Journal articles: 'Lasers in controlled fusion'

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Freeman, R. R., C. Anderson, J. M. Hill, J. King, R. Snavely, S. Hatchett, M. Key, et al. "High-intensity lasers and controlled fusion." European Physical Journal D - Atomic, Molecular and Optical Physics 26, no. 1 (September 1, 2003): 73–77. http://dx.doi.org/10.1140/epjd/e2003-00246-x.

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Wong, H., K. Dawson, G. A. Ravi, L. Howlett, R. O. Jones, and C. J. Sutcliffe. "Multi-Laser Powder Bed Fusion Benchmarking—Initial Trials with Inconel 625." International Journal of Advanced Manufacturing Technology 105, no. 7-8 (November 9, 2019): 2891–906. http://dx.doi.org/10.1007/s00170-019-04417-3.

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Abstract Production rate is an increasingly important factor in the deployment of metal additive manufacturing (AM) throughout industry. To address the perceived low production rate of metal AM systems based on single-laser powder bed fusion (L-PBF), several companies now offer systems in which melting has been parallelised by the introduction of multiple, independently controlled laser beams. Nevertheless, a full set of studies is yet to be conducted to benchmark the efficiency of multi-laser systems and, at the same time, to verify if the mechanical properties of components are compromised due to the increase in build rate. This study addresses the described technology gaps and presents a 4-beam L-PBF system operating in “single multi” (SM) mode (SM-L-PBF) where each of the four lasers is controlled so that it melts all of a particular components’ layers and produces specimens for comparison with standard L-PBF specimens from the same machine. That is all four lasers making all of some of the parts were compared to a single-laser manufacturing all of the parts. Build parameters were kept constant throughout the manufacturing process and the material used was Inconel 625 (IN625). Stress-relieving heat treatment was conducted on As-built (AB) specimens. Both AB and heat-treated (HT) specimen sets were tested for density, microstructure, tensile strength and hardness. Results indicate that the stress-relieving heat treatment increases specimen ductility without compromising other mechanical properties. SM-L-PBF has achieved a build rate of 14 cm3/h when four 200 W lasers were used to process IN625 at a layer thickness of 30 μm. An increase in the build rate of 2.74 times (build time reduction: 63%) has been demonstrated when compared to that of L-PBF, with little to no compromises in specimen mechanical properties. The observed tensile properties exceed the American Society for Testing Materials (ASTM) requirements for IN625 (by a margin of 22 to 26% in the 0.2% offset yield strength). Average specimen hardness and grain size are in the same order as that reported in literatures. The study has demonstrated that a multi-laser AM system opens up opportunities to tackle the impasse of low build rate in L-PBF in an industrial setting and that at least when operating in single mode there is no detectable degradation in the mechanical and crystallographic characteristics of the components produced.

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Atzeni, Stefano. "Light for controlled fusion energy: A perspective on laser-driven inertial fusion." EPL (Europhysics Letters) 109, no. 4 (February 1, 2015): 45001. http://dx.doi.org/10.1209/0295-5075/109/45001.

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DEEBA, FARAH, KAMALUDDIN AHMED, MAHNAZ QADAR HASEEB, and ARSHAD M. MIRZA. "IMPLOSION DYNAMICS OF HIGH-DENSITY FIBER PLASMA DRIVEN BY IMPLODING MULTICASCADE LINER." Modern Physics Letters B 19, no. 22 (September 30, 2005): 1095–105. http://dx.doi.org/10.1142/s0217984905009006.

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The dynamics of a high density D-T fiber plasma driven by a multi cascade system (N multiple shells of finite thicknesses) has been investigated with a view to suppress Rayleigh–Taylor (R–T) instability. Our numerical results show that the plasma parameters of the D-T fiber sensitively depends upon the shell mass ratios and thicknesses. Large values of puff-thickness and mass-ratios provide stabilization against the R–T instability in the final stage of compression but adversely affect fusion conditions. Our analysis, however, suggests that optimum values of the puff-thicknesses and mass ratios are needed to achieve fusion parameters in a multi cascade liner staged Z-pinch devices. The relevance of our present investigation to ultra high magnetic fluxes, X-ray lasers as well as controlled thermonuclear fusion is also pointed out.

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Adhikari, B. R., and R. Khanal. "Introduction to the Plasma State of Matter." Himalayan Physics 4 (December 23, 2013): 60–64. http://dx.doi.org/10.3126/hj.v4i0.9430.

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Plasma is a quasineutral gas of charge and neutral particles which exhibits collective behavior. Because of its distinct behavior it is often termed as the fourth state of matter. It is of interest as it has found applications in diverse areas such as, controlled thermonuclear fusion, gas lasers, lightning, medicine, space science, electronics, etc. In this article we present an introduction to the plasma state of matter and discuss some of its applications.The Himalayan Physics Vol. 4, No. 4, 2013 Page: 60-64 Uploaded date: 12/23/2013

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HORA, HEINRICH. "Developments in inertial fusion energy and beam fusion at magnetic confinement." Laser and Particle Beams 22, no. 4 (October 2004): 439–49. http://dx.doi.org/10.1017/s0263034604223242.

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The 70-year anniversary of the first nuclear fusion reaction of hydrogen isotopes by Oliphant, Harteck, and Rutherford is an opportunity to realize how beam fusion is the path for energy production, including both branches, the magnetic confinement fusion and the inertial fusion energy (IFE). It is intriguing that Oliphant's basic concept for igniting controlled fusion reactions by beams has made a comeback even for magnetic confinement plasma, after this beam fusion concept was revealed by the basically nonlinear processes of the well-known alternative of inertial confinement fusion using laser or particle beams. After reviewing the main streams of both directions some results are reported—as an example of possible alternatives—about how experiments with skin layer interaction and avoiding relativistic self-focusing of clean PW–ps laser pulses for IFE may possibly lead to a simplified fusion reactor scheme without the need for special compression of solid deuterium–tritium fuel.

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Pratama, Ryan Arya, and Akihisa Ohya. "State Estimation and Control of an Unmanned Air Vehicle from a Ground-Based 3D Laser Scanner." Journal of Robotics and Mechatronics 28, no. 6 (December 20, 2016): 878–86. http://dx.doi.org/10.20965/jrm.2016.p0878.

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[abstFig src='/00280006/12.jpg' width='300' text='UAV state estimation from laser scanner' ] In this work, we present a system to estimate the state of and control an Unmanned Air Vehicle (UAV) from a ground-based 3D laser scanner. The main contributions of this work are on data fusion between a low-frequency 3D laser scanner with considerable delay and an on-board 6-DOF IMU, and on automatic position control of a UAV using state estimate obtained from the fusion. We measured laser delay using data from a manually controlled flight. We have devised a method to perform online estimation and compensation of accelerometer offset using delay-corrected laser measurement. We then use the UAV state estimation in a nested controller with a high-frequency velocity control inner loop and a low-frequency position control outer loop. We demonstrated the state estimation and control in a series of experiments on velocity control and position control, including a comparison between position control using fusion data and only laser data.

