Science.gov

Sample records for laser transformation hardening

  1. Laser Hardening Prediction Tool Based On a Solid State Transformations Numerical Model

    SciTech Connect

    Martinez, S.; Ukar, E.; Lamikiz, A.

    2011-01-17

    This paper presents a tool to predict hardening layer in selective laser hardening processes where laser beam heats the part locally while the bulk acts as a heat sink.The tool to predict accurately the temperature field in the workpiece is a numerical model that combines a three dimensional transient numerical solution for heating where is possible to introduce different laser sources. The thermal field was modeled using a kinetic model based on Johnson-Mehl-Avrami equation. Considering this equation, an experimental adjustment of transformation parameters was carried out to get the heating transformation diagrams (CHT). With the temperature field and CHT diagrams the model predicts the percentage of base material converted into austenite. These two parameters are used as first step to estimate the depth of hardened layer in the part.The model has been adjusted and validated with experimental data for DIN 1.2379, cold work tool steel typically used in mold and die making industry. This steel presents solid state diffusive transformations at relative low temperature. These transformations must be considered in order to get good accuracy of temperature field prediction during heating phase. For model validation, surface temperature measured by pyrometry, thermal field as well as the hardened layer obtained from metallographic study, were compared with the model data showing a good adjustment.

  2. Applications of Crank-Nicolson method with ADI in laser transformation hardening

    NASA Astrophysics Data System (ADS)

    Kartono, Agus; Tofany, Novan; Ahmad, Mohammad Fadhli; Mamat, Mustafa; Husain, Mohd Lokman

    2012-12-01

    A two-dimensional numerical solution for pulsed laser transformation hardening is developed using the finite difference method (FDM). The FDM has been developed using Crank-Nicolson scheme which solved by using alternating-direction implicit method. If this present model was compared to the analytical solution, then the Crank-Nicolson scheme showed better results in terms of accuracy, consistency, stability, convergence, and performance than to the explicit scheme. The longer heating duration, higher laser beam intensity, and greater number of pulse had influences on increasing the maximum temperature. The repetitive heating had influences on extending the heat duration and increasing the initial temperature of domain. The shorter cooling duration in repetitive pulse produced higher maximum temperature. The thinner material's thickness increased the cooling rate, which finally increased the possibility of austenite to transform into martensite phase. In addition, it was also found that the higher maximum temperature always reduced the cooling rate value when temperature cools down toward to the starting temperature of martensite formation. It reduced the possibility of martensite formation. It was also seen that the heat was conducted more effective to the axial direction than to the radial direction.

  3. The influence of phase transformation hardening on continuous laser processing of notches for fracture splitting of a C70S6 connecting rod

    NASA Astrophysics Data System (ADS)

    Kou, S. Q.; Gao, Y.; Shi, Z.

    2017-01-01

    The dynamic process of local material microstructure and hardness of continuous laser grooving for fracture splitting of a C70S6 connecting rod was studied. According to the phase transformation characteristics of C70S6 steel during laser processing, the coupling calculation between the transient temperature field and phase transformation process of continuous laser grooving was carried out, and then the phase transformation process and phase compositions in the heat affected zone (HAZ) was obtained. The research results showed that the HAZ was composed of martensite and pearlite as well as residual austenite after continuous laser grooving, and the generation of the martensite in the HAZ is beneficial to the subsequent splitting process; meanwhile, the hardening effect of continuous laser grooving is remarkable on the HAZ, and the requirement for the cutting tool and technique used at the subsequent machining process for the fine boring of the big end hole should be higher.

  4. Laser hardening process simulation for mechanical parts

    NASA Astrophysics Data System (ADS)

    Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Cuccolini, G.

    2007-02-01

    In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

  5. Numerical-experimental analysis of the effect of surface oxidation on the laser transformation hardening of Cr-Mo steels

    NASA Astrophysics Data System (ADS)

    Cordovilla, Francisco; García-Beltrán, Ángel; Dominguez, Jesús; Sancho, Paula; Ocaña, José L.

    2015-12-01

    Laser surface hardening is a technology that enables important advantages to be obtained in comparison with conventional techniques in terms of accuracy of the heat affected zone and productivity. Nevertheless, the development of realistic and flexible models has to be fulfilled in order to control the effects of every set of process conditions. Despite many different models having been developed, very few of them deal with the increment of absorption related with the instantaneous value of the layer of oxide growth during the process in a non-protective atmosphere. This work analyzes the problem of oxide formation at the external surface using kinetic relations, whose parameters have been related with the process variables, considering non-equilibrium conditions. Then, the oxide thickness was associated with a value of absorption through an innovative formula that considers the path of the laser radiation in the interface oxide-base material. The thermal calculations obtained by this method have allowed phase changes to be predicted using Avrami law. Both thermal and metallurgical results for different process conditions have been compared with experimental data showing an excellent agreement.

  6. Laser hardening of diesel engine valve

    SciTech Connect

    Androsov, A.P.; Aleksenko, S.I.; Boyarkin, M.V.; Kusidis, V.G.; Petrov, V.I.

    1988-07-01

    Results are presented of a complex investigation of the effect of laser treatment on the structure and properties of steel 40Kh10S2M and of engine tests with diesel engine valves hardened by the newly devised technology. Results of the investigation of the microstructure of steel 40Kh10S2M, heat-treated by a laser beam, showed that when a specimen is hardened with fusion of the surface layer, it contains two distinct zones of laser action. Results of the effect of laser treatment on the fatigue limit and the wear resistance of the steel and engine tests permit the conclusion that the suggested method of treating valves of internal engine valve gear has good prospects.

  7. Diamond films for laser hardening

    NASA Technical Reports Server (NTRS)

    Albin, S.; Watkins, L.; Ravi, K.; Yokota, S.

    1989-01-01

    Laser-damage experiments were performed on free-standing polycrystalline diamond films prepared by plasma-enhanced CVD. The high laser-induced stress resistance found for this material makes it useful for thin-film coatings for laser optics. Results for diamond-coated silicon substrates demonstrate the enhanced damage threshold imparted by diamond thin-film coatings to materials susceptible to laser damage.

  8. Pulsed laser surface hardening of ferrous alloys.

    SciTech Connect

    Xu, Z.; Reed, C. B.; Leong, K. H.; Hunter, B. V.

    1999-09-30

    A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.

  9. Surface hardening of steel by laser and electron beam. (Latest citations from METADEX). Published Search

    SciTech Connect

    Not Available

    1994-09-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined. (Contains a minimum of 93 citations and includes a subject term index and title list.)

  10. Surface hardening of steel by laser and electron beam. (Latest citations from Metadex). Published Search

    SciTech Connect

    1996-08-01

    The bibliography contains citations concerning electron beam hardening of steels and alloys. Among the materials surface hardened are carbon and alloy steels, aircraft spur gears, nitrocarburized steel, turbine blades, titanium-carbon steel, titanium, and rolling bearings. Effect of transformation plasticity on residual stress fields in laser surface hardening treatment is also examined.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  11. Phase-transformation-induced hardening in Zn-22Al alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yangming; Zeng, Xuduo; Yang, Lijing; Sun, Keqing; Song, Zhenlun

    2013-06-01

    A phase-transformation-induced hardening effect is reported in Zn-22Al (Al: 22 wt.%) alloys. The Zn-22Al specimens were held at 300 °C for 10 h and then quenched in water. A hardening effect took place in subsequent artificial aging at 100-200 °C, which was accompanied by a phase decomposition of a soft α 2 phase and a grain coarsening. The phase-transformation-induced hardening affects the hardness more than the grain-coarsening-induced softening, which leads to the age-hardening phenomenon.

  12. Laser hardening techniques on steam turbine blade and application

    NASA Astrophysics Data System (ADS)

    Yao, Jianhua; Zhang, Qunli; Kong, Fanzhi; Ding, Qingming

    Different laser surface hardening techniques, such as laser alloying and laser solution strengthening were adopted to perform modification treatment on the local region of inset edge for 2Cr13 and 17-4PH steam turbine blades to prolong the life of the blades. The microstructures, microhardness and anti-cavitation properties were investigated on the blades after laser treatment. The hardening mechanism and technique adaptability were researched. Large scale installation practices confirmed that the laser surface modification techniques are safe and reliable, which can improve the properties of blades greatly with advantages of high automation, high quality, little distortion and simple procedure.

  13. Transformation hardening of steel sheet for automotive applications

    NASA Astrophysics Data System (ADS)

    Takechi, H.

    2008-12-01

    Among high-strength steels, transformation hardening steels such as dual-phase (DP) steel and transformation-induced plasticity (TRIP) steel offer a superior relationship between tensile strength (TS) and elongation (El) on a commercial scale. As demand has grown for lighter-weight automobiles, so also has the demand for higher TS, lower yield ratio, and higher hole expansion ratio grown. Recently DP steel has been developed with precipitation hardening and grain refining by TiC. A new TRIP steel composed of 5Mn-2Si and control-rolled with niobium addition suggests the formation of retained austenite ( γ R ) as much as 30% and TS × El = 3,000 kgf/mm2·%.

  14. 3D transient model for CO II laser hardening

    NASA Astrophysics Data System (ADS)

    Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Ascari, A.

    2008-01-01

    A 3D numerical model for the surface hardening process simulation carried out by means of a CO2 laser source is presented. The model is able to predict the extension of the treated area into the workpiece, the type of the resulting micro-structure and the optimal laser path strategy in order to minimize the micro-structural softening due to the tempering effect. The Fourier equation is solved using the Finite Difference Method (FDM) applied on a generical grid obtained by means of the domain discretization. The resulting time dependent temperature distribution into the workpiece is used for the evaluation of the induced heating cycle. By calculating the cooling velocity, the micro-structure transformation is determined together with the hardness in every point of the domain. The hardness reduction due to the tempering effect is also predictible. The computational times are small and the software is very suitable in industrial environment in the early stage of the process planning when several simulation runs must be performed. The modeling activity was developed by considering the class of the hypo-eutectoid steel. The experimental tests were realized on a C43 steel plate. The good agreement between the theoretical and experimental results is shown.

  15. Protection performance evaluation regarding imaging sensors hardened against laser dazzling

    NASA Astrophysics Data System (ADS)

    Ritt, Gunnar; Koerber, Michael; Forster, Daniel; Eberle, Bernd

    2015-05-01

    Electro-optical imaging sensors are widely distributed and used for many different purposes, including civil security and military operations. However, laser irradiation can easily disturb their operational capability. Thus, an adequate protection mechanism for electro-optical sensors against dazzling and damaging is highly desirable. Different protection technologies exist now, but none of them satisfies the operational requirements without any constraints. In order to evaluate the performance of various laser protection measures, we present two different approaches based on triangle orientation discrimination on the one hand and structural similarity on the other hand. For both approaches, image analysis algorithms are applied to images taken of a standard test scene with triangular test patterns which is superimposed by dazzling laser light of various irradiance levels. The evaluation methods are applied to three different sensors: a standard complementary metal oxide semiconductor camera, a high dynamic range camera with a nonlinear response curve, and a sensor hardened against laser dazzling.

  16. Effect of shot peening on the microstructure of laser hardened 17-4PH

    NASA Astrophysics Data System (ADS)

    Wang, Zhou; Jiang, Chuanhai; Gan, Xiaoyan; Chen, Yanhua

    2010-12-01

    In order to investigate the influence of shot peening on microstructure of laser hardened steel and clarify how much influence of initial microstructure induced by laser hardening treatment on final microstructure of laser hardened steel after shot peening treatment, measurements of retained austenite, measurements of microhardness and microstructural analysis were carried out on three typical areas including laser hardened area, transitional area and matrix area of laser hardened 17-4PH steel. The results showed that shot peening was an efficient cold working method to eliminate the retained austenite on the surface of laser hardened samples. The surface hardness increased dramatically when shot peening treatments were carried out. The analyses of microstructure of laser hardened 17-4PH after shot peening treatment were carried out in matrix area and laser hardened area via Voigt method. With the increasing peening intensity, the influence depth of shot peening on hardness and microstructure increased but the surface hardness and microstructure did not change when certain peening intensity was reached. Influence depth of shot peening on hardness was larger than influence depth of shot peening on microstructure due to the kinetic energy loss along the depth during shot peening treatment. From the microstructural result, it can be shown that the shot peening treatment can influence the domain size and microstrain of treated samples but laser hardening treatment can only influence the microstrain of treated samples.

  17. The Effect of Hardenability Variation on Phase Transformation of Spiral Bevel Gear in Quenching Process

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Shi, Wankai; Yang, Lin; Gu, Zhifei; Li, Zhichao

    2016-07-01

    The hardenability of gear steel is dependent on the composition of alloying elements and is one of important criteria to assess process of phase transformation. The variation of hardenability has to be considered in control of the microstructures and distortion during gear quenching. In this paper, the quantitative effect of hardenability has been investigated on phase transformations of spiral bevel gears in die quenching. The hardenability deviation of 22CrMoH steel was assessed by using Jominy test. The dilatometry experiments were conducted to build phase transformation kinetic models for steels with low and high hardenability, respectively. The complete die quenching process of spiral bevel gear was modeled to reveal the significant difference on microstructures and temperature history with variation of hardenability. The final microstructures of the gear are martensite in surface layer after quenching process. There are bainite inside the gear tooth and the mixture of bainite and ferrite inside gear for the gear with low hardenability. The microstructure is bainite inside the gear with high hardenability.

  18. Ferritic, martensitic, and precipitation hardening stainless steel laser weldings

    NASA Astrophysics Data System (ADS)

    Daurelio, Giuseppe; Ludovico, Antonio D.; Panagopoulos, Christos N.; Tundo, Corrado

    1998-07-01

    Even if many steels and alloys have been welded on the last years, nowadays there are some other stainless steel alloys that need a further comprehension when they have to be welded. Typically these alloys are martensitic and precipitation hardening ones that still present some problems to be weld, i.e. hot cracks, fragile beads, an excessive grain size and other surface defects. In this work some martensitic stainless steels of which a AISI 420B, a AISI 440C and a AISI 630 have been studied. The last one is always with a martensitic structure but, in particular, some interesting mechanical properties are reached by a precipitation hardening process. This research has experimented and studied the mechanical and technological properties of the welds obtained on the above cited AISI 420B, AISI 440C and AISI 630, welded by 1.5 kW CO2 laser. The results have also been compared with the ones obtained on ferritic stainless steels AISI 430 and 430F. A technological characterization of the welds has followed as metallographic tests and evaluations, microhardness, tensile and fatigue tests.

  19. Development of a Flexible Laser Hardening & Machining Center and Proof of Concept on C-45 Steel

    NASA Astrophysics Data System (ADS)

    Bouquet, Jan; Van Camp, Dries; Vanhove, Hans; Clijsters, Stijn; Amirahmad, Mohammadi; Lauwers, Bert

    The production of hardened precision parts is conventionally done in 3 steps. Rough machining of a workpiece in soft stage is followed by a hardening step, usually a batch process, and finalized by a hard machining finishing step. To omit the inevitable time delay and loss of accuracy because of part re-clamping, these steps should be incorporated within one flexible machining center. This paper describes the development of this machining center which allowsmachining and laser hardening in one setup, followed by a proof of concept for hardening C45 steel on this setup.

  20. Analysis of the regimes in the scanner-based laser hardening process

    NASA Astrophysics Data System (ADS)

    Martínez, S.; Lamikiz, A.; Ukar, E.; Calleja, A.; Arrizubieta, J. A.; Lopez de Lacalle, L. N.

    2017-03-01

    Laser hardening is becoming a consolidated process in different industrial sectors such as the automotive industry or in the die and mold industry. The key to ensure the success in this process is to control the surface temperature and the hardened layer thickness. Furthermore, the development of reliable scanners, based on moving optics for guiding high power lasers at extremely fast speeds allows the rapid motion of laser spots, resulting on tailored shapes of swept areas by the laser. If a scanner is used to sweep a determined area, the laser energy density distribution can be adapted by varying parameters such us the scanning speed or laser power inside this area. Despite its advantages in terms of versatility, the use of scanners for the laser hardening process has not yet been introduced in the thermal hardening industry because of the difficulty of the temperature control and possible non-homogeneous hardness thickness layers. In the present work the laser hardening process with scanning optics applied to AISI 1045 steel has been studied, with special emphasis on the influence of the scanning speed and the results derived from its variation, the evolution of the hardened layer thickness and different strategies for the control of the process temperature. For this purpose, the hardened material has been studied by measuring microhardness at different points and the shape of the hardened layer has also been evaluated. All tests have been performed using an experimental setup designed to keep a nominal temperature value using a closed-loop control. The tests results show two different regimes depending on the scanning speed and feed rate values. The experimental results conclusions have been validated by means of thermal simulations at different conditions.

  1. The conception for creation of industrial CO laser for dismantlement of reactors and hardening of rails

    NASA Astrophysics Data System (ADS)

    Baranov, I. Ya.

    2007-02-01

    The way of transfer from CO small-scale model installation to industrial CO laser is proposed. A calculation model scaling of CO laser with RF discharge is developed. The calculation model is used for scaling small-scale experimental CO laser installation on which laser generation is received. It is proposed industrial CO laser for dismantlement of obsolete nuclear reactors and laser-hardening of working surfaces of railway rails. Estimated cost proposed CO laser makes several hundred thousand US dollars. Proposed CO laser can work without an optical cable due to installation of the laser head on the manipulator.

  2. Laser beam hardening of cast carbon steels, plain cast irons, and high-speed steels

    NASA Astrophysics Data System (ADS)

    Bylica, Andrzej; Adamiak, Stanislaw; Bochnowski, Wojciech; Dziedzic, Andrzej

    2000-11-01

    The examinations of the structure, hardness and abrasion resistance of surface layer of Fe-C alloys having the contents of carbon up to 4% and high-speed steel: 6-5-2, 4- 4-2-5+C after laser hardening are presented in the paper. They are compared with the properties obtained after conventional hardening. Laser of impulse operation - YAG:Nd and of continuous operation - CO2 were used. Analysis of structure was carried out based on metallographic and fractographic examinations as well as on X-ray properties, parameters of laser and conventional heat treatment of steels were defined.

  3. On the Precipitation Hardening of Selective Laser Melted AlSi10Mg

    NASA Astrophysics Data System (ADS)

    Aboulkhair, Nesma T.; Tuck, Chris; Ashcroft, Ian; Maskery, Ian; Everitt, Nicola M.

    2015-08-01

    Precipitation hardening of selective laser melted AlSi10Mg was investigated in terms of solution heat treatment and aging duration. The influence on the microstructure and hardness was established, as was the effect on the size and density of Si particles. Although the hardness changes according to the treatment duration, the maximum hardening effect falls short of the hardness of the as-built parts with their characteristic fine microstructure. This is due to the difference in strengthening mechanisms.

  4. Beam hardening correction for interior tomography based on exponential formed model and radon inversion transform

    NASA Astrophysics Data System (ADS)

    Chen, Siyu; Zhang, Hanming; Li, Lei; Xi, Xiaoqi; Han, Yu; Yan, Bin

    2016-10-01

    X-ray computed tomography (CT) has been extensively applied in industrial non-destructive testing (NDT). However, in practical applications, the X-ray beam polychromaticity often results in beam hardening problems for image reconstruction. The beam hardening artifacts, which manifested as cupping, streaks and flares, not only debase the image quality, but also disturb the subsequent analyses. Unfortunately, conventional CT scanning requires that the scanned object is completely covered by the field of view (FOV), the state-of-art beam hardening correction methods only consider the ideal scanning configuration, and often suffer problems for interior tomography due to the projection truncation. Aiming at this problem, this paper proposed a beam hardening correction method based on radon inversion transform for interior tomography. Experimental results show that, compared to the conventional correction algorithms, the proposed approach has achieved excellent performance in both beam hardening artifacts reduction and truncation artifacts suppression. Therefore, the presented method has vitally theoretic and practicable meaning in artifacts correction of industrial CT.

  5. Hardening characteristics of CO2 laser welds in advanced high strength steel

    NASA Astrophysics Data System (ADS)

    Han, Tae-Kyo; Park, Bong-Gyu; Kang, Chung-Yun

    2012-06-01

    When the CO2 laser welder with 6 kW output was used to weld 4 TRIP steels, 2 DP steels and a precipitation-hardened steel, which have the tensile strength in the range of 600-1000 MPa, the effect of welding speed on hardening characteristics was investigated. In the weld of TRIP steels and DP steels, the maximum hardness was shown in the fusion zone and the HAZ near the bond line, and the hardness was decreased from the HAZ to the base metal. Only in the PH600 steel, the maximum hardness was shown in the fusion zone and the hardness was decreased from bond line to the base metal. The maximum hardness value was not changed due to the variation of the welding speed within a given range of the welding speed. When the correlation with maximum hardness value using 6 known carbon equivalents was examined, those of CEL (=C+Si/50+Mn/25+P/2+Cr/25) and PL (=C+Mn/22+14B) were 0.96 and 0.95 respectively, and CEL was better because it could reflect the contribution of Si and Cr added to AHSS. The maximum hardness value could be calculated by the equation "Hmax=701CEL+281". The phase transformation analysis indicated that only martensitic transformation was expected in the given range of the welding conditions. Therefore, the maximum hardness of the weld was the same as that of water cooled steel and not changed with the variation of the welding speed

  6. Precipitation Reactions in Age-Hardenable Alloys During Laser Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Jägle, Eric A.; Sheng, Zhendong; Wu, Liang; Lu, Lin; Risse, Jeroen; Weisheit, Andreas; Raabe, Dierk

    2016-03-01

    We describe and study the thermal profiles experienced by various age-hardenable alloys during laser additive manufacturing (LAM), employing two different manufacturing techniques: selective laser melting and laser metal deposition. Using scanning electron microscopy and atom probe tomography, we reveal at which stages during the manufacturing process desired and undesired precipitation reactions can occur in age-hardenable alloys. Using examples from a maraging steel, a nickel-base superalloy and a scandium-containing aluminium alloy, we demonstrate that precipitation can already occur during the production of the powders used as starting material, during the deposition of material (i.e. during solidification and subsequent cooling), during the intrinsic heat treatment effected by LAM (i.e. in the heat affected zones) and, naturally, during an ageing post-heat treatment. These examples demonstrate the importance of understanding and controlling the thermal profile during the entire additive manufacturing cycle of age-hardenable materials including powder synthesis.

  7. Pulse transformer for GaAs laser

    NASA Technical Reports Server (NTRS)

    Rutz, E. M.

    1976-01-01

    High-radiance gallium arsenide (GaAs) laser operating at room temperature is utilized in optical navigation system. For efficient transformer-to-laser impedance match, laser should be connected directly to pulse transformer secondary winding.

  8. High-power multibeam lasers and their applications for surface hardening

    NASA Astrophysics Data System (ADS)

    Bukhanova, I. F.; Divinsky, V. V.; Zhuravel, V. M.

    2000-07-01

    The paper deals with laser technological units (LTU) based on multi-beam lasers of 1 to 10 kW power. To save working gases the laser technological units employ regeneration systems. The LTU have been the basic units used in multipurpose systems for laser processing various parts of the kind of rotation bodies or plane parts, cranckshafts, etc., as well as in special-purpose systems and automatic lines with the full cycle of auxiliary technological operations which are necessary to perform laser processing. The technologies of heat treatment of parts with the use of multi-beam lasers have been developed for the purposes of improvement of heavy-loaded rubbing parts wear resistance; local treatment of non-rigid parts; reduction of labor consumption in some cases of thermo-chemical treatment or induction (bulk) hardening replacement with laser irradiation; reconditioning of worn parts by precision facing, alloying or similar processes.

  9. Fatigue Hardening Behavior of 1.5 GPa Grade Transformation-Induced Plasticity-Aided Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Sugimoto, Koh-Ichi; Hojo, Tomohiko

    2016-11-01

    Low cycle fatigue hardening/softening behavior of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-1.0 pct Cr-0.2 pct Mo-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel consisting of a wide lath martensite structure matrix and a narrow lath martensite-metastable retained austenite mixture was investigated. The steel exhibited notable fatigue hardening in the same way as TRIP-aided bainitic ferrite steel, although conventional martensitic steel such as SCM420 steel with the same tensile strength exhibited fatigue softening. The considerable fatigue hardening of this steel is believed to be associated mainly with the compressive internal stress that results from a difference in flow stress between the matrix and the martensite-austenite-like phase, with a small contribution from the strain-induced transformation and dislocation hardenings.

  10. Ablation of work hardening layers against stress corrosion cracking of stainless steel by repetitive femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Nishimura, Akihiko; Minehara, Eisuke J.; Tsukada, Takashi; Kikuchi, Masahiko; Nakano, Junichi

    2004-10-01

    Femtosecond laser pulses successfully ablated the work hardening layers on SUS316L used in boiling water reactors. The measurement of hardness inside the material clarified this new technique to reduce the risk of Stress Corrosion Cracking.

  11. Laser Welding of Coated Press-hardened Steel 22MnB5

    NASA Astrophysics Data System (ADS)

    Siltanen, Jukka; Minkkinen, Ari; Järn, Sanna

    The press-hardening process is widely used for steels that are used in the automotive industry. Using ultra-high-strength steels enables car manufacturers to build lighter, stronger, and safer vehicles at a reduced cost and generating lower CO2 emissions. In the study, laser welding properties of the coated hot stamped steel 22BMn5 were studied. A constant 900 °C temperature was used to heat the steel plates, and two different furnace times were used in the press-hardening, being 300 and 740 seconds. Some of the plates were shot blasted to see the influence of the partly removed oxide layer on the laser welding and quality. The welding set-up, welding, and testing of the weld specimens complied with the automotive testing code SEP 1220.

  12. Laser Surface Hardened Patterns for Increased Ballistic Protection

    DTIC Science & Technology

    1983-04-01

    dictate the severity of quench. In other words, unique martensitic/ bainitic microstructures, which cannot be developed by the conventional heat...alloy composition and the metallurgical conditions produced by the laser (finer grain size and martensitic/ bainitic phase) could be expected to lower

  13. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Hardening of aluminium by YAG : Nd laser radiation with an average power of 0.8 kW

    NASA Astrophysics Data System (ADS)

    Kovsh, Ivan B.; Strekalova, M. S.

    1994-02-01

    An investigation is reported of the effects of a surface heat treatment of aluminium by a YAG : Nd laser beam with a power up to 0.8 kW. In particular, a study was made of the influence of the treatment conditions on the microhardness, as well as on the residual stresses and their sign in hardened surface layers of aluminium. The efficiency of aluminium hardening by radiation from a cw YAG : Nd laser was found to be considerably higher than in the case of a cw CO2 laser.

  14. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.

    PubMed

    Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

    2011-05-01

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. Copyright © 2010 Elsevier B.V. All rights reserved.

  15. Effect Of Laser Hardening On Microstructure And Wear Resistance In Medium. Carbon/Chromium Steels

    NASA Astrophysics Data System (ADS)

    Kusinski, Jan; Thomas, Gareth

    1986-11-01

    Metallographical (optical, TEM, SEM), spectroscopic, abrasive wear resistance and microhardness investiga-tions of Fe/Cr/Mn/C steels heat-treated by a continuous CO2 laser are described. Laser hardening resulted in wear resistance of 1.4 - 1.6 times better than that of conventionally hardened steels. Laser melting followed by rapid solidification allows formation of a solidified layer with high wear resistance only when the scanning velocity and mass of the samples were sufficient to realize high cooling rates. The variations in the wear resistance and microhardness with distance from the heated surface were similar. The grain refinement caused by rapid laser-heating and high stresses induced during cooling create essentially fine, highly dislocated lath and internally twinned martensites with some amount of stable, interlath retained austenite. This structure has in turn beneficial effects on wear resistance, and toughness. Laser-heat treatment for deep melting of the surface layers of the steels shows only a small improvement in wear resistance. Such heat-treatment results in delta ferrite retention (10Cr steel) and chromium segregation to cell-boundaries.

  16. Diagnostics hardening for harsh environment in Laser Megajoule (invited).

    PubMed

    Bourgade, J L; Marmoret, R; Darbon, S; Rosch, R; Troussel, P; Villette, B; Glebov, V; Shmayda, W T; Gomme, J C; Le Tonqueze, Y; Aubard, F; Baggio, J; Bazzoli, S; Bonneau, F; Boutin, J Y; Caillaud, T; Chollet, C; Combis, P; Disdier, L; Gazave, J; Girard, S; Gontier, D; Jaanimagi, P; Jacquet, H P; Jadaud, J P; Landoas, O; Legendre, J; Leray, J L; Maroni, R; Meyerhofer, D D; Miquel, J L; Marshall, F J; Masclet-Gobin, I; Pien, G; Raimbourg, J; Reverdin, C; Richard, A; Rubin de Cervens, D; Sangster, C T; Seaux, J P; Soullie, G; Stoeckl, C; Thfoin, I; Videau, L; Zuber, C

    2008-10-01

    The diagnostic designs for the Laser Megajoule (LMJ) will require components to operate in environments far more severe than those encountered in present facilities. This harsh environment will be induced by fluxes of neutrons, gamma rays, energetic ions, electromagnetic radiations, and, in some cases, debris and shrapnel, at levels several orders of magnitude higher than those experienced today on existing facilities. The lessons learned about the vulnerabilities of present diagnostic parts fielded mainly on OMEGA for many years, have been very useful guide for the design of future LMJ diagnostics. The present and future LMJ diagnostic designs including this vulnerability approach and their main mitigation techniques will be presented together with the main characteristics of the LMJ facility that provide for diagnostic protection.

  17. Diagnostics hardening for harsh environment in Laser Megajoule (invited)

    SciTech Connect

    Bourgade, J. L.; Marmoret, R.; Darbon, S.; Rosch, R.; Troussel, P.; Villette, B.; Aubard, F.; Baggio, J.; Bazzoli, S.; Bonneau, F.; Boutin, J. Y.; Caillaud, T.; Chollet, C.; Combis, P.; Disdier, L.; Gazave, J.; Girard, S.; Gontier, D.; Jacquet, H. P.; Jadaud, J. P.

    2008-10-15

    The diagnostic designs for the Laser Megajoule (LMJ) will require components to operate in environments far more severe than those encountered in present facilities. This harsh environment will be induced by fluxes of neutrons, gamma rays, energetic ions, electromagnetic radiations, and, in some cases, debris and shrapnel, at levels several orders of magnitude higher than those experienced today on existing facilities. The lessons learned about the vulnerabilities of present diagnostic parts fielded mainly on OMEGA for many years, have been very useful guide for the design of future LMJ diagnostics. The present and future LMJ diagnostic designs including this vulnerability approach and their main mitigation techniques will be presented together with the main characteristics of the LMJ facility that provide for diagnostic protection.

  18. Improved manufacturing techniques for RF and laser hardening of missile domes. Phase I. Technical report

    SciTech Connect

    Pawlewicz, W.T.; Mann, I.B.; Martin, P.M.; Hays, D.D.; Graybeal, A.G.

    1982-07-01

    This report summarizes key results and accomplishements during the first year of a Manufacturing Methods and Technology project to adapt an existing Pacific Northwest Laboratory (PNL) optical coating capability developed for high-power fusion-laser applications to the case of rf and laser hardening of plastic missile domes used by the US Army (MICOM). The primary objective of the first year's work was to demonstrate rf hardening of Hellfire and Copperhead 1.06-micron missile domes by use of transparent conductive Indium Tin Oxide (ITO) coatings. The project thus involved adaptation of a coating material and process developed for flat glass components used in fusion lasers to the case of hemispherical or conical heat-sensitive plastic domes used on laser-guided missiles. Specific ITO coating property goals were an electrical sheet resistance of 10 Ohms/square, a coated-dome transmission of 80% or more at 1.06 micron wavelength (compared to 90% for a bare dome), and good adhesion. The sheet resistance goal of 10 Ohms/square was expected to result in an rf attenuation of 30 dB at the frequencies of importance.

  19. Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening

    NASA Astrophysics Data System (ADS)

    Xia, Weiguang; Li, Lei; Wei, Yanpeng; Zhao, Aimin; Guo, Yacong; Huang, Chenguang; Yin, Hongxiang; Zhang, Lingchen

    2016-04-01

    Laser shock peening (LSP) is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts. Cr5Mo1V steel exhibits a gradient hardened layer after a LSP process. A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer. Assuming a linearly gradient distribution of impact toughness, the parameters controlling the impact toughness of the gradient hardened layer were given. The influences of laser power densities and the number of laser shots on the impact toughness were investigated. The impact toughness of the laser peened layer improves compared with an untreated specimen, and the impact toughness increases with the laser power densities and decreases with the number of laser shots. Through the fracture morphology analysis by a scanning electron microscope, we established that the Cr5Mo1V steel was fractured by the cleavage fracture mechanism combined with a few dimples. The increase in the impact toughness of the material after LSP is observed because of the decreased dimension and increased fraction of the cleavage fracture in the gradient hardened layer.

  20. Phase transformations and age-hardening behaviors related to Au3Cu in Au-Cu-Pd alloys.

    PubMed

    Winn, H; Udoh, K; Tanaka, Y; Hernandez, R I; Takuma, Y; Hisatsune, K

    1999-09-01

    Phase transformation behaviors in Au-Cu-Pd alloys were investigated by means of electrical resistivity measurements, hardness tests, X-ray diffraction and transmission electron microscopy. Anisothermal and isothermal annealing were performed. Two types of phase transformations were found, namely related to the single phase of Au3Cu and the coexistent phase of Au3Cu and AuCu I. The latter produced more remarkable hardening than the former. Hardening was brought about by the antiphase domain size effect of Au3Cu ordered phase in the single phase and by the formation of AuCu I ordered phase in the Au3Cu ordered matrix. There are three modes of phase transformation in the coexistent region depending on the composition. Each sequence is discussed.

  1. Laser treatment of powder high-speed steels with prior vacuum hardening and surface impregnation

    NASA Astrophysics Data System (ADS)

    Tarasov, A. N.

    2000-02-01

    Laser treatment of powder steels R0M6F3-MP, R6M5-MP, and R6M5-P preliminarily subjected to vacuum quenching or vacuum cyanidation with quenching promotes the formation of surface layers having an elevated wear resistance under contact-abrasive action, for example, in machining ceramic and refractory heat-resistant materials or under the surface action of ion-plasma jets of a high specific power. The structure of laser-hardened surface layers consists of pseudo-acicular martensite and an elevated amount of finely dispersed carbides, which prevents spalling and chipping of thin functional edges in blades for continuous machining under cyclic thermal loads.

  2. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Surface hardening of steels with a strip-shaped beam of a high-power CO2 laser

    NASA Astrophysics Data System (ADS)

    Dubovskii, P. E.; Kovsh, Ivan B.; Strekalova, M. S.; Sisakyan, I. N.

    1994-12-01

    A comparative analysis was made of the surface hardening of steel 45 by high-power CO2 laser beams with a rectangular strip-like cross section and a traditional circular cross section. This was done under various conditions. The treatment with the strip-like beam ensured a higher homogeneity of the hardened layer and made it possible to increase the productivity by a factor of 2-4 compared with the treatment by a beam of the same power but with a circular cross section.

  3. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  4. Unveiling the Origin of Work Hardening Behavior in an Ultrafine-Grained Manganese Transformation-Induced Plasticity Steel by Hydrogen Investigation

    NASA Astrophysics Data System (ADS)

    Zhu, Xu; Li, Wei; Zhao, Hongshan; Han, Qihang; Wang, Li; Jiao, Huisheng; Jin, Xuejun

    2016-09-01

    To reveal the origin of work hardening behavior in an ultrafine-grained manganese transformation-induced plasticity (TRIP) steel, specific experiments were designed with the assistance of hydrogen. Although the effect of hydrogen on the austenite transformation was negligible, the work hardening rate ( Θ) was apparently reduced for hydrogenated samples, indicating that TRIP effect cannot account for the high Θ alone. The collaborative effect of dislocation accumulation in ferrite and austenite transformation is proposed to explain the responsible mechanism.

  5. Effect of laser shot peening on precipitation hardened aluminum alloy 6061-T6 using low energy laser

    NASA Astrophysics Data System (ADS)

    Sathyajith, S.; Kalainathan, S.

    2012-03-01

    Mechanical properties of engineering material can be improved by introducing compressive residual stress on the material surface and refinement of their microstructure. Variety of mechanical process such as shot peening, water jet peening, ultrasonic peening, laser shot peening were developed in the last decades on this contrast. Among these, lasers shot peening emerged as a novel industrial treatment to improve the crack resistance of turbine blades and the stress corrosion cracking (SCC) of austenic stainless steel in power plants. In this study we successfully performed laser shot peening on precipitation hardened aluminum alloy 6061-T6 with low energy (300 mJ, 1064 nm) Nd:YAG laser using different pulse densities of 22 pulses/mm 2 and 32 pulses/mm 2. Residual stress evaluation based on X-ray diffraction sin 2 ψ method indicates a maximum of 190% percentage increase on surface compressive stress. Depth profile of micro-hardness shows the impact of laser generated shock wave up to 1.2 mm from the surface. Apart from that, the crystalline size and micro-strain on the laser shot peened surfaces have been investigated and compared with the unpeened surface using X-ray diffraction in conjunction with line broadening analysis through the Williamson-Hall plot.

  6. Laser quench hardening of steel: Effects of superimposed elastic pre-stress on the hardness and residual stress distribution

    NASA Astrophysics Data System (ADS)

    Meserve, Justin

    Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.

  7. Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

    2014-12-01

    The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

  8. Studies of a laser/nuclear thermal-hardened body armor. Final report, 31 Jan 91-30 Sep 91

    SciTech Connect

    Misconi, N.Y.; Caldarella, G.J.; Roach, J.F.

    1992-08-01

    The problem of laser/nuclear hardening of body armors and other applications, such as rigid wall, etc, has been investigated in this study. Earlier results from studies of hardening against space systems, which were supported by the Air Force Office of Scientific Research (AFOSR) and carried out by the Principal Investigator during 1984 to 1989 are summarized. The concepts of particle layer and photon multiple scattering inside the layers were utilized in developing a laser shield to protect against laser weapons in the 0.22 to 2.4 micrometer region of the spectrum. Protection against the threats from C02 laser weapons are addressed, and the development of a protective shield is detailed. It is now possible to apply a coating that will protect against laser/nuclear threats and reduction of solar loads for 0.22 to 16 micrometers of the spectrum. Applications are expected for rigid walls (Army containers), human body armor, thermal jackets for military hardware, etc. Finally, a mathematical model was created to help predict how the laser hardening material will behave under specific constraints that have not yet been tested in the laboratory. Also, this model can be used to extrapolate the performance of similar materials/coatings in the mid- to far-infrared wavelengths and also predict the broadband performance.

  9. Real-time monitoring of laser surface hardening of ferrous alloys.

    SciTech Connect

    Xu, Z.; Leong, K. H.; Reed, C. B.

    1999-09-30

    An infrared process monitor was used to monitor in real-time the infrared emissions during laser surface hardening of gray cast iron and 1045 steel. The signal from the monitor was correlated with the hardness and case depth of the laser-treated tracks. Test data show that a linear relationship exists between the monitor output DC level voltage and hardness up to the maximum hardness possible and also between the monitor output DC level voltage and case depth. This simple relationship of the monitor voltage signal with hardness and case depth makes it easy to monitor process hardness, case depth and quality. A calibration test on prototypic material can be used to determine at what voltage level melting occurs and the heat treating process hardness and case depth can be monitored easily by setting an upper and lower bound for the voltage signal. The monitor is also capable of tracking changes in surface quality or flatness of the part that is being treated.

  10. Prediction of Phase Transformation and Hardness Distribution of AISI 1045 Steel After Spot Continual Induction Hardening

    NASA Astrophysics Data System (ADS)

    Zhu, Shengxiao; Wang, Zhou; Qin, Xunpeng; Mao, Huajie; Gao, Kai

    2015-10-01

    An numerical and experimental study of spot continual induction hardening (SCIH) for AISI 1045 steel was carried out to gain a better understanding of this non-stationary and transverse flux induction hardening treatment. The SCIH device was set up by assembling the single-turn coil inductor to a five-axis cooperating computer numerical control system. The influence of inductor velocity, input current, and quenching medium on temperature field was estimated via the SCIH model, and the simulated micro-hardness and microstructure were validated by experimental verification. The heating delay phenomenon appearing in the SCIH process had been analyzed.

  11. Impact properties and hardening behavior of laser and electron-beam welds of V-4Cr-4Ti

    SciTech Connect

    Chung, H.M.; Strain, R.V.; Tsai, H.C.; Park, J.H.; Smith, D.L.

    1996-10-01

    The authors are conducting a program to develop an optimal laser welding procedure that can be applied to large-scale fusion-reactor structural components to be fabricated from vanadium-base alloys. Results of initial investigation of mechanical properties and hardening behavior of laser and electron-beam (EB) welds of the production-scale heat of V-4Cr-4Ti (500-kg Heat 832665) in as-welded and postwelding heat-treated (PWHT) conditions are presented in this paper. The laser weld was produced in air using a 6-kW continuous CO{sub 2} laser at a welding speed of {approx}45 mm/s. Microhardness of the laser welds was somewhat higher than that of the base metal, which was annealed at a nominal temperature of {approx}1050{degrees}C for 2 h in the factory. In spite of the moderate hardening, ductile-brittle transition temperatures (DBTTs) of the initial laser ({approx}80{degrees}C) and EB ({approx}30{degrees}C) welds were significantly higher than that of the base metal ({approx}{minus}170{degrees}C). However, excellent impact properties, with DBTT < {minus}80{degrees}C and similar to those of the base metal, could be restored in both the laser and EB welds by postwelding annealing at 1000{degrees}C for 1 h in vacuum.

  12. Thermal relaxation behavior of residual stress in laser hardened 17-4PH steel after shot peening treatment

    NASA Astrophysics Data System (ADS)

    Wang, Zhou; Chen, Yanhua; Jiang, Chuanhai

    2011-09-01

    In order to investigate the residual stress relaxations of shot peened layer, isothermal annealing treatments were carried out on tempered and laser hardened 17-4PH steel after shot peening with different temperatures from 300 °C to 600 °C. The results showed that the residual stresses were relaxed in the whole deformation layer especially under higher temperature. The maximum rates of stress relaxation took place at the initial stage of annealing process in all conditions. The relaxation process during isothermal annealing could be described by Zener-Wert-Avrami function. The thermal stability of residual stress in tempered 17-4PH was higher than that in laser hardened 17-4PH as well as that in α-iron, which was due to the pinning effects of ɛ-Cu precipitates on the dislocation movement. As massive ɛ-Cu precipitates formed in the temperature about 480 °C, the activation enthalpies for stress relaxation in laser hardened 17-4PH were the same as that in tempered 17-4PH in the conditions of isothermal annealing temperatures of 500 °C and 600 °C.

  13. Thermostructural Analysis of Carbon Cloth Phenolic Material Tested at the Laser Hardened Material Evaluation Laboratory

    NASA Technical Reports Server (NTRS)

    Clayton, J. Louie; Ehle, Curt; Saxon, Jeff (Technical Monitor)

    2002-01-01

    RSRM nozzle liner components have been analyzed and tested to explore the occurrence of anomalous material performance known as pocketing erosion. Primary physical factors that contribute to pocketing seem to include the geometric permeability, which governs pore pressure magnitudes and hence load, and carbon fiber high temperature tensile strength, which defines a material limiting capability. The study reports on the results of a coupled thermostructural finite element analysis of Carbon Cloth Phenolic (CCP) material tested at the Laser Hardened Material Evaluation Laboratory (the LHMEL facility). Modeled test configurations will be limited to the special case of where temperature gradients are oriented perpendicular to the composite material ply angle. Analyses were conducted using a transient, one-dimensional flow/thermal finite element code that models pore pressure and temperature distributions and in an explicitly coupled formulation, passes this information to a 2-dimensional finite element structural model for determination of the stress/deformation behavior of the orthotropic fiber/matrix CCP. Pore pressures are generated by thermal decomposition of the phenolic resin which evolve as a multi-component gas phase which is partially trapped in the porous microstructure of the composite. The nature of resultant pressures are described by using the Darcy relationships which have been modified to permit a multi-specie mass and momentum balance including water vapor condensation. Solution to the conjugate flow/thermal equations were performed using the SINDA code. Of particular importance to this problem was the implementation of a char and deformation state dependent (geometric) permeability as describing a first order interaction between the flow/thermal and structural models. Material property models are used to characterize the solid phase mechanical stiffness and failure. Structural calculations were performed using the ABAQUS code. Iterations were made

  14. Double Sided Irradiation for Laser-assisted Shearing of Ultra High Strength Steels with Process Integrated Hardening

    NASA Astrophysics Data System (ADS)

    Brecher, Christian; Emonts, Michael; Eckert, Markus; Weinbach, Matthias

    Most small or medium sized parts produced in mass production are made by shearing and forming of sheet metal. This technology is cost effective, but the achievable quality and geometrical complexity are limited when working high and highest strength steel. Based on the requirements for widening the process limits of conventional sheet metal working the Fraunhofer IPT has developed the laser-assisted sheet metal working technology. With this enhancement it is possible to produce parts made of high and highest strength steel with outstanding quality, high complexity and low tool wear. Additionally laser hardening has been implemented to adjust the mechanical properties of metal parts within the process. Currently the process is limited to lower sheet thicknesses (<2 mm) to maintain short cycle times. To enable this process for larger geometries and higher sheet thicknesses the Fraunhofer IPT developed a system for double sided laser-assisted sheet metal working within progressive dies.

  15. LASER APPLICATIONS AND OTHER TOPICS IN LASER TECHNOLOGY: Combination of laser quenching and tempering for hardening tool steels

    NASA Astrophysics Data System (ADS)

    Gureev, D. M.; Mednikov, S. I.

    1988-08-01

    A study was made of the influence of laser quenching and tempering on the structural phase composition and hardness of surface layers of KhVG and ÉP657 (R12M3F2K8) tool steels subjected to volume quenching and tempering. It was found to be advisable, in addition to performing laser quenching, to carry out laser tempering before and after in order to take into account the initial state of the material and to obtain stable results on improvements in the wear resistance of cutting and stamping tools.

  16. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Structure and properties of aluminum-silicon alloys hardened locally by concentrated energy sources

    NASA Astrophysics Data System (ADS)

    Voronin, S. V.; Gureev, D. M.; Zolotarevskiĭ, A. V.

    1990-06-01

    An investigation was made of some characteristics of the formation of the structure of Al-Si alloys containing 10%, 12% and 20 % Si, and also of the commercial alloy V124 under conditions of surface fusion by laser-arc and laser sources. It was established that as a result of local fusion there was a change in the silicon deposition morphology, the α solid solution became oversaturated, and the eutectic point was shifted toward high silicon concentrations. It was found that the hardened layer retained its high hardness when treated at temperatures up to 250 °C. The commercial alloy V124 was used as an example to show that an alloyed layer with a controlled silicon concentration can be obtained on the surface by using a laser-arc or laser source.

  17. Characterization of the thermal performance of high heat flux systems at the Laser Hardened Materials Evaluation Laboratory

    NASA Astrophysics Data System (ADS)

    Lander, Michael L.; Bagford, John O.; North, Mark T.; Hull, Robert J.

    1996-11-01

    When developing a high-heat-flux system, it is important to be able to test the system under relevant thermal conditions and environmental surroundings. Thermal characterization testing is best performed in parallel with analysis and design. This permits test results to impact materials selection and systems design decisions. This paper describes the thermal testing and characterization capabilities of the Laser Hardened Materials Evaluation Laboratory located at Wright-Patterson Air Force Base, Ohio. The facility features high-power carbon dioxide (CO2$ and neodymium:glass laser systems that can be teamed with vacuum chambers, wind tunnels, mechanical loading machines and/or ambient test sites to create application-specific thermal and environmental conditions local to the material sample or system. Representative results from recently conducted test series are summarized. The test series described demonstrate the successful use of a high power CO2 laser paired with environment simulation capability to : 1) simulate the expected in-service heat load on a newly developed heat transfer device to ensure its efficient operation prior to design completion, 2) simulate the heat load expected for a laser diode array cooler, 3) produce thermal conditions needed to test a radiator concept designed for space-based operation, and 4) produce thermal conditions experienced by materials use din solid rocket motor nozzles. Test diagnostics systems used to collect thermal and mechanical response data from the test samples are also described.

  18. Transverse intensity transformation by laser amplifiers

    NASA Astrophysics Data System (ADS)

    Litvin, Igor A.; King, Gary; Collett, Oliver J. P.; Strauss, Hencharl J.

    2015-03-01

    Lasers beams with a specific intensity profile such as super-Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping. We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.

  19. Precipitation Hardening of Laser-Surfaced Layer of Maraging Alloy at the Surface of Steel 3Kh3M3F

    NASA Astrophysics Data System (ADS)

    Stavrev, D. S.; Shcherbakov, V. S.

    2016-09-01

    The structure and fracture behavior of a layer of maraging alloy deposited by laser surfacing on steel 3Kh3M3F is studied in the initial condition and after precipitation hardening at 550 and 600°C. Microhardness is measured in layer cross sections, and fractures after surfacing and aging are analyzed in an electron microscope.

