scholarly journals Numerical and Experimental Studies of the Attenuation Characteristics of Friction Torque in a Wet Multidisc Clutch

2021 ◽  
Vol 11 (2) ◽  
pp. 814
Author(s):  
Man Chen ◽  
Bin Zhang ◽  
Yuqing Feng ◽  
Liang Wang ◽  
He Wang
Keyword(s):  
Growth Rate ◽  
Numerical Model ◽  
Contact Pressure ◽  
Applied Pressure ◽  
Experimental Studies ◽  
Friction Torque ◽  
Bench Test ◽  
Single Pair ◽  
Attenuation Characteristics

A numerical model is proposed to calculate both the contact pressure and the friction torque (FT) of the friction components considering the spline friction in a wet multidisc clutch, which is verified by the bench test. The results indicate that the spline friction of components is an important factor causing the axial attenuation of contact pressure on friction pairs. As the applied pressure increases, the attenuation amplitude of contact pressure increases gradually. In addition, the average single-pair FT decreases with the increasing number of friction pairs, thus leading to the decrease of the growth rate of total FT. Therefore, when the number of friction pairs reaches a certain number, it is not reliable to obtain a good torque enhancement, indicating that the effect of spline friction needs to be weakened to reduce the attenuation of contact pressure.

Influences of the uneven contact pressure and the initial temperature on the hot judder behavior in a multi-disc clutch

2019 ◽  
Vol 234 (4) ◽  
pp. 500-514 ◽  
Author(s):  
Liang Yu ◽  
Biao Ma ◽  
Il yong Kim ◽  
Heyan Li
Keyword(s):  
Contact Pressure ◽  
Friction Surface ◽  
Heat Dissipation ◽  
Dynamic Models ◽  
Initial Temperature ◽  
Friction Torque ◽  
Bench Test ◽  
Radial Temperature ◽  
Actual Structure ◽  
Rotating Speed

This paper presents an investigation of the hot judder behavior in a multi-disc clutch with the uneven contact pressure and the initial temperature taken into account. Considering the actual structure of clutch, the pressure function is achieved to describe the uneven contact pressure distribution due to the circlip constraint. Moreover, the pin-on-disc test is conducted to obtain the formula of the coefficient of friction with the contact pressure, surface temperature, and rotating speed involved. The thermal and dynamic models are established and coupled to evaluate the hot judder behavior. The results demonstrate that the uneven contact pressure has a slight influence on the clutch hot judder, but it expands the radial temperature difference on the friction surface; meanwhile, the friction torque generated on the friction surface closer to the circlip is larger. Although the increase of initial temperature can shorten the clutch engagement time, the clutch hot judder will be shriller, as verified in the SAE#2 bench test. Furthermore, in order to reduce the clutch hot judder, the circlip should be optimized to smooth the radial contact pressure, and the advanced thermal management method should be applied to strengthen the clutch heat dissipation.

scholarly journals Effect of Silicon Carbide Nanoparticles on the Friction-Wear Properties of Copper-Based Friction Discs

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 587
Author(s):  
Changsong Zheng ◽  
Zhiwei Ma ◽  
Liang Yu ◽  
Xu Wang ◽  
Liangjie Zheng ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Variable Coefficient ◽  
Automatic Transmission ◽  
Applied Pressure ◽  
Friction Torque ◽  
Bench Test ◽  
Friction Materials ◽  
Wear Characteristics ◽  
Rotating Speed ◽  
Silicon Carbide Nanoparticles

To study the influence of nano-additives on the friction-wear characteristics of friction materials, the nano-sized silicon carbide particles which have excellent chemical and physical properties are considered to add in composite to form the modified friction material. The influence of the silicon carbide nanoparticles (SCN) on the friction-wear characteristics of copper-based friction materials (CBFM) is investigated via the SAE#2 (made in Hangzhou, China) clutch bench test with the applied pressure, rotating speed, and automatic transmission fluid (ATF) temperature taken into account. Moreover, the variations of friction torque and temperature are considered to evaluate the friction performance, and the variable coefficient is employed to describe the friction stability. The wear characteristics of friction materials are investigated by the disc changes in thickness and micro-morphology. The results show that the CBFM with SCN can provide a higher friction torque, which increased by 30% to 50% compared with CBFM. The variable coefficient of CBFM with SCN changes from 674 to 52 with the rotating speed raised from 600 rpm to 3000 rpm, which shows that the friction stability is relatively worse. Furthermore, the micromorphology shows that the CBFM with SCN has lower porosity and surface roughness, which increases the microscopic contact area and the coefficient of friction (COF). Simultaneously, the reduction in porosity also leads to a decrease in the cooling quality, bringing about a rapid temperature rise. Thus, the wear amount of CBFM with SCN increases significantly, especially for the friction disc in the axial middle position.

