bluuebunny/crossref_metadata_2025 huggingface dataset:
TESTING METHOD FOR MEASURING IMPACT STRENGTH OF BGA SOLDER JOINTS ON ELECTRONIC PACKAGE
Authors: ADACHI TADAHARU , GOTO HIROTAKA , ARAKI WAKAKO , OMORI TAKAHIRO , KAWAMURA NORIYASU , MUKAI MINORU , KAWAKAMI TAKASHI
Published: June 2008

A pendulum-impact testing machine was developed to measure the impact strength of ball-grid-array (BGA) solder joints between an electronic package and a circuit board. Ball solders were connected to daisy-chain between a dummy electronic package and a circuit board. The upper side of the package was directly bonded to a load cell. The rear side of the circuit board was also bonded to an aluminum alloy block fixed on a base. A pendulum made of aluminum alloy was collided into the load cell to apply tensile impact to the solder joints through the load cell. The history of the impact load could be controlled by raising the angle of the pendulum. The fracture of a BGA solder joint was detected by measuring the resistance of the daisy-chain circuit on the board. Therefore, the impact strengths of the solder joints at electrical disconnection and mechanical breaking of all joints could be determined. The experimental results showed that this method is useful for measuring the impact strength of BGA solder joints.
VERIFICATION OF THE SHB TEST RESULTS BASED ON THE ONE-DIMENSIONAL STRESS WAVE THEORY
Authors: MASUDA TOMOKAZU , SAITO KENJI , MORITA IZUMI , IKEDA SHUSHI , MAKII KOICHI , OGAWA KINYA
Published: June 2008

In order to evaluate dynamic deformation behaviors under high strain rates, Kobe Steel has developed and applied a Split-Hopkinson Bar (SHB) apparatus. This paper discusses the validity of the strain measurements and strain rates measured by this SHB apparatus. The strain waves that propagated in the incident and transmitted bars and the specimen are captured using a high-resolution type high-speed photography in detail. The strain wave propagated many times in the incident and transmitted bars and the specimen when the specimen was not broken. The amount of the deformation of the specimen decreases with the propagation frequency of the incident wave. On the other hand, to improve accuracy at the strain and strain rate calculated by the one-dimensional stress wave theory, Young's modulus, the longitudinal wave speed, and the density were accurately determined. It was understood that the calculation value showed the strain and strain rate captured with the high-speed photography are a good agreement. As a result, the validity of the measurement accuracy of this SHB could be shown.
A DEVELOPMENT OF ACCELERATED LIFE TEST METHOD FOR BLOWER MOTOR FOR AUTOMOBILE USING INVERSE POWER LAW MODEL
Authors: SHIN WAE-GYEONG , LEE SOO-HONG
Published: June 2008

Reliability of automotive parts has been one of the most interesting fields in the automotive industry. Especially small DC motor was issued because of the increasing adoption for passengers' safety and convenience. This study was performed to develop the accelerated life test method using Inverse power law model for small DC motors. The failure mode of small DC motor includes brush wear-out. Inverse power law model is applied effectively the electronic components to reduce the testing time and to achieve the accelerating test conditions. Accelerated life testing method was induced to bring on the brush wear-out as increasing voltage of motor. Life distribution of the small DC motor was supposed to follow Weibull distribution and life test time was calculated under the conditions of B 10 life and 90% confidence level.
PENETRATION CONCRETE TARGETS EXPERIMENTS WITH NON-IDEAL & HIGH VELOCITY BETWEEN 800 AND 1100M/S
Authors: WU HAIJUN , WANG YINAN , HUANG FENGLEI
Published: June 2008

In this paper, three types of projectiles were designed, which are based on the physical mechanism of high-speed penetrating into concrete targets. The three types of projectiles are ogive nose followed by cylinder, cone and grooved cone shank respectively, which are made of 30 CrMnSiNi2A with the yield strength 1570MPa. The unconfined compressive strength of concrete target for test is 50MPa. Seven experiments for striking velocities between 800 and 1100m/s were conducted. The experiments showed that the projectiles of cone and grooved cone shank have better penetration performances and the penetration channels were very straight. Compared with the cylinder shank projectiles, the cone and grooved cone shank projectiles are more effective under the condition of high velocity penetrating into complex geological materials as concrete or rock.
DYNAMIC TENSILE AND COMPRESSIVE STRESS-STRAIN CHARACTERISTICS OF MAGNESIUM ALLOYS AT ELEVATED TEMPERATURES
Authors: ARAMOTO TEPPEI , TACHIYA HIROSHI , HORI AKIYOSHI , HOJO AKIHIRO , MIYAZAKI YUSUKE
Published: June 2008

