bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Particle Swarm Optimization Based on Biological Chemotaxis
Authors: Xia Hui
Published: August 2014

Standard particle swarm algorithm for function optimization prone to local optimal and premature convergence, and thus the biological chemotaxis principle introduction to particle swarm optimization algorithm, this paper proposed an improved algorithm to maintain the diversity of the populationand the choice of key parameters. Simulation results show that, compared with the traditional particle swarm optimization algorithm, an improved particle swarm algorithm for dealing with complex multimodal function optimization problem can be significantly improved algorithm for global optimization.
Trial-Preparation of RSS Based Composite Containing GF
Authors: Wu Chuan Bao , Liu Xiang Li
Published: August 2014

In order to explore the enhancing method of rice straw based composites, glass fiber (GF) was introduced into the preparation of composites of poly (vinyl alcohol) (PVA) and rice straw slice (RSS). The tensile performances and hardness of composites were characterized. Results showed that GF had obvious enhancing role on PVA/RSS composites. The tensile strength of the composites first increased and then decreased with increasing GF amount. When the mass ratio of RSS, PVA and GF was 20:15:7, the composite reached its maximum strength of 23.45 MPa, which increased by 1.49 times compared to the composites without GF. The strength at tensile break of composites increased with the increase of GF amount. The maximum of strength at tensile break was 23.12 MPa when GF amount was 9 g. The stretch of composites first increased and then decreased with increasing GF amount. The addition of GF had no effect on the hardness of composites.
Study of the Preparation and Properties of Carbon Nano-Tubes Doped TiO2/Glass Fiber Reinforced Plastics
Authors: Bai Ling Yun , Jiang Long Fa , Wang Yue Ping , Xu Yan Qing
Published: August 2014

Carbon nanotubes (CNTs) doped TiO2/glass fiber reinforced plastics (GRP) hybrid materials with different TiO2and CNTs contents were prepared by first step sol-gel and then hand lay-up method, using modified CNTs doped tetrabutyl titanate as precursor. The results showed that high TiO2and CNTs contents obtained GRP with high temperature stability and high electrical conductivity, but slowed down the solidification process of epoxy resin to obtain GRP.
Preparation and Performance Testing of Flexible PDLC Films
Authors: An Ya Jing , Guo Xin Liang , Zhang Sheng Han , Du Zong Qiang
Published: August 2014

A new kind of polymer dispersed liquid crystal (PDLC) films based on nematic liquid crystal E7 and pre-polymeric composition epoxy resin E51 were prepared by polymerization induced phase separation via heating curing in this paper. The electro-optical properties of PDLC films were affected by many processing factors, for example, the weight ratio of the pre-polymer and liquid crystal, the curing temperature, curing time and film thickness. The electro-optical properties of PDLCs fabricated under different conditions were tested. The performance parameters such as contrast ratio, threshold voltage and the saturation voltage were calculated. In our case, the optimal preparation condition was 65% liquid crystal content with a curing time of 6 hours at 65oC. The PDLC film prepared in this paper showed a threshold voltage of 14.11V and a saturation voltage of 49.47V. The effect of film thickness on the electro-optical properties of PDLCs had been analyzed as well. The threshold voltage and saturation voltage of PDLC increase as the film thickness increases as so as the contrast ratio.
To Measure Mechanical Properties along Thickness in FSW Welded Zone by Applied ESPI Technology
Authors: Chen Thai Ping , Chien Chi Hui , Tsay Tsu Lin , Tzeng Yen Ming , Cheng Hsu Hsuan
Published: August 2014

The purposes of this paper are to weld dissimilar aluminum alloys joints, AA1050 and AA6061, and to find Young’s modulus on the welded zone along the thickness. Dissimilar aluminum alloys plates are friction stir welded in the butt configuration by using an adapted milling machine. Young’s modulus of components is found out by applied a reverse method and the out-of-plane displacement is measured by Electronic Speckle Pattern Interferometry. The out-of-plane displacement of the welded cantilever beam is subjected to a concentrated load. The results reveal that Young’s modulus in the welded zone is the deeper the smaller.
Die-Bending of Adhesively Bonded Sheet Metals
Authors: Takiguchi Michihiro , Tokuda Taro , Yoshida Tetsuya , Uemori Takeshi , Yoshida Fusahito
Published: August 2014

In this paper, the deformation behavior of adhesive layer in die-bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-bending. (2) The punch radius has a large influence on the die-bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-bending at high speed as well as air-bending.
FEM Simulation of Quenching Process and Investigation of Residual Stresses of Crankshafts
Authors: Qin Wen Jie , Dong Chao
Published: August 2014

Compressive residual stresses and high hardness introduced by induction quenching are often used to improve the mechanical performance of crankshafts in engines. In this paper, in order to predict the fatigue strength of the crankshafts in a diesel engine accurately, the quenching process and the stress fields of the crankshaft are simulated by finite element method (FEM) and then the residual stresses are obtained. Quenching is a high non-linear process because of the coupling of the temperature, phase transformation and stress/strain fields. The transient temperature field is firstly solved using a quasi-coupling method to simulate the relationship of the temperature and the phase transformation. Based on the results of the temperature and phase transformation fields, the thermo-elastic-plastic analysis is then carried out to calculate the stress fields including the thermal stresses and the phase transformation stresses. At last the residual stress distribution at the room temperature is obtained.
Thermal Ratcheting of Solder-Bonded Layered Plates
Authors: Ohno Nobutada , Mizushima Satoshi , Tanie Hisashi
Published: August 2014

