Appreciable Increase in Pitting Limit of Contact Surfaces Under Rolling and Sliding Conditions

1978 ◽  
Vol 100 (3) ◽  
pp. 440-450 ◽  
Author(s):  
A. Ishibashi ◽  
T. Yokote ◽  
H. Yoshino
Keyword(s):  
Friction Coefficient ◽  
Contact Surface ◽  
Small Area ◽  
Testing Machine ◽  
Contact Forces ◽  
Appreciable Increase ◽  
Metallic Contacts ◽  
Contact Surfaces

This work was conducted to discover the highest pitting limits of the contact surfaces under combined rolling/sliding conditions. Appreciable increases in pitting limits were obtained in rollers with hardnesses in the range 190 to 335 HB using an improved testing machine made by the authors. The allowable contact forces corresponding to the new pitting limits were about four times greater than those corresponding to the earlier pitting limits. Some factors which might prevent appreciable increases in pitting limits were examined and a new experiment was conducted using rollers with a pit-producing ability limited to a small area of less than 0.1 percent of whole contact surface of the rollers. It was found that the local metallic contacts which cause only a slight increase in the friction coefficient can bring about severe pitting failure before 107 rotations.

Analysis of Vibration Characteristics for Last Stage Blade With Friction Contact Surfaces of Steam Turbine

2011 ◽  
Author(s):  
Yutaka Yamashita ◽  
Koki Shiohata ◽  
Takeshi Kudo
Keyword(s):  
Dynamic Response ◽  
Steam Turbine ◽  
Contact Surface ◽  
Contact Forces ◽  
Analysis Method ◽  
Friction Damping ◽  
Normal Contact ◽  
Damping Characteristics ◽  
Last Stage ◽  
Contact Surfaces

Friction damping devices such as under platform dampers are installed for modern turbine blades to suppress dynamic vibrations of the blades. In order to secure the reliability of the blades, it is important to predict the dynamic response and friction damping characteristics accurately. In this present paper, the dynamic response and friction damping characteristics of a last stage blade (LSB) of a steam turbine with contact surfaces at the cover, tie-boss and blade root was investigated. Especially, it is focused on the effect of the non-uniform normal contact forces at the contact surface. To investigate the effect of non-uniform normal contact forces, an analysis method was developed. Analysis model of the LSB with contact surfaces was discretized by finite elements. Tangential forces at the contact surfaces were modeled by multi-DOF macro-slip modeling. The non-linear frequency responses of the LSB were obtained by using the harmonic balance method. Using this analysis method, the relationship between the contact surface behavior and the dynamic response was studied.

scholarly journals Effects of Object Compliance on Three-Digit Grasping

2009 ◽  
Vol 101 (5) ◽  
pp. 2447-2458 ◽  
Author(s):  
Sara A. Winges ◽  
Stephanie E. Eonta ◽  
John F. Soechting ◽  
Martha Flanders
Keyword(s):  
Contact Surface ◽  
Muscle Activation ◽  
Ring Finger ◽  
Contact Forces ◽  
Load Force ◽  
Electromyographic Activity ◽  
Dependent Manner ◽  
Muscle Activation Patterns ◽  
Contact Points ◽  
Contact Surfaces

Compared with rigid objects, grasping and lifting compliant objects presents additional uncertainties. For any static grasp, forces at the fingertips depend on factors including the locations of the contact points and the contact forces must be coordinated to maintain equilibrium. For compliant objects, the locations and orientations of the contact surfaces change in a force-dependent manner, thus changing the force requirements. Furthermore, every force adjustment then results in additional changes in object shape. This study characterized force and muscle activation patterns in this situation. Fingertip forces were measured as subjects grasped and lifted a 200-g object using their thumb, index, and ring fingers. A spring was sometimes placed under the index and/or ring finger contact surface. Surface electromyographic activity was recorded from ten hand muscles and one proximal arm muscle. The patterns of grip (normal) force and muscle activity were similar across conditions during the load and lift phases, but their amplitude depended on whether the contact surface was compliant. Specifically, the grip force increased smoothly during the load phase of the task under all conditions. To the contrary, the tangential contact (load) force did not increase monotonically when one or more of the contact surfaces were compliant, resulting in a decoupling of the grip and load forces.

