How can I measure the Residual stress?

Hi Everyone,
I would like to measure the residual stress imposed pattern through thickness of the plate by forming process (bending). Is it possible?

I came to know that residual stress measurement through HOLE DRILLING METHOD offers only on the surface. That too, applicable only when residual stress imposed is uniform through thickness (like shot blasting process). If any one came across the experience of residual stress measurement, please throw some light in this regard.

Thanks in advance
M Gopalakrishnan