Conical Distribution Research Articles

Dynamic gas emission during coal seam drilling under the thermo-hydro-mechanical coupling effect: A theoretical model and numerical simulations

The potential risk of coal and gas outbursts has increased with the depth of coal mining, posing the threat of heavy casualties, vast economic losses, and harm to the ecological environment. Considering the limitations of existing coal and gas outburst prediction methods, novel indicators or methods are needed. In this study, a fully coupled dynamic drilling gas emission THM model of gas diffusion, seepage, and flow is established, and the reliability of the model was verified by the measured data. The validated model was applied to single-factor and multi-factor impact analysis of dynamic drilling gas emission. The simulation results showed that (1) During the drilling process, the increase in permeability is mainly attributed to the coal seam damage and disturbance caused by the borehole and the coupling effects of the THM model, which increase the porosity around the borehole. Driven by the pressure gradient and temperature gradient, the gas pressure and temperature of the coal seam around the borehole show a conical distribution. (2) In the single-factor analysis, increasing the values of coal seam parameters (initial gas pressure, initial permeability, and initial coal temperature) and drilling parameters (borehole radius) will promote gas emissions in the drilling process to different degrees. The most significant promoting effect is the initial permeability, and the weakest is the initial coal temperature. (3) The response surface analysis results of the four factors show that the interaction between initial coal temperature C and borehole radius D is the least significant, and the interaction between initial gas pressure A and initial permeability B is the most significant. Meanwhile, the established multiple regression model characterizes the relationship between borehole gas emissions and initial coal seam gas pressure, and the idea of using drilling gas emission volume to predict coal and gas outbursts was proposed.

The simulation and analysis of the spraying status of large sprinkler machines loaded with atomizing micro-sprinklers

Due to the typically high flow rate of nozzles on large sprinkler machines, direct use for pesticide application can lead to pesticide waste and non-point source pollution. To fulfill the multifunctional needs of large sprinkler machines for irrigation, fertilization, and pesticide application, this study installed atomizing micro-sprinklers on the machines to enable their pesticide application capabilities. Based on the spraying patterns of the atomizing micro-sprinklers, three types were selected for this study: hollow cone, solid cone, and fan-shaped micro-sprinklers. Three working pressure levels were set at 0.2 MPa, 0.3 MPa, and 0.5 MPa, with the height of the micro-sprinklers above the ground set at three levels: 0.8 m, 1.2 m, and 1.5 m. A completely randomized design was used for the experiment, which included hydraulic performance tests and software simulation. The results indicated that the spray volume of the hollow cone, solid cone, and fan-shaped atomizing micro-sprinklers approximately presented a hollow conical, solid conical, and normal distribution, respectively. The spray intensity (average and maximum values) of the atomizing micro-sprinklers increased with the increase in pressure, while the median showed an initial increase followed by a decrease as pressure increased. Under the same pressure conditions, the spray intensity of the different atomizing micro-sprinklers decreased with the increase in height above the ground, while the spray width increased with height. By comparing the spraying characteristics of micro-sprinklers with various patterns, large sprinkler machines can select atomizing micro-sprinklers in different spraying statuses according to actual conditions and determine the optimal height of the atomizing micro-sprinklers above the ground to achieve efficient and uniform pesticide application effects. This reduces the evaporation and drift loss of liquid medicine. The research findings provide a scientific basis for achieving the pesticide application function of large sprinkler machines and expanding their usage capabilities.

