In the present paper, some experiments and numerical simulations about nano imprinting of glass devices using finite element method are investigated. Thermo-viscoelastic properties of the glass materials were estimated using undirectional compression creep test based on traditional thermoviscoelastic theory. In this study, D263 were used as glass materials. Glass nano imprinting was carried out with Glassy Carbon mold given to groove patterns machined by focused ion beam (FIB). The adaptive condition of molding temperature which given appropriate transcription profile of the glass was investigated. Moreover, numerical simulation for nano imprinting of the glass was carreid out by finite element method using universal FEM code (ANSYS ver.11.0). As a result of comparing experimental results with numerical ones, the transcription of height of groove obtained by experiment approximately agree with numerical value when the friction coefficient were 0.4 or more.
In order to improve interfacial properties of adhesively bonded composites, surface modification using Nanoimprint lithography (NIL) is investigated. Since the interfacial properties such as bonded strength or fracture toughness are highly depend on a surface morphology, these properties can be improved by designing and fabricating microstructures appropriately in the interface. Considering this fact, we introduced NIL technique to the curing process of composites and fabricated microstructures on the surface of composites, which gives us stiff interface without any surface preparation such as sand blasting or chemical etching. We simulated the behavior of crack propagation along the interface with Finite element method using cohesive zone model and estimated mode I apparent fracture toughness of adhesive joints.
Surface modification by nanoimprint lithography (NIL) is applied to an adherend of the bonded composite joints. We developed a silicon mold with micro scale structures by photolithography and anisotropic etching. By forming CFRP on the mold with microstructures, the microstructures are transferred to the CFRP surface. Since this surface modification can be conducted during the curing of composites, it reduces the time required and costs involved in conventional surface preparation such as sand blasting, chemical etching etc. In this paper, the effect of microstructure size on the mode I fracture toughness was investigated. A size ratio A was defined and DCB tests about some values of A was conducted. As a result, it was confirmed that as A increased, fracture toughness became stronger.
This paper deals with the fatigue strength the paper-based friction materials under cyclic shear-compressive loading which is regarded as a real loading condition in an automotive automatic transmission. The influence of ratios between the shear and compressive stress on the fatigue strength was examined. The fatigue strength decreases with increasing number of cycles. The static fracture strength and fatigue limit is high under the dominant compressive stress condition. The amount of deformation of the paper-based friction materials does not change with the compressive stress under the compressive loading, while the Young's moduli increase with increasing compressive stress.
Recently, because the micro-machine is noticed and electronic equipments are made much lighter and smaller, the demand for micro materials is increasing. However the mechanical properties data of the micro materials obviously run short. Therefore, the establishment of the test method for the micro materials is very necessary. In this study, Cu thin sheets with thicknesses of 10μm and 20μm were used. Specimens were manufactured using electro-spark machining. Afterwards, the machined surface was polished. The fatigue tests were carried out using these specimens. As the results, fatigue lives of specimen with thickness of 10μm were shorter than those with thickness of 20μm in high stress amplitude area. The dispersion in the fatigue life of specimen with thickness of 10μm and 20μm were almost equal.
In order to investigate the creep deformation behavior of stainless steel thin sheet belt under high temperature, creep fatigue tests were carried out at high temperature using specimens of SUS305, SUS430 and SUS632. As the results, creep fatigue lives of SUS305 and SUS430 decreased with increasing temperature, and creep fatigue life of SUS632 did not decreasing with increasing temperature. Creep strain of SUS305 was almost equal from 100℃ to 300℃, and increased over 300℃. Creep strain of SUS430 increased with increasing temperature. Creep strain of SUS430 increased from 100℃ to 200℃, and decreased from 200℃ to 400℃.
The purpose of this study is to characterize the damping properties of Polyarylate fiber reinforced plastics. The damping properties of the composites laminates were evaluated by vibration test. Also, the effects of the stacking sequence of the Polyarylate-Carbon hybrid composites on damping properties were examined. Plain weave Polyarylate and Carbon have been used as reinforcing materials. It is recognized that damping properties of polyarylate fiber composites are greater than that of carbon fiber composites. Further, polyarylate-outside clustered configuration gives higher damping properties.
The influence of domain orientation on the mechanical properties of lead zirconate titanate (PZT) piezoelectric ceramics has been investigated using un-poled and poled PZT ceramics. Good mechanical properties, e.g., high elastic modulus and compressive strength, were obtained for the poled PZT ceramics due to strain hardening caused by more severe domain switching during the loading process compared to the un-poled ceramics. Fracture mechanics of the ceramics were influenced by the direction of the tetragonal lattice structure since cracks propagate along the long axis of the tetragonal structure (c-axis). Using x-ray diffraction and electron back scatter diffraction analysis, the domain switching characteristics could be clarified.
