Fig. 15 shows the influence of the residual-stress intensity on
the effect of the proposed method taking material D in Fig. 7 as an
example. The press pressure P was determined as 310 MPa, which
is 120% of the 1% proof stress 1% of 264 MPa. When the maximum
residual stress rsmax is 190 MPa, which has a similar residual stress
distribution to the experimental value, the bending moment Mrs
is certainly levelled to zero. Light press is a stable and effective
method which can level the bending moment Mrs less than 1/3 of
the initial value within the very wide range of 1% from 130 to
280 MPa. However, if the residual stress does not exist in the sheet
metal, i.e. rsmax = 0 MPa, the press should not be given to the sheet
metal without the residual stress as it could cause the warp in the
opposite direction.
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