Page 323 - 00. Complete Version - Progress Report IPEN 2014-2016

Materials and Nanotechnology | Progress Report 323

(10-19%) after 140 hours of HA (150°C) for all relationship was confirmed by the overlap of
ceramics. Extrapolating the depth of the trans- the results found in the distribution of the mi-
formed zone results to 37°C, it was calculated crostrain of the crystalline lattice with the re-
that the front of the transformed zone would sidual stress along the thickness in the plasti-
take around 1053 and 2104 years to reach cally deformed region.
62.67μm and 85.55μm, depth that decreased
the mechanical strength of the YZ and LP, re- The results of the x-ray diffraction tests show
spectively. The association of HA and mechan- an existence of tensile anisotropy between
ical cycling did not present a deleterious effect the planes generated by stacking faults and
for the YZ. The OCT was validated as a precise, the dislocations density. Therefore, to obtain
easy and fast method to evaluate the depth of the values of the microstress, the factors of
the transformed zone and for kinetics studies. the elastic constants and the crystallograph-
ic planes must be considered. The method ap-
Residual stress plied was the modified Williamson-Hall.

Some effects caused by shot peening on Cr-Si-V In addition, the study of the distribution of
steel have been studied, a process that aims the mean crystallite size along the thickness
to increase fatigue resistance. For this study, of the X-ray diffraction profile was provided
he variation of parameters in the process are and the results showed that this distribution
tools to better understand the mechanisms varies inversely with microstrain. The rela-
that influence this property. The parameters tionship between the mean crystallite size
used in this work were the variation of the grit and the variation of the interplanar distanc-
and the pre-tensioning of the samples applied es corresponds directly to changes in the den-
in leafs used in automotive springs of chrome sities of dislocations occurring in the material,
silicon vanadium alloy steel (SAE 9254 + V). which in turn are linked to the microstrain of
the crystalline lattice.
The evaluation of the residual stress profile
was performed by x-ray diffraction using the
sen2ο method along the thickness in the re-
gion where the stress is compressive. The re-
sults show an anomalous effect in relation to
the characteristic profile of the residual stress
distribution with the decrease of compression
in the initial layers in relation to the blasted
surface. With the use of scanning electron mi-
croscopy, the region affected by grit blasting
was observed, noting that the plastically de-
formed regions are located in the same regions
where the compressive residual stress decrease.

The profile obtained by X-ray diffraction pro-
vides necessary information with the aim
of combining the effects of microstress (mi-
crostrain) on macrostress (residual stress). This