Linear Friction Damper Consisted of Cylindrical Block and Inclined Lever (Improvement to Avoid Sprag-Slip Problem and Analytical Model to Verify Cause)

2011 ◽  
Author(s):  
Hideya Yamaguchi ◽  
Hidehisa Yoshida
Keyword(s):  
Analytical Model ◽  
Friction Force ◽  
Friction Damper ◽  
Friction Forces ◽  
Constant Friction ◽  
Linear Friction ◽  
New Type ◽  
Passive Isolation ◽  
Isolation Systems ◽  
Cylindrical Block

For the passive isolation systems, the ordinary friction damper of constant friction force has performance limitations. This is, because the isolation characteristic declines and the displacement remains apart from the equilibrium position after the disturbance disappears, when the friction force is large. It is known that the above drawbacks are improved when the friction force varies depending on the displacement. The authors have proposed a new type of friction damper in our previous paper. This friction damper uses an inclined lever, which contacts the cylindrical block by means of a rotational spring. The angle of inclination of the lever varies together with the displacement of the cylindrical block. Then, the normal and friction forces on the contact surface vary depending on the displacement. However, “Sprag-slip” vibration occurred in some cases in the experiments. This paper investigates the cause of the vibration and a design to prevent it. Then, an analytical model is proposed to simulate the problem and to estimate the effect of improvement.

Two-Dimensional Linear Friction Damper Consisting of Concave Cone and Cylindrical Member (Investigation of Performance by Numerical Simulation and Experiment)

2015 ◽  
Author(s):  
Hideya Yamaguchi ◽  
Hidehisa Yoshida
Keyword(s):  
Numerical Simulations ◽  
Friction Force ◽  
Vibration Isolation ◽  
Two Dimensions ◽  
Resonant Peak ◽  
Friction Damper ◽  
Isolation System ◽  
Friction Forces ◽  
Vibration Isolation System ◽  
Linear Friction

A passive vibration isolation system consisting of a constant friction force has performance limitations; the isolation performance declines and the residual displacement becomes large in the case of the large friction force, while the resonant peak becomes large in the case of the small friction force. It is known that above drawbacks are avoidable when the friction force varies in proportion to the relative displacement. Recently, authors have proposed a simple linear friction damper mechanism that consists of a cylindrical block and a tilt lever supported with a pivot or a leaf spring. Performance of the vibration isolation system equipped with the proposed damper is investigated, and its effectiveness is confirmed by numerical simulations and the experiments. However, the motion of the mechanism is limited to one-dimension. This paper proposes an extended mechanism that can be applied to motion moving in two dimensions by combining the concave cone and the cylindrical member. The concave cone is supported with a universal joint on the apex side and its tilting motion is constrained by the restoring spring. The rounded edge of the cylindrical member is set up to contact the inside flank of the concave cone. When the cylindrical member moves in an arbitrary direction on the planar floor and pushes the concave cone, the normal and friction forces at the contact point vary depending on the displacement of the cylindrical member. The fundamental property and the performance of the proposed mechanism are investigated by numerical simulations and experiments.

Friction Forces between Sheet Molding Compound Charge and Mold Cavity Surface in Compression Molding

2011 ◽  
Vol 471-472 ◽  
pp. 733-738 ◽  
Author(s):  
Mahmood M. Shokrieh ◽  
Reza Mosalmani
Keyword(s):  
Friction Force ◽  
Compression Molding ◽  
Molding Pressure ◽  
Cavity Surface ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Constant Friction ◽  
Proposed Model

In this study, three relevant friction ‎forces: constant friction force, hydrodynamic friction force and coulomb friction force are ‎considered between sheet molding compound (SMC) charge and contact surface of the mold. The power ‎law model is implemented to propose a model for prediction of hydrodynamic friction as the dominant friction of the SMC compression molding. The proposed model ‎is simple and does not need any extra experimental parameters. Finally, a model has been developed to predict the molding pressure under non-isothermal conditions. The obtained results of the model are in a very good agreement with the experimental data.

Forced Response of Shrouded Blades With Intermittent Dry Friction Force

2008 ◽  
Author(s):  
Weiwei Gu ◽  
Zili Xu ◽  
Lv Qiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Normal Load ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Gap Size ◽  
Algebraic Equations ◽  
Friction Damper ◽  
Friction Forces ◽  
Contact Points

The gap friction damper model is presented in this paper, which is employed to simulate the friction forces at the contact points of the shroud interface. Using the harmonic balance method (HBM), the friction force can be approximated by a series of harmonic functions. The governing differential equations of blade motion are transformed into a set of nonlinear algebraic equations, which can be solved iteratively to yield the steady-state response. The results show that the forced response is attenuated due to the additional damping introduced by frictional slip. The predicted results agree well with those of the Runge-Kutta method. In addition, the effect of parameters of damping structures such as the gap size, friction coefficient and normal load on the forced response of blades were studied. The results show that increasing the damper gap size causes a increase in resonant response. However, the increment isn’t obvious. In addition, an increase in friction coefficient or normal load decreases the forced response of blade.

scholarly journals Influence of Nanoscale Textured Surfaces and Subsurface Defects on Friction Behaviors by Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1617 ◽  
Author(s):  
Ruiting Tong ◽  
Zefen Quan ◽  
Yangdong Zhao ◽  
Bin Han ◽  
Geng Liu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Friction Force ◽  
Copper Substrate ◽  
Dynamics Simulation ◽  
Textured Surfaces ◽  
Friction Forces ◽  
Subsurface Structures ◽  
Texture Orientation ◽  
Subsurface Defects

