bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocatalytic Removal of 2,4-D Herbicide on Lanthanum Oxide-Modified Titanium Dioxide
Authors: Siah Wai Ruu , Roslan Nur Azmina , Lintang Hendrik O. , Shamsuddin Mustaffa , Yuliati Leny
Published: July 2015

Titanium dioxide (TiO2) has been recognized as an active photocatalyst for degradation of various organic pollutants. In this study, in order to improve the photocatalytic activity of TiO2, the effect of lanthanum oxide modification was investigated by using commercial P25 as the benchmark. Lanthanum oxide/P25 TiO2 composites with 0.1, 0.5, 1 and 5 mol% of La loadings were prepared via an impregnation method. The resultant composites were characterized by X-ray diffraction (XRD), UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES) and electrochemical impedance spectroscopy (EIS). It was confirmed that the addition of lanthanum oxide did not much affect the crystallinity, crystal structure and the morphology of P25 TiO2. The catalytic activities of the lanthanum oxide/P25 TiO2 catalysts were tested by using 2,4-dichlorophenoxyacetic acid (2,4-D) as the test pollutant and UV light as the irradiation source. The reaction was caried out for 1 hour at room temperature and the percentage removal was determined using a UV spectrophotometer. The results showed that La loading was an important factor that influenced the photocatalytic activity of the composites. After 1 hour reaction, the best catalyst with 0.1 mol% of La loading showed 24% higher photocatalytic activity than the unmodified P25 TiO2 catalyst. It is shown by EIS that the enhanced photocatalytic activity of the composites was due to the ability of lanthanum oxide in improving the charge separation of the photogenerated electron-hole pairs in TiO2.
Enhanced Photocatalytic Performance of Copper-Modified Titanium Dioxide Prepared by UV Reduction Method
Authors: Roslan Nur Azmina , Lintang Hendrik O. , Yuliati Leny
Published: July 2015

In the present study, commercial Hombikat N100 TiO2 that consists of 100% of anatase phase was modified with copper (Cu) as a co-catalyst via two different preparation methods, which were photocatalytic UV reduction and impregnation methods. The Cu loading was fixed to be 0.1 wt%. The X-ray diffraction (XRD) patterns showed that Cu/TiO2 sample prepared via different preparation methods gave different crystallinity and/or crystallite size. The Cu/TiO2 sample prepared by photocatalytic UV reduction method has lower crystallinity and/or crystallite size than the sample prepared by impregnation method. The performance of the TiO2 and Cu/TiO2 samples was evaluated for degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). After 1 hour reaction, the TiO2 showed percentage removal of 31%, while the Cu/TiO2 sample prepared by photocatalytic UV reduction and impregnation methods gave 39 and 28%, respectively. It was proposed that the higher activity on the Cu/TiO2 sample prepared by photocatalytic UV reduction method was caused by the more successful suppression of electron-hole recombination, as supported by the emission spectra.
Raman Spectra of Multiferroics TbMnO3
Authors: Handayani Ismudiati Puri , Mufti N. , Nugroho Agustinus Agung , Palstra T.T.M. , van Loosdrecht P.H.M.
Published: July 2015

The dream to have multifunctional materials has triggered an intense study of multiferroicity, i.e. of materials in which magnetic and electric polarizations are simultaneously present and strongly coupled. Here we study TbMnO3, a perovskite manganite exhibiting multiferroicity. It has an incommensurate antiferromagnetic ordering transition at 41 K and a transition into a multiferroic spin spiral state at 26 K. In this study, Raman spectroscopy has been used to elucidate the nature of the excitations related to phase transitions. We show that the optical phonons in TbMnO3 resemble the phonon characteristics typical for perovskite manganites, corresponding to MnO6 octahedral vibrations. The appearance of a new low energy modes at 32 cm-1, 40 cm-1, and 63 cm-1 observed below 41 K signifies the antiferromagentic ordering in TbMnO3. The 32 cm- 1 and 63 cm-1 are interpreted as spin ordering activated phonon while the 40 cm-1 is interpreted as spin ordering induced splitting of Tb quasi doublet cystal field level.
Photovoltaic Characteristics of Inverted Bulk-Heterojunction Organic Solar Cells with Titanium Doped ZnO as their Electron Transport Layer
Authors: Handayani Yolla Sukma , Wulandari Priastuti , Hidayat Rahmat
Published: July 2015

Bulk-heterojunction (BHJ) organics solar cells based on conjugated polymers and fullerene derivatives with an inverted structure configuration have been fabricated using titanium doped ZnO (TiZO) as their electron transport layer (ETL). TiZO was prepared via sol gel route with 2-methoxyethanol as the solvent. In order to investigate photovoltaic characteristics and interfacial charge transfer properties, current–voltage (I-V) characterizations and electrochemical impedance spectroscopies (EIS) have been carried out. Among the samples, solar cell with 3-layers of TiZO exhibited relatively larger open circuit voltage (Voc) of about 0.55 V and higher short-circuited photocurrent density (Jsc) of about 11 mA/cm2 under AM 1.5 irradiation. Its filling factor is about 0.38 and its power conversion efficiency (CPE) is thus about 2.4%. The Nyquist plots obtained from the EIS measurements indicate that solar cells with TiZO have larger charge transfer resistance, which may be due to less trap states present in its TiZO layer.
Composite Electrolyte of SOFC Based on Stabilized Zirconia 1Yb10ScSZ Nanopowder
Authors: Raharjo Jarot , Arjasa Oka , Agustanhakri Agustanhakri , Damisih Damisih
Published: July 2015

