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Автор: Grafiati
Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Shear band formations"

1

Herle, Vishweshwara, Peter Fischer, and Erich J. Windhab. "Shear thickening and shear induced band formations in solutions of wormlike micelles." Journal of Central South University of Technology 14, S1 (February 2007): 213–17. http://dx.doi.org/10.1007/s11771-007-0248-0.

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2

Stevens, Jeffry L., and Steven M. Day. "Shear velocity logging in slow formations using the Stoneley wave." GEOPHYSICS 51, no. 1 (January 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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3

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, no. 2 (2014): I_441—I_451. http://dx.doi.org/10.2208/jscejam.70.i_441.

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4

Ingram, J. D., C. F. Morris, E. E. MacKnight, and T. W. Parks. "Direct phase determination of S‐wave velocities from acoustic waveform logs." GEOPHYSICS 50, no. 11 (November 1985): 1746–55. http://dx.doi.org/10.1190/1.1441864.

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Анотація:
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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5

Yang, Jiaqi, Bikash K. Sinha, and Tarek M. Habashy. "Estimation of formation shear and borehole-fluid slownesses using sonic dispersion data in well-bonded cased boreholes." GEOPHYSICS 76, no. 6 (November 2011): E187—E197. http://dx.doi.org/10.1190/geo2010-0413.1.

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Анотація:
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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6

Li, Jun Li, Gang Liu, Dong Jin Zhang, and Ming Chen. "A FEM Study on Chip Formation in Orthogonal Turning Nickel-Based Superalloy GH80A." Materials Science Forum 575-578 (April 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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7

Wei, Zhoutuo, Xiaoming Tang, and Jingji Cao. "Acoustic radiation and reflection of a logging-while-drilling dipole source." Geophysical Journal International 219, no. 1 (May 2, 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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8

Kirshbaum, Daniel J., and Dale R. Durran. "Observations and Modeling of Banded Orographic Convection." Journal of the Atmospheric Sciences 62, no. 5 (May 1, 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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9

Randall, C. J., D. J. Scheibner, and P. T. Wu. "Multipole borehole acoustic waveforms: Synthetic logs with beds and borehole washouts." GEOPHYSICS 56, no. 11 (November 1991): 1757–69. http://dx.doi.org/10.1190/1.1442988.

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Анотація:
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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10

Maiti, Payel, Dhrubajyoti Sadhukhan, Jiten Ghosh, and Anoop Kumar Mukhopadhyay. "Nanoscale plasticity in titania densified alumina ceramics." Journal of Applied Physics 131, no. 13 (April 7, 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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Більше джерел

Дисертації з теми "Shear band formations"

1

Herrin, Elizabeth Anne. "Experimental study of shear and compaction band formation in berea sandstone." Thesis, [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3176.

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2

Shojaaee, Zahra [Verfasser], Dietrich E. [Akademischer Betreuer] Wolf, and Stefan [Akademischer Betreuer] Luding. "Shear Bands in Granular Materials : Formation and Persistence at Smooth Walls / Zahra Shojaaee. Gutachter: Stefan Luding. Betreuer: Dietrich E. Wolf." Duisburg, 2012. http://d-nb.info/1023643758/34.

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3

Wang, Lu. "Shear-Band Formation and Thermal Activation in Metallic Glasses." 2011. http://trace.tennessee.edu/utk_graddiss/1236.

