The stability problem of thin triangular plates by the small elastoplastic deformation theory, was studied in [3]. Basing on the theory of elastoplastic processes, this problem again has been investigated in [4] with incompressible material. In this paper we continue to study the mentioned problem with compressible material. The relation for determining critical forces is established. In particular the explicit expression of the critical force for the linear hardening material is found. Some numerical calculations have been given and discussed. .
