bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Non-Rubber Components on Properties of Sulphur Crosslinked Natural Rubbers
Authors: Smitthipong Wirasak , Tantatherdtam Rattana , Rungsanthien Kanokwan , Suwanruji Potjanart , Klanarong Sriroth , Radabutra Siriwat , Thanawan Sombat , Vallat Marie France , Nardin Michel , Mougin Karine , Chollakup Rungsima
Published: November 2013

Non-rubber components (mainly proteins and lipids) in natural rubber (NR) play important roles for controlling the properties of NR. Crosslinking process creates intermolecular chemical bonds in order to obtain a three-dimensional network, resulting in more elastic rubber. Sulphur crosslinking is the most popular method and is applied in the present study. Two types of NR were prepared, namely, whole natural rubber (WNR) and purified natural rubber (PNR). PNR was deproteinized by centrifugation method and then acetone extraction. These rubbers were crosslinked by an efficient vulcanization (EV) system. They were cured for three curing times (1xt90, 2xt90, 3xt90) at 150°C. WNR presents shorter curing time than PNR because there are some phospholipids and proteins which are natural accelerators for curing reaction. The presence of non-rubber components seems to play a major role on crosslinking density and adhesion phenomenon for rubber/glass system. AFM images of WNR show more heterogeneity and roughness compared to PNR.
Improved Deproteinization Process for Protein-Free Natural Rubber Latex
Authors: Pichayakorn Wiwat , Suksaeree Jirapornchai , Taweepreda Wirach
Published: November 2013

Hev b1-14 type proteins in natural rubber latex (NRL) have been identified as allergens in immunogenic responses. Several methods have been developed to reduce these proteins from NRL such as enzyme treatment, centrifugation, creaming, simple or ultrasonic leaching, and chlorination. In this work, the improvement of deproteinization of NRL was developed using the combination of enzyme treatment and leaching processes. The fresh NRL was incubated with 0.2 phr proteolytic alcalase enzyme, and preserved with 2%v/v paraben concentrate in the presence of a 2%v/v sodium lauryl ether sulfate (SLES) as a surfactant at 37°C for 24 hours, and then centrifuged. The upper rubber mass was then leached for three times with either distilled water, a 1%v/v SLES solution, or a mixture of 1%v/v SLES and 2.5%v/v ethanol, and then finally re-dispersed in distilled water. It was found that the increasing process of leaching with either 1%v/v SLES or a mixture of 1%v/v SLES and 2.5%v/v ethanol had the higher efficacy to reduce the remained protein in deproteinized NRL (DNRL). The best deproteinized process was the enzyme treatment and followed by the three times leaching process with a mixture of 1%v/v SLES and 2.5%v/v ethanol, that could completely reduce the proteins in DNRL to 0%. This DNRL had the pH value, viscosity, dry rubber content, and total solid content of 7.41, 13.82 cps, 42.57%, and 44.63%, respectively. Its particle size was 626.23 nm with low polydispersity index of 0.16. The negative charge of SLES could increase the higher negative charge of DNRL to-63.20 mV that exhibited very good physical stability during storage. In conclusions, the combination of enzyme treatment and leaching process with both SLES and ethanol was successful to produce the protein-free DNRL. This DNRL could be further used for several applications including medical skin products.
Physical Properties of Polymer Blend: Natural Rubber Glove Waste/Polystyrene Foam Waste/ Cellulose Fiber via Brabender
Authors: Phummor Patompong , Riyajan Sa Ad , Tangboriboonrat Pramuan
Published: November 2013

The polymer blend was prepared from the wastes of natural rubber glove (NRG) and polystyrene foam (PSf) blended with cellulose via brabender method. NRG was masticated by two-roll mill at ambient temperature, and then blended with PSf with or without sugar cane leave fiber (fsu) by brabender at 120°C. Then, the polymer blend sheet was continued to compress by compression machine at 120 ๐C for 5 min. The effects of epoxidized natural rubber (ENR) having 25% mol epoxidation (ENR-25) and fsu on the physical properties of polymer blend were investigated. At 20 phr of fsu, the highest tensile strength of this sample was achieved. The toluene resistance of the polymer composite was improved by adding ENR-25 and fsu. In addition, the elongation of the polymer composite was enhanced by addition of ENR-25. The best condition of the polymer blend was 50/50 PSf /NRG, 23 phr ENR-25 and 23 phr fsu.
Water Absorption and Swelling Property of Interpenetrating Network Hydrogel from Crosslinked Natural Rubber and Modified Rice Starch
Authors: Puapermpoonsiri Utsana , Pratoomted Jatuporn , Sila-On Warisada , Vudjung Chaiwute
Published: November 2013

