{"created":"2023-06-19T12:44:56.803150+00:00","id":4573,"links":{},"metadata":{"_buckets":{"deposit":"a7cb2cad-650f-4462-8681-b4d9fed9d760"},"_deposit":{"created_by":3,"id":"4573","owners":[3],"pid":{"revision_id":0,"type":"depid","value":"4573"},"status":"published"},"_oai":{"id":"oai:tokyo-metro-u.repo.nii.ac.jp:00004573","sets":["1647:623:625:1189:1192"]},"author_link":["15363","15364"],"control_number":"4573","item_2_alternative_title_19":{"attribute_name":"その他のタイトル","attribute_value_mlt":[{"subitem_alternative_title":"通電加熱を用いたマイクロ塑性加工における純チタン箔材の変形特性に関する研究"}]},"item_2_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"2015-09-30","bibliographicIssueDateType":"Issued"}}]},"item_2_creator_2":{"attribute_name":"著者(ヨミ)","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"チェン, チウ"}],"nameIdentifiers":[{"nameIdentifier":"15364","nameIdentifierScheme":"WEKO"}]}]},"item_2_date_granted_66":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2015-09-30"}]},"item_2_degree_grantor_64":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"首都大学東京"}]}]},"item_2_degree_name_63":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（工学）"}]},"item_2_description_4":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"As the tendency of miniaturization, microparts are widely used in micro-electromechanical systems (MEMS) such as micro springs for electronics, tweezers for surgery, and micro gears in wristwatch. Pure titanium (Ti) is often used for the manufacture of microparts in biomedical devices and implants because of its light weight, biocompatibility, and outstanding corrosion resistance. Due to its high productivity, near-net-shape, and good properties of the formed products, microforming has been received much attention in the manufacture of microparts. However, the material flow becomes inhomogeneous and the process is unpredictable when scaling down the size of the products. In addition, the conventional plastic theory such as material properties cannot be used directly for the manufacture of microparts due to the occurrence of size effects in microforming. Heat assisted microforming is an effective way to reduce size effects in microforming process. Moreover, resistance heating (RH) method is an effective approach to improve the heating rate and reduce the consumption of energy. By conducting microbending process assisted by RH, the springback was found to decrease with increasing temperature. Even though microforming processes, such as micro deep drawing and microbending, were conducted with pure Ti foils at elevated temperatures by RH method, the mechanical properties of thin pure Ti foils at elevated temperatures and the size effects of heat on the mechanical properties are not clarified yet. In addition, the mechanism of springback behavior for thin foils bended at elevated temperatures and the size effects of heat on the springback are also not clear. These unclear fields make the design of RH-assisted microforming process difficult. Within the above background, this study aims to clarify the mechanism of material deformation of thin pure Ti foils at elevated temperatures and to contribute to the design of RH-assisted microforming process. To achieve this, a tensile testing system assisted by RH is first developed to investigate the tensile properties of thin pure Ti foils and to investigate the size effects of heat on the tensile properties. Then microbending tests assisted by RH are conducted to clarify the mechanism of springback behavior of the foils and to investigate the size effects of heat on the springback. To contribute to the prediction of springback, the analysis of springback of the foils is conducted by using the obtained material properties. A new theoretical model is proposed to predict the springback angles of thinner foils bent at elevated temperatures. In addition, the influence of temperature distribution on material deformation in microforming assisted by RH is investigated by commercial software ABAQUS to contribute to the design of the process. It is found that temperature has more influence on the foils with larger grain size. Compared with thick foils, the less springback of thinner foils observed at elevated temperatures indicates better accuracy of the products. The predicted springback angles by theoretical analysis using the proposed model show a good agreement with experimental results, which confirms the feasibility of the new model. Moreover, the design and optimization of temperature distribution can be realized by numerical analysis using ABAQUS. Being composed of six chapters, the introduction and research advances of this study are summarized below. Chapter 1 introduces the background of microforming and reviews its status of research achievements. Based on the issues in microforming, the motivation and objectives of this study are stated. Chapter 2 investigates the material properties of thin pure Ti foils at different temperatures. A tensile testing system assisted by RH is newly developed. The relatively uniform temperature distribution obtained along the gage length of the specimen confirms the feasibility of this system for performing tensile tests on thin metal foils. To investigate the material properties of thin pure Ti foils with different thickness of 0.02, 0.05, and 0.1 mm, uniaxial tensile tests are carried out at different temperatures by using the developed system. Relationships among strain hardening, strain rate sensitivity, and electric current density (ECD) are described. The size effects of heat on material properties are investigated by the tensile tests using the foils with different grain sizes. Chapter 3 investigates the springback behavior of thin pure Ti foils after bending at elevated temperatures. From the results, the springback angle is found to decrease as temperature