This work presents the nonlinear bending response of magnetostrictive/piezoelectric laminated devices under electromagnetic fields both numerically and experimentally. The devices are fabricated using thin Terfenol-D and PZT layers. The magnetostriction of the Terfenol-D layer bonded to the PZT layer is measured, and a nonlinear finite element analysis is performed to evaluate the second-order magnetoelastic constants in Terfenol-D layer using measured data. The deflection, internal stresses and induced voltage/magnetic field for the laminated devices under magnetic/electric fields are then discussed in detail.
Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In general, it is necessary to give large stretch to PVDF film when PVDF film is used as sensor or actuator element. However, we recently found that PVDF showed piezoelectricity without large stretch, which nano-clays are uniformly dispersed. The aim of present study is to investigate the possibilities of nano-clay/PVDF composite film as actuator element, and investigate its piezoelectric mechanism. Firstly, nano-clay/PVDF composite film is fabricated by solvent casting. Secondarily, we investigate the change of electrical displacement according to the input voltage of triangle wave by using Sawyer-tower bridge circuit. Then, the change of impedance is also measured at broad frequency by using impedance analyzer. Thirdly, we apply the input voltage of sine wave to fabricated films, and measure the output oscillation generated from films. Fourthly, X-ray analysis is conducted in order to investigate the nano and micro-structure in nano-clay/PVDF composite film. Finally, we discuss the possibilities of nano-clay/PVDF composite film as actuator element and its piezoelectric nature from present results.
We built up the way of fabricating IPMC actuator with palladium electrodes and evaluated its deformation behavior under various solvents and various frequencies of input voltage. We fabricated IPMC actuator by the non-electrolytic plating method, and investigated the deformation behavior of IPMC actuator. From the experimental observation, the bigger the ionic radius of cation became, the larger bending response IPMC actuator showed. When the electric field across its cross section was unloaded, IPMC actuator showed a large back relaxation under high temperature. In the experiment of the input voltage frequency response, IPMC showed good response to various frequencies from 0.1 to 6.0 Hz and we could observe resonant peak at 5.5 Hz.
Graphene is a single atomic layer of graphite which has two dimensional honeycomb structure. Although its structure is very simple, graphene has extraordinary physical properties. Its edge has a characteristic configuration called armchair (AC) or zigzag (ZZ). Graphene nanoribbons (GNRs) of various aspect ratios are equilibrated at low temperatures. The total energies of the multi-layered GNRs decrease with the increase of the number of layers and tensile strain. The amplitudes of out-of-plane deformations of the multi-layered GNRs decrease with the increase of the tensile strain.
Extrinsic grain boundary dislocations (EGBDs) are often observed in ultra fine-grained metals produced by severe plastic deformation (e.g. ECAP or ARB etc.). The mechanical properties of such metals are different from those of coarsegrained metals. That is, EGBDs could be important factor to elucidate the unique mechanical properties. In this study, introducing lattice dislocations into an equilibrium grain boundary by pre-deformation, we evaluate the influence of the EGBD component on the crack tip shielding effect using J-integral analyses.
We study statistical properties of energy bursts in a polycrystalline metal under uniaxial tension. Using acoustic emission (AE) technique, we measure the amplitude of AE waves and then analyze the statistical properties such as the maximum amplitude distributin, P(A_0), and the amplitude per unit avalanche event,P(A). As a result, we found that power law behaviors of both the maximum amplitude with the exponets have neatly same value with α=β〜3.0±0.1, which is twice of that of single crystalline metal reported in the literature.
In this study, a discrete dislocation dynamics analysis of microscopic composites is performed using a homogenization theory. A model lamellar structure consists of 400-nanometer-thickness matrices and 40 or 400-nanometer-thickness inclusions, and has one dislocation source in the periodic unit. The model is analyzed to investigate the effects of inclusion thicknesses and Young's modulus ratios on macroscopic stress-strain relations, stress distributions in the periodic unit, and dislocation pile-ups to interfaces.
This paper discusses the fracture probability analysis of a particle reinforced composites. As random variables, elastic property and strength of a component material are considered. It is assumed that an elastic property of a component material is randomly distributed according to the normal distribution, and the strength distributes according to the Weibull distribution. The random variation of the microscopic stresses are computed using the perturbation-based multiscale stress analysis method. With the numerical results, influence of the random variation of an elastic property on fracture probability is discussed.