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Metallic glasses (MGs) usually have high strength, high hardness and high elastic strain limit. However, the deformation mode and mechanism in metallic glasses are radically different from those in conventional crystalline materials with a long-range ordered structure. For crystalline materials, the intrinsic relationship between their mechanical properties and crystal structures has been well described by dislocation theory. In contrast, for amorphous materials, theories on the structures and controlling factors of localized shear-band formation are far from being complete. In this thesis, shear-banding behavior of MGs under nanoindentation was first reviewed. The hardness of MGs was found to be independent on the shape of indenter tip. The hardness drop during each pop-in was a constant for a given indenter tip. A nanoindentation-based method for measuring the shear resistance of MGs was further developed. The hardness of MGs was largely affected by residual stresses, especially the tensile residual stress. Significant softening could be caused by tensile residual stress and the softening was attributed to the creation of extra free volume. The hardness of MGs was demonstrated to be extremely sensitive to the initial free volume in the material. Spherical indentation was also conducted on stressed MG sample to study the effect of residual stress on the first shear-band formation. It was found the critical shear stress for the shear-band formation was essentially a constant. The constant critical shear stress was correlated with a critical free volume in the material. Spherical indentation was further carried out at elevated temperature but well below glass transition temperature to explore the temperature effect on shear-band nucleation. Localized shear-banding was observed to be the dominant deformation mode at all temperatures. The shear stress at first pop-in or the onset of yielding decreased with temperature, and the activation energy and the size of shear transformation zone (STZ) were measured. Shear-band nucleus was estimated to be 10~20 nm and independent on temperature. Micro-compression tests were further performed on micro-sized pillar samples at different temperatures. The strength-temperature relationship could be explained by the constant viscosity concept, suggesting shear-banding was a stress-induced glass transformation.
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4

Qing-De, Jiang, and 江慶德. "The Shear Band Formation in Compression of 7050 Aluminum Alloy." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/44475087803708355101.

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Анотація:
碩士
國立清華大學
材料科學工程學系
85
The microstructure and compressive deformation behavior of a 7050-T7451 aluminum alloy were studied. The shear bands formed during the process of compression are more visible on T plance than on L plane, and the tenency to form shear bands is higher in the center portion of the plate than in the outer portion. I was also found that when compressed in the short transverse direction, the strain in the longitudinal direction is at least 50% larger than that in the transverse direction. On T plane, two sets of slip bands which make an angle of about 70° with each other and having the longitudinal direction as their bisector were observed. On L plane, two sets of parallel slip traces which make an angle of about 40° with each other and having the transverse direction as their bisector were observed. Slip band formation is more evident when specimens were cold rolled in the longitudinal direction than in the transverse direction. The macroscopic shear bands are close related to the microscopic slip bands. All the phenomena described above are in association with textures. A duplex texture of two superimposed components, ｛1 －1 0｝〈0 0 1〉 Goss texture ＋｛1 1 0｝〈－1 1 2〉 Brass texture, were found in the 7050-T7451 aluminum alloy. Based on the effect of textures, an explanation of the phenomena described above is proposed in this study.
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5

Wang, Chong-An, and 王崇安. "The Shear Band formation in Plane Strain Compression of 7050 Aluminum Alloy." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/83692486280291125600.

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Анотація:
碩士
國立清華大學
材料科學工程學系
87
The evolution of shear band and mechanical properties in plane strain compression of 7050- T7451 aluminum alloy were studied. The shear bands or slip lines formed on L plane with L direction constrained are more diffuse than those formed on T plane with T direction constrained. The constrained surface is rougher when it is L plane than T plane. The shear band formation is mainly in accord with the macroscopic mechanics approach. The flow strength of specimens with constraint in L direction is higher than that with constraint in T direction, except the final stage of true stress- engineering curve of specimen cut from surface and deformed with constrained in L direction. The specimens form trapezoid shape and decrease the true stress we measured. Compared with the tensile properties in previous study, shear bands formed at a strain near but a little bit larger than the uniform strain in tension. There is no obvious hardening phenomenon after formation of shear bands. The maximum and minimum points appeared in true stress- engineering strain curves of family II specimens are related to the formation of shear band. Regarding microstructure and texture in the alloy, when T direction was constrained, most slip bands fell into two sets which make an angle of 35°to the longitudinal direction on T plane of the specimen. On L plane of the specimens with constraint in L direction, most slip bands fell into two sets roughly follow the direction of the shear bands and make an angle about 90°. By X-ray diffraction, it is found that the texture in the alloy is mainly a mixture of Goss texture and Brass texture . Goss texture is the main texture to deform when constrained in T direction. Multiple slip occurs when the constraint is in L direction.
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6

Wang, Yaw-Shing, and 王耀星. "The Effect of Precipitation Treatment upon the Formation of Shear Bands." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/13921086849957592513.

