記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：溶接学会九州支部  

リポジトリ公開URL： https://hdl.handle.net/2324/7325945

記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：溶接学会九州支部  

リポジトリ公開URL： https://hdl.handle.net/2324/7325944

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Laser-arc hybrid welding (LAHW) can significantly reduce weld deformation due to the lower heat input compared to conventional arc welding, which is the standard method used in the current hull construction stages. Because of its superior heat concentration, LAHW has a relatively larger plate thicknesses over which I-shaped groove joints can be fabricated than conventional arc welding.
One of authors reported that one-pass welding without backing material was possible for a 17 mm thick steel plate with I-shaped groove. However, it was necessary to insert a filler gauge into the groove face and set the gap across the weld line to 0.5 mm.
From the viewpoint of introducing LAHW into the construction stage of general merchant ships, this study examined the welding work conditions to fabricate sound welded joints by LAHW under the following conditions: (1) groove fabrication by plasma cutting and (2) I-shaped groove with zero initial gap width. With reference to our previous studies, a search was conducted for welding parameters (laser power, arc current and voltage, etc.) that would allow the joint to be fabricated by a single pass of construction. As a result, although welding conditions with good bead appearance were identified, hot cracking of the weld metal occurred in some of the joints. To prevent hot cracking, the number of welding passes was changed from one to two, the length of the molten pool formed in the first pass was shortened in the thickness direction, and the second pass was performed by arc welding alone to compensate for the insufficient reinforcement height. As a result, it was possible to fabricate welded joints with good bead appearance without hot cracking.

リポジトリ公開URL： https://hdl.handle.net/2324/7325691

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

It is known that fatigue crack growth behavior is dominated by cyclic plastic behavior near the crack tip. The purpose of this study is to improve the accuracy of measuring the dimensions of the alternating plastic region, which is the region where tensile and compressive plastic deformation overlap near the crack tip, using digital image correlation (DIC) method. To measure the dimensions of the alternating plastic region, fatigue crack propagation tests were conducted under two stress ratios using compact specimen (C(T) in ASTM E399). Two methods were employed to print speckle-patterns on the specimen surface for strain field measurement using the DIC method as analytical markers: (1) sprayed on the specimen surface with white and black ink, and (2) 3% nital etching solution was applied. To measure the alternating plastic zone (ῶ) under cyclic loading conditions, a high-speed camera was used to capture the strain fields near the crack tip under cyclic loading. To determine the dimensions of the alternating plastic zone, strain fields obtained from the results of the DIC method were analyzed. The elasto-plastic FE analysis was conducted to compare the results with DIC measurement. As the results, good agreement has been obtained in the low stress ratio condition rather than high stress ratio condition with the FE analysis.

リポジトリ公開URL： https://hdl.handle.net/2324/7325689

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

In the process of constructing the hull, additional anti-vibration measures are sometimes required during the commissioning phase after construction. However, the current process of installation involves welding, which results in paint burning and requires additional repair works to be painted. Therefore, the use of structural adhesives, which are a joining method that does not cause paint burning, is expected to replace welding.
In this study, as a basic study for the use of structural adhesives instead of welding for joining vibration isolation curling members, the joint strength under static three-point bending loading was compared with that of welded joints by experiments and finite element (FE) analysis. In these experiments, four types of specimens were prepared: an arc-welded joints (leg length of 5 mm) and three types of adhesives joints (adhesives thickness of 0.5 mm, 3 mm, and 5 mm) to not only compare welded joints with adhesives joints, but also to examine difference in strength due to the thickness of adhesives layer. The experimental results showed that all of the adhesives joints broke at lower loads than the arc-welded joints, but the adhesives joints also have sufficiently improved bending stiffness compared to the main plate alone and have not ruptured under the designed load. It was confirmed that the thinner the adhesives layer thickness, the greater bond strength. In the FE analysis, the interface region was defined in between steel and adhesives sections. It was confirmed that the elastic deformation before peeling could be simulated by applying appropriately material properties to each section. On the other hand, the adhesives modeling needs to be improved to estimate the peeling behavior and local strain distribution in vicinity of the adhesives part accurately.

リポジトリ公開URL： https://hdl.handle.net/2324/7325690

担当区分：最終著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

自動車シャシー部材の耐食性向上にあたり，亜鉛めっき鋼板の適用が有効である．他方で，シャシー部材の組立ではガスシールドアーク溶接による重ねすみ肉溶接継手が多く，ルート部近傍で亜鉛蒸気の気泡が発生し易い．この気泡が溶接金属内部で気孔となり，溶接継手の機械的特性の劣化を招く．そこで本報では，気孔の低減に有効な溶接プロセスを検証した結果について報告する．

DOI： 10.14920/jwstaikai.2024s.0_4

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Welding International  

Cyclic true stress - true strain curves were obtained using general-purpose shipbuilding steel in the large strain region. Test methods are incremental step test and static tensile test after cyclic loading. The stress–strain curves for static and cyclic loading were compared to investigate the cause of the difference between each other. A simple method for estimating the cyclic stress-strain curves was proposed. The diameter and curvature of the smallest cross-section of the specimen were measured using telecentric measurement device, and the true stress - true strain curve was obtained using the Bridgman correction method. Using the measurement method, cyclic stress-strain diagrams were obtained in the region where the true strain exceeded 1% by performing cyclic tensile tests using the incremental step method and static tensile tests after cyclic loading. The influence of the test method and maximum displacement conditions on the cyclic stress-strain curve was small within the scope of this study. There was little difference in the elongation between the static tensile test and the static tensile test after cyclic loading. The difference in yield stress between static and cyclic loading was discussed in terms of macro-yield mechanisms at intergranular and transgranular. A simple method for estimating cyclic stress-strain curves from a static stress-strain curve was proposed. The specimens used in this study are general-purpose shipbuilding steels, and the results should be applicable to similar steels for welding and structures.

