Measuring residual stresses in linear friction welded joints composed by dissimilar titanium

Abstract

The Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) titanium alloy is the main material used in manufacturing blades and disks of aero engines, and it is always jointed with different microstructures for the design constraints. In this work, the residual stresses of linear friction welding of β Ti17 and α + β Ti17 are measured by contour method and the X-ray diffraction method. The welding-induced tensions were found to be greater on the β side than that on the α + β side, and had an obvious reduction in the weld centre. After the post weld heat treatment (PWHT) of 630°C for 3 h, all tensions on the β side relax to a very limited value while some new PWHT-induced compressions are found on the α + β side.

On the effect of a thermal treatment on the tensile and fatigue properties of weak zones of similar Ti17 linear friction welded joints and parent material

“…There is some agreement in literature concerning the presence of tensile residual stresses parallel to the P axis at the TMAZ of titanium alloys LFW joints [42,43,44]. The authors of the present work have previously documented an early plastic activity in the vicinity of the WCZ exhibiting overmatching strength of a similar Ti6242 LFW joints that led to fatigue crack initiation during cyclic loading [31].…”

“…In a similar manner, [44] measured the residual stresses of a dissimilar Ti17(β)-Ti17(α + β) LFW joint by the contour method. They claimed that X-ray diffraction exhibits a low spatial resolution for LFW joints but nevertheless, it served well for comparison and validation of the contour method measurements.…”

“…They claimed that X-ray diffraction exhibits a low spatial resolution for LFW joints but nevertheless, it served well for comparison and validation of the contour method measurements. It should be pointed out that, for the FEA computation of the welded structure residual stresses, the Young s modulus of the PM was used for the entire cross-welded structure [44]. This is particularly arguable since, compared to the PM, the WCZ exhibits a significant lower Young s modulus and this may therefore have led to an overestimation of the residual stresses.…”

Innovative Approach for the Evaluation of the Mechanical Behavior of Dissimilar Welded Joints

“…This technique is easily applicable and particularly suitable to welded joints, owing to the fact that it is not affected by microstructural changes and inhomogeneities, and it is capable of capturing even steep stress gradients [44,45]. Indeed, it has been successfully employed on dissimilar joints, especially friction-welded [42,[46][47][48][49]; • since the contour method is a destructive technique and capable of measuring only one stress component per each cut, longitudinal stresses, which are generally larger in magnitude, should be measured as first followed by transverse stress; • subsequently, fatigue tests have to be performed in conjunction with a thermographic analysis of the increase in surface temperature of the specimens to monitor the failure zone [43];…”

Effect of the uncertainty of multi-cut contour method and friction coefficient on residual stresses of constrained groove pressing process

“…Residual stresses which generated by various production processes such as welding, 33–37 machining, 38 extrusion, 39 and forging, 40 and also, post-processing process such as laser peening, 41 and ultrasonic peening, 42 were investigated by the contour method. Validation of the results of the contour method in the various processes was performed by the slitting method, 36 hole drilling, 34 X-ray, 35 and neutron diffraction, 39 that it reveals, there is a positive agreement between the results of contour method and other methods of residual stress measurement. Estimation of uncertainty is a technique to determine the accuracy of measurement.…”