Zeitschriftenartikel: „Lobe diagrams“

1

Harrison, A. J. L., und T. R. A. Pearce. „Prediction of lobe growth and decay in centreless grinding based on geometric considerations“. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 216, Nr. 9 (01.09.2002): 1201–16. http://dx.doi.org/10.1243/095440502760291763.

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The growth and decay of lobes during centreless grinding have been studied by previous researchers using physical tests, time-domain simulation and identification of the roots of the Laplace transform of the characteristic equation. In this paper, the authors have extended these latter two methods to generate complete stability diagrams encompassing the entire practical range of machine set-up angles. These diagrams indicate that by varying the set-up angles in a prescribed manner during grinding, rapid rounding of arbitrarily lobed components can be achieved. This is verified via time-domain simulation. Secondly, a novel and arguably more intuitive method of predicting the lobe growth and decay during centreless grinding is presented. The method considers the locations of the three points of contact between a lobed workpiece and the regulating wheel, the support plate and the grinding wheel. Axial symmetry is assumed. A unique circle can be drawn through these three points. The centre and radius of this circle vary continually as the workpiece rotates, in a manner dependent upon the workpiece's profile and the set-up angles. An above-average instantaneous radius leads, via machine stiffness, to a correspondingly larger grinding force and so to an increased instantaneous depth of cut. If this occurs when the trough of a lobe is being ground, the trough will become deeper and lobe growth will result. By contrast, if the instantaneous radius is below average when the trough is being ground, the lobe will decay. From this simple geometric consideration, the authors have calculated the rates of decay and growth of a range of numbers of lobes, across a wide range of set-up angles. The results are shown to agree well with those given using the previous methods.

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Abele, E., und U. Fiedler. „Creating Stability Lobe Diagrams during Milling“. CIRP Annals 53, Nr. 1 (2004): 309–12. http://dx.doi.org/10.1016/s0007-8506(07)60704-5.

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3

Dhupia, Jaspreet S., Bartosz Powalka, A. Galip Ulsoy und Reuven Katz. „Effect of a Nonlinear Joint on the Dynamic Performance of a Machine Tool“. Journal of Manufacturing Science and Engineering 129, Nr. 5 (17.04.2007): 943–50. http://dx.doi.org/10.1115/1.2752830.

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This paper presents the effect of experimentally evaluated nonlinearities in a machine joint on the overall machine tool dynamic performance using frequency response functions and stability lobe diagrams. Typical machine joints are very stiff and have weak nonlinearities. The experimental evaluation of the nonlinear joint parameters of a commercial translational guide has been discussed in Dhupia et al., 2007, J. Vibr. Control, accepted. Those results are used in the current paper to represent the connection between the column and the spindle of an idealized column-spindle machine structure. The goal is to isolate and understand the effects of such joints on the machine tool dynamic performance. The nonlinear receptance coupling approach is used to evaluate the frequency response function, which is then used to evaluate the stability lobe diagrams for an idealized machine structure. Despite the weak nonlinearities in the joint, significant shifts in the natural frequency and amplitudes at resonance can be observed at different forcing amplitudes. These changes in the structural dynamics, in turn, can lead to significant changes in the location of chatter stability lobes with respect to spindle speed. These variations in frequency response function and stability lobe diagram of machine tools due to nonlinearities in the structure are qualitatively verified by conducting impact hammer tests at different force amplitudes on a machine tool.

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Hayati, Sajad, Mohammad Hajaliakbari, Yalda Rajabi und Sajad Rasaee. „Chatter reduction in slender boring bar via a tunable holder with variable mass and stiffness“. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, Nr. 12 (01.03.2017): 2098–108. http://dx.doi.org/10.1177/0954405417690554.

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In this study, a new strategy is presented to increase the machining stability due to chatter suppression for boring and turning machining processes. The proposed approach is based on varying the position of stability lobes via changing mechanical properties of the tool body such as the mass and stiffness. Because of the shape of stability lobe diagrams, having a tool with a tunable stability lobe diagram can be useful to alter an unstable condition to a stable condition. For this purpose, a structure for the tool body is designed that is consisted of a hollow body with a core as a tunable screw inside it. As the core gets in or out, it changes the mass and stiffness of the tool body that leads to change the position of stability lobe diagram. In order to study the effect of designed structure on stability, the structure is simulated using a validated finite element time domain model. The time domain simulation shows a considerable improvement in stability of process. The strategy is experimentally applied to the process via modulation of the tool structure in the machining process to validate the simulation results. The experimental results have a high coincidence with theory and show a good improvement in stability.

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Friedrich, Jens, Jonas Torzewski und Alexander Verl. „Online Learning of Stability Lobe Diagrams in Milling“. Procedia CIRP 67 (2018): 278–83. http://dx.doi.org/10.1016/j.procir.2017.12.213.

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6

Wiseman, Richard, und Adrian M. Owen. „Turning the Other Lobe: Directional Biases in Brain Diagrams“. i-Perception 8, Nr. 3 (18.05.2017): 204166951770776. http://dx.doi.org/10.1177/2041669517707769.

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Past research shows that in drawn or photographic portraits, people are significantly more likely to be posed facing to their right than their left. We examined whether the same type of bias exists among sagittal images of the human brain. An exhaustive search of Google images using the term ‘brain sagittal view’ yielded 425 images of a left or right facing brain. The direction of each image was coded and revealed that 80% of the brains were right-facing. This bias was present in images that did not contain any representation of a human head. It is argued that the effect might be aesthetic in nature, the result of the Western tradition of reading left to right or due to the facial factors that underlie the bias previously found in portraits.

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Zhao, D., und Q. Zhang. „Regenerative Chatter Stability and Hopf Bifurcation Analysis in Milling System“. Advanced Materials Research 739 (August 2013): 400–407. http://dx.doi.org/10.4028/www.scientific.net/amr.739.400.

