Applied Mathematics and Mechanics (English Edition) ›› 2020, Vol. 41 ›› Issue (3): 409-424.doi: https://doi.org/10.1007/s10483-020-2585-6

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Finite deformation swelling of a temperature-sensitive hydrogel cylinder under combined extension-torsion

M. SHOJAEIFARD, M. BAGHANI   

  1. College of Engineering, University of Tehran, Tehran 1417466191, Iran
  • 收稿日期:2019-08-01 修回日期:2019-12-06 出版日期:2020-03-01 发布日期:2020-02-17
  • 通讯作者: M. BAGHANI E-mail:baghani@ut.ac.ir

Finite deformation swelling of a temperature-sensitive hydrogel cylinder under combined extension-torsion

M. SHOJAEIFARD, M. BAGHANI   

  1. College of Engineering, University of Tehran, Tehran 1417466191, Iran
  • Received:2019-08-01 Revised:2019-12-06 Online:2020-03-01 Published:2020-02-17
  • Contact: M. BAGHANI E-mail:baghani@ut.ac.ir

摘要: The swelling behavior of a temperature-sensitive poly-N-isopropylacrylamide (PNIPAM) hydrogel circular cylinder is studied subjected to combined extension-torsion and varied temperature. In this regard, a semi-analytical solution is proposed for general combined loading. A finite element (FE) analysis is conducted, subjecting a hydrogel cylinder to the combined extension-torsion and the varied temperature to evaluate the validity and accuracy of the solution. A user-defined UHYPER subroutine is developed and verified under free and constrained swelling conditions. The FE results illustrate excellent agreement with the semi-analytical solution. Due to the complexity of the problem, some compositions and applied loading factors are analyzed. It is revealed that for larger cross-linked density and larger ending temperature, the cylinder yields higher stresses and smaller radial swelling deformation. Besides, the radial and hoop stresses increase by applying larger twist and axial stretch. The hoop stresses intersect at approximately R/Rout=0.58, where the hoop stress vanishes. Besides, the axial force has direct and inverse relationships with the axial stretch and the twist, respectively. However, the resultant torsional moment behavior is complex, and the position of the maximum point varies significantly by altering the axial stretch and the twist.

关键词: extension-torsion of the circular cylinder, temperature variation, finite element (FE) analysis, temperature-sensitive poly-N-isopropylacrylamide (PNIPAM) hydrogel, semi-analytical solution

Abstract: The swelling behavior of a temperature-sensitive poly-N-isopropylacrylamide (PNIPAM) hydrogel circular cylinder is studied subjected to combined extension-torsion and varied temperature. In this regard, a semi-analytical solution is proposed for general combined loading. A finite element (FE) analysis is conducted, subjecting a hydrogel cylinder to the combined extension-torsion and the varied temperature to evaluate the validity and accuracy of the solution. A user-defined UHYPER subroutine is developed and verified under free and constrained swelling conditions. The FE results illustrate excellent agreement with the semi-analytical solution. Due to the complexity of the problem, some compositions and applied loading factors are analyzed. It is revealed that for larger cross-linked density and larger ending temperature, the cylinder yields higher stresses and smaller radial swelling deformation. Besides, the radial and hoop stresses increase by applying larger twist and axial stretch. The hoop stresses intersect at approximately R/Rout=0.58, where the hoop stress vanishes. Besides, the axial force has direct and inverse relationships with the axial stretch and the twist, respectively. However, the resultant torsional moment behavior is complex, and the position of the maximum point varies significantly by altering the axial stretch and the twist.

Key words: extension-torsion of the circular cylinder, temperature variation, finite element (FE) analysis, temperature-sensitive poly-N-isopropylacrylamide (PNIPAM) hydrogel, semi-analytical solution

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