The cyclic growth and recovery of warpage were observed in experiments on Si/solder/Cu layered plates subjected to cyclic thermal loading [1]. In the present study, the experiments were analyzed using representative material models for the solder and Cu layers in finite element analysis. The warpage growth/recovery behavior observed was reproduced well in the analysis using the Armstrong-Frederick and Ohno-Wang models for the solder and Cu layers, respectively. Material ratcheting due to non-proportional cyclic loading was found to happen in the solder layer as a consequence of the CTE mismatch, while material ratcheting due to proportional cyclic loading occurred in the Cu layer as a result of the significant temperature dependence of viscoplasticity in the solder layer.
Cold Roll Forming Process and Die Design for Double-Gutter Frame of Drawer Slider
Authors: Sheu Jinn Jong , Hsieh Chia Cheng , Yu Cheng Hsien
Published: August 2014

In this paper, the main focus is to demonstrate a systematic method of designing the roll flower and corresponding dies for a double-gutter frame applied to the drawer slider. The blank development method was proposed to calculate the width of blank for bending with small radii. The cold roll forming process design was based on the maximum longitudinal strain minimization and the interference of rolls with the double-gutter geometry of product profile. Extra pre-bending was designed to avoid the occurrence of blank collision during forming process. The FEM method was adopted to evaluate the process and die designs. Due to the geometry complexity of the product, strain distribution is uneven which results in more spring back and stress concentration. A geometry setting design was proposed to create local strain redistribution and smooth strain distribution of entire section profile after final forming step. Using geometry setting die design, the spring back at the end point and the gutter areas of final product section are 0.07 mm and 0.1 mm, respectively. Without the geometry setting die design, the spring back at the end point and the gutter areas of final product section are 0.11 mm and 0.15 mm, respectively. The simulation results demonstrate the proposed methods are able to improve the accuracy of cold roll forming products.
Cold Forging Die Design and Process Simulation of a Disk with Inner Ring Gear
Authors: Yu Cheng Hsien , Sheu Jinn Jong
Published: August 2014

Cold forging die design and process simulation were studied in this paper for a disk with center boss and outer ring gear. The complexity of part geometry results in defects of under-filling and folding. The material flow interference in the radial and the axial directions at the corner areas is the main reason of the occurrence of defects. A multi-stage cold forging process was proposed to control the material flow and volume distribution simultaneously. FEM simulations were carried out to evaluate the designs of process and die. The proposed preform and web geometry designs were able to decrease the forging load and control the material flow. The simulation results showed the proposed methods were able to make this forged part without defects.
An Integral Approach to the Investigation of High Speed Metal Cutting
Authors: Zhang Liang Chi
Published: August 2014

High speed cutting (HSC) has been used widely in the metal machining industry. However, applications and investigations have shown that to optimize an HSC process, many issues need to be understood, such as the fluctuations of cutting forces and residual stresses. Extensive studies have found that these fluctuations are originated from the shear banding during chip formation and from the work-material properties influenced by the coupled attack of high strain rate and high temperature rise during cutting. Due to the complexity of the material deformation mechanisms during HSC, both experimental examination and theoretical analysis are essential. This keynote presentation reviews an integral approach of the author’s team to establishing the investigation chain of experimental analysis, constitutive modelling and numerical simulation to tackle the intricacy of HSC-induced deformation. It points out that while an experimental examination can provide insightful understanding of the deformation mechanisms, it is often limited to a narrow range of testing conditions. A numerical simulation can overcome such experimental difficulties through large-scale parametric studies, but can also bring about erroneous results if the constitutive behavior of a workpiece material is improperly described.
An Estimation of Joint Strength by Using Fe-Based Shape Memory Alloy Subjected to Bending Deformation at Various Deformation Rate
Authors: Fujita Kazuki , Nishikori Keizo , Iwamoto Takeshi
Published: August 2014

In various kinds of shape memory alloy (SMA), Fe-based SMA (Fe-SMA) shows smaller shape memory effect compared with the other SMAs. However, Fe-SMA shows huge advantages on the excellent formability, machinability, etc. Moreover, its production cost is cheaper than other SMAs; therefore, the alloy is attempted to be applied to structural members such as joints and dampers. Since bending deformation at higher deformation rate is generated in the members, especially the joints, due to impact force such as earthquake or wind, a clarification on the bending strength of the joints at various deformation rate is strongly required. In this study, at first, it is attempted that the bending strength and its rate sensitivity of the joints which consist of Fe-based SMA are experimentally estimated by the three-point bending test at various deformation rate. Then, the force balance equation is challenged to be derived to predict the bending strength.
Buckling Behavior and Atomic Elastic Stiffness in Defective Multi-Walled Carbon Nanotube under Axial Compression
Authors: Nishimura Masaomi , Takagi Yu , Arai Masahiro
Published: August 2014

