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...3], b) - according to J. Schijve [34]sConsidering the issues of life prediction of materials subjectedsto fatigue and creep, the most commonly method used is the linearshypothesis of damage summation =-=[2, 31, 32]-=-. The law describingsthe accumulation of damage in this case can be expressed in asform of the dependencies:sN N t t K i fi i N i zi i 1 11s ¦¦ ,s(5)swhere:stis– duration of load action on a given le...

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... are of hypothetic character, and relate to specificsconditions of cracking. One of the first attempts to formulate thescriterion of stability under the low-cycle fatigue was thatspresented by Manson =-=[22, 23]-=-.sHe suggested the relationshipsbetween the number of cycles to failure - Nz and the range ofsplastic deformation - 'Hp:sCNzps DH' ,s(1)sin which C and Dare the material constants.sExperimental test...

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...so the risk ofsuncontrolled development of cracks can be assessed, if they aresfound by the diagnostic tests in the pipeline.sThe basicscharacteristics of the material in this case is the diagram FADs=-=[2,49]-=-, which allows determining the dimensions of crack, whichswould cause damage to the pipeline.sCreep characteristics, which were and still are a major sourcesof data in the process of construction and ...

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... been fully resolved.sa)sb)sFig. 5. Characteristics presenting the effects of load sequence onsthe fatigue resistance of the material: a) - according to K.J. Millers[33], b) - according to J. Schijve =-=[34]-=-sConsidering the issues of life prediction of materials subjectedsto fatigue and creep, the most commonly method used is the linearshypothesis of damage summation [2, 31, 32]. The law describingsthe a...

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...3], b) - according to J. Schijve [34]sConsidering the issues of life prediction of materials subjectedsto fatigue and creep, the most commonly method used is the linearshypothesis of damage summation =-=[2, 31, 32]-=-. The law describingsthe accumulation of damage in this case can be expressed in asform of the dependencies:sN N t t K i fi i N i zi i 1 11s ¦¦ ,s(5)swhere:stis– duration of load action on a given le...

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...deformation - 'Hp:sCNzps DH' ,s(1)sin which C and Dare the material constants.sExperimental tests and an attempt to interpret the formula (1),swith the power generating approach, would allow Coffin =-=[24, 25]-=-sto present it as follows:sCN /zps 21H's(2)sThe power generating criteria represent the group of relationssbetween the fatigue components and number of load cycles, mostscommonly used to describe the...

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...and the Institute ofsFerrous Metallurgy, using their own classification of structures,sbased on the study of pearlite decomposition and carbide separationsprocesses within and at the grain boundaries =-=[15]-=-.s5. Computer-aided methods forsanalysing mechanical statessComponents of industrial facilities subjected to mechanicalsand thermal impacts, in addition to many common characteristics,sresulting from ...

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...svoids at grain boundaries. Over time, the degree of structuresdefects increases which, in turn, with the simultaneous influencesof time-varying thermal stress field, leads to the formation ofscracks =-=[2, 57, 58, 60]-=-.sOver the time, cracks increase their lengthsunder the influence of constant load in creep conditions, or due tosthe impacts of cyclical nature. Inside the structure of the material,schanges occur du...

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..., WNT, Warsaw,s1978 (in Polish).s[14] S. KocaĔda, A. KocaĔda, Low-cycle endurance of metal,sPWN, Warsaw, 1989.s[15] S. KocaĔda, J. Szala, Bases of fatigue calculations, PWN,sWarsaw, 1997 (in Polish).s=-=[16]-=- K.J. Miller, An introductory lecture on fatigue of metals,sCourse of Metal Fatigue, University of Sheffield, 1991.s[17] B. Tomkins, Fatigue failure and the integrity of structures,sCourse of Metal Fa...

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...ocaĔda, J. Szala, Bases of fatigue calculations, PWN,sWarsaw, 1997 (in Polish).s[16] K.J. Miller, An introductory lecture on fatigue of metals,sCourse of Metal Fatigue, University of Sheffield, 1991.s=-=[17]-=- B. Tomkins, Fatigue failure and the integrity of structures,sCourse of Metal Fatigue, University of Sheffield, 1991.s[18] K.J. Miller, The three thresholds For Fatigue CracksPropagation, Fatigue and ...

