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SEKIGUCHI Yasuhisa

    Department of Mechanical Engineering　Professor/Manager
Last Updated :2024/05/19

Researcher Information

Research funding number

  • 60226644

J-Global ID

Research Interests

  • 機械力学   

Academic & Professional Experience

  • 2019/04 - Today  Kindai UniversityFaculty of Engineering教授
  • 2007/04 - 2019/03  Hiroshima UniversityGraduate School of Engineering准教授
  • 2006/09 - 2007/03  Hiroshima UniversityGraduate School of Engineering助教授
  • 1990/04 - 2006/08  Hiroshima UniversityFaculty of Engineering助手

Education

  • 1986/04 - 1988/03  Kobe University  Graduate School, Division of Engineering  機械工学専攻
  • 1982/04 - 1986/03  Himeji Institute of Technology  工学部  機械工学科

Association Memberships

  • THE ADHESION SOCIETY OF JAPAN   日本設備管理学会   SOCIETY OF AUTOMOTIVE ENGINEERS OF JAPAN   JAPAN SOCIETY FOR DESIGN ENGINEERING   THE JAPAN SOCIETY OF MECHANICAL ENGINEERS   

Published Papers

  • Finite Element Analysis of the Load Factor and New Design Method for Bolted Joints Consisting of Dissimilar Hollow Cylinders Under Tensile Loads
    Shunichiro Sawa, Yasuhisa Sekiguchi
    ASME Journal of Pressure Vessel Technology 144 (5) 1 - 13 2022/10 [Refereed]
  • Simplified prediction of stability limit for oil film bearing rotor systems
    Yasuhisa Sekiguchi; Ryutaro Matsuda; Masahiro Okami; Osami Matsushita
    Transactions of the Japan Society of Mechanical Engineers 86 (885) 1 - 15 2020/05 [Refereed]
     
    Oil film bearings are often used in large rotating machinery because they have large load capacity and damping coefficients. They, however, generate fluid forces and cause unstable vibrations such as oil whirl and oil whip at high rotational speed. Because the amplitudes of such self-excited vibrations are severe, it is important to predict the stability limit of rotational speed to avoid the unstable vibration problems in rotor systems supported by oil film bearings. This paper describes the vibration analyses of a flexible rotor system supported by oil film bearings and the simplified prediction method for the rotational speed limits of the self-excited vibration induced by the fluid force in oil film bearings. In the vibration analyses, the equations of motion for the rotor system are simplified and modeled as a two-degree-of-freedom system with parallel and flexural modes of vibration. The stability analyses are conducted by introducing the approximation equations instead of complex eigenvalue calculations. The rotational speed limits for the stability of the system obtained by the present method are compared with the calculation results in the references to discuss the validity of the present method. This paper also shows the importance of anisotropic properties of oil film bearings to increase the accuracy of stability prediction when the clearance of the oil film bearing is large.
  • 部材の断面積を考慮した配置最適化手法の大規模骨組み構造への適用
    村上英治; 河村幸太郎; 関口泰久; 澤俊行
    日本機械学会論文集 85 (873) 1 - 13 2019/05 [Refereed]
  • Yohanes; Y. Sekiguchi
    Journal of Dynamic Behavior of Materials Springer International Publishing 4 (2) 190 - 200 2199-7454 2018/06 [Refereed]
     
