Computational Mechanics

, Volume 43, Issue 3, pp 415–429

The theory of Cosserat points applied to the analyses of wrinkled and slack membranes

Original Paper

DOI: 10.1007/s00466-008-0314-y

Cite this article as:
Banerjee, B., Shaw, A. & Roy, D. Comput Mech (2009) 43: 415. doi:10.1007/s00466-008-0314-y


Numerical simulations of wrinkling and slacking of geometrically nonlinear membrane structures are considered using planar Cosserat points. The finite element method (FEM) solves the problem by weakly projecting the governing PDEs and thus requires numerical integration. This is contrasted with Cosserat point elements wherein governing equations are solved in an averaged sense at a point. The point is equipped with a few directors and can describe the deformation kinematics of a finite region containing itself. Numerical modeling through the Cosserat point provides freedom from numerical integration and locking. Presently a plane stress quadrilateral Cosserat point element is used to study the wrinkling and slacking of isotropic membranes. The approach by Roddeman et al. (ASME J Appl Mech 54:884–892, 1987) is exploited to detect wrinkled/slack elements in the membrane structure. Here stretching parameters are employed to modify the deformation tensor to represent a fictive non-wrinkled surface. A variation of the algorithm to detect spatial variations of the stretching parameters within a point element is also described. Several numerical examples on static deformations of wrinkled/slack membranes are presented. Limited comparisons with a reported experiment and with results via the FEM as well as a mesh-free approach are provided to assess the performance of the approach.


Cosserat point Wrinkled/slack membranes Nonlinear elasticity Tension field theory 

List of symbols


ith director couple corresponding to body force


ith external director couple

σ1, σ2

principal Cauchy stresses

T1 ,T2

principal Cosserat stresses

\({\overline {\bf F}}\)

auxiliary deformation gradient


Cosserat deformation gradient


3D deformation gradient


average Cauchy stress tensor


Cauchy stress tensor


Cosserat stress tensor


homogeneous part of the strain energy


inhomogeneous part of the strain energy


ith inhomogeneous strain corresponding to the ith director


ith intrinsic director couple


total strain energy

γ1 ,γ2

stretching (wrinkliness) parameters

E, μ , ν

Young’s modulus, shear modulus and Poisson’s ratio

K1 ,K2 ,K3

inhomogeneous constitutive constants

\({\overline {\bf t}^i,\overline {\bf f}^i,\overline {\bf b}^i}\)

ith nodal quantity corresponding to t, f, b

θ1, θ2, θ3

locally convected curvilinear coordinates

\({\kappa_1^1 ,\kappa_1^2 ,\kappa_1^3}\)

normalized inhomogeneous strain measures

\({\overline{\bf D}_{\rm i},\overline {\bf d}_{\rm i} }\)

ith nodal deformed and deformed position vectors


transformation matrix

D0, D

initial and final thicknesses of the membrane element

Di, di

ith undeformed and deformed contravariant director vector

Di, di

ith undeformed and deformed covariant director vectors


homogeneous strain measure

Gi, gi

ith undeformed and deformed base vectors

H, L

width and length of the planar Cosserat point


constitutive tensor


mass of the Cosserat point

n1, n2

unit vectors representing principal stress directions

\({{\bf n^*}_{1}, {\bf n^*}_{2}}\)

unit vectors representing principal stress directions in 3D setup


unit surface normal

V, v

volumes of the Cosserat point in undeformed and deformed states

X, x

undeformed and deformed position vectors of a material point

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Structures Lab, Department of Civil EngineeringIndian Institute of ScienceBangaloreIndia

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