Axial compressive simulations are performed on defective and non-defective multiwalledcarbon nanotubes (MWCNTs) using the molecular dynamics method, and the effectof defects upon the buckling behavior is discussed. In our previous study, changes in atomicstresses in MWCNTs with three layers were evaluated until buckling occurred. That studysuggested that the transition from homogeneous stress distributions to inhomogeneous onesplays an important role in the occurrence of buckling in MWCNTs, though the critical stressesor strains relating to buckling are dependent upon the structure and location of defects. In thepresent study, the atomic elastic stiffness of each atom, Bij , is evaluated to discuss the onsetof local buckling in MWCNTs with five layers. The det(Bij) of all atoms is found to change toa negative value long before buckling occurs, while the second smallest eigenvalues of Bij forsome atoms change to a negative value just prior to buckling. The existence of dense regions ofatoms that have two negative eigenvalues of Bij are found to vary as a function of the defectlocation, and to correspond with onset points of local buckling.
Experimental Investigation and FEM Simulation on Material Behaviors of Cylinder with the Rotating Flat Die
Authors: Tzou Gow Yi , Hwang Yeong-Maw , Pan Sai Chih
Published: August 2014

The study aims at exploring the effects of rotating compression forming on the material behaviors of cylinder. The experiments have been carried out under various angular velocities to realize the flow stress, the compression force, the rotating torque, the grain size, and the hardness. Furthermore, the FEM simulation is also performed to compare with the experiments. From the experimental results, as the angular velocity increases, the compression force and the grain size decrease, but the rotating torque and the hardness increase. The results can provide the industry as the reference.
Development of Precision Flange Forming Die for Sheet Metal
Authors: Lin Yu Ting , Wang Jing Hui , Lin Chih Hao , Cheng Tseng Jen , Huang Chien Fa
Published: August 2014

With the rapid development of mechanical manufacturing technology and numerous demands of different technique products and the applied industry, commercial products trend miniature and precision. In order to satisfy the demands of miniature and precision components, the precision forming technology which takes advantages of high mass production, low costs and stable quality is proposed. This paper develops the precision flange forming die for sheet metal. In the paper, the SUS304 stainless steel was adopted to enhance the structural rigidity. The hollow flange sheet is manufactured by precision forming processes. The forming height, the sheet thickness and the other geometry parameters are considered and the technologies of hole-flanging forming, pressing and forging are applied in this study. The CAE (Computer-Aid Engineering) simulation tool is adopted as a reference to analyze the feasibility of the proposed forming processes. Both simulated and manufactured results show that the proposed precision forming technique can be a reliable process for the production of precision hollow flange sheet.
A Dislocation-Based Crystal Plasticity Simulation on Kink Band Formation and Evolution in Polycrystalline Mg Alloy with LPSO Phase
Authors: Ueta Ryo , Shizawa Kazuyuki
Published: August 2014

A three-dimensional compression analysis is performed by finite element method using a dislocation-based crystal plasticity model to clarify the formation mechanism of kink band in a polycrystalline Mg alloy with a long-period stacking ordered structure (LPSO) phase. The crystalline structure of LPSO phase is regarded as a HCP for simplicity, however, any deformation twinning is not taken into account. In addition, the activities of non-basal systems are considerably limited in the LPSO phase setting the values of their critical resolved shear stresses to large ones. We analyze a simple polycrystalline specimen composed of two α-Mg matrix phases and a LPSO phase both having a rectangular shape and twist grain boundaries are introduced into the interface. The obtained result shows that the kink band formation in the alloy is accomplished by the basal slips with different variants and the non-basal slips are activated on the grain boundary to maintain the continuity of deformation.
Effects of Laminate Misalignment on Thermoelastoviscoplastic Properties of Ultrafine Plate-Fin Structures
Authors: Yamanaka Yuki , Matsuda Tetsuya
Published: August 2014

Effects of laminate misalignment on the thermoelastoviscoplastic properties of ultrafine plate-fin structures are investigated using a homogenization theory for thermoelastoviscoplasticity. For this, a homogenization theory for time-dependent materials is combined with a homogenization theory for thermoelasticity. Moreover, the substructure method is introduced into the theory to deal with the random laminate misalignment in ultrafine plate-fin structures. The present method is then applied to the analysis of thermoelastoviscoplastic behavior of ultrafine plate-fin structures made of a Ni-based alloy subjected to a macroscopic temperature increment from 20 to 200. The number of fin layers in a unit cell is five kinds, i.e. N = 10, 20, 30, 40 and 50, for each of which, twenty patterns of random laminate misalignment are considered. In addition, five cases of periodic laminate misalignment are also considered for comparison. The results reveal the effects of the laminate misalignment on the macroscopic and microscopic thermoelastoviscoplastic properties of ultrafine plate-fin structures.
Study on Hydraulic Deep Drawing of Square Cups
Authors: Huang Te Fu , Hsien Hsin Yi , Chen Yan Jia
Published: August 2014

