bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Deformation Processes in a High-Alloy Cast TWIP Steel Determined by Acoustic Emission and Scanning Electron Microscopy
Authors: Weidner Anja , Vinogradov Alexei , Lazarev Alexei , Biermann Horst
Published: November 2013

High-alloy cast CrMnNi steels exhibit depending on the chemical composition either transformation induced plasticity (TRIP-effect) or twinning induced plasticity (TWIP effect). Whereas the TRIP effect is caused by a martensitic phase transformation from the f.c.c austenitic phase into the b.c.c α-martensite phase via the formation of deformation bands with high stacking fault density the so-called ε-martensite, the TWIP effect is the result of mechanical twinning during plastic deformation. The occurrence of both effects as well as the underlying microstructural processes are strongly affected by the austenite stability, the stacking fault energy and/or the test temperature. However, the onset stress and the kinetics of these deformation processes are still unknown. The in-situ measurement of acoustic emission signals during the plastic deformation of materials is a powerful tool for the investigation of such dynamic microstructural processes and their kinetics. In the present study acoustic emission measurements were performed during tensile deformation at room temperature on a high-alloy cast TWIP steel. The AE investigations were completed by SEM investigations on the deformed specimens. The statistical and cluster analysis of acoustic emission signals reveals different patterns of acoustic emission signals, which are correlated with underlying microstructural processes.
Effect of Heat Treatment on Formation of Al-Al3Ni Hypereutectic Alloys
Authors: Čelko Ladislav , Klakurková Lenka , Slámečka Karel , Smetana Bedřich , Płociński Tomasz , Grzonka Justyna , Žaludová Monika , Lewandowska Malgorzata , Švejcar Jiří
Published: November 2013

The paper deals with the mechanism of eutectic formation in a nickel coated aluminium system after heat treatment. The initial coating was produced from a nickel powder by means of high velocity oxyfuel (HVOF) spraying onto an aluminium sheet substrate. Specimens for investigations were manufactured immediately after the spraying. The specimens were heat-treated using a differential thermal analysis (DTA) apparatus up to the temperature of 700 or 900 °C and then cooled down to room temperature in argon atmosphere with a constant heating and cooling rate of 5 °C / min, under which Al-Al3Ni + Al3Ni hypereutectic alloys were formed within the initial substrate. Two different alloy microstructures consisting of intermetallic layers and coarse eutectic or an ultrafine well-dispersed eutectic were formed. Formation processes and resulting microstructures were studied by means of DTA, metallography, scanning electron microscopy, focused ion beam, energy dispersive microanalysis and image analysis techniques.
Formation of Structurally Complex U-Phase in Al72Pd12.8Co15.2 Alloy
Authors: Černičková Ivona , Svec Peter , Illeková Emília , Janickovic Dusan , Priputen Pavol , Janovec Jozef
Published: November 2013

The U-phase in the Al72Pd12.8Co15.2 alloy was studied under non-equilibrium (casting, differential thermal analysis) and near-equilibrium (long-term annealing) conditions to consider its compositional homogeneity. In the investigation, scanning electron microscopy including energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and differential thermal analysis were used. Contrary to the finding reported for the Al69.8Pd13.8Co16.4 alloy, the results obtained for the investigated Al72Pd12.8Co15.2 alloy did not confirm the compositional heterogeneity of the near-equilibrium U-phase after annealing at 700°C for 2000 h and at 850°C for 500 h.
Using Acoustic Emission in Fracture Monitoring of Cementitious Composites
Authors: Cséfalvay Gabriel , Trčka Tomas , Vodák Ondřej , Sedlak Petr
Published: November 2013

In order to predict the mechanical behavior of a material during its service life, it is important to evaluate its mechanical response under different types of external stresses by studying the initiation and development of cracks and the effects induced by damage and degradation. The non-destructive technique of analysis of acoustic emission, especially with source location and full wave-form analysis, provides excellent results on detecting and identifying initiations sites, cracking propagation and fracture mechanisms of polymer matrix composite, ceramic materials and rocks. For this study, loading tests in two different configurations were provided on specimens of same material and geometry. The significant AE features were monitored during each test and also locations of each AE event were estimated. Results of AE analysis are compared with a finite element analysis of the stress distribution and crack propagation within the specimens.
Microstructure-Related Scratch Resistance and Indentation Creep Behavior of PA6 and PA6 Nanocomposites
Authors: Rybnicek Jan , Lach Ralf , Schöne Jan , Tondl David , Dominguez Silvia Rial , Valek Robert , Grellmann Wolfgang
Published: November 2013

