Fig.4 Equivalent strain histograms for the 10th, 100th, 200th, and 300th
cycles (a) SP;(b) DP
As shown in Fig. 4, the height difference between any two columns under
the same contact stress displays the equivalent strain change value
between the corresponding cycles. The change rate of equivalent strain
is obtained from this height difference. Under SP and DP, the cyclic
softening rate decreases with the increase of the cycle number, and the
strain change rate increases as the contact stress increases. Combined
Fig. 3 and Fig. 4, the SP has a larger amount of strain under the same
conditions and its cyclic softening rate is also larger compared with
DP.
Fig. 5 shows the response behavior of axial strain and shear strain of
35CrMoA steel under SP and DP at the equivalent stress of 400MPa. The
axial strain and the shear strain are basically the same as the
equivalent strain change trend. This change trend has been described in
the analysis of equivalent strains. Corresponding to the equivalent
strain, under the same conditions, the shear strain, axial strain and
their change rates of SP are larger than DP. Compared with the shear
strain, the axial strain dominates the total strain. During the cyclic
softening process, the increase of the axial strain is much larger than
the increase of the shear strain. Therefore, the damage form of 35CrMoA
steel is mainly axial style.