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Special Issue "Application of Laser-Ultrasonics in Metal Processing"

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: 30 April 2023 | Viewed by 4718

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Special Issue Editors

Prof. Dr. Bevis Hutchinson
E-Mail Website
Guest Editor

Swerim AB, Kista, Sweden
Interests: laser ultrasound; elasticity in polycrystals; relationships between texture and wave propagation; control and characterization of texture and microstructure in metals

Dr. Malmström Mikael

E-Mail Website
Guest Editor

Swerim AB, 164 40 Kista, Sweden
Interests: laser ultrasonics; non-destructive testing; non-destructive evaluation; process monitoring

Dr. Lundin Peter

E-Mail Website
Guest Editor

Swerim AB, 164 40 Kista, Sweden
Interests: laser ultrasonics; non-destructive testing; laser induced breakdown spectroscopy

Special Issue Information

Dear Colleagues,

Since the development of the laser ultrasonic (LUS) technique in the 1980s and 1990s, the field has matured significantly. The key advantage of LUS is the unique feature of being able to measure material properties in a truly contactless manner with a working distance up to meters. This attractive feature has enabled commercialization in a broad range of areas and today there are available LUS systems for several industrial applications, e.g., wall thickness gauging for the extrusion of seamless pipes, real-time grain size monitoring in thermomechanical simulators, and the detection of defects in large components for the aviation industry. This research field contains a myriad of applications where laser ultrasound is a key enabler for understanding material processing and process behavior.

This Special Issue concerns the application of laser ultrasonics in metal processing and we invite the whole laser ultrasonics community to submit contributions on this topic.

Prof. Dr. Bevis Hutchinson
Dr. Malmström Mikael
Dr. Lundin Peter
Guest Editors

Manuscript Submission Information

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Keywords

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laser ultrasonics
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non-destructive testing
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metal processing
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process monitoring
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Published Papers (6 papers)

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Research

Open AccessFeature PaperArticle

Significance of Annealing Twins in Laser Ultrasonic Measurements of Grain Size in High-Strength Low-Alloy Steels

and

Appl. Sci. 2023, 13(6), 3901; https://doi.org/10.3390/app13063901 - 19 Mar 2023

Viewed by 322

Abstract

In this study, we demonstrate the significance of austenite annealing twin boundaries when calibrating laser ultrasonic measurements for gauging austenite grain size in situ during the thermomechanical processing of high-strength low-alloy steels. Simple calculations show how differences in twinning density can lead to errors in grain size measurements if twins are disregarded during calibration and the method is used for a broad range of steels. Conversely, when calibration is performed using alloys with a metastable austenite microstructure at room temperature, the same calibration is suitable for a broad range of HSLA steels, provided that annealing twins are taken into account. Since light optical microscopy does not allow the characterization of annealing twins in low-alloy steel, the verification of the laser ultrasonic results was conducted using the novel approach of comparing the twinned grain sizes obtained using the ultrasonic method in low-alloy steels with the austenite grain maps reconstructed from martensite orientation maps measured using electron backscatter diffraction. Finally, we show how differences in twinning density occur even for alloys with a roughly similar stacking fault energy, further highlighting the importance of annealing twins in the calibration of laser ultrasonic measurements for industrial use. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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Open AccessArticle

Imaging Microstructure on Optically Rough Surfaces Using Spatially Resolved Acoustic Spectroscopy

and

Appl. Sci. 2023, 13(6), 3424; https://doi.org/10.3390/app13063424 - 08 Mar 2023

Viewed by 405

Abstract

The microstructure of a material defines many of its mechanical properties. Tracking the microstructure of parts during their manufacturing is needed to ensure the designed performance can be obtained, especially for additively manufactured parts. Measuring the microstructure non-destructively on real parts is challenging for optical techniques such as laser ultrasound, as the optically rough surface impacts the ability to generate and detect acoustic waves. Spatially resolved acoustic spectroscopy can be used to measure the microstructure, and this paper presents the capability on a range of surface finishes. We discuss how to describe ’roughness’ and how this influences the measurements. We demonstrate that measurements can be made on surfaces with

R_{a}

up to 28

μ

m for a selection of roughness comparators. Velocity images on a range of real surface finishes, including machined, etched, and additively manufactured finishes in an as-deposited state, are presented. We conclude that the

R_{a}

is a poor descriptor for the ability to perform measurements as the correlation length of the roughness has a large impact on the ability to detected the surface waves. Despite this issue, a wide range of real industrially relevant surface conditions can be measured. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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Open AccessArticle

