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1
He, Yong, Nandini Duraiswamy, Andreas O. Frank, and James E. Moore. "Blood Flow in Stented Arteries: A Parametric Comparison of Strut Design Patterns in Three Dimensions." Journal of Biomechanical Engineering 127, no. 4 (February 10, 2005): 637–47. http://dx.doi.org/10.1115/1.1934122.
Повний текст джерелаАнотація:
Background: Restenosis after stent implantation varies with stent design. Alterations in secondary flow patterns and wall shear stress (WSS) can modulate intimal hyperplasia via their effects on platelet and inflammatory cell transport toward the wall, as well as direct effects on the endothelium. Method of Approach: Detailed flow characteristics were compared by estimating the WSS in the near-strut region of realistic stent designs using three-dimensional computational fluid dynamics (CFD), under pulsatile high and low flow conditions. The stent geometry employed was characterized by three geometric parameters (axial strut pitch, strut amplitude, and radius of curvature), and by the presence or lack of the longitudinal connector. Results: Stagnation regions were localized around stent struts. The regions of low WSS are larger distal to the strut. Under low flow conditions, the percentage restoration of mean axial WSS between struts was lower than that for the high flow by 10–12%. The largest mean transverse shear stresses were 30–50% of the largest mean axial shear stresses. The percentage restoration in WSS in the models without the longitudinal connector was as much as 11% larger than with the connector. The mean axial WSS restoration between the struts was larger for the stent model with larger interstrut spacing. Conclusion: The results indicate that stent design is crucial in determining the fluid mechanical environment in an artery. The sensitivity of flow characteristics to strut configuration could be partially responsible for the dependence of restenosis on stent design. From a fluid dynamics point of view, interstrut spacing should be larger in order to restore the disturbed flow; struts should be oriented to the flow direction in order to reduce the area of flow recirculation. Longitudinal connectors should be used only as necessary, and should be parallel to the axis. These results could guide future stent designs toward reducing restenosis.
2
Aihara, Aya, Victor Mendoza, Anders Goude, and Hans Bernhoff. "Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine." Energies 15, no. 7 (March 24, 2022): 2361. http://dx.doi.org/10.3390/en15072361.
Повний текст джерелаАнотація:
This paper compares three different numerical models to evaluate their accuracy for predicting the performance of an H-rotor vertical-axis wind turbine (VAWT) considering the influence of struts. The strut of VAWTs is one factor that makes the flow feature around the turbine more complex and thus influences the rotor performance. The focus of this study is placed on analyzing how accurately three different numerical approaches are able to reproduce the force distribution and the resulting power, taking the strut effect into account. For the 12 kW straight-bladed VAWT, the blade force is simulated at three tip speed ratios by the full computational fluid dynamics (CFD) model based on the Reynolds-averaged Navier–Stokes (RANS) equations, the actuator line model (ALM), and the vortex model. The results show that all the models do not indicate a significant influence of the struts in the total force over one revolution at low tip speed ratio. However, at middle and high tip speed ratio, the RANS model reproduces the significant decrease of the total tangential force that is caused due to the strut. Additionally, the RANS and vortex models present a clear influence of the struts in the force distribution along the blade at all three tip speed ratios investigated. The prediction by the ALM does not show such distinctive features of the strut impact. The RANS model is superior to the other two models for predicting the power coefficient considering the strut effect, especially at high tip speed ratio.
3
Yin, Yuming, Subhash Rakheja, Jue Yang, and Paul-Emile Boileau. "Design optimization of an articulated frame steering system." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 10 (November 11, 2017): 1339–52. http://dx.doi.org/10.1177/0954407017729052.
Повний текст джерелаАнотація:
The articulated frame-steered vehicles (AFSV) exhibit enhanced maneuverability but reduced yaw stability and greater steering power consumption. Apart from kinematics of the steering system, the dynamics of the actuating system strongly influence the performance of the AFSV, which is generally neglected in the reported studies. In this study, a yaw-plane model of the articulated vehicle coupled with the kinematic and dynamics properties of the steering struts is formulated to identify objective measures of the AFSV under steering inputs. The results suggest that the vehicle yaw oscillation/stability, steering power efficiency and maneuverability can be objectively measured in terms of the strut length, yaw oscillation frequency and damping ratio, steering gain, and steering response rate and overshoot. The layout of steering struts and properties of the steering valve and hydraulic fluid are optimized while employing the weighted-sum method and a combination of pattern search and sequential quadratic programming algorithms. The relative weights of individual performance measures were obtained using the analytic hierarchy process (AHP) model. The solutions of the optimization problem revealed more compact articulated frame steering (AFS) system design with over 20% reduction in strut length and 24% gain in the yaw oscillation frequency. Increasing the fluid bulk modulus resulted in more compact AFS layout and further increase in the yaw oscillation frequency with lower response overshoot. The optimal design based on weighted sum of various performance measures, however, revealed negligible changes in terms of the steering power efficiency.
4
Jiménez, Juan M., Varesh Prasad, Michael D. Yu, Christopher P. Kampmeyer, Abdul-Hadi Kaakour, Pei-Jiang Wang, Sean F. Maloney, et al. "Macro- and microscale variables regulate stent haemodynamics, fibrin deposition and thrombomodulin expression." Journal of The Royal Society Interface 11, no. 94 (May 6, 2014): 20131079. http://dx.doi.org/10.1098/rsif.2013.1079.
Повний текст джерелаАнотація:
Drug eluting stents are associated with late stent thrombosis (LST), delayed healing and prolonged exposure of stent struts to blood flow. Using macroscale disturbed and undisturbed fluid flow waveforms, we numerically and experimentally determined the effects of microscale model strut geometries upon the generation of prothrombotic conditions that are mediated by flow perturbations. Rectangular cross-sectional stent strut geometries of varying heights and corresponding streamlined versions were studied in the presence of disturbed and undisturbed bulk fluid flow. Numerical simulations and particle flow visualization experiments demonstrated that the interaction of bulk fluid flow and stent struts regulated the generation, size and dynamics of the peristrut flow recirculation zones. In the absence of endothelial cells, deposition of thrombin-generated fibrin occurred primarily in the recirculation zones. When endothelium was present, peristrut expression of anticoagulant thrombomodulin (TM) was dependent on strut height and geometry. Thinner and streamlined strut geometries reduced peristrut flow recirculation zones decreasing prothrombotic fibrin deposition and increasing endothelial anticoagulant TM expression. The studies define physical and functional consequences of macro- and microscale variables that relate to thrombogenicity associated with the most current stent designs, and particularly to LST.
5
Virgin, L. N. "Postbuckling dynamics of struts as related to their loading devices." Engineering Structures 8, no. 2 (April 1986): 127–33. http://dx.doi.org/10.1016/0141-0296(86)90028-3.
Повний текст джерела
6
Cheon, Gill-Jeong, and K. B. Chandran. "Transient Behavior Analysis of a Mechanical Monoleaflet Heart Valve Prosthesis in the Closing Phase." Journal of Biomechanical Engineering 116, no. 4 (November 1, 1994): 452–59. http://dx.doi.org/10.1115/1.2895796.
Повний текст джерелаАнотація:
In this paper, an analysis of the dynamics in the closing phase of the occluder of a mechanical monoleaflet heart valve prosthesis is presented. The dynamic analysis of the fluid in the vicinity of the occluder was based on the control volume approach. The backflow velocity of the fluid was computed by applying the continuity and momentum equations in the unsteady state. By considering the fluid pressure and gravity as external forces acting on the occluder, the moment equilibrium on the occluder was employed to analyze the motion of the occluder during closing and the force of impact between the occluder and the guiding struts. The computed magnitudes of the occluder tip velocities, as well as the backflow of the fluid during the closing phase using this model, were in agreement with previously reported experimental measurements. The maximum impact force between the occluder and guiding struts of 140–280 N was determined to occur during the initial impact for a duration of 35–45 μus. The results of such model studies may be extended for the analysis of the endurance limit of the valve prostheses as well as to determine the mechanical stresses on the formed elements and the incipience of cavitation bubbles during the closing phase of the valve function.
7
Chiastra, Claudio, Stefano Morlacchi, Diego Gallo, Umberto Morbiducci, Rubén Cárdenes, Ignacio Larrabide, and Francesco Migliavacca. "Computational fluid dynamic simulations of image-based stented coronary bifurcation models." Journal of The Royal Society Interface 10, no. 84 (July 6, 2013): 20130193. http://dx.doi.org/10.1098/rsif.2013.0193.