The friction holding effect and the friction reducing effect occurring during Hydraulic Deep Drawing and the pre-bulging resulting in more plastic deformation on products are applied on sheet hydro-forming. For Hydraulic Deep Drawing of a square cup, the thickness distribution and the relation between the height and the pressure of pre-bulging are simulated with SPCC steels as the specimen by the finite element method. An experimental apparatus of sheet hydro-forming has been constructed to carry out the hydraulic deep drawing experiments of square cups. Experimental thickness distribution and punch load are compared with simulation results. Good agreement was found. The flow patterns of the circular and square blanks with the condition of being firmly pressed against the punch observed from the experiments are in agreement with the predicted results.Keywords:Hydraulic Deep Drawing, sheet hydro-forming, finite element method
Finite Element Analysis on the Response of Local Sharp-Notched Circular Tubes under Cyclic Bending
Authors: Lee Kuo Long , Wang Yun , Pan Wen Fung
Published: August 2014

In this study, the finite element software ANSYS was used to analyze the mechanical behavior of local sharp-notched circular tubes under cyclic bending. The local sharp-notched depths include: 0.2, 0.4, 0.6, 0.8 and 1.0 mm, and the local sharp-notched directions include: 0, 30, 60 and 90 degrees. According to the experimental result, the notch depth has no influence on the moment-curvature relationship. But the notch depth increases, the unsymmetrical phenomenon of the ovalization-curvature relationship becomes more obvious and the speed of ovalization accelerates. In addition, the ovalization-curvature relationship becomes symmetrical when the direction angle increases. The ANSYS analysis was compared with the experimental finding. Although some differences between the experimental and simulated results, but both trends were very similar.
An Evaluation of Energy Absorption under Three-Point Bending Deformation at Higher Deflection Rate for TRIP Steel
Authors: Pham Hang Thi , Shi Lei Shi , Iwamoto Takeshi
Published: August 2014

In the last few decades, energy absorption of materials becomes an critical issue in a design process of a vehicle because risks of primary and secondary accidents against pedestrians, other road users and structures can be reduced by a performance of absorbing energy in its support structures. Among various materials used for the structures, TRIP steel with favorable mechanical properties such as excellent formability and higher impact energy absorption is attractive to automotive industries. Huge numbers of research works have been carried out to investigate deformation behavior of TRIP steel. However, just few studies can be found on the performance in TRIP steel, especially, at higher deformation rate during the crash of the vehicle. Kinetic energy by higher speed of the vehicle will be consumed by inelastic bending deformation of components. Thus, a consideration of bending deformation at high impact velocity is required for the evaluation of the performance. In this study, the performance in TRIP steel at high deformation rate is clarified by conducting both quasi-static and impact three-point bending tests for pre-cracked specimen.
Hot Forming a V-Shaped Ni-Ti Shape Memory Alloy Wire
Authors: Fann Kuang-Jau , Hsu Hau Chi
Published: August 2014

Ni-Ti shape memory alloys have shape memory effect, that if they are deformed from martensitic phase state at a lower temperature, they will recover their original shape by heating them to austenitic phase state. To have them for an application using this shape memory effect, usually they undergo a constraint aging after plastic deformation. That is, they are fixed with tool set and together heat treated in a furnace after they are formed at room temperature. However a large load is needed to form them at room temperature. Thus, this study is aimed to lower the forming load by combining the forming and aging process together in a furnace at high temperature. In this study, a Ni-Ti shape memory alloy wire having a diameter of 0.63 mm is bent in a heated chamber at 450°C, 500°C, 550°C, and 600°C, respectively, by a V-shaped punch of 2 mm in radius to an angle of 60°, then held along with the die set at its dead center in the chamber for maximum one hour long, and then quenched in the water. All of the bent wires have the shape memory effect. That is, the wires recover their bent geometry once they are unbent at about 4°C and heated again at about 100°C. The experiment results showed that the bent wires can have the geometry accuracy as desired because of stress relaxation found in the process, which depends on the process temperature and duration. As a result, the higher the process temperature is and the longer the duration is, the better the accuracy of the formed wires is.
Micro Sheet Hydroforming Process of Ultra-Thin Pure Titanium Foil
Authors: Sato Hideki , Manabe Kenichi , Wei Dong Bin , Jiang Zheng Yi , Kondo Daiki
Published: August 2014

A micro hydromechanical deep drawing is carried out using the pure titanium and the effect of fluid pressure on formability of pure titanium is investigated. The experiments are performed using the two kinds of pure titanium foils (TR270C-H and TR270C-O) and stainless steel foil (SUS304-H) with 50 thickness and the cylindrical and conical punches. As a result, it is found that the peeling off the oxide film of pure titanium can be reduced by applying the fluid pressure because the friction force and contact pressure between the blank and die decreases. However, the formability is lower for pure titanium than that for stainless steel because the tensile strength is low and the friction force is easy to increase as the friction force increases. In contrast, due to the low young modulus of pure titanium, the restriction of wrinkling, decrease of friction force and friction holding effect can be obtained at low fluid pressure.
Effect of Silica Coupling Agents on Texture Formation and Strengthening for Silica-Filled Rubber
Authors: Tomita Yoshihiro , Honma Takenori , Yashiro Kisaragi
Published: August 2014

