Academic literature on the topic 'Local deviation angle'
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Journal articles on the topic "Local deviation angle"
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Wu, Yuanhao, Chunyang Wang, Xuelian Liu, Chunhao Shi, and Xuemei Li. "A DASKL Descriptor via Encoding the Information of Keypoints and a 3D Local Surface for 3D Matching." Electronics 11, no. 15 (July 27, 2022): 2328. http://dx.doi.org/10.3390/electronics11152328.
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Three-dimensional matching is widely used in 3D vision tasks, such as 3D reconstruction, target recognition, and 3D model retrieval. The description of local features is the fundamental task of 3D matching; however, the descriptors only encode the surrounding surfaces of keypoints, and thus they cannot distinguish between similar local surfaces of objects. Therefore, we propose a novel local feature descriptor called deviation angle statistics of keypoints from local points and adjacent keypoints (DASKL). To encode a local surface fully, we first calculate a multiscale local reference axis (LRA); second, a local consistent strategy is used to redirect the normal direction, and the Poisson-disk sampling strategy is used to eliminate the redundancy in the data. Finally, the local surface is subdivided by two kinds of spatial features, and the histogram of the deviation angle between the LRA and the normal point in each subdivision space is generated. For the coding between keypoints, we calculate the LRA deviation angle between the nearest three keypoints and the adjacent keypoint. The performance of our DASKL descriptor is evaluated on several datasets (i.e., B3R, UWAOR, and LIDAR) with respect to Gaussian noise, varying mesh resolutions, clutter, and occlusion. The results show that our DASKL descriptor has achieved excellent performance in terms of description, robustness, and efficiency. Moreover, we further evaluate the generalization ability of the DASKL descriptor in a LIDAR real-scene dataset.
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Schuler, Alexander, Albert Weckenmann, and Tino Hausotte. "Enhanced measurement of high aspect ratio surfaces by applied sensor tilting." ACTA IMEKO 3, no. 3 (September 23, 2014): 22. http://dx.doi.org/10.21014/acta_imeko.v3i3.124.
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During tactile surface measurements the contact point between probing tip and surface varies depending on the local surface angle. To reduce the resulting measurement deviation on high slopes a probing principle is investigated that applies a dynamic surface dependent sensor tilt. This probing process and the logics for the angle determination have been evaluated by simulation. A test stand based on a nanometer coordinate measuring machine is developed and fitted with a rotation kinematic based on stacked rotary axes. Systematic positioning deviations of the kinematic are reduced by a compensation field. The test stand has been completed and results are presented.
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Tomków, Jacek, Anna Janeczek, Grzegorz Rogalski, and Adrian Wolski. "Underwater Local Cavity Welding of S460N Steel." Materials 13, no. 23 (December 4, 2020): 5535. http://dx.doi.org/10.3390/ma13235535.
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In this paper, a comparison of the mechanical properties of high-strength low-alloy S460N steel welded joints is presented. The welded joints were made by the gas metal arc welding (GMAW) process in the air environment and water, by the local cavity welding method. Welded joints were tested following the EN ISO 15614-1:2017 standard. After welding, the non-destructive—visual, penetrant, radiographic, and ultrasonic (phased array) tests were performed. In the next step, the destructive tests, as static tensile-, bending-, impact- metallographic (macroscopic and microscopic) tests, and Vickers HV10 measurements were made. The influence of weld porosity on the mechanical properties of the tested joints was also assessed. The performed tests showed that the tensile strength of the joints manufactured in water (567 MPa) could be similar to the air welded joint (570 MPa). The standard deviations from the measurements were—47 MPa in water and 33 MPa in the air. However, it was also stated that in the case of a complex state of stress, for example, bending, torsional and tensile stresses, the welding imperfections (e.g., pores) significantly decrease the properties of the welded joint. In areas characterized by porosity the tensile strength decreased to 503 MPa. Significant differences were observed for bending tests. During the bending of the underwater welded joint, a smaller bending angle broke the specimen than was the case during the air welded joint bending. Also, the toughness and hardness of joints obtained in both environments were different. The minimum toughness for specimens welded in water was 49 J (in the area characterized by high porosity) and in the air it was 125 J (with a standard deviation of 23 J). The hardness in the heat-affected zone (HAZ) for the underwater joint in the non-tempered area was above 400 HV10 (with a standard deviation of 37 HV10) and for the air joint below 300 HV10 (with a standard deviation of 17 HV10). The performed investigations showed the behavior of S460N steel, which is characterized by a high value of carbon equivalent (CeIIW) 0.464%, during local cavity welding.
