In seismic-active area, the buried pipeline is subjected to the axial tensile load exceeding the yield stress of pipe material due to the lateral flow induced by soil liquefaction. Designing a girth weld joint that does not fracture at girth weld but base metal which has high elongation capacity is feasible to ensure adequate ground displacement absorbing capacity of the girth weld joint. However, as for fine grain steel, the heat-affected zone (HAZ) is softened by welding heat input, and then, the zone of softened HAZ can be the origin of fracture under tensile load. The apparent strength of softened HAZ is affected by the plastic constraint from the surrounding weld metal and base metal during tensile loading, and the fracture location depends on the apparent strength of HAZ. This study investigates the tensile strength and fracture location of girth weld joints with softened HAZ in the static tensile test. The effect of geometric and mechanical heterogeneity of HAZ, strength overmatching of weld metal, and the width-thickness ratio of tensile test specimen on tensile strength are elucidated using parametric finite element analysis. Subsequently, an equation is proposed to predict the tensile strength and fracture location of the welded joint. Using the proposed equation, the condition of geometric and mechanical heterogeneity of the weld to confirm the girth weld joints that fracture at base metal under tensile load is clarified. The proposed equation can be used to design a girth weld joint with liquefaction earthquake resistance.
{"title":"ラインパイプ周溶接継手の軟化HAZを考慮した引張強度予測手法","authors":"Shoma ONUKI, Masaki MITSUYA, Mitsuru OHATA","doi":"10.2207/qjjws.41.263","DOIUrl":"https://doi.org/10.2207/qjjws.41.263","url":null,"abstract":"In seismic-active area, the buried pipeline is subjected to the axial tensile load exceeding the yield stress of pipe material due to the lateral flow induced by soil liquefaction. Designing a girth weld joint that does not fracture at girth weld but base metal which has high elongation capacity is feasible to ensure adequate ground displacement absorbing capacity of the girth weld joint. However, as for fine grain steel, the heat-affected zone (HAZ) is softened by welding heat input, and then, the zone of softened HAZ can be the origin of fracture under tensile load. The apparent strength of softened HAZ is affected by the plastic constraint from the surrounding weld metal and base metal during tensile loading, and the fracture location depends on the apparent strength of HAZ. This study investigates the tensile strength and fracture location of girth weld joints with softened HAZ in the static tensile test. The effect of geometric and mechanical heterogeneity of HAZ, strength overmatching of weld metal, and the width-thickness ratio of tensile test specimen on tensile strength are elucidated using parametric finite element analysis. Subsequently, an equation is proposed to predict the tensile strength and fracture location of the welded joint. Using the proposed equation, the condition of geometric and mechanical heterogeneity of the weld to confirm the girth weld joints that fracture at base metal under tensile load is clarified. The proposed equation can be used to design a girth weld joint with liquefaction earthquake resistance.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135611741","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}
Friction Stir Welding (FSW), which was developed at TWI in 1991, is a solid-phase welding process capable of joining linear and point welds, and is being put to practical use in the automotive, aerospace, and other industries for the purpose of weight reduction and multi-materials. In this paper, the effects of each factor on joint strength in friction stir spot welding are clarified using statistical methods, and optimized joint conditions are proposed. Specifically, the optimal joining structure is experimentally clarified for aluminum materials with composite coatings by utilizing the design of experiment method in terms of the degree of influence of tool geometry and tool motion. Only the shape of the tool's probe is triangular prism because it is known to be effective in bonding composite films to the material.
{"title":"Optimization of welding conditions for friction stir spot welding of A6063S-T5 with composite coated films using a triangular prism-shaped tool","authors":"Terumichi MURAKOSHI, Toshiya SHIBAYANAGI","doi":"10.2207/qjjws.41.273","DOIUrl":"https://doi.org/10.2207/qjjws.41.273","url":null,"abstract":"Friction Stir Welding (FSW), which was developed at TWI in 1991, is a solid-phase welding process capable of joining linear and point welds, and is being put to practical use in the automotive, aerospace, and other industries for the purpose of weight reduction and multi-materials. In this paper, the effects of each factor on joint strength in friction stir spot welding are clarified using statistical methods, and optimized joint conditions are proposed. Specifically, the optimal joining structure is experimentally clarified for aluminum materials with composite coatings by utilizing the design of experiment method in terms of the degree of influence of tool geometry and tool motion. Only the shape of the tool's probe is triangular prism because it is known to be effective in bonding composite films to the material.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135611742","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}
In resistance spot welding, which is widely used for assembling automobile bodies, reduction of weld spacing (short-pitch welding) has been put to practical use to improve the strength and stiffness of the welded assemblies and to advance collision safety and ride comfort. In short-pitch welding, shunt current going through the previously welded points is inevitable and delays nugget formation and growth, but it is difficult to know the degree of shunting because it varies depending not only on the weld spacing but also on the sheet combination. In order to study the shunt phenomenon, several theoretical models have been proposed, but they have some critical problems in practical use, such as overestimation of the shunt resistance and many parameters to be determined from experiments. In this study, a mathematical model is established which can easily predict the ratio of effective weld current (or non-effective shunt current) to the total input current with only one experimental parameter, in the case of two-sheet stack-up with a single existing (shunting) weld. By using this model, delayed nugget growth curve of the second weld can be predicted taking the shunting effects into account, from the known nugget growth curve of the first weld. Furthermore, the efficiency of the shunt current to ease some three-sheet stack-ups welding was shown experimentally, and the optimal weld-spacing to maximize the welding current range was estimated by the proposed model.