An electrolyte composite of 1Yb10ScSZ made of ZrOCl2.8H2O, Yb2O3 and Sc2O3 precursors has been investigated as solid electrolyte for SOFC. As first step, nano powders of 1Yb10ScSZ were synthesized using sol-gel and precipitation method towards water as medium employing l-arginine as organic substance to initiate the reaction. Subsequently, it was followed by calcinations with temperature variations of 600, 650 and 700°C to obtain a proper phase and particle size. Nano powders produced were cold-pressed utilizing 100 MPa of pressure and sintered at 1350°C of temperature to achieve solid electrolyte of 1Yb10ScSZ. The results of DLS and FESEM analysis of nano powders obtained from sol-gel method showed that the variations of calcinations temperature didn’t influence the particle size produced. Whereas DLS and FESEM analysis of nano powders made by precipitation method indicated that it affected size of particle. The microstructure analysis using FESEM revealed that precipitation method produced spherical structure with 10-30 nm of particle size. Porosity measurement employing Archimedes method exhibited density of pellet over 95%. The results of this study have met the necessary requirements as exceptional electrolyte for SOFC.
Structure and Magnetic Properties of Spark Plasma Sintered NdFeB
Authors: Sudiro Toto , Aryanto Didik , Djauhari Nenen Rusnaeni , Sinuraya Citra Wara Br , Humaidi Syahrul , Sudrajat Nanang
Published: July 2015

A spark plasma sintering technique was used to consolidate NdFeB compacts at four different temperatures as 750°C, 850°C, 950°C and 1030°C. The surface of specimens was polished to remove the carbon paper on the surface of NdFeB compacts by using SiC paper for up to #1500 in grit. The polished NdFeB compacts were then magnetized by using impulse magnetizer K-series. In this study, the effects of temperature on the structure and magnetic properties of NdFeB magnet were studied. The results show that depending on the fabrication temperature, the X-ray diffraction patterns of NdFeB compacts are distinct. This suggests that the structure of NdFeB compacts is changed with increase in fabrication temperature. Meanwhile, the remanance Br and energy product BH(max) of NdFeB magnets tend to decrease as fabrication temperature increase.
Absorbance Studies of Perovskite CH3NH3PbI(3-x)Clx as Light Harvester in Solar Cell
Authors: Noorlaily Prawistin , Ulfa Maria , Bisri Satria Zulkarnaen , Iskandar Ferry
Published: July 2015

Hybrid perovskite is one of the emerging materials which is currently being widely investigated for solar cells. Here we report the synthesis and characterization of perovskite compound which can be used as a light harvester in photovoltaic cells, which is CH3NH3PbI(3-x)Clx. The perovskite materials were synthesized using solution-based methods. Several parameters are investigated in the synthesis of CH3NH3PbI(3-x)Clx perovskite, which are the influence of precursor composition, synthesis temperature , precursor concentration, and the annealing temperature. These parameters are optimized against the absorbance and bandgap of the synthesized CH3NH3PbI(3-x)Clx thin film. The optimized perovskite thin film is obtained with excellent absorption capabilities for solar cell applications.
Supercapacitor Carbon Monoliths Electrodes from Activation of Precarbonized Biomass Fibers Added with Cellulose Powder
Authors: Soltaninejad Sepideh , Deraman Mohamad , Daik Rusli , Nor N.S.M. , Dolah B.N.M. , Basri N.H. , Sazali Noor Ezniera Shafieza , Hamdan Ellisa , Jasni M.R.M.
Published: July 2015

Fibers of oil palm empty fruit bunches were carbonized at low temperature, milled and sieved to produce self-adhesive carbon grain (SACG). Grain monolith (GMs) of SACG added with 0 %, 20 % and 40 % cellulose powder were carbonized and activated to produce porous activated carbon monolith (ACMs) supercapacitor electrodes. ACMs were investigated by nitrogen adsorption–desorption isotherm and cyclic voltammetry methods to determine the effect of cellulose on the porosity and specific capacitance of the electrodes, respectively. The results showed that the addition of cellulose in GMs reduced the specific surface area of the ACMs by a factor of 94 % to 97 %, coresponding to a decrease of 31 % to 54 % in the values of specific capacitor of the ACMs supercapacitor cells.
The Influence of Glucose Concentration to Resonant Wavelength Shift of Polymer-Based Microring Resonators
Authors: Mulyanti Budi , Hasanah Lilik , Hariyadi Tommi , Novitasari Rischa , Pantjawati Arjuni B. , Yuwono Heru , Khairurrijal Khairurrijal
Published: July 2015

Microring resonators (MRRs) is a compact and multi-functioned device which is mainly characterized by free spectral range (FSR) and quality factor (Q-factor). In this paper, the influence of glucose concentration to the resonant wavelength shift of MRRs is presented. The calculation was carried out using semi-numerical method for different values of FSR and Q-factor. The parameters used in the calculation including incident wavelength, ring radii of circular waveguide, gap sizes between circular and straight waveguides, the dimension of both waveguides, and refractive index of polymer, SiO2 and glucoce solution. The results show that glucose affects the resonant wavelength shift for each values of FSR and Q-factor. The increase of the glucose concentration causes the increase of the resonant wavelength shift, therefore this polymer-based MRR’s can be used for glucose sensing application.
Cytotoxicity Test of Brown Silk from Attacus atlas L. on Rat Smooth Muscle Cells
Authors: Ulum Mokhamad Fakhrul , Noviana Deni
Published: July 2015

