ORCID Profile
0000-0002-3644-4856
Current Organisation
Northwestern University
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Publisher: Center for Open Science
Date: 13-12-2017
Abstract: Earthmoving machines of varying sophistication, ranging from the simple garden spade to the hydraulic excavator, have evolved considerably over the centuries, but the scientific understanding of earthmoving processes lags considerably behind the technology. Historically much effort has been directed towards aspects of the machine, whereas relatively little attention has been given to the soil. For this reason, the problem has primarily engaged the interest of mechanical engineers. This paper provides a brief overview of the state of the art in analytical and numerical modeling, as well as some of the significant challenges that have yet to be overcome. It concludes with a description of the research program at Northwestern University, which includes analytical and numerical modeling of earthmoving processes and experiments completed using a new experimental facility. The preliminary results shown in the paper highlight key features of earthmoving processes and the potential for contributions from geotechnical engineers.
Publisher: Center for Open Science
Date: 06-03-2018
Abstract: This paper explores a pathway for increasing efficiency in numerical 3D limit analysis through r-h adaptivity, wherein nodal positions (r) and element lengths (h) are successively refined. The approach uses an iterative, nested optimization procedure involving three steps: (1) determination of velocities for a fixed mesh of rigid, translational elements (blocks) using second-order cone programming (2) adaptation of nodal positions using non-linear optimization (r adaptivity) and (3) sub ision of elements based on the magnitude of the velocity jumps (h adaptivity). Ex les show that the method can compute reasonably accurate limit loads at relatively low computational cost.
Publisher: Wiley
Date: 05-01-2012
DOI: 10.1002/NAG.1004
Publisher: Elsevier BV
Date: 12-2008
Publisher: Elsevier BV
Date: 02-2016
Publisher: American Society of Civil Engineers
Date: 07-03-2008
DOI: 10.1061/40971(310)70
Publisher: Center for Open Science
Date: 10-05-2018
Abstract: A general framework is proposed to incorporate rate and time effects into bounding surface (BS) plasticity models. For this purpose, the elasto-viscoplasticity (EVP) overstress theory is combined with bounding surface modeling techniques. The resulting constitutive framework simply requires the definition of an overstress function through which BS models can be augmented without additional constitutive hypotheses. The new formulation differs from existing rate-dependent bounding surface frameworks in that the strain rate is additively decomposed into elastic and viscoplastic parts, much like classical viscoplasticity. Accordingly, the proposed bounding surface elasto-viscoplasticity (BS-EVP) framework is characterized by two attractive features: (1) the rate-independent limit is naturally recovered at low strain rates (2) the inelastic strain rate depends exclusively on the current state. To illustrate the advantages of the new framework, a particular BS-EVP constitutive law is formulated by enhancing the Modified Cam-clay model through the proposed theory. From a qualitative standpoint, this simple model shows that the new framework is able to replicate a wide range of time/rate effects occurring at stress levels located strictly inside the bounding surface. From a quantitative standpoint, the calibration of the model for over-consolidated Hong Kong marine clays shows that, despite the use of only six constitutive parameters, the resulting model is able to realistically replicate the undrained shear behavior of clay s les with OCR ranging from 1 to 8, and subjected to axial strain rates spanning from 0.15%/hr to 15%/hr. These promising features demonstrate that the proposed BS-EVP framework represents an ideal platform to model geomaterials characterized by complex past stress history and cyclic stress fluctuations applied at rapidly varying rates.
Publisher: Inderscience Publishers
Date: 2017
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 04-2009
Publisher: Elsevier BV
Date: 11-2009
Start Date: 2016
End Date: 2018
Funder: Australian Research Council
View Funded ActivityStart Date: 2017
End Date: 2019
Funder: Directorate for Engineering
View Funded ActivityStart Date: 2015
End Date: 2017
Funder: Australian Research Council
View Funded ActivityStart Date: 2018
End Date: 2020
Funder: Australian Research Council
View Funded Activity