Normal 0 false false false EN-US X-NONE TH Interpenetrating network (IPN) hydrogel was a hydrogel fabrication from crosslinked polymers that was developed to enhance the mechanical and physical properties of conventional hydrogel. In this study, IPN hydrogel was fabricated by blending crosslinked natural rubber and crosslinked modified rice starch at room temperature with rubber to starch component ratio of 1:2. Crosslinked natural rubber was prepared via free radical polymerization of natural rubber latex with N,N′-methylenebisacrylamide (MBA) as a crosslinker. Crosslinked starch component was also prepared from pregelatinized starch with maleic acid by heat. The effects of MBA amount and different types of modified starch [glutinous rice starch (mGst) and rice starch (mRst)] on hydrogel properties such as water absorptions, swelling properties, physical morphology and crosslink density were investigated. The results showed that IPN hydrogel containing mRst provided higher water absorption and swelling property than mGst due to its amylose content. In addition, crosslinker amount in rubber component positively related to water absorption and swelling property. The results illustrated that IPN hydrogel with 2 phr MBA provided a greater water absorption and swelling property than IPN hydrogel with 1 phr MBA due to the interior porous structure within polymer matrix. Conclusively, IPN hydrogel comprising of NRL and modified starch was applicable to use as a pharmaceutical material in further study. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:14.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Cordia New"; mso-bidi-theme-font:minor-bidi;}
Dynamic Mechanical and Dielectric Properties of Poly(vinylidene fluoride) and Epoxidized Natural Rubber Blends
Authors: Salaeh Subhan , Boiteux Gisèle , Gain Olivier , Cassagnau Philippe , Nakason Charoen
Published: November 2013

The blending of semi-crystalline polymer, poly (vinylidene fluoride), (PVDF) and uncross-linked elastomer epoxidized natural rubber with 50 mol% epoxide (ENR-50) blends were prepared in an internal mixer by melt mixing process. Dynamic mechanical analysis (DMA) and dielectric analysis (DEA) of PVDF/ENR-50 blends were investigated. It was found that the pure PVDF showed higher storage modulus than that of the pure ENR-50 and storage modulus of the PVDF/ENR blends decrease with increasing ENR-50 content. Furthermore, PVDF showed two relaxation peaks correspond to αa-relaxation and αc-relaxation, while ENR-50 showed only a single relaxation that is related to α-relaxation or glass transition temperature (Tg). Two relaxation peaks were observed in the PVDF/ENR-50 blends due to phase separation. However, the maximum peak of relaxation shifted toward to higher and lower temperature compared with the pure components which indicates the partial miscible blends. Moreover, at high temperature, the neat polymer and blends showed a sharp increase of loss factor (ε) that correspond to conductivity and/or Maxwell-Wagner-Sillar (MWS) process.
Carbonate Apatite Bone Replacement
Authors: Kunio Ishikawa
Published: November 2013

Inorganic component of bone is not hydroxyapatite but carbonate apatite. Although pure carbonate apatite (CO3Ap) has not been prepared due to the limited thermal stability of CO3Ap, dissolution - precipitation method using precursor block allows fabrication of pure CO3Ap. Fabrication of CO3Ap, cell response, tissue response and improvement of CO3Ap will be discussed.
Freeze-Casted Nanostructured Apatite Scaffold Obtained from Low Temperature Biomineralization of Reactive Calcium Phosphates
Authors: Hesaraki Saeed
Published: November 2013

Macroporous nanostructured calcium phosphate scaffold was produced at low temperature using freeze casting technique. Aqueous suspension of tetracalcium phosphate and dicalcium phosphate anhydrous was freeze-casted into cylindrical samples using an automated freeze casting device and subsequently freeze-dried. The sample was stored at 37 °C and 100% relative humidity for 24h, and then kept in simulated body fluid (SBF) for 7 days. The phase composition and microstructure of scaffold was characterized by X-ray diffraction and scanning electronic microscopy, respectively. Cell proliferation and attachment was also studied using Rat calvarium osteoblasts. The results showed a porous structure with total porosity of 75% and pore diameter ranging 50-150 μm and compressive strength of 5 ± 1 Mpa. The scaffolds had been composed of needle-like nanocrystals at the range of 40-100 nm. The XRD and FTIR data confirmed complete conversion of tetracalcium phosphate and dicalcium phosphate reactants into carbonate-substituted apatite phase due to the immersion process without any other impure phases. The results of cell studies revealed well attachment of osteoblasts on the pores and walls of the scaffolds as well as a time dependent proliferation and increased alkaline phosphatase activity. The produced scaffold has the requirements of an osteoinductive material but more in vitro and in vivo studies are required to prove this suggestion.
Gellan Gum-Based Hydrogel Bilayered Scaffolds for Osteochondral Tissue Engineering
Authors: Pereira Diana R. , Canadas Raphael F. , Silva-Correia Joana , Marques Alexandra P. , Reis Rui L. , Oliveira Joaquim Miguel
Published: November 2013

It has been shown that hydrogel bilayered scaffolds combining cartilage- and bone-like layers are most advantageous for treating osteochondral defects. In this study, it is proposed the use of low acyl gellan gum (LAGG) for developing bilayered hydrogel scaffolds for osteochondral tissue engineering. The cartilage-like layer of the GG-based bilayered hydrogel scaffolds is composed of LAGG (2 wt%). By adding a 2 wt% LAGG aqueous solution to different amounts of HAp (5-20 wt%) it was possible to produce the bone-like layer. In vitro bioactivity tests were performed by means of soaking the LAGG/LAGG-HAp hydrogel scaffolds in a simulated body fluid solution up to 14 days. Scanning electron microscopy, Fourier transform infra-red spectroscopy and X-ray diffraction analyses demonstrated that apatite formation is limited to the bone-like layer of the LAGG/LAGG-HAp bilayered hydrogel scaffolds.
TiSiN Coatings for Improved Bond Strength of CoCr Alloy to Dental Ceramic
Authors: Dinu Mihaela , Braic Viorel , Colease Gabriel , Baciu Florin , Cotrut Mihai Cosmin , Braic Mariana , Tarcolea Mihai , Vitelaru Catalin , Vladescu Alina , Vrânceanu Maria-Diana
Published: November 2013

