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The results of the study of fine structure of continuous casted bars of oxygen-containing copper produced by casting in the belt water-cooled crystallizer are presented. The character of fractures of samples of copper cast bars in different directions depending on technological parameters of continuous casting was investigated. For determination of chemical composition of samples of cast bars and detection of presence of possible impurities in copper the microspectral analysis was carried out. It is shown that removing of sources of gasing of copper melt leads to decreasing of volume fraction of eutectic Cu-Cu2O, discontinuity flaws and pores in the structure of cast bars. [ABSTRACT FROM AUTHOR]

The probability of failure of a load bearing steel member is investigated using a new type of global sensitivity analysis subordinated to contrasts. The main objective of the probability-oriented sensitivity analysis is structural reliability. The structural reliability methodology uses random variables as inputs. The subject of interest is the identification of those random variables that are most important when the limit state of a steel bridge member is reached. The limit state is defined by the occurrence of brittle fracture, which results from stress changes caused by multiple repeated loads. The propagation of a single-edge crack from initial to critical size is analysed using linear fracture mechanics. The failure probability and sensitivity indices are calculated using sampling-based methods. The sensitivity indices are estimated using double- nested-loop simulation of the Latin Hypercube Sampling method. New findings indicate that interaction effects among input variables strongly influence the probability of failure especially at the beginning of the operating period. [ABSTRACT FROM AUTHOR]

The analysis of the post-cracking behavior of a large plate cast of fiber concrete shows a large variability due to the fiber alignment and dispersion. Therefore, one can expect, that the bending strength and other material parameters depend on the position in the plate. This means that the position the samples for testing are taken from may play a significant role in assessing the mechanical properties and strength of composite materials. Often, the investigation of fiber concrete properties have been performed by testing small size beams. The results can be influenced by the boundary restrictions, such as wall-effect, which influences the fiber distribution. In this study the four-point bending strength of beams cut out of a large plate was investigated, the results represent the local strength of the plate in this particular place. The fiber orientation and distribution have been evaluated by X-ray Computed Tomography and Image Analysis Method. The results of the experiments have shown that the position of the beam inside of a large-size plate has a strong influence on the mechanical properties and post-cracking behavior. The analysis of the obtained outcomes proposes the following conclusions: the beams that were located near the edges of the formwork have shown a strong, strain-hardening behavior, and the beams that were located on the way of the casting bucket (a zone of the high turbulence/perturbation/disturbance) have shown a weak, strain-softening behavior. [ABSTRACT FROM AUTHOR]

Zigana Tunnel is a new constructing tunnel, which will be the second in the world, and the longest in Europe, on the Gümüşhane-Trabzon highway. Two tunnels are being constructed between the Köstere village of Gümüşhane and the Başarköy village of Maçka district of Trabzon, each 14.5 kilometers long and 29 kilometers in length. The study theme is the reasons for the small scale collapse in the Zigana Tunnel Köstere Mevkii construction site; the location and size of possible fractures and / or cavity are investigated in the tunnel between 13km + 833 m and 13km + 783 m. The main aim of the study is to reveal the causes of collapse and to investigate whether a possible problem persists. For this purpose, ground penetrating radar (GPR) data were gathered on the inner wall and floor, processed and evaluated using a 50MHz unshielded and 250 MHz shielded antennas with RAMAC CII system, which can provided information about 45m forward depth on profiles formed on 2m intervals on the tunnel inner wall and 12m down depth on profiles gathered on the tunnel floor. In data processing, deconvolution and F-K filter were applied after traditional data processing which were move start time, dewow, background removal, bandpass filter. The background of the dent was displayed and the possible weak zones including transversal and longitudinal large fractures were identified successfully and the type of weak region was mapped. The result showed that GPR method was a non-destructive and most suitable method to map geological discontinuities to take precautions before during construction of a tunnel. [ABSTRACT FROM AUTHOR]

