Emergence of tangential stiffness through the use of inclined orthotropic material

2020 ◽  
pp. 095440622096796
Author(s):  
Tadayoshi Shoyama ◽  
Yutaka Wada ◽  
Osami Matsushita
Keyword(s):  
Orthotropic Material ◽  
Tangential Force ◽  
Reaction Force ◽  
Tangential Stiffness ◽  
Oil Whirl ◽  
Excited Vibration ◽  
Rotationally Symmetric ◽  
Tangential Forces ◽  
Degree Of Anisotropy ◽  
Stabilization Effect

A flexible bearing support structure is effective for stabilizing the self-excited vibration of a bearing, such as oil whirl. The stabilization effect is increased if the structure has static tangential stiffness, where the reaction force is perpendicular to the displacement. In this study, it is shown that a support component made of inclined orthotropic material, which exhibits shear–extension coupling, can have tangential stiffness.　The circumferential average of the tangential stiffness was found to vanish with a rotationally symmetric configuration of these components because the tangential forces of each component cancel out. However, the tangential force was recovered by allowing separation on the contact surface. A circular formation of an inclined orthotropic sheet that shows an axisymmetric stiffness matrix is proposed. Theoretical and numerical analyses clarified the effects of the friction coefficient, fitting interference, and degree of anisotropy of the material. Zero interference was found to be the best condition to maximize tangential stiffness.

Experimental Study of Tangential Micro Deflection of Interface of Machined Surfaces

1999 ◽  
Vol 123 (2) ◽  
pp. 365-367 ◽  
Author(s):  
Jun Ni ◽  
Zhenqi Zhu
Keyword(s):  
Experimental Study ◽  
Plastic Deformation ◽  
Elastic Deformation ◽  
Tangential Force ◽  
Experimental Results ◽  
Contact Interface ◽  
Tangential Stiffness ◽  
Tangential Forces ◽  
Elastic And Plastic Deformation ◽  
Machined Surfaces

This paper studies the characteristics of micro tangential deflection of the interface of mating machined surfaces subjected to normal and tangential forces. Experimental results show that contact interface subjected to a tangential force experiences elastic deformation, plastic deformation and micro slip before macro-breakaway occurs. The linearity of tangential stiffness is only valid in the stage of elastic deformation. The nonlinear tangential stiffness of the interface should be considered in the stages of elastic and plastic deformation before micro-breakaway occurs.

scholarly journals Micromechanism of the Breakage of Two Spherical Gypsum Particles under Normal–Tangential Contact Conditions

2021 ◽  
Vol 11 (9) ◽  
pp. 4039
Author(s):  
Yiran Niu ◽  
Lin Li ◽  
Yanwei Zhang ◽  
Shicai Yu ◽  
Jian Zhou
Keyword(s):  
Tangential Force ◽  
Coarse Grained ◽  
Spherical Particles ◽  
Contact Conditions ◽  
Normal Contact ◽  
Tangential Contact ◽  
Theoretical Predictions ◽  
Tangential Forces ◽  
Predicted Values ◽  
The Relationship

Contact breakage of particles makes a large difference in the strength of coarse-grained soils, and exploring the characteristics within the process of the breakage is of great significance. Ignoring the influence of particle shape, the micromechanism of two spherical particles breaking under normal–tangential contact conditions was investigated theoretically and experimentally. Through theoretical analysis, the breakage form, the shape and size of the conical core, and the relationship between the normal and tangential forces at crushing were predicted. Particle contact tests of two gypsum spheres were carried out, in which the breakage forms, features of the conical cores and the normal and tangential forces at crushing were recorded for comparison with the predicted values. The test results and the theoretical predictions showed good agreement. Both the analysis and test demonstrate that the presence of tangential forces causes the conical core to assume the shape of an oblique cone, and the breakage form to change. Moreover, with increasing normal contact force, the tangential force needed for crushing increases gradually first and then decreases suddenly.