  20. AISI/DOE Technology Roadmap Program: Development of Appropriate Resistance Spot Welding Practice for Transformation-Hardened Steels

    SciTech Connect

    Wayne Chuko; Jerry Gould

    2002-07-08

    This report describes work accomplished in the project, titled ''Development of Appropriate Resistance Spot Welding Practice for Transformation-Hardened Steels.'' The Phase 1 of the program involved development of in-situ temper diagrams for two gauges of representative dual-phase and martensitic grades of steels. The results showed that tempering is an effective way of reducing hold-time sensitivity (HTS) in hardenable high-strength sheet steels. In Phase 2, post-weld cooling rate techniques, incorporating tempering, were evaluated to reduce HTS for the same four steels. Three alternative methods, viz., post-heating, downsloping, and spike tempering, for HTS reduction were investigated. Downsloping was selected for detailed additional study, as it appeared to be the most promising of the cooling rate control methods. The downsloping maps for each of the candidate steels were used to locate the conditions necessary for the peak response. Three specific downslope conditions (at a fix ed final current for each material, timed for a zero-, medium-, and full-softening response) were chosen for further metallurgical and mechanical testing. Representative samples, were inspected metallographically, examining both local hardness variations and microstructures. The resulting downslope diagrams were found to consist largely of a C-curve. The softening observed in these curves, however, was not supported by subsequent metallography, which showed that all welds made, regardless of material and downslope condition, were essentially martensitic. CCT/TTT diagrams, generated based on microstructural modeling done at Oak Ridge National Laboratories, showed that minimum downslope times of 2 and 10 s for the martensitic and dual-phase grades of steels, respectively, were required to avoid martensite formation. These times, however, were beyond those examined in this study. These results show that downsloping is not an effective means of reducing HTS for production resistance spot

  1. Bifluorophores - radiation transformers of excimeric lasers

    SciTech Connect

    Samsonova, L.C.; Afanasiadi, L.S.; Degtyarenko, K.M.; Kopylova, T.N.; Tarasenko, V.F.; Turr, I.N.

    1985-12-01

    This article describes the method of transformation of radiation as the result of intramolecular energy transfer in molecules called bifluorophores. The aim of this work was to study the spectral luminescent properties of oxazole, its equimolar mixtures and bifluorophore systems based on them, and also the possibilities of transformation using them of the radiation of the XeCl laser into the blue-green region of the spectrum. The power of the laser reached 1 MW, the pulse duration at the half-height was 20-30 nsec, and the pulse repetition frequency was 1 Hz. The generation properties of the molecules in the solutions were studied on an apparatus described in detail. A lateral variant of the excitation was used, and the resonator was formed by a dull mirror and the surface of the cuvette. The spectral-luminescent properties were studied on a Specord UV-VIS spectrophotometer and a fluorimeter mounted on the base of a SF4A monochromator.

  2. Ordering Transformation and Age Hardening in a Ni-Cr-W Superalloy

    NASA Astrophysics Data System (ADS)

    Gao, Xiangyu; Hu, Rui; Li, Xiaolin; Luo, Gongliao; Li, Jinshan; Fu, Hengzhi

    2016-12-01

    The microstructural changes occurring in a Ni-Cr-W superalloy during prolonged exposure to proper temperature have been investigated using transmission electron microscopy. It is demonstrated that nanometer-sized C11b (Pt2Mo-type) and DO22 superlattices can precipitate in the Ni-Cr-W alloy by means of a simple aging treatment at temperatures varying in the range of 773 K to 973 K (500 °C to 700 °C). The mechanism of transformation to long-range order has been revealed to accord with continuous mode based on transmission electron microscopy results and variation trend in Vickers microhardness. No signs of overaging and coarsening of C11b and DO22 phases with further aging have been found, which indicates that both of them have a high-thermal stability. The orientation relationships and interfaces between C11b/DO22 precipitates and Ni-based matrix have been investigated by high-resolution transmission electron microscopy, and the results reveal that the interfaces between C11b/DO22 precipitates and surrounding matrix are coherent at the atomic scale. Because of the high-density nanometer-sized C11b/DO22 precipitates, the microhardness of the alloy is improved remarkably.

  3. Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Cai, Zhipeng; Feng, Zhenhua; Wang, Gang

    2015-12-01

    Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

  4. Practical aspects of systems hardening

    SciTech Connect

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system.

  5. Martensitic transformations in laser processed coatings

    SciTech Connect

    Burg, M. van den; De Hosson, J.T.M. . Dept. of Applied Physics)

    1993-09-01

    This paper concentrates on laser coating of Fe-22 wt% Cr and a duplex steel SAF2205 by injecting Cr[sub 2]O[sub 3] powder into the melt pool. In particular the work focuses on the stabilization of high temperature distorted spinel phases due to the high quench rates involved as well as on the a quantitative crystallographic analysis of the resulting morphologies. The microstructure observed in TEM indicates that the material does not solidify in the distorted spinel structure. The presence of a small amount of cubic (Fe, Cr)-spinel suggests that the distorted spinel in fact might be nucleated from the cubic spinel phase. The plate like morphology of the distorted spinel phase in combination with the twinned internal structure of the plates put forward the idea that the transformation might be martensitic. Martensitic calculations executed with the lattice parameters of the cubic and distorted (Fe, Cr)-spinel phases are in excellent agreement with the experimental data confirming that the transformation might be martensitic indeed.

  6. IR laser-induced protein crystal transformation

    SciTech Connect

    Kiefersauer, Reiner Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-05-01

    A novel method and the associated instrumentation for improving crystalline order (higher resolution of X-ray diffraction and reduced mosaicity) of protein crystals by precisely controlled heating is demonstrated. Crystal transformation is optically controlled by a video system. A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress.

  7. Hardening: Australian for Transformation

    DTIC Science & Technology

    2004-01-01

    core land force capabilities and turned the Army into little more than a strategic goalkeeper .20 Four key defense policy documents outline the...of war. History has proved that a nation’s approach to future warfare significantly influences its ability to effect change. The Germans reaction to...systems proved highly effective at engaging and destroying the Iraqis. But speed and information superiority became less decisive when combat

  8. Laser surface pretreatment of 100Cr6 bearing steel - Hardening effects and white etching zones

    NASA Astrophysics Data System (ADS)

    Buling, Anna; Sändker, Hendrik; Stollenwerk, Jochen; Krupp, Ulrich; Hamann-Steinmeier, Angela

    2016-08-01

    In order to achieve a surface pretreatment of the bearing steel 100Cr6 (1-1.5 wt.% Cr) a laser-based process was used. The obtained modification may result in an optimization of the adhesive properties of the surface with respect to an anticorrosion polymer coating on the basis of PEEK (poly-ether-ether-ketone), which is applied on the steel surface by a laser melting technique. This work deals with the influence of the laser-based pretreatment regarding the surface microstructure and the micro-hardness of the steel, which has been examined by scanning electron microscopy (SEM), light microscopy and automated micro-hardness testing. The most suitable parameter set for the laser-based pretreatment leads to the formation of very hard white etching zones (WEZ) with a thickness of 23 μm, whereas this pretreatment also induces topographical changes. The occurrence of the white etching zones is attributed to near-surface re-austenitization and rapid quenching. Moreover, dark etching zones (DEZ) with a thickness of 32 μm are found at the laser path edges as well as underneath the white etching zones (WEZ). In these areas, the hardness is decreased due to the formation of oxides as a consequence of re-tempering.

  9. Application of Laser Treatment for Hardening Parts of Gas Turbine Engines from Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Girzhon, V. V.; Ovchinnikov, A. V.

    2017-03-01

    X-ray diffraction analysis and light microscopy are used to study the structure of surface layers of helically extruded specimens of titanium alloy VT25U after laser fusion of the surface. It is shown that the rates of cooling of the melt promote formation of a martensitic α″-phase in the zone of laser fusion and of a submicrocrystalline microstructure. The microhardness in the zone of fusion of the initial specimens exceeds the microhardness of the specimens after the extrusion.

  10. Geometrical Transformation of Linear Diode-Laser Arrays for Longitudinal Pumping of Solid-State Lasers

    DTIC Science & Technology

    1992-05-26

    of Nd:YAG crystal vs incident power from the geometrically transformed laser - diode array. 24 12 TEM00 output power from Nd:YAG laser when pumped by n...MASSACHUSETTS INSTITUTE OF TECHNOLOGY LINCOLN LABORATORY GEOMETRICAL TRANSFORMATION OF LINEAR DIODE - LASER ARRAYS FOR LONGITUDINAL PUMPING OF SOLID-STATE...Photograph of pump spot at the lens focal plane. 22 10 Curvature of the laser - diode array emitting facet. 23 11 TEMOO output power from 1.06 pm transition

  11. IR laser-induced protein crystal transformation

    PubMed Central

    Kiefersauer, Reiner; Grandl, Brigitte; Krapp, Stephan; Huber, Robert

    2014-01-01

    A method and the design of instrumentation, and its preliminary practical realisation, including test experiments, with the object of inducing phase changes of biomolecular crystals by controlled dehydration through heating with infrared (IR) light are described. The aim is to generate and select crystalline phases through transformation in the solid state which have improved order (higher resolution in X-ray diffraction experiments) and reduced mosaic spread (more uniformly aligned mosaic blocks) for diffraction data collection and analysis. The crystal is heated by pulsed and/or constant IR laser irradiation. Loss of crystal water following heating and its reabsorption through equilibration with the environment is measured optically by a video system. Heating proved superior to traditional controlled dehydration by humidity change for the test cases CODH (carbon monoxide dehydrogenase) and CLK2 (a protein kinase). Heating with IR light is experimentally simple and offers an exploration of a much broader parameter space than the traditional method, as it allows the option of varying the rate of phase changes through modification of the IR pulse strength, width and repeat frequency. It impacts the crystal instantaneously, isotropically and homogeneously, and is therefore expected to cause less mechanical stress. PMID:24816092

  12. Laser ablation/Fourier transform mass spectrometry of polymers

    NASA Astrophysics Data System (ADS)

    Creasy, William R.; Brenna, J. T.

    1989-10-01

    Laser ablation/ionization followed by Fourier transform mass spectrometry is used to identify and characterize polymers. The mass spectra of several polymers are discussed, including polyimide, polyamic acid, Dupont Tefzel, and polyphenylene sulfide.

  13. Laser and Fourier Transform Spectroscopy of Novel Propellant Molecules

    DTIC Science & Technology

    1990-07-01

    Classification) 63 Laser and Fourier Transform Spectroscopy of Novel Propellant Molecules (U) 12. PERSONAL AUTHOR(S) Bernath, Peter F. 13a. TYPE OF REPORT...Publications (Supported by F04611-87-K-0020) 1. C.R. Brazier, P.F. Bernath, J.B. Burkholder and C.J. Howard, Fourier Transform Spectroscopy of the v3

  14. Analysis of Single-Event Effects in a Radiation-Hardened Low-Jitter PLL Under Heavy Ion and Pulsed Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Zhuojun; Lin, Min; Ding, Ding; Zheng, Yunlong; Sang, Zehua; Zou, Shichang

    2017-01-01

    A radiation-hardened low-jitter phase-locked loop (PLL) with a low-mismatch charge pump and a robust voltage-controlled oscillator is designed in a 130 nm PD-SOI process. In order to evaluate the overall response to single-event effects, the accumulated phase jitter has been put forward, which can exclude the inherent noise floor and accumulate all the radiation-induced noise. Then the single-event sensitivity of the proposed PLL is comprehensively analyzed by heavy ion and pulsed laser tests.

  15. Microstructure-Property Relationship in the Thermomechanically Processed C-Mn-Si-Nb-Al-(Mo) Transformation-Induced Plasticity Steels Before and After Prestraining and Bake Hardening Treatment

    NASA Astrophysics Data System (ADS)

    Timokhina, I. B.; Enomoto, M.; Miller, M. K.; Pereloma, E. V.

    2012-07-01

    The effect of prestraining and bake hardening (PS/BH) on the development of microstructures and mechanical properties in thermomechanically processed transformation-induced plasticity (TRIP) steels with additions of Nb, Mo, and Al was studied by atom probe tomography (APT) and transmission electron microscopy (TEM). An increase in number density and sizes of clusters and nanoscale precipitates was observed in both steels but was more significant in the Nb-Al-Mo steel than in the Nb-Al steel. This increase could be explained by the possible fast diffusion of Nb and Mo atoms at low temperatures, as was observed for surface diffusivity. The contributions of cluster strengthening and precipitation strengthening to the yield strength increment after PS/BH were estimated.

  16. LASERS IN MEDICINE: Structure of matrices for the transformation of laser radiation by biofractals

    NASA Astrophysics Data System (ADS)

    Angel'skii, O. V.; Ushenko, A. G.; Arkhelyuk, A. D.; Ermolenko, S. B.; Burkovets, D. N.

    1999-12-01

    The changes in the state of polarisation of laser radiation transformed by biofractal objects are examined. The orientational angular structure of the matrix elements of the operator representing the optical properties of biofractals with different morphological structures (mineralised collagen fibres and myosin bundles) is investigated. An optical model for the description of fractal laser fields under the conditions of single light scattering is proposed.

  17. The African Laser Centre: Transforming the Laser Community in Africa

    NASA Astrophysics Data System (ADS)

    Mtingwa, Sekazi

    2012-02-01

    We describe the genesis and programs of the African Laser Centre (ALC), which is an African nonprofit network of laser users that is based in Pretoria, South Africa. Composed of over thirty laboratories from countries throughout the continent of Africa, the ALC has the mission of enhancing the application of lasers in research and education. Its programs include grants for research and training, equipment loans and donations, student scholarships, faculty grants for visits to collaborators' institutions, conferences, and technician training. A long-term goal of the ALC is to bring a synchrotron light source to Africa, most probably to South Africa. One highly popular program is the biennial conference series called the US-Africa Advanced Studies Institute, which is funded by the ALC in collaboration with the U.S. National Science Foundation and the International Center for Theoretical Physics in Trieste. The Institutes typically bring about thirty faculty and graduate students from the U.S. to venues in Africa in order to introduce U.S. and African graduate students to major breakthroughs in targeted areas that utilize lasers. In this presentation, we will summarize the ALC achievements to date and comment on the path forward.

  18. A Study of Phase and Structural Transformations of Hardened Low-Carbon Steel under Conditions of Multiple Intense Heat Effect

    NASA Astrophysics Data System (ADS)

    Panov, D. O.; Simonov, Yu. N.; Leont'ev, P. A.; Smirnov, A. I.; Zayats, L. Ts.

    2013-03-01

    The effect of conditions of rapid thermocycling treatment on phase transformations in heating and cooling and on the structure and mechanical properties of steel 12Kh2G2NMFT is studied. The dependence between the structural changes in thermocycling and the position of critical points Ac 1 and M s is determined.

  19. Hough Transform Based Corner Detection for Laser Beam Positioning

    SciTech Connect

    Awwal, A S

    2005-07-26

    In laser beam alignment in addition to detecting position, one must also determine the rotation of the beam. This is essential when a commissioning new laser beam for National Ignition Facility located at the Lawrence Livermore National Laboratory. When the beam is square, the positions of the corners with respect to one another provides an estimate of the rotation of the beam. This work demonstrates corner detection in the presence or absence of a second order non-uniform illumination caused by a spatial mask. The Hough transform coupled with illumination dependent pre-processing is used to determine the corner points. We show examples from simulated and real NIF images.

  20. Phase Transformation in Tantalum under Extreme Laser Deformation.

    PubMed

    Lu, C-H; Hahn, E N; Remington, B A; Maddox, B R; Bringa, E M; Meyers, M A

    2015-10-19

    The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. Molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).

  1. Phase transformation in tantalum under extreme laser deformation

    SciTech Connect

    Lu, C. -H.; Hahn, E. N.; Remington, B. A.; Maddox, B. R.; Bringa, E. M.; Meyers, M. A.

    2015-10-19

    The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. In conclusion, molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).

  2. Phase Transformation in Tantalum under Extreme Laser Deformation

    PubMed Central

    Lu, C.-H.; Hahn, E. N.; Remington, B. A.; Maddox, B. R.; Bringa, E. M.; Meyers, M. A.

    2015-01-01

    The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. Molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear). PMID:26478106

  3. Phase transformation in tantalum under extreme laser deformation

    DOE PAGES

    Lu, C. -H.; Hahn, E. N.; Remington, B. A.; ...

    2015-10-19

    The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centeredmore » cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. In conclusion, molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).« less

  4. Phase Transformation in Tantalum under Extreme Laser Deformation

    NASA Astrophysics Data System (ADS)

    Lu, C.-H.; Hahn, E. N.; Remington, B. A.; Maddox, B. R.; Bringa, E. M.; Meyers, M. A.

    2015-10-01

    The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. Molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).

  5. Laser induced structural transformation in chalcogenide based superlattices

    SciTech Connect

    Zallo, Eugenio Wang, Ruining; Bragaglia, Valeria; Calarco, Raffaella

    2016-05-30

    Superlattices made of alternating layers of nominal GeTe and Sb{sub 2}Te{sub 3} have been studied by micro-Raman spectroscopy. A structural irreversible transformation into ordered GeSbTe alloy is induced by high power laser light exposure. The intensity ratio of anti-Stokes and Stokes scattering under laser illumination gives a maximum average temperature in the sample of 177 °C. The latter is lower than the growth temperature and of 400 °C necessary by annealing to transform the structure in a GeSbTe alloy. The absence of this configuration after in situ annealing even up to 300 °C evidences an electronic excitation induced-transition which brings the system into a different and stable crystalline state.

  6. Mechanical properties and microstructure of 3D-printed high Co-Ni secondary hardening steel fabricated by laser melting deposition

    NASA Astrophysics Data System (ADS)

    Duan, Hui-ping; Liu, Xiao; Ran, Xian-zhe; Li, Jia; Liu, Dong

    2017-09-01

    The mechanical properties and microstructure of the 3D-printed high Co-Ni secondary hardening steel fabricated by the laser melting deposition technique was investigated using a material testing machine and electron microscopy. A microstructure investigation revealed that the samples consist of martensite laths, fine dispersed precipitates, and reverted austenite films at the martensite lath boundaries. The precipitates are enriched with Co and Mo. Because the sample tempered at 486°C has smaller precipitates and a higher number of precipitates per unit area, it exhibits better mechanical properties than the sample tempered at 498°C. Although the 3D-printed samples have the same phase constituents as AerMet 100 steel, the mechanical properties are slightly worse than those of the commercial wrought AerMet 100 steel because of the presence of voids.

  7. Analysis of dissolved C2H2 in transformer oils using laser Raman spectroscopy.

    PubMed

    Somekawa, Toshihiro; Kasaoka, Makoto; Kawachi, Fumio; Nagano, Yoshitomo; Fujita, Masayuki; Izawa, Yasukazu

    2013-04-01

    We have developed a laser Raman spectroscopy technique for assessing the working conditions of transformers by measuring dissolved C2H2 gas concentrations present in transformer oils. A frequency doubled Q-switched Nd:YAG laser (532 nm) was used as a laser source, and Raman signals at ~1972 cm(-1) originating from C2H2 gas dissolved in oil were detected. The results show that laser Raman spectroscopy is a useful alternative method for detecting transformer faults.

  8. Helium-neon laser treatment transforms fibroblasts into myofibroblasts.

    PubMed Central

    Pourreau-Schneider, N.; Ahmed, A.; Soudry, M.; Jacquemier, J.; Kopp, F.; Franquin, J. C.; Martin, P. M.

    1990-01-01

    The differentiation of myofibroblastic cells from normal human gingival fibroblasts in vitro has been established by transmission electron microscopy and quantitated by immunohistochemistry, using antigelsolin monoclonal antibodies. Untreated control cultures were compared to cultures exposed to Helium-Neon (He-Ne) laser irradiation. A direct and massive transformation of the cultured fibroblasts into myofibroblasts was observed as early as 24 hours after laser treatment, whereas control cultures were comprised of only resting fibroblasts and active fibroblasts. This in vitro induction of myofibroblasts may be analogous to that which occurs in vivo. Therefore we undertook a similar study using biopsies from gingival tissues after wisdom tooth extraction. Myofibroblasts were present in the connective tissue of laser-treated gums 48 hours after irradiation, but not in untreated contralateral control tissues. These data provide evidence that the primary biologic effect of the Helium-Neon laser on connective tissue is the rapid generation of myofibroblasts from fibroblasts. The induction of a phenotype with contractile properties may have clinical significance in the acceleration of the wound-healing process. Images Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 PMID:2372040

  9. Laser and Fourier-transform spectroscopy of KCa

    NASA Astrophysics Data System (ADS)

    Gerschmann, Julia; Schwanke, Erik; Pashov, Asen; Knöckel, Horst; Ospelkaus, Silke; Tiemann, Eberhard

    2017-09-01

    KCa was produced in a heat-pipe oven and its thermal emission spectrum around 8900 cm-1 was recorded with a high-resolution Fourier-transform spectrometer. In addition, many selected transitions of this spectrum between deeply bound vibrational levels of the X (1) 2Σ+ and (2) 2Σ+ states were studied using laser excitation to facilitate the assignment of the lines. The ground state is described for v''=0 -5 and the (2) 2Σ+ state for v'=0 -8 with rotational levels up to 175. For both states, Dunham coefficients, spin-rotation parameters, and potential energy curves are derived.

  10. Hardening of the arteries

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000171.htm Hardening of the arteries To use the sharing features on this page, please enable JavaScript. Hardening of the arteries, also called atherosclerosis, occurs when ...

  11. Laser induced structural phase transformation of cobalt oxides nanostructures.

    PubMed

    Ravindra, A V; Behera, B C; Padhan, P

    2014-07-01

    Face-centered-cubic (fcc) and hexagonal-close-packed (hcp) phases of cobalt monoxide (CoO) nanostructures are prepared using thermolysis route at the same reaction temperature 296 degrees C with synthetic approach conditions. These nanostructures show mixture of nearly spherical and nanoflake morphologies. The structural phases of these nanostructures transform to spinel-Co3O4 by application of heat or Raman excitation laser beam power. The absorbance spectra of fcc and hcp-CoO and Co3O4 nanostructures yield significantly higher values of band gap which can be explained by electron confinement. Such results provide new opportunities for optimizing and enhancing the properties and performance of cobalt oxide nanomaterial.

  12. Grazing incidence liquid metal mirrors (GILMM) for radiation hardened final optics for laser inertial fusion energy power plants

    SciTech Connect

    Moir, R W

    1999-06-30

    A thin film of liquid metal is suggested as a grazing incident liquid metal mirror (GILMM) for robust final optics of a laser inertial fusion energy (IFE) power plant. The amount of laser light the mirror can withstand, called the damage limit, of a sodium film 85{sup o} from normal is calculated to be 57 J/cm{sup 2} normal to the beam for a 20 ns pulse and 1.3 J/cm{sup 2} for a 10 ps pulse of 0.35 {micro}m light (2 m{sup 2} and 90 m{sup 2} of mirror area per 100 kJ of laser energy at 20 ns and 10 ps, respectively). Feasibility relies on keep the liquid surface flat to the required accuracy by a combination of polished substrate, adaptive (deformable) optics, surface tension and low Reynolds number, laminar flow in the film. The film's substrate must be polished to {+-} 0.015 pm. Then surface tension keeps the surface smooth over short distances (<10 mm) and low Reynolds number laminar flow keeps the surface smooth by keeping the film thickness constant to less than + 0.01 w over long distance >10 mm. Adaptive optics techniques keep. the substrate flat to within {+-} 0.06 pm over 100 mm distance and {+-}0.6 {micro}m over 1000 mm distances. The mirror can stand the x-ray pulse when located 30 m away from the microexplosions of nominal yield of 400 MJ (50 MJ of X rays) when Li is used but for higher atomic number liquids like Na there may be too high a temperature rise forcing use of other x-ray attenuation methods such as attenuation by xenon gas. The cumulative damage from neutrons causing warpage of the liquid film's substrate can be compensated by adaptive optics techniques giving the mirrors long life, perhaps 30 years. The GILMM should be applicable to both direct and indirect drive and pulse lengths appropriate to slow compression ({approx}20 ns) or fast ignition ({approx}10 ps). For direct drive laser beams near the poles (70{sup o}, where 90{sup o} is vertical), stable thin films become more challenging. Proof of concept experiments are needed to verify the

  13. An investigation of phase transformation and crystallinity in laser surface modified H13 steel

    NASA Astrophysics Data System (ADS)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2013-03-01

    This paper presents a laser surface modification process of AISI H13 tool steel using 0.09, 0.2 and 0.4 mm size of laser spot with an aim to increase hardness properties. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). X-ray diffraction analysis (XRD) was conducted to measure crystallinity of the laser-modified surface. X-ray diffraction patterns of the samples were recorded using a Bruker D8 XRD system with Cu K α ( λ=1.5405 Å) radiation. The diffraction patterns were recorded in the 2 θ range of 20 to 80°. The hardness properties were tested at 981 mN force. The laser-modified surface exhibited reduced crystallinity compared to the un-processed samples. The presence of martensitic phase was detected in the samples processed using 0.4 mm spot size. Though there was reduced crystallinity, a high hardness was measured in the laser-modified surface. Hardness was increased more than 2.5 times compared to the as-received samples. These findings reveal the phase source of the hardening mechanism and grain composition in the laser-modified surface.

  14. Evaluation of probe lasers employed in optical diagnostics for phase transformation of thin films during excimer laser crystallization

    NASA Astrophysics Data System (ADS)

    Kuo, Chil-Chyuan

    2008-06-01

    The stability and reliability of probe laser is an important factor affecting the inspection of the phase transformation process of Si thin films during excimer laser crystallization using in-situ time-resolved optical measurements. The changes in 2D intensity profile, peak power density, and beam wander of the commonly used helium-neon (He-Ne) and diode laser are investigated experimentally. It is found that the peak power density of He-Ne laser is higher than that of diode laser, while the total power of He-Ne laser is lower than that of diode laser. Although the instability in the peak power density of He-Ne laser will increase with increasing the operation time, the beam stability of He-Ne laser is better than that of diode laser. For long-time operation (>24 h) of optical measurements, the diode laser is a good candidate of probe laser. Conversely, the diode laser is suitable for the short-time operation (<24 h) of optical measurements because the beam-wander is higher than that of He-Ne laser.

  15. Case hardening of steel

    SciTech Connect

    Not Available

    1987-01-01

    The first chapter lays the groundwork for an understanding by covering absorption and diffusion of carbon, and the application of equilibrium data. Gas carburizing methods are presented, followed by other gaseous case hardening methods. Then, liquid case-hardening methods are discussed. Vacuum carburizing and pack carburizing are treated in a separate chapter. The second half of the volume deals with specific topics in relation to case hardening. First, heat-treatment considerations are presented, including chapters on cleaning and handling of parts, heat treatment, and furnaces and furnace parts and fixtures used in case hardening. The next chapter presents information on instrumentation and control the first section discussing temperature measurement and the second dealing with instrumentation for controlling carbonaceous atmospheres. Testing inspection and quality control are covered in sections detailing inspection and quality control, hardness testing of case-hardened parts, and methods of measuring case depth. The final chapter is an atlas of microstructures and macrostructures of case hardened parts.

  16. Laser Beam Processing - A Manufacturer's Viewpoint

    NASA Astrophysics Data System (ADS)

    Peng, Y. C. J.

    1985-09-01

    The ability of continuous wave high power CO2 Lasers to generate power densities of up to 108 watts Cm makes them useful for a variety of material processing tasks. Deep-penetration laser welding, high precision laser cutting, surface heat treating by martensitic phase transformation hardening, and surface alloying are the four major areas which are accepting laser processes. This paper will cover these four primary laser applications existing in production within a variety of industries. Each individual area will be discussed in detail, describing the advantages and various parameters to achieve maximum productivity and quality. Beam config-uration, integration, and manipulation are included also. Production examples of laser welding, cutting, surface hardening and surface alloying, are examined to demonstrate the laser processing advantages. This paper also reviews the present and future status of the laser metalsworking industry in respect to the growth potential, research and development, manufacturers responsibilities etc.

  17. Hardening [Chapter 12

    Treesearch

    Douglass F. Jacobs; Thomas D. Landis

    2009-01-01

    To promote survival and growth following outplanting, nursery stock must undergo proper hardening. Without proper hardening, plants do not store well over winter and are likely to grow poorly or die on the outplanting site. It is important to understand that native plant nurseries are different from traditional horticultural systems in that native plants must endure an...

  18. LASER MODES AND BEAMS: Tunable fractional-order Fourier transformer

    NASA Astrophysics Data System (ADS)

    Malyutin, A. A.

    2006-01-01

    A fractional two-dimensional Fourier transformer whose orders are tuned by means of optical quadrupoles is described. It is shown that in the optical scheme considered, the Fourier-transform order a in [0,1] in one of the mutually orthogonal planes corresponds to the transform order (2-a) in another plane, i.e., to inversion and inverse Fourier transform of the order a.

  19. Laser Surface Treatment

    NASA Astrophysics Data System (ADS)

    Gnanamuthu, D. S.

    1980-10-01

    Experimental procedures and current state-of-the-art are presented for laser surface treating methods such as alloying, cladding, grain refining, and transformation hardening using a cw CO2 laser. Microstructural and x-ray analyses of the treated surfaces indicate that a laser beam can locally enhance surface properties. Laser alloying offers the possibility to selectively modify a low cost workpiece surface so that it has the desired high quality surface properties characteristic of high performance alloys. Laser cladding offers feasibility to apply high melting cladding alloys on low melting workpieces, to reduce the amount of dilution of cladding alloy with the workpieces, and the potential to apply dense ceramic claddings to metallic workpieces. Laser grain refining offers potential to either minimize or eliminate surface defects such as inclusions, intermetallic compounds, and pores, and to provide a refined grain structure. Laser transformation hardening provides the treated workpieces with a hard martensitic surface that has compressive stresses for enhanced fatigue life; in addition, reduction in wear rate of treated surfaces is achieved. This experimental study indicates that the use of lasers for surface treatment has several limitations. Further studies will provide better understanding for maximum utilization of laser surface treating processes.

  20. Transforming graphite to nanoscale diamonds by a femtosecond laser pulse

    SciTech Connect

    Nueske, R.; Jurgilaitis, A.; Enquist, H.; Harb, M.; Larsson, J.; Fang, Y.; Haakanson, U.

    2012-01-23

    Formation of cubic diamond from graphite following irradiation by a single, intense, ultra-short laser pulse has been observed. Highly oriented pyrolytic graphite (HOPG) samples were irradiated by a 100 fs pulse with a center wavelength of 800 nm. Following laser exposure, the HOPG samples were studied using Raman spectroscopy of the sample surface. In the laser-irradiated areas, nanoscale cubic diamond crystals have been formed. The exposed areas were also studied using grazing incidence x-ray powder diffraction showing a restacking of planes from hexagonal graphite to rhombohedral graphite.

  1. SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: X-ray beam hardening correction for measuring density in linear accelerator industrial computed tomography

    NASA Astrophysics Data System (ADS)

    Zhou, Ri-Feng; Wang, Jue; Chen, Wei-Min

    2009-07-01

    Due to X-ray attenuation being approximately proportional to material density, it is possible to measure the inner density through Industrial Computed Tomography (ICT) images accurately. In practice, however, a number of factors including the non-linear effects of beam hardening and diffuse scattered radiation complicate the quantitative measurement of density variations in materials. This paper is based on the linearization method of beam hardening correction, and uses polynomial fitting coefficient which is obtained by the curvature of iron polychromatic beam data to fit other materials. Through theoretical deduction, the paper proves that the density measure error is less than 2% if using pre-filters to make the spectrum of linear accelerator range mainly 0.3 MeV to 3 MeV. Experiment had been set up at an ICT system with a 9 MeV electron linear accelerator. The result is satisfactory. This technique makes the beam hardening correction easy and simple, and it is valuable for measuring the ICT density and making use of the CT images to recognize materials.

  2. On Analytical Solutions to Beam-Hardening

    NASA Astrophysics Data System (ADS)

    Rigaud, G.

    2017-01-01

    When polychromatic X-rays propagate through a material, for instance in computerized tomography (CT), low energy photons are more attenuated resulting in a "harder" beam. The beam-hardening phenomenon breaks the monochromatic radiation model based on the Radon transform giving rise to artifacts in CT reconstructions to the detriment of visual inspection and automated segmentation algorithms. We propose first a simplified analytic representation for the beam-hardening. Besides providing a general understanding of the phenomenon, this model proposes to invert the beam-hardening effect for homogeneous objects leading to classical monochromatic data. For heterogeneous objects, no analytical reconstruction of the density can be derived without more prior information. However, the beam-hardening is shown to be a smooth operation on the data and thus to preserve the encoding of the singularities of the attenuation map within the data. A microlocal analysis encourages the use of contour extraction methods to solve partially the beam-hardening effect even for heterogeneous objects. The application of both methods, exact analytical solution for homogeneous objects and feature extraction for heterogeneous ones, on real data demonstrates their relevancy and efficiency.

  3. Transformation in iron-platinum thin film via nanosecond pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Yoshida, Yutaka; Yatsu, Shigeo; Watanabe, Seiichi; Yamauchi, Akira; Shibano, Jun-ichi

    2017-10-01

    The composite consists of disordered and ordered iron-platinum (FePt) alloys was induced by nanosecond pulsed laser (NPL) irradiation. The process was investigated by laser high-voltage electron microscopy (laser-HVEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses. The structural transformation upon NPL irradiation was monitored by laser-HVEM imaging, with the structure being modified in a short second after the one pulse. XRD analyses revealed expanded and contracted lattice distances before and after NPL irradiation, respectively. According to the XRD and TEM results, the surface of FePt alloys was transformed from fct to fcc structure with structural strain by NPL irradiation.

  4. Detecting laser-range-finding signals in surveying converter lining based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Li, Hongsheng; Yang, Xiaofei; Shi, Tielin; Yang, Shuzi

    1998-08-01

    The precision of the laser range finding subsystem has important influences on the performances of the whole measurement system applied to survey the steelmaking converter lining erosion state. In the system, the object of laser beams is some rough lighting surfaces in high temperature. the laser range finding signals to reach the microcomputer system would be submerged in intense disturb environments. Common laser range finding devices could not work normally. This paper presents a method based on the wavelet transform to test solving the problem. The idea of this method includes encoding the measuring signals, decomposing the encoded received signals of components in different frequency scales and time domains by the wavelet transform method, extracting the features of encoded signals according to queer points to confirm the arrival of signals, and accurately calculating out the measured distances. In addition, the method is also helpful to adopt some digital filter algorithms in time. It could make further in improvement on the precision.

  5. Echo signal processing of laser rapid scanning based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Chen, Jinling; Xu, Zhengfeng; Xie, Delin; Chen, Hongbin; Luo, Jian

    2007-12-01

    In order to get the edge message of a target, a laser scanning system was established. The laser scanning system steers a beam of laser energy which is dithered in two directions to scan the surface of the object. A laser energy detector detects laser energy reflected from the target. The reflected information is filtered to distinguish dither frequencies for signal in both directions. The signals are independently analyzed to determine the edge of the target by detecting the change of reflected laser energy. In order to get the fantastic point of echo signal, wavelet transform is used. Based on invariability of the quality factor of wavelet transform, combined with proper wavelet group, this paper discusses the application of wavelet transform for the detection of echo signal. On the basis of algorithm analysis, from aspects of detecting principle, detecting steps and computer emulation, the authors expatiate how to use wavelet transform to find the fantastic point of echo signal, finally to find the edge of the target being detected. Wavelet transform has the ability of denoting local signal characteristics, so it is fit to analyzing instantaneous and fantastic phenomena and can lay out signal components. The method in this paper will supply an algorithm gist and a reference for signal processing for the detection of edge message of target. The results are demonstrated by using Matlab programme. By the measure, the noise can be eliminated, and effective signals can be picked up. When applying the wavelet transform to experimentation, a satisfactory result was obtained. When using this method, the ability of edge detection can be greatly improved.

  6. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    NASA Astrophysics Data System (ADS)

    Li, T.; Lou, Q.; Dong, J.; Wei, Y.; Liu, J.

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating `hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.

  7. [Effect of He-Ne-laser irradiation on plasmid transformation of Escherichia coli bacteria].

    PubMed

    Tiflova, O A; Leonov, P G; Karbysheva, E A; Shakhnabatian, L G

    1997-01-01

    The influence of the of radiation a He-Ne laser (632.8 nm, 30 W/m2, 5-20 J/m2) on the transformation of Escherichia coli cells with plasmid DNA was studied. The irradiation of a mixture of bacterial cells and plasmid DNA increased the transformation efficiency 2.5-3 times, thus offering an alternative to the heat treatment commonly used. In contrast to the standard techniques, the laser-induced increase in the transformation efficiency was accompanied by a 1.7- to 2-fold increase in cell survival. The effect of the 632.8-nm light, know to be absorbed by membrane porphyrin components, is supposed to be mediated via a modification in the replication and transformation DNA-membrane complexes in E. coli cells.

  8. Diffractive optical elements for transformation of modes in lasers

    DOEpatents

    Sridharan, Arun K; Pax, Paul H; Heebner, John E; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

    2016-06-21

    Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

  9. Diffractive optical elements for transformation of modes in lasers

    DOEpatents

    Sridharan, Arun K.; Pax, Paul H.; Heebner, John E.; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

    2015-09-01

    Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

  10. 42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN AND TEMPER THE NAILS; WEST TUBES IN FOREGRPUND AND DRAWBACK TUBE IN THE CENTER - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  11. Laser Mode Behavior of the Cassini CIRS Fourier Transform Spectrometer at Saturn

    NASA Technical Reports Server (NTRS)

    Brasunas, John C.

    2012-01-01

    The CIRS Fourier transform spectrometer aboard the NASA/ESA/ASI Cassini orbiter has been acquiring spectra of the Saturnian system since 2004. The CIRS reference interferometer employs a laser diode to trigger the interferogram sampling. Although the control of laser diode drive current and operating temperature are stringent enough to restrict laser wavelength variation to a small fraction of CIRS finest resolution element, the CIRS instrument does need to be restarted every year or two, at which time it may start in a new laser mode. By monitoring the Mylar absorption features in uncalibrated spectra due to the beam splitter Mylar substrate, it can be shown that these jumps are to adjacent modes and that most of the eight-year operation so far is restricted to three adjacent modes. For a given mode, the wavelength stability appears consistent with the stability of the laser diode drive curren.t and operating temperature.

  12. Pulse transformer package for impedance matching a laser diode to a transmission line

    NASA Astrophysics Data System (ADS)

    Bender, G. M.

    1984-11-01

    This patent covers a package for matching the characteristics impedance of a transmission line to the impedance of a pulsed semiconductor laser diode so that short duration pulse of light can be produced with a fast repetition rate. The package has a toroidal transformer in a cavity of a mainbody, with a multiturn primary connected to a transmission line. The laser diode is mounted at the edge of a known sandwich between two thin metal plates separated by an insulating layer. A space and metal cover cap are placed over the sandwich, and a screw passing through holes of all the parts is threaded into the main body. The screw passing through the transformer core forms a one-turn secondary. Not only does this allow the matching of the characteristic impedance, but also provides heat sinking for the diode. Assembly with a screw makes the unit easy to fabricate, and to replace the laser diode sandwich.

  13. Microstructure and phase transformations in laser clad CrxSy/Ni coating on H13 steel

    NASA Astrophysics Data System (ADS)

    Lei, Yiwen; Sun, Ronglu; Tang, Ying; Niu, Wei

    2015-03-01

    Laser cladding was carried out onto H13 steel with preplaced NiCrBSi+Ni/MoS2 powders using CO2 laser under the optimized experimental parameters of laser power 2 kW, scanning velocity 6 mm/s and laser beam diameter 3 mm. An X-ray diffractometer and scanning electron microscope with energy dispersive spectroscopy were applied to analyze the microstructure and phase compositions of the coating. Thermodynamic calculation was performed with Thermo-Calc software on the basis of a commercially available Ni-based Alloys' database. The experimental results show that MoS2 decomposed and S reacted with Cr to form nonstoichiometric CrxSy during the laser cladding process. The coating consists of spherical CrxSy particles, primary γ-Ni dendrite, interdendritic eutectic (γ-Ni+NiMo) and precipitated NiMo. The precipitated NiMo was fine and uniformly distributed in primary γ-Ni dendrite. The calculated results and experimental data indicate that the solidification process in the coating during laser cladding process was liquid→liquid+CrxSy→ liquid+CrxSy+γ-Ni→liquid+CrxSy+γ-Ni+ eutectic (γ-Ni+NiMo). A solid state phase transformation (fine and uniformly distributed NiMo precipitated from γ-Ni) occurred after the solidification process. The calculations agree well with the experimental data and it is helpful to understand the phase transformation and microstructure evolution in the coating.

  14. The role of transforming growth factor β1 in fractional laser resurfacing with a carbon dioxide laser.

    PubMed

    Jiang, Xia; Ge, Hongmei; Zhou, Chuanqing; Chai, Xinyu; Deng, Hui

    2014-03-01

    The aim of this study was to investigate the role of transforming growth factor β1 in mechanisms of cutaneous remodeling induced by fractional carbon dioxide laser treatment. The dorsal skin of Kunming mice was exposed to a single-pass fractional CO2 laser treatment. Biopsies were taken at 1 h and at 1, 3, 7, 14, 21, 28, and 56 days after treatment. Transforming growth factor (TGF) β1 expression in skin samples was evaluated by ELISA, dermal thickness by hematoxylin-eosin staining, collagen and elastic fibers by Ponceau S and Victoria blue double staining, and types I and III collagens by ELISA. The level of TGF β1 in the laser-treated areas of skin was significantly increased compared with that in the control areas on days 1 (p < 0.05), 3 (p < 0.01), and 7 (p < 0.05) and then decreased by day 14 after treatment, at which time it had returned to the baseline level. Dermal thickness and the amount of type I collagen of the skin of the laser-treated areas had increased significantly (p < 0.05) compared with that in control areas on days 28 and 56. Fibroblast proliferation showed a positive correlation with TGF β1 expression during the early stages (r = 0.789, p < 0.01), and there was a negative correlation between the level of TGF β1 and type I collagen in the late stages, after laser treatment (r = -0.546, p < 0.05). TGF β1 appears to be an important factor in fractional laser resurfacing.

  15. Ultrafast Fourier Transform with a Femtosecond-Laser-Driven Molecule

    NASA Astrophysics Data System (ADS)

    Hosaka, Kouichi; Shimada, Hiroyuki; Chiba, Hisashi; Katsuki, Hiroyuki; Teranishi, Yoshiaki; Ohtsuki, Yukiyoshi; Ohmori, Kenji

    2010-05-01

    Wave functions of electrically neutral systems can be used as information carriers to replace real charges in the present Si-based circuit, whose further integration will result in a possible disaster where current leakage is unavoidable with insulators thinned to atomic levels. We have experimentally demonstrated a new logic gate based on the temporal evolution of a wave function. An optically tailored vibrational wave packet in the iodine molecule implements four- and eight-element discrete Fourier transform with arbitrary real and imaginary inputs. The evolution time is 145 fs, which is shorter than the typical clock period of the current fastest Si-based computers by 3 orders of magnitudes.

  16. Ultrafast Fourier transform with a femtosecond-laser-driven molecule.

    PubMed

    Hosaka, Kouichi; Shimada, Hiroyuki; Chiba, Hisashi; Katsuki, Hiroyuki; Teranishi, Yoshiaki; Ohtsuki, Yukiyoshi; Ohmori, Kenji

    2010-05-07

    Wave functions of electrically neutral systems can be used as information carriers to replace real charges in the present Si-based circuit, whose further integration will result in a possible disaster where current leakage is unavoidable with insulators thinned to atomic levels. We have experimentally demonstrated a new logic gate based on the temporal evolution of a wave function. An optically tailored vibrational wave packet in the iodine molecule implements four- and eight-element discrete Fourier transform with arbitrary real and imaginary inputs. The evolution time is 145 fs, which is shorter than the typical clock period of the current fastest Si-based computers by 3 orders of magnitudes.

  17. Manipulating mammalian cell by phase transformed titanium surface fabricated through ultra-short pulsed laser synthesis.

    PubMed

    Chinnakkannu Vijayakumar, Sivaprasad; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-15

    Developing cell sensitive indicators on interacting substrates that allows specific cell manipulation by a combination of physical, chemical or mechanical cues is a challenge for current biomaterials. Hence, various fabrication approaches have been created on a variety of substrates to mimic or create cell specific cues. However, to achieve cell specific cues a multistep process or a post-chemical treatment is often necessitated. So, a simple approach without any chemical or biological treatment would go a long way in developing bio-functionalized substrates to effectively modulate cell adhesion and interaction. The present investigation is aimed to study the manipulative activity induced by phase transformed titanium surface. An ultra-short laser is used to fabricate the phase transformed titanium surface where a polymorphic titanium oxide phases with titanium monoxide (TiO), tri-titanium oxide (Ti3O) and titanium dioxide (TiO2) have been synthesized on commercially pure titanium. Control over oxide phase transformed area was demonstrated via a combination of laser scanning time (laser pulse interaction time) and laser pulse widths (laser pulse to pulse separation time). The interaction of phase transformed titanium surface with NIH3T3 fibroblasts and MC3T3-E1 osteoblast cells developed a new bio-functionalized platforms on titanium based biomaterials to modulate cell migration and adhesion. The synthesized phase transformed titanium surface on the whole appeared to induce directional cues for cell migration with unique preferential cell adhesion unseen by other fabrication approaches. The precise bio-functionalization controllability exhibited during fabrication offers perceptible edge for developing a variety of smart bio-medical devices, implants and cardiovascular stents where the need in supressing specific cell adhesion and proliferation is of great demand.

  18. Semiconductor laser self-mixing micro-vibration measuring technology based on Hilbert transform

    NASA Astrophysics Data System (ADS)

    Tao, Yufeng; Wang, Ming; Xia, Wei

    2016-06-01

    A signal-processing synthesizing Wavelet transform and Hilbert transform is employed to measurement of uniform or non-uniform vibrations in self-mixing interferometer on semiconductor laser diode with quantum well. Background noise and fringe inclination are solved by decomposing effect, fringe counting is adopted to automatic determine decomposing level, a couple of exact quadrature signals are produced by Hilbert transform to extract vibration. The tempting potential of real-time measuring micro vibration with high accuracy and wide dynamic response bandwidth using proposed method is proven by both simulation and experiment. Advantages and error sources are presented as well. Main features of proposed semiconductor laser self-mixing interferometer are constant current supply, high resolution, simplest optical path and much higher tolerance to feedback level than existing self-mixing interferometers, which is competitive for non-contact vibration measurement.

  19. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis.

    PubMed

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-06-13

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis.

  20. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis

    PubMed Central

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-01-01

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  1. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  2. RHOBOT: Radiation hardened robotics

    SciTech Connect

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  3. Effect of Continuous and Isothermal Hardening on the Wear Resistance of Tools Produced from High-Speed Steels

    NASA Astrophysics Data System (ADS)

    Murav'ev, V. I.; Chernobai, S. P.

    2003-05-01

    The effect of isothermal hardening on the red-hardness (heat resistance) of steel R18 is studied. A complex dependence of the red hardness on the temperature of isothermal hardening and the hold time is shown. Tools from steel R18 are shown to have maximum heat resistance and wear resistance after bainitic hardening in the "pre-transformation" range.

  4. Nuclear effects hardened shelters

    NASA Astrophysics Data System (ADS)

    Lindke, Paul

    1990-11-01

    The Houston Fearless 76 Government Projects Group has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8' x 8' x 22' nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Corrpartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters. The specific levels of hardening to which the shelters were designed are classified and will not be mentioned during this presentation.

  5. Therapeutic low-intensity red laser for herpes labialis on plasmid survival and bacterial transformation.

    PubMed

    Sergio, Luiz Philippe da Silva; Marciano, Roberta da Silva; Teixeira, Gleica Rocha; Canuto, Keila da Silva; Polignano, Giovanni Augusto Castanheira; Guimarães, Oscar Roberto; Geller, Mauro; de Paoli, Flavia; da Fonseca, Adenilson de Souza

    2013-05-01

    A low-intensity laser is used in treating herpes labialis based on the biostimulative effect, albeit the photobiological basis is not well understood. In this work experimental models based on Escherichia coli cultures and plasmids were used to evaluate effects of low-intensity red laser on DNA at fluences for treatment of herpes labialis. To this end, survival and transformation efficiency of plasmids in E. coli AB1157 (wild type), BH20 (fpg/mutM(-)) and BW9091 (xthA(-)), content of the supercoiled form of plasmid DNA, as well as nucleic acids and protein content from bacterial cultures exposed to the laser, were evaluated. The data indicate low-intensity red laser: (i) alters the survival of plasmids in wild type, fpg/mutM(-) and xthA(-)E. coli cultures depending of growth phase, (ii) alters the content of the supercoiled form of plasmids in the wild type and fpg/mutM(-)E. coli cells, (iii) alters the content of nucleic acids and proteins in wild type E. coli cells, (iv) alters the transformation efficiency of plasmids in wild type and fpg/mutM(-)E. coli competent cells. These data could be used to understand positive effects of low-intensity lasers on herpes labialis treatment.

