bluuebunny/crossref_metadata_2025 huggingface dataset:
INTER-RELATIONSHIP BETWEEN THE HOUSING MARKET AND HOUSING FINANCE SYSTEM: EVIDENCE FROM MALAYSIA
Authors: Said Rosli , Adair Alaistair , McGreal Stanley , Majid Rohayu
Published: June 2014

The Malaysian housing market and associated housing finance system have expanded significantly as a result of rapid urbanisation since the late 1980s. The key aspect of this paper is to analyse the inter-relationship between the housing market and housing finance system in Malaysia. The paper employs Vector Autoregressive approach and Granger Causality test to empirically investigate this inter-relationship. In Malaysia, no housing studies has actually looked into or used this approach to identify the inter-relationship between these two elements. The key findings show that there is a strong inter-relationship between the housing market and housing finance system. The direction of causality shows that there is a bi-directional relationship between the housing market and housing finance system. These inter-relationships provide evidence that sound performance of the sub-markets within the housing finance system is a determinant prerequisite of the robustness of the housing finance system, if a healthy performance of the housing market is to be achieved.
Dynamic Deformation Behavior of ECAPed AZ31 Magnesium Alloy
Authors: Hu Hai Tao , Zhao Feng , Miao Ying Gang , Suo Tao , Deng Qiong , Li Yu Long
Published: June 2014

Equal channel angular pressing (ECAP) has been widely used for grain refinement in many alloys. In this article, the major emphasis was on the effect of grain size, temperature and strain rate on dynamic behavior of ECAPed AZ31. The dynamic mechanical properties of 6 pass and 8 pass ECAPed AZ31 were tested by split hopkinson pressing bar (SHPB) at wide temperatures range. At dynamic loading conditions, the ECAPed AZ31 shows strong strain hardening properties. The strain hardening rates decrease due to more slip systems’ opening with the increase of temperature. With the grain refinement, the fine-grain size and temperature show strong effect on the strain rate sensitivity.
Experimental Analysis of Visco-Plastic Properties of the Aluminium and Tungsten Alloys by Means of Hopkinson Bars Technique
Authors: Kruszka Leopold , Magier Mariusz , Zielenkiewicz Mariusz
Published: June 2014

The main aim of studies on dynamic behaviour of construction materials at high strain rates is to determine the variation of mechanical properties (strength, plasticity) as a function of the strain rate and temperature. On the basis of results of dynamic tests on the properties of constructional materials the constitutive models are formulated to create numerical codes applied to solve constructional problems with computer simulation methods. In the case of military applications connected with the phenomena of gunshot and terminal ballistics it's particularly important to develop a model of strength and armour penetration with KE projectile founded on reliable results of dynamic experiments and constituting the base for further analyses and optimization of projectile designs in order to achieve required penetration depth. Static and dynamic results of strength investigations of the EN AW-7012 aluminium alloy (sabot) and tungsten alloy (penetrator) are discussed in this paper. Static testing was carried out with the INSTRON testing machine. Dynamic tests have been conducted using the split Hopkinson pressure bars technique at strain rates up to 1,2·104 s-1 (for aluminium alloy) and 6·103 s-1 (for tungsten alloy).
Dynamic Compression Test of CFRP Laminates Using SHPB Technique
Authors: Kusaka Takayuki , Kono Takanori , Nomura Yasutoshi , Wakabayashi Hiroki
Published: June 2014

A novel experimental method was proposed for characterizing the compressive properties of composite materials under impact loading. Split Hopkinson pressure bar system was employed to carry out the dynamic compression tests. The dynamic stress-strain relations could be precisely estimated by the proposed method, where the ramped input, generated by the plastic deformation of a zinc buffer, was effective to reduce the oscillation of the stress field in the specimen. The longitudinal strain of gage area could be estimated from the nominal deformation of gage area, and consequently the failure process could be grasped in detail from the stress-strain relation. The dynamic compressive strength of the material was slightly higher than the static compressive strength. In addition, the validity of the proposed method was confirmed by the computational and experimental results.
A Study on Rate Sensitivity of Impedance in TRIP Steel during Deformation at Various Strain Rate under Two Kinds of Deformation Mode
Authors: Inoshita Daiki , Iwamoto Takeshi
Published: June 2014

TRIP steel possesses excellent mechanical properties dominated by strain-induced martensitic transformation (SIMT). For automotive industries, if TRIP steel can be applied to shock absorption members, it can be considered that the weight of automobile can be reduced. However, the strain rate sensitivity of TRIP steels has not been fully understood because the strain rate sensitivity and the deformation mode dependency of SIMT are still unclear. Therefore, it is important to reveal these sensitivity and dependency for confirming a reliability of TRIP steel. Therefore, in this study, it is attempted to estimate the amount of produced martensite in TRIP steel by measuring the inductance of TRIP steel. The specimen made of TRIP steel is used as a core of a prototype coil manufactured in this study. Then, the compressive and tensile tests are conducted by using a material testing machine and a drop weight testing machine using the specimen inside the coil. The inductance of the coil with the deformed specimen are measured continuously during the tests.
Strain Rate Effects on Strain-Induced Martensitic Transformation and Electrical Resistivity of Deforming Stainless Steel
Authors: Date Hidefumi
Published: June 2014