Natural brown silk biomaterial from silkworm Attacus atlas L. (A. atlas L.) is a biopolymer that has many advantages compared to commercial silk from Bombyx mori (B. mori). The aim of this study was to investigate the cytotoxicity of A. atlas L. silk on rat smooth muscle cells with the direct method of methyl thiazolyl tetrazolium assay compared to commercial surgical suture silk. The result showed that brown colored natural silk has low cytotoxicity as same as commercial surgical suture silk with slightly lower cell viability. It was found that A. atlas L. silk potentially can developed to be surgical suture thread as a new expectation of biopolymer material in biomedical products.
In Vitro Cytotoxicity and In Vivo Tissue Response Study of Foreign Bodies Iron Based Materials
Authors: Noviana Deni , Estuningsih Sri , Paramitha Devi , Fakhrul Ulum Mokhammad , Hermawan Hendra
Published: July 2015

A foreign body is any object originating outside the body. It may migrate from its entry site and cause pain, inflammation and infection. This study aims to examine in vitro cytotoxicity and in vivo tissue response at different implantation sites of two iron-based foreign body (FeFB) specimens: pure Fe wire, Cr-coated Fe wire, and SS316L wire as control. In vitro cytotoxicity was assessed towards rat smooth muscle cells with direct method of methyl thiazolyl tetrazolium (MTT) assay. In vivo tissue response was examined using mice animal model until day 14 after surgical implantation in subcutaneous nape area and intramuscular right femoral muscle. Cell viability, surface morphology and Fe ion release were examined. Implant density and tissue response were examined by using radiographic imaging and histology, respectively. Results showed that both FeFB specimens exhibited similar cell viability with SS316L. Iron ion concentration was higher in both FeFB medium compared to that of SS316L and with oxide layer formation on their surface. Radiographic analysis showed that the density of both FeFB implants end-side was increased. Meanwhile, histological tissue response at intramuscular sites for FeFB specimens showed a prominent inflammatory response compared to SS316L. Detailed analysis on cell and tissue-material interactions of the iron-based foreign body specimens is discussed further in this article.
Poly(Vinyl Alcohol)/Chitosan Nanofibrous Membrane Containing Anredera cordifolia (Ten.) Steenis
Authors: Nuryantini Ade Yeti , Munir Muhammad Miftahul , Rahma Annisa , Suciati Tri , Khairurrijal Khairurrijal
Published: July 2015

A novel nanofibrous membrane that has potential application as antimicrobial wound dressing has been developed. The membrane consisted of PVA and chitosan as a matrix and extract of Binahong leaves as an active antibacterial material for wound dressing. In this study, ex situ fabrication of nanofibrous membrane composed of poly(vinyl alcohol)/chitosan/extract of binahong leaves were described. The fibers were electrospun from a precursor solution composed of 10 ml of PVA 14 %w/v, 2 ml of chitosan 2 % w/v and 4 ml of extract of binahong leaves 2.5% w/v. Nanofibrous membrane yielded from this method was characterized by Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). SEM result showed that morphology and diameter of nanofibers were affected by applied voltage and flowrate. Through X-RD it was found that the addition of binahong leaves extract decreased the crystallinity of the electrospun PVA/chitosan nanofibrous membrane.
Synthesis of Chicken’s Eggshells-Based β-Tricalcium Phosphate Bioceramics
Authors: Dahlan Kiagus , Nuzulia Nur Aisyah
Published: July 2015

The use of bioceramics for orthopedic and dental application nowadays increases due to their good biocompatibility and osteoconductivity. β-tricalcium phosphate (β-TCP) bioceramics which have excellent biodegradation properties have been in use quite extensively. This paper reports the synthesis of β-TCP bioceramics from precipitation of calcined chicken’s eggshells and phosphoric acid (H3PO4). Chicken’s eggshells were calcined at 1000°C for 5 hours to form calcium oxide (CaO). Various molarities of CaO and H3PO4, between 0.4 M and 2.4 M, were used in this experiment with the Ca:P ratio was kept 1.5:1. After precipitation, the samples were filtered and heated at a sintering temperature of 1000°C for 7 hours. The X Ray Diffraction profile showed that the patterns were affected by the molarity. The patterns of 1.2 M CaO/0.8 M H3PO4 samples showed pure β-TCP, while those of 0.6 M CaO/0.4 M H3PO4 and 2.4 M CaO/1.6 M H3PO4 samples showed the presence of hydroxyapatite and octa calcium phosphate. These findings were also supported by Fourier transform infrared spectra. The purity of the samples shown by the atomic absorption spectroscopy resulted in Ca:P ratio of 1.48:1 which is very closed to that of standard β-TCP bioceramics.
Characterization of Various Types Coal Using Capacitance Measurement Technique
Authors: Haryono Didied , Desiani Desiani , Al Huda Mahfudz , Taruno Warsito P. , Baidillah Marlin R. , Maulana Irwin
Published: July 2015