The dynamic stress-strain characteristics of magnesium alloys have not been clarified sufficiently. Thus, the study investigated both the compressive and tensile dynamic stress-strain characteristics of representative magnesium alloys: AZ61A-F, ZK60A-T5 and AZ31B-F at wide strain rate and temperature ranges. About the strain rate dependency, the dynamic stresses are higher than the static ones under both compressive and tensile loads at elevated temperatures; however the dynamic stress-strain relations change slightly in the dynamic strain rate range. Thus, the magnesium alloys has little strain rate dependence. However, the elongation of the dynamic stress-strain relations under tensile load tends to be larger than that of static one. About the temperature dependency, the yield and flow stresses of the investigated magnesium alloys under compressive load decrease abruptly at temperatures higher than about 600 K in the wide strain rate range. Meanwhile, the ones under tensile load decrease with the temperature more gently. Totally, the magnesium alloys exhibit low temperature dependence. Furthermore, as well known, the yield stresses caused under the tensile load exhibit about twice as high as those under compressive load. This study verified that such a characteristic can be observed over a wide strain rate and temperature ranges.
HIGH STRAIN RATE STUDY OF CERAMICS USING HOPKINSON BAR SYSTEM
Authors: BASSIM M. N. , ODESHI A. G. , BOLDUC M.
Published: June 2008

There are at present several applications where high strength ceramics have replaced metals that are subjected to high speed impact from projectiles. This requires an evaluation of behavior of ceramics under impact at high strain rates. This current study provides information on high strain-rate behavior of alumina tested in shear using torsional Hopkinson bar. Dynamic stress-strain curves were generated to investigate deformation behavior prior to fracture while fractography of the broken specimens was carried out to establish the mode of failure. The results of this investigation are similar to what is obtainable in metallic materials in which mechanism of damage is controlled by strain localization and formation of adiabatic shear bands.
EFFECTS OF STRAIN RATE DEPENDENCY OF MATERIAL PROPERTIES IN LOW VELOCITY IMPACT
Authors: MINAMOTO HIROFUMI , SEIFRIED ROBERT , EBERHARD PETER , KAWAMURA SHOZO
Published: June 2008

Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of strain rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. Finite Element simulations using strain-rate dependent material behavior are carried out. In addition, Finite Element simulations with elastic-plastic material behavior, which ignore the strain rate dependency, are carried out as well as elastic material behavior. Comparisons between the experiments and the simulations using strain-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the strain rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.
INTEGRATED STUDY OF DYNAMICAL PROPERTIES OF AK4-1 ALUMINUM ALLOY
Authors: BRAGOV A. M. , KONSTANTINOV A. Yu. , LOMUNOV A. K. , SERGEICHEV I. V. , FILIPPOV A. R. , SHMOTIN Yu. N.
Published: June 2008

Results of experimental studies and numerical modeling of high strain rate of aluminum alloy AK4-1 (analog AU2GN) have been presented. Using Split Hopkinson Pressure Bar (SHPB) method stress-strain curves under compression and tension have been obtained. On the basement of these results appropriate parameters of some constitutive equations have been calculated. Strength and deformation material failure properties, dynamic crack resistance, dynamic friction factor for material pair aluminum-titanium have been obtained by carrying out of modificated SHPB tests. A verification of the constitutive equations has been realized by dynamic indentation method and modified Taylor test.
STRAIN RATE DEPENDENCE OF DYNAMIC FLOW STRESS OF 2017 ALUMINUM ALLOY AT VERY HIGH STRAIN RATES
Authors: SAKINO KIYOTAKA
Published: June 2008

To estimate the strain rate dependence of the dynamic flow stress of aluminum alloys, 2017-O and - T4, high strain rate and rate reduction tests are performed at strain rates ranging from about 1000/sec to 30000/sec. A steep increase in the flow stress is observed for 2017-O at the strain rate of about 3000/sec. For 2017-T4, the above phenomenon is observed at the strain rate above about 10000/sec. A simplified model for dislocation kinetics under dynamic plastic deformation is employed which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. It is expected that the steep increase in the flow stress observed at high strain rates is attributed to the rate dependence of the viscous drag on the dislocation motion.
IMPACT ANALYSIS AND TEST FOR THE SPACER GRID ASSEMBLY OF A NUCLEAR FUEL ASSEMBLY
Authors: SONG KEE-NAM , LEE SANG-HOON , LEE SOO-BUM
Published: June 2008

A spacer grid assembly is one of the main structural components of the nuclear fuel assembly for a Pressurized light Water Reactor (PWR). The spacer grid assembly supports and aligns the fuel rods, guides the fuel assemblies past each other during a handling and, if needed, sustains lateral seismic loads. The ability of a spacer grid assembly to resist these lateral loads is usually characterized in terms of its dynamic and static crush strengths, which are acquired from tests. In this study, a finite element analysis on the dynamic crush strength of spacer grid assembly specimens is carried out. Comparisons show that the analysis results are in good agreement with the test results to within about a 30 % difference range. Therefore, we could predict the crush strength of a spacer grid assembly in advance, before performing a dynamic crush test. And also a parametric study on the crush strength of a spacer grid assembly is carried out by adjusting the weld penetration depth for a sub-sized spacer grid, which also shows a good agreement between the test and analysis results.
DEFORMATION BEHAVIOR OF POLYMERIC MATERIALS BY TAYLOR IMPACT
Authors: SHIN HYUNG-SEOP , PARK SUNG-TAEK , KIM SEE-JO , CHOI JOON-HONG , KIM JEONG-TAE
Published: June 2008