Повний текст джерелаАнотація:
One of the relevant phenomenon associated with in-stent restenosis in coronary arteries is an altered haemodynamics in the stented region. Computational fluid dynamics (CFD) offers the possibility to investigate the haemodynamics at a level of detail not always accessible within experimental techniques. CFD can quantify and correlate the local haemodynamics structures which might lead to in-stent restenosis. The aim of this work is to study the fluid dynamics of realistic stented coronary artery models which replicate the complete clinical procedure of stent implantation. Two cases of pathologic left anterior descending coronary arteries with their bifurcations are reconstructed from computed tomography angiography and conventional coronary angiography images. Results of wall shear stress and relative residence time show that the wall regions more prone to the risk of restenosis are located next to stent struts, to the bifurcations and to the stent overlapping zone for both investigated cases. Considering a bulk flow analysis, helical flow structures are generated by the curvature of the zone upstream from the stent and by the bifurcation regions. Helical recirculating microstructures are also visible downstream from the stent struts. This study demonstrates the feasibility to virtually investigate the haemodynamics of patient-specific coronary bifurcation geometries.
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Manavi, Tejaswini, Masooma Ijaz, Helen O’Grady, Michael Nagy, Jerson Martina, Ciaran Finucane, Faisal Sharif, and Haroon Zafar. "Design and Haemodynamic Analysis of a Novel Anchoring System for Central Venous Pressure Measurement." Sensors 22, no. 21 (November 6, 2022): 8552. http://dx.doi.org/10.3390/s22218552.
Повний текст джерелаАнотація:
Background/Objective: In recent years, treatment of heart failure patients has proved to benefit from implantation of pressure sensors in the pulmonary artery (PA). While longitudinal measurement of PA pressure profoundly improves a clinician’s ability to manage HF, the full potential of central venous pressure as a clinical tool has yet to be unlocked. Central venous pressure serves as a surrogate for the right atrial pressure, and thus could potentially predict a wider range of heart failure conditions. However, it is unclear if current sensor anchoring methods, designed for the PA, are suitable to hold pressure sensors safely in the inferior vena cava. The purpose of this study was to design an anchoring system for accurate apposition in inferior vena cava and evaluate whether it is a potential site for central venous pressure measurement. Materials and Methods: A location inferior to the renal veins was selected as an optimal site based on a CT scan analysis. Three anchor designs, a 10-strut anchor, and 5-struts with and without loops, were tested on a custom-made silicone bench model of Vena Cava targeting the infra-renal vena cava. The model was connected to a pulsatile pump system and a heated water bath that constituted an in-vitro simulation unit. Delivery of the inferior vena cava implant was accomplished using a preloaded introducer and a dilator as a push rod to deploy the device at the target area. The anchors were subjected to manual compression tests to evaluate their stability against dislodgement. Computational Fluid Dynamics (CFD) analysis was completed to characterize blood flow in the anchor’s environment using pressure-based transient solver. Any potential recirculation zones or disturbances in the blood flow caused by the struts were identified. Results: We demonstrated successful anchorage and deployment of the 10-strut anchor in the Vena Cava bench model. The 10-strut anchor remained stable during several compression attempts as compared with the other two 5-strut anchor designs. The 10-strut design provided the maximum number of contact points with the vessel in a circular layout and was less susceptible to movement or dislodgement during compression tests. Furthermore, the CFD simulation provided haemodynamic analysis of the optimum 10-strut anchor design. Conclusions: This study successfully demonstrated the design and deployment of an inferior vena cava anchoring system in a bench test model. The 10-strut anchor is an optimal design as compared with the two other 5-strut designs; however, substantial in-vivo experiments are required to validate the safety and accuracy of such implants. The CFD simulation enabled better understanding of the haemodynamic parameters and any disturbances in the blood flow due to the presence of the anchor. The ability to place a sensor technology in the vena cava could provide a simple and minimally invasive approach for heart failure patients.
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Yin, Yuming, Subhash Rakheja, Jue Yang, and Paul-Emile Boileau. "Effect of articulated frame steering on the transient yaw responses of the vehicle." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 3 (June 16, 2017): 384–99. http://dx.doi.org/10.1177/0954407017702987.
Повний текст джерелаАнотація:
The directional performance characteristics of articulated frame steering vehicles are known to be strongly coupled with the kinematic characteristics and the dynamic characteristics of the steering system. The reported studies on articulated frame steering generally focus on the yaw divergence behaviour or the snaking tendency of the vehicle based on its free-yaw-oscillation response, while neglecting important contributions due to the kinematics and the dynamics of the steering system. This study characterizes both the free-yaw-oscillation response and the transient steering response of an articulated frame steering mining vehicle, considering the kinematics of the steering struts together with the dynamics of the flow volume-regulated steering valve and the actuating system. The validity of the analytical vehicle and steering system model is demonstrated using the measured data acquired for the vehicle. The free-oscillation behaviour of the articulated frame steering is characterized in terms of the yaw-mode natural frequency and the yaw damping ratio. The transient responses of the articulated frame steering are assessed in terms of the steering gain, the rate of articulation and the articulation overshoot. The effects of the variations in the various articulated frame steering parameters on the free response and the transient response are subsequently investigated and discussed so as to seek guidance for the design of the articulated frame steering system. It is shown that a higher bulk modulus of the hydraulic fluid and longer steering-arm lengths yield a higher yaw stiffness of the articulated frame steering system and thereby a higher frequency of the yaw oscillations. Higher leakage flows and higher viscous seal friction cause a higher yaw damping coefficient but decrease the steering gain and the articulation rate of the vehicle.
10
Boudet, J., V. N. D. Autef, J. W. Chew, N. J. Hills, and O. Gentilhomme. "Numerical simulation of rim seal flows in axial turbines." Aeronautical Journal 109, no. 1098 (August 2005): 373–83. http://dx.doi.org/10.1017/s000192400070042x.
Повний текст джерелаАнотація:
AbstractIn a gas turbine, ingestion of hot gas into the high-pressure turbine disc cavities could cause metal overheat. To prevent this, cool air is taken from the compressor and ejected through the cavities. However, this sealing flow also reduces the overall efficiency, and a compromise has to be found between the level of ingestion tolerated and the losses. Recent advances made in applying Computational Fluid Dynamics to such configurations are presented, with the aim of better understanding the physical phenomena and providing reliable design tools. First, results showing the pumping effect of the rotating disc are presented, including the influence of flow instabilities observed in both computational and experimental results. Second, the influence of the main annulus pressure asymmetries are analysed on a simplified representation of an available experiment, showing the combined influence of asymmetries generated by vanes and struts. Finally, a rim seal geometry representative of aero-engine design is studied in comparison to experiment, exhibiting the coupled influence of the cavity instabilities and annulus asymmetries.
11
Pecora, Rosario. "A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear." Applied Sciences 11, no. 9 (April 30, 2021): 4136. http://dx.doi.org/10.3390/app11094136.
Повний текст джерелаАнотація:
Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.
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Mani, M., A. Naghib-Lahouti, and M. Nazarinia. "Experimental and numerical aerodynamic analysis of a satellite launch vehicle with strap-on boosters." Aeronautical Journal 108, no. 1085 (July 2004): 379–87. http://dx.doi.org/10.1017/s0001924000005194.
Повний текст джерелаАнотація:
Abstract Results of numerical simulation of inviscid compressible flow around a generic satellite launch vehicle (SLV) with strap-on boosters using a commercial computational fluid dynamics (CFD) code named Star-CD are experimentally evaluated. Governing equations of flow around the SLV with two and two strap-on boosters were solved in three dimensions using the SIMPLE algorithm in an unstructured tetrahedral mesh, to determine longitudinal aerodynamic coefficients and surface pressure distribution at Mach numbers from 0·6 to 2·0, and angles-of-attack from 0° to 16°. To evaluate the numerical results, 1:100th scale models of the SLV were tested in a trisonic wind tunnel in the same configurations and flow conditions as those analysed numerically. Comparison of results shows reasonable agreement between numerical and experimental values, however, drag coefficients had to be corrected to compensate the effects of base flow and the struts connecting the boosters to the core rocket. This evaluation shows that a relatively simple simulation of flow using a commercial CFD code can be considered an efficient tool for prediction of aerodynamic characteristics of a multi body satellite launch vehicle with a level of accuracy acceptable in the process of preliminary aerodynamic design.
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Chondrou, I. T., G. Mavrantonakis, N. Tsagarakis, E. Vergis, D. Pangalos, and T. G. Chondros. "Design evaluation of the fractured main landing gear of a BAE Jetstream SX-SKY aircraft." International Journal of Structural Integrity 6, no. 4 (August 10, 2015): 468–92. http://dx.doi.org/10.1108/ijsi-08-2014-0039.