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The shifted Chebyshev polynomials and Floquet theory are both adopted for the prediction regenerative chatter stability and Hopf bifurcation in milling. The influences of the system parameter on the stability of the milling system have been analyzed. The stability lobe diagrams are obtained. The result shows that the shifted Chebyshev polynomials method is more accurate than the semi-discretion scheme for spindle speed lower than 3500 round per minutes. The stability in milling can well be predicted by the cutting depth and feed rate lobes diagrams. Only Hopf bifurcations are detected by the Eigen-value analysis. The stable solution transform from the stable equilibrium point to the quasi-periodic oscillation after Hopf bifurcation.

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Friedrich, Jens, Christoph Hinze, Anton Renner, Alexander Verl und Armin Lechler. „Estimation of stability lobe diagrams in milling with continuous learning algorithms“. Robotics and Computer-Integrated Manufacturing 43 (Februar 2017): 124–34. http://dx.doi.org/10.1016/j.rcim.2015.10.003.

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9

Löser, Michael, und Knut Großmann. „Influence of Parameter Uncertainties on the Computation of Stability Lobe Diagrams“. Procedia CIRP 46 (2016): 460–63. http://dx.doi.org/10.1016/j.procir.2016.04.031.

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10

Tyler, Christopher T., John Troutman und Tony L. Schmitz. „Radial depth of cut stability lobe diagrams with process damping effects“. Precision Engineering 40 (April 2015): 318–24. http://dx.doi.org/10.1016/j.precisioneng.2014.11.004.

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11

Denkena, Berend, Benjamin Bergmann und Svenja Reimer. „Analysis of different machine learning algorithms to learn stability lobe diagrams“. Procedia CIRP 88 (2020): 282–87. http://dx.doi.org/10.1016/j.procir.2020.05.049.

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12

Quintana, Guillem, Joaquim Ciurana, Inés Ferrer und Ciro A. Rodríguez. „Sound mapping for identification of stability lobe diagrams in milling processes“. International Journal of Machine Tools and Manufacture 49, Nr. 3-4 (März 2009): 203–11. http://dx.doi.org/10.1016/j.ijmachtools.2008.11.008.

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13

Kapylov, E. L., V. V. Neyolov, A. A. Samorodov und B. A. Samorodov. „Evaluation of systematic error of measuring object scattering diagrams caused by quasimonostatic character of measurement scheme using irradiator’s assembly sets in anechoic chamber of collimator type“. Issues of radio electronics 49, Nr. 5 (05.07.2020): 17–27. http://dx.doi.org/10.21778/2218-5453-2020-5-17-27.

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The main factors causing the occurrence of systematic errors in measuring the backscatter patterns of targets when using irradiator assemblies in collimator type radar measuring complexes are considered. It is shown that the implementation of a quasimonostatic measurement scheme with a bistatic angle determined by spatial separation of the phase centers of irradiators assembly is the most significant factor in the experimental determination of the backscattering characteristics of reflectors with highlighted directed properties, to which the monostatic-bistatic equivalence theorem is not applicable. To quantify the influence of this factor, it is proposed to use indicators characterizing the decrease of the maximum and average recorded cross-section of trihedral corner reflectors within the main lobe of the backscatter diagram, determined by the half power level. The listed indicators do not take into account the non-flatness of the phase surface of the probe field, however, they can be considered as reasonably justified lower bounds for systematic measurement errors for each irradiators assembly. Using the mathematical modeling, mono- and bistatic cross-section diagrams of trihedral corner reflectors of various wave sizes with different face shapes were calculated, error estimation for their backscattering diagrams were determined using a set of irradiator assemblies. Ratios are obtained for estimating of width of the lobe of the bistatic scattering indicatrix at the level of –3 dB of trihedral corner reflectors with triangular, radial, and square face shapes, and a recommendation on the rational choice of the working frequency of the assembly when implementing large-scale electrodynamic modeling is made.

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Paliwal, Vineet, und N. Ramesh Babu. „Prediction of Stability Lobe Diagrams in High-Speed Milling by Operational Modal Analysis“. Procedia Manufacturing 48 (2020): 283–93. http://dx.doi.org/10.1016/j.promfg.2020.05.049.

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15

Zatarain, Mikel, Jorge Alvarez, Iñigo Bediaga, Jokin Munoa und Zoltan Dombovari. „Implicit subspace iteration as an efficient method to compute milling stability lobe diagrams“. International Journal of Advanced Manufacturing Technology 77, Nr. 1-4 (21.10.2014): 597–607. http://dx.doi.org/10.1007/s00170-014-6470-7.

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16

Et. al., Jeevan Raju B,. „Design and optimized analysis of high speed precise machine tool spindles“. Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, Nr. 2 (11.04.2021): 2965–77. http://dx.doi.org/10.17762/turcomat.v12i2.2336.

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Upcoming machine tools need to be extremely efficient systems to maintain the needed intellectual performance and stability. The spindle tool system is necessary to optimize which enhances the rigidity of the spindle and in turn produces the cutting stability with higher productivity. Prediction of the dynamic behavior at spindle tool tip is therefore an important criterion for assessing the machining stability of a machine tool at design stage. In this work, a realistic dynamic high-speed spindle /milling tool holder/ tool system model is elaborated on the basis of rotor dynamics predictions. The integrated spindle tool system in analyzed with the Timoshenko beam theory by including the effects of shear and rotary deformation effects. Using the frequency response at the tool tip the corresponding stability lobe diagrams are plotted for the vertical end mill system. Furthermore an optimization study is carried out at design stage for the bearing system and the rotor positions for maximizing the chatter vibration free cutting operation at the desired depth of cuts with precise rotational speeds.It is markedly found that the first mode of vibration had a large impact on the dynamic stability of the system. The parametric studies are conducted such as tool overhang and bearing span and the influence of these on the system dynamics are identified and the corresponding stability lobe diagrams are plotted. It is evidently found that the second mode of the frequency response has critically affected the bearing span and competing lobes are identified. These results are assisted to design a spindle bearing system at the desired machining conditions. A neural network based observer is designed based on the simulation resultsto predict optimum design parameter values.

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17

Liu, Hong, und Guo Zhu Zhao. „Two Methods to Test Transducer Array Directivity“. Advanced Materials Research 912-914 (April 2014): 1485–88. http://dx.doi.org/10.4028/www.scientific.net/amr.912-914.1485.

