Research of our laboratory

Laboratory of material sciences and mechanics, investigates, develops, and designs materials and structures having adequate function for various aims from viewpoints of linkages of mechanics and material sciences by experimental, theoretical, and numerical analysis.

The objects of our research extend from automobiles and air planes to plant systems, nano- or micro-scale structures of materials to large scale mechanical structures made of metals, ceramics, polymer and their composites.

Recently, we are clarifying the mechanicsm of the phenomenon, considering physical mechanisms and proposing new evaluation methods of the mechines and structures..


Keywords

Mechanics of material, Material sciences, Mechanical properties of materials
Mechanical properties of structures, Composite materials
Fluid-Structure interaction


Current topics

□ Evaluation of Interfacial Strength by Nanoindentation Test

A new evaluation method was proposed for the interfacial strength between a thin film and its substrate by nanoindenation test. In this method, the released energy due to a coating delamination is obtained by estimating the shapes of the unloading curve at the points just after and before delamination on the load-displacement curve.

nanoindentation and delamination


□ Evaluation on Elastic Modulus of Closed Cell Aluminum Alloy Foam

In recent years, metallic foams have grown in use in a variety of engineering applications due to their lightweight structure and unique combination of physical, mechanical, thermal, electrical and acoustic properties. The flexural modulus of closed cell aluminum alloy foam has not yet been measured accurately. This study will focus on evaluating the elastic modulus of aluminum alloy foam by conducting experimental investigations.

Aluminum form


□ Analysis on Peeling Process of Adhesive Tape Using Cohesive Interface Force Model With Anisortropic Strength

To investigate the interface strength, the peel test under wide range of peel angle is necessary since peeling behavior depend on peel angle. However the mode ratio of nominal and shear deformation at peeling front between cohesive zone and adherend is not directly evaluated by the peel test. The objective of the study is to clarify the relationship between the peel angle and the mode ratio and to examine the influence of the stiffness of the base material to mode ratio with cohesive interface model.

peeling


□ Identification of Young’s Modulus from Indentation Testing and Inverse Analysis

In this study, a numerical method for the identification of the Young's modulus of linear elastic coated materials from continuous indentation test is explored. The identification is based on an inverse analysis where the minimization of a cost functional is performed by a gradient descent algorithm. The second part of this study is dedicated to the identification of elasto-plastic thin films Young's modulus.


□ Network Model Analysis of the Red Blood Cell Cytoskeleton subject to AFM Tensile Loading

We have developed a finite element model capturing non-linear elasticity and stochastic topology variation to support experimental measurements of mechanical properties of the cytoskeleton, a network of protein fibers in the Red Blood Cell that plays a key role in its mechanical behavior at large deformations. The model has been used to run Monte Carlo simulations of AFM tensile tests, results of which indicate AFM probe separation force to be sensitive to probe position. The statistical relationship established should enable modification of the AFM method to obtain precise measurements of inter-protein bond strengths which control deformation behavior in the cytoskeleton.

Red blood cell


□ Flexural Waves in Fluid-Filled Tubes Subject to Axial Impact

We experimentally studied the propagation of coupled fluid stress waves and tube flexural waves generated through projectile impact along the axis of a water filled tube. We tested mild steel tubes, Aluminum tubes, Polycarbonate tubes and composite tubes (GRRP & CFRP). A steel impactor was accelerated using an air cannon or by gravity and struck a polycarbonate buffer placed on the top water surface within the tube.

Elastic flexural waves were observed for impact speeds of 5-10 m/s and plastic waves appeared for impact speeds more than 20 m/s for a 0.8 mm thickness mild steel tube. We observed primary wave speeds of 1100 m/s in a 0.8 mm thickness tube, increasing to the water sound speed with 6.4 and 12.7 mm thickness tubes. Comparison of our measurements in the 0.8 mm thickness tube with Skalak's water hammer theory indicates reasonable agreement between predicted and measured peak strains as a function of the impact buffer speed. For thick-wall tubes, the correlation between experimentally determined peak pressures and strains reveals the importance of corrections for the through-wall stress distribution.

Hoop strain histories of tube wall in water hammer Tube buldge due to plastic deformation

Recently, we are studying not only water but two-phase and three phase flows; bubbly flow, water-air flow; slurry flow, mixture of solid particles and water. We are also interested in the cavitating phenomena in water hammer and mechanical damages due to cavitation errosion.

Cavitation bubbles in water hammer