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Nenajdenko, A. S., V. I. Poddubnyj, and A. I. Valekzhanin. "Modeling the movement control of a wheeled agricultural machine in real time." Traktory i sel hozmashiny 85, no. 3 (June 15, 2018): 32–38. http://dx.doi.org/10.17816/0321-4443-66386.
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The research, which purpose is the development of a motion control system for wheeled agricultural machines, is conducted in Polzunov Altai State Technical University. One of the most important steps in this case is the testing of the developed control algorithms. It is advisable to replace the field trials by real-time motion modeling, which allows to significantly reduce financial and time costs. The developed control algorithm can be conditionally divided into global and local regulation. Global regulation must determine the angle of rotation of the steered wheels (or the angle of the frame break) by a deviation from the specified trajectory, which ensures the motion along the specified trajectory. Input parameters are the specified path of motion, the current coordinates of the machine and the projection of speed on fixed axes. Local control provides the implementation of the set value of the angle of rotation of the steered wheels. To the input of the local adjustment program is given the values of the set and current angles of rotation of the wheels and the direction of rotation of the electric motor of the maneuvering device. The algorithm for determining the required angle of rotation of the wheels is based on the method of predicting the position of the wheeled vehicle through the predetermined forecast time. In real-time tests, the wheeled vehicle is replaced by its mathematical model, obtained using the differential equations of plane motion. The complex of equipment provides registration and generation of the necessary parameters for the operation of the control system in real time. The tests were carried out on the experimental stand «steering - front suspension of the vehicle». The front steerable wheels were rotated by an electromechanical maneuvering device to an angle providing movement along a given trajectory. The motion along rectilinear and curvilinear trajectories was modeled taking into account perturbations from the side of the support surface and without them. When moving along a curvilinear trajectory, the deviation from the specified trajectory does not exceed 0,3 meters at a speed of 3,33 m/s. Based on the results of the experiments, it was established that the implemented control algorithm ensures motion along a given trajectory with a sufficient degree of accuracy.
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SU, PING, WEN-CHEN ZHENG, and HONG-GANG LIU. "CALCULATION OF THE PHOTOLUMINESCENCE SPECTRA FOR Yb3+-DOPED CuInS2 CRYSTAL." Modern Physics Letters B 25, no. 30 (November 21, 2011): 2307–12. http://dx.doi.org/10.1142/s0217984911027455.
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Six crystal field energy levels obtained from the photoluminescence spectra of Yb 3+-doped CuInS 2 semiconductor crystal are calculated from the diagonalization (of energy matrix) method. The root-mean-square (r.m.s) deviation σ is 4.5 cm-1 and so the calculated results are in good agreement with the experimental values. The local tetragonal distortion angle θ for the Yb 3+ center in CuInS 2 (which is different from the corresponding angle θh in the host crystal) is obtained from the calculation.
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Fukuda, Yusuke, Kentaro Kutsukake, Takuto Kojima, Yutaka Ohno, and Noritaka Usami. "Study on electrical activity of grain boundaries in silicon through systematic control of structural parameters and characterization using a pretrained machine learning model." Journal of Applied Physics 132, no. 2 (July 14, 2022): 025102. http://dx.doi.org/10.1063/5.0086193.