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Анотація:
碩士
國立清華大學
材料科學工程學系
89
By changing the temperature and time of two step aging, three aging conditions of 7050 aluminum alloy, namely: under aging, peak aging and over aging were obtained. After aging, some of the materials were cold rolled to a reduction in thickness of 20%. The plane strain compression test in S direction to different amount of reduction in thickness in a channel die with T or L direction constrained was performed at room temperature. The formation of shear bands and the true stress -true strain curves were studied. In plane strain compressed specimens with either T or L direction constrained, macroscopic shear bands were visible on the constrained plane surface of the specimen. The shear bands formed along planes of maximum shear stress which make an angle 45 degree to the S and the non-constrained plane. The shear bands are more clear when T plane is the constrained plane. The maximum shear strain observed in a shear band is 2. It was noticed that the strength of specimens constrained in L direction were higher than that of their counterpart specimens constrained in T direction. For under aged specimen, the shear bands was sharply localized. Specimen will shear rupture along shear bands with a sudden drop of the stress. Similar but wider shear bands were observed in peak and over aged specimens. The width of over aged specimens was the largest. No rupture were observed in over aged specimens even when the true compression strain went up to 0.6 when the test ended. For under aged specimen with T direction constrained, the true strain of rupture is 0.32. For cold rolled specimen, the formation of shear bands occured at a smaller strain and the true strain of rupture is 0.27. When constrained in L direction, the rupture strain, 0.29 for underaged and 0.125 for underaged and cold rolled specimens was smaller than those in T direction. In contrast to the underaged case, for over aged specimens the stain of shear band formation was larger when constrained in L direction than in T direction. A model based on the dislocation- precipitate interaction was proposed to explain these observations. The effect of precipitates upon the formation of shear bands observed in the study was mainly macroscopic slip. No matter the plane strain compression by T direction constrained or L direction constrained, the angles between the macroscopic shear bands and compress plane are all about 45° which is the same with maximum shear plane. It is suggested that the effect upon the formation of shear bands were mainly subjected to the precipitates and maximum shear plane, and slight for the orientation in the individual grain or the texture.
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7

Fu, Chien Hao, and 傅建豪. "The Formation of Shear Bands in 7050 Aluminum Alloy and Alminum Single crystal." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/82472822794529121989.

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Анотація:
碩士
國立清華大學
材料科學工程學系
90
The formation of shear bands and the true stress - true strain curves were studied by plane strain compression of 7050 Al alloy and pure Al single crystal. Two types of plane strain compression specimens were studied. One is channel die specimens and the other is thin sheet specimens. The plane strain compression test was conducted at room temperature by compression in S direction to different amount of reduction in thickness with T or L direction constrained. Macroscopic shear band was observed in compression of 7050 Al alloy. Assuming that the formation of shear bands was determined by the plane of maximum shear stress in continuum mechanics, the fluctuation of true stress - true strain curves of channel die and thin sheet specimens can be simulated by the ideal σ/2τy vs. ε curve. Most of the angles of shear bands of channel die specimens are between 40˚ to 50˚. Most angles of shear bands of thin sheet specimens are between 45˚ to 57˚. This result can be explained by the shape of specimens and the characteristics of the dies. Pure Al single crystal specimen in Cubic {100}<001>, Goss {110}<001> and Brass{110}<1-12> orientation were plane strain compressed in a channel die. In contrast to 7050 Al alloys, no macroscopic shear bands were observed in Al single crystals specimens. For all single crystal specimens, the true flow strength increase monotonically with true strain. The Cubic and Brass oriented single crystals have nearly the same initial flow strength. They both show linear work hardening behavior but the work hardening rate of Cubic oriented crystal is higher than that of Brass oriented crystal. In contrast, the Goss oriented crystal shows a higher initial flow strength and a parabolic work hardening behavior with a decreasing work hardening rate. The flow strength of Cubic oriented crystal goes above that of Goss oriented crystal when the true strain is larger than 0.5. In the compression test, the initially cubic shaped Al single crystal in Brass orientation gradually turns into a parallelepiped. The acute angle of the parallelepiped as a function of compressive strain can be predicted by the slip of the active systems of Brass orientation.
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8

Zeng, Bao-Jin, and 曾寶瑾. "Effect of shear bands formation on the microstructure and mechanical properties of Zr65Cu17.5Ni10Al7.5 amorphous alloys." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/82334724189937693936.

