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Shuji Aihara - One of the best experts on this subject based on the ideXlab platform.
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an experimental study on k ca value to Arrest a running brittle Crack in structural model specimens with steel plate of 100 mm thickness for container ships
Journal of Marine Science and Technology, 2020Co-Authors: Tetsuya Tagawa, Hisakazu Tajika, Tsunehisa Handa, Teppei Okawa, Yusuke Shimada, Takehiro Inoue, Shota Nanno, Kazuyuki Matsumoto, Tomoya Kawabata, Shuji AiharaAbstract:With demand for ultra-large container ships, high-strength steel plates with extremely large thicknesses are applied to the structural elements around hatch side structures. The two longitudinal plates of the upper deck and hatch side coaming are the main structural elements that support bending stress during hogging of the ship structure, and brittle Crack Arrest toughness as well as Crack initiation toughness are required in these steel plates to avoid the catastrophic ship damage. Although the International Association of Classification Societies prescribes a unified requirement for brittle Crack Arrest steel plates providing the value of brittle Crack Arrest toughness Kca at − 10 °C for plate thicknesses of 80 mm or less, ultra-large container ships using steel plates with thicknesses exceeding 80 mm are continuously required and built. In the present work, brittle Crack Arrest tests with large scale structural model specimens which simulate the structural element of the hatch side structure were performed to investigate the Kca value required to Arrest a running brittle Crack for steel plates with the thickness of 100 mm. The present investigation suggested that the test plate simulating upper deck could Arrest a running brittle Crack at the plate Kca of 6000 N/mm3/2, nevertheless the Kca value of 8000 N/mm3/2 was needed in the test plate simulating hatch side coaming. The different Kca values required to Arrest a running Crack between the test plates simulating the upper deck and the hatch side coaming are also discussed from the viewpoint of the Arrested Crack size and shape.
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Effects of residual stress by EB welds on assessment of Crack Arrest temperature (CAT)
Welding in the World, 2020Co-Authors: Chiyomi Iwatake, Kazuyuki Matsumoto, Shuji Aihara, Masahito Kaneko, Tsutomu Fukui, Tomoya KawabataAbstract:The concept of brittle Crack Arrest has recently become an internationally focused issue for container ships. The International Association of Classification Society (IACS) also prescribed the unified requirement (UR) for brittle Crack Arrest design, and brittle Crack Arrest design has been internationally authorized. As one of the methods to evaluate brittle Crack Arrestability, the Crack Arrest temperature (CAT) concept, by isothermal Crack Arrest test, has been proposed since the 1990s. The concept has been applied mainly for tank design. However, no standard has been specified to describe the detailed evaluation procedure. This means that only limited organizations can evaluate CAT and it is considered to be a problem when Arrest evaluation is mandated as an international standard. In the background of such circumstances, Japanese research groups including the Japan Welding Engineering Society (JWES) and Nippon Kaiji Kyokai (ClassNK) started the standardization for CAT test in 2016. In the research programme, various aspects of control factors have been investigated based on the test results from many experiments and numerical calculations. The CAT test shall include the embrittled zone to initiate a brittle Crack. Either electron beam (EB) line remelting or a local temperature gradient (LTG) can be applied to the embrittled zone. Even if we focus on EB welding only, welding defects in the embrittled zone can be an influencing factor. In this report, we investigate the effects of residual stress by EB welding on the Crack driving force, which is quantified as the K value using a 3D finite element method (FEM). As a result, we confirmed the existence of the residual stress which cannot be ignored that is formed on the surface of the EB-welded portion; however, the influence of that on the K value is considered to be small if the CAT test conditions can sufficiently secure the Arrest Crack length. This result shows that the driving force at the Arrested point in the CAT test can be simply evaluated by the LEFM formula without consideration of the residual stress of the EB weld for embrittlement.