The deformation of polymers under high loading-rate conditions will be a governing factor to be considered in their impact-resistant applications such as protective shields and armors. In this study, the deformation and fracture behaviors of polymeric materials such as PE, PC and PEEK have been investigated by Taylor cylinder impact tests with the high speed photography. A 20 mm air gun was used to perform the impact experiments. Cylindrical projectiles have been impacted onto a hardened steel anvil at a velocity ranging from 120 to 320 m/s. After impact experiments, the shape of projectiles was examined and compared with high speed photographic images to distinguish the elastic deformation component from the deformation measured instantaneously. Each adopted material showed different deformation and fracture behaviors. As compared with the quasi-static cases all polymers showed a significant strain rate hardening when the strain rate used was over 6 × 103 s −1. This appeared most significant in PE.
DYNAMIC TENSILE PROPERTIES OF IRON AND STEELS FOR A WIDE RANGE OF STRAIN RATES AND STRAIN
Authors: KOJIMA NOBUSATO , HAYASHI HIROYUKI , YAMAMOTO TERUMI , MIMURA KOJI , TANIMURA SHINJI
Published: June 2008

The tensile stress-strain curves of iron and a variety of steels, covering a wide range of strength level, over a wide strain rate range on the order of 10−3 ~ 103 s −1, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the strain rate sensitivity of the flow stress for the large strain region, including the viscous term at high strain rates, the true fracture strength and the true fracture strain were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide strain rate range.
AN ANALYSIS OF RHT PARAMETERS IN 2D NUMERICAL SIMULATION OF CONCRETE PENETRATION WITH COMPOSITE PROJECTILES
Authors: HUANG XICHENG , CHEN YUZE , ZHONG WEIZOU , ZHANG FANGJU , LU YONGGANG , ZHU JIANSHI
Published: June 2008

The RHT concrete strength model and failure model are employed for the numerical simulations of composite projectile penetrating concrete targets. The simulations show that RHT parameters, specially the failure parameters, greatly influence the penetration depth, exit velocity. The failure mode of concrete should be paid great attentions in numerical analysis. If the crushing failure is the primary mechanism, RHT model seems effective. For the cracking process of concrete, the model should be tensile failure description. Reasonable material parameters are important in penetration simulations. Comparison between numerical analysis and experimental date is made for discussion about the parameter effects.
NON-IDEAL DETONATION PROPERTIES OF AMMONIUM NITRATE AND ACTIVATED CARBON MIXTURES
Authors: MIYAKE ATSUMI , ECHIGOYA HIROSHI , KOBAYASHI HIDEFUMI , OGAWA TERUSHIGE , KATOH KATSUMI , KUBOTA SHIRO , WADA YUJI , OGATA YUJI
Published: June 2008

To obtain a better understanding of detonation properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, steel tube tests with several diameters were carried out for various compositions of powdered AN and AC mixtures and the influence of the charge diameter on the detonation velocity was investigated. The results showed that the detonation velocity increased with the increase of the charge diameter. The experimentally observed values were far below the theoretically predicted values made by the thermodynamic CHEETAH code and they showed so-called non-ideal detonation. The extrapolated detonation velocity of stoichiometric composition to the infinite diameter showed a good agreement with the theoretical value.
FAILURE DISTANCES FOR THE BUILDINGS AND SETTING OF THE BLAST RESISTANT WALL UNDER VEHICLE BOMBS
Authors: WU JUN , LIU JINGBO , DU YIXIN
Published: June 2008

The terrorist explosion is dreadful for current world. In various explosive events, vehicle bomb explosion has been commonly used by terrorists to approach the targets. This paper evaluated and analyzed the minatory grades of various vehicle bombs, and calculated the failure distances of the buildings under the main impulse effect of air shock wave. Thereafter, a few kinds of setting methods of the blast resistant walls under various vehicle bombs are established. The research will provide effect protective measures for the survival ability of the important buildings under various vehicle bombs.
ENERGY ABSORPTION OF HONEYCOMB RANDOMLY FILLED WITH INCLUSIONS SUBJECTED TO IN-PLANE IMPACT
Authors: NAKAMOTO HIROAKI , ADACHI TADAHARU , ARAKI WAKAKO
Published: June 2008

The in-plane impact behaviors of honeycomb structures with some cells randomly filled with stiff inclusions were analyzed by using the finite element method (FEM). The effect of the random arrangement of inclusions on the deformation processes of the honeycomb structures was considered. During these deformation processes, the growth of shear bands was disturbed by the inclusions and the cell region surrounded by inclusions did not deform. The average stress increased and densification strain decreased with increasing volume fraction of inclusions. A honeycomb with volume fraction of inclusions of 0.5 could not be deformed. Below 0.5, the average stress steeply increased and densification strain approached zero. Some models for less than a volume fraction of inclusions of 0.25 had higher absorbed energy than the model with no inclusions and others had lower energy. Above 0.25, the absorbed energy decreased and linearly reached zero at a volume fraction of inclusions of 0.5.
ANALYSIS OF ELASTIC IMPACT ON THIN SHELL STRUCTURES
Authors: HER SHIUH-CHUAN , LIAO CHING-CHUAN
Published: June 2008