Повний текст джерелаАнотація:
Purpose – The purpose of this paper is to study the main landing gear (MLG) mechanism configuration. Design/methodology/approach – Mechanism kinematics and dynamics, stress analysis and sizing of the MLG structural members, and fatigue issues related with the mechanism operation. Spreadsheet solutions were incorporated to this survey to analyze the most conceivable loading situations, and important factors of the mechanism design for an initial evaluation of safety implications. Findings – MLG design approach along with conservative fatigue design factors lies in the area of accepted limits in commercial aircraft industry. Research limitations/implications – MLG loading associated with landing as well as those associated with ground maneuvers (steering, braking and taxiing) contribute significantly to fatigue damage, along with the stresses induced by manufacturing processes and assembly. The application of FEA methods for the design of the landing gear does not always guarantee a successful approach to the problem solution, if precise analytical solutions are not available in advance. Practical implications – From the investigation of this incident of fractured struts of the MLG it is confirmed that the reduction in Pintle Housing diameter on the upper part has contributed to the avoidance of damaging the fuel tank above the MLG that would lead to a catastrophic event. On the other hand, the airframe of the SKY-Jet was proved efficient for a belly landing with minor damages to the passengers and heavier damages for the aircraft. Social implications – On-line vibration monitoring sensors hooked up to the landing gear strut and Pintle House would greatly enhance safety, without relying in optical surveys in hard to access and inspect areas of the landing gears mechanisms housings. Originality/value – Analytic methods were adopted and spreadsheet solutions were developed for the MLG main loading situations, along with design issues concerning mechanism kinematics and dynamics, stress analysis and sizing of the MLG structural members, as well as fatigue issues related with the mechanism operation. Spreadsheet solutions were incorporated to this survey to analyze the most conceivable loading situations, and important factors of the mechanism design for an initial evaluation of safety implications.
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Xia, Chao, Xizhuang Shan, and Zhigang Yang. "Comparison of different ground simulation systems on the flow around a high-speed train." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 231, no. 2 (August 4, 2016): 135–47. http://dx.doi.org/10.1177/0954409715626191.
Повний текст джерелаАнотація:
The influence of different ground simulation systems on the air flow around a high-speed train with zero yaw angle is investigated. Force values, force development graphs, surface pressures, the underbody flow and the wake are studied in detail with Computational Fluid Dynamics, which is initially validated by wind tunnel testing. It shows that the stationary ground has severe deviations from the full moving ground on the aerodynamic performance due to the inaccurate pressure distribution on the underbody. This is mainly attributed to the high level of interaction between the underbody and the boundary layer development. In addition, a ground boundary layer separation bubble can be observed under the tail end of the train for the stationary ground on account of insufficient energy to overcome the increasing adverse pressure gradient. In order to guarantee a correct underbody flow, a partially moving ground is proposed, including the “3-moving ground” and the “1-moving ground”. Such ground simulation systems are well compatible with the fixed rail tracks and the bottom support struts compared to the full moving ground. As a conceivable method to reduce the influence of the boundary layer, raising the high-speed train model with different ground clearances is also studied. Overall, the 3-moving ground is suggested to be the best choice for the ground simulation systems in high speed train wind tunnel testing.
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Sanvito, Andrea, Vincenzo Dossena, and Giacomo Persico. "Formulation, Validation, and Application of a Novel 3D BEM Tool for Vertical Axis Wind Turbines of General Shape and Size." Applied Sciences 11, no. 13 (June 24, 2021): 5874. http://dx.doi.org/10.3390/app11135874.
Повний текст джерелаАнотація:
Low order models based on the Blade Element Momentum (BEM) theory exhibit modeling issues in the performance prediction of Vertical Axis Wind Turbines (VAWT) compared to Computational Fluid Dynamics, despite the widespread engineering practice of such methods. The present study shows that the capability of BEM codes applied to VAWTs can be greatly improved by implementing a novel three-dimensional set of high-order corrections and demonstrates this by comparing the BEM predictions against wind-tunnel experiments conducted on three small-scale VAWT models featuring different rotor design (H-shaped and Troposkein), blade profile (NACA0021 and DU-06-W200), and Reynolds number (from 0.8×105 to 2.5×105). Though based on the conventional Double Multiple Stream Tube (DMST) model, the here-presented in-house BEM code incorporates several two-dimensional and three-dimensional corrections including: accurate extended polar data, flow curvature, dynamic stall, a spanwise-distributed formulation of the tip losses, a fully 3D approach in the modeling of rotors featuring general shape (such as but not only, the Troposkein one), and accounting for the passive effects of supporting struts and pole. The detailed comparison with experimental data of the same models, tested in the large-scale wind tunnel of the Politecnico di Milano, suggests the very good predictive capability of the code in terms of power exchange, torque coefficient, and loads, on both time-mean and time-resolved basis. The peculiar formulation of the code allows including in a straightforward way the usual spanwise non-uniformity of the incoming wind and the effects of skew, thus allowing predicting the turbine operation in a realistic open-field in presence of the environmental boundary layer. A systematic study on the operation of VAWTs in multiple environments, such as in coastal regions or off-shore, and highlighting the sensitivity of VAWT performance to blade profile selection, rotor shape and size, wind shear, and rotor tilt concludes the paper.
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Tupy, David, Vaclav Slama, and Robert Kalista. "Experimental Research on the Flow in the Steam Turbine Axial Exhaust Hood." EPJ Web of Conferences 269 (2022): 01063. http://dx.doi.org/10.1051/epjconf/202226901063.
Повний текст джерелаАнотація:
There is the still remaining task to increase the efficiency of power plants and steam turbines. One possibility to increase the thermodynamic efficiency is to apply a suitable exhaust hood. Axial exhaust hoods are mainly designed for small turbines up to 180 MW. They are a very important part of steam turbines and its main purpose is to take away the steam from the last stage outlet to a condenser with minimal loss or even with pressure compression and an increase in the last stage enthalpy drop. This paper concerns experimental measurements on the axial exhaust hood wind tunnel model. The main goal of this paper is to determine how given geometrical and flow parameters affect the resulting pressure recovery coefficient. Main observed parameters are velocity and circumferential angle profiles at the diffuser inlet along with a number, shape and geometrical configuration of internal struts. Several geometrical variants are measured for two types of circumferential angles at the diffuser inlet and for two values of Mach number in the presented work. Multi-hole pneumatic probes and pressure taps are used for flow parameters measurement. The proposed experimental model, along with corresponding CFD (computational fluid dynamics) simulations, will help to optimize the flow parameters in the exhaust hood and allow a decrease in pressure losses in this part.
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Liu, Renjie, Chao Wang, Suduo Xue, and Yao Zou. "Analysis on the Collapse Resistance of the Loop-free Suspen-Dome Subjected to Cable or Strut Failure." Journal of the International Association for Shell and Spatial Structures 63, no. 1 (March 1, 2022): 5–15. http://dx.doi.org/10.20898/j.iass.2021.018_2.
Повний текст джерелаАнотація:
Current suspen-domes use loop cables which are key elements and carry large tensions. Loop-free suspen-dome was proposed for improving the collapse resistance and reducing cable tensions. The collapse resistance of loop-free suspen-dome has not been verified. In this paper, analysis on dynamic response of both current suspen-dome and loop-free suspen-dome induced by sudden cable or strut failure is performed to investigate the collapse resistance. Under the loaded state, cables or struts were suddenly removed from the structure to simulate cables or struts failure. Th residual bearing capacity of the structure after the rupture was also analyzed. It is concluded that collapse resistance of the loop-free suspen-dome is good. Failure mode of the loop-free suspen-dome is proportionate. The effect on the loop-free suspen-dome due to initial failure grows proportionately along with the quantity of failed members. It also turns out that cables in the loop-free suspen- dome are relatively independent. Only the failed cable loses tension, other cables still remain in tension. It is also found that the most important cable or strut in the loop-free suspen-dome is in the outermost layer of the cable-strut system. More concern should be shown to the cables and struts in the outermost layer.
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Sattar, Siamak, and Abbie B. Liel. "Seismic Performance of Nonductile Reinforced Concrete Frames with Masonry Infill Walls—I: Development of a Strut Model Enhanced by Finite Element Models." Earthquake Spectra 32, no. 2 (May 2016): 795–818. http://dx.doi.org/10.1193/90914eqs139m.
Повний текст джерелаАнотація:
Reinforced concrete (RC) frames with masonry infill walls are prevalent in high-seismicity areas worldwide and have experienced significant damage in earthquakes. This paper proposes a finite element–enhanced strut model to simulate the in-plane seismic response of masonry-infilled RC frames through time-history analysis. The strut backbone defining the behavior of the wall is developed from the response extracted from the finite element (FE) model(s) for the infill and frame configuration of interest. These struts are combined with models capturing flexural and shear failures of beam-columns to simulate building response. The strut model takes advantage of the accuracy of the FE modeling results, yet is computationally efficient for use in nonlinear dynamic analysis. The robustness of the proposed strut model is examined through comparison with experimental results for frames with different failure modes. This modeling approach is used in the companion paper to simulate the collapse response of 1920s-era California frames.
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Asiri, S., A. Baz, and D. Pines. "Periodic Struts for Gearbox Support System." Journal of Vibration and Control 11, no. 6 (June 2005): 709–21. http://dx.doi.org/10.1177/1077546305052784.
