Predictive Models of Web-to-Roller Traction

2005 ◽  
Vol 127 (1) ◽  
pp. 180-189 ◽  
Author(s):  
Brian S. Rice ◽  
Roger F. Gans
Keyword(s):  
Predictive Models ◽  
Full Range ◽  
Groove Depth ◽  
Squeeze Film ◽  
Asperity Contact ◽  
Process Variables ◽  
Design Variables ◽  
Dimensionless Groups ◽  
Air Film ◽  
Cylindrical Roller

We studied the traction developed between a thin, flexible web and a rotating circumferentially grooved cylindrical roller. We have developed a new two-dimensional analytic model that couples air film pressure, web deflection, and asperity contact to predict traction for circumferentially grooved rollers with arbitrary wrap angles. The entrance effects are incorporated into our new traction model by adapting the squeeze film concept using the distance from the entrance as a surrogate for time. We have verified this model experimentally on a series of 14 rollers and 19 webs. We tested both nongrooved and circumferentially grooved rollers. We showed experimentally that rough, ungrooved rollers that have their low areas unconnected produce significantly lower traction and do not fit the model introduced here. Such rollers should be avoided where traction is important. We introduce dimensionless groups that the roller designer can use to quantitatively assess the interactions of process variables (e.g., speed, tension, etc.) with design variables (e.g., groove depth, groove pitch, roughness, etc.) over the full range of practical wrap angles.

Investigation of the Squeeze Film Dynamics Underneath a Microstructure With Large Oscillation Amplitudes and Inertia Effects

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Nadim A. Diab ◽  
Issam A. Lakkis
Keyword(s):  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Squeeze Film ◽  
Dsmc Method ◽  
Inertia Effects ◽  
Flow Parameters ◽  
Fluid Behavior ◽  
Dimensionless Groups ◽  
Simulation Monte Carlo ◽  
The Impact

This paper presents direct simulation Monte Carlo (DSMC) numerical investigation of the dynamic behavior of a gas film in a microbeam. The microbeam undergoes large amplitude harmonic motion between its equilibrium position and the fixed substrate underneath. Unlike previous work in literature, the beam undergoes large displacements throughout the film gap thickness and the behavior of the gas film along with its impact on the moving microstructure (force exerted by gas on the beam's front and back faces) is discussed. Since the gas film thickness is of the order of few microns (i.e., 0.01 < Kn < 1), the rarefied gas exists in the noncontinuum regime and, as such, the DSMC method is used to simulate the fluid behavior. The impact of the squeeze film on the beam is investigated over a range of frequencies and velocity amplitudes, corresponding to ranges of dimensionless flow parameters such as the Reynolds, Strouhal, and Mach numbers on the gas film behavior. Moreover, the behavior of compressibility pressure waves as a function of these dimensionless groups is discussed for different simulation case studies.

scholarly journals Dynamic Performance of a Squeeze Film Damper with a Cylindrical Roller Bearing under a Large Static Radial Loading Range

Machines ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 14 ◽  
Author(s):  
Hans Meeus ◽  
Jakob Fiszer ◽  
Gabriël Van De Velde ◽  
Björn Verrelst ◽  
Wim Desmet ◽  
...  
Keyword(s):  
Roller Bearing ◽  
Squeeze Film ◽  
Stable Operation ◽  
Large Power ◽  
Squeeze Film Damper ◽  
Depth Analysis ◽  
Rotor Support ◽  
Cylindrical Roller Bearing ◽  
Radial Loading ◽  
Cylindrical Roller

Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive to unbalance excitation. Accordingly, most machines incorporate squeeze film damper technology to dissipate mechanical energy caused by rotor vibrations and to ensure stable operation. When developing a novel geared turbomachine able to cover a large power range, a uniform mechanical drivetrain needs to perform well over the large operational loading range. Especially, the rotor support, containing a squeeze film damper and cylindrical roller bearing in series, is of vital importance in this respect. Thus, the direct objective of this research project was to map the performance of the envisioned rotor support by estimating the damping ratio based on the simulated and measured vibration response during run-up. An academic test rig was developed to provide an in-depth analysis on the key components in a more controlled setting. Both the numerical simulation and measurement results exposed severe vibration problems for an insufficiently radial loaded bearing due to a pronounced anisotropic bearing stiffness. As a result, a split first whirl mode arose with its backward component heavily triggered by the synchronous unbalance excitation. Hence, the proposed SFD does not function properly in the lower radial loading range. Increasing the static load on the bearing or providing a modified rotor support for the lower power variants will help mitigating the vibration issues.

