bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Properties of the Laser Cladded Cobalt-Based Alloy Coating on T10 Tool Steel
Authors: Cui Cheng Yun , Cui Xi Gui , Zhang Yong Kong , Zhao Qian , Lu Jin Zhong
Published: January 2011

Co-based alloy coating was cladded on T10 tool steel by the powder feeding and continuous CO2 laser. The results showed that compared to the unreinforced T10 tool steel substrate, the microhardness of the Co-based reinforced composite was significantly enhanced and the maximum value was existed in the middle of the cladding coating. The corrosion resistance of the cladding coating was also improved. After cryogenic treatment, there is no obvious change for the structure of the cladding coating while the phase is transformed, leading to an increase in the microhardness of the cladding coating.
Carboxymethyl Chitosan Nonwoven Scaffold for Bone Regeneration
Authors: Bao Xu Xu , Teramoto Akira , Abe Koji
Published: January 2011

Natural bone is a composite mainly made from nano/micro-structure of hydroxyapatite and collagen fibers. For bone regeneration by tissue engineering, it is important to synthesize three dimension nano-composites with good biocompatibility, high bioactivity and great bonding property as potentially useful scaffold. In this study, we fabricated chitosan nano-nonwoven scaffold via electrospinning and modified chitosan scaffolds by carboxymethylation (CM) to improve the osteoconductive characteristics. Results of FTIR confirmed the existence of carboxymethyl groups of CMChitosan. Moreover by employed mice osteoblast (MC3T3-E1) cell for adhesion, proliferation and differentiation assays, we found that CMChitosan appeared to have effect on the late stages of osteoblast behavior (calcium deposit).
Effect of Easing Device on an Air-Jet Loom of Double Back Rest System
Authors: Wang Si Yong , Feng Zhi Hua , Lv Fan
Published: January 2011

In order to release the influence of shedding motion on warp tension fluctuation, easing device is often set on short looms with single back rest system. With the decrease of the beam’s diameter, the wrapping angle formed by warp and the active back rest will become bigger, and the effect of the easing device will be more significant. However, the wrapping angle of the double back rest system is a constant while the change of the beam’s diameter. The effect of easing device on air-jet looms of double back rests system is analyzed in this paper, and conclusion has been made that the easing device can be eliminated on the double back rests system.
The Energy Distribution of Tire-Road Noise and Noisy Speech Based on Wavelet Packet
Authors: He Zhi Yong , Luo Li Heng
Published: January 2011

Speech enhancement is very important for mobile communications or some other applications in car. The energy distribution of signal is the basis of algorithms which denoise noisy speech in time-frequency domain. In this work, the noise regarded is the tire-road noise when driving in expressway. Wavelet packets transform is used in the analysis. After decomposing noise signal and noisy speech signal by wavelet packet transform, the analysis for the difference of the energy distribution between noisy speech and noise is finished.
"OF + N" Theoretical Method and Practice to Create Inventive and Innovative Topics
Authors: Rui Yan Nian , Jiang Xiao Mei , Liu Kai Qiang
Published: January 2011

How to master the technology innovation and method and technique in product exploitation, has been always one of the issues of research and discussion. Based on more than 40 years’ experiences of engagement in mechanical and electrical technology on product research, design, teaching, the author proposed and constructed "OF + N" theoretical method (for short: method of creating inventive and innovative topics) suitable for technological innovation and product development. Some innovative design was implemented using the theoretical method through years of research and probe.
Research on Modeling of EPS with Bond-Graph Theory and Simulating of Steering Maneuverability
Authors: Tang Jian , Jiang Hao Bin , Geng Guo Qing , Xue Nian Wen
Published: January 2011

As a tool of modeling the system of multiple energy, bond-graph theory is applied to the modeling for electric power steering system which is electromechanical hybrid. Bond graph models for C type, P type and R type of EPS dynamic system are built respectively. The CH7140 type of car equipped with C type EPS is taken as a prototype and its maneuverable performance is simulated under typical working conditions. A PID control method with time delay transfer function is adopted to imitate the driver’s operation. Steering maneuverability test of the CH7140 car is conducted. The simulation result is consistent with the test result. It is shown that the bond-graph model of EPS is rational, and simulation model derived from bond-graph is effective which can be applied to EPS and full vehicle steering maneuverability simulation research.
Yarn Tension Analysis in Typical Carpet Tufting Equipment System
Authors: Xu Yang , Sun Zhi Jun , Meng Zhuo , Sun Yi Ze , Chen Guang Feng
Published: January 2011

Precise pile height is an essential quality measurement for sculptured-style jacquard carpet. Correct yarn tension analysis is the key to accurately control carpet pile height during manufacturing carpet. This paper described a standard tufting equipment system with essential components in the yarn path. The relationship of pile height and pile tension is formulated. The А.П.МИНаКОВ’s Euler formula is introduced into yarn tension modeling which including the yarn guides, sub-line frame, and puller rollers parts. Finally, this tension model is validated by comparing yarn tension simulation result data and experimental measuring data.
Automatic Location of Pills in Woven Fabric Based on Gabor Filter
Authors: Gao Wei Dong , Wang Shan Yuan , Pan Ru Ru , Liu Ji Hong
Published: January 2011

