Dynamics of Planar, Elastic, High-Speed Mechanisms Considering Three-Dimensional Offset Geometry: Analytical and Experimental Investigations

1983 ◽  
Vol 105 (3) ◽  
pp. 498-510 ◽  
Author(s):  
F. R. Stamps ◽  
C. Bagci
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Shock Loading ◽  
Dynamic Stress ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Planar Mechanisms ◽  
Elastic Systems ◽  
Stress Levels

Mechanisms in industrial applications in general operate as three-dimensional elastic systems, including planar mechanisms due to offsets between the planes of motion of links. This article investigates dynamic behaviors of planar mechanisms with offset geometry analytically and experimentally for dynamic stress and critical speed levels. Three-dimensional line element with irregular freedoms is used and generalized digital computer programs are prepared to perform kineto-elasto-static, dynamic stress, frequency, and critical speed analyses of three-dimensional mechanisms including the planar mechanisms with three-dimensional offsets. An experimental planar four-bar mechanism was tested for critical speed and elastodynamic stress levels with three levels of offsets. It has been determined that a mechanism experiences integer divisions of the integrated average of the three-dimensional fundamental natural frequency, ωinavg, within a cycle of the mechanism as critical speeds as well as its multiples. Recommended operating speeds of a mechanism are those in between two integer divisions of ωinavg at lower levels. Elastodynamic stress levels at these recommended speed levels are predicted analytically by kineto-elasto-static analysis and very conservatively even in the shock loading zones of the mechanism. The validity of the highly economical CGKES (Critical Geometry Kineto-Elasto-Statics) method for mechanisms having three-dimensional geometry is also verified by the experimental results.

Exploratory Studies on the Control of High-Speed Flows With Magnetogasdynamics

2002 ◽  
Author(s):  
Datta V. Gaitonde
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Control Mechanisms ◽  
Ground Testing ◽  
Simulation Efficiency ◽  
The Status ◽  
Physical Phenomena ◽  
Insight Into

Magnetogasdynamics (MGD) has the potential to lift many of the constraints presently inhibiting sustained hypersonic flight and affordable access to space. Given the difficulty of ground-testing under the expected harsh conditions, numerical methods can provide insight into the physical phenomena, and thus complement experimental investigations in the development of future concepts. This paper describes the status of an effort to develop a high-fidelity, fully three-dimensional method to explore MGD flow control in complex configurations. The theoretical model includes several non-ideal effects and takes recourse to a blend of first principles and phenomenological approaches to enhance simulation efficiency. Boundary conditions are summarized and sample verification exercises are presented. Exploratory calculations on a reentry vehicle and flow-through scramjet flowpath with MGD-bypass demonstrate the versatility of the approach and yield insight into dominant flow control mechanisms.

Advanced Manufacturing from Macro- to Nanoscale: Impact and Shock Loading

2018 ◽  
Vol 910 ◽  
pp. 58-63
Author(s):  
Athanasios G. Mamalis
Keyword(s):  
Biomedical Engineering ◽  
High Speed ◽  
Shock Loading ◽  
Industrial Applications ◽  
Plenary Lecture ◽  
Advanced Materials ◽  
Advanced Manufacturing ◽  
High Speed Impact ◽  
International Team ◽  
Over 40 Years

Trends and developments in advanced manufacturing from macro- to nanoscale, mainly associated with nanotechnology, precision/ultraprecision manufacturing and advanced materials under low/high speed impact and shock loading, with industrial applications to net-shape manufacturing, biomedical engineering, energy and transport, an outcome of the very extensive work over 40 years on these fields performed by the author and his research international team, are briefly outlined in the present Plenary Lecture of the 5th ESHP 2016 Symposium.

scholarly journals Dynamic characteristics of a high-speed train gearbox in the vehicle–track coupled system excited by wheel defects

2019 ◽  
Vol 234 (10) ◽  
pp. 1210-1226 ◽  
Author(s):  
Zhiwei Wang ◽  
Paul Allen ◽  
Guiming Mei ◽  
Zhonghui Yin ◽  
Yao Cheng ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Stress ◽  
Three Dimensional ◽  
Coupled System ◽  
Transmission System ◽  
Dynamic Responses ◽  
Connected Components ◽  
Dynamics Model ◽  
High Speed Trains ◽  
Polygonal Wear

To analyse and simulate the dynamic responses of the gearbox in a vehicle–track system, a three-dimensional vehicle–track coupled dynamics model for high-speed trains has been developed in this study with a comprehensive consideration of the transmission system. Using this dynamics model, the coupling effects between the gearbox housing and its connected components were analysed. Based on the dynamic results, the dynamic stress field of the gearbox housing can be obtained using the finite element methods. The model outputs were successfully validated through comparisons with field test data. Following model validation, the dynamic stress and its distribution throughout the gearbox housing were further investigated under different excitations, including track irregularities, wheel polygonal wear and flatness. The results demonstrate a significant increase in the stress levels of the oil level window aperture and the bottom face of the housing, which coincides with the location of cracks that are formed in the gearbox housing during frequent vehicle operation. While a specific case has been studied here, the proposed dynamics model can be applied to related dynamic assessments, such as vibration or suspension parameter analyses, as well as to stress analyses of any rail vehicle transmission system to guide the maintenance and design.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

