A modelling for craze behavior covering a wide range of strain rate and its application to simulation for fracture prediction of crystalline polymer

Junichi Takahashi, Toshiharu Yamamoto, Kazuyuki Shizawa

Research output: Contribution to journalArticle

Abstract

Polymers show peculiar mechanical responses that are not observed in metals, such as remarkable strain rate dependency and ductile fracture caused by craze which is an assembly consisting of micro-voids and fibrils. In the design process for polymeric products, we attempt generally to predict the fracture position by commercial FEM solvers. However, we can not precisely reproduce the fracture behavior of polymers, because a material model that can express an accumulation of craze is not installed yet on the current commercial solvers. Therefore, so as to predict fracture on the basis of craze behavior, we proposed a constitutive equation with craze effect, the craze evolution equation that can express propagation and growth cessation of craze, the evolution of mean normal plastic strain and criterion for craze initiation with strain rate dependency in our previous work. In this study, our craze evolution equation is extended to an enhanced type covering wide range of strain rate and is proposed as a material model by combining with non-coaxial elastoviscoplastic constitutive equation and the evolution equations proposed in the previous work. Then, numerical uni-axial tensile tests in which applied strain rate is given at five levels between 0.01s-1 and 100s-1 are conducted on a commercial FEM solver LS-DYNA to which the present material model is added via user subroutine. Furthermore, we predict computationally the fracture positions under the condition of wide range of strain rates by using the criteria of craze concentration and fibril strength.

Original languageEnglish
Pages (from-to)380-394
Number of pages15
JournalNihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
Volume79
Issue number800
DOIs
Publication statusPublished - 2013

Fingerprint

Strain rate
Polymers
Crystalline materials
Constitutive equations
Finite element method
Ductile fracture
Subroutines
Plastic deformation
Metals

Keywords

  • Commercial Solver
  • Constitutive Equation
  • Craze
  • Damage Mechanics
  • Ductile Fracture
  • Finite Element Method
  • High Polymer Materials
  • Plasticity
  • Wide Rage of Strain Rate

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Science(all)

Cite this

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title = "A modelling for craze behavior covering a wide range of strain rate and its application to simulation for fracture prediction of crystalline polymer",
abstract = "Polymers show peculiar mechanical responses that are not observed in metals, such as remarkable strain rate dependency and ductile fracture caused by craze which is an assembly consisting of micro-voids and fibrils. In the design process for polymeric products, we attempt generally to predict the fracture position by commercial FEM solvers. However, we can not precisely reproduce the fracture behavior of polymers, because a material model that can express an accumulation of craze is not installed yet on the current commercial solvers. Therefore, so as to predict fracture on the basis of craze behavior, we proposed a constitutive equation with craze effect, the craze evolution equation that can express propagation and growth cessation of craze, the evolution of mean normal plastic strain and criterion for craze initiation with strain rate dependency in our previous work. In this study, our craze evolution equation is extended to an enhanced type covering wide range of strain rate and is proposed as a material model by combining with non-coaxial elastoviscoplastic constitutive equation and the evolution equations proposed in the previous work. Then, numerical uni-axial tensile tests in which applied strain rate is given at five levels between 0.01s-1 and 100s-1 are conducted on a commercial FEM solver LS-DYNA to which the present material model is added via user subroutine. Furthermore, we predict computationally the fracture positions under the condition of wide range of strain rates by using the criteria of craze concentration and fibril strength.",
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AB - Polymers show peculiar mechanical responses that are not observed in metals, such as remarkable strain rate dependency and ductile fracture caused by craze which is an assembly consisting of micro-voids and fibrils. In the design process for polymeric products, we attempt generally to predict the fracture position by commercial FEM solvers. However, we can not precisely reproduce the fracture behavior of polymers, because a material model that can express an accumulation of craze is not installed yet on the current commercial solvers. Therefore, so as to predict fracture on the basis of craze behavior, we proposed a constitutive equation with craze effect, the craze evolution equation that can express propagation and growth cessation of craze, the evolution of mean normal plastic strain and criterion for craze initiation with strain rate dependency in our previous work. In this study, our craze evolution equation is extended to an enhanced type covering wide range of strain rate and is proposed as a material model by combining with non-coaxial elastoviscoplastic constitutive equation and the evolution equations proposed in the previous work. Then, numerical uni-axial tensile tests in which applied strain rate is given at five levels between 0.01s-1 and 100s-1 are conducted on a commercial FEM solver LS-DYNA to which the present material model is added via user subroutine. Furthermore, we predict computationally the fracture positions under the condition of wide range of strain rates by using the criteria of craze concentration and fibril strength.

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