    Dynamic stiffness and damping of epoxy adhesives are critical for ensuring the safety, reliability, and comfort of structures subjected to vibrations and impact loads. This study conducts split Hopkinson pressure bar (SHPB) tests to investigate the synergistic effects of silica micro-nanoparticles on these critical properties. Micro-nanoparticle content and composition ratio purity are varied at 2, 5, and 10% by weight (wt%) and from 0% (pure microparticles) to 100% (pure nanoparticles), respectively. Positive simultaneous stiffening and energy absorption effects are observed at a silica content of 5 wt% owing to improved nanoparticle dispersion this increases the interface area and induces cooperative matrix–filler interactions. At this silica content and a composition ratio of 50%, stiffness and damping are 45 and 40% larger than those of neat epoxy, respectively. Silica micro-nanoparticles are less effective in improving particle dispersion at more than 5 wt%. Conventional mechanical dispersion is limited to applications below a certain silica content the results suggest a simple, low-cost dispersion technique as an alternative to the in-situ technique and provide options for designing epoxy stiffness and damping appropriate for specific applications.
  • Effects of mixed micro and nano silica particles on the dynamic compressive performances of epoxy adhesive
    Yohanes; Yasuhisa Sekiguchi
    Applied Adhesion Science 5 1 - 12 2017/02 [Refereed]
  • KOTAJIMA Kazunari; SEKIGUCHI Yasuhisa; SAWA Toshiyuki
    Journal of The Adhesion Society of Japan The Adhesion Society of Japan 51 (4) 105 - 115 0916-4812 2015/04 [Refereed]
     
    Stepped-lap adhesive joints with similar solid and hollow cylinder adherends under static bending moments are analyzed using 3-DFEM.The effects of adhesive Young's modulus, the adhesive thickness,scarf angle,and then umber of steps on the interface stress distributions are examined.The code of FEM employed is ANSYS.The maximum principal stress σ1 is singular at the outside edge of the interfaces for both of the similar solid cylinder and hollow cylinder joint,while,the value of σ1 is larger at the outside diameter than that at the inside diameter for the similar hollow cylinder joints. The value of σ1 decreases as the adhesive thickness decreases and as adhesive Young's modulus, the number of steps and the scarf angle increase. The bending moments when the joints rupture are predicted using the measured stress-strain curve of the adhesive.The predicted ruptured bending moments for the both joints are in a fairy good agreement with the measured results. It is found that the rupture dbending moment for similar solid cylinder joints is slightly larger than that for similar hollow cylinder joints.
  • Hiroko Nakano; Yuya Omiya; Yasuhisa Sekiguchi; Toshiyuki Sawa
    INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES ELSEVIER SCI LTD 54 40 - 50 0143-7496 2014/10 [Refereed]
     
    The interface stress distributions in scarf adhesive joints with similar adherends under static tensile loadings were analyzed using two-dimensional and three-dimensional finite element calculations for the two cases where adhesive length and width of the adherends were held constant. The effects of adhesive Young's modulus, the scarf angle and the adhesive thickness on the interface stress distributions were examined. In addition, the joint strength was predicted using the interface stress distributions based on the maximum principal stress theory and von Mises' stress criterion. It was found that when the scarf angle was around 60, the singular stress at the edges of the interfaces was minimal in the 3-dimensional FEM calculations while the singular stresses vanished at 52 in the 2-dimensional FEM calculations. The value of the normalized maximum principal stress at the edges of the interfaces obtained from the 3-D FEM was larger than that from the 2-D FEM. It was found that the maximum principal stress increased at the edge of the interfaces as the scarf angle decreased. In addition, the effect of the adherends where the width was held constant was demonstrated. Experiments to measure strain and joint strengths were carried out. The measured strains were in a fairly good agreement with those obtained from the 3-D FEM calculations. Also, the measured joint strengths were fairly consistent with the predicted results based on the maximum principal stress theory. As a result, the maximum joint strength was observed when the scarf angle was around 60. The difference in the interface stress distributions was demonstrated between the two cases. (C) 2014 Elsevier Ltd. All rights reserved.
  • Kazunari KOTAJIMA; Yasuhisa SEKIGUCHI; Yuya OMIYA; Toshiyuki SAWA
    Journal of The Adhesion Society of Japan The Adhesion Society of Japan 50 (1) 12 - 22 0916-4812 2014/01 [Refereed]
  • 静的曲げモーメントを受けるバンド接着されたスカーフ接着継手の三次元有限要素法応力解析と強度予測
    中野博子; 大宮祐也; 関口泰久; 沢俊行
    日本接着学会誌 49 (10) 370 - 380 2013/10 [Refereed]
  • 静的曲げモーメントを受ける異種材料被着体によるスカーフ接着継手の三次元有限要素法解析と強度と強度について
    中野博子; 大宮祐也; 関口泰久; 沢俊行
    日本接着学会誌 49 (9) 320 - 330 2013/09 [Refereed]
  • 静的引張り荷重を受けるバンド接着されたスカーフ接着継手の三次元有限要素法応力解析と強度予測
    中野博子; 大宮祐也; 関口泰久; 沢俊行; 朴文官
    日本接着学会誌 49 (8) 282 - 292 2013/08 [Refereed]
  • 静的引張り荷重を受ける異種材料被着体によるスカーフ接着継手の三次元有限要素法応力解析と強度について
    中野博子; 大宮祐也; 関口泰久; 沢俊行
    日本接着学会誌 49 (7) 249 - 259 2013/07 [Refereed]
  • FEM stress analysis and strength prediction of scarf adhesive joints under static bending moments
    Hiroko Nakano; Yuya Omiya; Yasuhisa Sekiguchi
    International Journal of Adhesion and Adhesives 44 166 - 173 2013/07 [Refereed]
  • 関口泰久; 兼重力; 里信 純; 中川紀壽
    Journal of the Society of Plant Engineers Japan 日本設備管理学会 19 (2) 53 - 59 0915-5023 2007/08 [Refereed]
  • Chaoqun Wu; Noritoshi Nakagawa; Yasuhisa Sekiguchi
    EXPERIMENTAL THERMAL AND FLUID SCIENCE ELSEVIER SCIENCE INC 31 (8) 1083 - 1089 0894-1777 2007/08 [Refereed]
     
