bluuebunny/crossref_metadata_2025 huggingface dataset:
DETERMINATION OF PARAMETERS OF STEINBERG-GUINAN CONSTITUTIVE MODEL WITH SHOCK WAVE EXPERIMENTS
Authors: PENG JIANXIANG , HU CHANGMING , LI YINGLEI , ZHANG LIN , JING FUQIAN
Published: June 2008

Steinberg-Guinan constitutive model is widely used in impact engineering simulations. Shock wave profile measurements of Al , Cu , and W under shock pressures ranging from 4 GPa to 200 GPa were analyzed, and shear modulus G and yield strength Y of these materials were obtained by using the high-pressure sonic velocities and rate independent Lagrange analysis results. Then values of derivatives of G and Y with respect to pressure or temperature at the reference state of these three metals were determined. By analyzing the pressure and temperature dependence of shear modulus and yield strength, we conclude that the relations of Steinberg-Guinan constitutive model, Y/G=constant, are approximately correct on Hugoniot state for these materials. So this is a probable approach to solve the difficulty of measurement of Y under high-pressure and high-temperature directly.
STUDY ON DYNAMIC FAILURE MODEL OF LEAD-FREE SOLDERS USING SHPB TECHNIQUES
Authors: NIU XIAOYAN , YUAN GUOZHENG , LI ZHIGANG , SHU XUEFENG
Published: June 2008

The dynamic compressive properties of 96.3 Sn 3 Ag 0.7 Cu and 99.3 Sn 0.7 Cu solders were studied by means of a split Hopkinson pressure bar at strain rates ranging from 500 to 2000 s−1. Tests were conducted at room temperature and under uniaxial compressive conditions. Eutectic SnPb solders were used as the reference. From the data of tests, it was found that yield strength and flow stress increased remarkably with the increase of strain rate. On logarithmic scales, the yield strength increased linearly with strain rate. These lead-free solders revealed certain visco-plastic behavior and strain rate sensitivity, which predicted using Johnson-Cook material model. Related parameters in the model were determined from the experiment. Compared with the typical Pb -containing solder Sn63Pb37 , these lead-free solders showed some fine properties and could substitute some Pb -containing solder alloys in microelectronic components packaging and interconnects.
TENSILE STRESS STRAIN BEHAVIOR OF POLYPROPYLENE TOUGHENED WITH BI-MODAL SEBS
Authors: MAE HIROYUKI , OMIYA MASAKI , KISHIMOTO KIKUO
Published: June 2008

The objective is to characterize the effect of the bimodal distribution of rubber particles and its blend ratio on the mechanical properties of the thermoplastic polypropylene blended with two different styrene-ethylene-butadiene-styrene tri-block copolymer (SEBS) at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 10−1 to 102 (1/sec). Phase morphology is investigated to estimate the bi-modal rubber particle size distribution. In addition, the in-situ observation is conducted during uniaxially stretching within transmission electron microscopy (TEM) step by step to investigate the deformation events depending on the elongation of samples. The elastic modulus increased gradually as the blend ratio of large rubber particle increased. An increase in the rupture strain was found for the bimodal rubber-particle distributed blend system where the blend ratios of small rubber particle and large rubber particle were the same. This is because the smaller particles dominant blend systems show the band-like craze deformation while the localized plastic deformation is taken place in the larger particles dominated blend systems. The synergistic effect of these rubber particles gives rise to a strong increase in the ductility of these bimodal rubber-particle distributed polypropylene systems.
EFFECT OF PRE-FATIGUE ON DYNAMIC AND STATIC TENSILE PROPERTIES OF LASER WELDED BUTT JOINTS BETWEEN DIFFERENT HIGH STRENGTH STEEL PLATES
Authors: KOBAYASHI H. , DAIMARUYA M. , TSUDA H. , HORIKAWA K. , YAMADA Y.
Published: June 2008

In this research, the effects of pre-fatigue on the dynamic and quasi-static tensile properties of laser welded butt joints between three kinds of steel plates, i.e. HR270, HR590 and HR780 steels, were investigated using tensile split Hopkinson bar apparatus. There were no significant effects of pre-fatigue on the dynamic and static tensile properties of HR780-HR270 and HR780-HR590 joints. Their fracture occurred in the middle of the weaker base metal parts. However, one or two in three pre-fatigued HR780-HR780 joint specimens broke at the heat affected zone, irrespective of strain rate. Their elongation decreased dramatically from that of the virgin specimens, although there are no changes in the tensile strength.
EFFECTS OF TEMPERATURE AND COMPOSITION ON DYNAMIC DEFORMATION BEHAVIOR OF ZR-BASED AMORPHOUS ALLOYS
Authors: LEE DONG-GEUN , KIM YANG GON , HWANG BYOUNGCHUL , LEE YONGTAI , LEE SUNGHAK
Published: June 2008

Effects of test temperature and alloy composition on dynamic deformation behavior of Zr -based amorphous alloys were investigated in this study. Dynamic compressive tests were conducted in the temperature range from room temperature to 380°C using a compressive Kolsky bar. Dynamic compressive test results indicated that both maximum compressive stress and total strain of the amorphous alloys decreased with increasing test temperature because shear bands could propagate rapidly as the adiabatic heating effect was added at high temperatures. Maximum compressive stress and total strain of the alloy containing ductile β crystalline phases were higher than those of the monolithic amorphous alloys over the tested temperature range because β phases played a role in forming multiple shear bands. The alloys having lower T g or ductile phases had more excellent dynamic properties than the LM1 alloy.
PHASE TRANSITION AND CURRENT PROPERTIES OF PZT 95/5-2NB FERROELECTRIC CERAMIC UNDER DYNAMIC LOADING
Authors: LIU GAOMIN , ZHANG FUPING , DU JINMEI , TAN HUA , HE HONGLIANG
Published: June 2008

