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10 pages, 3902 KiB

Open AccessArticle

Using a High-Power Fibre Laser to Cut Concrete

by Kaori Nagai and Kazuki Shimizu

Appl. Sci. 2021, 11(10), 4414; https://doi.org/10.3390/app11104414 - 13 May 2021

Cited by 9 | Viewed by 4287

Abstract

Concrete cutting at construction sites causes problems such as noise, vibration, and dust. In particular, during the demolition and renovation work on buildings in urban areas, protection against noise, vibration, dust, etc., is needed. Concrete cutting using a CO₂ laser was investigated [...] Read more.

Concrete cutting at construction sites causes problems such as noise, vibration, and dust. In particular, during the demolition and renovation work on buildings in urban areas, protection against noise, vibration, dust, etc., is needed. Concrete cutting using a CO₂ laser was investigated 20 years ago. However, this method had never used because the equipment is difficult to carry. In this study, we used a portable fibre laser, which is convenient to carry. Two types of concretes with different strengths were prepared for the experiment. High-strength concrete has never been used in similar research before. High-strength concrete is just only used for skyscrapers because of its high quality and costs. Furthermore, it has already been used for skyscrapers in Japan. It is for this reason that we chose to use it in this study. Irradiation measurements were conducted under various conditions using laser powers of 6 and 9 kW. It was confirmed that the cutting effectiveness of CO₂ and fibre lasers was approximately identical for concretes with a thickness of 200 mm. Furthermore, the cutting effectiveness for the two concretes with different densities was almost the same. However, the situation after cutting was different because the vitrification of the cutting and glass formation progressed in low-density concrete and an explosion phenomenon occurred in high-density concrete, simultaneously. This study suggests that laser concrete cutting can be used as a solution when noise and dust are major problems. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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13 pages, 15200 KiB

Open AccessArticle

Effects of Heat Treatment of Selective Laser Melting Printed Ti-6Al-4V Specimens on Surface Texture Parameters and Cell Attachment

by Pei-Wen Peng, Jen-Chang Yang, Wei-Fang Lee, Chih-Yuan Fang, Chun-Ming Chang, I-Jan Chen, Chengpo Hsu and Tzu-Sen Yang

Appl. Sci. 2021, 11(5), 2234; https://doi.org/10.3390/app11052234 - 3 Mar 2021

Cited by 3 | Viewed by 1933

Abstract

Selective laser melting (SLM) is extensively used for fabricating metallic biomedical products. After 3D printing, it is almost always advisable to apply a heat treatment to release the internal tensions or optimize the mechanical properties of the printed parts. The aim of this [...] Read more.

Selective laser melting (SLM) is extensively used for fabricating metallic biomedical products. After 3D printing, it is almost always advisable to apply a heat treatment to release the internal tensions or optimize the mechanical properties of the printed parts. The aim of this paper is to investigate the effects of heat treatment of SLM printed Ti-6Al-4V (Ti64) circular specimens on the areal surface texture parameters and cell attachment. Areal surface texture parameters, including the arithmetic mean height (S_a), root-mean-square height (S_q), skewness (S_sk), and kurtosis (S_ku) were characterized. In addition, wavelet-based multi-resolution analysis was applied to investigate the characteristic length scales of untreated and heat-treated Ti64 specimens. In this study, the vertical distance between the highest and lowest position of cell attachment for each sampling area was defined as ΔH. Results showed that an increase in the periodic characteristic length scale was primarily due to the formation of large-scale aggregations of Ti64 metal powder particles on the heat-treated surface. In addition, MG-63 cells preferred lying in concave hollows; in heat-treated specimens, values of ΔH statistically significantly decreased from 31.6 ± 4.2 to 8.8 ± 2.8 μm, while S_ku decreased from 3.3 ± 1.4 to 2.6 ± 0.6, indicating a strong influence of S_ku on cell attachment. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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10 pages, 3159 KiB