In this paper, a solution method for the response of a thin shell structure subjected to low velocity impact by a sphere is presented. The governing equation of the impact process is obtained by simultaneously solving the equations of motions for the sphere and shell. The derivation is based on the explicit expression of the displacement of the mid-surface of the shell under a single impulse load acting normal to apex of the shell. Incorporating the theory of convolution and Hertz contact law, a non-linear integro-differential equation in terms of the indentation of the contact, for the impact process is derived. The non-linear integro-differential equation is solved by the numerical scheme of Runge-Kutta method to obtain the time history of the contact force at the impact point of the shell. The contact force is then applied on the apex of the shell, the dynamic responses of the shell including the displacement and stress are obtained by the finite element method. The results are validated with the experimental test and numerical calculation published in the literatures. The effects of the radius and velocity of the impactor on the impact response is investigated through parametric study.
LOW VELOCITY IMPACT OF PLATE AND HEMISPHERIC IMPACTOR: PHYSICAL EXPERIMENT, NUMERICAL COMPUTATION, AND APPLICATION TO REAL SYSTEM
Authors: PARK SUJIN , KIM MOONSAENG , DOKKO WOOK
Published: June 2008

Steel plates subjected to low velocity impact were numerically analyzed, and physically tested. The impactor has hemispheric tip nose, and the square plate has four fixed edges. Mindlin plate theory and Hertz contact law were used for the formulation of the impact problem, and some numerical treatments for the reduced integration, Newmark time integration scheme, associative flow rule, and plastic hardening were appropriately applied. A simple and efficient analysis program for plate impact was generated, and the results were compared with those of physical impact experiments. A drop test system was installed, and the impact behavior was measured with sensors. The comparison showed reasonable results, and the main parameters of plate impact were also analyzed.
AN EXPERIMENTAL STUDY OF BUCKLING OF CYLINDRICAL SHELLS SUBJECTED TO STATIC AND DYNAMIC AXIAL IMPACT
Authors: ABAKUMOV A. I. , KVASKOV G. A. , SOLOVYEV V. P. , SINITSYN V. V. , WALTHER H. P.
Published: June 2008

To study structure resistance to impact loads using thin-wall cylinder units, knowledge of energy absorption parameters of these test units is required, as well as evaluations of resistance force. Buckling of cylinder test units involves formation of both axisymmetric and non-axisymmetric folds. Repeatability of buckling patterns is an important parameter of the fold formation process and, eventually, of the absorbed energy magnitude. This paper discusses buckling patterns obtained for cylinder test units of three dimension types with scales relating as 1:2:10. The units were made of three materials (steel 09G2C and two aluminum alloys, AMg6 and AMcM) and subjected to static and impact loading. For static loading, a test unit was fixed on a long measuring rod and subjected to an impact by a projectile moving at a speed of V0. The experiments were performed at three loading speeds V0 10m/s, 50 m/s, 100 m/s. No less than 5-10 tests were performed for each type of test units, i.e. for each size, material and load level, to study buckling repeatability. Impact velocity and axial compression force history were recorded in the tests. It was obtained in the testing of cylinder test units that: Repeatability of buckling patterns was observed only in the formation of the first fold, which is axisymmetric. Then buckling, in most cases, follows a non-axisymmetric path; -With test unit scale (i.e. size) increasing, its relative energy absorption capacity under impact loading (in ratio to the test unit mass) increases; - There is clear evidence that strain rate influences the material strength properties, except for the aluminum alloy AMg6, whose strength properties depend rather weakly on strain rate. These experimental findings can be used as a benchmark for verification of computer codes, as well as to study the behaviors of cylinder test units subjected to axial impact, which involve both axisymmetric and non-axisymmetric buckling shapes.
ESTIMATION OF IMPACT LOAD IN THICK PLATE BY USING THEORETICAL GREEN FUNCTION AND EXPERIMENTAL MEASUREMENT OF VIBRATION
Authors: Kim H. W. , Lee S. K.
Published: June 2008

The classic plate theory (CPT) as a theoretical solution to an impact load has been used in a thin plate. However, The CPT is not any more useful solution for the impact load in the industrial power plant, which is generally constructed by the thick plate. In this paper a novel and effective approach is developed to determine the time history of the impact load on a thick aluminum plate based on the analysis of the acoustic waveforms measured by a sensor array located on the thick plate surface in combination with the theoretical Green's function for the plate. The Green's functions are derived based on either the exact elastodynamic or theory the approximate shear deformation plate theory (SDPT). If the displacement is measured on the plate, then the time history of impact load can be calculated by deconvolving the measured displacement with the theoretical Green's function. The reconstructed time history for impact load is compared with the time history of the impact load measured by the force transducer. A good prediction is found. This technique presents a valuable method for identification of source and may be applied to in-service structures under impact to signals recorded from acoustic emission of propagating cracks.
CRASHWORTHINESS EVALUATION OF THE KOREAN HIGH SPEED TRAIN USING A VIRTUAL TESTING MODEL
Authors: KIM SEUNG ROK , KWON TAE SOO , KOO JEONG SEO
Published: June 2008