This paper discusses inverse stochastic homogenization analysis to identify a microscopic random variation of a composite material. The inverse stochastic homogenization procedure is performed with the Monte-Carlo simulation and inverse homogenization analysis, and it estimates a random variation of an elastic property of a component material. In this presentation, outline of the proposed procedure is introduced. Also, from several numerical results, validity and effectiveness of the proposed approach are discussed.
In this study, a constitutive model of the homogenized elastic-viscoplastic behavior of periodic open structures subjected to internal pressure and macro-strain is developed. We consider periodic structures, made of metallic materials, having open spaces in which internal pressure acts independently of macro-strain. First, a homogenized elastic constitutive model of this class of periodic structures is rationally developed by evaluating analytically the anisotropic macro-stress induced by internal pressure. This elastic model is, then, extended to a homogenized elastic-viscoplastic model on the assumption that macro-strain rate is additively decomposed into elastic and viscoplastic parts. It is shown that the viscoplastic macro-strain rate depends on the difference between macro-stress and internal pressure. The homogenized constitutive model developed is verified by applying it to a plate-fin structure.
An adequate evaluation methodology of structural reliability is indispensable for full use of light weight advantage of carbon fiber reinforced plastic (CFRP) members. The residual strain and stress after cure process are decisive for strength of CFRP. We have developed simulation system to predict initial defects of CFRP members, the finite element discretization of which is executed with mesoscopic separation of resin and fiber. The simulation runs with small time step of heat transfer analysis with heat generation from resin, degree of cure analysis, strain analysis by thermal contribution and polymerization shrinkage, and visco-elastic analysis of resin under cure progress. A numerical solution is presented to demonstrate the prediction of residual stress and strain generated in CFRP Laminates.
Artificial hip joint which has been made of fiber reinforced plastics has advantages of high degree of freedom of the design parameters. Artificial hip joint consists of three parts, Cup, Head and Stem. In the artificial hip joint, the fixation of cup and pelvis is very important. Therefore, we made cups which have protuberances on surface and evaluated the mechanical characterization for the cups. In this study, the target is an evaluation of mechanical characterization for artificial joint cup considering various surface shapes, and the torsion-compression test has been carried out for the estimation of fixed torque using a cup with different density of protuberances and shape of different protuberances.
The purpose of this study is to estimate mechanical behaviors of a CFRP cup and bone based on finite element method (FEM). The details of the proposed method are as follows; Firstly, a numerical model of acetabulum has been prepared with CT image of patients, and the model of a CFRP cup are generated. The press-fit analysis, which means the estimation of the mechanical behavior to press the cup toward to the acetabulum, has been carried out with considering contact phenomena. As the examples, two kinds of cups are prepared. One is a CFRP cup, and another is a metal cup. The difference of the mechanical behaviors with both cups is discribed in this paper.
Optical Coherence Straingraphy (OCS) was developed, which could visualize micromechanical information, e.g. strain, tomographically and non-destructively. This method can execute the speckle deformation analysis based on cross-correlation technique of synthetic images, which are captured before and after loading by Optical Coherence Tomography. In this study, applying OCS to Polymer Matrix Composites (PMCs), e.g. plain-woven fiber-reinforced rubber, the experimental feasibility study was carried out to evaluate micro-mechanics. In order to verify experimental results, it was compared with numerical ones obtained by image-based FEM. Consequently, OCS could discover the strain concentration in the vicinity of the intersection of orthogonally oriented fiber bundles. It was confirmed that tomographic strain distribution had qualitative agreement with the simulated one. Therefore, OCS was verified to provide mechanical properties non-destructively as internal strain distribution at the micro scale resolution.
To predict the macroscopic compressive strengths of hardened cement paste, a digital-image-based finite element procedure for damage evolution due to local tension is developed and its applicability from practical viewpoint is studied through numerical experiments. In the procedure, microscopic three-dimensional geometries of hardened cement paste are assumed to be periodic and each phase is randomly generated by using auto-correlation function evaluated from a two-dimensional SEM image of specimen. Nonlocal isotropic damage model is employed to represented crack evolutions in the geometries. Predicted macroscopic uni-axial compressive strengths are qualitatively consistent with experimental results in terms of water-cement ratio and material age.