New finite element homogenization model with nonaffine constitutive equation of rubber is developed to study the deformation behavior of silica-filled rubber under monotonic and cyclic deformation. The obtained results clarified the effect of the volume fraction of the silica coupling agent and the networklike structure connecting the silica particles on essential physical enhancement mechanisms of deformation resistance and hysteresis loss for silica-filled rubber. The finding suggests that the material characteristics of silica-filled rubber are much more controllable than those of carbon-black-filled rubber.
Experimental Study on Transformation Plasticity in Terms of Three-Point Bending System
Authors: Hamdam M. Arif , Nagaki Shigeru , Oshita Kenichi
Published: August 2014

Three-point bending system with one end simple support and the other end fix support has been proposed to analyze the transformation plasticity (TP) behavior and obtain transformation plasticity coefficient. In this investigation two types of materials SCM440 steel and S45C steel have been studied. The specimens were heated to austenite temperature and the temperature kept constant for several minutes, then cooling and loading processes were performed. Austenite to martensite phase transformation with forced cooling for SCM440 steel and austenite to pearlite phase transformation with natural cooling for S45C steel due to bending stresses have been occurred. The deflections of specimen were measured during loading process. By obtaining the maximum deflection due to transformation plasticity, the transformation plasticity coefficient was determined.
Effect of Workpiece Thickness and Surface Texturing on the Micro Cupping Tests
Authors: Lin Heng Sheng , Lin Ying Chieh , Lee Ming Ru
Published: August 2014

The miniaturization of products has driven the demand for better realization in the micro forming process. Micro sheetmetal forming becomes more susceptible to friction attributed to the decrease in the weighting of body force and the increase in surface force, as the size of workpiece decreases. In this work, micro cupping tests were utilized to test the influence of workpiece thickness and surface texturing both on stainless steel and copper sheets under an oil-lubricated condition. Three thickness gauges of workpiece, 0.05, 0.1 and 0.2 mm, were selected in order to represent the micro, meso and macro forming conditions, respectively. Longitudinal and isotropic lay conditions were obtained through imprinting the textured rolls produced by grinding and sand blasting methods. The result of the micro cupping tests show that the cup heights are comparable for both longitudinal and isotropic lays in forming the sheets of 0.1 and 0.2 mm thickness. However, isotropic lay has a greater cup height than that of longitudinal lay in forming the 0.05 mm sheets. This indicates that surface texturing becomes influential in the formability of micro sheetmetal forming.
Effect of Punch Shapes on Micro Backward Extrusion of Brass
Authors: Chang Chao Cheng , Wu Lin Chi , Huang Jia Wei
Published: August 2014

This study considered four types of punch, which were flat, conical, spherical and standardized punched, to investigate the effect of the punch shapes on the micro backward extrusion of brass. Brass (JIS C2600) materials were annealed at 500 °C, 600 °C, and 700 °C and resulted in different microstructures with grain sizes of 50 μm, 70 μm and 111 μm, respectively. The annealed brass materials were carefully machined as cylindrical billets with the same dimension of 1.1 mm in diameter and length. The billets were later used in the experiments of the micro backward extrusion to form cups with 1.1 mm diameter and 0.2 mm thickness. The experimental results show that the type of punch affecting load in an increasing order are spherical, standardized, conical and flat punches. The results also show that load increases with the punch speed, and reduces as grain size increases.
Energetics of Slip Deformation in Beta-Sn: A First-Principles Study
Authors: Kinoshita Yusuke , Ohno Nobutada
Published: August 2014

The generalized stacking fault (GSF) energy surfaces of (110), (101), (121), (001), and(100) planes in -Sn are analyzed using first-principles density functional theory calculations. Fromthe minimum energy paths (MEPs) on the GSF energy surfaces analyzed, energetically preferableslip paths of 13 nonequivalent slip systems in -Sn are investigated. It is found that the MEP of(110)[111]/2, (101)[010], (101)[111]/2, (121)[101], and (121)[111]/2 deviates from the straight linepath and takes a curve line path. The results indicate that perfect dislocations on these five slip systemsdissociate into partial dislocations as in cubic and hexagonal crystals.
Deformation and Energy Absorption of Composite Sandwich Beams
Authors: Vcelka Martin , Durandet Yvonne , Berndt Christopher C. , Ruan Dong
Published: August 2014

Experimental observations and data are employed to elucidate the effect of indenter size on the deformation and energy absorption of composite sandwich beams. Unlike metal face sheets that yield and plastically deform to create an intact indentation zone; composite face sheets tend to fail in a brittle manner resulting in fibre breakage that leads to widespread fracture. This mode of failure can dictate how the load is transferred throughout the structure and directly affect the energy absorption character of the composite sandwich beam. Quasi-static and low velocity impact (LVI) three-point bending experiments with various indenter diameters were conducted to observe the interaction between indenter and face sheet and the energy absorption properties. The results are compared with existing analytical expressions.
Effect of Directional Grain Structure and Strain Rate on Impact Properties and Dislocation Substructure of 6061-T6 Aluminum Alloy
Authors: Lee Woei Shyan , Liu Mao Hung
Published: August 2014

