Beam Deviation Research Articles

Experimental and numerical study of dissimilar fiber laser welding of martensitic AISI 1060 carbon steel with different configuration with austenitic 304 and ferritic 420 stainless steel

Welding with fiber laser for two distinct stainless steel types was performed to join with the martensitic carbon steel (AISI 1060) in order to assess the effect of laser welding operating parameters for two dissimilar materials on the weld characterization thorough experimental design method and numerical investigation. A full central composite design (CCD) matrix in accordance with the response surface methodology (RSM) was developed to represent the responses variations by equations including quadratic and nonlinear interaction terms. Different laser welding parameters were taken into account, such as laser power, linear speed of welding, focal distance of the beam, and beam deviation. The responses considered were the temperature field next to the melt pool border line, the maximum penetration depth of the fusion zone and the ultimate tensile strength of the dissimilar weld joint. Additionally, the variation of the microstructure fusion zone and adjacent areas and failure mechanism of the weld joint were evaluated. The experimental results indicate that the temperature field measured at the vicinity of the melt pool fusion line with both 304 and 420 stainless steel which primarily influenced by the incident power of the laser and linear velocity of beam, respectively. Additionally, the numerical simulation results are in good agreement with temperature experimental results at vicinity of fusion line where the temperature measured, experimentally. Apart from this, at the center of the fusion zone, the temperature clearly predicts via numerical simulation results which is not possible to assess experimentally. A clear comparison between the temperature distribution with different joint configuration illustrates that distinct relation between the temperature variation rate and different thermal conductivity coefficient of AISI 1060 with different AISI 304 and 420 joint configuration resulted different temperature distribution. The weld joint microstructure for 420 stainless steel–AISI 1060 steel joint at fusion boundary zone consists of columnar dendrites and skeletal columnar ferrite. At the center of fusion zone, a cellular-type structure is seen. For 304 stainless steel joint, the fusion zone has composed of a remarkable part of skeletal delta-ferrite and dendritic microstructure at austenite matrix microstructure. The fracture section of 304 steel has a ductile fracture and the depth of fracture dimples and cavities toward 304 stainless steel are higher than AISI 1060 steel.

Beam Local Stress Prediction Model for Incremental Launching Construction Based on SSA-SVR Algorithm

In the multi-point incremental launching construction process, without setting temporary piers at the mid-span, it is difficult to ensure the synchronization of the launching equipment at the same pier, which can easily cause the beam to deviate from the design axis, leading to changes in the stress of the beam. Calculating the local maximum stress of the beam when lateral deviation occurs is beneficial for establishing a reasonable and reliable threshold for controlling beam deviations. To address this issue, this paper utilizes a finite element model of the bridge under typical adverse conditions, simulating the lateral deviation and asynchronous jacking of the beam to explore stress variation patterns. The results show that the beam stress increases as the lateral deviation and jacking differences increase, severely affecting the structural safety. To overcome the inefficiency of the finite element modeling method when dealing with multiple working conditions and to establish a reasonable deviation control threshold, this study proposes a beam local stress prediction model under the combined influence of lateral deviation and jacking height differences based on the SSA-SVR algorithm. The model calculates the local maximum stress of the beam for 2500 sets of parameters. An engineering case analysis shows that the prediction model has high calculation accuracy, reliable results, fast computational speed, and high efficiency. Based on the stress prediction results, it is recommended to set the jacking height difference control threshold at 20 mm. When the jacking height difference is less than 20 mm, the local maximum stress value under the combined influence of both parameters should be less than the standard limit. The corresponding lateral deviation control threshold can be dynamically adjusted according to the actual travel difference recorded by the jacking equipment, with the control precision improved to 1 mm.

Temperature impact on acoustic wave reflection in quasi-collinear acousto-optic devices.