Instrumented scratch test was carried out to determine the scratch resistance of polyamide 6 (PA 6) nanocomposites, where two kinds of nanofillers were tested, both based on silicates: montmorillonite (MMT) and halloysite nanotubes (HNT). In this work the influence of the sliding velocity, normal applied load and time-dependent recovery on the penetration depth and scratch hardness was investigated. Optical microscopy was utilized to determine the width of the scratch grooves and scanning electron microscopy revealed the damage features of the scratched surfaces. Both MNT and HNT nanofillers improve the scratch resistance of PA 6 considerably. As a result of the microstructure of the polymer nanocomposites MNT gives PA 6 a better residual depth resistance while HNT raises its scratch hardness (i.e. reduces the scratch width). Furthermore, via different depth-sensing indentation techniques in the nano-, micro- and macro-range of loading the short-term performance (Martens hardness and indentation modulus) and the time-dependent creep behavior have been analyzed for PA 6 and the PA 6 nanocomposites as a function of applied load and temperature. Additionally, WAXS (wide-angle X-ray scattering) and DSC (differential scanning calorimetry) measurements to establish morphology–property relationships of the materials investigated considering the skin–core structure of the injection molded samples were made.
Production of Al Metal Matrix Composites by the Stir-Casting Method
Authors: Anthymidis Konstantinos , David Kostas , Agrianidis Pavlos , Trakali Afroditi
Published: November 2013

It is well known that the addition of ceramic phases in an alloy e.g. aluminum, in form of fibers or particles influences its mechanical properties. This leads to a new generation of materials, which are called metal matrix composites (MMCs). They have found a lot of application during the last twenty-five years due to their low density, high strength and toughness, good fatigue and wear resistance. Aluminum matrix composites reinforced by ceramic particles are well known for their good thermophysical and mechanical properties. As a result, during the last years, there has been a considerable interest in using aluminum metal matrix composites in the automobile industry. Automobile industry use aluminum alloy matrix composites reinforced with SiC or Al2O3 particles for the production of pistons, brake rotors, calipers and liners. However, no reference could be cited in the international literature concerning aluminum reinforced with TiB particles and Fe and Cr, although these composites are very promising for improving the mechanical properties of this metal without significantly alter its corrosion behavior. Several processing techniques have been developed for the production of reinforced aluminum alloys. This paper is concerned with the study of TiB, Fe and Cr reinforced aluminum produced by the stir-casting method.
High Temperature Fatigue Strength and Quantitative Metallography of an Eutectic Al-Si Alloy for Piston Application
Authors: Konečná Radomila , Fintova Stanislava , Nicoletto Gianni , Riva Enrica
Published: November 2013

Eutectic Al-Si alloys are typically used for the production of internal combustion engine pistons. A high-cycle, high-temperature fatigue characterization of AlSi12 alloy performed using specimens extracted from actual pistons is presented and discussed. Fatigue strength at 107 cycles were obtained at test temperatures of 250 °C, 300 °C and 350 °C. The fatigue strength reduction was quantified. The micro structural features were quantified by quantitative metallography and fatigue fracture surfaces inspected to identify the initiation causes.
Effects of Different Microstructure on Resistance of EA4T Railway Axle Steel of Equal Strength to Fatigue Crack Growth
Authors: Černý Ivo , Linhart Václav
Published: November 2013

Fatigue crack growth (FCG) rates in an EA4T railway axle steel heat treated by two different methods in near threshold and stable regions of growth were evaluated. Quite significant differences were observed, when the obtained results were compared with those published in the literature. Participation of the laboratory in an Exova (GE Aviation) FCG measurement qualification round robin programme with very good results practically excluded errors in the experimental methodology used. Strength of the two different evaluated series of the experimental material was equivalent. Nevertheless, there were substantial differences in fatigue crack growth rates, about 5-times in stable FCG region and even more than 10-times in the near threshold region, when oil quenching and air hardening treatments were compared. The differences were explained by different microstructures of the two groups of materials. Some minor differences between the character of the FCG curve in the threshold region evaluated using SEN(B) and M(T) specimens, published in the literature, are discussed considering crack closure phenomenon.
Investigation of the Microstructure Factors Affecting the Brittle Fracture Initiation of Pre-Cracked Charpy-Type Samples of VVER-1000 RPV Steel
Authors: Kuleshova Evgenia A. , Artamonov Maxim A. , Erak Artem D.
Published: November 2013

The correlation between fracture toughness parameter KJc and cleavage initiation distance (CID) for the three point bending (3PB) pre-crecked Charpy type specimens of VVER-1000 reactor pressure vessel base and weld metals was observed. Two types of brittle fracture origin sites were found: nonmetallic inclusions and grain or subgrain boundaries. It was shown that KJc values are shifted to the higher temperature area for weld metal with respect to base metal data. In case when the initiation origin is grain or subgrain boundary, the KJc values are higher for base metal at the same CID values. This indicates the higher crack resistance of base metal.
Microstructure and Mechanical Properties of Rapidly Solidified Al-Fe-X Alloys
Authors: Voděrová Milena , Novák Pavel , Marek Ivo , Vojtech Dalibor
Published: November 2013

Rapidly solidified aluminium alloys have many interesting properties such as higher thermal stability and strength, when compared with conventional cast alloys. Due to these properties, RS alloys seem to be prospective for using in automotive or aircraft industry. Aim of this work was to compare the differences in microstructure of alloys containing Fe, Ni and Cr which were prepared by different solidification rate. Alloys were prepared by melt spinning, melting with follow-up quenching into the water and by conventional casting with pouring into brass mould. Microstructure of prepared alloys was investigated by scanning electron microscope; phase composition was determined by x-ray diffraction. In this experiment, microhardness was measured in the initial state of all types of alloys; rapidly solidified alloys were also annealed to determine thermal stability by microhardness measurement. Results indicate that higher solidification rate refines the microstructure which is composed of supersaturated solid solution of alloying elements in aluminium and stable and meta-stable intermetallic phases. Hardness of the alloys increases and microstructure refines with solidification rate.
Autowave Features of Plastic Deformation by Ductile Fracture
Authors: Orlova Dina , Danilov Vladimir , Zuev Lev B.
Published: November 2013