Повний текст джерелаАнотація:
Passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called “pass bands” and wave propagation is completely blocked within other frequency bands called “stop bands”. In this paper, the emphasis is placed on developing a new class of these periodic structures called passive periodic struts, which can be used to support gearbox systems on the airframes of helicopters. When designed properly, the passive periodic strut can stop the propagation of vibration from the gearbox to the airframe within critical frequency bands, consequently minimizing the effects of transmission of undesirable vibration and sound radiation to the helicopter cabin. The theory governing the operation of this class of passive periodic struts is introduced and their filtering characteristics are demonstrated experimentally as a function of their design parameters. The presented concept of the passive periodic strut can be easily used in many applications to control the wave propagation and the force transmission in both the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.
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Kong, De Sen, Yan Qing Men, and Li Hua Wang. "A Simplified Computational Method of Lateral Dynamic Impedance of Single Pile." Advanced Materials Research 243-249 (May 2011): 2985–89. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2985.
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Research of the pile-soil interaction effect is a complicated issue in civil engineering. Using the principle of soil dynamics and structural dynamics, a simplified computational method for computing the lateral dynamic impedance of single pile embedded in layered non-homogeneous subsoil is established based on a certain assumptions. Both non-homogeneity of soil strata and softening effect of soil layer around pile during vibration as well as separation of pile-soil interface are simultaneously taken into account in the proposed computational method. The characteristics of the frequency-dependency of lateral dynamic stiffness and damping of pile are reproduced. It is shown through the comparative study on a numerical example that the numerical results of dynamic impedance of pile computed by the proposed method are relatively rational and can well agree with the computational and experimental results currently available.
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Sayma, A. I., M. Vahdati, and M. Imregun. "Multi-bladerow fan forced response predictions using an integrated three-dimensional time-domain aeroelasticity model." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 12 (December 1, 2000): 1467–83. http://dx.doi.org/10.1243/0954406001523425.
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A non-linear integrated aeroelasticity system to predict the forced vibration response of aero-engine fans is presented in this paper. The computational fluid dynamics (CFD) solver, which uses Favre-averaged Navier-Stokes equations on unstructured grids of mixed elements, is coupled to a modal model of the structure so that the effects of blade flexibility can be accommodated. The structural motion due to unsteady fluid forces is computed at every time step and the flow mesh is moved to follow the structure so that the resulting flow unsteadiness is determined in a time-accurate fashion. Two fan forced response case studies are reported in detail. The first one deals with a high-pressure ratio fan, the excitation being due to the upstream variable-angle inlet guide vanes (VIGVs). The unsteady flow analysis with blade motion was conducted using a sector of three VIGVs and four rotor blades. The wake predictions were found to be in good agreement with the corresponding laser measurements. The flow was observed to be completely separated for high VIGV angles and the excitation encompassed several harmonics. The predicted rotor blade vibration levels were generally found to be within 30 per cent of the measured values. The forced response to upstream obstructions was studied in the next fan case study. Three whole bladerows, consisting of 11 struts, 33 VIGVs and 26 rotor blades, were modelled in full. The model also included a prescribed inlet distortion pattern so that the combined effects of stator wakes and inlet distortion on the response of the rotor blades could be studied. The unsteady flow calculations were conducted using a time-accurate non-linear viscous flow representation. Blade motion was also included. Such an undertaking required about 4.2 million grid points to include all three bladerows in a complete stage calculation. To reduce the computational effort, a number of smaller computations were conducted by considering the stator and rotor domains separately: the outflow solution of the stator domain was used as an inflow boundary condition to the rotor domain. The results indicated that such isolated bladerow computations were likely to under-predict the response levels because of neglecting rotor-stator interactions. A number of low engine order (LEO) harmonics were identified from an inspection of the unsteady forcing created by the inlet distortions. Good agreement was obtained for cases where experimental data were available.
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Chen, Li Jing, Jian Zheng, and Cheng Ke Zhang. "Research on Numerical Simulation Model for Crack Growth Driven by Detonation Gas in High-Deep Rock Strata." Applied Mechanics and Materials 170-173 (May 2012): 824–29. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.824.
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The effect of detonation gas upon rock fracture is the cross-frontier research project of fluid dynamics coupling and rock dynamics of crack dynamic growth, having the important scientific significance and explicit application value. In the process of detonation gas driven fracture growth, the varying law of the denotation gas pressure distribution in cracks is inter-influent with the geometric morphology variations in crack growth. This paper analyzes the denotation gas flowing behaviors, establishes the flowing model for denotation gas in rock cracks and the models for the rock crack dynamic response. Also suggests the fluid-solid coupling model for the denotation gas flowing, rock crack response and the numerical model for simulating crack growth driven by the denotation gas. The simulation program is developed on the large-sized rock engineering finite element software (FINAL platform). This numerical analysis platform is used to carry out the systematic numerical experimental study of several main influencing factors of core problems concerning pressure fracture length.
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Bovo, Marco, Michele Tondi, and Marco Savoia. "Infill Modelling Influence on Dynamic Identification and Model Updating of Reinforced Concrete Framed Buildings." Advances in Civil Engineering 2020 (June 19, 2020): 1–16. http://dx.doi.org/10.1155/2020/9384080.
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In order to correctly capture the dynamic behavior of infilled framed buildings, the importance to take into account in seismic design the infill panels’ contribution is nowadays well recognized since they could modify in a significant way the global and local response of the whole building. Despite about sixty years of continuous research in the field, the modelling of the frame-infill interaction still represents a serious issue for the daily practical design since there is no reference model proven to be suitable to cover a wide record of possible cases. Moreover, few works are available in the literature, comparing the results of different modelling proposals with outcomes of dynamic tests on a full-scale building. To this regard, starting from the results of induced vibration dynamic tests performed on a 7-story building with reinforced concrete frames with masonry infill, in the present paper, the effects of the infill presence have been evaluated by comparing experimental outcomes, achieved using a MDOF Circle-Fit identification procedure, with the results obtained by means of numerical analyses performed on finite element models. Using a model updating procedure, the optimal width to assign to the masonry equivalent struts modelling the infill panels was defined. Furthermore, several literature proposals for the definition of the equivalent strut width have been analysed. Thirteen different proposals have been selected and implemented in thirteen different finite element models. The reliability of each proposal has been investigated and quantified by comparing the dynamic properties of the models with the building dynamic response obtained by the experimental tests. The main outcomes of the analyses highlight that different proposals provide a great variability for the strut width. This brings to a large variability of the mechanical properties of the equivalent struts, and as a consequence, the modelling choice also influences the dynamic behaviour of the numerical models. Currently, this represents a serious issue for the daily designers’ activity. The outcomes provided in the paper, although established for a specific case study, can be extended to a wide range of buildings and should drive the future research studies in order to provide more robust criteria for the modelling of this worldwide building class.
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Lin, Qing, and Jie Ren. "Investigation on the Horizontal Landing Velocity and Pitch Angle Impact on the Soft-Landing Dynamic Characteristics." International Journal of Aerospace Engineering 2022 (January 25, 2022): 1–16. http://dx.doi.org/10.1155/2022/3277581.
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The dynamic analysis of the soft landing of the lunar probe is very important to the design of the probe. The initial movement and attitude parameters of the probe during landing have a direct influence on the landing impact. In order to investigate the lunar probe soft-landing dynamic impact by different initial horizontal velocities, pitch angles, and inclinations of the lunar slope, an inertial force-based 7-DOF soft-landing dynamic model is applied under two conditions: the upward and downward slope landing surfaces. The impact on the dynamic characteristics of soft landing is analyzed in terms of body displacement, body overload, and the forces of the primary and secondary buffer struts due to the change of initial horizontal velocity and initial pitch angle of the probe. The result shows that, in 2-2 landing mode, the stress conditions on the primary and secondary struts are obviously impacted by initial horizontal velocity, and the initial pitch angle affects the body overload and the loading state of the secondary buffer strut. The body overload and landing impact could be significantly mitigated if the lunar probe’s horizontal landing speed is limited within 1 m/s, the pitch angle is limited within 12°, and the landing is along the uphill terrain with the inclination of the lunar slope less and equal to 9°. The analysis can directly determine the range of the horizontal speed and pitch attitude angle to ensure the safety of landing, and provide a reference for the reasonable control design of the lander’s horizontal speed and pitch attitude.
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Chen, Lianmeng, Zebin Li, Yijie Liu, Kaiyu Huang, Yihong Zeng, Yiyi Zhou, and Shilin Dong. "Analysis and Evaluation of the Progressive Collapse Behaviour of a Cable Dome Structure." Buildings 12, no. 10 (October 16, 2022): 1700. http://dx.doi.org/10.3390/buildings12101700.