One-Dimensional Contact Pressure Distribution of Radial Tires in Motion

1995 ◽  
Vol 23 (2) ◽  
pp. 116-135 ◽  
Author(s):  
H. Shiobara ◽  
T. Akasaka ◽  
S. Kagami ◽  
S. Tsutsumi
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Experimental Studies ◽  
Rolling Resistance ◽  
Leading Edge ◽  
Forward Direction ◽  
Contact Pressure Distribution ◽  
Support Ring ◽  
One Dimensional ◽  
Lowered Pressure

Abstract The contact pressure distribution and the rolling resistance of a running radial tire under load are fundamental properties of the tire construction, important to the steering performance of automobiles, as is well known. Many theoretical and experimental studies have been previously published on these tire properties. However, the relationships between tire performances in service and tire structural properties have not been clarified sufficiently due to analytical and experimental difficulties. In this paper, establishing a spring support ring model made of a composite belt ring and a Voigt type viscoelastic spring system of the sidewall and the tread rubber, we analyze the one-dimensional contact pressure distribution of a running tire at speeds of up to 60 km/h. The predicted distribution of the contact pressure under appropriate values of damping coefficients of rubber is shown to be in good agreement with experimental results. It is confirmed by this study that increasing velocity causes the pressure to rise at the leading edge of the contact patch, accompanied by the lowered pressure at the trailing edge, and further a slight movement of the contact area in the forward direction.

scholarly journals Hydraulic Transients in Viscoelastic Pipeline System with Sudden Cross-Section Changes

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4071
Author(s):  
Michał Kubrak ◽  
Agnieszka Malesińska ◽  
Apoloniusz Kodura ◽  
Kamil Urbanowicz ◽  
Michał Stosiak
Keyword(s):  
Numerical Model ◽  
Cross Section ◽  
Laboratory Data ◽  
Experimental Studies ◽  
Distribution Networks ◽  
Water Hammer ◽  
Fluid Distribution ◽  
Pipeline System ◽  
Hydraulic Transients ◽  
Single Pipe

It is well known that the water hammer phenomenon can lead to pipeline system failures. For this reason, there is an increased need for simulation of hydraulic transients. High-density polyethylene (HDPE) pipes are commonly used in various pressurised pipeline systems. Most studies have only focused on water hammer events in a single pipe. However, typical fluid distribution networks are composed of serially connected pipes with various inner diameters. The present paper aims to investigate the influence of sudden cross-section changes in an HDPE pipeline system on pressure oscillations during the water hammer phenomenon. Numerical and experimental studies have been conducted. In order to include the viscoelastic behaviour of the HDPE pipe wall, the generalised Kelvin–Voigt model was introduced into the continuity equation. Transient equations were numerically solved using the explicit MacCormack method. A numerical model that involves assigning two values of flow velocity to the connection node was used. The aim of the conducted experiments was to record pressure changes downstream of the pipeline system during valve-induced water hammer. In order to validate the numerical model, the simulation results were compared with experimental data. A satisfactory compliance between the results of the numerical calculations and laboratory data was obtained.

Improving the Long-Term Performance of Elastomeric Seals by Material Behavior Design

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ryan B. Sefkow ◽  
Nicholas J. Maciejewski ◽  
Barney E. Klamecki
Keyword(s):  
Energy Density ◽  
Contact Pressure ◽  
Strain Energy ◽  
Applied Pressure ◽  
Material Behavior ◽  
Time Dependent ◽  
Ring Section ◽  
Stiff Material ◽  
Elastomeric Seals

Previously it was shown that including smaller inset regions of less stiff material in the larger O-ring section at locations of high stress results in lower strain energy density in the section. This lower energy content is expected to lead to improved long-term seal performance due to less permanent material deformation and so less loss of seal-housing contact pressure. The shape of the inset region, the time-dependent change in material properties, and hence change in seal behavior over time in use were not considered. In this research experimental and numerical simulation studies were conducted to characterize the time-dependent performance of O-ring section designs with small inset regions of different mechanical behaviors than the larger surrounding section. Seal performance in terms of the rate of loss of contact pressure of modified designs and a baseline elastic, one-material design was calculated in finite element models using experimentally measured time-dependent material behavior. The elastic strain energy fields in O-ring sections were calculated under applied pressure and applied displacement loadings. The highest stress, strain, and strain energy regions in O-rings are near seal-gland surface contacts with significantly lower stress in regions of applied pressure. If the size of the modified region of the seal is comparable to the size of the highest energy density region, the shape of the inset is not a major factor in determining overall seal section behavior. The rate of loss of seal-housing contact pressure over time was less for the modified design O-ring sections compared with the baseline seal design. The time-dependent performance of elastomeric seals can be improved by designing seals based on variation of mechanical behavior of the seal over the seal section. Improvement in retention of sealing contact pressure is expected for seal designs with less stiff material in regions of high strain energy density.

