An optimization structure for frictional plasticity

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Abstract

A theoretical framework of rigid plasticity is presented that is based on optimization and includes frictional dissipation. It has been used in this paper as a foundation for existing and modified models of granular materials consisting of rigid granules. It has the major advantage that it enables yield criteria to be created numerically, which is particularly useful when analytical expressions cannot be found. This framework is constructed by first postulating: (i) a dissipation function that can depend on the current components of stress, but is always homogeneous of degree one and positive definite, (ii) a volume constraint function that is also homogeneous of degree one, and (iii) a balance of the rate of doing work and the rate at which energy needs to be dissipated. A mathematical process similar to the construction of a dual norm in convex analysis then leads to: a flow rule; a single natural representation of the yield surface; and a useful constitutive inequality involving the components of stress and strain rate.

Dissipation functions appropriate for the Drucker–Prager and Matsuoka–Nakai yield surfaces are investigated when a simple dilation rule is the volume constraint. These include a case where an explicit expression for the yield function is not found and, instead, the yield function is found numerically. Such numerical yield functions have been checked graphically against carefully constructed envelopes and found to be consistent with them.

Original languageEnglish
Pages (from-to)2005-2020
Number of pages16
JournalProceedings of the Royal Society A: Mathematical, Physical, and Engineering Sciences
Volume463
Issue number2084
DOIs
Publication statusPublished - 8 Aug 2007

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Structure Optimization
plastic properties
Plasticity
optimization
Dissipation
dissipation
Convex Analysis
Granular Materials
Granular materials
granular materials
Strain Rate
Dilation
norms
Positive definite
Envelope
strain rate
Strain rate
envelopes
Norm
Optimization

Keywords

  • optimization
  • granular materials
  • material modelling
  • dilatancy
  • dissipation function

Cite this

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abstract = "A theoretical framework of rigid plasticity is presented that is based on optimization and includes frictional dissipation. It has been used in this paper as a foundation for existing and modified models of granular materials consisting of rigid granules. It has the major advantage that it enables yield criteria to be created numerically, which is particularly useful when analytical expressions cannot be found. This framework is constructed by first postulating: (i) a dissipation function that can depend on the current components of stress, but is always homogeneous of degree one and positive definite, (ii) a volume constraint function that is also homogeneous of degree one, and (iii) a balance of the rate of doing work and the rate at which energy needs to be dissipated. A mathematical process similar to the construction of a dual norm in convex analysis then leads to: a flow rule; a single natural representation of the yield surface; and a useful constitutive inequality involving the components of stress and strain rate. Dissipation functions appropriate for the Drucker–Prager and Matsuoka–Nakai yield surfaces are investigated when a simple dilation rule is the volume constraint. These include a case where an explicit expression for the yield function is not found and, instead, the yield function is found numerically. Such numerical yield functions have been checked graphically against carefully constructed envelopes and found to be consistent with them.",
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N2 - A theoretical framework of rigid plasticity is presented that is based on optimization and includes frictional dissipation. It has been used in this paper as a foundation for existing and modified models of granular materials consisting of rigid granules. It has the major advantage that it enables yield criteria to be created numerically, which is particularly useful when analytical expressions cannot be found. This framework is constructed by first postulating: (i) a dissipation function that can depend on the current components of stress, but is always homogeneous of degree one and positive definite, (ii) a volume constraint function that is also homogeneous of degree one, and (iii) a balance of the rate of doing work and the rate at which energy needs to be dissipated. A mathematical process similar to the construction of a dual norm in convex analysis then leads to: a flow rule; a single natural representation of the yield surface; and a useful constitutive inequality involving the components of stress and strain rate. Dissipation functions appropriate for the Drucker–Prager and Matsuoka–Nakai yield surfaces are investigated when a simple dilation rule is the volume constraint. These include a case where an explicit expression for the yield function is not found and, instead, the yield function is found numerically. Such numerical yield functions have been checked graphically against carefully constructed envelopes and found to be consistent with them.

AB - A theoretical framework of rigid plasticity is presented that is based on optimization and includes frictional dissipation. It has been used in this paper as a foundation for existing and modified models of granular materials consisting of rigid granules. It has the major advantage that it enables yield criteria to be created numerically, which is particularly useful when analytical expressions cannot be found. This framework is constructed by first postulating: (i) a dissipation function that can depend on the current components of stress, but is always homogeneous of degree one and positive definite, (ii) a volume constraint function that is also homogeneous of degree one, and (iii) a balance of the rate of doing work and the rate at which energy needs to be dissipated. A mathematical process similar to the construction of a dual norm in convex analysis then leads to: a flow rule; a single natural representation of the yield surface; and a useful constitutive inequality involving the components of stress and strain rate. Dissipation functions appropriate for the Drucker–Prager and Matsuoka–Nakai yield surfaces are investigated when a simple dilation rule is the volume constraint. These include a case where an explicit expression for the yield function is not found and, instead, the yield function is found numerically. Such numerical yield functions have been checked graphically against carefully constructed envelopes and found to be consistent with them.

KW - optimization

KW - granular materials

KW - material modelling

KW - dilatancy

KW - dissipation function

U2 - 10.1098/RSPA.2007.1860

DO - 10.1098/RSPA.2007.1860

M3 - Article

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EP - 2020

JO - Proceedings of the Royal Society A: Mathematical, Physical, and Engineering Sciences

JF - Proceedings of the Royal Society A: Mathematical, Physical, and Engineering Sciences

SN - 1364-5021

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