Residual Stresses in As‐Cast Billets: Neutron Diffraction Measurement and Thermomechanical Modeling

Drezet, Jean‐Marie; Pirling, Th.; Jaquerod, C.

doi:10.1002/9781118359259.ch192

Cited by 4 publications

(1 citation statement)

References 10 publications

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“…The wavelength was fixed to ' 1.57 Å , which allows measurement of the peak from the (311) planes at a scattering angle 2 close to 90 . This set of planes was chosen since they are known to be less susceptible to intergranular stresses, thus better resembling the bulk stresses in the material (Drezet et al, 2012). The configuration of this experiment can be found in Fig.…”

Section: Constant-wavelength Measurements Of Weld Residual Stressesmentioning

confidence: 99%

Neutron diffraction measurements of weld residual stresses in three-pass slot weld (Alloy 600/82) and assessment of the measurement uncertainty

et al. 2020

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This paper describes in detail two neutron diffraction residual stress measurements, performed on the ENGIN-X neutron scattering instrument at the ISIS facility in the UK and on the SALSA instrument at the Institut Laue–Langevin in Grenoble, France. The measurements were conducted as part of the NeT Task Group 6 (TG6) international measurement round robin on an Alloy 600/82 multi-pass weldment – a slot in an Alloy 600 plate filled with three Alloy 82 weld beads, simulating a repair weld. This alloy/weld combination is considered challenging to measure, due to the large grain size and texture in the weld, and large gradients in the stress-free lattice parameter between the parent and weld metal. The basic principles of the neutron diffraction technique are introduced and issues affecting the reliability of residual stress characterization are highlighted. Two different analysis strategies are used for estimation of residual stresses from the raw data. Chemical composition studies are used to measure the mixing of parent and weld metal and highlight the steep lattice parameter gradients that arise as a consequence. The inferred residual stresses are then compared with three sets of measurements performed on the same plate by other NeT partners on E3 at the HZB in Berlin, STRESS-SPEC at the FRM II in Munich and KOWARI in Sydney. A robust Bayesian estimation average is calculated from the combined five-instrument data set, allowing reliable best estimates of the residual stress distribution in the vicinity of the weldment. The systematic uncertainties associated with the residual stress measurements are determined separately in the weld and parent materials, and compared with those in the NeT TG4 benchmark. This is a three-pass slot-welded plate fabricated from American Iron and Steel Institute AISI 316L(N) austenitic stainless steel, and is normally considered less challenging to measure using diffraction techniques than all nickel welds. The uncertainties in the stress measurements by neutron diffraction for these two weldments seem to be comparable.

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Section: Constant-wavelength Measurements Of Weld Residual Stressesmentioning

confidence: 99%

Neutron diffraction measurements of weld residual stresses in three-pass slot weld (Alloy 600/82) and assessment of the measurement uncertainty

et al. 2020

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Modelling and Simulation

Park¹,

LUCA²,

COUTELLIER³

2013

Direct‐Chill Casting of Light Alloys

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Neutron Diffraction Measurement of As‐Cast Residual Stresses in AA7050 Rolling Plate Ingots: Influence of a Wiper

et al. 2014

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During casting, thermally induced deformations give birth to ingot distortions and residual stresses. For some high strength alloys, ingot cracking can happen during casting per se or during cooling down. Ingot distortions such as rolling face pull-in, but curl and but swell are rather easy to quantify as opposed to internal stresses. As aluminium is rather transparent to neutrons, residual stress measurements using neutron diffraction appeared to be a good way to validate the thermomechanical models aimed at simulating the stress build-up during casting. This technique has been applied to DC cast AA7050 rolling plate ingots with special attention to the stress generation in the transient start-up phase, i.e. in the foot of the ingot. Additional results using the hole drilling method complement the measurements. The measured stress distributions are compared with the results of a numerical model of DC casting for ingots cast with and without a wiper. I IntroductionIn the fabrication of aluminum rolling plates, the first step is the semi-continuous casting of a rectangular ingot. The most commonly used process is known as direct chill (DC) casting [1]. This process gives rise to large thermally induced strains that lead to several types of casting defects (distortions, cold cracks, porosity, solidification cracking, etc.). During casting, thermally induced stresses are partially relieved by permanent deformation. When these residual stresses overcome the deformation limit of the alloy, cracks are generated either during solidification (hot tears) or during cooling (cold cracks). The formation of these cracks results in rejection of the cast part. Furthermore, thermally induced stresses can cause downstream processing issues during the sawing stage prior to rolling. For large ingot formats and high strength alloys, sawing becomes a delicate task owing to the risk of saw pinching or crack initiation ahead of the saw. The use of wipers during casting largely reduces the level of as-cast stresses.The computation of stresses during DC casting of aluminum alloys has been the scope of several studies since the late 90's [2-10] and is a well established technique nowadays. Many numerical models have allowed researchers to compute the ingot distortions and the associated residual stresses. The validation of these models was often done by comparing the computed and measured ingot distortions, e.g. the butt-curl [8] and the rolling face pull-in for rolling sheet ingots produced by DC [9] or electromagnetic casting [11].Validation against the computed room-temperature residual stresses is limited simply owing to the difficulty of measuring the internal strains and the high variability in the measurements. While some measurements are available for quenching [12] or welding [13], they remain rare, uncertain and usually are limited to one or two components of the stress tensor, and to the skin of round billets for as-cast materials [14][15]. In contrast to destructive methods for measuring residual stresses (hole-drilli...

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Residual Stresses in As‐Cast Billets: Neutron Diffraction Measurement and Thermomechanical Modeling

Cited by 4 publications

References 10 publications

Neutron diffraction measurements of weld residual stresses in three-pass slot weld (Alloy 600/82) and assessment of the measurement uncertainty

Neutron diffraction measurements of weld residual stresses in three-pass slot weld (Alloy 600/82) and assessment of the measurement uncertainty

Modelling and Simulation

Neutron Diffraction Measurement of As‐Cast Residual Stresses in AA7050 Rolling Plate Ingots: Influence of a Wiper

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