End Effect Attenuation in Tapered Roller Contacts

2009 ◽  
Author(s):  
Emanuel Diaconescu
Keyword(s):  
Pressure Distribution ◽  
Finite Length ◽  
Contact Length ◽  
Maximum Pressure ◽  
End Effect ◽  
End Effects ◽  
Maximum Value ◽  
Line Contacts ◽  
Tapered Roller

The end effect attenuation in finite length line contacts is mainly approached for cylindrical bodies. Multi-radius crowning may remove end effects in tapered roller contacts. Another method for leveling maximum pressure in these contacts is the use of polynomial generatrix. This paper investigates the effect of this generatrix in tapered roller contacts. An improved pressure distribution is obtained. This has a nearly flat maximum value along most of contact length.

A New Approach to End Effect Attenuation in Elastic Finite Length Line Contacts Between Revolution Bodies

2008 ◽  
Author(s):  
Emanuel Diaconescu
Keyword(s):  
Finite Length ◽  
Maximum Pressure ◽  
Elastic Contact ◽  
End Effect ◽  
End Effects ◽  
New Approach ◽  
Order Polynomial ◽  
Line Contacts ◽  
Even Order ◽  
Roller Profile

There are many methods for attenuation of end effects in finite length line Hertz contacts. A new one is proposed herein by using an even polynomial generatrix for the equivalent rigid roller. The elastic contact between high order polynomial surfaces is used to get a nearly flat maximum pressure along the line contact. According to a reversed method, contact half-axes and central pressure are imposed. The longitudinal roller profile found numerically is indeed an even order polynomial. The method is validated numerically by a GC-DCFFT method.

Simulation of Plasto-Elastohydrodynamic Lubrication in Line Contacts of Infinite and Finite Length

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tao He ◽  
Jiaxu Wang ◽  
Zhanjiang Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Finite Length ◽  
3D Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Axial Direction ◽  
Contact Length ◽  
Line Contact ◽  
Line Contacts ◽  
3D Surface Topography

Line contact is common in many machine components, such as various gears, roller and needle bearings, and cams and followers. Traditionally, line contact is modeled as a two-dimensional (2D) problem when the surfaces are assumed to be smooth or treated stochastically. In reality, however, surface roughness is usually three-dimensional (3D) in nature, so that a 3D model is needed when analyzing contact and lubrication deterministically. Moreover, contact length is often finite, and realistic geometry may possibly include a crowning in the axial direction and round corners or chamfers at two ends. In the present study, plasto-elastohydrodynamic lubrication (PEHL) simulations for line contacts of both infinite and finite length have been conducted, taking into account the effects of surface roughness and possible plastic deformation, with a 3D model that is needed when taking into account the realistic contact geometry and the 3D surface topography. With this newly developed PEHL model, numerical cases are analyzed in order to reveal the PEHL characteristics in different types of line contact.

An Investigation Hydrodynamic Fluid Pressure at Wedge-Shaped Gap between Grinding Wheel and Workpiece

2010 ◽  
Vol 44-47 ◽  
pp. 970-974
Author(s):  
Chang He Li ◽  
Jing Yao Li ◽  
Ya Li Hou
Keyword(s):  
Pressure Distribution ◽  
Fluid Pressure ◽  
Hydrodynamic Pressure ◽  
Contact Length ◽  
Coolant Fluid ◽  
Grinding Wheel ◽  
Maximum Pressure ◽  
Work Surface ◽  
Good Surface ◽  
Peripheral Surface

In the grinding process, conventional method of flood delivering coolant fluid by a nozzle in order to achieve good surface integrity. However, hydrodynamic fluid pressure can be generated ahead of the contact zone due to the wedge effect between wheel peripheral surface and work surface. In the paper, a theoretical hydrodynamic pressure modeling is presented for flow of coolant fluid through the grinding zone in flood delivery grinding. Moreover, coolant induced force can be calculated by integrate the hydrodynamic pressure distribution over the whole contact length. The theoretical results show that the hydrodynamic pressure was proportion to grinding wheel velocity, and inverse proportion to the minimum gap between wheel and work surface and the maximum pressure value was generated just in the minimum gap region in which higher fluid pressure gradient occuring. It can also be concluded the pressure distribution was uniform in the direction of width of wheel except at the edge of wheel because of the side-leakage.