Austenitic stainless steel was compressed at a strain rates of 103 s-1 using a Hopkinson pressure bar apparatus at temperatures of 77 K and 293 K. The electrical resistivity was measured to determine the volume fraction of martensite of a deforming specimen. A compressive specimen of the dumbbell type was suitable for attaching the lead-in wires of four-point probes to the specimen. The volume fraction of martensite formed at a strain rate of 103 s-1 was lower than that formed at a low strain rate regardless of the temperature, and the effect of the strain rate on the electrical resistivity was slight. However, since the volume fraction of martensite is expressed as a linear function of the electrical resistivity ratio as well as in the results obtained by the tensile test, the electrical resistivity was available as an index for estimating the volume fraction of martensite induced by dynamic deformation. The duration of the input wave was approximately 150 μs, and the appearance of the peak value of transient resistivity was approximately 1ms after the arrival of the input wave at the specimen. These results showed that the structure change evaluated using electrical resistivity was not completed in the time required for the stress wave to pass through the specimen, although the electrical resistivity immediately after dynamic deformation closely approached that obtained by the static test.
Batter Pile Behavior Modeling Using Finite Difference Analysis
Authors: Chen Chien Yuan , Tsai Chi Xun
Published: June 2014

Pile foundation has been widely used in supporting various structures, for example, bridges and tall buildings in Taiwan. With the development of mountainous area, pile foundation has been used as mitigation slope movement. Batter piles used in a group pile subjected to lateral forces are common. In this study, we used 3D finite difference program to analyze the mechanical response of a batter pile subjected to lateral soil movement. In order to verify the correction of the numerical simulation, its validation was compared with a published case study. The analysis of a single pile in different incline angles subjected to lateral soil movement was modeled. Results of the analysis show that batter pile under the conditions of lateral soil movement will cause pile larger lateral displacement and increasing bending moment on the pile shaft. The pile displacement reduced with the increasing pile incline angle. Vertical pile shaft subjected to negative and positive moment during soil movement, while, only positive moment distributed in the batter pile shaft. The moment is higher in batter pile shaft in weak layer than in non-weak layer. The pile shaft maximum moment occurred nearby the interface of weak layer and stable layer. The moment increased with the incline angle of batter pile. While, the moment increasing ratio reduced with the increased incline angle.
Study on Dynamic Shear Resistance of RC Beams
Authors: Somraj Amornthep , Fujikake Kazunori , Li Bing
Published: June 2014

The aim of this study was to investigate the dynamic shear failure behavior of RC beams under rapid loading through an experimental study and also to set up a strut-and-tie model with loading rate effect to predict the dynamic shear resistance of RC beams. Thus, rapid loading test with 24 RC beams with a shear span-to-deep ratio of 1.9 was performed, in which shear reinforcement ratio and loading rate were variable. All of the RC beams exhibited shear compression failure. Although the shear resistance increases with increasing loading rate, the influence of loading rate on the shear resistance clearly depends on shear reinforcement ratio. The strut-and-tie model with loading rate effect was finally developed, in which the thickness of the compression strut was formulated to be increased with an increase in loading rate. The developed strut-and-tie model was good agreement with the experimental results.
Micro-Tomography to Characterize Size Distribution of Fragments Created by Laser Shock-Induced Micro-Spallation of Metallic Sample
Authors: Loison D. , de Resseguier T. , Dragon A.
Published: June 2014

Dynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied science. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. We present laser shock experiments on tin and aluminium, to pressure ranging from about 50 to 300 GPa, with complementary diagnostics including a Photonic Doppler Velocimeter (PDV) set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta1, and a soft recovery device consisting of a low density gel to collect debris. Optical microscopy of these gel collectors reveals the presence of droplets which confirm shock-induced melting prior to fragmentation. To quantify size distribution of the collected debris, 3D micro-tomography has been performed, using the consistent and high-energy X-ray irradiation available at the ESRF synchrotron facility in France (similar to Japan SPRING-8), where sub-micrometer spatial resolution could be achieved. In this paper, the resulting size distributions are presented and compared with theoretical predictions based on a one-dimensional description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. Discrepancies between measured and calculated size distributions are discussed. Finally, combining size and velocity data provides access to the ballistic properties of debris and their kinetic energy, which are key issues for anticipating the damage produced by their impacts on nearly equipments.
Mechanisms of Energy Absorption during High Rate Loading of Cellular Lattice Structures
Authors: Cotton Matthew , Winter Ron , Harris Ernie
Published: June 2014