The high density ferroelectric ceramic with composition near Pb 0.99( Zr 0.95 Ti 0.05)0.98 Nb 0.02 O 3 ( PZT 95/5-2 Nb ) has been studied under dynamic loading. To characterize its ferroelectric-to-antiferroelectric(FE/AFE) phase transition under shock wave compression, reverse-impact experiments were conducted to determine the Hugoniot states of poled and unpoled PZT 95/5-2 Nb , and the shock-induced depoling currents were examined in an external circuit under short-circuit conditions for the poled PZT 95/5-2 Nb . The Hugoniot data and current results identify that the phase transition of FE/AFE has occured in the stress range of 0.4 GPa~1.8 GPa. In the phase transition stress range, the measured short-circuit currents show the increasing of rise time and the decreasing of final levels with the increase of shock stress.
STRAIN RATE EFFECTS ON COMPRESSIVE PROPERTIES OF A BIODEGRADABLE PLASTIC
Authors: NISHIDA MASAHIRO , TANAKA KOICHI , ITO NORIOMI
Published: June 2008

The compressive properties of a biodegradable plastic were measured over a wide range of strain rates from 10−5 to 104 s −1, using a universal testing machine and a split Hopkinson pressure bar method. The yield stress of the biodegradable plastic increased with increasing strain rate and decreased with temperature and water absorption. Empirical equations for the yield stresses were derived for the strain rates from 10−5 to 103 s −1 and from 103 to 104 s −1, respectively.
DYNAMIC COMPRESSIBILITY OF HIGH-POROSITY DAMPERS OF THERMAL AND SHOCK LOADINGS: MODELING AND EXPERIMENT
Authors: BRAGOV ANATOLY , KONSTANTINOV ALEXANDER , LOMUNOV ANDREY , SADYRIN ANATOLY , SERGEICHEV IVAN , KRUSZKA LEOPOLD
Published: June 2008

High-porosity materials, such as chamotte and mullite, possess a heat of fusion. Owing to their properties, these materials can be used with success as damping materials in containers for airplane, automobile, etc. transportation of radioactive or highly toxic materials. Experimental studies of the dynamic properties have been executed with using some original modifications of the Kolsky method. These modified experiments have allowed studying the dynamic compressibility of high-porosity chamotte at deformations up to 80% and amplitudes up to 50 MPa. The equations of the mathematical model describing shock compacting of chamotte as a highly porous, fragile, collapsing material are presented. Deformation of high-porous materials at non-stationary loadings is usually accompanied by fragile destruction of interpore partitions as observed in other porous ceramic materials. Comparison of numerical and experimental results has shown their good conformity.
EFFECT OF COMPRESSIVE RESIDUAL STRESS INDUCED DURING FABRICATING PROCESS IN THE CORE OF CLAMPED SANDWICH PLATE UNDER SHOCK LOADING
Authors: ZHAO GUIPING , LEE SANG-KYO , CHO CHONGDU
Published: June 2008

Sandwich panels can be manufactured in many ways like lamination press, closed mold fabrication, and vacuum bag compaction. During manufacturing, the core and the sheets are attached under certain applied pressure and temperature, associated with a deformation and stress remaining in the sandwich core. This study presents an evaluation of the compressive residual stress effect of the core which occurs during the localized shock loading at the mid-span of a clamped sandwich plate. We simulate such a square lattice core sandwich plate by commercial finite element code, ABAQUS/Explicit. We apply uniform distributed loading on upper face sheet and temperature difference occurred during the manufacturing process is taken here before the impact simulation step. These loadings induce certain amount of residual stresses in core structure of sandwich panel. The computational result from non-residual stress case is verified by comparing with the results of published experimental data on similar investigation. In addition, the effect of existing residual stress at core is analyzed. We also compare the dynamic responses of two clamped sandwich plates with and without pre-stressed core. And impact resistance of sandwich panel is explained in the view of energy capacity. Results show that the shock loading behavior of sandwich panel depends on its manufacturing process and panels with compressive residual stresses have less deformation and high impact energy absorption characteristics.
STUDY ON THE RELATION BETWEEN MECHANICAL AND BALLISTIC PROPERTIES OF SOME CERAMICS
Authors: KIM CHEOL SOO , KIM CHANG WOOK
Published: June 2008

In this study, we analyzed the relation between mechanical and ballistic properties of several engineering ceramics that were expected to be used as armor materials. After the measurements of mechanical properties (Young's modulus, density, hardness, flexural strength and toughness), we measured the ballistic properties against a long rod KE projectile ( L / D =10.7, Kinetic Energy, tungsten heavy alloy) and copper jet projectile (40mm shaped charge warhead). The ballistic properties were generally increased as the increasing ratio of mechanical properties and density. As the HEL/density ratio was increased, it especially appeared that the ballistic properties were lineally increased.
THE REDUCTION OF STRESS WAVE PROPAGATION THROUGH POROUS MATERIALS
Authors: KIDA SOTO AKI , FUKUSHIMA KEITA , MATSUMOTO MASAYA
Published: June 2008

