scholarly journals STATIC INTERACTION OF ROUGH SURFACES UNDER NORMAL FORCE

2020 ◽  
Vol 17 (2) ◽  
pp. 110-115
Author(s):  
S. Khairaliyev ◽  
Keyword(s):  
Contact Interaction ◽  
Frictional Contact ◽  
Normal Force ◽  
Random Functions ◽  
Static Interaction ◽  
Initial Stage ◽  
Engineering Designs ◽  
Friction Surfaces ◽  
Two Bodies ◽  
Individual Body

Modern mechanical engineering designs (and some others) make more and more demands on the development of mathematical models of units in which friction is present. A condition that significantly complicates the study of the properties of a frictional contact is its discreteness with different geometric parameters of two contacting bodies, as a result of which the contact is formed only between a part of the roughness of the rubbing bodies (base and slide). The geometry of the contacting surfaces can most accurately be described by random functions, however, methods for calculating friction nodes based on random functions are very complicated. This work is the initial stage of building a model of contact interaction of two rough bodies with roughness parameters that are different for the two bodies, but constant for each individual body. In addition, the model of contact interaction is considered with a variable force compressing the contacting bodies, in the absence of an external shear force in the contact plane, and this work allows you to check the accuracy of constructing a model of interaction of friction surfaces with a relatively simple scheme of interaction of these surfaces.

Control Concepts for a Vibration Absorber With an Adaptive Joint Connection

2014 ◽  
Author(s):  
Pascal Reuss ◽  
Lothar Gaul
Keyword(s):  
Harmonic Balance ◽  
Frictional Contact ◽  
Normal Force ◽  
Dynamic Stiffness ◽  
Control Variable ◽  
Harmonic Balance Method ◽  
Direct Control ◽  
Additional Degree ◽  
Nonlinear Relation ◽  
Joint Connection

The use of absorbers to reduce vibrations of machines is common in industry and can be found in various applications. In most cases passive absorbers are used to cancel one particular eigenfrequency. The disadvantage of this solution is that due to the introduction of an additional degree-of-freedom two resonance peaks occur next to the absorbed eigenfrequency. Given the case that the machine operates in a wider frequency band these two eigenfrequencies could be excited and feature similarly high amplitudes. To address this concern, in the present case an adaptive absorber is used, which is able to adjust its eigenfrequency to the actually excited frequency. Therefore, the anti-resonance can be shifted such that a full cancellation of the resonance is possible. The absorber consists of a mass and two springs. One spring is fixed to the mass permanently and the second can be coupled to the system by an adaptive joint connection. The normal force in the frictional contact serves as control variable to achieve adaptivity of the dynamic eigenfrequency of the absorber. Two control concepts are presented. Both concepts include isolated curves characterizing the nonlinear relation between the dynamic stiffness and the related normal force based on simulations using the Harmonic Balance Method. Due to the isolation of the nonlinearity, linear control concepts like LQR can be applied, which is done in the present case. Furthermore, a direct control of the eigenfrequency is done. The adaptive absorber is applied to a simplified machine tool carriage.

Without God

2021 ◽  
pp. 9-29
Author(s):  
Eric Schliesser
Keyword(s):  
Necessary Condition ◽  
The Universe ◽  
Two Bodies ◽  
Individual Body

This chapter argues that when Newton drafted the first edition of the Principia in the mid-1680s, he thought that (at least a part of) the cause of gravity is the disposition inherent in any individual body, but that the force of gravity is the actualization of that disposition; a necessary condition for the actualization of the disposition is the actual obtaining of a relation between two bodies having the disposition. The cause of gravity is not essential to matter because God could have created matter without that disposition. Nevertheless, at least a part of the cause of gravity inheres in individual bodies and were there one body in the universe it would inhere in that body. The force of gravity is neither essential to matter nor inherent in matter, because it is the actualization of a shared disposition. We can distinguish among (i) accepting gravity as causally real, (ii) positing the cause(s) of the properties of gravity, (iii) making claims about the mechanism or medium by which gravity is transmitted.

Sliding Friction Behavior of Bulk Ti3SiC2 under Difference Normal Pressures

2007 ◽  
Vol 280-283 ◽  
pp. 1353-1356 ◽  
Author(s):  
Zhen Ying Huang ◽  
Hong Xiang Zhai ◽  
Yang Zhou ◽  
Yi Fan Wang ◽  
Zhi Li Zhang
Keyword(s):  
Friction Coefficient ◽  
Sliding Friction ◽  
Transition Period ◽  
Low Carbon Steel ◽  
Normal Pressure ◽  
Low Carbon ◽  
Friction Behavior ◽  
Steady Stage ◽  
Initial Stage ◽  
Friction Surfaces