A series of experiments at high strain rates have been conducted to study the deformation of lattice structures formed by additive manufacture. Gas gun plate impact experiments have been used to produce the desired conditions, and the transmitted wave profile analysed for information on the lattice compression and deformation. Additional pre-and post-experiment imagery of the lattice has also been gathered. These experiments have been supported by a series of calculations to offer comparisons to experimental data and to assist in the design and optimisation of new structures. Of particular interest are the variations seen at high (106) strain rates, where severe hydrodynamic flow appears to become significant. This may have implications for the design of open cell structures which are expected to experience high rate conditions.
Partial Destruction of Reinforced Concrete Wall by Small Blasting
Authors: Nishino Kana , Kubota Shiro , Wada Yuji , Ogata Yuji , Ito Norio , Nagano Masayuki , Nakamura Satoki , Taguchi Takuya , Fukuda Atsuya
Published: June 2014

The crater on the reinforced concrete wall generated by the explosion of a few grams of Composition C4 explosive was investigated. A series of the single-shot blast experiment were conducted. The structural specimens for the reinforced concrete wall (750 mm × 750 mm × 250 mm) were used for estimation of the crater size. The diameter of the borehole was fixed 16 mm, and the length of borehole was varied to generate the various size of crater. The amount of explosive was also varied from 3.0 to 8.0 g. The effect of the length of the borehole to the crater depth was examined. High-speed photography was used to observe the fracture process of the crater. As the results, in the difference of the side where the crater was generated, the situation of crushing was different. The strain measurements were also conducted.
Experimental and Numerical Study on the Dynamic Fracture Characteristics of Gray Cast Iron FC200
Authors: Cho Kyuchun , Simozono Chikara , Fujimoto Takehiro , Nishioka Toshihisa
Published: June 2014

Recently, some improvements made to machine performance have caused accidents as a result of impact fracture. These fractures were caused by unexpected dynamic loads. To suppress the damage in these accidents, it is necessary to clarify the dynamic fracture mechanism, many reports have been published on dynamic fracture phenomena [1, 2, 3]. Cast iron is used to repair some structural and mechanical parts following fracture accidents. The brittle behavior of cast iron is not desirable for preventing dynamic fracture. It is necessary to clarify the dynamic fracture mechanism of cast iron for the safety design and maintenance of structures. The dynamic behavior of deformation and fracture depends on the size of a structure. In some cases, an experimental approach using specimens at industrial scale is difficult. As a first step, dynamic fracture without a huge mass effect should be discussed. In this study, a normal sized three point bending specimen consisting of cast iron was used in dynamic experiment. An ultra-high speed camera was used to observe crack propagation. Some fractures were caused under eccentric loading, non-straight cracks propagated in this condition. According to the experimental results, the path and velocity of crack propagation were estimated. Fracture criteria were discussed from the results of numerical simulation. To simulate the behavior of crack propagation a moving finite element method based on Delaunay automatic triangulation was used. The prediction of fracture paths based on the fracture mechanics theory was demonstrated in these numerical simulations. The predicted fracture path agreed with the experimental fracture path.
Dynamic Fragmentation Tests of LY12 Aluminum Alloy Using a SHPB Based Expanding Ring Technique
Authors: Zheng Yu Xuan , Zhou Feng Hua , Hu Shi Sheng
Published: June 2014

A new experimental technology based on the Split Hopkinson Pressure Bar (SHPB) is developed for conducting expanding ring tests. The technique is useful for the studies of the dynamic tensile deformation and the fracture (fragmentation) properties of ductile metallic materials. The loading fixture includes a hydraulic cylinder filled with the incompressible fluid, which is pushed by a piston connected to the input bar. As the liquid is driven, it transfers the pressure to the specimen, compressing and expanding the metallic ring specimen in the radial direction. The approximately incompressible property of the liquid makes it possible to transfer a relatively low piston-driving velocity to a very high radial-expansion velocity of the specimen, as the sectional area of the cylinder narrows significantly. Using this experimental technology the ring specimens made of LY12 aluminum alloy were dynamically expanded and fragmentized. Results show apparent increases of the fragment numbers and fracture strain of the specimen with the increase of the impact velocity. The recovered ring fragments were examined and measured to obtain the average fragment sizes (lengths) during each test. These fragment sizes were compared with the estimates from the classical fragmentation theory that was initiated by N.F. Mott and later developed by D.E. Grady. It was found that the Mott-Grady theory provides reasonably good predictions of the fragment sizes for ductile materials. This conclusion agrees with the recent findings of ours based on the numerical simulations and physical arguments.
Velocity-Toughening and Crack Speed Oscillations in the Dynamic Fracture of PMMA Plates
Authors: Zhang Zhen Ya , Duan Zhong , Zhou Feng Hua
Published: June 2014

To study the propagating behavior of a dynamic crack in brittle materials, an experimental technique was developed that measures the propagation speed of a fast crack in a preloaded brittle strip. The specimen is a rectangular PMMA plate clamped by two heavy steel fixtures that are attached to a MTS test machine. After the specimen was tensile loaded to a prescribed load level, a sharp crack was initiated at the middle point on one side of the specimen. Due to the brittleness of the material, the crack propagates quickly across the specimen. The propagation velocity of the crack was measured by using the equally spaced conductive lines that were painted on the specimen surface before the tests. High speed video camera was also used for monitoring the propagation behavior of the cracks. The experimental results show that for each preloaded plate, the crack arrives at a steady velocity v0 after a short acceleration stage. In the steady stage crack propagation is in self-similar state. The steady velocity of the crack was found to be an increasing function of the energy Gc stored in the preloaded strip, which means that the material has a "velocity-toughening" property. When the crack speed exceeds a threshold, the crack exhibits apparent speed oscillations. This speed oscillation corresponds to the occurrence of the periodic grooves on the fractured surface. Further increase of the preload results in the bending, micro branching, and full bifurcations of the crack paths.
Numerical Analysis of the Brittle-Ductile Transition in the Failure-Mode in Polymeric Materials
Authors: Aranda-Ruiz Josué , Loya J.A.
Published: June 2014