DOI： 10.1080/09507116.2023.2282231

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リポジトリ公開URL： https://hdl.handle.net/2324/7159364

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 溶接学会  

DOI： 10.2207/jjws.93.300

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Laser-arc hybrid welding (LAHW) is an advanced welding process that combines arc and laser welding as one molten pool. Compared with conventional arc welding, LAHW can be performed higher welding speeds with narrower grooves, and weld deformation can be significantly reduced. When LAHW is applied to construction of structural members, the welding is generally performed in a flat position because it is automatic welding system is applied from the viewpoint of safety in the work environment. / Flat position (PA), it is expected to be applied to many welds of large steel structures by applying LAHW to horizontal position. However, the application of LAHW in the construction of large structures is expected by expanding the applicable welding position. / In this study, butt joints with a plate thickness of 20 mm were fabricated in the horizontal position (PC) as a target of welding position in LAHW. By trial and error, referring to the welding conditions in the flat position, the welding conditions that produced a sound weld bead appearance were derived. However, molten metal was sagging at some of lower weld bead edge of the front bead. A sliding jig was designed to prevent the front bead sagging. As a result, the sagging was prevented and it was expected that the jig was effective in relaxing the shape of the weld toe for improving the fatigue strength of the joint. / In the construction stages of large structures, it is difficult to maintain a constant root gap over the entire length of the weld line, so it is desirable to extend the allowable range of the initial gap. Therefore, we attempted to process with an initial root gap of 1.5 mm. However, we were unable to find welding conditions that would avoid undercutting and melting-in, and confirmed that the applicable limit of the initial root gap is 1.0 mm for the construction method studied in this study.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

In numerical simulations of fatigue crack propagation, the true stress-true strain relationship under cyclic loading should be considered, but in simulations modelling crack opening behaviour, the stress-strain relationship of the material is regarded as rigid plastic or isotropically hardened elastic-plastic material from the point of view of model simplification. / In this study, the true stress-true strain relationship under cyclic loading, estimated from the true stress-true strain relationship under monotonic tensile loading, is implemented in fatigue crack propagation simulations of work-hardened materials proposed by some of authors. / Fatigue crack growth curves under the following three loadings, (1) constant cyclic loading under different stress ratios, (2) two-stage block loading cycles, (3) constant cyclic loading with a spike load, were estimated and compared with the measured results obtained in previous studies. / The results show that the accuracy of the fatigue crack growth estimation is better than the conventional stress-strain relationship assuming elastic-perfectly plastic materials.

CiNii Research

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

The purpose of this paper is to confirm fatigue strength of welded joints can be improved by grain refinement using laser irradiation and localized carburization considering corrosion and abrasion. / Comparing measured temperature history of laser irradiation with theoretical solutions of moving heat source and instantaneous line heat source, and effective temperature range of grain refinement are investigated. Only moving heat source agreed with the measured values. Maximum temperature and time required from 800 ℃ to 500 ℃ (Δt8/5) of the grain refinement region are obtained by applying moving heat source. It is reasonable based on the theory of phase transformation. / Four-point bending fatigue tests were conducted on T-joint specimens as welded, laser irradiated, and locally carburized. As a result, number of cycles to failure of the specimens which locally carburized and laser irradiated were equivalent and they are longer than that of the specimens as-welded. The main reason is locally carburized and laser irradiated had more gentler toe shapes than as-welded. However, the porosity was observed in the carburized specimen. It can affect fatigue strength, further improvement of fatigue strength was expected by eliminating it.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Welding International  

Advanced high strength steel sheet (AHSS) is widely used in the automotive body for weight reduction and the improvement of crash performance. For example, TS1500 MPa class hot stamped steel (1500HS steel) sheet is applied to many vehicle models. However, there is a concern that performance of spot welded joints will decline as steel strength increases. In order to further expand the application of AHSS, it is very important to have knowledge about the characteristics of spot welded joints. In this report, we investigated the tensile shear strength (TSS) of the 1500HS steel sheet. Then, we compared the joint strength and failure position of the same kind material joints and the dissimilar material joints with the 1500HS steel sheet in case of the plug failure. As a result, it was found that TSS of dissimilar material joints depend on base metal strength on lower strength steel side. However, fracture occurred on the 1500HS steel side except for joints with large difference of base metal strength. The mechanism is thought that the effect of strain concentration at the edge of nugget on the 1500HS steel side due to the increase of rotational deformation around the nugget.

DOI： 10.1080/09507116.2023.2202949

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Welding in the World  

A method for improving the fatigue strength of thin steel sheet gas metal arc (GMA)-welded joints using weaving welding was evaluated. Weaving created peaks and valleys at the weld toe. The valley has high stress triaxiality, and plastic deformation is unlikely to occur. Fatigue cracks occurred from the peaks with gentle toe shapes. Therefore, it is considered that the fatigue strength is improved by reducing the initiation points of the crack and stress concentration at the toe. The fatigue test results showed that the fatigue limit of the weaving welding joint was improved compared with that of the normal welding joint. Furthermore, the optimal weaving condition, which is the relationship between the weaving wavelength and torch swing amplitude, was evaluated. As a consequence, when the wave density is small, the crack initiation point is not restricted to the peak. On the other hand, when the wave density is large, the peak and valley shapes merge and the weaving effect disappears. In addition, undercuts occurred when the swing amplitude became too large. The mechanism of improving the fatigue strength was considered by observing the initiation point of the fatigue microcracks.