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a simplified method for evaluation of brittle Crack Arrest toughness of steels in scaled down bending tests
Engineering Fracture Mechanics, 2019Co-Authors: Yuki Nishizono, Shuji Aihara, Tomoya Kawabata, Teppei OkawaAbstract:Abstract The wide-plate Crack Arrest test under tensile load for characterizing the brittle Crack Arrest toughness of high strength shipbuilding steel requires high economical cost and long lead-time, so there is still a substantial industry need for the simplified evaluation using the scaled-down specimen. The alternative method using a single edge-notched bending specimen, which assumes the complete load redistribution during the Crack propagation, was recently proposed. However, it was confirmed that the results obtained using this method exhibited a low correlation with the Arrest toughness obtained using the wide-plate tests. A new scaled-down version of the Crack Arrest test under bending load and a series of simplified evaluation based on the dynamic elasto-plastic FEA were introduced to characterize the Crack Arrest performance of the two types of steel plates in this investigation. The specimen is a single edge-notched tapered plate subjected to a three-point bending load in an isothermal environment. The geometry was selected so that the dynamic Crack driving force calculated using FEA decreases monotonically with the Crack propagation. For adopting a simplistic analytical approach considering the dynamic effect, the dynamic FEA simulation assumed the constant Crack velocity and flat Crack front and output the opening stress distributed ahead of the growing Crack. The experimentally obtained values of the Arrested Crack length and the analytically obtained transition curves of the dynamic SIF were employed to characterize the Crack Arrest performance of the two steels. The results obtained using the simplified method developed in this investigation exhibited a high correlation with the Arrest toughness obtained using the wide-plate Crack Arrest test.
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Development of simplified evaluation method of brittle Crack Arrest toughness on small-scale bending test in steels
Procedia Structural Integrity, 2018Co-Authors: Yuki Nishizono, Tomoya Kawabata, Shuji AiharaAbstract:Abstract The priority items in the safety evaluation of steel structural components generally include an ability to Arrest Crack propagation, which is necessary to prevent a catastrophic failure even if a brittle fracture occurs. The ‘double integrity’ concept of brittle Crack initiation control and Arrest has been considered to be an effective and rational methodology for several decades. The wide plate tensile test such as ESSO test is one of the major methods for evaluating brittle Crack Arrest toughness of steel plates. Although ESSO test makes it possible to accurately evaluate Arrest toughness which indicates the Arrhenius type temperature dependence, it is not suitable for quality assurance test at mass production of steel plates due to its high economical cost and long lead-time. Thus, a number of studies has attempted to establish simplified evaluation method of brittle Crack Arrest toughness for many years. Generally, bending test is certainly one of the most hopeful methods since it does not require a relatively high test load. However, the phenomenon that brittle Crack propagates at extremely high speed in bending condition becomes highly complicated. When brittle Crack propagates at almost the same speed as stress wave in bending condition, stress distribution is the middle of the initial state and fully reallocated state by the static equilibrium. It is not easy to make out the detail only by theoretical consideration. In this study, by performing the dynamic elasto-plastic FEA in various test designs based on SEN(B) test, the authors calculated the stress distribution at the Crack tip and developed a new test design suitable for evaluating Arrest toughness. Moreover, the authors investigated the correlation between the result of ESSO tests and that of the developed tests and presented its applicability.
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Effect of dispersed retained γ-Fe on brittle Crack Arrest toughness in 9% Ni steel in cryogenic temperatures
Materials Science and Engineering: A, 2018Co-Authors: Daiki Nakanishi, Tomoya Kawabata, Shuji AiharaAbstract:Abstract In structural steels, high Crack Arrest toughness is required to stop brittle Cracks from propagating to prevent eventual fracture of the structure. It is known that Ni can reduce the risk of cleavage fracture of α-Fe, as it exists in a solid solution as a substitutional alloying element. Additionally, Ni can enhance the stability of γ-Fe between the martensite-laths, leading to improved toughness. Although there are several interpretations of the effect of retained γ on the fracture toughness, especially regarding dynamic Crack propagation, there is little knowledge on the role of retained γ. In this study, the relationship between the amount of transformation and Crack Arrest toughness is evaluated by an experimental approach. As a result, it is revealed that the γ-α transformation at the propagating Crack tip enhances the Crack Arrest properties. Furthermore, compared to static loading conditions, γ-Fe seems reluctant to transform to martensite as a result of an adiabatic temperature increase due to plastic work. Stress relaxation effects due to deformation-induced transformation of γ-Fe are the proposed mechanism of enhancement of the Crack Arrest properties.
Tomoya Kawabata - One of the best experts on this subject based on the ideXlab platform.