Location method of ill-conditioned microseismic source and its engineering application

Microseismic event location is one of the core parameters in microseismic monitoring, and the accuracy of localization will directly affect the effectiveness of engineering applications. However, limited by spatial factors, the geometry of the sensor installation will be close to linear, which makes the localization equation suffer from the pathological problem, and the localization accuracy is greatly reduced. To address this problem, the reasons for the pathological problem are analyzed from the perspective of the objective function residuals and coefficient matrix. The pathological problem is caused by the combined effect of the poorer sensor array and data errors, and its residual isosurface shows a conical distribution, and as the residual value decreases, the apex of the isosurface gradually extends to the far side, and the localization results do not converge. For this reason, an improved regularized Newton downhill localization algorithm is proposed. In this method, firstly, the Newtonian downhill method is improved so that the magnitudes of the seismic source parameters are the same, and the condition number of the coefficient matrix is reduced; then, the L-curve method is used to calculate the regularization factor for the pathological equations, and the coefficient matrix is improved; finally, the pathological equations are regularized, and the seismic source coordinates are obtained by the improved Newtonian downhill method. The results of engineering applications show that compared with the traditional algorithm based on automatic of P-arrival picking, the number of effective microseismic events calculated by the proposed localization algorithm is increased by 194.7 %, and the localization accuracy is substantially improved. The proposed algorithm reduces the problem of low accuracy of S-arrival picking and allows localization using only P-wave arrival. The method reduces the quality requirements of the data and significantly improves the utilization of microseismic events and positioning accuracy.

Modeling Ion Conic Formation in Io's Auroral Footprint

AbstractEnergetic ions outflowing from Jupiter's atmosphere was observed during Juno's 12th perijove crossing (PJ12) in the vicinity of Io's auroral footprint and reported by prior studies. It was hypothesized that Wave‐Particle Interactions (WPI) with ion cyclotron waves observed coincident with the ion outflow may be responsible for the heating and subsequent outflow. This study uses numerical simulation and data model comparison to test whether ion cyclotron resonant heating is indeed a plausible mechanism to explain the intense ion outflow observed. Our simulations assume that the wave heating is of limited duration due to Io's footprint motion. The simulations are moreover compared to the previously published Jupiter Energetic Particle Detector Instruments (JEDI) observations at high energies, and the lower energy Jovian Auroral Distributions Experiment (JADE) observations that were not previously reported. We find that the ion cyclotron resonant heating mechanism can indeed lead to ion conic formation and strong vertical transport under certain assumptions about the distribution of wave power with altitude. We also find that the ion outflow is energized quickly with very rapid formation of the ion conic distribution. The implications of the intense ion outflow are also examined and it is found that such strong wave heating can lead to a depletion of the topside ionosphere.

Three-dimensional transient heat transfer analysis of micro-plasma arc welding process using volumetric heat source models

Abstract The micro plasma arc welding process is associated with different physical phenomena simultaneously. This results in complexities to comprehend the actual mechanism involved during the process. Therefore, a robust numerical model that can compute the weld pool shape, temperature distribution, and thermal history needs to be addressed. Unlike, other arc welding processes, the micro plasma arc welding process utilizes thin sheets of thickness between 0.5 and 2 mm. However, joining thin sheets using a high-density arc welding process quickens the welding defects such as burn-through, thermal stresses, and welding-induced distortions. The incorporation of a surface heat source model for computational modeling of the high energy density welding process impedes heat transfer analysis. In that respect, researchers have developed numerous volumetric heat source models to examine the welding process holistically. Although, selecting volumetric heat source models for miniature welding is a significant task. The present work emphasis developing a rigorous yet efficient model to evaluate weld pool shape, temperature distribution, and thermal history of plasma arc welded Ti6Al4V sheets. The computational modeling is performed using a commercially available COMSOL Multiphysics 5.4 package with a finite element approach. Two different prominent thermal models, namely, Parabolic Gaussian and Conical power energy distribution models are used. A comparative analysis is carried out to determine the most suitable heat source model for evaluating temperature distribution, peak temperature, and thermal history. The analysis is done by juxtaposing the simulated half-cross-section weld macrographs with the published experimental results from independent literature. The numerical results showed that the proximity of top bead width magnitude was obtained using the Parabolic Gaussian heat source model for low heat input magnitude of 47.52 and high heat input magnitude of 65.47 J·mm−1, respectively. In terms of percentage error, the maximum top bead width percentage error for the Parabolic heat source model is 13.26%. However, the maximum top bead width percentage error for the Conical heat source model is 18.36%. Likewise, the maximum bottom bead width percentage error for the Parabolic heat source model and the Conical heat source model is 12.3 and 25.8%, respectively. Overall, it was observed that the Parabolic heat source model produces the least deviating outcomes when compared with the Conical distribution. It was assessed that the Parabolic Gaussian heat source model can be a viable heat source model for numerically evaluating micro-plasma arc welded Ti6Al4V alloy of thin sheets.