A novel method for locating the pills in woven fabric based on Gabor filter is proposed in this paper. The process of capturing the fabric image is first introduced and the hardware and software of the system is given simultaneously. Gabor filter is then carried out in the pilled fabric image to remove the fabric texture and enhance the pill information. In the enhanced fabric image, threshold method is used to segment and locate the fabric pills. The location of fabric pills lays the foundation for constructing the whole system of evaluating the fabric pilling grade.
3D Discrete Dislocation Modelling of High Temperature Plasticity
Authors: Záležák Tomáš , Dlouhý Antonín
Published: January 2011

A 3D model is presented that addresses an evolution of flexible dislocation lines at high temperatures. The model is based on the linear theory of elasticity. A smooth dislocation line is approximated by a piecewise curve composed of short straight dislocation segments. Each dislocation segment is acted upon by a Peach-Koehler force due to a local stress field. All segment-segment interactions as well as an externally applied stress are considered. A segment mobility is proportional to the Peach-Koehler force, temperature-dependent factors control climb and glide motion of the segments. The potential of the model is demonstrated in simulations of simple high temperature processes including interactions of dislocations with secondary particles.
Numerical Study of the Influence of the Crack Front Curvature in the Evolution of the Plastic Zone along the CT Specimen Thickness
Authors: Camas Daniel , Lopez-Crespo Pablo , González-Herrera Antonio
Published: January 2011

This paper presents a numerical study of the influence of the load level and the crack front curvature on the plastic zone in the area close to the crack front. The aim of the work is to determine the influence of these parameters on fatigue crack closure. For this, a CT aluminum specimen has been modelled tri-dimensionally and several finite elements calculations have been made considering a large combination of the variables under consideration.
Hydroformability of Bulge Forming Light-Weight Tubes via Micro-Hardness Dependence
Authors: Wang G.D. , Chan Luen Chow
Published: January 2011

To evaluate the hydroformablility of tubular components in the tube hydroforming (THF) process, the conventional method is to measure the deformed square or circle grids printed on the surface of the tubular parts. However, the reliability of those measured data is affected greatly by the grid size and its measurement method on the curved surface. It is well-known that material hardness varies under different plastic deformation conditions, especially before and after the forming process. And it is more convenient to obtain the Vickers’ hardness values and distribution around the burst area of deformed components. This paper mainly presents an effective and reliable approach to evaluate the hydroformability of tubular components using micro-hardness measurement. At first, the Vickers’ hardness values and distribution around the burst area of the deformed components were obtained. The plastic strain, together with its distribution in such an area could then be derived by the measured micro-hardness through the developed equations. As a result, it was found to be more suitable to evaluate the hydroformability of tubes using this approach instead of the traditional grids measurement.
Wear of Cutting Tools Used in Milling Treatments
Authors: Anthymidis K.G. , Balouktsis A. , David Kostas , Trakali A.
Published: January 2011

The usage of Computer Numerical Controlled Machines has been generalized over the last decades due to the increased demands for the production of mechanical parts with précised dimensions, higher production rates and products with better treated surface quality. It is well known that the duration of life of a cutting tool is one of the most important parameters during the cutting of metal parts, because it affects the cost of the manufacturing process substantially. Therefore, it is important to know accurately, the relation between the duration of life of the cutting tool and the conditions of the machinery such as cutting velocity, feed rate (fz), the depth of cut (radial and axial) etc. The purpose of this research is to conduct a proper number of cutting experiments in milling, measuring the wear of the cutting tools, in order to conclude in a mathematical model the wear cutting tool. This model can be implemented for the prediction of the cutting tool life, which is very important for the determination of the best cutting conditions. From the experimental diagrams we can come to conclusions for the course of the wear of the cutting tool in connection with the velocity of cutting, for the machinability of the materials used etc. The wear of the used cutting tools was determined by means of optical microscopy and stereoscopy.
Tearing and Delaminating of a Polymer Laminate
Authors: Kao-Walter Sharon , Walter M. , Dasari A. , Leon A.
Published: January 2011

The fracture behaviour of laminated materials was studied in this work. The materials used in this work were low-density polyethylene (LDPE) laminated on polyethylene (PET). The thickness of the LDPE was 27 µm and the PET was 100 µm. Experiments were performed by using a 2-leg trousers specimen to analyse the tearing behaviour of the laminate in relation to the delamination. A clear delamination zone was observed during the crack propagation by tearing. Furthermore, a finite element calculation was performed to simulate the behavior around the crack tip during the tearing. A correlation between adhesion and crack propagation was discussed. Finally, the theory of Essential Work of Fracture (EWF) was used for predicting the specific total work of fracture along the tear path across the plastic zones.
The Effect of Polymer Pipe Weld Geometry on Creep Lifetime
Authors: Ševčík Martin , Knésl Zdeněk , Hutař Pavel , Náhlík Luboš
Published: January 2011