DOI： 10.1007/s40194-023-01480-z

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 溶接学会  

Cyclic true stress - true strain curves were obtained using general-purpose shipbuilding steel in the large strain region. Test methods are incremental step test and static tensile test after cyclic loading. The stress-strain curves for static and cyclic loading were compared to investigate the cause of the difference between each other. A simple method for estimating the cyclic stress-strain curves was proposed. The diameter and curvature of the smallest cross-section of the specimen were measured using telecentric measurement device, and the true stress - true strain curve was obtained using the Bridgman correction method. Using the measurement method, cyclic stress-strain diagrams were obtained in the region where the true strain exceeded 1% by performing cyclic tensile tests using the incremental step method and static tensile tests after cyclic loading. The influence of the test method and maximum displacement conditions on the cyclic stress-strain curve was small within the scope of this study. There was little difference in the elongation between the static tensile test and the static tensile test after cyclic loading. The difference in yield stress between static and cyclic loading was discussed in terms of macro-yield mechanisms at intergranular and transgranular. A simple method for estimating cyclic stress-strain curves from a static stress-strain curve was proposed. The specimens used in this study are general-purpose shipbuilding steels, and the results should be applicable to similar steels for welding and structures.

DOI： 10.2207/qjjws.41.217

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Theoretical and Applied Fracture Mechanics  

This study investigates the dominant factors of fatigue strength at the root of thin-sheet lap fillet arc welds, which are frequently used in automobile chassis components. A method to improve the root fatigue strength was investigated. The direction of fatigue crack propagation at the root coincided with the direction of maximum circumferential stress range. The circumferential stress was reduced by increasing the distance from the toe to the root (penetration width). Fatigue strength originating from the root was improved in welded joints where the penetration width was increased by adjusting the welding aim point and heat input.

DOI： 10.1016/j.tafmec.2022.103667

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 溶接学会  

Advanced high strength steel sheet (AHSS) is widely used in the automotive body for weight reduction and the improvement of crash performance. In general, weldability and formability of steel sheet tends to decline as steel strength increases. Hot stamping is a technique that achieves both formability and strength of steel sheet, and TS1500MPa class hot stamped steel sheet is applied to many vehicle models. On the other hand, since the joint strength characteristics of the spot weld are dominated by the melt-solidified zone and weld heat affected zone, there is a concern that performance of spot welded joints will decline as steel strength increases. In other words, in order to further expand the application of AHSS, it is very important to have knowledge about the characteristics of spot welded joints. In this report, we investigated the TSS of the TS1500MPa class hot stamped steel sheet, focusing on the characteristics of tensile shear joints. Then, we compared the joint strength and failure position of the same kind material joints and the dissimilar material joints with the TS1500MPa class hot stamped steel sheet in case of the plug failure. As a result, it was found that TSS of dissimilar material joints depend on base metal strength on lower strength steel side. However, fracture occurred on the TS1500MPa class hot stamped steel side except for joints with large difference of base metal strength. The mechanism is thought that the effect of strain concentration at the edge of nugget on the TS1500MPa class hot stamped steel side due to the increase of rotational deformation around the nugget.

DOI： 10.2207/qjjws.40.216

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：溶接学会九州支部  

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：溶接学会九州支部  

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：溶接学会九州支部  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Welding International  

Weld residual stress of the lap fillet GMA welding joints which was performed using two strength grades of steel sheets and two strength grades of welding wires were measured. In addition, to consider the effects of steel sheet strength and weld metal strength on welding residual stress, thermal elastoplastic analysis using FEM was carried out for the experiments. As a result of the analysis using the temperature history of the heat-affected zone as a fitting parameter, the residual stress distributions near the toe were in agreement with the measurement in the FE analysis. Comparing the residual stress distributions in the direction perpendicular to the weld line on the weld metal surface near the toe, which is the occurring point of fatigue cracks in the FE analysis results, with the same steel sheet, the higher the weld metal strength the smaller the tensile residual stress. And comparing with the same wire, the higher the steel sheet strength the higher the tensile residual stress. The reason for the former is that when using high-strength wire, cooling transformation occurs at a lower temperature than using low-strength wire. As a result, it is considered that the tensile residual stress was effectively reduced by causing transformation expansion while the surrounding strength was high. The reason for the latter is considered to be that each stress value changes based on the yield stress of the steel sheet and weld metal because the plastic strain continues to occur in each direction until transformation occurs after welding. It was considered that the larger the ratio of the hardness of the weld metal to the base metal, the smaller the ratio of the residual stress of the weld metal near the toe to the yield stress.

DOI： 10.1080/09507116.2022.2030536

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Science and Technology of Welding and Joining  

The effect of galvannealed (GA) coating on the corona bond strengths of resistance spot welding joints was investigated. A cross tensile test was performed with removal of the nugget, using GA steel sheets and steel sheets whose coating had been removed via pickling. The maximum load with coating was lower than that without coating. When the nugget diameter was small (3√t, t: sheet thickness), GA coating reduced the corona bond strength (MPa). In contrast, when the nugget diameter was large (5√t), GA coating did not change the corona bond strength but reduced the corona bond area.

