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A review of fatigue failures in LWR plants in Japan
Fatigue Abstracts This section contains abstracts of selected articles, technical reports, dissertations and patents concerned with fatigue. It is prepared in collaboration with Materials Information, a joint service of The Institute of Materials and ASM International. Readers wishing to obtain the full text of articles abstracted here should contact either: The Institute of Materials, 1 Carlton House Terrace, London SWIY 5DB, UK, or: ASM International, Metals Park, OH 44073, USA (not International Journal of Fatigue). The fees charged for photocopyiung articles are £7.00 for the first ten pages and £3.00 per additional ten pages (UK office), or $10.00 for the first ten pages and $4.00 per additional ten pages (US Office).
A differential CDM m o d e l f o r f a t i g u e o f unidirectional metal m a t r i x composites. Arnold, S.M. N A S A Technical M e m o r a n d u m TM-105726 1992 22 pp
Calculation f o r rolling contact f a t i g u e life and strength o f cesu-herdened gear materials b y computer. Jiang, B., Zheng, X. and Wang, M. ASTMJ. Test. Eval. (Jan. 1993) 21 (1), 9 - 1 3
A multiaxial, isothermal, continuum damage mechanics model for fatigue of a unidirectional metal-matrix composite volume element is presented. The model is phenomenological, stress-besed, and assumes a single scalar internal damage variable, the evolution of which is snisotropic. The development of the fatigue damage model (i.e. evolutionary law) is based on the definition of an initially transversely isotropic fatigue limit surface, a static fracture surface and a normalized stress amplitude function. The anisotropy of these surfaces and function, and therefore the model, is defined through physically meaningful invsriants reflecting the local stress and material orientation. This transversely isotropic model is shown, when taken to its isotropic limit, to simplify directly to a previously dsveloped and validated isotropic fatigue continuum damage model. Results of a non-dimensional parametric study illustrate the flexibility of the present formulation in attempting to characterize a class of composite materials and the capability of the formulation in predicting anticipated qualitative trends in the fatigue behaviour of unidirectional metal-matrix composites. Also, specific material parameters representing an initial characterization of the composite system SiC/Ti 15-3 and the matrix material (Ti 15-3) are reported. Graphs, 43 ref.
An analysis of the roling contact fatigue process of case-hardened gear material by means of elasticity and fracture mechanics theory has been made; the stress intensity range Ak and equation for crack growth da/dN = c (Ak)" was put forward to calculate their fatigue life and strength. The results show that the calculated data are in good agreement with the experimental ones for compound-treated, sprayed, and csrbonitrided specimens. The relative errors of logarithm of cycle number are all <5%. Graphs, 11 ref. Fatigue design, q u a l i t y control and maintenance o f t h e Ssto Ohashi Bridge. Miki, C. and Okukawa, A.
Proc. Conf. Mechanical Behaviour of Materials-VI, Kyoto, Japan, 29 July2 Aug. 1991, Vol. 2, pp. 173-180 To examine the influences of weld defects, residual stresses and secondary stresses due to structural details on fatigue strengths, various fatigue tests are carried out under the Honshu-Shikoku Bridge project, which includes 45 and 75 mm thick welded joint specimens, full-scale and large-scale structural models of high-strength steels. Based on these tests, the fatigue design code was established and quality control procedures were incorporated in the fabrication code. Graphs, 8 ref.
A r e v i e w o f f a t i g u e failures in LWR plants in Japan. lids, K. Nucl. Eng. Des. (Dec. 1992) 138 (3), 2 9 7 - 3 1 2 A review is made of fatigue failures of nuclear power plant components in Japan, experienced in service and during periodical inspection. No case has been recently reported of a service fatigue failure of a reactor pressure vessel itself, excluding nozzle corner cracks that occurred many years ago. but service fatigue failures have been experienced occasionally in piping systems, pumps and valves, on which fatigue design seems to have been inadequately applied. The causes of fatigue failures can be divided into two categories: machanicel-vibration-induced fatigue and thermal-fluctuation-induced fatigue. Vibration-induced fatigue failure occurs more frequently than is generally thought. The lesson gleaned from the present ! surve;/ is a recognition that a service fatigue failure may occur due to any one or a combination of the following factors: (1) lack of communication between designers and f~'bricetion engineers; (2)lack of knowledge about the possibility of fatigue and inadequate consideration of the effects of residual stresses; (3)lack of consideration of possible vibration in the design and fabrication stages; and (4) lack of fusion or poor penetration in a welded joint. 316L stainless is discussed. Graphs, 5 ref.
