研究者詳細 - 楢原　弘之

論文 - 楢原　弘之

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Simplified Prediction of Melt Pool Shape in Metal Additive Manufacturing Using Maraging Steel 査読有り国際誌

T. Fukunaga , H. Narahara

International Journal of Automation Technology ( 富士技術出版株式会社 ) 16 ( 5 ) 609 - 614 2022年09月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

This paper describes a method to represent and predict the melting and solidifying shape of metal powder materials in the selective laser melting (SLM) method of metal addition manufacturing using a small number of physical properties. This is a processing method to complete a three-dimensional modeling object by layer-by-layer stacking. A laser beam is used to create objects with minimal voids and distortion by appropriately setting the scanning speed, output intensity, spot diameter, hatch spacing, and other conditions. Repeating actual experiments to determine the optimal build conditions increases the cost of operating the machine, such as electricity and labor, and the cost of materials when a modeling failure occurs. In recent years, attempts have been made to determine the optimal build conditions by analyzing the melting and solidification phenomena of metallic materials through precise simulations. However, it is necessary to set many physical property values as the parameters. Many physical property values are difficult to measure, and if these values are incorrect, the analysis results can differ significantly. In this study, a theoretical model for predicting the cross-sectional area and cross-sectional thickness of the melt pool using a single-track laser was developed using a small number of physical properties, such as melting point, thermal conductivity, and latent heat. To further examine the validity of the theoretical model, experiments were conducted for comparison purposes. In this experiment, 5 × 1 × 1 mm rectangular specimens were stacked and fabricated by a metal additive manufacturing machine using different laser beam irradiation conditions. The fabricated samples were cut, polished, and etched with nital, and the melt pool shapes were measured. Finally, experimental and theoretical values were compared to confirm the validity of the constructed theoretical model. This indicates that the proposed model can predict the melt pool shape.

DOI： 10.20965/ijat.2022.p0609

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Improvement in the permeability characteristics of injection mold fabricated by additive manufacturing and irradiated by electron beams 査読有り国際誌

Koresawa H., Fujimaru H., Narahara H.

International Journal of Automation Technology ( 富士技術出版株式会社 ) 11 ( 1 ) 97 - 103 2017年01月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017, Fuji Technology Press. All rights reserved.This paper describes a metal mold with permeability fabricated by metal laser sintering with high-speed milling, which is an additive manufacturing method, and discusses the improvement in permeability. In this method, the sintered body is produced with gas exhaust tubes based on the porous structure. To maintain permeability, ensuring that the gas exhaust tube is not blocked is essential. Blockages may occur because of reasons such as the deformation of the gas exhaust tube due to the milling process during fabrication and generation of mold deposits within the gas exhaust tube during injection molding. In this research, by irradiating the surface of a sintered body, with a gas exhaust tube, by an electron beam, water repellency attributed to the reduction in surface free energy and recovery of permeability are confirmed. Further, in a fundamental experiment with an injection molding machine, the permeability of a permeable sintered body irradiated an electron beam increased by approximately 2.8 times as compared to the permeability of a sintered body that was not irradiated.

DOI： 10.20965/ijat.2017.p0097

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Improvement and Evaluation of the Interlaminar Bonding Strength of FDM Parts by Atmospheric-Pressure Plasma 査読有り国際誌

Narahara H., Shirahama Y., Koresawa H.