DOI： 10.1080/13621718.2021.2023964

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki MATSUDA, Shinji KODAMA, Effect of the strength of steel sheet and wire on residual stress of thin sheet arc weld, Preprints of the National Meeting of JWS, 109, Pages 230-231, September 21 - 28, 2021.

DOI： https://doi.org/10.14920/jwstaikai.2021f.0_230

その他リンク： https://doi.org/10.14920/jwstaikai.2021f.0_230

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 溶接学会  

Weld residual stress of the lap fillet GMA welding joints which was performed using two strength grades of steel sheets and two strength grades of welding wires were measured. In addition, in order to consider the effects of steel sheet strength and weld metal strength on welding residual stress, thermal elastoplastic analysis using FEM was carried out for the experiments. As a result of analysis using the temperature history of the heat-affected zone as a fitting parameter, the residual stress distributions near the toe were in agreement with the measurement in the FE analysis. Comparing the residual stress distributions in the direction perpendicular to the weld line on the weld metal surface near the toe, which is the occurring point of fatigue cracks in the FE analysis results, with the same steel sheet, the higher the weld metal strength the smaller the tensile residual stress. And comparing with the same wire, the higher the steel sheet strength the higher the tensile residual stress. The reason for the former is that when using high-strength wire, cooling transformation occurs at a lower temperature than using low-strength wire. As a results, it is considered that the tensile residual stress was effectively reduced by causing transformation expansion due to while the surrounding strength was high. The reason for the latter is considered to be that the each stress value changes based on the yield stress of the steel sheet and weld metal because the plastic strain continues to occur in each direction until transformation occurs after welding. It was considered that the larger the ratio of the hardness of the weld metal to the base metal, the smaller the ratio of the residual stress of the weld metal near the toe to the yield stress.

DOI： https://doi.org/10.2207/qjjws.39.218

その他リンク： https://doi.org/10.2207/qjjws.39.218

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier  

Fatigue tests were conducted on a thin sheet arc welded part using two types of welding wires. Microscopic observations of specimens tested at the fatigue limit stress revealed that microcracks were initiated in the micro-ripples on the weld metal surface. Furthermore, a coarse ferrite structure often contains existing microcracks. A method for quantitatively evaluating the effects of microscopic irregularities on the weld metal surface and macroscopic toe shape on the fatigue strength is proposed. It was found that microscopic irregularities on weld metal have a significant impact on the fatigue limit, depending on their metallurgical structure.

DOI： https://doi.org/10.1016/j.ijfatigue.2020.106087

その他リンク： https://doi.org/10.1016/j.ijfatigue.2020.106087

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki MATSUDA, Shinji KODAMA, Observation of Micro Fatigue Cracks at Arc Welded Joint of Thin Steel Sheet (Report 2), Preprints of the National Meeting of JWS, Pages 164-165, September 09 - 11, 2020.

DOI： https://doi.org/10.14920/jwstaikai.2020f.0_164

その他リンク： https://doi.org/10.14920/jwstaikai.2020f.0_164

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 溶接学会  

Fatigue tests were performed on GMA welded joints using a prototype steel sheets with varying amounts of C. In addition, the origin of the fatigue cracks in the thin steel GMA welded joints were investigated through observation the micro cracks in the specimens that were judged to be not fractured by fatigue limit stress in the fatigue test. As a result of plane bending fatigue test of bead-on-plate welding sheet, fatigue limit of the welded specimen did not differ much between the steel sheets. Observing the specimens which were not fractured at the fatigue limit, micro cracks often occurred at the bottom of the ripples on the weld metal surface and in the ferrite structure. It was founded that fatigue cracks in thin steel sheet GMA welding using mixed gas occurred parallel along the bottom of the ripples and parallel cracks merged with the crack growth, resulting in a zigzag propagation path on the weld joint surface. The effect of ripple on the fatigue limit was predicted by comparing estimating the fatigue limit without considering the ripple with the fatigue limit obtained from experiment. Finally, the effect of ripple on the fatigue limit was more than 10% and less than 20%. And it was implied that higher the strength of the material, the greater the effect of ripple on the fatigue limit.

DOI： https://doi.org/10.2207/qjjws.38.157

その他リンク： https://doi.org/10.2207/qjjws.38.157

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki MATSUDA, Shinji KODAMA, Stress analysis of lap fillet joint using thin steel sheet, Preprints of the National Meeting of JWS, Pages 226-227, 2019

DOI： https://doi.org/10.14920/jwstaikai.2019f.0_226

その他リンク： https://doi.org/10.14920/jwstaikai.2019f.0_226

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Sage Publishing  

A simple method to evaluate the strength of corona bond of resistance spot welding is proposed and verified by removing the nugget of welded specimen before conducting a cross tension test. The strength of the corona bond is evaluated using thin steel sheets of different strengths. The result indicates that the higher the strength of the steel sheet, the higher the strength of the corona bond. A tensile test of the corona bond part is conducted using the small tensile test technique to verify the corona bond strength. A comparison of the stress value at the same strain (1%) indicates that the stress of the small tensile test is in the order of the strength of the steel sheet.

