Large Deflection Angles Research Articles

Fabrication and cutting performance of an Al2O3/TiC/TiN ceramic cutting tool in turning of an ultra-high-strength steel

An Al2O3/TiN/TiC micro-nano-composite ceramic tool material was fabricated by using the hot-pressing method. Micro-structure and mechanical properties of the ceramic material were examined, and high-speed cutting experiments on ultra-high-strength steel 300 M were conducted. The cutting performance and wear behaviors of the Al2O3/TiN/TiC ceramic tool AT10N20 were investigated in comparison with the commercial Al2O3/TiC ceramic tool CC650. The results showed that with a sintering temperature of 1650 °C, a holding time of l5 min, and a sintering pressure of 35 MPa, AT10N20 had the best comprehensive mechanical properties. The crack propagation modes of AT10N20 ceramic tool materials involved intergranular fracture and transgranular fracture, and the crack propagation path was irregular with a large deflection angle. With the increase of cutting speeds, the tool life of AT10N20 approached to that of CC650 gradually. Meanwhile, the cutting lengths of both two ceramic cutting tools first increased and then decreased gradually. Crater wear and tool nose wear were found to occur on the AT10N20. Abrasive wear and adhesion wear were the predominant wear mechanisms of AT10N20. It indicated that AT10N20 ceramic tool was a good alternative to the CC650 in the high-speed turning of ultra-high-strength steel 300 M.

EBSD spatial resolution for detecting sigma phase in steels

The spatial resolution of the electron backscatter diffraction signal is explored by Monte Carlo simulation for the sigma phase in steel at a typical instrumental set-up. In order to estimate the active volume corresponding to the diffracted electrons, the fraction of the backscattered electrons contributing to the diffraction signal was inferred by extrapolating the Kikuchi pattern contrast measured by other authors, as a function of the diffracted electron energy. In the resulting estimation, the contribution of the intrinsic incident beam size and the software capability to deconvolve patterns were included.A strong influence of the beam size on the lateral resolution was observed, resulting in 20nm for the aperture considered. For longitudinal and depth directions the resolutions obtained were 75nm and 16nm, respectively. The reliability of this last result is discussed in terms of the survey of the last large-angle deflection undergone by the backscattered electrons involved in the diffraction process.Bearing in mind the mean transversal resolution found, it was possible to detect small area grains of sigma phase by EBSD measurements, for a stabilized austenitic AISI 347 stainless steel under heat treatments, simulating post welding (40h at 600°C) and aging (284h at 484°C) effects—as usually occurring in nuclear reactor pressure vessels.

Large deflection angle, high-power adaptive fiber optics collimator with preserved near-diffraction-limited beam quality.

We report on the development of a monolithic adaptive fiber optics collimator, with a large deflection angle and preserved near-diffraction-limited beam quality, that has been tested at a maximal output power at the 300 W level. Additionally, a new measurement method of beam quality (M2 factor) is developed. Experimental results show that the deflection angle of the collimated beam is in the range of 0-0.27 mrad in the X direction and 0-0.19 mrad in the Y direction. The effective working frequency of the device is about 710 Hz. By employing the new measurement method of the M2 factor, we calculate that the beam quality is Mx2=1.35 and My2=1.24, which is in agreement with the result from the beam propagation analyzer and is preserved well with the increasing output power.

Integrated monolithic 3D MEMS scanner for switchable real time vertical/horizontal cross-sectional imaging.

We present an integrated monolithic, electrostatic 3D MEMS scanner with a compact chip size of 3.2 × 2.9 mm(2). Use of parametric excitation near resonance frequencies produced large optical deflection angles up to ± 27° and ± 28.5° in the X- and Y-axes and displacements up to 510 μm in the Z-axis with low drive voltages at atmospheric pressure. When packaged in a dual axes confocal endomicroscope, horizontal and vertical cross-sectional images can be collected seamlessly in tissue with a large field-of-view of >1 × 1 mm(2) and 1 × 0.41 mm(2), respectively, at 5 frames/sec.

Effect of large deflection angle on the laser intensity profile produced by acousto-optic deflector scanners in high precision manufacturing

Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies such as printing, patterning, and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. The purpose of this study is to analyze an acousto-optic deflector (AOD) to achieve high diffraction efficiency and high deflection angle. Conventional AODs are operated with one-dimensional refractive index variation induced by modulating only the acoustic wave frequency. The effect of two-dimensional refractive index variations, which can be achieved by modulating both the phase and frequency of the acoustic waves, is analyzed. This study, therefore, advances the current AOD technology from just acoustic wave frequency modulation to a new class of AODs involving both phase and frequency modulations. This new type of AOD is designed by developing an analytic model based on the propagation of a laser beam through the AOD in which the refractive index varies in two dimensions. The model predicts a specific index modulation strength to achieve 100% diffraction efficiency. Also a fairly large diffraction efficiency can be obtained over a large angle of incidence, which is not possible in conventional AODs where the maximum diffraction efficiency occurs only at Bragg angle of incidence.