In the case of large diameter polyethylene (PE) and polypropylene (PP) pipes the most usual joint is the butt weld. This paper focuses on the influence of a weld bead on the service life of welded pipes from a fracture mechanics perspective. To this aim the stress concentrator created by the connection between the weld bead and the pipe’s free surface is modelled as a notch. Global parameters defining properties of stress and strain field in the notch region are calculated for materials with a prevailing Norton-type creep. It is demonstrated that in the case of creep loading conditions and ductile failure mode the existence of such stress concentrators has no negative influence on the lifetime of pipes.
Stability of Ultrafine-Grained Microstructure in Fcc Metals Processed by Severe Plastic Deformation
Authors: Gubicza Jenő , Nguyen Quang Chinh , Dobatkin Sergey V. , Khosravi E. , Langdon Terence G.
Published: January 2011

The thermal stability of ultrafine-grained (UFG) microstructure in face centered cubic metals processed by severe plastic deformation (SPD) was studied. The influence of the SPD procedure on the stability was investigated for Cu samples processed by Equal-Channel Angular Pressing (ECAP), High-Pressure Torsion (HPT), Multi-Directional Forging and Twist Extrusion at room temperature (RT). It is found that HPT results in the lowest thermal stability due to the very high dislocation density. Furthermore, the effect of the low stacking fault energy of Ag on the stability is also investigated. It is revealed that the UFG microstructure produced in Ag by ECAP is recovered and recrystallized during storage at room temperature. The driving force for this unusual recovery and recrystallization is the high dislocation density developed during ECAP due to the high degree of dislocation dissociation caused by the very low stacking fault energy of Ag.
Effect of Atomic Hydrogen Concentration in the Study of Adsorption on Graphene
Authors: Pak A.V. , Lebedev Nikolay G.
Published: January 2011

The results of theoretical quantum-statistical research of atomic hydrogen adsorption on the graphene surface within the framework of the periodic Anderson’s model have been presented. The band structure of graphene with adsorbed hydrogen atoms is calculated by the Green's function method. The work is supported by The Education Ministry of Russian Federation (project No. NK-16(3)).
Modelling of Fibre-Matrix Interface of Brittle Matrix Long Fibre Composite by Application of Cohesive Zone Method
Authors: Kozák Vladislav , Chlup Zdeněk
Published: January 2011

Ceramic matrix composites reinforced by unidirectional long ceramic fibre are very perspective materials. The only disadvantage of such materials is relatively high brittleness at room temperature. The main micromechanism acting as toughening mechanism is the pull out. There are other mechanisms as crack bridging, crack deflection etc. but the primer mechanism is mentioned pull out which is governed by interface between fibre and matrix. The contribution shows a way how to predict and/or optimise behaviour of composite by application of cohesive zone method using the FEM numerical package Abaqus. The presented results from numerical calculations are compared with experimental data.
Characteristics of Duplex Coating on Austenitic Stainless Steel
Authors: Joska Z. , Kadlec J. , Hruby Vojtěch , Mrázková T. , Maňas K.
Published: January 2011

The aim of the article is describe duplex treatment of austenitic stainless steel X12CrNi 18 8 surface. Combination of both plasma nitriding and PVD coating by TiN/TiCN as a surface treatment has been used to improve material hardness and wear resistance without decreasing corrosion resistance. GDOES, confocal microscopy, microhardness, indentation test were applied to characterize the chemical composition, surface morphology, adhesion and hardness of duplex treated specimens.
Residual Stresses Assessment in Coated Materials: Complementarity between Neutron and X-Ray Techniques
Authors: Rogante M. , Mikula Pavol , Vrána Miroslav
Published: January 2011

The residual stress (RS) status induced in the substrate of coated materials by the coating process plays frequently a major role in lending the component’s characteristics. RS assessment can give, thus, a substantial contribution in justifying different cases of failure or else bad performance of coated components due to e.g. the coating delamination or to other occurrences which are not simply interpretable via the conventional mechanical tests or microstructure analyses. The adoption of both neutron diffraction (ND) and X-ray diffraction (XRD) techniques has revealed its usefulness in assessing the RS values in proximity of the coating interface area, respectively, without any layer removal or hole drilling at the extreme surface. In this paper, some real cases of RS determination in coated materials by using these techniques and exploiting their complementarity are described. ND, in particular, is very suitable for crucial applications, where a much different stress situation than that assessed by XRD could be present at some depth below the surface. The results achieved can yield trends adoptable in monitoring of the coating features.
Plasma Nitriding of Deep Narrow Cavities
Authors: Pokorný Z. , Hruby Vojtěch
Published: January 2011

Technology of plasma nitriding is widely used to increase the surface hardness, fatigue strength, wear and corrosion resistance of steels [1, 2]. In this study, the properties of plasma nitrided steel of various diameters at various pressures are investigated. There was obtained new information about possibilities of plasma nitriding technology and its applications to the cavities with diameters of 6, 8 and 10 mm and a penetration depth of 400 mm.
New Methods of EDC and 3DMST Fractal Analysis in the Examination of Biomaterial Surface Fractures
Authors: Stach Sebastian
Published: January 2011