Quasi-collinear geometry is a special configuration of acousto-optic (AO) diffraction that applies the acoustic wave reflection from the AO cell input optical face and provides an extremely large interaction length for achieving abnormally high spectral resolution of AO tunable filters. As a result, it becomes possible to implement the multifrequency diffraction which has found important applications for laser pulse shaping. The operation of quasi-collinear AO devices in the multifrequency diffraction regimen is accompanied by the appearance of the longitudinal and transverse temperature gradients in the crystal, mainly due to the acoustic power absorption. Temperature changes the AO cell material stiffness moduli, affecting the characteristics of the incident and reflected acoustic waves (propagation velocities and walk-off angles), and the reflection condition in general. On the example of paratellurite crystal is shown that the AO cell heating near the reflecting facet leads to a deviation of the reflected acoustic beam propagation direction from that specified during the AO cell manufacturing. The deviation magnitude depends on the reflection geometry choice and, in the paratellurite, may exceed several degrees, which adversely affects the AO diffraction characteristics, reducing the AO interaction efficiency and distorting the transmission function shape. The reflected beam deviation may be compensated by means of choosing the angle between the AO cell reflecting face and the piezoelectric transducer face, taking into account the operating AO device thermal regimen.

Exploring the Beam Squint Effects on Reflectarray Performance: A Comprehensive Analysis of the Specular and Scattered Reflection of the Unit Cell.

In this article, the phenomena of beam deviation in reflectarray is discussed. The radiation pattern of the unit cell, which plays a vital role in shaping the beam of the reflectarray, is analyzed by considering undesired specular and scattered reflections. These unwanted reflections adversely affect the pattern of the single unit cell, thereby reducing the overall performance of the reflectarray. To conduct our investigations, three cases of reflectarray-i.e., (i) a center-fed with broadside beam (Case-I), (ii) a center-fed with the beam at 30° (Case-II), and (iii) off-center-fed with the beam at 30° reciprocal to feed position with reference to the broadside direction (Case-III)-are simulated. Different degrees of beam deviation are analyzed in each reflectarray by assessing the radiation pattern of a single element. The simulation results shows that maximum of 0°, 3.4°, and 0.54° beam squint across the bandwidth found in Case-I, Case-II, and Case-III, respectively; this leads to aperture efficiencies of 31.2%, 11.9%, and 31.2%, respectively. The significance of specular reflections is further confirmed by half (left half and right half) aperture analysis of Case-II. This involves simulating the half-plane aperture illuminated by horn antenna, resulting in a distinct beam angle at the same frequency. However, deviations of -4.71 to +4.1 for the left half aperture and -1.82 to +1.1 for the right half aperture are noticed. Although the analysis specifically focuses on the three cases of the reflectarray, the proposed methodology is applicable to any type of reflectarray. The study presented in this work provides an important insight into the practical aspects of reflectarray operation, particularly in terms of quantifying undesirable effects that are normally overlooked in the design of this class of arrays. To achieve a good performance, a new design of the dielectric loaded horn feed is proposed. This design approach is both simple and applicable to any reflectarray, with the added benefit of maintaining a low profile for the RA. Moreover, this work holds significant potential for remote sensing satellite systems as beam deviation can adversely impact data collection accuracy and compromise observation precision, resulting in distorted images, reduced data quality, and overall hindrance to the system's performance in capturing reliable information.

Dynamical and kinematical X-ray diffraction in a bent crystal

Numerical modeling of kinematical and dynamical X-ray diffraction in a bent crystal was performed on the basis of two approaches to integrating the Takagi–Taupin equations, and using two-dimensional recurrence relations. Within the framework of kinematical diffraction, a new equation is obtained that describes the distribution of diffracted intensity inside a bent crystal. The time taken for numerical calculations based on this equation is significantly reduced in comparison with the use of algorithms of the dynamical diffraction theory. The simulation shows for the first time that, for strongly bent crystals, the maximum value of the diffraction intensity is formed inside the deformed structure and not on its surface. In the case of strong bending of the crystal structure, the deviation of the X-ray beam from the Bragg angle does not change the diffraction pattern but shifts it along the lateral direction. The results of calculations of diffraction in a strongly bent crystal based on the equations of dynamical and kinematical diffraction coincide, while the computations for weakly bent crystals differ. The possibility of estimating the primary extinction length of a bent crystal as a function of the bending radius is shown. In the case of kinematical diffraction in bent crystalline microsystems, a new method has been developed to calculate X-ray reciprocal-space mapping.