In this paper we analyze, using the Finite Element Method, the process of brittle-ductile transition in the failure mode observed in polycarbonate notched specimens under impact loads. In order to analyze this transition we have implemented, through a user subroutine, a damage model which combines a tensional fracture criterion and an energetic, acting simultaneously. The competition between both criteria predicts the difference in material behavior from a critical impact velocity, and how this transition is produced on different planes through the thickness of the specimen. These results show the necessity of employing three-dimensional models for its study.
Evaluation of Impact Fracture Toughness of AZ31 Magnesium Alloy
Authors: Kawa Tomoaki , Nagao Masaki , Mukai Toshiji
Published: June 2014

The mechanical properties of magnesium alloys under dynamic loading have not been explored in sufficient depth. This research aims to estimate the impact fracture toughness of AZ31 magnesium alloy by finite element (FE) analysis. An FE model of impact three-point bending with three elastic bars is developed. FE analysis is presented for AZ31 magnesium alloy and compared with the results for 7075-T6 aluminum alloy as a reference. The FE analysis showed that the plastic deformation region is wider and the crack propagating rate is lower in the AZ31 specimen than in the 7075-T6 specimen. Moreover, the energy absorption capability and impact fracture toughness of AZ31 alloy were found to be higher than those of 7075-T6 alloy.
Effect of Pre-Tension on Ballistic Resistance of Woven Fabric
Authors: Shim V.P.W. , Guo Y.B. , Tan X.Y.
Published: June 2014

An experimental investigation into projectile penetration of pre-tensioned woven fabric samples – Tawron® CT 717 (plain weave) – is undertaken. Specimens are clamped at their top and bottom edges, and pre-stretched by forces of 200N, 1000N, 2000N, 3000N and 4000N respectively. They are then oriented at various angles (0, 7.5°, 15° and 30°) from the vertical (perpendicular to the horizontal axis of a gas gun), and subjected to impact by a 12mm diameter steel sphere. A high-speed camera is utilized to observe the deformation and failure of the fabric, and to determine the residual projectile velocity. For normal incidence, the ballistic limit initially increases, then decreases with pre-tension, displaying a maximum resistance for a pre-tension of about 2000N. With respect to the angle of incidence (obliquity of impact), for target inclinations of 7.5° and 15°, pre-tension has minimal influence on the ballistic limit, while for an inclination of 30°, the effect of pre-tension on the ballistic limit is similar to that for normal impact.
Experimental and Numerical Study of a Combined Blast and Ballistic Protection
Authors: Gilson Lionel , Gallant Johan , Rabet Luc
Published: June 2014

The work presented in this paper concerns a project on the optimization of protections subjected to explosions (IED’s threat). Explosions generate two types of threats for a protective structure: blast and impact of fragments. Perforating and non-perforating impact tests were performed in our laboratory with steel spherical projectiles impacting a target based on Kevlar® textile layers and a crushable material, Crushmat®. These tests required to develop a specific experimental test setup in order to contain the composite protective structure and to be able to measure the relevant parameters. The experiments allow us to determine the ballistic performance and basic parameters of the protection, and to validate finite element numerical models (LS-DYNA) resulting in a performant prediction tool. The approach used for the simulation consists in the representation of the full textile architecture with solid elements. Therefore, the textile material is explicitly represented in the model in order to have a good representation of the physical phenomena occurring during impact. For the crushable material, a representation using SPH was chosen in order to take the granular behaviour of this material into account. Good results are obtained with such models. However, these models are very complicated and computing time consuming. The geometry has to be well adapted and symmetry has to be exploited. On the other hand, representation of a granular material with SPH does not take into account some characteristics of this material during impact, such as the pulverisation process of the granular material. Solutions to take these phenomena into account in the model are proposed.
Microstructural Evolution from Shaped Charge through Steel Plates
Authors: Bassim M. Nabil , Boakye-Yiadom S. , Bolduc Manon
Published: June 2014

A set of 18 armour steel plates were stacked on top of each other and subjected to shape charges that went through the plates and created a hole that decreased in diameter as it went through consecutive plates. Afterwards, the plates were examined and the hardness near the hole and away from the hole was taken to determine the effect of the passing of the shaped charge through the plates. Also, specimens from the walls of the holes were taken to determine changes in the microstructure due to the shock wave and the resulting excessive heating from the shape charge. It was observed that the shock wave produced significant changes in the microstructure resulting in the appearance adiabatic shear bands (ASBs). These ASBs persisted in holes in plates placed further down the stack (up to 8thin the stack). More complex microstructural mechanisms are thought to take place as opposed to erosion from the flow of the molten metal through the holes in the plates.
Effect of Impact Compression on Age Hardening Behavior of Aluminum Alloys
Authors: Kitani Yuki , Horikawa Keitaro , Kobayashi Hidetoshi , Tanigaki Kenichi , Ogura Tomo , Hirose Akio
Published: June 2014