Direct evidence of lubrication in ceramic-on-ceramic total hip replacements

2001 ◽  
Vol 215 (3) ◽  
pp. 265-268 ◽  
Author(s):  
S L Smith ◽  
D Dowson ◽  
A A J Goldsmith ◽  
R Valizadeh ◽  
J S Colligon
Keyword(s):  
Squeeze Film ◽  
Asperity Contact ◽  
Surface Separation ◽  
Total Hip Replacements ◽  
Hip Simulator ◽  
Hip Replacements ◽  
Acetabular Components ◽  
Thin Conducting Film ◽  
Film Lubrication ◽  
Ceramic On Ceramic

A study of surface contact and separation of ceramic-on-ceramic joints was undertaken in 25 per cent bovine serum using a hip simulator. An electrical resistivity technique was used to detect the extent of surface separation throughout a complete walking cycle. The femoral and acetabular components were coated in a thin conducting film of titanium nitride to allow application of the resistivity technique to non-conducting ceramic. Surface separation of the acetabular and femoral components was detected throughout each simulated walking cycle. Fluctuations in the applied voltage across the joint were observed which could not be attributed to elastohydrodynamic or squeeze-film lubrication effects. The probable cause of the voltage fluctuations was brief and occasional contact between the surfaces caused by a combination of asperity contact and subsequent detachment of the conductive coating.

An Investigation of the Squeeze Film Between Rotating Annuli

1970 ◽  
Vol 92 (3) ◽  
pp. 435-440 ◽  
Author(s):  
C. W. Allen ◽  
A. A. McKillop
Keyword(s):  
Experimental Investigation ◽  
Melting Point ◽  
Liquid Metal ◽  
Decay Rates ◽  
Squeeze Film ◽  
Centrifugal Effect ◽  
Experimental Values ◽  
Free Falling ◽  
Air Film ◽  
Good Agreement

The squeeze film between two plane annuli is examined theoretically and experimentally. The theoretical analysis considers the inertia due to the “centrifugal effect” but neglects all other inertia terms. The experimental investigation is by means of a free-falling spinning rotor which is decelerated by the squeeze film. Fluids examined are kerosene, SAE 10 oil, and a low melting point liquid metal. Good agreement between the predicted and actual decay rates is obtained for kerosene but that for the oil and liquid metal is only fair. The theoretical and experimental values of film thickness are in good agreement. The results for the liquid metal suggest the possibility of a thin air film between the rotor and the liquid metal.

Forced Coefficients for a Short Length, Open-Ends Squeeze Film Damper With End Grooves: Experiments and Predictions

2015 ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung ◽  
Gary Bradley
Keyword(s):  
Aircraft Engine ◽  
Groove Depth ◽  
Forced Response ◽  
Short Length ◽  
Effective Length ◽  
Single Frequency ◽  
Squeeze Film ◽  
Thin Film Flow ◽  
Static Eccentricity ◽  
Total Oil