Demonstration of Three-dimensional Spiral Injection for the J-PARC Muon g – 2/EDM Experiment

In the J-PARC Muon g-2/EDM experiment, to measure muon anomalous magnetic moment (g-2) and electrical dipole moment (EDM), it is necessary to accumulate 300MeV/c muon beams with a 66 cm diameter region with a 3 T solenoid-type magnetic field. A new three-dimensional spiral injection scheme has been invented to achieve this target. Since this is the first instance to employ this injection scheme, a scale-down experiment with an electron beam of 297 keV/c and storage beam diameter of 24 cm is established at KEK. A simplified storage beam monitor using scintillating fiber has been designed and fabricated to measure the stored beam. The 100 ns width pulsed beam is injected and the signal maintains a few microseconds by the stored beam observed. According to this result, the beam storage is confirmed. The recent result implies that the stored beam deviated from the design orbit and caused betatron oscillations. To measure the beam deviation quantitatively and tune the beam, the storage monitor has been updated. The data from this stored beam monitor are the primary data for considering the conceptual design of the beam monitor for the muon g-2/EDM experiment. This poster will discuss the measurement of beam storage by three-dimensional spiral injection and beam tuning using a scintillating fiber monitor.

Modelling Investigation of Atmospheric Turbulence-Induced Beam Deviation for LEO/GEO FSO Communication Link

The uplink analytical simulation scenario of atmospheric turbulence-induced beam deviation can give the insight needed to understand and create the mitigation techniques that could support novel applications in the fields of free-space optical communications (FSOC) and the generation of laser guide stars. One of the significant challenges that causes wandering and fading of the beam from the receiver aperture is beam deviation. In this study, two uplink numerical modelling scenarios for low-earth orbit (LEO) and geostationary (GEO) satellites will be investigated and discussed. The work seeks to visualize the effective parameters and analytically simulate atmospheric optical propagation, especially for the wandering effect, which can give concrete milestones for developing a new scientific investigation era and deeper insight into the system’s theoretical demonstration of free-space optical communications.

Kinematically excited beam vibrations under random perturbations

There is numerous information in the technical and scientific literature that often the sources of forced kinematically excited oscillations have a clearly expressed random nature. Kinematically excited vibrations of beams are considered. Their sources are random disturbances. Steady (in a probabilistic sense) vibrations of beams are studied. As a consequence, the transverse vibrations of the beam will also be random, and it becomes necessary and expedient to switch to stochastic motion models.
 Introduction. For a random perturbation process, a spectral matrix is specified. Initial conditions for the equations are not required. The boundary conditions are similar to those used for free and kinematically excited deterministic oscillations. The task is to find the spectral matrix of the random field of beam deviations and dispersion for a given spectral matrix. The question of determining the mathematical expectation is not raised. It is argued that it can be easily reduced to known deterministic problems.
 Methods. To carry out specific calculations, a model of kinematic disturbances is used in the form of a vector N-dimensional stationary random process with stationary connected components that have hidden periodicities (characteristic frequencies). A test example was completed to determine the dispersion and standard deviation of displacements. The numerical integration step was adopted after numerical experiments. When performing calculations, the parity of the integrand was taken into account. The lower limit of integration is taken to be zero, followed by doubling of the final result.
 Results. For small values of the broadband parameter, the results of the stochastic and deterministic problems differ little. Examples are presented that are stochastic analogs of harmonic oscillations. For beams under kinematic harmonic disturbances, test examples were performed to determine dispersions and standard deviations.
 The discussion of the results. The results of calculations in the article are presented by curves having numbers that coincide with the numbers of the matrices. The first matrix corresponds to the absolute correlation of disturbances. The second matrix corresponds to the absolute correlation between the first and third, second and fourth disturbances, while these pairs are absolutely uncorrelated. The third matrix describes random perturbations when the indicated pairs, being perfectly positively correlated within, are absolutely perfectly negatively correlated between pairs. The fourth curve corresponds to the case of ideal correlation of the first three disturbances with each other, while the movements of the fourth support are in antiphase with them. In the latter case, the movements of the outer supports are in antiphase with the movements of the middle ones, which favors the greatest bending of the beam. Therefore, the elastic line has a curvature that is significantly greater than the others.

