Akio Yonezu

Akio Yonezu
Chuo University · Department of Precision Mechanics

Doctor of Engineering

About

198
Publications
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935
Citations

Publications

Publications (198)
Article
Titanium nitride (TiN) is used in various applications because of its excellent wear and corrosion resistance. TiN with a rock-salt-type crystal structure has been investigated extensively, but the existence of non-rock-salt-type phases (e.g., Ti 2 N) has only been reported recently from first-principles calculations. Molecular dynamics (MD) simula...
Article
This study investigated creep deformation behavior of a porous polymer membrane under biaxial stress by using the small-punch test. We first conducted a mechanical test for creep deformation, using uniaxial tension to examine creep compliance, which revealed that creep compliance was strongly dependent on applied stress in a nonlinear creep-deforma...
Article
Porous polymer membranes are typically polymeric materials that consist of many pores and complex network structures. As a result of these features, the membranes sometimes undergo anisotropic elastoplastic deformation. Hence, it is important to investigate the deformation behavior of these materials, including anisotropic deformation under multiax...
Conference Paper
Porous polymer membranes are generally polymeric materials having numerous pores and complicate network structure. Due to their features, these materials sometimes exhibit anisotropic deformation in their elasto-plastic deformation. It is thus important to investigate the deformation behavior of materials, including anisotropic deformation under mu...
Conference Paper
It is well known that plastic deformation behavior of metallic material depends on the length-scale and time-scale due to dislocation motions in material. The plasticity affected by scale down and higher strain rate is still open to discuss. In other words, both size effect and strain rate effect are critical issue for plasticity. Macro-scale exper...
Conference Paper
Adhesion bonding of metals and polymers is attracting attention as an innovative bonding technology to realize high functionality and weight reduction of various mechanical parts and structural materials. This technology has been significantly demanded with the rapid development of multi-materials in recent years. However, it has been reported that...
Article
Direct bonding of metals with resin plays a critical role in the jointing of dissimilar materials. The adhesion strength is known to be dependent on strain (loading) rate due to the strain rate sensitivity of polymeric resin. This study evaluated the adhesion durability of an epoxy resin adhesive on an aluminum alloy under cyclic impact loading. Fi...
Article
Full-text available
This study experimentally and numerically investigated the crack propagation behavior of porous polymer membranes in order to identify the criterion for crack propagation. A notch was introduced into the membrane as an initial crack (pre-crack), and a uniaxial loading was applied to produce stable crack propagation. During the test, crack propagati...
Article
Full-text available
This study evaluated the interfacial adhesive strength between aluminium alloy and epoxy resin (Al/epoxy resin) over a wide range of strain rates (loading rates). We conducted three types of tests with different loading rate, i.e., a quasi-static tensile test for the range of lower loading rate, a Split Hopkinson Bar (SHB) for the range of middle l...
Article
Full-text available
This study aims to evaluate coating adhesion durability using the laser shock-wave adhesion test (LaSAT). In particular, the interfacial strength with respect to the applied loading cycle is evaluated quantitatively. This method uses strong elastic waves induced by pulsed laser irradiation, as interfacial fracture of the coating occurs due to a str...
Conference Paper
This study investigated the crack growth behavior of porous polymer membranes, experimentally and numerically, in order to clarify the criterion of crack growth. A notch was introduced into the membrane as an initial crack (pre-crack) and a uniaxial loading was applied for the stable crack propagation. During the test, crack propagation behavior wa...
Conference Paper
Direct bonding of metal-resin plays a critical role in jointing of dissimilar materials and the adhesion strength is known to be dependent on strain rate (loading rate) due to the strain rate sensitivity of polymeric resin. This study evaluated adhesion strength and adhesion durability against repetitive loading for the interface between aluminum a...
Article
In this study, we have proposed an indentation method to characterize a surface degraded layer due to UV light irradiation of polymers. Here, we assume that the degraded layer has a homogeneous and isotropic nature, and that the target material is a bilayer system (i.e., the degraded layer is formed on the substrate of the non-degraded base materia...
