6.10. RESIDUAL STRESS EXAMPLE: THIN, SHOT-PEENED BEAM 137
ful smoothing of the peened surface using water-cooled 400-grade silicon carbide paper
results in little change in the stress distribution (sample 4); and
• after removal of a further 50 m layer from the shot peened and smoothed surface (sample
E5) using a honing process (water cooled), it can be seen that a significant proportion of
the compressive layer remains; much of the near-surface distribution from sample 5 is
similar in profile to samples E3 and E4, but shifted by an amount corresponding to the
thickness of the material layer removed.
(b)(a)
Residual Stresses MPa
800
600
400
200
0
-200
-400
-600
-80
-1000
-1200
E1. Wire-EDM
E2. Abraded and Polished
E3. Peened
E4. Peened and Smoothed
E5. Peened and Abraded; -50 microns
0 Depth 10050 µm 150 200 250 300 350 400
E3
Figure 6.14: Surface process sample; gauge installation and stress distributions (photos courtesy
of Stresscraft Ltd.).
6.10 RESIDUAL STRESS EXAMPLE: THIN, SHOT-PEENED
BEAM
e example shown in Figures 6.15a and 6.15b is a steel alloy beam of cross section 0.9 mm
10 mm that has been subjected to an intense shot peening process. Rosette F, a 1/32” Type A
pattern, has been installed at the center of the top of the beam and drilled. A second rosette (G)
has been installed on the underside of the beam, offset by 6 mm from the beam mid-length to
reduce any interference from the previously drilled hole to an undetectable level. For each rosette,
the hole drilling procedure has been carried out with the beam supported on a layer of cement.
is prevents flexure caused by drilling forces to ensure control of the drill depth. e relaxed
strain data from the two rosettes has been processed using the Integral Method incorporating
coefficients derived from a series of finite element models of “intermediate” thickness plates.
Distributions of longitudinal stresses from the two gauges are shown in Figure 6.15c.
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