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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Corrosion and Protection".

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 47939

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Special Issue Editors

Prof. Dr. José L. Ocaña

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Guest Editor

Department of Applied Physics and Materials Engineering, E.T.S. Ingenieros Industriales, Polytechnical University of Madrid, 28040 Madrid, Spain
Interests: laser shock processing; laser additive manufacturing; materials characterization
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Janez Grum

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Guest Editor

Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, 1000 Ljubljana, Slovenia
Interests: material characterization; microstructure; mechanical properties; mechanical behavior of materials; materials processing; advanced materials; surface engineering; heat treatment; coatings; corrosion

Special Issue Information

Dear Colleagues,

Laser Shock Processing (LSP) has been developed as an effective technology for improving the surface and mechanical properties of metallic alloys. In addition, it is an emerging technology that is being manufactured with direct competitive advantages in comparison with other established technologies, such as shot peening, whether in manufacturing or maintenance/repair operations.

The level of maturity of Laser Shock Processing has been increasing during the last few years, and several thematic international conferences have been organized (the 7^th ICLPRP will be held in Singapore, June 17–22, 2018), where different developments on a number of key aspects have been discussed, i.e.:

Fundamental Laser Interaction Phenomena
Material Behavior at High Deformation Rates/Under Intense Shock Waves
Laser Sources and Experimental Processes Implementation
Induced Microstructural/Surface/Stress Effects
Mechanical and Surface Properties Experimental Characterization and Testing
Numerical Process Simulation
Development and Validation of Applications
Comparison of LSP to Competing Technologies
Novel Related Processes

which have been treated by renowned specialists, providing a firm basis for the further development of the technology in its path to industrial penetration.

However, the application of LSP (and related technologies) to different types of materials, envisaging different types of applications (ranging from the always demanding aeronautical/aerospatial field to the energy generation, automotive and biomedical fields), still requires extensive efforts in the elucidation and mastering of different critical aspects, which deserve deep analysis as a necessary step prior to their industrial readiness level.

This Special Issue aims to collect, mainly for the use of LSP application developers in different target sectors, a number of high quality and relevant papers representing the present state-of-the-art of the technology, which can be also useful to newcomers in realizing its wide and relevant prospects as a key manufacturing technology.

Consequently, and in an additional and complementary way to papers presented at the thematic ICLPRP Conferences, a call is made to those authors willing to prepare a high quality and relevance paper for their submission to the journal (https://www.mdpi.com/journal/metals), with the confidence that their work will make part of a fundamental collection providing the present state-of-the-art of the LSP technology.

Prof. Dr. José L. Ocaña
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Laser shock processing
fundamental phenomena
mechanical properties
surface properties
residual stresses
crack propagation
fatigue
corrosion
materials behaviour
numerical simulation

Published Papers (12 papers)

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Editorial

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3 pages, 175 KiB

Open AccessEditorial

Laser Shock Processing and Related Phenomena

by José Luis Ocaña and Janez Grum

Metals 2020, 10(6), 797; https://doi.org/10.3390/met10060797 - 16 Jun 2020

Cited by 2 | Viewed by 1495

Abstract

Laser Shock Processing (LSP) is continuously developing as an effective technology for improving the surface and mechanical properties of metallic alloys and is emerging in direct competition with other established technologies, such as shot peening, both in preventive manufacturing treatments and maintenance/repair operations [...] Read more.

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

Research

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18 pages, 3780 KiB

Open AccessFeature PaperArticle

Integrated Numerical-Experimental Assessment of the Effect of the AZ31B Anisotropic Behaviour in Extended-Surface Treatments by Laser Shock Processing

by Ignacio Angulo, Francisco Cordovilla, Ángel García-Beltrán, Juan A. Porro, Marcos Díaz and José L. Ocaña

Metals 2020, 10(2), 195; https://doi.org/10.3390/met10020195 - 29 Jan 2020

Cited by 5 | Viewed by 2493

Abstract

In recent years, an increasing interest in designing magnesium biomedical implants has been presented due to its biocompatibility, and great effort has been employed in characterizing it experimentally. However, its complex anisotropic behaviour, which is observed in rolled alloys, leads to a lack of reliable numerical simulation results concerning residual stress predictions. In this paper, a new model is proposed to focus on anisotropic material hardening behaviour in Mg base (in particular AZ31B as a representative alloy) materials, in which the particular stress cycle involved in Laser Shock Processing (LSP) treatments is considered. Numerical predictions in high extended coverage areas obtained by means of the implemented model are presented, showing that the realistic material’s complex anisotropic behaviour can be appropriately computed and—much more importantly—it shows a particular non-conventional behaviour regarding extended areas processing strategies. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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17 pages, 3981 KiB