Article
An energy-saving system containing ion-exchange or nanoporous materials and carbonate ions is proposed, which is capable of capturing CO 2 from ambient air simply by controlling the amount of water (moisture) in contact with the sorbent. The system binds CO 2 from the air when the surrounding is dry, whereas it desorbs CO 2 when it is wet. A design...
Article
This study aims to provide a fundamental understanding of the morphological transition of film buckling–delamination in an elastomeric bilayer spherical shell system. We developed an experimental system in which surface delamination buckles emerge because of biaxial compression of the elastomeric bilayer spherical shell driven by an air-pressured (...
Article
Ion hydration is well known as a fundamental process in many natural phenomena. To capture CO2 efficiently, this study explores a novel “moisture-driven CO2 sorbent” based on diffusion of ions and the structure of ion hydration complexes forming inside water-laden resin structures. We present a quantitative analysis, with atomistic modeling, to inv...
Article
Direct metal-resin bonding plays a critical role for jointing of dissimilar materials and is widely used for various mechanical parts and structural components. In actual use, impact or dynamic force is repeatedly applied, resulting in interfacial delamination. Therefore, it is essential to quantitatively evaluate the adhesion strength and the adhe...
Article
Porous polymer membrane having numerous pores may exhibit large deformation and its anisotropy, which is dependent on inherent porous structure. For such anisotropic porous materials, it is important to investigate the deformation behavior under multiaxial and biaxial tensile loadings. However, such experiment may be difficult using conventional te...
Conference Paper
This study develops a new experimental system to investigate surface buckling patterns that emerge due to the biaxial compression of elastomeric bilayer spherical shell. The sample used in this study is a thick PDMS (polydimethylsiloxane) substrate and a thin PDMS film. In order to induce biaxial strain to the surface of PDMS substrate, air pressur...
Conference Paper
This study investigates the deformation behavior of porous polymer materials with 3D random pore structure. The test sample has sub-micron-sized pores with an open cellular structure, which plays a critical role for water purification. The base polymer is PVDF (polyvinylidene difluoride). First, the surface and cross section of the sample are obser...
Conference Paper
This study aims to evaluate the adhesion strength and durability of hard coatings in a non-contact manner by using Laser Shock Adhesion Test (LaSAT). Both heat-treated and as-plated (non-heat-treated) Ni-P coatings deposited on carbon steel substrate by electroless plating method were prepared as specimens for this study. LaSAT uses strong elastic...
Conference Paper
This study systematically investigates the uniaxial and biaxial tensile deformation behavior of polytetrafluoroethylene (PTFE) membranes which are used for water purification. The present PTFE membrane has micron size pores with open cell structure, and the pore is anisotropic shape. During the uniaxial tensile test, the membranes undergo elastic d...
Conference Paper
This study evaluates the interfacial fracture strength and toughness of an epoxy resin/aluminum alloy based on two different tests of impact loading and quasi-static loading. In the impact test, we carried out the Laser Shock Adhesion Test (LaSAT). This method uses a strong ultrasonic wave induced by pulsed laser irradiation to induce interfacial f...
Article
This study evaluated interfacial fracture strength and toughness of epoxy resin/aluminum alloy based on two different tests of impact loading and quasi-static loading. In the impact test, we carried out Laser Shock Adhesion Test (LaSAT), which employs laser shock wave to induce interfacial delamination. To evaluate interfacial strength, we first id...
Article
We investigate the adhesion strength (interfacial strength) of the oxide film formed on a carbon steel substrate by using a laser shock adhesion test (LaSAT). A rolled carbon steel (SS400) plate is first heated at high temperature (700 °C) under the atmosphere (heat treatment) to cause the formation of oxide films about 20-50 μm thick on the steel...
Article
Increased applications of nanoporous graphene in nanoelectronics and membrane separations require ordered and precise perforation of graphene, whose scalablility and time/cost effectiveness represent a significant challenge in existing nanoperforation methods, such as catalytical etching and lithography. A strain‐guided perforation of graphene thro...
Article
Polyamide 6 (PA6) shows significant water absorbability and hygroscopicity, which affect its mechanical properties such as Young’s modulus and yield strength, as water content enhances deformability. This study aims to investigate the effect of water molecules on the deformation behavior of PA6 and to elucidate the deformation mechanism at a molecu...