The friction behavior of Ti3SiC2 sliding against low carbon steel was studied. Tests were carried out on a block-on-disk type friction tester, with the normal pressures from 0.2 MPa to 0.8 MPa and the sliding speed of 20 m/s. The results showed that, irrespective of the normal pressure, the friction coefficient exhibits a transition period in the initial stage of a sliding friction process, in which the friction coefficient increases from an initial value and tends to a saturation value, and then enters into a relatively steady stage. The results also showed that, the friction coefficient of the steady stage decreases gradually from 0.35 to 0.26 with increase in normal pressure from 0.2 MPa to 0.8 MPa. The friction surfaces were observed by using SEM. It was found that all the surfaces were covered by a layer consisting of the frictional products with antifriction effect, and that the denseness and the thickness of the layer were increased with increase in normal pressure applied.

scholarly journals METHODOLOGY IN DEFINITION OF CONROD BEARINGS LIFE OF HEAT-ENGINE

2016 ◽  
Vol 2016 (3) ◽  
pp. 46-57
Author(s):  
Игорь Леванов ◽  
Igor Levanov ◽  
Елена Задорожная ◽  
Elena Zadorozhnaya ◽  
Артём Дудников ◽  
...  
Keyword(s):  
Contact Interaction ◽  
Heat Engine ◽  
Hydrodynamic Theory ◽  
Connecting Rod ◽  
Slider Bearing ◽  
Minimum Thickness ◽  
Regular Form ◽  
Lubrication Layer ◽  
Definition Of ◽  
Friction Surfaces

The paper reports the sequence of the definition of bearings resource in a crank gear of heatengines. A brief description is given regarding the procedure for the computation of bearing hydromechanical properties in terms of hydrodynamic theory of lubrication and that of the procedure for the definition of an area of contact interaction. The input equations for the computation of dynamics and lubrication are: the equation for the field of hydrodynamic pressures in a lubrication layer separating random loaded surfaces (Reynolds equation); the equations set of plane motion of a shaft journal center; the heatbalance equation manifesting the equality of heat values mean in a cycle of load disseminated in a lubrication layer of a bearing and heat removed by lubricant flowing out in its faces. The procedure for the determination of an area of a contact interaction is developed in accordance with a molecular-mechanical theory of friction and a fatigue theory of wear according to I.V. Kragelsky. The extension of the area of a contact interaction (an area of the violation of a hydrodynamic mode of lubrication) in a slider bearing was defined in terms of the computation of the de-pendence of a minimum thickness in a lubrication layer of a bearing of a connecting rod upper head upon a rotation angle of a crankshaft. At the same time there were taken into account: the non-Newton’s properties of a lubricant; the presence of oil feeding sources on friction surfaces; possible deviations of friction surfaces from a regular form. The procedures presented at the given stage can be used for a comparative assessment of tribocouplings life in heatengines at an initial stage of designing.

The mechanism of the initial stage of selective transfer during frictional contact

Wear ◽  
1978 ◽  
Vol 47 (1) ◽  
pp. 133-138 ◽  
Author(s):  
I.V. Kragelskii ◽  
N.M. Mikhin ◽  
N.K. Myshkin ◽  
M.A. Bronovets ◽  
M.N. Dobychin ◽  
...  
Keyword(s):  
Frictional Contact ◽  
Selective Transfer ◽  
Initial Stage

Reaction couples of ceramic thin films prepared by CVD

1988 ◽  
Vol 46 ◽  
pp. 798-799
Author(s):  
D.W. Susnitzky ◽  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Thin Film ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Solid State Reactions ◽  
Spatial Distributions ◽  
Diffusion Couples ◽  
Kinetics Studies ◽  
Ceramic Thin Films ◽  
Initial Stage

Solid-state reactions have traditionally been studied in the form of diffusion couples. This ‘bulk’ approach has been modified, for the specific case of the reaction between NiO and Al2O3, by growing NiAl2O4 (spinel) from electron-transparent Al2O3 TEM foils which had been exposed to NiO vapor at 1415°C. This latter ‘thin-film’ approach has been used to characterize the initial stage of spinel formation and to produce clean phase boundaries since further TEM preparation is not required after the reaction is completed. The present study demonstrates that chemical-vapor deposition (CVD) can be used to deposit NiO particles, with controlled size and spatial distributions, onto Al2O3 TEM specimens. Chemical reactions do not occur during the deposition process, since CVD is a relatively low-temperature technique, and thus the NiO-Al2O3 interface can be characterized. Moreover, a series of annealing treatments can be performed on the same sample which allows both Ni0-NiAl2O4 and NiAl2O4-Al2O3 interfaces to be characterized and which therefore makes this technique amenable to kinetics studies of thin-film reactions.

Decoration technique and surface physics

1978 ◽  
Vol 36 (1) ◽  
pp. 436-437 ◽  
Author(s):  
H. Bethge
Keyword(s):  
Diffusion Path ◽  
Special Importance ◽  
Surface Physics ◽  
Step Structure ◽  
Initial Stage ◽  
Special Cases ◽  
Atomic Surface ◽  
The Mean ◽  
Bulk Structure ◽  
Decoration Technique

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

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