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X-ray diffraction apparatus for life assessment of boiler feed water pump shaft
C h a r a c t c r i ~ el' ~-hanlcully alloyed AI-LI alloy, AL-905XL. Tsukuta, K., likubo, 7". and Hira, H. Denki Seiko (Electric Furnace Steel) ( May 1993) 64 (2), 116-122 (in Chinese ) Characteristics of mechanically alloyed carbide and oxide dispersion strengthenod AI-Li alloy, IncoMAP alloy AL-905XL, extrusion and its forging were investigated to examine whether it could be applied to structural materials in aircraft, aerospace, and other industries. The following results were obtained. (I) No age hardening occurred, although AL-905XL contains 1.3 mass% lithium which is a precipitation hardening element. (2) Hardness and microstructure did not change after long exposure at 573 K. (3) By forging the extruded bar, though 0.2% proof stress decreased, ductility, fracture toughness, and crack growth resistance were improved. As for anisotropy of these characteristics of the forging, longitudinal direction was much better than both long and short transverse ones which showed comparable values. In comparison with conventional aluminium alloys, proof stress and ductility were equal to or better than 7075-T7351, and fracture toughness was between 7075-T651 and 7074-T7351. The crack growth rate was comparable to 7075T7351 at higher AK; however, it was slightly larger at lower AK. (4) Fatigue property of AL-905XL extrusion was superior to 7075-T6. (5) Stress corrosion cracking resistance of AL-905XL forging was comparable to 7075-T7351. Exfoliation corrosion resistance was much better than 7075-T651. Graphs, diffraction patterns, photomicrographs, 10 ref. Thermal fatigue property of ferritic stainless cast steels.
Nagashima, T. and Ikubo, T. Denki Seiko (Electric Furnace Steel) (May 1993) 64 (2), 99-106 (in Chinese) The exhaust components of automobile engines are being made of ferritic stainless steel or ferritic stainless cast steel in place of ductile cast iron for not only improving heat resistance but also weight saving. The thermal fatigue properties are most important for these. The thermal fatigue test with external restraint and the thermal shock test with internal restraint for various ferfitic stainless cast steels (Fe-0.05C-18.86Cr-1.96W-0.98Nb-0.56-Si 0.51Mn-0.11Ni, Fe-0.15C- 17.72Cr-0,55Mn-0.34Si-0.19Nb0.09Ni, Fe-0.03C-17.91Cr-0.65Mn-0.57Si-0.19Nb-0.06Ni) and ductile cast iron were performed. The plastic deformation caused by thermal stress through ferritic stainless cast steels can be evaluated by measuring the dimensional change of specimen after the thermal shock test. It decreases by increasing high temperature strength and increases by crystalline transformation. A ferritie stainless cast steel composed of 0.05C-19Cr-INb-2W results in the longest thermal fatigue life and the least plastic deformation of all tested steels. Graphs, 23 ref. Fatigue performance of nine bolt materials in air and in seawater with cathodic protection. Slind, T., Eggen, T.G., Bardal, E. and Haagensen, P.K. Acorn (1993) (1), 1-6 The hydrogen sensitivity of various bolt materials (Marinel, Monel K-500, Inconel 625, Incoloy 925, SAF 2507, Cronifer 2419MoN, 254SMO, A320 L7) for subsea use has been determined. The fatigue crack growth rates of eight materials were found in air and in artificial seawater/3%NaCI solution with cathodic protection (CP0). S - N tests of threaded bolts, using a high mean stress were carried out in seawater with CP for two materials. The materials are grouped in three classes on their H susceptibility based on the crack growth results. Design curves determined from the S - N test results are compared with various standard design curves. Graphs, numeric data, 12 ref. Fatigue damage evaluation under random str~s sequences in terms of effective stress. Takahashi, T., lida, T. and lkai, Y. J. Soc. Mater. Sci. Jpn (June 1993) 42 (477) 670--675 (in Japanese) A cumulative fatigue damage rule has been proposed for random stress sequences from a viewpoint of internal stress and effective stress. Applied stress was divided into two parts through practical measurements and simulation: internal stress as a backward stress for the deformation and effective stress as a drag due to plastic flow. For the fatigue damage evaluation, a cumulative damage rule like Miner's was operated with the help of an ES-N diagram and effective stress measurements during the fatigue process. The former was obtained by fatigue tests where effective stresses were kept constant during the tests, which resulted in an experimental expression of formulae. It was found that the internal stress at a given cycle can be expressed in a regressive form in terms of the stress level and the internal stress of the latest cycle. That is, orion) F(cr.(,-1), ~ri(n-l), ~r.(n)) where subscripts ( n - l ) and (n) are the latest number of cycles and the current number of cycles, respectively. The damage rule and experimental expression of effective stress were examined on two materials with or without strain-ageing bardenability, $35C steel and At-I. 1 mass% Mn alloy. Agreement between the experimental results and the simulations was found to be fairly good. Numeric data, graphs, 12 ref. =
A technique for detecting inconsistent knowledge in a selection system of retrofitting method of fatigue damage in steel bridges.