Impact stress wave propagating through porous materials is investigated in order to examine the ability of the shock absorbing effect. The specimens are modeled as the porous medium with different porous diameters made of the acrylic resin plate. When these models are impacted with different impact velocities, the impact stress waves propagating before and after the porous parts are measured using the strain gages in the experiments. As the reduction effect of the impact stress wave propagating in the porous medium, we pay attention to the maximum stresses and the duration times from the histories of the impact stress waves. One-dimensional wave theory and dynamic element method simulated this model are applied in order to explain these phenomena.
A COMPARATIVE DAMAGE STUDY OF AIR- AND WATER-BACKED PLATES SUBJECTED TO NON-CONTACT UNDERWATER EXPLOSION
Authors: RAJENDRAN R. , LEE J. M.
Published: June 2008

The response of the side shell to non-contact underwater explosion is of major concern in ship design. While extensive research is carried out on air-backed plates, relatively less attention is paid to water-backed plates. Nevertheless, the response of the water-backed plates becomes relevant when the water filled side shells are exposed to an underwater shock loading. Availability of scant information on the experimental results of water-backed plates is the primary motivating factor to make analytical estimates. These estimates are provided in comparison with an air-backed plate for identical attack geometry and target parameters. This work aims to bring out a comparative procedure for the damage assessment between air- and water-backed plates so that the response of the latter can be presented in terms of that of the former.
IDENTIFICATION OF IMPACT LOCATION IN A PLATE BASED ON ELASTODYNAMICS AND HIGHER ORDER TIME FREQUENCY METHOD
Authors: LEE S. K. , KIM S. J.
Published: June 2008

In a nuclear power plant, impact force due to loose part is related to the structural damage in the plant. In general, the steam generator of the nuclear power plant is structured by thick plate. The paper presents a novel approach to locate an impact load in a thick plate. The approach is based on the analysis of the acoustic waveforms measured by a sensor array located on the plate surface. For accurate estimation of the location of the impact source, the time differences in the arrival times of the waves at the sensors and their propagation velocities are determined. The dispersion curves for multi modes of Lamb wave are calculated by using exact plate theory and SDPT. It is difficult to measure directly the group velocity for Lamb mode of acoustic waveform in the thick plate because they are dispersive wave. However, most of the energy in the wave is carried by the flexural waves (A0 mode), the group velocity of this mode is extracted using the CHOTF technique for estimating the impact source location. The estimates are shown to be in excellent agreement with the actual locations and it is applied to the damage analysis due to the loose part in a nuclear power plant.
NUMERICAL SIMULATION OF VISCOELASTIC EFFECTS ON THE ROD DEFORMATION OF TAYLOR IMPACT TEST
Authors: KIM SEE JO , LIM KYUNG HUN , SHIN HYUNG-SEOP , KIM JEONG-TAE , CHOI JOON HONG
Published: June 2008

In this study we analyzed the deformation of the polymeric rod impacting on the rigid wall which is called "Taylor impact test."" We simulated three-dimensional Taylor impact test depending on the various polymeric materials using the explicit finite element method by employing DYNA3D code. In simulation, polymeric materials were modeled using viscoelastic constitutive relations with the relaxation time and shear modulus. We have carried out the numerical simulation for the transient deformation characteristics and discussed effects of the viscoelastic constants on the deformation of the polymeric rod under impact.
STRESS ANALYSIS OF TRANSVERSELY ISOTROPIC CYLINDER UNDER ARBITRARY AXISYMMETRIC LOAD
Authors: LIU BIN , LIU QUAN-SHENG
Published: June 2008

Power series method is used to analyze the distribution of stresses of the transversely isotropic cylinder under arbitrary axisymmetrical normal load. The stress function and normal load are expanded as the form of Fourier series. Unknown parameters in equations are determined using boundary conditions and final solutions of stress and displacement are obtained accordingly. The analysis of stresses obtained from different material parameters shows that the axial stress is significantly affected by Young's modulus and the circumference stress is sensitive to the variation of Poisson's ratio.
DYNAMIC ANALYSIS AND DESIGN OF SEPARATION SCREEN MECHANISM IN A PLANT OF MOISTURIZED WASTES
Authors: MOON BYUNG YOUNG , KIM KWANG HOON , KWAK KWANG HOON , KANG GYUNG JU , HONG CHUL HYUN
Published: June 2008

In this study, theoretical super screen vibration analysis has been carried out to predict the dynamic characteristics of interactive waste particles. The vibrating screen is modeled of three assemblies such as screen, wastes guide, and supported screen. Then materials (or particles) of different size is to be separated by using the eccentric vibrator and classifying tilt plates. In processing separation mechanism, much lighter construction wastes (wood, Styrofoam, etc) and heavier materials are separated by staying time delay in a super screen. The design results, separation screen were able to know that small and larger particles are conspicuous difference each motion character according to trajectory particles, and small particles raise the probability in classifying tilt plates.
A STUDY OF 954-2A/IM7 COMPOSITE LAMINATES CONTAINING A CENTRAL HOLE
Authors: KIM HYUNGWON
Published: June 2008

