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1
Herle, Vishweshwara, Peter Fischer i Erich J. Windhab. "Shear thickening and shear induced band formations in solutions of wormlike micelles". Journal of Central South University of Technology 14, S1 (luty 2007): 213–17. http://dx.doi.org/10.1007/s11771-007-0248-0.
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Stevens, Jeffry L., i Steven M. Day. "Shear velocity logging in slow formations using the Stoneley wave". GEOPHYSICS 51, nr 1 (styczeń 1986): 137–47. http://dx.doi.org/10.1190/1.1442027.
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We apply an iterative, linearized inversion method to Stoneley waves recorded on acoustic logs in a borehole. Our objective is to assess inversion of Stoneley wave phase and group velocity as a practical technique for shear velocity logging in slow formations. Indirect techniques for shear logging are of particular importance in this case because there is no shear head wave arrival. Acoustic logs from a long‐spaced sonic tool provided high‐quality, low‐noise data in the 1 to 10 kHz band for this experiment. A shear velocity profile estimated by inversion of a 60 ft (18 ⋅ 3 m) section of full‐wave acoustic data correlates well with the P‐wave log for the section. The inferred shear velocity ranges from 60 to 90 percent of the sound velocity of the fluid. Formal error estimates on the shear velocity are everywhere less than 5 percent. Moreover, application of the same inversion method to synthetic waveforms corroborates these error estimates. Finally, a synthetic acoustic waveform computed from inversion results is an excellent match to the observed waveform. On the basis of these results, we conclude that Stoneley‐wave inversion constitutes a practical, indirect, shear‐logging technique for slow formations. Success of the shear‐logging method depends upon availability of high‐quality, low‐noise waveform data in the 1 to 4 kHz band. Given good prior estimates of compressional velocity and density of the borehole fluid, only rough estimates of borehole radius and formation density and compressional velocity are required. The existing inversion procedure also yields estimates of formation Q inferred from spectral amplitudes of Stoneley waves. This extension of the method is promising, since amplitudes of Stoneley waves in a slow formation are highly sensitive to formation Q. Attenuation caused by formation Q dominates over attenuation caused by fluid viscosity if the viscosity is less than about [Formula: see text]. However, Stoneley‐wave amplitudes are also sensitive to gradients in shear velocity in the direction of propagation. In some cases, correction for the effects of shear‐velocity gradients is required to obtain the formation Q from Stoneley‐wave attenuation.
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KIRIYAMA, Takatoshi. "Numerical Study on Shear Band Formations during Tri-axial Compression Test". Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)) 70, nr 2 (2014): I_441—I_451. http://dx.doi.org/10.2208/jscejam.70.i_441.
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Ingram, J. D., C. F. Morris, E. E. MacKnight i T. W. Parks. "Direct phase determination of S‐wave velocities from acoustic waveform logs". GEOPHYSICS 50, nr 11 (listopad 1985): 1746–55. http://dx.doi.org/10.1190/1.1441864.
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A new technique for producing S-wave logs from borehole acoustic waves has been developed. The procedure is based on direct phase calculations for time‐windowed waveforms obtained with an acoustic logging tool. A window is positioned over the S-wave portion of the signals, and window moveout is chosen to give zero‐phase differences in a band of frequencies across the array of receivers. A major issue in application of this method is the error introduced by windowing and by interfering signals such as casing arrivals, residual P-waves, and modes propagating in the borehole. Examples using synthetic data are presented illustrating these errors and the means of reducing them. A capture effect, characteristic of phase methods, may be exploited to reduce the effect of interference. Examples are presented showing logs made in different lithologies using a conventional two‐receiver long‐spacing tool. A pulsed transmitter was used with energy in a frequency range 10 to 20 kHz. In hard formations there is little difficulty in obtaining good shear logs. In softer formations, with reduced shear amplitudes, the problems caused by interfering waves become more severe. Careful choice of frequency bands used in the analysis can reduce interference problems and may improve logs in soft formations.
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Yang, Jiaqi, Bikash K. Sinha i Tarek M. Habashy. "Estimation of formation shear and borehole-fluid slownesses using sonic dispersion data in well-bonded cased boreholes". GEOPHYSICS 76, nr 6 (listopad 2011): E187—E197. http://dx.doi.org/10.1190/geo2010-0413.1.
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New inversion algorithms have been developed for estimating the formation shear and borehole-fluid slownesses, using either the borehole Stoneley or dipole flexural dispersion in well-bonded cased boreholes surrounded by a fast or slow isotropic and purely elastic formation. Two inversion algorithms have been developed for each type of formation. The first algorithm inverts either the measured borehole Stoneley or flexural dispersion at select frequencies for the formation shear slowness when all other model parameters are known. The second algorithm inverts either the borehole Stoneley or flexural dispersion for both the formation shear and borehole-fluid compressional slownesses. Optimal bandwidths for the inversion of the Stoneley and dipole flexural dispersions for the formation shear slowness range from about 5 to 8 kHz. The well-bonded cased borehole dispersion sensitivity to formation shear slowness becomes larger at these higher frequencies than in an open-hole. Moreover, the Stoneley dispersion sensitivity to the borehole-fluid compressional slowness is so large that it becomes necessary to input an extremely accurate estimate of fluid compressional slowness in the inversion algorithm. Inverted formation shear slowness from the Stoneley data in a fast formation exhibits an uncertainty of about 3%, whereas the input borehole-fluid slowness has an uncertainty of 0.5%. Given a certain amount of uncertainty in the borehole-fluid slowness, one can then estimate possible variances in the inverted formation shear slowness. In contrast, inversion of the flexural dispersion for formation shear slowness is less sensitive to the input borehole-fluid compressional slowness in the preferred frequency band of 5 to 8 kHz. Inverted formation shear slownesses in slow formations that use either the Stoneley or flexural dispersion are also far less sensitive to uncertainties in the borehole-fluid compressional slowness.
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Li, Jun Li, Gang Liu, Dong Jin Zhang i Ming Chen. "A FEM Study on Chip Formation in Orthogonal Turning Nickel-Based Superalloy GH80A". Materials Science Forum 575-578 (kwiecień 2008): 1370–75. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.1370.
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The nickel-based superalloy GH80A is a typical difficult-to-cut material. It has been used in a good many kinds of aeronautical key structures because of its high yield stress and anti-fatigue performance at high temperature. But selection of cutting parameters in actual machining process mainly depends on experience and lacks of scientific utterance. In this paper, finite element method (FEM) was introduced to study the chip formation process when machining nickel-based superalloy GH80A. By the way of lagrangian finite element approach and material failure, adiabatic shear band (ASB) and periodic fracture were simulated with the help of former researchers’ studies on the material constitutive relation. Both the mechanism of adiabatic shearing phenomenon at primary shear zone and periodic crack in the free surface were analyzed, chip formations under different cutting parameters were got and compared carefully. The root cause of saw-tooth chip formation under different cutting speeds was discussed.
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Wei, Zhoutuo, Xiaoming Tang i Jingji Cao. "Acoustic radiation and reflection of a logging-while-drilling dipole source". Geophysical Journal International 219, nr 1 (2.05.2019): 108–28. http://dx.doi.org/10.1093/gji/ggz193.