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An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

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Fukumoto, Shinji, Taiju Matsuo, Daisuke Kuroda und Harushige Tsubakino. „Micro-Resistance Spot Welding of Nickel Free Austenitic Stainless Steel“. Materials Science Forum 539-543 (März 2007): 4081–86. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4081.

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Micro-resistance spot weldability of nickel free stainless steel sheet was studied to fabricate medical implants. Weld lobe was established and the effect of welding parameters on joint strength was investigated. Weld nugget represented a rapidly quenched austenitic cellular structure whose cell size is several μm with a little ferrite. The amount of δ-ferrite in weld nugget is smaller than that predicted by some Schaefller diagrams due to rapid solidification during micro-resistance spot welding.

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Molnár, Tamás G., und Tamás Insperger. „On the Effect of Distributed Regenerative Delay on the Stability Lobe Diagrams of Milling Processes“. Periodica Polytechnica Mechanical Engineering 59, Nr. 3 (2015): 126–36. http://dx.doi.org/10.3311/ppme.7995.

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20

Montiel, Óscar I., Mario A. Ayala und Lácides Ripoll S. „Design and simulation of a non-resonant antenna: waveguide slot antenna for 30 GHz“. Visión electrónica 10, Nr. 1 (20.06.2016): 49–56. http://dx.doi.org/10.14483/22484728.11611.

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The main contribution of this article is the design and simulation of a non-resonant slot antenna based on wave guides to operate in the range of microwaves. The design is done using MATLAB and the Chebyshev synthesis to determine the distribution of current in each element. Based on this information, the size and distribution of the elements are calculated. Different design conditions are simulated, such as: changes in the level from main lobe to secondary and dierent number of slots at one frequency. The slots are interleaved with respect to the axis of the waveguide and separated by a distance (d). To determine its dimensions, it is necessary to deduce the conductances of the array. A particular design case is compared with simulations from the software CST Microwave Studio. It is observed that radiation diagrams are very similar in both number and amplitude of the lobes, validating the tool used.

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Brecher, Christian, Prateek Chavan und Alexander Epple. „Efficient determination of stability lobe diagrams by in-process varying of spindle speed and cutting depth“. Advances in Manufacturing 6, Nr. 3 (14.06.2018): 272–79. http://dx.doi.org/10.1007/s40436-018-0225-x.

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22

Terada, Yoshihiro, Kenji Ohkubo, Tetsuo Mohri und Tomoo Suzuki. „Site preference determination in intermetallic compounds by thermal conductivity measurement“. Journal of Materials Research 16, Nr. 8 (August 2001): 2314–20. http://dx.doi.org/10.1557/jmr.2001.0318.

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A method for the determination of site preference of substitutional elements in intermetallic compounds is proposed. It is demonstrated in Ni3Al–X alloys that the ridge direction in thermal conductivity contours in the ternary γ′ phase agrees with that of the solubility lobe of the γ′ phase in ternary phase diagrams. The ridge direction is a reliable indication of site preference of substitutional elements in intermetallic compounds. The present method is conveniently applied to a normal polycrystalline specimen with small size, and therefore, a versatile class of brittle compounds can be studied.

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Mokhtari, Ali, Abbas Mazidi und Mohammad M. Jalili. „Investigation of rotary inertial dynamic effects on chatter boundary in milling process using three-dimensional Timoshenko tool model“. Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 233, Nr. 1 (26.07.2018): 93–110. http://dx.doi.org/10.1177/1464419318788504.

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Chatter prediction is essential to conduct stable machining. Many of the previous studies made to simulate milling process have not considered gyroscopic and rotary inertial dynamics effects. The aim of this research is to investigate the effects of rotary inertial dynamics on prediction of chatter in the milling operation. For this purpose, a three-dimensional rotating cantilever Timoshenko beam is considered for modeling the cutting tool. In the proposed model, cutting forces are applied at the end of the beam. Imposing spectral finite element model, the governing delay partial differential equations of the system reduce to nondelay ordinary differential equations. The main contributions of the current research are modeling the cutting tool as a continuous model by Timoshenko beam theory, finding and solving nondelay ordinary differential equations of the cutter via spectral finite element model, and studying the effects of gyroscopic and rotary inertial dynamics, completely. For validating, the system stability predictions obtained from the presented model are compared with experimental outcomes from the literature. Besides the common stability lobe diagram which is in terms of depth of cut and the spindle speed, other stability diagrams based on cutter length and diameter are illustrated. Using this model, influences of rotary inertial dynamics on these stability diagrams are investigated. The results show that ignoring the rotary inertial dynamics causes significant errors in prediction of chatter boundaries especially in high angular velocity of the tool. In addition, the effect of number of the cutter teeth on the stability of milling process is studied. The presented stability diagram may help a machinist to choose a better set of parameters, such as tool length and diameter, number of cutter flutes, depth of cut, and spindle velocity, for doing a stable milling process.

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Rempel, J., P. Jacobi, J. Friedrich, A. Prof Verl, P. Prof Wiederkehr und D. Prof Biermann. „Simulationsbasierte Fräsprozessauslegung*/Simulation-based design of milling-processes - Sensitivity analysis of stability lobe diagrams for automotive large-scale production“. wt Werkstattstechnik online 107, Nr. 11-12 (2017): 841–46. http://dx.doi.org/10.37544/1436-4980-2017-11-12-65.

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In diesem Fachartikel werden die Einflüsse von Unsicherheiten in den Modellparameterwerten auf die Stabilitätsgrenze einer Stabilitätskarte aufgezeigt. Dazu wird an einem Beispielsystem eine Sensitivitätsanalyse für ein Verfahren zur Erzeugung von Stabilitätskarten durchgeführt. Zur Bestimmung des dynamischen Verhaltens der Werkzeugmaschine kommt eine Methode der Frequenzgang-Kopplung zum Einsatz.   To estimate the effect of uncertainties on the prediction of stability limits, a sensitivity analysis was conducted for a procedure to determine stability lobe diagrams for an example system. Thereby, a method of receptance coupling to identify the dynamic behavior of the tool center point was applied.