The kinetics of fracture was examined for a wide range of metallic materials. Using speckle photography technique, displacement vector fields were recorded for the deforming sample. The deformation localization is an autowave process, which manifests macroscopic inhomogeneities from yield point to necking. This involves a changeover in the autowave types: phase autowave stationary dissipative structure propagating autowave collapse of autowave. The loading curves obtained for all studied materials have a similar autowave pattern emerging at the pre-fracture stage, no matter what is crystalline or microstructural state of material. Using experimental data on the kinetics of autowave collapse, the space-time coordinates of failure can be predicted for the object under load long before symptoms of fracture are detected visually.
Planar Defects and Dislocations in C40 and FCC Lattices
Authors: Paidar Vaclav
Published: November 2013

Atomic planes at three different positions ABC form the stacking along the <111> directions in the FCC lattice and similarly along the <0001> hexagonal axis in the C40 structure in transition metal silicides. However, the structures of silicides are constituted of several stacking of identical atomic planes at four different positions: AB in C11b structures of e.g. MoSi2, ABC in C40 structures of e.g. VSi2 and ABDC in C54 structures of e.g. TiSi2 disilicides. The occurrence of the fourth position essentially influences the properties of defects and consequently the mechanical properties of C40 materials.
Influence of Heat Treatment of High-Speed Steel on its Microstructure, Hardness and Fracture Toughness
Authors: Cajner Franjo , Leskovšek Vojteh , Pustaić Dragan
Published: November 2013

The correlation between fracture toughness, hardness and microstructure of vacuum heat-treated high-speed steel AISI M2 was investigated. Our intention was to investigate the influence of microstructural parameters such as the volume fraction of undissolved eutectic carbides, their mean diameter, the mean distance between the carbides, as well as the volume fraction of retained austenite in the matrix, on the above mentioned mechanical and fracture properties. The experimental investigations were performed on the high-speed steel. This steel had the following chemical composition (mass content in %): 0.89% C, 0.20% Si, 0.26% Mn, 0.027% P, 0.001% S, 3.91% Cr, 4.74% Mo, 1.74% V and 6.10% W.
Fatigue Characteristic of Aluminium Alloy 2024 under Cyclic Bending with the Controlled Energy Parameter
Authors: Marcisz Ewa , Marciniak Zbigniew , Rozumek Dariusz , Macha Ewald
Published: November 2013

In this paper the results of fatigue tests under cyclic bending of 2024 aluminium alloy with amplitude of strain energy density parameter control are presented. Based on these tests, energy fatigue characteristic of the tested material was elaborated.
Influence of the Titanium and its Alloys Microstructure on the Fatigue Crack Paths
Authors: Rozumek Dariusz , Hepner Maria , Faszynka Sebastian
Published: November 2013

The paper contains the results of tests on the fatigue crack growth in titanium Gr.1 and Ti-6Al-4V as well as Ti-3Cu titanium alloys. The chosen materials contained titanium but their structure was different. Plane specimens with the stress concentrators in form of one-sided sharp notches were tested. Influence of the microstructure on the crack paths in plane specimens was observed.
Fatigue Fracture of Turbine Blades: Case Studies
Authors: Kianicová Marta , Pokluda Jaroslav
Published: November 2013

Fracture surfaces of two sets of rotor blades failed after strong testing procedures of aircraft engines in the test-stand are investigated by means of SEM. While the process of fatigue fracture in the first set of blades did not reveal any defect features, both the initiation and propagation of fatigue cracks was strongly influenced by casting defects.
Bending Fatigue Behaviour of Diffusion and Thermal Barrier Coating Systems
Authors: Slámečka Karel , Němec Karel , Čelko Ladislav , Kianicová Marta , Horníková Jana , Pokluda Jaroslav , Švejcar Jiří
Published: November 2013

Room temperature fatigue behaviour of two variants of diffusion aluminide coatings and conventional air plasma sprayed CoNiCrAlY + ZrO2-Y2O3 thermal barrier system, which were deposited on a cast nickel-based supperalloy substrate, was studied under symmetrical bending loading regime. The study elucidates the differences in a fatigue crack initiation micromechanism with respect to applied stress level and its impact on the fatigue performance of studied coating systems.
Nanoindentation and Microstructural Study of Cu-Co Alloys after Severe Plastic Deformation
Authors: Buršík Jiří , Král Petr , Svoboda Milan , Dvořák Jiří , Sklenička Václav
Published: November 2013