New Investigations of Finite Length Line Contact

2004 ◽  
Author(s):  
Marilena Glovnea ◽  
Emanuel Diaconescu
Keyword(s):  
Finite Length ◽  
Contact Area ◽  
Numerical Procedure ◽  
Metallic Surface ◽  
End Effects ◽  
Flat Surfaces ◽  
Dog Bone ◽  
Modified Surfaces ◽  
Line Contacts ◽  
Previous Proposal

Important end effects occur in Hertz-like finite length line contacts. If the length of shorter contacting cylinder is bounded by flat surfaces, the pressure tends to infinity at both ends. Many design measures were advanced to reduce or attenuate these pressure riser effects. These imply modification of contact geometry and, in most cases, numerical investigations. Few experiments were performed to check the actual contact between modified surfaces. Applying a previous proposal, contact area between a modified steel roller and a sapphire window is measured by scanning the reflectivity of metallic surface. A typical “dog bone” shape for this area is found. Lateral extensions of contact area, measured experimentally for a roller with rounded edges, agree well with numerical results obtained by a new, refined numerical procedure.

A New Experimental Technique to Measure Contact Pressure

2003 ◽  
Author(s):  
Emanuel N. Diaconescu ◽  
Marilena L. Glovnea ◽  
Ovidiu Petrosel
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Amorphous Solid ◽  
Time Interval ◽  
Optical Parameters ◽  
Point Contacts ◽  
End Effects ◽  
Line Contacts ◽  
A New Technique ◽  
Theoretical Considerations

A new technique to measure the pressure in a real contact is proposed. One of contacting surfaces is covered, prior to contact establishment, by a special gel. The contact closing removes the excess gel and, during a certain time interval, the contact pressure transforms the entrapped substance in an amorphous solid. In each point, the refractive index of this solid depends on the pressure acting during transformation. After contact opening, the reflectivity of this coating depends on the former contact pressure and it is mapped by aid of a laser profilometer and becomes an indicator of contact pressure. Theoretical considerations show that the gel must possess certain optical parameters for the method to work. Several experimental reported results offer a clear image upon pressure distribution in Hertz point contacts, end effects in finite length line contacts, pressure distribution between rough surfaces and indicate the onset of plastic deformation.

The Effects of Small Sinusoidal Load Variations in Elastohydrodynamic Line Contacts

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
C. J. Hooke ◽  
G. E. Morales-Espejel
Keyword(s):  
Pressure Distribution ◽  
Maxwell Model ◽  
Total System ◽  
Low Frequencies ◽  
Load Variations ◽  
Entrainment Velocity ◽  
Line Contacts ◽  
Sinusoidal Load ◽  
Voigt Model ◽  
Low Amplitude

A method of determining the response of elastohydrodynamic line contacts to low amplitude, sinusoidal variations in load is presented. It is shown that the load variations alter the Hertz width, cyclically increasing and reducing the effective entrainment velocity. This produces clearance variations in the inlet, which are transported through the conjunction altering the pressure distribution as they pass. The resulting pressure and clearance changes can be many times greater than when the load changes slowly. The results are used to determine the flexibility and damping of the conjunctions. These vary depending on the number of transported waves inside the contact. It is shown that a Maxwell model rather than the usual Voigt model is required to define the contact's behavior. While the Voigt model may be used at low frequencies, it has a damping coefficient that is not unique to the contact but depends on the total system stiffness.

scholarly journals Standard reference values of weight and maximum pressure distribution in healthy adults aged 18–65 years in Germany

2020 ◽  
Vol 39 (1) ◽  
Author(s):  
D. Ohlendorf ◽  
K. Kerth ◽  
W. Osiander ◽  
F. Holzgreve ◽  
L. Fraeulin ◽  
...  
Keyword(s):  
Body Weight ◽  
Pressure Distribution ◽  
Reference Values ◽  
Effect Size ◽  
Weight Distribution ◽  
Age Groups ◽  
Healthy Adults ◽  
The Body ◽  
Maximum Pressure ◽  
Left And Right

Abstract Background The aim of this study was to collect standard reference values of the weight and the maximum pressure distribution in healthy adults aged 18–65 years and to investigate the influence of constitutional parameters on it. Methods A total of 416 healthy subjects (208 male / 208 female) aged between 18 and 65 years (Ø 38.3 ± 14.1 years) participated in this study, conducted 2015–2019 in Heidelberg. The age-specific evaluation is based on 4 age groups (G1, 18–30 years; G2, 31–40 years; G3, 41–50 years; G4, 51–65 years). A pressure measuring plate FDM-S (Zebris/Isny/Germany) was used to collect body weight distribution and maximum pressure distribution of the right and left foot and left and right forefoot/rearfoot, respectively. Results Body weight distribution of the left (50.07%) and right (50.12%) foot was balanced. There was higher load on the rearfoot (left 54.14%; right 55.09%) than on the forefoot (left 45.49%; right 44.26%). The pressure in the rearfoot was higher than in the forefoot (rearfoot left 9.60 N/cm2, rearfoot right 9.51 N/cm2/forefoot left 8.23 N/cm2, forefoot right 8.59 N/cm2). With increasing age, the load in the left foot shifted from the rearfoot to the forefoot as well as the maximum pressure (p ≤ 0.02 and 0.03; poor effect size). With increasing BMI, the body weight shifted to the left and right rearfoot (p ≤ 0.001, poor effect size). As BMI increased, so did the maximum pressure in all areas (p ≤ 0.001 and 0.03, weak to moderate effect size). There were significant differences in weight and maximum pressure distribution in the forefoot and rearfoot in the different age groups, especially between younger (18–40 years) and older (41–65 years) subjects. Discussion Healthy individuals aged from 18 to 65 years were found to have a balanced weight distribution in an aspect ratio, with a 20% greater load of the rearfoot. Age and BMI were found to be influencing factors of the weight and maximum pressure distribution, especially between younger and elder subjects. The collected standard reference values allow comparisons with other studies and can serve as a guideline in clinical practice and scientific studies.