The aim of this study was to gather methodological clues in the scope of a fractal description of non-planar surfaces, which clues can be used for testing biomaterials. The fundamentals of a few most popular fractal methods of surface analysis are discussed here and two new methods are proposed by presenting their basic assumptions. On this basis, appropriate programs for numerical calculations have been developed, while simultaneously using measuring files from instruments which enable stereometric measurement of surfaces (profilographometers, confocal microscopes, etc.).
A Study of Phase Transformations in Complex Metallic Alloys Al73Mn23Pd4 and Al73Mn21Pd6
Authors: Priputen Pavol , Černičková Ivona , Kusý Martin , Illeková Emília , Svec Peter , Buršík Jiří , Svoboda Milan , Dolinšek Jani , Janovec Jozef
Published: January 2011

The microstructure characterization of Al73Mn23Pd4 and Al73Mn21Pd6 alloys was done after annealing at 900°C for 312 h and subsequent water quenching, as well as after thermal cycling. DTA and EDX/WDX/SEM techniques were used in the investigation. It was found out that the alloys consist of the single ternary T-phase after annealing and water quenching. The DTA experiment confirmed the stability of this phase also at lower temperatures. After DTA, the alloys exhibited double-phase microstructure consisting of the ternary T-phase and probably the icosahedral I-phase. It was proved an incongruent transformation of the ternary T-phase into the liquid and vice versa.
Quantification of Carbide Distribution in PM Tool Steels with Niob Addition
Authors: Bureš Radovan , Saxl Ivan , Fáberová Mária
Published: January 2011

Powder of tool steel STN 19830 with 1.9 wt.% of Nb addition was prepared by atomization. Compact material was prepared using of hot isostatic pressing (HIP) and followed by heat treatment to improve the carbides distribution. The aim of this work was to evaluate and quantify the influence of heat treatment parameters on size, shape and spatial distribution of the carbides. Light optical microscopy and image analysis was used to obtain relevant data. Area fraction of carbides was used as parameter of carbide distribution in steel matrix. Sensitivity and accuracy of this method was compared with technique based on Voronoi tessellation. Result shows that size characteristics of tessellation and area fraction analysis are both sufficiently sensitive to indicate the deviation between different states of the respective material and could be used for quantification of size and spatial distribution of the carbides in PM tool steels. Positive effect of used heat treatment on size and distribution of carbides was verified.
Microstructure, Thermal and Electrical Properties of Ultrafine Aluminium
Authors: Rodak Kinga , Moskal Grzegorz , Grabowski Andrzej
Published: January 2011

In article the influence of large effective deformation on microstructure, thermal diffusivity and electrical conductivity is described. The tested material was monocrystalline aluminum deformed by the cyclic extrusion compression (CEC) method. The evolution of misorientation distribution, sub(grain) size was determined by using electron back scattered diffraction (EBSD) technique. The second part of the study was to evaluation of thermal diffusivity by using the laser-flash method. The LFA 427 laser-flash facility were applied. The electrical properties as electrical impedance was made by impedance bridge RLC type. The obtained results show that with increase of deformation the insignificant decrease in thermal diffusivity and electrical conductivity occurred.
RTS Noise of CMOS Technology
Authors: Chvátal Miloš , Pavelka Jan , Sedláková Vlasta , Trčka Tomas , Škarvada Pavel
Published: January 2011

Experiments were carried out for n-channel devices, processed in a 300 nm CMOS technology. The investigated devices have a gate oxide thickness of 6 nm and the effective interface area is AG = 1.5 m2. The RTS measurements were performed for constant gate voltage, where the drain current was changed by varying the drain voltage. The capture time constant increases with increasing drain current. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant c on the drain current we can calculate x-coordinate of the trap position. Electron concentration in the channel decreases linearly from the source to the drain contact. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. Lateral component of the electric field intensity is inhomogeneous in the channel and it has a minimum value near the source contact and increases with the distance from the source to the drain. It reaches maximum value near the drain electrode.
Strain Mapping by Scanning Low Energy Electron Microscopy
Authors: Mikmeková Šárka , Man Ondřej , Pantělejev Libor , Hovorka Miloš , Müllerová I. , Frank Luděk , Kouřil Miloslav
Published: January 2011

The use of the scanning low energy electron microscopy (SLEEM) has been slowly making its way into the field of materials science, hampered not by limitations in the technique but rather by relative scarcity of these instruments in research institutes and laboratories. This paper reports the results obtained from an investigation of the microstructure of ultra fine-grained (UFG) copper fabricated using equal channel angular pressing (ECAP) method, namely in the as-pressed state and after annealing. SLEEM is very sensitive to the perfection of crystal lattice and using SLEEM, local strain can be effectively imaged.
Influence of Hardening and Tempering Vs. Austempering on Mechanical and Fracture Properties of 65Si7 Steel
Authors: Pustaić Dragan , Cajner Franjo
Published: January 2011