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SUMMARY With the comparison to the resistivity ultra-deep measurement, the single-well reflection survey in acoustic logging-while-drilling (ALWD) measurement lags far behind, especially ALWD dipole measurement has long been thought to be little added value. In this paper, we extended the dipole shear-wave (S-wave) reflection survey technology in wireline logging into ALWD and demonstrated the theoretical feasibility of adopting a dipole source–receiver system to perform ALWD reflection survey. For this purpose, we investigated the radiation patterns of radiantSH, SV and P waves, the energy fluxes of guided and radiant waves and their acoustical radiation efficiencies from an LWD dipole acoustic source by comparisons with the wireline results. The analysis results reveal that a dominant excitation-frequency band does exist in ALWD dipole S-wave reflection. Consequently, the expected excitation frequency should be located in the band of the signal with high radiation efficiency, guaranteeing the best radiation performance. In fast formations, SH wave is the best candidate for ALWD reflection survey due to its highest radiation efficiency. In contrast, the dominant excitation-frequency band of SH wave gets wider in a slow formation. Besides, the SV- and P-wave radiation efficiencies are also remarkable, implying that both waves can also be used for ALWD reflection survey in slow formations. We expounded the SH-, SV- and P-reflection behaviours at three typical excitation frequencies by our 3-D finite difference. Simulations to single-well reflection validate the key role of dominant excitation-frequency band and demonstrate the theoretical feasibility of applying the technology to ALWD. Our results can guide the design and measurement methods of ALWD dipole S-wave reflection survey tool, which could have extensive application prospect for geo-steering.
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Kirshbaum, Daniel J., i Dale R. Durran. "Observations and Modeling of Banded Orographic Convection". Journal of the Atmospheric Sciences 62, nr 5 (1.05.2005): 1463–79. http://dx.doi.org/10.1175/jas3417.1.
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Abstract Radar images and numerical simulations of three shallow convective precipitation events over the Coastal Range in western Oregon are presented. In one of these events, unusually well-defined quasi-stationary banded formations produced large precipitation enhancements in favored locations, while varying degrees of band organization and lighter precipitation accumulations occurred in the other two cases. The difference between the more banded and cellular cases appeared to depend on the vertical shear within the orographic cap cloud and the susceptibility of the flow to convection upstream of the mountain. Numerical simulations showed that the rainbands, which appeared to be shear-parallel convective roll circulations that formed within the unstable orographic cap cloud, developed even over smooth mountains. However, these banded structures were better organized, more stationary, and produced greater precipitation enhancement over mountains with small-scale topographic obstacles. Low-amplitude random topographic roughness elements were found to be just as effective as more prominent subrange-scale peaks at organizing and fixing the location of the orographic rainbands.
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Randall, C. J., D. J. Scheibner i P. T. Wu. "Multipole borehole acoustic waveforms: Synthetic logs with beds and borehole washouts". GEOPHYSICS 56, nr 11 (listopad 1991): 1757–69. http://dx.doi.org/10.1190/1.1442988.
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We give a two‐dimensional (2-D) velocity‐stress finite‐difference (vs-fd) formulation for the multipole borehole acoustic logging problem. Irregular boreholes, horizontal bedding, and axially varying alteration are encompassed by the model. Excellent agreement is obtained with transform techniques for constant radius boreholes and homogeneous formations. The method is used to generate waveforms for many positions of transmitter and receiver array relative to beds and washouts as in logging. First motion and semblance techniques are applied to the waveforms to extract formation slownesses, resulting in synthetic multipole logs which demonstrate the response of ideal multipole logging tools and signal processing to several environmental effects. For monopole, compressional, first‐motion logs, residual slowness errors remain at borehole washouts after borehole compensation. These errors increase as the effective measure point in the waveforms is moved back in time from true first motion, admitting greater interference from reflected and mode‐converted waves. Errors at bed boundaries are typically smaller than those at washouts. Stoneley slowness logs are obtained by narrow‐band filtering of low frequency monopole waveforms and application of the semblance slowness extraction algorithm STC. Similar processing applied to low frequency dipole waveforms yields flexural mode slowness logs. A small correction satisfactorily accounts for flexural mode dispersion properties, yielding formation shear slowness. Slowness errors for both Stoneley and dipole shear logs at washouts and bed boundaries are quite small, typically on the order of a few percent. Borehole compensation is of marginal benefit for both of these logs since they are based on modes of the borehole rather than head‐waves.
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Maiti, Payel, Dhrubajyoti Sadhukhan, Jiten Ghosh i Anoop Kumar Mukhopadhyay. "Nanoscale plasticity in titania densified alumina ceramics". Journal of Applied Physics 131, nr 13 (7.04.2022): 135107. http://dx.doi.org/10.1063/5.0081872.
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The present study explores the physics behind the loading rate (dP/dt or [Formula: see text]) dependent nanoscale plasticity (NSP) events observed during carefully controlled nanoindentation (NI) experiments on 1, 3, and 5 wt. % Titania Densified Alumina (TDA) ceramics. Characterizations of the TDA ceramics are carried out by x-ray diffraction, field emission scanning electron microscopy (FESEM), and NI techniques. A significant enhancement (∼30%) of the nanohardness of TDA ceramics occur with an enhancement in [Formula: see text]. The results confirm that both the critical load ( Pc) at which micro-pop-in or the NSP events initiate and the corresponding critical depth ( hc) are sensitive functions of relative density, size of relatively finer grains, loading rate, and the amount of sintering aids. The experimentally observed empirical power law dependence of all the NSP related parameters on [Formula: see text] is rationalized theoretically and qualitatively. It is suggested that the shear induced homogeneous dislocation nucleation underneath the nanoindenter may be the main factor contributing to the occurrence of the NSP events at relatively lower loading rates. However, especially at the relatively higher loading rates, the FESEM based evidence and the data obtained from the related NI experiments suggest that there is a more acute interconnection between the homogeneous dislocation nucleation induced profuse occurrence of the NSP events, shear band formations, and microcrack formation in the TDA ceramics. Finally, the design implications of the present results for the development of better alumina ceramics for load and strain tolerant applications are discussed.
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Rösner, Harald, Christian Kübel, Stefan Ostendorp i Gerhard Wilde. "In Situ Generated Shear Bands in Metallic Glass Investigated by Atomic Force and Analytical Transmission Electron Microscopy". Metals 12, nr 1 (6.01.2022): 111. http://dx.doi.org/10.3390/met12010111.
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Plastic deformation of metallic glasses performed at temperatures well below the glass transition proceeds via the formation of shear bands. In this contribution, we investigated shear bands originating from in situ tensile tests of Al88Y7Fe5 melt-spun ribbons performed under a transmission electron microscope. The observed contrasts of the shear bands were found to be related to a thickness reduction rather than to density changes. This result should alert the community of the possibility of thickness changes occurring during in situ shear band formation that may affect interpretation of shear band properties such as the local density. The observation of a spearhead-like shear front suggests a propagation front mechanism for shear band initiation here.