    A cylindrical ultrasonic reactor radiated by a BLT (bolted Langevin transducer) with a large horn operated at 27.3 kHz was employed to investigate the behaviors of bubbles in the present research. The characteristics of this reactor were analyzed using experimental methods. It was found that traveling transient bubbles can eliminate the effect of standing wave on cleaning efficiency. Fresh tap water and degassed water were employed as test liquids. In tap water, a conical cavitation structure was observed as the input voltage of transducer was increased over 100 V. The detail of the conical cavitation structure was anatomized and its shape varied with the change of input voltage. In degassed water, ultrasonic fireworks were observed and special attention was paid to their subsequences, snowflake bubble clouds and water jet. (c) 2006 Elsevier Inc. All rights reserved.
  • 関口泰久; 板倉有吾; 里信純; 中川紀壽
    日本設備管理学会誌 日本設備管理学会 18 (2) 60 - 65 0915-5023 2006/08 [Refereed]
  • Analysis of Chaotic Behavior of Ball Bearing Vibration
    Yasuhisa Sekiguchi; Toshihiro Ogawa; Jun Satonobu; Noritoshi Nakagawa
    Journal of Japan Society for Design Engineering 41 (4) 54 - 59 2006/04 [Refereed]
     
    This paper describes a vibration analysis based on the chaos theory to diagnose ball bearings. First, experiments are carried out to obtain the time series of ball bearing vibration. Then, analyses of the vibration based on the chaos theory are carried out to detect the fault of the bearing. In the experiments, we test normal bearings and bearings with faults in various sizes on the outer race, the inner race, or the ball. In the analyses, the followings are used: (1) the attractor, (2) the recurrence plot, (3) Lyapunov exponent, and (4) the nonlinear prediction. As a result of this study, the chaotic behavior shows the difference between with and without faults. Therefore, we confirmed that the chaos theory was useful for the diagnosis of the ball bearing.
  • Sound Analysis and Diagnosis of Ball Bearing Based on Pattern Recognition Technique
    Yasuhisa Sekiguchi; Noritoshi Nakagawa
    Journal of Japan Society for Design Engineering 39 (4) 18 - 24 2004/04 [Refereed]
     