{"title":"A Mathematical Model of Shunting in Resistance Spot Welding","authors":"Manabu FUKUMOTO, Naoya TADA","doi":"10.2207/qjjws.41.302","DOIUrl":"https://doi.org/10.2207/qjjws.41.302","url":null,"abstract":"In resistance spot welding, which is widely used for assembling automobile bodies, reduction of weld spacing (short-pitch welding) has been put to practical use to improve the strength and stiffness of the welded assemblies and to advance collision safety and ride comfort. In short-pitch welding, shunt current going through the previously welded points is inevitable and delays nugget formation and growth, but it is difficult to know the degree of shunting because it varies depending not only on the weld spacing but also on the sheet combination. In order to study the shunt phenomenon, several theoretical models have been proposed, but they have some critical problems in practical use, such as overestimation of the shunt resistance and many parameters to be determined from experiments. In this study, a mathematical model is established which can easily predict the ratio of effective weld current (or non-effective shunt current) to the total input current with only one experimental parameter, in the case of two-sheet stack-up with a single existing (shunting) weld. By using this model, delayed nugget growth curve of the second weld can be predicted taking the shunting effects into account, from the known nugget growth curve of the first weld. Furthermore, the efficiency of the shunt current to ease some three-sheet stack-ups welding was shown experimentally, and the optimal weld-spacing to maximize the welding current range was estimated by the proposed model.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135612396","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}
Arc efficiencies of gas tungsten arc welding (GTAW) were measured using two different methods, liquid nitrogen calorimetry and water-cooled copper anode calorimetry, across a range of welding currents from 98 A to 302 A. Arc efficiencies determined with water-cooled copper anode calorimetry remained constant throughout the entire current range, while those measured with liquid nitrogen calorimetry exhibited a concave curve. A hypothesis was proposed to explain the changes in arc efficiency with varying welding currents. Accordingly, a decrease in arc efficiency at 149 A welding current was caused by reduced Joule heating due to increased electrical conduction from iron-vapor contamination in an arc. For welding currents above 227 A, a decrease in arc efficiency was attributed to increased penetration depth, leading to more uniform heating in the base metal beneath the arc column, thereby preventing heat conduction within the metal. Thereafter, the relationship between penetration depth and arc efficiency was experimentally confirmed. Comparing with the arc efficiency of gas metal arc welding (GMAW), it was found that the mechanism in which arc efficiency changes with welding current in GTAW was different from that in GMAW.
{"title":"水冷銅板及び液体窒素を用いたアーク溶接の熱効率測定と 影響を与える要因の考察","authors":"Shoji FUJIYAMA, Yuki ASAI, Hisaya KOMEN, Manabu TANAKA","doi":"10.2207/qjjws.41.248","DOIUrl":"https://doi.org/10.2207/qjjws.41.248","url":null,"abstract":"Arc efficiencies of gas tungsten arc welding (GTAW) were measured using two different methods, liquid nitrogen calorimetry and water-cooled copper anode calorimetry, across a range of welding currents from 98 A to 302 A. Arc efficiencies determined with water-cooled copper anode calorimetry remained constant throughout the entire current range, while those measured with liquid nitrogen calorimetry exhibited a concave curve. A hypothesis was proposed to explain the changes in arc efficiency with varying welding currents. Accordingly, a decrease in arc efficiency at 149 A welding current was caused by reduced Joule heating due to increased electrical conduction from iron-vapor contamination in an arc. For welding currents above 227 A, a decrease in arc efficiency was attributed to increased penetration depth, leading to more uniform heating in the base metal beneath the arc column, thereby preventing heat conduction within the metal. Thereafter, the relationship between penetration depth and arc efficiency was experimentally confirmed. Comparing with the arc efficiency of gas metal arc welding (GMAW), it was found that the mechanism in which arc efficiency changes with welding current in GTAW was different from that in GMAW.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135800429","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}
A simple technique of restraining fatigue crack growth utilizing wedge effects of corrosion products was newly proposed and experimentally tested. Crack growth restraining sheets with a high water content gel were manufactured by way of trial and applied to notched plate specimens of steel, and the efficacy of the sheets to restrain crack growth was evaluated by fatigue tests. In the fatigue tests, the crack growth restraining sheet was renewed at proper timing to maximize its performance. In order to find a local humid (or wet) corrosive environment, which is most suitable for the crack growth restraint by wedge effects of corrosion products on the crack surfaces, water components absorbed in the gel and effects of a cathode layer as promoting factors of the corrosive reaction were comparatively examined. As a result, it was found that all the proposed crack growth restraining sheets were effective and extend the failure life in the range of 2.1 ~ 9.6 times as compared with the bare base metal specimen. Especially, the efficacy of the gel sheets with 3% salt water and synthetic sea water was remarkable (4.1~9.6 times extension in failure life), and the cathode layer (copper-leaf tape) produced certain additional positive effects in those gel sheets. From fracture mechanical analyses with FE analyses, it was found that the crack restraining effect of the gel sheet greatly varies depending on the water gel content and the existence of cathode layer. In situ observations around the growing cracks and macro- and microscopic observations of the fracture surfaces were also performed for a comparative study between the different types of crack growth restraining sheets.
