Experimental assessment of residual stresses induced by the thermal autofrettage of thick-walled cylinders

Abstract

In this work, an experimental study of the residual stresses present in the thermally autofrettaged thick-walled cylinders is carried out. The idea of thermal autofrettage has been conceived recently, and due to its simplicity, it has the potential to be competitive with the existing hydraulic and swage autofrettage processes. In thermal autofrettage, the beneficial compressive residual stresses at the inner wall are produced by means of thermal gradient across the wall thickness. In this work, the residual stresses setup in the cylinders are determined experimentally using Sachs boring method. The experimental results are compared with the analytically determined residual stresses and found to be in good agreement. In addition to the Sachs boring method, two other methods, namely, microhardness test and the measurement of opening angle as a result of cutting through the wall of the cylinders, are also carried out in order to infer the generation of residual stresses in the autofrettaged cylinders. All three experimental methods advocate the feasibility of thermal autofrettage for producing beneficial compressive residual stresses at the inner wall.

Comparison of plane-stress, generalized-plane-strain and 3D FEM elastic–plastic analyses of thick-walled cylinders subjected to radial thermal gradient

“…The effect of strain hardening was considered in the plane stress model [18] . However, the generalized plane strain model [19] did not include the strain hardening, although the theoretical results matched well with the experiments [20] .…”

A comparative study of thermal and hydraulic autofrettage

“…The experimental validation of the expressions using Sachs boring technique has been presented in Refs. [22,23] for SS202, SS304 and mild steel. The experimental results match well with theoretical predictions.…”

“…The properties of mild steel are as follows: Young's modulus of elasticity, E = 219 GPa, yield stress, σ Y = 352 MPa, Poisson's ratio, n = 0.3 and coefficient of thermal expansion, α = 13×10 -6 /°C. The thermal autofrettage was achieved by creating a temperature difference of 230°C in an experimental setup described in Kamal et al [22,23]. Afterward Sachs boring test was carried out to determine the residual stresses in the cylinder as described in Ref.…”

“…Afterward Sachs boring test was carried out to determine the residual stresses in the cylinder as described in Ref. [22]. The experimentally obtained residual stress distribution is shown in Fig.…”

Experimental assessment of the redistribution of 3-D residual stresses during early fatigue at split-sleeve cold expanded reamed A/C fastener holes

“…Depending on the shape, there are several efficient techniques presented. An elegant destructive method of measuring residual stresses in tubes and rods is the Sachs method [52][53][54]. This method entails cutting thin layers from the bore of a hollow cylinder to measure the resulting changes in strains from the perimeter.…”