    This paper describes the fault detection of ball bearings based on sound information by using the pattern recognition technique. In the experiment, normal bearings and bearings with three kinds of faults were used: a fault on the inner race, the outer race, or the ball. First, the sound generated by each bearing was monitored with a microphone and the sound spectrum was obtained with an FFT analyzer. Second, the reference pattern for each fault was calculated by using the sound spectrum. Third, the diagnosing patterns were compared with the reference patterns to detect the faults of the bearings and to determine the kinds of faults. As a result of this study, by using the pattern recognition technique, we can diagnose the faults of ball bearings with more accuracy than by the standard sound spectral analysis.
  • Chaos Analysis and Diagnosis of Ball Bearing Vibration
    Yasuhisa Sekiguchi; Noritoshi Nakagawa; Hirokazu Yoshida; Naoyuki Saruwatari
    Journal of Japan Society for Design Engineering 39 (2) 46 - 53 2004/02 [Refereed]
     
    This paper describes a vibration analysis based on chaos theory to diagnose ball bearings. First, experiments are carried out to obtain the time series of ball bearing vibration. Then, analyses of the vibration based on the chaos theory are carried out to detect the fault of the bearing. In the experiments, we test normal bearings and bearings with faults in various sizes on the inner race, the outer race, or the ball. In the analyses, the following chaotic behavior and parameters are used for the diagnosis: (1) the attractor, (2) the correlation dimension, and (3) Lyapunov exponent. To describe the useful attractors for the diagnosis, we investigate the appropriate reconstruction time delay. We also investigate the correlation dimension of the bearing vibration with and without faults. Furthermore, Lyapunov exponent is calculated to diagnose and monitor bearing operating conditions. As a result of this study, we confirmed that the chaos theory was useful to diagnose the ball bearing vibration.

Conference Activities & Talks

  • Chaos time series vibration analyses of rolling element bearings for failure diagnosis  [Not invited]
    Kota Shimizu; Yasuhisa Sekiguchi
    日本機械学会中国四国支部第62期総会・講演会  2024/03
  • 滑り軸受で支持された回転機械の不安定振動のシミュレーション  [Not invited]
    日美勇人; 関口泰久
    日本機械学会中国四国支部 第61期総会・講演会  2023/03
  • 多孔板を有する吸引器の騒音振動解析  [Not invited]
    横山侑雅; 関口泰久
    日本設計工学会中国支部研究講演発表会  2021/06
  • 回転機械における軸受の振動診断  [Invited]
    関口泰久
    計測制御シンポジウム2020 「振動と騒音の計測と制御」  2020/09
  • 多孔壁ホーンを用いた管内共鳴音の低減  [Not invited]
    伏谷昂; 関口泰久
    日本機械学会 中国四国支部 第58期総会・講演会  2020/03
  • 回転機械の軸受に起因する振動の解析と異常診断  [Not invited]
    大上雅弘; 関口泰久
    日本機械学会 中国四国支部 第58期総会・講演会  2020/03

MISC

Awards & Honors

  • 2005/05 日本設計工学会 論文賞
     
    受賞者: 関口 泰久
  • 1986/03 日本機械学会 畠山賞
     
    受賞者: 関口 泰久

Research Grants & Projects

  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2022/04 -2025/03 
    Author : 関口 泰久
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2013/04 -2016/03 
    Author : Sekiguchi Yasuhisa
     
    The present research investigated bearing diagnoses based on chaos time series analyses. First, rolling fatigue tests were conducted to measure vibration and sound generated by rolling bearings during their lifetime. Then, obtained data were analyzed with chaos time series analyses for the bearing diagnoses. In the diagnoses, the largest Lyapunov exponent analysis and the trajectory parallel measure method were used to identify the change of data. Also, conventional methods, such as skewness, kurtosis, crest factor, and frequency spectra, were calculated for the comparison of diagnosis results. Finally, the effectiveness of chaos time series analyses was confirmed in the bearing diagnoses.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2000 -2001 
    Author : NAKAGAWA Noritoshi; HIGASHI Akihiko; SEKIGUCHI Yasuhisa
     
