Experimental analysis of 12X18H10T stainless steel specimens subjected to
strain-controlled cyclic loading that comprises sequential monotonic and cyclic
loading under uniaxial tension-compression and standard temperature is used to
identify some features and dissimilarities of isotropic and kinematic hardening
processes that occur during monotonic and cyclic loading. In order to describe these
features in terms of the plasticity theory (the Bondar model), which can be classified
as a combined-hardening flow theory, plastic-strain redirection criterion and the
memory surface concept are introduced in the plastic-strain tensor space so as to
separate monotonic and cyclic strain. Evolution equations for isotropic and kinematic
hardening processes are derived to describe the monotonic-to-cyclic and
cyclic-to-monotonic evolutions in transients. The basic experiment used to determine
the material functions consists of three stages: cyclic loading, monotonic loading and
subsequent cyclic loading until fracture. The results of the basic experiment are
fundamental to the proposed method for identifying the material functions.
Basic-experiment results and the identification method are used to identify the
room-temperature material functions of 12X18H10T stainless steel. The paper
compares the computational analysis and the experimental analysis of stainless
steel subjected to a strain-controlled fatigue test (loading) in five and seven
stages monotonic and cyclic loading until fracture. It further compares the
computational and experimental kinetics of stress-strain state throughout
the deformation process. Changes in the amplitude and mean cycle stress
during the cyclic stress stages are subsequently analyzed. These stages are
characterized by hysteresis loop stabilization. Computational and experimental
results fit reliably. The theory adequately describes the processes of how
the kinetic, the range, and the middle cycle stress alter when subjecting a
specimen to strain-controlled loading, which enables a more adequate description
of stress-controlled loading, especially when loading is nonstationary and
nonsymmetric.
Keywords
monotonic and cyclic loading, plasticity theory, isotropic
and anisotropic hardening, memory surface, basic
experiment, identification method
