BACKGROUND: A rolling bearing bush alloy of a feed water pump that is part of a waste heat boiler of an oil refinery has failed. OBJECTIVE: We try to analyze the reasons that caused the working surface of the bearing bush of the water pump to fall off and then give some suggestions to this failure. METHODS: The composition, microstructure, pit, and crack morphology of the bearing bush alloy were analyzed by the X-ray fluorescent analysis, the energy spectrum analysis, the optical microscope and the scanning electron microscope, respectively. RESULTS: The content of Pb in the bearing bush alloy was high, and the Cu content was low. The primary crystal Cu6Sn5 was low, and the crystal of SnSb with low density moved upward and segregated. The above phenomenon reduced the fatigue resistance of the babbitt alloy. The bearing bush was subjected to alternating loads in service, and several small cracks were generated on the bearing bush alloy working surface. The cracks continued to expand and connected with each other. Fatigue pitting occurred on the bearing bush working surface, a large number of pits were formed, and several large alloy blocks fell off. CONCLUSIONS: The Pb content in the failed bearing bush alloy was too high and did not meet the requirements of the Sn-based babbitt alloys in the national standard. At the same time, the primary crystal Cu6Sn5 formed by Cu and Sn was low due to the low Cu content, and the crystal SnSb with a small density moved upward and segregated. The composition of the babbitt alloy, especially the Cu content, should be strictly controlled to ensure the safe and reliable operation of the bearing.
{"title":"Failure analysis of a bearing bush of a feed water pump","authors":"Han Zhang, Yihang Hou, Mengli Li, Ming Zhang","doi":"10.3233/sfc-210262","DOIUrl":"https://doi.org/10.3233/sfc-210262","url":null,"abstract":"BACKGROUND: A rolling bearing bush alloy of a feed water pump that is part of a waste heat boiler of an oil refinery has failed. OBJECTIVE: We try to analyze the reasons that caused the working surface of the bearing bush of the water pump to fall off and then give some suggestions to this failure. METHODS: The composition, microstructure, pit, and crack morphology of the bearing bush alloy were analyzed by the X-ray fluorescent analysis, the energy spectrum analysis, the optical microscope and the scanning electron microscope, respectively. RESULTS: The content of Pb in the bearing bush alloy was high, and the Cu content was low. The primary crystal Cu6Sn5 was low, and the crystal of SnSb with low density moved upward and segregated. The above phenomenon reduced the fatigue resistance of the babbitt alloy. The bearing bush was subjected to alternating loads in service, and several small cracks were generated on the bearing bush alloy working surface. The cracks continued to expand and connected with each other. Fatigue pitting occurred on the bearing bush working surface, a large number of pits were formed, and several large alloy blocks fell off. CONCLUSIONS: The Pb content in the failed bearing bush alloy was too high and did not meet the requirements of the Sn-based babbitt alloys in the national standard. At the same time, the primary crystal Cu6Sn5 formed by Cu and Sn was low due to the low Cu content, and the crystal SnSb with a small density moved upward and segregated. The composition of the babbitt alloy, especially the Cu content, should be strictly controlled to ensure the safe and reliable operation of the bearing.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-210262","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70191300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
OBJECTIVE: The aim of this work is to present the methodology for grading the Functionally Graded Material (FGM) using Level Set (LS) sign distance function around the multiple holes and parametrically analyse the maximum stresses for a pair of inclined unequal circular holes surrounded by the FGM layer in an infinite plate subjected to uniaxial tensile load using the Extended Finite Element Method (XFEM). METHODS: The LS method has the ability to represent the multiple geometrical boundaries with a single sign distance function which can be effectively used for grading the FGM around the multiple discontinuities such as holes, inclusions, cracks, etc. When dealing with FGM material grading around multiple discontinuities, it is important to have smooth grading to minimise the stress concentration. The grading of the material with multiple functions may result in sharp changes in the material properties at the interference region which may lead to high stresses. The LS function-based FGM material grading eliminates such sharp changes as it uses a single function. RESULTS: The parametric analysis shows that applying the LS function-based power law FGM layer of Titanium – Titanium Mono Boride (Ti-TiB) around the pair of inclined unequal circular holes significantly reduces the values of maximum tensile as well as compressive hoop stresses when compared with the homogeneous material case.