    The sound quality evaluation system is investigated under consideration of human auditory sense by loudness. The mechanical sounds collected from some kinds of machine are processed from the stand point of A-frequency weighting network, band level, and loudness. Each processed and reduced sound is compared by hearing investigators. The sound evaluation by using Zwicker's loudness is done by summing the 26 band levels. It was found that the sound processed by A-frequency weighting network is effective to sound in the range of low frequency, and the sound processed by loudness is effective to the higher frequency.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2000 -2001 
    Author : NAKAGAWA Noritoshi; ENOKI Yoshimi; HUJITA Etsunori; SEKIGUCHI Yasuhisa
     
    In recent years, accompanying the practical use of permanent magnets that have a high coercive force and high residual magnetic flux density, researches about magnetic bearings, MR dampers and so on, which use magnetic force and magnetic fluid to control vibration are flourishing. In this study, the spring characteristic, which is in a quasi-zero state under specific displacement range, has been created. This characteristic has been obtained by combing negative spring constant of metal spring withnon-linear characteristic of magnet-spring using a resisting force of magnet^<1)>. This magnet is made from rare-earth magnets (Nd-Fe-B) that have a high coercive force and high residual magnetic flux density. But, because this system needs large magnets and complicated mechanism of link, it has the point at issue of huger device, heat loss of link part and so on. So a magnet-circuit with a periodic magnetic field has been created to solve these points at issue^<2)>. In this system, the non-linear characteristics of a magnet-circuit with a periodic magnetic field and the linear characteristics of the metal spring are combined to create a spring characteristic which has linear characteristics when the spring constant is in a quasi-zero state under normal conditions of use, but which overall is a non-linear spring constant. In this paper, to expand the displacement range that the spring constant is in quasi-zero state, the circuit was improved by increasing pole of outside magnet. And a pendulum suspension system model using this characteristic (experimental model) was built, and the vibration characteristics of this model were confirmed.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1998 -1999 
    Author : 関口 泰久
     
    本研究では,複数個の音源が存在する音場内での,音源個数,音源表面の振動速度(音源音圧と同等),および音源位置の同時同定を行った.同定では,音場内に観測点として複数個のマイクロホンによりアレイを構成し,各観測点での音圧情報を基に,境界要素法による数値シミュレーションを用いて未知パラメータの計算を行った.その際には逆問題を解く方法として一般的に使用されているように,評価関数を設定し,最適化問題として逐次パラメータ更新を行うことで同定を進めた.評価関数には,観測点での測定音圧と,数値シミュレーションで仮想音源が作り出す観測点位置での音圧の差を用いた.したがって,実音源が作る観測点での音圧と,仮想音源が作る観測点での音圧の差が最小となるように,仮想音源の個数,振動速度,および位置を収束が得られるまで変化させることになる. 研究では,実音源が1〜5個の場合について,それらの個数と,ひとつひとつの音源の位置と振動速度の同時同定を行った.計算時には,音源個数が増え,同定パラメータが増加すると同定精度が著しく悪化することが観測された.そのために,観測点として用いる複数個のマイクロホンのうち,同定に適しているマイクロホンを自動的に選択しながら同定を進める.「観測点選択手法」を新たに提案し,同定精度を大きく向上した. また,予め位置がわかっている音源に対して,音源の振動周波数を変化させた場合に,各音源ごとに,かつ各周波数ごとに,音源の振動速度を求めることも成功した.これは,今後本研究成果の応用として位置づけている,リモート音響計測による機械の異常診断法の基礎として重要な成果が得られたと考えている.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1995 -1996 
    Author : NAKAGAWA Noritoshi; SEKIGUCHI Yasuhisa; IKEDA Takashi
     
