Abstract
The plastic deformation resulting from shot peening treatments applied to the ferritic heat resistant steel
FV448 has been investigated. Two important effects have been quantified: surface roughness and strain
hardening. 2D and 3D tactile and optical techniques for determining surface roughness amplitude parameters
have been investigated; it was found that whilst Ra and Sa were consistent, Sz was generally higher
than Rz due to the increased probability of finding the worst case surface feature. Three different methods
for evaluating the plastic strain profile have been evaluated with a view to establishing the variation in
yield strength near the surface of a shot peened component. Microhardness, X-ray diffraction (XRD) line
broadening and electron backscatter diffraction (EBSD) local misorientation techniques were applied to
both uniaxially deformed calibration samples of known plastic strain and samples shot peened at intensities
varying from 4A to 18A to establish the variation in plastic strain and hence the variation in yield
strength. The results from the three methods were compared; XRD and EBSD profiles were found to be
the most similar with microhardness profiles extending much deeper into the sample. Changes in the
measured plastic strain profile after exposure to low cycle fatigue and the correlation of these changes
with the cyclic stress–strain behaviour of the material are also discussed with a view to assessing the
importance of the dislocation profile in component life assessment procedures.
2013 Elsevier Ltd. All rights reserved.
FV448 has been investigated. Two important effects have been quantified: surface roughness and strain
hardening. 2D and 3D tactile and optical techniques for determining surface roughness amplitude parameters
have been investigated; it was found that whilst Ra and Sa were consistent, Sz was generally higher
than Rz due to the increased probability of finding the worst case surface feature. Three different methods
for evaluating the plastic strain profile have been evaluated with a view to establishing the variation in
yield strength near the surface of a shot peened component. Microhardness, X-ray diffraction (XRD) line
broadening and electron backscatter diffraction (EBSD) local misorientation techniques were applied to
both uniaxially deformed calibration samples of known plastic strain and samples shot peened at intensities
varying from 4A to 18A to establish the variation in plastic strain and hence the variation in yield
strength. The results from the three methods were compared; XRD and EBSD profiles were found to be
the most similar with microhardness profiles extending much deeper into the sample. Changes in the
measured plastic strain profile after exposure to low cycle fatigue and the correlation of these changes
with the cyclic stress–strain behaviour of the material are also discussed with a view to assessing the
importance of the dislocation profile in component life assessment procedures.
2013 Elsevier Ltd. All rights reserved.
| Original language | English |
|---|---|
| Pages | 106 |
| Number of pages | 117 |
| Publication status | Published - 2 Jun 2013 |