The effect of directional grain structure and strain rate on the impact properties and dislocation substructure of 6061-T6 aluminum alloy is studied. Impact tests are performed at strain rates ranging from 1x103 to 5x103s-1 using a split Hopkinson pressure bar system. Cylindrical specimens are prepared from the rolled plates in longitudinal direction, transverse direction and through-thickness direction, respectively. The results show that the flow stress is strongly dependent on the strain rate and displays complex variations with grain structure direction. The flow stress increases with increasing strain rate. For all tested strain rates, the flow stress is the highest in the transverse specimen, followed by the through-thickness specimen and longitudinal specimen. However, at the strain rate of 5x103s-1, the flow stress in longitudinal specimen is higher than that in through-thickness specimen due to the change of dislocation multiplication rate. The plastic flow occurs within the deformation regions, and becomes more pronounced at high strain rates, especially for the longitudinal specimen. Dislocation density increases markedly with increasing strain rate. Strengthening effect is the highest in the transverse specimen, followed by the longitudinal specimen and through-thickness specimen.
Fully-Modeled Unit Cell Analysis for Macro/Micro Elastic-Viscoplastic Behavior of Quasi-Isotropic CFRP Laminates
Authors: Goto Keita , Matsuda Tetsuya , Kubota Naoto
Published: August 2014

A fully-modeled unit cell analysis is performed to investigate the macroscopic and microscopic elastic-viscoplastic behaviors of a quasi-isotropic carbon fiber-reinforced plastic (CFRP) laminate. To this end, a quasi-isotropic CFRP laminate and its microstructure composed of carbon fibers and a matrix material are considered three-dimensionally. Then, a hexagonal prism-shaped unit cell fully modeled with fibers and a matrix including interlaminar areas is defined. For this quasi-isotropic laminate, a homogenization theory for nonlinear time-dependent composites with point-symmetric internal structures is applied, enabling us to analyze both the macroscopic and microscopic elastic-viscoplastic behaviors of the laminate. The substructure method is introduced into the theory to reduce computational costs. The present method is then applied to the elastic-viscoplastic analysis of a quasi-isotropic carbon fiber/epoxy laminate subjected to an in-plane uniaxial tensile load, to investigate the macroscopic elastic-viscoplastic behavior of the laminate and the microscopic stress and strain distributions in them.
Grain Size Effect on Mechanical Properties of Titanium Alloy
Authors: Jiang Cho-Pei , Huang Zong Han
Published: August 2014

The aim of this study is to investigate the effect of grain size on mechanical properties of commercially pure grade 2 (CP2) titanium bar with a diameter of 5 mm. The results reveal that the microstructure of β-phase forms when the annealing temperature exceeds 800oC. The formation of β-phase leads to reduce the ductility but increase hardness. The strength coefficient, yielding stress and hardness decrease with increasing of grain size when the microstructure of specimen is the α-phase.
Hot Deformation Resistance of an AA5083 Alloy under High Strain Rate
Authors: Chen Shi Rong , Wu Chung Yung , Ou Yi Liang , Yeh Yen Liang
Published: August 2014

Axisymmetric compression tests using Gleeble 3800 simulator were carried out to investigate hot deformation behaviors of an AA5083 alloy under high strain rate conditions. Sharp temperature rise and load cell ringing characterized by severely vibrational load responses were encountered at strain rates higher than 20 s-1 and sample buckling occurred at low temperatures. The load cell ringing was corrected using a moving average method with a two-way filtering operation to correct phase distortion. Isothermal flow curves were obtained by fitting the instantaneous temperatures into a binomial function, while buckling was correlated with sample height and Young’s modulus. After the corrections, hyperbolic sine equation was successfully used to extend from the hot tensile data having strain rates lower than 3 s-1 to 100 s-1. Quantitative analyses were accordingly made over the effects of temperature, strain rate and work hardening behavior on the flow curves. The previous constitutive equation in form of temperature, strain and strain rate was modified to predict the hot deformation resistance of the AA5083 alloy at temperatures of 250-450oC under the high strain rate operations.
Numerical Simulation on Correcting Camber and Wedge of Steel Slabs in Hot Rolling Mill
Authors: Aoh Jong Ning , Hsu Han Kai , Dai Wei Ting , Lin Chun Yen , Yeh Yen Liang
Published: August 2014

In the hot rolling process, the steel slab may experience a temperature gradient along its transverse direction which may cause camber and wedge after rolling. Camber and wedge phenomenon will affect the quality of the steel plate. To eliminate camber and wedge phenomenon, a pair of side guides is placed before and behind the hot rolling mill. The position mode and the force mode are the control modes for side guides to correct the slab shape and to guide the slab to follow rolling direction. Finite element analysis using ABAQUS was applied to simulate hot rolling process to find the correction mechanism of rolling equipment. The centerline of slab was traced and the shape of slab was predicted. The difference of rolling load between work side and drive side of roller was determined. Furthermore, the load, stress and velocity distribution on the slab at roll bite were analyzed. By using numerical model, hot rolling parameters including side guide control strategy can be predicted, which can provide the hot rolling line as a guideline to improve the quality of the steel slab.
A Study of Corrolink Structural Insulated Panel (SIP) to Windborne Debris Impacts
Authors: Chen Wen Su , Hao Hong
Published: August 2014