Procedia CIRP 42 754 - 759 2016年01月

担当区分：筆頭著者,　最終著者,　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）

© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.Additive Manufacturing has the feature that the on-demand manufacture of the arbitrary shape can be performed. However, as one of weak points, interlaminar bonding strength is low. It is because the building principle is based on lamination. This research aims at improvement in the adhesive strength between laminations by performing hydrophilization treatment to the lamination plane of a FDM parts using atmospheric pressure plasma. Atmospheric-pressure plasma is characterized by generating glow-discharge condition under an atmospheric pressure. It can use for surface treatment etc. using active species (radical ion, an electron, etc.). For example, they are cleaning effects, such as soil removal of an organic substance, an effect to the roughened surface for forming unevenness in the surface, etc. Although a tensile test is usually performed on evaluation of adhesive strength, a lot of hours are needed for experimental preparation. The surface free energy of an object surface is effective as one of the evaluation indices for evaluating the adhesive strength of a lamination plane. However, in order to find an experimental condition in research initial stages, such as material search and manufacturing conditions, it can become effective in respect of an hour and cost to use surface free energy as an evaluation index. In this paper, the effect to the surface free energy by atmospheric pressure plasma is investigated first. And the influence on the rupture strength improvement by atmospheric pressure plasma is investigated. Next, it is searched for the effective irradiation conditions of atmospheric pressure plasma. The influence of the atmospheric pressure plasma to the building parts of FDM was experimented based on surface free energy. The rupture test was done and improvement in rupture stress was confirmed by plasma irradiation. The result that the irradiation range and irradiation distance of an atmospheric-pressure-plasma head had large influence on the increase in surface free energy was obtained. It was observed that surface free energy increases about 75% to an initial sample by irradiation of atmospheric pressure plasma.

DOI： 10.1016/j.procir.2016.02.314

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Low-energy injection molding process by a mold with permeability fabricated by additive manufacturing 査読有り

Koresawa H., Tanaka K., Narahara H.

International Journal of Automation Technology 10 ( 1 ) 101 - 105 2016年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016, Fuji Technology Press. All rights reserved.This paper describes the improvement of flow length and realization of low-energy molding in the injection molding process, by focusing on the injection mold with permeability fabricated by additive manufacturing. The mold is equipped with a sintered body with permeability, which is used as a mold insert. The inside of the sintered mold insert is structured so that the permeability should not be degraded, even if the thickness is increased. With respect to the effect of the sintered mold insert with permeability, the flow length and low-energy molding are evaluated by the filling rate of a thin section of moldings, and the electric energy of the injection molding machine that drives the screw in the injection process. Through fundamental experiments, the mold using the sintered mold insert with permeability was found to improve the flow length. The electric energy of the injection molding machine in the injection process is reduced by 6%–13% compared with the sintered mold insert without permeability.

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Permeability performance on porous structure of injection mold fabricated by metal laser sintering combined with high speed milling 査読有り国際誌

Narahara H., Takeshita S., Fukumaru H., Koresawa H., Suzuki H.

International Journal of Automation Technology 6 ( 5 ) 576 - 583 2012年09月

担当区分：筆頭著者,　最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Metal Laser Sintering Combined with High Speed Milling is the technology in which high speed cutting is united with the selective laser sintering process. By changing the conditions of laser beam irradiation, it is possible to build a sintered porous media which has a hole in an arbitrary part by this process. If the mold tool of this structure is used for injection molding, it is proved that the compressed air imprisoned in the mold and the gas coming out of resin are discharged from it, poor molding can be reduced. However, as sintered porous media is hard to control for the size and position of an ordered macroporous structure, it is difficult to build porous media with an ordered macroporous structure deliberately. This results in a smaller amount of airflow and a greater variation in airflow. In order to solve this problem, latticework is proposed as a new gas permeable structure in this paper. Different from a lower density sintered structure, metallic powder is sintered and fused using a laser beam with a high energy density, and fusion is carried out into the latticework structure. The fused gaps of the structure serve as a hole. Since each hole will keep the position and become the ordered macroporous structure even if lamination continues, the improvement in performance of gas permeability is expected. The airflow equation for the structural design to satisfy a required airflow rate is also examined in this paper.

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Reaction Heat Effects on Initial Linear Shrinkage and Deformation in Stereolithography 査読有り国際誌

Hiroyuki Narahara,Fumiki Tanaka(Hokkaido Univ.),Takeshi Kishinami(Hokkaido Univ.),Satoru Igarashi(Hokkaido Univ.),Katsumasa Saito(Gunma Polytech College)

Rapid Prototyping Journal 5 ( 3 ) 120 - 128 1999年04月

除去時のひずみエネルギーに基づいた金属積層造形サポート形状の研究

佐藤凜太郎, 楢原弘之, 是澤宏之

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2024S ( 0 ) 525 - 526 2024年02月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

金属積層造形では造形時、造形物の放熱促進や変形抑制のためサポートが用いられる。造形後、造形物からサポートを除去する必要があるが金属製のため除去が容易でないことが課題である。サポート無しで造形をする研究も行われているが造形できる形状がまだ限定される。本研究では亀裂解析のシミュレーションによるパラメータ設計で造形物の変形を抑制しつつ、除去しやすいサポート形状をひずみエネルギーに基づいて検討する。

