High temperature shear modulus determination using a laser-ultrasonic surface acoustic-wave device

Nadal, Marie-Hélène; Hubert, C.; Oltra, R.

doi:10.1063/1.3176495

Cited by 19 publications

(5 citation statements)

References 24 publications

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“…38 It is necessary to note that, unless this condition is satisfied, there is no agreement between our experiment and numerical model, which proves that onset of melting is accompanied by vanishing of shear modulus, i.e. loss of shear rigidity within molten pool, resulting in the delay of shear wave arrivals observed in our experiment.…”

Section: Aip Advances 7 075203 (2017)mentioning

confidence: 63%

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

et al. 2017

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Nanosecond laser pulse-induced melting thresholds in refractory (Nb, Mo, Ta and W) metals are measured using detected laser-generated acoustic shear waves. Obtained melting threshold values were found to be scaled with corresponding melting point temperatures of investigated materials displaying dissimilar shearing behavior. The experiments were conducted with motorized control of the incident laser pulse energies with small and uniform energy increments to reach high measurement accuracy and real-time monitoring of the epicentral acoustic waveforms from the opposite side of irradiated sample plates. Measured results were found to be in good agreement with numerical finite element model solving coupled elastodynamic and thermal conduction governing equations on structured quadrilateral mesh. Solid-melt phase transition was handled by means of apparent heat capacity method. The onset of melting was attributed to vanished shear modulus and rapid radial molten pool propagation within laser-heated metal leading to preferential generation of transverse acoustic waves from sources surrounding the molten mass resulting in the delay of shear wave transit times. Developed laser-based technique aims for applications involving remote examination of rapid melting processes of materials present in harsh environment (e.g. spent nuclear fuels) with high spatio-temporal resolution.

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Section: Aip Advances 7 075203 (2017)mentioning

confidence: 63%

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

et al. 2017

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“…The shear modulus of the elemental foils is well above that of the Ti matrix, particularly at the welding temperature (see e.g. references [9] and [19][20][21], resulting in flow of the Ti matrix around the foil during the hotter 'slipping' conditions alternating with the combined flow of the foil and matrix together during the colder 'sticking' conditions. This causes the variations in foil distributions, surface features, and machine forces observed in these welds.…”

Section: Resultsmentioning

confidence: 99%

Enhancing the weldability of CP titanium friction stir welds with elemental foils

Fonda

Knipling

Levinson

et al. 2019

Science and Technology of Welding and Joining

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Friction stir welding (FSW) has proven to be a viable technique for joining a wide variety of alloys. However, thick section welding of alpha and near-alpha Ti alloys has proven particularly challenging. Previous research at the Naval Research Laboratory using Ni markers in CP Ti friction stir welds indicated that elemental additions of Ni to the joint line can provide substantial benefits for improved weldability of these alloys. The current study surveys the effects of Ni and other elemental additions to CP Ti friction stir welds to determine their influence on the resultant weld microstructure, weld surface finish, and welding machine forces. These results reveal that Ni provides the most benefits for the concentrations examined, but other elements may also provide benefits at lower concentrations. The addition of these elements may improve the weldability and weld quality for FSW of CP Ti, enabling thick section welding of this and similar alloys.

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“…Simulations have also been performed on the basis of data on the temperature dependent thermophysical properties of tungsten drawn from References [5,6,7,8], as summarized in Fig. 2, with the optical reflectivity increasing from 0.45 to 0.55 between room temperature and the melting point.…”

Section: Available Thermophysical Datamentioning

confidence: 99%

Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

Every

Utegulov²,

Veres

2015

AIP Conference Proceedings

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Measurement of frequency gaps and waveguiding in phononic plates with periodic stepped cylinders using pulsed laser generated ultrasound Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold J. Appl. Phys. 98, 033104 (2005); 10.1063/1.1999827 Ablation of solids by femtosecond lasers: Ablation mechanism and ablation thresholds for metals and dielectrics Abstract. The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.

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High temperature shear modulus determination using a laser-ultrasonic surface acoustic-wave device

Cited by 19 publications

References 24 publications

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

Enhancing the weldability of CP titanium friction stir welds with elemental foils

Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

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