A dynamic goniometer-spectrometer with angle-to-time conversion

We present a dynamic goniometer–spectrometer for measuring the refractive index (RI) of transparent triangular prisms by converting the beam deviation angles into time intervals. The proposed measuring scheme allows the automatic determination of the RI simultaneously for several different wavelengths by measuring the time intervals between the moments of autocollimation of the reference and refracted rays reflected from a mirror continuously rotating around the object with constant angular speed. This makes it possible to avoid the use of an expensive ring laser or encoder for angle measurements and to use relatively inexpensive instruments for time measurements, which reduces the cost of measuring equipment. To calculate the RI value, we used the minimum deviation technique. A functional diagram of the measuring equipment is given. A reference prism made of NBK-7 Schott optical glass was experimentally studied and the measurement errors were estimated. The proposed measuring scheme can be used for automated RI measurement and to study the dispersion characteristics of triangular prisms made of optically transparent materials and liquid optically transparent substances filling a hollow triangular prism.

Direction-of-Arrival Estimation of Bottom-Mounted Horizontal Linear Array Based on the Weighted Phase Velocity

The direction-of-arrival (DOA) estimation of an underwater bottom-mounted horizontal linear array (HLA) based on weighted phase velocity has been proposed in this paper. The directional response is mainly affected by differences in the modal phase velocities and the sound speed of the water column. Based on the mode theory, the acoustic intensity distribution characteristics and beam deviation were analyzed. The beamforming result obtained provides a distinguishing feature of bearing deviation when the measured sound speed was used. By applying the modal weighted phase velocity instead, source bearing can be well estimated. Particularly, in the presence of a thermocline, the propagating modes can be selected on the basis of the mode trapping theory. Both surface and submerged sources were taken into account based on the experimental data, and the deviation was well explained and reduced. For a source near the end-fire direction, the bearing estimation error was reduced from several degrees to tenths of degrees.

Segmented Four-Element Photodiodes in a Three-Dimensional Laser Beam Angle Measurement

Based on the registration of two laser beam projections, a method for measuring the angular deviation of a laser beam from its initial position in three-dimensional space is proposed and experimentally demonstrated. The laser ray is directed into the beam-splitting cube, which distributes the ray into two mutually orthogonal parts, on the path of which, two four-segment photodiodes are located at different distances from the beam-splitting cube. The value of the angular deviation from a certain initial position of the laser beam in three-dimensional space is obtained after the mathematical processing of the measured position of the laser beam projections’ centers in the photodiodes coordinates systems. The innovation of this method is that the resulting angular deviation of the laser beam is in three-dimensional space due to the registration of a pair of projections. The experimental results also demonstrate that the proposed method has a high speed-measuring potential and can be used for solving a wide range of problems.

How Relevant Is the Parallax Effect on Low Centered Pelvic Radiographs in Total Hip Arthroplasty.

The correct cup position in total hip arthroplasty (THA) is usually assessed on anteroposterior low centered pelvic radiographs, harboring the risk of misinterpretation due to projection of a three-dimensional geometry on a two-dimensional plane. In the current study, we evaluate the effect of this parallax effect on the cup inclination and anteversion in THA. In the course of a prospective clinical trial, 116 standardized low centered pelvic radiographs, as routinely obtained after THA, were evaluated regarding the impact of central beam deviation on the cup inclination and anteversion angles. Measurements of the horizontal and vertical beam offset with two different methods of parallax correction were compared with each other. Furthermore, the effect of parallax correction on the accuracy ofmeasuring the cup position was investigated. The mean difference between the two parallax correction methods was 0.2° ± 0.1° (from 0° to 0.4°) for the cup inclination and 0.1° ± 0.1° (from -0.1° to 0.2°) for the anteversion. For a typically intended cup position of a 45° inclination and 15° anteversion, the parallax effect led to a mean error of -1.5° ± 0.3° for the inclination and 0.6° ± 1.0° for the anteversion. Central beam deviation resulted in a projected higher cup inclination up to 3.7°, and this effect was more prominent in cups with higher anteversion. In contrast, the projected inclination decreased due to the parallax effect up to 3.2°, especially in cups with high inclination. The parallax effect on routinely obtained low centered pelvic radiographs is low and not clinically relevant due to the compensating effect of simultaneous medial and caudal central beam deviation.