In this work we studied the microstructure evolution due to equal channel angular pressing of Cu-2wt.%Co alloy after various heat treatments. Several subsequent passes were performed at room temperature. The microstructure was characterized using electron backscatter diffraction technique in a scanning electron microscope. Local mechanical properties were studied by means of nanoindentation experiments using a Hysitron PI85 picoindenter operated inside an electron microscope.
Mechanical Aspects of Plastic Deformation of Nickel Based Superalloy
Authors: Nowotnik Andrzej , Rokicki Paweł , Pędrak Paweł , Kotowski Slawomir , Sieniawski Jan , Mrówka-Nowotnik Grazyna
Published: November 2013

Variations of a true stress vs. true strain illustrate behaviour of materials during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests. Results of these tests provide crucial information pertaining to the stress values which are necessary to run deformation process at specified temperature and cooling rate. Uniaxial compression tests at temperatures below the γ solvus were conducted on nickel based superalloy CMSX-4, to study the effect of temperature and strain rate on its flow stress. On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (σpl -T i σpl - ἐ) and compression data were used to determine material constants. These constants allow to derive a formula that describes the relationship between strain rate, deformation temperature and true stress.
Fatigue Cracking and Acoustic Emission Regularities in Metals: Crack Origination and Growth
Authors: Shanyavskiy Andrey , Banov Mukharbiy
Published: November 2013

Specimens of Al-and Ti-alloys and turbine blades of Ni-based alloy were considered in the case of crack origination at the surface, subsurface, and at the inner surface of turbine blades. Aircraft structures such as hydrocylinders of Al-based alloy and landing gear of high-strength-steel were also considered. There was used acoustic emission (AE) monitoring to fix moment of crack occurring and, then, analyzing its growth. Fracture surface features appearance was compared with AE-signals regularities based on fractographic analyses. To indicate the crack origination moment it was introduced α-criterion. This criterion characterized drastically increase in summarized AE-signals appearing in dependence on cyclic loads number. During crack propagation, there was used Elber-portion of opened crack to register AE-signals in cyclic loads. It was demonstrated crack increment in unloading portion of cyclic loads with fatigue striations formation. Two aircraft structures of hydrocylinders and shock strut of landing gear were tested on the special test facilities and AE-monitoring was conducted. Effectiveness of α-criterion using for crack registration in the high-cycle fatigue regime was demonstrated applicably to crack appearance on the internal surface and subsurface. The discovered dependences of summarized AE-signals on number of cycles were compared with fracture surface patterns and briefly discussed.
Deformation Behaviour of Asymmetrically Fatigue Cycled Metallic Materials
Authors: Dutta Krishna , Ray Kalyan Kumar
Published: November 2013

This investigation aims to examine the influence of asymmetric fatigue cycling on the nature of strain accumulation and its influence on post fatigue tensile properties of three materials namely 6063 aluminum alloy, interstitial free steel and α-brass. The results highlight that strain accumulation provides improvement in yield and tensile strength of the investigated materials, with associated reduction in their %uniform elongation. However, %total elongation is found to be strong function of post-necking elongation which is governed by substructural features of the ratcheted material. Increase in strength values has been correlated with increased cyclic damage of the materials.
An Effect of the First Non-Singular Term of the Williams Asymptotic Expansion to the Stability of the Bi-Material Orthotropic Notch
Authors: Profant Tomáš , Klusák Jan , Ševeček Oldřich , Kotoul Michal , Hrstka Miroslav , Marcián Petr
Published: November 2013

The domain of the generalized stress intensity factors dominance ahead of the notch tip can be rather small with respect to the length of the perturbing cracks initiated from the tip of the notch. Thus the non-singular terms of the stress asymptotic expansion at the notch tip would play an important role in the notch tip stability. Following the procedures dealing with complex potential theory and path-independent two-state integrals developed for the singular stress analysis of the stress concentrators one can evaluate their magnitude and include them to the energy release rate of the preexisting crack initiated from the notch tip applying the matched asymptotic procedure. The presented analysis should lead to better understanding of the notch stability process and precising of the notch stability criteria.
Fatigue Crack Growth of Thin Wall Magnesium AZ91 Alloy Cast
Authors: Brynk Tomasz , Romelczyk-Baishya Barbara , Jastrzębska Anna , Nowak Katarzyna , Pakiela Zbigniew
Published: November 2013

The paper presents the results of fatigue crack growth rate tests performed in magnesium AZ91 alloy cast of different wall thicknesses. Due to the limited size of investigated cast the tests were carried on mini-samples of 4x4x1 mm gauge section dimensions. The samples were cut from the 5, 10 and 30 mm thick walls. The optical displacement measurement technique, namely Digital Image Correlation, and inverse method were applied for determination of the stress intensity factors and the crack tip coordinates during tests. There were also performed uniaxial tensile tests in mini-samples for the determination of the mechanical properties changes related to different cast thicknesses. The relation between the microstructure and the results of mechanical tests was discussed.
Deformation and Fracture of a Magnesium Alloy at Elevated Temperatures
Authors: Lukáč Pavel , Donič Tibor , Chalupová Mária , Palček Peter , Trojanová Zuzanka , Tillová Eva , Rusz Stanislav , Bastovansky Ronald
Published: November 2013