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...deformation - 'Hp:sCNzps DH' ,s(1)sin which C and Dare the material constants.sExperimental tests and an attempt to interpret the formula (1),swith the power generating approach, would allow Coffin =-=[24, 25]-=-sto present it as follows:sCN /zps 21H's(2)sThe power generating criteria represent the group of relationssbetween the fatigue components and number of load cycles, mostscommonly used to describe the...

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...Nz> 104, Manson proposes the approximation ofsthe fatigue plot with the equation:sJH'H'H' c c zzzsp NE ANMs(3)sThe M and A’ constants are determined [13,23] from the staticstensile test.sCoffin =-=[27]-=- proposed the dependency taking into account theseffect of load frequency - Z:sss1kk1nnz n 1k z NE CA N C sDDD ZZ H' ,s(4)swhere A, C, k, D, n, k1 are the constants depending on thestem...

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...artment of Mechanics of Materials of Silesian University ofsTechnology.sThe aim of the study was to attempt a physical interpretationsof damage accumulation under fatigue with variable loadsamplitude =-=[35]-=-. The interpretation was based on the energysapproach to the process in which the free energy released at thestime of the formation of cracks was adopted as the size criterion.sThe problem of damage a...

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...o use the multiple criteria approach [2, 40]. Thescurrently R5 and R6 standards used in the United Kingdom, andsproposals of the European standards SINTAP - StructuralsIntegrity Assessment Procedures =-=[49]-=-, describe the procedures forspredicting crack development and damage criteria associated withsthe achievement of the limit state. The so called FAD (FailuresAssessment Diagram) was introduced (fig. 6...

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...ols used by modern materials science.sDiscovery of the many phenomena occurring in the structure ofsmaterials and crucial for their decohesion, for which a modelsapproach was developed in the fifties =-=[50, 51]-=- of the last century,swas possible with the aid of the transmission electron microscopy.sIn the transmission microscopes used in the late fifties and earlys45 Analysis and modelling Life and operation...

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...croscopy. Observations conducted by this method on thessurface of samples subjected to fatigue and fatigue fracture, madesit possible to identify the mechanisms of formation andsdevelopment of cracks =-=[52, 53]-=-. Research in that area wassparticularly intense in the seventies [54, 55]. To date, observationsof fractures is one of the basic methods of determining the causessof failures of items of equipment op...

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...been taken into account. In thescalculations the surface film conductance values were assumed.sThe boundary coefficients were adopted based on a handbook bysZbigniew OráoĞ entitled “Thermal Stresses” =-=[59]-=-, thus assumingsintensive heat exchange both under heating conditions, in contactsof the inner surface with superheated steam, and in coolingsconditions, in contact of the inner surface with water mis...

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...parts of the installation. In the case of an overall crack, asgap would occur which indicative shape is shown in Figure 27a.sFor the crack in Figure 27a, the stress intensity factors aresexpressed by =-=[69]-=- the dependencies:smmI FRK 4SVsorsttI FRK 4SVsorsbbI FRK 4SV ,s(15)swhere Vm, Vt, Vb denote stress resulting from the internal pressure,saxial force or bending moment, Fm, Ft, Fb denote functions of t...

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...d target projects.sReferencess[1] W. BĊczkowski, Power plants, WNT, Warsaw, 1965s(in Polish).s[2] G.A. Webster, R.A. Ainsworth, High TemperaturesComponent Life Assessment, ChapmansHall, London,s1994.s=-=[3]-=- A. Hernas, Thermal strength of steels and alloys, SilesiansUniversity of Technology Press, Gliwice, 1999 (in Polish).s[4] PN-92/M-34031: Pipelines of steam and hot water. Generalsrequirements and exa...

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...til recently, the UDT (Polish Office of TechnicalsInspection) requirements did not take into account the life aspects,srelated to the possible presence of cracks in the elements ofspressure equipment =-=[6]-=-. In the latest edition of the Conditions ofsthe Technical Inspection Office, on the pressure equipment,sfailure caused by the presence of cracks is included in a form ofsgeneral guidelines recommendi...

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...train in creep conditions inside the structure of the material,sdefects may occur. For technical applications the structure classes,scorresponding to the level of its degradation, have been developeds=-=[2, 7, 8, 12]-=-. Based on the operating experience, the necessarysactions have been determined, which need to be taken by the user,safter finding a certain degree of the structure defect. Figure 3sprovides a schemat...