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Pieruschka, P., L. Cicchitelli, R. Khoda-Bakhsh, E. Kuhn, G. H. Miley, and H. Hora. "Volume ignition of inertial confinement fusion of deuterium-helium(3) and hydrogen-boron(ll) clean fusion fuel." Laser and Particle Beams 10, no. 1 (March 1992): 145–54. http://dx.doi.org/10.1017/s0263034600004274.

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Since DT laser fusion with 10-MJ laser pulses for 1000-MJ output now offers the physics solution for an economical fusion energy reactor, the conditions are evaluated assuming that controlled ICF reactions will become possible in the future using clean nuclear fusion fuel such as deuterium-helium(3) or hydrogen-boron(11). Using the transparent physics mechanisms of volume ignition of the fuel capsules, we show that the volume ignition for strong reduction of the optimum initial temperature can be reached for both types of fuels if a compression about 100 times higher than those in present-day laser compression experiments is attained in the future. Helium(3) laser-pulse energies are then in the same range as for DT, but ten times higher energies will be required for hydrogenboron(11).

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Badziak, J. "Laser nuclear fusion: current status, challenges and prospect." Bulletin of the Polish Academy of Sciences: Technical Sciences 60, no. 4 (December 1, 2012): 729–38. http://dx.doi.org/10.2478/v10175-012-0084-8.

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Abstract In 2009, in Lawrence Livermore National Laboratory, USA, National Ignition Facility (NIF) - the largest thermonuclear fusion device ever made was launched. Its main part is a multi-beam laser whose energy in nanosecond pulse exceeds 1MJ (106 J). Its task is to compress DT fuel to the density over a few thousand times higher than that of solid-state DT and heat it to 100 millions of K degrees. In this case, the process of fuel compression and heating is realized in an indirect way - laser radiation (in UV range) is converted in the so-called hohlraum (1 cm cylinder with a spherical DT pellet inside) into very intense soft X radiation symmetrically illuminating DT pellet. For the first time ever, the fusion device’s energetic parameters are sufficient for the achieving the ignition and self-sustained burn of thermonuclear fuel on a scale allowing for the generation of energy far bigger than that delivered to the fuel. The main purpose of the current experimental campaign on NIF is bringing about, within the next two-three years, a controlled thermonuclear ‘big bang’ in which the fusion energy will exceed the energy delivered by the laser at least ten times. The expected ‘big bang’ would be the culmination of fifty years of international efforts aiming at demonstrating both physical and technical feasibility of generating, in a controlled way, the energy from nuclear fusion in inertial confined plasma and would pave the way for practical realization of the laser-driven thermonuclear reactor. This paper briefly reviews the basic current concepts of laser fusion and main problems and challenges facing the research community dealing with this field. In particular, the conventional, central hot spot ignition approach to laser fusion is discussed together with the more recent ones - fast ignition, shock ignition and impact ignition fusion. The research projects directed towards building an experimental laser-driven thermonuclear reactor are presented as well

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KONG, HONG JIN, JIN WOO YOON, JAE SUNG SHIN, DU HYUN BEAK, and BONG JU LEE. "Long term stabilization of the beam combination laser with a phase controlled stimulated Brillouin scattering phase conjugation mirrors for the laser fusion driver." Laser and Particle Beams 24, no. 4 (October 2006): 519–23. http://dx.doi.org/10.1017/s026303460606068x.

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Laser fusion requires very high energy/power output with high repetition rate over 10 Hz, which is very difficult with the current laser technologies. However, the recent research work on the phase controlling of the stimulated Brillouin scattering wave enables the realization of this kind of laser fusion driver. The recent progress of controlling the phase has been successfully demonstrated by the self-generated density modulation method proposed by one of the authors (Kong). Nevertheless, it showed a long-term fluctuation of the phase because of the long-term fluctuation of the density of the SBS medium due to the thermal fluctuation. This long-term thermal fluctuation is inevitable a fact in nature. The authors used a specially designed stabilizing system for the phase controlling system, which has the PZT control of the mirror for phase controlling SBS-PCM (the so-called feedback mirror). This system stabilizes the phase controlling system very well for more than 1 h. This technique will help the laser fusion driver to be realized sooner than expected. In addition, we propose a similar scheme to be applied to the ultra-fast pulse laser system, which must operate at high repetition rate for the laser fusion energy power plant.

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Santos, Luís, Joel de de Jesus, Luís Borrego, José A. M. Ferreira, Rui F. Fernandes, José D. M. da da Costa, and Carlos Capela. "Fatigue Behavior of Hybrid Components Containing Maraging Steel Parts Produced by Laser Powder Bed Fusion." Metals 11, no. 5 (May 19, 2021): 835. http://dx.doi.org/10.3390/met11050835.

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This investigation concerns about of fatigue behavior under controlled loading and under strain control for hybrid specimens with parts produced with conventional processes in steel AISI H13 and the stainless steel AISI 420 and the rest part produced by laser powder bed fusion in AISI 18Ni300 steel. The controlled loading tests were performed in constant and variable amplitude. Fatigue failure of hybrid samples occurs mostly in laser-melted parts, initiated around the surface, in many cases with multi-nucleation and propagated predominantly between the deposited layers. Fatigue strength of hybrid parts, tested under displacement control is similar, but for specimens tested under load control the fatigue strength the fatigue strength of hybrid specimens is progressively lesser than laser powder bed fusion samples. Despite a tendency to obtain conservative predictions, Miner’s law predicts reasonably the fatigue lives under block loadings. The interface between materials presented an excellent joining and fatigue strength because the fatigue failure of hybrid samples occurred mostly in laser melted parts out of the interface.

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Moyne, Robert Le. "Controlled Fusion Strategy Using Ultra-Intense Laser Derived Positron Generation for Initiation." Journal of Applied Mathematics and Physics 06, no. 04 (2018): 693–703. http://dx.doi.org/10.4236/jamp.2018.64062.

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Çilesiz, Inci, Tom Springer, Sharon Thomsen, and A. J. Welch. "Controlled temperature tissue fusion: Argon laser welding of canine intestine in vitro." Lasers in Surgery and Medicine 18, no. 4 (1996): 325–34. http://dx.doi.org/10.1002/(sici)1096-9101(1996)18:4<325::aid-lsm1>3.0.co;2-u.

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CANG, Y., F. OSMAN, H. HORA, J. ZHANG, J. BADZIAK, J. WOLOWSKI, K. JUNGWIRTH, K. ROHLENA, and J. ULLSCHMIED. "Computations for nonlinear force driven plasma blocks by picosecond laser pulses for fusion." Journal of Plasma Physics 71, no. 1 (January 13, 2005): 35–51. http://dx.doi.org/10.1017/s0022377804002983.

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The concept of the fast ignitor for laser fusion has led to some modifications in applying petawatt-picosecond (PW-ps) laser-produced high intensity particle beams to ignite deuterium-tritium (DT) fuel. Some very anomalous measurements of ion emission from targets irradiated by picosecond laser pulses led to the development of a skin depth interaction scheme where a defined control of prepulses is necessary. Based on these experimental facts, we have applied a one-dimensional two-fluid hydrodynamic code to understand how the nonlinear ponderomotive force generates two plasma blocks, one moving against the laser light (ablation) and the other moving into the target. This compressed block produces an ion current density of above 10$^{11}$ A cm$^{-2}$ and an ion energy of about 100 keV. This may be a rather promising option to use PW-ps laser pulses for igniting fusion in solid density DT fuel, realizing very high gain controlled fusion reactions.