Predicting microcracking properties of the composite laminates in nonuniform stress conditions was the subject in this paper. The uniform stress field meant the stresses were independent of the width direction. The material was the 954-2A/IM7 laminates containing a central hole. Microcracks initiated at the edge of the hole and propagated into the laminate. Because the tensile stress concentration decreased with distance, the microcracks were arrested before the edge of the laminate. Because carbon fiber composites were opaque, a x-ray method was used to detect the length of the propagating microcracks. The microcracking at the near edge of the hole could be reasonably predicted by considering the local laminate stresses and the microcracking toughness measured in unnotched laminates. However, the data away from the hole did not agree with the predictions. The local microcrack density was always much higher than that predicted by the local laminate stress.
FRACTURE PHENOMENA OF BRITTLE MATERIAL AGAINST A SHAPED CHARGE JET
Authors: CHOI JOON HONG , CHANG SOON NAM
Published: June 2008

In order to study the protection behavior of brittle materials against a shaped charge jet, the jet penetration and the fracture behavior have been investigated by the series of photographs taken by the IMACON high speed camera. The examined materials were glass, fused silica, and single crystalline quartz. The trend of crack growth in BK7 glass and fused silica indicated conical shape. In the case of the single crystalline quartz, it was observed that the crack grows fast along the axis of crystal growth. The velocity of shock wave (~ 6km/sec) into glass and fused silica was faster than the sonic velocity. However, the velocity of shock wave in the single crystalline quartz showed to be similar to its sonic velocity. The ballistic protection capability of single crystalline quartz showing fast crack growth has been evaluated to be lower than that of fused silica which has relatively slow crack growth, although the quartz has higher physical and mechanical properties.
THEORY OF NON-DESTRUCTIVE INSPECTION OF CERAMICS BASED ON FLAW-SIZE DISTRIBUTION
Authors: MATSUO YOHTARO
Published: June 2008

Two kinds of theory for non-destructive inspection of ceramics were reviewed, which were derived by the authors using flaw-size distribution. In the sufficient condition theory (Realistic NDI), we had discussed about the screening flaw-size and a screening region. In the necessary and sufficient condition theory (Ideal NDI), we found that the screening flaw-size should be changed depending on stress state and specimen configuration. It was proved that there is one-to-one correspondence between Ideal NDI and a proof test. Applications to machining damage problems and surface strengthening of ceramics were also presented.
THE MECHANISM OF SHOCK COMMINUTION OF 3D C/SIC COMPOSITE SUBJECTED TO HIGH VELOCITY IMPACT
Authors: ZHANG QINGMING , HUANG FENGLEI , CHEN LI , HAN LIMING , LI JINZHU
Published: June 2008

In this paper, experimental investigation and theoretical analysis are carried out in an attempt to study the response of SiC ceramic matrix composite reinforced with three dimensional braided fabric(3 D C/SiC ) under high velocity impact. The results show that 3 D C/SiC composite will be turned into comminution if the pressure of the impact point resulted from the projectile impacting 3 D C/SiC composite sample is larger than 780Mpa. Based on the analysis of the mechanism of composite comminution, a theoretical model has been developed.
QUASI-STATIC COMPRESSION AND ROLLING CONTACT ANALYSIS OF MAXXIS VICTRA MA-Z1 TIRE ON DRY ROADWAY
Authors: JENQ S. T. , TING YUCHENG , LIANG S. M. , LIN DAVID , SHIH MIKE
Published: June 2008

Quasi-static contact behavior of an inflated MAXXIS VICTRA MA-Z1 (235/45/R17) radial tire is reported in this work. Compressional response of the inflated tire with a prescribed weight loaded quasi-statically was examined. Both experimental and numerical results were obtained and compared. In addition, dynamic contact simulation of the tire rolling on a dry-flat roadway was also studied. A commercial finite element commercial Code (LS-DYNA) was used to construct the complex tire model and to perform both quasi-static contact and dynamic rolling simulations. The Mooney-Rivlin constitutive relationship was adopted to describe the non-linear elastic behavior of rubber material, and the classical laminated theory was used to model the stress-strain behavior of the fiber reinforced composite layers of tire. Quasi-static contact force and compression displacement of tire were measured and numerically simulated. Contact pressure distribution of the tire tread in touch with simulated rigid dry-flat road surface was also numerically and experimentally obtained. Good relationship between the test findings and simulated results were reported. In addition, the dynamic contact simulations of the inflated tire rolling on a dry-flat rigid roadway with a prescribed weight loaded are presented, and the deformation pattern and local contact stress distribution are also reported.
NUMERICAL AND EXPERIMENTAL APPROACH FOR THE OPTIMAL DESIGN OF A DUAL PLATE UNDER BALLISTIC IMPACT
Authors: YOO JEONGHOON , CHUNG DONG-TEAK , PARK MYUNG SOO
Published: June 2008

To predict the behavior of a dual plate composed of 5052-aluminum and 1002-cold rolled steel under ballistic impact, numerical and experimental approaches are attempted. For the accurate numerical simulation of the impact phenomena, the appropriate selection of the key parameter values based on numerical or experimental tests are critical. This study is focused on not only the optimization technique using the numerical simulation but also numerical and experimental procedures to obtain the required parameter values in the simulation. The Johnson-Cook model is used to simulate the mechanical behaviors, and the simplified experimental and the numerical approaches are performed to obtain the material properties of the model. The element erosion scheme for the robust simulation of the ballistic impact problem is applied by adjusting the element erosion criteria of each material based on numerical and experimental results. The adequate mesh size and the aspect ratio are chosen based on parametric studies. Plastic energy is suggested as a response representing the strength of the plate for the optimization under dynamic loading. Optimized thickness of the dual plate is obtained to resist the ballistic impact without penetration as well as to minimize the total weight.
SIMULATION OF COLLISION CONTACTS AMONG DISJOINED SOIL-STRUCTURE BODIES UNDER SEISMIC MOTIONS
Authors: WANG CHING-JONG
Published: June 2008