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Анотація:
碩士
義守大學
材料科學與工程學系
104
Bulk metallic glasses (BMGs) have attracted attention due to their high strength and outstanding thermal properties. However, the low workability at room temperature of BMGs limited their applications. Therefore, reseachers developed different methods to solve the problem of poor room temperature ductility. For example, the methods of the adding of minor element, themal treatments, rolling and friction are used to improve the mechanical properties of BMGs by the formation of phase transformation and microstructure variation. According to the literature results showed that the method of rolling process is a possible way to increase the room temperature plasticity. 　　Zr65Cu17.5Ni10Al7.5 bulk metallic glass is the base alloy in this study, which has high GFA (Trg = 0.594) and the fracture stress is about 1200 MPa. The results show that the brittle Zr65Cu17.5Ni10Al7.5 BMGs was plastically deformation at room temperature by the introducing of rolling process before compression test. The compressive fracture strength and strain increased form 1156 MPa and 5.8% (the base alloy) to 1914 MPa and 32.81% (cold-rolled specimen with average true strain 10.03%). The great enhancement of plastic strain can be attributed to the formation of pre-introduced shear bands (called pre-shear band and secondary shear bands) after the pre-rolling process. Dense dispersion of pre-introduced shear bands impeded the propagation of primary shear bands during the compression test and the improved of plasticity of alloys with increasing rolling average true strain (up to average true strain 10.03%).
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9

Detwiler, Andrew Thomas. "Aspects of network formation and property evolution in glassy polymer networks." 2011. https://scholarworks.umass.edu/dissertations/AAI3482611.

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Experimental and theoretical characterization techniques are developed to illuminate relationships between molecular architecture, processing strategies, and physical properties of several model epoxy-amine systems. Just beyond the gel point partially cured networks are internally antiplasticized by unreacted epoxy and amine which leads to enhanced local chain packing and strain localization during deformation processes. Additional curing causes the antiplasticization to be removed, resulting in lower modulus, density, yield stress, and less strain localization. Physical and mechanical probes of network formation are discussed with respect to several different partially cured model epoxy-amine chemistries. The non-linear fracture energy release rate and the molecular architecture of virgin and healed epoxy networks are related through an effective crack length model. The inelastic component of the fracture energy release rate is attributed to the failure of network strands in a cohesive zone at the crack tip. Data from fracture and healing experiments are in good agreement with the model over more than three orders of magnitude. Changes in the shape of the process zone and deviation from planar crack growth cause deviations from the model for the toughest networks tested. Double network epoxies are created from stoichiometric blends of an epoxy resin cured sequentially with aliphatic and aromatic amine curing agents. Unreacted epoxide and aromatic amine functionality antiplasticize the partially cured materials. The thermal and mechanical properties of the fully cured networks vary according to composition. No evidence of phase separation is observed across the entire composition and conversion range. However, the breadth of the glass transition in the double networks increases due to the difference in the molecular stiffness of the two curing agents. Techniques are developed to monitor the evolution of residual stresses and strength in complex multicomponent epoxy-amine based coatings. The evolution of properties is attributed to loss of volatile small molecules from the coatings. The stresses that develop in biaxially constrained membranes are monitored through mechanical excitation. The strength of the membranes is determined by monitoring the size and shape of center cracks. This fracture analysis technique allows the evolution of stresses and toughness of the materials to be monitored simultaneously.
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Polyzois, Ioannis. "Prediction of the formation of adiabatic shear bands in high strength low alloy 4340 steel through analysis of grains and grain deformation." 2014. http://hdl.handle.net/1993/30072.