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Großmann, Alexander, Julian Felger, Tilman Frölich, Julian Gosmann, and Christian Mittelstedt. "Melt pool controlled laser powder bed fusion for customised low-density lattice structures." Materials & Design 181 (November 2019): 108054. http://dx.doi.org/10.1016/j.matdes.2019.108054.

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Semenov, A. S. "Edward Teller Medal—international prize for outstanding work on laser controlled thermonuclear fusion." Soviet Journal of Quantum Electronics 22, no. 4 (April 30, 1992): 377. http://dx.doi.org/10.1070/qe1992v022n04abeh003457.

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Andreev, N. E., Leonid M. Gorbunov, and Vladimir T. Tikhonchuk. "Physics of the plasma corona in the problem of laser controlled thermonuclear fusion." Quantum Electronics 24, no. 9 (September 30, 1994): 755–58. http://dx.doi.org/10.1070/qe1994v024n09abeh000185.

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Winterberg, F. "Mini Fission-Fusion-Fission Explosions (Mini-Nukes). A Third Way Towards the Controlled Release of Nuclear Energy by Fission and Fusion." Zeitschrift für Naturforschung A 59, no. 6 (June 1, 2004): 325–36. http://dx.doi.org/10.1515/zna-2004-0603.

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Chemically ignited nuclear microexplosions with a fissile core, a DT reflector and U238 (Th232) pusher, offer a promising alternative to magnetic and inertial confinement fusion, not only burning DT, but in addition U238 (or Th232), and not depending on a large expensive laser of electric pulse power supply. The prize to be paid is a gram size amount of fissile material for each microexplosion, but which can be recovered by breeding in U238.In such a “mini-nuke” the chemical high explosive implodes a spherical metallic shell onto a smaller shell, with the smaller shell upon impact becoming the source of intense black body radiation which vaporizes the ablator of a spherical U238 (Th232) pusher, with the pusher accelerated to a velocity of ∼200 km/s, sufficient to ignite the DT gas placed in between the pusher and fissile core, resulting in a fast fusion neutron supported fission reaction in the core and pusher. Estimates indicate that a few kg of high explosives are sufficient to ignite such a “mini-nuke”, with a gain of ∼103, releasing an energy equivalent to a few tons of TNT, still manageable for the microexplosion to be confined in a reactor vessel.A further reduction in the critical mass is possible by replacing the high explosive with fast moving solid projectiles. For light gas gun driven projectiles with a velocity of ∼ 10 km/s, the critical mass is estimated to be 0.25 g, and for magnetically accelerated 25 km/s projectiles it is as small as ∼ 0.05 g.With the much larger implosion velocities, reached by laser- or particle beam bombardment of the outer shell, the critical mass can still be much smaller with the fissile core serving as a fast ignitor.Increasing the implosion velocity decreases the overall radius of the fission-fusion assembly in inverse proportion to this velocity, for the 10 km/s light gas gun driven projectiles from 10 cm to 5 cm, for the 25 km/s magnetically projectiles down to 2 cm, and still more for higher implosion velocities.

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Park, Changkyoo, and Eun-Joon Chun. "Influence of Laser-Assisted Fusing on Microstructural Evolution and Tribological Properties of NiWCrSiB Coating." Metals 10, no. 4 (April 23, 2020): 548. http://dx.doi.org/10.3390/met10040548.

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The present study examines the applicability of a diode laser-assisted fusing treatment and a temperature-control system to the NiWCrSiB thermal spray coating to develop the enhanced wear resistance of continuous-casting molds. As a result of the use of the lasers, the variations in the microstructure and the hardening behavior during the fusing treatment could be controlled. Fine secondary phases (approximately 0.05–10 μm in size) homogeneously present in the coating after the laser-assisted fusing were observed to be Cr-, Mo- and W-based carbides and borides. Transmission electron microscope analysis was used to characterize these fine secondary phases as M7C3 and M23C6 carbides and M5B3 boride. Because of these fine secondary phases, the hardness increased from 730 (as-sprayed status) to 1230 HV (after fusing at a temperature of 1473 K). Finally, given the formation of fine secondary phases and the occurrence of surface hardening, the laser-assisted fusing treatment was deemed to enhance the tribological performance of the thermal-sprayed coating, in that it exhibited a lower coefficient of friction and lower wear rate than the as-sprayed coating.

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Korobkin, V. V., and M. Yu Romanovsky. "Scaling of plasmas, heated and ponderomotively confined by powerful laser radiation." Laser and Particle Beams 16, no. 2 (June 1998): 235–52. http://dx.doi.org/10.1017/s0263034600011575.

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It is shown that a powerful laser beam is capable of the ponderomotive confinement of plasma with electron density exceeding the critical density for the radiation under review. The theory describing force and heat balances of the plasma together with the propagation of the laser radiation is developed. The laws of the dense plasma scaling for controlled thermonuclear fusion (CTF) and other applications are formulated.

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Tikhonchuk, V. T. "Progress and opportunities for inertial fusion energy in Europe." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2184 (October 12, 2020): 20200013. http://dx.doi.org/10.1098/rsta.2020.0013.

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In this paper, I consider the motivations, recent results and perspectives for the inertial confinement fusion (ICF) studies in Europe. The European approach is based on the direct drive scheme with a preference for the central ignition boosted by a strong shock. Compared to other schemes, shock ignition offers a higher gain needed for the design of a future commercial reactor and relatively simple and technological targets, but implies a more complicated physics of laser–target interaction, energy transport and ignition. European scientists are studying physics issues of shock ignition schemes related to the target design, laser plasma interaction and implosion by the code developments and conducting experiments in collaboration with US and Japanese physicists, providing access to their installations Omega and Gekko XII. The ICF research in Europe can be further developed only if European scientists acquire their own academic laser research facility specifically dedicated to controlled fusion energy and going beyond ignition to the physical, technical, technological and operational problems related to the future fusion power plant. Recent results show significant progress in our understanding and simulation capabilities of the laser plasma interaction and implosion physics and in our understanding of material behaviour under strong mechanical, thermal and radiation loads. In addition, growing awareness of environmental issues has attracted more public attention to this problem and commissioning at ELI Beamlines the first high-energy laser facility with a high repetition rate opens the opportunity for qualitatively innovative experiments. These achievements are building elements for a new international project for inertial fusion energy in Europe. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.

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Çilesiz, Inci, Sharon Thomsen, and A. J. Welch. "Controlled temperature tissue fusion: Argon laser welding of rat intestine in vivo, Part One." Lasers in Surgery and Medicine 21, no. 3 (1997): 269–77. http://dx.doi.org/10.1002/(sici)1096-9101(1997)21:3<269::aid-lsm7>3.0.co;2-o.

