Residual Strain Analysis in Linear Friction Welds of Similar and Dissimilar Titanium Alloys Using Energy Dispersive X -
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NTRODUCTION
LINEAR friction welding (LFW) is commonly used in the aerospace industry to produce cost-effective and high-quality welds in components made from titanium (Ti) alloys, such as bladed discs or blisks. One of the benefits of the LFW process is joining dissimilar materials, thereby allowing components to possess location-specific properties. During the welding process, one reciprocating surface is brought into contact with a stationary surface at high frequency under applied load. This results in a steep temperature gradient across the
RITWIK BANDYOPADHYAY and DIWAKAR NARAGANI are with the School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN 47907. JOHN ROTELLA is with the School of Materials Engineering, Purdue University, West Lafayette, IN 47907. JUN-SANG PARK is with the Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439. MICHAEL EFF is with the Edison Welding Institute, 1250 Arthur E. Adams Dr., Columbus, OH 43221. MICHAEL D. SANGID is with the School of Aeronautics and Astronautics, Purdue University and also with the the School of Materials Engineering, Purdue University. Contact e-mail: [email protected]. Manuscript submitted June 6, 2018. Article published online December 6, 2018 704—VOLUME 50A, FEBRUARY 2019
weld interface. Such localized heating along with microstructural variations and poor thermal conductivity of Ti alloys results in highly localized residual stresses in the weld region.[1–3] The role of residual stress in the failure of engineering component is well recognized.[4] Therefore, it is necessary to provide a detailed characterization of the residual stress present in LFW joints of similar and dissimilar Ti alloys. Residual stress distributions can be characterized using a wide range of techniques.[5] In particular, diffraction-based techniques using X-rays or neutron beam measure the inter-planar spacing, which is used to compute the lattice strains. These lattice strain measurements coupled with appropriate constitutive relationships provide information regarding the residual stress in the material.[6] Energy-dispersive X-ray diffraction (EDD) method has been used to quantify the residual stresses in engineering components in the past.[7–11] This method is particularly attractive because (i) high energy X-rays can penetrate tens of millimeters of typical engineering alloys, (ii) the incident X-ray beam can be reduced to offer sub-mm spatial resolution in the directions perpendicular to the beam in a typical setup, and (iii) acquisition time is relatively short. These characteristics enable spatial mapping of residual strain
METALLURGICAL AND MATERIALS TRANSACTIONS A
in an engineering component. Additionally, the sample can be manipulated to measure the strains along multiple directions to determine the strain tensor (and thereby stress tensor). There are a few studies available in literature characterizing the residual stress distributions in the LFW joints of Ti alloys.[12–16] Most of the works involve welds of similar Ti alloys[12–15]
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