The characteristics of inconsistent phenomena are pursued and fragmental knowledge is replaced with comprehensive knowledge. A method of detecting inconsistent knowledge is discussed. Inconsistent phenomena are distinguished as global (dynamic) and local (static) inconsistency. Global inconsistency is recognized when the inference is processed dynamically. On the other hand, the local inconsistency can be detected statically before inferring within the arranged knowledge. To solve global inconsistencies, the inference engine must have a hypothetical inference mechanism which detects and solves the inconsistencies. To solve local inconsistencies, fragmental knowledge is replaced with a systematic network model, where the inconsistencies are detected. The model is modified so that consistency is produced. Systematization is also discussed. 5 ref. A system with knowledge-reusing function for selecting steel bridge fatigue
dam~e retronmns.
Mikami, 1., Kitagishi, H., Kanbe, K. and Tanaka, S. Technology Reports of Kansai University (Mar. 1993) (35), 197-212 A technique for obtaining and adjusting the professional knowledge for 90 cases of fatigue cracking was developed. In the previous paper, a system for selecting the reasonable retrofitting methods was constructed. Since this inference engine has learning ability, the system can be improved. While the inference engine was able to deal with a complicated network and to give flexible inference results, it produced neither secondary results nor valueadded information. In the present paper, a model-based reasoning on qualitative reasoning is of concern. The previous inference engine has been structured so as to give it a model-based reasoning ability, and a structured knowledge model is generated by causality. Using the engine and the structured knowledge model, inference results including secondary knowledge and value-added knowledge can be obtained. 6 ref. A diagnostic expert system with analogical Inference and negative learning ability.
Mikami, 1., Yoneda, S., Tanaka, S. and Kurachi, A. Technology Reports of Kansai University (Mar. 1993) (35), 213-231 Expert systems may be used effectively in the maintenance of existing civil engineering structures, because a wide range of expert engineering knowledge is indispensable in such maintenance. In the preceding paper, the construction of a system for selecting the retrofitting methods of fatigue cracking in steel bridges was explained and discussed. The knowledge used was acquired from 90 cases of fatigue cracking in existing steel bridges, and was represented as causal relations in a knowledge-base. Using a neural network model with C language, an inference engine endowed with a learning ability was developed. Ideas for the further development of this same system with regard to knowledge, inference, and learning ability are advanced. A greater wealth of knowledge is acquired by incorporating information concerning a further 75 cases. With this new knowledge base, the system can perform the inference by analogy, an inference engine being developed, equipped with a greater learning ability, i.e. consisting of both positive and negative learning. The present system is capable of giving appropriate and sufficient inference results. Graphs, 10 ref. Data base of damaged steel bridges.
Mikami, 1., Sakano, M. and Shibata, H. Technology Reports of Kansai University (Mar. 1993) (35), 185-196 About 500 cases of steel bridges damaged owing to fatigue, corrosion, etc. are summarized in a database, in order to discuss various features and tendencies concerning the service period previous to damage, damage type of each type of structure, causes of damage, and countermeasures against damage. Occurrence of fatigue cracking in railway bridges has been reported continually since the 1950s in Japan, the number of these rapidly increasing in the 1970s. On the other hand, fatigue cracking of highway steel bridges was detected for the first time in Japan in the 1970s, and the number of such cases increased rapidly after 1980. As there is at present a dearth of information concerning damage due to corrosion, the present tendency of this kind of damage is not yet clear; it is, however, expected to increase in the future. 6 ref. Development of bridge monitoring system.
Ujiwara, T., Kajimoto, K. Yajima, M., Mural, R., Murakoshi, J. and Yamamoto, S. Mitsubishi Juko Giho (1993) 30 (3), 230-234 (in Japanese) In order to carry out unmanned continuous and objective surveillance of fatigue cracks in steel bridges, two methods to detect cracks - ultrasonic flaw detection and self-breaking crack gauge - have been examined. Sensors and device using these methods for long-term surveillance of cracks in existing bridges have also been developed. The newly developed device has been put to use in a fatigue test using a bridge component model to prove that the new device works sufficiently well and has high performance. Graphs, 3 ref. X-ray diffraction apparatus for life assessment of boiler feed water pump shaft.