Open AccessArticle

Finite Element Analysis of Laser Peening of Thin Aluminum Structures

by Kristina Langer, Thomas J. Spradlin and Michael E. Fitzpatrick

Metals 2020, 10(1), 93; https://doi.org/10.3390/met10010093 - 06 Jan 2020

Cited by 19 | Viewed by 3077

Abstract

Laser shock peening has become a commonly applied industrial surface treatment, particularly for high-strength steel and titanium components. Effective application to aluminum alloys, especially in the thin sections common in aerospace structures, has proved more challenging. Previous work has shown that some peening conditions can introduce at-surface tensile residual stress in thin Al sections. In this study, we employ finite element modeling to identify the conditions that cause this to occur, and show how these adverse effects can be mitigated through selection of peen parameters and patterning. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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17 pages, 29943 KiB

Open AccessArticle

Fatigue Properties of Maraging Steel after Laser Peening

by Luca Petan, Janez Grum, Juan Antonio Porro, José Luis Ocaña and Roman Šturm

Metals 2019, 9(12), 1271; https://doi.org/10.3390/met9121271 - 28 Nov 2019

Cited by 7 | Viewed by 2300

Abstract

Maraging steels are precipitation hardening steels used for highly loaded components in aeronautical and tooling industry. They are subjected to thermomechanical loads and wear, which significantly shorten their service life. Improvements of their surface mechanical properties to overcome such phenomena are of great interest. The purpose of our research was to investigate the influence of pulse density and spot size of a laser shock peening (LSP) process on the surface integrity with the fatigue resistance of X2NiCoMo18-9-5 maraging steel. Surface integrity was analyzed through roughness, residual stress, and microhardness measurements. The tests performed on resonant testing machine confirmed LSP is a promising process for increasing fatigue resistance of a component. Fatigue crack occurs, when the resonance frequency decreases. This moment, when the fatigue crack initiation phase ends and the fatigue crack propagation phase starts, was chosen as the moment of failure. We have proved LSP is a successful method in improving fatigue resistance of maraging steel by appropriate combination of laser spot size and pulse density tested in our research. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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27 pages, 10255 KiB

Open AccessArticle

Simulation and Experimental Comparison of Laser Impact Welding with a Plasma Pressure Model

by Sepehr Sadeh, Glenn H. Gleason, Mohammad I. Hatamleh, Sumair F. Sunny, Haoliang Yu, Arif S. Malik and Dong Qian

Metals 2019, 9(11), 1196; https://doi.org/10.3390/met9111196 - 07 Nov 2019

Cited by 15 | Viewed by 4561

Abstract

In this study, spatial and temporal profiles of an Nd-YAG laser beam pressure pulse are experimentally characterized and fully captured for use in numerical simulations of laser impact welding (LIW). Both axisymmetric, Arbitrary Lagrangian-Eulerian (ALE) and Eulerian dynamic explicit numerical simulations of the collision and deformation of the flyer and target foils are created. The effect of the standoff distance between the foils on impact angle, velocity distribution, springback, the overall shape of the deformed foils, and the weld strength in lap shear tests are investigated. In addition, the jetting phenomenon (separation and ejection of particles at very high velocities due to high-impact collision) and interlocking of the foils along the weld interface are simulated. Simulation results are compared to experiments, which exhibit very similar deformation and impact behaviors. In contrast to previous numerical studies that assume a pre-defined deformed flyer foil shape with uniform initial velocity, the research in this work shows that incorporation of the actual spatial and temporal profiles of the laser beam and modeling of the corresponding pressure pulse based on a laser shock peening approach provides a more realistic prediction of the LIW process mechanism. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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13 pages, 4957 KiB

Open AccessArticle

Improving Fatigue Performance of Laser-Welded 2024-T3 Aluminum Alloy Using Dry Laser Peening

by Tomokazu Sano, Takayuki Eimura, Akio Hirose, Yosuke Kawahito, Seiji Katayama, Kazuto Arakawa, Kiyotaka Masaki, Ayumi Shiro, Takahisa Shobu and Yuji Sano