Simultaneous distribution between the deflection angle and the lateral displacement under the Molière theory of multiple scattering

Simultaneous distribution between the deflection angle and the lateral displacement of fast charged particles traversing through matter is derived by applying numerical inverse Fourier transforms on the Fourier spectral density solved analytically under the Moliere theory of multiple scattering, taking account of ionization loss. Our results show the simultaneous Gaussian distribution at the region of both small deflection angle and lateral displacement, though they show the characteristic contour patterns of probability density specific to the single and the double scatterings at the regions of large deflection angle and/or lateral displacement. The influences of ionization loss on the distribution are also investigated. An exact simultaneous distribution is derived under the fixed energy condition based on a well-known model of screened single scattering, which indicates the limit of validity of the Moliere theory applied to the simultaneous distribution. The simultaneous distribution will be valuable for improving the accuracy and the efficiency of experimental analyses and simulation studies relating to charged particle transports.

Influence research of profile chords ratio on aerodynamic characteristics of tandem compressor cascade

Efficiency improvement of gas turbine compressors is ensured by the extensive use of tandem blade rows in straightener blades of the last stages of multistage axial compressors. Their installation provides large flow deflection angles in the unstalled flow of blade rows and, consequently, a low level of losses in the design mode of the compressor. The problem of influence research of the first- and second-row blade chords ratio in tandem blade rows in a wide range of angles of attack is relevant and is of practical interest in developing recommendations for ensuring the gas-dynamic stability of gas turbine compressors. To solve the problem, the method of the computational experiment was used and characteristics of tandem compressor cascade with different first- and second-row blade chords ratios were calculated in the paper. The calculation results of the characteristics of tandem cascade were compared with the characteristics of an equivalent single compressor cascade. For the computational domain of the studied tandem and equivalent single cascades, small adaptive unstructured grid and the second-order design scheme with the local use of the first-order design scheme (High resolution) was applied. The Menter's SST model was used to solve the problems. The results showed that the aerodynamic characteristics of the tandem compressor cascades essentially depend on the first- and second-row blade chords ratio. With positive angles of attack, the quality parameter of tandem cascades is higher than that of single, with the first- and second-row blade chords ratio, corresponding to the position of the slot x щ =(0,3 ... 0,4)b ∑ . With negative angles of attack, the quality parameter of tandem cascades is higher than that of single, with the first- and second-row blade chords ratio, corresponding to the position of the slot x щ =(0,5 ... 0,7)b ∑ .

ASSESSMENT OF THE CAPABILITY OF 3D STRATIFIED FLOW FINITE ELEMENT MODEL IN CHARACTERIZING MEANDER DYNAMICS

There have been attempts to simulate meander dynamics (Langbein and Leopold 1966, Oodgard 1989, Campoerale et. al 2007, da Silva and El-Tahawy 2008, Duan and Julien 2010, Blanckaert and de Vriend 2010, Esfahani and Keshavarzi 2011). Meandering geometry is complex phenomena (Chanson 2004, Wu 2008), this would include the dynamics of flow properties and of morphology. Simulating meander flow dynamics is mostly popular using either Finite Element Method (FEM) or Finite Volume Method (FVM) where are based on Eulerian description, and based on stationer grid-based methods (Wormleaton and Ewunetu 2006, Wu 2008, Duan and Julien 2010, Gomez-Gesteira et. al 2010). As such this model is lack of capability in simulating the dynamics of meander morphology; much effort is put through to overcome this issue with such as Smoothed Particle Hydrodynamics (SPH), Boundary Element Methods, Arbitrary Lagrangian Eulerian, etc. This paper has two objectives; to identify meander flow characteristics and sediment transport distribution patterns, and to simulate meander flow characteristics and sediment transport distribution patterns using FEM. This study has identified that the key of dynamics of flow characteristics are helical flow and coherent structures, and the key of dynamics of transport characteristics are erosion-deposition zone patterns. The finite element model using in this study, RMA has shown its capability to simulate the meander key characteristics above, for small deflection angles (30°) location of maximum erosion-deposition zones near the crossover of the sinuosity, for intermediate deflection angles (70°) location of maximum erosion-deposition zones between the crossover and apex of the sinuosity, and for large deflection angles (110°) location of maximum erosion-deposition zones near the apex of the sinuosity, these are agreed with experiments of Odgaard 1989, da Silva 2006, da Silva et. al 2006, and Esfahani and Keshavarzi (2012). These results can be used as a reference to develop a method to model meander morpho-dynamics.