A computational multiple scattering simulation method was applied to analyze the characteristics of the ultrasonic shear wave that propagates in unidirectional carbon-fiber-reinforced epoxy composites with its polarization direction parallel to the fibers. The numerical simulations were carried out for regular as well as random fiber arrangements and for different frequencies. The results were combined with the one-dimensional theory describing the macroscopic propagation behavior, in order to identify the phase velocity and the attenuation coefficient of the composites. The phase velocity was found to be almost independent of the frequency. On the other hand, the attenuation coefficient was found to be nearly proportional to the frequency. Furthermore, the present analysis showed a good agreement with the experimental data.
This work investigates influence of boiling liquid on mechanical behavior of fiber reinforced polymers. R-134a used as pressure-liquefied gas at 273 K was boiled by instantaneous depressurization. A compressor was used to re-liquefy boil-off gas and to achieve a cyclic liquid-vapor condition. Specimens of glass fiber reinforced polymers (GFRP) were immersed in the cyclic condition. After immersion, micrographs showed microcrack development. short-beam three-point bending tests were performed. To evaluate the influence of the boiling condition on interlaminar shear strength of GFRP.
This paper studies the fracture behavior of carbon nanotube (CNT)-based polymer composites by a combined numerical-experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic-plastic finite element simulations of the tests were then performed to evaluate the J-integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy (SEM) examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed.
Cryogenic tensile properties of carbon nanocoil (CNC)/poly-dicyclopentadiene (poly-DCPD) composites fabricated by ultrasonic technique have been investigated experimentally. Tensile tests were carried out with flat tensile specimens at room temperature (RT) and liquid nitrogen temperature (77K). The effects of temperature, CNC volume fraction and ultrasonication time on the tensile properties of CNC/polyDCPD composites were discussed. A scanning electron microscope (SEM) was also used to observe the fracture surface morphology of CNC/poly-DCPD composites. Results indicate that the tensile strength of CNC/poly-DCPD composites at RT and 77K is affected by ultrasonication time and there is a trade-off between improving dispersion and damaging the CNC.
In the present study, the impact property of CNF/CFRP hybrid laminates and influence of carbon nanofiber interlayer on impact properties were investigated using the drop weight impact tests. Vapor grown carbon fiber has been employed for the toughener of the interlayer on the CFRP laminates. Drop wight impact tests has been carried out using 'Dynatup' impact test equipment. Damage area occurring in the interface of the CFRP laminate was observed by ultrasonic flaw detection system. The impact characteristic of the CNF/CFRP hybrid laminates were considered from the viewpoint of the relationship between damage area and impact energy. It was found that the delamination area can be reduced by inserting carbon nanofiber interlayer. The optimal quantity of carbon nanofiber for the interlayer was about 20 g/m^2 in the case of VGCF interlayer.
The object of this study is to establish CFD simulation code of LES so as to calculate a thermally-stratified turbulent boundary layer which is often observed and affects the climate. First, to evaluate a prediction precision of various SGS models of LES under the modeled condition of flow field in urban environment, various thermally-stratified turbulent boundary layers are calculated by the evaluated LES models. Also, LES is the effective calculation technique for an analysis of a turbulent heat and mass transfer in large Reynolds and Prandtl numbers fluids, because LES can calculate turbulent heat and mass transfer phenomena using fewer grid points as compared with DNS. In this study, these SGS models are evaluated in comparison with DNS database, in which problems of LES in the prediction of various thermally-stratified boundary layers are clarified.
With speedup of railways, hydrodynamic phenomena such as vibration or noise have become a significant problem. For further speedup, these phenomena have to be considered to improve comfortability of the ride. It is known that shape of the vehicle affects these phenomena, and in this study, we estimate the effects of rear shape of the vehicle on the flow in terms of pressure coefficient as the preliminary study. We use lattice Boltzmann method and virtual flux method for analyzing the flow around the moving vehicle in a tunnel. As a result, we confirmed that rear shape of the vehicle affects the pressure coefficient on the tunnel wall.
Recently, terrorism with chemical weapons is one of most daunted danger in the world. Chemical terror have particularly high mortality rate. VX gas is one of chemical agent used to commit terrorism. VX gas has severe toxicity and long-period damage because of persistent agent. In the present study, VX gas emission from a contaminated object surface is researched. VX gas emission is unusually analyzed with experiments, since the experiment is so dangerous because of the toxicity. Therefore, in this study, computational fluid dynamics is used to analyze the emission. We proposed a volatilization model which estimates the volatilization quantity of a chemical agent. The numerical results by the model agree with the experimental data. In this study, we research the effects of flows on the volatilization.