Metals 2019, 9(11), 1192; https://doi.org/10.3390/met9111192 - 06 Nov 2019

Cited by 16 | Viewed by 3202

Abstract

The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance of laser-welded 2024 aluminum alloy containing welding defects such as undercuts and blowholes. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. As a result, DryLP treatment improved the fatigue performances of welded specimens with and without the weld reinforcement almost equally. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes, as stress concentration at the defects did not significantly influence the fatigue performance. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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15 pages, 4223 KiB

Open AccessArticle

Experimental Determination of Electronic Density and Temperature in Water-Confined Plasmas Generated by Laser Shock Processing

by Cristóbal Colón, María Isabel de Andrés-García, Cristina Moreno-Díaz, Aurelia Alonso-Medina, Juan Antonio Porro, Ignacio Angulo and José Luis Ocaña

Metals 2019, 9(7), 808; https://doi.org/10.3390/met9070808 - 22 Jul 2019

Cited by 6 | Viewed by 3207

Abstract

In this work, diagnoses of laser-induced plasmas were performed in several Laser Shock Processing (LSP) experiments using the Balmer Hα-line (656.27 nm) and several Mg II spectral lines. A Q-switched laser of Nd:YAG was focused on aluminum samples (Al2024-T351) in LSP experiments. Two methods were used to diagnose the plasma. The first method, which required two different experiments, was the standard for establishing the electronic temperature through the use of a Boltzmann Plot with spectral lines of Mg II and self-absorption correction. The Stark width of the Balmer Hα-line was used to determine the electron density in each of the cases studied. The second method had lower accuracy, but only required an experimental determination. Two parameters, the electronic temperature and the electron density, were obtained with the aid of the Hα-line in a single data acquisition process. The order of magnitude of the temperature obtained from this last method was sufficiently close to the value obtained by the standard method (within a factor lower than 2.0), which is considered to be important in order to allow for its possible use in industrial conditions. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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13 pages, 1051 KiB

Open AccessArticle

Laser Shock Peening: Toward the Use of Pliable Solid Polymers for Confinement

by Corentin Le Bras, Alexandre Rondepierre, Raoudha Seddik, Marine Scius-Bertrand, Yann Rouchausse, Laurent Videau, Bruno Fayolle, Matthieu Gervais, Leo Morin, Stéphane Valadon, Romain Ecault, Domenico Furfari and Laurent Berthe

Metals 2019, 9(7), 793; https://doi.org/10.3390/met9070793 - 17 Jul 2019

Cited by 26 | Viewed by 4548

Abstract

This paper presents the first extensive study of the performances of solid polymers used as confinement materials for laser shock applications such as laser shock peening (LSP) as opposed to the exclusively used water-confined regime up to now. The use of this new confinement approach allows the treatment of metal pieces needing fatigue behavior enhancement but located in areas which are sensitive to water. Accurate pressure determination in the polymer confinement regime was performed by coupling finite element simulation and experimental measurements of rear free-surface velocity using the velocity interferometer system for any reflector (VISAR). Pressure could reach 7.6 and 4.6 GPa for acrylate-based polymer and cross-linked polydimethylsiloxane (PDMS), respectively. At 7 and 4.7 GW/cm

^{2}

, respectively, detrimental laser breakdown limited pressure for acrylate and PDMS. These results show that the pressures produced were also as high as in water confinement, attaining values allowing the treatment of all types of metals with LSP and laying the groundwork for future determination of the fatigue behavior exhibited by this type of treated materials. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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11 pages, 6311 KiB

Open AccessArticle

The Effect of Laser Peening without Coating on the Fatigue of a 6082-T6 Aluminum Alloy with a Curved Notch

by Enrico Troiani and Nicola Zavatta

Metals 2019, 9(7), 728; https://doi.org/10.3390/met9070728 - 28 Jun 2019

Cited by 14 | Viewed by 2905

Abstract

Laser shock peening has established itself as an effective surface treatment to enhance the fatigue properties of metallic materials. Although a number of works have dealt with the formation of residual stresses, and their consequent effects on the fatigue behavior, the influence of material geometry on the peening process has not been widely addressed. In this paper, Laser Peening without Coating (LPwC) is applied at the surface of a notch in specimens made of a 6082-T6 aluminum alloy. The treated specimens are tested by three-point bending fatigue tests, and their fatigue life is compared to that of untreated samples with an identical geometry. The fatigue life of the treated specimens is found to be 1.7 to 3.3 times longer. Brinell hardness measurements evidence an increase in the surface hardness of about 50%, following the treatment. The material response to peening is modelled by a finite element model, and the compressive residual stresses are computed accordingly. Stresses as high as −210 MPa are present at the notch. The ratio between the notch curvature and the laser spot radius is proposed as a parameter to evaluate the influence of the notch. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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14 pages, 24195 KiB

