Comparative measurements on autofrettaged cylinders with large Bauschingerreverse yielding zones

A comparative study to map the residual strain/stress states through the wa lls of autofrettaged thick-walled steel cylinders has been conducted with n eutron diffraction, Sachs boring and the compliance methods. Test samples w ith different wall thickness ratios were prepared to have significant amoun ts of reverse yielding due to the Bauschinger effect. All three methods ind icate that the autofrettage action primarily influenced the hoop stresses, which varied rapidly close to the bores from compressive to tensile within the first half of the wall thickness. Quantitatively, results from the neut ron diffraction and Sachs boring techniques compare favourably across large regions of the cylinder walls, while the compliance results showed differe nt features. The existence of reverse yielding close to the cylinder bores has been sensed to different magnitudes and distances from the bores. Plast ically yielded material regions identified from the neutron diffraction res ults correlated well with theoretical modelling.