A feasibility s t u d y o n t h e application o f localized heating as s lifee n h a n c e m e n t technique. Rajic, N. and Wong, A.K. Mech. Mater. (Dec. 1992) 14 (2), 105-125 The possibility of using spot heating to introduce known levels of localized elastic compressive stress in a small region (over a crack tip for example) is investigated. An efficient numerical approach is used to solve the thermal stress problem arising from the application of a concentrated surface heat flux on several axisymmetric bodies, varying from a thin carbon steel plate to a semi-infinite geometry, It is found that a sufficiently large and reversible compressive stress can be generated rapidly in a small region with a relatively low flux energy. This has significant implications in terms of its potential use as a 'smart' fetigue-life enhancement technique. Graphs, 14 ref.
Specimen edge effeets on b e n d i n g f a t i g u e o f cedburized steel. Cohen,
R.E., Mattock, D.K. and Krauss, G. J. Mater. Eng. Perform. (Oct. 1992) 1 (5), 6 9 5 - 7 0 4 The effects of specimen geometry on the fatigue behaviour of SAE 4320 steel csrburized at 927~ were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison with the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenita in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the squareedged samples at a location epprox 200-900 Wn from the square edge. The implications of this study for laboratory analyses of the bending fatigue performance of carburized gear steels are discussed. Graphs, photomicrographs, 22 ref.
The influence o f p r o l o n g e d e x p o s u r e t o o p e r a t i n g t e m p e r a t u r e s e n d strain ageing on t h e materiel p r o p e r t i e s o f nuclear p o w e r plant reactor vessels end pipings. Karzov, G.P., Timofeev, B.T. and Filchagin, Y.G. Int. J. Pressure Vessels and Piping (1993) 53 (2), 195-216 The impact of operating temperature on the mechanical properties of steels and their welded joints in the production of NPP apparatus and pipings used in WER and RBMK reactors is presented. Together with the properties characteristic of types 20, 20K, O8X18H12T and 15 x 2MFA steels after exposure to the temperature range of 250-400 °C for 104 h, the values of the mechanical properties of these materials and their weldments (cut from the real components of an operating NPP) after exposure for 105 h at material operating temperatures are given. Variation in properties after such prolonged operation periods is negligible and, moreover, the values of UTS, YS, A and Zare not inferior to those required by the USSR 'norms of strength calculation'. The estimation of structural strength (low-cycle fatigue resistance, and static and cyclic crack resistance) has been carried out as related to pipings manufactured from O8X18H12T steel after their operation period of 105 h. No visible variations of these characteristics have been observed.The influence of strain ageing in the operating temperature range 150-400 °C on low-cycle fatigue resistance of the 15X2MFA, 15x2HMFA and 22K steels, and their welded joints produced by various welding processes (manual, automatic under flux, electroslag weldings) has also been studied. It has been found that, with the application of specific temperatures and strain rates, the ageing effect may predetermine the material long-term lifetime related to a decrease at the stage of fatigue crack initiation. The strain ageing effect is most evident with low-carbon weld metal after manual arc welding without preheating, which is the welding process that may be applied during assembly. Graphs. 26 ref. Notch effect of w e l d e d j o i n t s subjected t o antipiane shear loading.
Radaj, D. and Zhang, S. Eng. Fract. Mech. (Nov. 1992) 43 (4), 6 6 3 - 6 6 9 Complementary to existing solutions of the plane problem of notch stress concentration of mild steel welded joints, the antiplane problem is solved using the boundary element method. Typical shape examples of welded joints are considered. Tensile loading is compared with longitudinal shear loading. Based on these solutions, bisxial and oblique loading are dealt with, taking the cruciform joint and transverse stiffener as examples. The fatigue notch factor is determined based on the microstructural support hypothesis proposed by Neuber. Graphs, 8 ref. Sudden burst o f • b l o w e r impeller. Welding in the World (Nov.-Dec. 1992) 30 (11-12), 294-296 (in English and French) Investigation of the failure of an impeller in an exhaust gas dust extraction system in an LD converter is presented. The impeller design was modified as a result of an examinstion of the feiiure, which was found to have been caused by fatigue cracking. Photomicrographs.