DOI： https://doi.org/10.1080/13621718.2019.1613010

その他リンク： https://doi.org/10.1080/13621718.2019.1613010

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki Matsuda, Shinji Kodama, Evaluation of Corona Bond Area Strength of Resistance Spot Welding, Preprints of the National Meeting of JWS, Pages 240-241, 2018.

DOI： https://doi.org/10.14920/jwstaikai.2018f.0_240

その他リンク： https://doi.org/10.14920/jwstaikai.2018f.0_240

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki Matsuda, Yoshinari Ishida, Shinji Kodama, Observation of Micro Cracks at Arc Welded Steel Sheet, Preprints of the National Meeting of JWS, Pages 18-19, 2017.

DOI： https://doi.org/10.14920/jwstaikai.2017f.0_18

その他リンク： https://doi.org/10.14920/jwstaikai.2017f.0_18

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：一般社団法人 溶接学会  

Kazuki Matsuda, Yoshinari Ishida, Shinji Kodama, Yasunobu Miyazaki, Evaluation of Fatigue Crack Propagation Properties of Thin Steel Plate welds, Preprints of the National Meeting of JWS, Pages 368-369, 2016.

DOI： https://doi.org/10.14920/jwstaikai.2016f.0_368

その他リンク： https://doi.org/10.14920/jwstaikai.2016f.0_368

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：日本船舶海洋工学会  

Kazuki Matsuda, Koji Gotoh, A Study of Replacing Method to the Single-Frequency Stress History to the Superimposed Stress History with Multiple Frequency Components, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, Pages 489-492, 2015.

DOI： https://doi.org/10.14856/conf.20.0_489

その他リンク： https://doi.org/10.14856/conf.20.0_489

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier  

Fatigue crack propagation behavior under superimposed stress histories containing different frequency components with several mean stress conditions was investigated. Numerical simulation of fatigue crack propagation based on an advanced fracture mechanics approach using the RPG (Re-tensile Plastic zone Generating) stress criterion for fatigue crack propagation was improved to extract the effective part from the applied stress history for fatigue crack propagation. The parameter, which is based on the plastic hysteresis energy consumed in the vicinity of a crack tip, was applied and implemented into the numerical simulation code of fatigue crack propagation. Fatigue crack propagation tests under various superimposed stress conditions with several mean stress conditions were performed and compared with the fatigue crack propagation histories obtained from the improved numerical simulations. These comparisons show the validity of the proposed procedure for extracting the effective stress history from the superimposed stress histories with different frequency components and mean stresses. Additionally, practical fatigue strength evaluations based on the linear cumulative fatigue damage parameter were conducted to investigate the tendency of the fatigue damage value under these stress conditions.

DOI： https://doi.org/10.1016/j.marstruc.2014.12.005

その他リンク： https://doi.org/10.1016/j.marstruc.2014.12.005

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本船舶海洋工学会  

Fatigue crack propagation behavior under superimposed loading histories with several mean stress conditions is highlighted.Numerical simulation of fatigue crack propagation based on an advanced fracture mechanics approach using the RPG (Re-tensile Plastic zone Generating) stress criterion for fatigue crack propagation is improved to enable the extraction of the effective loading history for fatigue crack propagation. The parameter, which is based on the plastic hysteresis consuming in the vicinity of a crack tip,is applied to extract the effective loading for fatigue crack propagation and implemented into the numerical simulation code of fatigue crack propagation. Fatigue crack propagation tests under various superimposed loading conditions, which contain several constants and variable mean stress, are performed and comparison of fatigue crack propagation histories obtained from the improved numerical simulations with the measurements is performed. These comparisons show the validity of the proposed procedure for extracting the effective loading history from the superimposed loading histories with different frequencies. Subsequently, practical fatigue strength evaluation based on the linear cumulative fatigue damage parameter were conducted to investigate the tendency of fatigue damage value affected by mean stresses.

DOI： https://doi.org/10.2534/jjasnaoe.20.119

その他リンク： https://doi.org/10.2534/jjasnaoe.20.119

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Fatigue crack propagation behavior under simulated whipping loadings which contain two different frequency components is highlighted. Numerical simulation of fatigue crack propagation based on an advanced fracture mechanics approach using the RPG (Re-tensile Plastic zone Generating) stress criterion for fatigue crack propagation is improved to enable the extraction of the effective loading history. The critical value of the plastic hysteresis for the stress versus strain relationship occurring in the vicinity of a crack tip is defined as the control parameter for extracting the effective loading history. Comparison of fatigue crack propagation curves obtained from the improved numerical simulations with the measurements which were conducted by Sumi (2010) is performed. These comparisons show the validity of the proposed procedure for extracting the effective loading history from the superposed loading history containing different frequencies. In addition, imperfection of the S-N curves approach, which corresponds to the combination of the linear cumulative damage law and the loading cycle count by the rain flow method, is conducted.

DOI： https://doi.org/10.1115/OMAE2013-10985

その他リンク： https://doi.org/10.1115/OMAE2013-10985

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本船舶海洋工学会  

Fatigue crack propagation behaviour under superposed loading histories which contain two different frequency components is highlighted. Numerical simulation of fatigue crack propagation based on an advanced fracture mechanics approach using the RPG (Retensile Plastic zone Generating) stress criterion for fatigue crack propagation is improved to enable the extraction of the effective loading history. The critical value of the plastic hysteresis for the stress versus strain relationship occurring in the vicinity of a crack tip is defined as the control parameter for extracting the effective loading history. Comparison of fatigue crack propagation curves obtained from the improved numerical simulations with the measurements under the superposed loading histories is performed. These comparisons show the validity of the proposed procedure for extracting the effective loading history from the superposed loading history containing different frequencies. Besides, the insufficiency of S-N curves approach with the cumulative damage law for the superposed loading history condition containing different frequency components is conducted.