Dynamic Characteristics of Rock Holes with Gravel Sediment Drilled by Bit Anchor Cable Drilling

Gravel and sediment frequently build up in holes during the anchor cable installation process, which makes it harder to install the anchor cable and causes reinforcement to fail, which can lead to accidents. In this paper, a bit anchor setup approach is proposed to set up a drill bit at the front of the anchor cable to aid the anchor cable drilling. The feasibility of this approach is established with the aid of DEM-MBD joint simulation and proves the correctness of the simulation model. The major elements affecting drilling effectivity have been studied by the use of ‘check + simulation’. The effects exhibit that the axial velocity and working aperture are negatively correlated with the drilling resistance of the anchor cable; the feed price is positively related to the anchor cable drilling resistance; with the increase in anchor cable pitch, the drilling resistance of the anchor cable changes into a hump shape. When the bit is 0.2 m from the backside of the hole, the particle pace vector at the decrease stop of the bit gives a conical distribution. This paper is of fantastic magnitude in relation to the environment-friendly setup of anchor cables and protection against disasters.

Energetic proton acceleration by EMIC waves in Io’s footprint tail

In this study, we present a survey of energetic proton observations associated with Io’s footprint tail (FPT) and compare their signatures with in situ measurements of the plasma waves and lower-energy electron environments. We find further supporting evidence that proton acceleration in Io’s FPT is likely a consequence of wave–particle interactions via electromagnetic ion cyclotron waves that are generated by precipitating electrons into Jupiter’s ionosphere. This idea was originally proposed by Clark et al. (2020) and Sulaiman et al. (2020) based on NASA’s Juno mission likely transiting Io’s Main Alfvén Wing (MAW) during its twelfth orbit (i.e., PJ12). Additionally, the analysis of > 50 keV protons presented here highlights important observational details about the Io–Jupiter interaction as follows: 1) proton acceleration in Io’s FPT is a persistent feature and the energy flux carried by the protons is highest at smaller Io-Alfvén tail distances; 2) energetic protons exhibit positive correlations with both plasma waves and <100 keV/Q electrons; 3) during a small number of Io FPT crossings, the protons display finer spatial/temporal structure reminiscent of the electron observations reported by Szalay et al. (2018); and 4) the proton pitch angle distributions are characterized by two types: conic distributions in or near Io’s MAW and isotropic elsewhere.

Conical liquid sheet morphology and 3D droplet distribution of aviation kerosene pressure-swirl spray with digital off-axis holography

In this study, the test performance of high-resolution digital off-axis holography for the non-spherical droplet characteristics and spatial distribution in the primary breakup region of a pressure-swirl nozzle were experimentally investigated, with spatial resolution of 4.5μm and 3.0μm. The field of interest (FOI) was restricted within 9 mm downstream of the nozzle outlet, where the primary and some secondary breakup processes take place. The liquid investigated here is RP-3 kerosene, and the injection pressure and liquid temperature were controlled in the range of 0.5 ∼ 1.0 MPa and 250 ∼ 291 K separately. Clear spray morphology and deformed droplet image were obtained through the holographic reconstruction process. Droplet extraction criteria were proposed to distinguish deformed droplets from ligaments. The overall drop size and ellipticity distribution were quantified and discussed. The results show that the overall drop size distributions near the nozzle are also typical single-peaked curves. The proportions of non-spherical droplet increase as the fuel pressure and temperature increase. The spatial Sauter mean diameter (SMD) distributions of spray at different positions downstream of the nozzle were calculated, with the grid size of 1 × 1 × 1 mm3, showing the doughnut-like annular SMD and droplet number distribution profiles of the hollow conical spray. As the temperature and fuel pressure decrease, SMD distribution becomes uneven and larger. Fine droplets exist in the region where the perforation and primary breakup process occur, and the SMD increases over the axial distance due to the breakup process of ligaments near the nozzle. Results also prove that digital off-axis holography presented here is expected to realize the 3D viewing of the conical liquid sheet and statistical quantification of the droplet where primary and secondary breakup processes mainly occurred.