Open AccessArticle

The Effect of Laser Nitriding on Surface Characteristics and Wear Resistance of NiTi Alloy with Low Power Fiber Laser

by Hao Wang, Ralf Nett, Evgeny L. Gurevich and Andreas Ostendorf

Appl. Sci. 2021, 11(2), 515; https://doi.org/10.3390/app11020515 - 7 Jan 2021

Cited by 7 | Viewed by 2596

Abstract

The laser nitriding was performed in nitrogen gas at room temperature (20 °C) and low temperature (−190 °C) by a low power fiber laser to modify the wear and abrasion resistance of NiTi alloy. The surface roughness and element composition were analyzed by [...] Read more.

The laser nitriding was performed in nitrogen gas at room temperature (20 °C) and low temperature (−190 °C) by a low power fiber laser to modify the wear and abrasion resistance of NiTi alloy. The surface roughness and element composition were analyzed by roughness device and energy-dispersive X-ray spectroscopy respectively. The results of roughness show that laser treatment can change the surface roughness due to the laser remelting. The effect of laser nitriding on the microhardness, friction coefficient, and worn scars of NiTi alloy was also studied, which shows that the microhardness of the NiTi alloy increases after laser nitriding. The optical microscope and scanning electron microscope were used to characterize the surface of NiTi alloy after wear testing to observe the microstructure of worn scars. The results show that the laser nitriding with different parameters can induce a nitride layer with different thicknesses and the higher energy deposition is the key factor for the formation of the nitride layer, which can decrease the friction coefficient and reduce wear loss during the application of NiTi alloy. The improvement of wear resistance can be attributed to the hard nitriding layer. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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12 pages, 4876 KiB

Open AccessArticle

High-Pressure Sensors Based on Laser-Manufactured Sintered Silicon Carbide

by Stefano Salvatori, Gennaro Salvatore Ponticelli, Sara Pettinato, Silvio Genna and Stefano Guarino

Appl. Sci. 2020, 10(20), 7095; https://doi.org/10.3390/app10207095 - 13 Oct 2020

Cited by 14 | Viewed by 2256

Abstract

In this work Sintered Silicon Carbide (S-SiC) samples have been used to fabricate fiber-optic-coupled pressure sensors. The sensor structure reproduces a low-finesse Fabry–Perot (FP) interferometer. Laser manufacturing of cylindrical S-SiC samples was performed to define the thin membrane geometry of sensors. FP cavity [...] Read more.

In this work Sintered Silicon Carbide (S-SiC) samples have been used to fabricate fiber-optic-coupled pressure sensors. The sensor structure reproduces a low-finesse Fabry–Perot (FP) interferometer. Laser manufacturing of cylindrical S-SiC samples was performed to define the thin membrane geometry of sensors. FP cavity is defined by the end-face of a single mode fiber and the S-SiC diaphragm surface. Hence, pressure is evaluated by measuring the cavity depth by a dedicated optoelectronic system coupled to the single mode fiber. Exploiting the excellent properties of S-SiC, in terms of high hardness, low thermal expansion, and high thermal conductivity, realized devices have been characterized up to 20 MPa. Experimental results demonstrate that produced sensors exhibit a non-linearity around ±0.6%F.S. and a high input dynamics. The all-optic sensing system proposed in this work would represent a good alternative to conventional solutions based on piezoelectric effects, overcoming the drawback related to electromagnetic interference on the acquired signals. In addition, the mechanical characteristics of S-SiC allow the use of the sensor in both automotive and aerospace hostile environments as pressure monitors in combustion engines. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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22 pages, 10652 KiB

Open AccessArticle

Experimental Investigation of Industrial Laser Cutting: The Effect of the Material Selection and the Process Parameters on the Kerf Quality

by Silvio Genna, Erica Menna, Gianluca Rubino and Vincenzo Tagliaferri

Appl. Sci. 2020, 10(14), 4956; https://doi.org/10.3390/app10144956 - 19 Jul 2020

Cited by 23 | Viewed by 8611

Abstract

Laser beam cutting is a non-contact, production-flexible and highly productive technique that allows accurate profiling of a wide range of sheet materials. To these and further benefits, laser machining is increasingly being adopted by industry. This paper investigates the effect of material type, [...] Read more.