Study on friction characteristics of sliding interface of feed system

2020 ◽  
Vol 72 (7) ◽  
pp. 865-871
Author(s):  
Pan-Pan Li ◽  
Feng Gao ◽  
Yan Li ◽  
Bo Yang
Keyword(s):  
Friction Coefficient ◽  
Peer Review ◽  
Working Conditions ◽  
Contact Surface ◽  
Testing Machine ◽  
Mixed Lubrication ◽  
Wear Testing ◽  
Feed System ◽  
Content Type ◽  
Start Up

Purpose The serious friction caused by the fluctuation of friction occurs when start-up and will reduce the positioning accuracy of the servo axes of high precision machine tools, the purpose of this paper is to study the friction fluctuation characteristics of friction coefficients between interfaces under different working conditions. Design/methodology/approach HT200 and 45# materials were experimentally studied by friction and wear testing machine UMT-3, the variation of friction coefficient under different working conditions (different start-up conditions, the variation of lubrication state area and different roughness) were measured. Findings The results show that the larger start-up acceleration shortens the pre-sliding time of the interface friction, makes the friction coefficient decrease faster, reduces the mixed lubrication area of the contact surface and makes the contact surface reach the stable lubrication state quickly. It can be concluded that the larger roughness surface will lead to the larger mixed lubrication area, the larger static friction coefficient and the larger drop between static and dynamic friction coefficient and easy to cause friction vibration. Originality/value The results reveal the friction fluctuation rule of the metal interface during the different start-up process, which is of guiding significance to reveal the lubrication principle and mechanism of the mechanical interface. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0482/

Dynamics Characteristics for Contact Surface of Machine Tool

2014 ◽  
Vol 538 ◽  
pp. 91-94
Author(s):  
Wei Ping Luo
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Contact Surface ◽  
Dynamic Performance ◽  
Virtual Prototype ◽  
Prototype Model ◽  
Ansys Software ◽  
Dynamic Analyses ◽  
Contact Surfaces

A virtual prototype model of Machine Tool has been constructed by using the Pro/E software and the ANSYS software. Considering the effects of contact surfaces, dynamic analyses of Machine Tool are studied. The effects of contact surfaces on the dynamic characteristics of machine tool are studied. So that the purpose predicting and evaluating synthetically the machine tool dynamic performance without a physical sample can be achieved.

Estimation of Gear Friction Coefficient using Directional Parameter of Tooth Surface

2021 ◽  
pp. 1-27
Author(s):  
Junichi Hongu ◽  
Ryohei Horita ◽  
Takao Koide
Keyword(s):  
Friction Coefficient ◽  
Contact Surface ◽  
Gear Tooth ◽  
Correction Term ◽  
Tooth Surface ◽  
Oil Film ◽  
Tooth Surfaces ◽  
Frictional Coefficients ◽  
Finishing Processes ◽  
The Relationship

Abstract This study proposes a modification of the Matsumoto equation using a directional parameter of tooth surfaces to adapt various gear finishing processes. The directional parameters of a contact surface, which affect oil film formations, have been discussed in the field of tribology; but this effect has been undetermined on the meshing gear tooth surfaces having directional machining marks. Thus, this paper investigates the relationship between the gear frictional coefficients and the directional parameters (based on ISO25178) of their tooth surfaces with the various finishing processes; and modifies the Matsumoto equation by introducing a new directional parameter to augment the various gear finishing processes. Our findings indicate that through optimizing the coefficient of the correction term the include the new directional parameter, the calculated friction values using the modified Matsumoto equation correlate more highly to the experimental friction values than that using the unmodified Matsumoto equation.

Worm gear wear and coefficient of efficiency during their running-in period

2021 ◽  
pp. 22-25
Author(s):  
Keyword(s):  
Friction Coefficient ◽  
Velocity Vector ◽  
Worm Gear ◽  
Worm Gears ◽  
Contact Surfaces

The process of worm gear wear is considered. The reasons for the change in the coefficient of efficiency of worm gears during the running-in period are analyzed. Keywords: worm gear, line of engagement, contact surfaces, involute worm, velocity vector, friction coefficient. [email protected]

The Dependence of the Friction Coefficient on the Size and Course of Sliding Speed

2014 ◽  
Vol 693 ◽  
pp. 305-310 ◽  
Author(s):  
Eva Labašová
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Testing Machine ◽  
Current Component ◽  
Sliding Speed ◽  
Rectangular Shape ◽  
Coefficient Increase ◽  
The Coefficient Of Friction ◽  
Ring Method ◽  
Run Up

The coefficient of friction for the bronze material (CuZn25Al6) with insert graphite beds and other bronze material (CuSn12) are investigated in this paper. Friction coefficient was investigated experimentally by the testing machine Tribotestor`89 which uses the principle of the ring on ring method. The external fixed bushing was exposed to the normal load of the same size in all tests. Process of load was increased from level 50 N to 600 N during run up 300 s, after the run up the appropriate level of load was held. The internal bushing performed a rotational movement with constant sliding speed. The value of sliding speed was changed individually for every sample (v = 0.2 (0.3, 0.4) m.s-1). The forth test had a rectangular shape of sliding speed with direct current component 0.3 m.s-1 and the amplitude 0.1 m.s-1 period 300 s, the whole test took 2100 s. The obtained results reveal that friction coefficient increase with the increase of sliding speed.