The aim of the performed investigations was to determine the influence of two different heat treatment procedures, i. e. hardening and tempering vs. austempering, on some mechanical properties, such as strength, hardness, ductility, contraction, toughness etc., as well as the influence of these procedures on the magnitude of some fracture mechanics parameter for example stress intensity factor K. The experimental investigations were performed on the specimens made of 65Si7 steel (chemical composition: 0.69% C, 1.56% Si and 0.90% Mn).
The Effect of a Low Angle Grain Boundary on the Short Fatigue Crack Growth
Authors: Hansson Per , Melin Solveig
Published: January 2011

The influence on the fatigue crack growth behaviour of a short edge crack due to different configurations of a nearby located low angle grain boundary is investigated under quasi-static and plane strain conditions. The geometry is modelled by dislocation dipole elements in a boundary element approach, and the plasticity is modelled by discrete dislocations. The crack is assumed to grow in a single shear mechanism due to nucleation, glide and annihilation of dislocations in the material. It was found that the sign of the dislocations in the grain boundary, the distances between them and the placement of the dislocations in the grain boundary with respect to preferred slip plane directions, all strongly influenced the growth behaviour.
Experimental Analysis of the Thermal Behaviour of Concrete under Low-Intensity Short Duration Cyclic Compressive Loads
Authors: Antonaci Paola , Bocca Pietro G. , Masera Davide
Published: January 2011

Experimental researches conducted in recent years at the Non Destructive Testing Laboratory of Politecnico di Torino have revealed an unexpected thermal response of concrete subject to short duration cyclic compressive tests: a cooling phenomenon has been observed on medium-quality concrete cores and this contradicts Kelvin’s thermodynamic laws. Such a decrease in temperature is not to be ascribed to the evaporation of absorbed water, while it depends on the applied load intensity, the application frequency and the total number of cycles performed. Moreover, the cooling phenomenon is accompanied by such mechanical effects as performance enhancement and increasing brittleness, observed through static tests performed at the end of cyclic compression: an increase in the failure strength and the elastic modulus of the material as well as a reduction in max. displacement at failure are seen to occur. The present research takes its starting point in the above observations and aims to investigate the relations between thermal and mechanical effects in concrete, in order to check the possibility to use the variation of temperature at the end of a short duration cyclic compressive test as an indicator for the evaluation of damage, the final aim being to develop in the future a methodology for diagnosis of existing structures.
Fatigue Crack Propagation Monitoring by Acoustic Emission Signal Analysis
Authors: Antonaci Paola , Bocca Pietro G. , Masera Davide
Published: January 2011

The aim of this work is to analyse the mechanical response of the masonry specimens under long-term action by means of cyclic tests. To this end laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino. The Acoustic Emission technique was employed to assess the damage evolution, and the mechanical properties decay in order to evaluate the extent and the evolution of micro and macro-cracking due to cyclic action until structural collapse in masonry blocks and mortar layers.
Enhanced Plasticity of a Mg-8Li Alloy Reinforced with SiC Particles
Authors: Trojanová Zuzanka , Száraz Zoltán
Published: January 2011

Mg8Li alloy reinforced by 7 vol.% SiC particles was processed by a powder metallurgical method. Samples were deformed in tension and compression at temperatures from room temperature up to 300 °C. The yield stress as well as the maximum stress decrease with increasing temperature. Decreasing stresses detected at temperatures higher than 150 °C indicate possible presence of recovery process/es. Estimated activation enthalpy is close to the activation enthalpy for the grain boundary sliding. Strain rate sensitivity was estimated at elevated temperatures. Enhanced plasticity was estimated at 300 °C. Light and scanning electron microscopy revealed the cavitations during the high temperature deformation.
Deformation Behaviour of TRIP Steel Monitoring by in-Situ Neutron Diffraction
Authors: Zrník Jozef , Muránsky Ondrej , Sittner Petr , Oliver E.C.
Published: January 2011

The paper presents results of in-situ neutron diffraction experiments aimed on monitoring the phase evolution and load distribution in TRIP steel when subjected to tensile loading. Tensile deformation behaviour of TRIP steel with different initial microstructures showed that the applied tensile load is redistributed at the yield point and the harder retained austenite (Feγ) bears larger load then ferrite (Feα) matrix. After load partioning is finished, macroscopic yielding comes through simultaneous activity of the martensite transformation (in the austenite) and plastic deformation process in ferrite. The steel with higher volume fraction of retained austenite and less stronger ferrite appears to be a better TRIP steel having efficient structure for better plasticity purpose.
Effect of Alloying Elements on Microstructure and Properties of Fe-Al and Fe-Al-Si Alloys Produced by Reactive Sintering
Authors: Novák Pavel , Šerák Jan , Vojtěch Dalibor , Zelinková Michala , Mejzlíková Lucie , Michalcová Alena
Published: January 2011

Pressureless reactive sintering production of iron aluminides is always connected with high porosity of the product. Previous research showed that silicon reduces the porosity significantly. In this work, the effect of alloying elements (Cu, Ni) on the reactive sintering behaviour and on the porosity of Fe-Al and Fe-Al-Si alloys was studied. Microstructure, phase composition, mechanical and tribological properties were studied as functions of alloy composition.
K-S Relationship Identification Technique by EBSD
Authors: Marinelli M.C. , Moscato M.G. , Signorelli Javier , El Bartali A. , Alvarez-Armas I.
Published: January 2011