DOI： https://doi.org/10.2534/jjasnaoe.17.75

その他リンク： https://doi.org/10.2534/jjasnaoe.17.75

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Numerical simulation of fatigue crack propagation under superposed loading histories with two different frequencies, Koji GOTOH，Kazuki MATSUDA，O KITAMURA, Proc. HYDROELASTICITY 2012, pp 287～297

開催年月日： 2024年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県   国名：日本国  

リポジトリ公開URL： https://hdl.handle.net/2324/7325944

開催年月日： 2024年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kure, Hiroshima   国名：日本国  

It is known that fatigue crack growth behavior is dominated by cyclic plastic behavior near the crack tip. The purpose of this study is to improve the accuracy of measuring the dimensions of the alternating plastic region, which is the region where tensile and compressive plastic deformation overlap near the crack tip, using digital image correlation (DIC) method. To measure the dimensions of the alternating plastic region, fatigue crack propagation tests were conducted under two stress ratios using compact specimen (C(T) in ASTM E399). Two methods were employed to print speckle-patterns on the specimen surface for strain field measurement using the DIC method as analytical markers: (1) sprayed on the specimen surface with white and black ink, and (2) 3% nital etching solution was applied. To measure the alternating plastic zone (ῶ) under cyclic loading conditions, a high-speed camera was used to capture the strain fields near the crack tip under cyclic loading. To determine the dimensions of the alternating plastic zone, strain fields obtained from the results of the DIC method were analyzed. The elasto-plastic FE analysis was conducted to compare the results with DIC measurement. As the results, good agreement has been obtained in the low stress ratio condition rather than high stress ratio condition with the FE analysis.

リポジトリ公開URL： https://hdl.handle.net/2324/7325689

開催年月日： 2024年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kure, Hiroshima   国名：日本国  

Laser-arc hybrid welding (LAHW) can significantly reduce weld deformation due to the lower heat input compared to conventional arc welding, which is the standard method used in the current hull construction stages. Because of its superior heat concentration, LAHW has a relatively larger plate thicknesses over which I-shaped groove joints can be fabricated than conventional arc welding. One of authors reported that one-pass welding without backing material was possible for a 17 mm thick steel plate with I-shaped groove. However, it was necessary to insert a filler gauge into the groove face and set the gap across the weld line to 0.5 mm. From the viewpoint of introducing LAHW into the construction stage of general merchant ships, this study examined the welding work conditions to fabricate sound welded joints by LAHW under the following conditions: (1) groove fabrication by plasma cutting and (2) I-shaped groove with zero initial gap width. With reference to our previous studies, a search was conducted for welding parameters (laser power, arc current and voltage, etc.) that would allow the joint to be fabricated by a single pass of construction. As a result, although welding conditions with good bead appearance were identified, hot cracking of the weld metal occurred in some of the joints. To prevent hot cracking, the number of welding passes was changed from one to two, the length of the molten pool formed in the first pass was shortened in the thickness direction, and the second pass was performed by arc welding alone to compensate for the insufficient reinforcement height. As a result, it was possible to fabricate welded joints with good bead appearance without hot cracking.

開催年月日： 2024年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kure, Hiroshima   国名：日本国  

In the process of constructing the hull, additional anti-vibration measures are sometimes required during the commissioning phase after construction. However, the current process of installation involves welding, which results in paint burning and requires additional repair works to be painted. Therefore, the use of structural adhesives, which are a joining method that does not cause paint burning, is expected to replace welding. In this study, as a basic study for the use of structural adhesives instead of welding for joining vibration isolation curling members, the joint strength under static three-point bending loading was compared with that of welded joints by experiments and finite element (FE) analysis. In these experiments, four types of specimens were prepared: an arc-welded joints (leg length of 5 mm) and three types of adhesives joints (adhesives thickness of 0.5 mm, 3 mm, and 5 mm) to not only compare welded joints with adhesives joints, but also to examine difference in strength due to the thickness of adhesives layer. The experimental results showed that all of the adhesives joints broke at lower loads than the arc-welded joints, but the adhesives joints also have sufficiently improved bending stiffness compared to the main plate alone and have not ruptured under the designed load. It was confirmed that the thinner the adhesives layer thickness, the greater bond strength. In the FE analysis, the interface region was defined in between steel and adhesives sections. It was confirmed that the elastic deformation before peeling could be simulated by applying appropriately material properties to each section. On the other hand, the adhesives modeling needs to be improved to estimate the peeling behavior and local strain distribution in vicinity of the adhesives part accurately.