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In this study, the progressive collapse behaviour of a cable dome structure was analysed and evaluated according to the importance of element. First, the dynamic response and collapse mode caused by the removal of different types of cables and struts from a cable dome structure were studied using the instantaneous unloading method of full dynamic equivalent load. Second, a method was developed for element importance classification based on collapse modes, and the importance coefficient was introduced after comparing the node displacements before and after the removal of different elements. On this basis, the correlations of the importance coefficient of an element with its importance classification and the collapse mode caused by its removal were examined. Third, the influences of some design parameters on the resistance of cable dome structures to progressive collapses and on the importance coefficients of components were analysed and evaluated. Finally, a method was proposed to determine the critical value of the element importance category. The results of this study indicated that Cable-Strut elements differed in their antiprogressive collapse effects and importance coefficients, and thus produced different dynamic responses and collapse modes when they were removed. Cable domes differed in their critical importance coefficients for Cable-Strut elements, and design parameters differed in their influence on the antiprogressive collapse resistance of cable domes.
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Zhao, Yongjie, Ziqiang Zhang, and Gang Cheng. "Inverse rigid-body dynamic analysis for a 3UPS-PRU parallel robot." Advances in Mechanical Engineering 9, no. 2 (February 2017): 168781401769319. http://dx.doi.org/10.1177/1687814017693194.
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Inverse rigid-body dynamic analysis for a 3UPS-PRU parallel robot are conducted in this research. The position, velocity, acceleration, jerk, and singularity are considered in the inverse kinematics analysis. The rigid-body dynamic model is developed by means of the principle of virtual work and the concept of link Jacobian matrices. The driving torque, driving power, and required output work of motors have been computed in the inverse rigid-body dynamics analysis. For the pre-defined trajectory, the required output work generated by the driving motor is achieved by numerical integration technique. The inverse kinematics and rigid-body dynamics have been investigated in an exhaustive decoupled way. The effects of the velocity of the moving platform on the components of the joint acceleration, joint jerk, driving torque, and driving power, which are related to the velocity of the moving platform, are investigated. There are linear relationships between the acceleration of the moving platform and the components of the joint acceleration, joint jerk, driving torque, and driving power, which are related to the acceleration of the moving platform. The total driving torques, the torques related to the acceleration, velocity, and gravity, the torques related to the moving platform, strut connected with the moving platform, strut connected with the base platform, and motor rotor-coupler are calculated. The total driving powers, the powers related to the acceleration component of torque, velocity component of torque, gravity component of torque, and the powers related to the moving platform, strut connected with the moving platform, strut connected with the base platform, and motor rotor-coupler are also achieved.
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Suresh, PS, Niranjan K. Sura, and K. Shankar. "Investigation of nonlinear landing gear behavior and dynamic responses on high performance aircraft." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 15 (July 1, 2019): 5674–88. http://dx.doi.org/10.1177/0954410019854628.
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The dynamic responses simulation of aircraft as rigid body considering heave, pitch, and roll motions, coupled onto a tricycle landing gear arrangement is presented. Equation of motion for each landing gear consists of un-sprung mass vertical and longitudinal motions considering strut nonlinear stiffness and damping combined with strut bending flexibility. Initially, the nonlinear dynamic response model is subjected to an input of riding over staggered bump and the responses are compared with linear landing gear model. It is observed that aircraft dynamics and important landing gear events such as vertical, spin-up and spring-back are truly represented with nonlinear stiffness and damping model considering strut bending flexibility. Later, landing response analysis is performed, with the input from nonlinear flight mechanics model for several vertical descent rate cases. The aircraft and landing gear dynamic responses such as displacement, velocity, acceleration, and reaction forces are obtained. The vertical and longitudinal drag forces from the nonlinear dynamic response model is compared with “Book-case method” outlined in landing gear design technical specifications. From the reaction force ratio calculation, it is shown that for lower vertical descent rate case the predicted loads are lesser using nonlinear dynamic response model. The same model for higher vertical descent rate cases predicts higher ratios on vertical reaction for main landing gear and longitudinal reaction for nose landing gear, respectively. The scope for increase in fatigue life for low vertical descent rate landing covering major design spectrum and the concern for static strength and structural integrity consideration for higher vertical descent rate cases are discussed in the context of event monitoring on aircraft in services.
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Chen, Hu, Xingbo Fang, and Hong Nie. "Analysis of Carrier-Based Aircraft Catapult Launching Based on Variable Topology Dynamics." Applied Sciences 11, no. 19 (September 28, 2021): 9037. http://dx.doi.org/10.3390/app11199037.
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The catapult process of a carrier-based aircraft includes multiple links such as catapult tensioning, separation of the holding rod, dragging and running, separation of the catapult and drag shuttle, and free running. The connection relationships between the front landing gear of the carrier-based aircraft and other related components in each link are different, therefore, it is necessary to adjust the topological relationships of the dynamic model in real time, when solving the catapult dynamics of a carrier-based aircraft. In this paper, a dynamic model of the multibody system of the catapult take-off is established, and a variable topology solution is carried out for the dynamic model by adjusting dynamic augmentation equations; in addition, a dynamic analysis of a carrier-based aircraft catapult and take-off process is carried out. A catapult dynamics model and variable topology solution method were established, which solved the changes at the moment of the restraining rod separation, catapult rod separation, and catapult tackle during the aircraft catapult take-off. After the restraining rod was separated from the front landing gear, the catapult force was transmitted to the rear strut, which instantly increased the load of the rear strut by 238.5 kN. In addition, after the carrier-based aircraft reached the end of the catapult’s stroke, the catapult rod was separated from the catapult tow shuttle then unloaded, and the load of the rear strut was reduced from 486.2 kN to −20.3 kN. Under the protruding effect of the nose gear, the pitch angle of the carrier-based aircraft increased rapidly from −0.93° and reached 0.54° when the carrier-based aircraft rushed out of the deck.
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Wang, Zhiqiang, Jingkai Li, Chao Wu, Wenyu Lv, Jiao Zhang, Peng Wang, Zhen Li, and Hengzhe Qu. "Study on Influence Laws of Strata Behaviors for Shallow Coal Seam Mining beneath Gully Terrain." Shock and Vibration 2021 (July 2, 2021): 1–12. http://dx.doi.org/10.1155/2021/3954659.
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The study on influence laws of strata behaviors is the basic guarantee of safety mining for shallow coal seam beneath gully terrain. Taking 3302 mining face of Zhujiamao Coal Mine as the engineering background, the laws of strata behaviors for shallow coal seam mining beneath gully terrain are studied by field detection, theoretical analysis, and numerical simulation. The strata pressure observation and the hydraulic support working resistance show that the dynamic strata behaviors appear violently during mining beneath the gully bottom. The theoretical analysis shows that the rotation and breaking of key stratum beneath gully bottom under nonuniform load is the fundamental cause of strong dynamic strata behaviors. The numerical simulation of overburden movement and fissure development characteristics shows that the strata behaviors beneath the gully bottom are stronger than the strata behaviors beneath other areas. Additionally, according to the laws of dynamic strata behaviors, the safety measures for mining beneath gully bottom are put forward.
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Shobeiri, Vahid. "Determination of strut-and-tie models for structural concrete under dynamic loads." Canadian Journal of Civil Engineering 46, no. 12 (December 2019): 1090–102. http://dx.doi.org/10.1139/cjce-2018-0780.
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This proposed study aims to develop reliable and efficient numerical optimization methods for generating optimal strut-and-tie models (STMs) in structural concrete members under dynamic loads. The numerical models are developed based on the bidirectional evolutionary structural optimization (BESO) method for the stiffness maximization problems. In this method, a controlling index based on the minimum weight and maximum stiffness is defined as the optimization criterion function and the element virtual strain energy is taken as the element removal and addition criterion. By the dynamical analysis, optimal strut-and-tie models are established based on the BESO method. Several examples are presented to show the efficiency of the proposed approach in finding optimal STMs under dynamic loads. It is shown that optimal STMs and reinforcement layouts under dynamic loads generally differ from those obtained under static loads. The developed numerical models based on dynamic responses can be used by practicing design engineers for the analysis and design of STMs in concrete structures.
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Modi, Raghvendra R. "Seismic Performance Assessment of Masonary Infilled RC Frames by Using Staad PRO." International Journal for Research in Applied Science and Engineering Technology 10, no. 5 (May 31, 2022): 3908–18. http://dx.doi.org/10.22214/ijraset.2022.43272.