Mikami, L, Yoneda, S., Maeda, H.H. and Tanaka, S. Technology Reports of Kansai University (Mar. 1993) (35), 233-245
Hayashi, M., Ueyama, Y., Hashimoto, Y., Ogiso, K. and Sasaki, K. J. Soc. Mater. Sci. Jpn (June 1993) 42(477), 634--640 (in Japanese)
An expert system for the selection of retrofitting methods for fatigue damage in steel bridges has been constructed. Several techniques may be applied to the inference engine in order to improve its function, but fragmental knowledge obtained from mutual relations between two terms includes many inconsistencies. As long as the inconsistent knowledge is processed only by the interpretation based on priority, although undesirable results can in this way be removed, the inconsistent knowledge is processed only superficially.
Boiler feed water pump shafts are subjected to severe thrust loads and cyclic bending moments. Half-value width and residual stress measurements by Xray diffraction methods, which are sensitive to fatigue damage, are employed for the fatigue life assessments of pump shafts. To establish a damage detection system, a portable, lightweight X-ray diffraction apparatus with a rotating receiving slit and X-ray detector and a small diameter X-ray tube has been developed. Consequently, the residual stress can be measured within
518 Fatigue, 1994, Vol 16, October
20 min, which is about one-half the time required using a conventional apparatus. The X-ray apparatus has been installed in a system with a specially designed mechanical scanner for a pump shaft and as a result, the fatigue damage can be automatically measured on the pump shaft surface. The system has been applied to >150 actual pump shafts in a factory during inservice inspections. SCR415 steel is discussed. Graphs, 11 ref. Effect of tempering temperature on estimation curve of Km~ or A K ~ for Xray fractography.
Akita, K., Kodama, S., Misawa, H., Tobe, S. and Yoshimura, H. J. Soc. Mater. Sci. Jpn (June 1993) 42 (477), 613-619 (in Japanese) Fatigue tests were carried out under various load controlled conditions using a Ni-Cr-Mo steel, JIS SNCM439 equivalent to AISI 4340, tempered at three different temperatures. The residual stress was measured by an X-ray diffraction method on the fatigue fractured surface. The relation between
the residual stress and the stress factor was discussed. The main results obtained were as follows. (1) The residual stress on the fatigue fractured surface was separated into the tensile and compressive components and the relations between these components and the stress intensity factor were established quantitatively for the three tempering temperatures. (2) The fatigue crack propagation rate could be estimated by using the results (1). (3) The tensile residual stress component was higher for lower tempering temperature. (4) The maximum value of the tensile residual stress component was nearly equal to the yield stress of the material. (5) The absolute value of the compressive residual stress component was higher for lower tempering temperature. (6) Under the positive load ratio, the residual stress on the fatigue fractured surface was not affected by the contact of the fractured surfaces due to the crack closure. (7) The effect of roughness on the shape of the estimated curve could be ignored if the roughness was nearly constant throughout the whole range of stress intensity factor. Numeric data, graphs, photomicrographs, 6 ref.
Fatigue, 1994, Vol 16, October
519
Nagashima, T. and Ikubo, T. Denki Seiko (Electric Furnace Steel) (May 1993) 64 (2), 99-106 (in Chinese) The exhaust components of automobile engines are being made of ferritic stainless steel or ferritic stainless cast steel in place of ductile cast iron for not only improving heat resistance but also weight saving. The thermal fatigue properties are most important for these. The thermal fatigue test with external restraint and the thermal shock test with internal restraint for various ferfitic stainless cast steels (Fe-0.05C-18.86Cr-1.96W-0.98Nb-0.56-Si 0.51Mn-0.11Ni, Fe-0.15C- 17.72Cr-0,55Mn-0.34Si-0.19Nb0.09Ni, Fe-0.03C-17.91Cr-0.65Mn-0.57Si-0.19Nb-0.06Ni) and ductile cast iron were performed. The plastic deformation caused by thermal stress through ferritic stainless cast steels can be evaluated by measuring the dimensional change of specimen after the thermal shock test. It decreases by increasing high temperature strength and increases by crystalline transformation. A ferritie stainless cast steel composed of 0.05C-19Cr-INb-2W results in the longest thermal fatigue life and the least plastic deformation of all tested steels. Graphs, 23 ref. Fatigue performance of nine bolt materials in air and in seawater with cathodic protection. Slind, T., Eggen, T.G., Bardal, E. and Haagensen, P.K. Acorn (1993) (1), 1-6 The hydrogen sensitivity of various bolt materials (Marinel, Monel K-500, Inconel 625, Incoloy 925, SAF 2507, Cronifer 2419MoN, 254SMO, A320 L7) for subsea use has been determined. The fatigue crack growth rates of eight materials were found in air and in artificial seawater/3%NaCI solution with cathodic protection (CP0). S - N tests of threaded bolts, using a high mean stress were carried out in seawater with