STABILITY OF ORTHOTROPIC VISCOELASTIC SHELLS
Abstract
The authors review the basic principles of the closed quasilinear quadratic theory of viscoelasticity of physically nonlinear media as proposed by A. A. Il'yushin and P. M. Ogibalov. A system of nonlinear equations of bending and stability is proposed for flexible (i.e. with regard to geometric nonlinearity) shallow plates and shells made from orthotropic materials with linear properties (fiberglass-reinforced plastics). It is assumed that the hypothesis of straight normals is applicable to these plates and shells. It is also assumed that stresses normal to the middle surface are insignificantly small compared to the other components and that the shells and plates remain orthotropic throughout the entire deformation process. A method of solving the proposed equations is outlined and illustrated by analysis of the stability of a rectangular orthotropic plate of slightly curved panel of fiberglass-reinforced plastic with given stress relaxation curves. The results agree satisfactorily with experimental data on creep in a square plate hinged at the edges. Methods are also given for determining the upper and lower critical loads as related to the loading conditions and the critical time. A viscoelastic solution is found by the proposed method for the problem of stability of a compressed cylindrical shell and compared with an elastic solution found by the Ritz method.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1969
- Accession Number
- AD0693509
Entities
People
- M. A. Koltunov
- P. M. Ogibalov
Organizations
- Air Force Systems Command