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BAXEVANIS, TH, TH KATSAOUNIS i A. E. TZAVARAS. "ADAPTIVE FINITE ELEMENT COMPUTATIONS OF SHEAR BAND FORMATION". Mathematical Models and Methods in Applied Sciences 20, nr 03 (marzec 2010): 423–48. http://dx.doi.org/10.1142/s0218202510004295.
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We study numerically an instability mechanism for the formation of shear bands at high strain-rate deformations of metals. We use a reformulation of the problem that exploits scaling properties of the model, in conjunction with adaptive finite element methods of any order in the spatial discretization and implicit Runge–Kutta methods with variable step in time. The numerical schemes are of implicit–explicit type and provide adequate resolution of shear bands up to full development. We find that from the initial stages, shear band formation is already associated with collapse of stress diffusion across the band and that process intensifies as the band fully forms. For fully developed bands, heat conduction plays an important role in the subsequent evolution by causing a delay or even stopping the development of the band.
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Ikeda, Takumi, Hiroyuki Miyamoto, Toshiyuki Uenoya, Satoshi Hashimoto i Alexei Vinogradov. "Formation of Deformation Twins and Related Shear Bands in Copper Single Crystals Pressed by ECAP". Materials Science Forum 654-656 (czerwiec 2010): 1231–34. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1231.
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The pure copper single crystals with specific crystallographic orientated were subjected to ECAP for one pass at room temperature. Two types of shear bands were observed. Type 1 shear bands were constructed with clusters of distorting micro shear bands and matrix. Micro shear band and matrix were delineated by large-angle grain boundaries, and these two orientations are in a twinning relationship. Parallel sets of deformation twins were observed in the matrix. Type 2 shear bands had no crystallographic feature, and shear band and matrix were considered as low-angle grain boundaries. Deformation twin was not observed both in matrix and the shear bands.
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Duan, Chun Zheng, Wei Sen Kong, Zhao Xi Wang i Min Jie Wang. "Adiabatic Shear Localization in High Speed Cutting of Hardened Steel". Applied Mechanics and Materials 55-57 (maj 2011): 983–87. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.983.
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The formation and development of adiabatic shear localization in serrated chips have great significance to study of mechanism of high speed cutting. This paper investigates the theory prediction and experimental verification of the critical cutting speed of adiabatic shear localization, distribution of adiabatic shear band in serrated chip and the geometry of adiabatic shear band during high speed cutting of hardened steel. The results indicated that the theoretical prediction of critical cutting speed is consistent with the experimental results.With the increase of cutting speed, the width and spacing of adiabatic shear bands in the serrated chips decrease linearly. There are two types of adiabatic shear bands during the formation and development of adiabatic shear localization, i.e. the deformation shear band and the transformed shear band.
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Duan, Chun Zheng, Hong Hua Li, Min Jie Wang i Yu Jun Cai. "Study on Chip Morphology and Adiabatic Shear in High Speed Cutting of Alloy Steels with Different Hardness". Applied Mechanics and Materials 26-28 (czerwiec 2010): 875–79. http://dx.doi.org/10.4028/www.scientific.net/amm.26-28.875.
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The chip morphology and the formation and development of the adiabatic shear band within the serrated chips formed in high speed cutting of 30CrNi3MoV steel with two tempering hardness were observed and analyzed using optical microscope and SEM. The investigation shows that as the adiabatic shear phenomenon occurs and develops, the chip morphology changes as follows: ribbon chip→serrated chip with deformed band→serrated chip with transformed band→fractured chip. The cutting speed and tempering hardness is the two main factors affecting adiabatic shear, in the case of lower cutting speed the formation and development of adiabatic shear band are more sensitive to tempered hardness increase. The deformed shear bands are constituted by large deformed microstructure, while the formation of the transformed shear bands has experienced the large plastic deformation and grain refinement.
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Su, Guo Sheng, i Zhan Qiang Liu. "The Analysis of Saw-Tooth Chip Formation in High Speed Machining through Material Micro-Hardness Measurement". Advanced Materials Research 188 (marzec 2011): 9–14. http://dx.doi.org/10.4028/www.scientific.net/amr.188.9.
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The material micro-hardness is used to reflect the plastic deformation within the localized shear band and the segment of saw-tooth chip. A high strength alloy steel Aermet 100 is taken as the workpiece material. The saw-tooth chip roots are obtained by cutting operation. The material micro-harnesses along the shortly initiated localized shear band, across the shortly initiated localized shear band and fully developed localized shear band, and within the segment are examined and analyzed. The localized shear band initiation and propagation are revealed by a new proposed model. The results show the localized shear band initiates firstly at the tool tip end of the primary shear band, and consequently another localized shear nucleates at the free surface end of the primary shear band. These two localized shears propagate face to face until the whole localized shear band is formed.
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Mania, I., H. Paul, R. Chulist, P. Petrzak i M. Prażmowski. "Crystallographic aspect of shear bands formation in pure iron deformed at high strain rates". IOP Conference Series: Materials Science and Engineering 1270, nr 1 (1.12.2022): 012099. http://dx.doi.org/10.1088/1757-899x/1270/1/012099.
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In this paper results on shear bands developed in pure iron are presented. The main focus was put on microstructural characterization and crystal lattice rotation in sheared regions. The hat-shaped samples were deformed at a high strain rate of 560 s−1 using a drop-hammer. The microstructure of deformed specimen was investigated by optical microscopy and scanning electron microscopy equipped with a high-resolution electron backscattered diffraction facility. The changes of mechanical properties in the band area and neighbouring matrix were investigated using nano-indentation test. This paper clearly shows that initial stages of shear bands formation are associated with the formation of kink-type bands. The orientation maps revealed the crystallographic determination of the shear band formation. During deformation in each grain located within the sheared region, one of the {110}-type planes situate along the macro-shear band plane and <111> direction situates along the shear direction. In consequence, the formation of specific texture components within the shear band region was observed, different from texture observed in deformed matrix. In micro-scale no effects of dynamic recrystallization were observed. Nano-hardness tests indicated that notable increase of strain hardening is related to the strain localization in narrow shear band’ regions, while the matrix undergoes almost no deformation.
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Yadav, Shwetabh, i Dinakar Sagapuram. "In situ analysis of shear bands and boundary layer formation in metals". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, nr 2234 (luty 2020): 20190519. http://dx.doi.org/10.1098/rspa.2019.0519.
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Shear banding is a plastic instability in large deformation of solids where the flow becomes concentrated in narrow layers, with broad implications in materials processing applications and dynamic failure of metals. Given the extremely small length and time scales involved, several challenges persist in studying the development of shear bands. Here, we present a new approach to study shear bands at low speeds using low melting point alloys. We use in situ imaging to directly capture the essential features of shear banding, including transition from homogeneous to shear banded flow, band nucleation and propagation dynamics, and temporal evolution of the flow around a developing band. High-resolution, time-resolved measurements of the local displacement and velocity profiles during shear band growth are presented. The experiments are complemented by an analysis of the shear band growth as a Bingham fluid flow. It is shown that shear banding occurs only beyond a critical shear stress and is accompanied by a sharp drop in the viscosity by several orders of magnitude, analogous to the yielding transition in yield-stress fluids. Likewise, the displacement field around a nucleated band evolves in a manner that resembles boundary layer formation, with the band thickness scaling with time as a power law.