In this paper, a virtual testing model (VTM) for the Korean high speed train (KHST) is developed to meet several design purposes, and an improved collision safety assessment method is also suggested. Although twisting, buckling, zigzagging, chain reactions, overriding and derailment have long been recognized as the important elements that can affect the safety of passengers in the event of a collision, the means by which such behaviors can be predicted have been restricted. To address this, a VTM, supported by the technological advancements of numerical analysis software and high-performance computers, was developed to simulate and evaluate such behaviors. The VTM for KHST was modeled using finite elements, in order to obtain such collision behaviors. In addition, the VTM was simulated in a variety of accident scenarios, and the results were analyzed and compared with the results obtained using other modeling techniques. Since factors such as the deformation of individual members, serial collisions and twisting of the train body were incorporated into the VTM, this simulation provides more practical collision responses than other modeling techniques. This shows that it can predict more nonlinear collision behaviors, giving it a wider range of applications.
STATIC AND DYNAMIC ANALYIS OF AIR BEARING SLIDER FOR SMALL FORM FACTOR DRIVES
Authors: SHI B. J. , SHU D. W. , GU B. , LU G. X. , PARLAPALLI M. R. , DELLA C. N. , LI Y. J.
Published: June 2008

As the areal recording density increases in hard disk drives (HDDs), the flying physical spacing between the head and the disk decreases and the likelihood of head-disk contact during full speed rotation increases. Therefore, the simulation and modeling of the air bearing slider with ultra-low flying heights becomes an important issue for the operational shock simulation. The static/dynamic properties, including the influence of the radial position and the skew angle of the slider, the rotating speed of the disk, and the shock simulation, of the air bearing slider were analyzed. Generally speaking, for a given rotating speed of the disk, as the slider moves from the inner diameter to the outer diameter, the maximum contact pressure, the skew angle, the pitch angle, and the maximum air bearing pressure increase; while the flying height decreases. These trends are strengthened by a faster rotating speed of the disk. There are obvious oscillations in the air bearing force and the minimum spacing when contact occurs during a shock.
STUDIES ON DYNAMIC DAMAGE EVOLUTION FOR PP/PA POLYMER BLENDS UNDER HIGH STRAIN RATES
Authors: SUN ZI-JIAN , WANG LI-LI
Published: June 2008

The dynamic damage evolution for PP/PA blends with different compatibilizers is studied in high strain rates from two different approaches, namely by determining the unloading elastic modulus of specimen experienced impact deformation and by combining the split Hopkinson pressure bar (SHPB) experimental technique with the back-propagation (BP) neural network. The results obtained by both approaches consistently show that a threshold strain εthexists for dynamic damage evolution, and both the damage evolution and εthare dependent on strain and strain rate. For non-linear visco-elastic materials, the damage evolution determined by the unloading elastic modulus provides an underestimation of real damage evolution.
FINITE ELEMENT ANALYSIS OF HONEYCOMB IMPACT ATTENUATOR
Authors: YANG SEUNG-YONG , CHOI SEUNG-KYU , KIM NOHYU
Published: June 2008

To participate in Student Formula Society of Automotive Engineers (SAE) competitions, it is necessary to build an impact attenuator that would give an average deceleration not to exceed 20g when it runs into a rigid wall. Students can use numerical simulations or experimental test data to show that their car satisfies this safety requirement. A student group to study formula cars at the Korea University of Technology and Education has designed a vehicle to take part in a SAE competition, and a honeycomb structure was adopted as the impact attenuator. In this paper, finite element calculations were carried out to investigate the dynamic behavior of the honeycomb attenuator. Deceleration and deformation behaviors were studied. Effect of the yield strength was checked by comparing the numerical results. ABAQUS/Explicit finite element code was used.
AN ROCK-PHYSICS-BASED COMPLEX PORE-FLUID-DISTRIBUTION MODEL TO SEISMIC DYNAMICAL RESPONSE
Authors: ZHANG CHENGYUAN , LIU XIAOYAN , XI DAOYING , LIU QUANSHENG
Published: June 2008

It is very important to know how the reservoir rock and its fluid properties are linked to seismic dynamic response. Literatures show that there are a variety of rock-physics models such as the most famous Biot-Gassmann equation aimed at the relationship between seismic velocity and liquid saturation. Most of these models make a fundamental assumption of one fluid phase or homogeneous phase within the pore volume. In this paper, we discuss possible seismic velocities change in a two immiscible pore fluids (i.e. water-gas) saturated reservoir with patchy saturation distribution. It is found that P-wave velocity of a reservoir rock with the same saturation but different pore fluid distribution exhibits noticeable variation and deviate overall from Gassmann's results. We use DEM theory to explain this phenomenon. It belongs to hybrid approach in rock-physics modeling and can handle complex pore-fluid-distribution cases. Based on the modeling study, we found that various fluid-distribution models may significantly affect the modulus and P-wave velocity. The seismic reflection time, amplitude and phase characteristics may change with the choice of pore-fluid-distribution models. Relevant rock mechanical experiments indicate the same trend of seismic responses. It also be proven by seismic reservoir monitoring experiment (time lapse study) that incorrect conclusion may be drawn about the strong seismic reflection in pure Utsira Sand if the microscopic pore-fluid-distribution effects are not taken into account.
THE ANALYSIS OF DYNAMICAL RESPONSE OF TRANSVERSELY ISOTROPIC MATERIAL UNDER BLASTING LOAD
Authors: WU YUE-XIU , LIU QUAN-SHENG
Published: June 2008