scholarly journals IMPROVING DYNAMIC REGIME OF ROLLING FOR INCREASING DURABILITY OF BALL-ROLLING MILL ROLLS

2019 ◽  
Vol 61 (12) ◽  
pp. 927-932 ◽  
Author(s):  
V. Yu. Rubtsov ◽  
O. I. Shevchenko ◽  
M. V. Mironova
Keyword(s):  
Contact Pressure ◽  
Rotational Speed ◽  
Rolling Mill ◽  
Experimental Studies ◽  
Rolling Process ◽  
Operating Conditions ◽  
Frequency Method ◽  
Rolling Mills ◽  
Ball Rolling ◽  
Progressive Technology

One  of  the  important  reasons  for  the  downtime  of  ball  rolling  mills  is  replacement  of  rolls  due  to  their  wear  and  tear.  The  degree  and  zones  of  critical  wear  of  ball  rolling  rolls  are  investigated  in  the  article, where the greatest wear is observed over the flanges in zone of billet  capture.  Conditions  necessary  to  capture  the  blank  and  to  perform  rolling  process  are  analytically  determined.  Variable  frequency  method  of  roll  rotations  is  proposed  as  a  progressive  technology  for  blank supply. The results of tests for its variations in accordance with  linear  and  quadratic  law  are  presented.  Known  formulas  determining  average  strain  rate  at  rolls  rotational  speed  change  are  converted  for  linear and quadratic dependences. Experimental studies have been carried  out  in  conditions  of  EVRAZ  Nizhnetagilsky  Metallurgical  Plant  ball rolling mills during rolling of 60mm ball made of Sh-3G steel. Experiments  were  performed  for  given  parameters  of  manual  change  in  rolls rotation speed at blank capture by rollers. The results have shown  a  significant  effect  of  change  in  rotational  speed  on  average  specific  pressure during blank capture. Evaluation of torque-time and average  contact  pressure  for  calculated  and  experimental  data  are  presented.  Empirical characteristics are also described at variable rotational speed  of rolls according to linear and quadratic law. Acceptable convergence  of results of calculated and empirical characteristics is determined. Engineering solution has been proposed for that task. It consists in installation of a thyristor converter. This solution allows reduction of rolls  speed before blank capture. Also, this solution will increase frequency  to  the  nominal  value  according  to  the  given  law  after  blank  capture.  As an obtained result, there is uniform distribution of average contact  pressure over the entire length of the roll under different operating conditions  of  mill  in  automatic  mode. Application  of  this  technique  will  reduce wear degree of the rolling tool. At the same time, productivity  of ball rolling mill will be maintained. Rolls consumption and number  of rolls change will decrease due to rolls wear.

scholarly journals Uniform Pressing Mechanism in Large-Area Roll-to-Roll Nanoimprint Lithography Process

2021 ◽  
Vol 11 (20) ◽  
pp. 9571
Author(s):  
Ga Eul Kim ◽  
Hyuntae Kim ◽  
Kyoohee Woo ◽  
Yousung Kang ◽  
Seung-Hyun Lee ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Nanoimprint Lithography ◽  
Applied Pressure ◽  
Machine Learning Techniques ◽  
Conventional System ◽  
Large Area ◽  
High Productivity ◽  
Roll To Roll ◽  
Learning Techniques ◽  
Roller Machine

We aimed to increase the processing area of the roll-to-roll (R2R) nanoimprint lithography (NIL) process for high productivity, using a long roller. It is common for a long roller to have bending deformation, geometric errors and misalignment. This causes the non-uniformity of contact pressure between the rollers, which leads to defects such as non-uniform patterning. The non-uniformity of the contact pressure of the conventional R2R NIL system was investigated through finite element (FE) analysis and experiments in the conventional system. To solve the problem, a new large-area R2R NIL uniform pressing system with five multi-backup rollers was proposed and manufactured instead of the conventional system. As a preliminary experiment, the possibility of uniform contact pressure was confirmed by using only the pressure at both ends and one backup roller in the center. A more even contact pressure was achieved by using all five backup rollers and applying an appropriate pushing force to each backup roller. Machine learning techniques were applied to find the optimal combination of the pushing forces. In the conventional pressing process, it was confirmed that pressure deviation of the contact area occurred at a level of 44%; when the improved system was applied, pressure deviation dropped to 5%.