CP for two materials. The materials are grouped in three classes on their H susceptibility based on the crack growth results. Design curves determined from the S - N test results are compared with various standard design curves. Graphs, numeric data, 12 ref. Fatigue damage evaluation under random str~s sequences in terms of effective stress. Takahashi, T., lida, T. and lkai, Y. J. Soc. Mater. Sci. Jpn (June 1993) 42 (477) 670--675 (in Japanese) A cumulative fatigue damage rule has been proposed for random stress sequences from a viewpoint of internal stress and effective stress. Applied stress was divided into two parts through practical measurements and simulation: internal stress as a backward stress for the deformation and effective stress as a drag due to plastic flow. For the fatigue damage evaluation, a cumulative damage rule like Miner's was operated with the help of an ES-N diagram and effective stress measurements during the fatigue process. The former was obtained by fatigue tests where effective stresses were kept constant during the tests, which resulted in an experimental expression of formulae. It was found that the internal stress at a given cycle can be expressed in a regressive form in terms of the stress level and the internal stress of the latest cycle. That is, orion) F(cr.(,-1), ~ri(n-l), ~r.(n)) where subscripts ( n - l ) and (n) are the latest number of cycles and the current number of cycles, respectively. The damage rule and experimental expression of effective stress were examined on two materials with or without strain-ageing bardenability, $35C steel and At-I. 1 mass% Mn alloy. Agreement between the experimental results and the simulations was found to be fairly good. Numeric data, graphs, 12 ref. =
A technique for detecting inconsistent knowledge in a selection system of retrofitting method of fatigue damage in steel bridges.
The characteristics of inconsistent phenomena are pursued and fragmental knowledge is replaced with comprehensive knowledge. A method of detecting inconsistent knowledge is discussed. Inconsistent phenomena are distinguished as global (dynamic) and local (static) inconsistency. Global inconsistency is recognized when the inference is processed dynamically. On the other hand, the local inconsistency can be detected statically before inferring within the arranged knowledge. To solve global inconsistencies, the inference engine must have a hypothetical inference mechanism which detects and solves the inconsistencies. To solve local inconsistencies, fragmental knowledge is replaced with a systematic network model, where the inconsistencies are detected. The model is modified so that consistency is produced. Systematization is also discussed. 5 ref. A system with knowledge-reusing function for selecting steel bridge fatigue
dam~e retronmns.
Mikami, 1., Kitagishi, H., Kanbe, K. and Tanaka, S. Technology Reports of Kansai University (Mar. 1993) (35), 197-212 A technique for obtaining and adjusting the professional knowledge for 90 cases of fatigue cracking was developed. In the previous paper, a system for selecting the reasonable retrofitting methods was constructed. Since this inference engine has learning ability, the system can be improved. While the inference engine was able to deal with a complicated network and to give flexible inference results, it produced neither secondary results nor valueadded information. In the present paper, a model-based reasoning on qualitative reasoning is of concern. The previous inference engine has been structured so as to give it a model-based reasoning ability, and a structured knowledge model is generated by causality. Using the engine and the structured knowledge model, inference results including secondary knowledge and value-added knowledge can be obtained. 6 ref. A diagnostic expert system with analogical Inference and negative learning ability.
Mikami, 1., Yoneda, S., Tanaka, S. and Kurachi, A. Technology Reports of Kansai University (Mar. 1993) (35), 213-231 Expert systems may be used effectively in the maintenance of existing civil engineering structures, because a wide range of expert engineering knowledge is indispensable in such maintenance. In the preceding paper, the construction of a system for selecting the retrofitting methods of fatigue cracking in steel bridges was explained and discussed. The knowledge used was acquired from 90 cases of fatigue cracking in existing steel bridges, and was represented as causal relations in a knowledge-base. Using a neural network model with C language, an inference engine endowed with a learning ability was developed. Ideas for the further development of this same system with regard to knowledge, inference, and learning ability are advanced. A greater wealth of knowledge is acquired by incorporating information concerning a further 75 cases. With this new knowledge base, the system can perform the inference by analogy, an inference engine being developed, equipped with a greater learning ability, i.e. consisting of both positive and negative learning. The present system is capable of giving appropriate and sufficient inference results. Graphs, 10 ref. Data base of damaged steel bridges.