Structure bodies and surrounding soils in certain types of bridges and tunnels may be prone to collisions during earthquake. A dynamic system composed of discrete and finite elements is developed using explicit formulation for equations of motion, and nonlinearities in soils and at interfaces of disjoined regions are implemented. Time history solutions are carried out to examine the plastic deformation in soils as well as the integrity of structures. Two case studies are presented in which collisions among disjoined regions are anticipated in the event of extremely large earthquakes. Case one is based on a replica from a quake-stricken bridge, to illustrate that a backfill with moderate soil strength may be used as an energy-dissipating buffer to contain the shaken loose decks. The other case involves an underground subway station box with slurry walls alongside, to exemplify the seismic resistance of the dual-wall system.
NUMERICAL SIMULATIONS OF DROP DEFORMATION IN A CYLINDRICAL TUBE USING MOVING AND FIXED GRID METHODS
Authors: KIM SEE JO , HWANG WOOK RYOL , LIM KYUNG HUN , SHIN HYUNG-SEOP
Published: June 2008

It is quite meaningful in an engineering aspect to investigate liquid drop behaviors in two-phase flow, on which dispersive mixing or overall rheological characteristics heavily depend. There are two approaches numerically to deal with two-phase flow problems, which are the moving- and the fixed-grid methods: that is, interface tracking and interface capturing methods. In this study, we developed multiphase flow codes in both Lagrangian and Eulerian frameworks and compared each solution for the single drop problem in an axisymmetric channel flow. Deformation patterns of drops were observed by these two methods and we have discussed the characteristic features of two methods from the deformation of drop for the moving boundary problems.
FORMULATION ON THE EMPIRICAL EQUATION OF THE CASK IMPACT FORCES BY DIMENSIONAL ANALYSIS
Authors: LEE YOUNG-SHIN , KIM YONG-JAE , CHOI YOUNG-JIN , LEE EUN-YUP
Published: June 2008

Radioactive material is used in the various fields. The numbers of transport for radioactive material have been gradually increased in both domestic and international regions. The safety of the cask should be secured to safely transport of radioactive material. The Korean atomic law and the IAEA safety standards prescribe regulations for the safe transport of radioactive material. The cask for spent fuel is comprised of the body and the impact limiter.

In this study, the empirical equation of the cask impact force was proposed based on the dimensional analysis. Using this empirical equation the characteristics of the impact limiter were analyzed. The results are also validated by comparing with the previous results of the impact area method and the finite element analysis. The present method can be used to predict the impact force of the cask.
ORBITAL FORMING SIMULATION OF AUTOMOTIVE HUB BEARING USING THE EXPLICIT FINITE ELEMENT METHOD
Authors: CHO HYUN-JIK , KOO JEONG-SEO
Published: June 2008

In this paper, the orbital forming simulation of an automotive hub bearing was studied to predict forming conditions and performances using the explicit finite element method. To set up an efficient solution technique for the orbital forming, axisymmetric finite element models and 3D solid element models were numerically solved and compared to each other. The time scaling and mass scaling techniques were introduced to reduce the excessive computational time caused by small element size in case of the explicit finite element method. It was found from the numerical results on the orbital forming that the axisymmetric element models showed the similar results to the 3D solid element models in forming loads whereas the deformations at the bearing inner race were quite different. Finally the strains at the bearing inner race and the forming forces of the peen were measured by test for the same product used in the numerical analysis, and were compared with the 3D solid element results. It was shown that the test results were in good agreements with the numerical ones.
HIGH SPEED PROCESSING OF NI-ALUMINIDES-REINFORCED NI-MATRIX COMPOSITES BY PULSED-CURRENT HOT PRESSING (PCHP)
Authors: MIZUUCHI KIYOSHI , SUGIOKA MASAMI , ITAMI MASAO , INOUE KANRYU , LEE JUN-HEE , KAWAHARA MASAKAZU , MAKINO YUKIO
Published: June 2008

Nickel-aluminides-reinforced nickel-matrix composites were fabricated from 0.05mm-thick nickel foils and 0.012mm-thick aluminum foils, in a process using a pulsed-current hot pressing (PCHP) equipment, and the effect of reaction temperature on mechanical properties of the composites was investigated. The composites were of laminated structure and composed of Ni and reacted layers containing Ni -aluminides. The chemical composition of the reacted layers was dependent on reaction temperature in the temperature range employed. Tensile testing at room temperature revealed that the reaction temperature evidently influences mechanical properties, including tensile strength, elongation and fracture mode, of the composites. The tensile strength and elongation of composites fabricated at 1373K were 500MPa and 3.8%, respectively. Microstructure observations of fractured specimens revealed that Ni layers of the composite played a significant role in prohibiting the growth of numerous cracks emanating from Ni -aluminides. In the case of composites fabricated at 1373K, in addition, crack propagation between Ni -rich Al -solid-solution layers and cellular Ni 3 Al in the Ni -aluminides were prevented by mutual interaction.
INTRODUCTION OF MACRO-STRAIN WITH RELEASING MICRO-STRAIN BY CAVITATION SHOTLESS PEENING
Authors: SOYAMA HITOSHI
Published: June 2008