Orthotropic Characteristics of Glass-Fibre-Epoxy Laminates under Plane Stress

1973 ◽  
Vol 15 (2) ◽  
pp. 102-108 ◽  
Author(s):  
R. M. Ogorkiewicz
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Uniaxial Tension ◽  
Plane Stress ◽  
Glass Fibre ◽  
Orthotropic Material ◽  
Glass Fibres ◽  
Degree Of Anisotropy

Deformational characteristics of laminates of unidirectionally arranged glass fibres and epoxy resin under plane stress are shown to correspond very closely under uniaxial tension and, to a lesser extent, under shear to the theroetical pattern of stiffness of an orthotropic material. The anisotropy in stiffness is also shown to be accompanied by an even greater degree of anisotropy in tensile strength.

Dynamic behaviors of a high-speed turbocharger rotor on elliptical floating-ring bearings

2019 ◽  
Vol 233 (12) ◽  
pp. 1785-1799 ◽  
Author(s):  
Congcong Zhang ◽  
Yongliang Wang ◽  
Rixiu Men ◽  
Hong He ◽  
Wei Chen
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Low Cost ◽  
Dynamic Behaviors ◽  
Oil Whirl ◽  
Excited Vibration ◽  
Dynamic Performances ◽  
Simulation Results ◽  
Bearing Design ◽  
Run Up

Floating-ring bearings are commonly used in automotive turbocharger applications due to their low cost and their suitability under extreme rotation speeds. This type of bearings, however, can become a source of noise due to oil whirl-induced sub-synchronous vibrations. The scope of this paper is to examine whether the concept of a floating-ring bearing with an elliptical clearance might be a solution to suppress sub-synchronous vibrations. A very time-efficient approximate solution for the Reynolds equation to the geometry of elliptical bearings is presented. The nonlinear dynamic behaviors of a turbocharger rotor supported by two concepts of elliptical floating-ring bearings are systematically investigated using run-up simulations. For the first concept of elliptical floating-ring bearings i.e. the outer bearing of the floating-ring bearing changed in the form of elliptical pattern (see Figure 1(b) in the article), some studies have pointed out that its steady-state and dynamic performances are superior to plain cylindrical floating-ring bearings but, the nonlinear run-up simulation results shown that this type of elliptical floating-ring bearings is not conducive to reduce the self-excited vibration levels. However, for the second type of elliptical floating-ring bearings i.e. both the inner and outer films of the floating-ring bearing changed in the form of elliptical pattern (see Figure 1(c) in the article), it is shown that the sub-synchronous vibrations have been considerably suppressed. Hence, the second noncircular floating-ring bearing design is an attractive measure to suppress self-excited vibrations.[Figure: see text]

scholarly journals Numerical Analysis of Effects of Arms with Different Cross-Sections on Straight-Bladed Vertical Axis Wind Turbine

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2106
Author(s):  
Yutaka Hara ◽  
Naoki Horita ◽  
Shigeo Yoshida ◽  
Hiromichi Akimoto ◽  
Takahiro Sumi
Keyword(s):  
Cross Sections ◽  
Tangential Force ◽  
Past Research ◽  
Vertical Axis ◽  
Rotational Axis ◽  
Vertical Axis Wind Turbine ◽  
Vertical Axis Wind Turbines ◽  
Resistance Torque ◽  
Tangential Forces ◽  
Computational Fluid Dynamics Cfd

Most vertical axis wind turbines (VAWTs) need arms connecting the blades with the rotational axis. The arms increase the power loss of VAWTs; however, the distribution between the pressure and friction influences and their degrees of influence have not yet been investigated in detail in past research. We applied computational fluid dynamics (CFD) targeting a small-sized straight-bladed VAWT to elucidate the effects of arms on turbine performance. In the analysis, three kinds of arms with different cross-sections (NACA 0018 airfoil, 18% rectangular, circular) with the same height were added to an armless rotor. The tangential forces and resistance torques caused by the added arms were recalculated by dividing the pressure and friction influences based on the surface pressure and friction distributions obtained by the CFD on an arm or a blade. The pressure-based tangential force of an arm, regardless of the cross-section, had a tendency to increase near the connection part between the arm and a blade. Though the value was small, the friction on the rectangular arm generated a driving force, whereas the friction on the other arms generated resistance forces. The pressure-based tangential force of a blade increased for a wide region around the connection part. The friction-based tangential force of a blade dropped around the connection part of every arm-equipped rotor. The arm resistance torque added to a VAWT by the existence of arms was larger than the added blade resistance torque in the cases of rectangular and circular arm rotors. Conversely, in the case of the airfoil arm rotor, the resistance torque added to blades became larger than that of arms.