Each type of coal has different composition and properties, which determine the coal rank. One of the new methods for determining the quality of coal is by measuring its capacitance. It is formerly known that the difference in the moisture content of coal can be determined from the difference in its dielectric properties. The purpose of this paper is to characterize the various types of coal based on capacitance measurement. The samples used are Lignite, Sub-bituminous, Bituminous, and Anthracite. The proximate analysis testing was done to determine the content of moisture, volatile matter, ash, and fixed carbon. Capacitance value is measured using 2-channel data acquisition system (DAS) and parallel plate capacitive sensor at frequency 2.5 MHz. The results shows that the capacitance values of each type of coal are different. The capacitance value is affected by moisture content of coal since the moisture content and capacitance value have a linear correlation. And also, the signal characterization using frequency from 1 kHz to 5 MHz was performed to verify whether the frequency used in the DAS is able to characterize coal types.
Effect of TiO2 and MgO on Microstructure of α-Alumina Ceramics and its Sintering Behavior
Authors: Raharjo Jarot , Rahayu Sri , Mustika Tika , Masmui Masmui , Budiyanto Dwi
Published: July 2015

Observation on the effect of adding titanium oxide (TiO2) and magnesium oxide (MgO) on the sintering of α-alumina (Al2O3) has been performed. In this study, technical alumina used as basic material in which the sample is formed by the pressureless sintering/cold press and sintered at 1500°C which is lower than alumina sintering temperature at 1700°C. Elemental analysis, observation of microstructure, hardness, fracture toughness and density measurements were carried out to determine the physical and mechanical properties of alumina. The results indicate a change in the microstructure where the content of the platelet structure are much more than the equilateral structure. At sintering temperature of 1500°C, neck growth occurs at ceramics grain, supported by the results of the density test which indicate perfect compaction has occurred in this process.
Effect of Fabrication Method by Powder Metallurgy on Frangibility Green Bullet Cu-10%Sn as Eco-Friendly Bullet
Authors: Metrima Firmansyah Khoiril , Septyantoko Albertus , Ghulam Isaq Khan Mochammad , Jhony Paiman , Mardliah Rosena , Widyastuti Widyastuti
Published: July 2015

The bullet is used for immobilize object. However it can harm the shooter because it can be ricochet. Thus it, we develop frangible bullet which can be broken when hit the hard target. Conventional bullets are made of lead base material which poison. Therefore frangible bullet does not use lead as base material, so it is classified as green bullet. Green bullet is made by powder metallurgy method. Powder metallurgy process are measuring copper and tin powder, dry mixing, and compacting 600 Mpa in pressure for 10 minutes in holding time, and sintering at 300, 500, 700°C for 0,5; 1; and 1,5 hours in holding time. Then, measure the sinter density and analyze the sample by XRD and SEM-EDX. Based on experiment, we found that the bullet Cu-10%wt which sintering 500 °C in temperature for 1 hour has the best frangibility. The highest theoretical density , compression strength, and hardness are 8.8 gr/cm3, 280.45 MPa, 60.67 HRF. The observer result by scanning electron microscope showed that the phase homogeneity at sintering temperature 500°C for 1 hour in holding times was better than the other variable. By observing phase formed, in XRD pattern show that identified new phase Cu10Sn3 caused the material properties fragile.
Physical and Chemical Characteristics of Corals from Bidong Island, Terengganu, Malaysia
Authors: Ahmad Zubir Ahmad Annuar , Yusof Yusri , Muhamad Nor Mohd Al Amin
Published: July 2015

Coral and converted coralline hydroxyapatites have been widely used in biomedical application as orbital implant and bone graft substitute. The aim of this study was to characterize the physical and chemical properties of various corals found in Bidong Island and determines their potential for development of bone graft substitute. Five species of coral which is commonly found in Bidong Island, Terengganu was collected and identified. The physical properties of corals such as density and porosity were determined using the Archimedes Principle, whereas a mechanical strength was determined using a universal testing machine. The structure of corals such as pore sizes and shape, distribution and pore connectivity was observed using Scanning Electron Microscope (SEM). Chemical properties of corals were characterized using X-ray diffraction (XRD), and energy dispersive x-ray (SEM-EDX). Five species of coral were identified as Leptoria, Porites, Platygyra, Acropora and Pocillopora. The densities of corals range from 2.00 to 19.00 g/cm3 while the porosity range from 15 to 60%. The corals structure consists of interconnected open pores with mean pore sizes in range of 100 to 600μm. Their compressive strengths are in the range of 4.92 to 27 MPa, which is higher than the reported strength for cancellous bone. SEM-EDX analysis shows the elements calcium carbonate (C, O and Ca) found in Platygyra. This result was supported by XRD analysis, which shows the calcium carbonate phase in form of aragonite presence in Platygyra. Aragonite phase was suitable for transforming coral to hydroxyapatite via hydrothermal treatment. Based on this finding, coral species in Bidong Island, Terengganu has been great potential to be used as bone graft substitutes.
Stress – Strain Analysis on ZnO Nanostructures Synthesized via Wet Chemistry Method
Authors: Sholehah Amalia , Yuwono Akhmad Herman
Published: July 2015