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Mokhtari, Ali, Mohammad Mahdi Jalili und Abbas Mazidi. „Optimization of different parameters related to milling tools to maximize the allowable cutting depth for chatter-free machining“. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 235, Nr. 1-2 (11.07.2020): 230–41. http://dx.doi.org/10.1177/0954405420937536.

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Determination of optimal parameters of cutting tool is one of the most significant factors in any operation planning of metal elements, especially in micro-milling process. This article presents an optimization procedure, based on genetic algorithms, to optimize some parameters related to micro-milling tool including number of teeth, shank diameter, fluted section diameter, shank length, taper length, and length of fluted section. The aim of this optimization is maximizing the minimum value of cutting depth on the border of stability lobe diagrams, which is called allowable cutting depth, for chatter-free machining. Cutting tool is modeled as a three-dimensional spinning cantilever Timoshenko beam based on strain gradient elasticity theory. Structural nonlinearity, gyroscopic moment, rotary inertia, and velocity-dependent process damping are also considered in the cutting tool model. The values of natural frequency, damping ratio, and material length scale of the micro-milling tool are calculated using a system identification based on genetic algorithm to match the analytical response with recorded experimental vibration signal. Using beam model, the allowable cutting depth is increased in the optimization process for a specific range of spindle speed to avoid the chatter phenomenon. Analytical study of micro-milling process stability is carried out to determine the cost function of the genetic algorithm. A plot of the greatest fitness in each generation is sketched. In addition, stability lobe diagrams before and after optimization process are presented to show the efficiency of the optimized micro-milling tool. In the presented examples, the results of genetic algorithm may lead to design or find a micro-milling tool that its acceptable cutting depth increases up to 1.9313 times.

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Wang, Yong, Rong Yan, Fang Yu Peng und Feng Qiu. „Stability Modeling and Analysis of Orthogonal Turn-Milling with Variable Cutting Depth and Cutting Thickness“. Advanced Materials Research 852 (Januar 2014): 419–26. http://dx.doi.org/10.4028/www.scientific.net/amr.852.419.

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In orthogonal turn-milling process, both of the workpiece and the cutter rotate at the same time, which causes cutting depth and cutting thickness to change instantaneously. In this paper, a new 2D stability model of orthogonal turn-milling is established, in which the effect of variable cutting depth and cutting thickness is considered. The stability lobe diagrams are obtained by using Full-discretization Method. By analyzing the stability of orthogonal turn-milling, it is found that it is better than that of ordinary milling in same machining conditions. It means that in orthogonal turn-milling process deep cutting depth can be chosen and high machining efficiency can be obtained compared to that in ordinary milling process.

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Gómez-González, V. M. A., J. A. Toalá, M. A. Guerrero, H. Todt, L. Sabin, G. Ramos-Larios und Y. D. Mayya. „Planetary nebulae with Wolf–Rayet-type central stars – I. The case of the high-excitation NGC 2371“. Monthly Notices of the Royal Astronomical Society 496, Nr. 1 (03.06.2020): 959–73. http://dx.doi.org/10.1093/mnras/staa1542.

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ABSTRACT We present the analysis of the planetary nebula (PN) NGC 2371 around the [Wolf–Rayet] (WR) star WD 0722+295. Our Isaac Newton Telescope intermediate dispersion spectrograph spectra, in conjunction with archival optical and ultraviolet images, unveil in unprecedented detail the high ionization of NGC 2371. The nebula has an apparent multipolar morphology, with two pairs of lobes protruding from a barrel-like central cavity, a pair of dense low ionization knots misaligned with the symmetry axis embedded within the central cavity, and a high-excitation halo mainly detected in He ii. The abundances from the barrel-like central cavity and dense knots agree with abundance determinations for other PNe with [WR]-type central stars of PNe. We suggest that the densest knots inside NGC 2371 are the oldest structures, remnant of a dense equatorial structure, while the main nebular shell and outer lobes resulted from a latter ejection that ended the stellar evolution. The analysis of position–velocity diagrams produced from our high-quality spectra suggests that NGC 2371 has a bipolar shape with each lobe presenting a double structure protruding from a barrel-like central region. The analysis of the spectra of WD 0722+295 results in similar stellar parameters as previously reported. We corroborate that the spectral subtype corresponds with a [WO1] type.

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Maher, Louis J., und David M. Mickelson. „Palynological and Radiocarbon Evidence for Deglaciation Events in the Green Bay Lobe, Wisconsin“. Quaternary Research 46, Nr. 3 (November 1996): 251–59. http://dx.doi.org/10.1006/qres.1996.0064.

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A new and significant site of organic silty sand has been found beneath the Valders till at Valders Quarry in northeastern Wisconsin. This is now the earliest known late-glacial site associated with red till ice advances in the western Great Lakes area. Leaves of terrestrial plants washed into a small depression provide a date of 12,965 ± 200 yr B.P. (WIS-2293), which is significantly older than the Two Creeks Forest Bed (ca. 11,800 yr B.P.). Percentage and concentration pollen diagrams suggest that the site was open and distant from a closed Picea forest. No wood or Picea needles have been found. This date is statistically indistinguishable from 12,550 ± 233 yr B.P., the mean of three dates for the end of inorganic varve sedimentation at Devils Lake, 160 km southwest at the terminus of the Green Bay Lobe. Assuming that the Green Bay lobe vacated its outermost moraine in the interval from 13,000 to 12,500 yr B.P., only a short time was available for retreat of the ice margin over 350 km, drainage of red sediment from Lake Superior into the Lake Michigan basin, readvance of over 250 km, retreat of at least 80 km, and advance to this site. The time for these events appears to have been too short to resolve by current radiocarbon technique. This extremely rapid collapse of the Green Bay lobe has a calibrated age of about 15,000 cal yr B.P., about that of the dramatic warming seen in the Greenland ice cores.