The current research is focused on the investigation of response to static and dynamic loading condition and corrosive environment with respect to micro constituents of heat-treated alloyed ductile cast iron (DCI). DCI specimens with carbon equivalent (CE) 4.14 & 4.30 underwent annealing, normalizing, quench & tempering, austempering heat treatments processes by austenitization at 1000°C followed by subsequent cooling/quenching techniques. The dual matrix structure (DMS) heat-treatment process was carried out at austenitizing temperature of 800°C and then quenching into mineral oil maintained at 100°C. The mechanical properties viz. UTS, 0.2% YS, % elongation, Vickers hardness and impact strength was determined following respective ASTM standard and correlated with morphological aspects. To study the response to corrosive environment, respective as-cast and heat-treated specimens of alloys were immersed in sea water for 12 weeks, and at regular interval of 1 week the contaminated water was replaced by fresh sea water. The corrosion rate does not appear to follow a specific pattern, which was due to the replacement of fresh sea water with the contaminated one after every interval. The DMS-treated specimens were found to be more corrosion resistive as compared to other heat treated and as-cast specimens irrespective to the alloy composition. The morphological investigation revealed that graphitic corrosion is the primary phenomena that ultimately resulted in high rate of corrosion in specimens treated with normalizing, quench & tempering and austempering processes yielding to higher nodule count. [ABSTRACT FROM AUTHOR]

The authors have carried out uniaxial compression tests of 200 mm side cube specimens made of artificial layered geomaterial with the bedding angles of 0, 30, 45, 60 and 90 deg and with the different strength of the layers to study the process of deformation to failure using the multiparametric equipment designed for synchronous recording of physical fields of stresses, macrostrains, microseismic emission (MSE) and microstrains by speckle method. The integrated analyses of MSE signals, microstrains, stresses and strains has shown that each of the selected methods offers satisfactory characterization of evolution of crack formation. Moreover, there is a clear interconnection between the regular patterns of change in MSE parameters, microstrains and their velocities and the stress-deformation diagram. In the first loading stage, under stresses not to exceed 0.25-0.5 of the peak load, a few MSE signals are recorded at a wideband frequency. The field of the microstrains is chaotically non - uniform, and there is nearly no variation in the microstrain field components. In the second stage of deformation, at the stresses from 0.4-05 to 0.7-0.8 of the ultimate strength, the number of MSE signals grows, their amplitudes increase, the frequency spectrum narrows and shifts toward the lower frequencies. The field of the microstrains becomes more nonuniform, zones of maximum microstrains appear, where microstrains exceed average values over the surface of the specimen. In the third stage of loading under stresses from 0.8 of the ultimate strength and up to the peak load, the number of MSE signals grows several times as compared with the previous deformation stage, the amplitude of the signals grows, too, while the frequency spectrum considerably narrows and even more shifts toward the lower frequencies. The maps of the space - and - time distribution of MSE signals demonstrate their essentially nonuniform distribution within the volume of the specimen. The localization of the zones of maximum microstrains in a specimen is reflective of the initiation of a main crack; the place where the main crack reaches the specimen surface can be determined under stresses lower than the peak load. When the main crack reaches the surface of a specimen, a strong low - frequency signal is generated. Under the uniaxial compression of the cubic specimens of geomaterial, the macroscopic fracture modes are in the good agreement with the spatial location of MSE signals and with the fields of the microstrains. [ABSTRACT FROM AUTHOR]

Copyright of Proceedings of the International Scientific Conference of Daugavpils University / Daugavpils Universitates Starptautiskas Zinatniskas Konferences Materiali is the property of Daugavpils University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Deformation of specimens made of artificial geomaterials under load to failure was tested in a laboratory. Stresses, strains and microseismic emission were recorded synchronously during the tests. The degree of anisotropy (angle of stratification) of the specimens has considerable effect on strength and deformation properties. The integrated analysis of the test data shows the character of change in the parameters of microseismic signals depending on deformation process stages, which allows revealing dynamics of the destructive processes inside the test specimens and tracking initiation of a main crack. [ABSTRACT FROM AUTHOR]