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...8 Zylinderschalen unter inneremsÜberdruck. Berechung auf Wechselbeanspruchung durchsschwellenden Innerdruck bzw. durch kombiniertesInnerdruck und Temperaturänderungen, 1 Ausg. 4.75, 1975s(in German).s=-=[9]-=- I.A. Shibli Overview of HIDA Project, Proceedings of thes2th International HIDA Conference, Stuttgart, 2000.s[10] Nuclear Electric Ltd, Assessment Procedure for the HighsTemperature Response of Struc...

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...train in creep conditions inside the structure of the material,sdefects may occur. For technical applications the structure classes,scorresponding to the level of its degradation, have been developeds=-=[2, 7, 8, 12]-=-. Based on the operating experience, the necessarysactions have been determined, which need to be taken by the user,safter finding a certain degree of the structure defect. Figure 3sprovides a schemat...

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...the value of the number ofscycles to failure Nz> 104, Manson proposes the approximation ofsthe fatigue plot with the equation:sJH'H'H' c c zzzsp NE ANMs(3)sThe M and A’ constants are determined =-=[13,23]-=- from the staticstensile test.sCoffin [27] proposed the dependency taking into account theseffect of load frequency - Z:sss1kk1nnz n 1k z NE CA N C sDDD ZZ H' ,s(4)swhere A, C, k, D, n,...

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...ard EN 13480-3:2002 (E).s[12] RWTÜV, Replicas for parts under creep according to TRDs508, Recommendation, 1983, 451-1983/1.s[13] S. KocaĔda, Fatigue fracture of metals, WNT, Warsaw,s1978 (in Polish).s=-=[14]-=- S. KocaĔda, A. KocaĔda, Low-cycle endurance of metal,sPWN, Warsaw, 1989.s[15] S. KocaĔda, J. Szala, Bases of fatigue calculations, PWN,sWarsaw, 1997 (in Polish).s[16] K.J. Miller, An introductory lec...

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...on fatigue of metals,sCourse of Metal Fatigue, University of Sheffield, 1991.s[17] B. Tomkins, Fatigue failure and the integrity of structures,sCourse of Metal Fatigue, University of Sheffield, 1991.s=-=[18]-=- K.J. Miller, The three thresholds For Fatigue CracksPropagation, Fatigue and Fracture Mechanics, ASTM STPs1296 (1997) 267-286.s[19] N.N. Malinin, Creep calculations of the machines and thesstructures...

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...structures,sCourse of Metal Fatigue, University of Sheffield, 1991.s[18] K.J. Miller, The three thresholds For Fatigue CracksPropagation, Fatigue and Fracture Mechanics, ASTM STPs1296 (1997) 267-286.s=-=[19]-=- N.N. Malinin, Creep calculations of the machines and thesstructures, Maszynostrojenije, Moscow, 1981 (in Russian).s[20] A. Jakowluk, Contemporary lines of research of creep ofsmateriale, II Symphosy:...

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...sis for the modelling andsforecasting the effects of creep processes, and are based onshypotheses related to the material properties [19-21]. Thespotential of the creep rate is, among others, assumed =-=[20]-=-. At thissstage, a general approach, allowing a description of the behavioursof materials in a variety of conditions, determined by state ofsstress, temperature and the type of material, does not seem...

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... are of hypothetic character, and relate to specificsconditions of cracking. One of the first attempts to formulate thescriterion of stability under the low-cycle fatigue was thatspresented by Manson =-=[22, 23]-=-.sHe suggested the relationshipsbetween the number of cycles to failure - Nz and the range ofsplastic deformation - 'Hp:sCNzps DH' ,s(1)sin which C and Dare the material constants.sExperimental test...

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...nents and number of load cycles, mostscommonly used to describe the life. Typically, they rely onsidentifying the work of plastic strain based on the course of theshysteresis loop. Feltner and Morrow =-=[26]-=- assumed that the failuresoccurs when the work of plastic deformation, measured as thessurface area of the hysteresis loop under cyclic load, reaches thesvalue of energy dissipated in the material dur...

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...y - Z:sss1kk1nnz n 1k z NE CA N C sDDD ZZ H' ,s(4)swhere A, C, k, D, n, k1 are the constants depending on thestemperature and material type.sBased on the criterion of Coffin, Moskwitin =-=[28]-=- attempts asmore general approach to the life in conditions of complex stress.sMonographs [29, 30] provide an analysis of a series of life criteriasin relation to the thermal and mechanical fatigue. T...