ASSESSMENT OF THE CAPABILITY OF 3D STRATIFIED FLOW FINITE ELEMENT MODEL IN CHARACTERIZING MEANDER DYNAMICS

There have been attempts to simulate meander dynamics (Langbein and Leopold 1966, Oodgard 1989, Campoerale et. al 2007, da Silva and El-Tahawy 2008, Duan and Julien 2010, Blanckaert and de Vriend 2010, Esfahani and Keshavarzi 2011). Meandering geometry is complex phenomena (Chanson 2004, Wu 2008), this would include the dynamics of flow properties and of morphology. Simulating meander flow dynamics is mostly popular using either Finite Element Method (FEM) or Finite Volume Method (FVM) where are based on Eulerian description, and based on stationer grid-based methods (Wormleaton and Ewunetu 2006, Wu 2008, Duan and Julien 2010, Gomez-Gesteira et. al 2010). As such this model is lack of capability in simulating the dynamics of meander morphology; much effort is put through to overcome this issue with such as Smoothed Particle Hydrodynamics (SPH), Boundary Element Methods, Arbitrary Lagrangian Eulerian, etc. This paper has two objectives; to identify meander flow characteristics and sediment transport distribution patterns, and to simulate meander flow characteristics and sediment transport distribution patterns using FEM. This study has identified that the key of dynamics of flow characteristics are helical flow and coherent structures, and the key of dynamics of transport characteristics are erosion-deposition zone patterns. The finite element model using in this study, RMA has shown its capability to simulate the meander key characteristics above, for small deflection angles (30°) location of maximum erosion-deposition zones near the crossover of the sinuosity, for intermediate deflection angles (70°) location of maximum erosion-deposition zones between the crossover and apex of the sinuosity, and for large deflection angles (110°) location of maximum erosion-deposition zones near the apex of the sinuosity, these are agreed with experiments of Odgaard 1989, da Silva 2006, da Silva et. al 2006, and Esfahani and Keshavarzi (2012). These results can be used as a reference to develop a method to model meander morpho-dynamics.

Sub-gigahertz beam switching of vertical-cavity surface-emitting laser with transverse coupled cavity

We report a high-speed electrical beam switching of vertical cavity surface emitting laser with a transverse coupled cavity. A high speed (sub-gigahertz) and large deflection angle (>30°) beam switching is demonstrated by employing the transverse mode switching. The angular switching speed of 900 MHz is achieved with narrow beam divergence of below 4° and extinction ratio of 8 dB. We also measured the near- and far-field patterns to clarify the origin of the beam switching. We present a simple one-dimensional Bragg reflector waveguide model, which well predicts the beam switching characteristic.

Concept for a transmissive, large angle, light steering device with high efficiency.

A device concept is presented to allow very large angle deflection of light passing through a transmissive device. Deflection of light, switchable between angles larger than ±60 deg, is shown to be possible with efficiencies approaching 100%.

Scanning system development and digital beam control method for electron beam selective melting

Purpose – The purpose of this paper is to correct the beam deflection errors and beam defocus by using a digital scanning system. Electron beam selective melting (EBSM) is an additive manufacturing technology for metal parts. Beam deflection errors and beam defocus at large deflection angles would greatly influence the accuracy of the built parts. Design/methodology/approach – The 200 × 200 mm2 scanning area of the electron beam is discretized into 1001 × 1001 points arranged in array, based on which a digital scanning system is developed. To correct the deflection errors, the electron beam scans a 41 × 41 testing grid, and the corrective algorithm is based on the bilinear transformation from the grid points’ nominal coordinates to their measured coordinates. The beam defocus is corrected by a dynamic focusing method. A three-dimensional testing part is built with and without using the corrective algorithm, and their accuracies are quantitatively compared. Findings – The testing grid scanning result shows that the accuracy of the corrected beam deflection system is better than ± 0.2 mm and beam defocus at large deflection angles is eliminated visibly. The testing part built with using the corrective algorithm is of greater accuracy than the one built without using it. Originality/value – Benefiting from the digital beam control method, the model-to-part accuracy of the system is effectively improved. The digital scanning system is feasible in rapid manufacturing large and complex three-dimensional metal parts.