Effects of Load and Rotate Speed on the Friction of NBR by 45# Steel in Crude Oil Medium

2011 ◽  
Vol 230-232 ◽  
pp. 1079-1083
Author(s):  
Yi Zhang ◽  
Shi Jie Wang ◽  
Zhong Feng Guo ◽  
Zhong Wei Ren
Keyword(s):  
Friction Coefficient ◽  
Crude Oil ◽  
Constant Temperature ◽  
Testing Machine ◽  
Butadiene Rubber ◽  
Nitrile Butadiene Rubber ◽  
Friction Testing ◽  
Low Load ◽  
Test Result

Select two types of nitrile-butadiene rubber (NBR) which they are different in ingredients, under two types of crude oil medium respectively, the test is carried out on the friction testing machine. The test result shows that under the constant intermediate-low rotate speed and constant temperature, the friction coefficient decreases as the load increases; under the constant intermediate-low load and constant temperature, the friction coefficient increases as the rotate speed increases.

Research for a Projectile Positioning Structure for Stacked Projectile Weapons

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Qiao Luo ◽  
Xiaobing Zhang
Keyword(s):  
Friction Coefficient ◽  
Structural Parameters ◽  
Static Friction ◽  
Element Model ◽  
Ballistic Performance ◽  
Static Friction Coefficient ◽  
Key Technologies ◽  
Contact Surfaces ◽  
Proper Material ◽  
Multibody Contact

One of the key technologies of stacked projectile weapons is projectile positioning. However, the present projectile positioning structures have their respective advantages and shortcomings. A new structure based on the self-locking principle is put forward in this paper and verified as feasible by static analysis if the proper material and structural parameters are chosen. In order to check the strength and verify the feasibility of the structure under launch conditions, the multibody contact finite element model of the structure is established, coupled with dynamic load in the interior ballistic cycle. According to simulations and analysis, the projectile positioning structure is feasible and the strength of the projectile can meet the strength requirement for launch conditions. For different maximum static friction coefficients, simulations show that an increase in the maximum static friction coefficient between the contact surfaces of the positioning ring and barrel improves the positioning performance, but an increase in the maximum static friction coefficient between the contact surfaces of the positioning ring and projectile worsens. On the basis of great computation, it is found that an increase in the upper thickness and height of the positioning ring improves the positioning performance, but an increase in the lower thickness worsens the positioning performance. Further, a lower thickness affects the positioning performance more greatly. As a result, the positioning ring will be thin and light to improve the positioning performance. Compared with other positioning structures, the new structure has little influence on the ballistic performance and is a good application prospect.

scholarly journals Calculation of accurate interatomic contact surface areas for the quantitative analysis of non-bonded molecular interactions

2019 ◽  
Vol 35 (18) ◽  
pp. 3499-3501 ◽  
Author(s):  
Judemir Ribeiro ◽  
Carlos Ríos-Vera ◽  
Francisco Melo ◽  
Andreas Schüller
Keyword(s):  
Surface Area ◽  
Contact Surface ◽  
Web Server ◽  
Software Tool ◽  
Solvent Accessible Surface Area ◽  
Surface Areas ◽  
Contact Surfaces ◽  
Accessible Surface ◽  
Solvent Accessible Surface ◽  
Interatomic Contact

Abstract Summary Intra- and intermolecular contact surfaces are routinely calculated for a large array of applications in bioinformatics but are typically approximated from differential solvent accessible surface area calculations and not calculated directly. These approximations do not properly take the effects of neighboring atoms into account and tend to deviate considerably from the true contact surface. We implemented an extension of the original Shrake-Rupley algorithm to accurately estimate interatomic contact surface areas of molecular structures and complexes. Our extended algorithm is able to calculate the contact area of an atom to all nearby atoms by directly calculating overlapping surface patches, taking into account the possible shielding effects of neighboring atoms. Here, we present a versatile software tool and web server for the calculation of contact surface areas, as well as buried surface areas and solvent accessible surface areas (SASA) for different types of biomolecules, such as proteins, nucleic acids and small organic molecules. Detailed results are provided in tab-separated values format for analysis and Protein Databank files for visualization. Direct contact surface area calculation resulted in improved accuracy in a benchmark with a non-redundant set of 245 protein–DNA complexes. SASA-based approximations underestimated protein–DNA contact surfaces on average by 40%. This software tool may be useful for surface-based intra- and intermolecular interaction analyses and scoring function development. Availability and implementation A web server, stand-alone binaries for Linux, MacOS and Windows and C++ source code are freely available from http://schuellerlab.org/dr_sasa/. Supplementary information Supplementary data are available at Bioinformatics online.

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