In this study the interfacial morphology of different polymers joined by various assembly injection molding (AIM) technologies were discussed. Melt streams were injected successively using tools with core-back or rotation techniques. To compare bulk specimen strength and weld line strength, the fracture behavior of different specimen scales and thin sections were investigated. An in-situ SEM tensile test and a new thin section testing device which is used in polarized (transmitted) light microscopy were used to observe specimen failure. The effects of processing on spherulitic structures were linked to bonding strength and mechanical properties. [ABSTRACT FROM AUTHOR]

Introduction to the practice of new criteria designing of ice strength is a complex task, because one or another criterion of equivalence can be the basis for practical calculations of durability only subject to it empirical testing and the experiment results are reasonably close to the results of theoretical calculation. There are new results in determining of ice strength in massive (the method of logging tool tests) and in the mechanisms of destruction of ice field edge (consideration of vertical and horizontal radial and the circular cracks). Besides according to practical research in the field of mechanics of solid deformable body was defined that the energetical hypothesis of the strength is suitable for solution of ice fracture task. Subject to specific fracture energy of ice, the mathematical expressions for calculation of ice load are simplified, they become simple and clear. Investigations of the specific energy of mechanical fracture of ice via DBT method both in laboratory and in-situ were previously performed has shown the complete invariant nature of this criterion of ice strength, inclusive of high predictability and reproducing of results. Taking into account the laws of ice plate edges fracture, the methodological approach for calculation of ice load on vertical support of structure subject to specific energy of mechanical fracture of ice was considered herein. [ABSTRACT FROM AUTHOR]

Separation is often observed after Charpy V-notch tests or Drop Weight Tear Tests (DWTT). Separation is defined as the fracture morphology whereby many cracks were formed parallel to the rolling plane. On the other hand, an arrowhead fracture is often observed near the surface of DWTT. The morphology of the arrowhead fracture is similar to that of separation. In this study, the relationship between arrowhead fracture and microstructure was investigated as compared with that between separation and microstructure. From this study, it was thought that the mechanism of arrowhead fracture formation was the same as that of separation formation although stress constraint in arrowhead fracture was different from that in separation. [ABSTRACT FROM AUTHOR]

Multiscale computer simulation was used for simulation of the damage nucleation and fracture of ZrB2 - ZrO2, ZrB2 - B4C, Al2O3 - ZrO2 - Y2O3, Al2O3 - B4C nanocomposites under dynamic loading. The aim of research was the study transition from brittle to quasibrittle fracture of nanocomposites under dynamic loading. It was shown that isolated microand mesoscale cracks can be nucleate in ceramic nanocomposites near voids under stress pulse amplitude less than the Hugoniot elastic limit. The critical fracture stress on mesoscale level depends not only on relative volumes of voids and particles concentration, but also sizes of corresponding structure elements. Results of simulation have shown the Hugoniot elastic limit and ceramics damage kinetics under dynamic loading depends on a volume concentration of nano-particles and nano-voids clusters. [ABSTRACT FROM AUTHOR]

Fracture prediction in a block cave of underground mine is very important to monitor the structure of the fracture that can be harmful to the mining activities. Many methods can be used to obtain such information, such as TDR (Time Domain Relectometry) and open hole. Both of them have limitations in range measurement. Passive seismic tomography is one of the subsurface imaging method. It has advantage in terms of measurements, cost, and rich of rock physical information. This passive seismic tomography studies using Fresnel zone to model the wavepath by using frequency parameter. Fresnel zone was developed by Nurhandoko in 2000. The result of this study is tomography of P and S wave velocity which can predict position of fracture. The study also attempted to use sum of the wavefronts to obtain position and time of seismic event occurence. Fresnel zone tomography and the summation wavefront can predict location of geological structure of mine area as well. [ABSTRACT FROM AUTHOR]