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We report on the effects of grain boundary (GB) structures on the carrier recombination velocity at GB ( vGB) in multicrystalline Si (mc-Si). The fabricated artificial GBs and an originally developed machine learning model allowed an investigation of the effect of three macroscopic parameters, misorientation angle α for Σ values, asymmetric angle β, and deviation angle θ from the ingot growth direction. Totally, 13 GBs were formed by directional solidification using multi-seeds with controlled crystal orientations. vGB was evaluated directly from photoluminescence intensity profiles across GBs using a pre-trained machine learning model, which allowed a quantitative and continuous evaluation along GBs. The evaluation results indicated that the impact of θ on vGB would be relatively large among the three macroscopic parameters. In addition, the results for the Σ5 and Σ13 GBs suggested that the minimum vGB would be related to the GB energy. These results were discussed in terms of the complexity of the local reconstruction of GB structures. The deviation would make a more complex reconstructed GB structure with local distortion, resulting in an increase in the electrical activity of GBs. The obtained knowledge will contribute to improving various polycrystalline materials through a comprehensive understanding of the relationship between GB structures and their properties.
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Oldmixon, E. H., J. P. Butler, and F. G. Hoppin. "Dihedral angles between alveolar septa." Journal of Applied Physiology 64, no. 1 (January 1, 1988): 299–307. http://dx.doi.org/10.1152/jappl.1988.64.1.299.
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To determine the dihedral angle, alpha, at the characteristic three-way septal junctions of lung parenchyma, we examined photomicrographs of sections. The three angles, A, formed where three septal traces meet on section, were measured and found to range between approximately 50 and 170 degrees. Theoretical considerations predicted that the dispersion of alpha is much narrower than that of A. The mean of A and alpha is identically 120 degrees. The standard deviation of alpha was inferred from the cumulative distribution function of A. In lungs inflated to 30 cmH2O (VL30), the standard deviation of alpha was very small (approximately 2 degrees) and increased to approximately 6 degrees in lungs inflated to 0.4 VL30. These findings imply that at VL30 tensions exerted by septa are locally homogeneous (2% variation) and at lower lung volumes become less so (6% variation). At high distending pressures, tissue forces are thought to dominate interfacial forces, and therefore the local uniformity of tensions suggests a stress-responsive mechanism for forming or remodeling the connective tissues. The source of the local nonuniformity at lower volumes is unclear but could relate to differences in mechanical properties of alveolar duct and alveoli. Finally, local uniformity does not imply global uniformity.
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AlRatrout, Ahmed, Martin J. Blunt, and Branko Bijeljic. "Wettability in complex porous materials, the mixed-wet state, and its relationship to surface roughness." Proceedings of the National Academy of Sciences 115, no. 36 (August 17, 2018): 8901–6. http://dx.doi.org/10.1073/pnas.1803734115.
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A quantitative in situ characterization of the impact of surface roughness on wettability in porous media is currently lacking. We use reservoir condition micrometer-resolution X-ray tomography combined with automated methods for the measurement of contact angle, interfacial curvature, and surface roughness to examine fluid/fluid and fluid/solid interfaces inside a porous material. We study oil and water in the pore space of limestone from a giant producing oilfield, acquiring millions of measurements of curvature and contact angle on three millimeter-sized samples. We identify a distinct wetting state with a broad distribution of contact angle at the submillimeter scale with a mix of water-wet and water-repellent regions. Importantly, this state allows both fluid phases to flow simultaneously over a wide range of saturation. We establish that, in media that are largely water wet, the interfacial curvature does not depend on solid surface roughness, quantified as the local deviation from a plane. However, where there has been a significant wettability alteration, rougher surfaces are associated with lower contact angles and higher interfacial curvature. The variation of both contact angle and interfacial curvature increases with the local degree of roughness. We hypothesize that this mixed wettability may also be seen in biological systems to facilitate the simultaneous flow of water and gases; furthermore, wettability-altering agents could be used in both geological systems and material science to design a mixed-wetting state with optimal process performance.
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Frayssinhes, Rémy, Stéphane Girardon, Louis Denaud, and Robert Collet. "Modeling the Influence of Knots on Douglas-Fir Veneer Fiber Orientation." Fibers 8, no. 9 (August 21, 2020): 54. http://dx.doi.org/10.3390/fib8090054.
