SYMPOSIA PAPER Published: 01 January 1985
STP36217S

The Use of Anisotropic Yield Surfaces in Cyclic Plasticity

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An anisotropic plasticity approach is used to determine the plastic strains developed in two mechanical ratchetting processes, (a) thin-walled tubes subjected to cyclic plastic shear strain and a sustained axial stress, and (b) thin-walled tubes subjected to cyclic plastic tension and compression with a sustained steady hoop stress. The anisotropic plastic potential includes linear terms which enables Bauschinger effects to be incorporated in the general approach. The coefficients, representing the state of anisotropy, are expressed in terms of the uniaxial and shear yield stresses of the material and can be easily determined from simple tests.

Results are presented showing the cyclic properties developed, together with the results of uniaxial tests showing the development of anisotropic material properties due to axial and hoop strain accumulation.

Using the anisotropic material data, yield surfaces are developed and used to predict the axial and hoop strain within a cycle of plastic strain for the mechanical ratchetting processes. The justification for using equi-plastic strain surfaces is discussed, and the results are compared with those obtained using current or instantaneous yield surfaces.

The results presented indicate that the latter approach is more appropriate, but more material data are required in order to test its validity for other loading systems.

The problems associated with developing realistic yield surfaces for the period immediately after cyclic stress reversal is discussed together with the influence of micro residual stresses.

Author Information

Harvey, SJ
Department of Combined Engineering, Coventry (Lanchester) Polytechnic, Coventry, U.K.
Toor, AP
Department of Combined Engineering, Coventry (Lanchester) Polytechnic, Coventry, U.K.
Adkin, P
Department of Combined Engineering, Coventry (Lanchester) Polytechnic, Coventry, U.K.
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Developed by Committee: E08
Pages: 49–63
DOI: 10.1520/STP36217S
ISBN-EB: 978-0-8031-4921-2
ISBN-13: 978-0-8031-0444-0