To understand the dynamic response of transversely isotropic material under explosion load, the analysis is done with the help of ABAQUS software and the constitutive equations of transversely isotropic material with different angle of isotropic section. The result is given: when the angle of isotropic section is settled, the velocity and acceleration of measure points decrease with the increasing distance from the explosion borehole. The velocity and acceleration in the loading direction are larger than those in the normal direction of the loading direction and their attenuation are much faster. When the angle of isotropic section is variable, the evolution curves of peak velocity and peak acceleration in the loading direction with the increasing angles are notching parabolic curves. They get their minimum values when the angle is equal to 45 degree. But the evolution curves of peak velocity and peak acceleration in the normal direction of the loading direction with the increasing angles are overhead parabolic curves. They get their maximum values when the angle is equal to 45 degree.
CURVE FITTING IN THE TRANSITION REGION OF CHARPY IMPACT DATA
Authors: SHIN HYUNG-SEOP , PARK JONG-SEO , LEE HAE-MOO
Published: June 2008

The toughness data obtained from Charpy impact tests are presented by a temperature-energy relationship. Data fitting for quantitative evaluation of the transition temperature, upper shelf energy and ductile-brittle transition, in other words, the representation with general mathematical model equation for energy variation according to the temperature is necessary. In this study, the Charpy impact tests to two representative steels were carried out as a research work for the material property standardization technique development. The fitting procedure of the scattering in data according to materials and temperature in the transition region was described. The data fitting procedure using the tangent hyperbolic function was established through variances treatment in the transition region.
CHARACTERIZATION OF SUBSURFACE DAMAGE OF EXPLOSIVELY INDENTED SILICON NITRIDE CERAMICS
Authors: KIM JONG HO , KIM HANEUL , KIM DO KYUNG , CHANG SOON NAM
Published: June 2008

In this study, explosive indentations were used to characterize the dynamic damage behavior of silicon nitride ceramics with different microstructures. Three grades of silicon nitrides with different grain size and shape were prepared. Subsurface damage of specimens was characterized extensively using optical and electron microscopy. It was found that the dynamic damage response depends strongly on the microstructure of specimens, particularly on the glassy grain boundary phase.
A NEW METHOD TO CALCULATE THE MECHANICS PARAMETERS OF SLIP SURFACES
Authors: SHEN Q. , XU J. , CHEN C. X. , YE Z. H. , WANG R.
Published: June 2008

Obtaining the more exact parameters of slip surfaces is proved to be crucial in the analysis of landslide stability, and there are four study methods available i.e. in-site test, laboratory test, back analysis and theoretical analysis. In general, the former two are the basic one, whereas the latter two are secondary. A set of test values about shearing stress and direct stress can be obtained through in-situ and lab tests, then the parameters of slip surface should be calculated to fitting for the test value by the least square method usually, but the effect of anomalous values should increase markedly because the quadratic sum of residual errors is adopted in calculations. In order to reduce the effect of anomalous value, a new method based on the robust regression analysis and the particle swarm optimization method are adopted to calculate the mechanics parameter of landslides in this paper. In the new method, the sum of residual absolute values is used to replace the quadratic sum of residual error, and then the quadratic sum of anomalous value can be avoided. Comparing to the least square method, the new method can reduce availably the effect of abnormal values, and the results are more credible. Furthermore, an engineering example is cited to show the validity.
SIMULATION TECHNIQUE FOR ONE-DIMENSIONAL ELASTIC WAVE PROPAGATION
Authors: SHIBATA H. , TANABE Y. , ISHIHARA S.
Published: June 2008

The total stress in a structure changes dynamically by the stress multiplication phenomenon in the case of a fixed boundary condition. Therefore, it is important to evaluate the reflected stress waves under an impact loading in structures. In many problems, the method of the classical position-time diagram of wave fronts is effective to analyze the maximum stress in the structure under the impact loading and for a simple arrangement of members along the axis of the one-dimensional structure. In this study, stress analyses in one-dimensional structures based on the position-time diagram of stress wave fronts were realized as a computational method with and without attenuation of stress wave. This method was applied to the problem of stress analyses in a bone under an impact loading, and the stress states were compared with the experimental results.
PREDICTION OF GROUND VIBRATIONS AROUND THE TURNOUT SYSTEM INDUCED BY THE TILTING TRAIN
Authors: EUM KI-YOUNG , UM JU-HWAN , SHIN MIN-HO , LEE CHIN-HYUNG
Published: June 2008