  6. Numerical estimation of phase transformations in solid state during Yb:YAG laser heating of steel sheets

    SciTech Connect

    Kubiak, Marcin Piekarska, Wiesława; Domański, Tomasz; Saternus, Zbigniew; Stano, Sebastian

    2015-03-10

    This work concerns the numerical modeling of heat transfer and phase transformations in solid state occurring during the Yb:YAG laser beam heating process. The temperature field is obtained by the numerical solution into transient heat transfer equation with convective term. The laser beam heat source model is developed using the Kriging interpolation method with experimental measurements of Yb:YAG laser beam profile taken into account. Phase transformations are calculated on the basis of Johnson - Mehl - Avrami (JMA) and Koistinen - Marburger (KM) kinetics models as well as continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for S355 steel. On the basis of developed numerical algorithms 3D computer simulations are performed in order to predict temperature history and phase transformations in Yb:YAG laser heating process.

  7. Laser desorption studies of high mass biomolecules in Fourier-transform ion cyclotron resonance mass spectrometry.

    PubMed Central

    Solouki, T; Russell, D H

    1992-01-01

    Matrix-assisted laser desorption ionization is used to obtain Fourier-transform ion cyclotron resonance mass spectra of model peptides (e.g., gramicidin S, angiotensin I, renin substrate, melittin, and bovine insulin). Matrix-assisted laser desorption ionization yields ions having appreciable kinetic energies. Two methods for trapping the high kinetic energy ions are described: (i) the ion signal for [M+H]+ ions is shown to increase with increasing trapping voltages, and (ii) collisional relaxation is used for the detection of [M+H]+ ions of bovine insulin. Images PMID:1378614

  8. Controlling the femtosecond laser-driven transformation of dicyclopentadiene into cyclopentadiene

    PubMed Central

    Goswami, Tapas; Das, Dipak K.; Goswami, Debabrata

    2013-01-01

    Dynamics of the chemical transformation of dicyclopentadiene into cyclopentadiene in a supersonic molecular beam is elucidated using femtosecond time-resolved degenerate pump–probe mass spectrometry. Control of this ultrafast chemical reaction is achieved by using linearly chirped frequency modulated pulses. We show that negatively chirped femtosecond laser pulses enhance the cyclopentadiene photoproduct yield by an order of magnitude as compared to that of the unmodulated or the positively chirped pulses. This demonstrates that the phase structure of femtosecond laser pulse plays an important role in determining the outcome of a chemical reaction. PMID:24098059

  9. Plasma Plume Oscillations Monitoring during Laser Welding of Stainless Steel by Discrete Wavelet Transform Application

    PubMed Central

    Sibillano, Teresa; Ancona, Antonio; Rizzi, Domenico; Lupo, Valentina; Tricarico, Luigi; Lugarà, Pietro Mario

    2010-01-01

    The plasma optical radiation emitted during CO2 laser welding of stainless steel samples has been detected with a Si-PIN photodiode and analyzed under different process conditions. The discrete wavelet transform (DWT) has been used to decompose the optical signal into various discrete series of sequences over different frequency bands. The results show that changes of the process settings may yield different signal features in the range of frequencies between 200 Hz and 30 kHz. Potential applications of this method to monitor in real time the laser welding processes are also discussed. PMID:22319311

  10. Precipitation, strength and work hardening of age hardened aluminium alloys

    NASA Astrophysics Data System (ADS)

    Ryen, Ø.; Holmedal, B.; Marthinsen, K.; Furu, T.

    2015-08-01

    The strength and work hardening of age hardened AA6063 and AA6082 alloys have been investigated in terms of a detailed characterization of precipitate and dislocation structures obtained by TEM and SEM. Tensile and compression tests were performed at as quenched, peak aged and severely aged conditions. A strong work hardening in the as quenched condition was found, similar to AlMg alloys with twice as much alloying elements in solid solution. It was found that the initial work hardening rate and the critical failure strain are both smallest at the peak aged condition. During large deformations the needle-shaped precipitates are sheared uniformly by dislocations altering their <001> orientations, which indicates extensive cross slip. In the overaged condition the early initial work hardening is larger than at the peak aged condition, but followed by a weak linear work hardening, apparently directly entering stage IV at a low strain. Cracked, needle-shaped precipitates were seen at larger strains.

  11. In-situ laser ultrasonic measurement of the hcp to bcc transformation in commercially pure titanium

    SciTech Connect

    Shinbine, A. Garcin, T.; Sinclair, C.

    2016-07-15

    Using a novel in-situ laser ultrasonic technique, the evolution of longitudinal velocity was used to measure the α − β transformation during cyclic heating and cooling in commercially pure titanium. In order to quantify the transformation kinetics, it is shown that changes in texture can not be ignored. This is particularly important in the case of titanium where significant grain growth occurs in the β-phase leading to the ultrasonic wave sampling a decreasing number of grains on each thermal treatment cycle. Electron backscatter diffraction measurements made postmortem in the region where the ultrasonic pulse traveled were used to obtain an estimate of such local texture and grain size changes. An analysis technique for including the anisotropy of wave velocity depending on local texture is presented and shown to give self consistent results for the transformation kinetics. - Highlights: • Laser ultrasound and EBSD interpret the hcp/bcc phase transformation in cp-Ti. • Grain growth and texture produced variation in velocity during similar treatments. • Texture was deconvoluted from phase addition to obtain transformation kinetics.

  12. Phase-space analysis for ionization processes in the laser-atom interaction using Gabor transformation

    NASA Astrophysics Data System (ADS)

    Shu, X. F.; Liu, S. B.; Song, H. Y.

    2016-04-01

    In this paper, the ionization processes during laser-atom interaction are investigated in phase-space using Gabor transformation. Based on the time-dependent Schrödinger equation (TDSE), the depletion of the whole system caused by the mask function is taken into consideration in calculating the plasma density. We obtain the momentum distribution via the Gabor transformation of the escaping portions of the time-dependent wave packet at the detector-like points on the interior boundaries from which the kinetic energies carried by the escaping portions are calculated.

  13. Transform-limited pulses generated by an actively Q-switched distributed fiber laser.

    PubMed

    Cuadrado-Laborde, C; Pérez-Millán, P; Andrés, M V; Díez, A; Cruz, J L; Barmenkov, Yu O

    2008-11-15

    A single-mode, transform-limited, actively Q-switched distributed-feedback fiber laser is presented, based on a new in-line acoustic pulse generator. Our technique permits a continuous adjustment of the repetition rate that modulates the Q factor of the cavity. Optical pulses of 800 mW peak power, 32 ns temporal width, and up to 20 kHz repetition rates were obtained. The measured linewidth demonstrates that these pulses are transform limited: 6 MHz for a train of pulses of 10 kHz repetition rate, 80 ns temporal width, and 60 mW peak power. Efficient excitation of spontaneous Brillouin scattering is demonstrated.

  14. EXAFS measurement of iron bcc-to-hcp phase transformation in nanosecond-laser shocks.

    PubMed

    Yaakobi, B; Boehly, T R; Meyerhofer, D D; Collins, T J B; Remington, B A; Allen, P G; Pollaine, S M; Lorenzana, H E; Eggert, J H

    2005-08-12

    Extended x-ray absorption fine structure (EXAFS) measurements have demonstrated the phase transformation from body-centered-cubic (bcc) to hexagonal-close-packed (hcp) iron due to nanosecond, laser-generated shocks. The EXAFS spectra are also used to determine the compression and temperature in the shocked iron, which are consistent with hydrodynamic simulations and with the compression inferred from velocity interferometry. This is a direct, atomic-level, and in situ proof of shock-induced transformation in iron, as opposed to the previous indirect proof based on shock-wave splitting.

  15. LASER BEAMS: Use of the fractional Fourier transform in π/2 converters of laser modes

    NASA Astrophysics Data System (ADS)

    Malyutin, A. A.

    2004-02-01

    The possibility of using the fractional Fourier transform (FrFT) in optical schemes for astigmatic π/2 converters of Hermite—Gaussian modes to donut Laguerre—Gaussian modes is considered. Several schemes of converters based on the FrFT of the half-integer and irrational orders are presented. The lowest FrFT order than can be used in astigmatic mode converters is found. The properties of converters based on the fractional and ordinary Fourier transforms are compared.

  16. Second-Generation Discrete Fourier Transform Signal Processor for Laser Velocimetry

    DTIC Science & Technology

    1986-12-01

    AEDC-TR-86-33 C.7- eAR 0 0 1987 Second- Generation Discrete Fourier Transform Signal Processor for Laser Velocimetry Thomas Chris Layne Calspan...available to the general public, including foreign nations. APPROVAL STATEMENT This report has been reviewed and approved. ROBERT W. SMITH...IFIFI) SECURITY CLASSIFICATION OF THIS PAGE UNCLASSIFIED SECURITY C L ~ S I F I C A T I O N OF THIS PAGE 11. TITLE Second- Generation Discrete

  17. Topological phase for spin-orbit transformations on a laser beam.

    PubMed

    Souza, C E R; Huguenin, J A O; Milman, P; Khoury, A Z

    2007-10-19

    We investigate the topological phase associated with the double connectedness of the SO(3) representation in terms of maximally entangled states. An experimental demonstration is provided in the context of polarization and spatial mode transformations of a laser beam carrying orbital angular momentum. The topological phase is evidenced through interferometric measurements, and a quantitative relationship between the concurrence and the fringes visibility is derived. Both the quantum and the classical regimes were investigated.

  18. Femtosecond laser induced coordination transformation and migration of ions in sodium borate glasses

    SciTech Connect

    Liu Yin; Zhu Bin; Wang Li; Qiu Jianrong; Dai Ye; Ma Hongliang

    2008-03-24

    We report on the coordination transformation of B{sup 3+} ions and migration of Na{sup +} and O{sup 2-} ions in sodium borate glasses, induced by 250 kHz, 800 nm femtosecond laser irradiation. Micro-Raman spectra show that the ratio of the integrated intensity of the two peaks at 806 and 774 cm{sup -1} decreases at first and then increases with increasing distance from the center of the laser modified zone. Electron dispersive x-ray spectra show that a portion of Na{sup +} and O{sup 2-} ions migrate from the vicinity of focal point after the femtosecond laser irradiation. A possible mechanism is proposed to explain the observed phenomena.

  19. Structural transformations in femtosecond laser-processed n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Rehman, Z. U.; Janulewicz, K. A.

    2016-11-01

    We present a comprehensive study of morphological modification induced on and below the surface of n-type 4H-SiC by irradiation with femtosecond laser pulses under tight focusing condition. Spectroscopic investigation of local electronic and structural transformations in SiC-micro/nanostructures suggested bond breaking i.e. transformation of crystalline SiC to amorphous silicon (a-Si) and amorphous carbon (a-C). These observations were augmented by investigations applying atomic force microscopy (AFM), micro-photoluminescence (PL) spectroscopy, and high resolution X-ray diffraction (HRXRD). A high-resolution cross-sectional study of laser-modified region with transmission electron microscope (TEM) showed a thin amorphous layer in the vicinity of the geometrical focus with deformations and stacking faults in the sub-surface area. Having considered the existing ablation theories, a complex interplay of fast laser heating followed by melting and rapid re-solidification as well as dynamic relaxation of the laser-induced stresses seems to be responsible for formation of the observed structural changes.

  20. Industrial Hardening Demonstration.

    DTIC Science & Technology

    1980-09-01

    less severe conditions than thermal cracking (850’ - 950°F and 10 to 20 psi). Zeolitic or molecular sieve- base catalysts are used. Catalytic reforming...with Potential Industrial Hardening A-1 Participants B Post-Attack Petroleum Refining (and Production) B-1 from Crude Oil V List of Figures Number Page...the Key Worker Shelter 116 viii B-1 Proportions of the Products Obtained by Distillation B-2 of Six Crude Oils B-2 Generalized Flow Chart of the

  1. The mechanism of the surface morphology transformation for the carbon nanotube thin film irradiated via excimer laser

    SciTech Connect

    Chien, Yun-Shan; Lee, I-Che; Yang, Po-Yu; Wang, Chao-Lung; Tsai, Wan-Lin; Wang, Kuang-Yu; Chou, Chia-Hsin; Cheng, Huang-Chung

    2013-05-06

    In this paper, the surface morphology transformation of the sprayed carbon nanotube (CNT) thin film irradiated with the excimer laser has been systematically investigated. Under the excimer-laser irradiation, two phenomena, including the annealing and ablation effects, were found to be dependent on the incident laser energy and overlapping ratios. Moreover, the extremely high protrusions would be produced in the interface between the annealing and ablation regions. The mechanism of the CNT thin film under the excimer laser irradiation was, therefore, proposed to derive the surface morphology modifications and the further reinforced crystallinity with proper laser energy densities and overlapping ratios.

  2. Rational Chebyshev spectral transform for the dynamics of broad-area laser diodes

    SciTech Connect

    Javaloyes, J.

    2015-10-01

    This manuscript details the use of the rational Chebyshev transform for describing the transverse dynamics of broad-area laser diodes and amplifiers. This spectral method can be used in combination with the delay algebraic equations approach developed in [1], which substantially reduces the computation time. The theory is presented in such a way that it encompasses the case of the Fourier spectral transform presented in [2] as a particular case. It is also extended to the consideration of index guiding with an arbitrary transverse profile. Because their domain of definition is infinite, the convergence properties of the Chebyshev rational functions allow handling the boundary conditions with higher accuracy than with the previously studied Fourier transform method. As practical examples, we solve the beam propagation problem with and without index guiding: we obtain excellent results and an improvement of the integration time between one and two orders of magnitude as compared with a fully distributed two dimensional model.

  3. Influence of Laser Peening on Phase Transformation and Corrosion Resistance of AISI 321 steel

    NASA Astrophysics Data System (ADS)

    Karthik, D.; Swaroop, S.

    2016-07-01

    The objective of this study is to investigate the influence of laser peening without coating (LPwC) on austenitic to martensitic (γ → α') phase transformation and corrosion behavior of austenitic stainless steel AISI 321 in 3.5% NaCl environment. Results indicate that LPwC induces a large compressive residual stresses of nearly -854 MPa and γ → α' phase transformation of about 18% (volume fraction). Microstructures of peened surface confirmed the γ → α' phase transformation and showed no grain refinement. Hardness increased slightly with a case depth of 900 μm. Despite the smaller surface roughness introduced, corrosion resistance improved after peening due to compressive residual stresses.

  4. Ultrasonic velocity measurements during phase transformations in steels using laser ultrasonics

    NASA Astrophysics Data System (ADS)

    Dubois, Marc; Moreau, André; Bussière, Jean F.

    2001-06-01

    This article presents accurate laser-ultrasonic measurements of longitudinal velocity in the 500-1000 °C temperature range in carbon steel samples for different conditions known to affect phase transformations such as cooling rate, carbon concentration, and rolling. Measurements were performed during continuous heating and cooling at rates varying between 0.1 and 20 °C/s. Carbon concentrations ranged from 0.0% to 0.72%. Hot-rolled and cold-rolled samples were measured. For the hot-rolled samples, a reproducible hysteresis was observed in the dependence of the ultrasonic velocity versus temperature of samples having a significant carbon concentration. This hysteresis is attributed to the combined effects of the phase transformation and of the ferromagnetic-paramagnetic transition. In particular, the rate of change of velocity with temperature during heating suddenly diminishes at the Curie temperature, and the velocity behavior during cooling shows clearly the start and end of phase transformations, even allowing discrimination between ferrite and pearlite nucleations. For the cold-rolled samples, significant drops in ultrasonic velocity were observed at the transformation temperatures when the samples were heated for the first time. However, the magnitude of these drops decreased for subsequent heating. These drops are attributed to irreversible crystallographic orientation changes caused by phase transformations. This effect was modeled using the Kurdjumov-Sach transformation relationship. The model calculation agrees well with the experimental data.

  5. Tomography of homogenized laser-induced plasma by Radon transform technique

    NASA Astrophysics Data System (ADS)

    Eschlböck-Fuchs, S.; Demidov, A.; Gornushkin, I. B.; Schmid, T.; Rössler, R.; Huber, N.; Panne, U.; Pedarnig, J. D.

    2016-09-01

    Tomography of a laser-induced plasma in air is performed by inverse Radon transform of angle-resolved plasma images. Plasmas were induced by single laser pulses (SP), double pulses (DP) in collinear geometry, and by a combination of single laser pulses with pulsed arc discharges (SP-AD). Images of plasmas on metallurgical steel slags were taken at delay times suitable for calibration-free laser-induced breakdown spectroscopy (CF-LIBS). Delays ranged from few microseconds for SP and DP up to tens of microseconds for SP-AD excitation. The white-light and the spectrally resolved emissivity ε(x,y,z) was reconstructed for the three plasma excitation schemes. The electron number density Ne(x,y,z) and plasma temperature Te(x,y,z) were determined from Mg and Mn emission lines in reconstructed spectra employing the Saha-Boltzmann plot method. The SP plasma revealed strongly inhomogeneous emissivity and plasma temperature. Re-excitation of plasma by a second laser pulse (DP) and by an arc discharge (SP-AD) homogenized the plasma and reduced the spatial variation of ε and Te. The homogenization of a plasma is a promising approach to increase the accuracy of calibration-free LIBS analysis of complex materials.

  6. Damage detection in membrane structures using non-contact laser excitation and wavelet transformation

    NASA Astrophysics Data System (ADS)

    Huda, Feblil; Kajiwara, Itsuro; Hosoya, Naoki

    2014-08-01

    In this paper, a vibration testing and health monitoring system based on an impulse response excited by laser is proposed to detect damage in membrane structures. A high power Nd: YAG pulse laser is used to supply an ideal impulse to a membrane structure by generating shock waves via laser-induced breakdown in air. A health monitoring apparatus is developed with this vibration testing system and a damage detecting algorithm which only requires the vibration mode shape of the damaged membrane. Artificial damage is induced in membrane structure by cutting and tearing the membrane. The vibration mode shapes of the membrane structure extracted from vibration testing by using the laser-induced breakdown and laser Doppler vibrometer are then analyzed by 2-D continuous wavelet transformation. The location of damage is determined by the dominant peak of the wavelet coefficient which can be seen clearly by applying a boundary treatment and the concept of an iso-surface to the 2-D wavelet coefficient. The applicability of the present approach is verified by finite element analysis and experimental results, demonstrating the ability of the method to detect and identify the positions of damage induced on the membrane structure.

  7. Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)

    NASA Technical Reports Server (NTRS)

    Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)

    2017-01-01

    Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.

  8. Imaging Fourier transform spectroscopy of the boundary layer plume from laser irradiated polymers and carbon materials

    NASA Astrophysics Data System (ADS)

    Acosta, Roberto I.

    The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.

  9. Cross modulation method of transformation of the spatial coherence of pulsed laser radiation in a nonlinear medium

    SciTech Connect

    Kitsak, M A; Kitsak, A I

    2008-04-30

    The cross modulation method of transformation of the spatial coherence of low-power pulsed laser radiation in a nonlinear medium is proposed. The method is realised experimentally in a multimode optical fibre. The estimates of the degree of spatial coherence of radiation subjected to the phase cross modulation demonstrated the high efficiency of this radiation decorrelation mechanism. (control of laser radiation parameters)

  10. Influence of Laser Power on the Hardening of Ti6Al4V Low-Pressure Steam Turbine Blade Material for Enhancing Water Droplet Erosion Resistance

    NASA Astrophysics Data System (ADS)

    Mann, B. S.; Arya, Vivek; Pant, B. K.

    2011-03-01

    To overcome water droplet erosion of Ti6Al4V alloy blade material used in low-pressure steam turbine (LPST) of high-rating nuclear and super critical thermal power plants, high-power diode laser (HPDL) surface treatment at two temperatures corresponding to two different power levels was carried out. During incubation as well as under prolonged erosion testing, the HPDL surface treatment of this alloy has enhanced its resistance significantly. This is due to the formation of fine-grained martensitic (ά) phase due to rapid heating and cooling associated with laser treatment. The droplet erosion test results after HPDL surface treatment on this alloy, SEM, XRD analysis, and residual stresses developed due to HPDL surface treatment are given in this paper.

  11. Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer

    NASA Astrophysics Data System (ADS)

    Scott, Jill R.; Tremblay, Paul L.

    2002-03-01

    Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (˜5 μm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ˜9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

  12. Highly Reproducible Laser Beam Scanning Device for an Internal Source Laser Desorption Microprobe Fourier Transform Mass Spectrometer

    SciTech Connect

    Scott, Jill Rennee; Tremblay, Paul Leland

    2002-03-01

    Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (~5 µm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ~9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

  13. CONTROL OF LASER RADIATION PARAMETERS: Simple scheme for the astigmatic transformation of laser modes

    NASA Astrophysics Data System (ADS)

    Malyutin, A. A.

    2003-11-01

    A simple astigmatic scheme for obtaining focused Laguerre—Gaussian beams upon the π/2 conversion of Hermite—Gaussian radiation modes is described. A zone in the vicinity of the focal region of a lens is estimated where the beam satisfies the conditions for the capture and confinement of microparticles. It is shown that this optical scheme uses the fractional Fourier transform, whose application in the π/2 converter is demonstrated for the first time.

  14. Transformation of irregular shaped silver nanostructures into nanoparticles by under water pulsed laser melting

    NASA Astrophysics Data System (ADS)

    Yadavali, S.; Sandireddy, V. P.; Kalyanaraman, R.

    2016-05-01

    The ability to easily manufacture nanostructures with a desirable attribute, such as well-defined size and shape, especially from any given initial shapes or sizes of the material, will be helpful towards accelerating the use of nanomaterials in various applications. In this work we report the transformation of discontinuous irregular nanostructures (DIN) of silver metal by rapid heating under a bulk fluid layer. Ag films were changed into DIN by dewetting in air and subsequently heated by nanosecond laser pulses under water. Our findings show that the DIN first ripens into elongated structures and then breaks up into nanoparticles. From the dependence of this behavior on laser fluence we found that under water irradiation reduced the rate of ripening and also decreased the characteristic break-up length scale of the elongated structures. This latter result was qualitatively interpreted as arising from a Rayleigh-Plateau instability modified to yield significantly smaller length scales than the classical process due to pressure gradients arising from the rapid evaporation of water during laser melting. These results demonstrate that it is possible to fabricate a dense collection of monomodally sized Ag nanoparticles with significantly enhanced plasmonic quality starting from the irregular shaped materials. This can be beneficial towards transforming discontinuous Ag films into nanostructures with useful plasmonic properties, that are relevant for biosensing applications.

  15. Graphene Q-switched distributed feedback fiber lasers with narrow linewidth approaching the transform limit.

    PubMed

    Yao, B C; Rao, Y J; Huang, S W; Wu, Y; Feng, Z Y; Choi, C; Liu, H; Qi, H F; Duan, X F; Peng, G D; Wong, C W

    2017-04-03

    A compact all-in-line graphene-based distributed feedback Bragg-grating fiber laser (GDFB-FL) with narrow linewidth of hundreds kHz is demonstrated and investigated in this study. Performing as an optical saturable absorber, graphene oscillates the initially kHz linewidth DFB-FL, and generates high-quality passively Q-switched pulses. Pumped with a 980 nm continuous-wave laser, the Q-switched GDFB-FL observes ~1 μs pulse durations, with pulse energies up to ~10 nJ and approaching the transform limit. The peak power is ~600 times higher than the original DFB-FL laser. By optimizing the cavity design and the graphene material, it is predicted that fast Q-switched pulses with more than MHz repetition rates and sub-100 ns pulse durations are achievable. Such transform-limited Q-switched GDFB-FLs with narrow linewidth of sub-MHz have long coherence length, good tunability, stability, compactness and robustness, with potential impact in optical coherent communications, metrology and sensing.

  16. EXAFS Measurements of Laser-Shocked V and Ti and Crystal Phase Transformation in Ti

    SciTech Connect

    Yaakobi, B; Meyerhofer, D D; Boehly, T R; Rehr, J J; Remington, B A; Allen, P G; Pollaine, S M; Albers, R C

    2004-03-10

    Extended X-Ray Absorption Fine Structure (EXAFS), using a laser-imploded target as a source, can yield the properties of laser-shocked metals on a nanosecond time scale. EXAFS measurements of vanadium shocked to {approx}0.4 Mbar yield the compression and temperature in good agreement with hydrodynamic simulations and shock-speed measurements. In laser-shocked titanium at the same pressure, the EXAFS modulation damping is much higher than warranted by the predicted temperature increase. This is shown to be due to the {alpha}-Ti to {omega}-Ti crystal-phase transformation, known to occur below {approx}0.1 Mbar for slower shock waves. The dynamics of material response to shock loading has been extensively studied in the past [1]. The goal of those studies has been to understand the shock-induced deformation and structural changes at the microscopic level [2]. Laser-generated shocks can be employed to broaden these studies to higher pressures ({approx}1 Mbar) and strain rates ({approx} 10{sup 7}-10{sup 8} s{sup -1}). Recently, laser-shocked materials have been studied with in-situ x-ray diffraction [3,4]. The goal of this work is to examine the use of in-situ EXAFS [5] as a complementary characterization of laser-shocked metals. EXAFS is the modulation in the x-ray absorption above the K edge (or L edge) due to the interference of the photoelectron waves with the waves reflected from neighboring atoms. The frequency of EXAFS modulations is related to the inter-particle distance, hence to the compression. The damping rate of the modulation can yield the lattice temperature, which is not readily available by other methods.

  17. Laser spot tracking based on modified circular Hough transform and motion pattern analysis.

    PubMed

    Krstinić, Damir; Skelin, Ana Kuzmanić; Milatić, Ivan

    2014-10-27

    Laser pointers are one of the most widely used interactive and pointing devices in different human-computer interaction systems. Existing approaches to vision-based laser spot tracking are designed for controlled indoor environments with the main assumption that the laser spot is very bright, if not the brightest, spot in images. In this work, we are interested in developing a method for an outdoor, open-space environment, which could be implemented on embedded devices with limited computational resources. Under these circumstances, none of the assumptions of existing methods for laser spot tracking can be applied, yet a novel and fast method with robust performance is required. Throughout the paper, we will propose and evaluate an efficient method based on modified circular Hough transform and Lucas-Kanade motion analysis. Encouraging results on a representative dataset demonstrate the potential of our method in an uncontrolled outdoor environment, while achieving maximal accuracy indoors. Our dataset and ground truth data are made publicly available for further development.

  18. Laser Spot Tracking Based on Modified Circular Hough Transform and Motion Pattern Analysis

    PubMed Central

    Krstinić, Damir; Skelin, Ana Kuzmanić; Milatić, Ivan

    2014-01-01

    Laser pointers are one of the most widely used interactive and pointing devices in different human-computer interaction systems. Existing approaches to vision-based laser spot tracking are designed for controlled indoor environments with the main assumption that the laser spot is very bright, if not the brightest, spot in images. In this work, we are interested in developing a method for an outdoor, open-space environment, which could be implemented on embedded devices with limited computational resources. Under these circumstances, none of the assumptions of existing methods for laser spot tracking can be applied, yet a novel and fast method with robust performance is required. Throughout the paper, we will propose and evaluate an efficient method based on modified circular Hough transform and Lucas–Kanade motion analysis. Encouraging results on a representative dataset demonstrate the potential of our method in an uncontrolled outdoor environment, while achieving maximal accuracy indoors. Our dataset and ground truth data are made publicly available for further development. PMID:25350502

  19. Chlorpromazine transformation by exposure to ultraviolet laser beams in droplet and bulk.

    PubMed

    Andrei, Ionut Relu; Tozar, Tatiana; Dinache, Andra; Boni, Mihai; Nastasa, Viorel; Pascu, Mihail Lucian

    2016-01-01

    Multiple drug resistance requires a flexible approach to find medicines able to overcome it. One method could be the exposure of existing medicines to ultraviolet laser beams to generate photoproducts that are efficient against bacteria and/or malignant tumors. This can be done in droplets or bulk volumes. In the present work are reported results about the interaction of 266nm and 355nm pulsed laser radiation with microdroplets and bulk containing solutions of 10mg/ml Chlorpromazine Hydrochloride (CPZ) in ultrapure water. The irradiation effects on CPZ solution at larger time intervals (more than 30min) are similar in terms of generated photoproducts if the two ultraviolet wavelengths are utilized. The understanding of the CPZ parent compound transformation may be better evidenced, as shown in this paper, if studies at shorter than 30minute exposure times are made coupled with properly chosen volumes to irradiate. We show that at exposure to a 355nm laser beam faster molecular modifications of CPZ in ultrapure water solution are produced than at irradiation with 266nm, for both microdroplet and bulk volume samples. These effects are evidenced by thin layer chromatography technique and laser induced fluorescence measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Hidden corrosion detection in aircraft aluminum structures using laser ultrasonics and wavelet transform signal analysis.

    PubMed

    Silva, M Z; Gouyon, R; Lepoutre, F

    2003-06-01

    Preliminary results of hidden corrosion detection in aircraft aluminum structures using a noncontact laser based ultrasonic technique are presented. A short laser pulse focused to a line spot is used as a broadband source of ultrasonic guided waves in an aluminum 2024 sample cut from an aircraft structure and prepared with artificially corroded circular areas on its back surface. The out of plane surface displacements produced by the propagating ultrasonic waves were detected with a heterodyne Mach-Zehnder interferometer. Time-frequency analysis of the signals using a continuous wavelet transform allowed the identification of the generated Lamb modes by comparison with the calculated dispersion curves. The presence of back surface corrosion was detected by noting the loss of the S(1) mode near its cutoff frequency. This method is applicable to fast scanning inspection techniques and it is particularly suited for early corrosion detection.

  1. Time-resolved Fourier transform intracavity spectroscopy with a Cr2+:ZnSe laser

    PubMed Central

    Picqué, Nathalie; Gueye, Fatou; Guelachvili, Guy; Sorokin, Evgeni; Sorokina, Irina T.

    2010-01-01

    Intracavity laser absorption spectroscopy (ICLAS) with an evacuated Cr2+: ZnSe laser is performed with a high-resolution time-resolved Fourier transform interferometer with a minimum detectable absorption coefficient equal to 4 10−9 cm−1 Hz−½ in the 2.5μm region. This represents the extreme limit presently reached in the infrared by ICLAS with Doppler limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO2 bands observed up to now only in the Venus atmosphere are recorded for the first time in a laboratory. H2O detection limit down to 0.9 ppbv is also demonstrated. PMID:16389848

  2. High resolution infrared spectroscopy of planetary molecules using diode lasers and Fourier transform spectrometers

    NASA Technical Reports Server (NTRS)

    Jennings, Donald E.

    1990-01-01

    Modern observations of infrared molecular lines in planets are performed at spectral resolutions which are as high as those available in the laboratory. Analysis of such data requires laboratory measurements at the highest possible resolution, which also yield accurate line positions and intensities. For planetary purposes the spectrometer must be coupled to sample cells which can be reduced in temperature and varied in pressure. An approach which produces the full range of required molecular line parameters uses a combination of tunable diode lasers and Fourier transform spectrometers (FTS). The FTS provides board spectral coverage and good calibration accuracy, while the diode laser can be used to study those regions which are not resolved by the FTS.

  3. [Study on miniature static Fourier transform spectrometer used in laser warning receiver].

    PubMed

    Tian, Er-Ming; Zhang, Ji-Long; Li, Xiao; Zhang, Yue; Wang, Zhi-Bin

    2009-03-01

    A miniature static Fourier transform spectrometer (MSFTS) as the component of coherent discriminating laser warning receiver (CDLWR) was designed in the present study by using a modified wedge interfering etalon (MWIE), a linear charge couple device (CCD) and a fast digital signal processor (DSP). The MSFTS possesses some advantages such as small volume, low cost, high speed, stable performance and good signal to noise ratio. MSFTS can detect the spectrum of HIPL, the short pulse width of laser is about 10 ns, and the spectrum scope is from 400 to 1 100 nm. The key element of MSFTS is MWIE which is composed of two triangle prisms, one of which is a right angle prism with two equal acute angles of 45 degrees, another prism has no right angle, one of the acute angles is 45 degrees, and another is slightly smaller than 45 degrees. The long sides of the two prisms were bonded by transparent glass glue, and the adhesive surface is plated with special material which serves as a beam splitter (BS). The incident laser will be split into two equal strength beams with continuously changing optical path difference, the two beams will interfere and form interferogram which will be focused by a cylinder as a line and transformed as s electronic signal by CCD. The electronic signal was processed by using a DSP, and finally we obtained the spectrum of the incident hostile laser by applying fast Fourier transform (FFT). We have established the experiment system of MSFTS, and used the system and the spectrometer Q8344A made by Advantest Company in Japan to measure the spectra of the seven lasers with different central wavelengths: 635, 650, 670, 780, 808, 850 and 980 nm. The measurement result shows that the worst wavelength resolution is 8. 845 nm at 1 100 nm, the best wavelength resolution is 1.170 nm at 400 nm, the relative average error of central wavelength is 0.269 nm, the absolute average error is 0.919 nm and signal-to-noise ratio of our experiment system is better than

  4. Detection and measurement of electroreflectance on quantum cascade laser device using Fourier transform infrared microscope

    SciTech Connect

    Enobio, Eli Christopher I.; Ohtani, Keita; Ohno, Yuzo; Ohno, Hideo

    2013-12-02

    We demonstrate the use of a Fourier Transform Infrared microscope system to detect and measure electroreflectance (ER) from mid-infrared quantum cascade laser (QCL) device. To characterize intersubband transition (ISBT) energies in a functioning QCL device, a microscope is used to focus the probe on the QCL cleaved mirror. The measured ER spectra exhibit resonance features associated to ISBTs under applied electric field in agreement with the numerical calculations and comparable to observed photocurrent, and emission peaks. The method demonstrates the potential as a characterization tool for QCL devices.

  5. Adaptive-feedback spectral-phase control for interactions with transform-limited ultrashort high-power laser pulses.

    PubMed

    Liu, Cheng; Zhang, Jun; Chen, Shouyuan; Golovin, Gregory; Banerjee, Sudeep; Zhao, Baozhen; Powers, Nathan; Ghebregziabher, Isaac; Umstadter, Donald

    2014-01-01

    Fourier-transform-limited light pulses were obtained at the laser-plasma interaction point of a 100-TW peak-power laser in vacuum. The spectral-phase distortion induced by the dispersion mismatching between the stretcher, compressor, and dispersive materials was fully compensated for by means of an adaptive closed-loop. The coherent temporal contrast on the sub-picosecond time scale was two orders of magnitude higher than that without adaptive control. This novel phase control capability enabled the experimental study of the dependence of laser wakefield acceleration on the spectral phase of intense laser light.

  6. Experimental insight into the cyclic softening/hardening behavior of austenitic stainless steel using ultrasonic higher harmonics

    NASA Astrophysics Data System (ADS)

    Zhang, Jianfeng; Xuan, Fu-zhen; Xiang, Yanxun; Zhao, Peng

    2014-11-01

    The correlation of cyclic hardening/softening behavior of 304 stainless steel (SS) was investigated using nonlinear ultrasonic wave technique. Results reveal that primary hardening leads to the increase of acoustic nonlinearity, while secondary hardening causes the reverse tendency. This distinct phenomenon is governed by two competitive mechanisms: in the primary-hardening stage, the ascended acoustic nonlinearity is related to the increase of planar dislocation structures. While in the second-hardening stage, the decrease of acoustic nonlinearity is partly caused by the development of cell structures. In addition, the deformation-induced martensitic transformation also contributes to the increase of acoustic nonlinearity under higher stress amplitudes.

  7. Industrial Hardening: 1980 Technical Report.

    DTIC Science & Technology

    1981-06-01

    AD-AI02 621 SCIENTIFIC SERVICE INC REDWOOD CITY CA F/6 15/3 INDUSTRIAL HARDENING: 1980 TECHNICAL REPORT . (U) JUN 81 J V ZACCOR, C WILTON. R D BERNARD...INDUSTRIAL HARDENING. 1980 TECHNICAL REPORT zFINAL REPORT OL ELTC : -. brCc -i ’ Approved for public release; Contract No. EMW-C-0154 distribution...TYPE Of REPORT & PERIOD COVERED INDUSTRIAL HARDENING: 198k TECHNICAL REPORT , Final Ppoe t *PEg 8’Wo-C"EPT UMBER 7. AUTHOR(@) S. CONTRACT OR GRANT

  8. System-Level Radiation Hardening

    NASA Technical Reports Server (NTRS)

    Ladbury, Ray

    2014-01-01

    Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

  9. Surface oxidation and phase transformation of the stainless steel by hybrid laser-waterjet impact

    NASA Astrophysics Data System (ADS)

    Weiss, L.; Aillerie, M.; Tazibt, A.; Tidu, A.

    2014-09-01

    Hybrid jets (laser guided by water jet) are commonly used in the area of microelectronics for cutting thin wafer plates and for the design of special pieces. In this context, the hybrid jet works with a low power and low pressure. Efforts are made to apply and to improve this hybrid technology for cutting thicker metallic materials. In order to facilitate this development, we have studied the effects induced by a water jet-laser system coupled to the same point on a metallic material. The pressure of the water jet is about 1 MPa and the power of the laser source is about 400 W, which is much higher than the actual hybrid jet power. As a result, in the case of 301 L steel plates, we have noticed the formation of a magnetite layer around the cut in accordance with the high temperature reactions between water and iron, but, surprisingly, in this case, the reaction is practically instantaneous. A small percentage of hematite also appears, from a secondary reaction of reduction of magnetite. By using different techniques (Raman spectroscopy, optical microscopy, SEM, XRD…) we have observed, firstly, that the width of the oxidized zone is proportional to the cutting speed and on the other hand, that there exists a phase transformation in a small heat-affected zone, consistent with the hybrid jets literature.

  10. Matrix-assisted laser desorption fourier transform mass spectrometry for biological compounds

    SciTech Connect

    Hettich, R.; Buchanan, M.

    1990-01-01

    The recent development of matrix-assisted UV laser desorption (LD) mass spectrometry has made possible the ionization and detection of extremely large molecules (with molecular weights exceeding 100,000 Daltons). This technique has generated enormous interest in the biological community for the direct examination of large peptides and oligonucleotides. Although this matrix-assisted ionization method has been developed and used almost exclusively with time-of-flight (TOF) mass spectrometers, research is currently in progress to demonstrate this technique with trapped ion mass spectrometers, such as Fourier transform ion cyclotron resonance mass spectrometry (FTMS). The potential capabilities of FTMS for wide mass range, high resolution measurement, and ion trapping experiments suggest that this instrumental technique should be useful for the detailed structural characterization of large ions generated by the matrix-assisted technique. We have recently demonstrated that matrix-assisted ultraviolet laser desorption can be successfully used with FTMS for the ionization of small peptides. The objective of this report is to summarize the application and current limitations of matrix-assisted laser desorption FTMS for the characterization of peptides and oligonucleotides at the isomeric level. 4 refs., 3 figs., 2 tabs.

  11. Contact allergy to epoxy hardeners.

    PubMed

    Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta

    2014-09-01

    Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Case hardenability at high carbon levels

    SciTech Connect

    Walton, H.W.

    1995-02-01

    Loss of hardenability in the case was thought to be responsible for a lower than specified hardness found on a large carburized bushing. Pseudo Jominy testing on several high hardenability carburizing grades confirmed that hardenability fade was present at carbon levels above 0.65% and particularly for those steels containing molybdenum. Analysis of previous work provided a formula for calculating Jominy hardenability at various carbon levels. Again the results confirmed that the loss of hardenability was more severe in steels containing molybdenum.

  13. Mid-infrared imaging Fourier transform spectrometry for high power fiber laser irradiated fiberglass composites

    NASA Astrophysics Data System (ADS)

    Acosta, R. I.; Gross, K. C.; Perram, G. P.

    2012-03-01

    New measurement techniques to study continuous wave (CW) laser-material interactions are emerging with the ability to monitor the evolving, spatial distribution of the state of the surface-gas boundary layer. A qualitative analysis of gas phase combustion plumes above the surface of laser irradiated fiberglass composites is developed from fast framing hyperspectral imagery observations. An imaging Fourier Transform Spectrometer (IFTS) operating in the mid-infrared (MWIR) with high framing rate has recently been developed at the Air Force Institute of Technology (AFIT) in collaboration with Telops Inc. A 320 x 256 indium antimonide (InSb) focal plane array with spectral response from 1.5 - 5.5 μm is mated with a Michelson interferometer to achieve spectral resolutions as high as 0.25 cm-1. The very fast 16- tap InSb array frames at 1.9 kHz for the full 320 x 256 frame size. The single pixel field of view of 0.3 mrad provides a spatial resolution of 1 mm at the minimum focal distance of 3 m. Painted and unpainted fiberglass composites are irradiated with a 1064 nm CW Nd:YAG laser for 60 s at 100 W in air at atmospheric pressure. Selective emission in the region of 2100 - 3200 cm-1 is readily evident and is used to develop a time-dependent spatial map of both temperature and plume constituents. The time evolution of gas phase combustion products such as CO and CO2 molecules are monitored, with a spectral resolution of 2 cm-1. High-speed imagery is obtained using a low-pass filter for the interferograms, illustrating significant turbulent behavior during laser irradiation. Spatial brightness temperature maps exceed 600 K. Spatial variation in the ratio of [CO2]/[CO] indicates an interplay between heterogeneous and homogeneous kinetics.

  14. TRANSFORMATION

    SciTech Connect

    LACKS,S.A.

    2003-10-09

    Transformation, which alters the genetic makeup of an individual, is a concept that intrigues the human imagination. In Streptococcus pneumoniae such transformation was first demonstrated. Perhaps our fascination with genetics derived from our ancestors observing their own progeny, with its retention and assortment of parental traits, but such interest must have been accelerated after the dawn of agriculture. It was in pea plants that Gregor Mendel in the late 1800s examined inherited traits and found them to be determined by physical elements, or genes, passed from parents to progeny. In our day, the material basis of these genetic determinants was revealed to be DNA by the lowly bacteria, in particular, the pneumococcus. For this species, transformation by free DNA is a sexual process that enables cells to sport new combinations of genes and traits. Genetic transformation of the type found in S. pneumoniae occurs naturally in many species of bacteria (70), but, initially only a few other transformable species were found, namely, Haemophilus influenzae, Neisseria meningitides, Neisseria gonorrheae, and Bacillus subtilis (96). Natural transformation, which requires a set of genes evolved for the purpose, contrasts with artificial transformation, which is accomplished by shocking cells either electrically, as in electroporation, or by ionic and temperature shifts. Although such artificial treatments can introduce very small amounts of DNA into virtually any type of cell, the amounts introduced by natural transformation are a million-fold greater, and S. pneumoniae can take up as much as 10% of its cellular DNA content (40).

  15. Process design of press hardening with gradient material property influence

    SciTech Connect

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-04

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  16. CONTROL OF LASER RADIATION PARAMETERS: Cross modulation method of transformation of the spatial coherence of pulsed laser radiation in a nonlinear medium

    NASA Astrophysics Data System (ADS)

    Kitsak, M. A.; Kitsak, A. I.

    2008-04-01

    The cross modulation method of transformation of the spatial coherence of low-power pulsed laser radiation in a nonlinear medium is proposed. The method is realised experimentally in a multimode optical fibre. The estimates of the degree of spatial coherence of radiation subjected to the phase cross modulation demonstrated the high efficiency of this radiation decorrelation mechanism.

  17. TRANSFORMER

    DOEpatents

    Baker, W.R.

    1959-08-25

    Transformers of a type adapted for use with extreme high power vacuum tubes where current requirements may be of the order of 2,000 to 200,000 amperes are described. The transformer casing has the form of a re-entrant section being extended through an opening in one end of the cylinder to form a coaxial terminal arrangement. A toroidal multi-turn primary winding is disposed within the casing in coaxial relationship therein. In a second embodiment, means are provided for forming the casing as a multi-turn secondary. The transformer is characterized by minimized resistance heating, minimized external magnetic flux, and an economical construction.

  18. Gaussian laser beam transformation into an optical vortex beam by helical lens

    NASA Astrophysics Data System (ADS)

    Janicijevic, Ljiljana; Topuzoski, Suzana

    2016-01-01

    In this article, we investigate the Fresnel diffraction characteristics of the hybrid optical element which is a combination of a spiral phase plate (SPP) with topological charge p and a thin lens with focal length f, named the helical lens (HL). As incident a Gaussian laser beam is treated, having its waist a distance ζ from the HL plane and its axis passing through the centre of the HL. It is shown that the SPP introduces a phase singularity of pth order to the incident beam, while the lens transforms the beam characteristic parameters. The output light beam is analyzed in detail: its characteristic parameters and focusing properties, amplitude and intensity distributions and the vortex rings profiles, and radii, at any z distance behind the HL plane, as well as in the near and far field.

  19. Wavelet transform based on the optimal wavelet pairs for tunable diode laser absorption spectroscopy signal processing.

    PubMed

    Li, Jingsong; Yu, Benli; Fischer, Horst

    2015-04-01

    This paper presents a novel methodology-based discrete wavelet transform (DWT) and the choice of the optimal wavelet pairs to adaptively process tunable diode laser absorption spectroscopy (TDLAS) spectra for quantitative analysis, such as molecular spectroscopy and trace gas detection. The proposed methodology aims to construct an optimal calibration model for a TDLAS spectrum, regardless of its background structural characteristics, thus facilitating the application of TDLAS as a powerful tool for analytical chemistry. The performance of the proposed method is verified using analysis of both synthetic and observed signals, characterized with different noise levels and baseline drift. In terms of fitting precision and signal-to-noise ratio, both have been improved significantly using the proposed method.

  20. Single-pulse transformation of Ag thin film into nanoparticles via laser-induced dewetting

    NASA Astrophysics Data System (ADS)

    Oh, Yoonseok; Lee, Myeongkyu

    2017-03-01

    In this study, we show that Ag thin films deposited on glass can be transformed into nanoparticles by laser-induced dewetting using a nanosecond-pulsed Nd:YAG laser. The film could be completely dewetted by a single pulse and the pulse energy density required for a 10 nm-thick Ag film was 86 mJ/cm2 at λ = 1064 nm. This made it possible to dewet a film area of ∼10 cm2 by a single pulse with energy of 850 mJ. The produced particles exhibited a monomodal size distribution and the mean particle size increased as the initial film thickness increased. Repeated exposure to pulses induced no noticeable change in the particle size distribution. The initial film thickness was the only factor that determined the mean particle size. The absorption spectra of dewetted films were well consistent with the surface plasma resonance behaviors of metal nanoparticles. This process provides a facile and scalable method of forming metal nanoparticle arrays for plasmonic and other applications.

  1. Exploiting high resolution Fourier transform spectroscopy to inform the development of a quantum cascade laser based explosives detection systems

    NASA Astrophysics Data System (ADS)

    Carlysle, Felicity; Nic Daeid, Niamh; Normand, Erwan; McCulloch, Michael

    2012-10-01

    Fourier Transform infrared spectroscopy (FTIR) is regularly used in forensic analysis, however the application of high resolution Fourier Transform infrared spectroscopy for the detection of explosive materials and explosive precursors has not been fully explored. This project aimed to develop systematically a protocol for the analysis of explosives and precursors using Fourier Transform infrared spectroscopy and basic data analysis to enable the further development of a quantum cascade laser (QCL) based airport detection system. This paper details the development of the protocol and results of the initial analysis of compounds of interest.

  2. Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route

    NASA Astrophysics Data System (ADS)

    Karatutlu, Ali; Little, William; Ersoy, Osman; Zhang, Yuanpeng; Seker, Isa; Sapelkin, Andrei

    2015-12-01

    In this study, with the aid of Raman measurements, we have observed transformations in small (˜3 nm and ˜10 nm) free-standing Ge nanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Ge powder and by colloidal synthesis route. We found that the transformation path depends on laser power and exposure time. At relatively low values of the laser power (2 mW) over a period of 100 min, the Raman signal indicates transformation of the sample from a nanocrystaline to bulk-like state, followed by partial oxidation and finally a conversion of the entire sample into alpha-quartz type GeO2. However, when the laser power is set at 60 mW, we observed a heat release during an explosive crystallization of the nanocrystalline material into bulk Ge without noticeable signs of oxidation. Together with the transmission electron microscopy measurements, these results suggest that the chemical stain etching method for the preparation of porous Ge may not be a top-down process as has been widely considered, but a bottom up one. Systematic studies of the laser exposure on Ge nanoparticles prepared by colloidal synthesis results in the fact that the explosive crystallisation is common for H-terminated and partially disordered Ge nanoparticles regardless of its particle size. We suggest possible bio-medical applications for the observed phenomena.

  3. Laser-induced particle size tuning and structural transformations in germanium nanoparticles prepared by stain etching and colloidal synthesis route

    SciTech Connect

    Karatutlu, Ali E-mail: ali.karatutlu@bou.edu.tr; Seker, Isa

    2015-12-28

    In this study, with the aid of Raman measurements, we have observed transformations in small (∼3 nm and ∼10 nm) free-standing Ge nanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Ge powder and by colloidal synthesis route. We found that the transformation path depends on laser power and exposure time. At relatively low values of the laser power (2 mW) over a period of 100 min, the Raman signal indicates transformation of the sample from a nanocrystaline to bulk-like state, followed by partial oxidation and finally a conversion of the entire sample into alpha-quartz type GeO{sub 2}. However, when the laser power is set at 60 mW, we observed a heat release during an explosive crystallization of the nanocrystalline material into bulk Ge without noticeable signs of oxidation. Together with the transmission electron microscopy measurements, these results suggest that the chemical stain etching method for the preparation of porous Ge may not be a top-down process as has been widely considered, but a bottom up one. Systematic studies of the laser exposure on Ge nanoparticles prepared by colloidal synthesis results in the fact that the explosive crystallisation is common for H-terminated and partially disordered Ge nanoparticles regardless of its particle size. We suggest possible bio-medical applications for the observed phenomena.