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High strain rate plastic deformation of metals results in the formation of localized zones of severe shear strain known as adiabatic shear bands (ASBs), which are a precursor to shear failure. The formation of ASBs in a high-strength low alloy steel, namely AISI 4340, was examined based on prior heat treatments (using different austenization and tempering temperatures), testing temperatures, and impact strain rates in order to map out grain size and grain deformation behaviour during the formation of ASBs. In the current experimental investigation, ASB formation was shown to be a microstructural phenomenon which depends on microstructural properties such as grain size, shape, orientation, and distribution of phases and hard particles—all controlled by the heat treatment process. Each grain is unique and its material properties are heterogeneous (based on its size, shape, and the complexity of the microstructure within the grain). Using measurements of grain size at various heat treatments as well as dynamic stress-strain data, a finite element model was developed using Matlab and explicit dynamic software LSDYNA to simulate the microstructural deformation of grains during the formation of ASBs. The model simulates the geometrical grain microstructure of steel in 2D using the Voronoi Tessellation algorithm and takes into account grain size, shape, orientation, and microstructural material property inhomogeneity between the grains and grain boundaries. The model takes advantage of the Smooth Particle Hydrodynamics (SPH) meshless method to simulate highly localized deformation as well as the Johnson-Cook Plasticity material model for defining the behavior of the steel at various heat treatments under high strain rate deformation.The Grain Model provides a superior representation of the kinematics of ASB formation on the microstructural level, based on grain size, shape and orientation. It is able to simulate the microstructural mechanism of ASB formation and grain refinement in AISI 4340 steel, more accurately and realistically than traditional macroscopic models, for a wide range of heat treatment and testing conditions.
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Книги з теми "Shear band formations"

1

Leʹsniewska, Danuta. Analysis of shear band pattern formation in soil. Gdaʹnsk: Instytut Budownictwa Wodnego PAN, 2000.

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Franson, Jeffrey R. Formation of adiabatic shear bands in metal-forming processes. 1992.

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3

Kumazawa, Makoto. Acceleration waves in micropolar elastic media and formation of shear bands. 1988.

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Частини книг з теми "Shear band formations"

1

Wright, T. W. "Susceptibility to Shear Band Formation in Work Hardening Materials." In Anisotropy and Localization of Plastic Deformation, 95–98. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3644-0_22.

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Shearer, M., F. X. Garaizar, and M. K. Gordon. "Formation of Shear Bands in Models of Granular Materials." In IUTAM Symposium on Mechanics of Granular and Porous Materials, 343–52. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5520-5_31.

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3

Gutierrez, Marte S. "Effects of Constitutive Parameters on Shear Band Formation in Granular Soils." In Soil Stress-Strain Behavior: Measurement, Modeling and Analysis, 691–706. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6146-2_50.

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Hori, M., M. S. Anders, and T. Mizutani. "Analysis of periodic shear band formation: model experiments and numerical simulation." In Bifurcation and Localisation Theory in Geomechanics, 311–19. London: CRC Press, 2021. http://dx.doi.org/10.1201/9781003210931-43.

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Rhim, Sung Han, Hyung Wook Park, and Soo Ik Oh. "Finite Element Analysis of Adiabatic Shear Band Formation during Orthogonal Metal Cutting." In The Mechanical Behavior of Materials X, 885–88. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-440-5.885.

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Flaherty, Joseph E., Peter K. Moore, and John Walter. "Adaptive Methods for Parabolic Partial Differential Equations with Applications to Shear Band Formation." In Computational Mechanics ’95, 2487–92. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79654-8_413.

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To, Sandy Suet, Victor Hao Wang, and Wing Bun Lee. "Dynamic Modelling of Shear Band Formation and Tool-Tip Vibration in Ultra-Precision Diamond Turning." In Materials Characterisation and Mechanism of Micro-Cutting in Ultra-Precision Diamond Turning, 253–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-54823-3_10.

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Triantafyllidis, T., H. Wolf, and D. König. "On the Factors Affecting the Formation of Shear Band Systems in Non-Cohesive Soils Under Extensional Strain." In Springer Proceedings in Physics, 463–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/978-3-540-35724-7_27.

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Dhokia, V. G., S. T. Newman, P. Crabtree, and M. P. Ansell. "The Formation of Adiabatic Shear Bands as a result of Cryogenic CNC Machining of Elastomers." In Proceedings of the 36th International MATADOR Conference, 235–38. London: Springer London, 2010. http://dx.doi.org/10.1007/978-1-84996-432-6_54.

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"formation of shear bands." In Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik, 556. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41714-6_62473.

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Тези доповідей конференцій з теми "Shear band formations"

1

Liang, Lin, Ting Lei, and Matthew Blyth. "AUTOMATIC LOGGING-WHILE-DRILLING DIPOLE SONIC SHEAR PROCESSING ENABLED BY PHYSICS-DRIVEN MACHINE LEARNING." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0059.

