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Article
Title Assessment of Residual Stresses in ITER CS Helium Inlet Welds Fatigue Tested at Cryogenic Temperature
Author(s) Sgobba, S (CERN) ; Aviles Santillana, I (CERN) ; Langeslag, S (CERN) ; Fernandez Pison, P (CERN ; Carlos III U., Madrid) ; Castillo Rivero, S (CERN ; Seville U.) ; Libeyre, P (Euratom, St. Paul Lez Durance) ; Jong, C (Euratom, St. Paul Lez Durance) ; Everitt, D (Oak Ridge, U.S. ITER) ; Freudenberg, K (Oak Ridge, U.S. ITER)
Publication 2019
Number of pages 6
In: IOP Conf. Ser. Mater. Sci. Eng. 502 (2019) 012095
In: 27th International Cryogenic Engineering Conference - International Cryogenic Materials Conference 2018, Oxford, United Kingdom, 3 - 7 Sep 2018, pp.012095
DOI 10.1088/1757-899x/502/1/012095
Subject category Accelerators and Storage Rings
Accelerator/Facility, Experiment ITER
Abstract The ITER Central Solenoid (CS) consists of six independent wound modules. The cooling of the cable-in-conduit conductor is assured by a forced flow of supercritical He at 4.5 K supplied by He inlets located at the innermost radius of the coil. The inlets consist of a racetrackshaped boss welded to the outer conduit wall through a full penetration Tungsten Inert Gas (TIG) weld. They are critical structural elements submitted to severe cyclic stresses due to the electromagnetic forces acting on the coils. The weld contour is shape-optimised and locally processed by Ultrasonic Shot Peening (USP), conferring large compressive residual stresses on a subsurface layer of several millimetres thickness to improve fatigue strength. The distribution of the residual stresses and the effect of USP on microstructure and mechanical properties is assessed, with reference to the results of a cryogenic fatigue test campaign, performed on peened and as-welded inlets for comparison.
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