Partner: O.T. Bruhns


Ostatnie publikacje
1.Raniecki B., Bruhns O.T., Bounds to bifurcation stresses in solids with non-associated plastic flow law at finite strain, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/0022-5096(81)90021-1, Vol.29, No.2, pp.153-172, 1981

Streszczenie:

In the present paper, Hill's theory of bifurcation and stability in solids obeying normality is generalized to include a non-associated flow law. A one-parameter family of linear comparison solids has been found that admits a potential and has the property that if uniqueness is certain for the comparison solid then bifurcation and instability are precluded for the underlying elastic-plastic solid. The uniqueness criterion derived may be used as a device to determine lower bounds to the magnitudes of primary bifurcation and instability stresses which are ordinarily unknown. A second linear solid is introduced whose constitutive relations have the same form as the elastic-plastic solid “in loading”. The first eigenstate of this solid gives an upper bound to the primary bifurcation state of the underlying elastic-plastic solid. The search for the genuine primary bifurcation state is therefore replaced by a search for upper and lower bounds in the situation when normality fails to hold. The theory is applied to problems of homogeneous stress states.

Afiliacje autorów:

Raniecki B.-IPPT PAN
Bruhns O.T.-other affiliation
2.Bruhns O., Mielniczuk J., Zur Theorie der Verzweigungen nicht-isothermer elastoplastischer Deformationen, Ingenieur-Archiv, ISSN: 0020-1154, DOI: 10.1007/BF00534960, Vol.46, pp.65-74, 1977

Streszczenie:

The paper presents a theory of non-isothermal bifurcation of deformations for compressible elasticplastic bodies. The constitutive relations introduced are based on a coupled thermoplasticity with J 2-flow theory and von Mises yield criterion in the plastic range. To determine the critical load a rate boundary value problem is formulated and tested for nonunique modes of deformation. The general analysis is applied to the necking process in cylindrical specimens.

Afiliacje autorów:

Bruhns O.-other affiliation
Mielniczuk J.-IPPT PAN