Structural insulated panel (SIP) is considered as a green panel in construction industry because of the low thermal conductivity of the sandwiched EPS core (i.e extended polystyrene). It is a lightweight composite structure and is widely used in commercial, industrial and residential buildings to construct the building envelop including roof and wall. The windborne debris driven by cyclone or hurricane usually imposes intensive localized impact on the structural panel, which might create opening to the structure. The opening on the building envelope might cause internal pressures increase and result in substantial damage to the building structures, such as roof lifting up and wall collapse. The Australian Wind Loading Code (version 2011) [1] requires structural panels to resist projectile debris impact at a velocity equal to 40% of the wind speed, which could be more than 40 m/s in the tropical area with the wind speed more than 100m/s. In this study, two kinds of SIP under projectile debris impact were investigated, i.e. “Corrolink” and “Double-corrolink” composite panels shown in Fig. 1. Laboratory tests were carried out by using pneumatic cannon testing system to investigate the dynamic response of composite panels subjected to wooden projectile impacts. The failure modes were observed. The structural dynamic responses were also examined quantitatively based on the deformation and strain time histories measured in the tests. The penetration resistance capacity of panels subjected to windborne debris impact was assessed.Fig. 1 Schematic diagrams (L) Corrolink panel; (R) Double-corrolink panel [2]
Effects of the Covalent Bonding Entrapment of Tetrapyrrole Macrocycles Inside Translucent Monolithic ZrO2 Xerogels
Authors: Salas-Bañales Eduardo , Quiroz-Segoviano R. Iris Y. , Rojas-González Fernando , Campero Antonio , García-Sánchez Miguel A.
Published: August 2014

While searching for adequate sol-gel methodologies for successfully trapping in monomeric and stable form either porphyrins or phthalocyanines, inside translucent monolithic silica xerogels, it was discovered that the interactions of these trapped tetrapyrrole macrocycles with Si-OH surface groups inhibit or spoil the efficient display of physicochemical, especially optical, properties of the confined species. Consequently, we have developed strategies to keep the inserted macrocycle species as far as possible from these interferences by substituting the surface-OH groups foralkylorarylgroups or trapping these species inside alternative metal oxide networks, such as ZrO2, TiO2, and Al2O3. In the present manuscript, we present, for the first time to our knowledge, a methodology for preserving the spectroscopic characteristics of metal tetrasulfophthalocyanines and cobalt tetraphenylporphyrins trapped inside the pores of ZrO2xerogels. The results obtained are contrasting with analogous silica systems and demonstrate that, in ZrO2networks, the macrocyclic species remain trapped in stable and monomeric form while keeping their original spectroscopic characteristics in a better way than when captured inside silica systems. This outcome imply a lower hydrophilic character linked to the existence of a smaller amount of surface hydroxyl groups in ZrO2networks, if compared to analogous SiO2xerogel systems. The development and study of the possibility of trapping or fixing synthetic or natural tetrapyrrole macrocycles inside inorganic networks suggest the possibility of synthesizing hybrid solid systems suitable for important applications in technological areas such as optics, catalysis, sensoring and medicine
Silk Fibroin Nano-Coated Textured Silk Yarn by Electrospinning Method for Tendon and Ligament Scaffold Application
Authors: Ghiasi Mostafa , Naghashzargar Elham , Semnani Dariush
Published: August 2014

In recent years, the use of combined nanofibers with textile structures for various applications such as tissue engineering has been highly regarded. Among the different methods, electrospinning mechanism is more important to produce polymeric nanofibers in extensive diameters that has been used to fabricate silk fibroin nanofibers in this research. On the basis of the statistical analysis and analytic hierarchy process optimization method, the optimum electrospinning parameters to produce good morphology of nanofibers and the best conditions of texturing process to fabricate suitable structure of textured silk yarn have been obtained, respectively. The following step to produce nanocoated textured yarn was defined as a nanocoating process on the surface of textured silk yarn. Finally, the morphological and mechanical properties of these samples including no-textured silk yarn, textured silk yarn and nanocoated textured silk yarn analyzed and compared. Based on the finding of this study, the nanocoated textured silk yarn was found to be a promising construct for engineered scaffolds in tendon and ligament tissue engineering.
Measurement of Young’s Modulus and Shear Modulus of Some Structures Welded Using Flux Cored Wire by Vibration Tests
Authors: Bereteu Liviu , Vodǎ Mircea , Drăgănescu Gheorghe
Published: August 2014