Magnesium alloy EZ10 was deformed in tension at temperatures from room temperature up to 400 °C with an initial strain rate of 2.7x10-3 s-1. Deformation tests showed a rapid decrease of the tensile yield strength at temperatures higher than 300 °C. Microstructure of the deformed samples was analysed with light microscope. Fracture mechanisms were estimated using scanning electron microscopy.
Short Crack Growth Behavior in Ferrite-Bainite Dual Phase Steels
Authors: Kumar Ashok , Ray Kalyan Kumar
Published: November 2013

The effect of bainite content on the short crack growth behavior of three ferrite bainite dual phase steels has been examined using a rotating bending machine together with examinations of the microstructural constituents associated with the fatigue crack path. The magnitude of ΔKthsc for ferrite bainite dual phase steels, in general, is found to increase with increasing amount of bainite. Critical examinations of the crack paths indicate that it is inter-granular for steels with < 70% bainite while it is intra-granular for steels containing > 70% bainite.
Transition from Straight to Fractal Cracks due to Projectile Penetration
Authors: Halász Zoltán , van Steeden Frank , Kun Ferenc
Published: November 2013

We present a theoretical study of the fracture of two-dimensional disc-shaped samples due to projectile penetration focusing on the geometrical structure of the crack pattern. The penetration of a cone is simulated into a plate of circular shape using a discrete element model of heterogeneous brittle materials varying the speed of penetration in a broad range. As the cone penetrates a destroyed zone is created from which cracks run to the external boundary of the plate. Computer simulations revealed that in the low speed limit of loading two cracks are generated with nearly straight shape. Increasing the penetration speed the crack pattern remains regular, however, both the number of cracks and their fractal dimension increases. High speed penetration gives rise to a crack network such that the sample gets fragmented into a large number of pieces. We give a quantitative analysis of the evolution of the system from simple cracking through fractal cracks to fragmentation with a connected crack network.
The Effect of Temperature on the Course of Refractory Castables Cracking
Authors: Suwak Renata , Wojsa Józef
Published: November 2013

Factors determining the durability of a material include among others its thermal shock resistance, as a non-homogenous temperature field may trigger the formation and propagation of cracks. To evaluate thermal shock resistance by means of one of the resistance criteria: the Rst or R4 parameter, it is necessary to know the work of fracture (γWOF), which is determined in a cracking test. Technical testing conditions influence the recording of crack propagation in a material sample. Ordinary and refractory castables are a group of materials in which the effect of temperature on the course of their cracking is among others related to the presence of deformations, internal stresses and cracks. Tests were performed for mullite, andalusite and boxite doped chromia castables, having known phase compositions, for which the temperature of liquid phase appearance in the matrix was calculated. A considerable increase in the value of castables γWOF at 900°C was noted compared to the values at 300°C and 600°C. In the group of the examined castables the highest γWOF value was obtained for andalusite castable. The applied methods of testing enabled simultaneous presentation of crack propagation in terms of energy (load vs. deformation) and kinetics (load vs. time).
Temporal and Spatial Evolution of Bursts in a Fiber Bundle Model of Creep Rupture
Authors: Danku Zsuzsa , Kun Ferenc
Published: November 2013

We present a theoretical study of the creep rupture of heterogeneous materials based on a fiber bundle model which provides a direct connection between the microscopic fracture mechanisms and the macroscopic time evolution. In the model, material elements fail either due to immediate breaking or undergo a damage accumulating ageing process. We found that on the micro-level the competition of the two failure modes gives rise to bursts of breakings with power law distributed size and waiting time between events. We demonstrate that approaching macroscopic failure the system accelerates which can be fully described as a non-homogeneous Poissonian process for long range load sharing, however, when localization occurs breaking events get clustered. Bursts are composed of sub-avalanches which lead to a non-trivial temporal shape comparable to measurements. The pulse shape proved to be sensitive to the range of load sharing.
The True Shape of Persistent Slip Markings in Fatigued Metals
Authors: Polák Jaroslav , Man Jiří , Kuběna Ivo
Published: November 2013

Persistent slip markings (PSMs) were experimentally studied in 316L steel fatigued to early stages of the fatigue life. High resolution SEM, combined with focused ion beam (FIB) technique and atomic force microscopy (AFM) were used to assess the true shape of PSMs in their early stage of development. General features of PSMs in fatigued metals are extrusions and intrusions. Their characteristic features were determined. They were discussed in relation with the theories of surface relief formation and fatigue crack initiation based on the formation, migration and annihilation of point defects in the bands of intensive cyclic slip - persistent slip bands (PSBs)
Thermodynamics of Dislocation Pattern Formation at the Mesoscale
Authors: Gröger Roman
Published: November 2013

We introduce a mesoscopic framework that is capable of simulating the evolution of dislocation networks and, at the same time, spatial variations of the stress, strain and displacement fields throughout the body. Within this model, dislocations are viewed as sources of incompatibility of strains. The free energy of a deformed solid is represented by the elastic strain energy that can be augmented by gradient terms to reproduce dispersive nature of acoustic phonons and thus set the length scale of the problem. The elastic strain field that is due to a known dislocation network is obtained by minimizing the strain energy subject to the corresponding field of incompatibility constraints. These stresses impose Peach-Koehler forces on all dislocations and thus drive the evolution of the dislocation network.
Complex Evaluation of Fatigue Tests Results of Plain C30/37 and C45/55 Class Concrete Specimens
Authors: Šimonová Hana , Kucharczyková Barbara , Havlíková Ivana , Seitl Stanislav , Keršner Zbyněk
Published: November 2013