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an experimental study on k ca value to Arrest a running brittle Crack in structural model specimens with steel plate of 100 mm thickness for container ships
Journal of Marine Science and Technology, 2020Co-Authors: Tetsuya Tagawa, Hisakazu Tajika, Tsunehisa Handa, Teppei Okawa, Yusuke Shimada, Takehiro Inoue, Shota Nanno, Kazuyuki Matsumoto, Tomoya Kawabata, Shuji AiharaAbstract:With demand for ultra-large container ships, high-strength steel plates with extremely large thicknesses are applied to the structural elements around hatch side structures. The two longitudinal plates of the upper deck and hatch side coaming are the main structural elements that support bending stress during hogging of the ship structure, and brittle Crack Arrest toughness as well as Crack initiation toughness are required in these steel plates to avoid the catastrophic ship damage. Although the International Association of Classification Societies prescribes a unified requirement for brittle Crack Arrest steel plates providing the value of brittle Crack Arrest toughness Kca at − 10 °C for plate thicknesses of 80 mm or less, ultra-large container ships using steel plates with thicknesses exceeding 80 mm are continuously required and built. In the present work, brittle Crack Arrest tests with large scale structural model specimens which simulate the structural element of the hatch side structure were performed to investigate the Kca value required to Arrest a running brittle Crack for steel plates with the thickness of 100 mm. The present investigation suggested that the test plate simulating upper deck could Arrest a running brittle Crack at the plate Kca of 6000 N/mm3/2, nevertheless the Kca value of 8000 N/mm3/2 was needed in the test plate simulating hatch side coaming. The different Kca values required to Arrest a running Crack between the test plates simulating the upper deck and the hatch side coaming are also discussed from the viewpoint of the Arrested Crack size and shape.
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Effects of residual stress by EB welds on assessment of Crack Arrest temperature (CAT)
Welding in the World, 2020Co-Authors: Chiyomi Iwatake, Kazuyuki Matsumoto, Shuji Aihara, Masahito Kaneko, Tsutomu Fukui, Tomoya KawabataAbstract:The concept of brittle Crack Arrest has recently become an internationally focused issue for container ships. The International Association of Classification Society (IACS) also prescribed the unified requirement (UR) for brittle Crack Arrest design, and brittle Crack Arrest design has been internationally authorized. As one of the methods to evaluate brittle Crack Arrestability, the Crack Arrest temperature (CAT) concept, by isothermal Crack Arrest test, has been proposed since the 1990s. The concept has been applied mainly for tank design. However, no standard has been specified to describe the detailed evaluation procedure. This means that only limited organizations can evaluate CAT and it is considered to be a problem when Arrest evaluation is mandated as an international standard. In the background of such circumstances, Japanese research groups including the Japan Welding Engineering Society (JWES) and Nippon Kaiji Kyokai (ClassNK) started the standardization for CAT test in 2016. In the research programme, various aspects of control factors have been investigated based on the test results from many experiments and numerical calculations. The CAT test shall include the embrittled zone to initiate a brittle Crack. Either electron beam (EB) line remelting or a local temperature gradient (LTG) can be applied to the embrittled zone. Even if we focus on EB welding only, welding defects in the embrittled zone can be an influencing factor. In this report, we investigate the effects of residual stress by EB welding on the Crack driving force, which is quantified as the K value using a 3D finite element method (FEM). As a result, we confirmed the existence of the residual stress which cannot be ignored that is formed on the surface of the EB-welded portion; however, the influence of that on the K value is considered to be small if the CAT test conditions can sufficiently secure the Arrest Crack length. This result shows that the driving force at the Arrested point in the CAT test can be simply evaluated by the LEFM formula without consideration of the residual stress of the EB weld for embrittlement.
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reproducibility of pop ins in fracture test of heterogeneous welds and numerical assessment of Crack Arrest
Journal of Testing and Evaluation, 2020Co-Authors: Sohei Kanna, Yoichi Yamashita, Tomoya KawabataAbstract:For the occurrence of a “pop-in,” which represents the initiation, propagation, and Arrest of a brittle Crack in a three-point bending test, the evaluated fracture toughness may be very small. To experimentally verify whether the pop-in occurring at the specimen level is even included in the actual structure, the purpose of this study was to first induce pop-ins in a three-point bending test. It was possible to reproduce a pop-in at a local brittle zone (LBZ) by preparing heterogeneous weld specimens and considering the temperature dependence of the toughness of each welding material. Furthermore, a Crack propagation analysis by the nodal release method was conducted. The Crack opening stress including dynamic effects was compared before and after the pop-in. Because of the initiation of brittle Cracks in the LBZ, the high-stress area shifted from the center with low toughness to the edge with high toughness. Decrease in the Crack opening stress was determined as a factor contributing to the Crack Arrest.