Optimisation of the bottom blowing process for a 200 t converter

ABSTRACT In the converter steelmaking process, bottom blowing stirring is essential for the molten pool mixing effect of the top-bottom combined blown converter. In this study, ANSYS FLUENT19.3 commercial software is used to investigate the effect of bottom blow nozzle flow and arrangement on kinetic conditions of the converter by coupling the volume of fluid and discrete particle models. Gas is injected into the molten pool from the bottom blow nozzle, forming an inverted conical velocity distribution. As the bottom blowing intensity increases from 0.04 to 0.15 Nm3 t–1·min–1. The mixing time and dead zone ratio are reduced accordingly; the minimum mixing time is 48.4 s, and the minimum dead zone area ratio is 24.43%. The converter achieves good fluidity when the bottom nozzle is arranged at Case A. The simulation results are verified by a water model experiment with a 1:8 ratio of the model and prototype converters.

Investigation of a new modulated aperture using speckle techniques

BackgroundA design of equally spaced eight-circles placed at equal distances from the origin is suggested. Three models corresponding to the eight-circle design considering conic, linear, and quadratic distributions are investigated. This arrangement is considered for the sake of improving both microscope resolution and image contrast as compared with the pure annular aperture. This design is different compared with other recent work on aperture modulation.Results and discussionsThe point spread function (PSF) is computed in all the models using the fast Fourier transform (FFT) algorithm that computes the discrete Fourier transform (DFT) corresponding to the models and compared with the corresponding PSF in the case of uniform circular aperture. In addition, the autocorrelation images for the apertures are shown differently. It is shown smooth pattern for the circular arrangement as compared with the deformation and shrinking appeared in the central peak in case of conic model. Finally, the speckle images corresponding to the considered apertures are investigated. Reconstructed apertures are obtained from the speckle images using the FFT algorithm.ConclusionsThe PSF is computed for the described models, and the autocorrelation corresponding to the apertures showed difference. The reconstructed apertures from the speckle images can be improved using filtering techniques. It is noted that MATLAB codes are constructed in the computations of all images and plots.

Commissioning a multileaf collimator virtual cone for the stereotactic radiosurgery of trigeminal neuralgia.

A multileaf collimator (MLC), virtual‐cone treatment technique has been commissioned for trigeminal neuralgia (TGN) at Tri‐Cities Cancer Center (TCCC). This novel technique was initially developed at the University of Alabama in Birmingham (UAB); it is designed to produce a spherical dose profile similar to a fixed, 5‐mm conical collimator distribution. Treatment is delivered with a 10‐MV flattening‐filter‐free (FFF) beam using a high‐definition MLC on a Varian Edge linear accelerator. Absolute dose output and profile measurements were performed in a 20 × 20 × 14 cm3 solid‐water phantom using an Exradin W2 scintillation detector and Gafchromic EBT3 film. Dose output constancy for the virtual cone was evaluated over 6 months using an Exradin A11 parallel plate chamber. The photo‐neutron dose generated by these treatments was assessed at distances of 50 and 100 cm from isocenter using a Ludlum Model 30–7 Series Neutron Meter. TGN treatments at TCCC have been previously delivered at 6‐MV FFF using a 5‐mm stereotactic cone. To assess the dosimetric impact of using a virtual cone, eight patients previously treated for TGN with a 5‐mm cone were re‐planned using a virtual cone. Seven patients have now been treated for TGN using a virtual cone at TCCC. Patient‐specific quality assurance was performed for each patient using Gafchromic EBT‐XD film inside a Standard Imaging Stereotactic Dose Verification Phantom. The commissioning results demonstrate that the virtual‐cone dosimetry, first described at UAB, is reproducible on a second Edge linear accelerator at an independent clinical site. The virtual cone is a credible alternative to a physical, stereotactic cone for the treatment of TGN at TCCC.

