Major Research Accomplishments
Since 1986, I have been working in several research areas in the field of computational mechanics including structural dynamics, multibody system dynamics, coupled structural-acoustic systems, and optimal design of structural and material systems.
My major findings are summarized in 60 articles in refereed journals and transactions, 59 articles in refereed conference and symposium proceedings, 12 refereed conference abstracts, 41 non-refereed conference abstracts, and 1 book chapter. I have received 5 best paper awards from the Japan Association of Automatic Control Engineers (1988), the Japan Society of Mechanical Engineers (1991), the Society of Automotive Engineers (1991), the Japan Society for Industrial and Applied Mathematics (1995), and the American Society of Mechanical Engineers (2003. My research has been cited by many other research groups. I have been invited for a number of seminars and lectures outside the University of Michigan including Rensselaer Polytechnic Institute, Tokyo Institute of Technology (Japan), Saitama Institute of Technology (Japan), Beijing Institute of Technology (China), Jilin University (China), US Army TACOM, US Air Force Research Laboratory, Boeing Company, Ford Motor Company, DaimlerChrysler, Eaton, Gets, MSC, Nissan Motor Company, China FAW Co. I have also been elected as a member of the ASME Technical Committee of Multibody Systems and Nonlinear Dynamics.
Summaries of Major Contributions
Structural Dynamics
My contributions to structural dynamics include the following five major findings. 1) Developed a general approach to component mode synthesis which unified major existing component mode synthesis methods and extended these methods to be more general, more efficient and more flexible. 2) Developed an advanced mode-superposition technique (Ma-Hagiwara method), which can be used to compensate for truncation errors for both high-frequency modes and low-frequency modes. This new method represents the third generation of mode-superposition techniques following the Mode Displacement Method and the Mode Acceleration Method. 3) Developed a new class of component modes, called Quasi-Static Modes (QSM). The QSM can be used in component mode synthesis for the efficient analysis of mid-frequency NVH problems. 4) Developed a Quasi-Static Load Dependent Ritz Vectors Method (QSRV), which is an extension and improvement over the existing Load Dependent Ritz Vectors Method. 5) Developed a Quasi-Static Dynamic Data Recovery Method (QSDR), which is an extension and improvement of the current Dynamic Data Recovery Method based on the Mode Acceleration Method.
Multibody Dynamics
My contributions to multibody dynamics include seven major findings. 1) Developed and implemented a nonlinear viscoelastic bushing model for the dynamic simulation of automotive systems. 2) Developed and implemented a new and efficient track vibration model into a general multibody dynamics simulation code (DADS) for use in the dynamic simulation of tracked vehicles. 3) Developed a finite element track model for simulating track-wheel-terrain interactions for tracked vehicles. 4) Developed an integrated vehicle/powertrain model for the dynamic simulations of military tracked vehicles. 5) Developed an engine-modeling template using a recursive formulation of multibody system dynamics with bearing models for the up-front design of engines. 6) Developed a special CAE tool, called DKAD (Design kit for Accessory Drives), which has been extensively used inside DaimlerChrysler for their daily design tasks. 7) Developed advanced gluing algorithms for distributed simulation and design of structural and mechanical systems.
Coupled Structural-Acoustic Systems
My contributions to coupled structural-acoustic systems include five major findings. 1) Developed a new mode-superposition technique for analyzing coupled structural-acoustic systems, which employ state equations with asymmetrical coefficient matrices. This new technique made it possible to directly use mode-superposition ideas for coupled structural-acoustic systems without first symmetrizing system matrices, thus leading to a more efficient analysis. 2) Extended the Ma-Hagiwara mode-superposition technique to coupled structural-acoustic systems. This technique allows truncating both high-frequency modes and low-frequency modes thereby further improving computational efficiency for coupled system analysis. 3) Developed a new sensitivity analysis method for eigenvalue problems, including systems with repeated eigenvalues, direct frequency response problems, and modal frequency response problems for coupled structural-acoustic systems. 4) Developed a numerical approach for simulating rattle noise of automotive vehicle systems. 5) Extended the topology optimization technique to structural-acoustic systems.
Advanced Design Methodologies and Innovative Structural and Material Systems
My contributions to advanced design methodologies and innovative structural and material systems include nine major findings. 1) Sensitivity analysis methods based on the Ma-Hagiwara mode-superposition technique for eigenvalues, frequency responses, and transient responses of structural systems and coupled structural-acoustic systems. 2) Extensions of the topological optimization technique based on a homogenization method for vibrating structures, including structural design for desired eigenfrequencies and minimizing dynamic response of structural systems. 3) Development of a modified optimality criteria method (MOC) for dynamic problems of topological optimization. 4) Development of a new optimization algorithm, Generalized Sequential Approximate Optimization (GSAO), for large-scale structural optimization problems. This new method can be considered as a generalization and improvement over the popular SAO algorithms, i.e., CONLIN, MMA, DSQP, and MOC, and it can significantly improve the convergence and solution efficiency for structural design problems of large size. 5) Developed a new design methodology, called Function-Oriented Material Design, and associated CAE tools for developing innovative structural and material concepts. This work has received a best paper award from ASME Design Engineering Division, Vehicle Design Committee. 6) Developed new design methodologies and composite material systems for ballistic and blast protections. 7) Developed a systematic and general "Magic Cube" approach for crashworthy design. 8) Developed a new design concept with associated design methodologies for an inflatable bumper (I-bumper) for improved vehicle safety. 9) Developed new design methodologies and concepts for reactive structures in military and commercial applications.
Patents and Licenses
Invention: A software system called DKAD (Design Kit for Accessory Drives), displayed at one of the eight booths in 2003 Celebrate Invention Reception of the University of Michigan, Michigan League Ballroom, October 1, 2003. This code was developed under DaimlerChrysler Challenge Fund and it has been extensively used in DaimlerChrysler Corporation.