Effect of the reflector system thermal behavior on the pointing accuracy of large radio telescopes

The thermal behavior of the reflector system under solar radiation has great effects on the pointing accuracy of large radio telescopes. To estimate the dynamic pointing error of large radio telescopes caused by the thermal behavior of the reflector system under solar radiation, the nonuniform temperature field and the thermal deformation of the Wuqing 70 m radio telescope (WRT70) on three specific sunny days are first simulated by finite-element (FE) software. Then the pose variations of the reflector system are calculated equivalently based on the FE thermal-structural coupling analysis of the reflector system. Finally, the dynamic pointing errors of the WRT70 on three specific sunny days, caused by the thermal behavior of the reflector system, are estimated according to the beam deviation factor. The research results show that the rotations of the main reflector and the offsets of the subreflector on sunny days have great influences on the pointing error of large radio telescopes. In addition, the pointing error caused by the rotations of the main reflector and the pointing error caused by the offsets of the subreflector cancel each other out, but the pointing error caused by the rotations of the main reflector plays a dominant role. Furthermore, the effect of the thermal behavior of the reflector system on the pointing accuracy of large radio telescopes is less than the influence of the thermal behavior of the alidade. These findings could provide valuable references for the compensation of dynamic pointing errors of large radio telescopes.

Accounting for speckle-scale beam bending in classical ray tracing schemes for propagating realistic pulses in indirect drive ignition conditions

We propose a semi-analytical modeling of smoothed laser beam deviation induced by plasma flows. Based on a Gaussian description of speckles, the model includes spatial, temporal, and polarization smoothing techniques, through fits coming from hydrodynamic simulations with a paraxial description of electromagnetic waves. This beam bending model is then incorporated into a ray tracing algorithm and carefully validated. When applied as a post-process to the propagation of the inner cone in a full-scale simulation of a National Ignition Facility (NIF) experiment, the beam bending along the path of the laser affects the refraction conditions inside the hohlraum and the energy deposition, and could explain some anomalous refraction measurements, namely, the so-called glint observed in some NIF experiments.

Three-Dimensional Method Combining Linearly Structured Light Sensing and Rotary Scanning for Measuring Aviation Bearings

The geometric parameters of aviation bearings need to be accurately measured to ensure that the bearings are correctly assembled for reliable operation and quality purposes. This study aimed to solve the problems presented by the low accuracy and low efficiency of the existing method while avoiding the error introduced by the deviation of the measurement beam from the center of the aviation bearings during measurement. This method determines the spatial posture of the axis of the rotary table using linear structured light sensing, and extracts the spatial point-cloud data of the aviation bearings based on rotary scanning. We propose algorithms for spatial property determination and point-cloud segmentation. To avoid the error caused by the deviation of the measurement beam from the center of the aviation bearings, the point-cloud data are transformed to a new coordinate system prior to extracting the features of the datum plane and raceway. An aviation bearing is measured to verify the validity of the proposed method. The radius and eccentricity of the raceway are 4.900 mm and 0.010 mm with experimental standard deviations of 0.002 mm and 0.001 mm, respectively. For comparison purposes, experiments with a coordinate measuring machine and contourgraph were also performed. The expanded measurement uncertainty considering the repeatability, reference instruments, and temperature drift is 1.6 μ m. The proposed method can be extended to precision noncontact measurements of workpieces with rotary structures.

Advances in the Technologies for Marine Salinity Measurement

As one of the most important physical parameters of seawater, salinity is essential to study climatological change, to trace seawater masses and to model ocean dynamics. The traditional way to conduct salinity measurement in hydrographical observation is to use a standard conductivity-temperature-depth (CTD) probe where the salinity determination is based on a measurement of electrical conductivity. This article describes some developments of recent years that could lead to a new generation of instruments for the determination of salinity in seawater. Salinity determination with optical salinity sensor based on the refractive index measurement have been extensively studied. Different ways to conduct refractive index measurements are summarized, including measurements based on beam deviation, light wave mode coupling and swelling of surface coating material, among which the optical fiber sensors are promising candidates for further commercialization. Complementary to the above-mentioned direct measurement salinity point sensors, seismic observation takes advantages of large scale multichannel seismic data to retrieve the ocean salinity with high lateral resolution of ∼10 m. This work provide comprehensive information in the techniques related to the marine salinity measurement.