The area of real contact and the shear strength of monomolecular layers of a boundary lubricant

1955 ◽  
Vol 227 (1171) ◽  
pp. 500-515 ◽  
Keyword(s):  
Shear Strength ◽  
Molecular Layer ◽  
Tangential Force ◽  
Surface Damage ◽  
Calcium Stearate ◽  
A Value ◽  
Boundary Lubricant ◽  
Tangential Forces ◽  
Monomolecular Layers ◽  
Single Molecular Layer

A method has been developed by which molecularly smooth surfaces may be placed together and the area of contact formed between them measured. Selected sheets of mica were cleaved to be free from cleavage steps on both sides of the sheets. These were bowed up and mounted as crossed cylinders in an apparatus in which normal and tangential loads could be applied. The area of contact formed between the surfaces has been examined using multiple-beam interference techniques. Examination of the hue and intensity of the central region of the interferograms enables a separation of the mica sheets to be detected even if this is of only a few ångströms. This means that the boundary of the region of contact may be determined with a greater precision than has hitherto been possible. Fringes of equal chromatic order provide a sensitive means for the detection of small particles of accidental contamination and have been used to show when the contact is intimate over the whole region. Normal and tangential forces have been applied to the mica specimens, both when in a clean condition and when covered with a monomolecular layer of calcium stearate. The area of contact was observed simultaneously. The area and the force required to shear it being known, the shear strength of the junctions has been calculated. The damage occurring during the process has been examined using reflexion electron microscopy. At certain values of the tangential force smooth sliding takes place on the lubricated surfaces and no surface damage can be detected. Further increase of the tangential force produces a rapid slip causing fragments to be torn out of the surface and some damage occurs. No smooth sliding was detected on unlubricated surfaces of mica and the damage produced during the slip was extensive. The force required to shear the junction formed between clean smooth mica surfaces is very high. A value of 10 Kg/mm 2 has been obtained. For the monomolecular layers of calcium stearate the value obtained is about forty times lower but is by no means negligible. This means that a considerable force is required to shear a film of boundary lubricant and accounts for the otherwise unexplained observation that when metals are lubricated with a single molecular layer of soap or fatty acid the frictional force is reduced by only a factor of 10 while the wear decreases by a factor of 10000 or more.

scholarly journals In Situ Investigation of Load-Dependent Nonlinearities in Tangential Stiffness and Damping of Spherical Contacts

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Melih Eriten ◽  
Shixuan Chen ◽  
Ahmet D. Usta ◽  
Karthik Yerrapragada
Keyword(s):  
Tangential Force ◽  
Damping Capacity ◽  
Material Damping ◽  
Sem Images ◽  
Tangential Stiffness ◽  
In Situ Investigation ◽  
Classical Models ◽  
Stiffness And Damping ◽  
Force Displacement

Abstract Seemingly stationary (pre-sliding) interfaces between different materials, parts, and components are major sources of compliance and damping in structures. Classical pre-sliding contact models assume smooth elastic contact and predict that frictional slip leads to a well-defined set of stiffness and damping nonlinearities. However, reported data deviate from those predictions, and literature lacks a conclusive evidence leading to those deviations. In this work, the authors measure tangential stiffness and damping capacities inside a scanning electron microscope (SEM) while monitoring contacts between a rigid spherical probe and two materials (high-density polyethylene (HDPE) and polyurethane elastomer). Measured force, displacement, contact area, stiffness, and damping are then compared with predictions of classical models. In situ SEM images synchronized to the tangential force–displacement responses are utilized to relate the degree of plasticity and geometric alterations to stiffness and damping nonlinearities. In agreement with the classical models, increasing tangential loads cause softening in contacts under light normal preloads. In contrast, stiffness for HDPE increases with increasing tangential loads at heavy normal preloads due to plasticity and pileups over the contact. Material damping is prevalent for all loading cases in polyurethane samples thanks to nearly fully adhered contact, whereas for only light tangential loads in HDPE. With increasing tangential loading, specific damping capacity of HDPE contacts increases tenfold. This nonlinear increase is due to plastic shearing and frictional losses induced by tangential loading. Those findings suggest that predictive interface models should include geometric alterations of contact, plasticity, and material damping.