DOI： 10.11522/pscjspe.2024s.0_525

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金属積層造形における造形環境が造形品質に与える影響

郭笑蕾, 楢原弘之, 是澤宏之

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2024S ( 0 ) 527 - 528 2024年02月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

近年，金属積層造形法は革新な技術として注目され，幅広く応用されている．造形する際にレーザー光で局所的に急激な温度変化を繰り返すため，熱ひずみが発生し，熱変形の抑制は金属積層造形における重要な課題の一つとなる．本研究は金属積層造形の造形品質を向上させるため，造形環境を研究対象とする．造形室内の雰囲気ガスなどの条件を考慮した造形実験を行い，造形環境の違いによる造形物の変形に与える影響について調べる．

DOI： 10.11522/pscjspe.2024s.0_527

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射出成形金型の変形に伴う成形不良に関する研究

道平和樹, 石井将規, 是澤宏之, 楢原弘之, 村上直

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2024S ( 0 ) 201 - 202 2024年02月

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）

射出成形法で用いる金型は弾性体であるため，樹脂による大きな圧力で変形が生じる．この変形挙動は未解明であるとともに，様々な成形不良が生じている．本報では，樹脂圧力により金型分割面が変形し間隙が生じることによって発生する成形不良に着目する．よって成形機を含めた構造解析等により金型変形について検討した．

DOI： 10.11522/pscjspe.2024s.0_201

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Effect of Processing Conditions on Mechanical Properties of Snap-Fit with Different Aspect Ratios Fabricated by FDM 査読有り

Taguchi H., Kunimatsu Y., Narahara H.

Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering ( 公益社団法人精密工学会 ) 90 ( 4 ) 376 - 382 2024年01月

担当区分：最終著者記述言語：日本語掲載種別：研究論文（学術雑誌）

Snap-fit is one of the most important joining methods for plastic products. Since the function and performance of snap-fit often require sensitivity evaluation, prototyping befbre mass production is important. FDM is one of Additive Manufacturing, and FDM is considered to be suitable for snap-fit prototyping. On the other hand, since the mechanical properties of FDM vary depending on the processing conditions, it is important to verify the relationship between the processing conditions and snap-fit mechanical properties. In addition, in recent years, plastic products have become smaller in some areas. In the case of cantilever-type snap-fit, it is necessary to evaluate the effect of shear deformation as the aspect ratio decreases. In this study, the effect of processing conditions on mechanical properties of snap-fit with different aspect ratios fabricated by FDM were investigated.

DOI： 10.2493/jjspe.90.376

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造形姿勢変更による金属積層造形品の変形の定量評価

郭笑蕾, 坂本燎瑚, 楢原弘之, 是澤宏之

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2023A ( 0 ) 647 - 648 2023年08月

担当区分：最終著者,　責任著者記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

本研究は金属積層造形における造形姿勢の変更により、造形品の変形の定量評価を行う。先行研究によって、4種類の造形姿勢及び3種類のサポート密度を造形条件とし、2つの実験を分別に実施し、造形品の変形量を測定した。本研究は先行研究から得られた結果の信頼性を検証するため、上記挙げる条件を組み合わせ、計12組の実験を行い、変形の定量評価を通じて造形品変形量の並べ替えと最小変形量を見出す。

DOI： 10.11522/pscjspe.2023a.0_647

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射出成形金型の成形中の変形挙動に関する研究

道平和樹, 是澤宏之, 楢原弘之, 村上直

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2023A ( 0 ) 721 - 722 2023年08月

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）

射出成形法で用いる金型は弾性体であるため，成形中に樹脂による大きな圧力で変形が生じる．しかし，この変形挙動を詳しく解明できていない．よって様々な成形不良が生じている．本報ではその中でバリという成形不良に着目する．バリは樹脂圧力により金型分割面に間隙が生じることが一つの原因である．よって射出成形機の変形も考慮した構造解析を用いて金型分割面に生じる間隙を求め，検討した．

DOI： 10.11522/pscjspe.2023a.0_721

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AMで作成したスナップフィット部品曲げ試験時の積層パターン影響調査

