Engineering Mechanics Lab.

We are interested in the fundamental understanding of the mechanics of smart materials and structures; including piezoelectric materials, functionally graded materials, elastomers & gels, rods, plates and shells. We also offer the design principles for relevant applications ranging from the micro-sensors & actuators to the macro-structural elements.

People 2018


Ashida, Fumihiro

Associate Professor

Morimoto, Takuya





Mehcanics of Functionally Graded Piezoelectric Materials

Thermal shock of functionally graded piezoelectric thin films

This study deals with a one-dimensional elastodynamic problem of a functionally graded piezoelectric thin film. It is assumed that one surface of the thin film is fixed to a flat rigid body and the other surface is suddenly subjected to a uniform impact pressure and that electric potentials are prescribed on both surfaces. The analytical solution is derived by employing the Laplace transform technique. Numerical results show that a complicated stress oscillation induced in the thin film can be suppressed by applying appropriate electric potentials.

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Optimum design of smart composite disks

This study deals with a stress control problem in a composite disk constituting of a structural layer onto which functionally graded piezoelectric material (FGPM) layers are bonded. When a heating temperature distribution acts on the structural layer surface, the maximum thermal stress in the structural layer can be suppressed by applying appropriate voltages to electrodes arranged on each FGPM layer. In order to maximize the performance of stress control, variation in material properties of the FGPM layers is optimally designed. Obtained numerical results show that the performance of stress control is greatly improved through the optimum design of the FGPM layers.

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Mechanics of Soft Materials

Elastic instability of a sliding rubber block

We study an elastic instability of a rubber block sliding on a hard rough surface. In a macroscopic sense we focus on how the aspect ratio of a rubber block and the applied normal force affect the transition from uniform deformation to localized deformation of the block when the frictional motion initiates. Experimental observations reveal the effects of the parameters such as aspect ratio, normal force, and surface roughness on the critical strain fields at the onset of frictional motion.

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Controlling surface patterns in soft materials

Elastic instabilities of hard films on soft substrates emerge spontaneously from a homogeneous state during global deformation induced by growth/swelling, drying or confinement. Small compression of the system creates sinusoidal wrinkles with a broad spatial energy distribution while large compression creates sharp folds with localized energy. The wrinkle-to-fold transition has been mostly focused on two-dimensional plane-strain models under uniaxial compression. In experiments, however, the biaxial compression often lead to complex three-dimensional spatial structure due to the interplay between elasticity and geometry. The nucleation and growth of folds in biaxial compression remain elusive. Here, we explore folding dynamics of neo-Hookean bilayer systems under biaxial compression in a systematic way.

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