Residual Stress Evolution during Manufacture of Aerospace Forgings

Abstract

The residual stresses present through the quenching, ageing, and machining processes in sub-scale forgings of RR1000 have been measured experimentally using neutron diffraction, and the contour method. The forgings, 88.9mm in diameter, and 25.4-50.8mm thickness, were of small enough geometry to allow neutron strain measurement in 3 directions throughout most of the bulk. The contour method was employed successfully to generate a full 2D map of the hoop stress in the as-aged and machined samples. The two experimental data sets have been shown to agree very well. Finite element modelling predictions based on an experimentally derived heat transfer coefficient (HTC) curve allowed further comparison and generated additional data. Agreement between the experimental and simulated data was found to be reasonable with some discrepancy visible in the axial direction. The water quenching process was found to generate peak stresses up to 1400MPa in the hoop and radial direction, which were relaxed by as much as 700MPa through ageing. Material removal by machining had a less significant impact in most cases, relaxing residual stress by 100-200MPa.

Measurements of residual stress and microstructural evolution in electron beam welded Ti-6Al-4V using multiple techniques

“…A recent review by Fairfax and Steinzig [13], which analysed 147 residual stress related incidents within the ASM Failure Analysis Database™, found that over 37% of incidents were directly attributable to joining-related failures. Additionally, residual stresses may lead to distortion during the manufacturing process of machining due to material removal which leads to the redistribution of residual stresses [14]. Determining the nature and magnitude of such stresses is therefore of critical importance to the manufacture and performance of welded Ti-6Al-4V components.…”

Residual Stress Control for Superalloys Disk in Cooling Treatments

“…The sketch map for the positions of residual stress measurement and tensile test sampling is shown in Figure 9. P1, P2, P3 are surface residual stress measurement position using XRD (Hoop stress and Radial stress, mid-value and errors of 6 measured values); P4, P5, P6 are inside residual stress measurement position using contour method (details on the contour method are given in [3]); S1, S2, S3, S4, S5, S6 are sampling position for tensile tests (in the tangential direction).…”

“…Due to the uneven plastic deformation, residual stress is usually inevitable to be introduced during processing for forgings. The precise residual stress distribution is of importance to engine manufacturers for two distinct reasons [2,3]. Firstly, machining processes remove constraining material, which causes the component to distort as the residual stresses re-distribute to reach a new equilibrium state.…”