In Korea, it has been planned to apply high speed tilting train, which operates at the maximum speed of 200km/h, to conventional lines by the year of 2010. However, for the application of the tilting train to conventional lines, it is prerequisite to establish a stable turnout system allowing the tilting train to pass through it without reducing speed. Therefore, the improved turnout system for the speed-up of conventional lines has been developed and the prototype of the turnout system has been constructed. However, levels of impact-induced ground vibrations from the discontinuous part of the turnout system have not been clarified. In this study, analysis of ground vibrations around the improved turnout system is performed in order to predict the generation level of ground vibrations due to the passage of the tilting train through the improved turnout system.
MATERIAL INTERFACE TRACKING IN MULTI-MATERIAL EULERIAN FEM FOR LARGE DEFORMATIONS
Authors: LEE MINHYUNG , CHUNG WAN JIN
Published: June 2008

A method has been described for tracking material interface in a 3-Dim, rectangular-grid, time-dependent, Eulerian hydrodynamics code. The accuracy is crucial to the overall accuracy of the simulations. A 2nd order accuracy interface reconstruction method based on the Youngs' scheme has been implemented in our new dynamic FEM code. The method is applicable to the type of code in which the layout of materials is described solely by the volume fraction of the various materials in each computational cell. The volume fraction distribution is used to construct a plane interface in each mixed cell. The position of interface determines the flow across cell sides and hence enables volume fractions to be updated to the next time level. In this paper, the 2nd order accuracy method has been compared with the new 1st order accuracy method which we recently implemented based on the SLIC (Simple Line Interface Calculation).
CUMULATIVE IMPACT DAMAGE EVALUATION OF AUTOMOTIVE ALUMINUM BUMPER BEAM
Authors: KIM HEON YOUNG , CHOI JONG GIL , KIM MIN GUN , LEE KANG WOOK , HA DAE YUL , YEO TAE JUNG
Published: June 2008

We performed numerical analyses using an explicit code to evaluate the cumulative impact damage of an automotive aluminum front-end bumper back beam during low-speed crash events, as described by CMVSS215. we used a coupled numerical analysis scheme and considered the several fracture criterion such as EWK rupture model and plastic strain limit in the PAM-CRASH code to improve our damage and fracture estimates. Tensile test experiments for the notched and un-notched specimens were conducted to tune the performance of the EWK rupture model; The resulting material properties and fracture criterion were incorporated into the numerical analyses of the low-speed crash events. The simulation results were compared with the impact test.
NUMERICAL MODELING OF UNDERWATER EXPLOSION PROPERTIES FOR NONIDEAL EXPLOSIVES
Authors: LEE JAIMIN
Published: June 2008

Underwater experiments for an ideal explosive, TNT, and two nonideal explosives, CETR emulsion and DXD-04, were performed, and numerically simulated. For TNT, calculations done by using program-burn models based on the rate-independent Chapman-Jouguet theory were in a good agreement with experimental results, which validated the wide use of program-burn models for ideal explosives. For CETR emulsion and DXD-04, experimental observations could be reproduced with high precision only when reaction rates were employed. These results demonstrated that detonation in nonideal explosives can be modeled only by using properly calibrated reaction rates.
COMPUTATIONAL MODELING OF DYNAMIC BRITTLE FAILURE USING THREE-DIMENSIONAL EXPLICIT FEM
Authors: HWANG CHAN , RHIM SUNG-HAN , CHUNG DONG-TEAK , OH SOO-IK
Published: June 2008

Ceramic materials show good mechanical properties. However, the brittleness makes it difficult to predict their dynamic behavior of ceramic materials, and further the discrete nature of brittle failure requires a three-dimensional computation. In this paper, a computational model was developed for analyzing high velocity impact situations of brittle materials, incorporating with node separation scheme to describe the distinctive behavior of a brittle failure. This material behavior model was applied in a three-dimensional explicit code with Lagrangian description, which was developed to compute problems of dynamic brittle failure using four-node tetrahedral elements. To effectively handle the complex contact situations, involving multiple collisions and self-contact of severely deformed and fragmented bodies, careful considerations were paid to the global and local contact searching. In addition, an edge contact algorithm was developed to handle contacts between sharp edges. To validate the developed computational model and three-dimensional explicit code, oblique penetration into sandwiched ceramic plate by long rod was simulated, and the results were compared with experiments.
POSSIBILITY OF UNDERWATER EXPLOSIVE WELDING FOR MAKING LARGE-SIZED THIN METAL PLATE CLAD BY OVERLAPPING PLATES
Authors: HOKAMOTO KAZUYUKI , MORI AKIHISA , FUJITA MASAHIRO
Published: June 2008

The authors have developed a new method of explosive welding using underwater shock wave for the welding of thin plate on a substrate. Considering the size limitation of the welding area in using the technique, the possibility of overlapping thin plates to make large-sized welding area is investigated. In general, the results for the welding of Inconel 600 on 304 stainless steel show a macroscopically successful weld, but the microstructure shows some melting spots caused due to the trapping of metal jet during the welding process when the welding condition is changed. The welding process is discussed based on the experimental results in comparison with some numerically simulated results obtained by AUTODYN-2D code.
EFFECT OF SPECIMEN DIAMETER ON WELDABILITY OF IMPAT WELDING
Authors: DATE HIDEFUMI
Published: June 2008