Visualization of Contact-Pressure Distribution between Material and Backing Plate in Friction Stir Processing

2018 ◽  
Vol 765 ◽  
pp. 199-203
Author(s):  
Takahiro Ohashi ◽  
Xin Tong ◽  
Zi Jie Zhao ◽  
Hamed Mofidi Tabatabaei ◽  
Tadashi Nishihara
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Friction Stir Processing ◽  
Maximum Pressure ◽  
Height Distribution ◽  
Contact Pressure Distribution ◽  
Friction Stir ◽  
Backing Plate ◽  
Load Sensor ◽  
Tool Position

In this study, the authors evaluated pressure distribution on a backing plate in friction-stir processing (FSP) utilizing an embedded pressure pin connected to a load sensor. They conducted FSP on aluminum alloy plates repeatedly offsetting the path-lines from the center of the pin and recorded change of forming pressure with tool position, which was compiled from the bearing load of the pin. The authors mapped the results to visualize the two-dimensional contact pressure distribution on a backing plate during FSP. They then compared the height distribution of the wall fabricated by friction-stir forming (FSF) utilizing a die having a groove with the observed distribution of pressure. Consequently, maximum pressure was observed beneath the rim of the tool probe at the retreating side (RS), and the highest points of the wall were observed at the RS.

PRESSURE DISTRIBUTION DUE TO STERN TAB DEFLECTION AT MODEL SCALE

2021 ◽  
Vol 157 (A1) ◽  
Author(s):  
T Arnold ◽  
J Lavroff ◽  
M R Davis
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Lift Force ◽  
Force Measurement ◽  
Maximum Pressure ◽  
Model Scale ◽  
Measure Model ◽  
Overall Resistance ◽  
Hydraulics Laboratory ◽  
The University

Trim tabs form an important part of motion control systems on high-speed watercraft. By altering the pitch angle, significant improvements in propulsion efficiency can be achieved by reducing overall resistance. For a ship in heavy seas, trim tabs can also be used to reduce structural loads by changing the vessel orientation in response to encountered waves. In this study, trials have been conducted in the University of Tasmania hydraulics laboratory using a closed- circuit water tunnel to measure model scale trim tab forces. The model scale system replicates the stern tabs on the full- scale INCAT Tasmania 112 m high-speed wave-piercer catamaran. The model was designed for total lift force measurement and pressure tappings allowed for pressures to be measured at fixed locations on the underside of the hull and tab. This investigation examines the pressures at various flow velocities and tab deflection angles for the case of horizontal vessel trim. A simplified two-dimensional CFD model of the hull and tab has also been analysed using ANSYS CFX software. The results of model tests and CFD indicate that the maximum pressure occurs in the vicinity of the tab hinge and that the pressure distribution is long-tailed in the direction forward of the hinge. This accounts for the location of the resultant lift force, which is found to act forward of the tab hinge.

A fast thermoelastic model based on the half-space theory applied to elastohydrodynamic lubrication of line contacts involving free boundaries

2021 ◽  
pp. 1-29
Author(s):  
Ali Yalpanian ◽  
Raynald Guilbault
Keyword(s):  
Finite Dimension ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Pressure Profile ◽  
Distribution Center ◽  
Maximum Pressure ◽  
Free Boundaries ◽  
Heat Flows ◽  
Line Contacts ◽  
Contact Models

Abstract This study allows contact models based on semi-analytical methods including the impacts of thermoelastic deformations in contacts of finite dimension bodies. The proposed method controls heat flows crossing free boundaries. A comparison with FEA reveals that the proposed method can reduce the calculation times by more than 98%. The paper introduces the thermoelasticity effects into thermal-elastohydrodynamic lubrication (TEHL) modeling of line contact problems. The analysis reveals that including thermoelastic deformations changes the pressure profile and tends to localize the pressure close to the distribution center. Compared to TEHL simulations, the examined configurations caused an overall increase in the maximum pressure by about 9%, an overall film thickness reduction of about 7%, and an overall temperature increase of about 2 K.

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