Fatigue, 1994, Vol 16, February 151
A differential CDM m o d e l f o r f a t i g u e o f unidirectional metal m a t r i x composites. Arnold, S.M. N A S A Technical M e m o r a n d u m TM-105726 1992 22 pp
Calculation f o r rolling contact f a t i g u e life and strength o f cesu-herdened gear materials b y computer. Jiang, B., Zheng, X. and Wang, M. ASTMJ. Test. Eval. (Jan. 1993) 21 (1), 9 - 1 3
A multiaxial, isothermal, continuum damage mechanics model for fatigue of a unidirectional metal-matrix composite volume element is presented. The model is phenomenological, stress-besed, and assumes a single scalar internal damage variable, the evolution of which is snisotropic. The development of the fatigue damage model (i.e. evolutionary law) is based on the definition of an initially transversely isotropic fatigue limit surface, a static fracture surface and a normalized stress amplitude function. The anisotropy of these surfaces and function, and therefore the model, is defined through physically meaningful invsriants reflecting the local stress and material orientation. This transversely isotropic model is shown, when taken to its isotropic limit, to simplify directly to a previously dsveloped and validated isotropic fatigue continuum damage model. Results of a non-dimensional parametric study illustrate the flexibility of the present formulation in attempting to characterize a class of composite materials and the capability of the formulation in predicting anticipated qualitative trends in the fatigue behaviour of unidirectional metal-matrix composites. Also, specific material parameters representing an initial characterization of the composite system SiC/Ti 15-3 and the matrix material (Ti 15-3) are reported. Graphs, 43 ref.
An analysis of the roling contact fatigue process of case-hardened gear material by means of elasticity and fracture mechanics theory has been made; the stress intensity range Ak and equation for crack growth da/dN = c (Ak)" was put forward to calculate their fatigue life and strength. The results show that the calculated data are in good agreement with the experimental ones for compound-treated, sprayed, and csrbonitrided specimens. The relative errors of logarithm of cycle number are all <5%. Graphs, 11 ref. Fatigue design, q u a l i t y control and maintenance o f t h e Ssto Ohashi Bridge. Miki, C. and Okukawa, A.
Proc. Conf. Mechanical Behaviour of Materials-VI, Kyoto, Japan, 29 July2 Aug. 1991, Vol. 2, pp. 173-180 To examine the influences of weld defects, residual stresses and secondary stresses due to structural details on fatigue strengths, various fatigue tests are carried out under the Honshu-Shikoku Bridge project, which includes 45 and 75 mm thick welded joint specimens, full-scale and large-scale structural models of high-strength steels. Based on these tests, the fatigue design code was established and quality control procedures were incorporated in the fabrication code. Graphs, 8 ref.
A r e v i e w o f f a t i g u e failures in LWR plants in Japan. lids, K. Nucl. Eng. Des. (Dec. 1992) 138 (3), 2 9 7 - 3 1 2 A review is made of fatigue failures of nuclear power plant components in Japan, experienced in service and during periodical inspection. No case has been recently reported of a service fatigue failure of a reactor pressure vessel itself, excluding nozzle corner cracks that occurred many years ago. but service fatigue failures have been experienced occasionally in piping systems, pumps and valves, on which fatigue design seems to have been inadequately applied. The causes of fatigue failures can be divided into two categories: machanicel-vibration-induced fatigue and thermal-fluctuation-induced fatigue. Vibration-induced fatigue failure occurs more frequently than is generally thought. The lesson gleaned from the present ! surve;/ is a recognition that a service fatigue failure may occur due to any one or a combination of the following factors: (1) lack of communication between designers and f~'bricetion engineers; (2)lack of knowledge about the possibility of fatigue and inadequate consideration of the effects of residual stresses; (3)lack of consideration of possible vibration in the design and fabrication stages; and (4) lack of fusion or poor penetration in a welded joint. 316L stainless is discussed. Graphs, 5 ref.