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Homan, W., L. Decin, A. Richards und P. Kervella. „Signs of rotating equatorial density enhancements around SRb pulsators“. Proceedings of the International Astronomical Union 14, S343 (August 2018): 421–22. http://dx.doi.org/10.1017/s1743921318005884.

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AbstractWe observed the circumstellar environments (CSEs) of the semiregular AGB stars L2 Puppis, R Doradus and EP Aquarii with ALMA. (1) The molecular emission in the L2 Pup nebula reveals an edge-on rotating disk. (2) PV diagrams of the 28SiO emission in the inner CSE of R Dor expose a pattern pointing to an inclined rotating disk. (3) The CO emission in the CSE of EP Aqr reveals a nearly face-on equatorial density enhancement (EDE). The inner EDE strongly resembles theoretical wind-Roche-lobe-overflow models. The SiO emission points to a potential companion. The combination of (1), (2) and (3) suggests that a link may exist between the type of AGB pulsations and the morphological nature of the CSE.

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Iglesias, Alex, Zoltan Dombovari, German Gonzalez, Jokin Munoa und Gabor Stepan. „Optimum Selection of Variable Pitch for Chatter Suppression in Face Milling Operations“. Materials 12, Nr. 1 (31.12.2018): 112. http://dx.doi.org/10.3390/ma12010112.

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Cutting capacity can be seriously limited in heavy duty face milling processes due to self-excited structural vibrations. Special geometry tools and, specifically, variable pitch milling tools have been extensively used in aeronautic applications with the purpose of removing these detrimental chatter vibrations, where high frequency chatter related to slender tools or thin walls limits productivity. However, the application of this technique in heavy duty face milling operations has not been thoroughly explored. In this paper, a method for the definition of the optimum angles between inserts is presented, based on the optimum pitch angle and the stabilizability diagrams. These diagrams are obtained through the brute force (BF) iterative method, which basically consists of an iterative maximization of the stability by using the semidiscretization method. From the observed results, hints for the selection of the optimum pitch pattern and the optimum values of the angles between inserts are presented. A practical application is implemented and the cutting performance when using an optimized variable pitch tool is assessed. It is concluded that with an optimum selection of the pitch, the material removal rate can be improved up to three times. Finally, the existence of two more different stability lobe families related to the saddle-node and flip type stability losses is demonstrated.

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Konov, K. I., und K. N. Klimov. „Suppression of the Side Lobe Level in the Model Problem on Radiation of an Antenna Array with Given Partial Diagrams“. Journal of Communications Technology and Electronics 66, Nr. 6 (Juni 2021): 694–706. http://dx.doi.org/10.1134/s1064226921060164.

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Azka, Muizuddin, Keiji Yamada, Mahfudz Al Huda, Kyosuke Mani, Ryutaro Tanaka und Katsuhiko Sekiya. „Hilbert-Huang Transform Analysis of Machining Stability in Ball-Nose End-Milling of Curved Surface“. International Journal of Automation Technology 14, Nr. 3 (05.05.2020): 500–511. http://dx.doi.org/10.20965/ijat.2020.p0500.

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This paper investigates the machining stability in ball-end-milling of curved surface in which the inclination of tool continuously changes. Initially, the influence of inclination angle is geometrically investigated on the parameters such as immersion angle and cutting velocity. Then, the paper presents the stability lobe diagrams of the process. Curved surface milling is simulated by slot milling on a cylindrical workpiece using a ball-end-mill to obtain the cutting force and vibration, which are used for fast-Fourier transform and Hilbert-Huang transform (HHT) analyses. Experimental results show that the cutting force increases, and the stability becomes worse with the inclination angle, while the machining errors decrease with the inclination. The vibration analysis showed that the HHT can detect the transition from stable to unstable during milling of curved surface in the time-frequency plots.

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WIGG, CRISTINA MARIA DUARTE, und LUIZ ANTONIO ALVES DURO. „Evaluation of two infants with myotonic dystrophy by the McFie's diagram from the results of WISC“. Arquivos de Neuro-Psiquiatria 56, Nr. 3B (September 1998): 633–38. http://dx.doi.org/10.1590/s0004-282x1998000400018.

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In this paper the authors disclose the result of a research carried out on two brothers whose parents were first cousins, being the gene transmitted by the father. The psychological test Wechsler Intelligence Scale of Children (WISC) was used in two occasions in order to assess the verbal and non-verbal skills. FRM and IRM were nine and eleven-year-old respectively, in the first examination, being the former thirteen and the latter fifteen-year-old on the second one. A comparison between the McFie's diagram and the WISC scores was made: the McFie's diagram showed the impairment severity in each cortical lobe when the left hemisphere was compared with the right one. The McFie's diagram was made from WISC's scores: the McFie's diagram showed the impairment severity in each cortical lobe when the left hemisphere was compared with the right one. On the second examination the performance was worse than in the first, mainly in the non-verbal aspects. The IRM's diagram showed a reduction in the right frontal and parietal lobes. In the FRM's diagram a reduction in the left frontal, temporal and parietal lobes, and also, in the right parietal lobe was found. The visual-spatial constructive aspects showed greatest impairment in this result.

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Shaik, Jakeer Hussain, und J. Srinivas. „Dynamic Stability of a Motorized High Speed Machine Tool Spindle Supported on Bearings“. Applied Mechanics and Materials 612 (August 2014): 29–34. http://dx.doi.org/10.4028/www.scientific.net/amm.612.29.

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Dynamic behaviour of spindle system influences chatter stability of machine tool considerably. Self-excited vibrations of the tool results in unstable cutting process which leads to the chatter on the work surface and it reduces the productivity. In this paper, a system of coupled spindle bearing system is employed by considering the angular contact ball bearing forces on stability of machining. Using Timoshenko beam element formulation, the spindle unit is analyzed by including the gyroscopic and centrifugal terms. Frequency response functions at the tool-tip are obtained from the dynamic spindle model. In the second phase, solid model of the system is developed and its dynamic response is obtained from three dimensional finite element analysis. The works on analysis of the stability of milling processes focus on calculating the stability boundary of the machining parameters based on the dynamic models characterizing the milling processes. The stability lobe diagrams are generated from frequency response functions (FRF’s) lead to an stability limit prediction for the system at high speed ranges.