{"title":"Level Set function-based Functionally Graded Material for the reduction of maximum stresses around a pair of inclined unequal circular holes","authors":"Vikas Goyat, S. Verma, R. Garg","doi":"10.3233/sfc-210273","DOIUrl":"https://doi.org/10.3233/sfc-210273","url":null,"abstract":"OBJECTIVE: The aim of this work is to present the methodology for grading the Functionally Graded Material (FGM) using Level Set (LS) sign distance function around the multiple holes and parametrically analyse the maximum stresses for a pair of inclined unequal circular holes surrounded by the FGM layer in an infinite plate subjected to uniaxial tensile load using the Extended Finite Element Method (XFEM). METHODS: The LS method has the ability to represent the multiple geometrical boundaries with a single sign distance function which can be effectively used for grading the FGM around the multiple discontinuities such as holes, inclusions, cracks, etc. When dealing with FGM material grading around multiple discontinuities, it is important to have smooth grading to minimise the stress concentration. The grading of the material with multiple functions may result in sharp changes in the material properties at the interference region which may lead to high stresses. The LS function-based FGM material grading eliminates such sharp changes as it uses a single function. RESULTS: The parametric analysis shows that applying the LS function-based power law FGM layer of Titanium – Titanium Mono Boride (Ti-TiB) around the pair of inclined unequal circular holes significantly reduces the values of maximum tensile as well as compressive hoop stresses when compared with the homogeneous material case.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":"216 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70191419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.
{"title":"Crack divergence phenomena in tempered glass","authors":"S. Aratani","doi":"10.3233/sfc-204002","DOIUrl":"https://doi.org/10.3233/sfc-204002","url":null,"abstract":"High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48041878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Scaling effects on the creep crack growth behaviour are investigated by analyzing the results of compact tension (CT) tests on different-sized notched steel specimens appearing in the literature. Creep crack growth rate data are correlated to the elastic stress-intensity factor in terms of a Paris-type law, da∕dt = C0Kq, where C0 turns out to be a crack-size dependent coefficient of proportionality. Considering specimens with the same loading configuration (CT) and the same thickness, the observed crack-size effect on the creep crack growth rate is discussed on the basis of self-similarity considerations, and geometrically interpreted in terms of fractal tortuosity of the crack profile. A size-independent formulation of the creep crack growth law correlating renormalized quantities is finally deduced and confirmed by the experimental results.
{"title":"Fractal scaling and crack-size effects on creep crack growth","authors":"A. Carpinteri, G. Niccolini, A. Rubino","doi":"10.3233/sfc-200260","DOIUrl":"https://doi.org/10.3233/sfc-200260","url":null,"abstract":"Scaling effects on the creep crack growth behaviour are investigated by analyzing the results of compact tension (CT) tests on different-sized notched steel specimens appearing in the literature. Creep crack growth rate data are correlated to the elastic stress-intensity factor in terms of a Paris-type law, da∕dt = C0Kq, where C0 turns out to be a crack-size dependent coefficient of proportionality. Considering specimens with the same loading configuration (CT) and the same thickness, the observed crack-size effect on the creep crack growth rate is discussed on the basis of self-similarity considerations, and geometrically interpreted in terms of fractal tortuosity of the crack profile. A size-independent formulation of the creep crack growth law correlating renormalized quantities is finally deduced and confirmed by the experimental results.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-200260","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46412373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BACKGROUND: Under plane strain conditions, a crack model was developed on a plane interface between two different materials, which assumes the existence near its tip of the faces contact area and a narrow lateral pre-fracture zone in a less crack-resistant material of the composite compound. The pre-fracture zone is modeled by the line of normal displacement rupture, on which the normal stress is equal to the tensile strength of the material. Assuming that the dimensions of the pre-fracture zone and the contact zone have the same order of magnitude and are significantly smaller than the crack length, the problem is reduced to the vector Wiener–Hopf equation. METHODS: An approximate method for solving the vector Wiener–Hopf equation was developed, which was used to obtain the equations for determining the sizes of the pre-fracture zone and the contact faces area. The pre-fracture zone orientation was determined from the condition of the potential energy maximum accumulated in the zone. Numerical calculations of the indicated parameters and analysis of their dependences on the configuration and module of external load are executed. RESULTS: A significant mutual influence of the pre-fracture zone and crack faces contact on their sizes and orientation of the zone was revealed.