In this work, TiSiN coatings were selected to improve the adhesion between dental ceramic and CoCr substrate. The coatings were prepared by the cathodic arc technique in N2 reactive atmosphere, at different bias voltages, and analyzed for elemental composition, surface roughness, wettability and corrosion resistance in Fusayama Meyer artificial saliva. After the coating deposition, low-fusing dental ceramic film was fired on coated alloy, using a dental furnace. The bond strength of these specimens was tested using a 3-point bending test.
Effects of Commercial Inert Glass (CIG) Addition on Mechanical and Microstructural Properties of Chicken Hydroxyapatite (CHA)
Authors: Demirkol N. , Oral Ahmet Yavuz , Oktar Faik Nuzhet , Kayali E.S.
Published: November 2013

Hydroxyapatite (HA) can be obtained by both synthetic and natural methods. The synthetic hydroxyapatite is the most commonly used type of HA and it is highly reliable. However fabrication of synthetic hydroxyapatite is complex and expensive. The production of natural hydroxyapatite is easy and inexpensive. In spite of being a biocompatible and bioactive material, hydroxyapatite has a limited usage as an implant material because of its weak mechanical properties. For this reason, HA based composites are required to supply improvement of strength and toughness of the implant materials without losing biocompatibility. In this study, HA composites were synthesized by using natural chicken hydroxyapatite (CHA) reinforced with 5 and 10wt. % commercial inert glass (CIG) powders. Then their physical, mechanical, microstructural properties were characterized. Finally, the most suitable CIG containing CHA composite for orthopedical applications was determined.
Bioceramic and Fibrin Sealant in High Tibial Valgus Osteotomy: Prospective Clinical Study
Authors: Guy Daculsi , Rouvillain Jean Louis , Fabre Thierry , Catonné Yves , Bagot d'Arc Maurice , N'Guyen Jean Michel , Durand Marlene
Published: November 2013

The association of Micro Macroporous Biphasic Calcium Phosphate granules and t fibrin sealant has been developed to answer a challenging request of orthopaedic surgeons: a biocompatible, osteogenic, mouldable, and self-hardening bone substitute able to fill bone defects. The aim of this study was the evaluation of the performance and safety of the bioactive composite in regeneration of functional bone. A clinical study design was set up as an exploratory prospective French multicentric phase II study sponsored by INSERM. The application was the HTVO (Tibial Osteotomy of Valgisation) using osteosynthesis and bone substitute (BS) for filling the space created. The follow up was 12 months with safety checks, clinical assessments, high-sensitivity X-ray, and CT-scan imaging. A bone sample was collected from the reconstructed area at 12 months. 13 patients with stage I gonarthrosis have been included in the study. This clinical follow up revealed only one case of correction loss. X-ray and CT-scan imaging indicated a progressive disappearance of the peripheric radioluency and a decrease of the radiopacity of the implanted area due to bioceramic resorption and bone ingrowth at the expense of the implant. Histological analysis revealed BS large resorption and bone ingrowth both into the pores and at the expense of the bioceramic. X-Ray and micro CT scan revealed a well organised and mineralised structure in the newly-formed bone.
Bridging and Repairing Patient Specific Acetabular Defects with a New Custom Acetabular Cage
Authors: Costin Serban , Micu Constantin Anton , Cristea Stefan
Published: November 2013

Sever acetabular defects can usually be addressed with a standard acetabular cage. The procedure is more complicated, as standard devices have to be adapted to different shapes of acetabular defects, especially when they are bigger and widespread. The proposed cage tries to fix problems that standard cages sometimes do not resolve for example insufficient fixation due to the fact that the inferior flange did not engage the ischium, graft resorption and at the same time tries to remain affordable. The implant is being built based on the 3D reconstruction of the patient hip from CT scans with the help of additive technologies and uses standard components (cup, screws). The particular implant was designed and produced and it is available for patient implantation. The proposed solution offers a better fit alternative for the patient but realization of the implant is very time consuming, although a systematized process was tried and achieved.
Synthesis of Carbonate Apatite Foam Using β-TCP Foams as Precursors
Authors: Tsuru Kanji , Nikaido Taro , Munar Melvin L. , Maruta Michito , Matsuya Shigeki , Nakamura Seiji , Kunio Ishikawa
Published: November 2013

The present study reports the synthesis of carbonate apatite foam with fully interconnecting pores from βTCP foam by hydrothermal treatment in 1 mol·L-1 disodium carbonate solution at 200°C. The βTCP foam were prepared; 1) using 3 mol% Mg as βTCP stabilizer, 2) using αTCP foam as a precursor by heat treatment at 900°C for 100 hours. The βTCP foam containing Mg could not transform to carbonate apatite foam completely. Meanwhile, the βTCP foam heat-treated at 900°C transformed to carbonate apatite after hydrothermal treatment for 10 days without morphological change. Compressive strength measurement indicated that the value of carbonate apatite foam derived from βTCP was significantly higher than that from αTCP.
Traversing Phase Fields towards Nanosized Beta Tricalcium Phosphate
Authors: Gross K. , Andersons Juris , Misevicius Martynas , Švirksts Janis
Published: November 2013