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Abstract: Now a days construction of the RC frame is common because of the simplicity in construction. The masonry walls are mainly used for partition and insulation purposes rather than for structural purposes. However, during the earthquake, this filling contributes to the response of the structure and the behavior of the filling frame is different from that expected for the structure of the bare frame. The fill acts as a compression strut between column and beam. For this purpose, linear dynamic analysis were carried out on the structure of the RC masonry frame to study the influence of the resistance variation of the structure with n without a infill wall, filling effect on dynamic parameters such as the natural period, displacement and state of the hinge. In this rear-end collision effect high building is studied. All analysis are performed by the STAAD PRO v8i software. building modeling and analysis are performed on STAAD PRO v8i. For the analysis the building with G + 10 RCC frame is modeled. In this analysis the width of the strut is calculated manually according to the expression given in the FEMA-356. The infill panels are modeled as equivalent single diagonal struts. Several equations for calculation are considered for these diagonals. In this study the comparison of time verses acceleration , time verses velocity , time verses displacement with respect to the floor is made . The study shows that the influence of filling on the structure is significant. It increases the rigidity of the structure and makes the structure able to withstand a seismic region with respect to the bare frame. Keywords: Infill walls, Seismic force, base shear , STAAD Pro. , Time History, response spectrum.
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Lin, Shengmao, Pengfei Dong, Changchun Zhou, Luis Augusto P. Dallan, Vladislav N. Zimin, Gabriel T. R. Pereira, Juhwan Lee, et al. "Degradation modeling of poly-l-lactide acid (PLLA) bioresorbable vascular scaffold within a coronary artery." Nanotechnology Reviews 9, no. 1 (December 12, 2020): 1217–26. http://dx.doi.org/10.1515/ntrev-2020-0093.
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AbstractIn this work, a strain-based degradation model was implemented and validated to better understand the dynamic interactions between the bioresorbable vascular scaffold (BVS) and the artery during the degradation process. Integrating the strain-modulated degradation equation into commercial finite element codes allows a better control and visualization of local mechanical parameters. Both strut thinning and discontinuity of the stent struts within an artery were captured and visualized. The predicted results in terms of mass loss and fracture locations were validated by the documented experimental observations. In addition, results suggested that the heterogeneous degradation of the stent depends on its strain distribution following deployment. Degradation is faster at the locations with higher strains and resulted in the strut thinning and discontinuity, which contributes to the continuous mass loss, and the reduced contact force between the BVS and artery. A nonlinear relationship between the maximum principal strain of the stent and the fracture time was obtained, which could be transformed to predict the degradation process of the BVS in different mechanical environments. The developed computational model provided more insights into the degradation process, which could complement the discrete experimental data for improving the design and clinical management of the BVS.
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Wang, Daoyong, Wencan Zhang, Mu Chai, and Xiaguang Zeng. "Research on the dynamic characteristic of semi-active hydraulic damping strut." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 6 (October 18, 2019): 1779–91. http://dx.doi.org/10.1177/0954407019881514.
Повний текст джерелаАнотація:
To reduce the vibration and shock of powertrain in the process of engine key on/off and vehicle in situ shift, a novel semi-active hydraulic damping strut is developed. The purpose of this paper is to study and discuss the dynamic stiffness model of the semi-active hydraulic damping strut. In this study, the dynamic characteristics of semi-active hydraulic damping strut were analyzed based on MTS 831 test rig first. Then, the dynamic stiffness model of semi-active hydraulic damping strut was established based on 2 degrees of freedom vibration system. In this research, a linear, fractional derivative and friction model was used to represent the nonlinear rubber bushing characteristic; the Maxwell model was used to describe the semi-active hydraulic damping strut body model; and the parameters of rubber bushing and semi-active hydraulic damping strut body were identified. The dynamic stiffness values were calculated with solenoid valve energized and not energized at amplitudes of 1 mm and 4 mm, which were consistent with experimental results in low-frequency range. Furthermore, the simplified dynamic stiffness model of the semi-active hydraulic damping strut was discussed, which showed that bushing can be ignored in low-frequency range. Then, the influence of equivalent spring stiffness, damping constant, and rubber bushing stiffness on the stiffness and damping capacity of the semi-active hydraulic damping strut were analyzed. Finally, the prototype of the semi-active hydraulic damping strut was developed and designed based on the vehicle in situ shift and engine key on/off situations, and experiments of the vehicle with and without semi-active hydraulic damping strut were carried out to verify its function.
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Wang, Dao-Yong, Wen-Can Zhang, and Xia-Guang Zeng. "Investigation on a semi-active hydraulic damping strut to reduce vehicle in situ shift vibration." Journal of Vibration and Control 26, no. 1-2 (November 12, 2019): 3–18. http://dx.doi.org/10.1177/1077546319874921.
Повний текст джерелаАнотація:
In order to reduce the shock and vibration caused by torque disturbance of the gearbox in vehicles equipped with automatic transmission in the process of in situ shift, a novel semi-active hydraulic damping strut is introduced in the powertrain mounting system. The dynamic response evaluation indexes of vehicle in situ shift are put forward, and a 13-degree of freedom vehicle dynamic model including the semi-active hydraulic damping strut is established. The optimized dynamic characteristic parameters are acquired according to the principle of sharing force and the 13-degree of freedom vehicle dynamic model. The dynamic response evaluation indexes with and without the semi-active hydraulic damping strut are calculated using the 13-degree of freedom vehicle dynamic model in the process of in situ shift, and the calculation results show that the vibration of a vehicle can be reduced by the introduction of a semi-active hydraulic damping strut. Experiments are carried out to analyze the vibration response of the vehicle with and without a semi-active hydraulic damping strut, and the results show that the shock and vibration of the vehicle are reduced by introducing the semi-active hydraulic damping strut. The theoretical calculation values of active-side acceleration of the engine mount and torque strut are consistent with the experimental values, which show that the 13-degree of freedom vehicle dynamic model is reasonable.
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SWARTZ, M. A., and M. J. D. HAYES. "KINEMATIC AND DYNAMIC ANALYSIS OF A SPATIAL ONE-DOF FOLDABLE TENSEGRITY MECHANISM." Transactions of the Canadian Society for Mechanical Engineering 31, no. 4 (December 2007): 421–31. http://dx.doi.org/10.1139/tcsme-2007-0030.
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This paper presents a mechanical analysis of a spatial 1-DOF tensegrity mechanism created by connecting three planar tensegrity mechanisms to form a triangular prism. The subsequent investigation produced kinematic and dynamic models that allow the workspace-boundary singularities and minimum energy configuration to be determined. Singularities were found to occur when the mechanism is folded in the vertical X, Y plane or in the horizontal X, Z plane. The minimum energy configuration, formed by the angle between the horizontal plane and the actuated strut, was found to be θ = π/4. However, when the system was linearized to determine the analytic solution for the dynamics, the minimum energy configuration become θ = 1 due to the inherent error produced by the system linearization. The dynamic response of the mechanism to an initial small displacement was determined for each case of critically damped, overdamped, and underdamped systems.
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Pan, Junfeng, Shaohong Liu, Shuwen Wang, and Yongxue Xia. "A New Theoretical View of Rockburst and Its Engineering Application." Advances in Civil Engineering 2018 (August 16, 2018): 1–12. http://dx.doi.org/10.1155/2018/4683457.
Повний текст джерелаАнотація:
Traditionally, rockburst is considered as a dynamic phenomenon of sudden destruction of coal/rock mass. In this study, rockburst is treated as an event process rather than a phenomenon. This paper introduces typical rockburst process, its classification, mechanism of internal and external causes, and energy criterion. Analysis indicates that rockburst is a dynamic process that includes three sequential phases: burst start-up, burst energy transfer, and rockburst pressure behavior. Excessive static stress concentration in the strata nearby the target zone appears to be the internal cause of rockburst start-up, while the external cause is the disturbance of the static stress concentration and additional load transfer by the concentrated dynamic load occurred at further distance. Potential burst start-up area is the highest stress concentration zone within the region where stress is in the critical equilibrium state. With the identified internal and external factors that contribute to rockburst start-up, it is concluded that the rockburst preventive measures should focus on the monitoring and controlling of originating source of static and dynamic stress concentrations. Field practice proves that the reunderstanding of rockburst and the derived preventive measures are feasible and successful.
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Yue, Shuai, Hong Nie, Ming Zhang, Mingyang Huang, He Zhu, and Dafu Xu. "Dynamic analysis for vertical soft landing of reusable launch vehicle with landing strut flexibility." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 4 (January 16, 2018): 1377–96. http://dx.doi.org/10.1177/0954410017753209.
Повний текст джерелаАнотація:
Based on oleo-honeycomb dampers, a 6-DOF vertical soft landing dynamic model for reusable launch vehicle considering landing strut flexibility is constructed. In order to better analyze the lateral deflection and friction force of the “cantilever beam” type landing strut, a new model for strut is incorporated. Static analysis is first performed based on the rotation angle compatibility equations to attain the equivalent inertia moment. Then the strut lateral vibration model and friction force model are obtained by simplifying it as viscoelastic beam with a tip mass. After that, the ADAMS models are established to perform the comparison and verification analysis of the 6-DOF dynamic model. The results show that the results of 6-DOF dynamic model can approximately approach to the results of rigid-flex coupling model established in ADAMS. Furthermore, the research of the influence of assembly gap between cylinders and bearings, bearing’s elastic modulus, friction coefficient and initial overlapping length on the vehicle landing performance is carried out. The results show that each parameter has different influence on the landing performance, and a reasonable selection of these parameters accordingly enables a higher landing performance.