    The colIision mechanism was investigated by characteristic evaluation of impact, vibration and sound as follows. 1.Experiment and analysis from the viewpoint of characteristic evaluation of impact The impact deformation of impacted body was measured by the high-speed camera to obtain the deformation characteristics. The restitution coefficient is obtained and the sweet-area which gives the high restitution coefficient was visualized. It was found that the sweet-area exists in the field near the grip part from the center of gravity of the racket. 2.Experiment and analysis from the viewpoint of characteristic evaluation of vibration The transient vibrations of the system subjected to the impulsive force are analyzed by the wavelet transformation method. It was found the changes of the response spectrum with time depend on the frequency. 3.Experiment and analysis from the viewpoint of characteristic evaluation of sound To investigate the characteristics of transient sound the changes of spectrum with time for three kinds of sound were analyzed. The sound quality was evaluated by the semantic differential method. The sound quality is discriminated with pure tone level. When the damping of the system becomes large, the vibration energy flow can be estimated with the sound energy flow.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1995 -1995 
    Author : 関口 泰久
     
    一般に機械による騒音問題は,騒音レベルの増減としてとらえられがちであるが,それだけにとどまらず,日常の生活において情報伝達を行う際の音響品質の低下や,個人の生活感情にそぐわない音の強制といったコミュニケーションを阻害する様々な状況を引き起こしている.また,音環境を考える上で重要な要素である人の耳の能力は,機械に置き換えることが困難な程優れていると言われているが,人の環境に対する関心の持ち方に大きく左右される. そこで本研究は,環境に応じて必要な音や,望ましい音の特徴を調べることを目的とする.具体的には,環境に対する音の相応性,空調機の室外機の音質分析,および対象音源の音質評価の3つの観点から研究を行った.まず,様々な環境に対する音の相応性をアンケートを通して調査し,どのような音が不快にあるいは心地よく聞こえるかを示し.つぎに,その結果を踏まえて,空調機の室外機騒音を例に取り,人の聴覚特性である臨界帯域幅を考慮した周波数分析を行い,因子分析法による音質評価と比較した.その結果,定常音の調和を調べる上で,臨界帯域幅を考慮した純音度レベルによる評価の有用性を示した. 今後さらにこの研究を発展させ,機械騒音の音質改善を行う際の指標となる評価方法を確立することを試みる.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1995 -1995 
    Author : 中川 紀寿; 藤川 猛; 小嶋 直哉; 関口 泰久; 池田 隆; 永村 和照
     
    音響エネルギーに関してテーマを以下の3つに絞り、総合的研究を行った。 1.高品位音響エネルギーの発生に関する研究 音響エネルギーの利用を考える上で必要となる音響エネルギーの高品位なものについて、企画調査を行った。 2.音響エネルギーの計測・制御に関する研究 音響エネルギー利用に必要となるエネルギーの計測・制御について計測デバイスなどの企画調査を行った。 3.音響エネルギーの利用に関する研究 以上の研究結果を下にその利用についての企画調査を、音響浮上、搬送、伝熱促進などについて行った。 本研究グループに参加している研究者の専門は、機械系、物理系、電気系と多岐にわたり、また大学関係、企業関係から成っている。そのため研究推進のための打ち合わせ会議を2回開催し、長時間に及ぶ討論を重ねて、各テーマについての具体的取り組み方と検討項目を明らかにした。これらの貴重な結果を将来の研究に結びつけるために重点領域研究の研究領域に発展させることを決議し、資料を整えて申請を行った。
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1993 -1993 
    Author : 中川 紀壽; 関口 泰久; 池田 隆
     