increases, which indicates better accuracy of the products deformed at elevated temperatures. In the scaled microbending tests by using the same hardness pure Ti foils with various thickness, it is found that the springback angle increases with decreasing foil thickness at room temperature, while at the temperature of 573 K or higher, the springback is found to decrease with decreasing foil thickness. To clarify the mechanism of springback, nanoindentation tests are conducted. The more influence of surface area during bending at elevated temperatures is suggested to be the reason for the more decrease in springback of thinner foils. To investigate the grain size effects of heat on the springback, microbending tests are performed by using annealed foils with different grain sizes. The springback angle is found to decrease with increasing grain size, and the reduction of springback angle shows the tendency increases with increasing grain size. The mechanism and size effects of heat on springback behavior are discussed. Chapter 4 conducts the numerical and theoretical analyses of the springback behavior of thin pure Ti foils in RH-assisted microbending. Finite element (FE) models for the numerical analysis of microbending process assisted by RH are developed with commercial software ABAQUS. The calculated springback angles by numerical analysis for the same hardness foils with different thickness show a good agreement with the experimental results for 0.1 mm-thick foils, while a more decrease in springback angle from experiments at elevated temperatures is observed for the foils with thickness of 0.02 and 0.05 mm. To predict the springback angles for thinner foils, a new theoretical model that the surface area increases with increasing temperature is proposed. The calculated springback angles by using the proposed model for the same hardness foils with thickness of 0.02 and 0.05 mm show good agreement with experimental results, which verified the proposed model for the prediction of springback angles in microbending assisted by RH. To discuss the influence of strain gradient on the springback, a composite constitutive model involving statistically stored dislocation (SSD) and geometrically necessary dislocation (GND) is established. The strain gradient induced in microbending influences the springback of the foils significantly at low temperatures, while the size effect caused by strain gradient decreases with increasing temperature due to the more homogeneous material flow. The advantage of improving the accuracy of the products by conducting microforming process with the assistance of RH method is confirmed. Chapter 5 investigates the influence of temperature distribution on material deformation in microforming process assisted by RH. To realize the design of RH-assisted microforming process with thin pure Ti foils, the information of temperature distribution and the influence of temperature distribution on material deformation behavior are required. To obtain this information, FE models for the numerical analysis of micro drawing process assisted by RH are developed with ABAQUS. It is found that the temperature distribution of the blank is caused not only by the difference in ECD of the foils, but also by the heat transfer from the material to the tools. The design and optimization of the shape of the blank and the contact positions between the blank and electrodes are realized to control the temperature distribution of the blank by using the developed FE models. The influence of temperature distribution on material deformation can be obtained successfully from the numerical analysis. The formability of the material can be improved by obtaining more uniform temperature distribution. Chapter 6 summarizes the whole thesis. The innovation and contribution of this study is presented. The remaining problems and future works are suggested.","subitem_description_type":"Abstract"}]},"item_2_description_5":{"attribute_name":"内容記述","attribute_value_mlt":[{"subitem_description":"首都大学東京, 2015-09-30, 博士（工学）","subitem_description_type":"Other"}]},"item_2_dissertation_number_67":{"attribute_name":"学位授与番号","attribute_value_mlt":[{"subitem_dissertationnumber":"甲第604号"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"鄭, 秋"}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-08-05"}],"displaytype":"detail","filename":"Zheng_Qiu_comments.pdf","filesize":[{"value":"132.3 kB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"Zheng_Qiu_comments.pdf","url":"https://tokyo-metro-u.repo.nii.ac.jp/record/4573/files/Zheng_Qiu_comments.pdf"},"version_id":"9a906cef-741a-4ba6-9424-8ec0ca4a9dca"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-08-05"}],"displaytype":"detail","filename":"Zheng_Qiu_abstract.pdf","filesize":[{"value":"109.2 kB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"Zheng_Qiu_abstract.pdf","url":"https://tokyo-metro-u.repo.nii.ac.jp/record/4573/files/Zheng_Qiu_abstract.pdf"},"version_id":"2209f08a-029b-4930-8323-c0ac232a8280"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Investigation on Material Deformation Behavior of Thin Pure Titanium Foils in Microforming Assisted by Resistance Heating","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Investigation on Material Deformation Behavior of Thin Pure Titanium Foils in Microforming Assisted by Resistance Heating","subitem_title_language":"en"}]},"item_type_id":"2","owner":"3","path":["1192"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2016-07-04"},"publish_date":"2016-07-04","publish_status":"0","recid":"4573","relation_version_is_last":true,"title":["Investigation on Material Deformation Behavior of Thin Pure Titanium Foils in Microforming Assisted by Resistance Heating"],"weko_creator_id":"3","weko_shared_id":-1},"updated":"2023-08-15T02:02:40.397135+00:00"}