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Liu, Bingheng, Lingwei Kong, Chengsheng Li i Juntao Wang. "Evolution of Shear Band in Plane Strain Compression of Naturally Structured Clay with a High Sensitivity". Applied Sciences 12, nr 3 (23.01.2022): 1180. http://dx.doi.org/10.3390/app12031180.
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The formation of the shear band is associated with the failure of soil. However, there has been relatively little investigation on the evolution of shear bands in naturally structured clay with a high sensitivity. In this study, undrained plane strain compression tests, digital image correlation (DIC) analyses, and scanning electron microscopy (SEM) tests were performed to investigate the characteristics of shear bands in naturally structured clay. The basic mechanical properties and stress–strain relationships show that naturally structured clay exhibits a strong structure and high sensitivity. Compared with plane strain compression tests under low confining pressure, more localized shear bands emerge in the specimens during the tests under high confining pressures; however, when the specimens fail, only one shear band is fully developed, and the local deformation in the developed shear band is much larger than those in other localized shear bands. Moreover, the local stress–strain relationships inside and outside the shear band show distinct discrepancies. The SEM results show distinct micro-structures of clays inside and outside the shear band, which are caused by the development of the shear band. The findings in this work provide new insight into the failure of structured clay.
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Feng, Shi-Dong, Keith Chan, Lei Zhao, Li-Min Wang i Ri-Ping Liu. "Molecular Dynamics Simulation of Structural Signals of Shear-Band Formation in Zr46Cu46Al8 Metallic Glasses". Materials 11, nr 12 (17.12.2018): 2564. http://dx.doi.org/10.3390/ma11122564.
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The evolution from initiation to formation of a shear band in Zr46Cu46Al8 metallic glasses is presented via molecular dynamics simulation. The increase in number and the decrease in average size of clusters with the quasi-nearest atoms being 0 correspond to the shear-band evolution from initiation to formation. When the shear band is completely formed, the distribution of the bond orientational order q6 reaches a minimum. The maximum of the number of the polyhedral loss of Cu-centered <0, 0, 12, 0> and the minimum of the number of the polyhedral loss of Zr-centered <0, 2, 8, 5> correspond to the shear-band formation. These findings provide a strong foundation for characterizing the evolution from initiation to formation of shear bands.
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Duan, Chun Zheng, Zhao Xi Wang, Min Jie Wang i Wei Sen Kong. "Component Analysis of Adiabatic Shear Band Formed in High Speed Cutting of High Strength Alloy Steel". Applied Mechanics and Materials 52-54 (marzec 2011): 1482–85. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1482.
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The component distribution of adiabatic shear banding during high speed cutting(HSC) is important to understand the phase transformation during formation of adiabatic shear band and mechanism of serrated chip formation. This paper analyzed element distribution inside and near the adiabatic shear bands formed during HSC of 30CrNi3MoV high strength steel using electronic probe. It was found that there is no obvious element segregation, but carbon element tends to gather towards adiabatic shear band’s boundaries. The density of carbon inside the shear bands tends to increase with the increase of cutting speed. The results indicated that the diffusion and gather of carbon may occur during formation of adiabatic shear band. The diffusion mechanism may be short-range diffusion driven by high-speed deformation and high temperature rise.
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Murakami, Kenichi, N. Morishige i Kohsaku Ushioda. "The Effect of Cold Rolling Reduction on Shear Band and Texture Formation in Fe-3%Si Alloy". Materials Science Forum 715-716 (kwiecień 2012): 158–63. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.158.
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The effect of cold rolling reduction on shear band formation and crystal orientation within shear bands and annealing texture were investigated in Fe-3%Si {111}<112> single crystals. Several types of shear bands were observed with different angles to rolling direction, dependent on rolling reduction. As for shear band formation, those with smaller angles were formed earlier and those with larger angles were formed later. Regarding crystal orientation along shear bands after rolling reduction, orientation distribution from the initial became large in accordance with reduction and even exceeded Goss orientation when rolling reduction became larger than 40%. After annealing, however, recrystallized grains along shear bands were mainly Goss grains regardless of reduction. The speculated reason for the dominance of Goss after annealing is that Goss subgrains with less density of dislocations were surrounded by largely deformed areas.
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Dong, Xin Long, Lai Ze Li, Ying Qian Fu i Feng Hua Zhou. "A FEM Study on Adiabatic Shear Band Formation in Tube Compression Driven by Electro-Magnetic Loading". Applied Mechanics and Materials 566 (czerwiec 2014): 517–21. http://dx.doi.org/10.4028/www.scientific.net/amm.566.517.
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The adiabatic shear bands (ASB) of the thick-walled cylinder have been studied by many researchers in the recent years. The onset and evolutions of the multiple shear failure of metal cylinder under explosive loadings are affected by many factors such as the characteristics of the impulsive loadings, the dynamic behavior of the materials, etc. In this work, a tube compression driven by electro-magnetic forces is introduced, which enables to carry out the experiments of the spontaneous evolution of multiple adiabatic shear bands in metal tube. The FEM simulation was conducted to investigate the evolution process of strain localization with coupled thermo-mechanical analysis. The FEM results show that ASB initiates when the stress drops rapidly and strain growth and not when it reaches the maximum shear stress. Once the shear band is formed, elastic unloading occurs beside the shear band. The different behaviors of the damage introduced in the strain softening model affect the initial nucleation strain and the distribution of ASBs. With the increase of material damage softening, the initial strain of shear band decreases and the number of shear bands increases.
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Madani, Mahnoush, Maniya Maleki i M. Reza Shaebani. "Shearing of granular materials in a confined split-bottom Couette cell". EPJ Web of Conferences 249 (2021): 03004. http://dx.doi.org/10.1051/epjconf/202124903004.
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Formation of shear bands is one of the most remarkable phenomena in the dynamics of granular matter. Several parameters have been so far identified to influence the behavior of the shear bands. We carried out experiments to investigate the evolution of the shear bands in the split-bottom Couette cell in the presence of confining pressure. We employed the Particle Image Velocimetry (PIV) to characterize the shear band both in the absence and presence of external pressure. Our results show that the location and width of the shear band are affected by both the confining pressure and the filling height. The shear zone evolves towards the middle of the cylinder and expands to a broader region with increasing applied pressure or filling height; also the angular velocity decreases relative to the rotation rate of the bottom disk. Our findings are consistent with prior empirical observations on the formation of wide shear bands at free surfaces.
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Tribula, D., D. Grivas, D. R. Frear i J. W. Morris. "Observations on the Mechanisms of Fatigue in Eutectic Pb-Sn Solder Joints". Journal of Electronic Packaging 111, nr 2 (1.06.1989): 83–89. http://dx.doi.org/10.1115/1.3226526.
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Near-eutectic Pb-Sn solders are widely used for joints in electrical devices. These are liable to failure by thermal fatigue during operation of the device. Since the thermal fatigue load is often in shear, mechanisms of thermal fatigue in shear are of particular interest. Recent research has shown that the thermal fatigue of eutectic solders in shear is preceded by the formation of bands of coarsened material in the eutectic microstructure, which concentrate the deformation and cause the nucleation of fatigue cracks. Such coarsened bands are also observed in isothermal fatigue and unidirectional creep in shear. Since creep experiments are relatively simple to conduct and analyze, these have been used to study the formation and growth of coarsened bands. The mechanism includes three steps: the formation of inhomogeneous shear bands, the onset of recrystallization in the shear band to create a planar region of coarsened material, and the propagation of the coarsened band by progressive recrystallization at its tip. The results are applied to thermal fatigue and some of their implications are discussed.