    近年の科学技術の急速な進歩に伴ない,工学分野における問題も複雑な様相を呈し,音環境下における機械や機器システムの連成応答問題,すなわち,音励振を受ける機械構造物や機器の性能維持および破損に関する安全性の問題が重要となってきている.そこで本研究では,このような音環境と機械構造システムとの連成問題を実験と理論の面から解析し,機械エネルギと音響エネルギ間の変換メカニズムを解明する.さらに,音場の制御として音響アクティブコントロールを行い,実験によりその有効性を検証する.以上の目的の下に行った研究結果を次に示す. 1.定常および非定常音場内における音圧分布の解析 ダクト内の音圧分布やスピーカによる音励振を受ける円板周囲の音圧分布を解析すると共に,実験結果との比較を行った.その結果,定常音場については良い一致を得,さらに三次元音響インテンシティを用いる音場の可視化を試みた.非定常音場については,今後さらに研究を進める. 2.音響境下における機械構造システムの動的応答 音環境下における機械システムの具体的対象物としてコンパクトディスク(CD)プレーヤをとり挙げ,レーザドップラ振動計を用いて,その動的変位応容とスペクトルの解析を行った.円板の回転速度や支持条件が固有振動数に与える影響について調べ,さらに音環境によるCDプレーヤの音飛び現象を実験で確かめ,ディスクの振動振幅とピックアップのフォーカス方向のサーボ特性により音飛びの発生することを明らかにした. 3.機械・音響エネルギ間のエネルギ変換メカニズム 機械構造として一般的な平板について,振動・音響インテンシティ流れを求め,各エネルギの変換メカニズムについて考察し,それぞれのエネルギ分布の対応が可能となる条件を明らかにした. 4.機械構造システムの音響アクティブコントロールに関しては,ダクトについて基礎的研究を行いその有効性を確認した.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1991 -1991 
    Author : 中川 紀壽; 関口 泰久; 池田 隆
     
    近年の科学技術の急速な進歩に伴い、音響環境下における機械や機器システムの問題,すなわち,音響励振を受ける機械構造物や機器の破損に関する安全性や性能維持の問題が重要となってきている.宇宙工学におけるロケット打上げ時や飛翔時の高音響が,人工衛星や搭載機器に及ぼす場合や,これに比べると音響の程度は低いが,VTRなどの音響機器において、駆動モ-タやベアリングから発生する音や振動の複雑な作用により生じる,VTRの性能低下が厳しく問われる場合などは,これら音響環境が機械システムに影響を及ぼす典型的な例である.本研究では,このような音響と機械システムとの連成問題を系統的に解析するため,まず音源より発生する複雑な音場を実験と理論面から解析し、機械システムに作用する音圧や音響インテンシティの音場内分布を明らかにする.次に,そのような音圧による機械システムの応答を理論解析し,実験結果と比較すると共に,音響のアクティブコントロ-ルについての基本的な知見を得る.本研究で得られた主な結果を以下に示す. (1)振動する矩形板により生じる音場や箱型空間内における音場の音圧,および三次元音響インテンシティを測定し,音圧分布および音響エネルギ-流れを明らかにした.また音場設計を効果的に行うため,複数音源によって形成される定常および過渡音場の可視化を行った. (2)音源としてスピ-カを用いた場合の,音響加振によるCDプレ-ヤの応答を解析し,音響励振がプレ-ヤまたは再生音に与える影響を,エラ-信号を用いて調べた.その結果,1kHzまでに3個あるディスクの共振点近傍の音響励振が,再生音の音質にそれぞれ特徴的な影響を及ぼすことを明らかにした. (3)箱型音場内における音場を能動的に制御するため,複素音響インテンシティから得られる音圧と粒子速度の位相差を用いる方法を提案し,その有効性を確かめた.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1990 -1991 
    Author : NAKAGAWA Noritoshi; NAGAMURA Kazuteru; SUEZAWA Takahiko; MORITA Shigeru; SEKIGUCHI Yasuhisa; IKEDA Takashi
     
    By the tendency of both high power and the control by computer of the machine system, an accident causes larger extent of damage. It is, therefore, desired to diagnose the machine system always or periodically. In this research, the diagnosis system by using sound informations instead of vibratory informations was developed to diagnose and restore the machine system. The following main results were obtained. (1) The data-base which maintains the characteristics of abnormal sound and furthermore restricts the amount of data with respect to the original sound waves was constructed. (2) By analyzing the sound pressure, acoustic intensity, and sound spectra, the sound parameters which characterize the abnormality of machine system were obtained. (3) The steady state and transient sound fields were visualized. by use of the three dimensional acoustic intensity. (4) By using the active noise control or the restoring technique, the diagnosis system of prototype was developed.

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