concern. Welding is very convenient and inexpensive way of joining two or more different components in such kind of facility. With the rapid development in the industry and our never ending hunger for energy nuclear power plants have came into existence. These plant though very efficient in terms of producing electricity carries risk of failing which has been explained earlier. Therefore taking full care of the power plant and its component has to be a main concern of any design engineer and with rapid development of the latter, its components are now given more and more attention. Now as we have discussed earlier about the effect on the welded joint in a nuclear power plant we can say that at many cross sections there is a chance of welding of two dissimilar metal which causes us to show different material properties in the Heat Affected Zone. In this heat affected zone because of non linear temperature distribution and coefficient of thermal expansion there occur some residual stresses in heat affected zone. These residual stresses actually propagates the crack propagation and stresses at the crack tip is called as Stress Intensity Factors. For problems related to crack, Paris law is actually used for evaluating crak growth. However Paris law is actually based upon LEFM approach which helps in evaluating the crack growth and fatigue life does not contributes in the
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evaluation of SIF accurately [24]. Hence use of FEA has been introduced nowadays. As 2-dimensional modeling in FEA is easier and hence less accurate that’s why use of 2D modeling for a pressurized base weld component (PBWC) is restricted. 3-Dimensional modeling is used for the PBWC because of the kind of the structure PBWC possess. A pipe is a 3D model of a cylinder. We are not making analysis on a 2D projection of a cylindrical pipe. Though 3D modeling is tough and time taking, it gives accurate and best result according to the problem formulated. FEM requires special techniques and nowadays for saving time people are using the hybrid between between 2D and 3D model. Though conditioned based maintenance system are in trend in any nuclear power plant but still a more accurate working systems and software are still needed as it does not tell us the information regarding the fatigue failure and crack propagation accurately. Apart from that these softwares are the kind of software which works according to the specific set of plan, the do not self analyze the condition and tell the operator the assessment of the situation regarding the components in the nuclear power plant or in any thermal power plant. Also crack propagation actually takes place at the surface of the pipes as the fluid flows through it at very high speed and temperature which causes repetitive fluctuating loads over the surface of the pipe. Thus pipe after some time start showing the sign of fracture. It is same as when gunshot is fired through a barrel though the fluid does not flows through It as fast as a bullet but then again it actually flows through it with some speed at very high temperature leaving the pipe in a very bad position. Hence it was proposed to increase the allowable pressure of the cylindrical pipe component so as to increase the pipe’s life cycle. This phenomenon is same as a autofrettage which tends to take place in the gun barrel. It was first discovered by the Jacob of the French artillery in 1907. He said that the allowable pressure of the gun barrel must be increased so that shot can be fired to a great distance. Here our aim is not to fire the fluid to great distance but to minimize the residual stresses at the surface of the pipe. And this is the normal ASS pipe we are talking about not the welded joint between the cross section of a pipe. Where because of the coefficient of expansion residual stress emerge. And it has been proved before that these residual stresses actually influence the crack propagation. Beside even if we increase the size of the cylindrical pipe component or any other component it will take more space which is not useful and not ideal already. For design engineer using of the floor space area efficiently is very important as it reduces the cost of the transportation. Nowadays autofrettage has been developed further for producing better result not only in the field of weaponry but also in the field of cylindrical pressure vessel. We know pressure vessels is also a kind of a cylinder but a close one from both of the ends. Cylindrical pipes however are open in both the direction to facilitate the flow of fluid in a nuclear power plant. Therefore these cylindrical structures are called as thin walled structures. Therefore crack initiation actually takes place in the radial direction or axial direction because of the hoop stresses being larger in magnitude in that direction. The structural integrity is actually based upon the Stress Intensity Factor in order to bring out the crack growth and its life cycle hence it is really important to perform the proper FEA test on it in order to get the accurate result. In the calculation of stress intensity factor various parameters should be calculated like S.Suresh et al.[25] explained the need of calculating the geometry correction factor for the purpose of better accuracy in result. However most of the results are limited to the Mode-I of the failure which is the tensile stresses normal to the surface of the specimen. Mode II and Mode III of the failure have been neglected by most of the researches because of the hard and time taking calculation of the FEA experiment. Calculation of Stress intensity factor works best under high constraints because if not this may lead to the deviation of the crack tip from the SSY solution hence a high constraint SIF would lead to a better and accurate result for the purpose of evaluating of the fatigue crack life[26]. 2. Summary of work From the studies so far it is clear that the researches so far have been done on many specimen for example similar metal, dissimilar metal, joining of two metal of different geometry and also in various cylindrical component of the nuclear power plant or in any thermal power plant or in the day to day welding methods. Every studies have shown that the residual stresses has the influence over the stress intensity factor which actually leads to the initiation of the crack formation. Hence for the evaluating of the fatigue crack growth calculation related to the stress intensity factor and the residual stresses is very important. Also stress intensity factor without proper constraints function will not lead to a good result which is undesirable. The review work is summarized in table 1.
