scholarly journals A Numerical Model for Railroad Freight Car-to-Car End Impact

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Chao Chen ◽  
Mei Han ◽  
Yanhui Han
Keyword(s):  
Numerical Model ◽  
Relative Displacement ◽  
Friction Forces ◽  
Impact Speed ◽  
Local Linearization ◽  
Model Based ◽  
D’Alembert Principle ◽  
Freight Car ◽  
Contact Surfaces ◽  
Fourth Order Method

A numerical model based on Lagrange-D'Alembert principle is proposed for car-to-car end impact in this paper. In the numerical model, the friction forces are treated by using local linearization model when solving the differential equations. A computer program has been developed for the numerical model based on Runge-Kutta fourth-order method. The results are compared with the Multibody Dynamics/Kinematics software SIMPACK results and they are close. The ladings' relative displacement to struck car and the relative displacement between two ladings get larger as impact speed increases. There is no displacement between two ladings when the contact surfaces have the same friction coefficient.

scholarly journals The Contact Mechanics of Novikov’s Surface-Hardened Gearing during Running-in Process

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Alexey Beskopylny ◽  
Nikolay Onishkov ◽  
Viktor Korotkin
Keyword(s):  
Cold Deformation ◽  
Contact Fatigue ◽  
High Hardness ◽  
Contact Spot ◽  
The State ◽  
Contact Strength ◽  
Friction Forces ◽  
Contact Surfaces ◽  
Defective Surface ◽  
The Impact

The article is devoted to the analysis of the state of the contact surfaces of the higher kinematic pair in the general case of relative motion, that is, in the presence of rolling, sliding, and twisting, which is characteristic of Novikov’s circular-screw gears. The purpose of the work is to assess the impact of friction forces, the state of contact surfaces after tool processing, and the localization of the instantaneous contact spot on the level of contact—fatigue durability of gears. Power contact in the presence of geometric slippage of the mating surfaces leads to a significant change in the initial geometry and the mechanical properties of surface layers. In the existing methods of calculations of contact strength, the effect of running-in is investigated insufficiently, which leads to an incorrect result, especially for gear with high hardness of the teeth. In this work, the conditions of contact interaction close to the real requirements are studied on the basis of experimental material, numerical solution of the contact problem, determination of the terms of the contact areas of slip, and adhesion within the instantaneous spot. The shape of the instant contact spot has asymmetry and can be approximated by an ellipse with the introduction of a correction factor. The running-in period is of a plastic nature with cold deformation and reduction of the roughness of surfaces. As a result of the run-in period, the area of actual contact (tooth height) is increased by 2 or more times. It is not desirable to spread the area of contact at the area of adhesion that initiates the formation of pitting. The presence of defective surface area on the level of contact strength does not have significant influence, because of the running-in period, but increases the risk of spalling and brittle fracture.

Forced Harmonic Response of Grouped Blade Systems: Part II—Application

1996 ◽  
Vol 118 (1) ◽  
pp. 137-145 ◽  
Author(s):  
L. F. Wagner ◽  
J. H. Griffin
Keyword(s):  
Numerical Model ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Turbine Blades ◽  
Modal Identification ◽  
Harmonic Response ◽  
Model Based ◽  
Grouped Blades ◽  
Flexible Disk ◽  
Symmetric Structures

The vibration of grouped blades on a flexible disk should, for purposes of economy and clarity of modal identification, be analyzed using procedures developed for cyclically symmetric structures. In this paper, a numerical model, based on the theory of cyclically symmetric structures, is applied to the vibration analysis, and in particular, the harmonic response, of a flexible disk supporting a number of groups, or packets, of turbine blades. Results are presented to show variations in the modal participation factors as a function of such parameters as disk flexibility, blade density, and the total number of assembled groups. It is also shown that many characteristics of the system spectra of natural frequencies are strongly dependent on the number of blade groups.

scholarly journals Model-Based Optimization of Velocity Strategy for Lightweight Electric Racing Cars

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Mirosław Targosz ◽  
Wojciech Skarka ◽  
Piotr Przystałka
Keyword(s):  
Numerical Model ◽  
Energy Efficient ◽  
Atmospheric Conditions ◽  
Vehicle Model ◽  
Model Based ◽  
Race Track ◽  
Functional Features ◽  
Race Conditions ◽  
Vehicle Dynamic Model ◽  
And Control

The article presents a method for optimizing driving strategies aimed at minimizing energy consumption while driving. The method was developed for the needs of an electric powered racing vehicle built for the purposes of the Shell Eco-marathon (SEM), the most famous and largest race of energy efficient vehicles. Model-based optimization was used to determine the driving strategy. The numerical model was elaborated in Simulink environment, which includes both the electric vehicle model and the environment, i.e., the race track as well as the vehicle environment and the atmospheric conditions. The vehicle model itself includes vehicle dynamic model, numerical model describing issues concerning resistance of rolling tire, resistance of the propulsion system, aerodynamic phenomena, model of the electric motor, and control system. For the purpose of identifying design and functional features of individual subassemblies and components, numerical and stand tests were carried out. The model itself was tested on the research tracks to tune the model and determine the calculation parameters. The evolutionary algorithms, which are available in the MATLAB Global Optimization Toolbox, were used for optimization. In the race conditions, the model was verified during SEM races in Rotterdam where the race vehicle scored the result consistent with the results of simulation calculations. In the following years, the experience gathered by the team gave us the vice Championship in the SEM 2016 in London.