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Ganguli, A., A. Deraemaeker, M. Horodinca und A. Preumont. „Active Damping of Chatter in Machine Tools - Demonstration with a ‘Hardware-in-the-Loop’ Simulator“. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 219, Nr. 5 (01.08.2005): 359–69. http://dx.doi.org/10.1243/095965105x33455.

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The motivation of the work is twofold: (a) understand the physics behind regenerative chatter and the influence of structural damping and (b) demonstrate an active damping technique based on collocated actuator/sensor pairs. A numerical stability analysis is performed using the root locus method and it is shown that, along with the structural poles, eigenvalues due to the delay parameter may contribute to instability. Since experimental demonstration of chatter in real machines is difficult, an alternative way of demonstration via a mechatronic simulator is presented, using the ‘hardware-in-the-loop’ concept. The mathematical model of the regenerative cutting process in turning is simulated in a computer and this is interfaced to a beam, representing the structural dynamics of the machine, via a displacement sensor and force actuator. In this way, a hardware and a software loop are combined. In a second step, an additional control loop is added, consisting of an accelerometer sensor and a collocated inertial actuator. Numerical and experimental stability lobe diagrams are compared, with and without active damping.

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Zhang, Hongyan, S. Jack Hu, Jacek Senkara und Shaowei Cheng. „A Statistical Analysis of Expulsion Limits in Resistance Spot Welding“. Journal of Manufacturing Science and Engineering 122, Nr. 3 (01.08.1999): 501–10. http://dx.doi.org/10.1115/1.1285873.

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Expulsion is an important phenomenon in resistance spot welding. It involves loss of metal from the liquid nugget, which often results in the reduction of weld strength. Various models have been proposed to understand expulsion mechanisms. In these models the occurrence of expulsion is often treated as a deterministic event, and depicted by a line (boundary) in conventional lobe diagrams. In this study, statistical analysis is employed to explore expulsion with consideration of the influence of random factors. Models are built based on experimental data, and one steel and two aluminum alloys are used as examples. Expulsion probabilities are presented as a function of electrode force, welding current, and time. Analytical models and their graphical form of expression (contours and surfaces) are created to present expulsion limits under various combinations of welding parameters. This study provides not only quantitative model predictions on expulsion limits for the materials studied, but also a generic statistical methodology that can be used for analyzing expulsion in various material systems. [S1087-1357(00)00602-X]

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Lv, Shujie, und Yang Zhao. „Stability of Milling Process with Variable Spindle Speed Using Runge–Kutta-Based Complete Method“. Mathematical Problems in Engineering 2021 (09.02.2021): 1–10. http://dx.doi.org/10.1155/2021/6672513.

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The variable-spindle-speed (VSS) technique is effective in preventing regenerative chatter in milling processes. However, spindle-speed-modulation parameters should be deliberately selected to augment the material removal rate. Stability-prediction algorithms of stability predicting play an important role in this respect, as they allow the prediction of stability for all ranges of a given spindle speed. The increase in calculation time in variable-spindle-speed milling, which is caused by the modulation frequency, hinders its practical use in the workshop. In this paper, a Runge–Kutta-based complete discretization method (RKCDM) is presented to predict the stability of milling with variable spindle speeds, which is described by a set of delay differential equations (DDEs) with time-periodic coefficients and time-varying delay. The convergence and calculation efficiency are compared with those of the semidiscretization method (SDM) under different testing configurations and milling conditions. Results show that RKCDM is more accurate and saves at least 50% of the calculation time of SDM. The effects of modulation parameters on the stability of VSS milling are explored through stability lobe diagrams produced from RKCDM.

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Chen, Ming, Xiao Hui Zhang und Wei Wei Ming. „Fuzzy Chatter Stability Lobes Model in Milling“. Key Engineering Materials 443 (Juni 2010): 308–13. http://dx.doi.org/10.4028/www.scientific.net/kem.443.308.

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Based on the conventional chatter stability model, stability Lobes diagram in die & mould steel milling system is obtained. The derived diagram can be divided into two independent regions by a Lobes curve: absolutely stable and instable region. In fact, it is more reasonable that there should be a transition stage between the stable and instable state. That is to say, grade of stability (GOS) should be in a closed interval [0, 1], rather than Boolean logic. Due to the different stability sensibilities for different order Lobe curve in milling system, there should be different widths of transition belts for different order curve. Thus, with the help of Sigmoid transfer function widths of each order Lobe curve are studied. Finally, the fuzzy chatter stability is implemented by an adjustable slope coefficient.

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Ksica, Filip, und Zdenek Hadas. „Prediction of position-dependent stability lobes based on reduced virtual model“. MATEC Web of Conferences 211 (2018): 17005. http://dx.doi.org/10.1051/matecconf/201821117005.

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The stability of a machining process is directly affected by the dynamic response between the tool and the workpiece. However, as the tool moves along the path, the dynamic stiffness of the machine tool changes. To determine the position-dependent dynamic stiffness accurately, a computationally efficient methodology based on a complex virtual model is presented. The virtual model is assembled using Finite Element Method and is effectively reduced via Component Mode Synthesis and transformation to a State-Space Multi-Input-Multi-Output system. Combination of these techniques allows time-efficient response simulations with significantly less computational effort than the conventional full Finite Element models. Furthermore, they describe the behaviour of the complex structure more accurately opposed to the commonly used models based on a simple 1 Degree-of-Freedom systems. The reduced model is used to simulate dynamic response of the structure to a cutting force during operation. A response is measured on an existing machine to modify the virtual model by incorporating fuzzy parameters, such as damping. The stability regions are calculated for variable positions, resulting in position-dependent lobe diagrams. The presented approach can be used to create a map of stable zones to predict and prevent unstable behaviour during operation.

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KĘCIK, KRZYSZTOF, RAFAŁ RUSINEK und JERZY WARMIŃSKI. „STABILITY LOBES ANALYSIS OF NICKEL SUPERALLOYS MILLING“. International Journal of Bifurcation and Chaos 21, Nr. 10 (Oktober 2011): 2943–54. http://dx.doi.org/10.1142/s0218127411030258.