In the present work, ZnO nanostructures were synthesized via wet chemistry method. The seeding solution was prepared from zinc nitrate tetrahydrate and hexamethylenetetramine. Prior to the heating process, the seeding solution was immersed in cold bath (0°C). XRD analysis had shown sharp peaks in diffractogram, indicating the high crystallinity of ZnO nanostructures. The crystallite size was determined using Scherrer equation and Williamson-Hall method. Other relevant parameters including stress, strain, and energy density were calculated using Williamson-Hall assuming UDM, UDSM, and UDEDM. The results had revealed that crystallite size calculated with Williamson-Hall method is more accurate than Scherrer equation.
Experimental Waviness Evolution of Interstitial Free - IF Steel Sheet under Biaxial Stretching
Authors: Bressan José Divo , Unfer Ricardo Kirchoff
Published: July 2015

The purpose of present study is to present experimental results and a mathematical model for the evolution of surface waviness parameters with plastic strain of Interstitial Free - IF steel sheet under uniaxial and biaxial stretching tests. Roughness and waviness are very important quality parameters to be evaluated in sheet metal forming. Various waviness profile parameters such as the arithmetic average waviness Wa, the total height peak-valley waviness Wt, maximum peak height Pp and maximum valley depth Pv were measured during uniaxial and biaxial tests. Tensile test specimens at 0º, 45º and 90º to the direction of rolling and Nakazima type specimens of IF steel were fabricated. After preparing the test specimens, incremental simple tensile and Nakazima biaxial tests with flat punch were performed to characterize the negative and positive quadrant of the Map of Principal Surface Limit Strains, MPLS, of IF steel sheet. Measurements of waviness parameters of the specimen surface at incremental plastic strain stages were performed at the same surface site. Also, during the uniaxial and biaxial tests, the following plastic strains were calculated from printed circular mesh at each incremental step: ε1 longitudinal major strain and ε2 transverse minor strain. From these data, curves of waviness parameters versus equivalent strain were plotted to obtain a phenomenological equation of 4th or 3rd degree polynomial type. Furthermore, the growth rates of Wa and Wt parameters with the equivalent plastic strain were assessed. From the growth rate curves, it was possible to verify how the sheet thickness imperfections evolves during straining, being possible to predict the influence of plastic strain on the waviness values of IF steel sheets. From the analysis of Wa and Wt growth rates during straining, it was possible to proposed a criteria for the onset of local necking or limit strains in the MPLS. The waviness parameters Wt is the best for characterizing the onset of local necking in sheet metal forming.
Extension of Process Limitations in Swing Folding by the Integration of a Modular Heating Unit
Authors: Husmann Simon , Kreimeier Dieter
Published: July 2015

From an industrial point of view it is interesting to extend the process limitations in swing folding by creating a possibility of forming sheet metals of materials with low formability by an integrative heating module. The experimental setup and the performed experiments with the corresponding results and an outlook to future investigations will be presented in this paper.
Formability Evaluation of Grade 1 Titanium Sheets Depending on the Temperature by FE Analyses
Authors: Formisano Antonio , Astarita Antonello , Boccarusso Luca , Capece Minutolo F. , Carrino Luigi , Durante Massimo , Langella Antonio , Squillace Antonino
Published: July 2015

Nowadays, the need of developing high flexible forming processes matches with the need of weight reduction. In this light, the incremental forming of titanium alloys sheets can guarantee both these aspects by combining the flexibility of the process, particularly suggested for small batches and customized parts, with the good properties of titanium alloys, in particular for aerospace applications.The aim of this work was to obtain information useful to enhance the general knowledge of the hot incremental forming processes of grade 1 titanium sheets at different temperatures.First, both tensile and straight groove tests were carried out by varying the test temperature; in this phase, information regarding both the forming forces and the wear phenomena due to the tool-sheet contact was acquired.Successively, on the basis of the mechanical characterization of the sheets previously carried out, explicit analyses, effectuated by a non-linear FE code, allowed to determine the formability curves of the sheets for the different temperatures.
Plasticity Criterion for Hot Forming of Aluminum-Lithium Alloy
Authors: Younes Wael , Giraud Eliane , dal Santo Phillippe
Published: July 2015

Anisotropic behavior at high temperature of an Aluminum-Lithium alloy was studied. Mechanical tests at a temperature of 350°C and a strain rate of 10-2 s-1 were carried out on samples taken at different angles with respect to the rolling direction of the sheet. Two plasticity criteria (HILL48 and HU2005) were identified and implemented in ABAQUS to predict the anisotropic behavior of the alloy for other angles. Results show that: (i) the alloy exhibits an anisotropic behavior at high temperature and some recrystallization occurs during plastic deformation; (ii) the coefficients of anisotropy depend on strain level and (iii) HU2005 criterion allows describing the behavior of the alloy at high temperature.
Innovations in Descaling and Deburring
Authors: Mortsch Martin , Schmid Alois
Published: July 2015