The aim of this work was to determine by vibration tests the longitudinal elastic modulus and shear modulus of welded joints by flux cored arc welding. These two material properties are characteristic elastic constants of tensile stress respectively torsion stress and can be determined by several non-destructive methods. One of the latest non-destructive experimental techniques in this field is based on the analysis of the vibratory signal response from the welded sample. An algorithm based on Pronys series method is used for processing the acquired signal due to sample response of free vibrations. By the means of Finite Element Method (FEM), the natural frequencies and modes shapes of the same specimen of carbon steel were determined. These results help to interpret experimental measurements and the vibration modes identification, and Youngs modulus and shear modulus determination.
Mechanical Effects of Simulated Pressure and Temperature Conditions on Porcelain Dental Bridges
Authors: Tarcolea Mihai , Vlasceanu Daniel , Cotrut Mihai Cosmin , Vrânceanu Maria Diana , Comăneanu Raluca Monica
Published: August 2014

A dental bridge, designed in STL format on a Dental Scanner software, was covered with the porcelain layer in 3-matic Design ©Materialise NV. FEA simulations were made in ANSYS ® Workbench TM ©SAS, Inc. Firstly, was performed the thermal analysis with the Transient Thermal module, and secondly, the structural static analysis with the Static Structural module. The applied masticatory force was of 300 N, and the studied temperatures were 36°C as reference and, as extremes, 0° and 50°C. The purpose was to determine mechanical effects in the bridge structure for a specific design of the dental bridge geometry in order to optimize its design.
The Synthesis and Characterization of PVA-Ketoprofen Cryogel, Biomaterial with Extended Drug Release Properties for Cartilage Replacement
Authors: Stamate Monica Cretan , Stamate Ciprian
Published: August 2014

The present paper aims to study the possibility to modify the properties of polyvinyl alcohol (pva) cryogels prepared in the presence of ketoprofen in order to replace the damaged articular cartilage. Articular cartilage is the most important part of articulation characterized by very low friction, high wear resistance, and poor regenerative qualities. Polyvinyl alcohol is a non-expensive polymer, versatile and adaptable to various needs, with exceptional properties such as water solubility, biocompatibility, non-toxicity and with capability to form hydrogels by chemical or physical methods. The aims of this paper are the synthesis, the physicochemical characterization and analysis of the tribological properties of pva cryogels for cartilage replacement and the introduction of new concept in medication by creating the cryogel like a controlled drug release system. The morphology of the cryogels, the interaction between the pva macromolecular chains and medicament has been studied by Scanning Electronic Microscopy. The gels swelling in physiologic ser have been monitored by gravimetric method in order to evidence the hydrophilic properties. The mechanical properties of the cryogels have been investigated by dynamic mechanical measurements. In conclusion, the biomaterial obtained provides good swelling properties, mechanical resistance and it is ideal for extended drug release implantable systems.
Wear Particle Analysis, the Result of Tribological Phenomena of Biomaterials Couplings-Ultra Hight Molecular Weight Polyethylene and Magnesium Aluminosilicate Ceramic
Authors: Stamate Ciprian , Munteanu Corneliu , Stamate Monica Cretan
Published: August 2014

Joint prosthesis involves the combination in the form of friction couplings of the different materials such as two metals, metal-polymer and polymer-ceramic. This paper aims to analyze the wear particles produced from the friction between two biomaterials: ultra hight molecular weight polyethylene( uhmwpe ) and magnesium aluminosilicate ceramic. To obtain the wear particles using a tribometer cetr umt-2 type that can reproduce the wear phenomena of different biomaterials in different humidity conditions and at various speeds of movement. The tests were performed in dry and lubricated friction conditions using saline solution, the best imitating biological conditions. The movement is similar to the friction torques of the hip joint: a semicircular motion of the polymer piece on the circular surface of the ceramic piece. Movement speed chosen is 0.25 m/s. Wear particles obtained were isolated from biomaterial surfaces and studied using scanning electron microscope. The images obtained are analyzed, particle's dimensions are extracted and then imported into autocad can provide information about the shape, size and surface of the particles. In light of these facts, we can say the inflammatory risk of biomaterial particles. In conclusion, the biomaterial particles are very small and the inflammatory rick is reducing to minimum in lubricated conditions.
Correlation between Microstructure and Magnetic Properties on MnZn Ferrite with Bi2O3 Increasing Addition
Authors: Branzei Mihai , Cristea Ionut , Ciuca Ion , Bibiș Adrian , Feder Marcel
Published: August 2014

The aim of this paper is quantitative characterization of a MnZn ferrite with Bi2O3increasing addition using the Image-Pro Plus software from Media Cybernetics. The sample matrix is a ferrite with the following chemical composition: Mn0.54Zn0.37Fe2.06O4. We applied the conventional ceramic technology in order to obtain the samples. Thus, the raw materials, i.e. αFe2O3, Mn3O4, and ZnO, in a molar ratio 53:28:19 were mixed in suitable proportions in a steel ball-mill using demineralized water. The mixture was burn off at 800 °C for 1 hour, in air. The pre-sintered powder was milled in steel ball-mill with increasing addition of Bi2O3(0.00, 0.01, 0.03, 0.05, 0.07, 0.10, 0.30, 0.50 wt %). For quick references, the sample without bismuth ions was denoted and the samples with increasing concentrations were numbered from 1, 7.