The effect of impact compression on age hardening behavior was examined for Meso20 and 6061 aluminum alloys using a single stage gun. The hardness of Meso20 and 6061 aluminum alloy applied with an impact compression (about 5.0GPa) after the solution treatment increased with the aging time. The cluster of point defects like stacking fault tetrahedral (SFT) was observed in the 6061 aluminum alloys with the impact compression (5.3GPa) after the solution treatment. Even after the impact compression, distribution of the aging precipitates was clearly identified.
Dynamic Impact Behavior of Ti-Ni Shape Memory Alloys in Two Different Compositions
Authors: Young Sung Yong , Jin Doo Han , Chung Dong Teak
Published: June 2014

Stress vs. strain curves of two kinds of Ti–Ni shape memory alloys under dynamic compressive loading condition were obtained by the split Hopkinson pressure bar experiment. One is Ni-rich, 50.75Ni–49.25Ti (at%) alloy and the other is Ti-rich, 49.5Ni–50.5Ti (at%). The former exists as austenite phase to show superelastic behavior at the room temperature, and the latter is martensitic phase at the room temperature. The dynamic stress–strain curves were compared with quasi-static compressive test results. The Ni-rich specimen displayed a much higher stress level at the high strain rate than at the quasi-static test, but the Ti-rich specimen exhibited a similar stress level in the two types of tests.
Measurements of Combined Pressure-Shear Waves by the Oblique-Parallel Impact Experiment
Authors: Ogata Kenichi , Liu X. , Mashimo Tsutomo
Published: June 2014

Measurements of shear wave under shock compression give important information of the shear modulus and strength. We had started the measurements of the combined pressure-shear waves by the oblique parallel-impact experiments on sapphire (α-Al2O3single crystal) in several 10s of GPa region by the electromagnetic-gauge method and inclined-mirror method. The samples used ware c-cut sapphire plates. In this paper, the experimental method and configuration of the system are describes. The result will be presented at the conference.
Numerical Analysis of Vehicle Occupant Responses during Rear Impact Using a Human Body Model
Authors: Pramudita Jonas A. , Kikuchi Shunsuke , Tanabe Yuji
Published: June 2014

Understanding vehicle occupant responses during real-world rear collision accidents is very important in the development of appropriate safety technologies for neck injury lessening. In this study, numerical analysis of vehicle occupant responses during rear impact were conducted by using a human multi-body model, a seat finite element model and crash accelerations obtained from real-world accidents. The human multi-body model was developed based on the body characteristics of a typical Japanese male, including the outer body geometry, inertial properties of body segments and passive joint characteristics. The seat finite element model was extracted from a detailed car finite element model. A small modification was done to the seat model to deal with the rear impact simulations. The crash accelerations were obtained from the drive recorder database of rear collision accidents occurred in Japan. Several crash accelerations were selected and used as input conditions during the rear impact simulations. Kinematic responses of the occupants during the accidents can be reasonably predicted by the simulations. Furthermore, different level of accelerations leads to different kinematics responses that may cause variation in injury occurrence and injury severity.
Thermo-Elastic-Plastic Constitutive Model for Numerical Analysis of Metallic Structures under Local Impulsive Loadings
Authors: Chernobryvko Marina , Kruszka Leopold , Vorobiev Yuorii
Published: June 2014

The tasks of dynamic behavior of constructions’ elements under the impulsive loadings modeling are examined. Mathematical models are taken into account to calculate thermo-elastic-plastic deformations, dynamic properties of materials, large deformations and strains. Numerical calculations of the dynamic stress-strain state for steel constructions are conducted for a local impulsive loading.
Numerical Study of the Effects of Metallic Plates in the Attenuation of the HRAM Phenomenon
Authors: Varas David , López-Puente Jorge , Zaera Ramón
Published: June 2014

Hydrodynamic Ram (HRAM) is a phenomenon that occurs when a high-energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure increasing the risk of catastrophic failure and excessive structural damage. In this work a numerical study of the influence of metallic plates, inside a fluid-filled aluminium tube, in the attenuation of the HRAM phenomenon effects is performed. The numerical results regarding walls displacement and pressure inside the tank will be compared with a case in which there are no barriers inside the tube. The simulations are performed with the software LS-DYNA applying the ALE technique.
Response of Sandwich Panels with Tubular Cores to Blast Load
Authors: Yuen Steeve Chung Kim , Nurick Gerald , du Plessis Misha C.
Published: June 2014