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...the constants depending on thestemperature and material type.sBased on the criterion of Coffin, Moskwitin [28] attempts asmore general approach to the life in conditions of complex stress.sMonographs =-=[29, 30]-=- provide an analysis of a series of life criteriasin relation to the thermal and mechanical fatigue. Thesphenomenological description of test results proposed in thisspaper, however, requires further ...

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...the constants depending on thestemperature and material type.sBased on the criterion of Coffin, Moskwitin [28] attempts asmore general approach to the life in conditions of complex stress.sMonographs =-=[29, 30]-=- provide an analysis of a series of life criteriasin relation to the thermal and mechanical fatigue. Thesphenomenological description of test results proposed in thisspaper, however, requires further ...

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... time period, the localsdeformation process will proceed in a different way, which can bescharacterized by the course of the hysteresis loop in the stress –sstrain coordinates. Coffin [36] and Manson =-=[37]-=- havesdistinguished four basic types of load cycles. They also proposedsa method of estimating the life, involving the separation of thestime intervals which can relate to the basis cycles in case of ...

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... rate at cyclically changingsload.sNowadays, the dominant approach to the problem of lifesprediction in structures subjected to mechanical and thermalsimpacts is to use the multiple criteria approach =-=[2, 40]-=-. Thescurrently R5 and R6 standards used in the United Kingdom, andsproposals of the European standards SINTAP - StructuralsIntegrity Assessment Procedures [49], describe the procedures forspredicting...

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...s of the structure, the description ofsthe material failure process, models integrating several criteriasparameters are applied. In a study of 18-8 grade steel crack rate,sin creep conditions at 650° =-=[41]-=-, a mathematical model includingsthe effect of stress concentration factor KV, and of the nominalsstress Vn were applied, for the crack initiation time ti:ss1iin CtKs DV V ,s(10)swhere: Di, C1 - ma...

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...croscopy. Observations conducted by this method on thessurface of samples subjected to fatigue and fatigue fracture, madesit possible to identify the mechanisms of formation andsdevelopment of cracks =-=[52, 53]-=-. Research in that area wassparticularly intense in the seventies [54, 55]. To date, observationsof fractures is one of the basic methods of determining the causessof failures of items of equipment op...

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...subjected to fatigue and fatigue fracture, madesit possible to identify the mechanisms of formation andsdevelopment of cracks [52, 53]. Research in that area wassparticularly intense in the seventies =-=[54, 55]-=-. To date, observationsof fractures is one of the basic methods of determining the causessof failures of items of equipment operating under the conditionssof fatigue.sThe introduction of electron micr...

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...subjected to fatigue and fatigue fracture, madesit possible to identify the mechanisms of formation andsdevelopment of cracks [52, 53]. Research in that area wassparticularly intense in the seventies =-=[54, 55]-=-. To date, observationsof fractures is one of the basic methods of determining the causessof failures of items of equipment operating under the conditionssof fatigue.sThe introduction of electron micr...

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...are applied, which are particularly useful in evaluating strength insthe possible extreme conditions.sThe values of stress, displacement and strain are determinedsby building models of the structures =-=[56, 57]-=- (Fig. 7).s(a) (b)sFig. 7. An example of a pipeline subjected to tests, with markedsselected fastening points; (a) - the entire pipeline; (b) -pipelinespart for which stress distributions have been pr...

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...are applied, which are particularly useful in evaluating strength insthe possible extreme conditions.sThe values of stress, displacement and strain are determinedsby building models of the structures =-=[56, 57]-=- (Fig. 7).s(a) (b)sFig. 7. An example of a pipeline subjected to tests, with markedsselected fastening points; (a) - the entire pipeline; (b) -pipelinespart for which stress distributions have been pr...

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...essarily lead to deteriorationsof material properties. It can be observed, for example, that theslow-cycle fatigue strength of steel alloys used for the powerspipelines increases with the time of use =-=[58, 60]-=-. However, thesstrength properties are deteriorated, which is illustrated, forsexample, by the course of cyclic deformation curves. The lifesevaluation requires, therefore, a very cautious interpretat...

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... materials are the basis of FITNET SINTAPsprocedures.s9. Research programs on fracturesmechanics and "structural integrity”sEnded some years ago, the program HIDA (High TemperaturesDefect Assessment) =-=[70]-=- funded by the European Commissionsconcerned the methods of determining the life of elementssworking under the influence of elevated temperature andsmechanical stress in power industry. Continuation o...