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Çilesiz, Inci, Sharon Thomsen, A. J. Welch, and Eric K. Chan. "Controlled temperature tissue fusion: Ho:YAG laser welding of rat intestine in vivo, Part Two." Lasers in Surgery and Medicine 21, no. 3 (1997): 278–86. http://dx.doi.org/10.1002/(sici)1096-9101(1997)21:3<278::aid-lsm8>3.0.co;2-n.

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Stevens-Kalceff, Marion A., Joe Wong, and Andre Stesmans. "Microcharacterization of Defects Induced in Fused Silica by High Power 3ω UV (355nm) Laser Pulses." Microscopy and Microanalysis 7, S2 (August 2001): 496–97. http://dx.doi.org/10.1017/s1431927600028555.

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There are many technical challenges to be overcome before controlled fusion reactions can be achieved. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is being developed to initiate fusion reactions using the world's most powerful laser. Essential components of the Facility are the ultra pure silica (SiO2) lenses that focus the powerful laser beams on to the target. Irradiation with a high power laser has been observed to damage the silica lenses, resulting in the formation of defects. The ensuing degradation of the lens performance necessitates its replacement. It is therefore critical to characterize the induced defects and understand the laser damage initiation and evolution, so that damage mitigation strategies can be developed.Cathodoluminescence (CL) microscopy and spectroscopy enables high spatial resolution and high sensitivity detection of defects in poorly conducting materials. It is therefore an ideal microanalytical technique with which to study laser irradiation-induced defects.

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Cobbinah, Prince Valentine, Rivel Armil Nzeukou, Omoyemi Temitope Onawale, and Wallace Rwisayi Matizamhuka. "Laser Powder Bed Fusion of Potential Superalloys: A Review." Metals 11, no. 1 (December 30, 2020): 58. http://dx.doi.org/10.3390/met11010058.

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The laser powder bed fusion (LPBF) is an additive manufacturing technology involving a gradual build-on of layers to form a complete component according to a computer-aided design. The LPBF process boasts of manufacturing value-added parts with higher accuracy and complex geometries for the transport, aviation, energy, and biomedical industries. TiAl-based alloys and high-entropy alloys (HEAs) are two materials envisaged as potential replacements of nickel-based superalloys for high temperature structural applications. The success of these materials hinge on optimization and implementation of tailored microstructures through controlled processing and appropriate alloy manipulations that can promote and stabilize new microstructures. Therefore, it is important to understand the LPBF technique, and its associated microstructure-mechanical property relationships. This paper discusses the metallurgical sintering processes of LPBF, the effects of process parameters on densification, microstructures, and mechanical properties of LPBFed TiAl-based alloys and HEAs. This paper also, presents updates and future studies recommendations on the LPBFed TiAl-based alloys and HEAs.

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Chen, Shihao, and Ziwei Chen. "A Way to Realize Controlled Nuclear Fusion by γ-Laser or γ-Ray." World Journal of Nuclear Science and Technology 08, no. 04 (2018): 190–96. http://dx.doi.org/10.4236/wjnst.2018.84016.

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Bird, Robert F., Patrick Gillies, Michael R. Bareford, Andy Herdman, and Stephen Jarvis. "Performance Optimisation of Inertial Confinement Fusion Codes using Mini-applications." International Journal of High Performance Computing Applications 32, no. 4 (November 2, 2016): 570–81. http://dx.doi.org/10.1177/1094342016670225.

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Despite the recent successes of nuclear energy researchers, the scientific community still remains some distance from being able to create controlled, self-sustaining fusion reactions. Inertial Confinement Fusion (ICF) techniques represent one possible option to surpass this barrier, with scientific simulation playing a leading role in guiding and supporting their development. The simulation of such techniques allows for safe and efficient investigation of laser design and pulse shaping, as well as providing insight into the reaction as a whole. The research presented here focuses on the simulation code EPOCH, a fully relativistic particle-in-cell plasma physics code concerned with faithfully recreating laser-plasma interactions at scale. A significant challenge in developing large codes like EPOCH is maintaining effective scientific delivery on successive generations of high-performance computing architecture. To support this process, we adopt the use of mini-applications – small code proxies that encapsulate important computational properties of their larger parent counterparts. Through the development of a mini-application for EPOCH (called miniEPOCH), we investigate a variety of the performance features exhibited in EPOCH, expose opportunities for optimisation and increased scientific capability, and offer our conclusions to guide future changes to similar ICF codes.

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Iinuma, T., T. Karino, S. Kondo, T. Kubo, H. Kato, T. Suzuki, S. Kawata, and A. I. Ogoyski. "Control of fuel target implosion non-uniformity in heavy ion inertial fusion." Laser and Particle Beams 34, no. 4 (November 2, 2016): 729–34. http://dx.doi.org/10.1017/s0263034616000677.

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AbstractIn inertial fusion, one of scientific issues is to reduce an implosion non-uniformity of a spherical fuel target. The implosion non-uniformity is caused by several factors, including the driver beam illumination non-uniformity, the Rayleigh–Taylor instability (RTI) growth, etc. In this paper, we propose a new control method to reduce the implosion non-uniformity; the oscillating implosion acceleration δg(t) is created by pulsating and dephasing heavy-ion beams (HIBs) in heavy-ion inertial fusion (HIF). The δg(t) would reduce the RTI growth effectively. The original concept of the non-uniformity control in inertial fusion was proposed in [Laser Part. Beams (1993) 11, 757–768]. In this paper, it was found that the pulsating and dephasing HIBs illumination provide successfully the controlled δg(t) and that δg(t) induced by the pulsating HIBs reduces well the implosion non-uniformity. Consequently the pulsating HIBs improve a pellet gain remarkably in HIF.

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André, M., D. Babonneau, C. Bayer, M. Bernard, J.-L. Bocher, J. Bruneau, A. Coudeville, et al. "Progress in inertial confinement fusion physics at Centre d'Etudes de Limeil-Valenton." Laser and Particle Beams 12, no. 3 (September 1994): 329–42. http://dx.doi.org/10.1017/s0263034600008181.

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The laser program developed at the Centre d'Etudes de Limeil-Valenton, Saint-Georges, France (CEL-V) is concentrated on a systematic investigation of indirect drive fusion; by comparison with direct drive, this process is expected to provide the required irradiation uniformity with relaxed constraints on laser beam quality. The main concerns are radiative transfer and preheat, hydrodynamic instabilities, and high-density X-ray driven implosions. Ablative implosion experiments have been conducted with the two beams at the Phebus facility (5 kJ, 1.3 ns, 0.35 μm). Symmetry was proved to be controlled by the casing structure, following scaling laws describing hohlraum physics. A compressed DT density ∼100 ρ0 (ρ0 liquid DT density) has been deduced from activation measurements. Different aspects of the soft X-ray transfer processes, and particularly of the ablation of a low-Z material, which drives the capsule implosion, are dealt with in detailed investigations. Reported here are results on X-ray reemission and penetration in several materials, and on induced hydrodynamics of accelerated foils. The laser energy required to reach fuel ignition conditions has been evaluated from numerical simulations as well as from analytical models, taking into account hohlraum physics, capsule implosion, hot spot formation, and burn propagation. Several crucial parameters have been drawn, the most important being the radiation temperature. A target gain in the order of 10 appears achievable with a 2-MJ laser.