{"title":"Trial Manufacture and Performance Evaluation of Fatigue Crack Growth Restraining Sheets Using a High Water Content Gel","authors":"Ichihiko TAKAHASHI","doi":"10.2207/qjjws.41.289","DOIUrl":"https://doi.org/10.2207/qjjws.41.289","url":null,"abstract":"A simple technique of restraining fatigue crack growth utilizing wedge effects of corrosion products was newly proposed and experimentally tested. Crack growth restraining sheets with a high water content gel were manufactured by way of trial and applied to notched plate specimens of steel, and the efficacy of the sheets to restrain crack growth was evaluated by fatigue tests. In the fatigue tests, the crack growth restraining sheet was renewed at proper timing to maximize its performance. In order to find a local humid (or wet) corrosive environment, which is most suitable for the crack growth restraint by wedge effects of corrosion products on the crack surfaces, water components absorbed in the gel and effects of a cathode layer as promoting factors of the corrosive reaction were comparatively examined. As a result, it was found that all the proposed crack growth restraining sheets were effective and extend the failure life in the range of 2.1 ~ 9.6 times as compared with the bare base metal specimen. Especially, the efficacy of the gel sheets with 3% salt water and synthetic sea water was remarkable (4.1~9.6 times extension in failure life), and the cathode layer (copper-leaf tape) produced certain additional positive effects in those gel sheets. From fracture mechanical analyses with FE analyses, it was found that the crack restraining effect of the gel sheet greatly varies depending on the water gel content and the existence of cathode layer. In situ observations around the growing cracks and macro- and microscopic observations of the fracture surfaces were also performed for a comparative study between the different types of crack growth restraining sheets.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135611737","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}
Zr55Al10Ni5Cu30 metallic glass (bulk amorphous alloy) have unique properties such as highly resistant to corrosion, high strength and elastic deformation over whole deformation range, so that it is expected to be the next-generation machine materials. To develop further industrial applications, joining technology for the metallic glass is necessary. In this study, surface modification with Cu on Zr55Al10Ni5Cu30 metallic glass using laser cladding and the consequent solderability improvement were studied. As a result, the interface between Cu thin film and Zr55Al10Ni5Cu30 metallic glass were continuously welded by the laser cladding. XRD showed that there are no crystalline and reaction layer in the weld interface. Furthermore, it was found, by XPS, that the Cu modified layer on the Zr55Al10Ni5Cu30 metallic glass surface inhibited the formation of a strong oxide film. Consequently, the Cu modified layer played an important role in improving the solderability to the Zr55Al10Ni5Cu30 metallic glass.
{"title":"レーザクラッディングによるZr基金属ガラスのCu表面改質と はんだぬれ性の改善","authors":"Takeshi TERAJIMA, Kazuki SHINSHI","doi":"10.2207/qjjws.41.257","DOIUrl":"https://doi.org/10.2207/qjjws.41.257","url":null,"abstract":"Zr55Al10Ni5Cu30 metallic glass (bulk amorphous alloy) have unique properties such as highly resistant to corrosion, high strength and elastic deformation over whole deformation range, so that it is expected to be the next-generation machine materials. To develop further industrial applications, joining technology for the metallic glass is necessary. In this study, surface modification with Cu on Zr55Al10Ni5Cu30 metallic glass using laser cladding and the consequent solderability improvement were studied. As a result, the interface between Cu thin film and Zr55Al10Ni5Cu30 metallic glass were continuously welded by the laser cladding. XRD showed that there are no crystalline and reaction layer in the weld interface. Furthermore, it was found, by XPS, that the Cu modified layer on the Zr55Al10Ni5Cu30 metallic glass surface inhibited the formation of a strong oxide film. Consequently, the Cu modified layer played an important role in improving the solderability to the Zr55Al10Ni5Cu30 metallic glass.","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135611739","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":"Quality Assurance and Quality Management","authors":"H. Harasawa","doi":"10.2207/jjws.81.434","DOIUrl":"https://doi.org/10.2207/jjws.81.434","url":null,"abstract":"","PeriodicalId":20941,"journal":{"name":"Quarterly Journal of The Japan Welding Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80964830","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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