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A semi-analytical study on helical springs made of shape memory polymer

Baghani, M ; Sharif University of Technology | 2012

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  1. Type of Document: Article
  2. DOI: 10.1088/0964-1726/21/4/045014
  3. Publisher: 2012
  4. Abstract:
  5. In this paper, the responses of shape memory polymer (SMP) helical springs under axial force are studied both analytically and numerically. In the analytical solution, we first derive the response of a cylindrical tube under torsional loadings. This solution can be used for helical springs in which both the curvature and pitch effects are negligible. This is the case for helical springs with large ratios of the mean coil radius to the cross sectional radius (spring index) and also small pitch angles. Making use of this solution simplifies the analysis of the helical springs to that of the torsion of a straight bar with circular cross section. The 3D phenomenological constitutive model recently proposed for SMPs is also reduced to the 1D shear case. Thus, an analytical solution for the torsional response of SMP tubes in a full cycle of stress-free strain recovery is derived. In addition, the curvature effect is added to the formulation and the SMP helical spring is analyzed using the exact solution presented for torsion of curved SMP tubes. In this modified solution, the effect of the direct shear force is also considered. In the numerical analysis, the 3D constitutive equations are implemented in a finite element program and a full cycle of stress-free strain recovery of an SMP (extension or compression) helical spring is simulated. Analytical and numerical results are compared and it is shown that the analytical solution gives accurate stress distributions in the cross section of the helical SMP spring besides the global loaddeflection response. Some case studies are presented to show the validity of the presented analytical method
  6. Keywords:
  7. Analytical method ; Analytical solutions ; Axial forces ; Circular cross-sections ; Cross section ; Curvature effect ; Cylindrical tubes ; Direct shear ; Exact solution ; Finite element programs ; Load-deflection response ; Numerical results ; Pitch effects ; Semi-analytical ; Shape memory polymers ; Small pitch ; Spring index ; Stress-free strains ; Torsional loadings ; Torsional response ; Helical springs ; Numerical analysis ; Shape memory effect ; Stress concentration ; Torsional stress ; Tubes (components) ; Three dimensional
  8. Source: Smart Materials and Structures ; Volume 21, Issue 4 , 2012 ; 09641726 (ISSN)
  9. URL: http://iopscience.iop.org/article/10.1088/0964-1726/21/4/045014/meta;jsessionid=F2A6BDBEEAEED070160D4F95BF13C45A.c1.iopscience.cld.iop.org