The difficulty of beta tricalcium phosphate (β-TCP) crystallization in aqueous media opens the question whether β-TCP can be produced using an alternative pathway. Amorphous calcium phosphate (ACP) is metastable in an aqueous environment and prefers a more stable apatite phase. Others have transformed a crystallized calcium deficient hydroxyapatite (Ca-def HAp) into β-TCP, but automatic transformation from ACP to Ca-def HAp followed by transformation to β-TCP has not been addressed. This work shows the formation of Ca-def HAp after different aging times of ACP and the subsequent transition to β-TCP. An amorphous phase with a Ca/P ratio of 1.5 was synthesized, rinsed, filtered and excess fluid removed for maturation. The resulting apatite was monitored with X-ray diffraction at different temperatures. Heating at 700 °C then investigated the transition to β-TCP. It was found that Ca-def HAp formed at short aging times produced a combination of alpha and beta phases, but a longer aging time led to pure β-TCP.
Numerical Investigation on the Size Effect of a WC/Co 3D Representative Volume Element Based on the Homogenized Elasto-Plastic Response and Fracture Energy Dissipation
Authors: Ozden Utku Ahmet , Chen Geng , Bezold Alexander , Broeckmann Christoph
Published: November 2013

Tungsten carbide-cobalt (WC/Co) is a two phase material composed of two distinct interpenetrating phases having different mechanical properties. The hard and brittle WC phase behaves elastically whereas the Co phase demonstrates an elasto-plastic response. In order to predict the global behavior of the material from its microscopic constitution, the representative volume element (RVE) model has to satisfy basic requirement of a certain size. Moreover the homogenized response of the RVE has to be characterized with respect to the macroscopic mechanical property of interest. Taking into consideration such phenomenon the current study investigates the size of 3D RVEs that are adequate to reflect the global elasto-plastic response and the fracture (damage) energy dissipation. The results of the homogenized elasto-plastic responses were compared to a macroscopic experimental stress-strain curve and the fracture energy dissipation was validated by a convergence study. It has been observed from the numerical simulation that, despite the randomness of the structure, the development of volume averaged elastic potential, plastic and as well as the fracture energy dissipation would stabilize with the increasing size of the RVE.
Inaccuracy in Residual Stress Estimation and its Influence on the Residual Lifetime of Polymer Pipes
Authors: Ševčík Martin , Poduška Jan , Náhlík Luboš , Kučera Jaroslav , Hutař Pavel
Published: November 2013

This paper presents a methodology suitable for estimation of residual lifetime of polymer pipes. The linear and non-linear distribution of residual stresses in the pipe wall is studied using FEM analysis. The approximate relation for the stress intensity factor calculation is presented. It is shown that the presented relation gives a stress intensity factor similar to the FEM analysis for the linear or non-linear distribution of residual stress. The suggested procedure produces a slightly conservative lifetime estimation where the accuracy of the procedure increases with increasing ratio between applied internal pressure level to residual stress level. The accuracy of the residual stress estimation and corresponding stress intensity factor is discussed and a final recommendation for lifetime determination based on simplified methodology is given.
Critical Value for Crack Propagation from Sharp V-Notch
Authors: Náhlík Luboš , Štegnerová Kateřina , Hutař Pavel , Majer Zdeněk
Published: November 2013

The contribution is focused on estimation of a critical value of generalized stress intensity factor for crack propagation from sharp V-notches. Stress distribution around the tip of the V-notch is described on the base of generalized linear elastic fracture mechanics, because V-notch is a singular stress concentrator with stress singularity exponent different from 0.5 (depending on V-notch opening angle). Then also stability criteria based on strain energy density factor and average critical stress are generalized for the stress singularity different from 0.5. Using FE analysis the critical stresses for crack initiation was estimated and compared with experimental data from the literature.
Strength of an Elastic Plane with a Square Lattice of Circular Holes under External Loading
Authors: Mokryakov Viacheslav
Published: November 2013

Strength characteristics of an elastic plane weakened by round holes arranged in a quadratic order are considered. The stress concentrations in the three different hole lattices are studied in conditions of the uniaxial tension/compression with different directions (0°÷45°, it is enough, because the lattices are symmetrical). The minimal and maximal concentrations values are calculated; the stress fields are considered in different lattices. It is shown that in the particular conditions of fracture at compression can occur in the inner zone of the material rather than at the hole contours. It is demonstrated that in dense lattices a power-like type of the concentrations dependencies on the structural parameter takes place; the parameter is a ratio of the holes interval to the hole radius. Next, the modes of initiation of fracture in elastic perforated plates (lattices) under external uniaxial compression are considered. Special attention is paid to the internal mode of initiation (i.e., to the case of fracture initiation inside the material, and not on the contours of the holes). The parametric region of the internal mode is studied, it depends on the angle of the applied external loads and the structural lattice parameter; the size of the region (extreme values) is calculated. A particular point of the region is found; it is shown that at this point there are three possibilities of fracture initiation: two positions at the hole contour, and one position inside of material. Keywords: elasticity, perforated plates, lattice of circular holes, fracture initiation, uniaxial compression.
An Experimental, Numerical and SEM Study of Fracture in a Thin Polymer Film
Authors: Andreasson Eskil , Mehmood Nasir , Mao Tan , Kao-Walter Sharon
Published: November 2013

