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You searched for subject:(shear band propagation). Showing records 1 – 2 of 2 total matches.

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Georgia Tech

1. Kim, Sihyun. Shear band and landslide dynamics in submerged and subaerial slopes.

Degree: PhD, Civil and Environmental Engineering, 2014, Georgia Tech

Submarine landslides, commonly triggered by earthquakes, significantly affect tsunami wave heights. Subaerial landslides can also generate tsunamis (if the land flows into a body of water) and may be catastrophic in nature, causing human casualties and direct property damage. This work focuses on landslides associated with shear band that develops beneath the slipping mass. Accordingly, we consider a landslide as a dynamic process when a shear band emerges along the potential failure surface. Within this band, the shear strength decreases due to the softening behaviour of the particulate material. Material above the band moves downwards, causing the band to propagate dynamically. This already produces a landslide velocity before the slide reaches the post-failure stage and begins separating from the substrata and generating tsunami. However, existing models of tsunamigenic landslides assume zero initial slide velocity. Previous analyses of the catastrophic shear band propagation in slopes of normally- and over-consolidated sediments have shown that a relatively short initial failure zone is sufficient to cause a full-scale landslide. For the shear band to propagate, the energy produced in the body by an incremental propagation of the shear band must exceed the energy required for the propagation. This consideration separates the shear band growth into progressive (stable) and catastrophic (dynamic) stages and treats the band growth as a true physical process rather than an instantaneously appearing discontinuity. This work considers a dynamic shear band problem formulated within the framework of the Palmer and Rice’s [1973] approach. We obtain the exact, closed-form solution for the shear band and landslide velocities as well as for the spatial and temporal distributions of strain and material velocity. This solution assesses when the slide fails due to the limiting condition near the propagating tip of the shear band. We also obtain a simple asymptotic solution, which is compared to the exact solution. In the case of submerged slopes, the obtained solutions are used in landslide and tsunami height analyses. Our results suggest that the conventional static approach to the slope stability analysis leads to a significant underestimation of the slide size (volume). In most cases, the volumes of catastrophic slides are roughly twice the volumes of progressive slides. For submerged slides, this dynamic effect further manifests itself in increasing the tsunami magnitude compared to the static case. Advisors/Committee Members: Germanovich, Leonid (advisor), Frit, Hermann (committee member), Lowell, Robert P. (committee member), Huang, Haiying (committee member), Yavari, Arash (committee member), Puzrin, Alexander (committee member).

Subjects/Keywords: Submarine landslides; Shear band propagation; Fracture mechanics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Kim, S. (2014). Shear band and landslide dynamics in submerged and subaerial slopes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54245

Chicago Manual of Style (16th Edition):

Kim, Sihyun. “Shear band and landslide dynamics in submerged and subaerial slopes.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 23, 2019. http://hdl.handle.net/1853/54245.

MLA Handbook (7th Edition):

Kim, Sihyun. “Shear band and landslide dynamics in submerged and subaerial slopes.” 2014. Web. 23 Apr 2019.

Vancouver:

Kim S. Shear band and landslide dynamics in submerged and subaerial slopes. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Apr 23]. Available from: http://hdl.handle.net/1853/54245.

Council of Science Editors:

Kim S. Shear band and landslide dynamics in submerged and subaerial slopes. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/54245


NSYSU

2. Chen, Hai-min. Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites.

Degree: PhD, Materials and Optoelectronic Science, 2009, NSYSU

On the toughening of bulk metallic glasses (BMGs), successful results in the phase-separated Zr63.8Ni16.2Cu15Al5 BMG have achieved compressive ductility over 15% through the computational-thermodynamic approach. In this study, the phase-separated Zr63.8Ni16.2Cu15Al5 BMG was compressed to nominal strains of 3%, 7%, and 10% at low strain rates (~10-4 s-1) and the results demonstrated that the BMG exhibited apparent uniform deformation initially, followed by visible local shear bands development. Afterwards, a single shear along the principal shear plane was soon developed and mainly dominated the whole deformation process. The principal shear contributed more than 2/3 of the overall plastic strain until failure. It was also found that the local shear strain varied along the principal shear plane and decreased monotonically from the shear band initiation site. Subsequently, in-situ compression experiments were conducted to monitor the change of sample shape during deformation in order to properly correlate with the stress-strain curve. The observed images showed that there was a one-to-one correspondence between the intermittent sample sliding and flow serration in the plastic region of stress-strain curve. Further investigations on flow serration were conducted on the Pd40Ni40P20 BMG through the compression experiments equipped with high-sensitivity strain gauges directly attached to two opposite sides of the test sample. There was an accompanied displacement burst when a shear band starts to propagate during deformation and this displacement burst would be accurately captured by the high-sensitivity strain gauges. Based on the displacement-time profile for one serration, shear-band propagating speed can be estimated and found to be insensitive to the applied strain rates (or the applied crosshead speeds). The disappearance of flow serration at high strain rates should be a result that the signal of displacement burst was overwhelmed by the applied strain rate. Using the shear strain rate data, the measured viscosity within a propagating shear band was found to be relatively low, which is in similar to the viscosity values reported in the supercooled liquid region during homogeneous deformation. In comparison with shear band propagation in the brittle Mg58Cu31Y6Nd5 and Au49Ag5.5Pd2.3Cu26.9Si16.3, moderately ductile Cu50Zr43Al7 and Pd40Ni40P20, and highly ductile phased-separated Zr63.8Ni16.2Cu15Al5 systems, the ductility of BMGs appears to be closely related to the dynamics during shear band propagation. The more ductile in nature the metallic glass is, the slower the shear band propagating speed would become. We also made attempts to investigate the shear band propagation in the porous Mo particles reinforced Mg58Cu28.5Gd11Ag2.5 bulk metallic glass composites (BMGCs) with up to 10% compressive failure strain. It was found that flow serration was absent in the stress-strain curve. Using high-sensitivity strain gauges, no distinct displacement burst was detected in the displacement-time profile. The diappearance of flow… Advisors/Committee Members: Ker-Chang Hsieh (chair), Shian-Ching Jang (chair), Jinn Chu (chair), Chih-Ching Huang (committee member), Po-We Kao (chair).

Subjects/Keywords: shear band propagation; plastic strain; bulk metallic glasses; flow serration

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chen, H. (2009). Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-201234

Chicago Manual of Style (16th Edition):

Chen, Hai-min. “Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites.” 2009. Doctoral Dissertation, NSYSU. Accessed April 23, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-201234.

MLA Handbook (7th Edition):

Chen, Hai-min. “Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites.” 2009. Web. 23 Apr 2019.

Vancouver:

Chen H. Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites. [Internet] [Doctoral dissertation]. NSYSU; 2009. [cited 2019 Apr 23]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-201234.

Council of Science Editors:

Chen H. Analysis of Plasticity and Shear Band Deformation Mechanism in Bulk Metallic Glasses and Composites. [Doctoral Dissertation]. NSYSU; 2009. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1116109-201234

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