309 A Consideration on Critical Speed of An Upper and Lower Vibration Model for A Railroad Vehicle

2008 ◽  
Vol 2008.83 (0) ◽  
pp. _3-14_
Author(s):  
Makoto KATOH ◽  
Takeo HOSOKAWA ◽  
Daisuke OUCHI ◽  
Tadayuki KANEHIRA
Keyword(s):  
Critical Speed ◽  
Vibration Model ◽  
Railroad Vehicle

A Study of the Wheel Geometry Effect on the Dynamic Behavior of Railroad Vehicles

2005 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Mahmoud Tobaa ◽  
Khaled E. Zaazaa
Keyword(s):  
Critical Speed ◽  
Single Point ◽  
Vehicle Stability ◽  
Point Contacts ◽  
Vehicle Model ◽  
Geometric Properties ◽  
Railroad Vehicles ◽  
Wheel Profile ◽  
The Stability ◽  
Railroad Vehicle

The effect of the geometry of a wheel profile that allows only a single point of contact between the wheel and the rail is investigated in this study. The local geometric properties of this profile are compared with the local geometric properties of a profile that allows for two-point contacts in order to understand the basic differences between the two profiles. A simple model is first used to examine the effect of the profile geometry on the stability and nonlinear dynamics of a suspended wheel set. The results obtained in this paper show that the wheel profile can significantly alter the critical speed. Using surface parameters that define the wheel and rail geometry, the global representations of the positions of the points on the wheel and rail surfaces are obtained and used to define the conditions of the contact between the wheel and the rail. Numerical results are presented for a full railroad vehicle model and the effect of the wheel profile on the vehicle stability is investigated. A comparison between the results obtained using the two wheel profiles in the case of wheel climb scenarios is presented.

Analysis on Torsional Vibration of Low-Speed Diesel

2012 ◽  
Vol 562-564 ◽  
pp. 528-531
Author(s):  
Zhong Ming Liu ◽  
Kai Liu ◽  
Xiao Qin Hou
Keyword(s):  
Shear Stress ◽  
Torsional Vibration ◽  
Critical Speed ◽  
Angular Displacement ◽  
Good Condition ◽  
Lumped Mass ◽  
Main Bearing ◽  
Bolt Preload ◽  
Lumped Mass Method ◽  
Vibration Model

In order to analysis the torsional vibration of crankshaft train in various assembly conditions, a 5S60 diesel model is presented based on AVL-EXCITE. A torsional vibration model is established by using the lumped mass method. And the deformation of main bearing is calculated under the bolt preload and outbreak of combustion. In addition to rated conditions, a state of one cylinder out of service is considered in this project. According to the calculation of the critical speed, torsion modes, angular displacement, shear stress in crankpin and minimum oil film thickness, the torsional vibration characteristics are analyzed. The study revealed that this system performs in good condition and the resonance is not obvious.

Formation of Standing Waves in Radial Tires

1984 ◽  
Vol 12 (1) ◽  
pp. 44-63 ◽  
Author(s):  
Y. D. Kwon ◽  
D. C. Prevorsek
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Unit Length ◽  
Standing Waves ◽  
Rolling Resistance ◽  
Damping Coefficient ◽  
Circular Membrane ◽  
Critical Speeds ◽  
Steel Cord ◽  
The Individual

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

Optimum Design of Journal Bearings Dimensions for Rotating Machines

2020 ◽  
Vol 38 (10A) ◽  
pp. 1481-1488
Author(s):  
Tariq M. Hammza ◽  
Ehab N. Abas ◽  
Nassear R. Hmoad
Keyword(s):  
Aspect Ratio ◽  
Dynamic Response ◽  
Numerical Solution ◽  
Critical Speed ◽  
Design Method ◽  
Considerable Effect ◽  
Journal Bearings ◽  
Rotating Machines ◽  
Bearing Clearance ◽  
Study Results

The values of Many parameters which involve in the design of fluid film journal bearings mainly depend on the bearing applied load when using the conventional design method to design the journal bearings, in this study, as well as applied bearing load, the dynamic response and critical speed have been used to calculate the dimensions of journal bearings. In the field of rotating machine, especially a heavy-duty rotating machines, the critical speed and response are the main parameters that specify bearing dimensions. The bearing aspect ratio (bearing length to bore diameter) and bearing clearance have been determined based on rotor maximum critical speed and minimum response displacement. The analytical solution of rotor Eq. of motion was verified by numerical solution via using ANSYS Mechanical APDL 18.0 and by comparing the numerical solution with the preceding study. The final study results clearly showed that the bearing aspect ratio has little effect on the critical speed, but it has a high effect on the dynamic response also the bearing clearance has little effect on the critical speed and considerable effect on the dynamic response. The study showed that the more accurate values of bearing aspect ratio to make the response of rotor as low as possible are about 0.65 - 1 and bearing percent clearance is about 0.15 - 0.2 for different rotor dimensions.

Coupled vibration model of cables and its parameter analysis

2015 ◽  
Vol 32 (3) ◽  
pp. 231
Author(s):  
Haitao Liu ◽  
Minghai Wei ◽  
Kun Lin ◽  
Yiqing Xiao
Keyword(s):  
Parameter Analysis ◽  
Coupled Vibration ◽  
Vibration Model

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

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