For weight reducing and functional reasons, hollow shafts should be used in gear units in the near future. Inside they have a big cylindrical cavity, which is only accessible through small inlet holes. This cavity may have large diameter variations along its length. There is an undesirable scale-formation, if high temperatures occur during the manufacturing process. If there are cross bores in areas, then there are also burrs in the area of cross bore section. While this area is oil flooded, it must be free of scale and burrs. Some mechanical tools and a thermal process are able to remove the burr in cross holes. The deburring could often be done over the transverse bore. Even small cross holes can be safely trimmed. A big problem is the removal of scale in difficult to reach hollow areas. With an innovative cutting tool it would be possible to remove the scale in difficult to reach areas. Measurement methods are shown, which would be automatically check if the surface is free of scales and burrs.
Comparison of Several Behaviour Laws Intended to Produce a Realistic Ti6Al4V Chip by Finite Elements Modelling
Authors: Ducobu François , Arrazola Pedro José , Rivière-Lorphèvre Edouard , Filippi Enrico
Published: July 2015

The final aim of finite elements modelling is to help in the choice of the cutting parameters and in the comprehension of the involved phenomena. Representing correctly the behaviour of the machined material is hard due to the extreme conditions encountered, although this is a key parameter to develop a realistic model. Four laws are used in this paper to represent the Ti6Al4V. They are all based on the Johnson-Cook law. This study shows that the influence of the behaviour law is high on the chip morphology and on the forces and that the strain softening phenomenon should be taken into account. For the cutting conditions adopted, it is however necessary to add damage properties in the chip to obtain a morphology and a cutting force evolution close to the experimental reference.
Study of Formability of Sandwich Shells with Metal Foam Cores Based on Punch Penetration Test
Authors: Mata H. , Natal Jorge Renato , Santos A.D. , Parente M.P.L. , Valente Robertt , Fernandes A.A.
Published: July 2015

The objective of this work is the study of the mechanical behaviour of a sandwich structure, composed by two out layers in aluminium sheets, separated by a core in metal foam also in aluminium, by penetration of a spherical punch. Considering a structure composed by these two different materials, each one presents a different mechanical behaviour separately [1, 2].The set up used in the present experimental work is composed by a punch, with a radius r, which imposes a displacement/force to a specimen fixed in its boundary.In these tests, specimens with four different length were considered; 25 mm, 50 mm, 75 mm and 150 mm. The values of force/displacement of the punch were registered.
Simulation of Incremental Forming Processes Using a Thermo-Mechanical Partitioned Algorithm
Authors: Khaled Mahmoud , Ramadan Mohamad , Elmarakbi Ahmed , Fourment Lionel
Published: July 2015

The aim of this paper is to study the simulation of cogging process using a thermo-mechanical partitioned algorithm. The thermal and mechanical problems are solved separately. The mechanical problem is based on the balance equation whereas the thermal problem is based on the heat equation. The two physics are coupled trough the mechanical parameters that depends on the thermal problem and vice versa. The results obtained using the software Forge3 show that the mechanical deformation is high inside the zone of deformation and negligible outside whereas the temperature is high overall the mesh with a gradient at the zone of contact between the dies and the work piece.
Identification Problem of Internal Variables Model of Material
Authors: Szeliga Danuta , Kuziak Roman , Pietrzyk Maciej
Published: July 2015

The paper deals with the identification of material model based on the internal variable. The model with one internal variable, which was average dislocation density, was considered. Identification was performed using inverse analysis (IA) of uniaxial compression tests. In this work IA was transformed to an optimization task and the goal function was defined as difference (in Euclid's norm) between measured and calculated parameters: loads in plastometric tests (used to identify flow stress) and stresses in stress relaxation tests (used to identify recrystallization kinetics). Exploring a possibility of making the identification more reliable by application the Sensitivity Analysis (SA) was the main objective of the work. The IA was preceded by SA of the model output with respect to the model parameters to select an efficient optimization algorithm and/or eliminate local minima. Selected results of identification for different materials are presented in the paper, as well.
An Engineering Approach to Strain Rate and Temperature Compensation of the Flow Stress Established by the Hydraulic Bulge Test
Authors: Mulder J. , Vegter Henk , van den Boogaard Ton
Published: July 2015

Optical measuring systems enable a very accurate determination of the flow stress for the hydraulic bulge test. The flow stress is strain rate and temperature dependent and for the description of work hardening an approximation of the temperature during the test is required. Measuring the temperature during the test usually interferes with the optical strain measurement. A model for the temperature distribution on the bulged surface is developed based on heat generated by plastic work, convection to air on the outer surface, conduction to the tools at the die diameter and conduction to oil on the inside. The plastic work is derived from an approximation of the shape of the bulged surface and an approximation for the thickness distribution, starting from the initial thickness at the die ring to the established thickness at the pole, making use of volume conservation for the bulged sheet. The parameters of the model are tuned to bulge test temperature measurements of four different steel grades using a thermo couple at the pole. The results of the analytical temperature model are in good agreement with the measurements.
Multi-Objective Optimization under Uncertainty and Decision-Making Support for Sheet Metal Forming
Authors: Nguyen Von Dim , Adragna Pierre Antoine , Lafon Pascal
Published: July 2015

Uncertainty is inevitable in sheet metal metal forming process. Aleatory uncertainties in material properties, blank thickness and friction condition are inherent irreducible variabilities in sheetmetal forming. However, optimal design conﬁgurations which are obtained by conventional designoptimization methods are not always able to meet the desired targets due to the effect of uncertainties.In order to tackle this problem, a multi-objective robust design optimization (MORDO) applied forsheet metal draw bending process is introduced in this paper. In addition, since the MORDO of sheetmetal forming involves considering serveral conﬂicting criteria, a Pareto multiple objective criteriadecision-making approach based on capability indices is proposed.
Comparison of the Thermo-Mechanical Conditions in an Industrial Sized Hot Aluminium Extrusion Process in Relation to those in Corresponding Small Sized Laboratory Processes
Authors: Valberg Henry , Torabzadeh Khorasani Sepinood , Nolte Dirk
Published: July 2015