Open AccessArticle

Effect of Laser Peening Process Parameters and Sequences on Residual Stress Profiles

by Zina Kallien, Sören Keller, Volker Ventzke, Nikolai Kashaev and Benjamin Klusemann

Metals 2019, 9(6), 655; https://doi.org/10.3390/met9060655 - 04 Jun 2019

Cited by 26 | Viewed by 4668

Abstract

Laser Peening (LP) is a surface modification technology that can induce high residual stresses in a metallic material. The relation between LP process parameters, in particular laser sequences, as well as pulse parameters and the resulting residual stress state was investigated in this study. The residual stress measurements, performed with the hole drilling technique, showed a non-equibiaxial stress profile in laser peened AA2024-T3 samples with a clad layer for certain parameter combinations. Shot overlap and applied energy density were found to be crucial parameters for the characteristic of the observed non-equibiaxial residual stress profile. Furthermore, the investigation showed the importance of the advancing direction, as the advancing direction influences the direction of the higher compressive residual stress component. The direction of higher residual stresses was parallel or orthogonal to the rolling direction of the material. The effect was correlated to the microstructural observation obtained via electron backscattered diffraction. Additionally, for peening with two sequences of different advancing directions, the study showed that the order of applied advancing directions was important for the non-equibiaxiality of the resulting residual stress profile. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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Review

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11 pages, 6291 KiB

Open AccessFeature PaperReview

Quarter Century Development of Laser Peening without Coating

by Yuji Sano

Metals 2020, 10(1), 152; https://doi.org/10.3390/met10010152 - 19 Jan 2020

Cited by 41 | Viewed by 5458

Abstract

This article summarizes the development of laser peening without coating (LPwC) during the recent quarter century. In the mid-1990s, the study of LPwC was initiated in Japan. The objective at that time was to mitigate stress corrosion cracking (SCC) of structural components in operating nuclear power reactors (NPRs) by inducing compressive residual stresses (RSs) on the surface of susceptible components. Since the components in NPRs are radioactive and cooled underwater, full-remote operation must be attained by using lasers of water-penetrable wavelength without any surface preparation. Compressive RS was obtained on the top-surface by reducing pulse energy less than 300 mJ and pulse duration less than 10 ns, and increasing pulse density (number of pulses irradiated on unit area). Since 1999, LPwC has been applied in NPRs as preventive maintenance against SCC using frequency-doubled Q-switched Nd:YAG lasers (λ = 532 nm). To extend the applicability, fiber-delivery of intense laser pulses was developed in parallel and has been used in NPRs since 2002. Early first decade of the 2000s, the effect extending fatigue life was demonstrated even if LPwC increased surface roughness of the components. Several years ago, it was confirmed that 10 to 20 mJ pulse energy is enough to enhance fatigue properties of weld joints of a structural steel. Considering such advances, the development of 20 mJ-class palmtop-sized handheld lasers was initiated in 2014 in a five-year national program, ImPACT under the cabinet office of the Japanese government. Such efforts would pave further applications of LPwC, for example maintenance of infrastructure in the field, beyond the horizons of the present laser systems. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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29 pages, 7033 KiB

Open AccessReview

Laser Shock Peening, the Path to Production

by Allan H. Clauer

Metals 2019, 9(6), 626; https://doi.org/10.3390/met9060626 - 29 May 2019

Cited by 82 | Viewed by 8736

Abstract

This article describes the path to commercialization for laser shock peening beginning with the discovery of the basic phenomenology of the process through to its implementation as a commercial process. It describes the circumstances leading to its invention, the years spent on exploring and defining characteristics of the process, and the journey to commercialization. Like many budding technologies displaying unique characteristics, but no immediately evident application, i.e., “a solution looking for a problem”, there were several instances where its development may have been delayed or ended except for an unanticipated event that enabled it to move forward. An important contributor to the success of laser peening, is that nearly 15 years after its invention, universities world-wide began extensive research into the process, dramatically broadening the knowledge base and increasing confidence in, and understanding of its potential. Finally, a critical problem in need of a solution, laser peening, appeared, culminating in its first industrial application on aircraft turbine engine fan blades. Full article

(This article belongs to the Special Issue Laser Shock Processing and Related Phenomena)

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