The aim of this paper is to summarize basic fatigue parameter values obtained for plain C30/37 and C45/55 class concrete specimens during dynamic tests. Selected approximation curves for relative mechanical-fracture parameter values over time − compressive cube strength, modulus of elasticity, effective fracture toughness and specific fracture energy − were used to determine the most accurate fatigue parameter values corresponding to the age of specimens at the time dynamic tests were performed. Three models are used for standard description of the S−N curve: the Weibull and Gumbel models developed by Castillo et al. as well as the power law equation. Fatigue properties were obtained from three point bending tests conducted on beam specimens (100×100×400 mm nominal size) with a central edge notch (depth 10 mm).
The Role of Second Phase Intermetallic Precipitates in Fatigue Fracture Mechanism for Aluminum Alloy AW 7075
Authors: Chruścielski Grzegorz , Korusiewicz Leszek
Published: November 2013

This paper presents the results of durability tests of AW7075 aluminium alloy, which is widely used in producing high-durable and particularly reliable constructions in aeronautical and automotive industries. The plain-strain fracture toughness, depending on the orientation of fracture direction with respect to the rolling direction of the material, and the fatigue crack growth rate were determined. Based on scanning electron microscope (SEM) studies the two stages of fatigue fracture are shown: the first is plastic striations and the second is phenomenon of connecting micropores that were formed around intermetallic second phase particles. As a results of research a model of fatigue crack for the second stage is presented.
Lattice-Spring Modeling of Graphite Accounting for Pore Size Distribution
Authors: Morrison Craig N. , Jivkov Andrey P. , Smith Gillian , Yates John R.
Published: November 2013

Lattice models allow length scale dependent micro-structural features and damage mechanisms to be incorporated into analyses of mechanical behaviour. They are particularly suitable for modelling the fracture of nuclear graphite, where porosity generates local failures upon mechanical and thermal loading. Our recent 3D site-bond model is extended here by representing bonds with spring groups. Experimentally measured distributions of pore sizes in graphite are used to generate models with pores assigned to the bonds. Microscopic damage is represented by failure of normal and shear springs with different criteria based on force and pore size. Macroscopic damage is analysed for several loading cases. It is shown that, apart from uniaxial loading, the development of micro-failures yields damage-induced anisotropy in the material. This needs to be accounted for in constitutive laws for graphite behaviour in FEA of cracked reactor structures.
Effects of Lubrication in Ferrite Rolling of Interstitial Free Steel
Authors: Kong Ning , Tieu Kiet , Zhu Hong Tao , Zhu Qiang , Gandy Peter
Published: November 2013

Ferrite rolling of interstitial free steel strip in the temperature range 650-850°C can effectively reduce furnace costs and scale formation as a result of lower strip reheating temperatures. Different lubrication conditions of lubricating oil, solid lubricant and dry condition were used during ferrite rolling tests of thin interstitial free steel strip on a 2-high Hille 100 experimental rolling mill. Different rolling speed, rolling temperature and reductions were applied to the rolling process. The rolling force and roll roughness were affected by the lubrication conditions and rolling parameters. Solid lubricant indicated an improved performance in terms of the roll roughness, as well as the oxidation property of the strip surface during ferrite rolling.
Prediction of Ferrite-Martensite Dual-Phase Steels Mechanical Properties by Use of Artificial Neural Networks
Authors: Ghiami Amir , Khamedi Ramin
Published: November 2013

This paper presents an investigation of the capabilities of artificial neural networks (ANN) in predicting some mechanical properties of Ferrite-Martensite dual-phase steels applicable for different industries like auto-making. Using ANNs instead of different destructive and non-destructive tests to determine the material properties, reduces costs and reduces the need for special testing facilities. Networks were trained with use of a back propagation (BP) error algorithm. In order to provide data for training the ANNs, mechanical properties, inter-critical annealing temperature and information about the microstructures of many specimens were examined. After the ANNs were trained, the four parameters of yield stress, ultimate tensile stress, total elongation and the work hardening exponent were simulated. Finally a comparison of the predicted and experimental values indicates that the results obtained from the given input data reveal a good ability of the well-trained ANN to predict the described mechanical properties.
A Misorientation Dependent Criterion of Crack Opening in FCC Single Crystal
Authors: Huynh Nam N. , Lu Cheng , Michal Guillaume , Tieu A. Kiet
Published: November 2013

