## You are here

# ANSYS shell99

Wed, 2008-10-29 19:22 - pirexengaer

Does anyone knows what's the theory of the element shell99 in Ansys? I tried to search in ANSYS Help, but didn't find anything. Is it kirchoff classical plates theory?

Forums:

## Re: Ansys Shell99

I found some information on it reasonably quickly (in ANSYS v 11).

The asssumptions appear to be :

14.99.2. Assumptions and Restrictions

Normals to the centerplane are assumed to remain straight after deformation, but not necessarily normal to the centerplane.Each pair of integration points (in the r direction) is assumed to have the same material orientation.There is no significant stiffness associated with rotation about the element r axis. A nominal value of stiffness is present using the approach of Zienkiewicz(39), however, to prevent free rotation at the node.

The references cited are

1) Ahmad, S., Irons, B. M. and Zienkiewicz, O. C., "Analysis of Thick and Thin Shell Structures by Curved Finite Elements", International Journal for Numerical Methods in Engineering, Vol. 2, No. 3, pp. 419-451 (1970).

2) Cook, R. D., Concepts and Applications of Finite Element Analysis, Second Edition, John Wiley and Sons, New York (1981).

3) Yunus, S. M., Kohnke, P. C. and Saigal, S. "An Efficient Through-Thickness Integration Scheme in an Unlimited Layer Doubly Curved Isoparametric Composite Shell Element", International Journal for Numerical Methods in Engineering, Vol. 28, pp. 2777-2793 (1989).

-- Biswajit

## As far as i know you can

As far as i know you can take help from the book named "Theory of beams and shells". It will be of great help to you. You can get the book from any library of mechanical department

## This element is for

This element is for modeling laminated composite materials. It follows Kirchoff's Classical plate theory (KCPT) - suitable for thin composite laminates.

Regards,

- Ramdas

## Re: Ansys Shell99 .ne. Kirchhoff theory

The manual says

"Normals to the centerplane are assumed to remain

straightafter deformation,but not necessarily normalto the centerplane."That is not an assumption of Kirchhoff theory. The element is probably closer to Mindlin-Reissner theory. Need to look at the detailed formulation to be able to say for sure. Could someone set the matter straight and normal?

-- Biswajit

## Thanks a lot!!!

Thanks a lot!!!

## FSDT

If normal are straight and not perpendicular to center plane means it is following First Order Shear Deformation Theory (FSDT). Prof. J.N. Reddy's book on Theory of ELastic Plate (other one Composite plate is also nice) is a good one. It describes FSDT and TSDT also.

With regards,

- Ramdas