{"title":"Mutual influence of the faces contact area and the pre-fracture zone near the tip of the interfacial crack","authors":"M. Dudyk","doi":"10.3233/sfc-204003","DOIUrl":"https://doi.org/10.3233/sfc-204003","url":null,"abstract":"BACKGROUND: Under plane strain conditions, a crack model was developed on a plane interface between two different materials, which assumes the existence near its tip of the faces contact area and a narrow lateral pre-fracture zone in a less crack-resistant material of the composite compound. The pre-fracture zone is modeled by the line of normal displacement rupture, on which the normal stress is equal to the tensile strength of the material. Assuming that the dimensions of the pre-fracture zone and the contact zone have the same order of magnitude and are significantly smaller than the crack length, the problem is reduced to the vector Wiener–Hopf equation. METHODS: An approximate method for solving the vector Wiener–Hopf equation was developed, which was used to obtain the equations for determining the sizes of the pre-fracture zone and the contact faces area. The pre-fracture zone orientation was determined from the condition of the potential energy maximum accumulated in the zone. Numerical calculations of the indicated parameters and analysis of their dependences on the configuration and module of external load are executed. RESULTS: A significant mutual influence of the pre-fracture zone and crack faces contact on their sizes and orientation of the zone was revealed.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-204003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47667422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Scaling effects governing the creep behaviour of unnotched and uncracked metallic specimens are investigated by applying similarity considerations and fractal modelling to experimental results provided in the literature. The focus is on stress rupture tests conducted at elevated temperatures on Cr-Mo-V steel cylindrical bars of different sizes. The observed specimen-size effects on the 𝜎 versus tR creep resistance diagrams are interpreted in terms of incomplete self-similarity and fractal weakening (lacunarity) of the specimen reacting cross-section. That leads to a scale-invariant (fractal) formulation of the creep rupture law in terms of renormalized stress.
{"title":"Fractal scaling and specimen-size effects on creep resistance","authors":"A. Carpinteri, G. Niccolini, A. Rubino","doi":"10.3233/sfc-200259","DOIUrl":"https://doi.org/10.3233/sfc-200259","url":null,"abstract":"Scaling effects governing the creep behaviour of unnotched and uncracked metallic specimens are investigated by applying similarity considerations and fractal modelling to experimental results provided in the literature. The focus is on stress rupture tests conducted at elevated temperatures on Cr-Mo-V steel cylindrical bars of different sizes. The observed specimen-size effects on the 𝜎 versus tR creep resistance diagrams are interpreted in terms of incomplete self-similarity and fractal weakening (lacunarity) of the specimen reacting cross-section. That leads to a scale-invariant (fractal) formulation of the creep rupture law in terms of renormalized stress.","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":"1 1","pages":"1-10"},"PeriodicalIF":0.7,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-200259","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49351984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Preface","authors":"Teruo Kishi, A. Carpinteri, Shouwen Yu","doi":"10.3233/sfc-190247","DOIUrl":"https://doi.org/10.3233/sfc-190247","url":null,"abstract":"","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-190247","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41659556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Ethics in science","authors":"K. Schwalbe","doi":"10.3233/sfc-190238","DOIUrl":"https://doi.org/10.3233/sfc-190238","url":null,"abstract":"","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-190238","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41497185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chen Zhanbiao, P. Huang, Xinyan Guo, Xiao-Hong Zheng, Yang Yi
{"title":"Fatigue equation of structural materials and members under hot-wet environment and cyclic bending loads","authors":"Chen Zhanbiao, P. Huang, Xinyan Guo, Xiao-Hong Zheng, Yang Yi","doi":"10.3233/sfc-190241","DOIUrl":"https://doi.org/10.3233/sfc-190241","url":null,"abstract":"","PeriodicalId":41486,"journal":{"name":"Strength Fracture and Complexity","volume":"12 1","pages":"119-125"},"PeriodicalIF":0.7,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/sfc-190241","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70185869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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