Compensation for Beam Deviation from a Specified Direction Based on Atmospheric Backscattering

Compensation for Beam Deviation from a Specified Direction Based on Atmospheric Backscattering

Investigating the mechanical properties and fusion zone microstructure of dissimilar laser weld joint of duplex 2205 stainless steel and A516 carbon steel

Laser welding of dissimilar A516 low carbon steel and duplex stainless steel was conducted to evaluate the effect of fiber laser welding parameters (e.g., laser power, welding speed, nozzle distance and beam deviation) on the responses of tensile strength, depth of the melt pool, microstructure, temperature near the melt pool and melt pool hardness. The maximum tensile strength of 500 MPa and 18 percent elongation were obtained at the laser power of 400 W, welding speed of 300 mm/min and the focal point. The absorbed power of laser and linear speed of welding had the most notable impact on the tensile strength of the weld. The fusion zone microstructure was composed of a combination of ferrite–austenite distribution from duplex stainless steel (DSS) based on different cooling and heating cycles. During the nucleation process, ferrite grains were transformed to austenite grains from different areas of the fusion zone. Also, the weld fusion zone microstructure at A516 side was composed of fully martensitic structure, according to the higher heat input upper critical temperature of steel (AC3), thereby leading to rapid cooling. The EDS analysis also showed that the Fe percentage was continually reduced at the fusion line from A516 to DSS, although Ni and Cr were distributed at the fusion zone with some minor changes of weight percentage. Therefore, Cr and Ni had a crucial effect on elemental alloy composition in this laser welding process. The ductility of the A516 fracture surface with bigger and deeper fracture dimples was caused by applying higher laser energy density, which effectively improved the fracture ductility of the welded samples.

Reconfigurable dual‐beam leaky‐wave antenna based on spoof surface plasmon polariton

AbstractIn this paper, a reconfigurable leaky‐wave antenna (LWA) based on spoof surface plasmon polariton (SSPP) transmission line (TL) is proposed. Patches placed nearby the SSPP TL effectively convey the energy from the transmission mode to the radiation mode. SSPP units are loaded with variable capacitors, which enable the antenna to achieve free switching between fixed‐beam and beam scanning. When the antenna is working on a fixed beam in broadside, operating at 7.6–8.6 GHz, and the beam deviation is within ±1° by adjusting the capacitors. When the proposed antenna operates at fixed frequencies, up to 28° scanning range can be obtained with a stable gain. The antenna is fabricated and proved effective in the experiment. The proposed SSPP LWA provides a solution to narrow‐band and point‐to‐point communication systems.

Broadband Fixed-Beam Leaky-Wave Antenna With Consistent and High Gain Based on Ridge Gap Waveguide

In most communication scenarios, antennas are often required to achieve broadband and directional radiation, and beam squint with frequency is unfavorable for broadband signal transmission. The traditional leaky-wave antennas (LWAs) have beam squint with frequency. In this letter, an LWA with fixed beam direction in a broadband is designed with consistent gain over the band. A ridge gap waveguide (RGW) is adopted to construct a nondispersive structure, and one lateral side is connected to a parallel plate filled with dielectric slab. Thus, leakage radiation is produced at the interface between the RGW and the parallel plate, generating a beam with fixed direction and high gain. The novelty is that in theory the fixed beam can be realized in infinite band owing to the nondispersive waveguide. Finally, a broad band of up to 58% (from 22 to 40 GHz) is achieved due to the limitations of the stopband structure and feeding port. The measured beam is fixed at 41° over the whole band, with a slight beam deviation of 2.6°. The realized gain is consistent over the band with a peak gain of 19.3 dBi. The designing method provides a simple and efficient way to realize the broadband fixed-beam LWAs.