scholarly journals RANS MODELLING OF CROSS-SHORE SEDIMENT TRANSPORT AND MORPHODYNAMICS IN THE SWASH-ZONE

2020 ◽  
pp. 14
Author(s):  
Joost Kranenborg ◽  
Geert Campmans ◽  
Niels Jacobsen ◽  
Jebbe van der Werf ◽  
Robert McCall ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Navier Stokes ◽  
Swash Zone ◽  
Rans Equations ◽  
Model Based ◽  
Numerical Studies ◽  
Reynolds Averaged Navier Stokes ◽  
Averaged Models

Most numerical studies of sediment transport in the swash zone use depth-averaged models. However, such models still have difficulty predicting transport rates and morphodynamics. Depth-resolving models could give detailed insight in swash processes but have mostly been limited to hydrodynamic predictions. We present a depth-resolving numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations, capable of modelling sediment transport and morphodynamics in the swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/PB8Vs0LJq88

Model-Based Analysis of Friction-Induced Sub-Synchronous Whirl for a Rotor Contacting With Clearance Bearings Under Axial Load

2015 ◽  
Author(s):  
Matthew O. T. Cole ◽  
Lawrence Hawkins
Keyword(s):  
Axial Load ◽  
Coulomb Friction ◽  
Friction Forces ◽  
Root Finding ◽  
Model Based ◽  
Simple Physical Interpretation ◽  
Level Of Agreement ◽  
Model Based Analysis

For rotors supported by active magnetic bearings (AMBs), clearance bearings are commonly used to provide backup support under loss of AMB functionality. Test data from real machines shows that rotor vibration during touchdown on backup bearings may involve steady forward whirling at a sub-synchronous frequency. This excitation is believed to be due to friction forces transmitted between the rotor and a bearing end-face under axial load. This paper proposes a new analytical approach to model and predict such friction-driven forward whirl behaviors. A set of constraint equations are derived that relate a circular whirl motion of arbitrary orbital speed to the frequency response functions of the rotor-housing structure. This model is coupled with an evaluation of Coulomb friction associated with slip between the rotor and the supporting end-face of a thrust bearing. The resulting equations can be used to compute a set of possible whirl motions via a root-finding procedure. A case study is undertaken for a 140 kW energy storage flywheel. Model-based predictions are compared with measured data from spin-down tests and show a good level of agreement. The study confirms the role of friction-related forces in driving forward-whirl response behaviors. It also highlights the key role of housing and machine support characteristics in response behavior. This influence is shown to be complex and not open to simple physical interpretation. Therefore, the proposed analytical method is seen as a useful tool to investigate this influence while avoiding the need for time consuming numerical simulations.

Fretting Wear Mechanisms and Their Effects on Fretting Fatigue

1988 ◽  
Vol 110 (3) ◽  
pp. 517-524 ◽  
Author(s):  
Y. Berthier ◽  
Ch. Colombie´ ◽  
L. Vincent ◽  
M. Godet
Keyword(s):  
Fretting Fatigue ◽  
Relative Displacement ◽  
Contact Condition ◽  
Fretting Wear ◽  
Initial Contact ◽  
Great Care ◽  
Third Body ◽  
Body Formation ◽  
The Third ◽  
Contact Surfaces

Fretting wear and fretting fatigue are governed by the rate of formation of materials (third-bodies) between the initial contact surfaces. Furthermore, the third-bodies must be maintained within the contact. The issue of the race between third-body formation and subsurface damage conditions the effect of fretting on fatigue. That race lasts for only a few hundred or at best a few thousand cycles. Effective third-bodies (or good anti-fretting lubricants) must adhere strongly to the rubbing surfaces, and be able to accommodate at least part of the relative displacement. Great care in the design of test equipment has to be exercised before definitive results on the effect of amplitude and frequency on either fretting fatigue or fretting wear can be obtained for a given contact condition, given materials and given environments.

Optical brake induced by laser shock waves

2021 ◽  
pp. 2050010
Author(s):  
Qiao Kang ◽  
Dongyi Shen ◽  
Jie Sun ◽  
Xin Luo ◽  
Wei Liu ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Optical Method ◽  
Close Contact ◽  
Surface Friction ◽  
Laser Shock ◽  
Free Standing ◽  
Friction Forces ◽  
Optical Levitation ◽  
Contact Surfaces

We demonstrate an optical method to modify friction forces between two close-contact surfaces through laser-induced shock waves, which can strongly enhance surface friction forces in a sandwiched confinement with/without lubricant, due to the increase of pressure arising from excited shock waves. Such enhanced friction can even lead to a rotating rotor’s braking effect. Meanwhile, this shock wave-modified friction force is found to decrease under a free-standing configuration. This technique of optically controllable friction may pave the way for applications in optical levitation, transportation, and microfluidics.

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