scholarly journals Revisiting Models for Spheroidal Graphite Growth

2018 ◽  
Vol 925 ◽  
pp. 118-124 ◽  
Author(s):  
Mathias Karsten Bjerre ◽  
Mohammed Azeem ◽  
Peter D. Lee ◽  
Jesper Henri Hattel ◽  
Niels Skat Tiedje
Keyword(s):  
Growth Rate ◽  
Cast Iron ◽  
Numerical Model ◽  
Final Stage ◽  
Nucleation And Growth ◽  
Ductile Cast Iron ◽  
Spheroidal Graphite ◽  
Microstructure Formation ◽  
X Ray ◽  
Graphite Growth

Recent experiments resolved nucleation and growth of graphite during solidification of ductile cast iron in 4D using synchrotron X-ray tomography. A numerical model for microstructure formation during solidification is compared with the experiments. Despite very good overall agreement between observations of spheroidal graphite growth and model results, significant deviations exist towards the end of solidification. We use the experimental observations to analyse the relation between graphite growth rate and the state of the particle neighbourhood to pinpoint possible links between growth rate of individual graphite spheres and the overall solidification state. With this insight we revisit existing models for growth of spheroidal graphite and discuss possible modifications in order to correctly describe the critical final stage of solidification.

Numerical analysis of the transient wear and lubrication behaviors of misaligned journal bearings caused by linear shaft misalignment

2021 ◽  
pp. 1-17
Author(s):  
Tianyou Yang ◽  
Yanfeng Han ◽  
Yijia Wang ◽  
Guo Xiang
Keyword(s):  
Numerical Model ◽  
Film Thickness ◽  
Contact Pressure ◽  
Elastic Deformation ◽  
Journal Bearing ◽  
Fluid Pressure ◽  
Axial Direction ◽  
Wear Depth ◽  
Wear Process ◽  
Journal Misalignment

Abstract The purpose of this study is to investigate the role of the misalignment journal, caused by journal elastic deformation, on the transient wear and mixed lubrication performances using a numerical model. In the numerical model, the transient geometry lubrication clearance considering the journal misalignment, the transient elastic deformation and the transient wear depth are incorporated to evaluate the transient film thickness during wear process. The evolutions, under different external loads, of the wear depth, wear rate, elastic deformation, film thickness, fluid pressure and contact pressure are calculated by the numerical model. Furthermore, the calculated results of the misaligned journal bearing are compared with those of the aligned journal bearing. The results show that the distributions of the wear depth, film pressure and elastic deformation are asymmetric along the axial direction and the peak values of them shift toward the back end when the journal misalignment is considered. The maximum wear depth, maximum fluid pressure, maximum contact pressure and maximum elastic deformation of the misaligned journal condition are significantly larger than those of the aligned journal condition.

Experimental study on the friction stability of paper-based clutches concerning groove patterns

2019 ◽  
Vol 72 (4) ◽  
pp. 541-548 ◽  
Author(s):  
Liang Yu ◽  
Biao Ma ◽  
Man Chen ◽  
He Yan Li ◽  
Jikai Liu
Keyword(s):  
Experimental Study ◽  
Surface Temperature ◽  
Design Methodology ◽  
Automatic Transmission ◽  
Applied Pressure ◽  
Friction Torque ◽  
Content Type ◽  
Rotating Speed ◽  
Wet Clutch ◽  
Transmission Fluid

Purpose This paper aims to study and compare the friction stability of wet paper-based clutches with regard to the radial grooves (RG) and waffle grooves (WG). Design/methodology/approach This paper presents an experimental study of a wet clutch concerning the effect of groove patterns on the friction torque and surface temperature. The friction stabilities of RG and WG are investigated with the applied pressure, rotating speed and automatic transmission fluid (ATF) temperature taken into consideration. Findings The friction torque and surface temperature of WG are larger than those of RG under the same operating condition. The friction torque difference between RG and WG grows with the increase of applied pressure and narrows with the increase of ATF temperature. Additionally, their temperature difference expands via increasing the rotating speed and ATF temperature or reducing the applied pressure; in this way, not only the variable coefficient difference between RG and WG can be narrowed, but also the friction stability of the clutch can be improved dramatically. Originality/value This paper explains the thermodynamic differences between RG and WG; moreover, it is verified experimentally that WG has a better friction stability than RG.

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