AGN orientation through the spectroscopic correlations and model of dusty cone shell

ABSTRACT The differences between Narrow Line Seyfert 1 galaxies (NLS1s) and Broad Line AGNs (BLAGNs) are not completely understood; it is thought that they may have different inclinations and/or physical characteristics. The FWHM(H β)–luminosities correlations are found for NLS1s and their origin is the matter of debate. Here we investigated the spectroscopic parameters and their correlations considering a dusty, cone model of AGN. We apply a simple conical dust distribution (spreading out of broad line region, BLR), assuming that the observed surface of the model is in a good correlation with MIR emission. The dusty cone model in combination with a BLR provides the possibility to estimate luminosity dependence on the cone inclination. The FWHM(H β)–luminosities correlations obtained from model in comparison with observational data show similarities which may indicate the influence of AGN inclination and structure to this correlation. An alternative explanation for FWHM(H β)–luminosities correlations is the selection effect by the black hole mass. These FWHM(H β)–luminosities correlations may be related to the starburst in AGNs, as well. The distinction between spectral properties of the NLS1s and BLAGNs could be caused by multiple effects: beside physical differences between NLS1s and BLAGNs (NLS1s have lighter black hole mass than BLAGNs), inclination of the conical AGN geometry may have important role as well, where NLS1s may be seen in lower inclination angles.

Characteristics of Suprathermal Electrons in Small-Scale Magnetic Flux Ropes and Their Implications on the Magnetic Connection to the Sun

Small-scale magnetic flux ropes (SMFRs) are observed more frequently than larger-scale magnetic flux ropes (e.g., magnetic clouds) in interplanetary space. We selected 235 SMFRs by applying cylindrical linear force-free fitting to 20-year observations of the Wind satellite, which meets the criteria of low beta, low temperature, an enhanced magnetic field, and a rotation feature. By examining the pitch angle distribution of suprathermal electrons for these events, we found that approximately 45.1% of the SMFRs were accompanied by unidirectional beams (strahl). A much smaller percentage of SMFRs (∼10.7%) were associated with bidirectional beams. We also found a small percentage (∼7.2%) of (sunward) conic distributions during SMFR events. Last, the remaining ∼37.0% of SMFRs were associated with complex electron distributions. The unidirectional beams and most of the conics (together corresponding to ∼50% of the total 235 SMFRs) imply open-field SMFRs with only one end connected to the Sun. For ∼37.7% of the unidirectional beam SMFRs, the local IMF field polarity was orthogonal or inverted (possibly due to interchange reconnection). Based on the solar wind conditions around the bidirectional beams, we suggest that more than half of the bidirectional beams were not necessarily closed-field-line SMFRs.

All-optical shaping non-conventional beams based on spatial cross-phase modulation

All-optical shaping non-conventional beams are demonstrated experimentally by means of spatial cross-phase modulation in the solution of azo-containing material. We report here that an annular beam is able to be generated and manipulated through a light-control-light system, including a focused controlling beam and a parallel controlled beam. As the intensity of controlling light is enhanced above the threshold, the circular dark core turns to a triangular shape gradually. The formation of the polygonal dark core is mainly attributed to the nonaxis-symmetrical thermal convection in the solution sample induced by the heat of controlling light, which breaks the symmetry in vertical direction of the refractive index distribution. In addition, when the controlled light is convergent, a series of concentric rings instead of annular beam is obtained. The formation of two kinds of non-conventional beams is discussed in terms of the conical distribution of the changed reflective index. This all-optical beam shaping reveals potential applications in optical limiting, all-optical modulation, optical trapping, etc.