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Hwang, Junggeun, i Hoe I. Ling. "Soil Particle Movement and Shear Band Development during Plane Strain Compression". E3S Web of Conferences 92 (2019): 06006. http://dx.doi.org/10.1051/e3sconf/20199206006.
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Most geotechnical structures failed by formation and development of shear bands in soils. Thus, shear deformation and shear bands development evaluation are necessary to understand shear failure mechanism. During shearing, deformation behaviour analysis for soil particles within entire soil specimen are evaluated to understand the soil behaviour and shear strength characteristics. In this paper, a series of plane strain compression tests using Nevada sand and Ottawa sand were conducted to identify the shear strain and shear failure mechanism. With the results of plane strain compression tests, image analyses using Particle Image Velocimetry (PIV) were carried out in order to measure the change in position of soil particles and shear bands development. Deformation vectors and contours were constructed to see the entire deformation mechanism in the soil specimen. During shearing, shear band was identified after peak stress and most visually distinctive at residual state. However, shear band started to develop invisibly immediately after starting loading and this invisible development was able to be observed by horizontal and vertical movement analyses of PIV. Soil particles moved actively in horizontal and vertical direction to generate shear band in the beginning of shearing. After development of shear band, soil particles moved along the shear band.
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Cao, Qingping, Feng Xu, Jingwei Liu, Lianyi Chen, Xiaodong Wang, Jianzhong Jiang, Alexander Minkow i in. "Initiation and evolution of shear bands in bulk metallic glass under tension—An in situ scanning electron microscopy observation". Journal of Materials Research 24, nr 9 (wrzesień 2009): 2924–30. http://dx.doi.org/10.1557/jmr.2009.0341.
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The initiation and evolution of shear bands in Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass tensile samples has been investigated in situ by scanning electron microscopy. The initial shear band originates from the highest stressed area, and does not propagate during further tension, which is attributed to the weakening of the stress field in front of the shear band tip, possibly caused by atomic rearrangement and local temperature rise. As a result, multiple shear bands occur in sequence with gradually increased length and offset. This result is due to the fact that the stress in front of the tip of the initial shear band does not concentrate again during further tension above the shear yield strength. Numerical analysis was carried out to investigate the stress distribution under tension, suggesting that the maximum pressure-dependent shear stress criterion overestimates the yield strength, while the shear plane criterion describes the conditions for the formation of shear bands well.
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Shao, Yang, Guannan Yang i Kefu Yao. "Nanocrystalline Phase Formation inside Shear Bands of Pd-Cu-Si Metallic Glass". Advances in Materials Science and Engineering 2014 (2014): 1–4. http://dx.doi.org/10.1155/2014/490181.
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Pd77.5Cu6Si16.5metallic glass was prepared by fluxing treatment and water quenching method. To avoid possible artifacts, shear bands were created by indentation after TEM sample preparation. Bright field image, diffraction pattern, and the dark field image of TEM that covered the shear band region were presented. A few nanocrystalline phases were noticed inside the shear bands, which favored the plastic deformation ability and supported the explanation of mechanical deformation-induced crystallization.
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Esin, Maxim, Arcady V. Dyskin i Elena Pasternak. "Large-Scale Deformation Patterning in Geomaterials Associated with Grain Rotation". Advanced Materials Research 891-892 (marzec 2014): 872–77. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.872.
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Modelling of large-scale deformation patterning in geomaterials is important for predicting instabilities and failures in the Earths crust. Shear band formation and the evolution of the bands is a predominant mechanism of deformation patterning. Independent rotations of separate grains/particles can affect the pattern formation by adding the effect of rotational degrees of freedom to the mechanism of instability. To model this mechanism we use a special experimental technique based on digital image correlation in order to recover both displacement and independent rotation fields in 2D physical models of granular material. In the physical model the particles are represented by smooth steel monodispersed disks with speckles painted on them to enable the rotation reconstruction. During the loading the deformation pattern undergoes stages of shear band formation followed by its dissolution due to re-compaction and particle rearrangement with the subsequent formation of multiple shear bands merging into a single one and the final dissolution. Also, patterns of rotations are observed at an intermediate scale between the scale of the particles and the scale of the shear band.
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Johari, Mohd Aidy Faizal, Asmawan Mohd Sarman, Saiful Amri Mazlan, Ubaidillah U, Nur Azmah Nordin, Siti Aishah Abdul Aziz, Norhasnidawani Johari, Nurhazimah Nazmi i Shahir Mohd Yusuf. "An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope". Materials 14, nr 16 (5.08.2021): 4384. http://dx.doi.org/10.3390/ma14164384.
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Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.
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Wang, Xiaodi, Shaojie Wu, Ruitao Qu i Zhefeng Zhang. "Shear Band Evolution under Cyclic Loading and Fatigue Property in Metallic Glasses: A Brief Review". Materials 14, nr 13 (28.06.2021): 3595. http://dx.doi.org/10.3390/ma14133595.
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The fatigue damage and fracture of metallic glasses (MGs) were reported to be dominated by shear band. While there exist several reviews about the fatigue behavior of MGs, an overview that mainly focuses on shear bands under cyclic loading is urgent, and is of great importance for the understanding of fatigue mechanisms and properties. In this review paper, based on the previous research results, the shear band evolution under cyclic loading including shear band formation, propagation and cracking, was summarized and elucidated. Furthermore, one strategy of enhancing the fatigue property through manipulating the microstructure to suppress the shear band formation was proposed. Additionally, the applications of the effect of annealing treatment and processing condition on fatigue behaviors were utilized to verify the strategy. Finally, several future directions of fatigue research in MG were presented.
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Pieła, Krzysztof, i Andrzej Korbel. "Mechanism of kink band formation in zinc single crystals". International Journal of Materials Research 112, nr 1 (1.01.2021): 63–67. http://dx.doi.org/10.1515/ijmr-2020-7831.
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Abstract This paper is focused on the mechanism of kink band formation. In the general case, lattice rotation in a kink band may be realized by two sequentially activated simple elastic shears in nearly perpendicular planes. In the case of zinc crystals, compressed along (0001) plane at the temperature 523 K, the first shear may result from stress-induced temporary lattice instability (movement of atoms towards metastable positions in tetrahedric holes), while the second shear occurring along a temporary ‘new-positioned’ basal plane immediately ‘rebuilds’ the stable lattice.
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Lee, Jung G., Kee Sun Sohn, Sung Hak Lee, Nack J. Kim i Choong Nyun Paul Kim. "Microfracture Observation of Zr-Based Bulk Metallic Glasses". Key Engineering Materials 345-346 (sierpień 2007): 645–48. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.645.