When cavitation bubble is collapsed, shock wave which can deform metallic materials is produced. Cavitation impacts can be used for surface modification to enhance fatigue life of metallic materials in the same way as shot peening. As a peening method using cavitation impact does not require shots in shot peening, it is called “cavitation shotless peening CSP”. Although CSP can introduce compressive residual stress, i.e., macro-strain into metallic materials, full width at half maximum of diffractive X-ray profile was decreased by CSP. In the present paper, tool alloy steel for forging die was chosen as tested material to investigate mechanism of improvement of fatigue life, as CSP improved the life time of the forging die. The introduction of macro-strain was revealed by measuring residual stress, which was evaluated by X-ray diffraction method. The fatigue life was investigated by using a plate bending fatigue test changing with processing time of CSP. The micro-strain was evaluated by a fundamental parameter approach, which is one of X-ray diffraction method. It was concluded that the fatigue life of the steel was improved about 90 times by CSP and CSP can introduce macro-strain, i.e., compressive residual stress and releasing micro-strain. The micro-strain becomes about 1/20 of heat treated specimen by CSP.
A STUDY OF DRY COATING PROCESS
Authors: HONG JOO-PYO , MIN DONG-KYUN , CHUNG DONG-TEAK
Published: June 2008

Dry zinc coating processes similar to the shot pinning was studied in the aspects of environmentally benign process to substitute traditional wet type phosphate coating of the work-piece, which is for protection from the deterioration of the surface quality and the shortening of the lifetime of the die during cold extrusion. Experiment and simulation on the collision and coating process of the zinc coated steel balls onto the steel target was performed. Coating patterns on the target and damage of the zinc shell of the ball with respect to the colliding speed were observed during the experiment. Explicit finite element analysis showed the deformation and the fracture of the zinc shell were similar to the experimental results even though the adhesion of the zinc layer onto the work-piece could not be expressed directly. The optimal velocity of the balls was obtained considering effective zinc coating and maximum lifetime of the ball.
DYNAMIC ANALYSIS OF HEAD IMPACT TEST OF PASSENGER AIR-BAG MODULE ASSEMBLY OF VEHICLE USING FEM
Authors: KIM MOON SAENG , LEE JOON HO , MOON BYUNG YOUNG
Published: June 2008

In this study, dynamic impact analysis for the passenger air-bag(PAB) module has been carried out by using FEM to predict the dynamic characteristics of vehicle ride safety against head impact. To carry out the dynamic analysis of head impact test of the PAB module assembly of automobile, the FE models, which are consist of instrument panel, PAB Module, and head part, are combined to the whole module system. Then, impact analysis is carried out by the explicit solution procedure with assembled FE model. And the dynamic characteristics of the head impact are observed to prove the effectiveness of the proposed method by comparing with the experimental results. As a result, the better optimized impact characteristics are proposed by changing the tie bracket's width and thickness of module. The proposed approach of impact analysis will provides an efficient vehicle to improve the design quality and reduce the design period and cost.
PREDICTION OF MAXIMUM MOMENT OF CIRCULAR TUBES SUBJECTED TO PURE BENDING IN CONSIDERATION OF THE LENGTH EFFECT
Authors: MASUDA KENICHI , CHEN DAI-HENG , OZAKI SHINGO , USHIJIMA KUNIHARU
Published: June 2008

In the present study, the bending collapse of an elastoplastic cylindrical tube subjected to static pure bending is investigated using the finite element method (FEM). The moment of the elastoplastic cylindrical tube is controlled by the flattening rate of the tube cross-section. For a long tube, the flattening rate can be expressed in terms of the axial and circumferential stresses that, in turn, depend on the material and geometrical properties and the curvature of the tube. On the other hand, for a short tube, the boundary condition of the fixed walls prevents the flattening rate. In order to account for the length effect of tubes, we propose a new method in which flattening is considered as a deflection problem of a fixed curved beam. The proposed method was able to predict the change in the flattening rate as the curvature was increased. A rational prediction method is proposed for estimating the maximum bending moment of cylindrical tubes that accounts for the length effect. Its validity is demonstrated by comparing it predictions with numerical results obtained using the finite element method.
ENERGY ABSORPTION EFFICIENCY IN CELLULAR SOLIDS
Authors: USHIJIMA KUNIHARU , CHEN DAI-HENG , NISITANI HIRONOBU
Published: June 2008

In this paper, a new type of honeycomb structure is proposed to enhance the energy absorption capacity for a honeycomb structure, and investigated its energy absorption efficiency (absorbed energy per unit volume) by finite element method (FEM). This model has small arc-shaped parts on the double cell wall, and can be manufactured by a similar way of standard honeycomb structures. Also, the proposed structure has large rigidity of plastic bending without increasing the mass. In this paper, effects of geometrical properties on the energy absorption characteristics are discussed.
NUMERICAL ANALYSIS OF ROLLOVER AND HEAD-ON CRASH RESPONSE OF NON-STEP BUS
Authors: KIM YOO-SUK , CHO JIN-RAE
Published: June 2008

As a next-generation metropolitan transportation means, nowadays non-step bus is in the spotlight world widely. However, in the design of non-step bus, the most important consideration should be focused on the securing of the survival space for passengers in unexpected traffic accident. In this context, this paper presents the finite element analysis of the rollover and head-on crash response of a composite non-step bus. A 3-D full-scale finite element model of the non-step bus, together with the simulation conditions which are consistent with the safety test rules established in Europe, is employed for the realistic and reliable numerical analysis.
A STUDY ON THE MECHANISM OF OCCUPANT'S CERVICAL INJURY BY LOW SPEED REAR-END COLLISION OF AUTOMOBILES
Authors: CHO WONHAK , KIM YONGCHUL , CHOI HYEONKI
Published: June 2008