Observations and analysis of samples from scanning electron microscopic (SEM) micrographs has been concerned in this work. The samples originate from fractured mechanical mode I tensile testing of a thin polymer film made of polypropylene used in the packaging industry. Three different shapes of the crack; elliptical, circular and flat, were used to investigate the decrease in load carrying capacity. The fracture surfaces looked similar in all studied cases. Brittle-like material fracture process was observed both by SEM micrographs and the experimental mechanical results. A finite element model was created in Abaqus as a complementary tool to increase the understanding of the mechanical behaviour of the material. The numerical material models were calibrated and the results from the simulations were comparable to the experimental results.
Calibration of Selected Ductile Fracture Criteria Using Two Types of Specimens
Authors: Kubík Petr , Šebek František , Petruška Jindřich , Hůlka Jiří , Růžička Jan , Španiel Miroslav , Džugan Jan , Prantl Antonín
Published: November 2013

This paper presents the calibration of three universal ductile fracture criteria with the stress triaxiality and the normalized third invariant of deviatoric stress dependence. Xue-Wierzbicki, Bai-Wierzbicki and Extended Mohr-Coulomb criteria are calibrated using butterfly specimen and newly designed notched tube specimen for an austenitic stainless steel. Different stress states necessary for successful calibration are generated by suitable combination of tension/compression-shear or tension/compression-torsion loading of both specimens, respectively. Suitability of the specimens for ductile fracture criteria calibration is evaluated comparing the range of reached stress states, the homogeneity of stress in process zone and appropriateness for the computational simulation of tests. Possible combination of above mentioned results with tensile testing of standard and notched cylindrical specimens is discussed, too.
Localized Plastic Flow Autowaves and the Hall-Petch Relation for Al
Authors: Zuev Lev B. , Zarikovskaya Natalya
Published: November 2013

The localization of plastic deformation was examined for polycrystalline aluminum samples having grain sizes in the range from 8·10-3to 10 mm. It is found that the length of localized deformation autowaves is determined by the grain size of material. The localized plastic flow patterns emergent in the polycrystalline aluminum samples are found to be connected to the Hall-Petch relation. Two types of flow stress dependencies of grain size are distinguished.
Mathematical Modeling of Caries Initiation and Progression Occurring in Dental Enamel
Authors: Izyumov Roman I. , Rusakov Sergey V. , Zuev Andrew L. , Gileva Olga S. , Muraveva Maria A.
Published: November 2013

The paper is concerned with the investigation of dental caries treatment by the modern method based on the application of special composite material that can diffuse into the damaged zone, harden by light and prevent tooth decay. Carious disease was modeled as a diffusion process of acid penetration from the oral cavity into the tooth enamel with further dissolution of dental hard tissues in the subsurface layer of enamel. The model of dental caries was mathematically formulated. The solution was obtained by a numerical method using MATLAB. It is shown that the proposed model adequately describes the properties of the examined dental system.
Evaluation of Developed Texture during Cold-Rolling Deformation of Ti-Nb-Ta-Zr Biocompatible Alloy
Authors: Cojocaru Vasile Danut , Thibon Isabelle , Raducanu Doina , Cinca Ion , Gloriant T. , Gordin Doina Margareta
Published: November 2013

During the last decade the titanium alloys were extensively used in a variety of applications due to their good mechanical properties, high biocompatibility and corrosion resistance. β-type Ti alloys composed of Nb, Ta and Zr elements have received much attention, because they feature high specific strength, bio-corrosion resistance, no allergic problems and biocompatibility. A Ti-29Nb-9Ta-10Zr (wt.%) alloy was subjected to thermo-mechanical processing and testing. Two states were investigated: recrystallized and 80% cold-rolled. Data concerning phase structure and developed texture, expressed by Inverse Pole Figures (IPFs) and Orientation Distribution Functions (ODFs), was obtained and analyzed.
Nanoindentation of Thin Copper Coatings
Authors: Hansson Per , Jansson Maria
Published: November 2013

The structure of interest is a thin, metallic coating of fcc copper, of thickness down to a few nanometers only, resting on a stiffer substrate. The elastic and plastic properties of the thin coating using nanoindentation under different geometrical features such as size of the indenter and coating thickness are determined. The force-displacement curve is monitored during indentation and the precise conditions for the occurrence of so called pop-ins during loading are investigated. To simulate the nanoindentation process, a molecular dynamics approach is used, where an infinitely stiff indenter is pushed into the coating under displacement control. The coating is modeled as a thin rectangular plate, with the bottom atom layers locked from movement, simulating the stiffer substrate, and periodic boundary conditions in the plane of the plate are applied.
Stress Analysis of Highly Constrained Copper Strips with through Crack Shaped Voids Using Molecular Dynamics
Authors: Johansson Dan , Hansson Per , Melin Solveig
Published: November 2013