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Table- 1 Summary of the work S.No. 1.
2.
3.
4.
5. 6.
7. 8.
9. 10.
Effective of SIF & Residual stress and Methodology used in the analysis The effect of residual stress on the Preferential Intergranular Oxidation of Alloy600 Determination of mixed-mode stress intensity factors, fracture toughness, and crack turning angle for anisotropic foam material material and residual stress consideration associated with the weld clad component
Materials/ Component shape Alloy600
Stress intensity interaction between dissimilar semi-elliptical surface Cracks H.E. Coules Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes Modified Stress Intensity Factor Equations for Semi-Elliptical Surface Cracks in Finite Thickness and width Plates Influence of Residual Stress on Stress Intensity Factor Estimation of Multiple Cracks in a Dissimilar Welded Joint Modeling, Prediction and Validation of Thermal Cycles, Residual Stresses and Distortion in type 316 LN Stainless Steel Weld Joint made by TIG Welding Process
Dissimilar semielliptical surface
Estimation of residual stresses influence on oscillation modes of welded housing part Experimental determination of residual stresses in the hard-faced layers after hard-facing and tempering of hot work steels
Anisotropic material
foam
Weld component
clad
Welded Stainless Steel Pipes Finite Thickness and width Plates
Authors /Journal G.Bertali,et al. International Journal of Corrosion Science Nagaraj K. Arakere a, Erik C. Knudsen et al International Journal of Solids and Structures G Benghalia, J Wood et alInternational Journal of Pressure Vessels and Piping H.ECoules, International Journal of Pressure Vessels and Piping Chang-Gi Han a, et al..Nuclear Engineering and Tec hnology Yang PENGa et al, Procedia Engineering
Year 2016
2008
2014
2016
2016 2011
Dissimilar Welded Joint
S. Suresh Kumar,
2014
316 LN Stainless Steel Weld Joint made by TIG Welding Process
K.C. Ganesh et al. Procedia Engineering 86 ( 2014 ) 767 – 774
2014
Welded housing part
2015
Hard-faced layers after hardfacing
Yaushev A.A et al, Procedia Engineering 129 ( 2015 ) 75 – 80 Vuki Lazic et al, Procedia Engineering 153 ( 2016 ) 392 – 399
2016
11.
Calculation of stress intensity factors KI, KII and KIII of cracked components submitted to flexural and torsional loads
KI, KII and KIII of cracked components
J. Isidoro et al, Procedia Engineering 160 (2016 ) 131 – 136
2016
12.
Analytical Stress Intensity Factors for cracks at blunted V-notches
blunted V-notches
2014
13.
Prediction of welding residual stress profile in dissimilar metal nozzle butt weld of nuclear power plant
Dissimilar metal nozzle butt weld of nuclear power plant
Alberto Sapora et al, Procedia Materials Science 3 ( 2014 ) 738 – 743 Tae-Kwang Song et al., Procedia Materials Science 3 ( 2014 ) 784 – 789
2014
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14.
Simulations of a large-scale four point bending experiment; influence of residual stresses from a repair weld
Weld material
Son Do et al., Volume 3, 2014, Pages 1599–1605
2014
15.
3D simulation of residual stress developed during TIG welding of stainless steel pipes
TIG welding of stainless steel pipes
Varma Prasad V.M. et al., Procedia Technology 24 ( 2016 ) 364 – 371
2016
16.
Automated ultrasonic system residual stresses in the welded joints of the circulation pipe NPP Nonlinear stress intensity factors in fracture mechanics and their application
Welded joints of the circulation pipe NPP
S.I. Minin et al.,
2016
V. shllyanikov, Structural Integrity Procedia 00 (2016) 000–000
2016
16.