Efficient Models of Three-Dimensional Tilting Pad Journal Bearings for the Study of the Interactions Between Rotor and Lubricant Supply Plant

2016 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea Rindi ◽  
Stefano Rossin ◽  
R. Conti ◽  
A. Frilli ◽  
E. Galardi ◽  
...  
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
3D Models ◽  
Industrial Applications ◽  
Journal Bearings ◽  
Research Activity ◽  
Steady State Condition ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearings

In many industrial applications, tilting pad journal bearings (TPJBs) are increasingly used because they are very suitable both for high-speed and high external loads. Their study is fundamental in rotating machines and a compromise between accuracy and numerical efficiency is mandatory to achieve reliable results in a reasonable time. This paper mainly focuses on the development of efficient three-dimensional (3D) models of TPJBs, in order to contemporaneously describe both the rotor dynamics of the system and the lubricant supply plant in long simulations (from the initial transient phase to the steady-state condition). Usually, these two aspects are studied separately, but their interactions must be considered if an accurate description of the whole system is needed. The proposed model architecture considers all the six degrees-of-freedom (DOFs) between supporting structures and rotors and can be applied to different types of TJPB layout with different lubricant supply plants. In this research activity, the whole model has been developed and validated in collaboration with Nuovo Pignone General Electric S.p.a. which provided the required technical and experimental data.

Experimental Investigations of Transfer Phenomena in a Confined Plane Turbulent Impinging Water Jet

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Amine Koched ◽  
Michel Pavageau ◽  
Fethi Aloui
Keyword(s):  
Time Scales ◽  
High Speed ◽  
Impinging Jets ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Confined Water ◽  
Wide Range ◽  
Plane Jets ◽  
Component Velocity ◽  
Lagrangian Tracking

In this study, we are interested in the hydrodynamics of impinging plane jets. Plane jets are widely used in ambience separation in HVAC, fire safety, food process engineering, cooling of electronic components etc. Despite their important industrial applications, plane jets have not been studied as extensively as axisymmetric jets. Plane jets exhibit different kind of instabilities stemming from either streamlines with strong curvature in the impingement region or inflection points in the transverse profile of the streamwise component velocity in the lateral mixing layers. Previous works in the GEPEA laboratory were performed on these flows. These works and the majority of the studies reported in the literature deal with turbulent air jets in various configurations. Very little studies have been done on water impinging jets. Taking into account the fact that the viscosity of water is smaller than air, at the same Reynolds number, it is easier to detect phenomena such as vortices. Phenomena can be observed at lower velocities making it possible to record signals with standard frequency bandwidths. This makes it easier also to do a Lagrangian tracking of vortices. We specially focused our study on the impinging zone of the jet. The dynamics of the impinging zone has not formed the subject of numerous studies. There were no studies that characterize the vortices at the impinging region of water jets in terms of size, centre position, vortex intensity, convection velocities, eccentricity, statistical distribution and turbulent length and time scales. Consequently, a confined water plane jet impinging a flat plate was studied using standard and high speed PIV (Particle Image Velocimetry). We used POD decomposition for filtering PIV data. Then, we applied the λ2 criterion to the recorded velocity fields to detect and characterize the vortices at the impingement. A statistical analysis was then performed. Turbulent length scales, time scales and convection velocities of eddies occurring at the impingement were determined using two point space time correlations. The obtained results were correlated to the dynamics and geometric properties of the jet. A wide range of Reynolds numbers is considered: 3000, 6000, 11000 and 16000. The corresponding results are presented in this paper.

On the Extent of Dominance of Asymptotic Elastodynamic Crack-Tip Fields: Part I—An Experimental Study Using Bifocal Caustics

1991 ◽  
Vol 58 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Sridhar Krishnaswamy ◽  
Ares J. Rosakis
Keyword(s):  
High Speed ◽  
Dynamic Stress ◽  
Dynamic Stress Intensity Factor ◽  
Three Dimensional ◽  
Crack Tip ◽  
Mode I ◽  
Transient Effects ◽  
Crack Tip Fields ◽  
Optical Configuration ◽  
Point Bend

The question of the domain of dominance of mode I asymptotic elastodynamic crack-tip fields is investigated experimentally for the cases of dynamically loaded stationary cracks as well as dynamically propagating cracks. The experiments reported are on three-point bend specimens loaded dynamically using a drop-weight tower. An optical configuration leading to a bifocal high-speed camera is proposed. This is used in conjunction with the method of caustics to obtain apparent dynamic stress intensity factor measurements simultaneously from two different regions around the crack tip. The results of this study indicate that three-dimensional and transient effects necessarily have to be taken into account in the interpretation of dynamic fracture experiments.