Squeeze Film Dampers (SFDs) are effective to ameliorate shaft vibration amplitudes and to suppress instabilities in rotor-bearing systems. Compact aero jet engines implement ultra-short length SFDs (L/D ≤ 0.2) to satisfy stringent weight and space demands with low parts count. This paper describes a test campaign to identify the dynamic forced response of an open ends SFD (L=25.4 mm, D=125.7 mm), single film land and oil fed through three holes (120° apart), operating with similar conditions as in an aircraft engine. Two journals make for two SFD films with clearances cA=0.129 mm and cB=0.254 mm (small and large). The total oil wetted length equals Ltot=36.8 mm that includes deep end grooves, width and depth = 2.5 × 3.8 mm, for installation of end seals. In the current experiments, the end seals are not in place. A hydraulic static loader pulls the bearing cartridge (BC) to a preset static eccentricity (eS) and two electromagnetic shakers excite the BC with single frequency loads to create circular orbits, centered and off-centered, over a prescribed frequency range ω=10–100Hz. The whirl amplitudes range from r=0.05cA–0.6cA and r=0.15cB–0.75cB while the static eccentricity increases to eS=0.5cA and eS=0.75cB, respectively. Comparisons of force coefficients between the two identical dampers with differing clearances show that the small clearance damper (cA) provides ∼4 times more damping and ∼1.8 times the inertia coefficients than the damper with large clearance (cB). The test results demonstrate damping scales with ∼1/c3 and inertia with ∼1/c, as theory also shows. Analysis of the measured film land pressures evidence that the deep end grooves contribute to the generation of dynamic pressures enhancing the dynamic forced response of the test SFDs. A thin film flow model with an effective groove depth delivers predictions that closely match the test damping and inertia coefficients. Other predictions, based on the short length bearing model, use an effective length Leff ∼1.17L to deliver damping coefficients 15% larger than the experimental results; however, inertia coefficients are ½ of the identified magnitudes. The experiments and analysis complement earlier experimental work conducted with centrally grooved SFDs.

Research on the Wet Clutch Engagement Torque

2014 ◽  
Author(s):  
Yingying Zhang ◽  
Changle Xiang
Keyword(s):  
Rough Surface ◽  
Automatic Transmission ◽  
Squeeze Film ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Time Flow ◽  
Clutch Engagement ◽  
Wet Clutch ◽  
Lubrication Oil ◽  
Engagement Process

The driving performance of the vehicle with automatic transmission is influenced by the performance of the wet clutch directly. But at present it is still a challenge to build a reliable predictable model for the torque of the engagement process of the wet clutch. Focusing on the wet clutch of vehicle, this paper starts from mechanism analysis, and a modified Reynolds equation with the consideration of the centrifugal force of the squeeze-film is established. In the model, we can consider the speeds of the friction and separator plates independently. At the same time, flow factors have been used to research the impacts of rough surface on the flow of the lubrication oil. In the three-dimensional solution domain, the circumferential pressure gradient of lubrication oil is considered. The model is solved with the finite volume method. The simulation of the torque of the asperity contact calculates the real contact area changed with the engagement process, and the microscopic texture direction of rough surface is considered. Subsequently, the squeeze-film flow model is combined with the asperity contact model to create an integrated clutch engagement model. Finally, the influence of applied force, viscosity of lubrication oil, friction material, the depth of grooves and the width of the grooves are investigated. Based on the comparison with the experimental data, the performance of the proposed model is found satisfactory. Because in this model more detail properties of material and geometric features of the friction plate are include, the wet clutch model developed in this research can become a baseline model for the prediction of the engagement behavior of a real wet clutch. The present model may become an efficient alternative to laboratory testing and lead to designs that can not be envisioned by other approaches.

Numerical Running-In Method for Modifying Cylindrical Roller Profile Under Mixed Lubrication of Finite Line Contacts

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Yazhao Zhang ◽  
Hui Cao ◽  
Alexander Kovalev ◽  
Yonggang Meng
Keyword(s):  
Contact Pressure ◽  
Hydrodynamic Pressure ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Pressure Distributions ◽  
Line Contacts ◽  
Finite Line ◽  
Roller Profile ◽  
Rough Surface Contact ◽  
Cylindrical Roller

A numerical method for modifying cylindrical roller profile was proposed to smooth axial pressure distributions of finite line contacts under the mixed lubrication regime. The mixed lubrication model, in which the Reynolds equation modified by Patir and Cheng has been solved with implementing the rough surface contact model of Kogut and Etsion for the stochastic solution of hydrodynamic pressure and asperity-contact pressure, was established and it is validated by the comparison between simulation results and experiments. Some common roller profiles were carried into the mixed lubrication model and obvious increment of pressure appears near the roller ends or at the central contact area. A numerical running-in method was developed to smooth pressure shapes and the crown drop of roller profile was modified gradually implementing Archard's wear law, where a higher asperity-contact pressure leads to a larger crown drop on a roller profile. The results of the numerical running-in method indicated that pressure distributions of finite line contacts are uniform if the optimized roller profile is employed.