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Iwasa, Yuki, Kohei Yamanoi, Yumi Kaneyasu, and Takayoshi Norimatsu. "Controlled Generation of Double Emulsions for Laser Fusion Target Fabrication Using a Glass Capillary Microfluidic Device." Fusion Science and Technology 73, no. 2 (November 28, 2017): 258–64. http://dx.doi.org/10.1080/15361055.2017.1372988.

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Demirorer, Mete, Wojciech Suder, Supriyo Ganguly, Simon Hogg, and Hassam Naeem. "Development of laser welding of high strength aluminium alloy 2024-T4 with controlled thermal cycle." MATEC Web of Conferences 326 (2020): 08005. http://dx.doi.org/10.1051/matecconf/202032608005.

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An innovative process design, to avoid thermal degradation during autogenous fusion welding of high strength AA 2024-T4 alloy, based on laser beam welding, is being developed. A series of instrumented laser welds in 2 mm thick AA 2024-T4 alloys were made with different processing conditions resulting in different thermal profiles and cooling rates. The welds were examined under SEM, TEM and LOM, and subjected to micro-hardness examination. This allowed us to understand the influence of cooling rate, peak temperature, and thermal cycle on the growth of precipitates, and related degradation in the weld and heat affected area, evident as softening. Although laser beam welding allows significant reduction of heat input, and higher cooling rates, as compared to other high heat input welding processes, this was found insufficient to completely supress coarsening of precipitate in HAZ. To understand the required range of thermal cycles, additional dilatometry tests were carried out using the same base material to understand the time-temperature relationship of precipitate formation. The results were used to design a novel laser welding process with enhanced cooling, such as with copper backing bar and cryogenic cooling.

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Lin, Ping, Bai Yu Liu, Yong Sheng Gou, Yong Lin Bai, Bo Wang, and Xue Qing Zhao. "Arbitrary Waveform Generator Based on GaAs FET and Tapered Micro-Strip Line." Advanced Materials Research 655-657 (January 2013): 1581–86. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.1581.

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In order to improve the output power of laser pulse in the inertia confinement fusion experiment, an arbitrary waveform generator is fabricated to shape the laser pulse. The arbitrary waveform generator is based on the impedance tapered micro-strip line technology and GaAs Field Effect Transistor set which has a good ability of generating voltage-controlled current. With the impedance tapered micro-strip line technology, the arbitrary waveform generator generates shaping electrical pulse with duration less than 10 ns, 330 ps time-domain adjustment. We use the shaping electrical pulse to modulate semiconductor laser which has the characteristic of direct modulate, the experiment results show the shaped laser pulse is obtained based on the shaping electrical pulse.

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Shakirov, Ivan, Pavel Kuznetsov, Mikhail Staritsyn, Anton Zhukov, and Vitaliy Bobyr. "The study of the regularities of structure formation and properties of the L-PBF metal as a set of processes on the way to create a controlled structure." MATEC Web of Conferences 315 (2020): 13001. http://dx.doi.org/10.1051/matecconf/202031513001.

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In this work, to study the effect of laser powder bed fusion (L-PBF) parameters on the microstructure and mechanical properties of 321 austenitic steel, a series of samples were created combining various combinations of L-PBF technological modes, such as: laser spot diameter, scanning speed, laser power, scanning strategy. The possibility of controlling the structure formation of steel in the L-PBF process with the aim of obtaining a given crystallographic texture, grain size and morphology is estimated. The relationship between the resulting anisotropic structure and mechanical properties is investigated.

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Asnafi, Nader. "Application of Laser-Based Powder Bed Fusion for Direct Metal Tooling." Metals 11, no. 3 (March 10, 2021): 458. http://dx.doi.org/10.3390/met11030458.

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The journey of production tools in cold working, hot working, and injection molding from rapid tooling to additive manufacturing (AM) by laser-based powder bed fusion (L-PBF) is described. The current machines and their configurations, tool steel powder materials and their properties, and the L-PBF process parameters for these materials are specified. Examples of production tools designed for and made by L-PBF are described. Efficient design, i.e., high tooling efficiency and performance in operation, should be the primary target in tool design. Topology and lattice structure optimization provide additional benefits. Using efficient design, L-PBF exhibits the greatest potential for tooling in hot working and injection molding. L-PBF yields high tooling costs, but competitive total costs in hot working and injection molding. Larger object sizes that can be made by L-PBF, a larger number of powder metals that are designed for different tooling applications, lower feedstock and L-PBF processing costs, further L-PBF productivity improvement, improved surface roughness through L-PBF, and secured quality are some of the targets for the research and development in the future. A system view, e.g., plants with a high degree of automation and eventually with cyber-physically controlled smart L-PBF inclusive manufacturing systems, is also of great significance.

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Dias, David, Osmar Santos, Wellington Alves, Milton Lima, and Maria Silva. "Fiber Laser Surface Melting of a NiTi Superelastic Alloy: Influence on Structural and Mechanical Properties." Metals 9, no. 12 (November 27, 2019): 1268. http://dx.doi.org/10.3390/met9121268.

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The surface melting of a NiTi superelastic alloy using a high-power laser Yb:Fiber was investigated. The influence of this process on the microstructural and mechanical properties was also examined. The reference material was a 3 mm nitinol strip with a homogeneous austenitic B2 phase. For the laser surface melting process, input fluences were applied from 17.5 to 45 J/mm2. The morphology of the structure and the chemical composition of several regions were determined by optical microscopy, scanning electron microscopy, dispersive energy spectra, and X-ray diffraction techniques. The mechanical properties, such as modulus of elasticity and hardness, were determined using nanoindentation and microindentation techniques. The greatest surface finishing of the fusion zone was observed for the condition 35 J/mm2. Three well-defined regions (fusion zone (FZ), heat-affected zone (HAZ), base metal (BM)) could be observed and dimensions of grain size, width, and depth of the melted pool were directly affected by the laser fluence. The geometry of the molten pool could be controlled by the optimization of the laser parameters. High laser fluence caused preferential volatilization of nickel, dynamic precipitation of intermetallic phases, including Ti2Ni, Ni3Ti, and Ni4Ti3, as well as solubilization of TiC in the matrix, which led to grain refinement. Thus, high laser fluence is a suitable technique to enhance mechanical properties such as hardness and Young’s modulus.

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Chen, Xi, Zhenglong Lei, Yanbin Chen, Yu Han, Meng Jiang, Ze Tian, Jiang Bi, Sanbao Lin, and Nan Jiang. "Effect of Laser Beam Oscillation on Laser Welding–Brazing of Ti/Al Dissimilar Metals." Materials 12, no. 24 (December 11, 2019): 4165. http://dx.doi.org/10.3390/ma12244165.