Neck injury in rear-end car collisions is an increasing concern in the field of traffic safety. This injury commonly occurs at rear-end impact, however the injury mechanisms for whiplash remain a mystery. The purpose of this study is to quantitatively analyze the head and neck kinematics during the low-speed rear-end impact of automobiles. It is important to produce data that is related as closely as possible to the in vivo situation. So, we performed a sled test which simulated rear-end impacts with a velocity of 0.6 m/s with five normal healthy male subjects. 3-D motion analysis system was used to document motion data of two situations. When we compare the values of angular velocity and acceleration of head and neck, the peak magnitudes of inclined seated posture were smaller than those of upright seated posture. The result of this study is expected to provide insight that will aid in determining the mechanism of whiplash which is crucial to the identification of possible injury mechanisms.
A STUDY ON IMPACT ANALYSIS OF SIDE KICK IN TAEKWONDO
Authors: LEE JUNG-HYUN , LEE YOUNG-SHIN , HAN KYU-HYUN
Published: June 2008

Taekwondo is a martial art form and sport that uses the hands and feet for attack and defense. Taekwondo basic motion is composed of the breaking, competition and poomsea motions. The side kick is one of the most important breaking motions. The side kick with the front foot can be made in two steps. In the first step, the front foot is extended forward from the back stance free-fighting position. For the second step, the rear foot is followed simultaneously. Then, the side kick is executed while the entire body weight rests on the rear foot. In this paper, the impact analysis on a human model for kicking posture was carried out. The ADAMS/LifeMOD used numerical modeling and simulation for the side kick. The numerical human models for assailant and opponent in competition motion were developed. The maximum impact force on the human body was obtained by experiment and was applied to impact simulation. As a result, the impact displacement and velocity of the numerical human model were investigated.
DEFORMATION BEHAVIORS OF Zr-BASED BULK METALLIC GLASS UNDER IMPACT INDENTATION
Authors: SHIN HYUNG-SEOP , CHANG SOON-NAM , KIM DO KYUNG
Published: June 2008

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications under impact loading. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation to a Zr -based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact or shock loading conditions. Results were compared with those of spherical indentation under quasi-static and impact loading and were discussed. The interface bonded specimen method was adopted in order to observe the subsurface damage, especially the formation of shear bands induced during indentation under different loading conditions.
INITIAL SHIP DESIGN USING A PEARSON CORRELATION COEFFICIENT AND ARTIFICIAL INTELLIGENCE TECHNIQUES
Authors: MOON BYUNG YOUNG , KIM SOO YOUNG , KANG GYUNG JU
Published: June 2008

In this paper we analyzed correlation between geometrical character and resistance, and effective horse power by using Pearson correlation coefficient which is one of the data mining methods. Also we made input data to ship's geometrical character which has strong correlation with output data. We calculated effective horse power and resistance by using Neuro-Fuzzy system. To verify the calculation, 9 of 11 container ships' data were improved as data of Neuro-Fuzzy system and the others were improved as verification data. After analyzing rate of error between existing data and calculation data, we concluded that calculation data have sound agreement with existing data.
SILK FIBROIN FILMS CRYSTALLIZED BY MULTIWALLED CARBON NANOTUBES
Authors: KIM H.-S. , PARK W.-I. , KIM Y. , JIN H.-J.
Published: June 2008

Silk films prepared from regenerated silk fibroin are normally stabilized by β-sheet formation through the use of solvents (methanol, water etc.). Herein, we report a new method of preparing water-stable films without a β-sheet conformation from regenerated silk fibroin solutions by incorporating a small amount (0.2 wt%) of multiwalled carbon nanotubes (MWCNTs). To extend the biomaterial utility of silk proteins, forming water-stable silk-based materials with enhanced mechanical properties is essential. Scanning electron microscopy and transmission electron microscopy were used to observe the morphology of the MWCNT-incorporated silk films. The wide-angle X-ray diffraction provided clear evidence of the crystallization of the silk fibroin induced by MWCNT in the composite films without any additional annealing processing. The tensile modulus and strength of the composite films were improved by 108% and 51%, respectively, by the incorporation of 0.2 wt% of MWCNTs, as compared with those of the pure silk films. The method described in this study will provide an alternative means of crystallizing silk fibroin films without using an organic solvent or blending with any other polymers, which may be important in biomedical applications.
A STUDY ON FRACTURE CHARACTERISTICS OF THE SM53C USED IN THE CAM SHAFT
Authors: JEON HYUN-BAE , SONG TAE-HOON , PARK SUNG-HO , HUH SUN-CHUL , PARK WON-JO
Published: June 2008

This experimental study investigates the fracture characteristics of the camshaft made with newly developed SM53C material. As part of the countermeasure, use the surface hardening heat treatment. Cam shaft which is a part of automobile engine is very essential when traveling and significant to fuel injection timing. Stiffness and efficiency are important for automobile sash which have a durability of the engine. High hardness and durability are necessary, because engine output is affected by cam shaft directly. So, high-frequency induction hardening is very important because of increasing the surface strength. The shape of hardening depth, hardened structure, hardness, and fracture characteristics of SM53C composed by carbon steel are also investigated.
ANALYSIS AND DESIGN OF PINION WITH INNER HELICAL GEAR BY FEM
Authors: KANG GYUNG JU , KIM JEONG , KANG BEOM SOO , MOON BYUNG YOUNG
Published: June 2008