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SHEKASTEHBAND, B., and K. ABEDI. "DYNAMIC PROPAGATION OF SNAP-THROUGH BUCKLING IN TENSEGRITY STRUCTURES." International Journal of Structural Stability and Dynamics 14, no. 01 (December 17, 2013): 1350049. http://dx.doi.org/10.1142/s0219455413500491.
Повний текст джерелаАнотація:
Tensegrity structures under certain conditions may be prone to snap-through buckling. The temporary loss of equilibrium due to snap-through normally results in a dynamic force being applied to each node associated with the snap-through. This paper presents a numerical study on the progressive collapse behavior of tensegrity structures due to the buckling of struts. Emphasis is given to the dynamic nature of the coupled member and nodal snap-through effects on the overall structural behavior. Member buckling is taken into consideration by carefully following the buckling load–displacement response of the member. It is assumed that the structure is subjected only to static gravitational load. Results of the present study allow one to assess the effects of various design parameters such as self-stress levels, effective-length factor of struts and damping characteristics on the propagation of snap-through buckling in these structures. The conclusions, drawn from this study, lead to the suggestion of some guidelines and recommendations for the design of such structures.
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Abaturova, I. V., L. A. Storozhenko, E. D. Nugmanova, and V. S. Kozlov. "Dynamics of Engineering and Geological Conditions of Mineral Deposits (from Exploration to Exploitation)." Вестник Пермского университета. Геология 20, no. 3 (2021): 222–28. http://dx.doi.org/10.17072/psu.geol.20.3.222.
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The development of mineral deposits has strong transformative effect on the geological environment. At the same time, all the components of geotechnical conditions (relief, structure of rock massifs, hydrogeological and geocryological conditions etc.), formed over a long geological time, are actively changing. Geological processes are activated and new mining-geological processes are formed. New strata are formed on the Earth's surface along with the technogenic formations and technogenic deposits. Today, the scale of technogenesis in mining is comparable to the results of geological activities that have been going on for many millions of years. The reaction of the geological environment is immediate and is expressed in the development of large-scale engineering and geological processes, which often do not allow the further development of mineral resources and threaten the human life. Therefore, even at the early stages of prospecting and/or exploration, it is necessary to understand the dynamics of changes in surrounding medium in order to develop methods for proper managing of the ore extraction. By the example of a number of objects, all the stages of study of engineering-geological conditions are considered, the dynamics of their change, which led to the formation of engineering-geological processes affecting the further development of mineral resource, is estimated.
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Lai, Xingping, Leiming Zhang, Yun Zhang, Pengfei Shan, Peifeng Wan, and Kaiwen Mu. "Research of the Backfill Body Compaction Ratio Based on Upward Backfill Safety Mining of the Close-Distance Coal Seam Group." Geofluids 2022 (March 7, 2022): 1–11. http://dx.doi.org/10.1155/2022/8418218.
Повний текст джерелаАнотація:
During upward backfill mining of the close-distance coal seam group, the reasonable design of the backfill body compaction ratio (BBCR) of lower coal seam goaf plays a key role in controlling overburden strata movement and deformation. In this paper, the feasibility discrimination method of upward caving mining was adopted; it was found that when the coal seam spacing was small, the recovery was not possible due to the instability of the upper coal strata equilibrium structure caused by the mining. Hence, the upward backfill mining method was proposed; combined with the migration control mechanism of backfill mining overburden strata, the dynamic evolution of crack propagation height of overburden strata during upward backfill mining was analyzed. Based on that, a layer spacing-BBCR-mining height (L-R-H) prediction model based on multiple linear regression analysis was established and the BBCR of close-distance coal seam group safe upward mining was determined combined with the engineering background. The results demonstrate that the main controlling factors of crack propagation in overburden strata during upward backfill mining were BBCR and mining height; the crack propagation height in overburden strata caused by mining decreased exponentially with the increase of BBCR and increased with the increase of mining height linearly. The lower coal seam engineering safety BBCR of upward backfill mining in the Dafosi Coal Mine was 87.2%, and the close-distance coal seam group safe upward mining was realized.
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Kan, Ziyun, Haijun Peng, Biaoshong Chen, Xiaohui Xie, and Lining Sun. "Investigation of strut collision in tensegrity statics and dynamics." International Journal of Solids and Structures 167 (August 2019): 202–19. http://dx.doi.org/10.1016/j.ijsolstr.2019.03.012.
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Abaturova, Irina V., Ivan A. Savintsev, Liubov A. Storozhenko, Elvina D. Nugmanova, and Vladislav S. Kozlov. "Sequence of studying engineering and geological conditions of mineral deposits from exploration to development." Izvestiya vysshikh uchebnykh zavedenii Gornyi zhurnal 7, no. 7 (November 11, 2020): 83–91. http://dx.doi.org/10.21440/0536-1028-2020-7-83-91.
Повний текст джерелаАнотація:
geological environment. Actively change all the components of engineering-geological conditions (EGC), formed during the long geological time: the topography, structure of rocks, hydrogeological and permafrost conditions, are formed by geological processes and, at the same time on the surface of the Earth formed a new strata of man-made structures, and often man-made deposits. The scale of technogenesis in mining today is comparable to the results of geological activity that took place over many millions of years. Therefore, even at the early stages of studying the EGC MD, it is necessary to understand the dynamics of changes in the EGC in order to provide preliminary protective measures. Purpose of work. Consideration of striking examples of the dynamics of the EGC MD (from exploration to development), in order to provide methods for managing these changes. Methodology. The article considers the stages of obtaining engineering and geological information for the period of MD operation, which will solve the problems of rational use of the subsoil and protection of the geological environment. Results. For example, the number of objects marked all the stages of learning to yoke the dynamics of their changes, which led to the formation of engineering-geological processes that adversely affect the further testing of MD. Summary. The reaction of the geological environment in the development of MD is not long in coming and is expressed in the development of large-scale engineering and geological processes, which often do not allow further development of MD and threaten people's lives. Therefore, even at the early stages of studying the EGC MD, it is necessary to understand the dynamics of changes in the EGC in order to provide preliminary protective measures.
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Zhao, Yongjie, and Feng Gao. "Inverse dynamics of the 6-dof out-parallel manipulator by means of the principle of virtual work." Robotica 27, no. 2 (March 2009): 259–68. http://dx.doi.org/10.1017/s0263574708004657.
Повний текст джерелаАнотація:
SUMMARYIn this paper, the inverse dynamics of the 6-dof out-parallel manipulator is formulated by means of the principle of virtual work and the concept of link Jacobian matrices. The dynamical equations of motion include the rotation inertia of motor–coupler–screw and the term caused by the external force and moment exerted at the moving platform. The approach described here leads to efficient algorithms since the constraint forces and moments of the robot system have been eliminated from the equations of motion and there is no differential equation for the whole procedure. Numerical simulation for the inverse dynamics of a 6-dof out-parallel manipulator is illustrated. The whole actuating torques and the torques caused by gravity, velocity, acceleration, moving platform, strut, carriage, and the rotation inertia of the lead screw, motor rotor and coupler have been computed.
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Zhang, Jie, Bin Wang, Wenyong Bai, and Sen Yang. "A Study on the Mechanism of Dynamic Pressure during the Combinatorial Key Strata Rock Column Instability in Shallow Multi-coal Seams." Advances in Civil Engineering 2021 (March 2, 2021): 1–11. http://dx.doi.org/10.1155/2021/6664487.
Повний текст джерелаАнотація:
In order to study the pressure changes and support failure in mining face under concentrated coal pillar in shallow coal seam, the concentrated coal pillar in 30105 working face of Nan Liang Coal Mine was selected as the research object. In this study, the mechanism of dynamic mine pressure in mining face under concentrated coal pillar was investigated through multiple simulation experiments, numerical simulations, and theoretical analysis. The results of similar simulation experiment indicate that the dynamic mine pressure occurred at 25 m under the concentrated coal pillar and 7 m beyond the coal pillar. The strata roof was observed with sliding down, resulting in collapse and severe fractures commonly seen in rock column. The overlying strata caused the overall subsidence and collapse synchronously, resulting in the sudden increase of the resistance of the support in the working face, and the dynamic load coefficients reach 3.4 and 3.5. The theoretical analysis indicates that the two hard strata in the overlying strata of 3−1 coal meet the theoretical criterion of the combined key strata with the concentrated coal pillar of 2−2 coal in the weak interlayer of the combined key strata. The combined key strata bear the load of the whole overlying strata. The sliding instability featured with the rock column-type fracture located in the combined key strata is considered as the primary trigger of the abnormal resistance of the support and the dynamic mine pressure in the mining face under the concentrated coal pillar. The dynamic pressure model of “combination key strata—immediate roof-support” was established, along with the dynamic load coefficient calculation related to the rock column-type fracture and instability. The characteristics of dynamic load coefficient of the rock column-type fracture and instability under different overlying rock structure conditions were analyzed, providing references and insights into mining under similar geographic conditions.