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Logging-while-drilling (LWD) dipole sonic tools have been introduced to the industry as a supplement to monopole and quadrupole measurement because they can provide shear slowness anisotropy, which is essential for formation characterization and well completion applications. Due to the presence of the collar, which acts as a strong waveguide, the recorded formation signal is significantly affected at low frequencies. Consequently, an automated interpretation of LWD dipole sonic data re-mains a challenge. The traditional dispersive semblance-based method requires accurate estimates of parameters such as borehole size and/or mud slowness to avoid bias in the dispersion model used in the processing. Recently, a frequency-slowness domain inversion scheme has been developed that can invert for both the formation shear slowness and mud slowness by minimizing the guidance-mismatch cost function. However, this method uses an isotropic dispersion model and requires selecting narrow-band dispersion data in the low-frequency range with good-quality, which can limit the range of applicability of the method and also requires user input through-out the process. We have previously developed a physics-driven machine learning-based method to enhance the interpretation of wireline dipole sonic data. However, the LWD scenario introduces additional complexity. This work extends the method to support the interpretation of LWD dipole sonic. An anisotropic root-finding mode-search algorithm is first used to generate extensive synthetic formation flexural dispersion curves that can match dispersion measurements in strong anisotropic formations in high-angle and horizontal wells, with a known tool model. Special care needs to be taken to pick the formation flexural mode from several co-existing modes arising from the strong coupling between tool and formation. After quality control and verification, this comprehensive synthetic dataset is used to train a neural network model. We then develop an inversion-based algorithm, taking advantage of this efficient neural network model and combining it with a clustering algorithm, to reliably label and ex-tract the formation flexural mode, processed from either the modified Prony’s method, or a broadband dispersion analysis algorithm. The extraction around the formation flexural kick-in frequency is used for developing a quality control method. The strongest collar arrival, on the other hand, can be confidently removed due to the fundamental difference in its dispersion characteristics from the formation flexural mode. This novel method can automatically and efficiently label the formation flexural mode and simultaneously invert it for formation shear slowness together with other relevant parameters such as mud slowness without user intervention. Since this method is built upon an anisotropic model, it can be applied to the full frequency range of the data spectrum without the traditional isotropic model assumption. Additionally, the regression analysis of the inverted mud slownesses can further provide physical constraint to reduce uncertainties in the inverted shear slowness. The algorithm has been tested on field data showing good performance. It makes edge deployment possible so that LWD telemetry can be optimized to transmit the processed data to the surface in real-time, which is essential to leverage the advantages of the conveyance method.
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Fazlali, Mohammadreza, Mauricio Ponga, and Xiaoliang Jin. "Analysis of the Unique Mechanics of Shear Localization in Metal Cutting Processes." In ASME 2022 17th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/msec2022-85645.

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Abstract Recent experimental observations show that the frequency of stress and temperature fluctuations on the cutting tool’s rake face and the frequency of residual stress fluctuation at the finished surface of the workpiece are equal to the shear band formation’s frequency. In this article, new experimental observations of the shear band formation in cutting processes are presented. Then, the spacing between neighboring shear bands (which determines the shear band formation’s frequency) is obtained from different theoretical methods and compared with the experimental results. It is shown that the shear band spacing in cutting processes cannot be obtained from the theories developed in other dynamic deformation applications, including dynamic compression and torsion tests and ballistic impacts, due to the unique mechanics of cutting. In addition, we show that due to the intense plastic deformation in the primary deformation zone, the cooling rate of the shear band formed during cutting processes is considerably higher than the workshop cooling rates (6.85 × 108 K·s−1 for the cutting speed of 60 m·min−1 compared to 50 K·s−1 - 2 × 104 K·s−1 for workshop cooling rate of Ti-6Al-4V). The rapid cooling rate indicates the considerable amount of heat transferred into the cutting tool and explains the ductile to brittle transition in the fracture mechanism of shear band formation in cutting processes.
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Owolabi, Gbadebo, Daniel Odoh, Akindele Odeshi, and Horace Whitworth. "Modeling and Simulation of Adiabatic Shear Bands in AISI 4340 Steel Under Impact Loads." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89084.