Research on Phased Array Ultrasonic Total Focusing Method and its Calibration

Total focusing method is an imaging approach using full matrix data which has become a research hotspot due to its advantages such as high accuracy, flexibility and so on. To solve the calibration problem in inspection with wedge coupled, full matrix data and its capture are described, a dual-medium energy attenuation model is established, three parts of calibration coefficient are given by analytical expressions which are directivity, transmission and diffusion attenuation, and a calibration based total focusing method is designed. Three images of the phased array test block type-B are formed using total focusing method. Experimental results show that it is good for the remote reflector with the calibration of root-square-distance, using the attenuation calibration model the attenuation caused by long path length and large deflection angle is better corrected and the energy of the image is more uniform. This calibration based total focusing method has the ability to detect the defects at large deflection angle. The research result shows that missing rate and sizing error can be reduced by calibration based total focusing method effectively.

A GEOMETRICALLY SUPPORTED z ∼ 10 CANDIDATE MULTIPLY IMAGED BY THE HUBBLE FRONTIER FIELDS CLUSTER A2744

The deflection angles of lensed sources increase with their distance behind a given lens. We utilize this geometric effect to corroborate the $z_{phot}\simeq9.8$ photometric redshift estimate of a faint near-IR dropout, triply-imaged by the massive galaxy cluster Abell 2744 in deep Hubble Frontier Fields images. The multiple images of this source follow the same symmetry as other nearby sets of multiple images which bracket the critical curves and have well defined redshifts (up to $z_{spec}\simeq3.6$), but with larger deflection angles, indicating that this source must lie at a higher redshift. Similarly, our different parametric and non-parametric lens models all require this object be at $z\gtrsim4$, with at least 95\% confidence, thoroughly excluding the possibility of lower-redshift interlopers. To study the properties of this source we correct the two brighter images for their magnifications, leading to a SFR of $\sim0.3 M_{\odot}$/yr, a stellar mass of $\sim4\times10^{7} M_{\odot}$, and an age of $\lesssim220$ Myr (95\% confidence). The intrinsic apparent magnitude is 29.9 AB (F160W), and the rest-frame UV ($\sim1500 \AA$) absolute magnitude is $M_{UV,AB}=-17.6$. This corresponds to $\sim0.1 L^{*}_{z=8}$ ($\sim0.2 L^{*}_{z=10}$, adopting $dM^{*}/dz\sim0.45$), making this candidate one of the least luminous galaxies discovered at $z\sim10$.

Investigation on Flatness of Shim Rings in Blanking

Flatness of blanked parts is important as well as the cut edge quality and often becomes worse when blanking the low stiffness parts such as narrow shim rings. In this study, the affecting factors on the flatness of shim rings in conventional blanking were investigated through the experiments varying the ring widths and materials. Flatness was evaluated with the deflection angle. It was found that the shim ring with a smaller width and the material having a larger n value exhibited larger deflection angles. Deformation during blanking was analyzed by FE simulation and the experimental results were explained based on the strain distributions.

Transmission of highly charged ions through nanocapillaries of noncircular cross sections

We report on effects from the geometrical shape of the guiding channels on the ion transmission profile. We find that capillaries of rhombic cross section produce rectangular shaped ion transmission profiles and, vice versa, capillaries of rectangular geometry give a rhombic beam shape. Our trajectory simulations for the incidence of 14-keV Ne7+ ions give clear evidence that the observed effect is due to the image forces experienced by the transmitting ions. They gain transverse energy due the image charge attraction towards the inner surfaces of the capillary. This leads to a defocusing of the ions leaving the capillaries. Due to the blocking of large deflection angles at the exit of the capillary, the transmitted ion beam is tailored into certain geometrical patterns.