This paper proposes a criterion for crack opening in FCC single crystals based on analyses of lattice orientation and interface energy of two adjacent crystals in a crystal plasticity finite element model (CPFEM). It also demonstrates the implementation of the criterion in Abaqus/Standard to simulate crack initiation and propagation in single-edged notch single crystal aluminium samples. Elements in the FEM mesh that have crystalline structures satisfying the crack opening criterion are removed from the mesh at the end of every loading step and FEM analyses are restarted on the new mesh in the next loading step. Removed elements effectively act as voids in the material due to crack nucleation. Similarly, the coalescence of newly removed elements at the end of a loading step with the existent ones simulates crack growth in the material. Two advantages of this approach are noted. Firstly, crack nucleation and its subsequent growth in the material is simulated solely based on lattice evolution history in the material without any presumptions of crack paths or regions where cracks are likely to occur. Secondly, as the criterion for crack nucleation is evaluated based on, and thus changes with, the lattice evolution during loading, a predefined energy criterion for crack opening, which could be erroneous, is avoided. Preliminary results of void nucleation and void growth around the notch tip in Cube and Brass oriented samples using CPFEM modelling appear to agree with molecular dynamics simulations of void growth in FCC single crystals.
Study on the Dynamic Recrystallization of Austenite in the Isothermal Compression of 300M Steel
Authors: Liu Yin Gang , Li Miao Quan
Published: November 2013

The 300M steel was isothermally compressed on a Gleeble-3500 simulator at the deformation temperatures ranging from 1123 K to 1473 K, the strain rates ranging from 0.1 s-1 to 25.0 s-1 and a strain of 0.51. The morphology of austenite grains in the isothermally compressed 300M steel was observed using an OLYMPUS PMG3 microscope. The experimental results show that the deformation temperature and strain rate have an interaction effect on austenite grains in the isothermally compressed 300M steel. Dynamic recrystallization occurs more easily at high deformation temperature and low strain rate. Dynamic recrystallization occurs completely and the coarse grains occur at the deformation temperature above 1413 K. The austenite grain size increases as the deformation temperature increases while it decreases as the strain rate increases.
Design, Fabrication and Properties of Textured Self-Lubricated Tools in Dry Cutting
Authors: Deng Jian Xin , Wu Ze , Lian Yun Song
Published: November 2013

Textured self-lubricated tools were designed and fabricated. Dry cutting tests were carried out on with these self-lubricated tools and a conventional tool. The tool wear and the friction coefficient at the tool chip interface were measured. It was shown that the tool wear and the friction coefficient of the textured self-lubricated tools were reduced compared with that of the conventional tool. Two mechanisms responsible were found, the first one is explained as the formation of a lubricating film with low shear strength at the tool-chip interface, which was released from the texturing and smeared on the rake face, and served as lubricating additive during dry cutting; the other one was explained by the reduced contact length at the tool-chip interface of the textured tools, which contributes to the decrease of the direct contact area between the chip and rake face. It is suggested that the using of textured self-lubricated tools is an effective way to reduce the tool wear in dry cutting.
Optimization of Cutting Parameters for End Milling AlSi/AlN Metal Matrix Composite Using the Taguchi Method
Authors: Tomadi Siti Haryani , Ghani Jaharah A. , Che Haron Che Hassan , Daud Abdul Razak
Published: November 2013

In this paper, the optimization of cutting parameters is investigated to assess surface roughness and cutting force in the end milling of AlSi/AlN metal matrix composite. Eighteen experiments (L18) with five factors (cutting speed, feed rate, depth of cut, volume of particle reinforcement, and type of coated insert) were performed based on Taguchi designs of the experiment method. Two types of coating (TiB2 and TiN/TiCN/TiN) of the carbide cutting tool were employed to machine various volumes of AlN particle (5%, 7% and 10%) reinforced AlSi alloy matrix composite under dry cutting conditions. Signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were applied to investigate the optimum cutting parameters and their significance. The S/N analysis of the obtained results showed that the optimum cutting conditions for the cutting force were; A2 (triple coating of the insert), B2 (cutting speed: 200m/min), C1 (feed rate: 0.6mm/tooth), D1 (axial depth: 0.6mm) and E1 (5% reinforcement). At the mean time, the optimum cutting conditions for surface roughness were; A1 (single coating of insert), B3 (cutting speed: 250m/min), C2 (feed rate: 0.75mm/tooth), D1 (axial depth: 0.6mm) and E1 (5% reinforcement).The study confirmed that, with a minimum number of experiments, the Taguchi method is capable of determining the optimum cutting conditions for the cutting force and surface roughness for this new material under investigation.
Fabrication of a Hybrid Aspheric Lens Using Glass and Thermosetting Polymer Molding Technique
Authors: Huang Chien Yao , Chen Chun Chieh , Chang Chia Rong , Chou Hsiao Yu , Lin Yu Wei , Hwang Chi Hung
Published: November 2013