Wood screw design: influence of thread parameters on the withdrawal capacity

Self-tapping wood screws are important fasteners in timber construction. A characteristic of these screws is their high axial load-bearing capacity, which also depends on their withdrawal capacity. This is used for structural design and is thus an important optimization parameter for wood screws. To increase the withdrawal capacity, knowledge of the influence of the thread parameters, such as outer diameter, pitch or flank angle, is required. The influences of pitch and flank angle on the withdrawal capacity have not yet been sufficiently subjected to research and are therefore investigated in this study. A total of ten specially developed screw prototypes with pitches in the range of 3.04 mm and 5.9 mm and flank angles in the range of 35° and 45° are used. The screw prototypes are flat ribbed bars with uncoiled screw thread. The effect on the withdrawal capacity is measured using an experimental setup based on test standard EN 1382:2016. The pitch showed a significant influence (p = 0.000, f = 0.37) whereas the influence of flank angle was not significant (p = 0.283). A smaller pitch leads to a higher withdrawal capacity, irrespective of the flank angle. The experimental results are explained based on the theoretical models of bonding mechanisms and conical stress distribution. To optimize the withdrawal capacity of a ø 8 mm screw, a smaller pitch is preferable. The determined influence of the pitch can also be used to improve the accuracies of calculation models for the withdrawal capacity.

A high numerical aperture terahertz all-silicon metalens with sub-diffraction focus and long depth of focus

A high numerical aperture (NA = 0.92) square all-silicon metalens is designed for a wavelength of λ= 0.11883 mm with a focal length of 16.8λ and a side length of 104.4λ. Based on the waveguide effect, anisotropic rectangular silicon pillars with different dimensions are arranged on the silicon substrate according to the conical phase distribution, and then the rotation angle of each rectangular pillar is adjusted to realize the polarization conversion. Furthermore, a polarization-independent square antireflection silicon pillar array is proposed to be patterned at the other side of the substrate. The metalens can efficiently convert the normally incident x- (or y-) polarized plane wave into the radially (or azimuthally) polarized beam and conduct the sub-diffraction tight-focusing simultaneously, thus the shape of the focus can be flexibly switched. The numerical simulation results show that, under high-NA conditions, our metalens can obtain a tighter focus compared with linearly polarized metalens and a longer depth of focus (DOF) compared with metalens based on the hyperboloidal phase distribution. Under x- (or y-) polarized plane wave incidence, a circular-spot-shaped (or doughnut-shaped) focus with a full width at half maximum of 0.4λ (or 0.3λ) is obtained and the DOF is 26.509λ (or 18.935λ). In addition, under x-polarized beam incidence, the influence of the incident beam intensity distribution on the focusing results is also discussed. The use of a single material makes our metalens more favorable in fabrication and it is expected that our study is of great significance for applying terahertz wave in imaging and communication systems, high-resolution microscopy, optical coherence tomography and manipulation of particles.

Identification of independent modes in two inputs free space communications system

The study proves the concept of using a system with two inputs laser-beam, modulated independently by helical and conical phase distributions followed by their superposition in the same physical path for free space optical communications. Both phase distributions generate annular intensities with specific geometry according to the modulating parameters. The modes are multiplexed in an emission unit and propagate via laboratory free space as rings with optimized radii, without interfering, to the reading phase mask of the receiving unit. The reading mask acts as matching filter which embeds planar phase information such that to distribute the helical and conical components on mutual perpendicular directions. Identification occurs when the parameters of the reading mask match those of the input modes as predicted by a 2-dim inner product model developed here and confirmed experimentally by the occurrence of maximum intensities in the specific centers. Splitting the matrix-like diffracted beam in enabler and processing branches allows to double check and to identify the matching cases by the properties of the associated histogram without affecting subsequent signal retrieval. Crosstalk levels are examined.