This paper focuses on the identification of activated slip system in flat specimens of hot- and cold-rolled UNS S32750 DSS plates subjected to low-cycle fatigue, paying particular attention on the existence of the K-S relationship. Electron Backscattered Diffraction (EBSD) technique was used to determine the local crystallographic properties of both phases. Although 27182 couples of α/γ grains were analyzed, the crystallographic K-S relationships were rarely observed between them. As a conclusion, it was observed that microcracks were mostly nucleated at grain boundaries and rarely at the extrusions.
Experimental Study on the Relation between Elastic and Thermal Deformation of the AZ31 Magnesium Alloy and Composite
Authors: Drozd Zdeněk , Trojanová Zuzanka , Lukáč Pavel
Published: January 2011

The dilatation characteristics of the continuosly cast AZ31 alloy and composite with AZ31 matrix reinforced by SiC nanoparticles were investigated in the temperature range of 20-410 °C. The axis of specimens was either parallel or perpendicular to the casting texture. The linear thermal expansion of the alloy as well as the composite was measured in an argon protective atmosphere using a Netzsch 410 dilatometer. The relative elongation and coefficient of thermal expansion are the main experimental results obtained using dilatometry. The temperature dependence of the elastic modulus can be calculated using analysis of the dilatometry results.
Structural Changes, Evolution of Damage Parameters and Crack Propagation Behaviour in Welded Plastic Pipes
Authors: Lach R. , Hutař Pavel , Vesely P. , Nezbedova E. , Knésl Zdeněk , Grellmann W.
Published: January 2011

The microstructure as well as the local mechanical and fracture behaviour of welded joints in plastic pipes made form polyethylene and material zones outside of the welded joints have been analysed using recording microhardness testing, laser extensometry and crack resistance curve tests. In has been found that the mechanical basic properties and damage kinetics are clearly depending on the welding parameters and additional notching.
Creep of Fe–Al Alloys with Additions of Niobium and Carbon
Authors: Dobeš Ferdinand
Published: January 2011

High-temperature creep of a Fe3Al-type iron aluminide alloyed by niobium and different additions of carbon was studied in the temperature range from 600 to 800 °C. The alloys contained (atomic %) (i) 27.6 Al, 1.15 Nb, 0.19 C and (ii) 27.1 Al, 1.11Nb, 0.76 C (Fe balance). Creep tests were performed in compression at constant load with stepwise loading. Stress exponent and activation energy of the creep rate were determined. Creep resistance of the low-carbon alloy is better at lower temperatures, while the opposite is true at temperature of 800 °C.
Role of Pyrolysis Conditions on Fracture Behaviour of Fibre Reinforced Composites
Authors: Chlup Zdeněk , Černý Martin , Strachota Adam , Dlouhý Ivo
Published: January 2011

Fracture response of matrix prepared by pyrolysis of polysiloxane resin used for composite reinforced by long fibres was the main goal of this contribution. A set of composites with matrix prepared by partial pyrolysis of polysiloxane resin was studied. An effect of pyrolysis temperature on the composite behaviour and fracture resistance was monitored. An optimal procedure of pyrolysis was established. Heat treatment at 1550°C in air atmosphere was conducted on fully pyrolysed matrix to explore its high temperature potential. Determination of reliable parameters characterising microstructural changes in the matrix by instrumented indentation technique was used. Both optical and scanning electron microscopy was employed in microstructural observations and fracture mechanism qualification. Observation of indents and associated cracking caused by microstructural changes as well as 3D surface reconstruction using confocal microscopy was employed.
On the Development of Physically Based Life Prediction Models in the Thermo Mechanical Fatigue of Ni-Base Superalloys
Authors: Antolovich Stephen D. , Amaro Robert L. , Neu Richard W. , Staroselsky A
Published: January 2011

In a world increasingly concerned with environmental factors and efficient use of resources, increasing operating temperatures of high temperature machinery can play an important role in meeting these goals. In addition, the cost of failure of such devices is rapidly becoming prohibitive. For example, in an airline crash airframe and engine manufacturers are, on average, held liable for 1,000,000 euros per fatality excluding the loss of property. Thus there is considerable pressure to make machinery that can operate much more safely at high temperatures. This means that the old ways of guarding against high temperature fatigue failure (e.g. factor of safety, S/N curves, creep life) are no longer acceptable; more reliable, accurate, and efficient means are needed to manage life, durability and risk. In this paper, high temperature fatigue is considered in terms of past successes and current challenges. Particular emphasis is placed on understanding damage mechanisms and their interactions both in terms of scientific interest and technological importance. Materials used in nuclear reactors (e.g. selected steels and solid solution Ni-base alloys) and in hot sections of jet engines (e.g. superalloys) are used as vehicles to illustrate damage evolution and interaction. Phenomenological life prediction models are presented and compared with physics-based damage evolution/interaction models which are based on observed physical processes such as creep/fatigue/environment interactions. It is shown that in many cases, in spite of the emphasis on creep-fatigue interactions, the most damaging forms of damage that occur under thermo-mechanical fatigue (TMF) loading result from the interaction of slip bands with oxidized boundaries.
Reliability and Simulation of Lead-Free Solder Joint Behavior in 3D Packaging Structure
Authors: Nicák Michal , Švecová Olga , Pulec Jiří , Šandera Josef , Szendiuch Ivan
Published: January 2011