Multi-Dimensional Mapping of Design Imprecision

1996 ◽  
Author(s):  
William S. Law ◽  
Erik K. Antonsson
Keyword(s):  
Linear Approximation ◽  
Full Range ◽  
Preliminary Design ◽  
Design Information ◽  
Performance Variables ◽  
Performance Variable ◽  
Extremal Points ◽  
Design Variables ◽  
Map Design ◽  
Variable Space

Abstract Preliminary design information is characteristically imprecise or fuzzy: specifications and requirements are subject to change, and the design description is vague and incomplete. The Method of Imprecision uses the mathematics of fuzzy sets to explicitly represent and manipulate imprecise preliminary design information, enabling the designer to better understand the full range of designs and performances that satisfy an imprecise set of specifications and requirements. This paper discusses the foundations of this methodology, and introduces pragmatic extensions that provide computationally tractable methods to map design imprecision from multiple design variables onto multiple performance variables. These methods attempt to minimize the number of function evaluations required while retaining an appropriate level of accuracy. This is achieved by using optimization to obtain extremal points for each performance variable and selectively applying a linear approximation for the mapping from the design variable space (DVS) to the performance variable space (PVS) to interpolate between extremal points. This linear approximation is constructed using regression techniques adapted from experiment design.

Optimal Design of Process Variables in Multi-Pass Wire Drawing by Genetic Algorithms

1996 ◽  
Vol 118 (2) ◽  
pp. 244-251 ◽  
Author(s):  
S. Roy ◽  
S. Ghosh ◽  
R. Shivpuri
Keyword(s):  
Genetic Algorithm ◽  
Wire Drawing ◽  
Deformation Energy ◽  
Process Variables ◽  
Total Deformation ◽  
Area Reduction ◽  
Design Variables ◽  
Micro Genetic Algorithm ◽  
The Difference ◽  
Number Of Passes

This paper describes a new method for design optimization of process variables in multi-pass wire drawing processes. An adaptive Micro Genetic Algorithm (μGA) has been implemented for minimizing the difference between maximum and minimum effective plastic strains in the end product and also for minimizing the total deformation energy in a multi-pass wire drawing process. The chosen design variables are die angles, area reduction ratios, and the total number of passes. Significant improvements in the simulated product quality and reduction in the number of passes have been observed as a result of the Genetic Algorithm based optimization process. The choice of annealing passes for further reduction of the total deformation energy and residual stresses has also been studied.

Laser-Assisted Waterjet Micro-Grooving of Silicon Wafers for Minimizing Heat Affected Zone

2016 ◽  
Vol 861 ◽  
pp. 133-138
Author(s):  
Xiang Ning Pan ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu ◽  
Peng Yao
Keyword(s):  
Heat Affected Zone ◽  
Predictive Models ◽  
Functional Materials ◽  
Groove Depth ◽  
Silicon Wafers ◽  
Machining Process ◽  
Laser Machining ◽  
Micro Machining ◽  
Micro Grooving ◽  
Haz Width

Laser-assisted waterjet micro-machining can significantly reduce the thermal damages to the workpiece as compared to the traditional laser machining process, and hence can overcome the problems associated with laser machining, such as the formation of heat-affected zone, which is a serious issue for thermal sensitive and functional materials. An experimental study on micro-grooving of monocrystalline silicon wafers is reported in this study to explore the effects of process parameters on the groove depth and width as well as the heat-affected zone (HAZ) width. Predictive models based on dimensionl analysis are then developed for estiamting the groove characteristics.

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