Article
It is well known that polycarbonate (PC) undergoes time-dependent deformation (i.e., creep deformation), and nonlinear creep deformation is often experienced at high stress level. Using the time–temperature–stress superposition principle (TTSSP), we obtain a new master curve, which covers higher stress level, and successfully establish a new modeli...
Article
This study evaluated the mechanical properties of the surface degradation of polycarbonate (PC) which was exposed in outdoor (i.e. Tokyo, Okinawa, and Arizona) for long period of time. We made several degradation samples which was exposed in the outdoors for 3 to 24 months. An indentation test was conducted to evaluate the mechanical properties of...
Article
Graphene is a monolayer of carbon atoms arranged in a honeycomb network and possesses unique properties such as superior mechanical flexibility, large surface area, and high thermal, electrical and chemical stability. Because nano porous graphene is potentially useful for various applications, such as DNA sequencing, water desalination, and filtera...
Article
Coatings and films are widely used in various fields, including electronic devices to improve the mechanical properties of substrate materials. In actual use of such dissimilar materials, dynamic and impact loadings are sometimes applied to the interface, resulting in interfacial fracture under higher loading rate. Therefore, the evaluation of adhe...
Article
This study aims to evaluate the interfacial strength of aluminum alloy/epoxy resin adhesive by using two different tests of impact loading and quasi-static loading. For the impact test, laser shock adhesion test (LaSAT) was carried out. This method uses a strong shock wave induced by a laser ablation in order to apply the tensile stress at interfac...
Article
This study aims to indicate fundamental understanding of surface patterns of film buckling and delamination on an elastomeric bilayer spherical shell system. Here, we report the developed experimental system to generate such surface patterns that emerge due to the biaxial compression of elastomeric bilayer spherical shell. The sample in this study...
Article
There is a rich diversity of surface topologies controllably engineered by patterning cavities embedded beneath the surface of soft materials. Upon external compression, the surface undergoes the reversible transformation from the flat surface to various surface topographies, including a periodic checkerboard pattern with alternate convex and conca...
Article
Wrinkle formation followed by sharp strain localization is commonly observed in compressed stiff film/soft substrate systems. However, cavities or defects beneath the film may directly trigger the formation of local ridges and then folding configurations at a relatively small compressive strain, and a mixture of wrinkles and folds upon further comp...
Article
Atomic force microscopy (AFM) has been widely used to study the measure surface topography, friction force, adhesive force, and deformation response at nanoscale. In particularly, AFM nano indentation enables to measure deformation response at molecular level in polymer materials. This study aims to investigate the mechanism of elasto-plastic defor...
Article
This study evaluates adhesion strength of oxide films on steel substrate by using laser-induced ultrasonic wave. Strong pulsed laser irradiates onto the back surface of steel substrate, inducing ablation, and strong elastic wave propagation. The elastic wave propagates from the substrate to the coating surface. When a large stress is applied to the...
Article
It is well known that nylon 6 possesses water absorbability and hygroscopicity, affecting their mechanical properties such as Young's modulus and yield strength. This study aims to investigate the effect of water content on the mechanical property of nylon6 using experiment and molecular dynamics (MD) simulation. First, uni-axial loading and micro...
Article
This study aims to evaluate the interfacial fatigue strength of the surface coatings using Laser Shock Adhesion Test (LASAT). This method uses strong ultrasonic wave induced by repetitive pulsed laser irradiations. For this irradiation, grease layer is foamed on the back surface of substrate and a pulsed laser is irradiated, so that ablation occurs...
Article
Atomic force microscopy (AFM) has been widely used to measure surface topography, friction force, adhesive force, and deformation response at nanoscale. In particularly, AFM nano indentation enables to measure deformation response at molecular level in polymer materials. This study aims to investigate the mechanism of elasto-plastic deformation by...
Article
This study aims to evaluate coating adhesion, i.e. the interfacial strength of coatings and thin films by using Laser Shock Adhesion Test (LaSAT). This method uses strong elastic wave induced by pulsed laser ablation. The elastic wave causes the coating delamination, when the maximum stress wave reaches the critical value (interfacial strength). In...