國松遙平, 楢原弘之, 是澤宏之, 田口宏之

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2023A ( 0 ) 654 - 655 2023年08月

担当区分：最終著者記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

スナップフィットとは、接合時梁部分がたわみ、材料の弾性を利用して元の形状に戻り、接合する方法である。これは環境に配慮した方法であり、様々な用途で使われる。私の研究では、AM品をスナップフィット部品の試作品として実用化することを最終目標としている。しかし、AMで作成時、積層パターンによってたわみ量が変動すると考えられる。そこで本研究では、曲げ試験を行い積層パターンがたわみ量に及ぼす影響を調査した。

DOI： 10.11522/pscjspe.2023a.0_654

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Effect of FDM Processing Conditions on Snap-Fit Characteristic in Assembly 査読有り

Taguchi H., Kunimatsu Y., Narahara H.

International Journal of Automation Technology ( 富士技術出版株式会社 ) 17 ( 4 ) 326 - 334 2023年07月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Snap-fit allows plastic products to have assembly and disassembly capabilities without the use of screws, bolts, or other additional parts. For this reason, snap-fit is used in all kinds of plastic products from stationery to automotive parts. Because the mechanical and other functions of a snap-fit are greatly affected by its shape and material properties, it is desirable to fully evaluate them at the design stage. In addition, as the assembly and disassembly of products by snap-fit is generally performed by people, it is important to evaluate not only virtually but also with actual plastic parts. Therefore, there is a strong need to make a prototype and evaluate the feel of the product during assembling and disassembling, before finalizing on the shape and materials. In the past, making precise prototype required expensive molds, but in recent years, additive manufacturing has made it possible to make prototype efficiently and at low cost. In additive manu-facturing, fused deposition modeling (FDM) is consid-ered suitable for snap-fit prototype because it can use the same materials as mass-produced products. Thus, it may be possible to make a snap-fit prototype with rigidity, strength, and other characteristics similar to those of mass-produced products. However, FDM has various processing conditions such as tool path, noz-zle temperature, and height of one layer. They are ex-pected to have a significant effect on the snap-fit char-acteristics. Snap-fit is required to meet various re-quirements depending on the plastic products. The re-quirements can be divided into three major categories: in assembly, in disassembly, and when to use. In this study, we investigated the effect of FDM processing conditions on snap-fit characteristic in assembly.

DOI： 10.20965/ijat.2023.p0326

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Tool condition monitoring method by anomaly segmentation of time-frequency images using acoustic emission in small hole drilling 査読有り

Nakano T., Koresawa H., Narahara H.

Journal of Advanced Mechanical Design, Systems and Manufacturing ( 一般社団法人日本機械学会 ) 17 ( 3 ) JAMDSM0034 - JAMDSM0034 2023年06月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Tool wear leads to a reduction in dimensional accuracy and surface quality, as well as unexpected sudden tool failure. A broken tool can cause irreparable damage to an expensive workpiece, resulting in increased operating costs and production delays. Since the mechanical strength of small-diameter drills is inadequate for the load and prone to breakage, tool condition monitoring and diagnosis is important to prevent sudden tool breakage, increase productivity, and promote automation in machining process. The present work is aimed to investigate a tool condition monitoring method based on the analysis of acoustic emission (AE) signals emitted during small-hole drilling. We propose DDM (Deep feature Distribution Modeling), a method for image-level anomaly detection and anomaly segmentation in time-series signal analysis. The peck drilling experiments on SKD61 steels were performed with high-speed steel (HSS) drills. The continuous wavelet transform (CWT) was applied to generate time-frequency (TF) image of the AE signals during the drilling process. The TF images were quantified as anomaly scores using the DDM, which establishes normality by fitting a multivariate Gaussian (MVG) to pre-trained deep features. The anomaly detection capability of the DDM and the convolutional autoencoder (CAE) was compared using dummy data for validation. The digital microscope was employed to measure tool wear. Chip morphology was also observed by the laser microscopy. As the tool wear progressed, the anomaly score increased or decreased, with several sharp increases observed between holes 3805 and 3869 just prior to tool failure. An increase in the width of the shear layer spacing of the chips was also observed just prior to failure. Changes in the anomaly score associated with tool wear were more clearly identified by creating anomaly maps. The present investigation shows that waveform processing of AE signals using the CWT and anomaly detection based on the DDM are efficient methods for tool condition monitoring. Our proposed approach makes it possible to visualize the differences in anomaly states using a more subdivided layer context by generating multiple anomaly maps with deep feature vectors obtained from multiple layers.