PD-0042: Development of a new virtual source model for portal image prediction

Purpose/Objective: Electronic Portal Imaging Devices (EPIDs) are widely used for quality assurance in radiotherapy, and also for dosimetric verifications. For this latter application, the image obtained during the treatment session can be compared to a pre-calculated reference image in order to highlight dose delivery errors. A Monte Carlo(MC)-based method to predict high-resolution reference images was recently developed. However, the use of this method in clinical routine is still hampered by the need to store huge phase space (PS) files. This study aims at developing a new virtual source model (VSM) which retains all the existing correlations between particle characteristics stored in the PS file, and hence to provide a more compact way to model the irradiation beam, while keeping the accuracy of using a PS file. Materials and Methods: A model of the studied linac (Elekta Synergy) was first developed using both the MC codes EGSnrc and PENELOPE, and commissioned. Using this model, a reference PSF (PSFr) was calculated after the flattening filter using EGSnrc, where the axial symmetries assumed, and particles were sorted out in three sub-sources according to the position of their last interaction (target, primary collimator or flattening filter). Each particle is described by its radial position (r) in the PS plane,its energy (E), and its polar and azimuthal angles (phi, theta), representing the particle deviation compared to its direction after bremsstrahlung, and the orientation of this deviation. For each subsource, a 4D histogram was built by storing the particle distributions accordingto their r, E, phi, theta values. Our VSM hence contains all correlations existing between these four variables contrary to other existing VSMs. This new VSM is now being implemented in the PENELOPE code, and its accuracy is being tested by comparing first the PSF build using our VSM with the PSFr, and then dose distributions in water and portal images calculated with the MSV and PSFr. Results: Figure 1 shows for each sub-source the correlated 2D histogram depicting particle energy against their radial position. Some characteristics are shared by all sources. Few particles are beyond the collimator aperture (4.5 cm from the linac axis). The annihilation photons at 511 keV are always visible. However, the content of a histogram depends widely of the sub-source it represents: the target produces the most energetic particles. The flattening filter and the primary collimator sub-sources generate particles beyond 4.5 cm of lower energy, because of their large deflection angle. Conclusions: A new VSM taking into account for all correlations between particle characteristics was developed and implemented in the PENELOPE code. It will be used to calculate accurate reference portal images for quality assurance in radiotherapy.

Electro-optic and Acousto-optic Laser Beam Scanners

Abstract Optical solid state deflectors rely on the electro-optical or acousto-optic effect. These Electro-Optical Deflectors (EODs) and Acousto-Optical Deflectors (AODs) do not contain moving parts and therefore exhibit high deflection velocities and are free of drawbacks associated with mechanical scanners. A description of the principles of operation of EODs and AODs is presented. In addition, characteristics, properties and the (dis)advantages of EODs and AODs, when compared to mirror based mechanical deflectors, is discussed. Deflection angles, speed and accuracy are discussed in terms of resolvable spots and related quantities. Also, response time, damage threshold, efficiency and the type and magnitude of beam distortions is addressed. Optical deflectors are characterized by high angular deflection velocities, but small deflection angles. Whereas mechanical mechanical scanners are characterized by relatively small deflection velocities, but large deflection angles. Arranging an optical deflector and a mechanical scanner in series allows to take advantage of the best of both worlds.

Electrically controlled diffraction employing electrophoresis, supercapacitance, and total internal reflection

The reflectance of a surface can be altered by controlling the concentration of dye ions in a region adjacent to an optically transparent and electrically conductive thin film. We present a method for nonmechanical light deflection achieved by altering the reflectance of a diffraction grating, an approach that creates new diffraction peaks that lie between those associated with the original grating spacing. We have demonstrated this effect by applying an electrical potential difference between interdigitated indium-tin oxide (ITO) electrodes and measuring the intensity of one of the new diffraction peaks. The measured diffraction peak intensities were found to reversibly deflect approximately 7% of the reflected light to previously nonexistent peaks. The diffraction grating was formed by patterning a thin film of planar, untreated ITO on a glass substrate using standard photolithography techniques. The size scale for this method of electrically controlled diffraction is limited only by the lithographic process; thus there is potential for the grating to deflect light to angles greater than those achievable using other methods. This approach could be used in applications such as telecommunications, where large deflection angles are required, or other applications where alternate beam-steering methods are cost prohibitive.

Compliant articulation structure using superelastic NiTiNOL

A device that can provide articulation to surgical tool tips is needed in natural orifice transluminal endoscopy surgery (NOTES). In this paper, we propose a compliant articulation structure that uses superelastic NiTiNOL to achieve a large deflection angle and force in a compact size. Six geometric parameters are used to define this structure, and constraints based on the fabrication process are imposed. Using finite element analysis, a family of designs is evaluated in terms of the free deflection angle and blocked force. The same family of designs is evaluated for both NiTiNOL and stainless steel. It can be seen that significant benefits are observed when using NiTiNOL compared to 316 stainless steel; a maximum free deflection angle of 64.8° and maximum blocked force of 24.7 N are predicted. The structures are designed to avoid stress concentrations, and design guidelines are recommended. The meso-scale articulation structure is fabricated using both a Coherent Avia Q-switched, 355 nm laser and a Myachi Unitek 200 W single mode pulsed fiber laser with active water cooling. Select fabricated structures are then tested to validate the finite element models.