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ZHOU, Xiaochen, Yubo LUO, Pu XUE, and Jianguo LU. "Design method of interconnection struts between flaps of large transport aircraft." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 40, no. 4 (August 2022): 717–22. http://dx.doi.org/10.1051/jnwpu/20224040717.
Повний текст джерелаАнотація:
In the design of the modern large transport aircraft, flap system has become a standard configuration, which can increase the maximum wing lift and the climb rate of the aircraft. Meanwhile, the reliability of the flap system has always been the focus point of the aviation industry. The interconnection strut between flaps is a kind of redundancy design, which mitigates the failure of flap system enhancing flap system reliability. Since 1980s, aircraft manufacturers such as Airbus and Boeing have designed many kinds of ICS for the large transport aircraft like A320, B737. Meanwhile, there is some study on ICS in China, which is still in its infancy. In this paper, the design method of ICS is studied, and the important design parameters of ICS are proposed. A new kind of ICS is designed, and the validity and rationality of ICS design are verified. Firstly, the multi-body dynamic model for the flap system is established and the working principle and important design parameters of ICS between flaps are studied; and then the energy absorbing characteristics of ICS energy absorbing elements are studied; finally, a new ICS is designed, and its mechanical properties and mitigation effect on flap system failure are simulated to verify the effectiveness and rationality of the design.
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Stiehm, Michael, Carolin Wüstenhagen, Stefan Siewert, Hüseyin Ince, Niels Grabow, and Klaus-Peter Schmitz. "Impact of strut dimensions and vessel caliber on thrombosis risk of bioresorbable scaffolds using hemodynamic metrics." Biomedical Engineering / Biomedizinische Technik 64, no. 3 (May 27, 2019): 251–62. http://dx.doi.org/10.1515/bmt-2017-0101.
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AbstractBioresorbable scaffolds (BRS) promise to be the treatment of choice for stenosed coronary vessels. But higher thrombosis risk found in current clinical studies limits the expectations. Three hemodynamic metrics are introduced to evaluate the thrombosis risk of coronary stents/scaffolds using transient computational fluid dynamics (CFD). The principal phenomena are platelet activation and effective diffusion (platelet shear number, PSN), convective platelet transport (platelet convection number, PCN) and platelet aggregation (platelet aggregation number, PAN) were taken into consideration. In the present study, two different stent designs (thick-strut vs. thin-strut design) positioned in small- and medium-sized vessels (reference vessel diameter, RVD=2.25 mm vs. 2.70 mm) were analyzed. In both vessel models, the thick-strut design induced higher PSN, PCN and PAN values than the thin-strut design (thick-strut vs. thin-strut: PSN=2.92/2.19 and 0.54/0.30; PCN=3.14/1.15 and 2.08/0.43; PAN: 14.76/8.19 and 20.03/10.18 for RVD=2.25 mm and 2.70 mm). PSN and PCN are increased by the reduction of the vessel size (PSN: RVD=2.25 mm vs. 2.70 mm=5.41 and 7.30; PCN: RVD=2.25 mm vs. 2.70 mm=1.51 and 2.67 for thick-strut and thin-strut designs). The results suggest that bulky stents implanted in small caliber vessels may substantially increase the thrombosis risk. Moreover, sensitivity analyses imply that PSN is mostly influenced by vessel size (lesion-related factor), whereas PCN and PAN sensitively respond to strut-thickness (device-related factor).
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Tahir, Hannan, Alfons G. Hoekstra, Eric Lorenz, Patricia V. Lawford, D. Rodney Hose, Julian Gunn, and David J. W. Evans. "Multi-scale simulations of the dynamics of in-stent restenosis: impact of stent deployment and design." Interface Focus 1, no. 3 (March 30, 2011): 365–73. http://dx.doi.org/10.1098/rsfs.2010.0024.
Повний текст джерелаАнотація:
Neointimal hyperplasia, a process of smooth muscle cell re-growth, is the result of a natural wound healing response of the injured artery after stent deployment. Excessive neointimal hyperplasia following coronary artery stenting results in in-stent restenosis (ISR). Regardless of recent developments in the field of coronary stent design, ISR remains a significant complication of this interventional therapy. The influence of stent design parameters such as strut thickness, shape and the depth of strut deployment within the vessel wall on the severity of restenosis has already been highlighted but the detail of this influence is unclear. These factors impact on local haemodynamics and vessel structure and affect the rate of neointima formation. This paper presents the first results of a multi-scale model of ISR. The development of the simulated restenosis as a function of stent deployment depth is compared with an in vivo porcine dataset. Moreover, the influence of strut size and shape is investigated, and the effect of a drug released at the site of injury, by means of a drug-eluting stent, is also examined. A strong correlation between strut thickness and the rate of smooth muscle cell proliferation has been observed. Simulation results also suggest that the growth of the restenotic lesion is strongly dependent on the stent strut cross-sectional profile.
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Wang, Dao-Yong, Xue-Zhi Zhao, and Wen-Bin Shangguan. "Design method for a powertrain mounting system to decrease the vehicle key on/off vibrations." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 9 (September 19, 2017): 1221–36. http://dx.doi.org/10.1177/0954407017728190.
Повний текст джерелаАнотація:
Five dynamic response evaluation indices from the viewpoint of the powertrain mount system and the vehicle system during the vehicle key on/off periods (i.e. the engine start and stop) are proposed. By analysis using different methods to minimize the powertrain vibration, it was found that an increase in the mount system damping can decrease the vehicle key on and key off vibration. For this reason, in this paper a semi-active hydraulic damping strut is designed and made which can provide high damping for a mount system when the vehicle key on/off but switches to lower damping to isolate high-frequency vibrations under normal conditions. The calculated longitudinal acceleration of the powertrain, the jerk of the powertrain, the dynamic force of the mount and the vibration dose value for a vehicle with the semi-active hydraulic damping strut and without the semi-active hydraulic damping strut are compared on the basis of the excitation force identified for the powertrain using a 13-degree-of-freedom vehicle model. Experiments were carried out, and the results show that the use of the semi-active hydraulic damping strut can decrease the engine start and stop vibrations to a large extent. Finally, the experimental results are compared with the calculated values from the 13-degree-of-freedom vehicle model.
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Horr, A. M., and L. C. Schmidt. "Complex Fractional-Spectral Method for Space Curved Struts: Theory and Application." International Journal of Space Structures 12, no. 2 (June 1997): 59–67. http://dx.doi.org/10.1177/026635119701200201.
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Based on the theory of fractional calculus and the complex spectral theory of vibration, a new spectrally-formulated finite-element method of analysis is developed which is capable of making accurate predictions of the dynamic response of damped structures with curved struts. The frequency-dependent and temperature-dependent damping characteristics of structural materials can be modelled accurately using the fractional derivative model. The main features of the complex-spectral element method of analysis are presented in this paper. Although most structural systems can be analysed and designed by using the conventional finite element method, in order to guarantee stability and accuracy of the solution the number of elements used to model the structure may be very large. Hence, it appears that, for large structures, it may be more effective to use the spectral approach presented in this paper.
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Xiao, Meng, Jie Cui, Ya-dong Li, and Van-Quang Nguyen. "Nonlinear Seismic Response Based on Different Site Types: Soft Soil and Rock Strata." Advances in Civil Engineering 2022 (March 20, 2022): 1–10. http://dx.doi.org/10.1155/2022/5370369.
Повний текст джерелаАнотація:
Site condition is an important part of urban underground space development and construction. The seismic fortification of the site plays an important role in the safety of the whole project. To study the seismic dynamic response of the site under different geological conditions, seismic waves of different intensities (Chichi wave and Kobe wave) were input to a rock site with good geological conditions and a soft soil site, respectively. In this paper, the dynamic responses of these two types of free sites were calculated and analyzed using DEEPSOIL numerical simulation software. The dynamic responses of different types of sites under strong shock and persistent earthquakes are discussed under the equivalent linear and nonlinear conditions, and the related dynamic parameters are studied. The results show that the equivalent linear method is more effective than the nonlinear method, especially in the calculation of the strong nonlinear soft soil response induced by strong earthquakes. The amplification effect is more obvious in rock layer sites under strong earthquakes, and the “weakening” effect of soft soil sites is more obvious. Arias’s strength values show that both types of sites are safe under the incident of the two waves, but soft soil sites have better seismic performance. The results calculated by the equivalent linear method are larger and more unsafe; in particular, in the case of a strong earthquake with a stronger nonlinear Kobe wave, the results are more inaccurate. The purpose of this study is to provide a reference for seismic design and reinforcement measures of underground engineering.