Sand erosion is a phenomenon whereby solid particles impinging on a wall cause serious mechanical damage to the wall surface. Aircraft engines operating in a particulate environment are subjected to the performance and lifetime deterioration due to sand erosion. Especially, the fan blades of the aircraft engines are severely damaged. There are some researches for sand erosion of fan, compressor and turbine. However, there are no researches for fan erosion with nose cone. In the present study, we apply our three dimensional sand erosion prediction code to an axial fan with a nose cone. We numerically investigate the change of the flow field, the particle trajectories, and the eroded wall shape, to clarify the effects of nose cone shape on sand erosion.
Ice accretion is the phenomenon that super-cooled water droplets impinge and accrete on a body. It is well known that ice accretion on blades and airfoils leads to performance degradation and severe accidents. For this reason, experimental investigations have been done using flight tests or an icing tunnel. However, it is too expensive, dangerous, and difficult to set actual conditions. Hence, computational fluid dynamics is useful to predict ice accretion. The rotor blade is one of the aircraft components where ice accretes. Therefore, we focus on the ice accretion on a rotor blade in this study. We simulate three-dimensional icing phenomena on the rotor blade of a commercial axial fan. The ice accretion on the rotor blade is numerically discussed.
Yearly, concerns on environmental problem of the earth are growing on. One of the typical issues is desertification. To inhibit harmful effects of desertification, the prediction methods which clarify mechanism of desertification are required. It is expected that numerical simulations are useful for the purpose. However, the numerical procedure and the physical models for predictions have not been established yet. Hence, our purposes are to construct the holistic simulation technique which reasonably reproduces a sand transfer, and to apply it to create an effective prevention method of desertification. The present target of our computation is wind tunnel experiments of sand transfer around a cube on the sand surface conducted by Tominaga (2007). Numerical results are compared with the experiments. In the computation, we confirmed that the results are quantitatively similar to the experiments, for example, the eroded sand height around the cube. Finally we estimated sand transfer around a cuboid to obtain a method to prevent sand suppression.
We studied the influential factors on heat transfer at Au-toluene interface modified by dodecanethiol self-assembled monolayer (SAM). The thermal boundary conductance was calculated for different temperatures using nonequilibrium molecular dynamics simulation. As a result, the overall thermal boundary conductance at Au-SAM-toluene interface decreases as the temperature increases. We analyzed the temperature dependence of SAM structure and discussed the relation between SAM structure and thermal boundary conductance.
In this paper, we investigated mass transfer of Fe^<2+> ions adjacent to the magnetite (Fe_3O_4) solid surface from the microscopic viewpoint by using the molecular dynamic simulations. Not only mass transfer characteristic across the interface, but also that along the interface has to be elucidated in order to predict the strict transport path and diffusion process of ions in the vicinity of the interface. Therefore, we here evaluated two-dimensional free energy surface along the interface according to the ion translation. With Fe^<2+> ions fixed at a certain surface separation distance (SSD), the umbrella sampling/WHAM (weighted histogram analysis method) procedure which can be applied to two-dimensional space was adopted for free energy calculations. As a result, it was found that the free energy surface is significantly influenced by the surface charge distribution of the magnetite surface.
Microscopic contact angle at a moving contact line among water-vapor-platinum interfaces was investigated with molecular dynamics calculations. The extended simple point charge (SPC/E) model was used for the water molecules and the interactions between water and platinum plate were calculated with the potential model proposed by Zuh and Philpott(1994). The simulations were performed in a Couette flow geometry in which water slug were placed between two parallel plates of platinum. The simulation results show that the static contact angle decreased with the increment in the temperature. The dynamic contact angle, which depends on the wall velocity Vw, became less sensitive to Vw as the temperature was increased. The ordered structure of the water molecules was observed in the vicinity of the wall surface, and was disordered as the temperature was raised. This should be responsible for the lowering of the sensitivity of the dynamic contact angle in the high temperature condition.
In this research, we reported the dependence of pore size on the characteristics of transport phenomena of confined water in a nano slit pore by molecular dynamics (MD) simulation. The two surfaces were made of graphite, whose distance was set at 15, 30, and 60 A. The interaction potential between water and carbon was Lennard-Jones potential, and that between water molecules was SPC/E. The water formed a film in each system. The film moved when constant fictitious force parallel to the walls was given to water molecules in the pore. From the results, we examined dependence on width of the velocity of water in the slit pores.