Mikami, 1., Sakano, M. and Shibata, H. Technology Reports of Kansai University (Mar. 1993) (35), 185-196 About 500 cases of steel bridges damaged owing to fatigue, corrosion, etc. are summarized in a database, in order to discuss various features and tendencies concerning the service period previous to damage, damage type of each type of structure, causes of damage, and countermeasures against damage. Occurrence of fatigue cracking in railway bridges has been reported continually since the 1950s in Japan, the number of these rapidly increasing in the 1970s. On the other hand, fatigue cracking of highway steel bridges was detected for the first time in Japan in the 1970s, and the number of such cases increased rapidly after 1980. As there is at present a dearth of information concerning damage due to corrosion, the present tendency of this kind of damage is not yet clear; it is, however, expected to increase in the future. 6 ref. Development of bridge monitoring system.
Ujiwara, T., Kajimoto, K. Yajima, M., Mural, R., Murakoshi, J. and Yamamoto, S. Mitsubishi Juko Giho (1993) 30 (3), 230-234 (in Japanese) In order to carry out unmanned continuous and objective surveillance of fatigue cracks in steel bridges, two methods to detect cracks - ultrasonic flaw detection and self-breaking crack gauge - have been examined. Sensors and device using these methods for long-term surveillance of cracks in existing bridges have also been developed. The newly developed device has been put to use in a fatigue test using a bridge component model to prove that the new device works sufficiently well and has high performance. Graphs, 3 ref. X-ray diffraction apparatus for life assessment of boiler feed water pump shaft.
Mikami, L, Yoneda, S., Maeda, H.H. and Tanaka, S. Technology Reports of Kansai University (Mar. 1993) (35), 233-245
Hayashi, M., Ueyama, Y., Hashimoto, Y., Ogiso, K. and Sasaki, K. J. Soc. Mater. Sci. Jpn (June 1993) 42(477), 634--640 (in Japanese)
An expert system for the selection of retrofitting methods for fatigue damage in steel bridges has been constructed. Several techniques may be applied to the inference engine in order to improve its function, but fragmental knowledge obtained from mutual relations between two terms includes many inconsistencies. As long as the inconsistent knowledge is processed only by the interpretation based on priority, although undesirable results can in this way be removed, the inconsistent knowledge is processed only superficially.
Boiler feed water pump shafts are subjected to severe thrust loads and cyclic bending moments. Half-value width and residual stress measurements by Xray diffraction methods, which are sensitive to fatigue damage, are employed for the fatigue life assessments of pump shafts. To establish a damage detection system, a portable, lightweight X-ray diffraction apparatus with a rotating receiving slit and X-ray detector and a small diameter X-ray tube has been developed. Consequently, the residual stress can be measured within
518 Fatigue, 1994, Vol 16, October
20 min, which is about one-half the time required using a conventional apparatus. The X-ray apparatus has been installed in a system with a specially designed mechanical scanner for a pump shaft and as a result, the fatigue damage can be automatically measured on the pump shaft surface. The system has been applied to >150 actual pump shafts in a factory during inservice inspections. SCR415 steel is discussed. Graphs, 11 ref. Effect of tempering temperature on estimation curve of Km~ or A K ~ for Xray fractography.
Akita, K., Kodama, S., Misawa, H., Tobe, S. and Yoshimura, H. J. Soc. Mater. Sci. Jpn (June 1993) 42 (477), 613-619 (in Japanese) Fatigue tests were carried out under various load controlled conditions using a Ni-Cr-Mo steel, JIS SNCM439 equivalent to AISI 4340, tempered at three different temperatures. The residual stress was measured by an X-ray diffraction method on the fatigue fractured surface. The relation between
the residual stress and the stress factor was discussed. The main results obtained were as follows. (1) The residual stress on the fatigue fractured surface was separated into the tensile and compressive components and the relations between these components and the stress intensity factor were established quantitatively for the three tempering temperatures. (2) The fatigue crack propagation rate could be estimated by using the results (1). (3) The tensile residual stress component was higher for lower tempering temperature. (4) The maximum value of the tensile residual stress component was nearly equal to the yield stress of the material. (5) The absolute value of the compressive residual stress component was higher for lower tempering temperature. (6) Under the positive load ratio, the residual stress on the fatigue fractured surface was not affected by the contact of the fractured surfaces due to the crack closure. (7) The effect of roughness on the shape of the estimated curve could be ignored if the roughness was nearly constant throughout the whole range of stress intensity factor. Numeric data, graphs, photomicrographs, 6 ref.
Fatigue, 1994, Vol 16, October
519