A small rectangular strip of fcc Cu, containing a through crack on the nanoscale and subjected to loading under displacement control, is simulated using molecular dynamics (MD). The geometry is highly constrained and chosen to mimic that of a thin strip between two stiff layers. The Lennard-Jones pair potential is used for the inter-atomic forces. The centrally placed crack shaped void is created by removing a few atoms inside the specimen. The crack is loaded perpendicular to the crack plane and the tensile stress is studied as it varies over the thickness of the strip. Comparisons with finite element calculations are made and the goal is to find a limit in model size beneath which the finite element (FE) solutions and linear elastic fracture mechanics (LEFM) lose their accuracy.
Assessment of the Unstressed Lattice Parameters for Residual Stresses Determination by Neutron Diffraction in Engineering Materials
Authors: Rogante M. , Mikula Pavol , Vrána Miroslav
Published: November 2013

Thermal neutrons are very useful probe in a nondestructive determination of internal stress/strains, due to their high penetration into most materials. In comparison with conventional X-ray techniques, real bulk information on both macro-and micro-strains in materials can be obtained by neutron diffraction (ND) techniques. Knowledge of the spatial and directional distribution of internal residual stresses (RS) is increasingly considered fundamental to determine their influence on properties of engineering materials and a consequent material behaviour. As the assesment of stresses is always related to the stress free material state, an accurate evaluation of the unstressed lattice parameters (e.g., the interplanar distance), in order to determine RS by ND is one of the key tasks. It helps to avoid inacceptable errors in the course of the real material strain and stress evaluation. The availability of carefully measured zero-strain standards is also essential to confirm the absence of systematic instrumental effects determining the diffraction profile at a chosen scattering angle. In this paper, the state of the art of the main analytical and experimental procedures currently established or adoptable to determine these critical parameters, particularly regarding industrial applications, is presented.
A Comparative Study on Infrared Thermography during Ultrasonic Fatigue Testing of Cast Steel 42CrMo4 and Cast Aluminium Alloy AlSi7Mg
Authors: Krewerth Dominik , Weidner Anja , Biermann Horst
Published: November 2013

The present paper illustrates a comparison of infrared thermography during ultrasonic fatigue testing of cast steel 42CrMo4 and cast aluminium alloy AlSi7Mg. Against the background of different material properties (e.g. mechanical properties as well as thermal properties) the benefit of this non-destructive material testing method in terms of determining the crack initiation point and time during fatigue testing as well as crack propagation is evaluated and discussed. Moreover, correlations between fractography and infrared thermography are performed for both materials.
A FPGA-PC Based Acoustic Emission System with Logarithmic Preamplifier for Fracture Monitoring
Authors: Vondra Marek , Cséfalvay Gabriel , Sedlak Petr
Published: November 2013

Acoustic emission (AE) is one of the most used nondestructive technique since it offers a great potential due to its ability of quantitative evaluation such as source location and source characterization. A common set of recorded acoustic emission signals has an extraordinarily wide dynamic range. Thus, the input gain of the A/D converter plays a key role due in information loss considering limitation of high signal amplitudes and domination of quantization noise at low levels. The usage of a logarithmic preamplifier extends the dynamic range of conventional A/D converters, thus increases the accuracy and signal-to-noise ratio of weak acoustic emission signals.
Detection of Inhomogeneities and Cracks in Composite Materials by the Method of Partial Discharges
Authors: Koktavý Pavel , Trčka Tomas , Koktavý Bohumil , Stoudek Richard
Published: November 2013

Composite materials such as concrete or polymer fiber composites contain a large number of inhomogeneities. It is possible to use the method of partial discharges to detect existing inhomogeneities. Tested materials covered with metal electrodes on both sides represent a parallel plate capacitor. Partial discharges have an impact on conductivity at a high electric field and they are important sources of current noise and acoustic emission signals. The concrete samples were measured before and after mechanical loading by the method of partial discharges and the correlation between them was studied. This method may be used for the diagnosis of inhomogeneities and cracks in composite materials.
Fracture of Irradiated Austenitic Stainless Steel with Special Reference to Irradiation Assisted Stress Corrosion Cracking
Authors: Hojna Anna , Michalicka Jan , Srba Ondrej
Published: November 2013

This paper deals with fracture of neutron irradiated austenitic Ti-stabilized stainless steel 08Ch18N10T. The steel had been tested in air and in water environment (320°C) using several tests representing different stress strain conditions for crack initiation and growth; Slow Strain Rate and Crack Growth Rate tests were performed in the water. Without irradiation the steel did not suffer from stress corrosion cracking in the water, but on irradiated specimens appeared areas of intergranular fracture mixed with transgranular cleavage-like facets and secondary cracks typical for IASCC phenomenon. The differences between fracture of irradiated and non-irradiated specimens in air and in water are documented and discussed.
Intergranular Embrittlement of Nuclear Reactor Pressure Vessel Steels
Authors: Zabusov Oleg O. , Gurovich Boris A. , Kuleshova Evgenia A. , Saltykov Michail A. , Fedotova Svetlana V. , Dementjev Alexey P.
Published: November 2013