リポジトリ公開URL： https://hdl.handle.net/2324/7325690

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：北海道科学大学   国名：日本国  

自動車シャシー部材の耐食性向上にあたり，亜鉛めっき鋼板の適用が有効である．一方で，めっき由来の亜鉛蒸気は溶接金属内部に気孔として残留する場合があり，気孔を安定的に低減する方法が求められる．この課題に対し，ウィービング溶接は気孔の抑制に有効であることが判った．本報では溶接ワイヤ成分がウィービング溶接の気泡排出挙動に及ぼす影響を調査した結果について報告する．

DOI： https://doi.org/10.14920/jwstaikai.2024f.0_174

リポジトリ公開URL： https://hdl.handle.net/2324/7341500

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：北海道科学大学   国名：日本国  

WAAM方式の積層造形技術確立のため，軟鋼用ワイヤを用いてCO2溶接による溶接ビード積層の条件探索を実施した．そして，熱伝導解析により求めた積層中の温度履歴と試験における測定結果をフィッティングして熱弾塑性解析を行い，造形後の基板の反り変形を推定した．また，得られた温度履歴を基に冷却速度からビッカース硬さ分布を推定した．製造条件から推定した硬さ・変形は測定結果と良好な一致を示した．

DOI： https://doi.org/10.14920/jwstaikai.2024f.0_426

リポジトリ公開URL： https://hdl.handle.net/2324/7341504

開催年月日： 2024年4月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：大阪大学　中之島センター   国名：日本国  

DOI： https://doi.org/10.14920/jwstaikai.2024s.0_4

開催年月日： 2023年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Busan   国名：大韓民国  

In numerical simulations of fatigue crack propagation, the true stress-true strain relationship under cyclic loading should be considered, but in simulations modelling crack opening behaviour, the stress-strain relationship of the material is regarded as rigid plastic or isotropically hardened elastic-plastic material from the point of view of model simplification. In this study, the true stress-true strain relationship under cyclic loading, estimated from the true stress-true strain relationship under monotonic tensile loading, is implemented in fatigue crack propagation simulations of workhardened materials proposed by some of authors. Fatigue crack growth curves under the following three loadings, (1) constant cyclic loading under different stress ratios, (2) two-stage block loading cycles, (3) constant cyclic loading with a spike load, were estimated and compared with the measured results obtained in previous studies. The results show that the accuracy of the fatigue crack growth estimation is better than the conventional stressstrain relationship assuming elastic-perfectly plastic materials.

リポジトリ公開URL： https://hdl.handle.net/2324/7157018

開催年月日： 2023年10月

記述言語：英語  

開催地：Busan   国名：大韓民国  

The purpose of this paper is to confirm fatigue strength of welded joints can be improved by grain refinement using laser irradiation and localized carburization considering corrosion and abrasion. Comparing measured temperature history of laser irradiation with theoretical solutions of moving heat source and instantaneous line heat source, and effective temperature range of grain refinement are investigated. Only moving heat source agreed with the measured values. Maximum temperature and time required from 800 ℃ to 500 ℃ (Δt8/5) of the grain refinement region are obtained by applying moving heat source. It is reasonable based on the theory of phase transformation. Four-point bending fatigue tests were conducted on T-joint specimens as welded, laser irradiated, and locally carburized. As a result, number of cycles to failure of the specimens which locally carburized and laser irradiated were equivalent and they are longer than that of the specimens as-welded. The main reason is locally carburized and laser irradiated had more gentler toe shapes than as-welded. However, the porosity was observed in the carburized specimen. It can affect fatigue strength, further improvement of fatigue strength was expected by eliminating it.

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開催年月日： 2023年10月

記述言語：英語  

開催地：Busan   国名：大韓民国  

Laser-arc hybrid welding (LAHW) is an advanced welding process that combines arc and laser welding as one molten pool. Compared with conventional arc welding, LAHW can be performed higher welding speeds with narrower grooves, and weld deformation can be significantly reduced. When LAHW is applied to construction of structural members, the welding is generally performed in a flat position because it is automatic welding system is applied from the viewpoint of safety in the work environment. Flat position (PA), it is expected to be applied to many welds of large steel structures by applying LAHW to horizontal position. However, the application of LAHW in the construction of large structures is expected by expanding the applicable welding position. In this study, butt joints with a plate thickness of 20 mm were fabricated in the horizontal position (PC) as a target of welding position in LAHW. By trial and error, referring to the welding conditions in the flat position, the welding conditions that produced a sound weld bead appearance were derived. However, molten metal was sagging at some of lower weld bead edge of the front bead. A sliding jig was designed to prevent the front bead sagging. As a result, the sagging was prevented and it was expected that the jig was effective in relaxing the shape of the weld toe for improving the fatigue strength of the joint. In the construction stages of large structures, it is difficult to maintain a constant root gap over the entire length of the weld line, so it is desirable to extend the allowable range of the initial gap. Therefore, we attempted to process with an initial root gap of 1.5 mm. However, we were unable to find welding conditions that would avoid undercutting and melting-in, and confirmed that the applicable limit of the initial root gap is 1.0 mm for the construction method studied in this study.

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開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県   国名：日本国  

Tsukasa Shimooka, Koji Murakami, Kazuki Matsuda and Koji Gotoh, Experimental Investigation on Stress-Strain Relationship of Steel under Cyclic Loading, Annual meeting of the Kyushu Branch of the Japan Welding Society held on 1 September, 2022.

リポジトリ公開URL： http://hdl.handle.net/2324/4798534

開催年月日： 2022年9月

記述言語：日本語  

開催地：福岡県   国名：日本国  

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開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県   国名：日本国  

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開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tokyo   国名：日本国  

Kazuki Matsuda, Yoshinari Ishida, Shinji Kodama, Fatigue strength improvement method for thin sheet GMA welding joints by weaving, International Institute of Welding, XII-2494-2022, Tokyo, July 20-21, 2022

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：WEB開催   国名：日本国  

Kazuki MATSUDA, Shinji KODAMA, Effect of the strength of steel sheet and wire on residual stress of thin sheet arc weld, Preprints of the National Meeting of JWS, September 21 - 28, 2021.