Laser beam cutting is a non-contact, production-flexible and highly productive technique that allows accurate profiling of a wide range of sheet materials. To these and further benefits, laser machining is increasingly being adopted by industry. This paper investigates the effect of material type, workpiece thickness, cutting speed and assistant gas pressure on cut quality for industrial-relevant applications using a CO₂ laser. AlMg3 aluminum alloy, St37-2 low-carbon steel and AISI 304 stainless steel were selected to represent the most established materials in many industrial fields and gain insight into different processes (i.e., inert-assisted fusion cutting and oxygen cutting) and absorption behaviors with respect to CO₂ laser wavelength. The aim was to enhance the understanding of the mechanisms through which laser cutting parameters and workpiece parameters interact in order to identify general criteria and well-optimized process parameters which guarantee the kerf quality. The quality of laser cut was analyzed in its basic terms: kerf geometry, surface roughness and cut edge quality. The experiments were performed by using a systematic experimental design approach based on Design of Experiments, and the results were validated via Analysis of Variance. Quality assessment was presented and discussed. The visual inspection of cut sections confirms good overall quality and limited presence of laser cut imperfections. The experimental investigation demonstrates that the different materials can be successfully processed within a wide range of the tested values. In addition, optimum cutting conditions which satisfy the straight requirement of the quality standard adopted are identified for each material. This study involves an analysis of both phenomenological and practical issues. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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14 pages, 7555 KiB

Open AccessArticle

An Optimal Genetic Algorithm for Fatigue Life Control of Medium Carbon Steel in Laser Hardening Process

by Gennaro Salvatore Ponticelli, Stefano Guarino and Oliviero Giannini

Appl. Sci. 2020, 10(4), 1401; https://doi.org/10.3390/app10041401 - 19 Feb 2020

Cited by 20 | Viewed by 3141

Abstract

This study proposes a genetic algorithm-optimized model for the control of the fatigue life of AISI 1040 steel components after a high-power diode laser hardening process. First, the effect of the process parameters, i.e., laser power and scan speed, on the fatigue life [...] Read more.

This study proposes a genetic algorithm-optimized model for the control of the fatigue life of AISI 1040 steel components after a high-power diode laser hardening process. First, the effect of the process parameters, i.e., laser power and scan speed, on the fatigue life of the components after the laser treatment was evaluated by using a rotating bending machine. Then, in light of the experimental findings, the optimization model was developed and tested in order to find the best regression model able to fit the experimental data in terms of the number of cycles until failure. The laser treatment was found to significantly increase the fatigue life of the irradiated samples, thus revealing its suitability for industrial applications. Finally, the application of the proposed genetic algorithm-based method led to the definition of an optimal regression model which was able to replicate the experimental trend very accurately, with a mean error of about 6%, which is comparable to the standard deviation associated with the process variability. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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11 pages, 9955 KiB

Open AccessArticle

Groove Formation in Glass Substrate by a UV Nanosecond Laser

by Joonghan Shin and Kimoon Nam

Appl. Sci. 2020, 10(3), 987; https://doi.org/10.3390/app10030987 - 3 Feb 2020

Cited by 5 | Viewed by 4656

Abstract

This study reports the laser grooving of glass. In this study, an ultraviolet (UV) nanosecond laser is used to produce grooves in soda lime glass by varying laser power, scan speed, pulse repetition rate, and number of scans. The threshold power density to [...] Read more.