Service life of VVER-type nuclear reactor is limited by decrease in brittle fracture resistance of reactor pressure vessel produced of low-alloy low-carbon steel under effect of irradiation and/or elevated temperatures. In this work fracture surfaces were studied by Auger-electron spectroscopy in order to estimate the contribution of intergranular embrittlement to the degradation of reactor pressure vessel steels under the influence of operating conditions.
It was demonstrated that irradiation induced segregation leads to an increase of P content in grain boundaries that promotes intergranular brittle fracture on fracture surfaces. The similar effect but to a lesser degree was shown in the case of long-term temperature exposure.
The grain boundary structure was examined and an effect of carbides located on the grain boundaries is supposed due to increased phosphorus segregation on carbide/matrix interface boundaries.
Influence of Cooling Rate on Final Properties of Laboratory Rolled Products
Authors: Kawulok Petr , Schindler Ivo , Čmiel Karel Milan , Sojka Jaroslav , Rusz Stanislav , Kawulok Rostislav
Published: November 2013

The objective of investigation was to determine the influence of chosen cooling rates after finish rolling on final microstructural and mechanical properties of the laboratory rolled products from steel 42CrMo4. Metallographic analysis showed that microstructure of rolled products, which were after finish rolling cooled down in accelerated manner by water sprays, was composed mostly by hardening phases and by smaller amount of ferrite. Microstructure of the rolled product cooled down in furnace in decelerated manner was formed by pearlitic blocks with minority occurrence of ferrite. Laboratory rolled products cooled down by more complicated modes, which consisted of combination of their cooling by water sprays with subsequent annealing in furnace, showed different phase morphology and distinct band structure. Results of tensile test have proved that the applied modes of cooling of rolled products by accelerated manner had only very small influence on their final mechanical properties. Considerably cooling the rolled product by decelerated manner in furnace resulted in drop yield strength, but on the other hand in an increase of ductility. More complicated modes of cooling the rolled products, which comprised also their annealing, showed the possibilities of significant influencing the strength, and particularly the plastic properties of the steel 42CrMo4.
Determining Elastic-Plastic Properties of Al6061-T6 from Micro-Indentation Technique
Authors: Amiri Sina , Lecis Nora , Manes Andrea , Mombelli Davide , Giglio Marco
Published: November 2013

Different approaches have been proposed in order to determine the material behavior of ductile materials. Since, the mechanical properties of a mechanical component are modified during manufacturing process due to plastic deformation, heat treatment and etc, a non-destructive indentation experimental procedure addressed to predict the elastic-plastic properties of material after manufacturing process is of interest. This is especially true for small size components where it is complex to extract specimens to test on standard test system. Based on dimensionless analysis and the concept of a representative strain, different approaches have been proposed to determine the material properties of power law materials by using indentation process. In this work, the Johnson-Cook (JC) constitutive model of the aluminum alloy Al6061-T6 is characterized by means of a well-defined optimization procedure based on micro-indentation testing and high fidelity finite element models and an optimization procedure but without the concept of dimensionless analysis and a representative strain. This methodology allows determining a set of JC constants for Al6061-T6. The obtained results have good agreement with parameters calibrated by means of universal standard tests and reverse engineering approach.
Standing Contact Fatigue Analyse of Steels with Different Microstructures
Authors: Vuorinen Esa , Ranga Naveen Kumar , Linz Mathias , Kankanala Anusha , Bäck Fredrik
Published: November 2013

A Standing Contact Fatigue (SCF) test set up has been developed in order to facilitate quick testing of contact fatigue resistance of material surfaces. In this method the sample is pressed against a hard ball rapidly and the resulting crack formation is studied in order to evaluate the SCF resistance. Induction hardened surfaces of cam-ring steel and steels with pearlitic, martensitic, bainitic, ausferritic and quench and tempered microstructures have been studied. Characterization was performed by optical microscopy, scanning electron microscopy and hardness measurements. Ring-cone cracks were found at the edge of the indentations but inside the indent in the surface hardened cam-ring steel samples. Sectional views revealed that these cracks also grow underneath the indentation. Radial cracks were found in non-surface hardened samples. The test of the SCF resistance of steels with different microstructures showed that the ausferritic microstructures tested shoved better SCF resistance than the quench and tempered samples with similar hardness. A comparison between different tempering temperatures of surface hardened steels showed that samples tempered at the higher temperature 240 °C resulted in better SCF resistance.
Relation between Microstructure and Tribological Properties of High Density Polyethylene Hybrid Composites Filled with Untreated Glass Spheres, Talc and Calcium Carbonate
Authors: Taşdemir Münir
Published: November 2013

In the present work, high density polyethylene based composites filled with glass spheres, talc and calcite particles were prepared. Fillers contents in the HDPE were 5, 10, 15, and 20 wt%. The mechanical, morphological and tribological properties of the polymer composites were investigated. Substantial improvements in the some mechanical properties were obtained by the addition of filler. For example, the results showed that the elasticity modulus of composites improved with increasing the filler content. The addition of fillers to the HDPE changed significantly the friction coefficient and wear rate of the composites. HDPE filled with a high level content of fillers showed higher wear rate than pure HDPE under dry sliding. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM).
Thermal Effects while Fatigue Cracking Growth under Bending
Authors: Rozumek Dariusz , Szmolke Norbert
Published: November 2013