Cold forging of pinion gear with shape of outer spur gear and inner helical gear have been investigated in this study. A numerical analysis for preform design substituting cutting process in gear forging was developed by means of upsetting process. By using the finite element program DEFORM-3D, the analysis is carried out. Using this simulation, the preform of pinion and helical gear forging process were designed. The suggested process is verified by experiment. Compared to the traditional CNC processing, the upsetting process can form a preform without cutting, which leads to shorter forming time and reduce material usage.
SOLUTIONS TO ZERO-SUM EXPONENT EQUATIONS OVER FINITE CYCLIC GROUPS OF EXPONENT GREATER THAN TWO
Authors: FERLINI VINCENT
Published: June 2008

Lyndon initiated a study of equations over cyclic groups [8] and his approach led him to consider a class of equations of the form ah= (tpat-p)(tqat-q)(tpat-p)-1(tqat-q)-1where t is the variable and the cyclic group is Cn= 〈a|an〉. Work by Ferlini, Goldstein, and Salpukis [3] concentrated, more generally, on equations with the exponent sum of the variable being zero over C2. This paper continues along the path started by Lyndon and shows that a large class of the equations above do have solutions over Cnwhere n ≥ 4. Our approach involves the use of pictures. We also include a result that the equations with h = 1, 2, p = 1, and q = 2 do not have a solution over C3.
WORD EQUATIONS OVER GRAPH PRODUCTS
Authors: DIEKERT VOLKER , LOHREY MARKUS
Published: June 2008

For monoids that satisfy a weak cancellation condition, it is shown that the decidability of the existential theory of word equations is preserved under graph products. Furthermore, it is shown that the positive theory of a graph product of groups can be reduced to the positive theories of those factors, which commute with all other factors, and the existential theories of the remaining factors. Both results also include suitable constraints for the variables. Larger classes of constraints lead in many cases to undecidability results.
DIFFERENTIAL MODES
Authors: KRAVCHENKO A. V. , PILITOWSKA A. , ROMANOWSKA A. B. , STANOVSKÝ D.
Published: June 2008

Modes are idempotent and entropic algebras. Although it had been established many years ago that groupoid modes embed as subreducts of semimodules over commutative semirings, the general embeddability question remained open until Stronkowski and Stanovský's recent constructions of isolated examples of modes without such an embedding. The current paper now presents a broad class of modes that are not embeddable into semimodules, including structural investigations and an analysis of the lattice of varieties.
NOETHER SYMMETRY APPROACH TO SCALAR-FIELD-DOMINATED COSMOLOGY WITH DYNAMICALLY EVOLVING G AND Λ
Authors: BONANNO ALFIO , ESPOSITO GIAMPIERO , RUBANO CLAUDIO , SCUDELLARO PAOLO
Published: June 2008

This paper studies the cosmological equations for a scalar field φ in the framework of a quantum gravity modified Einstein–Hilbert Lagrangian where G and Λ are dynamical variables. It is possible to show that there exists a Noether symmetry for the point Lagrangian describing this scheme in a FRW universe. Our main result is that the Noether Symmetry Approach fixes both Λ = Λ(G) and the potential V = V(φ) of the scalar field. The method does not lead, however, to easily solvable equations, by virtue of the higher dimensionality of the reduced configuration space involved, the additional variable being the running Newton coupling.
THE CHIRAL AND FLAVOR PROJECTION OF DIRAC–KÄHLER FERMIONS IN THE GEOMETRIC DISCRETIZATION
Authors: WATTERSON STEVEN
Published: June 2008

It is shown that an exact chiral symmetry can be described for Dirac–Kähler fermions using the two complexes of the geometric discretization. This principle is extended to describe exact flavor projection and it is shown that this necessitates the introduction of a new operator and two new structures of complex. To describe simultaneous chiral and flavor projection, eight complexes are needed in all and it is shown that projection leaves a single flavor of chiral field on each.
Cretaceous characiform fishes (Teleostei: Ostariophysi) from Northern Tethys: description of new material from the Maastrichtian of Provence (Southern France) and palaeobiogeographical implications
Authors: Otero O. , Valentin X. , Garcia G.
Published: June 2008

The order Characiformes (Teleostei: Otophysi) is one of the most diverse freshwater fish groups. It contains around 1400 living species in South and Central America and Africa. Their fossil record starts in the Cretaceous on both continents and also in Europe. Here, we describe and discuss the occurrences of new characiform fish teeth from Provence (Maastrichtian, S. France). Five morphological types are recognized. They belong to possibly three different taxa, and they are regarded as Characiformes indet. However, two of them have resemblances to alestin fishes and could be related to the African family Alestidae. The characiform fishes from Provence are among the oldest known in Europe, together with a freshwater characiform fish occurring in Romania, and the recently described marine fish
Sorbinicharax
from Italy. The biogeographical history of characiform fishes has been intensively discussed during the last three decades. The group is generally accepted to be Gondwanan and its diversification linked with the break-up of this continent, with two main scenarios depending on whether the group is archaeo- or telolimnic. Some authors also propose a Pangaean origin. The recent discoveries of
Sorbinicharax
and of the fossils from Provence change our view on the Cretaceous characiform diversity and their early ecology, and they also enable us to re-evaluate the proposed biogeographical scenarios, reinforcing the hypothesis of the telolimny of the group.