This study reports the laser grooving of glass. In this study, an ultraviolet (UV) nanosecond laser is used to produce grooves in soda lime glass by varying laser power, scan speed, pulse repetition rate, and number of scans. The threshold power density to generate damage on glass surface is found to be ~6.37 × 10⁸ W/cm². According to the result of a single laser scan, at a high laser power and low scan speed, material removal does not nearly occur, and only volume melting underneath the glass surface and large thermal crack are induced. With the decreasing laser power and increasing scan speed, a groove with a smooth surface is formed owing to the melting-dominant material removal process. The groove of rough surface morphology is produced with the further increase of the scan speed due to shattering induced by shock wave. Under this condition, it is found that either small cracks are produced or a crack-free groove is obtained. In this study, the fabrication of the microchannel for bio-chip application is also attempted by multiple laser scans. The near rectangular-shaped and crack-free groove (width × depth: ~220 μm × ~500 μm) with quite a smooth surface is fabricated by the multiple laser scans with a non-zero scan spacing. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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13 pages, 7436 KiB

Open AccessFeature PaperArticle

Laser Finishing of Ti6Al4V Additive Manufactured Parts by Electron Beam Melting

by Silvio Genna and Gianluca Rubino

Appl. Sci. 2020, 10(1), 183; https://doi.org/10.3390/app10010183 - 25 Dec 2019

Cited by 12 | Viewed by 3129

Abstract

In this work, the feasibility of laser surface finishing of parts obtained by additive manufacturing (AM) was investigated. To this end, a 450 W fiber laser (operating in continuous wave, CW) was adopted to treat the surface of Ti-6Al-4V samples obtained via electron [...] Read more.

In this work, the feasibility of laser surface finishing of parts obtained by additive manufacturing (AM) was investigated. To this end, a 450 W fiber laser (operating in continuous wave, CW) was adopted to treat the surface of Ti-6Al-4V samples obtained via electron beam melting (EBM). During the tests, different laser energy densities and scanning speeds were used. In order to assess the quality of the treatment, either the as-built or the treated samples were analyzed by means of a three-dimensional (3D) profilometer, digital microscopy, and scanning electron microscopy. Analysis of variance (ANOVA) was performed to check which and how process parameters affected the finishing. The results show that, in the best conditions, the laser treatment reduced surface roughness by about 80%. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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Review

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12 pages, 838 KiB

Open AccessReview

Laser Metal Deposition of Ti6Al4V—A Brief Review

by Chongliang Zhong, Jianing Liu, Tong Zhao, Thomas Schopphoven, Jinbao Fu, Andres Gasser and Johannes Henrich Schleifenbaum

Appl. Sci. 2020, 10(3), 764; https://doi.org/10.3390/app10030764 - 21 Jan 2020

Cited by 51 | Viewed by 7998

Abstract

Laser metal deposition (LMD) is one of the most important laser additive manufacturing processes. It can be used to produce functional coatings, to repair damaged parts and to manufacture metal components. Ti6Al4V is one of the most commonly used titanium alloys, since it [...] Read more.

Laser metal deposition (LMD) is one of the most important laser additive manufacturing processes. It can be used to produce functional coatings, to repair damaged parts and to manufacture metal components. Ti6Al4V is one of the most commonly used titanium alloys, since it features a good balance of the mechanical properties of strength and ductility. The LMD of Ti6Al4V is attracting more and more attention from both science and engineering. The interest in processing Ti6Al4V with LMD in industry, especially in aerospace and medical branches, has been increasing in the last few years. In this paper, the state of the art for LMD of Ti6Al4V is reviewed. In the first part, the basics for Ti6Al4V, including, for example, the development history, the material properties, the applications, the crystal structure, the heat treatment and the mechanical properties, are introduced. In the second part, the main emphasis is on state of the art for LMD of Ti6Al4V. Initially, the process parameters of the current state of the art in the last years and their effects are summarized. After that, the typical microstructure after LMD is discussed. Then, the conducted heat treatment methods and the achievable mechanical properties are presented. In the end, some of the existing, current challenges are mentioned, and the possible research directions for the future are proposed. Full article

(This article belongs to the Special Issue Laser Manufacturing of Advanced Materials)

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