In this research the momentum transport phenomena in a nanoscale liquid bridge were simulated by Molecular Dynamics method and its nanoscale characteristics were analyzed. Water was assumed as the lubricant. Momentum flux was generated in a liquid bridge by controlling the velocity of a part of the liquid bridge. Using the velocity gradient of the liquid bridge and the momentum flux, viscosity coefficients of the liquid bridge were obtained. We analyze the dependence of the width of the liquid bridge on the viscosity coefficient and the differences of the viscosity coefficients between liquid bridges and bulk water were confirmed.
Molecular dynamics analyses have been performed on the electricosmotic flow in parallel plates. Though positive ions move over the whole region in the case of a channel width of 〜8 nm suggesting the overlap of electric double layer, positive ions travel within the regions near the channel walls in the case of a channel width of 〜20 nm suggesting the formation of electric double layer near the channel walls. Also, a fully-developed electroosmotic flow is analyzed based on Gouy-Chapman model by the finite difference method. The distributions of positive ion density for fully-developed flow by the finite difference method agree with in some degree the trajectories of positive ions by the molecular dynamics. The electroosmotic flow velocity estimated by the finite difference method is 2.5 mm/s and 3.6 mm/s for channel widths of 〜8 nm and 〜20 nm, respectively.
Nonequilibrium molecular dynamics simulations were conducted for lipid bilayers with ambient water under two directions of shear flow along the bilayer plane to investigate mechanisms of momentum transfer characteristics in the membranes. Under a shear flow parallel to the bilayer plane, intermolecular interaction contributes to momentum flux positively in the lipid tail area, while negative flux due to intramolecular interaction arises. In the lipid head area, positive and negative contributions of each interaction invert. Under a shear flow perpendicular to the bilayer plane, the largest fraction to total momentum flux in the lipid bilayer is in the lipid head groups. This indicates that the contribution of the head group is the most dominant to surface shear viscosity in the lipid bilayer.
This study describes the property of proton transfer in Nafion membrane analyzed by molecular dynamics (MD) simulation including both Vehicle and Grotthus mechanism. To treat Grotthus mechanism, Empirical Valence Bond(EVE) method was introduced to MD simulation. The potential energy barrier of proton hopping obtained by EVB method was adjusted to the computational result of Density Functional Theory (DFT). After adjusting EVB potential, it is confirmed that protons hop along the hydrogen bond network consecutively. The parameter for the simulation of Nafion membrane was water contents λ, which is defined as the ratio of water molecules and hydronium ions to sulfo groups, SO_<3^->, obtained by λ=N_<H2O,H3O+>/N_<SO3->. The changes of transferring properties and structure of molecules with the changes of λ were analyzed by Mean Square Displacement and Radial Distribution Function, respectively.
Molecular Dynamics (MD) was used to simulate dissociative adsorption of hydrogen molecule on Pt(1l1) surface considering the movement of the surface atoms and gas molecules. Embedded Atom Method (EAM) was applied to represent the interaction potential. A number of MD simulations of gas molecules impinging on Pt(111) surface were carried out changing initial orientations, incident azimuth angles, and impinging positions on the surface using uniform random numbers with fixed initial translational energy, initial rotational energy, and incident polar angle. The number of incidents that dissociated gas molecules was counted to compute dissociation probability. The dissociation probability was analyzed and expressed by a mathematical function of initial conditions of impinging molecule, namely translational energy, rotational energy, and incident polar angle. And the model was verified by comparing with MD simulation results of molecular beam experiments.
The nonequilibrium molecular dynamics simulation was conducted in order to clarify the effects of the surface adherent structures in nanometer scale on a thermal resistance at a liquid-solid interface as well as the reduction mechanism. The surface structural clearances and the potential parameter between liquid molecules and solid atoms were changed as the calculation parameters in order to discuss general nanostructural effects on the interfacial thermal resistance. The local nonequilibrium behaviors were observed between the nanostructures depending on the degrees of freedom of the liquid molecules and the diffusion coefficients of liquid molecules at the interface are enhanced by the local nonequilibrium state depending on the surface adherent structures in nanometer scale only in the case of Lennard-Jones potential liquid model.
In this paper, we investigated the effect of intermolecular potential model on thermodynamic properties of cryogenic hydrogen. We applied three empirical potential models and one ab-initio potential which was derived by Molecular Orbital (MO) calculation. We performed NVE constant Molecular Dynamics (MD) calculation to obtain Equation Of State (EOS). Calculation results were compared with NIST data using the principle of corresponding date. As a result, it was confirmed that every potential showed the same tendency and cannot reproduce NIST data at the high density region.