その他リンク： https://doi.org/10.14920/jwstaikai.2021f.0_230

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：WEB開催   国名：日本国  

Moe SHINOHARA, Kazuki MATSUDA, Seiji FURUSAKO, Shinji KODAMA, Evaluation of spot welded joints strength in different-strength steel sheets including 1.5 GPa grade steel sheets, Preprints of the National Meeting of JWS, 21-28 September, 2021.

その他リンク： https://doi.org/10.14920/jwstaikai.2021f.0_188

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：WEB開催   国名：日本国  

Kazuki MATSUDA, Shinji KODAMA, Observation of Micro Fatigue Cracks at Arc Welded Joint of Thin Steel Sheet (Report 2), Preprints of the National Meeting of JWS, September 09 - 11, 2020.

その他リンク： https://doi.org/10.14920/jwstaikai.2020f.0_164

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

Kazuki MATSUDA, Shinji KODAMA, Stress analysis of lap fillet joint using thin steel sheet, Preprints of the National Meeting of JWS, September 17-19, 2019.

その他リンク： https://doi.org/10.14920/jwstaikai.2019f.0_226

開催年月日： 2018年11月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Fukuoka   国名：日本国  

開催年月日： 2018年9月

記述言語：日本語  

開催地：愛媛県   国名：日本国  

Kazuki Matsuda, Shinji Kodama, Evaluation of Corona Bond Area Strength of Resistance Spot Welding, Preprints of the National Meeting of JWS, September 12-14, 2018.

その他リンク： https://doi.org/10.14920/jwstaikai.2018f.0_240

開催年月日： 2017年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡県   国名：日本国  

Kazuki Matsuda, Yoshinari Ishida, Shinji Kodama, Observation of Micro Cracks at Arc Welded Steel Sheet, Preprints of the National Meeting of JWS, September 11-13, 2017.

その他リンク： https://doi.org/10.14920/jwstaikai.2017f.0_18

開催年月日： 2016年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：群馬県   国名：日本国  

Kazuki Matsuda, Yoshinari Ishida, Shinji Kodama, Yasunobu Miyazaki, Evaluation of Fatigue Crack Propagation Properties of Thin Steel Plate welds, Preprints of the National Meeting of JWS, September 14-16, 2016.

その他リンク： https://doi.org/10.14920/jwstaikai.2016f.0_368

開催年月日： 2016年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：群馬県   国名：日本国  

Shinji Kodama, Kazuki Matsuda, Yoshinari Ishida, Yasunobu Miyazaki, Improvement in fillet lap joints of high strength thin plates by using high strength welding wire, Preprints of the National Meeting of JWS, 14-16, Sep. 2016.

その他リンク： https://doi.org/10.14920/jwstaikai.2016f.0_378

開催年月日： 2015年5月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

Kazuki Matsuda, Koji Gotoh, A Study of Replacing Method to the Single-Frequency Stress History to the Superimposed Stress History with Multiple Frequency Components, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, May 25-26, 2015.

その他リンク： https://doi.org/10.14856/conf.20.0_489

開催年月日： 2014年12月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：大阪   国名：日本国  

Kazuki MATSUDA, Koji Gotoh, Numerical Simulation of Fatigue Crack Propagation under Various Loading Condition by Using Equivalent Fatigue Stress Range Method, Welding Structure Symposium, Dec. 2014

開催年月日： 2014年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Istanbul   国名：トルコ共和国  

開催年月日： 2014年5月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：宮城   国名：日本国  

Kazuki Matsuda, Koji Murakami, Koji Gotoh, Numerical simulation of fatigue crack propagation under superimposed loading histories –(Part 2) Effect of variation in stress amplitude and mean stress for fatigue crack propagation-, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, May 2014.

開催年月日： 2013年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nantes   国名：フランス共和国  

DOI： https://doi.org/10.1115/OMAE2013-10985

開催年月日： 2013年5月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：広島   国名：日本国  

Kazuki Matsuda, Koji Murakami, Koki Sugino, Koji Gotoh, Numerical Simulation of Fatigue Crack under Superposed Loading Histories–Mean Stress Effect for Fatigue Crack Propagation–, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, 27-28 May 2013.

開催年月日： 2012年11月

記述言語：日本語  

開催地：千葉   国名：日本国  

Kazuki Matsuda, Ryutaro Tsuji, Koji Murakami, Koji Gotoh, Experimental investigation of the fatigue crack growth behavior from the shearing mode to the opening mode, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, 26-27 Nov. 2012.

開催年月日： 2012年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tokyo   国名：日本国  

開催年月日： 2012年7月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島   国名：日本国  

開催年月日： 2012年5月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：兵庫県   国名：日本国  

Koji Gotoh, Kazuki Matsuda, Numerical Simulation of Fatigue Crack Propagation Under Superimposed Variable Amplitude Loading, Conference Proceedings The Japan Society of Naval Architects and Ocean Engineers, 17-18 May, 2012.

開催年月日： 2011年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Incheon   国名：大韓民国  

開催年月日： 2011年7月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：熊本   国名：日本国  

種別：査読等 

外国語雑誌　査読論文数：5

種別：大会・シンポジウム等 

種別：査読等 

外国語雑誌　査読論文数：4

国際会議録　査読論文数：1