This paper reports on the response of cladding sandwich panels with tubular cores to uniform blast load. The panels consist of thin-walled circular tubes (38 mm in diameter) made from aluminium 6063-T6 riveted laterally between the skin plates at varying spacing arrangements to provide four different types of panels. The skin exposed to the blast load is made from DOMEX 700 Steel while the back face skin is made from mild steel. Varying charge masses of explosive (ranging from 5 g to 40 g) with a prescribed load diameter of 40mm is detonated at a stand-off distance of 200 mm to provide a “uniform” blast load to the sandwich panels. Energy is dissipated mostly through the plastic deformation of the tubular cores. The results show an increase in average deflection with an increase in charge mass/impulse for the different types of panels. The cladding panels with the least interaction between the tubular cores are observed to have the highest energy absorption capabilities for a given charge mass.
Mass Impact of Density-Graded Cellular Metals in a Temperature Field
Authors: Zheng Zhi Jun , Wang Xiao Kai , Yu Ji Lin
Published: June 2014

We consider the problem of a density-graded cellular rod in a temperature gradient field axially subjected to a mass impact. Two-dimensional cell-based finite element models and one-dimensional shock models are employed to explore the mechanisms of deformation and wave propagation. The yield stress distribution in a cellular specimen depends on both the density gradient field and the temperature gradient field. The stress distribution and the yield stress distribution are analyzed. For the increasing yield stress along the impact direction, one shock front propagates from the proximal end to the distal end of the specimen. For the decreasing yield stress along the impact direction, two shock fronts propagate in opposite directions and the one close to the proximal end ceases at a particular time. The predicted stresses of the extended shock models are compared well with the numerical results.
Study on Impact Collapse Characteristics of CFRP Double-Hat Members According to Stacking Angle
Authors: Choi Ju Ho , Hwang Woo Chae , Yang Yong Jun , Cha Cheon Seok , Yang In Young
Published: June 2014

There has been greater demand on fuel mileage improvement and reduced CO2 emission in automobile without sacrificing safety. To meet these requirements, light weight car body is widely adopted. In addition, advanced country already started the strict regulation on fuel mileage and exhaust gas emission because of energy depletion by automobile and severe environmental contamination. Especially, during the initial stage of car design, side member of front side that absorbs significant amount of energy should be precisely evaluated for collapsing and energy absorption prior to estimate safety performance on frontal collision of car. Therefore, CFRP double hat and hat-shaped member were prepared to supplement the issues of splitting between “ᄃ” shaped member and planar one. According to stacking configuration, energy absorption characteristics via impact collapsing experiment were evaluated to acquire CFRP double-hat shaped member.
High Strain-Rate Compressive Behavior and Constitutive Modeling of Selected Polymers Using Modified Ramberg-Osgood Equation
Authors: Nakai Kenji , Yokoyama Takashi
Published: June 2014

The present paper is concerned with constitutive modeling of the compressive stress-strain behavior of selected polymers at strain rates from 10-3 to 103/s using a modified Ramberg-Osgood equation. High strain-rate compressive stress-strain curves up to strains of nearly 0.08 for four different commercially available extruded polymers were determined on the standard split Hopkinson pressure bar (SHPB). The low and intermediate strain-rate compressive stress-strain relations were measured in an Instron testing machine. Six parameters in the modified Ramberg-Osgood equation were determined by fitting to the experimental stress-strain data using a least-squares fit. It was shown that the monotonic compressive stress-strain behavior over a wide range of strain rates can successfully be described by the modified Ramberg-Osgood constitutive model. The limitations of the model were discussed.
Quasi-Static and Dynamic Compressive Properties of AZ31 Magnesium Alloy Processed by Equal Channel Angular Pressing
Authors: Yu Xia , Suo Tao , Zhao Feng , Li Yu Long
Published: June 2014

Equal channel angular pressing (ECAP) was applied to control the microstructure of AZ31B magnesium alloy. Compression properties of both as-received and grain refined AZ31B alloy were investigated under quasi-static and dynamic loadings. The yield strength, ultimate strength, failure strain and flow stress under compression loading were studied. Both the as-received alloy and ECAPed alloy show strong strain rate sensitivity. Grain size, texture and strain rate jointly affect the deformation mechanisms. Through fractography analysis, the fracture mechanism was analyzed.
Identification Methods of Parameters for Johnson-Cook Constitutive Equation – Comparison
Authors: Grązka Michał , Janiszewski Jacek , Kruszka Leopold , Cadoni Ezio , Forni Daniele , Riganti Gianmario
Published: June 2014

The paper presents two identification methods of parameters for the Johnson-Cook constitutive equation. The Johnson-Cook equation is one of the most popular semi-empirical constitutive models to describe the equivalent of plastic stress-strain curves. The first presented method is the approximation method of plastic hardening stress-strain curves, obtained during split tension Hopkinson bar tests. The second proposed method to determine parameters of the Johnson-Cook equation is based on solutions of the inverse problem. This means that during optimization and identity calculations, physical phenomenon is simulated as, for example, an axially symmetric deformation, i. e., the Taylor impact test.
Effect of Magnesium Coating Prior to Lithium Loading over SBA-15 for Stabilization of its Mesostructure
Authors: Ayoub Muhammad , Abdullah Ahmad Zuhairi
Published: June 2014