A new constitutive model and numerical approach for the analysis of elastic behavior, damage accumulation and cracking problems has been proposed within the framework of the non-local bond-based peridynamic (PD) theory. This model inherits the capability of analyzing spontaneous crack propagation from the peridynamic theory. Meanwhile, to take the internal length effect of long-range forces into account, the micromodulus of PD bonds is defined as a continuous function of the distance between two particles within the material horizon, and which is demonstrated to be more accurate than the commonly used constant stiffness for quantitative calculation. Numerical approaches including local damping and step-loading method have been introduced to the proposed model so that quasi-static analysis can be performed. The qualitative and quantitative validity of the model has been established through numerical examples and making comparisons to analytical prediction and experimental measurements. [ABSTRACT FROM AUTHOR]

The article discusses research which examined the use of circumferentially cracked bar to determine the critical tip opening displacement (CTOD) concept in X65 grade steel. Topics discussed include single edge crack in tension (SENT) and circumferential cracked bar (CCB) analysis and geometry and types of tensile tests.

The article discusses research which examined the application of materials in the environment of the arctic and cold regions. Topics discussed include specific aspects related to the ferritic steel application, an overview of the Barents2020 project designed to harmonize requirements between Russia and Norway for safe exploration and exploitation of oil and gas resources and scope of the ISO TC67/SC8/WG5 working group.

Study of structural changes occurring in the surface layer modified by ion-beam irradiation was carried out by means of optical, scanning and transmission electron microscopy. It was shown that irradiation induces the structure modification not only in the surface layer, but along the entire cross section of 1 mm thick specimens. It was elucidated that the complex pattern of structural changes is responsible for the pronounced variation of mechanical properties taking place under static tension and cyclic alternating bending. [ABSTRACT FROM AUTHOR]

It is shown that strain-induced defects of all kinds are nucleated in local curvature zones of the interfaces between 3D-crystals and 2D-planar subsystem similar to a laser pumping mechanism. Mobile curvature solitons are generalized wave structural carriers of plastic flow. Fracture is the structural phase decay of a crystal in the zones of very high curvature. [ABSTRACT FROM AUTHOR]

The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer. [ABSTRACT FROM AUTHOR]

General regularities in the failure kinetics of steel of main gas pipelines (17GS) are established using the method of complete stress-strain curves, meanwhile in-service degradation of metals is taken into account. The influence of material degradation on material properties under static tensioning is considered using two independent approaches: the phenomenological model of damage accumulation in metals, and the fractographic analysis method. The accumulation of in-service damage is found to increase a degree of material opening and lead to partial "embrittlement" of the steel matrix due to the microdefects accumulation in the vicinity of metal cracking caused by hydrogenation. [ABSTRACT FROM AUTHOR]

The peculiarities of using the surface as a damage sensor of the A2024 aluminum alloy under significant plastic strains are analyzed. Physical and mechanical regularities in the spatial self-organization of the structural and mechanical defects are found, and their relationship with the pore formation and deformation processes inside the material is established. It is proved that the surface relief formation can be used as the engineering parameter of the A2024 aluminum alloy damage under static deformation. [ABSTRACT FROM AUTHOR]

An evolutionary approach to earthquake development is proposed. A medium under loading is treated as a multiscale nonlinear dynamic system. Its failure involves a number of stages typical of any dynamic system: dynamic chaos, self-organized criticality, and global stability loss in the final stage of its evolution. In the latter stage, the system evolves in a blow-up mode accompanied by catastrophic superfast movements of the elements of this geomedium. [ABSTRACT FROM AUTHOR]

In the present paper the multiscale approach to the construction of rheological models of brittle materials with heterogeneous internal structure is implemented within the numerical method of movable cellular automata. An example of application of the implemented approach to determine the mechanical properties (including parameters of the rheological model and strength) of brittle materials with complicated internal structure at both macroscopic and mesoscopic scales is described. The effect of strain rate on brittle materials behavior under uniaxial compression and tension is analyzed. [ABSTRACT FROM AUTHOR]