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This study presents a method for predicting the local fiber orientation of veneers made from peeled Douglas-fir logs based on the knowledge of the tree branch characteristics (location, radius, insertion angle, azimuth angle, and living branch ratio). This model is based on the Rankine oval theory approach and focuses on the local deviation of the fiber orientation in the vicinity of knots. The local fiber orientation was measured online during the peeling process with an in-house-developed scanner based on the tracheid effect. Two logs from the same tree were peeled, and their ribbons were scanned. The knot locations and fiber orientation were deduced from the scanner data. The first objective was to compare the fiber orientation model with measurements to enhance and validate the model for French Douglas-fir. The second objective was to link data measurable on logs to veneer quality.
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Machado, R. R., S. Low, and A. Germak. "CCM pilot study overview: geometrical measurement of the Rockwell diamond indenter." ACTA IMEKO 9, no. 5 (December 31, 2020): 250. http://dx.doi.org/10.21014/acta_imeko.v9i5.979.
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This paper describes an overview of the capability of the NMIs that participated on the CCM Pilot Study measurement systems, conducted by the CIPM/CCM/Working Group on Hardness, to characterize the Rockwell hardness diamond indenter geometry, by measuring the included cone angle, the straightness of the generatrix, the spherical tip radius, the deviation of the local radius and the tilt angle. <br />Nine NMIs took part in this study: INMETRO (Brazil); INRiM (Italy); KRISS (South Korea); NIM/PR (China); NIMT (Thailand); NIST (USA); PTB (Germany); TUBITAK UME (Turkey); VNIIFTRI (Russia), where INMETRO (Brazil) served as pilot laboratory.
Conference papers on the topic "Local deviation angle"
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Rani, Sarma L., and Margaret S. Wooldridge. "Quantitative Flow Visualization Using a Water Table." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0903.
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Abstract The current work describes the development of a new, non-intrusive optical method for the evaluation of water heights along a gravity wave in shooting water flows in an experimental water table facility. The technique involves superimposing alternating dark and clear mechanical fringes on the water flow. Images of the fringe deviation patterns formed due to the gravity waves are obtained. The images are analyzed to determine the angles and the lengths of fringe deviations, which are related to the local flow heights. It is proposed that the deviations can be simulated using flat-topped optical prisms oriented along the direction of the gravity wave. The height of such a prism corresponds to the local water height. In the present work, shooting flows past a wedge profile for a zero angle of attack have been studied. The variation of flow field heights along a gravity wave has been obtained by the optical technique and by a conventional intrusive depth-gauge technique. The results are in good agreement.
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Perdichizzi, A., and V. Dossena. "Incidence Angle and Pitch-Chord Effects on Secondary Flows Downstream of a Turbine Cascade." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-184.
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This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 degrees, and for three pitch-chord ratios: s/c = 0.58,0.73,0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five hole probe in a plane located at 50% of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots show in detail how much the secondary flow field is modified both by incidence and cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch averaged loss and of the deviation angle, when incidence or pitch-chord ratio is varied.
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Arnott, W. Patrick, and Philip L. Marston. "Backscattering from a slightly spheroidal air bubble in water: a novel unfolding of the optical glory." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.fr4.
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The optical glory, which is related to a weak focusing of backscattered light, is known to exist for spherical bubbles.1 This caustic, however, is affected by small deviations from sphericity. Hydrodynamics causes freely rising air bubbles in pure water to become slightly spheroidal if the bubble diameter ≳ 250 μm. We modeled and photographed the near backward scattering from slightly spheroidal horizontally illuminated bubbles. Spherical bubbles produce backward-directed glory wavefronts having the local shape of a circular torus. Our model introduces the leading perturbation of those wavefronts resulting from a small deviation from sphericity. The cross-polarized scattering from a sphere1 has a fourfold symmetric sin22φ azimuthal dependence where φ denotes the azimuthal angle. For the spheroids, both the model and the observation give a twofold symmetric pattern. Detailed features of the modeled patterns are confirmed by the observations. This gives a specific example of broken symmetry resulting in an unfolding of a caustic which would otherwise have an infinite codimension.2
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Yang, N. H., H. N. Hashemi, and P. Canavan. "Finite Element Analysis of the Knee: The Effect of Tibiofemoral Alignment and Weight on the Stresses in the Knee." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192912.