Cutting Force Changes during One Cut in End Milling with a Throw-Away Insert - Difference between Up-Cut and Down-Cut –

2019 ◽  
Vol 825 ◽  
pp. 123-128
Author(s):  
Kota Matsuda ◽  
Ryutaro Tanaka ◽  
Katsuhiko Sekiya ◽  
Keiji Yamada
Keyword(s):  
Cutting Force ◽  
End Milling ◽  
Tangential Force ◽  
Chip Thickness ◽  
Radial Force ◽  
Depth Of Cut ◽  
Radial Depth ◽  
Aisi 1045 ◽  
Tangential Forces ◽  
Coated Carbide

In this study, the transition of cutting force in the tangential and radial direction during one cut was investigated in milling of AISI-1045, AISI-304, and Ti-6Al-4V with a TiN coated carbide throw-away insert. In the case of 1045 and Ti-6Al-4V, there was not obvious difference in tangential forces between up-cut and down-cut. However, up-cut showed larger radial force than down-cut in any material. In down-cut, tangential force showed almost the same regardless of radial depth of cut. 304 and Ti-6Al-4V caused larger radial force with the increase of radial depth of cut at the same cut chip thickness.

Mechanisms for Force Adjustments to Unpredictable Frictional Changes at Individual Digits During Two-Fingered Manipulation

1998 ◽  
Vol 80 (4) ◽  
pp. 1989-2002 ◽  
Author(s):  
Ingvars Birznieks ◽  
Magnus K. O. Burstedt ◽  
Benoni B. Edin ◽  
Roland S. Johansson
Keyword(s):  
Contact Surface ◽  
Normal Force ◽  
Tangential Force ◽  
Sensory Information ◽  
Load Force ◽  
Normal Forces ◽  
Tangential Forces ◽  
Contact Surfaces ◽  
The Right ◽  
Fingertip Forces

Birznieks, Ingvars, Magnus K. O. Burstedt, Benoni B. Edin, and Roland S. Johansson. Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation. J. Neurophysiol. 80: 1989–2002, 1998. Previous studies on adaptation of fingertip forces to local friction at individual digit–object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces increased at both fingers. Thus to independently adapt fingertip forces to the local friction the normal forces were controlled at an interdigital level by using sensory information from both engaged digits. Furthermore, subjects used both short- and long-term anticipatory mechanisms in a manner consistent with the notion that the central nervous system (CNS) entertains internal models of relevant object and task properties during manipulation.

Experimental Pressures and Film Forces in a Squeeze Film Damper

1993 ◽  
Vol 115 (1) ◽  
pp. 134-140 ◽  
Author(s):  
G. L. Arauz ◽  
L. A. San Andres
Keyword(s):  
Tangential Force ◽  
Radial Force ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Fluid Inertia ◽  
Damping Force ◽  
Inertia Effects ◽  
Squeeze Film Dampers ◽  
Tangential Forces ◽  
Lubricant Viscosity

The effect of whirl frequency and lubricant viscosity on the dynamic pressures and force response of an open end and a partially sealed squeeze film dampers (SFD) with a radial clearance of 0.38 mm is determined experimentally. The experiments are carried out in a damper test rig executing circular centered orbits and for whirl frequencies ranging from 33 to 83 Hz. The experimental results show that the sealed SFD configuration produces larger tangential forces than the open end SFD. The tangential (damping) force increases linearly with increasing whirl frequency. For this radial clearance fluid inertia effects in the damper are found to be negligible since the squeeze film Reynolds number is less than 1.20. Cavitation was observed in both damper configurations at high frequencies and high lubricant viscosities. This condition limited the rate of increment of the damping (tangential) force with increasing frequency and reduced the radial force when lubricant viscosity increased.

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