This study developed a precise hybrid optical lens (PHOL) that included polymer and glass materials. Although glass offers superior anti-thermal, anti-environmental, anti-scraped corrosion resistance and optical properties than polymer materials, it is difficult to fabricate glass materials. Therefore, it is difficult to obtain a high-accuracy aspheric glass lens. This paper presents the fabrication of a PHOL that combined aspheric polymer and glass bases using a glass-molding technique. The PHOL can be used to reduce aberration errors in optical systems using two materials. The PHOL maintains the advantages of glass materials, and the cost of aspheric polymer is lower than that of the aspheric glass layer. Thermosetting polymer was used as the aspheric part in this study. Compared to UV-curable polymer, thermosetting polymer has higher thermal stability, and the molds are not limited by glass materials, which must be transmissible by UV light. First, a glass sphere lens was used as a base of the PHOL. Subsequently, the ultra-precise diamond turning technique was used to fabricate the mold with an aspheric profile. During the molding process, the thermosetting polymer was formed into an aspheric layer and covered on the glass base. The PHOL of 11.2 mm in diameter was obtained using controlled cooling. Finally, the surface accuracy (PV) of the PHOL was less than 0.5μm, has been successfully fabricated in this study.
Contact Analysis of Tooth Surface in Gear Meshing Based on Infrared Ray Imagery
Authors: Nakajima Kouji , Hirogaki Toshiki , Aoyama Eiichhi , Nagata Masaki
Published: November 2013

Improving accuracy ofthe gear tooth surface has become an important challenge, because the toothsurface accuracy greatly influences vibration of gears. However, for the spiralbevel gear, the tooth surface accuracy is considered to be very difficult toevaluate because the geometrical theory is difficult. Generally, the managementof tooth surface accuracy has conventionally been substituted by the toothsurface contact evaluation with red lead, which is a kind of paint. However,the results of visual examinations are too subjective. We therefore focused onthe infrared ray imagery to investigate the gear tooth meshing. In this research,a high response infrared thermography was used to estimate the tooth contact ofa hypoid gear under running conditions. Specifically, we looked at the increasein temperature on the tooth surface caused by gear meshing. The results clearlyshowed that the temperature was affected by load, sliding speed between toothsurfaces, and the average peripheral speed of tooth surface. We also proposedan equation that predicts tooth surface temperature rise and showed its utility.Thus, the proposed method effectively evaluates the tooth surface accuracy ofhypoid gear.
On Generation of Micro-Feature on Silicon with an Industrial Laser
Authors: Mon Thet Thet , Chuen Yap Tze , Bidin Noriah , Mahadzir
Published: November 2013

Generation of a micro feature on mono-crystalline silicon surface using an industrial laser is presented. The main objective is to investigate the capability of the industrial laser, Nd:YAG, in generating a micro-feature on silicon surface. The unpolished silicon surface was irradiated with the Nd:YAG laser beam of controlled pulse width and power. In phase 1, the irradiations were done without incorporating an assist gas into the process. In phase 2, the compressed air maintaining its pressure at 4 bars, was supplied as an assist gas during laser irradiation. Design of experiment was adopted to systematically determine the number of experimental runs in each phase as well as to fine tune the important parameters through the statistical analysis. Laser-generated structures were observed under scanning electron microscope. Micrographs reveal that most of the features appear to be cone-like with an almost true circle at the base. The diameter of the cone is found to be as small as 200 m. The quality of such micro-features and analysis of the effect of the process parameters on the feature quality show that in general, laser pulse width has more appreciable effect than the laser power on the micro-feature geometry as well as quality. Laser irradiation without the assist gas produces better results in terms of a feature size
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Investigation of Characteristics of Ni-P-PTFE Coating on Optical Molds
Authors: Cheng Yuan Chieh , Wang Pei Jen , Hsu Wei Yao
Published: November 2013

In recent years, plastic lenses have been widely adopted for optical components in consumer products because of the significant improvement in microelectronics technology. Currently, plastic lenses are mass produced for applications in 3G/4G smart mobile phones, digital still/motion cameras, and micro-projectors. During mass production, one of the key factors in costs reduction is to enhance lifetime of the molding tools. Electroless nickel phosphorus plating (Ni-P) is the most popular mold and die surface treatment process because of its excellent machinability in single-point diamond turning process. However, Ni-P plated molds cannot sustain satisfactory tool life under the adhesion forces between the mold surface and the molten plastic. In this study, a novel material made of a nickel-phosphorus-polytetrafluoroethylene (Ni-P-PTFE) compound was plated electrolessly on experimental dies to study relevant properties. Since Ni-P-PTFE exhibits strong anti-adhesion properties, it is noted to improve the lifetime of the dies. After machining of the dies, the surface roughness was measured by confocal microscopy together with the particle size being measured by scanning electron microscopy (SEM). In conclusion, the adhesion phenomenon is interpreted via hydrophobic contact angles showing that hydrophobic contact angle of Ni-P-PTFE surfaces is smaller when compared to Ni-P surfaces which infers the anti-adhesion properties of Ni-P-PTFE materials.
Intelligentized Technologies for Welding Manufacturing
Authors: Chen Shan Ben , Ye Zhen , Fang Gu
Published: November 2013

This paper presents some newest and potential developments on artificial intelligent technologies for welding manufacturing process in Shanghai Jiao Tong University (SJTU), which contains multi-information acquirement and fusion processing of arc welding dynamical process; Intelligent computing for welding process; Intelligent control methods for welding process and quality control; artificial intelligent technologies for welding robot systems and robotic welding process; and some application in welding engineering. The ideas of intelligentized welding manufacturing technology (IWMT) and intelligentized welding manufacturing engineering (IWME) are presented in this paper for systematization of intending researches and applications on intelligentized technologies for modern welding manufacturing.