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Ti4Al6V and 6061 Al dissimilar metals were butt welded by the laser oscillating welding method. The effects of laser offset, oscillation frequency, and energy distribution on the formation, microstructure, and tensile properties of dissimilar metal joints are discussed in detail. The experimental results show that the Ti6Al4V was micro melted with a laser offset of 1.1 mm, and a large number of intermetallic compounds (IMCs) were formed on the side of the Ti6Al4V. Additionally, there were some porosity defects in the fusion zone (FZ) due to an inappropriate laser oscillation frequency. When the laser offset was increased to 1.2 mm, the IMC distribution was uniform and the thickness was controlled below 2 μm. The porosity defects in the FZ decreased and the tensile strength of the joints increased significantly. The maximum value of tensile strength reached 173 MPa at a laser frequency of 28 Hz.

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37

Tirlapur, Uday K., Erhard Kranz, and Mauro Cresti. "Characterisation of isolated egg cells,in vitrofusion products and zygotes ofZea maysL. using the technique of image analysis and confocal laser scanning microscopy." Zygote 3, no. 1 (February 1995): 57–64. http://dx.doi.org/10.1017/s0967199400002380.

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SummaryChanges in membrane Ca2+, calcium receptor protein calmodulin, endoplasmic reticulum (ER), mitochondria and cellulose in unfixed, living, isolated egg cells and fusion products of pairs of one egg and one sperm cell ofZea maysL. have been investigated using chlorotetracycline, fluphenazine, immunocytochemical techniques, 3,3'dihexyloxa-carbocyanine iodide (DiOC6(3)) and calcofluor white in conjuction with computer-controlled video image analysis. In addition, confocal laser scannig microscopy has been used in conjuction with ethidium bromide to detect the nature and location of the sperm cell nuclear chromatin before and after karyogamy. Digitised video images of chlorotetra cycline (CTC) fluorescence reveal that egg cells contain high levels of membrane Ca2+in organelles present around the nucleus while the cytosolic signal is relatively low. Intense CTC fluorescence is invariably present just below the plasma membrane of egg cells and a certain degree of regionalised distribution of Ca2+in cytoplasm is also discrnible. Similarly, the fluphenazine (FPZ)-detectable calmodulin (CaM) and that localised immunocytochemically using monoclonal anti-CaM antibodies reveal high levels of Cam in the vicinity of the nucleus in egg cells. Only a few ER profiles and mitochondria could be visualised in the egg cell and no calcofluor fluorescence could be detected. Followingin vitrofertilisation of single isolated eggs substantial changes in the Ca2+levels occur which include an increase in the membrane Ca2+of the fusion product, particularly in the cytosol and around the nucleus. Unlike in the eggs the fine CTC fluorescence signal below the plasma membrane is not detectable in the fusion products. Compared with isolated egg cell protolasts an increase in the CaM level in the cytoplasm was observed in the fusion products. There is a slight increase in the CaM level in the cytoplasm was observed in the fusion products. There is a slight increase in the fluorescene around the fusion product is visible after 16 h in in culture. The sperm cell chromatin in the fusion product is highly condensed, unlike that of the egg cell, and confocally imaged serial optical sections of thein vitrofusion product reveal the occurrence of karyogamy 35 min following gamete fusion. First visual evidence for intermingling of sperm nuclear chromatin in the zygotic nuclei is also provided.

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Cheepu, Muralimohan, D. Venkateswarlu, P. Nageswara Rao, S. Senthil Kumaran, and Narayanan Srinivasan. "Effect of Process Parameters and Heat Input on Weld Bead Geometry of Laser Welded Titanium Ti-6Al-4V Alloy." Materials Science Forum 969 (August 2019): 613–18. http://dx.doi.org/10.4028/www.scientific.net/msf.969.613.

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Laser beam welding is one of the most favorable welding technique and its importance in industry is demanding due to higher welding speeds and lower dimensions and distortions in the welds. Moreover, its high strength to weld geometries and minimal heat affected zones makes favorable for various industrial applications. In the present study, laser welding of titanium alloy was investigated to observe the effects of parameters on the bead geometry and metallurgical properties. The laser power and welding speeds were varied to identify their impact on the formation of weld geometry. The width and depth of the fusion zone is varied with welding conditions. The finer grains identified in weld zone and the width of heat affected zone was significantly changes with laser welding power. The mechanical properties of the weld joint are controlled by obtaining optimum weld bead geometry and width of the head affected zone in the welds.

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39

Lei, Zheng, Zongtao Zhu, Xiaoyi Yang, Yishuai Jiang, and Hui Chen. "Microstructure and mechanical properties of high strength TMCP steel hybrid disk laser-MAG welded joint." International Journal of Modern Physics B 34, no. 01n03 (December 19, 2019): 2040063. http://dx.doi.org/10.1142/s0217979220400639.

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Hybrid laser-arc welding (HLAW) was carried out on high strength thermo-mechanical controlled process (TMCP) steel of 14 mm thickness using single-pass welding (SPW) and multi-pass welding (MPW) processes. Well-formed weld joints with good performance were successfully obtained. The results showed that the microstructure of weld was pre-eutectoid ferrite, acicular ferrite and some granular bainite. There were mainly lath bainite, granular bainite and acicular ferrite in the heat-affected zone. The grain sizes of SPW were thicker than MPW, and the bainite content of MPW was higher than SPW. The average hardness value of the fusion zone was lower than that of the Heat affected zone, but higher than that of the base material. The weld was divided into upper arc domain zone (ADZ) and lower laser domain zone (LDZ). The ADZ was harder than the LDZ. The average absorbed energy of SPW and MPW in the fusion zone at −40[Formula: see text]C was 125.5 and 92 J/cm2, respectively. The influences of microstructure on impact toughness were summarized by analyzing the hardness distribution and microstructure of the welded joint. The brittle transition temperatures of the two processes obtained by the energy criterion and the morphology criterion were close to each other.

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40

Zhang, Meng, Chen-Nan Sun, Xiang Zhang, Phoi Chin Goh, Jun Wei, David Hardacre, and Hua Li. "Effect of heat treatment on fatigue crack initiation of laser powder bed fusion stainless steel 316L." MATEC Web of Conferences 165 (2018): 22006. http://dx.doi.org/10.1051/matecconf/201816522006.

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Laser powder bed fusion (L-PBF) is an emerging additive manufacturing technique for building structural components. L-PBF processing defects, such as lack of fusion pores, promote fatigue crack initiation and shorten the fatigue life. With well-controlled processing, critical pores can be avoided such that the microstructure-driven intergranular crack initiation mode becomes operative. In this work, the fatigue crack initiation behaviours of as-built and solution annealed L-PBF stainless steel 316L were studied. Crack initiation of the as-built samples is driven by de-bonding of the dendritic grain boundaries. High temperature annealing results in the formation of thermally-induced defects, possibly via the reheat cracking mechanism and the nucleation of pre-existing gas pores. As heat treating could have led to recrystallization and annihilation of the original grain boundary defects, the thermally-induced defects became the new sites for crack initiation. In addition, heat treatment incurred significant reduction in yield strength, such that the interaction of fatigue and ratcheting strain accumulation dominated the deformation behaviour of the material. The resulting fatigue strength in the finite life regime was reduced by about 13% but the fatigue endurance limit was not affected.

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41

Comley, Andrew James. "Laser beam zooming and deflection using a nonlinear metamaterial refracting medium." EPJ Applied Metamaterials 5 (2018): 8. http://dx.doi.org/10.1051/epjam/2018003.