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Osteoarthritis (OA) is a degenerative disease of articular cartilage that affects millions of people [1]. Local biomechanical factors may severely affect the initiation and progression of OA due to changes in loading conditions at the knee cartilage. Body weight and the frontal plane tibiofemoral alignment are two biomechanical factors that could increase the overall loading at the knee. A normal knee will have a tibiofemoral angle approximately 7° valgus [2]. Deviation from this angle leads to a knee joint with a varus or valgus condition. The tibiofemoral angle is measured by the intersection made between the mechanical axis of the femur and the tibia in the frontal plane and affects the magnitude of the varus knee moment, Fig. 1A. Biomechanical studies have shown the varus moment is a key determinant in the load distribution at the knee [3, 4], Fig. 1A, and has been linked to OA progression [5, 6].
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Bochio, Gustavo, and Gustavo R. S. Assi. "Numerical Investigation of the Effect of Blockage on the Hydrodynamic Coefficients of a Prolate Spheroid." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-22158.
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Experiments with submarine models in cavitation tunnels are limited by the length scale of the body in relation to the size of the test section. Especially for high angles of attack, the body will experience strong flow interference due to the proximity of the walls. Consequently, the hydrodynamic coefficients will normally require empirical corrections in order to be extrapolated to represent open-water flows. The present work investigates the effect of local hydrodynamic blockage, i.e. the ratio between the body frontal area to the cross area of the test section, on the determination of the hydrodynamic coefficients of a prolate spheroid. Numerical simulations of the flow around the body in various angles of attack were performed solving the Re-averaged Navier-Stokes equations for Reynolds numbers in the range of 60 million. The numerical domain is built to represent the test section of a large cavitation tunnel in full scale. Results for coefficients of lift, drag and pitching moment are compared for several cases with blockage ratio of 0%, 1% and 5% and angle of attack of 0 and 10 degrees. The maximum deviation of around 30% from the reference case was obtained at the angle of attack of 10 degrees for the highest blockage ratio. The topology of the flow showed no significant dependency on blockage for the tested range.
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Canavan, Paul K., Nicholas H. Yang, and Hamid Nayeb-Hashemi. "Method to Determine the Effect of the Frontal Plane Tibiofemoral Knee Angle on the Varus-Valgus Moment at the Knee During Stance and Gait." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192458.
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Osteoarthritis (OA) is a degenerative disease of articular cartilage that affects millions of people [1]. Local biomechanical factors may severely affect initiation and progression of OA due to changes in loading conditions at the cartilage. The frontal plane tibiofemoral alignment effects the varus/valgus moment which could increase the overall loading at the knee. Biomechanical studies have reported that the varus moment is a key determinant in the load distribution at the knee [2, 3] and has been linked to OA progression [4, 5]. A normal knee will have a tibiofemoral angle approximately 7° valgus [6]. Deviation from this angle leads to a knee joint with a varus or valgus condition. In this investigation, a motion analysis procedure was developed to determine the affect of the frontal plane tibiofemoral angle on the force and moment reactions at the knee. The results of these methods could be utilized in a subject specific finite element model to determine the stress and strain at the knee cartilage and to suggest measures to prevent OA.
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Xia, Yingxiang, Xuedao Shu, Bohai Ye, Jiabin Zheng, and Yanli Liu. "Finite Element Simulation and Micro-Grain Size Analysis of Sheet Metal Casing by Hot Power Spinning." In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-94161.
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Abstract Spinning is a typical continuous local plastic forming and an advanced manufacturing technology to achieve less cutting machining of thin-walled rotary parts. As the external bearing component of aero-engine, the mainstream manufacturing method of sheet metal casing is hot power spinning. Its forming quality includes dimensional, shape accuracy and macroscopic defects. The refinement and uniformity of micro grain size are also important indicators. The FE finite element) model of tapered sheet metal casing with variable wall thickness in hot power spinning was established by DEFORM-3D. The average deflection angle deviation Δθ and standard deviation of wall thickness error Δt was used as the evaluation indexes of 13 simulation schemes. The effect of the mandrel speed, the roller feed ratio, the roller fillet radius and the initial temperature on the forming quality was analyzed. Through the spinning experiment of SXY1000 double-roller CNC spinning machine, the metallographic structure of different forming regions and the micro grain size under different temperatures and roller feed ratios are explored. The micro grain size of the formed part is more refined with the increase of the initial temperature. It decreases as the feed ratio increases, while the microscopic grain size uniformity decreases.