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In this study, the effects of microstructure and strain rate on the occurrence and failure of adiabatic shear bands in AISI 4340 steel under high velocity impact loads are investigated using finite element analysis and experimental tests. The shear band generated due to impact load was divided into some set of elements separated by nodes using finite element method in ABAQUS environment with initial and boundary conditions specified. The material properties were assumed to be lower at the second element set in order to initialize the adiabatic shear bands. The strain energy density for each successive node was calculated successively starting from the first element where initial boundary condition, initial strain hardening constant, and stress resistance had been specified. As the load time is increased, its corresponding effect on the localized shear deformation and width of the adiabatic shear band was also determined. The finite element model was used to determine the maximum stress, the strain hardening, the thermal softening, and the time to reach critical strain for formation of adiabatic shear bands. Experimental results show that deformed bands were formed at low strain rates and there was a minimum strain rate required for formation of transformed band in the alloy. The experimental results also show that cracks were initiated and propagated along transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by strain-rates and the initial material microstructures. The numerical results obtained were compared with the experimental results obtained for the AISI 4340 steel under high strain-rate loading in compression using split impact Hopkinson bars. A good agreement between the experimental and simulation results are also obtained.
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Dey, T. N., and J. N. Johnson. "Shear band formation in plastic bonded explosive (PBX)." In The tenth American Physical Society topical conference on shock compression of condensed matter. AIP, 1998. http://dx.doi.org/10.1063/1.55648.

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Yadav, Shwetabh, and Dinakar Sagapuram. "Nucleation and Boundary Layer Growth of Shear Bands in Machining." In ASME 2019 14th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/msec2019-3022.

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Abstract An experimental study of shear band formation in cutting of metals is made using a low melting point Bi-based alloy as a model material system. High-speed imaging is used to capture the transition in the plastic flow, from laminar to shear banded flow, as a function of cutting speed. The dynamics of shear band nucleation is captured in situ and temporal evolution of localized plastic flow during shear band growth is quantitatively analyzed using an image correlation method, particle image velocimetry (PIV). The observations show that shear band nucleation is governed by a critical shear stress criterion, and accompanied by a large drop in the flow viscosity by several orders of magnitude, analogous to the phenomenon of yielding in yield-stress (Bingham) fluids. Likewise, the displacement field around a freshly nucleated shear band evolves in a manner resembling the boundary layer formation in planar flow of a Bingham fluid with a very small viscosity. Surprisingly, temperature has little influence on shear band nucleation or growth.
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Dey, Rajib, Bipul Hawlader, and Chen Wang. "Progressive Failure of Offshore Slopes due to Construction in Upslope Areas." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-42241.

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Human activities such as construction loading in upslope areas could be a potential triggering factor for many offshore landslides such as the 1979 Nice landslide. Post-slide investigations show that the existence of marine sensitive clay layers might be one of the potential causes of many large-scale submarine landslides. In this paper, a finite element (FE) modeling technique is developed to analyze the failure of a slope in undrained condition. Nonlinear strain softening behaviour of undrained shear strength of marine sensitive clays is incorporated in the FE analysis. Strain localization in narrow zones (i.e. shear bands) could be successfully simulated. The formation of shear bands and their propagation could explain some potential failure mechanisms. The FE results show that large-scale catastrophic failure of submarine slopes might have occurred due to shear band propagation through strain softening clay layers, which cannot be explained using the traditional limit equilibrium methods for slope stability analysis. Effects of different factors, such as thickness of the marine clay layer and its sensitivity, on stability of submarine slope are also examined.
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Gheisari, Reza, and Parisa Mirbod. "Experimental Study of Non-Colloidal Mono and Polydisperse Suspension in Taylor-Couette Flow." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21570.