Mesoporous material SBA-15 was synthesized using P123 and TEMOS as the templates. Lithium in the form of LiOH was loaded over a previously prepared SBA-15. The basic strength of the prepared samples of SBA-15 was found to increase but the mesoporous structure was severely destroyed. The mesoporous structure of the prepared SBA-15 was retained after coating it with 30 wt. % magnesium prior to LiOH loading. The stability of mesoporous structure was strongly influenced by the extent of magnesium coating. It was also noted that this structure was also affected by LiOH loading and significantly destroyed structure when magnesium coating value exceeded 20 %. These samples were thoroughly characterized for their surface area, pore volume, pore size, basic strength, SAXRD patterns and transmission electron microscopic (TEM) analysis.
Operational Training Management System (OPTRAMS) for Safe Operation in Process Plant
Authors: Aziz Hanida Abdul , Mohd Shariff Azmi , Rusli Risza
Published: June 2014

Many publications have reported about 37% of major accidents in petroleum, chemical, nuclear, aviation, and in the other process industries that occurred worldwide were due to human error. One of the keys contributing factors that could prevent these accidents is to provide appropriate training to the plant personnel. However, accidents still can happen if training is poorly managed and improperly trained personnel handling the operation of the plant. One of the established industrial standards to manage the training is Training element of Process Safety Management (PSM) 29 CFR 1910.119(g). This paper presents a system to manage training for safe operation following 29 CFR 1910.119(g) namely Operational Training Management System (OPTRAMS). It provides strategies to manage information and documentation related to training. OPTRAMS was implemented at the CO2-Hydrocarbon Absorption System (CHAS) pilot plant at Universiti Teknologi PETRONAS as a case study. The study showed that all operational training can be managed efficiently with OPTRAMS and also assists end users to identify the gaps that hinder training of PSM compliance. The implementation of this technique could help end users to prevent and minimize catastrophic accidents and comply with training of PSM standard.
Evaluation of Inherent Safety Strategies Using FAHP to Reduce Human Error
Authors: Abdul Wahab Nordiana , Rusli Risza , Mohd Shariff Azmi
Published: June 2014

Inherent safety concept has been introduced to overcome the shortcoming of traditional hazard assessments by allowing modification to be made at any stage of lifecycle of a process plant. However, most of the proposed inherent safety modifications were suitable to prevent fire, explosion and toxic hazards assessment but less attention on human and organizational factor. Therefore, this paper introduces the inherently safer analysis for human and organizational factor to be implemented during design stage or process operation. Analytic Hierarchy Process model integrated with fuzzy logic and known as FAHP was employed to rank identified inherently safer strategies. The model was applied to select inherently safer strategies to reduce collision risk of a floating production, storage and offload and the authorized vessel. The result shows that minimization of hazardous procedure when the procedure is unavoidable is the best strategy to increase human performance. It is proven that the proposed methodology is capable to select the inherently safer strategy without requiring a bunch of precise information to transfer expert judgment in human performances perspective.
Solubility Parameters Based on Refractive Index Data of Ionic Liquid
Authors: Abdullah Syamsul Bahari , Man Zakaria , Ismail L. , Mutalib Mohammed Ibrahim Abdul , Bustam Mohamad Azmi
Published: June 2014

This article reports on the estimation of solubility parameters using refractive index for a series of imidazolium-based ionic liquids (ILs) and their dependencies on the carbon number of alkyl side-chain of cation and anion. Gathering about 35 ILs of refractive indices data from the literature, the solubility parameters estimation fit well with the suggested correlation. The precision of the estimated solubility parameters obtained indicates that the refractive index-solubility parameters correlation can be an alternative tool to estimate solubility parameter value for ILs.
Effect of Aluminium Sol on Silica Nanoparticles Texture and Properties
Authors: Ellateif Tayseir M. Abd , Maitra Saikat , Murugesan T. , Azizli Khairun Azizi
Published: June 2014

This Silica sols were synthesized by alkali hydrolysis of tetraethyl orthosilicate (TEOS). These sols were modified with different percentage of aluminum sol to convert silica from hydrophilic to hydrophobic. The compositions of unmodified and modified silica nanoparticles were studied by X-ray fluorescence (XRF) and confirmed that the aluminum was anchor to the surface of silica nanoparticles. Further analysis by FESEM and Thermo gravimetric analysis (TGA) showed that the amount of modifier added to the silica sols had distinct effect on morphology and thermal stability of silica nanoparticles respectively. X-ray diffraction analysis illustrated that modified silica nanoparticles are amorphous.
Bio-Oil Derived from Palm Kernel Shell in Fluidized Bed Reactor: Effect of Particle Size
Authors: Norizan Ali , Uemura Yoshimitsu , Wissam N. Omar , Tsutsui Toshio
Published: June 2014