It is common to use scaled down laboratory extrusion processes in order to physicalmodel the industrial big-sized aluminum profile extrusion process. In industrial extrusion use ofbillets with a diameter size of ~210 mm, or above, is common. In the scaled-down laboratoryprocesses half this size is often used, and in mini-extrusion also 1/7th of this size. An investigationhas been undertaken in order to study what are the thermo-mechanical conditions in extrusionprocesses of such different sizes of processes, and to what extent a small-sized process is able tophysical model accurately the conditions in an industrial large sized process.
Curvature Based Forming Limit Prediction of High-Strength Steel Components with Superimposed Stretching and Bending in the Deep Drawing Process
Authors: Schalk-Kitting Daniela , Weiß Wolfgang , Suhr Bettina , Koplenig Michael
Published: July 2015

The state of deformation in deep drawing operations is characterized by superimposed stretching and bending (i.e. stretch-bending). Bending effects, especially for Advanced High Strength Steels (AHSS) are known to influence the material formability. Traditional formability measures such as the Forming Limit Curve (FLC) fail to reliably predict stretch-bending formability. Consequently, to ensure an efficient and economical use of AHSS in the industrial application, current research work is focusing on the reliable numerical prediction of stretch-bending formability of AHSS sheets.Within this work, a phenomenological concept to predict the forming limit (e.g. the onset of necking) in deep drawing processes taking bending effects into account is presented. The proposed concept is based on curvature-dependent (i.e. regarding the principle curvatures κ1 and κ2 of the stretch-bend (convex) sheet surface) forming limit surfaces representing the probability of failure and is calibrated with experimental results from stretch-bending tests and conventional forming test such as a Nakazima test. The results of the phenomenological forming limit criterion are promising and show a more accurate prediction of the drawing depth at failure than the conventional FLC approach. The method contributes also to a probabilistic view on the forming limit of deep drawing parts.
Validation of a FEM Model for the Simulation of the Cold Roll Forming Process
Authors: Formisano Antonio , Capece Minutolo F. , Caraviello Antonio , Carrino Luigi , Durante Massimo , Langella Antonio
Published: July 2015

Cold roll forming is a process for plastic deformation, which allows realizing profiles, with a defined section and established length, from the plastic deformation of a metal sheet. The sheet is induced to cross several stands of rolls, arranged along the same axis of advancing. The rolls induce plastic deformation in the sheet and then lead it to the desired geometric configuration. In order to control the geometric parameters of the plate during the profiling, it was created a FEM model to simulate the final stage of the technological process, developed by an industrial production line of a company located in Naples (Italy), that sells tubes with several cross sections. In this phase, the semi-finished product, having a circular cross section, is forced to cross through four stands of rolls. In this way, it changes the geometric condition of the cross section from circular to square. The model was carried out using a non-linear calculation code, which allows analyzing the parameters of interest in the different process steps. The results, obtained numerically, were compared with the experimental ones through the measurement of five specimens, obtained directly from technological process. The values of percentage deviation, regarding the external dimension and the thickness, for each step of advancement, do not exceed the 3% of error. Then, the analysis results denote the capability to simulate the cold roll forming process using finite element method.
Experimental Characterization and Modeling of Residual Stress Gradients across Straight and Bent Seamless Steel Tubes
Authors: Winter Gerald , Klarner Jürgen , Staron Peter , Buchmayr Bruno , Keckes Jozef
Published: July 2015

Abstract. Residual stress gradients across the wall of seamless steel tubes influence decisively the mechanical stability and reliability of automotive and industrial constructions. Irreversible bending moments imposed on the tubes induce gradual and asymmetric elasto-plastic deformation across the tube cross-sections which result in very complex residual stress distributions. The aim of this contribution is to present a novel methodology as well as complementary modeling approach to assess the three-dimensional distribution of triaxial residual stresses in bent steel tubes. The stress characterization was performed using high energy X-ray diffraction at the HEMS beamline of PETRAIII synchrotron source in Hamburg as well as using laboratory Drill-hole method. For the complementary modeling of the stress distribution, a FEM software package DEFORM HT was used. The results reveal that the stress gradients across the tube wall are primarily influenced by the martensite profile predetermined by the parameters for thermo-mechanical treatment of the tubes. The tube bending causes the formation of continually varying compressive and tensile stresses across the tube circumference whereas the stress magnitude across the wall thickness scales again with the martensite appearance. Finally the results document the importance of the cooling process control and the influence of the applied bending radius on the resulting stress distributions as well as related mechanical parameters like fracture toughness and fatigue behavior.
Numerical Modelling of Damage Evolution in Ingot Forging
Authors: Christiansen Peter , Martins Paulo A.F. , Bay Nils , Hattel Jesper
Published: July 2015