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In-process control of the focal spot size and pointing position of a laser as it interacts with a target (beam zooming and deflection) offers the possibility of unprecedented efficiency improvements in a number of applications, such as inertial confinement fusion and laser micromachining. Here is described a system in which the focussing characteristics of a laser beam at one wavelength can be controlled by a lower-intensity beam at another wavelength, via their mutual interaction with a nonlinear metamaterial refracting medium. Such a metamaterial approach permits the optical response of the medium to be tailored according to the wavelengths of interest and time response required in a given application. A metamolecule unit cell design is described in terms of an equivalent circuit based on a pair of LCR (inductance, capacitance, resistance) circuits coupled by a common nonlinear capacitor. The circuit is studied using an analytical approach to obtain an understanding of its properties and design relationships between circuit parameters. Potential realisations of the circuit are discussed.

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42

Balachandramurthi, Arun Ramanathan, Nitesh Raj Jaladurgam, Chamara Kumara, Thomas Hansson, Johan Moverare, Johannes Gårdstam, and Robert Pederson. "On the Microstructure of Laser Beam Powder Bed Fusion Alloy 718 and Its Influence on the Low Cycle Fatigue Behaviour." Materials 13, no. 22 (November 17, 2020): 5198. http://dx.doi.org/10.3390/ma13225198.

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Additive manufacturing of Alloy 718 has become a popular subject of research in recent years. Understanding the process-microstructure-property relationship of additively manufactured Alloy 718 is crucial for maturing the technology to manufacture critical components. Fatigue behaviour is a key mechanical property that is required in applications such as gas turbines. Therefore, in the present work, low cycle fatigue behaviour of Alloy 718 manufactured by laser beam powder bed fusion process has been investigated. The material was tested in as-built condition as well as after two different thermal post-treatments. Three orientations with respect to the building direction were tested to evaluate the anisotropy. Testing was performed at room temperature under controlled amplitudes of strain. It was found that defects, inclusions, strengthening precipitates, and Young’s modulus influence the fatigue behaviour under strain-controlled conditions. The strengthening precipitates affected the deformation mechanism as well as the cycle-dependent hardening/softening behaviour. The defects and the inclusions had a detrimental effect on fatigue life. The presence of Laves phase in LB-PBF Alloy 718 did not have a detrimental effect on fatigue life. Young’s modulus was anisotropic and it contributed to the anisotropy in strain-life relationship. Pseudo-elastic stress vs. fatigue life approach could be used to handle the modulus-induced anisotropy in the strain-life relationship.

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Flores Ituarte, Iñigo, Olli Wiikinkoski, and Anton Jansson. "Additive Manufacturing of Polypropylene: A Screening Design of Experiment Using Laser-Based Powder Bed Fusion." Polymers 10, no. 12 (November 22, 2018): 1293. http://dx.doi.org/10.3390/polym10121293.

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The use of commodity polymers such as polypropylene (PP) is key to open new market segments and applications for the additive manufacturing industry. Technologies such as powder-bed fusion (PBF) can process PP powder; however, much is still to learn concerning process parameters for reliable manufacturing. This study focusses in the process–property relationships of PP using laser-based PBF. The research presents an overview of the intrinsic and the extrinsic characteristic of a commercial PP powder as well as fabrication of tensile specimens with varying process parameters to characterize tensile, elongation at break, and porosity properties. The impact of key process parameters, such as power and scanning speed, are systematically modified in a controlled design of experiment. The results were compared to the existing body of knowledge; the outcome is to present a process window and optimal process parameters for industrial use of PP. The computer tomography data revealed a highly porous structure inside specimens ranging between 8.46% and 10.08%, with porosity concentrated in the interlayer planes in the build direction. The results of the design of experiment for this commercial material show a narrow window of 0.122 ≥ Ev ≥ 0.138 J/mm3 led to increased mechanical properties while maintaining geometrical stability.

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Moon, Kyung-Suk, Ji-Myung Bae, Sungho Jin, and Seunghan Oh. "Infrared-Mediated Drug Elution Activity of Gold Nanorod-Grafted TiO2Nanotubes." Journal of Nanomaterials 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/750813.

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The purpose of this research was to prepare gold nanorod- (GNR-) grafted TiO2nanotubes by thiolactic acid treatment and evaluate remote-controlled drug elution and antibacterial activity by infrared (IR) light irradiation. Tetracycline used as an antibiotic was loaded into GNR-grafted TiO2nanotubes by using 2 w/v% polylactic acid solutions. A near-IR laser (830 nm) was used for remote-controlled IR light irradiation. Results of SEM, TEM, XRD, and EDX revealed that GNR chemically bonded to the whole surface of the TiO2nanotubes. An antibiotic release test revealed that on-off drug elution was triggered effectively by the photothermal effect of GNR grafted on TiO2nanotubes. Furthermore, an antibacterial agar zone test indicated that the annihilated zone ofStreptococcus mutansin the experimental group with IR light irradiation was significantly larger than that of the corresponding group without IR light irradiation (P<0.05). Therefore, GNR-grafted TiO2nanotubes would be expected to extend the limited usage of TiO2, which show photocatalytic activity only within the ultraviolet (UV) to IR region, thereby allowing the development of novel fusion technologies in the field of implant materials.

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45

Katayama, Seiji, Sung Min Joo, Masami Mizutani, and Han Sur Bang. "Laser Weldability of Aluminum Alloy and Steel." Materials Science Forum 502 (December 2005): 481–86. http://dx.doi.org/10.4028/www.scientific.net/msf.502.481.

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With the intention of improving butt or lap joint of dissimilar materials, specially devised weld beads together with lap and butt-joints were produced between A5052 and SPCC, where A5052 butt-joint was melted by heat-conduction of SPCC weld bead in addition to the formation of a limited weld fusion zone at the lap part in A5052 alloy. The thickness of intermetallic compounds at the butt-joint interface was approximately 2 μm and free of cracks. It was also revealed that crack-free lap weld metals were formed between aluminum alloy and steel when the penetration was controlled to be of less than 0.3 mm in depth at small heat input. It was moreover found that the majority of a laser weld fusion zone solidified as alpha(bcc)-iron phase containing small amount of aluminum, and cracks were absent in the case of hard intermetallic (AlxFey type) layer of less than 10μm zone. It was confirmed that a weld with lap and butt joints possessed high strength (leading to the load 3500 N to 4,380 N for 40 mm width specimen). In addition, SPCC and A1100 or A5052 were subjected to lap welding with a cw YAG laser, where one to three passes were performed to produce wider bonded areas. Dissimilar steel and aluminum joints with good mechanical properties were obtained, since the fracture occurred in the aluminum alloy base metal in the tensile test. It is concluded that welded joints of high strength can be produced between aluminum alloy and steel with proper devices.

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46

Riva, Leonardo, Paola Serena Ginestra, and Elisabetta Ceretti. "Mechanical characterization and properties of laser-based powder bed–fused lattice structures: a review." International Journal of Advanced Manufacturing Technology 113, no. 3-4 (January 28, 2021): 649–71. http://dx.doi.org/10.1007/s00170-021-06631-4.

