P. Delobelle et al., EXPERIMENTAL-STUDY AND PHENOMENOLOGICAL MODELIZATION OF RATCHET UNDERUNIAXIAL AND BIAXIAL LOADING ON AN AUSTENITIC STAINLESS-STEEL, International journal of plasticity, 11(4), 1995, pp. 295-330
The comprehension and the quantitative description of the uni- and bid
irectional ratchet phenomena remains one of the final aspects to be co
rrectly modelized by the phenomenological approaches employing a model
with internal scalar and tensorial variables. Toward this end, the fi
rst step consists in creating a set of experimental basis of unidirect
ional and bidirectional ratchet. This has been done for an austenitic
stainless steel at 600 degrees C. With the aid of alternating tension
and torsion tests, the unidirectional ratchet can be quantified as a f
unction of the maximal and average stresses. It is shown that the prog
ressive strain only exists when the maximum stress is greater than 210
MPa and has a maximum for an average stress around 25 MPa and fixed m
aximum stress of 300 MPa. The tension-torsion ratchet is examined in a
detailed fashion, and the influence of both primary (axial direction)
and secondary (shear direction) loading parameters on the progressive
strain rate is demonstrated. To be able to integrate, during the mode
lization, the nonradiality effects present in this type of loading, se
veral cyclic out-of-phase tension-torsion tests are performed (Phi = 9
0 degrees). At ambient temperature, several axial-internal pressure ra
tchet tests agree with the results obtained from tension-torsion tests
. However, if ratchet tests were to be performed with two cyclic compo
nents (in or out of phase cyclic tension-torsion plus a static stress
due to internal pressure), it can be shown that the rate of diametral
ratchet is an increasing function of the phase angle between the cycli
c components. This set of tests constitutes the experimental basis nec
essary for the modelization of the ratchet phenomena. It is then shown
that it is possible to reasonably describe this set of experimental r
esults after taking into account a few modifications in the definition
of the evolutionary laws for the tensorial variables of kinematic har
dening. The nature of the modifications introduced in the kinematic ha
rdening variables depends on the type of ratchet to be modelized. For
uniaxial loadings, the progressive strain is governed by average stres
s effects, whereas for multiaxial loadings it is essentially governed
by directional flow effects.