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Microfracture mechanisms of Zr-based bulk metallic glass (BMG) alloy containing ductile crystalline particles were investigated by directly observing microfracture processes using an in situ loading stage. Strength of the BMG alloy containing crystalline particles was lower than that of the monolithic BMG alloy, while ductility was higher. According to the direct microfracture observation, crystalline particles initiated shear bands, acted as blocking sites of shear band or crack propagation, and provided the stable crack growth which could be confirmed by the R-curve analysis, although they negatively affected apparent fracture toughness. This increase in fracture resistance with increasing crack length improved overall fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.
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Li, Jin Quan, i Sheng Xu Wang. "The Formation of Adiabatic Shear Band and Analysis of its Characteristics in the Process of Penetration". Advanced Materials Research 472-475 (luty 2012): 2846–49. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2846.
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The characteristics and causes of the formation of adiabatic shear bands (ASB) in 30CrMnMo armor steel plate are analyzed by shooting 93W projectiles. The results show that adiabatic shear bands do not occur in the initial stages of the opening-crater and plugging. Adiabatic shear bands distributed sparsely appear in the stable penetrating phase because of the necessary strain volume. Adiabatic shear bands are formed along main shear stress lines at an angle of about 450 in relation to the penetrating direction. These are approximately consistent with the direction of the plastic deformation slip line. The non-homogenous deformation and centralizing of stress and strain inside the adiabatic shear band causes micro-cracks and micro-bores during cooling of the plate.
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Lorenz, John C., i Scott P. Cooper. "Natural fractures and their relationships to structure, stress, and permeability in the Raton Basin". Mountain Geologist 58, nr 4 (27.10.2021): 375–410. http://dx.doi.org/10.31582/rmag.mg.58.4.375.
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Fractures in Cretaceous and early Tertiary strata record several deformation events that were imposed on the formations that fill the Raton Basin in Colorado and New Mexico. A regional, generally WNW-ESE striking extension-fracture set is present across much of the basin, but fracturing also includes both dip-slip and strike-slip conjugate shear-fracture sets as well as irregular deformation-band shear fractures. In some areas of the basin, the extension fractures are dynamically-compatible with associated conjugate shear fractures, both recording a maximum compressive stress that was horizontal, trending predominantly WNW-ESE. Fracture strikes vary from NW-SE to ENE-WSW but are approximately normal to the front of the Laramide thrust-fault system that forms the western edge of the basin, implying that fracturing was the result of a horizontal compressive stress anisotropy created by indentation of the thrust system into the basin margin. Fracture anomalies occur over local structures including a N-S basement wrench-fault system that connects two large anticlines within the basin, the Tercio and Vermejo Park anticlines, where N-S strike-slip offset along the basement wrench faults caused folding and fracturing in the overlying strata. The Laramide stress system in the basin changed from thrust-related WNW-ESE horizontal compression to the present-day N-S maximum horizontal compressive stress in mid-Tertiary time as the thrust system became inactive and was replaced by regional E-W extension. No new fracture sets were formed by the re-oriented stress system, although stress-release fractures normal to the regional set formed in outcrops as overlying strata were eroded. Fracture datasets were derived from three sources during this study: outcrops, image logs, and cores. Each source provides a somewhat different perspective on the fractures that enhance permeability in Raton Basin reservoirs. Taken together, the three datasets provide the basis for a relatively complete conceptual model of the Raton fracture system. Fracture-controlled permeability anisotropy will be greatest in the WNW-ESE direction, parallel to the strike of the dominant set of Laramide-age natural fractures, but hydraulic stimulation fractures will propagate N-S, across the strike of those fractures under the influence of the present-day stress system. The apertures of the WNW-ESE fractures will be susceptible to closure under that stress system since the maximum horizontal compressive stress is approximately normal to fracture strike.
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Mallikarachchi, Hansini, i Kenichi Soga. "A Constitutive Model for Locally Drained Shear Bands in Globally Undrained Dense Sand". E3S Web of Conferences 92 (2019): 16005. http://dx.doi.org/10.1051/e3sconf/20199216005.
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When saturated granular materials which are dilative in nature are subjected to the undrained deformation, their strength increases due to the generation of negative excess pore pressure. This phenomenon is known as dilative hardening and can be witnessed in saturated dense sand or rocks during very fast loading. However, experimental evidence of undrained biaxial compression tests of dense sand shows a limit to this dilative hardening due to the formation of shear bands. There is no consensus in the literature about the mechanism which triggers these shear bands in the dense dilative sand under isochoric constraint. The possible theoretical reasoning is the local drainage inside the specimen under the globally undrained condition, which is challenging to be monitored experimentally. Hence, both incept of localisation and post-bifurcation of the saturated undrained dense sand demand further numerical investigation. Pathological mesh dependency hinders the ability of the finite element method to represent the localisation without advanced regularisation methods. This paper attempt to provide a macroscopic constitutive behaviour of the undrained deformation of the saturated dense sand in the presence of a locally drained shear band. Discontinuation of dilatant hardening due to partial drainage between the shear band and the adjacent material is integrated into the constitutive model without changing governing equilibrium equations. Initially, a classical bifurcation analysis is conducted to detect the inception and inclination of the shear band based on the underlying drained deformation. Then a post-bifurcation analysis is carried out assuming an embedded drained or partially drained shear band at gauss points which satisfy bifurcation criterion. The smeared shear band approach is utilised to homogenise the constitutive relationship. It is observed that the dilatant hardening in the saturated undrained dense sand is reduced considerably due to the formation of shear bands.
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Rowe, Russell A., Paul G. Allison, Anthony N. Palazotto i Keivan Davami. "Adiabatic Shear Banding in Nickel and Nickel-Based Superalloys: A Review". Metals 12, nr 11 (3.11.2022): 1879. http://dx.doi.org/10.3390/met12111879.
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This review paper discusses the formation and propagation of adiabatic shear bands in nickel-based superalloys. The formation of adiabatic shear bands (ASBs) is a unique dynamic phenomenon that typically precedes catastrophic, unpredicted failure in many metals under impact or ballistic loading. ASBs are thin regions that undergo substantial plastic shear strain and material softening due to the thermo-mechanical instability induced by the competitive work hardening and thermal softening processes. Dynamic recrystallization of the material’s microstructure in the shear region can occur and encourages shear localization and the formation of ASBs. Phase transformations are also often seen in ASBs of ferrous metals due to the elevated temperatures reached in the narrow shear region. ASBs ultimately lead to the local degradation of material properties within a narrow band wherein micro-voids can more easily nucleate and grow compared to the surrounding material. As the micro-voids grow, they will eventually coalesce leading to crack formation and eventual fracture. For elevated temperature applications, such as in the aerospace industry, nickel-based superalloys are used due to their high strength. Understanding the formation conditions of ASBs in nickel-based superalloys is also beneficial in extending the life of machining tools. The main goal of the review is to identify the formation mechanisms of ASBs, the microstructural evolutions associated with ASBs in nickel-based alloys, and their consequent effect on material properties. Under a shear strain rate of 80,000 s−1, the critical shear strain at which an ASB forms is between 2.2 and 3.2 for aged Inconel 718 and 4.5 for solution-treated Inconel 718. Shear band widths are reported to range between 2 and 65 microns for nickel-based superalloys. The shear bands widths are narrower in samples that are aged compared to samples in the annealed or solution treated condition.