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AbstractThe increasing demand for a wider access to additive manufacturing technologies is driving the production of metal lattice structure with powder bed fusion techniques, especially laser-based powder bed fusion. Lattice structures are porous structures formed by a controlled repetition in space of a designed base unit cell. The tailored porosity, the low weight, and the tunable mechanical properties make the lattice structures suitable for applications in fields like aerospace, automotive, and biomedicine. Due to their wide-spectrum applications, the mechanical characterization of lattice structures is mostly carried out under compression tests, but recently, tensile, bending, and fatigue tests have been carried out demonstrating the increasing interest in these structures developed by academy and industry. Although their physical and mechanical properties have been extensively studied in recent years, there still are no specific standards for their characterization. In the absence of definite standards, this work aims to collect the parameters used by recent researches for the mechanical characterization of metal lattice structures. By doing so, it provides a comparison guide within tests already carried out, allowing the choice of optimal parameters to researchers before testing lattice samples. For every mechanical test, a detailed review of the process design, test parameters, and output is given, suggesting that a specific standard would enhance the collaboration between all the stakeholders and enable an acceleration of the translation process.

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Guan, Chaoliang, and Wenqiang Peng. "Multiscale Modeling and Analysis of an Ultra-Precision Damage Free Machining Method." Journal of Multiscale Modelling 07, no. 01 (March 2016): 1640004. http://dx.doi.org/10.1142/s1756973716400047.

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Under the condition of high laser flux, laser induced damage of optical element does not occur is the key to success of laser fusion ignition system. US government survey showed that the processing defects caused the laser induced damage threshold (LIDT) to decrease is one of the three major challenges. Cracks and scratches caused by brittle and plastic removal machining are fatal flaws. Using hydrodynamic effect polishing method can obtain damage free surface on quartz glass. The material removal mechanism of this typical ultra-precision machining process was modeled in multiscale. In atomic scale, chemical modeling illustrated the weakening and breaking of chemical bond energy. In particle scale, micro contact modeling given the elastic remove mode boundary of materials. In slurry scale, hydrodynamic flow modeling showed the dynamic pressure and shear stress distribution which are relations with machining effect. Experiment was conducted on a numerically controlled system, and one quartz glass optical component was polished in the elastic mode. Results show that the damages are removed away layer by layer as the removal depth increases due to the high damage free machining ability of the HEP. And the LIDT of sample was greatly improved.

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Denti, Lucia, and Antonella Sola. "On the Effectiveness of Different Surface Finishing Techniques on A357.0 Parts Produced by Laser-Based Powder Bed Fusion: Surface Roughness and Fatigue Strength." Metals 9, no. 12 (November 29, 2019): 1284. http://dx.doi.org/10.3390/met9121284.

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Laser-based powder bed fusion (L-PBF) is an additive manufacturing (AM) technique that uses a computer-controlled laser beam as the energy source to consolidate a metal powder according to a layer-upon-layer strategy in order to manufacture a three dimensional part. This opens the way for an unprecedented freedom in geometry, but the layer-wise build-up strategy typically results in a very poor surface finish, which is affected by the staircase effect and by the presence of partially molten particles. Surface finishing treatments are therefore necessary to obtain an adequate surface finish, to improve the fatigue behavior and to meet mechanical and aesthetic needs. The present contribution systematically compares numerous surface finishing techniques, including laser shock processing, plastic media blasting, sand blasting, ceramic shot peening and metal shot peening with steel particles of different sizes (ϕ = 0.2 mm and ϕ = 0.4 mm). The results show that all the proposed methods improve the surface quality and the fatigue life of A357.0 L-PBF parts. However, the achievement of the lowest surface roughness does not necessarily correspond to the best fatigue performance, thus suggesting that multiple mechanisms may be active and that besides surface roughness also residual stresses contribute to increase the fatigue strength.

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Simoni, Helio Rubens, Antonio Jorge Abdalla, Carlos Antonio Reis Pereira Baptista, and Milton Sergio Fernandes de Lima. "Mechanical Behavior of Surface Nitrided and Heat-Treated Laser Welded Ti-6Al-4V." Advanced Materials Research 1135 (January 2016): 167–78. http://dx.doi.org/10.4028/www.scientific.net/amr.1135.167.

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The welding of the titanium alloy Ti-6Al-4V has been reported to be difficult because of the intrinsic reactivity with oxygen and also because the weld usually produces an unbalanced α/β structure. This contribution deals with a heat treatment of the laser welded Ti-6Al-4V alloy in a CVD nitriding chamber. The heat treatment aims to obtain a fusion zone structure similar to the base material. An additional advantage of the method is creating a hard nitride layer at the surfaces of the piece, increasing the hardness. The CVD treatment at 850°C per 2 hours proved to be efficient to transform the as-welded martensitic structure to a biphase α/β diffusion controlled structure. Although the fusion zone was soft after the treatment (330 HV), the surface is hard attaining about 750 HV. The tensile strength and ductility after welding were very similar to the base material. However, the yield strength decreased from 1030 MPa to 880 MPa and the uniform strain was reduced from 8 to 1% after the CVD treatment. The fatigue behavior was quite different depending on the testing conditions. For the rotating bending condition, the higher fatigue limits, around 400 MPa, were observed for the CVD-treated weld coupon. However, the fatigue behavior in uniaxial conditions was very similar to the as-welded condition and the CVD-treated weld, attaining the fatigue limits at 250 MPa.

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Huber, Florian, Dominic Bartels, and Michael Schmidt. "In-Situ Alloy Formation of a WMoTaNbV Refractory Metal High Entropy Alloy by Laser Powder Bed Fusion (PBF-LB/M)." Materials 14, no. 11 (June 4, 2021): 3095. http://dx.doi.org/10.3390/ma14113095.

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High entropy or multi principal element alloys are a promising and relatively young concept for designing alloys. The idea of creating alloys without a single main alloying element opens up a wide space for possible new alloy compositions. High entropy alloys based on refractory metals such as W, Mo, Ta or Nb are of interest for future high temperature applications e.g., in the aerospace or chemical industry. However, producing refractory metal high entropy alloys by conventional metallurgical methods remains challenging. For this reason, the feasibility of laser-based additive manufacturing of the refractory metal high entropy alloy W20Mo20Ta20Nb20V20 by laser powder bed fusion (PBF-LB/M) is investigated in the present work. In-situ alloy formation from mixtures of easily available elemental powders is employed to avoid an expensive atomization of pre-alloyed powder. It is shown that PBF-LB/M of W20Mo20Ta20Nb20V20 is in general possible and that a complete fusion of the powder mixture without a significant number of undissolved particles is achievable by in-situ alloy formation during PBF-LB/M when selecting favorable process parameter combinations. The relative density of the samples with a dimension of 6 × 6 × 6 mm3 reaches, in dependence of the PBF-LB/M parameter set, 99.8%. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements confirm the presence of a single bcc-phase. Scanning electron microscopy (SEM) images show a dendritic and/or cellular microstructure that can, to some extent, be controlled by the PBF-LB/M parameters.

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Journal articles on the topic 'Lasers in controlled fusion'

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