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In this paper, we study the stability of a high speed milling process of nickel superalloys Inconel 713C by methods used in nonlinear dynamics. Stability Lobe Diagram was a result of modal analysis and next verified by recurrence plots, recurrence quantification analysis and classical nonlinear methods. A stability lobes diagram shows the indistinct boundary between chatter-free stable machining and unstable processes. Nevertheless, some recurrence quantification analysis measures give interesting results.

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Sugimura, Hotaruko, Yasuyuki Kaneno und Takayuki Takasugi. „Alloying Behavior of Ni₃Nb, Ni₃V and Ni₃Ti Compounds“. Materials Science Forum 654-656 (Juni 2010): 440–43. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.440.

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The site preference of ternary additions in Ni3X-type GCP compounds was determined from the direction of solubility lobe of the GCP phase on the experimentally reported ternary phase diagrams. In Ni3Nb (D0a), Co and Cu preferred the substitution for Ni-site, Ti, V and W the substitution for Nb-site, and Fe the substitution for both sites. In Ni3V (D022), Co preferred the substitution for Ni-site, Cr the substitution for both sites, and Ti the substitution for V-site. In Ni3Ti (D024), Fe, Co, Cu, and Si preferred the substitution for Ni-site, Nb, Mo and V the substitution for Ti-site. The thermodynamic model, which was based on the change in total bonding energy of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The bond energy of each nearest neighbor pair used in the thermodynamic calculation was derived from the heat of compound formation by Miedema’s formula. The agreement between the thermodynamic model and the result of the literature search was excellent. Both transition and B-subgroup elements have two possibilities, i.e., the case of substitution for Ni-site or the case for X-site, depending on the relative value of two interaction energies.

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Li, Hong Kun, und Peng Shi Zhao. „Milling Stability Lobe Diagram Construction on FV520B Stainless Steel and Experimental Testing Investigation“. Applied Mechanics and Materials 437 (Oktober 2013): 586–89. http://dx.doi.org/10.4028/www.scientific.net/amm.437.586.

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This paper investigates the zero-order analytical method to construct milling stability lobe diagram to improve the impeller milling efficiency. It is used to determine FV520B material milling parameters optimization. This method can select the appropriate number of revolutions and the cutting depth processing avoiding chatter occurrence. It can keep the required accuracy and surface quality for the workpiece. At the same time, it improves the safety of the tool and machine reliability. Through experiments data analysis, parameters constructing lobe diagram can be obtained. Different testing points in the constructed lobes are used to verify the correctness of the method. The results show that this method has great significance in the actual impellers manufacturing process.

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Huang, Chao, Wen-An Yang, Xulin Cai, Weichao Liu und YouPeng You. „An Efficient Third-Order Full-Discretization Method for Prediction of Regenerative Chatter Stability in Milling“. Shock and Vibration 2020 (20.06.2020): 1–16. http://dx.doi.org/10.1155/2020/9071451.

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The prediction of regenerative chatter stability has long been recognized as an important issue of concern in the field of machining community because it limits metal removal rate below the machine’s capacity and hence reduces the productivity of the machine. Various full-discretization methods have been designed for predicting regenerative chatter stability. The main problem of such methods is that they can predict the regenerative chatter stability but do not efficiently determine stability lobe diagrams (SLDs). Using third-order Newton interpolation and third-order Hermite interpolation techniques, this study proposes a straightforward and effective third-order full-discretization method (called NI-HI-3rdFDM) to predict the regenerative chatter stability in milling operations. Experimental results using simulation show that the proposed NI-HI-3rdFDM can not only efficiently predict the regenerative chatter stability but also accurately identify the SLD. The comparison results also indicate that the proposed NI-HI-3rdFDM is very much more accurate than that of other existing methods for predicting the regenerative chatter stability in milling operations. A demonstrative experimental verification is provided to illustrate the usage of the proposed NI-HI-3rdFDM to regenerative chatter stability prediction. The feature of accurate computing makes the proposed NI-HI-3rdFDM more adaptable to a dynamic milling scenario, in which a computationally efficient and accurate chatter stability method is required.

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Yuvaraju, B. A. G., B. K. Nanda und J. Srinivas. „Investigation of stability in internal turning using a boring bar with a passive constrained layer damping“. FME Transactions 49, Nr. 2 (2021): 384–94. http://dx.doi.org/10.5937/fme2102384y.

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The vibrations produced in a boring tool in internal turning deteriorate the machined surface quality and reduce the tool life, which results in a massive noise during the machining. Therefore, unwanted vibrations are necessary to be eliminated by improving the boring bar's dynamic stiffness and damping capacity. This paper investigates a passive constrained layer damping (CLD) boring bar with a hybrid damping layer to study the internal turning system's stability. Initially, the dynamic models of the conventional and CLD tools are thoroughly studied using Euler-Bernoulli beam theory (EBT) and validated them with finite element modelling (FEM). The frequency response functions (FRFs) obtained from the impact hammer tests are used to estimate the modal parameters. With modal parameters, the semi-analytical stability lobe diagrams (SLDs) are plotted for the boring system with the conventional and CLD boring bar. Tool-tip responses for various cutting conditions are simulated numerically to validate and to study stability. The cutting experiments with traditional and CLD boring bar are conducted for stability analysis and compared tool-tip responses with numerical results. It is observed that both the numerical and experimental results agree with the selected cutting conditions from SLDs. It is also observed that the CLD boring bar with a hybrid damping layer reduced the vibration displacements by five times compared to the conventional one.

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Dottori, H., R. J. Diaz, M. P. Agüero, D. Mast und I. Rodrigues. „The secular evolution of M83 central bulge“. Proceedings of the International Astronomical Union 3, S245 (Juli 2007): 297–300. http://dx.doi.org/10.1017/s174392130801795x.