A feasibility s t u d y o n t h e application o f localized heating as s lifee n h a n c e m e n t technique. Rajic, N. and Wong, A.K. Mech. Mater. (Dec. 1992) 14 (2), 105-125 The possibility of using spot heating to introduce known levels of localized elastic compressive stress in a small region (over a crack tip for example) is investigated. An efficient numerical approach is used to solve the thermal stress problem arising from the application of a concentrated surface heat flux on several axisymmetric bodies, varying from a thin carbon steel plate to a semi-infinite geometry, It is found that a sufficiently large and reversible compressive stress can be generated rapidly in a small region with a relatively low flux energy. This has significant implications in terms of its potential use as a 'smart' fetigue-life enhancement technique. Graphs, 14 ref.
Specimen edge effeets on b e n d i n g f a t i g u e o f cedburized steel. Cohen,
R.E., Mattock, D.K. and Krauss, G. J. Mater. Eng. Perform. (Oct. 1992) 1 (5), 6 9 5 - 7 0 4 The effects of specimen geometry on the fatigue behaviour of SAE 4320 steel csrburized at 927~ were evaluated with two sets of cantilever bend specimens, one set machined with square edges and one set machined with round edges. The specimens with square edges exhibited a 13% lower fatigue limit. In comparison with the rounded samples, the lower fatigue limit in the square-edged samples was attributed to the presence of a higher volume fraction of retained austenita in the sample corners and a lower surface residual compressive stress. As a result of the differences in residual stress, preferential crack initiation sites existed in the squareedged samples at a location epprox 200-900 Wn from the square edge. The implications of this study for laboratory analyses of the bending fatigue performance of carburized gear steels are discussed. Graphs, photomicrographs, 22 ref.
The influence o f p r o l o n g e d e x p o s u r e t o o p e r a t i n g t e m p e r a t u r e s e n d strain ageing on t h e materiel p r o p e r t i e s o f nuclear p o w e r plant reactor vessels end pipings. Karzov, G.P., Timofeev, B.T. and Filchagin, Y.G. Int. J. Pressure Vessels and Piping (1993) 53 (2), 195-216 The impact of operating temperature on the mechanical properties of steels and their welded joints in the production of NPP apparatus and pipings used in WER and RBMK reactors is presented. Together with the properties characteristic of types 20, 20K, O8X18H12T and 15 x 2MFA steels after exposure to the temperature range of 250-400 °C for 104 h, the values of the mechanical properties of these materials and their weldments (cut from the real components of an operating NPP) after exposure for 105 h at material operating temperatures are given. Variation in properties after such prolonged operation periods is negligible and, moreover, the values of UTS, YS, A and Zare not inferior to those required by the USSR 'norms of strength calculation'. The estimation of structural strength (low-cycle fatigue resistance, and static and cyclic crack resistance) has been carried out as related to pipings manufactured from O8X18H12T steel after their operation period of 105 h. No visible variations of these characteristics have been observed.The influence of strain ageing in the operating temperature range 150-400 °C on low-cycle fatigue resistance of the 15X2MFA, 15x2HMFA and 22K steels, and their welded joints produced by various welding processes (manual, automatic under flux, electroslag weldings) has also been studied. It has been found that, with the application of specific temperatures and strain rates, the ageing effect may predetermine the material long-term lifetime related to a decrease at the stage of fatigue crack initiation. The strain ageing effect is most evident with low-carbon weld metal after manual arc welding without preheating, which is the welding process that may be applied during assembly. Graphs. 26 ref. Notch effect of w e l d e d j o i n t s subjected t o antipiane shear loading.
Radaj, D. and Zhang, S. Eng. Fract. Mech. (Nov. 1992) 43 (4), 6 6 3 - 6 6 9 Complementary to existing solutions of the plane problem of notch stress concentration of mild steel welded joints, the antiplane problem is solved using the boundary element method. Typical shape examples of welded joints are considered. Tensile loading is compared with longitudinal shear loading. Based on these solutions, bisxial and oblique loading are dealt with, taking the cruciform joint and transverse stiffener as examples. The fatigue notch factor is determined based on the microstructural support hypothesis proposed by Neuber. Graphs, 8 ref. Sudden burst o f • b l o w e r impeller. Welding in the World (Nov.-Dec. 1992) 30 (11-12), 294-296 (in English and French) Investigation of the failure of an impeller in an exhaust gas dust extraction system in an LD converter is presented. The impeller design was modified as a result of an examinstion of the feiiure, which was found to have been caused by fatigue cracking. Photomicrographs.
Fatigue, 1994, Vol 16, February 151