  4. Feasibility study for detecting copper contaminants in transformer insulation using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Aparna, N.; Vasa, Nilesh J.; Sarathi, R.; Rajan, J. Sundara

    2014-10-01

    In recent times, copper sulphide (Cu2S) diffusion in the transformer insulation is a major problem reducing the life of transformers. It is therefore essential to identify a simple methodology to understand the diffusion of Cu2S into the solid insulation [oil impregnated pressboard (OIP)]. In the present work, laser-induced breakdown spectroscopy (LIBS) was adopted to study the diffusion of Cu2S into the pressboard insulation and to determine the depth of diffusion. The diffusion of Cu2S in pressboard was confirmed by electrical discharge studies. In general, flashover voltage and increase in ageing duration of pressboard insulation/Cu concentration had inverse relationship. The characteristic emission lines were also studied through optical emission spectroscopy. Based on LIBS studies with Cu powder dispersed pressboard samples, Cu I emission lines were found to be resolvable up to a lowest concentration of 5 μg/cm2. The LIBS intensity ratio of Cu I-Ca II emission lines were found to increase with increase in the ageing duration of the OIP sample. LIBS studies with OIP samples showed an increase in the optical emission lifetime. LIBS results were in agreement with the electrical discharge studies.

  5. Surface Hardening by Laser Skin Melting

    DTIC Science & Technology

    1979-07-01

    0 C for 3.6xlO3 s followed by oil quenching. This produced the discernible fine bainitic / or martensitic structure; it should be noted that this...genization due to vigorous hydrothermal mixing and liquid super - heating. Computations by Greenwald (13) from a heat flow model are graphically represented

  6. Freeform beam shaping for high-power multimode lasers

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Laskin, Vadim

    2014-03-01

    Widening of using high power multimode lasers in industrial laser material processing is accompanied by special requirements to irradiance profiles in such technologies like metal or plastics welding, cladding, hardening, brazing, annealing, laser pumping and amplification in MOPA lasers. Typical irradiance distribution of high power multimode lasers: free space solid state, fiber-coupled solid state and diodes lasers, fiber lasers, is similar to Gaussian. Laser technologies can be essentially improved when irradiance distribution on a workpiece is uniform (flattop) or inverse-Gauss; when building high-power pulsed lasers it is possible to enhance efficiency of pumping and amplification by applying super-Gauss irradiance distribution with controlled convexity. Therefore, "freeform" beam shaping of multimode laser beams is an important task. A proved solution is refractive field mapping beam shaper like Shaper capable to control resulting irradiance profile - with the same unit it is possible to get various beam profiles and choose optimum one for a particular application. Operational principle of these devices implies transformation of laser irradiance distribution by conserving beam consistency, high transmittance, providing collimated low divergent output beam. Using additional optics makes it possible to create resulting laser spots of necessary size and round, elliptical or linear shape. Operation out of focal plane and, hence, in field of lower wavefront curvature, allows extending depth of field. The refractive beam shapers are implemented as telescopes and collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation.

  7. Verification of the windings axial clamping forces for high voltage power transformers by using passively mode-locked fiber lasers

    NASA Astrophysics Data System (ADS)

    Şchiopu, IonuÅ£ Romeo; ǎgulinescu, Andrei, Dr; Iordǎnescu, Raluca; Marinescu, Andrei

    2015-02-01

    The current paper describes an optoelectronic method for direct monitoring of the axial clamping forces both in static and in dynamic duty. As advantages of this method we can state that it can be applied both to new and refurbished transformers without performing constructive changes or affecting in any way the transformer safety in operation. For monitoring the axial clamping forces for high-voltage (HV) power transformers, we use an optical fiber that we integrate into the laser cavity of a passively mode-locked fiber laser (PMFL). To each axial clamp corresponds a solitonic optical spectrum that is changed at the periodical passing of the fundamental soliton pulse through the sensitive fiber inside the transformer. Moreover, as a specific characteristic, the laser stability is unique for each set of axial clamping forces. Other important advantages of using an optical fiber as compared to the classical approach in which electronic sensors are used consist in the good reliability and insulator properties of the optical fiber, avoiding any risk of fire or damage of the transformer.

  8. HARDENING FROG POINTS BY EXPLOSIVE ENERGY,

    DTIC Science & Technology

    Experiments were made to determine the most efficient method of strain hardening railroad frog points in order to increase their fatigue resistance...Mechanical strain hardening with rolls 40 mm in diameter under a load of 8 tons produced in standard frogs cast from G13L high-manganese steel (AISI...Hadfield steel) a work-hardened surface layer 3-5 mm thick with a hardness of 340 HB. In other experiments, the frogs were hardened by exploding a

  9. Precipitation hardening in aluminum alloy 6022

    SciTech Connect

    Miao, W.F.; Laughlin, D.E.

    1999-03-05

    Although the precipitation process in Al-Mg-Si alloys has been extensively studied, the understanding of the hardening process is still incomplete, since any change in composition, processing and aging practices, etc., could affect the precipitation hardening behavior. In this paper, hardness measurements, differential scanning calorimetry and transmission electron microscopy have been utilized to study the precipitation hardening behavior in aluminum alloy 6022.

  10. Laser vision: lidar as a transformative tool to advance critical zone science

    NASA Astrophysics Data System (ADS)

    Harpold, A. A.; Marshall, J. A.; Lyon, S. W.; Barnhart, T. B.; Fisher, B.; Donovan, M.; Brubaker, K. M.; Crosby, C. J.; Glenn, N. F.; Glennie, C. L.; Kirchner, P. B.; Lam, N.; Mankoff, K. D.; McCreight, J. L.; Molotch, N. P.; Musselman, K. N.; Pelletier, J.; Russo, T.; Sangireddy, H.; Sjöberg, Y.; Swetnam, T.; West, N.

    2015-01-01

    Laser vision: lidar as a transformative tool to advance critical zone science. Observation and quantification of the Earth surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of Critical Zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and ecosphere shape and maintain the "zone of life", extending from the groundwater to the vegetation canopy. Lidar holds promise as a transdisciplinary CZ research tool by simultaneously allowing for quantification of topographic, vegetative, and hydrological data. Researchers are just beginning to utilize lidar datasets to answer synergistic questions in CZ science, such as how landforms and soils develop in space and time as a function of the local climate, biota, hydrologic properties, and lithology. This review's objective is to demonstrate the transformative potential of lidar by critically assessing both challenges and opportunities for transdisciplinary lidar applications. A review of 147 peer-reviewed studies utilizing lidar showed that 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % have an interdisciplinary focus. We find that using lidar to its full potential will require numerous advances across CZ applications, including new and more powerful open-source processing tools, exploiting new lidar acquisition technologies, and improved integration with physically-based models and complementary in situ and remote-sensing observations. We provide a five-year vision to utilize and advocate for the expanded use of lidar datasets to benefit CZ science applications.

  11. Kinematic hardening in creep of Zircaloy

    NASA Astrophysics Data System (ADS)

    Sedláček, Radan; Deuble, Dietmar

    2016-10-01

    Results of biaxial creep tests with stress changes on Zircaloy-2 tube samples are presented. A Hollomon-type viscoplastic strain hardening model is extended by the Armstrong-Frederic nonlinear kinematic hardening law, resulting in a mixed (i.e. isotropic and kinematic) strain hardening model. The creep tests with stress changes and similar tests published in the literature are simulated by the models. It is shown that introduction of the kinematic strain hardening in the viscoplastic strain hardening model is sufficient to describe the creep transients following stress drops, stress reversals and stress removals.

  12. Physiological effects of indomethacin and celecobix: an S-transform laser Doppler flowmetry signal analysis

    NASA Astrophysics Data System (ADS)

    Assous, S.; Humeau, A.; Tartas, M.; Abraham, P.; L'Huillier, J. P.

    2005-05-01

    Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing of laser Doppler flowmetry (LDF) signals using the S-transform. The approach is motivated by the excellent localization, in both time and frequency, afforded by the wavelet basis functions. Suitably chosen Gaussian wavelet functions are used to characterize the subspace of signals that have a given localized time-frequency support, thus enabling a time-frequency partitioning of signals. In this paper, the goal is to study the influence of various pharmacological substances taken by the oral way (celecobix (Celebrex®), indomethacin (Indocid®) and placebo) on the physiological activity behaviour. The results show that no statistical differences are observed in the energy computed from the time-frequency representation of LDF signals, for the myogenic, neurogenic and endothelial related metabolic activities between Celebrex and placebo, and Indocid and placebo. The work therefore proves that these drugs do not affect these physiological activities. For future physiological studies, there will therefore be no need to exclude patients having taken cyclo-oxygenase 1 inhibitions.

  13. Surface Fatigue Resistance with Induction Hardening

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis; Turza, Alan; Chapman, Mike

    1996-01-01

    Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

  14. Potential scattering of electrons in the presence of intense laser fields using the Kramers-Henneberger transformation

    NASA Astrophysics Data System (ADS)

    Bhatt, R.; Piraux, B.; Burnett, K.

    1988-01-01

    The Kramers-Henneberger transformation is used to treat potential scattering of electrons in the presence of a strong laser field. As a first step, the one-dimensional scattering by a polarization potential is considered. It is shown that the static part of the effective potential, often called the dressed potential, may support more bound states than the original potential depending on the intensity and frequency of the field. Exact results for the transmission and reflection coefficients are presented and two approximations are discussed: A perturbative approach based on the above transformation and the adiabatic approximation.

  15. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  16. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  17. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  18. Microwave Hardening Technology Development Program.

    DTIC Science & Technology

    1988-12-20

    FIELD GROUP SUB-GROUP Microwave Hardening Limiters Fiber’-Optic Components Varistors Cost Benefit Analyses 19. ABSTRACT (Continue an everse If... varistor paint material applied to a co-planar waveguide transmission line when injected with micro- wave pulses, as well as the impact of the paint...needed on the results of these efforts, two other unpublished reports on the fiber-optics component direct injection tests and the varistor paint limiter

  19. Jarosite as a Storage Mineral for Small Organic Molecules: Investigations of Natural Samples Using an 'In Situ' Laser Desorption Fourier Transform Mass Spectrometry Technique

    NASA Astrophysics Data System (ADS)

    Kotler, J. M.; Hinman, N. W.; Yan, B.; Stoner, D. L.; Scott, J. R.

    2007-03-01

    The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various locations worldwide including jarosite precipitated in the lab by acidothiobacillus ferroxidans.

  20. [Accuracy Improvement of Temperature Calculation of the Laser-Induced Plasma Using Wavelet Transform Baseline Subtraction].

    PubMed

    Liu, Li; Xiao, Ping-ping

    2016-02-01

    Temperature is one of the most important parameters in studying of laser-induced plasma characteristics. To reduce the impact of continuous background on the calculation of temperatures using Boltzmann plots, the wavelet transform was used to decompose the spectrums, and the low-frequency signals represented the spectral baseline were deducted by using soft-threshold method. Selecting the appropriate wavelet decomposition level L and threshold coefficient a can increase the linear regression coefficient R2 of Boltzmann plots, and the calculation accuracy of plasma temperature was improved. The LIBS spectra of low alloy steel sample region from 417 to 445 nm were decomposed by using db4 wavelet, and then baseline subtraction and signal reconstruction were carried out, respectively. Twelve Fe atomic lines were chosen to establish Boltzmann plots, and the temperatures were calculated from the slope of the fitted lines in the plots. The value L and a were optimized according R², the results showed that the 8-layer db4 wavelet decomposition can gain the high R², while the value of a associated with the delay time td, e. g. , the optimum a corresponding to maximum values of R² is 0.3 when td ≤ 4.0 µs, and then decrease with the increasing of td, and reduced to 0 when td ≥ 6. 0 µs. The interference due to baseline on the spectral characteristic lines gradually reduced with the increasing of td, and therefore a decreased with td increase. After the baseline was deducted, the temperature calculated by Boltzmann plot decrease of about 2 000 to 3 000 K. The temperature gradually decreased with the increasing of the td, and the temperature fluctuation is reduced after baseline subtraction, these results are consistent with the physical process of plasma expansion.

  1. Computationally efficient method for Fourier transform of highly chirped pulses for laser and parametric amplifier modeling.

    PubMed

    Andrianov, Alexey; Szabo, Aron; Sergeev, Alexander; Kim, Arkady; Chvykov, Vladimir; Kalashnikov, Mikhail

    2016-11-14

    We developed an improved approach to calculate the Fourier transform of signals with arbitrary large quadratic phase which can be efficiently implemented in numerical simulations utilizing Fast Fourier transform. The proposed algorithm significantly reduces the computational cost of Fourier transform of a highly chirped and stretched pulse by splitting it into two separate transforms of almost transform limited pulses, thereby reducing the required grid size roughly by a factor of the pulse stretching. The application of our improved Fourier transform algorithm in the split-step method for numerical modeling of CPA and OPCPA shows excellent agreement with standard algorithms.

  2. Stress and Distortion Evolution During Induction Case Hardening of Tube

    NASA Astrophysics Data System (ADS)

    Nemkov, Valentin; Goldstein, Robert; Jackowski, John; Ferguson, Lynn; Li, Zhichao

    2013-07-01

    Simulation of stresses during heat treatment relates usually to furnace heating. Induction heating provides a very different evolution of temperature in the part and therefore different stresses. This may be positive for service properties or negative, reducing component strength or even causing cracks. A method of coupled simulation between electromagnetic, thermal, structural, stress, and deformation phenomena during induction tube hardening is described. Commercial software package ELTA is used to calculate the power density distribution in the load resulting from the induction heating process. The program DANTE is used to predict temperature distribution, phase transformations, stress state, and deformation during heating and quenching. Analyses of stress and deformation evolution were made on a simple case of induction hardening of external (1st case) and internal (2nd case) surfaces of a thick-walled tubular body.

  3. Energy-Efficient Thermomagnetic and Induction Hardening

    SciTech Connect

    2009-02-01

    This factsheet describes a research project that will develop and test a hybrid thermomagnetic and induction hardening technology to replace conventional heat treatment processes in forging applications.

  4. Radiation Hardened Electronics for Extreme Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

  5. DISPERSION HARDENING OF URANIUM METAL

    DOEpatents

    Arbiter, W.

    1963-01-15

    A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

  6. PHASE TRANSFORMATIONS IN METALS AND ALLOYS (SELECTED ARTICLES),

    DTIC Science & Technology

    Contents: Stabilization of reverse martensite transformation under the influence of intraphase work hardening; and Structural changes during decomposition of supersaturated solid solution of tungsten in cobalt.

  7. Analysis of structure and phase composition of rails subjected to differential hardening at different regimes

    SciTech Connect

    Gromov, V. E. Morozov, K. V. Konovalov, S. V.; Alsaraeva, K. V.; Semina, O. A.; Ivanov, Yu. F.; Volkov, K. V.

    2014-11-14

    Differential hardening of rails by compressed air in different regimes is accompanied by formation of morphologically different structure, being formed according to the diffusion mechanism of γ↔α transformation and consisting of grains of lamellar pearlite, free ferrite and grains of ferrite-carbide mixture. By methods of transmission electron microscopy the layer by layer analysis of differentially hardened rails has been carried out, the quantitative parameters of the structure, phase composition and dislocation substructure have been established and their comparison has been made for different regimes of hardening. It has been found that the structure-phase states being formed have gradient character, defined by the hardening regime, direction of study from the surface of rolling and by depth of location of layer under study.

  8. An Abel transform for deriving line-of-sight wind profiles from LEO-LEO infrared laser occultation measurements

    NASA Astrophysics Data System (ADS)

    Syndergaard, S.; Kirchengast, G.

    2016-03-01

    We have developed a formula for the retrieval of the line-of-sight (l.o.s.) wind speed from future low Earth orbit (LEO) satellite-to-satellite infrared laser occultation measurements. The formula involves an Abelian integral transform akin to the Abel transform widely used for deriving refractive index from bending angle in Global Navigation Satellite System radio occultation measurements. Besides the Abelian integral transform, the formula is derived from a truncated series expansion of the volume absorption coefficient as a function of frequency and includes a simple absorption-line-asymmetry correction term. A first-order formulation (referred to as the standard formula) is complemented by higher-order terms that can be used for high-accuracy computations. Under the assumptions of spherical symmetry and perfect knowledge of spectroscopy, the residual l.o.s. wind error from using the standard formula rather than the high-accuracy formula is assessed to be small compared to that anticipated from measurement errors in a real experiment. Applying the new formula just in standard form to future infrared laser transmission profiles would therefore enable the retrieval of l.o.s. stratospheric wind profiles with an accuracy limited mainly by measurement errors, residual spectroscopic errors, and deviations from spherical symmetry.

  9. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  10. Practical aspects of registration the transformation of a river valley by beavers using terrestrial laser scanning

    NASA Astrophysics Data System (ADS)

    Tyszkowski, Sebastian; Błaszkiewicz, Mirosław; Brykała, Dariusz; Gierszewski, Piotr; Kaczmarek, Halina; Kordowski, Jarosław; Słowiński, Michał

    2016-04-01

    Activity of beavers (Castor fiber) often significantly affects the environment in which they life. The most commonly observed effect of their being in environment is construction of beaver dams and formation a pond upstream. However, in case of a sudden break of a dam and beaver pond drainage, the valley below the dam may also undergo remodelling. The nature and magnitude of these changes depends on the quantity of water and its energy as well as on the geological structure of the valley. The effects of such events can be riverbank erosion, and the deposition of the displaced of erosion products in the form of sandbars or fans. The material can also be accumulated in local depressions or delivered to water bodies. Such events may occur multiple times in the same area. To assess their impact on the environment it is important to quantify the displaced material. The study of such transformations was performed within a small valley of the river of Struga Czechowska (Tuchola Pinewood Forest, Poland). The valley is mainly cut in sands and gravels. Its steep banks are overgrown with bushes and trees. The assessment of changes in morphology were based on the event of the beaver pond drainage of 2015. The study uses the measurements from the terrestrial laser scanning (scanner Riegl VZ-4000). The measurements were performed before and after the event. Each of the two models obtained for comparison was made up of more than 20 measurement stations. Point clouds were joined by Multi-Station Adjustment without placing in the terrain any objects of reference. During measurements attention was paid to the changes in morphology of both riverbed and valley surrounding. The paper presents the example of the recorded changes as well as the measurement procedure. Moreover, the aspects of fieldwork and issues related to post-processing, such as merging, filtering of point clouds and detection of changes, are also presented. This study is a contribution to the Virtual Institute of

  11. Effects of Er:YAG laser irradiation and manipulation treatments on dentin components, part 1: Fourier transform-Raman study

    NASA Astrophysics Data System (ADS)

    Soares, Luís Eduardo Silva; Do Espírito Santo, Ana Maria; Junior, Aldo Brugnera; Zanin, Fátima Antônia Aparecida; da Silva Carvalho, Carolina; de Oliveira, Rodrigo; Martin, Airton Abraha~O.

    2009-03-01

    The effects of laser etching, decontamination, and storage treatments on dentin components were studied using Fourier transform (FT)-Raman spectroscopy. Thirty bovine incisors were prepared to expose the dentin surface and then divided in two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in thymol aqueous solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ, and total energy of 12 J). Samples were analyzed by FT-Raman spectroscopy; we collected three spectra for each area (before and after treatment). The integrated areas of five Raman peaks were calculated to yield average spectra. The areas of the peaks associated with phosphate content (P<0.001), type I collagen, and organic C-H bonds (P<0.05) were reduced significantly in group A (control). Analyses of samples irradiated with reduced laser energies did not show significant changes in the dentin components. These results suggest that thymol storage treatment is advised for in vitro study; furthermore, 12 J of Er:YAG laser energy does not affect dentin components.

  12. Low-level laser therapy on MCF-7 cells: a micro-Fourier transform infrared spectroscopy study

    NASA Astrophysics Data System (ADS)

    Magrini, Taciana D.; dos Santos, Nathalia Villa; Milazzotto, Marcella Pecora; Cerchiaro, Giselle; da Silva Martinho, Herculano

    2012-10-01

    Low-level laser therapy (LLLT) is an emerging therapeutic approach for several clinical conditions. The clinical effects induced by LLLT presumably scale from photobiostimulation/photobioinhibition at the cellular level to the molecular level. The detailed mechanism underlying this effect remains unknown. This study quantifies some relevant aspects of LLLT related to molecular and cellular variations. Malignant breast cells (MCF-7) were exposed to spatially filtered light from a He-Ne laser (633 nm) with fluences of 5, 28.8, and 1000 mJ/cm2. The cell viability was evaluated by optical microscopy using the Trypan Blue viability test. The micro-Fourier transform infrared technique was employed to obtain the vibrational spectra of each experimental group (control and irradiated) and identify the relevant biochemical alterations that occurred due to the process. It was observed that the red light influenced the RNA, phosphate, and serine/threonine/tyrosine bands. We found that light can influence cell metabolism depending on the laser fluence. For 5 mJ/cm2, MCF-7 cells suffer bioinhibition with decreased metabolic rates. In contrast, for the 1 J/cm2 laser fluence, cells present biostimulation accompanied by a metabolic rate elevation. Surprisingly, at the intermediate fluence, 28.8 mJ/cm2, the metabolic rate is increased despite the absence of proliferative results. The data were interpreted within the retrograde signaling pathway mechanism activated with light irradiation.

  13. Reference Interferometer Using a Semiconductor Laser/LED Reference Source in a Cryogenic Fourier-Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    Martino, Anthony J.; Cornwell, Donald M.

    1998-01-01

    A combination of a single mode AlGaAs laser diode and broadband LED was used in a Michelson interferometer to provide reference signals in a Fourier transform spectrometer, the Composite Infrared Spectrometer, on the Cassini mission to Saturn. The narrowband light from the laser produced continuous fringes throughout the travel of the interferometer, which were used to control the velocity of the scan mechanism and to trigger data sampling. The broadband light from the LED produced a burst of fringes at zero path difference, which was used as a fixed position reference. The system, including the sources, the interferometer, and the detectors, was designed to work both at room temperature and instrument operating temperature of 170 Kelvin. One major challenge that was overcome was preservation, from room temperature to 170 K, of alignment sufficient for high modulation of fringes from the broadband source. Another was the shift of the source spectra about 30 nm toward shorter wavelengths upon cooldown.

  14. Accessing Extreme Spatiotemporal Localization of High-Power Laser Radiation through Transformation Optics and Scalar Wave Equations.

    PubMed

    Fedorov, V Yu; Chanal, M; Grojo, D; Tzortzakis, S

    2016-07-22

    Although tightly focused intense ultrashort laser pulses are used in many applications from nano-processing to warm dense matter physics, their nonparaxial propagation implies the use of numerical simulations with vectorial wave equations or exact Maxwell solvers that have serious limitations and thus have hindered progress in this important field up to now. Here we present an elegant and robust solution that allows one to map the problem on one that can be addressed by simple scalar wave equations. The solution is based on a transformation optics approach and its validity is demonstrated in both the linear and the nonlinear regime. Our solution allows accessing challenging problems of extreme spatiotemporal localization of high power laser radiation that remain almost unexplored theoretically until now.

  15. Radial current high power dummy load for characterizing the high power laser triggered transformer-type accelerator

    NASA Astrophysics Data System (ADS)

    Yin, Yi; Zhong, Hui-Huang; Liu, Jin-Liang; Ren, He-Ming; Yang, Jian-Hua; Zhang, Xiao-Ping; Hong, Zhi-qiang

    2010-09-01

    A radial-current aqueous resistive solution load was applied to characterize a laser triggered transformer-type accelerator. The current direction in the dummy load is radial and is different from the traditional load in the axial. Therefore, this type of dummy load has smaller inductance and fast response characteristic. The load was designed to accommodate both the resistance requirement of accelerator and to allow optical access for the laser. Theoretical and numerical calculations of the load's inductance and capacitance are given. The equivalent circuit of the dummy load is calculated in theory and analyzed with a PSPICE code. The simulation results agree well with the theoretical analysis. At last, experiments of the dummy load applied to the high power spiral pulse forming line were performed; a quasisquare pulse voltage is obtained at the dummy load.

  16. Improved hardening theory for cyclic plasticity.

    NASA Technical Reports Server (NTRS)

    Vos, R. G.; Armstrong, W. H.

    1973-01-01

    A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.

  17. An Investigation of the Massive Transformation from Ferrite to Austenite in Laser-Welded Mo-Bearing Stainless Steels

    NASA Astrophysics Data System (ADS)

    Perricone, M. J.; Dupont, J. N.; Anderson, T. D.; Robino, C. V.; Michael, J. R.

    2011-03-01

    A series of 31 Mo-bearing stainless steel compositions with Mo contents ranging from 0 to 10 wt pct and exhibiting primary δ-ferrite solidification were analyzed over a range of laser welding conditions to evaluate the effect of composition and cooling rate on the solid-state transformation to γ-austenite. Alloys exhibiting this microstructural development sequence are of particular interest to the welding community because of their reduced susceptibility to solidification cracking and the potential reduction of microsegregation (which can affect corrosion resistance), all while harnessing the high toughness of γ-austenite. Alloys were created using the arc button melting process, and laser welds were prepared on each alloy at constant power and travel speeds ranging from 4.2 to 42 mm/s. The cooling rates of these processes were estimated to range from 10 K (°C)/s for arc buttons to 105 K (°C)/s for the fastest laser welds. No shift in solidification mode from primary δ-ferrite to primary γ-austenite was observed in the range of compositions or welding conditions studied. Metastable microstructural features were observed in many laser weld fusion zones, as well as a massive transformation from δ-ferrite to γ-austenite. Evidence of epitaxial massive growth without nucleation was also found when intercellular γ-austenite was already present from a solidification reaction. The resulting single-phase γ-austenite in both cases exhibited a homogenous distribution of Mo, Cr, Ni, and Fe at nominal levels.

  18. A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform

    SciTech Connect

    Sheu, Yae-lin; Hsu, Liang-Yan; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

    2014-11-15

    This study introduces a new adaptive time-frequency (TF) analysis technique, the synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an ab initio level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type of TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation.

  19. Hardening of shear band in metallic glass.

    PubMed

    Wang, J G; Hu, Y C; Guan, P F; Song, K K; Wang, L; Wang, G; Pan, Y; Sarac, B; Eckert, J

    2017-08-01

    Strain hardening, originating from defects such as the dislocation, avails conventional metals of high engineering reliability in applications. However, the hardenability of metallic glass is a long-standing concern due to the lack of similar defects. In this work, we carefully examine the stress-strain relationship in three bulk monolithic metallic glasses. The results show that hardening is surely available in metallic glasses if the effective load-bearing area is considered instantly. The hardening is proposed to result from the remelting and ensuing solidification of the shear-band material under a hydrostatic pressure imposed by the normal stress during the shear banding event. This applied-pressure quenching densifies the metallic glass by discharging the free volume. On the other hand, as validated by molecular dynamics simulations, the pressure promotes the icosahedral short-range order. The densification and icosahedral clusters both contribute to the increase of the shear strength and therefore the hardening in metallic glasses.

  20. Radiation-induced segregation, hardening, and IASCC

    SciTech Connect

    Eason, E.D.; Nelson, E.E.

    1995-12-31

    Intergranular cracking has been discovered after extended radiation exposure in several boiling water reactor (BWR) internal components made of austenitic stainless steel and nickel-based alloys. There are fewer field observations of intergranular cracking in pressurized water reactors (PWR), but failures have occurred in bolts, springs, and fuel cladding. There is concern for other PWR components, some of which will receive greater radiation doses than BWR components during the plant lifetime. This paper presents the results of an investigation on the connection between radiation induced segregation, hardening and irradiation-assisted stress corrosion cracking (IASCC). A data base was developed containing the available data on austenitic stainless steel where the grain boundary composition was measured by Field Emission Gun-Scanning Transmission Election Microscopy (FEG-STEM), the stress corrosion susceptibility was measured by constant extension rate tests (CERT) in light water reactor environments, some estimate of irradiated strength was available and the irradiation was conducted in a power reactor. The data base was analyzed using advanced data analysis techniques, including tree-structured pattern recognition and transformation analysis codes. The most sensitive variables and optimal modeling forms were identified using these techniques, then preliminary models were calibrated using nonlinear least squares. The results suggest that more than one mechanism causes IASCC.

  1. A Transformative Imaging Capability Using Laser Driven Multi MeV Photon Sources

    NASA Astrophysics Data System (ADS)

    Gautier, Donald; Espy, Michelle; Palaniyappan, Sasi; Mendez, Jacob; Nelson, Ronald; Hunter, James; Fernandez, Juan; los alamos national laboratory Team

    2016-10-01

    Recent results from the LANL Trident Laser demonstrate the practical use of a laser of this class ( 70 J, 600 fs) as a multi MeV photon source. The utilization of novel targets operating in the relativistic transparency regime of laser-plasmas has enabled this development. The electron population made from these targets, when coupled to a suitable high-Z converter foil placed near the laser target, produces an intense >1 MeV photon source with a small source size compared to conventional sources. When coupled with efficient imaging detectors, this laser-driven hard x-ray source provides new capabilities to address current non-destructive and dynamic testing problems that require a quantum jump in resolution. ``Flash'' (pulse picosecond) photon imaging, micro-focus resolution enhancement, good object penetration, and magnification (4x) with sufficient dose (>10 Rad/sr) for practical application have all been demonstrated at the LANL Trident Laser, as summarized in this presentation.

  2. Development of high-performance multi-layer resist process with hardening treatment

    NASA Astrophysics Data System (ADS)

    Ono, Yoshiharu; Ishibashi, Takeo; Yamaguchi, Atsumi; Hanawa, Tetsuro; Tadokoro, Masahiro; Yoshikawa, Kazunori; Yonekura, Kazumasa; Matsuda, Keiko; Matsunobe, Takeshi; Fujii, Yasushi; Tanaka, Takeshi

    2007-03-01

    In the manufacture of devices beyond the 45 nm node, it is important to employ a high-performance multi-layer resist (MLR) process that uses silicon containing ARC (Si-ARC) and spin on carbon (SOC). We examined an additional hardening process of SOC by H II plasma treatment in order to improve the etching durability of the MLR. The dry etching durability of H II-plasma-hardened SOC film showed a drastic improvement, while the wiggling features of the MLR without H II treatment observed after SiO II etching disappeared completely. The hardening mechanism of SOC was analyzed by Fourier transform infrared spectroscopy (FTIR) with gradient shaving preparation (GSP) and Raman spectrometry. The formation of diamond-like amorphous carbon at a depth of approximately 50 nm was observed and was attributed to the improvement in the dry etching durability. In addition, the MLR stack with hardening has good reflectivity characteristics. The simulated reflectivity at the interface between the bottom of the resist and top surface of the MLR stack with hardening below 0.6% was attained over a wide range of Si-ARC thicknesses and hyper NA (~1.3) regions. The measured refractive indices of the hardened SOC film at 193 nm had a high value at the surface; however, they gradually decreased toward the inner region and finally became the same as those of untreated SOC. This might be the origin of the estimated excellent reflectivity characteristics.

  3. Effect of phase transformation on optical and dielectric properties of pulsed laser deposited ZnTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Jain, Praveen K.; Salim, Mohammad; Kaur, Davinder

    2016-04-01

    Zinc titanate (ZnTiO3) ceramics were prepared by conventional solid state reaction method using ZnO and TiO2 in a molar ratio of 1:1 with optimized parameters. It was found that the sample sintered at 800 °C for 12 h exhibit single hexagonal phase of ZnTiO3. ZnTiO3 thin film have been deposited on ITO coated glass substrate using pulsed laser deposition (PLD) technique employing a KrF laser source (λ = 248 nm). In present work, the effect of substrate temperature, which leads to transformation of hexagonal phase to cubic phase, has been studied. The XRD pattern revealed that pure hexagonal phase of ZnTiO3 appear upto 400 °C and more increment in substrate temperature leads to transformation of hexagonal phase to cubic phase. We have observed the blue shift in absorption edge at lower temperature. When the substrate temperature increases from 300 to 400 °C the band gap decreases due to strong hexagonal phase, but more increment in substrate temperature increases the band gap causes by change of phase from hexagonal to cubic. The dielectric constant of ZnTiO3 thin film increases as the substrate temperature increases due to the enhancement in crystallinity and improved morphology.

  4. Hybrid CO2 laser/waterjet (CO2-LWJ) cutting of Polycrystalline Cubic Boron Nitride (PCBN) blanks with phase transformation induced fracture

    NASA Astrophysics Data System (ADS)

    Wu, Zhuoru; Melaibari, Ammar A.; Molian, Pal; Shrotriya, Pranav

    2015-07-01

    The present paper investigates a transformation induced fracture mechanism for the cutting of Polycrystalline Cubic Boron Nitride (PCBN) sample by a hybrid CO2 laser/waterjet (CO2-LWJ) manufacturing process. In CO2-LWJ machining, a laser was used for local heating followed by waterjet quenching leading to fracture propagation along the sample surface. Cutting results indicate that as line energy of the laser was increased the sample response transitioned from scribing to through cutting. Raman spectroscopy analysis of the cut surface indicates that laser heated PCBN undergoes chemical phase transformation from sp3-bonded cubic Boron Nitride (cBN) into hexagonal Boron Nitride (hBN) and other sp2-bonded phases. The sp2-bonded structure occupies more volume than sp3-bonded structure such that the transformed material has a tendency to expand the original material and leads to surface deformation around the cutting path. Surface profile of the cut samples was experimentally measured using profilometry and compared with numerical predictions in order to estimate the expansion strain and dimensions of transformation region. Based on the obtained expansion strain and transformation zone, stress fields and crack driving forces were computed for channeling cracks that result in material separation. Comparison of the crack driving forces with fracture toughness of PCBN shows that transformation induced crack propagation is the feasible mechanism for cutting during CO2-LWJ machining.

  5. Modeling and Analysis of Deformation for Spiral Bevel Gear in Die Quenching Based on the Hardenability Variation

    NASA Astrophysics Data System (ADS)

    Zhang, Yingtao; Wang, Gang; Shi, Wankai; Yang, Lin; Li, Zhichao

    2017-07-01

    Spiral bevel gears are widely used to transmit energy between intersecting axes. The strength and fatigue life of the gears are improved by carburizing and quenching. A die quenching process is used to control the deformation of the gear. The deformation is determined by the variations in the hardenability for a certain die quenching process. The relationship between hardenability, phase transformation and deformation needs to be studied to minimize deformation during the adjustment of the die quenching process parameters. In this paper, material properties for 22CrMoH steel are determined by the results of Jominy tests, dilatometry experiments and static mechanical property tests. The material models were built based on testing results under the consideration of hardenability variation. An finite element analysis model was developed to couple the phase transformation and deformation history of the complete carburizing and die quenching process for the spiral bevel gears. The final microstructures in the gear were bainite for low hardenability steel and a mixture of bainite and ferrite for high hardenability steel. The largest buckling deformation at the gear bottom surface is 0.375 mm at the outer circle for the low hardenability gear and 0.091 mm at the inner circle for the high hardenability gear.

  6. Visualization of surface transformations during laser ablation of solids by femtosecond pump-probe time-resolved microscopy

    NASA Astrophysics Data System (ADS)

    Carrasco-García, Irene; Vadillo, José M.; Javier Laserna, J.

    2015-11-01

    A femtosecond time-resolved microscope (fs-TRM) based on pump-probe excitation has been used to follow the dynamic of the processes occurring during laser-matter interaction, from initial surface alterations to final solidification through transient melting. The time-resolved microscope described in the manuscript has been designed to allow a precise control of the excitation beam to cover ranges below and above the plasma formation energy, and a large temporal variation in the pump-probe delay to include the different timescales of the different processes occurring up to the plasma formation. The microscope has been demonstrated to be robust and allows the subpicosecond monitoring of laser ablation single-shot events, of importance in the analysis of ultra thin layers, or biological tissues. The fs-TRM excites (pump) the sample with 35-fs laser pulses at 800 nm and follows the processes by a second (probe) beam at 400 nm. The relative delay between both beams allows the acquisition of pictures with a temporal resolution of 200 fs up to 3 ns after the reaching of the pump pulse. In the ablative regime near the ablation threshold, transient surface reflectivity patterns (dynamic Newton fringes) are observed from a ps to ns time-scale. The timescale and number of such rings are affected by the fluence value. Significant differences between metals (Al, Cu and Sn), semiconductors (Si) and polymers (polytetrafluoroethylene and polyurethane) have been also observed in the transformation patterns.

  7. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate

    PubMed Central

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-01-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 104 about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H13CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line. PMID:26503257

  8. Vacuum compatible sample positioning device for matrix assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry imaging

    PubMed Central

    Aizikov, Konstantin; Smith, Donald F.; Chargin, David A.; Ivanov, Sergei; Lin, Tzu-Yung; Heeren, Ron M. A.; O’Connor, Peter B.

    2011-01-01

    The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in ∼1 × 10–8 mbar vacuum. The range of motion is set to 100 mm × 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The “oversampling” MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter. PMID:21639522

  9. Vacuum compatible sample positioning device for matrix assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry imaging

    SciTech Connect

    Aizikov, Konstantin; Lin, Tzu-Yung; Smith, Donald F.; Heeren, Ron M. A.; Chargin, David A.; Ivanov, Sergei; O'Connor, Peter B.

    2011-05-15

    The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in {approx}1 x 10{sup -8} mbar vacuum. The range of motion is set to 100 mm x 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The ''oversampling'' MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter.

  10. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate

    NASA Astrophysics Data System (ADS)

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-10-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 104 about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H13CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line.

  11. Glass transition and physical hardening of asphalts

    NASA Astrophysics Data System (ADS)

    Kriz, Pavel

    Glass transition and physical hardening was studied in straight-run paving asphalt binders. Two methods, modulated differential scanning calorimetry and dynamic mechanical analysis, were utilized in this study. Kinetic nature of the glass transition was observed in studied asphalts. The glass transition temperature, which represents the transition, was found to be a quantity dependent on observation time and thus meaningless without observation time being specified. The glass transition of asphalts was found to be very broad on the temperature scale due to complexity of the chemical composition. Asphalts were found to be multiphase systems, with glassy amorphous, non-glassy amorphous and crystalline domains existing between approximately 10 and -45°C. Physical hardening was observed in asphalts at broad range of temperatures. Physical aging, i.e. structural relaxation of the glass, was identified as a major process contributing to physical hardening. Direct effect of crystallization was rather insignificant in the temperature range of glass transition. However, the presence of crystals was suggested to affect the molecular mobility of the amorphous phase and thus increase the hardening rate and also extent the phenomenon to higher temperatures outside the normal glass transition range. The concept of rigid amorphous phase was offered. The effect of the physical hardening could generally be reversed upon heating to higher temperature. Although for semi-crystalline asphalt, temperature higher by 50°C than the isothermal storage temperature, was found not to be sufficient to successfully reverse the hardening. Effect of thermal stress on the hardening rate was studied. It was found that the imposed stress was either not significant factor affecting the asphalt hardening or the imposed stress was too low to affect hardening rate significantly. Rheological model able to capture the dependence of relaxation times on the isothermal storage time, reference temperature

  12. Femtosecond laser induced tunable surface transformations on (111) Si aided by square grids diffraction

    SciTech Connect

    Han, Weina; Jiang, Lan; Li, Xiaowei Liu, Yang

    2015-12-21

    We report an extra freedom to modulate the femtosecond laser energy distribution to control the surface ablated structures through a copper-grid mask. Due to the reduced deposited pulse energy by changing the scanning speed or the pulse fluence, a sequential evolution of three distinctly different surface patterns with periodic distributions is formed, namely, striped ripple lines, ripple microdots, and surface modification. By changing the scanning speed, the number of the multiple dots in a lattice can be modulated. Moreover, by exploring the ablation process through the copper grid mask, it shows an abnormal enhanced ablation effect with strong dependence of the diffraction-aided fs laser ablated surface structures on polarization direction. The sensitivity shows a quasi-cosinusoid-function with a periodicity of π/2. Particularly, the connection process of striped ripple lines manifests a preferential formation direction with the laser polarization.

  13. Method of Hardening Glass-Reinforced Plastics,

    DTIC Science & Technology

    1988-02-09

    373 NETHOD OF HARDENING GLASS -REINFORCED PLASTICS (U) 1/i FOREIGN TECHNOLOGY DIV idRIGHT-PATTERSON NFS ON V F DOLGIKH ET AL 89 FEB 88 FTD-ID(RS)T-M49...FTD-ID(RS)T-0049-88 9 February 1988 MICROFICHE NR: FTD-tES-C-00219 METHOD OF HARDENING GLASS -REINFORCED PLASTICS By: V.F. Dolgikh, S.L. Roginskiy, et...translation were extracted from the best quality copy available. If 1 11i METHOD OF HARDENING GLASS -REINFORCED PLASTICS V. F. Dolgikh, S. L. Roginskiy, E. L

  14. Cyclic hardening mechanisms in Nimonic 80A

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Gerold, V.

    1987-01-01

    A nickel base superalloy was fatigued under constant plastic strain range control. The hardening response was investigated as a function of plastic strain range and particle size of the gamma prime phase. Hardening was found to be a function of the slip band spacing. Numerous measurements of the slip band spacing and other statistical data on the slip band structures were obtained. Interactions between intersecting slip systems were shown to influence hardening. A Petch-Hall model was found to describe best this relationship between the response stress and the slip band spacing.

  15. Near-IR Fourier transform Raman spectroscopy in surgery and medicine: guidance system for laser angioplasty

    NASA Astrophysics Data System (ADS)

    Nie, Shuming; Ren, Qiushi; Redd, Douglas C. B.; Yu, Nai-Teng

    1992-08-01

    We have recently demonstrated the efficacy of a near-infrared-Raman fiberoptic sensor for use in laser angioplasty and cardiovascular surgery. A major advantage of the Raman-based system over existing guidance techniques is its fingerprinting capability with improved specificity for detecting atherosclerotic tissues both in-vitro and in-vivo. The use of such a fiberoptic sensor will improve the safety of laser angioplasty by eliminating the current risk of vessel wall perforation. Once developed, the device also will be well suited for in-vivo monitoring and characterization of restenosis after balloon angioplasty and in-vivo study of atheroma progression and regression in animal models.

  16. CONTROL OF LASER RADIATION PARAMETERS: Transformation of the spatial coherence of pulsed laser radiation transmitted in the nonlinear regime through a multimode graded-index fibre

    NASA Astrophysics Data System (ADS)

    Kitsak, A. I.; Kitsak, M. A.

    2006-01-01

    A method is proposed for transformation of the spatial coherence of pulsed laser radiation upon nonlinear interaction in a multimode fibre. The specific features of the transmission of correlation properties of radiation in a graded-index fibre with regular and irregular profiles of the refractive index of the fibre core are analysed. A comparative analysis of the parameter of global degree of radiation coherence at the output of inhomogeneous waveguide and non-waveguide media is performed. It is shown that the most efficient mechanism of decorrelation of pulsed radiation in an optical fibre is fluctuations of the phase of radiation scattered by inhomogeneities of the refractive index of the fibre core induced due to nonlinear interaction with radiation with the spatially inhomogeneous intensity distribution.

  17. Adaptive approach for variable noise suppression on laser-induced breakdown spectroscopy responses using stationary wavelet transform.

    PubMed

    Schlenke, Jan; Hildebrand, Lars; Moros, Javier; Laserna, J Javier

    2012-11-19

    Spectral signals are often corrupted by noise during their acquisition and transmission. Signal processing refers to a variety of operations that can be carried out on measurements in order to enhance the quality of information. In this sense, signal denoising is used to reduce noise distortions while keeping alterations of the important signal features to a minimum. The minimization of noise is a highly critical task since, in many cases, there is no prior knowledge of the signal or of the noise. In the context of denoising, wavelet transformation has become a valuable tool. The present paper proposes a noise reduction technique for suppressing noise in laser-induced breakdown spectroscopy (LIBS) signals using wavelet transform. An extension of the Donoho's scheme, which uses a redundant form of wavelet transformation and an adaptive threshold estimation method, is suggested. Capabilities and results achieved on denoising processes of artificial signals and actual spectroscopic data, both corrupted by noise with changing intensities, are presented. In order to better consolidate the gains so far achieved by the proposed strategy, a comparison with alternative approaches, as well as with traditional techniques, is also made. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Propagation of ultrashort laser pulses in water: linear absorption and onset of nonlinear spectral transformation.

    PubMed

    Sokolov, Alexei V; Naveira, Lucas M; Poudel, Milan P; Strohaber, James; Trendafilova, Cynthia S; Buck, William C; Wang, Jieyu; Strycker, Benjamin D; Wang, Chao; Schuessler, Hans; Kolomenskii, Alexandre; Kattawar, George W

    2010-01-20

    We study propagation of short laser pulses through water and use a spectral hole filling technique to essentially perform a sensitive balanced comparison of absorption coefficients for pulses of different duration. This study is motivated by an alleged violation of the Bouguer-Lambert-Beer law at low light intensities, where the pulse propagation is expected to be linear, and by a possible observation of femtosecond optical precursors in water. We find that at low intensities, absorption of laser light is determined solely by its spectrum and does not directly depend on the pulse duration, in agreement with our earlier work and in contradiction to some work of others. However, as the laser fluence is increased, interaction of light with water becomes nonlinear, causing energy exchange among the pulse's spectral components and resulting in peak-intensity dependent (and therefore pulse-duration dependent) transmission. For 30 fs pulses at 800 nm center wavelength, we determine the onset of nonlinear propagation effects to occur at a peak value of about 0.12 mJ/cm(2) of input laser energy fluence.

  19. Transforming benzophenoxazine laser dyes into chromophores for dye-sensitized solar cells: a molecular engineering approach

    SciTech Connect

    Schroder, Florian A. Y. N.; Cole, Jacqueline M.; Waddell, Paul G.; McKechnie, Scott

    2015-05-06

    The re-functionalization of a series of four well-known industrial laser dyes, based on benzophenoxazine, is explored with the prospect of molecularly engineering new chromophores for dye-sensitized solar cell (DSC) applications. Such engineering is important since a lack of suitable dyes is stifling the progress of DSC technology. The conceptual idea involves making laser dyes DSC-active by chemical modification, while maintaining their key property attributes that are attractive to DSC applications. This molecular engineering follows a step-wise approach. Firstly, molecular structures and optical absorption properties are determined for the parent laser dyes: Cresyl Violet (1); Oxazine 170 (2); Nile Blue A (3), Oxazine 750 (4). These reveal structure-property relationships which define the prerequisites for computational molecular design of DSC dyes; the nature of their molecular architecture (D-π-A) and intramolecular charge transfer. Secondly, new DSC dyes are computationally designed by the in silico addition of a carboxylic acid anchor at various chemical substitution points in the parent laser dyes. A comparison of the resulting frontier molecular orbital energy levels with the conduction band edge of a TiO2 DSC photoanode and the redox potential of two electrolyte options I-/I3- and Co(II/III)tris(bipyridyl) suggests promise for these computationally designed dyes as co-sensitizers for DSC applications.

  20. A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening

    NASA Astrophysics Data System (ADS)

    Fu, Yong-sheng; Zhang, Wei; Xu, Xiaowei; Li, Jiehua; Li, Jun; Xia, Mingxu; Li, Jianguo

    2017-09-01

    A novel heat treatment process for surface hardening of steel has been demonstrated and named as "metal melt surface hardening (MMSH)." A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.

  1. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  2. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  3. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  4. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  5. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  6. Process for hardening the surface of polymers

    DOEpatents

    Mansur, L.K.; Lee, E.H.

    1992-07-14

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

  7. Process for hardening the surface of polymers

    DOEpatents

    Mansur, Louis K.; Lee, Eal H.

    1992-01-01

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

  8. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  9. Extraordinary strain hardening by gradient structure.

    PubMed

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T

    2014-05-20

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures.

  10. Alloy solution hardening with solute pairs

    DOEpatents

    Mitchell, John W.

    1976-08-24

    Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

  11. Electromechanical Surface Hardening of Tubing Steels

    NASA Astrophysics Data System (ADS)

    Fedorova, L. V.; Fedorov, S. K.; Serzhant, A. A.; Golovin, V. V.; Systerov, S. V.

    2017-07-01

    Results of metallographic studies of the structure of steels 38G2S and 37G2F and steels of group D after electromechanical surface hardening of tube specimens over the external diameter are presented.

  12. Hardened Dunes in Arcadia Planitia

    NASA Image and Video Library

    2014-10-29

    NASA Mars Reconnaissance Orbiter HiRISE, with its high resolution and eight years in orbit about Mars, has shown that many dunes and ripples on the planet are active. This demonstrates that in some areas sand is loose enough and winds strong enough, that significant change can occur. Nevertheless, other Martian dunes are clearly *inactive*. This image in Arcadia Planitia shows dunes in a crater. Unlike active dunes on the planet, those here are bright, and, zooming in, there are several lines of evidence indicating that the dunes have become indurated, that is, hardened into cohesive sediment or even into sandstone rock. For example, the dune field at the southern edge is cut off by a step cliff, indicating erosion of hard material. Although fine scale ripples on the original dune surface are preserved, we also see large scale fluting from southwest to northeast, a common texture associated with wind-induced sand abrasion. How these dunes became indurated is unknown. One possibility is that this area of Mars was buried and then exhumed, a process that seems to have occurred many times in the Martian past over various areas of the planet. During burial, compaction and possibly ground water circulation would have indurated the dunes, leaving them as a hard sandstone that, when exhumed, was subsequently partially eroded. http://photojournal.jpl.nasa.gov/catalog/PIA18890

  13. [Beam hardening correction method for X-ray computed tomography based on subsection beam hardening curves].