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Kim, Byeong Ho, Kyung Chul Park, Sung Hak Lee, Yong Ho Park i Ik Min Park. "In Situ Fracture Behavior of AZ51 and AZT513 Alloy". Materials Science Forum 620-622 (kwiecień 2009): 177–80. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.177.
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The fracture behavior of Mg-5Al-1Zn and Mg-5Al-1Zn-3Sn alloy was investigated by direct observation of microfracture process using an in-situ loading stage installed inside a scanning electron microscope chamber. Crack was initiated at the interface of Mg/second-phase particles or second-phase particles. Fracture of the alloys was predominantly dimple or/and quasi-cleavage failure. The improvement of what could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting and shear band branching.
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Huráková, Mária, Kornel Csach, Jozef Miškuf, Alena Juríková, Václav Ocelík i Jeff T. M. de Hosson. "Crack Propagation in Metallic Glass Ribbon as a Function of the Position of Stress Concentrators". Materials Science Forum 891 (marzec 2017): 494–99. http://dx.doi.org/10.4028/www.scientific.net/msf.891.494.
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An amorphous metallic ribbon of Fe40Ni40B20 was used for in-situ observation of the crack propagation and shear band formation during tensile tests. Prior to the tensile tests, two holes (with different positions with respect to the tensile axis) were made by laser ablation as stress concentrators. The nucleation and propagation of shear bands on the ribbon surface during tensile tests were analysed with scanning electron microscopy (SEM). At room temperature inhomogeneous plastic deformation of amorphous alloy occurs via the development of primary and secondary shear bands. The influence of the different loading geometry on the topology of shear bands and crack propagation was studied.
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Chen, Tianyu, i Jianjun Li. "Modelling the Shear Banding in Gradient Nano-Grained Metals". Nanomaterials 11, nr 10 (22.09.2021): 2468. http://dx.doi.org/10.3390/nano11102468.
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Extensive experiments have shown that gradient nano-grained metals have outstanding synergy of strength and ductility. However, the deformation mechanisms of gradient metals are still not fully understood due to their complicated gradient microstructure. One of the difficulties is the accurate description of the deformation of the nanocrystalline surface layer of the gradient metals. Recent experiments with a closer inspection into the surface morphology of the gradient metals reported that shear bands (strain localization) occur at the surface of the materials even under a very small, applied strain, which is in contrast to previously suggested uniform deformation. Here, a dislocation density-based computational model is developed to investigate the shear band evolution in gradient Cu to overcome the above difficulty and to clarify the above debate. The Voronoi polygon is used to establish the irregular grain structure, which has a gradual increase in grain size from the material surface to the interior. It was found that the shear band occurs at a small applied strain in the surface region of the gradient structure, and multiple shear bands are gradually formed with increasing applied load. The early appearance of shear banding and the formation of abundant shear bands resulted from the constraint of the coarse-grained interior. The number of shear bands and the uniform elongation of the gradient material were positively related, both of which increased with decreasing grain size distribution index and gradient layer thickness or increasing surface grain size. The findings are in good agreement with recent experimental observations in terms of stress-strain responses and shear band evolution. We conclude that the enhanced ductility of gradient metals originated from the gradient deformation-induced stable shear band evolution during tension.
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Jiang, W. H., i M. Atzmon. "Rate dependence of serrated flow in a metallic glass". Journal of Materials Research 18, nr 4 (kwiecień 2003): 755–57. http://dx.doi.org/10.1557/jmr.2003.0103.
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Plastic deformation of amorphous Al90Fe5Gd5 was investigated using nanoindentation and atomic force microscopy. While serrated flow was detected only at high loading rates, shear bands were observed for all loading rates, ranging from 1 to 100 nm/s. However, the details of shear-band formation depend on the loading rate.
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Duan, Chun Zheng, Wei Sen Kong, Zhao Xi Wang i Min Jie Wang. "Microscopic Observation of White Band within Shear Zone of Chip Produced during High Speed Machining of AISI 1045 Hardness Steel". Key Engineering Materials 474-476 (kwiecień 2011): 1292–95. http://dx.doi.org/10.4028/www.scientific.net/kem.474-476.1292.
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To study the microstructure of white band is helpful for revealing formation mechanism of serrated chip. This paper investigates the microstructural characteristics of white bandsat primary and second deformation zone within the serrated chips produced during High Speed Machining (HSM) of AISI 1045 hardened steel usingoptical microscope, SEM, TEM, and electron microprobe, X-Ray diffraction. It was found that the white bands within primary and second deformation zone consist of small equiaxed grains which formed due to dynamic recrystallization during adiabatic shear, however, martensitic transformation just only taken place within the white band in second deformation zone. The re-distribution of chemical elements between the composition phases occurred due to the combined effect of adiabatic temperature rise and high speed deformation in formation process of white band. The former is result from adiabatic shear in primary deformation zone during formation of chip, while the latter is caused by the intense shear and friction between tool and chip.
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Hilgendorff, Philipp Malte, Andrei Grigorescu, Martina Zimmermann, Claus Peter Fritzen i Hans Jürgen Christ. "Simulation of the Interaction of Plastic Deformation in Shear Bands with Deformation-Induced Martensitic Phase Transformation in the VHCF Regime". Key Engineering Materials 664 (wrzesień 2015): 314–25. http://dx.doi.org/10.4028/www.scientific.net/kem.664.314.
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The experimental observation of the microstructural deformation behavior of a metastable austenitic stainless steel tested at the real VHCF limit indicates that plastic deformation is localized and accumulated in shear bands and martensite formation occurs at grain boundaries and intersecting shear bands. Based on these observations a microstructure-sensitive model is proposed that accounts for the accumulation of plastic deformation in shear bands (allowing irreversible plastic sliding deformation) and considers nucleation and growth of deformation-induced martensite at intersecting shear bands. The model is numerically solved using the two-dimensional (2-D) boundary element method. By using this method, real simulated 2-D microstructures can be reproduced and the microstructural deformation behavior can be investigated within the microstructural morphology. Results show that simulation of shear band evolution is in good agreement with experimental observations and that prediction of sites of deformation-induced martensite formation is possible in many cases. The analysis of simulated shear stresses in most critical slip systems under the influence of plastic deformation due to microstructural changes contributes to a better understanding of the interaction of plastic deformation in shear bands with deformation-induced martensitic phase transformation in the VHCF regime.
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Ikutomo, R., Masato Tsujikawa, Makoto Hino, Hisamichi Kimura, Kunio Yubuta i Akihisa Inoue. "Fine Crystalline Phase Dispersion in Zr-Based Bulk Metallic Glass by Laser Irradiation". Advanced Materials Research 26-28 (październik 2007): 747–50. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.747.
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Bulk metallic glass (BMG) exhibits remarkable properties such as high strength, good stiffness and good corrosion resistance. However, the wear resistance of amorphous metals is not excellent as expected their high strength. It is thought that large local shear bands easily change into cracks for debris formation. The effective obstruction of shear band formation might be applied to improve the wear resistance of BMG. In this study, we tried to suppress shear band deformation by fine crystalline phase dispersion formed by semi-conductor laser irradiation. The microstructures of irradiated Zr-based BMG specimens were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The fine dispersions of crystalline phases are observed in the amorphous matrix. The optimum condition for laser irradiation was discussed.