Elastodynamics of Horizontally Body-Guiding Cam-Driven Linkages Interacting With Robots, and Elastic Error Compensation for Robot Positioning

1996 ◽  
Author(s):  
Sirihari Kurnool ◽  
Cemil Bagci
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Industrial Applications ◽  
The Body ◽  
Cnc Machine ◽  
Cam Follower ◽  
Robot Positioning ◽  
Body Location ◽  
Exponential Method ◽  
Four Bar Linkage

Abstract Common industrial applications of body-guiding linkages occur with robot (or CNC machine) interaction at workstations in automated production and assembly lines in industry. A linkage in such cases is generally operated horizontally where large deflections at the body location occur creating positioning and orientation errors of the body. These errors must be delivered to the interacting robot to program its motions and operating geometries to eliminate effects of errors on the performed tasks at the workstations. Driving the linkage at high speed, generating dwells at workstations, experiencing efficient dynamic behaviors is an important phase of its design. In this article, a four-bar linkage guides the body. A disk cam with translating roller follower drives a slider-crank loop driving the body guiding linkage providing dynamically efficient motion of the guided-body along its path and the mechanism. Processes of programming motion of the rigid-body along its path, obtaining the corresponding motions of the links of the mechanism, designing the cam-follower mechanism, determnine elastic errors and their correction and minimization, and performing the elastodynamics of the system are offered. A three-dimensional isoparametric beam element and matrix exponential method are used to perform the elastodynamics of the cam-link mechanism, determining dynamic stresses, elastic errors, bearing forces, frequencies, and response with and without vibratory motion effects, and furnishing data for the interacting robot. Numerical results for a system are given.

Visualization of Three-Dimensional Flow Structures Caused by Rotating Instability

2019 ◽  
Author(s):  
Julija Peter ◽  
Paul Uwe Thamsen
Keyword(s):  
High Speed ◽  
Spectral Characteristics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Structures ◽  
Experimental Investigations ◽  
Flow Topology ◽  
Time Resolved ◽  
Characteristic Flow ◽  
Rotating Instability

Abstract The present study deals with the flow phenomenon Rotating Instability (RI), which is predominantly observed in axial compressors at off-design conditions e.g. near stall. It potentially induces noise and triggers blade vibrations. Despite numerous studies, the characteristics and the source of RI are not completely understood. The objective of this work is to identify and to visualize characteristic flow topology corresponding to RI by means of Stereo High Speed Particle Image Velocimetry (PIV). The experimental investigations were carried out in an annular compressor stator cascade with and without hub clearance at an inflow Mach number of Ma = 0.4 and the Reynolds number of Re = 300 000. The time-resolved 3C flow field is measured in a single blade passage in planes tangential to the hub. Additionally, the time-resolved pressure fluctuations are captured synchronously to the PIV system. By using combined correlation techniques the spectral characteristics, the spatial extension of the RI and the characteristic flow structures were identified and visualized in configurations with and without hub clearance. The investigations point out that the general flow mechanism of RI is similar in compressor cascades with and without hub clearance. Overall, this work gives important insights into the complex phenomenon Rotating Instability, which can be taken into account when developing compressors in the future.

Visualization of R410A Flowing in Copper and Stainless Steel Dimpled Tubes Enhanced by Petal-Shaped Patterns Under Evaporation Conditions

2020 ◽  
Author(s):  
Weiyu Tang ◽  
Zhichuan Sun ◽  
Yang Luo ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
High Speed ◽  
Three Dimensional ◽  
Superior Performance ◽  
Smooth Tube ◽  
Wall Material ◽  
Intermittent Flow ◽  
Experimental Investigations ◽  
The Impact

Abstract Experimental investigations were conducted to study the heat transfer characteristics and flow patterns of R410A during evaporation in three horizontal tubes having the same outside diameter of 12.70 mm and 180 mm in length. The tested tubes contain two tubes with three-dimensional enhanced surface structures (Cu-1EHT and SS-1EHT), and one equivalent smooth tube. This experiment was done at an evaporation temperature of 6 °C and mass flux from 100 to 200 kg/(m2·s) for vapor qualities varying from 0.2 to 0.8. For all the tube tested, flow pattern observations were obtained using a high-speed camera, and the impact of the actual flow regime on heat transfer was discussed. Results indicated that the transition from annular flow to intermittent flow began at a lower vapor quality for two enhanced tubes when compared to the smooth tube. Accordingly, both the Cu-1EHT tube and the SS-1EHT tube exhibited a superior performance than the smooth tube. In addition, the heat transfer coefficient of Cu-1EHT tube is higher than that of the stainless steel one, mainly due to the larger thermal conductivity of wall material.

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