This paper deals with behavior of lead-free solder joint applied in 3D electronic packaging structure. There are plenty of factors which influences reliability and life-time of solder compound connection. Type of substrates, selection of materials and process arrangement are the main areas to investigate. The content consists from three main parts. The first deals with introduction of designed test pattern, material, and process arrangement and applied testing methods. Second part continues with ANSYS software simulation of solder interconnections during thermo-mechanical stress tests and third part is aimed to experimental evaluation of results in the comparison to simulated results.
Utilization of Electromagnetic and Acoustic Emission in Monitoring of Fracture of Cementitious Composites
Authors: Koktavý Pavel , Veselý Václav , Keršner Zbyněk , Frantík Petr , Koktavý Bohumil
Published: January 2011

The paper is focused on the utilization of electromagnetic emission (EME) and acoustic emission (AE) phenomena within the non-destructive assessment of damage and fracture in cementitious composites. In the first part of the paper, the EME and AE responses from tests performed in two testing configurations differing considerably in stress distribution are investigated. Typical EME and AE response waveforms appear not to differ from each other for either of the loading configu-rations. However, a significant difference is observed in the frequency distribution of the time lag of the acoustic signal behind the electromagnetic one, which results from the different distribution of the fracture events over the specimen’s volume. In the second part of the paper, the failure process within the specimens in the used testing configurations is assessed from the fracture-mechanical point of view. A numerical 3D analysis of the stress distribution and crack propagation within the specimens was performed by using ATENA non-linear FEM code based on a fracture- and damage-mechanics, and plasticity approach. The predictions of the numerical model are in good agreement with the results obtained by AE/EME experimental measurements. The comparison of the AE/EME records from the tests with the results of performed numerical simulation can help in the understanding, interpretation and exploitation of AE/EME in research into damage to and failure of non-electric quasi-brittle silicate-based building materials.
Behavior of Short Fatigue Crack at Notch Root
Authors: Mizobe Koshiro , Kubota Masanobu , Kondo Yoshiyuki
Published: January 2011

It has been recognized that the threshold stress intensity factor range Kth of a short crack is lower than that of a long crack. The short crack behavior in plain specimen has been studied by many researchers. However, the behavior of a short crack at the root of a long notch is not yet clear. The crack closure behavior is considered to be affected by the constraint at notch root and it is dependent on the length and the root radius of notch. In this study, fatigue tests on specimens with short pre-crack at long notch were done and the difference in crack closure behavior was studied. As a result, short crack effect appeared in any notch root radius. In a sharp notch, the crack opening point easily reached its stable condition after a small amount of crack extension. On the contrary in a dull notch, the opening point was lower than the stable condition and consequently short crack effect lasted in relatively wide range of crack extension. The small crack effect of notched specimen was discussed based on crack closure behavior.
Combined Cycle Fatigue of Ni-Base Superalloy
Authors: Kunz Ludvík , Lukáš Petr , Konečná Radomila
Published: January 2011

Fatigue life of a cast Ni-base superalloy IN 713LC under combined cycle loading consisting of a superposition of low- and high-cycle fatigue at 800 °C was experimentally determined. No measurable effect of combined cycle was found for studied loading conditions. High scatter of fatigue life related to the initiation of cracks on casting defects was observed. Size of the largest defect in a specimen was predicted by the largest extreme value distribution method. The predicted size was compared with fractographic observation of defects resulting in final fatigue failure.
The Role of Grain Orientation and Martensitic Transformation during Propagation of Short Fatigue Cracks in Austenitic Stainless Steel
Authors: Krupp Ulrich , Roth I. , Christ Hans-Jürgen , Kübbeler M. , Fritzen Claus Peter , Scharnweber M. , Oertel C.G. , Skrotzki Werner
Published: January 2011

During high-cycle-fatigue loading of metastable austenitic steel AISI304L, the elastic anisotropy between neighboring grains causes the occurrence of stress peaks at grain boundaries, which again act as crack nucleation sites. This is in particular the case at twin boundaries. Cyclic crack tip plasticity leads to a transformation from  austenite to ´ martensite when different slip bands are activated, alternating during their operation. By means of in-situ fatigue testing in a scanning electron microscope (SEM) in combination with electron back-scattered diffraction (EBSD), the distributions of grain size, geometry, and crystallographic orientation relationship were correlated with the local occurrence of slip, martensite formation and fatigue-crack initiation and propagation. It was shown that the extent of martensite formation ahead of a propagating crack increases with increasing crack length and eventually, due to its higher specific volume, gives rise to transformation-induced crack-closure effects. The variation in the crack-propagation rate depending on the local microstructure was simulated by means of a short crack model, where the displacement fields within the crack, the adjacent plastic zone and the grain boundaries in combination with the martensite volume increase strain are superimposed by means of a boundary-element approach.
Use of Local Approach for Prediction of the Irradiation Effect on Fracture Toughness of Pressure Vessel Steel
Authors: Kotrechko Sergiy , Mamedov Sergii , Dlouhý Ivo , Kozák Vladislav
Published: January 2011