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Monodisperse and polydisperse suspension flows form an extensive section of natural and technological flows. These flow structures can be categorized to sedimenting or neutrally buoyant suspensions considering the density ratio between particle phase to dispersion phase. Biological systems, food processing, ceramic injection, dynamic filtration and air conditioning are examples of areas that such flows arise. Various complicated interparticle interactions and their inevitable influence on and from the continuous phase result in some interesting phenomena which are challenging to justify. This research studies axial instabilities of suspension flow in a partially filled Taylor-Couette setup. Previous observations show that when a monodisperse suspension undergoes a rotational shear motion in a partially filled horizontal Couette cell, particles leave their initial uniform distribution and migrate to regions with lower shear rate. This migration helps formation of ring-shape axial concentrated bands. This study examines the noncolloidal neutrally buoyant suspensions of hard spherical particles with average diameters of 150, 360, 850 micron. Using UCON oil (poly ethylene glycol-ran-glycol) as suspending fluid, monodisperse and polydisperse suspensions in partially filled Stokesian Couette-Taylor flow were studied. The results show strong dependence of band number and profile on suspension concentration and filling level. Moreover interesting phenomena in polydisperse suspensions such as different band shape and weak dependence of band formation time on size of constituents were observed.
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Muratov, R. V., P. N. Ryabov, and M. B. Soukharev. "2D numerical simulation of adiabatic shear bands formation." In INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2020. AIP Publishing, 2022. http://dx.doi.org/10.1063/5.0081581.

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Mahmood, Zafar, Kazuyoshi Iwashita, Masami Nakagawa, and Stefan Luding. "Influence of Bedding on Shear Band Formation of Quasistatic Granular Media." In POWDERS AND GRAINS 2009: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON MICROMECHANICS OF GRANULAR MEDIA. AIP, 2009. http://dx.doi.org/10.1063/1.3179936.

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YANG, DENGKE, PETER D. HODGSON, and CUIE WEN. "SHEAR BAND EVOLUTION AND NANOSTRUCTURE FORMATION IN TITANIUM BY COLD ROLLING." In Proceedings of the 6th International Conference on ICAMP. WORLD SCIENTIFIC, 2011. http://dx.doi.org/10.1142/9789814322799_0002.

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Звіти організацій з теми "Shear band formations"

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Burns, Timothy J. A mechanism for shear band formation in the high strain rate torsion test. Gaithersburg, MD: National Institute of Standards and Technology, 1989. http://dx.doi.org/10.6028/nist.ir.89-4121.

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Kerrisk, J. F. A model for shear-band formation and high-explosive initiation in a hydrodynamics code. Office of Scientific and Technical Information (OSTI), March 1996. http://dx.doi.org/10.2172/219526.

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Oliynyk, Kateryna, and Matteo Ciantia. Application of a finite deformation multiplicative plasticity model with non-local hardening to the simulation of CPTu tests in a structured soil. University of Dundee, December 2021. http://dx.doi.org/10.20933/100001230.

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In this paper an isotropic hardening elastoplastic constitutive model for structured soils is applied to the simulation of a standard CPTu test in a saturated soft structured clay. To allow for the extreme deformations experienced by the soil during the penetration process, the model is formulated in a fully geometric non-linear setting, based on: i) the multiplicative decomposition of the deformation gradient into an elastic and a plastic part; and, ii) on the existence of a free energy function to define the elastic behaviour of the soil. The model is equipped with two bonding-related internal variables which provide a macroscopic description of the effects of clay structure. Suitable hardening laws are employed to describe the structure degradation associated to plastic deformations. The strain-softening associated to bond degradation usually leads to strain localization and consequent formation of shear bands, whose thickness is dependent on the characteristics of the microstructure (e.g, the average grain size). Standard local constitutive models are incapable of correctly capturing this phenomenon due to the lack of an internal length scale. To overcome this limitation, the model is framed using a non-local approach by adopting volume averaged values for the internal state variables. The size of the neighbourhood over which the averaging is performed (characteristic length) is a material constant related to the microstructure which controls the shear band thickness. This extension of the model has proven effective in regularizing the pathological mesh dependence of classical finite element solutions in the post-localization regime. The results of numerical simulations, conducted for different soil permeabilities and bond strengths, show that the model captures the development of plastic deformations induced by the advancement of the cone tip; the destructuration of the clay associated with such plastic deformations; the space and time evolution of pore water pressure as the cone tip advances. The possibility of modelling the CPTu tests in a rational and computationally efficient way opens a promising new perspective for their interpretation in geotechnical site investigations.
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