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AbstractThe luminosity profile of M 83 bulge can be traced by a de Vaucouleurs' law between ≈ 200 pc and ≈ 800 pc. The inner part can be fitted by a n = −1/2 Sérsic profile. Also the IR (J − K) color shows difference between the periphery and the central part of the bulge, both properties indicating the presence of a pseudobulge. Previous Gemini-S 3-D, Paβ spectroscopy of the central ≈ 5″×13″ revealed spider like diagrams indicating disk like motion around three extended masses identified respectively with the optical nucleus (ON), with the center of the bulge isophotes, similar to the CO kinematical center (KC), and with a condensation hidden at optical wavelengths (HN), coincident with the largest lobe in 10 μm emission, most probably a cannibalized satellite. Numerical simulations show that they suffer strong evaporation and they would merge engulfing also the star forming arc in few hundred Myr, increasing the mass at the kinematical center by a factor o five or more. Upper mass limit of putative Black Holes associated to ON, KC and HN are a few ten thousand to a million solar masses. GMOS+Gemini imaging and spectroscopy of a chain of radio sources has yield no optical high redshift counterparts. This radio sources are aligned with ON, neither associated to SN nor to HII regions and might point to an older similar phenomenon, which left behind a kick-off spur.

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Sun, Shan Shan, Wei Xiao Tang und Xi Qing Xu. „Chatter Stability Prediction in High Speed Milling Considering Multi-Degree of Freedom“. Key Engineering Materials 431-432 (März 2010): 373–76. http://dx.doi.org/10.4028/www.scientific.net/kem.431-432.373.

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Chatter problems occurring during high speed milling affect the quality of the finished workpiece and, to a lesser extent, the tool life and the spindle life. Therefore, the prediction of stable milling regions is a critical requirement for high speed milling operations. In this paper, a dynamic model of a high speed spindle system considering the multi-mode dynamics is elaborated for the purposed of stability prediction. A stability lobes diagram (SLD) shows the boundary between chatter-free machining operations and unstable processes, in terms of axial depth of cut as a function of spindle speed. These diagrams are used to select chatter-free combinations of machining parameters. The proposed method enables a new stability lobes diagram to be established that takes into account the effect of spindle speed on multi-mode dynamic behavior.

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Shi, Xiang-dong, Sheng-bang Qian, Lin-jia Li und Wen-ping Liao. „HL Dra: an active Algol-like binary system with a pulsating component star and a cool third body“. Monthly Notices of the Royal Astronomical Society 505, Nr. 4 (06.07.2021): 6166–78. http://dx.doi.org/10.1093/mnras/stab1657.

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ABSTRACT HL Draconis (HL Dra) is an oscillating eclipsing binary with an orbital period of 0.944276 d. By analysing the light curves observed with the Transiting Exoplanet Survey Satellite (TESS), it has been detected that HL Dra is an Algol-like binary system with a mass ratio of 0.361, where the radius filling factor (=r/RL) of the primary and secondary component is $87\, {{\ \rm per\ cent}}$ and $98\, {{\ \rm per\ cent}}$, respectively. The secondary component is almost filling its critical Roche lobe, but not entirely. The absolute parameters of the component are estimated in this paper. Both the variable O’Connell effect and the existence of superflares indicate that the secondary should have strong magnetic activities. It is discovered that the O − C curve shows a sinusoidal variation with a period of 129.88 yr. This cyclic change might be caused by the effects of the light travel time as a result of the presence of a cool red dwarf third body. The correlations between the changes of the O − C diagrams and the variable O’Connell effect during TESS observations might be caused by the magnetic activity of the secondary (i.e. the Applegate mechanism). After removal of the binary model, a total of 252 pulsation frequencies are detected from the high-precision photometric data of TESS, including 28 multiplets of tidally split frequencies. We identify two radial modes, 21 non-radial p-modes and three non-radial f-modes from the possible independent frequencies. All of these features reveal that HL Dra is a very interesting system for further investigations of binary formation and evolution, and for tidal interactions on stellar pulsations and on magnetic activities.

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Zheng, Charles M., Chou-Fu Liang, Hai-Yi Cai und Shui-Shen Zhang. „Identification of process damping for chatter prediction in milling“. MATEC Web of Conferences 175 (2018): 02002. http://dx.doi.org/10.1051/matecconf/201817502002.

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Traditionally, forecasting stability lobe diagram in milling is limited by complex damping identification procedures, so only structural damping from the impact experiment is used for predicting stability lobe diagram in most milling cases. In this study, by using the mathematical expressions among damping ratio, “critical limiting depth of cut” and “worst spindle speed”, it is shown that the predicted “critical limiting depth of cut” based on the structural damping divided by the measured “critical limiting depth of cut” can be approximately equal to the structural damping divided by the total damping. Based on this relationship, it is easy to estimate the total damping or process damping from the experiment within the selected spindle speeds. In practice, this paper presents an easy method for predicting stability lobe diagram using the total damping. At the same time, experiments have confirmed that using the prediction model of total damping can more accurately predict the stability lobe diagram.

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Ibañez, Aratz Iturgaiz, Pedro Jose Arrazola und Klaus Bonde Ørskov. „Workpiece Material Influence on Stability Lobe Diagram“. Procedia Manufacturing 47 (2020): 479–86. http://dx.doi.org/10.1016/j.promfg.2020.04.342.

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Hsiao, Te Ching, und Shyh Chour Huang. „The Effect of Cutting Process Parameters on the Stability in Milling“. Advanced Materials Research 887-888 (Februar 2014): 1200–1204. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.1200.

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In the milling process, the dynamic system in the cutting process is composed of the tool, workpiece, and machine tools themselves. Therefore the mill geometric parameter, workpiece material behavior, and the modal parameters of the cutting system all will influence the stability in milling. Using FLN method and convolution force model to predict the chatter stability of milling process, and discussing the effect of milling parameter on the stability in this article. According to the result: with the increase of the tool diameter, stiffness, damping ratio or the reducing of tangential cutting force coefficient and radial width of cut, the stability lobe diagram tends to move upward. With the increase of natural frequency, the stability lobe diagram tends to move to right side. With the increase of the number of tooth, the stability lobe diagram tends to move downward.

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