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Brittle Crack Arrest behavior and its interpretation in an isothermal Crack Arrest test
Engineering Fracture Mechanics, 2020Co-Authors: Tetsuya Tagawa, Hisakazu Tajika, Tsunehisa Handa, Shota Nanno, Kazuyuki Matsumoto, Tomoya KawabataAbstract:Abstract Brittle Crack Arrest behavior in steel plates and its evaluation test technique were investigated exhaustively from the1950s to the 1980s. Nevertheless, similar discussions have been revived recently by issues related to brittle Crack Arrest design applicable to mega-container ships. For example, the issue of whether the brittle Crack Arrest properties of steel plates evaluated under isothermal conditions and gradient temperature conditions are equivalent or not, which was also an issue in earlier studies, has been discussed again since 2010. This discussion is the results of ongoing debate in the International Association of Classification Societies (IACS) concerning provisions for heavy-gauge brittle Crack Arrest (BCA) steel plates for mega-container ships. In the present work, the Crack Arrest temperature, abbreviated as CAT, was evaluated by an isothermal Crack Arrest test in a specimen with a Crack runway embrittled by electron beam weld (EBW) re-melting. The dependence of CAT and the Arrested Crack length on the Crack runway length were discussed. Crack Arrest toughness Kca was also evaluated based on test that resulted in Crack Arrest in the isothermal condition, and the results were compared with those of the gradient temperature Crack Arrest test. An unexpected variation was observed in the Kca values in the isothermal test, but it was suggested that this represents the R-curve behavior of a running brittle Crack. The R-curve concept can qualitatively explain the Crack Arrest behaviors with different Crack runway lengths. The analogical difference in Crack Arrest behaviors between the isothermal condition and gradient temperature condition were also discussed.
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a simplified method for evaluation of brittle Crack Arrest toughness of steels in scaled down bending tests
Engineering Fracture Mechanics, 2019Co-Authors: Yuki Nishizono, Shuji Aihara, Tomoya Kawabata, Teppei OkawaAbstract:Abstract The wide-plate Crack Arrest test under tensile load for characterizing the brittle Crack Arrest toughness of high strength shipbuilding steel requires high economical cost and long lead-time, so there is still a substantial industry need for the simplified evaluation using the scaled-down specimen. The alternative method using a single edge-notched bending specimen, which assumes the complete load redistribution during the Crack propagation, was recently proposed. However, it was confirmed that the results obtained using this method exhibited a low correlation with the Arrest toughness obtained using the wide-plate tests. A new scaled-down version of the Crack Arrest test under bending load and a series of simplified evaluation based on the dynamic elasto-plastic FEA were introduced to characterize the Crack Arrest performance of the two types of steel plates in this investigation. The specimen is a single edge-notched tapered plate subjected to a three-point bending load in an isothermal environment. The geometry was selected so that the dynamic Crack driving force calculated using FEA decreases monotonically with the Crack propagation. For adopting a simplistic analytical approach considering the dynamic effect, the dynamic FEA simulation assumed the constant Crack velocity and flat Crack front and output the opening stress distributed ahead of the growing Crack. The experimentally obtained values of the Arrested Crack length and the analytically obtained transition curves of the dynamic SIF were employed to characterize the Crack Arrest performance of the two steels. The results obtained using the simplified method developed in this investigation exhibited a high correlation with the Arrest toughness obtained using the wide-plate Crack Arrest test.
Alix De Pannemaecker - One of the best experts on this subject based on the ideXlab platform.
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identification of the fatigue stress intensity factor threshold for different load ratios r from fretting fatigue to c t fatigue experiments
International Journal of Fatigue, 2016Co-Authors: Alix De Pannemaecker, S Fouvry, Myriam Brochu, Jeanyves BuffiereAbstract:Abstract The aim of the study is to demonstrate the similar behaviour of Crack Arrest condition in mode I for partial slip simple fretting, prestressed fretting loadings, and conventional fatigue Crack growth experiments. The stress intensity factor range Δ K th threshold of long Crack is estimated based on Crack Arrest condition for partial slip fretting and prestressed fretting loadings, coupling experimental and FEM computations. The experimental work is performed on a cylinder (Ti–6Al–4V)/flat (Al-7050-T7451) interface. Fretting and prestressed fretting tests are performed to obtain the Crack length at a Crack Arrest condition. Conventional fatigue Crack growth experiments are performed on C(T) samples using a wide range of R to validate the fretting approach. The results and analysis show that using a reverse FEM analysis of Crack Arrest applied to fretting experiments, the fatigue long Crack threshold region is determined for stress ratios between −2 and 1.