Estimación de la conicidad de los conductos radiculares de primeros molares inferiores primarios utilizando Nano tomografía computarizada (Nano-CT): Estudio in vitro

Objetivo: Estimar la conicidad de conductos radiculares de primeros molares inferiores primarios por medio de Nano tomografía computarizada (Nano-CT).Material y Métodos: La muestra consistió en 10 dientes molares inferiores primarios. Los dientes fueron escaneados por medio de Nano-CT y las imágenes resultantes fueron analizadas con el software On-Demand 3D, considerando entre la evaluación las características anatómicas: la dimensión de los conductos radiculares y área de superficie de los mismos en toda la longitud radicular. Para la medida del mayor y menor diámetro de los conductos radiculares los test estadísticos fueron medidas de tendencia central, con un nivel de significancia de 5%. Resultados: En la raíz distal, mesio vestibular y mesio lingual la dimensión del conducto radicular con mayor promedio de la región cervical (D0) fue de 1.30, 1.00, 1.08 mm, respectivamente. El diámetro a la longitud más profunda (D11) para los mismos conductos fue de 0.29, 0.22, 0.18 mm. Mientras, la medida del área de superficie radicular distal, mesio vestibular y mesio lingual en la línea cervical (D0) fue de 1.43, 0.87, 1.01 mm. El área a la longitud más profunda (D11) fue de 0.09, 0.04, 0.03 mm. Conclusiones: La morfología de las raíces y de los conductos radiculares de primeros molares primarios presentaron una distribución cónica siendo sus diámetros y áreas mayor en la región cervical y disminuyen en la región apical.

Conical versus Gaussian terahertz emission from two-color laser-induced air plasma filaments.

In this Letter, we demonstrate that the far-field terahertz (THz) beam generated from a Ti:Sapphire two-color laser-induced filament can exhibit a conical or Gaussian distribution, depending on the filtering experimental conditions. Using both an incoherent Golay cell detector and a two-dimensional coherent electro-optic detection covering the 0.2-2.6 THz spectral range, in our experimental conditions, we provide evidence that the conical emission is due to photo-induced carriers in the silicon filter, typically used to block the remaining pump laser light. Moreover, the low-frequency THz beam retrieves an almost $ {{\rm TEM}_{00}} $TEM00 Gaussian spatial distribution when the silicon filter is preceded by a large bandgap ceramic filter, which stops the pump beam, thus preventing the carrier generation in the silicon filter.

Finite Element Simulation of Residual Stress Induced by High Energy Beam Welding in Dual Phase Steel

In this study, the residual stresses that arise during the high energy beam welding of dual phase steels were investigated using a sequentially coupled 3D finite element model. To accurately predict the sharp temperature gradients across the different weld zones, a moving volumetric heat source model, combining a spherical and a conical thermal flux distribution was developed. The temperature profiles computed with this heat source model were found to be in excellent agreement with the measured temperatures. Additionally, the simulated weld geometry was compared to the optical micrographs of the weld cross section to validate the heat source model parameters. The time-temperature history recorded at each node of the FE mesh served as input for the metallurgical and mechanical analyses, where the kinetics of phase transformations, the volumetric dilatations and thereby, the residual stresses in the weld joint were calculated. A metallurgical framework that includes the effect of volumetric strains occurring due to the phase transformations on the residual stresses was presented. The results show that the solid-solid phase transition occurring during cooling in a weld procedure can have a large influence on the magnitude of the residual stress. Furthermore, a comparison of the predicted welding residual stresses with the experimental drill-hole test results in both the weld seam and the base material was also reported.