Impact welding has been carried out using a projectile having a diameter of 11 and 5 mm at an impact velocity of 200 m/s or more. A large projectile regardless of the slenderness ratio, was welded to a stainless steel target. However, only a small projectile with a slenderness ratio less than 1.2 was welded to the same target. In order to examine the effect of the diameter of the projectile on the weldability, the temperature elevating process in two cylindrical projectiles subjected to a longitudinal impact was evaluated numerically using LS-DYNA. The numerical results indicated that since the deformation mechanism of a projectile with a slenderness ratio less than 1.0 is different of that of the projectile with the slenderness ratio more than 1.5, the small projectile with the slenderness ratio less than 1.0 can be welded to the target.
VIRTUAL TESTING OF COMPOSITE MOTORCYCLE HELMETS
Authors: CERNICCHI ALESSANDRO , GALVANETTO UGO , OLSSON ROBIN
Published: June 2008

A study about the response of motorcycle helmets to impacts is described in this paper and possible ways to improve current designs are discussed. Firstly, a simple unidimensional model of helmet is analyzed and the main parameters that affect its response are pointed out. Subsequently, the generation and testing of the Finite Element model of a commercially available helmet are described and numerical results are compared to experimental results. Finally, the FE modeled is used to compare different design configurations.
IMPACT TENSILE PROPERTIES OF YAG LASER WELDED BUTT JOINTS MADE BY DIFFERENT STEEL SHEETS FOR VEHICLES
Authors: TAKAHASHI Y. , DAIMARUYA M. , KOBAYASHI H. , TSUDA H. , FUJIKI H.
Published: June 2008

The tensile properties of YAG laser welded butt joints using different high strength steel sheets with a tensile strength of 270 MPa, 590 MPa and 980 MPa (denoted HR270, HR590 and HR980, respectively) were investigated at static and dynamic rates, together with the three kinds of laser welded joints made by the same steel sheets. The impact tensile tests were performed by using the vertical type of split Hopkinson tension bar apparatus, while the static tensile tests were carried out using a universal testing machine INSTRON5586. The impact tensile strengths were significantly increased in comparison with the static ones due to the effect of strain rate, which might be the contribution of the part of HR270 base metal. And in both of static and impact tests, the fracture strains of HR270-HR590 joint, HR270-HR980 joint and HR590-HR980 joint were about one half of the fracture strains observed in the same steel welded joints of HR270-HR270, HR270-HR270 and HR590-HR590, respectively.
THE INFLUENCES OF ARM RESIST MOTION ON A CAR CRASH TEST USING HYBRID III DUMMY WITH HUMAN-LIKE ARM
Authors: KIM YONGCHUL , YOUM YOUNGIL , BAE HANIL , CHOI HYEONKI
Published: June 2008

Safety of the occupant during the crash is very essential design element. Many researches have been investigated in reducing the fatal injury of occupant. They are focusing on the development of a dummy in order to obtain the real human-like motion. However, they have not considered the arm resist motion during the car accident. In this study, we would like to suggest the importance of the reactive force of the arm in a car crash. The influences of reactive force acting on the human upper extremity were investigated using the impedance experimental method with lumped mass model of hand system and a Hybrid III dummy with human-like arm. Impedance parameters (e.g. inertia, spring constant and damping coefficient) of the elbow joint in maximum activation level were measured by free oscillation test using single axis robot. The results showed that without seat belt, the reactive force of human arm reduced the head, chest, and femur injury, and the flexion moment of the neck is higher than that of the conventional dummy.
MECHANICAL CHARACTERISTICS OF REFLEX DURIGN UPRIGHT POSTURE IN PARALYZED SUBJECTS
Authors: KIM YONGCHUL , YOUM YOUNGIL , LEE BUMSUK , KIM YOUNGHO , CHOI HYEONKI
Published: June 2008

The characteristics of flexor reflexes have been investigated in the previous studies with human subjects who were seated or supine position. However, researchers did not describe how the spinal circuits are used in different hip angles for paralyzed subjects, such as the standing position with walker or cane. In upright posture the compatibility between a flexor reflex of leg and body balance is a special problem for lower limb injured subjects. Therefore, the purpose of this study was to investigate the effects of hip angle change on the flexor reflex evoked in standing paralyzed subjects supported by walker. In this study, six spinal cord injured and four stroke subjects were recruited through the inpatient physical therapy clinics of Korea national rehabilitation hospital. A single axis electronic goniometer was mounted on the lateral side of the hip joint of the impaired limb to record movements in the sagittal plane at this joint. The electronic goniometer was connected to a data acquisition system, through amplifiers to a computer. Since subject' posture influenced characteristics of the flexion reflex response, the subjects were supported in an upright posture by the help of parallelogram walder. Two series of tests were performed on each leg. The first series of the tests investigated the influence of hip angle during stationary standing posture on flexion reflex response. The hip angle was adjusted by the foot plate. The second examined the effect of the voluntary action of subject on swing motion during the gait. The electrically induced flexion reflex simultaneously produced the flexion of the hip, knee and dorsiflexion of the ankle enabling the swing phase of walking. Form the experimental results we observed that the reflex response of hip joint was largerwith the hip in the extended position than in the flexed position during standing posture. Under voluntary movement on flexion reflex during gaint, the peak hip angle induced by stimulation was increased in spinal cord injury and stroke patients by subject' voluntary movement.