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reverse identification of short long Crack threshold fatigue stress intensity factors from plain fretting Crack Arrest analysis
Engineering Fracture Mechanics, 2015Co-Authors: Alix De Pannemaecker, S Fouvry, Jeanyves BuffiereAbstract:Plain fretting systematically implies Crack Arrest condition when the Crack tip is far enough from the surface stressing. Considering such evolution, an original reverse FEM modelling of Arrested cylinder/plane fretting Cracks is introduced to extract the thresholds SIF of materials (ΔKth). Adjusting contact pressure and cylinder radius, short to long Crack Arrest responses are quantified and the corresponding “fretting” ΔKth identified. Steel and aluminium alloy analyses (35NiCrMo16, AISI-1034, 7075-T6, 2024-T351) confirm the stability of this approach: the dispersion between long Crack ΔKth fretting estimations and conventional fatigue data is less than 10% whereas the short Crack evolutions confirm the El-Haddad formalism.
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introduction of a reverse simulation approach to identify the fatigue stress intensity factor Crack Arrest threshold from fretting Cracking experiments
Tribology International, 2014Co-Authors: Alix De Pannemaecker, S Fouvry, Jeanyves BuffiereAbstract:Abstract The aim of this study was to estimate the Δ K th Crack Arrest stress intensity factor related to the Crack Arrest condition of a material subjected to partial slip fretting loadings, by coupled experimental and numerical simulation. The study focuses on a plane (Al-alloy)/cylinder (TA6V) interface. Fretting tests were performed for each configuration to obtain the Crack length as a function of the number of fretting cycles, in order to establish the Crack length related to Crack Arrest condition. Using a reverse FEM analysis of Crack Arrest fretting experiments, the thresholds Δ K th(fr) are extracted. Two 2196-T8 and 2196-UA aluminium alloys were compared, while the short Crack Arrest versus the Crack length evolutions were formalized using a Kitagawa Takahashi formalism.
C A Rodopoulos - One of the best experts on this subject based on the ideXlab platform.
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optimisation of the fatigue resistance of 2024 t351 aluminium alloys by controlled shot peening methodology results and analysis
International Journal of Fatigue, 2004Co-Authors: C A Rodopoulos, S A Curtis, E R De Los Rios, J SolisromeroAbstract:A methodology dedicated to the optimisation of the fatigue properties of aluminium alloys by controlled shot peening is presented. Selection of the peening conditions is made out of the use of the Design of Experiment and the Effects Neutralisation Model. Both techniques allowed the optimisation both in terms of life and Crack growth rates. Experimental determination and further analysis of the residual stress relaxation patterns revealed that at high stress levels, low cycle fatigue, life improvement is predominantly due to slow Crack growth rates, while in high cycle fatigue the extension of life is attributed to a prolonged period of Crack Arrest.
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analysis of the effects of controlled shot peening on fatigue damage of high strength aluminium alloys
International Journal of Fatigue, 2003Co-Authors: S A Curtis, E R De Los Rios, C A Rodopoulos, A LeversAbstract:The use of two micro-mechanical models for notch sensitivity and fatigue life allowed the development of boundary conditions that would evaluate potential life improvement after controlled shot peening (CSP) in high strength aluminium alloys. The boundary conditions describe the state of equal weight between surface roughening and residual stresses and the implication of material and loading parameters. From the boundary conditions, the performance of CSP on Crack Arrest and fatigue life can be investigated.
S A Curtis - One of the best experts on this subject based on the ideXlab platform.
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optimisation of the fatigue resistance of 2024 t351 aluminium alloys by controlled shot peening methodology results and analysis
International Journal of Fatigue, 2004Co-Authors: C A Rodopoulos, S A Curtis, E R De Los Rios, J SolisromeroAbstract:A methodology dedicated to the optimisation of the fatigue properties of aluminium alloys by controlled shot peening is presented. Selection of the peening conditions is made out of the use of the Design of Experiment and the Effects Neutralisation Model. Both techniques allowed the optimisation both in terms of life and Crack growth rates. Experimental determination and further analysis of the residual stress relaxation patterns revealed that at high stress levels, low cycle fatigue, life improvement is predominantly due to slow Crack growth rates, while in high cycle fatigue the extension of life is attributed to a prolonged period of Crack Arrest.
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analysis of the effects of controlled shot peening on fatigue damage of high strength aluminium alloys
International Journal of Fatigue, 2003Co-Authors: S A Curtis, E R De Los Rios, C A Rodopoulos, A LeversAbstract:The use of two micro-mechanical models for notch sensitivity and fatigue life allowed the development of boundary conditions that would evaluate potential life improvement after controlled shot peening (CSP) in high strength aluminium alloys. The boundary conditions describe the state of equal weight between surface roughening and residual stresses and the implication of material and loading parameters. From the boundary conditions, the performance of CSP on Crack Arrest and fatigue life can be investigated.