DOI： 10.1299/jamdsm.2023jamdsm0034

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熱溶解積層法用フィラメントの強度向上に関する基礎研究

日高明, 是澤宏之, 楢原弘之

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2023S ( 0 ) 226 - 227 2023年03月

Preface 査読有り国際誌

NARAHARA Hiroyuki, TANAKA Ryutaro

Journal of Advanced Mechanical Design, Systems, and Manufacturing ( 一般社団法人日本機械学会 ) 17 ( 1 ) JAMDSM0001 - JAMDSM0001 2023年01月

Magnetic Domain Observation of Milled Nanocrystalline Alloy Powder 査読有り

Takezawa M., Nagaki T., Motozuka S., Sasaki I., Ando Y., Narahara H., Mori N., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T.

IEEE Transactions on Magnetics 59 ( 11 ) 2023年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Fe-based nanocrystalline alloys have high magnetic flux density and low loss. Therefore, in this study, the magnetic domain structure of the ball-milled magnetic powders of these nanocrystalline alloys was observed using a Kerr effect microscope. The effect of strain removal heat treatment on the magnetic properties of the powder was also investigated by observing and comparing the magnetic domain structure of the milled powder before and after heat treatment during the preparation process of the nanocrystalline-milled powder. Our findings showed that the strain removal heat treatment changed the size and shape of the magnetic domains to a simple structure. In addition, the domain wall motion was found to be sensitive to the magnetic field, resulting in soft magnetic properties.

DOI： 10.1109/TMAG.2023.3283211

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Microstructure and Magnetic Characterization on Ball-Milled Fe-Based Nanocrystalline Alloy Sheet 査読有り国際誌

Nagata S., Horibe Y., Hiramoto S., Narahara H., Mori N., Sasaki I., Takezawa M., Ando Y., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T., Motozuka S.

Digests of the Intermag Conference 2023-May 2023年01月

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 this work, ball-milled iron (Fe)-based nanocrystalline alloy sheets and obtaining platelet particles are used to effectively utilize the end material and apply it to a soft magnetic composite. The instrumental analysis results reveal that, although a microstrain is introduced into the nanocrystalline α-Fe grains in the achieved alloy powder, the amorphous part filled among the grains experiences almost no change. The ball-milling treatment greatly increases the coercive force of the pulverized nanocrystalline sheet. Although the coercive force of the alloy powder decreases after the heat treatment, it remained approximately 10 times higher than that of the heat-Treated alloy sheet without the ball-milling treatment, even after the heat treatment. The magnetic process of the ball-milled and post-Annealed nanocrystalline alloy powder is discussed based on the results of the synchrotron radiation X-ray analysis and transmission electron microscopy with the Lorentz technique.

DOI： 10.1109/INTERMAG50591.2023.10265082

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Microstructure and Magnetic Characterization on Ball-milled Fe-based Nanocrystalline Alloy Sheet 査読有り国際誌

Nagata S., Horibe Y., Hiramoto S., Narahara H., Mori N., Sasaki I., Takezawa M., Ando Y., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T., Motozuka S.

2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings 2023年01月

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）

To realize the effective utilization of the end material and its application to a soft magnetic composite, Fe-based nanocrystalline alloy sheets were ball-milled, and platelet particles were obtained, in this work. Instrumental analyses revealed that although a micro strain was introduced into the nanocrystalline α-Fe grains in the achieved alloy powder, almost no changes were found in the amorphous part filled among the grains. The ball-milling treatment greatly increased the coercive force of the pulverized nanocrystalline sheet. Although the coercive force of the alloy powder decreased after the heat treatment, the coercive force remained to be approximately 10 times higher than that of the heat-treated alloy sheet without the ball-milling treatment, even after the heat treatment. The magnetic process of the ball-milled and heat treated nanocrystalline alloy powder will be discussed in detail in the conference based on the obtained results and Lorentz transmission electron microscopy.

DOI： 10.1109/INTERMAGShortPapers58606.2023.10228768

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