Estimation of Grain Size and Composition in Steel Using Laser UltraSonics Simulations at Different Temperatures

and

Appl. Sci. 2023, 13(2), 1121; https://doi.org/10.3390/app13021121 - 14 Jan 2023

Viewed by 918

Abstract

The applicability of laser ultrasonics for the determination of grain size and phase composition in steels under different temperatures was investigated. This was done by obtaining the velocity and attenuation of propagating ultrasonic waves in a simulated steel medium. Samples of ferrite and austenite with varying microstructures were modelled and simulated with the finite difference method, as were samples with varying ratios of austenite and martensite. The temperature of the medium was taken into account as an essential parameter, since both velocity and attenuation are temperature dependent. Results of the velocity and attenuation analysis showed that the use of the wave propagation velocity is not feasible for determination of grain size or phase composition due to a high sensitivity to temperature and sample thickness. The frequency-dependent ultrasonic wave attenuation was less sensitive to the variation of temperature and sample thickness. It can be concluded that accurate knowledge of the temperature is essential for obtaining a correct grain size or phase ratio estimation: a temperature accuracy of 100 °C yields a grain size accuracy in the order of a micrometer using the attenuation. Similarly, a temperature accuracy of 70 °C leads to a phase ratio estimation accuracy of 10%. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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Open AccessArticle

Laser Generated Broadband Rayleigh Waveform Evolution for Metal Additive Manufacturing Process Monitoring

Chaitanya Bakre

Seyed Hamidreza Afzalimir

and

Appl. Sci. 2022, 12(23), 12208; https://doi.org/10.3390/app122312208 - 29 Nov 2022

Cited by 2 | Viewed by 700

Abstract

This work proposes that laser pulses can generate finite amplitude Rayleigh waves for process monitoring during additive manufacturing. The noncontact process monitoring uses a pulsed laser to generate Rayleigh waves, and an adaptive laser interferometer to receive them. Experiments and models in the literature show that finite amplitude waveforms evolve with propagation distance and that shocks can even form in the in-plane particle velocity waveform. The nonlinear waveform evolution is indicative of the material nonlinearity, which is sensitive to the material microstructure, which in turn affects strength and fracture properties. The measurements are made inside a directed energy deposition additive manufacturing chamber on planar Ti-6Al-4V and IN-718 depositions. By detecting the out-of-plane particle displacement waveform, the in-plane displacement and velocity waveforms are also available. The waveform evolution can be characterized (i) for one source amplitude by reception at different points or (ii) by reception at one point by applying different source amplitudes. Sample results are provided for intentionally adjusted key process parameters: laser power, scan speed, and hatch spacing. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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Figure 1

Open AccessArticle

Application of Laser-Ultrasonics for Evaluating Textures and Anisotropy

Mikael Malmström

Anton Jansson

and

Bevis Hutchinson

Appl. Sci. 2022, 12(20), 10547; https://doi.org/10.3390/app122010547 - 19 Oct 2022

Cited by 5 | Viewed by 536

Abstract

Various approaches are reviewed for determining elastic anisotropy and its coupling to crystallographic texture, with special reference to ultrasonic measurements. Two new methods are described for measuring the anisotropy of P-wave velocity using laser-ultrasonics. Making measurements across the diameter of a cylindrical specimen as it is rotated makes it possible to maintain a very constant known path length. This permits extremely accurate measurements with a precision of better than 0.01%. Results on 316 stainless steel in different conditions are compared with calculated values obtained from EBSD textures together with measured densities and crystalline coefficients from the literature. Excellent agreement is obtained when applying the Hill geometrical average procedure. A similar approach is adopted to measure the variation of wave velocity in a martensitic steel, after tempering at a range of temperatures. Changes in the anisotropy associated with thermal softening are discussed. The second method uses Galvano mirrors to steer the generating laser to different positions over a sheet surface, allowing wave velocities to be determined along different directions in the anisotropic material. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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Open AccessArticle

Laser-Ultrasound-Based Grain Size Gauge for the Hot Strip Mill

and

Appl. Sci. 2022, 12(19), 10048; https://doi.org/10.3390/app121910048 - 06 Oct 2022

Cited by 3 | Viewed by 813

Abstract

The paper summarizes the creation of a robust online grain size gauge for a hot strip mill. A method and algorithm for calculating the grain size from the measured ultrasonic attenuation is presented. This new method is self-calibrating, does not rely on a geometrical reference sample and can cope with the effects of diffraction on the attenuation. The model is based on 52 quenched samples measured with more than 23,000 laser ultrasonics shots and has a correlation coefficient R² of 0.8. Typical online laser ultrasonic measurements from the hot strip mill and the calculated grain size versus length are presented for a couple of steel strips. Full article

(This article belongs to the Special Issue Application of Laser-Ultrasonics in Metal Processing)

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