The paper reports a molecular dynamics analysis of rotary properties of a transformational wave generated due to compressive influence. Studies are performed in the time interval prior to the onset of elastic precursor reflection from the free boundary. It is shown that the leading front of a rotary wave coincides with the transformational wave front. The rotary wave velocity for copper is determined, being equal to 1300 m/s. The values of angular moment projections onto the coordinate axes in a plane perpendicular to wave propagation are found to be symmetrical, and their total sum equals zero. [ABSTRACT FROM AUTHOR]

A method of numerical simulation of liquid-saturated porous media' that represents a combination of particle method and finite-difference method' namely' the hybrid cellular automaton method was proposed. It allows taking into account inelastic deformations' dilation and fracture of solid skeleton as well as the influence of pore pressure on the stress state of the skeleton and the redistribution of a liquid in filtration volume of porous medium. The method was applied to study the influence of viscous compressible liquid in pores of material on its strength and fracture. It has been shown that the strength of brittle liquid-saturated specimens depends on the material properties and the geometry of porosity' the physical-mechanical properties of the liquid etc. The latter shows the topicality of application of numerical methods to study and predict strength properties of fluid-saturated media under loading. [ABSTRACT FROM AUTHOR]

The results of changing the fracture toughness of materials are given for the VT6 titanium alloy. Its coarse grain structure was reduced down to ultrafine structure by forging. The specific energy of fracture y for the small-sized chevron-notched specimens was found thanks to the new technique. It is shown that severe plastic deformation reduces y at room temperature. The structure of the surface fracture of the VT6 alloy's ultrafine grain structure can be conceived as local zones of strong deformed material with a high concentration of pores. Such kind of structure cannot be formed only by means of crystallographic shears along close-packed planes. That fact proves the cardinal role of rotational modes of deformation in the origination and formation of a crack at various scale levels. [ABSTRACT FROM AUTHOR]

A numerical analysis of the deformation and fracture mechanisms involved in a material with a porous ceramic coating under tension and compression is presented. The dynamic boundary-value problem in the plane strain formulation is solved numerically by the finite difference method. To take an explicit account of the substrate-coating interface and porous coating microstructure in the calculations' a curvilinear mesh generation algorithm based on the solution according to elasticity theory has been developed. A two-dimensional curvilinear mesh generated in this work was used to simulate the uniaxial loading of a material with a porous coating. The fundamental difference between the fracture mechanisms operating in the coated material in the cases of tension and compression was found to be related with the formation of local regions experiencing bulk tension in both cases. [ABSTRACT FROM AUTHOR]

A numerical analysis of plastic strain localization and fracture in an aluminum alloy with a composite aluminum (Al) - titanium carbide (TiC) coating providing oxidation protection is presented. Boundary-value problems in plane strain and three-dimensional formulations are solved numerically by the finite-difference and finite-element methods' respectively. The Al-TiC interface geometry corresponds to the configuration found experimentally and is accounted for explicitly in calculations. An algorithm to build a 3D finite-element model of TiC particles is developed. To simulate the mechanical response of the aluminum substrate and composite coating' use was made of an elastic-plastic model with isotropic strain hardening and a fracture model taking into account crack initiation and growth in the regions experiencing tensile stresses. Local regions of bulk tension are shown to arise near the interfaces even under simple uniaxial compression of the coated material' which controls the mechanisms of plastic strain and fracture localization at the mesoscale level. The role of technological residual stresses is revealed. [ABSTRACT FROM AUTHOR]