Bio-oil production from pyrolysis of 0.15-0.5 mm and 1-2 mm palm kernel shell (PKS) has been investigated in a fluidized bed reactor under the nitrogen gas flow rate of 25 L(NTP)/min, with reactor temperature of 450°C. The pyrolysis unit has six successive condensers. Thus, six fractions of bio-oil samples were acquired from the six condensers. The calorific value, water content, ash content, and element content of each bio-oil samples were determined. The bio-oil yield from palm kernel shell with the size of 0.15-0.5 mm and 1-2 mm were 20 % and 26 %, respectively. The highest calorific value among the six bio-oil samples was 25.1 MJ/kg which was drawn from the forth condenser from pyrolysis of 0.15-0.5 mm of palm kernel shell. The incondensable gas was a mixture of hydrogen, methane, carbon dioxide and ethane.
In Situ Methanolysis of Jatropha curcas Seeds in Soxhlet Extractor
Authors: Prabaningrum Nunung , Ismail L. , Subbarao Duvvuri
Published: June 2014

Biodiesel is an alternative fuel to replace petro diesel with some advantages. One of the methods to produce biodiesel is in-situ transesterification. In this study, in-situ methanolysis of Jatropha curcas seeds in Soxhlet extractor was investigated. Normal hexane was added to enhance the solubility and extractability of methanol in the presence of NaOH as catalyst to Jatropha curcas oil. Response surface methodology based on Box Behnken design was used to determine the optimum reaction conditions. The ratio of mixture volume to seed weight (7.5; 12.5), catalyst concentration (1.75; 2.25 wt.%) and volume ratio of methanol to mixture (0.3; 0.7) were selected as experimental parameters. The biodiesel yield of (91.37 ± 0.57) %, which was insignificantly different with the predicted value, was obtained with the optimum conditions as follows: the ratio of the mixture volume to seed weight of 12.48 (ml/g), 1.75 wt.% of sodium hydroxide concentration, 0.31of the ratio of methanol volume to the mixture volume at 60 °C for 60 min reaction time. The maximum yield of (98.63 ± 2.9) % was achieved at optimum conditions during 3 hours reaction time at 60 °C.
Comparative Study on Two-Step Fatty Acid Methyl Ester (FAME) Production from High FFA Crude Palm Oil Using Microwave Technique and Conventional Technique
Authors: Bakar Suliana Abu , Yusup Suzana , Ahmad Murni Melati , Quitain Armando T. , Sasaki Mitsuru , Goto Motonobu , Uemura Yoshimitsu , Ahmad Junaid
Published: June 2014

The production of biodiesel from crude palm oil (CPO) using microwave technique is investigated and has been compared with conventional heating. Two-step biodiesel production process is applied to maximize the highest biodiesel yield in short reaction time using microwave method. Sulfuric acid (H2SO4) as acid catalysts is used in pre-treatment of feedstock by esterification process followed by potassium hydroxide (KOH) as base catalyst for transesterification process with low methanol to oil ratio. The main purpose of the pre-treatment process is to reduce the free fatty acids (FFA) content of CPO from higher value of FFA content (>6.8%) to a minimum level for biodiesel production (<1%). Esterification and transesterification is carried out in fully instrumented and controlled microwave reactor system to get higher yield in shorter time. This two-step esterification and transesterification process showed that the maximum conversion of palm biodiesel obtained is 95.1% with the process conditions of methanol-to-oil molar ratio of 6:1, reaction temperature 65oC, reaction time 15min, and 2% (wt/wt) KOH amount using microwave method compared to conventional heating where the palm oil methyl ester (POME) yield obtained is 81% at the same conditions. The result showed that, the biodiesel production using microwave technique proved to be a fast and easy route to get high yields of biodiesel.
Effect of Low Cu Addition and Thermo-Mechanical History on Precipitation in Al-Mg-Si Alloys
Authors: Saito Takeshi , Marioara Calin D. , Røyset Jostein , Holmestad Randi
Published: June 2014

The effect of cooling rate after solution heat treatment and its combination with 1% pre-deformation on precipitation hardening in two Al-Mg-Si alloys is investigated by transmission electron microscopy (TEM), and related to material hardness. Two alloys have been used, one Cu-free and the other with low Cu additions (~0.1 wt%), both having the same amounts of other solutes. A double peak hardness evolution during an isothermal heat treatment was observed with slow cooling after solution heat treatment. This effect was less pronounced in the Cu-added alloy. The 1% pre-deformation also made this effect less pronounced, but it led to faster initial hardness evolution and delayed over-aging. Maximum hardness was not influenced by cooling rate and the pre-deformation. Hardness was directly related to precipitate number densities.
Strain Induced Rapid Precipitation in Al-Er-Zr Alloy
Authors: Wen Sheng Ping , Li Bo Long , Rong Li , Gao Kun Yuan , Huang Hui , Wang Wei , Nie Zuo Ren
Published: June 2014

The high temperature strength of aluminum can be improved by forming thermal stable precipitates of microalloying elements such as Er, Sc and Zr. Our previous research indicates that composite addition of Er and Zr can improve the amount of precipitations, but the aging time to approach the peak hardness is relatively long. In this paper, we will focus on the deformation behavior of the Al-Er-Zr alloy during hot deformation process and the corresponding microstructure evolution. The results show that the strain can induce rapid precipitation in Al-Er-Zr alloy during hot working conditions. The mechanism of the rapid precipitation and its effect on thermomechanical processing are discussed.