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Wagner, Martin Franz-Xaver, i Philipp Frint. "Formation of bulk-laminated materials by localized deformation during ECAP of an AA6060 aluminum alloy". MATEC Web of Conferences 326 (2020): 08001. http://dx.doi.org/10.1051/matecconf/202032608001.
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This paper addresses localized plastic flow during equal-channel angular pressing (ECAP) of an AA6060 aluminum alloy. We observe an alternating formation of shear bands and matrix bands during ECAP that leads to pronounced strain partitioning without cracking. Local deformation is analyzed by considering the distortion of indents along flow lines in the center of a split billet. We estimate equivalent strains of about 3.6 inside the shear bands, whereas plastic deformation in the adjacent matrix bands is almost negligible. Microstructural analysis by SEM and STEM confirms that the shear bands exhibit typical features of severely plastically deformed microstructures at the onset of forming an ultrafine-grained microstructure. We further present statistics of band widths, and we discuss the roles material hardening as well as ECAP die geometry (in terms of the inner die radius) in facilitating the recurrent localized deformation that, in the absence of crack nucleation, leads to the production of an interesting and novel type of bulk-laminated materials by ECAP.
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Iliopoulos, Aggelos C., Nikolaos S. Nikolaidis i Elias C. Aifantis. "Analysis of serrations and shear bands fractality in UFGs". Journal of the Mechanical Behavior of Materials 24, nr 1-2 (1.05.2015): 1–9. http://dx.doi.org/10.1515/jmbm-2015-0001.
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AbstractTsallis nonextensive statistics is employed to characterize serrated flow, as well as multiple shear band formation in ultrafine grain (UFG) size materials. Two such UFG materials, a bi-modal Al-Mg alloy and a Fe-Cu alloy, were chosen. In the first case, at low strain rates serrated flow emerges as recorded in the stress-strain graphs, whereas at high strain rates, extensive shear banding occurs. In the second case, multiple shear banding is the only mechanism for plastic deformation, but serrations in the stress-strain graph are not recorded. The analysis aims at the estimation of Tsallis entropic index qstat (stat denotes stationary state), as well as the estimation of fractal dimension. The results reveal that the distributions of serrations and shear bands do not follow Gaussian statistics as implied by Boltzmann-Gibbs extensive thermodynamics, but are approximated instead by Tsallis q-Gaussian distributions, as suggested by nonextensive thermodynamics. In addition, fractal analysis of multiple shear band images reveals a (multi)fractal and hierarchical profile of the spatial arrangement of shear bands.
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Winter, Sven, Matthias Nestler, Elmar Galiev, Felix Hartmann, Verena Psyk, Verena Kräusel i Martin Dix. "Adiabatic Blanking: Influence of Clearance, Impact Energy, and Velocity on the Blanked Surface". Journal of Manufacturing and Materials Processing 5, nr 2 (13.04.2021): 35. http://dx.doi.org/10.3390/jmmp5020035.
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In contrast to other cutting processes, adiabatic blanking typically features high blanking velocities (>3 m/s), which can lead to the formation of adiabatic shear bands in the blanking surface. The produced surfaces have excellent properties, such as high hardness, low roll-over, and low roughness. However, details about the qualitative and quantitative influence of significant process parameters on the quality of the blanked surface are still lacking. In the presented study, a variable tool is used for a systematic investigation of different process parameters and their influences on the blanked surface of a hardened 22MnB5 steel. Different relative clearances (1.67% to 16.67%), velocities (7 to 12.5 m/s), and impact energies (250 J to 1000 J) were studied in detail. It is demonstrated that a relative clearance of ≤6.67% and an impact velocity of ≥7 m/s lead to adiabatic shear band formation, regardless of the impact energy. Further, an initiated shear band results in the formation of an S-shaped surface. Unexpectedly, a low impact energy results in the highest geometric accuracy. The influence of the clearance, the velocity, and the impact energy on the evolution of adiabatic shear band formation is shown for the first time. The gained knowledge can enable a functionalization of the blanked surfaces in the future.
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Asano, M., Tadashi Minoda, Y. Ozeki i Hideo Yoshida. "Effect of Copper Content on the Bendability of Al-Mg-Si Alloy Sheet". Materials Science Forum 519-521 (lipiec 2006): 771–76. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.771.
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The effects of the copper content on the bendability of Al-Mg-Si alloy T4 sheets were investigated. The Al-Mg-Si alloys with less than 0.01mass%Cu, 0.4mass%Cu and 0.8mass%Cu were prepared, and the time of solution heat treatment was changed to obtain different dispersion conditions of the second phase particles and to obtain different shear band formation conditions by bending. For the samples with less than 0.01mass%Cu and 0.4mass%Cu, no cracks were observed during the bending. For the sample with 0.8mass%Cu, the maximum depth of the crack by bending increased with the time of solution heat treatment up to 75 seconds, and then decreased over 75 seconds. The second phase particles decreased by increasing the solution heat treatment time, while the formation of shear bands by bending increased by increasing the solution heat treatment time and the copper content. The cause of the occurrence and the propagation of cracks by bending are considered to be the combined effect of the shear band formation across some grains and the micro-voids formed around the second phase particles. Improving of the bendability requires a decrease in the size and number of the second phase particles and/or reduced shear band formation during the bending.
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Subhash, Ghatu, i Hongwen Zhang. "Dynamic indentation response of ZrHf-based bulk metallic glasses". Journal of Materials Research 22, nr 2 (luty 2007): 478–85. http://dx.doi.org/10.1557/jmr.2007.0058.
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Static and dynamic Vickers indentations were performed on ZrHf-based bulk amorphous alloys. A decrease in indentation hardness was observed at higher strain rates compared with static indentation hardness. For equivalent loads, dynamic indentations produced more severe deformation features on the loading surface than static indentations. Using bonded interface technique, the induced shear band patterns beneath the indentations were studied. In static indentations, the majority of the deformation was primarily accommodated by closely spaced semicircular shear bands surrounding the indentation. In dynamic indentations two sets of widely spaced semicircular shear bands with two different curvatures were observed. The observed shear band patterns and softening in hardness were rationalized based on the variations in the confinement pressure, strain rate, and temperature within the indentation region during dynamic indentations. It is also proposed that free volume migration and formation of nano-voids leading to cracking are favored due to adiabatic heating and consequently cause the observed softening at high strain rates.
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Qiu, K. Q., Z. Y. Suo, Y. L. Ren i B. Yu. "Observation of shear bands formation on tungsten fiber-reinforced Zr-based bulk metallic glass matrix composite". Journal of Materials Research 22, nr 2 (luty 2007): 551–54. http://dx.doi.org/10.1557/jmr.2007.0067.
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A Zr-based metallic glass matrix composite with 40 vol% tungsten fiber reinforcement was loaded step by step. After each loading step, shear-band patterns and fracture surface were observed. The results show that shear bands, cracks, and voids form during plastic deformation, and they exhibit different feature characteristics at various loading stages. As reinforcement, the tungsten fiber substantially affects the deformation and fracture processes of the composite.