The ingot forging process is numerically simulated applying both the Shima-Oyane porous plasticity model as a coupled damage model and the uncoupled normalized Cockcroft & Latham criterion. Four different cases including two different lower die angles (120o and 180o) and two different sizes of feed (400mm and 800mm) are analysed. Comparison of the simulation results with recommendations in literature on ingot forging, indicates the normalized Cockcroft & Latham damage criterion to be the most realistic of the two.
Experimental and Numerical Investigation on Controlling the Material Flow in Open-Die Forging through Superimposed Manipulator Displacements
Authors: Wolfgarten Martin , Rosenstock Dirk , Freitag Jan , Hirt Gerhard
Published: July 2015

In the past, different methods have been investigated regarding the production of curved workpieces by open-die forging as a significant demand for open-die forged parts with excellent mechanical properties exists. Current ways to produce curved workpieces by open-die forging have the disadvantages of complex preforms and inflexibility. One alternative approach to realize the production of curved workpieces by open-die forging is to actively control the material flow in open-die forging by superimposed manipulator movements during a forging stroke. Since the currently formed material between the forging dies is in a plastic state during the deformation, the required bending forces can be reduced significantly. This concept is investigated in a first study for the cold-forging of an aluminum alloy by numerical simulation and experiments on laboratory scale. For the process, the bite ratio, height reduction and the intended bending angle were identified as most important process parameters. Both numerical and experimental investigation proved the feasibility of the process principle since the bending forces, moments and the bending work can be reduced significantly.
Internal Structure of the Sheared Textile Composite Reinforcement: Analysis Using X-Ray Tomography
Authors: Barburski Marcin , Straumit Ilya , Lomov Stepan
Published: July 2015

X-ray micro computed tomography (Micro-CT) is a non-destructive technique that can provide information on the internal structure of materials. The purpose of micro-CT is to assess the presence of defects as well as characterizing internal structures and potential damage present in the produced part. Simple shear is an interesting deformation mechanism for woven fabric draping. The internal structure change of the carbon fibre twill fabric after shear deformation is chosen as a subject of this paper. Parameters of the mesoscopic internal structure of the woven fabric like cross section, shape, area, and middle line coordinates can be obtained from micro-CT images through image processing procedures. Details of the image data processing for sheared fabric cross sections are discussed. This paper illustrates the possibilities of micro-focus computer tomography in materials research, namely for defining geometrical properties of textile. Image processing is also used for the recognition of fibre direction in the yarns. Described methodology can be applied for determining structure of a fabric, and the results can be used for further micromechanical modelling. Identification of the fibres orientation is important for estimation of the mechanical properties of composites and can be achieved with image processing techniques.
An Inverse Finite Element Approach to Calculate Full-Field Forming Strains
Authors: Ritt Roland , Machado Martín , Fischlschweiger Michael , Major Zoltan , Antretter Thomas
Published: July 2015

A methodology to calculate surface strains from a rectangular grid placed on a forming blank is introduced. This method consists of treating the grid points as nodes of a finite element (FE) model and assigning elements to the grid. The strains are then computed following FE analysis. If higher order elements are used, also more information within the element can be obtained which allows a coarser grid without loss of accuracy. This is the major advantage of the approach presented herein.
Manufacture of Carbon Nanotube-Grafted Carbon Fiber Reinforced Thermoplastic Composites
Authors: Sung Min Chang , Lee Geun Sung , Lee Seung Yong , Jeon Seong Ik , Ahn Cheol Hee , Youk Ji Ho , Lee Jin Yong , Yu Woong Ryeol
Published: July 2015

Carbon fiber reinforced composites (CFRCs) have been used in various high-end industries due to their outstanding specific mechanical properties. Recently, carbon nanotube (CNT)-grafted carbon fibers (CFs) made via direct growth has emerged as an advanced and hierarchical reinforcement that can improve the reinforcing effect of CFs in CFRCs. On the other hand, CF reinforced thermoplastic composites (CFRTPs) have attracted much attention because of their quick and mass production capability, e.g., which is important for automotive part manufacturing. Here, we report on the manufacture of CFRTPs using CNT-grafted CFs and their mechanical properties. First, the interfacial shear strength of CNT-grafted CFs with thermoplastic resins was characterized to demonstrate improved interfacial properties due to the CNTs grafted on CFs. Then, the composites were manufactured in two ways; polymer nanoparticles and in-situ polymerization. Polymer nanoparticles were used to improve the interfacial properties due to their small size and good mechanical locking with CF surfaces. In-situ polymerization was also used to manufacture CFRTPs, i.e., monomers with catalyst were transferred into CNT-grafted CF fabric preform using vacuum assisted resin transfer molding and then polymerized into solid matrix. This in-situ polymerization enabled the manufacture of CNT-grafted CF thermoplastic composites by overcoming the difficulties of filling the surface of CNT-grafted CFs with thermoplastic polymers. Finally, the mechanical, thermal, electrical, and damping properties of CNT-grafted CF thermoplastic composites were characterized and compared with their thermoset composites.
Finite Element Simulations for CFRP Press Forming Process
Authors: Kim Young Suk , Do Duy Tung , Ahn Dae Cheol , Shin Dong Woo
Published: July 2015

The macro-scale and meso/macro-scale simulations for press forming of CFRP sheet using ABAQUS S/W were both implemented to study the influence fiber orientation on the formability of CFRP sheet. The Hashin damage criterion was used to predict the fiber failure in the forming process. The properties of plain woven fiber fabric were obtained from the tensile test and bias extension test. The forming experiments with rectangular punch were carried out to validate the numerical results.