    PubMed

    Huang, Kui-dong; Zhang, Ding-hua

    2009-09-01

    After researching the forming principle of X-ray beam hardening and analyzing the usual methods of beam hardening correction, a beam hardening correction model was established, in which the independent variable was the projection gray, and so the computing difficulties in beam hardening correction can be reduced. By considering the advantage and disadvantage of fitting beam hardening curve to polynomial, a new expression method of the subsection beam hardening curves based on polynomial was proposed. In the method, the beam hardening data were fitted firstly to a polynomial curve which traverses the coordinate origin, then whether the got polynomial curve surged in the fore-part or back-part of the fitting range was judged based on the polynomial curvature change. If the polynomial fitting curve surged, the power function curve was applied to replace the surging parts of the polynomial curve, and the C1 continuity was ensured at the joints of the segment curves. The experimental results of computed tomography (CT) simulation show that the method is well stable in the beam hardening correction for the ideal CT images and CT images with added noises, and can mostly remove the beam hardening artifact at the same time.

  14. Decline in Radiation Hardened Microcircuit Infrastructure

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.

    2015-01-01

    Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.

  15. Work hardening behavior in aluminum alloy 2090

    SciTech Connect

    Tseng, Carol

    1993-12-01

    An investigation into the work hardening behavior of an aluminum alloy 2090-T81 Al-3.05Cu-2.16Li-0.12Zr at various test temperatures, heat treatment conditions and microstructures was conducted. One microstructure consisted of unrecrystallized, highly textured grains, and the other microstructure was composed of recrystallized grains. Microstructural effects on work hardening were divided into two levels of contribution: the grain structure level, which consisted of the grain size and shape, subgrains and texture, and the microconsistent level, which included the precipitates and solutes. Two heat treatments were studied: the as-received, peak-aged condition, and the solution heat treated condition where the as-received plate was resolutionized. Observations of the deformed surface of both as-received grain structures at various prestrains indicated that there was no correlation between an increase in slip homogeneity and an increase in work hardening. The increase in out-of-plane grain rotation at lower temperatures was not primarily responsible for the increase in work hardening. In addition, the fully plastic deformation microstructure for the unrecrystallized microstructure appeared very inhomogeneous as the grains deformed in bands; there were also bands of grains that had very little to no deformation. From the work hardening plots it was found that an unrecrystallized, (110)<112> textured grain structure with a homogeneous distribution of subgrains produced the highest rate of work hardening between 300 K and 77 K. When the microconstituents are added to both grain structures, both the work hardening rate in the elastic-plastic and fully plastic regimes and the level of work hardening at which the elastic-plastic to fully plastic transition occurred were affected.

  16. Properties and Commercial Application of Manual Plasma Hardening

    NASA Astrophysics Data System (ADS)

    Korotkov, V. A.

    2016-11-01

    A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.

  17. On shakedown analysis in hardening plasticity

    NASA Astrophysics Data System (ADS)

    Nguyen, Quoc-Son

    2003-01-01

    The extension of classical shakedown theorems for hardening plasticity is interesting from both theoretical and practical aspects of the theory of plasticity. This problem has been much discussed in the literature. In particular, the model of generalized standard materials gives a convenient framework to derive appropriate results for common models of plasticity with strain-hardening. This paper gives a comprehensive presentation of the subject, in particular, on general results which can be obtained in this framework. The extension of the static shakedown theorem to hardening plasticity is presented at first. It leads by min-max duality to the definition of dual static and kinematic safety coefficients in hardening plasticity. Dual static and kinematic approaches are discussed for common models of isotropic hardening of limited or unlimited kinematic hardening. The kinematic approach also suggests for these models the introduction of a relaxed kinematic coefficient following a method due to Koiter. Some models for soils such as the Cam-clay model are discussed in the same spirit for applications in geomechanics. In particular, new appropriate results concerning the variational expressions of the dual kinematic coefficients are obtained.

  18. On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation

    PubMed Central

    Gorrini, F.; Cazzanelli, M.; Bazzanella, N.; Edla, R.; Gemmi, M.; Cappello, V.; David, J.; Dorigoni, C.; Bifone, A.; Miotello, A.

    2016-01-01

    Nanodiamonds are the subject of active research for their potential applications in nano-magnetometry, quantum optics, bioimaging and water cleaning processes. Here, we present a novel thermodynamic model that describes a graphite-liquid-diamond route for the synthesis of nanodiamonds. Its robustness is proved via the production of nanodiamonds powders at room-temperature and standard atmospheric pressure by pulsed laser ablation of pyrolytic graphite in water. The aqueous environment provides a confinement mechanism that promotes diamond nucleation and growth, and a biologically compatible medium for suspension of nanodiamonds. Moreover, we introduce a facile physico-chemical method that does not require harsh chemical or temperature conditions to remove the graphitic byproducts of the laser ablation process. A full characterization of the nanodiamonds by electron and Raman spectroscopies is reported. Our model is also corroborated by comparison with experimental data from the literature. PMID:27731385

  19. On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation

    NASA Astrophysics Data System (ADS)

    Gorrini, F.; Cazzanelli, M.; Bazzanella, N.; Edla, R.; Gemmi, M.; Cappello, V.; David, J.; Dorigoni, C.; Bifone, A.; Miotello, A.

    2016-10-01

    Nanodiamonds are the subject of active research for their potential applications in nano-magnetometry, quantum optics, bioimaging and water cleaning processes. Here, we present a novel thermodynamic model that describes a graphite-liquid-diamond route for the synthesis of nanodiamonds. Its robustness is proved via the production of nanodiamonds powders at room-temperature and standard atmospheric pressure by pulsed laser ablation of pyrolytic graphite in water. The aqueous environment provides a confinement mechanism that promotes diamond nucleation and growth, and a biologically compatible medium for suspension of nanodiamonds. Moreover, we introduce a facile physico-chemical method that does not require harsh chemical or temperature conditions to remove the graphitic byproducts of the laser ablation process. A full characterization of the nanodiamonds by electron and Raman spectroscopies is reported. Our model is also corroborated by comparison with experimental data from the literature.

  20. On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation.

    PubMed

    Gorrini, F; Cazzanelli, M; Bazzanella, N; Edla, R; Gemmi, M; Cappello, V; David, J; Dorigoni, C; Bifone, A; Miotello, A

    2016-10-12

    Nanodiamonds are the subject of active research for their potential applications in nano-magnetometry, quantum optics, bioimaging and water cleaning processes. Here, we present a novel thermodynamic model that describes a graphite-liquid-diamond route for the synthesis of nanodiamonds. Its robustness is proved via the production of nanodiamonds powders at room-temperature and standard atmospheric pressure by pulsed laser ablation of pyrolytic graphite in water. The aqueous environment provides a confinement mechanism that promotes diamond nucleation and growth, and a biologically compatible medium for suspension of nanodiamonds. Moreover, we introduce a facile physico-chemical method that does not require harsh chemical or temperature conditions to remove the graphitic byproducts of the laser ablation process. A full characterization of the nanodiamonds by electron and Raman spectroscopies is reported. Our model is also corroborated by comparison with experimental data from the literature.

  1. LASER MODES AND BEAMS: Complex-order fractional Fourier transforms in optical schemes with Gaussian apertures

    NASA Astrophysics Data System (ADS)

    Malyutin, A. A.

    2004-10-01

    Several optical schemes performing the complex-order fractional Fourier transform are considered. It is shown that these schemes, containing only Gaussian apertures or their combination with lenses, have eigenbeams represented by Hermite—Gaussian modes with transverse indices m, n<=1 and Laguerre—Gaussian modes with p=0 and l=1. The wave front of the eigenbeams is, as a rule, spherical.

  2. Femtosecond laser-induced phase transformations in amorphous Cu{sub 77}Ni{sub 6}Sn{sub 10}P{sub 7} alloy

    SciTech Connect

    Zhang, Y.; Zou, G.; Wu, A.; Bai, H.; Liu, L.; Chen, N.; Zhou, Y.

    2015-01-14

    In this study, the femtosecond laser-induced crystallization of CuNiSnP amorphous ribbons was investigated by utilizing an amplified Ti:sapphire laser system. X-ray diffraction and scanning electronic microscope were applied to examine the phase and morphology changes of the amorphous ribbons. Micromachining without crystallization, surface patterning, and selective crystallization were successfully achieved by changing laser parameters. Obvious crystallization occurred under the condition that the laser fluence was smaller than the ablation threshold, indicating that the structural evolution of the material depends strongly on the laser parameters. Back cooling method was used to inhibit heat accumulation; a reversible transformation between the disordered amorphous and crystalline phases can be achieved by using this method.

  3. Structural transformations in Sc/Si multilayers irradiated by EUV lasers

    NASA Astrophysics Data System (ADS)

    Voronov, Dmitriy L.; Zubarev, Evgeniy N.; Pershyn, Yuriy P.; Sevryukova, Victoriya A.; Kondratenko, Valeriy V.; Vinogradov, Alexander V.; Artioukov, Igor A.; Uspenskiy, Yuriy A.; Grisham, Michael; Vaschenko, Georgiy; Menoni, Carmen S.; Rocca, Jorge J.

    2007-09-01

    Multilayer mirrors for the extreme ultraviolet (EUV) are key elements for numerous applications of coherent EUV sources such as new tabletop lasers and free-electron lasers. However the field of applications is limited by the radiation and thermal stability of the multilayers. Taking into account the growing power of EUV sources the stability of the optics becomes crucial. To overcome this problem it is necessary to study the degradation of multilayers and try to increase their temporal and thermal stability. In this paper we report the results of detailed study of structural changes in Sc/Si multilayers when exposed to intense EUV laser pulses. Various types of surface damage such as melting, boiling, shock wave creation and ablation were observed as irradiation fluencies increase. Cross-sectional TEM study revealed that the layer structure was completely destroyed in the upper part of multilayer, but still survived below. The layers adjacent to the substrate remained intact even through the multilayer surface melted down, though the structure of the layers beneath the molten zone was noticeably changed. The layer structure in this thermally affected zone is similar to that of isothermally annealed samples. All stages of scandium silicide formation such as interdiffusion, solid-state amorphization, silicide crystallization etc., are present in the thermally affected zone. It indicates a thermal nature of the damage mechanism. The tungsten diffusion barriers were applied to the scandium/silicon interfaces. It was shown that the barriers inhibited interdiffusion and increased the thermal stability of Sc/Si mirrors.

  4. Atomic force microscopy of swelling and hardening of intact erythrocytes fixed on substrate

    NASA Astrophysics Data System (ADS)

    Khalisov, M. M.; Timoshchuk, K. I.; Ankudinov, A. V.; Timoshenko, T. E.

    2017-02-01

    Peak force measurements with the aid of atomic force microscopy are used to quantitatively map nanomechanical properties of intact erythrocytes of rats under conditions that are close to physiological conditions. Erythrocytes that are immobilized on the substrate preliminary processed using poly-L-lysine predominantly exhibit plane shape. However, cells may also exhibit stepwise transformation to semispherical objects with an increase in volume and hardening. Possible reasons for such transformations are discussed.

  5. Induction hardening treatment and simulation for a grey cast iron used in engine cylinder liners

    NASA Astrophysics Data System (ADS)

    Castellanos-Leal, E. L.; Miranda, D. A.; Coy, A. E.; Barrero, J. G.; González, J. A.; Vesga Rueda, O. P.

    2017-01-01

    In this research, a technical study of induction hardening in a grey cast iron used in engine cylinder liners manufactured by LAVCO Ltda., a Colombian foundry company, was carried out. Metallurgical parameters such as austenitization temperature, cooling rate, and quenching severity were determined. These factors are exclusively dependent on chemical composition and initial microstructure of grey cast iron. Simulations of induction heating through finite elements method were performed and, the most appropriate experimental conditions to achieve the critical transformation temperature was evaluated to reach a proper surface hardening on the piece. Preliminary results revealed an excellent approximation between simulation and heating test performed with a full bridge inverter voltage adapted with local technology.

  6. Molecular identification of foreign inclusions in inflammatory tissue surrounding metal implants by Fourier transform laser microprobe mass spectrometry.

    PubMed

    De Nollin, S; Poels, K; Van Vaeck, L; De Clerck, N; Bakker, A; Duwel, V; Vandevelde, D; Van Marck, E

    1997-01-01

    Fourier transform laser microprobe mass spectrometry (FT LMMS) is a novel technique for micro-analysis of solids with a lateral resolution in the 5 microns range. One of the major advantages of the technique is the capability to perform characterisation of the molecular composition of both organic and inorganic compounds. The information is directly deduced from the signals without the aid of reference spectra. FT LMMS was applied to the characterisation of black tissue fragments in a biopsy from a patient, in which a constrained condylar nodular knee system was implanted ten years ago. The tissue contained numerous foreign giant cells with a black non-birefringent pigment in their cytoplasm. FT LMMS analysis allowed us to detect directly by means of molecular signals, that the debris consisted primarily of titanium oxide and not metallic titanium, while the implant itself only contained titanium.

  7. Optical properties transformations under heat and laser treatment of glasses in the Bi-Ge-O system

    NASA Astrophysics Data System (ADS)

    Stepanova, I. V.; Petrova, O. B.; Kolobkova, E. M.; Khomyakov, A. V.; Lipatiev, A. S.; Sigaev, V. N.; Avetissov, I. Ch.

    2017-10-01

    Chromium-doped bismuth-germanium oxide glasses with molar composition x Bi2O3-(100 - x) GeO2- y Cr2O3 ( x = 40, 50; y = 0, 0.01) were synthesized by melt-quenching technique and their physical properties were investigated. The glasses were transformed to glass ceramics by heat-treatment. The femtosecond laser-induced modification of glasses showed no glass devitrification up to the pulse energy of 400 nJ but the refractive index for all studied glasses increased on the order of 10-3. Structural and optical properties of the glasses and glass-ceramics were analyzed by X-ray diffraction, optical microscopy, and optical spectroscopy.

  8. Structural characterization of phospholipids by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Marto, J A; White, F M; Seldomridge, S; Marshall, A G

    1995-11-01

    Matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance mass spectrometry provides for structural analysis of the principal biological phospholipids: glycerophosphatidylcholine, -ethanolamine, -serine, and -inositol. Both positive and negative molecular or quasimolecular ions are generated in high abundance. Isolated molecular ions may be collisionally activated in the source side of a dual trap mass analyzer, yielding fragments serving to identify the polar head group (positive ion mode) and fatty acid side chains (negative ion mode). Azimuthal quadrupolar excitation following collisionally activated dissociation refocuses productions close to the solenoid axis; subsequent transfer of product ions to the analyzer ion trap allows for high-resolution mass analysis. Cyro-cooling of the sample probe with liquid nitrogen greatly reduces matrix adduction encountered in the negative ion mode.

  9. Phase Transformations During Solidification of a Laser-Beam-Welded TiAl Alloy—An In Situ Synchrotron Study

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Staron, Peter; Riekehr, Stefan; Stark, Andreas; Schell, Norbert; Huber, Norbert; Schreyer, Andreas; Müller, Martin; Kashaev, Nikolai

    2016-12-01

    An in situ highly time-resolved, high-energy X-ray diffraction investigation was carried out to observe the phase transformations of a TiAl alloy during laser beam welding. The diffraction patterns are recorded every 0.1 seconds by a fast area two-dimensional detector and plotted according to time, yielding the solidification pathway, the solid phase volume fraction, and the lattice parameter variation of different phases during the solidification and cooling process. Moreover, it is the first study that can demonstrate that the α phase without any Burgers orientation relationship, the so-called non-Burgers α, precipitates appear earlier than the Burgers α. The non-Burgers α grains are found to nucleate on the primary borides.

  10. Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

    SciTech Connect

    Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; Schultz, Bradley M.; Unocic, Raymond R.; Kennedy, Marian S.

    2016-01-13

    In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally, the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.

  11. Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

    DOE PAGES

    Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; ...

    2016-01-13

    In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

  12. Reference interferometer using a semiconductor laser/LED reference source in a cryogenic Fourier-transform spectrometer

    NASA Astrophysics Data System (ADS)

    Martino, Anthony J.; Cornwell, Donald M.

    1998-09-01

    A combination of a single mode AlGaAs laser diode and a broadband LED was used in a Michelson interferometer to provide reference signals in a Fourier transform spectrometer, the Composite Infrared Spectrometer, on the Cassini mission to Saturn. The narrowband light from a laser produced continuous fringe throughout the travel of the interferometer, which were used to control the velocity of the scan mechanism and to trigger data sampling. The broadband light from the LED produced a burst of fringes at zero path difference, which was used as a fixed position reference. The system, including the sources, the interferometer, and the detectors, was designed to work both at room temperature and at the instrument operating temperature of 170 Kelvin. One major challenge that was overcome was preservation, from room temperature to 170 K, of alignment sufficient for high modulation of fringes from the broadband source. Another was the shift of the source spectra about 30 nm toward shorter wavelengths upon cooldown.

  13. Characterization of organic aerosol in Beijing by laser desorption ionization coupled with Fourier Transform Ion Cyclotron Resonance Mass spectrometry

    NASA Astrophysics Data System (ADS)

    Xue, Jinjuan; Li, Yafeng; Xie, Xiaobo; Xiong, Caiqiao; Liu, Huihui; Chen, Suming; Nie, Zongxiu; Chen, Chuncheng; Zhao, Jincai

    2017-06-01

    In order to resolve the organic compositions in the atmospheric aerosol which is significant for understanding the formation mechanism of particulate matter and their harm for human health, a direct laser desorption ionization (LDI) coupled with Fourier Transform Resonance Mass (FT-ICR MS) was utilized for characterizing the aerosol particles collected in Beijing during winter. A lot of organic compounds can be detected by direct laser desorption ionization of the aerosol particular with different size collected on aluminum foil without complicated sample pretreatment process. In addition, semi quantification of the organic compounds can be achieved with solvent extraction procedure. It was found that the ubiquitous polycyclic aromatic hydrocarbons (PAHs) contaminants in the aerosol could serve as matrix, which helps the detection of many kinds of compounds including highly saturated amphiphilic long alkyl chain compounds (carbon number>16), like aliphatic amines in positive ion mode and organosulfates in negative ion mode. Based on the accurate mass measurement results, elemental compositions of over 1500 peaks in the mass spectrum were derived, and we categorized them into five groups according to their elemental compositions in order to provide helpful information for tracing the pollution source. It is demonstrated that abundant information about the organic components in the atmospheric aerosol can be provided by direct LDI FT-ICR MS method, and these information will largely facilitate further studies on origin and formation process of the aerosol.

  14. Rapid extraction and structural characterization of biomolecules in agarose gels by laser desorption Fourier transform mass spectrometry

    SciTech Connect

    Dunphy, J.C.; Busch, K.L. ); Hettich, R.L.; Buchanan, M.V. )

    1993-05-15

    A method originally developed for the extraction of biomolecules from agarose gel slices has been utilized as a rapid means of isolating biological compounds from gels for subsequent structural characterization by matrix-assisted laser desorption-ionization Fourier transform mass spectrometry (MALDI/FTMS). This [open quotes]freeze-squeeze[close quotes] extraction method involves pressure extrusion of fluid from frozen gel slices and provides near 50% recovery of analyte in less than 5 min. Experiments were directed at examining the recovery efficiency of the extraction method using [sup 14]C-labeled adenosine monophosphate and investigating the effect of high buffer concentrations on the laser desorption mass spectra. When coupled with this extraction technique, MALDI/FTMS can be used to detect and identify biomolecules at the low picomole level in agarose gel slices. The accurate mass measurements and MS/MS capabilities of the FTMS were exploited to provide detailed structural information at the isomeric level for oligonucleotides electrophoresed into agarose gels. 41 refs., 5 figs., 1 tab.

  15. Study on the Strain Hardening Behaviors of TWIP/TRIP Steels

    NASA Astrophysics Data System (ADS)

    Huang, T. T.; Dan, W. J.; Zhang, W. G.

    2017-10-01

    Due to the complex coupling of twinning-induced plasticity (TWIP), transformation-induced plasticity (TRIP), and dislocation glide in TWIP/TRIP steels, it is difficult as well as essential to build a comprehensive strain hardening model to describe the interactions between different deformation mechanisms ( i.e., deformation twinning, martensitic transformation, and dislocation glide) and the resulted strain hardening behaviors. To address this issue, a micromechanical model is established in this paper to predict the deformation process of TWIP/TRIP steels considering both TWIP and TRIP effects. In the proposed model, the generation of deformation twinning and martensitic transformation is controlled by the stacking fault energy (SFE) of the material. In the thermodynamic calculation of SFE, deformation temperature, chemical compositions, microstrain, and temperature rise during deformation are taken into account. Varied by experimental results, the developed model can predict the stress-strain response and strain hardening behaviors of TWIP/TRIP steels precisely. In addition, the improved strength and enhanced strain hardening in Fe-Mn-C TWIP/TRIP steels due to the increased carbon content is also analyzed, which consists with literature.

  16. Fourier Transform Infrared (FTIR) Observation Of Catalytically Active Intermediates Produced By Laser Photolysis Of Iron Pentacarbonyl

    NASA Astrophysics Data System (ADS)

    Paquette, Michael S.

    1984-05-01

    The pulsed laser excitation of iron pentacarbonyl in solutions of 1-pentene photoinitiates a highly active catalytic process for isomerization of the olefin. This process is observed in situ by rapid scanning FTIR spectroscopy, allowing subsecond acquisition of spectra. These are deconvoluted into discrete spectral components which are assigned molecular formulas. Specific activities have been obtained for two catalytically significant complexes from a correlation of catalytic activity with compositional changes. A similar interpretation of multipulse and cw experiments allowed development of a comprehensive cycle of thermal and photochemical interconversions among components.

  17. Transformations induced in bulk amorphous silica by ultrafast laser direct writing.

    PubMed

    Oliveira, Vitor; Sharma, Sahendra P; Herrero, Pilar; Vilar, Rui

    2013-12-01

    A transmission electron microscopy study of nanogratings formed in bulk amorphous silica by direct writing with an ultrafast pulsed laser with a radiation wavelength of 1030 nm and pulse duration of 560 fs is presented. The results achieved show that the nanogratings are composed of planar nanostructures with an average periodicity of 250 nm and typical thickness of about 30 nm, consisting of alternating layers of heavily damaged material and layers of material where a dense precipitation of nanocrystals occurred. The crystallization of silica to form these nanocrystals can be explained by the large pressures and temperatures reached in these regions as a result of nanoplasma formation and recombination.

  18. An optical system to transform the output beam of a quantum cascade laser to be uniform

    NASA Astrophysics Data System (ADS)

    Jacobson, Jordan M.

    Quantum cascade lasers (QCLs) are a candidate for calibration sources in space-based remote sensing applications. However, the output beam from a QCL has some characteris- tics that are undesirable in a calibration source. The output beam from a QCL is polarized, both temporally and spatially coherent, and has a non-uniform bivariate Gaussian prole. These characteristics need to be mitigated before QCLs can be used as calibration sources. This study presents the design and implementation of an optical system that manipulates the output beam from a QCL so that it is spatially and angularly uniform with reduced coherence and polarization. (85 pages).

  19. The secondary hardening phenomenon in strain-hardened MP35N alloy

    SciTech Connect

    Asgari, S.; El-Danaf, E.; Shaji, E.; Kalidindi, S.R.; Doherty, R.D.

    1998-10-09

    Mechanical testing and microscopy techniques were used to investigate the influence of aging on the structure and strengthening of MP35N alloy. It was confirmed that aging the deformed material at 600 C for 4 h provided additional strengthening, here referred to as secondary hardening, in addition to the primary strain hardening. The secondary hardening phenomenon was shown to be distinctly different from typical age hardening processes in that it only occurred in material deformed beyond a certain cold work level. At moderate strains, aging caused a shift in the entire stress-strain curve of the annealed material to higher stresses while at high strains, it produced shear localization and limited work softening. The secondary hardening increment was also found to be grain size dependent. The magnitude of the secondary hardening appeared to be controlled by the flow stress in the strain hardened material. A model is proposed to explain the observations and is supported by direct experimental evidence. The model is based on formation of h.c.p. nuclei through the Suzuki mechanism, that is segregation of solute atoms to stacking faults, on aging the strain hardened material. The h.c.p. precipitates appear to thicken only in the presence of high dislocation density produced by prior cold work.

  20. Organoapatites: materials for artificial bone. II. Hardening reactions and properties.

    PubMed

    Stupp, S I; Mejicano, G C; Hanson, J A

    1993-03-01

    This article reports on chemical reactions and the properties they generated in artificial bone materials termed "organoapatites." These materials are synthesized using methodology we reported in the previous article of this series. Two different processes were studied here for the transition from organoapatite particles to implants suitable for the restoration of the skeletal system. One process involved the hardening of powder compacts by beams of blue light derived from a lamp or a laser and the other involved pressure-induced interdiffusion of polymers. In both cases, the hardening reaction involved the formation of a polyion complex between two polyelectrolytes. In the photo-induced reaction an anionic electrolyte polymerizes to form the coulombic network and in the pressure-induced one, pressure forms the complex by interdiffusion of two polyions. Model reactions were studied using various polycations. Based on these results the organoapatite selected for the study was that containing dispersed poly(L-lysine) and sodium acrylate as the anionic monomer. The organomineral particles can be pressed at room temperature into objects of great physical integrity and hydrolytic stability relative to anorganic controls. The remarkable fact about these objects is that intimate molecular dispersion of only 2-3% by weight organic material provides integrity to the mineral network in an aqueous medium and also doubles its tensile strength. This integrity is essentially nonexistent in "anorganic" samples prepared by the same methodology used in organoapatite synthesis. The improvement in properties was most effectively produced by molecular bridges formed by photopolymerization. The photopolymerization leads to the "hardening" of pellets prepared by pressing of organoapatite powders. The reaction was found to be more facile in the microstructure of the organomineral, and it is potentially useful in the surgical application of organoapatites as artificial bone.

  1. Thermal stresses in chemically hardening elastic media with application to the molding process

    NASA Technical Reports Server (NTRS)

    Levitsky, M.; Shaffer, B. W.

    1974-01-01

    A method has been formulated for the determination of thermal stresses in materials which harden in the presence of an exothermic chemical reaction. Hardening is described by the transformation of the material from an inviscid liquid-like state into an elastic solid, where intermediate states consist of a mixture of the two, in a ratio which is determined by the degree of chemical reaction. The method is illustrated in terms of an infinite slab cast between two rigid mold surfaces. It is found that the stress component normal to the slab surfaces vanishes in the residual state, so that removal of the slab from the mold leaves the remaining residual stress unchanged. On the other hand, the residual stress component parallel to the slab surfaces does not vanish. Its distribution is described as a function of the parameters of the hardening process.

  2. Laser Light Induced Transformation of Molybdenum Disulphide-Based Nanoplatelet Arrays

    PubMed Central

    Jagminas, Arūnas; Niaura, Gediminas; Žalnėravičius, Rokas; Trusovas, Romualdas; Račiukaitis, Gediminas; Jasulaitiene, Vitalija

    2016-01-01

    One-pot hydrothermal synthesis of MoS2 nanoplatelet arrays on various substrates is perhaps the most promising approach to fabricate efficient electrocatalysts for hydrogen evolution reaction. However, the main challenges in this synthesis remain the purity and crystallinity of MoS2. In this study, we show for the first time that irradiation of amorphous, defect-rich MoS2 nanoplatelets with a green nanosecond laser at a proper irradiation dose, ca ≤0.35 J cm−2, can significantly improve the crystallinity and purity of MoS2 nanoplatelets. The effect was confirmed by Raman spectroscopy investigations demonstrating a surprising intensity increase of the A1g and modes after the laser irradiation. Further increase of irradiation energy, however, resulted in the photocorrosion and destruction of MoS2 nanoplatelets. The variation of A1g and Raman mode intensities ratio depending on the green light irradiation dose was also presented and is discussed below. PMID:27892489

  3. Transient absorption phenomena and related structural transformations in femtosecond laser-excited Si

    NASA Astrophysics Data System (ADS)

    Kudryashov, Sergey I.

    2004-09-01

    Analysis of processes affecting transient optical absorption and photogeneration of electron-hole plasma in silicon pumped by an intense NIR or visible femtosecond laser pulse has been performed taking into account the most important electron-photon, electron-electron and electron-phonon interactions and, as a result, two main regimes of such laser-matter interaction have been revealed. The first regime is concerned with indirect interband optical absorption in Si, enhanced by a coherent shrinkage of its smallest indirect bandgap due to dynamic Franz-Keldysh effect (DFKE). The second regime takes place due to the critical renormalization of the Si direct bandgap along Λ-axis of its first Brillouin zone because of DFKE and the deformation potential electron-phonon interaction and occurs as intense direct single-photon excitation of electrons into one of the quadruplet of equivalent Λ-valleys in the lowest conduction band, which is split down due to the electron-phonon interaction.

  4. Laser Light Induced Transformation of Molybdenum Disulphide-Based Nanoplatelet Arrays

    NASA Astrophysics Data System (ADS)

    Jagminas, Arūnas; Niaura, Gediminas; Žalnėravičius, Rokas; Trusovas, Romualdas; Račiukaitis, Gediminas; Jasulaitiene, Vitalija

    2016-11-01

    One-pot hydrothermal synthesis of MoS2 nanoplatelet arrays on various substrates is perhaps the most promising approach to fabricate efficient electrocatalysts for hydrogen evolution reaction. However, the main challenges in this synthesis remain the purity and crystallinity of MoS2. In this study, we show for the first time that irradiation of amorphous, defect-rich MoS2 nanoplatelets with a green nanosecond laser at a proper irradiation dose, ca ≤0.35 J cm‑2, can significantly improve the crystallinity and purity of MoS2 nanoplatelets. The effect was confirmed by Raman spectroscopy investigations demonstrating a surprising intensity increase of the A1g and modes after the laser irradiation. Further increase of irradiation energy, however, resulted in the photocorrosion and destruction of MoS2 nanoplatelets. The variation of A1g and Raman mode intensities ratio depending on the green light irradiation dose was also presented and is discussed below.

  5. Transformations of Gaussian Light Beams Caused by Reflection in FEL (free Electron Lasers) Resonators

    DTIC Science & Technology

    1988-10-27

    Box Y Malibu, CA 90265 Mail Stop 3 Building 9201 -2 Dr. A. Drobot Oak Ridge , TN 37830 Science Applications Intl. Corp. 1710 Goodridge Road Dr...r0 ) + yi2(ro ) Xo2 + Yo2 ( 0 i10 0 2 Ri(r0 ) 2R (r ( 12 ) The phase A(r ) depends on the angle 4 through the coordinate transformations Eqs. (3...202 (1987). 12 . P. Sprangle, A. Ting and C. M. Tang, Phys. Rev. A36, 2773 (1987). 14 42 C1-, 4 43- \\ zo zi ! /2 x Figure 2 Reflection geometry. I I I

  6. Phase development in the hardening process of two calcium phosphate bone cements: an energy dispersive X-ray diffraction study

    SciTech Connect

    Generosi, A.; Smirnov, V.V.; Rau, J.V.; Albertini, V. Rossi; Ferro, D.; Barinov, S.M.

    2008-03-04

    This work was aimed at the application of an energy dispersive X-ray diffraction technique to study the kinetics of phase development during the setting and hardening reactions in two calcium phosphate bone cements. The cements under study are based on either tricalcium phosphate or tetracalcium phosphate initial solid phase, and a magnesium carbonate-phosphoric acid liquid phase as the hardening liquid. The application of the energy dispersive X-ray diffraction method allowed to collect the diffraction patterns from the cement pastes in situ starting from 1 min of the setting and hardening process. The only crystallized phase in both cements was apatite-like phase, the primary crystallization process proceeds during a few seconds of the setting reaction. Both the compressive strength and the pH value changes during the hardening period can be attributed to the transformations occurring in the intergranular X-ray amorphous phase.

  7. Hardening of electromechanical properties in piezoceramics using a composite approach

    NASA Astrophysics Data System (ADS)

    K. V., Lalitha; Riemer, Lukas M.; Koruza, Jurij; Rödel, Jürgen

    2017-07-01

    Piezoelectric applications such as ultrasonic motors, transformers and therapeutic ultrasonics demand high power generation with low losses, which is facilitated by "hard" ferroelectrics. Hardening of piezoelectric properties, characterized by high mechanical quality factor (Qm), is usually achieved by doping with lower valence elements, thereby tailoring the domain wall dynamics. In the present study, we demonstrate a hardening mechanism by developing composites of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) with ZnO inclusions, as an alternative to chemical modifications. A decrease in the saturation polarization and total strain, higher internal bias fields, lower hysteretic losses and a two-fold increase in Qm are observed in comparison to NBT-6BT. The composite with 0.1 mole ratio of ZnO exhibits the highest Qm of 320 with d33 = 125 pC/N and Kp = 0.29. A one-to-one correspondence between the increase in Qm and the decrease in the domain wall mobility is established from the ac field dependence of permittivity, in the framework of the Rayleigh law. A further increase in ZnO content beyond a mole ratio of 0.1 reduces Qm, but retains it at a higher level, as compared to NBT-6BT. The results are explained based on the poling-induced strain incompatibility between the matrix and the hard ZnO phase. This composite approach is therefore considered a generic hardening concept and can be extended to other ferroelectric systems.

  8. Influence of slip system hardening assumptions on modeling stress dependence of work hardening

    NASA Astrophysics Data System (ADS)

    Miller, Matthew; Dawson, Paul

    1997-11-01

    Due to the discrete directional nature of processes such as crystallographic slip, the orientation of slip planes relative to a fixed set of loading axes has a direct effect on the magnitude of the external load necessary to induce dislocation motion (yielding). The effect such geometric or textural hardening has on the macroscopic flow stress can be quantified in a polycrystal by the average Taylor factor M¯. Sources of resistance to dislocation motion such as interaction with dislocation structures, precipitates, and grain boundaries, contribute to the elevation of the critically resolved shear strength τcrss. In continuum slip polycrystal formulations, material hardening phenomena are reflected in the slip system hardness equations. Depending on the model, the hardening equations and the mean field assumption can both affect geometric hardening through texture evolution. In this paper, we examine continuum slip models and focus on how the slip system hardening model and the mean field assumption affect the stress-strain response. Texture results are also presented within the context of how the texture affects geometric hardening. We explore the effect of employing slip system hardnesses averaged over different size scales. We first compare a polycrystal simulation employing a single hardness per crystal to one using a latent hardening formulation producing distinct slip system hardnesses. We find little difference between the amplitude of the single hardness and a crystal-average of the latent hardening values. The geometric hardening is different due to the differences in the textures predicted by each model. We also find that due to the high degree of symmetry in an fcc crystal, macroscopic stress-strain predictions using simulations employing crystal- and aggregateaveraged hardnesses are nearly identical. We find this to be true for several different mean field assumptions. An aggregate-averaged hardness may be preferred in light of the difficulty

  9. Phenomenological modeling of hardening and thermal recovery in metals

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    Modeling of hardening and thermal recovery in metals is considered within the context of unified elastic-viscoplastic theories. Specifically, the choices of internal variables and hardening measures, and the resulting hardening response obtained by incorporating saturation-type evolution equations into two general forms of the flow law are examined. Based on the analytical considerations, a procedure for delineating directional and isotropic hardening from uniaxial hardening data has been developed for the Bodner-Partom model and applied to a nickel-base superalloy, B1900 + Hf. Predictions based on the directional hardening properties deduced from the monotonic loading data are shown to be in good agreement with results of cyclic tests.

  10. Generation of 10 GHz transform-limited pulse train from dual-pump mode-locking erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    He, Li; Yang, Bojun; Zhang, Xiaoguang; Yu, Li

    2006-09-01

    A dual-pump 10 GHz mode-locking erbium-doped fiber laser was demonstrated. With 10-GHz signal modulation of the modulator, less than 12 ps mode-locked pulse at 10 GHz repetition rate with 1.097 mW average output power was obtained. The corresponding spectrum width is 0.277 nm, which is centered at 1561 nm. The corresponding product of time and bandwidth is Δv*Δt which equals 0.433. Gaussian pulse shape is assumed, the output pulse is almost transform limited. Compared with single-pump fiber ring laser, the dual-pump fiber ring laser is helpful for suppression of supermode noise, which make this kind of fiber ring laser more stable.

  11. An Anisotropic Hardening Model for Springback Prediction

    SciTech Connect

    Zeng, Danielle; Xia, Z. Cedric

    2005-08-05

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

  12. Radiation Hardened DDR2 SDRAM Solution

    NASA Astrophysics Data System (ADS)

    Wang, Pierre-Xiao; Sellier, Charles

    2016-08-01

    The Radiation Hardened (RH) DDR2 SDRAM Solution is a User's Friendly, Plug-and-Play and Radiation Hardened DDR2 solution, which includes the radiation tolerant stacking DDR2 modules and a radiation intelligent memory controller (RIMC) IP core. It provides a high speed radiation hardened by design DRAM solution suitable for all space applications such as commercial or scientific geo-stationary missions, earth observation, navigation, manned space vehicles and deep space scientific exploration. The DDR2 module has been guaranteed with SEL immune and TID > 100Krad(Si), on the other hand the RIMC IP core provides a full protection against the DDR2 radiation effects such as SEFI and SEU.

  13. Modeling of Irradiation Hardening of Polycrystalline Materials

    SciTech Connect

    Li, Dongsheng; Zbib, Hussein M.; Garmestani, Hamid; Sun, Xin; Khaleel, Mohammad A.

    2011-09-14

    High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.

  14. "Work-Hardenable" ductile bulk metallic glass.

    PubMed

    Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  15. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  16. Radiation Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Frazier, Donald O.; Patrick, Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

    2007-01-01

    Radiation Environmental Modeling is crucial to proper predictive modeling and electronic response to the radiation environment. When compared to on-orbit data, CREME96 has been shown to be inaccurate in predicting the radiation environment. The NEDD bases much of its radiation environment data on CREME96 output. Close coordination and partnership with DoD radiation-hardened efforts will result in leveraged - not duplicated or independently developed - technology capabilities of: a) Radiation-hardened, reconfigurable FPGA-based electronics; and b) High Performance Processors (NOT duplication or independent development).

  17. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  18. Multi-MGy Radiation Hardened Camera for Nuclear Facilities

    SciTech Connect

    Girard, Sylvain; Boukenter, Aziz; Ouerdane, Youcef; Goiffon, Vincent; Corbiere, Franck; Rolando, Sebastien; Molina, Romain; Estribeau, Magali; Avon, Barbara; Magnan, Pierre; Paillet, Philippe; Duhamel, Olivier; Gaillardin, Marc; Raine, Melanie

    2015-07-01

    be exposed. Another important element of the camera is the optical system that transports the image from the scene to the image sensor. This arrangement of glass-based lenses is affected by radiations through two mechanisms: the radiation induced absorption and the radiation induced refractive index changes. The first one will limit the signal to noise ratio of the image whereas the second one will directly affect the resolution of the camera. We'll present at the conference a coupled simulation/experiment study of these effects for various commercial glasses and present vulnerability study of typical optical systems to radiations at MGy doses. The last very important part of the camera is the illumination system that can be based on various technologies of emitting devices like LED, SLED or lasers. The most promising solutions for high radiation doses will be presented at the conference. In addition to this hardening-by-component approach, the global radiation tolerance of the camera can be drastically improve by working at the system level, combining innovative approaches eg. for the optical and illumination systems. We'll present at the conference the developed approach allowing to extend the camera lifetime up to the MGy dose range. (authors)

  19. idRHa+ProMod - Rail Hardening Control System

    NASA Astrophysics Data System (ADS)

    Ferro, L.

    2016-03-01

    idRHa+ProMod is the process control system developed by Primetals Technologies to foresee the thermo-mechanical evolution and micro-structural composition of rail steels subjected to slack quenching into idRHa+ Rail Hardening equipments in a simulation environment. This tool can be used both off-line or in-line, giving the user the chance to test and study the best cooling strategies or letting the automatic control system free to adjust the proper cooling recipe. Optimization criteria have been tailored in order to determine the best cooling conditions according to the metallurgical requirements imposed by the main rail standards and also taking into account the elastoplastic bending phenomena occurring during all stages of the head hardening process. The computational core of idRHa+ProMod is a thermal finite element procedure coupled with special algorithms developed to work out the main thermo-physical properties of steel, to predict the non-isothermal austenite decomposition into all the relevant phases and subsequently to evaluate the amount of latent heat of transformation released, the compound thermal expansion coefficient and the amount of plastic deformation in the material. Air mist and air blades boundary conditions have been carefully investigated by means of pilot plant tests aimed to study the jet impingement on rail surfaces and the cooling efficiency at all working conditions. Heat transfer coefficients have been further checked and adjusted directly on field during commissioning. idRHa+ is a trademark of Primetals Technologies Italy Srl

  20. Use of the Lorentz-Boosted Frame Transformation to Simulate Free-Electron Laser Amplifier Physics

    NASA Astrophysics Data System (ADS)

    Fawley, W. M.; Vay, J.-L.

    2009-01-01

    Recently [1] it has been pointed out that numerical simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz boosted frame. A particularly good example is that of short wavelength free-electron lasers (FELs) in which a high energy (E0⩾250 MeV) electron beam interacts with a static magnetic undulator. In the optimal boost frame with Lorentz factor γF, the red-shifted FEL radiation and blue shifted undulator have identical wavelengths and the number of required time-steps (presuming the Courant condition applies) decreases by a factor of γF2 for fully electromagnetic simulation. We have adapted the WARP code [2] to apply this method to several FEL problems including coherent spontaneous emission (CSE) from pre-bunched e-beams, and strong exponential gain in a single pass amplifier configuration. We discuss our results and compare with those from the "standard" FEL simulation approach which adopts the eikonal approximation for propagation of the radiation field.

  1. Use of the Lorentz-Boosted Frame Transformation to Simulate Free-Electron Laser Amplifier Physics

    SciTech Connect

    Fawley, W.M.; Vay, J.-L.

    2008-07-27

    Recently [1]it has been pointed out that numerical simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz boosted frame. A particularly good example is that of short wavelength free-electron lasers (FELs) in which a high energy (E0>_ 250 MeV) electron beam interacts with a static magnetic undulator. In the optimal boost frame with Lorentz factor gamma F, the red-shifted FEL radiation and blue shifted undulator have identical wavelengths and the number of required time-steps (presuming the Courant condition applies) decreases by a factor of g2 F for fullyelectromagnetic simulation. We have adapted the WARP code [2]to apply this method to several FEL problems including coherent spontaneous emission (CSE) from pre-bunched e-beams, and strong exponential gain in a single pass amplifier configuration. We discuss our results and compare with those from the"standard" FEL simulation approach which adopts the eikonal approximation for propagation ofthe radiation field.

  2. Use of the Lorentz-Boosted Frame Transformation to Simulate Free-Electron Laser Amplifier Physics

    SciTech Connect

    Fawley, W. M.; Vay, J.-L.

    2009-01-22

    Recently it has been pointed out that numerical simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz boosted frame. A particularly good example is that of short wavelength free-electron lasers (FELs) in which a high energy (E{sub 0}{>=}250 MeV) electron beam interacts with a static magnetic undulator. In the optimal boost frame with Lorentz factor {gamma}F, the red-shifted FEL radiation and blue shifted undulator have identical wavelengths and the number of required time-steps (presuming the Courant condition applies) decreases by a factor of {gamma}{sub F}{sup 2} for fully electromagnetic simulation.We have adapted the WARP code to apply this method to several FEL problems including coherent spontaneous emission (CSE) from pre-bunched e-beams, and strong exponential gain in a single pass amplifier configuration. We discuss our results and compare with those from the 'standard' FEL simulation approach which adopts the eikonal approximation for propagation of the radiation field.

  3. Gas-phase plume from laser-irradiated fiberglass-reinforced polymers via imaging fourier transform spectroscopy.

    PubMed

    Acosta, Roberto I; Gross, Kevin C; Perram, Glen P; Johnson, Shane M; Dao, Ly; Medina, David F; Roybal, Robert; Black, Paul

    2014-01-01

    Emissive plumes from laser-irradiated fiberglass-reinforced polymers (FRP) were investigated using a mid-infrared imaging Fourier transform spectrometer, operating at fast framing rates (50 kHz imagery and 2.5 Hz hyperspectral imagery) with adequate spatial (0.81 mm(2) per pixel) and spectral resolution (2 cm(-1)). Fiberglass-reinforced polymer targets were irradiated with a 1064 nm continuous wave neodymium-doped yttrium aluminum garnet (Nd:YAG) laser for 60 s at 100 W in air. Strong emissions from H(2)O, CO, CO(2), and hydrocarbons were observed between 1800 and 5000 cm(-1). A single-layer radiative transfer model was developed for the spectral region from 2000 to 2400 cm(-1) to estimate spatial maps of temperature and column densities of CO and CO(2) from the hyperspectral imagery. The spectral model was used to compute the absorption cross sections of CO and CO(2) using spectral line parameters from the high-temperature extension of the HITRAN. The analysis of pre-combustion spectra yields effective temperatures rising from ambient to 1200 K and suddenly increasing to 1515 K upon combustion. The peak signal-to-noise ratio for a single spectrum exceeds 60:1, enabling temperature and column density determinations with low statistical error. For example, the spectral analysis for a single pixel within a single frame yields an effective temperature of 1019 ± 6 K, and CO and CO(2) column densities of 1.14 ± 0.05 and 1.11 ± 0.03 × 10(18) molec/cm(2), respectively. Systematic errors associated with the radiative transfer model dominate, yielding effective temperatures with uncertainties of >100 K and column densities to within a factor of 2-3. Hydrocarbon emission at 2800 to 3200 cm(-1) is well correlated with CO column density.

  4. Detection of Biosignatures in Natural and Microbial Cultured Jarosites Using Laser- Desorption Fourier Transform Mass Spectrometry: Implications for Astrobiology

    NASA Astrophysics Data System (ADS)

    Kotler, J.; Hinman, N. W.; Yan, B.; Stoner, D. L.; Scott, J. R.

    2006-12-01

    The jarosite group minerals have received increasing attention since the discovery by the Mars Exploration Rover-Opportunity of jarosite on the Martian surface. The general chemical formula for jarosite is XFe3(SO4)2(OH)6 where the X represents both monovalent and divalent cations that can occupy the axial positions in the crystal structure. Commonly found ions include K+, Na+, H3O+, NH4+, and Pb2+ with reports of other large ions occupying this position in the literature. Modeling efforts have been performed to confirm that jarosite has the ability to incorporate a variety of "foreign" cations. The minerals unique ability to incorporate various large ions in its structure and its association with biological activity in terrestrial environments has lead to investigations regarding its use as an indicator of aqueous and/or biological activity. The use of laser desorption Fourier transform mass spectrometry (LD-FTMS) has revealed the presence of organic matter including the amino acid, glycine, in several jarosite samples from various worldwide locations. Iron precipitates derived from acidophilic microbial cultures were also analyzed. Using attenuated total reflectance infrared spectroscopy (ATR-IR), signals indicative of microbes or microbial exudates were weak and ambiguous. In contrast, LD-FTMS clearly detected bioorganic constituents in some desorption spots. However, the signals were sporadic and required the laser scanning/imaging capability of our laboratory built system to locate the microbial signatures in the heterogeneous samples. The ability to observe these bioorganic signatures in jarosite samples using the instrumental technique employed in this study furthers the goals of planetary geologists to determine whether signs of life (e.g., presence of biomolecules or biomolecule precursors) can be detected in the rock record of terrestrial and extraterrestrial samples.

  5. Multiphoton Ionization of Laser-Desorbed Neutral Molecules in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

    DTIC Science & Technology

    1990-05-19

    dissociates when irradiated with a gated pulse of light from a continuous wave carbon dioxide laser , forming two fragment ions at m/z = 200 and 171...this manner to laser photodissociation in a unique 3- laser experiment in which a third (gated, continuous- wave (cw) CO) laser has been used to...pathway shown in Figure 1), thus allowing the beam to travel through the center of the cell. Typical UV laser pulse energies were on the order of 50-100

  6. Photochemical transformations and laser flash photolysis studies of dibenzobarrelenes containing 1,2-dibenzoylalkene moieties

    SciTech Connect

    Kumar, C.V.; Murty, B.A.R.C.; Lahiri, S.; Chackachery, E.; Scaiano, J.C.; George, M.V.

