<i>In situ</i> neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminium alloy

Woo, Wanchuck; Feng, Zhili; Wang, Xun-Li; Brown, Donald W.; Clausen, B.; An, Ke; Choo, Hahn; Hubbard, Camden R.; David, S. A.

doi:10.1179/174329307x197548

Cited by 80 publications

(53 citation statements)

References 24 publications

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“…However, temperature measurements further away from the stir zone do not provide a good estimate of the quality of the weld. The maximum temperatures have been reported close to the stir zone border and present a decrease with increasing distance from the joint line [2,11]. Due to the complex geometry, material tolerances, clamping and backing of production parts, it is in practice impossible to predict the temperature in the joint line from measurements elsewhere.…”

Section: Fsw Temperature Measurement Methodsmentioning

confidence: 99%

“…It is also a complex technology and difficult to calibrate since it depends on the material state [28][29][30]. Another temperature method tested in FSW is the neutron source method, which is based on the use of in situ time-resolved neutron diffraction [7,11]. With this technique, temperature and stress fields of the weld can be acquired simultaneously [11].…”

Section: Fsw Temperature Measurement Methodsmentioning

confidence: 99%

“…Weld temperature measurements through experimental validation are difficult to perform due to the intense plastic deformation at the workpiece-tool interface, which is considered the hottest area in the weld [3,11]. The passage of the rotating pin makes it difficult to measure the temperature on the stir zone; therefore, acquiring peak temperature measurements from thermocouples inside the workpiece is problematic [2].…”

Section: Introductionmentioning

confidence: 99%

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Temperature measurements during friction stir welding

Silva

Backer

Bolmsjö

2016

Int J Adv Manuf Technol

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The increasing industrial demand for lighter, more complex and multi-material components supports the development of novel joining processes with increased automation and process control. Friction stir welding (FSW) is such a process and has seen a fast development in several industries. This welding technique gives the opportunity of automation and online feedback control, allowing automatic adaptation to environmental and geometrical variations of the component. Weld temperature is related to the weld quality and therefore proposed to be used for feedback control. For this purpose, accurate temperature measurements are required. This paper presents an overview of temperature measurement methods applied to the FSW process. Three methods were evaluated in this work: thermocouples embedded in the tool, thermocouples embedded in the workpiece and the tool-workpiece thermocouple (TWT) method. The results show that TWT is an accurate and fast method suitable for feedback control of FSW.

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Section: Fsw Temperature Measurement Methodsmentioning

confidence: 99%

Section: Fsw Temperature Measurement Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Temperature measurements during friction stir welding

Silva

Backer

Bolmsjö

2016

Int J Adv Manuf Technol

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“…However, measurement of stress is significantly more complicated, because changes in lattice parameter are not solely due to mechanical strains but also due to thermal expansion of the material and compositional variations associated with phase transformations. In spite of these difficulties, two attempts to measure stresses in situ along a one dimensional line have recently been reported in a friction stir weld on an aluminium alloy, which does not exhibit any phase transformations [23,24]. The magnitude of the mechanical, thermal and compositional contributions to the lattice parameter are similar; using the expressions of Onink and Root [18], a 50 • C temperature variation, which is at the limit of positioning accuracy for placing a neutron diffraction gauge volume near a thermocouple, corresponds to a change in lattice parameter of ferrite of 2.88 × 17.5 × 50 × 10 −6 = 2.52 × 10 −3Å .…”

Section: Introductionmentioning

confidence: 99%

Characterization of Phase Transformations and Stresses During the Welding of a Ferritic Mild Steel

Dye

Stone

Watson³

et al. 2014

Metall Mater Trans A

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The transient stresses and phase evolution have been characterised in the quasi-steady state produced around a gas tungsten arc welding (GTAW) torch in a plain carbon (ASTM 1018) steel using in situ neutron diffraction. A novel method has been developed to isolate the deviatoric or plane stress state in the presence of isotropic contributions to the lattice parameter, such as thermal expansion and solute content. The stress state was found to evolve in the anticipated manner, with compressive stresses ahead of the weld and tensile stresses behind the weld, in the weld and heat affected zone, and compression in the far field behind the weld. In particular, the region of compression in the heat-affected zone adjacent to and just behind the welding torch expected from weld models was observed. The evolution of phase fraction around the weld was also determined using the technique and the stresses obtained from the ferrite phase.

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“…On the other hand, in situ studies of stress accumulation in solidifying metals are rather limited. Woo et al [17] published in 2007 a study on in situ neutron diffraction measurements of stresses during friction stir welding of 6061-T6 aluminum alloy. Neutrons were also used to determine in situ the very moment when macroscopic strains and stresses appear in the mushy alloy.…”

mentioning

confidence: 99%

Measurement of Mechanical Coherency Temperature and Solid Volume Fraction in Al-Zn Alloys Using In Situ X-ray Diffraction During Casting

Drezet

Mireux

Kurtuldu

et al. 2015

Metall Mater Trans A

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During solidification of metallic alloys, coalescence leads to the formation of solid bridges between grains or grain clusters when both solid and liquid phases are percolated. As such, it represents a key transition with respect to the mechanical behavior of solidifying alloys and to the prediction of solidification cracking. Coalescence starts at the coherency point when the grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at mechanical coherency when the solid phase is sufficiently coalesced to transmit macroscopic tensile strains and stresses. Temperature at mechanical coherency is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for Al-Zn alloys using in situ X-ray diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is prevented. The cooling on both extremities of the mold induces a hot spot at the middle of the sample which is irradiated by X-ray. Diffraction patterns were recorded every 0.5 seconds using a detector covering a 426 9 426 mm 2 area. The change of diffraction angles allowed measuring the general decrease of the lattice parameter of the fcc aluminum phase. At high solid volume fraction, a succession of strain/stress build up and release is explained by the formation of hot tears. Mechanical coherency temperatures, 829 K to 866 K (556°C to 593°C), and solid volume fractions, ca. 98 pct, are shown to depend on solidification time for grain refined Al-6.2 wt pct Zn alloys.

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In situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminium alloy

Cited by 80 publications

References 24 publications

Temperature measurements during friction stir welding

Temperature measurements during friction stir welding

Characterization of Phase Transformations and Stresses During the Welding of a Ferritic Mild Steel

Measurement of Mechanical Coherency Temperature and Solid Volume Fraction in Al-Zn Alloys Using In Situ X-ray Diffraction During Casting

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