Article
This study investigated the tensile deformation behavior of porous polymer membranes (polytetrafluoroethylene; PTFE and Polyvinylidene difluoride; PVDF), which are used for water purification. The membranes have micron and sub-micron pores with open-cell structure. The surface and cross section of the membranes was observed by FESEM to carefully in...
Article
Full-text available
This research develops a new technique for the measurement of interfacial fracture toughness of films/surface coatings using laser-induced ultrasonic waves. Using pulsed laser ablation on the bottom substrate surface, strong stress waves are generated leading to interfacial fractures and coating delamination. Simultaneously, a laser ultrasonic inte...
Article
This study investigated the fracture properties of wrinkled metallic films on a polydimethylsiloxane (PDMS) soft substrate. In particular, the crack density of the wrinkled film during tensile deformation was examined. In order to achieve better deformability of metallic thin films, a method to fabricate a wrinkled thin film on a PDMS soft substrat...
Article
Polycarbonate (PC) is an important engineering polymer that has been used as the structural material in a wide range of applications. Using coarse-grained (CG) molecular dynamics (MD), this work systematically investigates the elastoplastic deformation of PC under two tension scenarios. To drastically improve computational efficiency, a new CG forc...
Article
Magnesium (Mg) alloys have been widely used in automotive and aerospace industries due to its merits of exceptional lightweight, super strong specific strength, and high corrosion-resistance, where intermetallic compounds with a small volume are very critical to achieve these excellent performance. This study proposes a reverse analysis that can be...
Article
Engineering polymers generally exhibit asymmetric yield strength in tension and compression due to different arrangements of molecular structures in response to external loadings. For the polymeric materials whose plastic behavior follows the Drucker- Prager yield criterion, the present study proposes a new method to predict both tensile and compre...
Article
This study aims to evaluate interfacial strength of surface coating by using laser induced ultrasonic wave. In this method, pulse laser beam is irradiated on the back surface of substrate, inducing strong elastic wave which propagates through the specimen thickness, and reflects at the top surface of the coating. The wave propagation and reflection...
Article
Among engineering polymers, polycarbonate (PC) has been widely used as structural components in various industries. This study investigated the molecular structural mechanism during tensile deformation behavior by using molecular dynamics (MD) simulation. In this simulation, coarse grain method was employed to reduce the number of atom and molecule...
Article
This study proposes a reverse analysis that can be employed to extract elastoplasticity dependent creep property of metallic materials from instrumented indentation with two sharp indenters. First, the creep deformation that obeys the Norton's law ( ε = Aσⁿ ) is studied and the dimensional function is established to determine parameters of A and n...
Article
This study investigated the compressive deformation behavior of hollow-strut cellular materials. The present cellular structure consists of pentagon and/or hexagonal shaped cellular network, where the individual strut cross-section is hollow triangular prism. Uni-axial compressive test is applied to the present material and we investigate macroscop...
Article
This study investigated the anisotropic compressive deformation of low density polymeric foam by using X-ray CT method to elucidate the microscopic and macroscopic deformation behavior. The foam used in this study has closed cell structure, whose pore is ellipse shape, leading to the anisotropic deformation (which is depending on uni-axial compress...
Article
This study aims to evaluate delamination characteristics of surface coating by using strong ultrasonic wave induced by pulsed laser irradiation. Strong tensile stress wave is induced by pulse laser irradiation, and delamination of the coating layer/substrate interface (or spallation) is produced by confined silicone grease breakdown (i.e. ablation)...
Article
The tensile deformation behavior of polyvinylidenedifluoride (PVDF) hollow fiber membranes used for water purification was studied. The present PVDF membrane has sub-micron pores with open cell structure. The surface and cross section of the membranes were observed by FESEM to investigate the microstructure (cell size and geometry of the cell ligam...
Article
This study investigates the compressive deformation behavior of a low-density polymeric foam. The present polymer material has micron-sized pores with a closed cell structure. The porosity is about 94 %. After a uni-axial compressive test, the macroscopic stress - strain curve indicates a plateau region during plastic deformation. Finite Element Me...