    1984-12-14

    Phototransformations of the dibenzobarrelenes 10 = 11,12-dibenzoyl-9,10-dihydro-9,10-ethenoanthracene, 11 = 11,12-dibenzoyl-9,10-dihydro-9-methyl-9,10-ethenoanthracene, 23 = 11,12-dibenzoyl-9,10-dihydro-9,10-dimethyl-9,10-ethenoenthracene, prepared by the reaction of the appropriate anthracenes with dibenzoylacetylenes, are reported. Irradiation of 10 and 11 in solvents such as benzene, methanol, and acetone gave the corresponding dibenzosemibullvalenes, 17 = 8c, 8d-dibenzoyl-4b,8b,8c,8d-tetrahydrodibenzo(a,f)cyclopropa(c,d)- and 18, respectively, in good yields. These dibenzosemibullvalenes on catalytic hydrogenation using 5% Pd on charcoal gave the corresponding cyclopropane ring-opened products, 21 and 22, respectively. Irradiation of 23 in benzene gave a mixture of 2,3-dibenzoyl-2,3-dihydro-1,4-dimethyl-2,3-benzonaphthalene 27 (2%), 1,4-dibenzoyl-5,8-dimethyl-2,3:6,7-dibenzocyclo-octatetraene (24, 20%), the carbinol (45%), and benzoic acid (7%). Irradiation of 23 in methanol gave a mixture of 27 (25%), 24 (27%), and benzoic acid (8%). Laser flash photolysis (337.1 nm) of 10, 11, and 23 led to transient species, characterized by strong absorptions in the 300-650-nm region. These transients are due to the triplet states of the substrates, as established by quenching studies involving oxygen, di-tert-butylnitroxide, azulene, and ..beta..-carotene. Energy-transfer sensitization of 10, 11, and 23 by benzophenone in benzene also gave rise to the same transients, as formed under direct irradiation. The quantum yields of triplet formation (PHI/sub T/) were estimated to be high for 10 and 11 (approx. 1), whereas it is significantly lower for 23 (approx. 0.7). 24 references, 3 figures, 2 tables.

  7. Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

    SciTech Connect

    Qiu, Weicheng; Hu, Weida Lin, Tie; Yin, Fei; Zhang, Bo; Chen, Xiaoshuang; Lu, Wei; Cheng, Xiang'ai Wang, Rui

    2014-11-10

    In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.

  8. [Microstructural changes in hardened beans (Phaseolus vulgaris)].

    PubMed

    Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy

    2015-06-01

    (Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.

  9. Fundamentals of viscoelastoplasticity and hardening theory revisited

    NASA Astrophysics Data System (ADS)

    Khoroshun, L. P.

    2008-02-01

    Thermodynamic and statistical methods for setting up the constitutive equations describing the viscoelastoplastic deformation and hardening of materials are proposed. The thermodynamic method is based on the law of conservation of energy, the equations of entropy balance and entropy production in the presence of self-balanced internal microstresses characterized by conjugate hardening parameters. The general constitutive equations include the relationships between the thermodynamic flows and forces, which follow from nonnegative entropy production and satisfy the generalized Onsager's principle, and the thermoelastic relations and the expression for entropy, which follow from the law of conservation of energy. Specific constitutive equations are derived by representing the dissipation rate as a sum of two terms responsible for kinematic and isotropic hardening and approximated by power and hyperbolic-sinus functions. The constitutive equations describing viscoelastoplastic deformation and hardening are derived based on stochastic microstructural concepts and on the linear thermoelasticity model and nonlinear Maxwell model for the spherical and deviatoric components of microstresses and microstrains, respectively. The problem of determining the effective properties and stress-strain state of a three-component material found using the Voigt-Reuss scheme leads to constitutive equations similar in form to those produced by the thermodynamic method

  10. SEU hardening of CMOS memory circuit

    NASA Technical Reports Server (NTRS)

    Whitaker, S.; Canaris, J.; Liu, K.

    1990-01-01

    This paper reports a design technique to harden CMOS memory circuits against Single Event Upset (SEU) in the space environment. A RAM cell and Flip Flop design are presented to demonstrate the method. The Flip Flop was used in the control circuitry for a Reed Solomon encoder designed for the Space Station.

  11. Strain hardening in bent copper foils

    NASA Astrophysics Data System (ADS)

    Hayashi, Ichiro; Sato, Masumi; Kuroda, Mitsutoshi

    2011-09-01

    A series of systematic tensile and microbend tests were conducted on copper foil specimens with different thicknesses. The specimens were made of a copper foil having almost unidirectional crystal orientations that was considered to be nearly single-crystal. In order to investigate the effects of slip system interactions, two different crystal orientations relative to the tensile direction were considered in the tests: one is close to coplanar double-slip orientation, and the other is close to the ideal cube orientation (the tensile direction nearly coincides to [0 0 1]) that yields multi-planar multi-slip deformation. We extended the microbend test method to include the reversal of bending, and we attempted to divide the total amount of strain-hardening into isotropic and kinematic hardening components. In the tensile tests, no systematic tendency of size dependence was observed. In the microbend tests, size-dependent kinematic hardening behavior was observed for both the crystal orientations, while size dependence of isotropic hardening was observed only for the multi-planar multi-slip case. We introduce an extended crystal plasticity model that accounts for the effects of the geometrically necessary dislocations (GNDs), which correspond to the spatial gradients of crystallographic slips. Through numerical simulations performed using the model, the origin of the size-dependent behavior observed in the microbend tests is discussed.

  12. Extraordinary strain hardening by gradient structure

    PubMed Central

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T.

    2014-01-01

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures. PMID:24799688

  13. Fuzzy Logic Classification of Imaging Laser Desorption Fourier Transform Mass Spectrometry Data

    SciTech Connect

    Timothy R. McJunkin; Jill R. Scott

    2008-06-01

    The fuzzy logic method is applied to classification of mass spectra obtained with an imaging internal source Fourier transform mass spectrometer (I2LD-FTMS). Traditionally, an operator uses the relative abundance of ions with specific mass-to-charge (m/z) ratios to categorize spectra. An operator does this by comparing the spectrum of m/z versus abundance of an unknown sample against a library of spectra from known samples. Automated positioning and acquisition allow the I2LD-FTMS to acquire data from very large grids, which would require classification of up to 3600 spectra per hour to keep pace with the acquisition. The tedious job of classifying numerous spectra generated in an I2LD-FTMS imaging application can be replaced by a fuzzy rule base if the cues an operator uses can be encapsulated. Appropriate methods for assigning fuzzy membership values for inputs (e.g., mass spectrum abundances) and choice of fuzzy inference operators to translate linguistic antecedent into confidence values for the consequence (or in this case the classification) is followed by using the maximum confidence and a necessary minimum threshold for making a crisp decision. This paper also describes a method for gathering statistics on ions, which are not currently used in the rule base, but which may be candidates for making the rule base more accurate and complete or to form new rule bases based on data obtained from known samples. A spatial method for classifying spectra with low membership values, based on neighboring sample classifications, is also presented.

  14. 'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle.

    PubMed

    Ennos, Antony Roland; Chan, Tak Lok

    2016-05-01

    It is usually assumed that 'fire hardening' the tips of spears, as practised by hunter-gatherers and early Homo spp., makes them harder and better suited for hunting. This suggestion was tested by subjecting coppiced poles of hazel to a fire-hardening process and comparing their mechanical properties to those of naturally seasoned poles. A Shore D hardness test showed that fire treatment slightly increased the hardness of the wood, but flexural and impact tests showed that it reduced the strength and work of fracture by 30% and 36%, respectively. These results suggest that though potentially slightly sharper and more durable, fire-hardened tips would actually be more likely to break off when used, as may have been the case with the earliest known wooden tool, the Clacton spear. Fire might first have been used to help sharpen the tips of spears, and fire-hardening would have been a mostly negative side effect, not its primary purpose.

  15. Glycine identification in natural jarosites using laser desorption Fourier transform mass spectrometry: implications for the search for life on Mars.

    PubMed

    Kotler, J Michelle; Hinman, Nancy W; Yan, Beizhan; Stoner, Daphne L; Scott, Jill R

    2008-04-01

    The jarosite group minerals have received increasing attention since the discovery of jarosite on the martian surface by the Mars Exploration Rover Opportunity. Given that jarosite can incorporate foreign ions within its structure, we have investigated the use of jarosite as an indicator of aqueous and biological processes on Earth and Mars. The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various locations worldwide. One of the ions from the natural jarosites has been attributed to glycine because it was systematically observed in combinations of glycine with synthetic ammonium and potassium jarosites, Na(2)SO(4) and K(2)SO(4). The ability to observe these organic signatures in jarosite samples with an in situ instrumental technique, such as the one employed in this study, furthers the goals of planetary geologists to determine whether signs of life (e.g., the presence of biomolecules or biomolecule precursors) can be detected in the rock record of terrestrial and extraterrestrial samples.

  16. Surface modification, martensitic transformation, and optical properties of hydrogenated ZrO2 nanocondensates via pulsed laser ablation in water

    NASA Astrophysics Data System (ADS)

    Wu, Chao-Hsien; Huang, Chang-Ning; Shen, Pouyan; Chen, Shuei-Yuan

    2011-12-01

    Pulsed laser ablation on Zr plate in water under Q-switch mode and a fluence of 700 and 800 mJ/pulse for a rather high power density of 1.5 and 1.7 × 1011 W/cm2, respectively, was employed to fabricate hydrogenated ZrO2 nanocondensates. X-ray diffraction and transmission electron microscopic observations indicated such nanocondensates are full of {111} and {100} facets and predominantly in monoclinic (m-) rather than cubic- and/or tetragonal (t-) crystal symmetry in particular when fabricated at 700 mJ/pulse. The hydrogenated ZrO2 nanocondensates underwent martensitic t → m transformation at a rather small critical size (ca. 20 nm) due to H+ signature and hence oxygen vacancy deficiency in the lattice. The resultant m-phase was free of twin and fault due to site saturation and rather limited growth of the nanosized particles. Spectroscopic characterizations indicated that the nanocondensates have a significant internal compressive stress, (H+, Zr2+, Zr3+) co-signature and hence a smaller band gap of 5.2-5.3 eV for potential applications in UV region.

  17. Glycine Identification in Natural Jarosites Using Laser Desorption Fourier Transform Mass Spectrometry: Implications for the Search for Life on Mars

    NASA Astrophysics Data System (ADS)

    Kotler, J. Michelle; Hinman, Nancy W.; Yan, Beizhan; Stoner, Daphne L.; Scott, Jill R.

    2008-04-01

    The jarosite group minerals have received increasing attention since the discovery of jarosite on the martian surface by the Mars Exploration Rover Opportunity. Given that jarosite can incorporate foreign ions within its structure, we have investigated the use of jarosite as an indicator of aqueous and biological processes on Earth and Mars. The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various locations worldwide. One of the ions from the natural jarosites has been attributed to glycine because it was systematically observed in combinations of glycine with synthetic ammonium and potassium jarosites, Na2SO4 and K2SO4. The ability to observe these organic signatures in jarosite samples with an in situ instrumental technique, such as the one employed in this study, furthers the goals of planetary geologists to determine whether signs of life (e.g., the presence of biomolecules or biomolecule precursors) can be detected in the rock record of terrestrial and extraterrestrial samples.

  18. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  19. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  20. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  1. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  2. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  3. Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: thermal behavior and phase transformation of human tooth enamel and dentin after irradiation by CO2 laser.

    PubMed

    Lin, C P; Lee, B S; Kok, S H; Lan, W H; Tseng, Y C; Lin, F H

    2000-06-01

    Acute trauma or trauma associated with occlusal disharmony can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. The responses of soft tissues to lasers of different wavelengths are fairly well known, but the reactions of hard tissues are still to be understood. The purpose of this research was to study the feasibility of using a medium energy continuous-wave CO(2) laser and a low melting-point bioactive glass to fuse or bridge tooth fractures. The present report is focused on the first part of the research, the analysis of changes in laser-irradiated human tooth enamel/dentin by means of X-ray diffractometer (XRD), Fourier-transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). After CO(2) laser irradiation, there were no marked changes in the X-ray diffraction pattern of the enamel when compared to that before laser treatment. However, a small peak belonging to alpha-TCP appeared at the position of 2theta=30.78 degrees C. After being treated with CO(2) laser, the dentin showed much sharper peaks on the diffraction patterns because of grain growth and better crystallinity. alpha-TCP and beta-TCP were identified after laser treatment. In the FTIR analysis, an HPO(4)(-2) absorption band was noted before laser treatment disappeared after the irradiation. No significant change in the absorption band of HPO(4)(-2) was found on the FTIR curves of enamel after laser treatment. The results of DTA/TGA indicated that loss of water and organic materials occurred in both enamel and dentin after laser treatment. Under SEM, melting and resolidification occurred in both enamel and dentin by medium energy of CO(2) laser. This implies that

  4. Laser vision: lidar as a transformative tool to advance critical zone science

    NASA Astrophysics Data System (ADS)

    Harpold, A. A.; Marshall, J. A.; Lyon, S. W.; Barnhart, T. B.; Fisher, B. A.; Donovan, M.; Brubaker, K. M.; Crosby, C. J.; Glenn, N. F.; Glennie, C. L.; Kirchner, P. B.; Lam, N.; Mankoff, K. D.; McCreight, J. L.; Molotch, N. P.; Musselman, K. N.; Pelletier, J.; Russo, T.; Sangireddy, H.; Sjöberg, Y.; Swetnam, T.; West, N.

    2015-06-01

    Observation and quantification of the Earth's surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of critical zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and biosphere shape and maintain the "zone of life", which extends from the top of unweathered bedrock to the top of the vegetation canopy. Fundamental to CZ science is the development of transdisciplinary theories and tools that transcend disciplines and inform other's work, capture new levels of complexity, and create new intellectual outcomes and spaces. Researchers are just beginning to use lidar data sets to answer synergistic, transdisciplinary questions in CZ science, such as how CZ processes co-evolve over long timescales and interact over shorter timescales to create thresholds, shifts in states and fluxes of water, energy, and carbon. The objective of this review is to elucidate the transformative potential of lidar for CZ science to simultaneously allow for quantification of topographic, vegetative, and hydrological processes. A review of 147 peer-reviewed lidar studies highlights a lack of lidar applications for CZ studies as 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % had an interdisciplinary focus. A handful of exemplar transdisciplinary studies demonstrate lidar data sets that are well-integrated with other observations can lead to fundamental advances in CZ science, such as identification of feedbacks between hydrological and ecological processes over hillslope scales and the synergistic co-evolution of landscape-scale CZ structure due to interactions amongst carbon, energy, and water cycles

  5. Detection of polychlorinated biphenyls in transformer oils in Vietnam by multiphoton ionization mass spectrometry using a far-ultraviolet femtosecond laser as an ionization source.

    PubMed

    Duong, Vu Thi Thuy; Duong, Vu; Lien, Nghiem Thi Ha; Imasaka, Tomoko; Tang, Yuanyuan; Shibuta, Shinpei; Hamachi, Akifumi; Hoa, Do Quang; Imasaka, Totaro

    2016-03-01

    Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Press-hardening of zinc coated steel - characterization of a new material for a new process

    NASA Astrophysics Data System (ADS)

    Kurz, T.; Larour, P.; Lackner, J.; Steck, T.; Jesner, G.

    2016-11-01

    Press-hardening of zinc-coated PHS has been limited to the indirect process until a pre-cooling step was introduced before the hot forming to prevent liquid metal embrittlement. Even though that's only a minor change in the process itself it does not only eliminate LME, but increases also the demands on the base material especially in terms of hardenability or phase transformations at temperatures below 700 °C in general. This paper deals with the characterization of a modified zinc-coated material for press-hardening with pre-cooling that assures a robust process. The pre-cooling step itself and especially the transfer of the blank in the hot-forming die is more demanding than the standard 22MnB5 can stand to ensure full hardenability. Therefore the transformation behavior of the modified material is shown in CCT and TTT diagrams. Of the same importance are the changed hot forming temperature and flow curves for material at lower temperatures than typically used in direct hot forming. The resulting mechanical properties after hardening from tensile testing and bending tests are shown in detail. Finally some results from side impact crash tests and correlations of the findings with mechanical properties such as fracture elongation, tensile strength, VDA238 bending angle at maximum force as well as postuniform bending slope are given as well. Fracture elongation is shown to be of little help for damage prediction in side impact crash. Tensile strength and VDA bending properties enable however some accurate prediction of the PHS final damage behavior in bending dominated side impact load case.

  7. Revealing cyclic hardening mechanism of a TRIP steel by real-time in situ neutron diffraction

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Yan; Chen, Xu

    2014-01-01

    Real-time in situ neutron diffraction was performed on a transformation-induced plasticity (TRIP) steel under cyclic loading at room temperature. By Rietveld refinement and single peak analysis, the volume fraction and average stress estimates as well as dislocation density of individual phases (austenite and martensite phase) were derived. The results reveal that the volume fraction of martensite phase, instead of individual phase strengthening, should be accounted for the remarkable secondary cyclic hardening.

  8. Transformation of medical grade silicone rubber under Nd:YAG and excimer laser irradiation: First step towards a new miniaturized nerve electrode fabrication process

    NASA Astrophysics Data System (ADS)

    Dupas-Bruzek, C.; Robbe, O.; Addad, A.; Turrell, S.; Derozier, D.

    2009-08-01

    Medical grade silicone rubber, poly-dimethylsiloxane (PDMS) is a widely used biomaterial. Like for many polymers, its surface can be modified in order to change one or several of its properties which further allow this surface to be functionalized. Laser-induced surface modification of PDMS under ambient conditions is an easy and powerful method for the surface modification of PDMS without altering its bulk properties. In particular, we profit from both UV laser inducing surface modification and of UV laser micromachining to develop a first part of a new process aiming at increasing the number of contacts and tracks within the same electrode surface to improve the nerve selectivity of implantable self sizing spiral cuff electrodes. The second and last part of the process is to further immerse the engraved electrode in an autocatalytic Pt bath leading in a selective Pt metallization of the laser irradiated tracks and contacts and thus to a functionalized PDMS surface. In the present work, we describe the different physical and chemical transformations of a medical grade PDMS as a function of the UV laser and of the irradiation conditions used. We show that the ablation depths, chemical composition, structure and morphology vary with (i) the laser wavelength (using an excimer laser at 248 nm and a frequency-quadrupled Nd:YAG laser at 266 nm), (ii) the conditions of irradiation and (iii) the pulse duration. These different modified properties are expected to have a strong influence on the nucleation and growth rates of platinum which govern the adhesion and the thickness of the Pt layer on the electrodes and thus the DC resistance of tracks.

  9. Clinical trial analyzing the impact of continuous defocused CO2 laser vaporisation on the malignant transformation of erosive oral lichen planus.

    PubMed

    Mücke, Thomas; Gentz, Irina; Kanatas, Anastasios; Ritschl, Lucas M; Mitchell, David A; Wolff, Klaus-Dietrich; Deppe, Herbert

    2015-10-01

    The erosive oral lichen planus (OLP) represents a management challenge to the clinician and can have debilitating consequences to patients' quality of life. The aims of this work were to determine the incidence of malignant transformation to squamous cell carcinoma (SCC) in patients undergoing traditional symptomatic treatments (oral salve containing lidocaine hydrochloride or systemic diclofenac) compared to patients that were managed with a defocused continuous CO2 laser beam. A total of 171 patients with histologically confirmed erosive OLP were included into this study. After treatment, patients were assessed until completion of wound healing, at least every 3-6 months for the first 2 years, and every 6-12 months thereafter. The study included 87 women (50.9%) and 84 men (49.1%). A total of 103 patients (60.2%) underwent symptomatic conservative treatment, and 68 patients (39.8%) underwent continuous defocused CO2 laser treatments. SCC developed in 16 patients (9.4%), 2 patients (2.9%) after continuous defocused CO2 laser treatment and 14 patients (13.6%) with symptomatic treatment only. This study provides insight into the potential impact of the CO2 laser in the management of patients with erosive OLP and the influence on the recurrence rate of erosive OLP, as well as malignant transformation to oral SCC.

  10. Anomalous temperature dependence of yield stress and work hardening coefficient of B2-stabilized NiTi alloys

    SciTech Connect

    Hosoda, Hideki; Mishima, Yoshinao; Suzuki, Tomoo

    1997-12-31

    Yield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49mol.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77 K, air at room temperature (R.T.) and in an argon atmosphere between 473 K and 873 K. Only at 77 K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be between 2 and 11GPa in all the test temperature range. The values are extremely high compared with Young`s modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650 K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.

  11. Structural heredity influence upon principles of strain wave hardening

    NASA Astrophysics Data System (ADS)

    Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

    2017-02-01

    It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

  12. Preliminary study of laser doppler perfusion signal by wavelet transform in patients with critical limb ischemia before and after revascularization.

    PubMed

    Ticcinelli, Valentina; Martini, Romeo; Bagno, Andrea

    2014-01-01

    The haemodynamics of skin microcirculation can be quantitatively evaluated by Laser Doppler Fluxmetry (LDF). LDF signal in human skin shows periodic oscillations. Spectral analysis by wavelet transform displays six characteristic frequency intervals (FI) from 0.005 to 2 Hz, related to distinct vascular structures activities: heart (0.6-2 Hz), sympathetic respiratory (0.145-0.6 Hz), myogenic (0.052-0.145 Hz), local sympathetic nerve (0.021-0.052 Hz) and endothelial cells NO dependent (0.0095-0.021 Hz) and NO independent (0.005-0.0095 Hz). The most advanced stage of peripheral arterial obstructive disease is the critical limb ischemia (CLI), which causes the reduction of blood perfusion threatening limb viability. Besides macrocirculatory alterations, many studies have shown microvascular misdistribution of skin blood flow as the main factor that leads patients to CLI. Revascularization can save limb and patient's life, too. In the present study, LDF signals have been recorded on the skin of the foot dorsum in 15 patients suffering from CLI. LDF signals have been analyzed before and after limb revascularization by means of the wavelet analysis. Significant changes in frequency distribution before and after limb revascularization have been detected: the median normalized values of spectral power increases for 49.8% (p = 0.0341) in the frequency range 0.050328-0.053707 Hz, whereas spectral power decreases for 77.1% (p = 0.0179) in the frequency range 0.018988-0.029284 Hz. We can conclude that changes in the frequency intervals occur after revascularization, shifting from a prevailing endothelial activity toward a prevailing sympathetic activity.

  13. Laser irradiation-induced {alpha} to {delta} phase transformation in Bi{sub 2}O{sub 3} ceramics and nanowires

    SciTech Connect

    Vila, M.; Diaz-Guerra, C.; Piqueras, J.

    2012-08-13

    The {alpha}-Bi{sub 2}O{sub 3} to {delta}-Bi{sub 2}O{sub 3} phase transformation has been locally induced by laser irradiation in ceramic samples and single-crystal nanowires of this oxide. The threshold power densities necessary to induce this transformation, as well as the corresponding transformation kinetics and its temporal stability, have been investigated in both kinds of samples by micro-Raman spectroscopy. The appearance of the {delta} phase was also monitored by spatially resolved photoluminescence spectroscopy. An emission band peaked near 1.67 eV, not observed in {alpha}-Bi{sub 2}O{sub 3}, is tentatively attributed to {delta}-Bi{sub 2}O{sub 3} near band gap transitions.

  14. Cyclic hardening in bundled actin networks.

    PubMed

    Schmoller, K M; Fernández, P; Arevalo, R C; Blair, D L; Bausch, A R

    2010-01-01

    Nonlinear deformations can irreversibly alter the mechanical properties of materials. Most soft materials, such as rubber and living tissues, display pronounced softening when cyclically deformed. Here we show that, in contrast, reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear. As a consequence, they exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain. This unique response is crucially determined by the network architecture: at lower crosslinker concentrations networks do not harden, but soften showing the classic Mullins effect known from rubber-like materials. By simultaneously performing macrorheology and confocal microscopy, we show that cyclic shearing results in structural reorganization of the network constituents such that the maximum applied strain is encoded into the network architecture.

  15. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  16. Plasma hardening of railway wheel surface

    NASA Astrophysics Data System (ADS)

    Isakaev, E. Kh.; Ivanov, P. P.; Tyuftyaev, A. S.; Paristyi, I. L.; Troitsky, A. A.; Yablonsky, A. E.; Filippov, G. A.

    1998-10-01

    A computer-controlled plasma technology was developed for the treatment of rolling stock wheels, providing the thermal hardening of tread and flange working surfaces. As a result of the plasma treatment the surface hardness of the wheel grows from 255 up to 420-450 HB. Herewith, the wear capability of the wheel metal grows 2-3 times and its resistance to the weariness-driven destruction grows 1.5 times due to the pecularities of the structural state of the steel, arising out of the thermal impact and of the alloying of the steel with nitrogen during the plasma treatment. Installation of several plants based on this technology in engine houses allowed to carry out a full scale experiment in order to assess the running characteristics of treated wheel sets in comparison with plain ones. Wheel life between mounting and truing or dismounting doubles due to plasma hardening.

  17. Terminal modeling of hardened integrated circuits

    NASA Astrophysics Data System (ADS)

    Kleiner, C. T.; Haas, R.; Peacock, M.; Mandel, G.; Messenger, G. C.; Weakley, D.; Demartino, V.

    1981-12-01

    Kleiner et al. (1979) have reported modeling and test verification techniques used to develop medium-scale, dielectrically isolated integrated circuits (DIIC). The current investigation is concerned with the approaches employed in modeling the new circuits for applications studied by design and radiation hardening engineers. The described technique improves significantly the cost-effective application of computer programs such as SYSCAP II. The terminal model offers the designer of radiation-hardened electronic circuits a method for evaluating the effects of radiation transients on single or multiple piece-part response at the circuit board level. Although the models presented were intended for TREE design and analysis, it is possible to extend the technique to EMP and SGEMP evaluations.

  18. RESIDUAL STRESS IN HARDENED STEEL CYLINDERS

    DTIC Science & Technology

    ultimate strength of the steel and in some instances caused cracking, and (4) stress patterns of interrupted quench specimens were not consistent enough to warrant a conclusion. (Author)...A study was conducted to (1) measure residual stress in hardened steel solid cylinders, (2) correlate the stress values with heat treatments, and (3...develop a dissolution technique. Residual stress patterns for 12 solid cylinders of 4160 steel, heat treated by various methods, were determined

  19. Hologram formation in hardened dichromated gelatin films.

    PubMed

    Lin, L H

    1969-05-01

    Hardened gelatin films sensitized with ammonium dichromate can be utilized to record high quality holograms. The maximum diffraction efficiency of the hologram approaches 90%. The light scattering from the hologram is so low that under ordinary light the hologram plate appears almost indistinguishable from a clear glass plate. Either a transmission or a reflection hologram can be recorded. Linear recording range of light amplitude is large. A practical method of preparing and processing the film is described, and the exposure characteristics are presented.

  20. Design of Radiation Hardened MNOS Memory

    DTIC Science & Technology

    1975-06-01

    OF BADIATION HARDENED MJ^OS MEMORY. up: is ^ u. 7^- 34 ia of o/wwiAflaw WAMB AWO ADOWKM \\ Sperry Gyroscope Great Neck, N.Y. 11020 READ...s.^<.*.:.!~^,-.,-.. ■ ■ .....ViJ^ —-T"--^ -i-.^-~^,immmmmmmmmKmmii. >-im.^. imimmmmm FOREWORD This report was prepared by the Sperry Rand...Corporation, Sperry Gyroscope Division, Great Neck, New York for the Air Force Avionics Laboratory, Wright- Patterson Air Force Base, Ohio. The

  1. UV Laser Pulse Temporal Profile Requirements for the LCLS Injector - Part I - Fourier Transform Limit for a Temporal Zero Slope Flattop

    SciTech Connect

    Limborg-Deprey, C.

    2005-01-31

    The temporal profile of the uv drive laser pulse for the LCLS injector is specified by the duration, the rise/fall time, and the maximum rms amplitude (for all frequencies) of residual modulation in the plateau region. The bandwidth of the uv laser system should accommodate pulses with a rise/fall time as low as 0.7 ps and an rms residual amplitude modulation (on the plateau) below 0.5% in the absence of a laser heater. Computations including the laser heater [3] relax this requirement to the 5% level. Numerical analyses of Fourier transform limited uv pulses show that the extent of frequency sidebands should extend to at least 1.5 THz on either side of the central uv frequency. For simplicity, we assume that the emitted electron beam profile matches the laser profile. The evolution of those electron beam distributions in the longitudinal phase space along the beamline as calculated with PARMELA/ASTRA are shown. Related spectral and shaping requirements on the fundamental ir pulses are briefly addressed.

  2. Helium irradiation induced hardening in MNHS steels

    NASA Astrophysics Data System (ADS)

    Cui, Minghuan; Wang, Ji; Wang, Zhiguang; Shen, Tielong; Wei, Kongfang; Yao, Cunfeng; Sun, Jianrong; Gao, Ning; Zhu, Yabin; Pang, Lilong; Wang, Dong; Zhu, Huiping; Han, Yi; Fang, Xuesong

    2017-09-01

    A recently developed reduced activation martensitic MNHS steel was irradiated with 200 keV helium (He) ions to a fluence of 1.0 × 1020 ions/m2 at 300 °C and 1.0 × 1021 ions/m2 at 300 °C and 450 °C. After irradiation, transmission electron microscopy (TEM) and nano-indentation measurements were used to investigate the hardness change and defects induced by He irradiation. Two kinds of defects including He bubbles and dislocation loops are observed by TEM. Irradiation induces hardening of MNHS steels and peak hardness values occur in all irradiated samples. Hardness increments induced by He bubbles and dislocation loops are predicted and fitted with the experimental peak hardness increment, based on the dispersed barrier-hardening (DBH) model and the size and number density of the two defects. A good agreement is got between the predicted and experimental hardness increment and the obstacle strength factor of He bubbles is a little stronger than the obstacle strength of dislocation loops. Other possible contributions to irradiation induced hardening are also discussed.

  3. Stage IV work hardening in cubic metals

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.; Doherty, R.D.

    1986-01-01

    The work hardening of fcc metals at large strains is discussed with reference to the linear stress-strain behavior often observed at large strains and known as Stage IV. The experimental evidence shows that Stage IV is a work hardening phenomenon that is found quite generally, even in pure fcc metals subjected to homogeneous deformation. A simple model for Stage IV in pure metals is presented, based on the accumulation of dislocation debris. Experiments are described for large strain torsion tests on four aluminum alloys. The level and extent of Stage IV scaled with the saturation stress that would represent the end of Stage III in the absence of a Stage IV. Reversing the torsion after large prestrains produced transient reductions in the work hardening. The strain rate sensitivity was also measured before and during the transient and found not to vary significantly. The microstructure observed at large strains in an Mg alloy suggest that Stage IV can occur in the absence of microband formation. Previous proposals for the cause of Stage IV are reviewed and found to be not supported by recent experimental data.

  4. Dislocation Multi-junctions and Strain Hardening

    SciTech Connect

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  5. Dislocation multi-junctions and strain hardening.

    PubMed

    Bulatov, Vasily V; Hsiung, Luke L; Tang, Meijie; Arsenlis, Athanasios; Bartelt, Maria C; Cai, Wei; Florando, Jeff N; Hiratani, Masato; Rhee, Moon; Hommes, Gregg; Pierce, Tim G; de la Rubia, Tomas Diaz

    2006-04-27

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects called dislocations. First proposed theoretically in 1934 (refs 1-3) to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening, a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions that tie the dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed 'multi-junctions'. We first predict the existence of multi-junctions using dislocation dynamics and atomistic simulations and then confirm their existence by transmission electron microscopy experiments in single-crystal molybdenum. In large-scale dislocation dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication, thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in body-centred cubic crystals.

  6. Strain Hardening in Bidisperse Polymer Glasses

    NASA Astrophysics Data System (ADS)

    Robbins, Mark O.; Hoy, Robert S.

    2009-03-01

    The connections between glassy and rubbery strain hardening have been a matter of great controversy in recent years. Recent experiments and our earlier simulations have suggested that the hardening modulus GR is proportional to the entanglement density in glasses, as it is to the crosslink density in rubbers. In this work we present more extensive studies of strain hardening in bidisperse glasses and its relation to microscopic conformational changes. The mixtures contain chains of very different lengths but equivalent chemistry. GR does not scale simply with the entanglement density. Instead it obeys a simple mixing rule, with GR equal to the volume fraction weighted average of the moduli of the two pure components. As in recent studies of monodisperse systems (R. S. Hoy and M. O. Robbins, Phys. Rev. Lett. 99, 117801 (2007)), the stress is directly correlated to the degree of chain orientation. Chains of a given length undergo almost the same degree of alignment in pure systems and mixtures, explaining why the simple mixing rule applies. The connection to recent analytic theories by K. Chen and K. S. Schweizer (PRL, in press) will be discussed.

  7. Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

    SciTech Connect

    Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.

    2015-06-06

    Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance were evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8 GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5 GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. Furthermore, the superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.

  8. Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

    DOE PAGES

    Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.

    2015-06-06

    Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance weremore » evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8 GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5 GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. Furthermore, the superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.« less

  9. [Lasers].

    PubMed

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  10. Lasers.

    PubMed

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  11. Empirical beam hardening correction (EBHC) for CT.

    PubMed

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-01

    Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (Tomo-Scope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C-arm CT scanner

  12. Empirical beam hardening correction (EBHC) for CT.

    PubMed

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelrieß, Marc

    2010-10-01

    Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. The onlya priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C-arm CT scanner

  13. Empirical beam hardening correction (EBHC) for CT

    SciTech Connect

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-15

    Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern

  14. Reverse-Martensitic Hardening of Austenitic Stainless Steel upon Up-quenching

    NASA Astrophysics Data System (ADS)

    Sato, Kiminori; Guo, Defeng; Li, Xiaohong; Zhang, Xiangyi

    2016-08-01

    Reverse-martensitic transformation utilizing up-quenching was demonstrated for austenitic stainless steel. Up-quenching was done following the stress-induced phase modification to martensite and then enrichment of the body-centered-cubic ferrite. Transmission-electron-microscopy observation and Vickers hardness test revealed that the reverse-martensitic transformation yields quench hardening owing to an introduction of highly-concentrated dislocation. It is furthermore found that Cr precipitation on grain boundaries caused by isothermal aging is largely suppressed in the present approach.

  15. Final report on LDRD project 52722 : radiation hardened optoelectronic components for space-based applications.

    SciTech Connect

    Hargett, Terry W.; Serkland, Darwin Keith; Blansett, Ethan L.; Geib, Kent Martin; Sullivan, Charles Thomas; Hawkins, Samuel D.; Wrobel, Theodore Frank; Keeler, Gordon Arthur; Klem, John Frederick; Medrano, Melissa R.; Peake, Gregory Merwin; Karpen, Gary D.; Montano, Victoria A.

    2003-12-01

    This report describes the research accomplishments achieved under the LDRD Project 'Radiation Hardened Optoelectronic Components for Space-Based Applications.' The aim of this LDRD has been to investigate the radiation hardness of vertical-cavity surface-emitting lasers (VCSELs) and photodiodes by looking at both the effects of total dose and of single-event upsets on the electrical and optical characteristics of VCSELs and photodiodes. These investigations were intended to provide guidance for the eventual integration of radiation hardened VCSELs and photodiodes with rad-hard driver and receiver electronics from an external vendor for space applications. During this one-year project, we have fabricated GaAs-based VCSELs and photodiodes, investigated ionization-induced transient effects due to high-energy protons, and measured the degradation of performance from both high-energy protons and neutrons.

  16. Laser-induced transformation of supramolecular complexes: approach to controlled formation of hybrid multi-yolk-shell Au-Ag@a-C:H nanostructures

    PubMed Central

    Manshina, A. A.; Grachova, E. V.; Povolotskiy, A. V.; Povolotckaia, A. V.; Petrov, Y. V.; Koshevoy, I. O.; Makarova, A. A.; Vyalikh, D. V.; Tunik, S. P.

    2015-01-01

    In the present work an efficient approach of the controlled formation of hybrid Au–Ag–C nanostructures based on laser-induced transformation of organometallic supramolecular cluster compound is suggested. Herein the one-step process of the laser-induced synthesis of hybrid multi-yolk-shell Au-Ag@a-C:H nanoparticles which are bimetallic gold-silver subnanoclusters dispersed in nanospheres of amorphous hydrogenated a-C:H carbon is reported in details. It has been demonstrated that variation of the experimental parameters such as type of the organometallic precursor, solvent, deposition geometry and duration of laser irradiation allows directed control of nanoparticles’ dimension and morphology. The mechanism of Au-Ag@a-C:H nanoparticles formation is suggested: the photo-excitation of the precursor molecule through metal-to-ligand charge transfer followed by rupture of metallophilic bonds, transformation of the cluster core including red-ox intramolecular reaction and aggregation of heterometallic species that results in the hybrid metal/carbon nanoparticles with multi-yolk-shell architecture formation. It has been found that the nanoparticles obtained can be efficiently used for the Surface-Enhanced Raman Spectroscopy label-free detection of human serum albumin in low concentration solution. PMID:26153347

  17. Determination of the sequence of intersecting lines from laser toner and seal ink by Fourier transform infrared microspectroscopy and scanning electron microscope / energy dispersive X-ray mapping.

    PubMed

    Wang, Yuanfeng; Li, Bing

    2012-06-01

    The aim of this study was to verify that the combination of Fourier transform infrared microspectroscopy and scanning electron microscope / energy dispersive X-ray mapping could be applied to line intersection problems. The spectral data of red seal ink, laser toner and their intersections, such as peak location and peak intensity, were described. Relative peak height ratios of different chemical components in intersecting lines were used to distinguish the sequences. Energy dispersive X-ray mapping characteristics of intersecting areas were also detailed. The results show that both the laser toner and the seal ink appear on the surface of intersections, regardless of the sequence. The distribution of the two inks on the surface is influenced not only by the sequence of heterogeneous lines but also by diffusion. Fourier transform infrared microspectroscopy and scanning electron microscope/energy dispersive X-ray mapping are able to explore the chemical components and the corresponding elemental distribution in the intersections. The combination of these two techniques has provided a reliable method for sequencing intersecting lines of red seal ink and laser toner, and more importantly, this method may be a basis for sequencing superimposed lines from other writing instruments.

  18. A comparison of heavy ion induced single event upset susceptibility in unhardened 6T/SRAM and hardened ADE/SRAM

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Zeng, Chuanbin; Geng, Chao; Liu, Tianqi; Khan, Maaz; Yan, Weiwei; Hou, Mingdong; Ye, Bing; Sun, Youmei; Yin, Yanan; Luo, Jie; Ji, Qinggang; Zhao, Fazhan; Liu, Jie

    2017-09-01

    Single event upset (SEU) susceptibility of unhardened 6T/SRAM and hardened active delay element (ADE)/SRAM, fabricated with 0.35 μm silicon-on-insulator (SOI) CMOS technology, was investigated at heavy ion accelerator. The mechanisms were revealed by the laser irradiation and resistor-capacitor hardened techniques. Compared with conventional 6T/SRAM, the hardened ADE/SRAM exhibited higher tolerance to heavy ion irradiation, with an increase of about 80% in the LET threshold and a decrease of ∼64% in the limiting upset cross-section. Moreover, different probabilities between 0 → 1 and 1 → 0 transitions were observed, which were attributed to the specific architecture of ADE/SRAM memory cell. Consequently, the radiation-hardened technology can be an attractive alternative to the SEU tolerance of the device-level.

  19. Phase transformation and tribological properties of Ag-MoO3 contained NiCrAlY based composite coatings fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Wang, Lingqian; Zhou, Jiansong; Xin, Benbin; Yu, Youjun; Ren, Shufang; Li, Zhen

    2017-08-01

    Ag-MoO3 contained NiCrAlY based composite coating was successfully prepared on GH4169 stainless steel substrate by high energy ball milling and laser cladding. The microstructure and phase transformation were investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction spectrum (XRD). The tribological behavior and mechanism from room temperature to 800 °C were investigated. Results showed that MoO3 in the composite powders transformed to Mo2C reinforcement under the high energy density of laser, and a series of opposite transformation occurred during friction process. The coating showed the lowest friction coefficient and low wear rate at 600 °C and 800 °C due to the generation of Ag2MoO4 during tribo-chemical reactions and the formation of lubrication glaze on the worn surface. Ag made effective lubrication when the temperature rose up to 200 °C. The coating displayed a relatively high friction coefficient (about 0.51) at 400 °C, because though MoO3 (oxidation products of Mo2C) and Ag2MoO4 were detected on the worn surface, they could not realize effective lubrication at this temperature. Abrasive wear, adhesive wear and plastic deformation contributed to the increased friction and wear.

  20. Constitutive modelling of evolving flow anisotropy including distortional hardening

    SciTech Connect

    Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-05-04

    The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.

  1. Optimization of the transition path of the head hardening with using the genetic algorithms

    NASA Astrophysics Data System (ADS)

    Wróbel, Joanna; Kulawik, Adam

    2016-06-01

    An automated method of choice of the transition path of the head hardening in heat treatment process for the plane steel element is proposed in this communication. This method determines the points on the path of moving heat source using the genetic algorithms. The fitness function of the used algorithm is determined on the basis of effective stresses and yield point depending on the phase composition. The path of the hardening tool and also the area of the heat affected zone is determined on the basis of obtained points. A numerical model of thermal phenomena, phase transformations in the solid state and mechanical phenomena for the hardening process is implemented in order to verify the presented method. A finite element method (FEM) was used for solving the heat transfer equation and getting required temperature fields. The moving heat source is modeled with a Gaussian distribution and the water cooling is also included. The macroscopic model based on the analysis of the CCT and CHT diagrams of the medium-carbon steel is used to determine the phase transformations in the solid state. A finite element method is also used for solving the equilibrium equations giving us the stress field. The thermal and structural strains are taken into account in the constitutive relations.

  2. Surface hardening of a ductile-cast iron roll using high-energy electron beams

    NASA Astrophysics Data System (ADS)

    Suh, Dongwoo; Lee, Sunghak; Koo, Yangmo; Kwon, Soon-Ju

    1997-07-01

    The effects of high-energy electron beam irradiation on surface hardening and microstructural modification in a ductile cast iron (DCI) roll are investigated in this study. The DCI roll samples were irradiated by using an electron accelerator (1.4 MeV), and then their microstructures and hardnesses were examined. Upon irradiation, the unirradiated microstructure containing graphites and the tempered bainite matrix was changed to martensite, ledeburite, and retained austenite, together with the complete or partial dissolution of graphites. This microstructural modification improved greatly the surface hardness due to transformation of martensite whose amount and type were determined by heat input during irradiation. In order to investigate these complex microstructures, a simulation test including thermal cycles of abrupt heating and quenching was carried out. The simulation results indicated that the irradiated surface was heated up to about 1100 °C to 1200 °C and then quenched to room temperature, which was enough to obtain surface hardening through martensitic transformation. Thermal analysis of the irradiated surface layer was also carried out using a finite difference method to understand the surface hardening of the DCI roll and to compare with the simulation test results.

  3. Numerical simulation of induction hardening of a cylindrical part based on multi-physics coupling

    NASA Astrophysics Data System (ADS)

    Tong, Daming; Gu, Jianfeng; Totten, George Edward

    2017-04-01

    An induction hardening process was simulated based on an electromagnetic-thermal-transformation coupled numerical model. Calculation of the microstructure fraction was introduced using a coupled electromagnetic-thermal field during heating and the temperature field of the subsequent cooling process. The isoconversional method was used to formulate the austenitization process during heating, model parameters were determined by continuous heating dilatometric curves, and JMAK and K–M equations were adopted to calculate the fraction of new phases formed during cooling. The temperature and microstructure evolution in a cylindrical part of JIS-SCM440 steel were simulated during the induction hardening process and the simulated temperature and final microstructure distribution fit well with experimental data. Simulation results also showed that the free cooling prior to spray quenching could be optimized to decrease the temperature gradient in the surface layer to avoid decomposition of austenite into non-martensite microstructure.

  4. Technology Developments in Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Howell, Joe T.

    2008-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.

  5. Radiation-hardened nonvolatile MNOS RAM

    SciTech Connect

    Wrobel, T.F.; Dodson, W.H.; Hash, G.L.; Jones, R.V.; Nasby, R.D.; Olson, R.J.

    1983-01-01

    A radiation hardened nonvolatile MNOS RAM is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s.

  6. A radiation hardened nonvolatile MNOS RAM

    NASA Astrophysics Data System (ADS)

    Wrobel, T. F.; Dodson, W. H.; Hash, G. L.; Jones, R. V.; Nasby, R. D.; Olson, R. J.

    1983-12-01

    A radiation hardened nonvolatile MNOS RAM (SA2998) is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The device requires +10 V and +25 V for operation. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s.

  7. Expecting the Unexpected: Radiation Hardened Software

    NASA Technical Reports Server (NTRS)

    Penix, John; Mehlitz, Peter C.

    2005-01-01

    Radiation induced Single Event Effects (SEEs) are a serious problem for spacecraft flight software, potentially leading to a complete loss of mission. Conventional risk mitigation has been focused on hardware, leading to slow, expensive and outdated on-board computing devices, increased power consumption and launch mass. Our approach is to look at SEEs from a software perspective, and to explicitly design flight software so that it can detect and correct the majority of SEES. Radiation hardened flight software will reduce the significant residual residual risk for critical missions and flight phases, and enable more use of inexpensive and fast COTS hardware.

  8. Enabling Strain Hardening Simulations with Dislocation Dynamics

    SciTech Connect

    Arsenlis, A; Cai, W

    2006-12-20

    Numerical algorithms for discrete dislocation dynamics simulations are investigated for the purpose of enabling strain hardening simulations of single crystals on massively parallel computers. The algorithms investigated include the /(N) calculation of forces, the equations of motion, time integration, adaptive mesh refinement, the treatment of dislocation core reactions, and the dynamic distribution of work on parallel computers. A simulation integrating all of these algorithmic elements using the Parallel Dislocation Simulator (ParaDiS) code is performed to understand their behavior in concert, and evaluate the overall numerical performance of dislocation dynamics simulations and their ability to accumulate percents of plastic strain.

  9. Strain hardening of steel EP836

    SciTech Connect

    Lyadskaya, A.A.; Lappa, R.M.; Spuskanyuk, V.Z.

    1986-03-01

    The authors investigate the effect of different combinations of cold hydraulic pressing and heat treatment on the physical and mechanical properties of steel EP836 (03N17K10V10MT), containing 0.03% C, 16-17% Ni, 10-11.5% Co, 9.5-11.5% W, 1% Ti, 1% Mo, and 0.15% A1. Deformation of the unaged steel resulted in insignificant hardening without a decrease in plasticity; this agrees with the results of investigations of other steels of this class.

  10. Thermomechanical and Heat Hardening of Building Steels

    NASA Astrophysics Data System (ADS)

    Odesskii, P. D.; Rudchenko, A. V.; Shabalov, I. P.

    2005-03-01

    Hardening treatment of steels used in welded metal structures like steelwork of industrial and civil buildings, towers, poles, reservoirs, railway bridge girders, cranes, construction machines, truck bodies, etc. is considered. The structures mentioned are produced from rolled stock supplied by metallurgy in an annual amount of tens of million of tons. In the first turn these are plates, shapes, rolled bars and sections, and pipes with different wall thickness and cross section. A classification of steels for metallic structures with respect to chemical composition and microstructure is presented.

  11. Spur Gear Laser Surface Hardening MM/T Program

    DTIC Science & Technology

    1982-03-01

    case profile for D6AC before ....... 34 and after temper 8. Charpy V-Notch impact test specimen configuration. 35 9. Charpy V-Notch impact strength of...analysis of D6AC ......................... 32 4. Longitudinal Charpy V-Notch impact strength ....... 36 of D6AC at two different hardness levels from...TOLERANCE:,.001 UNLESS SPECIFIED OTHERWISE ALL DIMENSIONS IN INCHES. Figure 8. Charpy V-notch impact test specimen configuration. 35 A TABLE 4

  12. A study on Fourier transform infrared spectroscopy, thermal, mechanical, NLO and laser damage properties on unidirectional Glycinium Picrate Mono Glycine crystal

    NASA Astrophysics Data System (ADS)

    Thilagavathy, S. R.; Rajesh, P.; Ramasamy, P.; Ambujam, K.

    2013-11-01

    By directional solidification, single crystal of Glycinium Picrate Mono Glycine (GPMG) was successfully grown by Sankaranarayanan-Ramasamy (SR) method. An optically transparent crystal of GPMG has been grown along <0 1 1> plane by a mixed solvent of acetone and double distilled water. The evaporation rate was controlled and a single crystal of 12 mm diameter and 35 mm length was obtained. Single crystal X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), thermal, mechanical, SHG and laser damage studies were carried out. The results are discussed in detail.

  13. A study on Fourier transform infrared spectroscopy, thermal, mechanical, NLO and laser damage properties on unidirectional Glycinium Picrate Mono Glycine crystal.

    PubMed

    Thilagavathy, S R; Rajesh, P; Ramasamy, P; Ambujam, K

    2013-11-01

    By directional solidification, single crystal of Glycinium Picrate Mono Glycine (GPMG) was successfully grown by Sankaranarayanan-Ramasamy (SR) method. An optically transparent crystal of GPMG has been grown along 〈011〉 plane by a mixed solvent of acetone and double distilled water. The evaporation rate was controlled and a single crystal of 12mm diameter and 35mm length was obtained. Single crystal X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), thermal, mechanical, SHG and laser damage studies were carried out. The results are discussed in detail. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Transform-limited x-ray pulse generation from a high-brightness self-amplified spontaneous-emission free-electron laser.