In nanomaterials, the surface or the subsurface structures influence the friction behaviors greatly. In this work, nanoscale friction behaviors between a rigid cylinder tip and a single crystal copper substrate are studied by molecular dynamics simulation. Nanoscale textured surfaces are modeled on the surface of the substrate to represent the surface structures, and the spacings between textures are seen as defects on the surface. Nano-defects are prepared at the subsurface of the substrate. The effects of depth, orientation, width and shape of textured surfaces on the average friction forces are investigated, and the influence of subsurface defects in the substrate is also studied. Compared with the smooth surface, textured surfaces can improve friction behaviors effectively. The textured surfaces with a greater depth or smaller width lead to lower friction forces. The surface with 45° texture orientation produces the lowest average friction force among all the orientations. The influence of the shape is slight, and the v-shape shows a lower average friction force. Besides, the subsurface defects in the substrate make the sliding process unstable and the influence of subsurface defects on friction forces is sensitive to their positions.

Experimental Study of a Variable Pressure Damper on Automotive Valve Motion

1996 ◽  
Author(s):  
Jin-Jang Liou ◽  
Grodrue Huang ◽  
Wensyang Hsu
Keyword(s):  
Experimental Study ◽  
Friction Coefficient ◽  
Friction Force ◽  
High Speed ◽  
Experimental Results ◽  
Variable Pressure ◽  
Friction Forces ◽  
Valve Spring ◽  
Valve Motion

Abstract A variable pressure damper (VPD) is used here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve bouncing phenomenon. The friction force on the valve spring is found experimentally, and the corresponding friction coefficient is also determined. Dynamic valve displacements at different speeds with different friction forces are calibrated. Bouncing and floating of the valve are observed when the camshaft reaches high speed. From the measured valve displacement, the VPD is shown to have significant improvement in reducing valve bouncing distance and eliminating floating. However, experimental results indicate that the valve bouncing can not be eliminated completely when the camshaft speed is at 2985 rpm.

scholarly journals Mathematical Modeling of Impact of Possible Shock Dynamic Loads on the Modern Composite Materials

2019 ◽  
Vol 224 ◽  
pp. 02012
Author(s):  
Eugenе Sosenushkin ◽  
Oksana Ivanova ◽  
Elena Yanovskaya ◽  
Yuliya Vinogradova
Keyword(s):  
Composite Materials ◽  
Friction Force ◽  
Equations Of Motion ◽  
Elastic Fiber ◽  
Dynamic Loads ◽  
Friction Forces ◽  
Absolute Value ◽  
A Value ◽  
The Absolute ◽  
The Impact

In this paper, we study the dynamic processes in materials reinforced with fibers, that can be represented as composite rods. There has been developed a mathematical model of wave propagation under the impact of a shock pulse in semi-infinite composite rods. It is believed that the considered composite rod consists of two layers formed by simpler rods of different isotropic materials with different mechanical properties. The cross sections of such rods are considered to be constant and identical. When such composite materials are impacted by dynamic loads, a significant part of the energy is dissipated due to the presence of friction forces between the contact surfaces of the rods. In this regard, we study the propagation of waves in an elastic fiber-rod, the layers of which interact according to Coulomb law of dry friction. The case of instantaneous excitation of rods by step pulses is investigated. The blow is applied to a rod made of a harder material. In the absence of slippage, the friction force gets a value not exceeding the absolute value of the limit. In the absence of slippage, the friction force takes a value not exceeding the absolute value of the limit. Let us consider the value of the friction force constant. Normal stresses and velocities satisfy the equations of motion and Hooke’s law. The problem statement results in the solution of inhomogeneous wave equations by the method of characteristics in different domains, which are the lines of discontinuities of the solution. Solutions are found in all constructed domains. On the basis of the analysis of the obtained solution, qualitative conclusions are made and curves are constructed according to the obtained ratios. From the found analytical solution of the problem it is possible to obtain ratios for stresses and strain rates in composite rods and composite materials.

scholarly journals Prophylaxis protocols and their impact on bracket friction force

2019 ◽  
Vol 89 (6) ◽  
pp. 883-888
Author(s):  
Sérgio Elias Neves Cury ◽  
Silvio Augusto Bellini-Pereira ◽  
Aron Aliaga-Del Castillo ◽  
Sérgio Schneider ◽  
Arnaldo Pinzan ◽  
...  
Keyword(s):  
Sodium Bicarbonate ◽  
Qualitative Analysis ◽  
Friction Force ◽  
Friction Forces ◽  
Debris Accumulation ◽  
Intergroup Comparison ◽  
Group 3 ◽  
Group 2 ◽  
Sliding Mechanics

ABSTRACT Objective: To evaluate the effect of two different prophylaxis protocols on the friction force in sliding mechanics during in vivo leveling and alignment. Materials and Methods: The sample comprised 48 hemi-arches divided into three groups according to the prophylactic protocol adopted. Group 1 consisted of patients undergoing prophylaxis with sodium bicarbonate, group 2 consisted of patients submitted to prophylaxis with glycine, and group 3 consisted of patients without prophylaxis, as a control. All patients received hygiene instructions and, with the exception of group 3, prophylaxis was performed monthly. After 10 months, the brackets were removed from the oral cavity and submitted to friction force tests and qualitative analysis by scanning electron microscopy. Analysis of variance followed by Tukey tests was performed for intergroup comparison regarding the friction force. Results: The experimental groups presented significantly smaller friction forces than the group without prophylaxis. Accordingly, qualitative analysis showed greater debris accumulation in the group without the prophylactic procedures. Conclusions: Prophylactic blasting with sodium bicarbonate or glycine can significantly prevent an increase of the friction force during sliding mechanics.

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