3. Conclusion: The summery of the work it is clear that the all the studies which have been done over the similar topic is however incomplete and there are variety of tests which are needed to be done over the estimation of the stress intensity factor at the welded cross section of the pipe component containing pressurized fluid which will eventually lead us to further evaluate the fatigue life of the pressurized based weld component. Further the effect of the residual stresses over the weld component in which some fluid is flowing at high temperature is needed to be analyzed and elaborated in the future studies. 4. References: [1] G. Bertali , F.Scenini ,M.G.Burke The effect of residual stress on the Preferential Intergranular Oxidation of
Alloy600 ; Corrosion
Science 111 (2016) 494–507 [2] P.L. Andresen, F.P. Ford, Life prediction by mechanistic modeling and system monitoring of environmental cracking of iron and nickel alloys in aqueous systems, Mater Sci Eng A A103 (1988) 167–184 [3] G Benghalia, J Wood etal material and residual stress consideration associated with the weld clad component; International Journal of Pressure Vessels and Piping 139-140 (2016) 146-158 [4] Fujimitsu Masuyama, John P. Shingledecker, 2013 ASME boilers and pressure vessel code section XI, New York, Procedia Engineering, Volume 55, 2013, Pages 314-325 [5] H.E. Coules , stress intensity interaction between similar and dissimilar semi elliptical surface cracks; International Journal of Pressure Vessels and Piping 146 (2016) 55-64 [6] Chang-Gi Han a, Yoon-Suk Chang a,*, Jong-Sung Kim b, and Maan-Won Kim, Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes; Nuclear Engineering and Tec hnology 48 (2016 ) 1412 -1422 [7] Chang-Gi Han a, Yoon-Suk Chang a,*, Jong-Sung Kim b, and Maan-Won Kim, Round Robin Analyses on Stress Intensity Factors of Inner Surface Cracks in Welded Stainless Steel Pipes; Nuclear Engineering and Tec hnology 48 (2016 ) 1412 -1422 [8] K Chandra,V K Jain, V Bhutani, VS Raj et al. Low temperature thermal ageing of the austenitic stainless steel; Mater. Sci. Eng. A 534 (2012) 163-175 [9] P.K. Singh et al, thermal ageing in the austenitic stainless steel weld; Trans. Struct. Mech. Reactor Technol. 23 (2015) 305. [10] Yang et al, Modified stress intensity factor equation semi elliptical surface crack in finite thickness, Procedia Engineering 14 (2011) 2601– 2608 [11] Son do et al simulation of large point bending experiment influence on the residual stresses, Volume 3, 2014, Pages 1599–1605 [12] Joy Varghese V M, Suresh M R and Siva Kumar D, Int. J. Adv. Man. Tech., (2012) [13] De A and DebRoy T, Sci. Tech. Wel. Jo., (2011), 16. [14] Eagar T W and Tsai N S, AWS Conv., (1983). [15] Tsai N S and Eagar T W, Mod. Cast. Weld. Pro., (1984). [16] Goldak J A, Chakravarti A and Bibby M, Meta. Tran. B, (1984), 15B. [17] Goldak J A, Oddy A, Gu M, Ma W, Mashaie A and Hughes E, IUTAM Symp., (1992). [18] Nguyen N T, Ohta A, Matsuoka K, Suzuki N and Maeda Y, Weld. Res. Sup., (1999). [19] Zhu X K and Chao Y J, Comp. Stru., (2002), 80. [20] Asserin O, Loredo A, Petelet M and Iooss B, Fini. Ele. Anal. Des., (2011), 47.
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[21] Barroso A, Canas J, Picon R, Paris F, Mendez C and Unanue I, Mat. Des (2010), 31. [22] Aarbogh H M, Hamide M, Fjaer H G, Mo A and Bellet M, J. Mat. Pro. Tech., (2010), 210 [23] Suresh Kumar, influence of residual stresses on stresses on the stress intensity factor, Volume 86, 2014, Pages 234–24 [24] Zenhua wu et al., prediction of the pavement cracking , Expert Systems with Applications, Volume 41, Issue 4, Part 1, March 2014, Pages 1021-1030 [25] S Suresh et al , influence of the residual stress intensity estimation; Volume 86, 2014, Pages 234–241 [26] Lee and Chang, influence of the residual stresses distortion on the structural behaviour; Construction and Building Materials, Volume 41, April 2013, Pages 766-776 [27] Albrecht, P and Yamada K. Rapid calculation of stress intensity factors. Journal of the Structural Division, ASCE. 103(2), 1977, pp. 377-389 [28] Newman J. A review and assessment of the stress intensity factors for surface cracks. Part-Through Crack Fatigue Life Prediction, ASTM STP 687, 1979, pp. 16-42. [29] Newman J and Raju I. An empirical stress-intensity factor equation for the surface crack. Engineering Fracture Mechanics, 1981, 15(1-2), pp. 185-192 [30] Experimental determination of residual stresses in the hard-faced layers after hard-facing and tempering of hot work steels Vuki Lazia, Dušan Arsia , Ružica R. Nikoli, Branislav Hadzimab; Procedia Engineering 153 ( 2016 ) 392 – 399