    PubMed

    McNeil, B W J; Thompson, N R; Dunning, D J

    2013-03-29

    A method to achieve high-brightness self-amplified spontaneous emission (HB-SASE) in the free-electron laser (FEL) is described. The method uses repeated nonequal electron beam delays to delocalize the collective FEL interaction and break the radiation coherence length dependence on the FEL cooperation length. The method requires no external seeding or photon optics and so is applicable at any wavelength or repetition rate. It is demonstrated, using linear theory and numerical simulations, that the radiation coherence length can be increased by approximately 2 orders of magnitude over SASE with a corresponding increase in spectral brightness. Examples are shown of HB-SASE generating transform-limited FEL pulses in the soft x-ray and near transform-limited pulses in the hard x-ray. Such pulses may greatly benefit existing applications and may also open up new areas of scientific research.

  15. Cow-eye microstructure evolution of laser pulse processed for ductile iron

    NASA Astrophysics Data System (ADS)

    Ba, Fahai; Gan, Cuihua; Yu, Gang

    2003-04-01

    Pulsed laser beam with lattice distribution was used to modify surface processing for ductile iron. The microstructures around the graphite were observed using OM, and Nanoindentation and micro-hardness of that measured from surface to inner of sample. The result shows that the graphite ball has an important effect on cow-eye microstructure evolution either in light molten area or in phase change hardened are. It is not true that assuming the material is uniform during laser rapid heating and fast cooling for the graphite ball as a dependant composition phase. The microstructures of cow-eye is made up of fine remnant austenite in light molten area, and consisted of martensite and bainite in laser modified are. The cow-eye microstructure has a transformation from martensite and bainite to pearlite with the distance increasing from surfce. At last, the microstructure evolution of cow-eye has been discussed.

  16. Beam hardening and partial beam hardening of the bowtie filter: Effects on dosimetric applications in CT

    NASA Astrophysics Data System (ADS)

    Lopez-Rendon, X.; Zhang, G.; Bosmans, H.; Oyen, R.; Zanca, F.

    2014-03-01

    Purpose: To estimate the consequences on dosimetric applications when a CT bowtie filter is modeled by means of full beam hardening versus partial beam hardening. Method: A model of source and filtration for a CT scanner as developed by Turner et. al. [1] was implemented. Specific exposures were measured with the stationary CT X-ray tube in order to assess the equivalent thickness of Al of the bowtie filter as a function of the fan angle. Using these thicknesses, the primary beam attenuation factors were calculated from the energy dependent photon mass attenuation coefficients and used to include beam hardening in the spectrum. This was compared to a potentially less computationally intensive approach, which accounts only partially for beam hardening, by giving the photon spectrum a global (energy independent) fan angle specific weighting factor. Percentage differences between the two methods were quantified by calculating the dose in air after passing several water equivalent thicknesses representative for patients having different BMI. Specifically, the maximum water equivalent thickness of the lateral and anterior-posterior dimension and of the corresponding (half) effective diameter were assessed. Results: The largest percentage differences were found for the thickest part of the bowtie filter and they increased with patient size. For a normal size patient they ranged from 5.5% at half effective diameter to 16.1% for the lateral dimension; for the most obese patient they ranged from 7.7% to 19.3%, respectively. For a complete simulation of one rotation of the x-ray tube, the proposed method was 12% faster than the complete simulation of the bowtie filter. Conclusion: The need for simulating the beam hardening of the bow tie filter in Monte Carlo platforms for CT dosimetry will depend on the required accuracy.

  17. Optical diagnostics of the laser-induced phase transformations in thin germanium films on silicon, sapphire, and fused silica

    NASA Astrophysics Data System (ADS)

    Novikov, H. A.; Batalov, R. I.; Bayazitov, R. M.; Faizrakhmanov, I. A.; Ivlev, G. D.; Prokop'ev, S. L.

    2015-03-01

    The in-situ procedure is used to study the modification of thin (200-600 nm) germanium films induced by nanosecond pulses of a ruby laser. The films are produced using the ion-beam or magnetron sputtering on single-crystalline silicon (Si), sapphire (Al2O3), and fused silica (α-SiO2) substrates. The results on the dynamics of the laser-induced processes are obtained using the optical probing of the irradiated region at wavelengths of λ = 0.53 and 1.06 μm. The results of probing make it possible to determine the threshold laser energy densities that correspond to the Ge and Si melting and the generation of the Ge ablation plasma versus the amount of deposited Ge and thermophysical parameters of the substrate. The reflection oscillograms are used to obtain the dependences of the melt lifetime on the laser-pulse energy density.

  18. Fabrication of periodical surface structures by picosecond laser irradiation of carbon thin films: transformation of amorphous carbon in nanographite

    NASA Astrophysics Data System (ADS)

    Popescu, C.; Dorcioman, G.; Bita, B.; Besleaga, C.; Zgura, I.; Himcinschi, C.; Popescu, A. C.

    2016-12-01

    Thin films of carbon were synthesized by ns pulsed laser deposition in vacuum on silicon substrates, starting from graphite targets. Further on, the films were irradiated with a picosecond laser source emitting in visible at 532 nm. After tuning of laser parameters, we obtained a film surface covered by laser induced periodical surface structures (LIPSS). They were investigated by optical, scanning electron and atomic force microscopy. It was observed that changing the irradiation angle influences the LIPSS covered area. At high magnification it was revealed that the LIPSS pattern was quite complex, being composed of other small LIPSS islands, interconnected by bridges of nanoparticles. Raman spectra for the non-irradiated carbon films were typical for a-C type of diamond-like carbon, while the LIPSS spectra were characteristic to nano-graphite. The pristine carbon film was hydrophilic, while the LIPSS covered film surface was hydrophobic.

  19. Hardened Client Platforms for Secure Internet Banking

    NASA Astrophysics Data System (ADS)

    Ronchi, C.; Zakhidov, S.

    We review the security of e-banking platforms with particular attention to the exploitable attack vectors of three main attack categories: Man-in-the-Middle, Man-in-the-PC and Man-in-the-Browser. It will be shown that the most serious threats come from combination attacks capable of hacking any transaction without the need to control the authentication process. Using this approach, the security of any authentication system can be bypassed, including those using SecureID Tokens, OTP Tokens, Biometric Sensors and Smart Cards. We will describe and compare two recently proposed e-banking platforms, the ZTIC and the USPD, both of which are based on the use of dedicated client devices, but with diverging approaches with respect to the need of hardening the Web client application. It will be shown that the use of a Hardened Browser (or H-Browser) component is critical to force attackers to employ complex and expensive techniques and to reduce the strength and variety of social engineering attacks down to physiological fraud levels.

  20. CID25: radiation hardened color video camera

    NASA Astrophysics Data System (ADS)

    Baiko, D. A.; Bhaskaran, S. K.; Czebiniak, S. W.

    2006-02-01

    The charge injection device, CID25, is presented. The CID25 is a color video imager. The imager is compliant with the NTSC interlaced TV standard. It has 484 by 710 displayable pixels and is capable of producing 30 frames-per-second color video. The CID25 is equipped with the preamplifier-per-pixel technology combined with parallel row processing to achieve high conversion gain and low noise bandwidth. The on-chip correlated double sampling circuitry serves to reduce the low frequency noise components. The CID25 is operated by a camera system consisting of two parts, the head assembly and the camera control unit (CCU). The head assembly and the CCU can be separated by up to 150 meter long cable. The CID25 imager and the head portion of the camera are radiation hardened. They can produce color video with insignificant SNR degradation out to at least 2.85 Mrad of total dose of Co 60 γ-radiation. This represents the first in industry radiation hardened color video system, based on a semiconductor photo-detector that has an adequate sensitivity for room light operation.

  1. Analytical ultrasonics for characterization of metallurgical microstructures and transformations

    NASA Technical Reports Server (NTRS)

    Rosen, M.

    1986-01-01

    The application of contact (piezoelectric) and noncontact (laser generation and detection) ultrasonic techniques for dynamic investigation of precipitation hardening processes in aluminum alloys, as well as crystallization and phase transformation in rapidly solidified amorphous and microcrystalline alloys is discussed. From the variations of the sound velocity and attenuation the precipitation mechanism and kinetics were determined. In addition, a correlation was established between the observed changes in the velocity and attenuation and the mechanical properties of age-hardenable aluminum alloys. The behavior of the elastic moduli, determined ultrasonically, were found to be sensitive to relaxation, crystallization and phase decomposition phenomena in rapidly solidified metallic glasses. Analytical ultrasonics enables determination of the activation energies and growth parameters of the reactions. Therefrom theoretical models can be constructed to explain the changes in mechanical and physical properties upon heat treatment of glassy alloys. The composition dependence of the elastic moduli in amorphous Cu-Zr alloys was found to be related to the glass transition temperature, and consequently to the glass forming ability of these alloys. Dynamic ultrasonic analysis was found to be feasible for on-line, real-time, monitoring of metallurgical processes.

  2. Radiation-hardened 16K-bit MNOS EAROM

    SciTech Connect

    Knoll, M.G.; Dellin, T.A.; Jones, R.V.

    1983-01-01

    A radiation-hardened silicon-gate CMOS/NMNOS 16K-bit EAROM has been designed, fabricated, and evaluated. This memory has been designed to be used as a ROM replacement in radiation-hardened microprocessor-based systems.

  3. Radiation-Hardened Electronics for the Space Environment

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    RHESE covers a broad range of technology areas and products. - Radiation Hardened Electronics - High Performance Processing - Reconfigurable Computing - Radiation Environmental Effects Modeling - Low Temperature Radiation Hardened Electronics. RHESE has aligned with currently defined customer needs. RHESE is leveraging/advancing SOA space electronics, not duplicating. - Awareness of radiation-related activities through out government and industry allow advancement rather than duplication of capabilities.

  4. Hardening treatment of friction surfaces of ball journal bearings

    NASA Astrophysics Data System (ADS)

    Gorlenko, A. O.; Davidov, S. V.

    2016-04-01

    The article presents the technology of finishing plasma hardening by the application of the multi-layer nanocoating Si-O-C-N system to harden the friction surfaces of the ball journal bearings. The authors of the paper have studied the applied wear-resistant anti-friction coating tribological characteristics, which determine the increase in wear resistance of the ball journal bearings.

  5. Hardening fertilization and nutrient loading of conifer seedlings

    Treesearch

    R. Kasten Dumroese

    2003-01-01

    Continuing to fertilize bareroot and container seedlings during the hardening process (from cessation of height growth until lifting) can improve seedling viability. The process of fertilizing during hardening has many names, but in the last decade a new term, nutrient loading, has come into use. The process of nutrient loading seedlings leads to luxury consumption...

  6. Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

    Treesearch

    Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

  7. Radiation-Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael; Cressler, John D.

    2008-01-01

    This conference poster explores NASA's Radiation-Hardened Electronics for Space Environments project. This project aims to advance the state of the art in high performance, radiation-hardened electronics that enable the long-term, reliable operation of a spacecraft in extreme radiation and temperature of space and the lunar surface.

  8. The hardening phenomenon in irritant contact dermatitis: an interpretative update.

    PubMed

    Watkins, Shannon A; Maibach, Howard I

    2009-03-01

    Irritant contact dermatitis (ICD) is common and poses a significant problem in high-risk populations. In most cases, ICD resolves despite continued exposure in a process known as 'hardening', allowing individuals to continue with their work. Those who cannot clear ICD develop chronic ICD, which is a significant source of emotional, physical, and financial distress for affected individuals. While hardening is well known among labourers and clinicians, its mechanism remains to be elucidated. Much can be learned from the study of self-healing processes like the hardening phenomenon. This overview briefly documents the pathogenesis of ICD, focuses on the latest advances pertaining to the hardening phenomenon in ICD, and then highlights potential avenues of productive research. A better understanding of the 'hardening' process in the skin will hopefully lead to advances for the treatment of ICD.

  9. New analytical approach for neutron beam-hardening correction.

    PubMed

    Hachouf, N; Kharfi, F; Hachouf, M; Boucenna, A

    2016-01-01

    In neutron imaging, the beam-hardening effect has a significant effect on quantitative and qualitative image interpretation. This study aims to propose a linearization method for beam-hardening correction. The proposed method is based on a new analytical approach establishing the attenuation coefficient as a function of neutron energy. Spectrum energy shift due to beam hardening is studied on the basis of Monte Carlo N-Particle (MCNP) simulated data and the analytical data. Good agreement between MCNP and analytical values has been found. Indeed, the beam-hardening effect is well supported in the proposed method. A correction procedure is developed to correct the errors of beam-hardening effect in neutron transmission, and therefore for projection data correction. The effectiveness of this procedure is determined by its application in correcting reconstructed images.

  10. A review of the stages of work hardening

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.

    1993-07-01

    Stages of work hardening are reviewed with emphasis on links between each stage. Simple quantitative descriptions are given for each stage. Similarities between stage I, easy glide, and stage IV, large strain hardening, are pointed out both in terms of magnitude of the hardening rate and of the underlying mechanism of dislocation debris accumulation. Stage II is described as an athermal hardening stage that occurs when statistical variations in the dislocation ``forest`` lead to geometrical storage of dislocations. The steadily decreasing hardening rate observed in stage III is characterized by the increasing rate of loss of dislocation density due to dynamic recovery. Stage III appears to have an asymptote to a saturation stress which is determined by the characteristics of the dislocation tangles, or cell walls. The imperfect nature of the dynamic recovery process, however, leads to the accumulation of dislocation debris and this, by analogy with stage 1, causes the apparent saturation stress to rise, thus causing stage IV.

  11. Detection of Non-aromatic Organic Compounds in Meteorites using Imaging Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Scott, J. R.; Hinman, N. W.; Richardson, C. D.; Mahon, R. C.; McJunkin, T. R.

    2009-12-01

    Our most extensive understanding of extraterrestrial organic matter is based on what has been learned from meteorites that have been delivered naturally to Earth. Meteorites have been analyzed by a variety of techniques ranging from extensive sample preparation with extraction and subsequent chromatography to direct laser desorption mass spectrometry (LDMS). While extraction studies have reported a variety of organics (e.g., aliphatic and aromatic hydrocarbons, ketones, aldehydes, and amino acids), LDMS studies have only reported polycyclic aromatic hydrocarbons (PAHs). This is rather surprising considering that Yan et al. (Talanta 2007, 72, 634-641) reported that even a small amount of PAH enables the detection of organics that are not otherwise ionized during the desorption event from minerals. Therefore, we have begun re-investigating meteorites because, regardless of the source of the organic compounds, the presences of PAHs should allow other organic molecules to be observed using imaging laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (LD-FTICR-MS). Indeed, we have mapped meteorites (e.g., EETA 79001) and found many mass-to-charge peaks that are non-aromatic as determined by analysis of their mass defects. Mapping also revealed that the distribution of organics is heterogeneous, which necessitates the collection of a mass spectrum from a single laser shot so that minor peaks of interest are not lost in signal averaging. These studies have implications for analyzing future returned samples from Mars or elsewhere with minimal preparation or damage.

  12. Implementation of Time-Resolved Step-Scan Fourier Transform Infrared (FT-IR) Spectroscopy Using a kHz Repetition Rate Pump Laser

    PubMed Central

    MAGANA, DONNY; PARUL, DZMITRY; DYER, R. BRIAN; SHREVE, ANDREW P.

    2011-01-01

    Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)3Cl2 in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers. PMID:21513597

  13. Implementation of time-resolved step-scan fourier transform infrared (FT-IR) spectroscopy using a kHz repetition rate pump laser.

    PubMed

    Magana, Donny; Parul, Dzmitry; Dyer, R Brian; Shreve, Andrew P

    2011-05-01

    Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)(3)Cl(2) in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers.

  14. Surface nano-hardness and microstructure of a single crystal nickel base superalloy after laser shock peening

    NASA Astrophysics Data System (ADS)

    Lu, G. X.; Liu, J. D.; Qiao, H. C.; Zhou, Y. Z.; Jin, T.; Zhao, J. B.; Sun, X. F.; Hu, Z. Q.

    2017-06-01

    Nanoindention tests and SEM microstructure observations were conducted on a single crystal nickel base superalloy after laser shock peening (LSP). Distinct surface hardening behavior was found to occur under the selected LSP technology. A large discrepancy in γʹ areas happened on laser shocked regions and the large plastic deformation embodied in γʹ phases' deformation brought a significant hardening effect.

  15. Jerky loads on surface-hardened gears

    NASA Technical Reports Server (NTRS)

    Rettig, H.; Wirth, X.

    1978-01-01

    Damage occurs again and again in practice in the form of transmissions with surface hardened gears which break after a very long operating time (explained by seldom occurring jerky loads). Gear drives are frequently exposed to jerky stresses which are greater than their fatigue limit. These stresses are considered in gear calculations, first, by shock factors when the transmission is to be designed as high endurance with regard to overloads and, second, in the form of operating ratios when the design is to be time enduring with regard to overloads. The size of the operating ratio depends not only on torque characteristics, drive and processing machine, but also on the material and heat treatment.

  16. Precipitation hardening in 350 grade maraging steel

    SciTech Connect

    Viswanathan, U.K. . Radiometallurgy Div.); Dey, G.K. . Metallurgy Division); Asundi, M.K. )

    1993-11-01

    Evolution of microstructure in 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni[sub 3] (Ti, Mo) and Fe[sub 2]Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  17. Keystroke Dynamics-Based Credential Hardening Systems

    NASA Astrophysics Data System (ADS)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  18. Hardened engineering test building: Conceptual design report

    SciTech Connect

    Not Available

    1984-05-01

    Both the special nuclear materials nuclear explosive-like assemblies (SNM NELA) engineering tests and the intrinsic radiation (INRAD) activity is a programmatic necessity supported by Lawrence Livermore National Laboratory (LLNL) management. A new facility conforming to DOE standards for hardening and providing adequate security is an urgent requirement. The total project cost of $3,300,000 includes site improvements, building construction, and supporting utility services, as well as engineering services. The conceptual design in this report is based on functional requirements and the applicable design criteria. The design is the result of close interaction between LLNL personnel and the conceptual design team. Siting, building configuration, structural method, material selection, and mechanical and electrical systems were considered in the course of the design process. The concepts were evaluated from the viewpoints of cost effectiveness, energy conservation, functional requirements, operational patterns, and the creation of a desirable working environment.

  19. Occurrence of two-stage hardening in C-Mn steel wire rods containing pearlitic microstructure

    NASA Astrophysics Data System (ADS)

    Singh, Balbir; Sahoo, Gadadhar; Saxena, Atul

    2016-09-01

    The 8 and 10 mm diameter wire rods intended for use as concrete reinforcement were produced/ hot rolled from C-Mn steel chemistry containing various elements within the range of C:0.55-0.65, Mn:0.85-1.50, Si:0.05-0.09, S:0.04 max, P:0.04 max and N:0.006 max wt%. Depending upon the C and Mn contents the product attained pearlitic microstructure in the range of 85-93% with balance amount of polygonal ferrite transformed at prior austenite grain boundaries. The pearlitic microstructure in the wire rods helped in achieving yield strength, tensile strength, total elongation and reduction in area values within the range of 422-515 MPa, 790-950 MPa, 22-15% and 45-35%, respectively. On analyzing the tensile results it was revealed that the material experienced hardening in two stages separable by a knee strain value of about 0.05. The occurrence of two stage hardening thus in the steel with hardening coefficients of 0.26 and 0.09 could be demonstrated with the help of derived relationships existed between flow stress and the strain.

  20. Spectral Hardening and Geoeffectiveness of Solar Flares

    NASA Astrophysics Data System (ADS)

    Jain, R.; Kumar, S.; Dave, H.; Deshpande, M. R.

    We present the results of a few typical flares that observed by the first space borne solar astronomy experiment of India namely "Solar X-ray Spectrometer (SOXS)" mission, which has completed one year of its successful operation in geostationary orbit. The SOXS mission onboard GSAT-2 Indian spacecraft was launched successfully by GSLV-D2 rocket on 08 May 2003 to study the energy release and particle acceleration in solar flares. The SOXS is composed of two independent payloads viz. SOXS Low Energy Detector (SLD) payload, and SOXS High Energy Detector (SHD) payload. We restrict our presentation to SLD payload that designed, developed and fabricated by Physical Research Laboratory (PRL) in collaboration with Space Application Centre (SAC), Ahmedabad and ISRO Satellite Centre (ISAC), Bangalore of Indian Space Research Organization (ISRO). We briefly present the scientific objectives and instrumentation of the SLD payload. The SLD payload employs the state-of-art solid state detectors viz. Si PIN and CZT detectors, which reveal sub-keV spectral and 100ms temporal resolution characteristics that are necessary to study the spectral response of the flare components. The dynamic range of Si and CZT detectors is 4-25 and 4-56 keV respectively. The SLD has observed more than 140 flares of C and M class since its commissioning in the orbit. We present the X-ray emission characteristics of a few typical flares in view of their spectral hardening and geo-effectiveness. We extend our study of these flares to optical and radio waveband observations in order to improve the relationship of X-ray spectral hardening and geo-effectiveness. The flares with harder spectra and associated with small or large CME, and radio emission at frequencies above 10 GHz are found geo-effective.

  1. Residual stress relaxation and fatigue behavior of an induction hardened microalloyed steel

    NASA Astrophysics Data System (ADS)

    Rivas, Ana Luisa Rivas De

    The thermal and mechanical relaxation of compressive residual stresses during tempering and cyclic loading of an induction hardened vanadium microalloyed steel has been evaluated. A microstructural analysis was also carried out on the microalloyed steel to correlate the residual stress relaxation behavior with microstructural characteristics of the material. Vanadium carbide particle size and distribution were analyzed as well as how these characteristics are affected by the application of normalizing and induction hardening heat treatments. To determine the effect of vanadium carbide particles on the residual stress relaxation response of the microalloyed steel a parallel study was conducted on a 1530 steel which is similar in chemistry to the microalloyed steel, but without the vanadium. The thermal relaxation of compressive residual stresses due to tempering for 2 hours after induction hardening was evaluated for a range of tempering temperatures from 177sp° C\\ (350sp° F) to 579sp° C\\ (1075sp° F). Mechanical residual stress relaxation was evaluated by subjecting specimens to cyclic loading conditions. For this part of the work a special type of specimen was designed. The specimen had an overall C-shape with a T-shaped cross section. This specimen geometry generates higher levels of stresses in the induction hardened outer layer than in the soft core material along the inner layer of the C-shaped geometry. The compressive residual stresses were generated by the phase transformation that occurs during hardening heat treatments and also by mechanical means. Additional compressive stresses were put into the outer surface region of the hardened C-shaped specimens by pre-straining them plastically through the application of compressive loads. Fine vanadium carbide precipitates were observed in the microalloyed steel in the as-forged condition. The application of a normalizing and induction hardening heat treatments caused coarsening of the vanadium carbide

  2. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2016-11-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  3. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2017-02-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  4. An extended crystal plasticity model for latent hardening in polycrystals

    NASA Astrophysics Data System (ADS)

    Bargmann, Swantje; Svendsen, Bob; Ekh, Magnus

    2011-12-01

    In this contribution, a computational approach to modeling size-dependent self- and latent hardening in polycrystals is presented. Latent hardening is the hardening of inactive slip systems due to active slip systems. We focus attention on the investigation of glide system interaction, latent hardening and excess dislocation development. In particular, latent hardening results in a transition to patchy slip as a first indication and expression of the development of dislocation microstructures. To this end, following Nye (Acta Metall 1:153-162, 1953), Kondo (in Proceedings of the second Japan national congress for applied mechanics. Science Council of Japan, Tokyo, pp. 41-47, 1953), and many others, local deformation incompatibility in the material is adopted as a measure of the density of geometrically necessary dislocations. Their development results in additional energy being stored in the material, leading to additional kinematic-like hardening effects. A large-deformation model for latent hardening is introduced. This approach is based on direct exploitation of the dissipation principle to derive all field relations and (sufficient) forms of the constitutive relations as based on the free energy density and dissipation potential. The numerical implementation is done via a dual-mixed finite element method. A numerical example for polycrystals is presented.

  5. Porosity and mechanically optimized PLGA based in situ hardening systems.

    PubMed

    Schloegl, W; Marschall, V; Witting, M Y; Volkmer, E; Drosse, I; Leicht, U; Schieker, M; Wiggenhorn, M; Schaubhut, F; Zahler, S; Friess, W

    2012-11-01

    Goal of the present study was to develop and to characterize in situ-hardening, porous PLGA-based systems for their future application as bone grafting materials. Therefore, we investigated the precipitation behavior of formulations containing PLGA and a water-miscible solvent, DMSO, PEG 400, and NMP. To increase porosity, a pore forming agent (NaCMC) was added and to enhance mechanical properties of the system, an inorganic filler (α-TCP) was incorporated. The behavior upon contact with water and the influence of the prior addition of aqueous media on the morphology of the corresponding hardened implants were investigated. We proved cell-compatibility by live/dead assays for the hardened porous polymer/ceramic-composite scaffolds. The IsHS formulations can therefore be used to manufacture hardened scaffolds ex vivo by using molds with the desired shape and size. Cells were further successfully incorporated into the IsHS by precultivating the cells on the α-TCP-powder prior to their admixing to the formulation. However, cell viability could not be maintained due to toxicity of the tested solvents. But, the results demonstrate that in vivo cells should well penetrate, adhere, and proliferate in the hardened scaffolds. Consequently, we consider the in situ hardening system being an excellent candidate as a filling material for non-weight-bearing orthopedic indications, as the resulting properties of the hardened implant fulfill indication-specific needs like mechanical stability, elasticity, and porosity.

  6. Time-Resolved Diffraction Profiles and Atomic Dynamics in Short-Pulse Laser-Induced Structural Transformations: Molecular Dynamics Study

    DTIC Science & Technology

    2006-05-16

    Touloukian , Thermophysical Properties of Matter, Vol. 4: Specific Heat: Metallic Elements and Alloys IFI/Plenum, New York, 1970. 31Y. S. Touloukian ...Thermophysical Properties of Matter, Vol. 12: Thermal Expansion: Metallic Elements and Alloys IFI/Plenum, New York, 1975. 32S. I. Anisimov and B...nm aluminum films irradiated with 120 fs laser pulses.11 The diffraction intensity over a range of scattering vectors was measured in this work

  7. Transformation of the diffraction patterns of screens into the diffraction patterns of additional screens in the course of scattering by a gas perturbation or by a particle in a laser beam caustic

    SciTech Connect

    Meshalkin, E A; Podmar'kov, Yu P; Frolov, M P

    1999-12-31

    The spatial distribution of the scattered-radiation energy during focusing, in atmospheric air, of the fourth-harmonic beam of a pulsed neodymium laser ({lambda} = 264 nm) with an annular cross section was studied experimentally. Shortening of the UV scattered-radiation by a factor of 2 - 5, compared with the duration of the laser pulse, was observed. An interference structure of the scattered radiation, varying with increase in the laser-pulse energy, was recorded. The diffraction rings and bands originating from screens were transformed into analogous diffraction rings and bands from additional screens. This can be accounted for by the scattering of the laser beam on a gas perturbation or on a particle in the caustic. Experiments were performed on the scattering of radiation with {lambda} = 0.63 {mu}m on formations with an abrupt boundary, which confirmed the above hypothesis. (laser applications and other topics in quantum electronics)

  8. Coupling thin-layer chromatography with vibrational cooling matrix-assisted laser desorption/ionization Fourier transform mass spectrometry for the analysis of ganglioside mixtures.

    PubMed

    Ivleva, Vera B; Elkin, Yuri N; Budnik, Bogdan A; Moyer, Susanne C; O'Connor, Peter B; Costello, Catherine E

    2004-11-01

    Thin-layer chromatography (TLC), which is widely used for separation of glycolipids, oligosaccharides, lipids, and compounds of environmental and pharmaceutical interest, can be readily coupled to matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometers, but this arrangement usually compromises mass spectral resolution due to the irregularity of the TLC surface. However, TLC can be coupled to an external ion source MALDI-Fourier transform (FT) MS instrument without compromising mass accuracy and resolution of the spectra. Furthermore, when the FTMS has a vibrationally cooled MALDI ion source, fragile glycolipids can be desorbed from TLC plates without fragmentation, even to the point that desorption of intact molecules from "hot"matrixes such as alpha-cyano-4-hydroxycinnamic acid is possible. In this work, whole brain gangliosides are separated using TLC; the TLC plates are attached directly to the MALDI target, where the gangliosides are desorbed, ionized, and detected in the FTMS with >70 000 resolving power.

  9. Acetylene weak bands at 2.5 μm from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy

    PubMed Central

    Girard, Véronique; Farrenq, Robert; Sorokin, Evgeni; Sorokina, Irina T.; Guelachvili, Guy; Picqué, Nathalie

    2010-01-01

    The spectral dynamics of a mid-infrared multimode Cr2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C2H2 in natural isotopic abundance are recorded around 4000 cm−1 with kilometric absorption path lengths and sensitivities better than 3 10−8 cm−1. Two cold bands are newly identified and assigned to the ν1+ν41 and ν3+ν51 transitions of 12C13CH2. The ν1+ν51 band of 12C2HD and fourteen 12C2H2 bands are observed, among which for the first time ν2+2ν42+ν5−1. PMID:21151826

  10. Study of cluster anions generated by laser ablation of titanium oxides: a high resolution approach based on Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Barthen, Nicolas; Millon, Eric; Aubriet, Frédéric

    2011-03-01

    Laser ablation of titanium oxides at 355 nm and ion-molecule reactions between [(TiO(2))(x)](-•) cluster anions and H(2)O or O(2) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO(2))(x)(H(2)O)(y)OH](-) and [(TiO(2))(x)(H(2)O)(y)O(2)](-•) oxy-hydroxide species with x=1 to 25 and y=1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO(2))(x)](-•) cluster anions as was previously reported, and (2) ion-molecule reactions during ion storage. Reactions of some [(TiO(2))(x)](-•) cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O(2) loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data.

  11. Characterization of the Ground State of Br 2 by Laser-Induced Fluorescence Fourier Transform Spectroscopy of the B3Π 0 +u- X1Σ +g System

    NASA Astrophysics Data System (ADS)

    Focsa, C.; Li, H.; Bernath, P. F.

    2000-03-01

    The laser-induced fluorescence (LIF) spectrum of the B3Π0+u-X1Σ+g system of Br2 was recorded by Fourier transform spectroscopy (FTS). The LIF spectra were obtained by using continuous-wave dye laser excitation in the spectral region 16 800-18 000 cm-1. About 1800 rotationally resolved lines were recorded in 96 fluorescence progressions, originating from the 10 ≤ v‧ ≤ 22 vibrational levels of the B3Π0+u state and involving the 2 ≤ v" ≤ 29 levels of the X1Σ+g ground state of the three isotopomers of bromine, 79Br2, 81Br2, and 79,81Br2. These data, together with 79Br2 data from a previous FTS absorption study [S. Gerstenkorn, P. Luc, A. Raynal, and J. Sinzelle, J. Phys. (France) 48, 1685-1696 (1987)], were analyzed to yield improved Dunham constants for the ground state. A Rydberg-Klein-Rees (RKR) potential energy curve was computed for the X1Σ+g state (v" = 0-29). The equilibrium bond length was found to be Re(X1Σ+g) = 2.2810213(20) Å.

  12. Phototherapy with low-level laser influences the proliferation of endothelial cells and vascular endothelial growth factor and transforming growth factor-beta secretion.

    PubMed

    Szymanska, J; Goralczyk, K; Klawe, J J; Lukowicz, M; Michalska, M; Goralczyk, B; Zalewski, P; Newton, J L; Gryko, L; Zajac, A; Rosc, D

    2013-06-01

    The healing process and the angiogenesis associated with it, is a very important but currently poorly understood area. Low level laser therapy (LLLT) has been reported to modulate the process of tissue repair by stimulation of cellular reaction such as migration, proliferation, apoptosis and cellular differentiation. The aim of this work was to evaluate the influence of laser radiation in the range of visible and infrared light on the proliferation of vascular endothelial cells in vitro and the secretion of angiogenic factors: vascular endothelial growth factor (VEGF)-A and transforming growth factor (TGF)-β. Vascular human endothelial cells (Ecs) were exposed to radiation with laser beam of the wavelengths: 635 nm (1.875 mW/cm²) and 830 nm (3.75 mW/cm²). Depending on the radiation energy density, the experiment was conducted in four groups : I) the control group (no radiation, 0 J/cm²); II) 635 nm - the energy density was 2 J/cm²; III) 635 nm - 4 J/cm²; IV635 nm - 8 J/cm², II) 830 nm - the energy density was 2 J/cm²; III) 830 nm - 4 J/cm²; IV) 830 nm - 8 J/cm². The proliferation and concentration of VEGF-A and TGF-β were examined. LLLT with wavelength 635 nm increases endothelial cell proliferation. Significant increase in endothelial cell proliferation and corresponding decrease in VEGF concentration may suggest the role for VEGF in this process. The wavelength of 830 nm was associated with a decrease in TGF-β secretion.

  13. Ecological Consequences of Shoreline Hardening: A Meta-Analysis

    PubMed Central

    Gittman, Rachel K.; Scyphers, Steven B.; Smith, Carter S.; Neylan, Isabelle P.; Grabowski, Jonathan H.

    2016-01-01

    Abstract Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems. PMID:28533564

  14. Work hardening and work conditioning interventions: do they affect disability?

    PubMed

    Lechner, D E

    1994-05-01

    The purpose of this article is to review the research on the effectiveness of work hardening and work conditioning programs. Twelve studies of work hardening and work conditioning programs in the United States and abroad were reviewed. One study produced convincing evidence in a randomized study that a work conditioning program was useful in producing a higher percentage of return to work and an earlier return to work in a group of patients off work for at least 2 months. Another study demonstrated that a work hardening program increased the rate of return to work by 52% in patients off work for greater than 4 months. Most of the other studies reviewed suggested positive results, but more carefully documented, randomized, and controlled studies are needed to support the efficacy of these programs and to determine the optimum and most cost-effective work hardening and work conditioning interventions.

  15. Possible correlation between work-hardening and fatigue-failure

    NASA Technical Reports Server (NTRS)

    Kettunen, P. O.; Kocks, U. F.

    1969-01-01

    Conceptual theory proposes that cyclic hardening due to non-uniform strain and stress amplitudes during testing, especially during the initial application of stress to a specimen, may correlate positively with the ultimate strength of the specimen under test.

  16. Microscopic Origin of Strain Hardening in Methane Hydrate.

    PubMed

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-03-24

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon.

  17. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  18. Ultimate bending capacity of strain hardening steel pipes

    NASA Astrophysics Data System (ADS)

    Chen, Yan-fei; Zhang, Juan; Zhang, Hong; Li, Xin; Zhou, Jing; Cao, Jing

    2016-04-01

    Based on Hencky's total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.

  19. Ecological Consequences of Shoreline Hardening: A Meta-Analysis.

    PubMed

    Gittman, Rachel K; Scyphers, Steven B; Smith, Carter S; Neylan, Isabelle P; Grabowski, Jonathan H

    2016-09-01

    Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.

  20. Microscopic Origin of Strain Hardening in Methane Hydrate

    PubMed Central

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  1. Radiation-hardened microwave communications system

    SciTech Connect

    Smith, S.F.; Crutcher, R.I.; Vandermolen, R.I. )

    1990-01-01

    The consolidated fuel reprocessing program (CFRP) at the Oak Ridge National Laboratory (ORNL) has been developing signal transmission techniques and equipment to improve the efficiency of remote handling operations for nuclear applications. These efforts have been largely directed toward the goals of (a) remotely controlling bilateral force-reflecting servomanipulators for dexterous manipulation-based operations in remote maintenance tasks and (b) providing television viewing of the work site. In September 1987, developmental microwave transceiving hardware operating with dish antennas was demonstrated in the advanced integrated maintenance system (AIMS) facility at ORNL, successfully implementing both high-quality one-way television transmissions and simultaneous bidirectional digital control data transmissions with very low error rates. Initial test results based on digital transmission at a 1.0-Mbaud data rate indicated that the error rates of the microwave system were comparable to those of a hardwired system. During these test intervals, complex manipulator operations were performed, and the AIMS transporter was moved repeatedly without adverse effects on data integrity. Results of these tests have been factored into subsequent phases of the development program, with an ultimate goal of designing a fully radiation-hardened microwave signal transmission system for use in nuclear facilities.

  2. Weldable, age hardenable, austenitic stainless steel

    DOEpatents

    Brooks, J.A.; Krenzer, R.W.

    1975-07-22

    An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

  3. Cylindrical shell buckling through strain hardening

    SciTech Connect

    Bandyopadhyay, K.; Xu, J.; Shteyngart, S.; Gupta, D.

    1995-04-01

    Recently, the authors published results of plastic buckling analysis of cylindrical shells. Ideal elastic-plastic material behavior was used for the analysis. Subsequently, the buckling analysis program was continued with the realistic stress-strain relationship of a stainless steel alloy which does not exhibit a clear yield point. The plastic buckling analysis was carried out through the initial stages of strain hardening for various internal pressure values. The computer program BOSOR5 was used for this purpose. Results were compared with those obtained from the idealized elastic-plastic relationship using the offset stress level at 0.2% strain as the yield stress. For moderate hoop stress values, the realistic stress-grain case shows a slight reduction of the buckling strength. But, a substantial gain in the buckling strength is observed as the hoop stress approaches the yield strength. Most importantly, the shell retains a residual strength to carry a small amount of axial compressive load even when the hoop stress has exceeded the offset yield strength.

  4. Cyber situational awareness and differential hardening

    NASA Astrophysics Data System (ADS)

    Dwivedi, Anurag; Tebben, Dan

    2012-06-01

    The advent of cyber threats has created a need for a new network planning, design, architecture, operations, control, situational awareness, management, and maintenance paradigms. Primary considerations include the ability to assess cyber attack resiliency of the network, and rapidly detect, isolate, and operate during deliberate simultaneous attacks against the network nodes and links. Legacy network planning relied on automatic protection of a network in the event of a single fault or a very few simultaneous faults in mesh networks, but in the future it must be augmented to include improved network resiliency and vulnerability awareness to cyber attacks. Ability to design a resilient network requires the development of methods to define, and quantify the network resiliency to attacks, and to be able to develop new optimization strategies for maintaining operations in the midst of these newly emerging cyber threats. Ways to quantify resiliency, and its use in visualizing cyber vulnerability awareness and in identifying node or link criticality, are presented in the current work, as well as a methodology of differential network hardening based on the criticality profile of cyber network components.

  5. Design concepts for hardened communications structures

    NASA Astrophysics Data System (ADS)

    Flathau, William J.; Smith, William G.

    1990-03-01

    An important component of any hardened command and control structure is the antenna system that provides communication with the outside world. Two types of antennae were considered; i.e., the whip type and the directional. The whip type is for short range communication and the directional is for use primarily with satellites. In the super high frequency range, the use of directional antennae having parabolic dishes greater than 8 feet in diameter are common. In the very extra high frequency range, dishes that are 2 to 3 feet in diameter are used. The whip type antenna should extend up to, say, 60 feet in the air. Based on this background, a family of structures was designed that can protect whip and directional antennae from the blast and shock effects from a 1-MT device for ground surface overpressure ranging from 15,000 to 500 psi. As the antennae, transmitters, receivers, power supplies, and lifting mechanisms will be located within such structures, appropriate shock spectra plots were developed to determine if the fragility level of pertinent equipment will be exceeded and for use in designing shock isolation systems. Button up periods of 1 and 4 weeks were considered.

  6. Open Source Radiation Hardened by Design Technology

    NASA Technical Reports Server (NTRS)

    Shuler, Robert

    2016-01-01

    The proposed technology allows use of the latest microcircuit technology with lowest power and fastest speed, with minimal delay and engineering costs, through new Radiation Hardened by Design (RHBD) techniques that do not require extensive process characterization, technique evaluation and re-design at each Moore's Law generation. The separation of critical node groups is explicitly parameterized so it can be increased as microcircuit technologies shrink. The technology will be open access to radiation tolerant circuit vendors. INNOVATION: This technology would enhance computation intensive applications such as autonomy, robotics, advanced sensor and tracking processes, as well as low power applications such as wireless sensor networks. OUTCOME / RESULTS: 1) Simulation analysis indicates feasibility. 2)Compact voting latch 65 nanometer test chip designed and submitted for fabrication -7/2016. INFUSION FOR SPACE / EARTH: This technology may be used in any digital integrated circuit in which a high level of resistance to Single Event Upsets is desired, and has the greatest benefit outside low earth orbit where cosmic rays are numerous.

  7. Morphological and chemical transformations of single silica-coated CdSe/CdS nanorods upon fs-laser excitation.

    PubMed

    Albrecht, Wiebke; Goris, Bart; Bals, Sara; Hutter, Eline M; Vanmaekelbergh, Daniel; van Huis, Marijn A; van Blaaderen, Alfons

    2017-03-29

    Radiation-induced modifications of nanostructures are of fundamental interest and constitute a viable out-of-equilibrium approach to the development of novel nanomaterials. Herein, we investigated the structural transformation of silica-coated CdSe/CdS nanorods (NRs) under femtosecond (fs) illumination. By comparing the same nanorods before and after illumination with different fluences we found that the silica-shell did not only enhance the stability of the NRs but that the confinement of the NRs also led to novel morphological and chemical transformations. Whereas uncoated CdSe/CdS nanorods were found to sublimate under such excitations the silica-coated nanorods broke into fragments which deformed towards a more spherical shape. Furthermore, CdS decomposed which led to the formation of metallic Cd, confirmed by high-resolution electron microscopy and energy dispersive X-ray spectrometry (EDX), whereby an epitaxial interface with the remaining CdS lattice was formed. Under electron beam exposure similar transformations were found to take place which we followed in situ.

  8. Pt metallization of laser transformed medical grade silicone rubber: Last step toward a miniaturized nerve electrode fabrication process

    NASA Astrophysics Data System (ADS)

    Dupas-Bruzek, C.; Dréan, P.; Derozier, D.

    2009-10-01

    Chronic nerve recording and stimulation became possible through the use of implanted electrodes cuffs. In particular, self-sizing spiral electrode cuffs limit mechanical damage to the tissue: these have been shown to be suitable for long term implantation in animal and in man. However, up to now, such electrode cuffs were handmade and were hardly reproducible. They possessed a small number of electrodes (dot contacts), each being linked to its own wire. In order to improve the selectivity of nerve recording and/or stimulation (functional electrical stimulation), the numbers of electrodes and tracks have to be increased within the same electrode cuff surface. To fulfill this requirement, we have developed a fabrication process that uses an UV laser to induce surface modification, which activates the silicone rubber and is used with a mask to give high definition tracks and electrodes. After this primary step, silicone rubber is immersed in a Pt autocatalytic bath leading to a selective Pt metallization of the laser activated tracks and electrodes. We report our process as well as the results on the Pt metallization, including its morphology, how the DC resistance of Pt tracks depends on the laser used and the irradiation conditions, and also the electrical resistance of Pt tracks submitted to Scotch tape tests or to imposed strains. We show that (i) the type of laser and the irradiation conditions have a strong influence on the nucleation and growth rate of platinum and thus on the DC resistance of the tracks, (ii) the tracks of width 400 μm and thickness 10 μm have a sheet resistivity of 0.2 Ω/sq, (iii) DC resistance does not change much during a 6 month soak in saline, (iv) strains above 2% breaks the track continuity, and (v) when strains below 53% are relaxed, the DC resistance returns to a low value. This recovery from large tensile strains means that nerve cuffs with such metallization could be handled by the surgeon without great care before and during

  9. Phase Transformation and Residual Stress in a Laser Beam Spot-Welded TiAl-Based Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Staron, Peter; Riekehr, Stefan; Stark, Andreas; Schell, Norbert; Huber, Norbert; Schreyer, Andreas; Müller, Martin; Kashaev, Nikolai

    2016-12-01

    The microstructure, chemical composition, residual stress, and lattice parameter evolution of the welding zone (WZ) and heat-affected zone (HAZ) of a laser-beam-welded TiAl-based alloy were investigated. It was found that both α 2 and γ phases remain highly restrained in the WZ edge, and the stresses are relieved in the HAZ. A grain refinement mechanism is proposed, which works by heating the material to the β or α + β phase field for a short time. The lamellar colonies are refined by the Nb-enriched segregations.

  10. Feasibility of Underwater Friction Stir Welding of Hardenable Alloy Steel

    DTIC Science & Technology

    2010-12-01

    bead-on-plate FSW traverses, approximately 64 inches (1.6 m) in total length, on 0.25 inch (6.4 mm) thick plates of a hardenable alloy steel . The...base plate. Based on preliminary findings, FSW of hardenable alloy steel is a feasible process and should be further researched and refined. 15...v ABSTRACT The objective of this thesis is to determine whether friction stir welding ( FSW ) is a feasible welding process for steels in an

  11. Approaches to radiation-hardened I2L technology

    NASA Astrophysics Data System (ADS)

    Bahraman, A.; Chang, S. Y.

    1980-12-01

    Design techniques are described for achieving radiation-hardened Schottky-base I2L (SBI2L) circuits. Radiation performance data are presented for this new technology and compared with results for conventional or Schottky-base I2L. This concept is extended to VLSI designs. Finally, as an application of SBI2L, a new design is presented for a radiation-hardened static random-access-memory (RAM) cell.

  12. Producing gapped-ferrite transformer cores

    NASA Technical Reports Server (NTRS)

    Mclyman, W. T.

    1980-01-01

    Improved manufacturing techniques make reproducible gaps and minimize cracking. Molded, unfired transformer cores are cut with thin saw and then fired. Hardened semicircular core sections are bonded together, placed in aluminum core box, and fluidized-coated. After winding is run over box, core is potted. Economical method significantly reduces number of rejects.

  13. Producing gapped-ferrite transformer cores

    NASA Technical Reports Server (NTRS)

    Mclyman, W. T.

    1980-01-01

    Improved manufacturing techniques make reproducible gaps and minimize cracking. Molded, unfired transformer cores are cut with thin saw and then fired. Hardened semicircular core sections are bonded together, placed in aluminum core box, and fluidized-coated. After winding is run over box, core is potted. Economical method significantly reduces number of rejects.

  14. Analytical considerations of beam hardening in medical accelerator photon spectra.

    PubMed

    Kleinschmidt, C

    1999-09-01

    Beam hardening is a well-known phenomenon for therapeutic accelerator beams passing through matter in narrow beam geometry. This study assesses quantitatively the magnitude of beam hardening of therapeutic beams in water. A formal concept of beam hardening is proposed which is based on the decrease of the mean attenuation coefficient with depth. On the basis of this concept calculations of beam hardening effects are easily performed by means of a commercial spreadsheet program. Published accelerator spectra and the tabulated values of attenuation coefficients serve as input for these calculations. It is shown that the mean attenuation coefficient starts at depth zero with an almost linear decrease and then slowly levels off to a limit value. A similar behavior is found for the beam hardening coefficient. A physically reasonable, semianalytical model is given which fits the data better than previously published functions. The energy dependence of the initial attenuation coefficient is evaluated and shown. It fits well to published experimental data. The initial beam hardening coefficient, however, shows no energy dependence. Its mean value (eta0) approximately 0.006 cm(-1)) is also in close agreement to the measured data.

  15. A study of latent hardening behavior in aluminum single crystals

    SciTech Connect

    Wang Mingzhang; Lin Shi; Li Chenghua; Xiao Jimei; Wang Zhongguang

    1996-11-15

    In order to obtain a better understanding or a complete description of plastic properties of polycrystals, especially in polycrystal modelling viewpoint, investigations on latent hardening behavior of single crystals have been performed in a great number. Recently, however, Wu et al. have pointed out that the definition of the yield stress of latent system using the conventional back extrapolation is ambiguous in terms of determining the latent hardening moduli because the initial rapid work-hardening of the transient zone is neglected. They proposed a more precise measure of the yield stress of latent system based on the decrease of the tangent modulus from the linear elastic modulus, and showed that the latent hardening, which would not plus the initial work-hardening of the transient zone, is actually lower than that obtained from the backward extrapolation. Thus, in their opinion, it is considered that the hardening behavior of latent system (such as the directionality, the effects of relative orientation and prestrain) need be newly or further studied in detail. Single crystals of aluminum have been grown with high purity to investigate this behavior.

  16. [Hardening and softening phenomena in beans: technological alternatives].

    PubMed

    Palma-Tirado, M L; Reyes-Moreno, C; Cárabez-Trejo, A; Montes-Rivera, R; Paredes-López, O

    1992-09-01

    The effect of accelerated hardening and soaking solutions on cooking time and microstructure of common bean (Phaseolus vulgaris) was studied. Two varieties (Canario and Mayocoba) were grown in the same location. Three hardening procedures were used: 1) End A. Soaking in acetate buffer, pH = 4.0 at 37 degrees C for 5 hs, 2) End B. Storage at 37 degrees C, 100% RH for 28 days and, 3) End C storage at 13-33 degrees C, 76% RH for 120 days. The salt solutions used for soaking were: Soln 1 (1% NaCl+0.75% NaHCO3) and Soln 2 (0.75% NaHCO3). Cooking times were determined using a Mattson bean cooker. In both varieties, the three hardening procedures decreased (38-50%) cotyledons water holding capacity and increased significantly (2-4 times) cooking times. During soaking in salt solutions hardened beans reached maximum water absorption in four hours. Soaking in salt solutions decreased drastically (2.6-10.6 times) cooking times. Fresh, hardened and softened seeds were examined by light microscopy, observing ultrastructural differences among them. The methods used in this research might well represent the central components of an industrial technological procedure for the utilization of hardened beans.