Concrete is a heterogeneous material consisting of aggregates embedded in a cement-sand matrix (mortar). The compression behavior of the aggregate is linear up till failure and the mortar is a brittle-linear material, with a reversible deformation up to its limit, followed by a sudden failure. The resulting concrete demonstrates a quasi-ductile behavior with a progressive decrease in load bearing capacity under incremental monotonic loading. The fracture mechanism of plain concrete on the other hand, is highly influenced by the bond strength in the interface and the tensile strength of the mortar. A Finite Element Model (FEM) was developed for analyzing the fracture characteristic of concrete in flexure. Two failure criteria were evaluated, the Mohr-Coulomb envelope and the Kupfer-Hilsdorf-Rusch criteria. The program was validated by experimentally tested specimens, and proven to be accurate. Further, this program served as tool to analyze the fracture response of a range of concrete strengths. This research work was conducted at the Structural and Material Laboratory, Diponegoro University in Semarang, Indonesia. [ABSTRACT FROM AUTHOR]

High-cycle fatigue properties of Ti-5Al-2.5Sn Extra Low Interstitial (ELI) alloy forging were investigated at low temperatures. The high-cycle fatigue strength at low temperatures of this alloy was relatively low compared with that at ambient temperature. The crystallographic orientation of a facet formed at a fatigue crack initiation site was determined by electron backscatter diffraction (EBSD) method in scanning electron microscope (SEM) to understand the fatigue crack initiation mechanism and discuss on the low fatigue strength at low temperature. Furthermore, in terms of the practical use of this alloy, the effect of the stress ratio (or mean stress) on the high-cycle fatigue properties was evaluated using the modified Goodman diagram. [ABSTRACT FROM AUTHOR]

The effect of the stress ratio R (the ratio of minimum stress to maximum stress) on the high-cycle fatigue properties of Ti-6Al-4V extra-low interstitial (ELI) alloy forging was investigated at 293 and 77 K. At 293 K, the fatigue strength at 107 cycles exhibited deviations below the modified Goodman line in the R=0.01 and 0.5 tests. Moreover, at 77 K, larger deviations of the fatigue strength at 107 cycles below the modified Goodman line were confirmed in the same stress ratio conditions. The high-cycle fatigue strength of the present alloy forging exhibit an anomalous mean stress dependency at both temperatures and this dependency becomes remarkable at low temperature. [ABSTRACT FROM AUTHOR]

The objective of this benchmark is to demonstrate the predictability of forming limits under nonlinear strain paths for a draw panel with a non-axisymmetric reversed dome-shape at the center. It is important to recognize that treating strain forming limits as though they were static during the deformation process may not lead to successful predictions of this benchmark, due to the nonlinearity of the strain paths involved in this benchmark. The benchmark tool is designed to enable a two-stage draw/reverse draw continuous forming process. Three typical sheet materials, AA5182- O Aluminum, and DP600 and TRIP780 Steels, are selected for this benchmark study. [ABSTRACT FROM AUTHOR]

This paper analyses the fracture behavior of the brazed BCBN grain by comparison with brazed PCBN grain through grinding test of Nickel-based superalloy. The self-sharpening effect is created by timing micro-fracture behavior for BCBN abrasive grains, but by macro-fracture behavior for PCBN abrasive grains. During grinding with brazed BCBN abrasive grains, the material is removed together with the consumption of the CBN particle. While for PCBN ones, the fracture pattern consists of the intercrystalline fracture and the intergranular bond fracture. The service life of brazed BCBN grinding tool is around 1.67 times longer than that of PCBN one, furthermore the material removal of PCBN grinding tool is just about 73% of that of BCBN grinding tool in this investigation. [ABSTRACT FROM AUTHOR]

Copyright of Convegni Nazionali IGF: Acta Fracturae is the property of Gruppo Italiano Frattura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Convegni Nazionali IGF: Acta Fracturae is the property of Gruppo Italiano Frattura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper we present a radio technique for detecting and measuring the extent of hydraulic fractures in subsurface rock layers using MF band. The method is based on transmission measurements among elements of vertical and horizontal arrays in the borehole before and after fracking process. To realize this system a novel super-miniaturized borehole antenna operating at 2MHz is also presented. The proposed antenna is based on a ferrite-loaded helical dipole antenna optimized to fit a volume λ0/1337 × λ0/1337 × λ0/80 while maintain a high radiation efficiency of about 10%. [ABSTRACT FROM PUBLISHER]