The paper presents the results of fatigue tests where temperature changes on specimen surfaces were registered. Some different materials were tested. A relation between the crack growth and temperature changes in the propagation place was found. The highest temperature gradients were measured on the crack growth path, and it was caused by molecular friction.
PSBs and Non-Propagation of Small Surface and Interior Cracks in Polycrystalline Copper
Authors: Stanzl-Tschegg Stefanie E. , Schönbauer Bernd M.
Published: November 2013

PSB formation and its relevance for an eventual fatigue limit of polycrystalline electrolytic copper was studied in the very-high cycle fatigue regime with the ultrasound fatigue loading method. PSBs are formed at much lower stress/strain amplitudes than reported in earlier literature, if a high enough number of cycles is applied. Fatigue fracture takes place at approximately 50% higher amplitudes than needed for PSB formation, which is likewise in contrast to former literature results. Non-propagation of small cracks, originating from intrusions or PSB-induced non-propagating grain-boundary cracks are made responsible for this different material response.
Trajectory and Crystallography of Crack Growth in Austenitic Steel after LCF Tests
Authors: Eterashvili Tamaz , Dzigrashvili Temur , Vardosanidze Manana
Published: November 2013

Analysis of microcrack and mesocrack formation in austenitic steel thin filmsprepared after low-cycle fatigue (LCF) testsfrom bulk samples is presented using TEM techniques. Location, orientation and interaction of microcracks with microstructure components of the steel were determined. Plastic zone ahead of mesocrack tip and the structure changes in it were analyzed. Crystallography of slip bands and deformation twins and their relation with the microcrack propagation direction were also determined. The impact of grain anisotropy and inhomogeneous distribution of stress relaxation ahead of mesocrack tip in plastic zone were considered. Influence of sizes of mesocracks [ and microcracks and their relation with the trajectory and crystallography of propagation are also discussed.
Experimental Investigation of Modes II and III Fatigue Crack Growth in Unalloyed Titanium
Authors: Vojtek Tomáš , Pokluda Jaroslav
Published: November 2013

The study is focused on finding and describing microscopic paths of modes II and III cracks in commercially pure α-titanium (hcp structure). Experiments were done on cylindrical bars with a circumferential cracked notch loaded in shear (modes II, III and II + III) and torsion (mode III). Fractography analysis showed that the crack growth was crystallography-controlled and the deflection and twisting angles of crack propagation direction (with respect to the shear plane) were relatively high. This behavior is a mixture of previously observed morphology in ARMCO iron (bcc) and austenitic steel (fcc). It can be understood in terms of a number of available slip systems in bcc, fcc and hcp lattices.
Non-Planar Dislocations in MoSi2
Authors: Paidar Vaclav , Vitek Vaclav
Published: November 2013

Non-planar dislocation dissociations and cores play a fundamental role in mechanical properties of many materials. In this contribution, we concentrate on the complex structures arising from a large number of possible metastable stacking faults in disilicides with the C11b structure, specifically MoSi2. First, gamma-surfaces for the planes with high atomic density in this intermetallic are presented. Employing these results, possible configurations of dislocation dissociations are discussed and related to the deformation behavior.
Stress Evolution during Tensile Twinning in MgAZ31 Alloy Processed by Extrusion
Authors: Raju K. Sitarama , Lynch Peter A. , Barnett Matthew R.
Published: November 2013

An in-situ laboratory based X-ray diffraction technique has been developed to directly measure lattice strain and stress evolution associated with {10.2} < 10.1 > twin nucleation and growth in rolled and extruded Mg alloys during tensile loading. A transmission diffraction geometry was utilised to measure peak position and intensity for the (10.0), (00.2) and (10.1) lattice planes while the sample was loaded in uni-axial tension. Lattice re-orientation arising from deformation twinning is utilizedto estimate the twin volume fraction by measuring the increase in the (10.0) peak intensity along with a simultaneous decrease in the (00.2) peak intensity as a function of applied load. From observation of the lattice strain plotted against applied stress for different orientations it was found that the (10.1) orientation displayed the anticipated linear behaviour within the whole stress range. Yielding in the (10.2) and (10.3) orientations was identified at around 75 and 90 MPa respectively, indicating theonset of basal slip. Twin nucleation was observed at at a stress of approximately 110 MPa.
Measuring the Mechanical Properties of Ground Ophthalmic Polymer Surfaces Using Nanoindentation
Authors: de Pellegrin Dennis V.
Published: November 2013

This work is motivated by the need to efficiently machine the edges of ophthalmic polymer lenses for mounting in spectacle or instrument frames. The polymer materials used are required to have suitable optical characteristics such high refractive index and Abbe number, combined with low density and high scratch and impact resistance. Edge surface finish is an important aesthetic consideration; its quality is governed by the material removal operation and the physical properties of the material being processed. The wear behaviour of polymer materials is not as straightforward as for other materials due to their molecular and structural complexity, not to mention their time-dependent properties. Four commercial ophthalmic polymers have been studied in this work using nanoindentation techniques which are evaluated as tools for probing surface mechanical properties in order to better understand the grinding response of polymer materials.