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Dong, Leilei, Qi Zhang, Yi Huang, Gang Liu, and Zhiyuan Li. "End Fitting Effect on Stress Evaluation of Tensile Armors in Unbonded Flexible Pipes Under Axial Tension." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62378.
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This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives lateral displacement of the wire, which is determined by minimization of the energy functional consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is validated with a finite element simulation. Comparisons between the model predictions and the finite element results in terms of the change in helical angle and transverse bending stress show good correlations. The validated model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear and friction could significantly increase the stress at the end fitting compared with the frictionless case.
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Zhang, Tiao, Jian Pu, and Jian-hua Wang. "EXPERIMENTAL STUDY OF TIME-RESOLVED FILM COOLING EFFECTIVENESS OF COMPOUND-ANGLED FAN-SHAPED FILM-HOLE AT CURVED WALL." In GPPS Xi'an21. GPPS, 2022. http://dx.doi.org/10.33737/gpps21-tc-257.
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Besides time-averaged cooling performances concerned in previous literature, unsteady film cooling jets require cooling unsteadiness level should be an additional parameter to evaluate the benefits of different film cooling geometries. In the present work, a time-resolved infrared thermal image system was applied to acquire the time-averaged film effectiveness fields and two-dimensional contours of standard deviation (SD) of effectiveness, in terms of typical fan-shaped film-holes in limited by the actual blade geometry. The level of SD directly reflects the strength of cooling unsteadiness, determined by the temporal variations of footprints of dominated secondary-vortices at walls. Deep discussions of the combined influences of compound angle (CA), wall curvature and cooling air flowrates on the cooling unsteadiness level and trends in time-averaged film effectiveness were conducted, to acquire the proper cooling scheme in different local regions of blade. Three typical CAs of 0°, 30° and 60° were chosen. Convex, concave and flat walls with typical dimensionless curvatures were designed to simulate three different local regions of blade. Blowing ratio (BR) of coolant-to-mainstream was varied from 0.5 to 3.0. The detailed comparisons of experimental results revealed the complex trends in film effectiveness and cooling unsteadiness level with CA, BR and wall curvature, which have been listed in Conclusions. In general, the shaped-hole with CA= 30° is significantly proper to reduce the local hot-spots at the convex and nearly-flat walls, due to the highest film effectiveness and lowest cooling unsteadiness level. However, the angled shaped-holes at the concave wall can produce the high-level unsteadiness, increasing the risk of thermal damage and bringing to a new challenge of modifications of hole-geometry to reduce the cooling unsteadiness level while keep the high effectiveness.
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Wang, Mingyi, Zhiheng Wang, Guang Xi, and Yurun Li. "Numerical Investigation on Propagation Characteristics of Inlet Total-Pressure Distortion in a Centrifugal Compressor." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59921.
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Abstract The propagation characteristics of inlet total-pressure distortion in a centrifugal compressor are investigated by full-annulus unsteady three-dimensional numerical simulation. The inlet distortions considered in the paper are the total-pressure distortions covering a 60-deg sector (60deg distortion) and three 20-deg sectors (3*20deg distortion), respectively. One is the classical distortion form, and the other is to simulate the downstream flow of the axial section of a centrifugal-axial combined compressor. By analyzing the distributions of flow parameters, the propagation of the total-pressure distortion in the centrifugal compressor is interpreted. The results show that, with the distortion propagating to the downstream, the low-pressure region produces a phase deviation along the streamwise direction relative to the opposite direction of impeller rotation direction, and the range of distortion region is reduced. Additionally, the propagation of the inlet distortion makes the three-dimensional characteristics of airflow more complex. The flow angle increases with different amplitudes along the direction of blade height corresponding to the distorted sector. The distortion region affects the location of blades which are in a low-pressure area, and the intensity of the distortion affects the increase of the flow angle. The distortion region causes more local relative flow losses, especially near the leading edge of blade suction surface.