Possibility of use of Local Approach (LA) to prediction of the effect of neutron irradiation on the fracture toughness of pressure vessel steel is discussed. The fundamental of new version of LA to fracture is briefly stated. Specific feature of this version of LA is that Weibull distribution is not used for description of distribution function of fracture probability. Probability of fracture is estimated by modeling of regularities of the crack nucleus formation and instability in polycrystal. Findings on simulation of fracture of reactor pressure vessel steel 2Cr-Mo-V in initial and irradiated states are presented.
Ductile-Brittle Behavior along Crack Front and T-Stress
Authors: Uhnáková Alena , Machová Anna , Hora Petr
Published: January 2011

We present new results of molecular dynamic (MD) simulations in 3D bcc iron crystals with embedded central through crack (001)[110] of Griffith type loaded in mode I. Two different sample geometries of the same crystallographic orientation were tested with negative and positive values of the T-stress, which change the ductile-brittle behavior along the crack front in 3D. This phenomenon is explained in the framework of stress analysis, both on the continuum and atomistic level.
First Principles Study of Ideal Composites Reinforced by Coherent Nano-Fibres
Authors: Černý Miroslav , Pokluda Jaroslav
Published: January 2011

Ab initio calculations of elastic moduli and theoretical tensile strength of composite lamina having continuous nano-fibre reinforcements are performed using pseudopotential approach within density functional theory. Results for molybdenum or tungsten nano-fibres in vanadium or niobium matrices, presented as case studies, reveal that the theoretical strength approaches the value corresponding to the strength of the reinforcement already at about 60-80% atomic concentration of reinforcing fibres in the composite.
Physical and Mechanical Properties of Co3(Al,W) with the L12 Structure in Single and Polycrystalline Forms
Authors: Inui Haruyuki , Oohashi Takashi , Okamoto Norihiko L. , Kishida Kyosuke , Tanaka Katsushi
Published: January 2011

The physical and mechanical properties of Co3(Al,W) with the L12 structure have been investigated both in single and polycrystalline forms. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co3(Al,W) experimentally determined by resonance ultrasound spectroscopy at liquid helium temperature are 15~25% larger than those of Ni3(Al,Ta) but are considerably smaller than those previously calculated. When judged from the values of Poisson’s ratio, Cauchy pressure and Gh (shear modulus)/Bh (bulk modulus), the ductility of Co3(Al,W) is expected to be sufficiently high. Indeed, the value of tensile elongation obtained in air is as large as 28 %, which is far larger than that obtained in Ni3Al polycrystals under similar conditions.
Nucleation on Polymer Nanofibers and their Controllable Conversion to Protective Layers: Preliminary Theoretical Study
Authors: Demo Pavel , Hošková Šárka , Davydova Marina , Tichá Petra , Sveshnikov Alexej , Krňanský Jan , Kožíšek Zdeněk
Published: January 2011

Nanofibers are very promising new type of material with a broad range of possible applications. The new NANOSPIDER technology opens a possibility to produce nanofabrics in an amount large enough for them to start being interesting as a construction material. There are many so-called passive applications of nanotextiles (including different types of filters and protective layers), and active applications, when the active chemical agent is incorporated in their structure. In the present paper, however, the new possible application of nanofabrics is proposed: as a base material on which technically interesting nanoclusters are heterogeneously nucleated. The basic thermodynamics of heterogeneous nucleation on nanofibers is considered. The extreme curvature of nanofibers manifests itself in an energetic barrier of nucleation, which is quite different from a case of nucleation on a flat surface. The expression for Gibbs energy of cluster formation is derived, taking into account the elastic strain resulting from a volume (or shape) changes during nucleation.
Advanced Seismic Countermeasures for Concrete Bridges by Using Polymer in Japan
Authors: Kawakami Makoto , Omata Fujio , Iketani Jun’ichi , Matsuoka Satoru
Published: January 2011

Modern infrastructures such as viaducts, bullet train (Shinkansen) elevated tracks, and subway facilities in addition to houses and buildings were greatly damaged at the Hyogo-Ken Nanbu Earthquake that hit heavily populated urban cities in 1995. As a learning lesson from this earthquake, seismic countermeasures for civil infrastructures have been rapidly reviewed and implemented. In this study, damage of bridge structures due to this strong earthquake was reported and the current effective seismic retrofit of concrete columns and bridge-falling prevention systems by use of concrete polymer composites in Japan were introduced. Two main seismic countermeasure methods were introduced and discussed: Steel plate and fiber jacketing methods for existing reinforced concrete piers/columns, and unseating devices for bridge-falling prevention. Both these countermeasures use epoxy resin as essential component.