  17. Evaluation of combined matrix-assisted laser desorption/ionization time-of-flight and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry experiments for peptide mass fingerprinting analysis.

    PubMed

    da Silva, David; Wasselin, Thierry; Carré, Vincent; Chaimbault, Patrick; Bezdetnaya, Lina; Maunit, Benoît; Muller, Jean-François

    2011-07-15

    Peptide Mass Fingerprinting (PMF) is still of significant interest in proteomics because it allows a large number of complex samples to be rapidly screened and characterized. The main part of post-translational modifications is generally preserved. In some specific cases, PMF suffers from ambiguous or unsuccessful identification. In order to improve its reliability, a combined approach using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICRMS) was evaluated. The study was carried out on bovine serum albumin (BSA) digest. The influence of several important parameters (the matrix, the sample preparation method, the amount of the analyte) on the MOWSE score and the protein sequence coverage were evaluated to allow the identification of specific effects. A careful investigation of the sequence coverage obtained by each kind of experiment ensured the detection of specific peptides for each experimental condition. Results highlighted that DHB-FTICRMS and DHB- or CHCA-TOFMS are the most suited combinations of experimental conditions to achieve PMF analysis. The association (convolution) of the data obtained by each of these techniques ensured a significant increase in the MOWSE score and the protein sequence coverage.

  18. Zinc coated sheet steel for press hardening

    NASA Astrophysics Data System (ADS)

    Ghanbari, Zahra N.

    Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

  19. Assessment of the microstructure and torsional fatigue performance of an induction hardened vanadium microalloyed medium-carbon steel

    NASA Astrophysics Data System (ADS)

    Rothleutner, Lee M.

    -martensitic transformation products in the induction-hardened case. In the total case region, vanadium reduced the total case depth by inhibiting austenite formation at low austenitizing temperatures; however, the non-martensitic constituents in the case microstructure and the reduced total case depth of the vanadium microalloyed steel did not translate directly to a degradation of torsional fatigue properties. In general, vanadium microalloying was not found to affect torsional fatigue performance significantly with one exception. In the 25 pct effective case depth condition, the 10V45 steel had a ~75 pct increase in fatigue life at all shear stress amplitudes when compared to the 1045 steel. The improved fatigue performance is likely a result of the significantly higher case hardness this condition exhibited compared to all other conditions. The direct influence of vanadium on the improved fatigue life of the 25 pct effective case depth condition is confounded with the slightly higher carbon content of the 10V45 steel. In addition, the 10V45 conditions showed a consistently higher case hardness than the in 1045 conditions. The increased hardness of the 10V45 steel did not increase the compressive residual stresses at the surface. Induction hardening parameters were more closely related to changes in residual stress than vanadium microalloying additions. Torsional fatigue data from the current study as well as from literature were used to develop an empirical multiple linear regression model that accounts for case depth as well as carbon content when predicting torsional fatigue life of induction hardened medium-carbon steels.

  20. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  1. Spectral transformation of femtosecond Cr:forsterite laser pulses in a flint-glass photonic-crystal fiber.

    PubMed

    Fedotov, A B; Serebryannikov, E E; Ivanov, A A; Zheltikov, A M

    2006-09-10

    Nonlinear-optical performance of photonic-crystal fibers (PCFs) made of highly nonlinear TF10 glass is studied and compared with the general tendencies of nonlinear-optical interactions in fused-silica PCFs. The loss of TF10 glass PCFs prevents the generation of supercontinuum emission with a broad and flat spectrum, which typically requires propagation lengths comparable with or exceeding the attenuation length of the fiber. However, dispersive-wave emission of solitons, induced by high-order dispersion, phase-matched four-wave-mixing processes, and self-phase-modulation-induced spectral broadening are substantially enhanced in TF10 glass PCFs due to the high material nonlinearity, providing a high efficiency of frequency conversion of Cr:forsterite laser pulses.

  2. High-Performance, Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

  3. Predictive Modeling of the Constitutive Response of Precipitation Hardened Ni-Rich NiTi

    NASA Astrophysics Data System (ADS)

    Cox, A.; Franco, B.; Wang, S.; Baxevanis, T.; Karaman, I.; Lagoudas, D. C.

    2017-03-01

    The effective thermomechanical response of precipitation hardened near-equiatomic Ni-rich NiTi alloys is predicted on the basis of composition and heat treatment using a microscale-informed model. The model takes into account the structural effects of the precipitates (precipitate volume fraction, elastic properties, elastic mismatch between the precipitates and the matrix, and coherency stresses due to the lattice mismatch between the precipitates and the matrix) on the reversible martensitic transformation under load as well as the chemical effects resulting from the Ni-depletion of the matrix during precipitate growth. The post-aging thermomechanical response is predicted based on finite element simulations on representative microstructures, using the response of the solutionized material and time-temperature-martensitic transformation temperature maps. The predictions are compared with experiments for materials of different initial compositions and heat treatments and reasonably good agreement is demonstrated for relatively low precipitate volume fractions.

  4. Predictive Modeling of the Constitutive Response of Precipitation Hardened Ni-Rich NiTi

    NASA Astrophysics Data System (ADS)

    Cox, A.; Franco, B.; Wang, S.; Baxevanis, T.; Karaman, I.; Lagoudas, D. C.

    2017-01-01

    The effective thermomechanical response of precipitation hardened near-equiatomic Ni-rich NiTi alloys is predicted on the basis of composition and heat treatment using a microscale-informed model. The model takes into account the structural effects of the precipitates (precipitate volume fraction, elastic properties, elastic mismatch between the precipitates and the matrix, and coherency stresses due to the lattice mismatch between the precipitates and the matrix) on the reversible martensitic transformation under load as well as the chemical effects resulting from the Ni-depletion of the matrix during precipitate growth. The post-aging thermomechanical response is predicted based on finite element simulations on representative microstructures, using the response of the solutionized material and time-temperature-martensitic transformation temperature maps. The predictions are compared with experiments for materials of different initial compositions and heat treatments and reasonably good agreement is demonstrated for relatively low precipitate volume fractions.

  5. Ammonia hardening of porous silica antireflective coatings

    NASA Astrophysics Data System (ADS)

    Belleville, Philippe F.; Floch, Herve G.

    1994-10-01

    The adhesion of sol-gel antireflective porous silica coatings on vitreous optical substrates has been dramatically improved by exposure to ammonia vapors or a dip in basic solutions. The approximately 70 to 270-nm thick coatings consisted of monolayers of spherical, 20-nm diameter amorphous silica particles deposited from ethanolic colloidal suspensions by conventional liquid coating techniques. Although, the as-deposited coatings had only low adhesion and were easily damaged when cleaned by standard drag-wiping procedures, coatings exposed over 5 hours to ammonia vapors passed both adhesive-tape and moderate abrasive- resistance tests. The increase in strength was accompanied by a roughly 20% shrinkage of the original coating thickness but the antireflective properties were retained. Our explanation of this chemical effect is a base-catalyzed phenomenon leading to surface silanol condensation and hydrogen-bonding of neighbor silica particles. In addition, since this basic treatment enhanced the laser damage resistance, such strengthened antireflective coatings have been successfully evaluated on flashlamps used on Phebus, Europe's most powerful laser. This allows an increase of the laser-disk pumping efficiency.

  6. A study and development of technology for surface induction hardening of railroad rails from low-alloy steel

    NASA Astrophysics Data System (ADS)

    Degtyarev, S. I.; Skoblo, T. S.; Sapozhnikov, V. E.

    1998-12-01

    A technology of heat treatment of railroad rails using induction heating has been developed and installed in the Azovstal' metallurgical works. It provides the requisite combination of properties in the metal of rail heads. However, the metal of the web and the bottom of the rails remains in the initial (unhardened) state. Under severe operational conditions (small-radius curves, high axial loads, and composite configuration of the road) the wear resistance of the head and the structural strength of the web and the bottom not hardened in the plant have to be increased. The properties of the rail steel can be improved by alloying it using the most effective and available elements. Currently, in Ukraine this is manganese. The present paper is devoted to the effect of manganese additives on the phase transformations in induction hardening and the specific features of the formed structure and properties of the rail steel. Optimum parameters for heat treatment of rails are recommended.

  7. Solute hardening and softening effects in B2 nickel aluminides

    SciTech Connect

    Pike, L.M.; Liu, C.T.; Anderson, I.M.; Chang, Y.A.

    1998-11-01

    The effect of substitutional solute additions including Fe, Mn, and Pd on the hardness of B2-ordered NiAl alloys was investigated. The solid solution hardening behavior of intermetallics is more complex than that of typical metallic solid solutions because of complications arising from the site preference of the solute as well as the effects of the solute on the concentrations of other point defects, e.g., vacancies and anti-site defects. For this reason, care was taken to experimentally establish solute site preferences and point defect concentrations in the NiAl alloys before analyzing the hardness data. By taking these factors into account it was possible to rationalize the observed unusual hardening effects. Three distinct categories of solid solution hardening behavior were encountered. The first was hardening by the solute addition itself. This was observed in the case of Pd additions to Al-poor NiAl. However, when fe or Mn is added to Al-poor NiAl a second category is observed; these elements are seen to soften the material. The third category of behavior is observed when Fe is added to NiAl with a constant Al concentration of 50 at. %. In this case it is vacancies, rather than solute atoms, which harden the material.

  8. Computer modelling of age hardening for cast aluminium alloys

    NASA Astrophysics Data System (ADS)

    Wu, Linda; Ferguson, W. George

    2009-08-01

    Age hardening, or precipitation hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. Although various age hardening models have been developed for aluminium alloys, from the large volume of literature reviewed, it appears that the bulk of the research has been concentrated on wrought aluminium alloys, only a few of the established precipitation models have been applied to the casting aluminium alloys. In the present work, there are two modelling methods that have been developed and applied to the casting aluminium alloys A356 and A357. One is based on the Shercliff-Ashby methodology to produce a process model, by which we mean a mathematical relationship between process variables (alloy composition, ageing temperature and time) and material properties (yield strength or hardness) through microstructure evolution (precipitate radius, volume fraction). The other method is based on the Kampmann and Wagner Numerical (KWN) model which deals with concomitant nucleation, growth and coarsening and is thus capable of predicting the full evolution of the particle size distribution and then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening.

  9. Reduction of work hardening rate in low-carbon steels

    NASA Astrophysics Data System (ADS)

    Yalamanchili, Bhaskar Rao

    Low carbon grades of steel rods are used to produce finished products such as fine wire, coat hangers, staples, and roofing nails. These products are subject to ductility failures during production due to excessively high work hardening rates during wire drawing. The high work hardening rates are attributed to the presence of residuals, free nitrogen, or combinations thereof. This research concludes that the most cost-effective way to reduce the work hardening rate during wire drawing is to combine boron with nitrogen to form boron nitride, and thus reducing its work hardening contribution. The results of this study also conclude the following: (1) Boron/Nitrogen ratio is the more significant factor than rod tensile strength, which affects work hardening rate. Higher ratio is better in the 0.79 to 1.19 range. (2) Maintaining this narrow B/N range requires precise process control. (3) Process conditions such as dissolved oxygen (<25 ppm), carbon (≤0.05%) and ladle refining temperature (<2930°F) are necessary for optimizing boron recovery. (4) An average of 89% boron recovery is obtained with the above controlled process conditions. (5) Use of Boron has no adverse effects on the several metallurgical properties tested except with minor difficulty with scale for descaling. North Star Steel Texas (North Star) benefited from this research by being able to provide a competitive edge in both quality and cost of its low carbon boron grades thus making North Star a preferred supplier of wire rod for these products.

  10. Detection of Biosignatures using Geomatrix-Assisted Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Implications for the Search for Life in the Solar System

    NASA Astrophysics Data System (ADS)

    Richardson, C. D.; Kotler, J. M.; Hinman, N. W.; Scott, J. R.

    2008-12-01

    Detection of bio/organic signatures, defined as an organic structure produced by living organisms or derived from other biogenic organic compounds, is essential to investigating the origin and distribution of extant or extinct life in the solar system. In conjunction with mineralogical, inorganic, and isotopic data, the detection and identification of bio/organic signatures can assist in linking biochemical and geochemical processes. Geomatrix-assisted laser desorption/ionization (GALDI) in conjunction with a Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is a proven method of obtaining bio/organic signatures from a range of geological materials. Sulfate salts were studied because they are found on Mars and Jovian satellites. The goal here was to determine (1) which combinations of bio/organic compounds and sulfate salts produced distinctive spectral signatures, and (2) the detection limit of the method. In these experiments, thenardite (Na2SO4) was mixed with stearic acid to determine the detection limit of GALDI-FTICR-MS, previously estimated to be 3 ppt, which corresponds to approximately 7 zeptomoles (10-21) per laser shot. All spectra were collected with little to no sample preparation and were acquired using a single laser shot. Unlike conventional analytical practices, the signal-to-noise ratio increased as the concentration of bio/organic compounds decreased relative to the mineral host. In combination with thenardite, aromatic amino acids were observed to undergo simple cation attachment ([M+Na]+) due to the π-bonded aromatic ring. Subsequent cation substitution of the carboxyl group led to formation of peaks representing double cation attachment ([M-H+Na]Na+). Spectra from naturally occurring thenardite and jarosite (XFe3(OH)6(SO4)2) revealed the presence of high mass cluster ions; analysis of their isotopic distribution suggested the presence of bio/organic compounds. High mass cluster ions, both organic and inorganic, readily

  11. Gradient boride layers formed by diffusion carburizing and laser boriding

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.

    2015-04-01

    Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was

  12. Radiation Hardened Silica-Based Optical Fibers

    DTIC Science & Technology

    1988-12-01

    Induced absorption occurs when existing defects in the glass form color centers by trapping electrons and holes generated by ionizing radiation. The...drawn fiber from capturing charge carriers and thereby forming color centers is to transform them into benign defects. The latter are defined as defects...which do not form color centers or which form centers that absorb out- side the wavelength range of interest. The passivation process is performed on

  13. Radiation Hardened Silica-Based Optical Fibers.

    DTIC Science & Technology

    1986-10-01

    Induced absorption occurs when existing defects in the glass form color centers by trapping electrons and holes generated by ionizing radiation. Three...I. Defect Passivation One method to prevent defects in as-drawn fiber from capturing carriers and forming color centers is to transform them into...benign defects. The lat- ter are defined as either defects which form color centers that absorb out- side the wavelength range of interest, or

  14. Ion-irradiation-induced hardening in Inconel 718

    NASA Astrophysics Data System (ADS)

    Hunn, J. D.; Lee, E. H.; Byun, T. S.; Mansur, L. K.

    2001-07-01

    Inconel 718 is a material under consideration for areas in the target region of the spallation neutron source (SNS), now under construction at Oak Ridge National Laboratory (ORNL) in the US. In these positions, displacement damage from protons and neutrons will affect the mechanical properties. In addition, significant amounts of helium and hydrogen will build up in the material due to transmutation reactions. Nanoindentation measurements of solution-annealed (SA) Inconel 718 specimens, implanted with Fe-, He-, and H-ions to simulate SNS target radiation conditions, have shown that hardening occurs due to ion-induced displacement damage as well as due to the build-up of helium bubbles in the irradiated layer. Precipitation-hardened (PH) Inconel 718 also exhibited hardening by helium build-up but showed softening as a function of displacement damage due to dissolution of the γ ' and γ″ precipitates.

  15. Secondary hardening steel having improved combination of hardness and toughness

    DOEpatents

    Parker, Earl R.; Zackay, Victor F.; Bhat, Manjeshwar S.; Garrison, Jr., Warren M.

    1979-01-01

    A secondary hardening alloy steel composition consisting essentially of about 0.25-0.5% carbon, about 0.5-1.0% manganese, about 1.5-3.0% nickel, about 0-1.0% chromium, about 1.75-2.5% molybdenum, about 0-0.4% vanadium, and an additive selected from about 1-3% aluminum and a combination of at least about 1% aluminum and at least about 1% silicon for a combined Al+Si content of about 2-4%, the balance being iron and impurity elements. The present steel composition has the following characteristics: it exhibits a flat tempering response, it is hardenable upon tempering to a Rockwell C hardness of at least 50, and it has an improved combination of hardness vs. toughness properties after tempering in the secondary hardening range. A method of preparation is also described.

  16. Branching structure and strain hardening of branched metallocene polyethylenes

    SciTech Connect

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M.

    2015-09-15

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers.

  17. Calibration laws based on multiple linear regression applied to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Williams, D Keith; Chadwick, M Ashley; Williams, Taufika Islam; Muddiman, David C

    2008-12-01

    Operation of any mass spectrometer requires implementation of mass calibration laws to translate experimentally measured physical quantities into a m/z range. While internal calibration in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) offers several attractive features, including exposure of calibrant and analyte ions to identical experimental conditions (e.g. space charge), external calibration affords simpler pulse sequences and higher throughput. The automatic gain control method used in hybrid linear trap quadrupole (LTQ) FT-ICR-MS to consistently obtain the same ion population is not readily amenable to matrix-assisted laser desorption/ionization (MALDI) FT-ICR-MS, due to the heterogeneous nature and poor spot-to-spot reproducibility of MALDI. This can be compensated for by taking external calibration laws into account that consider magnetic and electric fields, as well as relative and total ion abundances. Herein, an evaluation of external mass calibration laws applied to MALDI-FT-ICR-MS is performed to achieve higher mass measurement accuracy (MMA).

  18. A partial least squares and wavelet-transform hybrid model to analyze carbon content in coal using laser-induced breakdown spectroscopy.

    PubMed

    Yuan, Tingbi; Wang, Zhe; Li, Zheng; Ni, Weidou; Liu, Jianmin

    2014-01-07

    A partial least squares (PLS) and wavelet transform hybrid model are proposed to analyze the carbon content of coal by using laser-induced breakdown spectroscopy (LIBS). The hybrid model is composed of two steps of wavelet analysis procedures, which include environmental denoising and background noise reduction, to pretreat the LIBS spectrum. The processed wavelet coefficients, which contain the discrete line information of the spectra, were taken as inputs for the PLS model for calibration and prediction of carbon element. A higher signal-to-noise ratio of carbon line was obtained after environmental denoising, and the best decomposition level was determined after background noise reduction. The hybrid model resulted in a significant improvement over the conventional PLS method under different ambient environments, which include air, argon, and helium. The average relative error of carbon decreased from 2.74 to 1.67% under an ambient helium environment, which indicated a significantly improved accuracy in the measurement of carbon in coal. The best results obtained under an ambient helium environment could be partly attributed to the smallest interference by noise after wavelet denoising. A similar improvement was observed in ambient air and argon environments, thereby proving the applicability of the hybrid model under different experimental conditions.

  19. Glycine Identification in Natural Jarosites Using Laser-Desorption Fourier Transform Mass Spectrometry: Implications for the search for life on Mars

    SciTech Connect

    J. Michelle Kotler; Nancy W. Hinman; Beizhan Yan; Daphne L. Stoner; Jill R. Scott

    2008-04-01

    The jarosite group minerals have received increasing attention since the discovery of jarosite by the Mars Exploration Rover-Opportunity on the Martian surface. The mineral group has the ability to incorporate foreign ions in its structure leading to investigations regarding its use as an indicator of aqueous and/or biological activity on Earth and Mars. The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various worldwide locations. One of the organic cluster ions has been attributed to glycine based on results from combinations of glycine with synthetic jarosite and K2SO4. The ability to observe these organic signatures in jarosite samples with an “in situ” instrumental technique, such as employed in this study, furthers the goals of planetary geologists to determine whether signs of life (e.g., the presence of biomolecules or biomolecule precursors) can be detected in the rock record of terrestrial and extraterrestrial samples.

  20. The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2.

    PubMed

    León, I; Alonso, E R; Mata, S; Cabezas, C; Rodríguez, M A; Grabow, J-U; Alonso, J L

    2017-09-20

    The steric effects imposed by the isopropyl group of valine in the conformational stabilization of the capped dipeptide N-acetyl-l-valinamide (Ac-Val-NH2) have been studied by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy. The rotational and quadrupole coupling constants of the two (14)N nuclei determined in this work show that this dipeptide exists as a mixture of C7 and C5 conformers in the supersonic expansion. The conformers are stabilized by a C[double bond, length as m-dash]OH-N intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The observation of both conformers is in good agreement with previous results on the related dipeptides containing different residues, confirming that the polarity/non-polarity of the side chains of the amino acid is responsible for the conformational locking/unlocking. The voluminous isopropyl group is not able to prevent the less stable C5 conformer from forming but it destabilizes the C[double bond, length as m-dash]OH-N interaction.

  1. Comparison between Hilbert-Huang transform and scalogram methods on non-stationary biomedical signals: application to laser Doppler flowmetry recordings.

    PubMed

    Roulier, Rémy; Humeau, Anne; Flatley, Thomas P; Abraham, Pierre

    2005-11-07

    A significant transient increase in laser Doppler flowmetry (LDF) signals is observed in response to a local and progressive cutaneous pressure application on healthy subjects. This reflex may be impaired in diabetic patients. The work presents a comparison between two signal processing methods that provide a clarification of this phenomenon. Analyses by the scalogram and the Hilbert-Huang transform (HHT) of LDF signals recorded at rest and during a local and progressive cutaneous pressure application are performed on healthy and type 1 diabetic subjects. Three frequency bands, corresponding to myogenic, neurogenic and endothelial related metabolic activities, are studied at different time intervals in order to take into account the dynamics of the phenomenon. The results show that both the scalogram and the HHT methods lead to the same conclusions concerning the comparisons of the myogenic, neurogenic and endothelial related metabolic activities-during the progressive pressure and at rest-in healthy and diabetic subjects. However, the HHT shows more details that may be obscured by the scalogram. Indeed, the non-locally adaptative limitations of the scalogram can remove some definition from the data. These results may improve knowledge on the above-mentioned reflex as well as on non-stationary biomedical signal processing methods.

  2. Analysis of cancer cell lipids using matrix-assisted laser desorption/ionization 15-T Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Yang, Hyo-Jik; Park, Kyu Hwan; Lim, Dong Wan; Kim, Hyun Sik; Kim, Jeongkwon

    2012-03-30

    A combination of methodologies using the extremely high mass accuracy and resolution of 15-T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) was introduced for the identification of intact cancer cell phospholipids. Lipids from a malignant glioma cell line were initially analyzed at a resolution of >200,000 and identified by setting the mass tolerance to ±1 mDa using matrix-assisted laser desorption/ionization (MALDI) 15-T FT-ICR MS in positive ion mode. In most cases, a database search of potential lipid candidates using the exact masses of the lipids yielded only one possible chemical composition. Extremely high mass accuracy (<0.1 ppm) was then attained by using previously identified lipids as internal standards. This, combined with an extremely high resolution (>800,000), yielded well-resolved isotopic fine structures allowing for the identification of lipids by MALDI 15-T FT-ICR MS without using tandem mass spectrometric (MS/MS) analysis. Using this method, a total of 38 unique lipids were successfully identified.

  3. Comparison of field portable measurements of ultrafine TiO2: X-ray fluorescence, laser-induced breakdown spectroscopy, and Fourier-transform infrared spectroscopy

    PubMed Central

    Miller, Arthur L.; Stipe, Christopher; Brown, Jonathan; Murphy, Nate; Stefaniak, Aleksandr B.

    2016-01-01

    Laboratory measurements of ultrafin0e titanium dioxide (TiO2) particulate matter loaded on filters were made using three field portable methods (X-ray fluorescence (XRF), laser-induced breakdown spectroscopy (LIBS), and Fourier-transform infrared (FTIR) spectroscopy) to assess their potential for determining end-of-shift exposure. Ultrafine TiO2 particles were aerosolized and collected onto 37 mm polycarbonate track-etched (PCTE) filters in the range of 3 to 578 µg titanium (Ti). Limit of detection (LOD), limit of quantification (LOQ), and calibration fit were determined for each measurement method. The LOD's were 11.8, 0.032, and 108 µg Ti per filter, for XRF, LIBS, and FTIR, respectively and the LOQ's were 39.2, 0.11, and 361 µg Ti per filter, respectively. The XRF calibration curve was linear over the widest dynamic range, up to the maximum loading tested (578 µg Ti per filter). LIBS was more sensitive but, due to the sample preparation method, the highest loaded filter measurable was 252 µg Ti per filter. XRF and LIBS had good predictability measured by regressing the predicted mass to the gravimetric mass on the filter. XRF and LIBS produced overestimations of 4% and 2%, respectively, with coefficients of determination (R2) of 0.995 and 0.998. FTIR measurements were less dependable due to interference from the PCTE filter media and overestimated mass by 2% with an R2 of 0.831. PMID:23632878

  4. Comparing Laser Desorption Ionization and Atmospheric Pressure Photoionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry To Characterize Shale Oils at the Molecular Level

    USGS Publications Warehouse

    Cho, Yunjo; Jin, Jang Mi; Witt, Matthias; Birdwell, Justin E.; Na, Jeong-Geol; Roh, Nam-Sun; Kim, Sunghwan

    2013-01-01

    Laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze shale oils. Previous work showed that LDI is a sensitive ionization technique for assessing aromatic nitrogen compounds, and oils generated from Green River Formation oil shales are well-documented as being rich in nitrogen. The data presented here demonstrate that LDI is effective in ionizing high-double-bond-equivalent (DBE) compounds and, therefore, is a suitable method for characterizing compounds with condensed structures. Additionally, LDI generates radical cations and protonated ions concurrently, the distribution of which depends upon the molecular structures and elemental compositions, and the basicity of compounds is closely related to the generation of protonated ions. This study demonstrates that LDI FT-ICR MS is an effective ionization technique for use in the study of shale oils at the molecular level. To the best of our knowledge, this is the first time that LDI FT-ICR MS has been applied to shale oils.

  5. Kinematic Hardening: Characterization, Modeling and Impact on Springback Prediction

    SciTech Connect

    Alves, J. L.; Bouvier, S.; Jomaa, M.; Billardon, R.

    2007-05-17

    The constitutive modeling of the materials' mechanical behavior, usually carried out using a phenomenological constitutive model, i.e., a yield criterion associated to the isotropic and kinematic hardening laws, is of paramount importance in the FEM simulation of the sheet metal forming processes, as well as in the springback prediction. Among others, the kinematic behavior of the yield surface plays an essential role, since it is indispensable to describe the Bauschinger effect, i.e., the materials' answer to the multiple tension-compression cycles to which material points are submitted during the forming process. Several laws are usually used to model and describe the kinematic hardening, namely: a) the Prager's law, which describes a linear evolution of the kinematic hardening with the plastic strain rate tensor b) the Frederick-Armstrong non-linear kinematic hardening, basically a non-linear law with saturation; and c) a more advanced physically-based law, similar to the previous one but sensitive to the strain path changes. In the present paper a mixed kinematic hardening law (linear + non-linear behavior) is proposed and its implementation into a static fully-implicit FE code is described. The material parameters identification for sheet metals using different strategies, and the classical Bauschinger loading tests (i.e. in-plane forward and reverse monotonic loading), are addressed, and their impact on springback prediction evaluated. Some numerical results concerning the springback prediction of the Numisheet'05 Benchmark no. 3 are briefly presented to emphasize the importance of a correct modeling and identification of the kinematic hardening behavior.

  6. Determination of Anisotropic Hardening of Sheet Metals by Shear Tests

    SciTech Connect

    Schikorra, Marco; Brosius, Alexander; Kleiner, Matthias

    2005-08-05

    With regard to the increasing necessity of accurate material data determination for the prediction of springback, a material testing equipment has been developed and set up for the measurement of material hardening within cyclic loading. One reason for inaccurate springback predictions can be seen in a missing consideration of load reversal effects in a realistic material model description. Due to bending and unbending while the material is drawn from the flange over a radius of a deep drawing tool, a hardening takes place which leads to an expanding or shifting of the elastic area and yield locus known as isotropic, kinematic, or combined hardening. Since springback is mainly influenced by the actual stress state and a correct distinction between elastic and elastic-plastic regions, an accurate prediction of these stress and strain components is basically required to simulate springback accurately, too. The presented testing method deals with shearing of sheet metal specimens in one or more load cycles to analyze the change of yield point and yield curve. The experimental set up is presented and discussed and the results are shown for different materials such as aluminum A199.5, stainless steel X5CrNi18.10, dual phase steel DP600, and copper Cu99.99. To guarantee a wide experimental range, different sheet thicknesses were used additionally. Simulations using the finite element method were carried out to compare the measured results with calculated results from different yield criterions and different hardening laws mentioned above. It was possible to show that commonly used standard material hardening laws like isotropic and kinematic hardening laws often do not lead to accurate stress state predictions when load reversals occur. The work shows the range of occurring differences and strategies to obtain to a more reliable prediction.

  7. Transformational Learners: Transformational Teachers

    ERIC Educational Resources Information Center

    Jones, Marguerite

    2009-01-01

    Transformational learning, according to Mezirow (1981), involves transforming taken-for-granted frames of reference into more discriminating, flexible "habits of mind". In teacher education, transformative learning impacts on the development of students' action theories, self-efficacy and professional attributes. Although considered…

  8. The Transformations of Transformations.

    ERIC Educational Resources Information Center

    Lin, Francis Y.

    2000-01-01

    Harris's original idea of transformations has been changed several times in Chomsky's work. This article explicates these transformations, arguing that though their motivations are highly understandable, these transformations are not necessary for understanding the workings of natural languages. (Author/VWL)

  9. Statistical thermodynamics of strain hardening in polycrystalline solids

    DOE PAGES

    Langer, James S.

    2015-09-18

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  10. Strain Hardening in Polymer Glasses: Limitations of Network Models

    NASA Astrophysics Data System (ADS)

    Hoy, Robert S.; Robbins, Mark O.

    2007-09-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.

  11. Temperature influence on water transport in hardened cement pastes

    SciTech Connect

    Drouet, Emeline; Poyet, Stéphane; Torrenti, Jean-Michel

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

  12. Strain hardening in polymer glasses: limitations of network models.

    PubMed

    Hoy, Robert S; Robbins, Mark O

    2007-09-14

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.

  13. Statistical thermodynamics of strain hardening in polycrystalline solids.

    PubMed

    Langer, J S

    2015-09-01

    This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman [Acta Mat. 58, 3718 (2010)ACMAFD1359-645410.1016/j.actamat.2010.03.009]. It then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

  14. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, Jr., Holt; Harris, Ian D.; Ratka, John O.; Spiegelberg, William D.

    1994-01-01

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined.

  15. Method and apparatus for welding precipitation hardenable materials

    DOEpatents

    Murray, H. Jr.; Harris, I.D.; Ratka, J.O.; Spiegelberg, W.D.

    1994-06-28

    A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined. 5 figures.

  16. Impact of Scaled Technology on Radiation Testing and Hardening

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; Cohn, Lewis M.

    2005-01-01

    This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.

  17. Atomistic mechanisms of cyclic hardening in metallic glass

    NASA Astrophysics Data System (ADS)

    Deng, Chuang; Schuh, Christopher A.

    2012-06-01

    Molecular dynamics with an embedded-atom method potential is used to simulate the nanoindentation of Cu63.5Zr36.5 metallic glasses. In particular, the effects of cyclic loading within the nominal elastic range on the overall strength and plasticity of metallic glass are studied. The simulated results are in line with the characteristics of experimentally observed hardening effects. In addition, analysis based on local von Mises strain suggests that the hardening is induced by confined microplasticity and stiffening in regions of the originally preferred yielding path, requiring a higher applied load to trigger a secondary one.

  18. Validation of homogeneous anisotropic hardening approach based on crystal plasticity

    NASA Astrophysics Data System (ADS)

    Jeong, Youngung; Barlat, Frédéric; Tomé, Carlos; Wen, Wei

    2016-10-01

    The current study investigates constitutive models at two different scales: 1) the micromechanical crystal plasticity framework using a dislocation density-based hardening model [1, 2]; 2) macroscale constitutive model based on a yield function that evolves according to the homogeneous anisotropic hardening (HAH) model [3, 4]. The polycrystalline aggregate, tuned for a low-carbon steel, is used to calculate the evolution of the yield surface during monotonic uniaxial tension. The results of the crystal plasticity model are used to train the anisotropic yield function and HAH parameters to demonstrate the flexibility of the macroscale constitutive approach. Through comparison between the two models, an improved rule for the HAH model is suggested.

  19. Why semiconductors must be hardened when used in space

    SciTech Connect

    Winokur, P. S.

    2000-01-04

    The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest.

  20. Precipitation hardening of a novel aluminum matrix composite

    SciTech Connect

    Suarez, Oscar Marcelo

    2002-09-15

    Deterioration of properties in cast aluminum matrix composites (AMCs) due to matrix/reinforcement chemical reactions is absent when AlB{sub 2} particles are used as reinforcements. This communication reports the fabrication of a heat-treatable AMC reinforced with borides. Final hardness values can be adjusted by solution and precipitation, which harden the composite. Evolution of the microstructure is concisely presented as observed by secondary electron microscopy. Precipitation hardening of the aluminum matrix, observed by microhardness measurements, has been corroborated by differential thermal analysis.

  1. Diffusive Origin of the Cosmic-Ray Spectral Hardening

    NASA Astrophysics Data System (ADS)

    Tomassetti, Nicola

    2013-02-01

    Recent data from ATIC, CREAM and PAMELA revealed that the energy spectra of cosmic ray (CR) nuclei above 100 GeV/nucleon experience a remarkable hardening with increasing energy. This effect cannot be recovered by the conventional descriptions of CR acceleration and diffusive propagation processes. Using analytical calculations, I show that the hardening effect can be consequence of a spatial change of the CR diffusion properties in different regions of the Galaxy. I discuss the implications of this scenario for the main CR observables and its connections with the open issues of the CR physics.

  2. Age-hardening mechanisms in a commercial dental gold alloy containing platinum and palladium.

    PubMed

    Tani, T; Udoh, K; Yasuda, K; Van Tendeloo, G; Van Landuyt, J

    1991-10-01

    The age-hardening mechanism of a commercial dental gold alloy containing platinum and palladium (in wt.%, 15 Cu, 6 Ag, 5 Pt, 3 Pd, 3 Zn, with the balance as gold) was elucidated by means of electrical resistivity, hardness tests, x-ray and electron diffraction and electron microscopy, as well as high-resolution electron microscopy. The sequence of phase transformations during isothermal aging below the critical temperature, Tc = 825 K, was described as follows: disordered solid solution alpha 0 (FCC)----metastable AuCu I' ordered phase (FCT)----metastable alpha 2 disordered phase (FCC) equilibrium AuCu I ordered phase (FCT) + equilibrium alpha 2 disordered phase (FCC). The hardening was due to the introduction of coherency strain at the interface between the AuCu I' platelet and the matrix. These ordered platelets had mutually perpendicular c-axes to compensate for the strain introduced by their tetragonality. A loss of coherency at the interface brought about softening of the alloy, i.e., over-aging.

  3. Radiation Hardened Architecture of a Single-Ended Raman-Based Distributed Temperature Sensor

    NASA Astrophysics Data System (ADS)

    Di Francesca, D.; Girard, S.; Planes, I.; Cebollada, A.; Vecchi, G. Li; Alessi, A.; Reghioua, I.; Cangialosi, C.; Ladaci, A.; Rizzolo, S.; Lecoeuche, V.; Boukenter, A.; Champavère, A.; Ouerdane, Y.

    2017-01-01

    Raman-based Distributed Temperature Sensors (RDTS) allow performing spatially resolved (1 m) reliable temperature measurements over several km long Optical Fibers (OFs). These systems are based on the temperature dependence of the intensities of both the Stokes and anti-Stokes components of the Raman back-scattered signal. One of the specific issues associated with RDTS technology in radiation environments is the differential Radiation Induced Attenuation (RIA) between the two components that induces huge errors in the temperature evaluation. Such problem is particularly evident for commercially available single-ended DTS using one laser source. Double-ended configuration could be used to correct for the differential attenuation but are limited by RIA in terms of sensing range. In the present work, we show how a Radiation-Hardened-by-Design DTS (RHD-DTS) overcomes the observed radiation issues keeping the single-ended interrogation scheme. In the tested RHD-DTS two infrared excitation laser sources ( 1550 nm and 1650 nm) are employed: the wavelength of the Stokes component due to the first excitation source coincides with the wavelength of the second excitation; vice versa, the wavelength of the anti-Stokes component due to the second excitation source coincides with the wavelength of the first excitation. The overall result is that the two signal intensities are automatically corrected for the differential RIA all along the OF sensor length and the temperature measurements becomes robust against radiation effects. This study demonstrates the potential of such a sensor by reporting preliminary experimental results obtained with a prototype developed by Viavi Solutions exploiting radiation-sensitive or radiation-hardened optical fibers.

  4. Effect of chemical composition on the hardenability of high-strength rail steel

    NASA Astrophysics Data System (ADS)

    Safonova, K. É.; Velikanov, A. V.

    1981-05-01

    The hardenability nomograms developed for high-strength rail steels make it possible to select the composition of steel with a given hardenability, the minimal permissible value of which depends on the operating conditions.

  5. Strain hardening of polymer glasses: entanglements, energetics, and plasticity.

    PubMed

    Hoy, Robert S; Robbins, Mark O

    2008-03-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.

  6. Total dose performance of radiation hardened voltage regulators and references

    NASA Technical Reports Server (NTRS)

    McClure, S.; Gorelick, J.; Pease, R.; Rax, B.; Ladbury, R.

    2001-01-01

    Total dose test of commercially available radiation hardened bipolar voltage regulators and references show reduced sensitivity to dose rate and varying sensitivity to bias under pressure. Behavior of critical parameters in different dose rate and bias conditions is compared and the impact to hardness assurance methodology is discussed.

  7. A radiation-hardened 16/32-bit microprocessor

    SciTech Connect

    Hass, K.J.; Treece, R.K.; Giddings, A.E.

    1989-01-01

    A radiation-hardened 16/32-bit microprocessor has been fabricated and tested. Our initial evaluation has demonstrated that it is functional after a total gamma dose of 5Mrad(Si) and is immune to SEU from Krypton ions. 3 refs., 2 figs.

  8. 49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    49. INTERIOR VIEW OF HARDENER AREA SHOWING GAUGE THAT MEASURES HARDNESS, THE NAIL MUST BREAK IN THE CENTER RANGE OF THE CURVED BAR TO HAVE THE CORRECT HARDNESS (THE NAIL WILL BREAK TOO EASILY IF TOO HARD AND WILL BEND TOO MUCH IF TOO SOFT) - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  9. Iterative Beam Hardening Correction for Multi-Material Objects.

    PubMed

    Zhao, Yunsong; Li, Mengfei

    2015-01-01

    In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum.

  10. Hardening digital systems with distributed functionality: robust networks

    NASA Astrophysics Data System (ADS)

    Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

    2013-05-01

    Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

  11. Surface hardening of parts from ferrite-pearlite gray iron

    NASA Astrophysics Data System (ADS)

    Gurevich, Yu. G.; Ovsyannikov, V. E.; Marfitsyn, V. V.; Frolov, V. A.

    2011-10-01

    The possibility of a simple method of chromizing of parts from ferrite-pearlite gray iron is studied theoretically and proved experimentally. A process for diffusion chromizing of parts from this iron is suggested. When followed by surface hardening the process yields a high-hardness surface layer with abrasive strength comparable to that of white chromium cast iron.

  12. Hardening by twin boundary during nanoindentation in nanocrystals.

    PubMed

    Qu, Shaoxing; Zhou, Haofei

    2010-08-20

    The atomistic deformation processes of nanocrystals embedded with nanoscale twin boundaries during nanoindentation are studied by molecular dynamics simulations. Load-displacement curves are obtained and the hardening mechanisms associated with the nanoscale twin boundaries are revealed. Johnson's theoretical indentation model is adopted to estimate the elastic stage of the nanoindentation. In addition, twin boundary-mediated dislocation nucleation is observed and analyzed.

  13. BUSFET - A Novel Radiation-Hardened SOI Transistor

    SciTech Connect

    Dodd, P.E.; Draper, B.L.; Schwank, J.R.; Shaneyfelt, M.R.

    1999-02-04

    A partially-depleted SOI transistor structure has been designed that does not require the use of specially-processed hardened buried oxides for total-dose hardness and maintains the intrinsic SEU and dose rate hardness advantages of SOI technology.

  14. Beam hardening correction for sparse-view CT reconstruction

    NASA Astrophysics Data System (ADS)

    Liu, Wenlei; Rong, Junyan; Gao, Peng; Liao, Qimei; Lu, HongBing

    2015-03-01

    Beam hardening, which is caused by spectrum polychromatism of the X-ray beam, may result in various artifacts in the reconstructed image and degrade image quality. The artifacts would be further aggravated for the sparse-view reconstruction due to insufficient sampling data. Considering the advantages of the total-variation (TV) minimization in CT reconstruction with sparse-view data, in this paper, we propose a beam hardening correction method for sparse-view CT reconstruction based on Brabant's modeling. In this correction model for beam hardening, the attenuation coefficient of each voxel at the effective energy is modeled and estimated linearly, and can be applied in an iterative framework, such as simultaneous algebraic reconstruction technique (SART). By integrating the correction model into the forward projector of the algebraic reconstruction technique (ART), the TV minimization can recover images when only a limited number of projections are available. The proposed method does not need prior information about the beam spectrum. Preliminary validation using Monte Carlo simulations indicates that the proposed method can provide better reconstructed images from sparse-view projection data, with effective suppression of artifacts caused by beam hardening. With appropriate modeling of other degrading effects such as photon scattering, the proposed framework may provide a new way for low-dose CT imaging.

  15. KrF pulsed laser ablation of thin films made from fluorinated heterocyclic poly(naphthyl-imide)s.

    PubMed

    Damaceanu, Mariana-Dana; Rusu, Radu-Dan; Olaru, Mihaela Adriana; Timpu, Daniel; Bruma, Maria

    2012-06-01

    Among the many aspects of laser ablation, development of conical structures induced by excimer laser radiation on polyimide surfaces has been thoroughly investigated. Because the mechanisms that produce these surface textures are not fully understood, two theories, photochemical bond breaking and thermal reaction, have been introduced. Here we present the first study of ultraviolet laser ablation behavior of thin films made from fluorinated poly(naphthyl-imide)s containing oxadiazole rings and the investigation of the mechanism of cone-like structure formation at two laser fluences, 57 and 240 mJ/cm(2). The morphology of thin films before and after laser ablation was studied by using various spectroscopy techniques such as Fourier transform infrared spectroscopy, time-resolved emission and X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements. All of the data suggest impurities shielded at low fluence radiation (57 mJ/cm(2)) and a radiation hardening process at high value fluence (240 mJ/cm(2)), which are proposed as the main mechanisms for laser ablation of our polyimide films, and we bring evidence to support them.

  16. Effect of Quenching Rate on Distortion and Residual Stresses During Induction Hardening of a Full-Float Truck Axle Shaft

    NASA Astrophysics Data System (ADS)

    Li, Zhichao; Ferguson, B. Lynn; Nemkov, Valentin; Goldstein, Robert; Jackowski, John; Fett, Greg

    2014-12-01

    Computer simulation is used to predict the residual stresses and distortion of a full-float truck axle shaft that has been induction scan hardened. Flux2D® is used to model the electromagnetic behavior and the power distributions inside the axle shaft in terms of time. The power distributions are imported and mapped into DANTE® model for thermal, phase transformation, and stress analysis. The truck axle shaft has three main geometrical regions: the flange/filet, the shaft, and the spline. Both induction heating and spray quenching processes have significant effect on the quenching results: distortion and residual stress distributions. In this study, the effects of spray quenching severity on residual stresses and distortion are investigated using modeling. The spray quenching rate can be adjusted by spray nozzle design, ratio of polymer solution, and quenchant flow rate. Different quenching rates are modeled by assigning different heat transfer coefficients as thermal boundary conditions during spray quenching. In this paper, three heat transfer coefficients, 5, 12, and 25 kW/(m2 °C), are applied while keeping all other conditions constant. With the understanding of effects of heating and quenching on residual stresses and distortion of induction hardened parts, the induction hardening process can be optimized for improved part performance.

  17. Modeling of Plastic Deformation of Dispersion-Hardened Materials with L12 Superstructure Particles

    NASA Astrophysics Data System (ADS)

    Daneyko, O. I.; Kovalevskaya, T. A.; Kulaeva, N. A.

    2017-07-01

    The paper presents a mathematical model of plastic deformation in FCC materials strengthened with particles having L12 superstructure. The model is based on balance equations for various deformation defects with regard to their transformation during plastic deformation. Research results show that the size and distance between particles of the strengthening phase affect the thermal strengthening, strain hardening and the evolution of the dislocation subsystem of the FCC alloy strengthened with coherent particles with L12 superstructure. The temperature anomaly is detected for strength properties of materials having different volume fractions of the strengthening phase. It is shown that the incoherent strengthening phase increases the flow stress of the material and suppresses the temperature anomaly of its strength properties.

  18. Selective Emitter Pumped Rare Earth Laser

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L. (Inventor); Patton, Martin O. (Inventor)

    2001-01-01

    A selective emitter pumped rare earth laser provides an additional type of laser for use in many laser applications. Rare earth doped lasers exist which are pumped with flashtubes or laser diodes. The invention uses a rare earth emitter to transform thermal energy input to a spectral band matching the absorption band of a rare earth in the laser in order to produce lasing.

  19. Nanoscale characterization of the biomechanical hardening of bovine zona pellucida.

    PubMed

    Boccaccio, Antonio; Frassanito, Maria Cristina; Lamberti, Luciano; Brunelli, Roberto; Maulucci, Giuseppe; Monaci, Maurizio; Papi, Massimiliano; Pappalettere, Carmine; Parasassi, Tiziana; Sylla, Lakamy; Ursini, Fulvio; De Spirito, Marco

    2012-11-07

    The zona pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so-called zona hardening plays a key role in fertilization process, as it blocks polyspermy, which may also be caused by an increase in the mechanical stiffness of the ZP membrane. However, structural reorganization mechanisms leading to ZP's biomechanical hardening are not fully understood yet. Furthermore, a correct estimate of the elastic properties of the ZP is still lacking. Therefore, the aim of the present study was to investigate the biomechanical behaviour of ZP membranes extracted from mature and fertilized bovine oocytes to better understand the mechanisms involved in the structural reorganization of the ZP that may lead to the biomechanical hardening of the ZP. For that purpose, a hybrid procedure is developed by combining atomic force microscopy nanoindentation measurements, nonlinear finite element analysis and nonlinear optimization. The proposed approach allows us to determine the biomechanical properties of the ZP more realistically than the classical analysis based on Hertz's contact theory, as it accounts for the nonlinearity of finite indentation process, hyperelastic behaviour and material heterogeneity. Experimental results show the presence of significant biomechanical hardening induced by the fertilization process. By comparing various hyperelastic constitutive models, it is found that the Arruda-Boyce eight-chain model best describes the biomechanical response of the ZP. Fertilization leads to an increase in the degree of heterogeneity of membrane elastic properties. The Young modulus changes sharply within a superficial layer whose thickness is related to the characteristic distance between cross-links in the ZP filamentous network. These findings support the hypothesis that biomechanical hardening of bovine ZP is caused by an increase in the number of inter-filaments cross-links whose density should be higher in the ZP inner side.

  20. Characterization of petroleum products by laser-induced acoustic desorption in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer

    NASA Astrophysics Data System (ADS)

    Pinkston, David S.

    Many petroleum products, in particular large nonpolar saturated hydrocarbons, have proven difficult to analyze via mass spectrometry due to their low volatility, lack of basic or acidic groups needed for most ionization methods, and low activation energies for fragmentation after ionization. The above limitation has been addressed by using laser-induced acoustic desorption (LIAD) to evaporate nonvolatile and thermally labile petroleum components for analysis in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The gaseous neutral analytes were ionized by electron impact. Model compounds were studied first to test the viability of this method. After that, different types of asphaltenes were characterized successfully. For example, the molecular weight distribution of a North American asphaltene was determined. A comparison between asphaltene samples obtained from different geographical locations showed distinct molecular weight characteristics, possibly allowing for the determination of an unknown asphaltene sample's geographic origin. Asphaltenes were also characterized via electrospray ionization (ESI) in a linear quadrupole ion trap (LQIT). The observed molecular weight distribution had an extended tail past 2000 Da. Collision-activated dissociation (CAD) experiments on isolated ions revealed that water aggregation was present in this analysis. The observed molecular weight distribution of asphaltenes reduced dramatically when water was eliminated from the system. The usefulness of a new chemical ionization reagent, ClMn(H2O) +, is also discussed. This reagent has been shown to ionize hydrocarbons without fragmentation to yield [ClMnR]+, where R is the hydrocarbon, thus providing molecular weight information. CAD of the [ClMnR]+ ions is demonstrated to allow the differentiation of isomeric hydrocarbons. Finally, the LIAD/ClMn(H2O)+ mass spectrometric method was applied to the successful analysis of various petroleum fractions and asphaltene