Dynamic Contact Between a Rigid Indenter and a Zener Half-Space

2004 ◽  
Author(s):  
Florina Carmen Ciornei ◽  
Emanuel N. Diaconescu
Keyword(s):  
Half Space ◽  
Glass Plate ◽  
Experimental Tests ◽  
Dynamic Contact ◽  
Step Function ◽  
Contact Radius ◽  
Low Frequencies ◽  
Receding Contact ◽  
Contact Pressures ◽  
Good Agreement

This paper investigates the dynamic contact between an axi-symmetric rigid paraboloid and a standard solid (Zener) viscoelastic half-space. The load consists of a pulse cosine applied over a step function. Following the theory developed by Ting, analytical expression of contact radius for an advancing contact is derived. For receding contact, contact radius is numerically obtained. Contact pressures for increasing and decreasing contacts are derived. The influence of load frequency is evidenced. At low frequencies, contact pressure has an initial Hertz shape and then, as the contact increases, a relaxed one. As the contact reaches its maximum, the pressure tends again to an elastic pattern. Experimental tests were carried out on a contact between a polymeric sphere and a glass plate. A good agreement is found with theoretical results by measuring contact radius.

Dynamic Contact Between a Rigid Indenter and a Kelvin-Voigt Half-Space

2005 ◽  
Author(s):  
Florina Carmen Ciornei ◽  
Emanuel Diaconescu
Keyword(s):  
Experimental Data ◽  
Half Space ◽  
Dynamic Contact ◽  
Contact Radius ◽  
Phase Contact ◽  
Analytical Expression ◽  
Contact Pressures ◽  
Theoretical Results ◽  
Type Pressure

Following the theory developed by Ting, analytical expression of contact radius for an advancing contact is derived. For receding phase, contact radius is numerically obtained. Contact pressures for increasing and decreasing contacts are derived as a sum of two terms: the first is a Hertz-type pressure and the second term gives infinite pressure at the edge of the contact. Theoretical results are compared with the experimental data.

scholarly journals Experimental Methods for Measuring the Viscous Friction Coefficient in Hydraulic Spool Valves

2021 ◽  
Vol 13 (13) ◽  
pp. 7174
Author(s):  
Massimo Rundo ◽  
Paolo Casoli ◽  
Antonio Lettini
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Experimental Tests ◽  
Experimental Methods ◽  
Displacement Transducer ◽  
A Posteriori ◽  
Displacement Control ◽  
Spool Valves ◽  
The University ◽  
Good Agreement

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

A Compact Model for Spherical Rough Contacts

2004 ◽  
Author(s):  
M. Bahrami ◽  
M. M. Yovanovich ◽  
J. R. Culham
Keyword(s):  
Pressure Distribution ◽  
Entire Range ◽  
Present Model ◽  
Numerical Solutions ◽  
Contact Radius ◽  
Bulk Deformation ◽  
Dimensional Parameters ◽  
Maximum Contact ◽  
Good Agreement ◽  
Key Parameter

The contact of rough spheres is of high interest in many tribological, thermal, and electrical fundamental analyses. Implementing the existing models is complex and requires iterative numerical solutions. In this paper a new model is presented and a general pressure distribution is proposed that encompasses the entire range of spherical rough contacts including the Hertzian limit. It is shown that the non-dimensional maximum contact pressure is the key parameter that controls the solution. Compact expressions are proposed for calculating the pressure distribution, radius of the contact area, elastic bulk deformation, and the compliance as functions of the governing non-dimensional parameters. The present model shows the same trends as those of the Greenwood and Tripp model. Correlations proposed for the contact radius and the compliance are compared with experimental data collected by others and good agreement is observed.

Fluid Added Mass Effect in the Modal Response of a Pump-Turbine Impeller

2009 ◽  
Author(s):  
Eduard Egusquiza ◽  
Carme Valero ◽  
Quanwei Liang ◽  
Miguel Coussirat ◽  
Ulrich Seidel
Keyword(s):  
Natural Frequencies ◽  
Experimental Tests ◽  
Mass Effect ◽  
Added Mass ◽  
Mode Shapes ◽  
Pump Turbine ◽  
Modal Response ◽  
Surrounding Fluid ◽  
Turbine Impeller ◽  
Good Agreement

In this paper, the reduction in the natural frequencies of a pump-turbine impeller prototype when submerged in water has been investigated. The impeller, with a diameter of 2.870m belongs to a pump-turbine unit with a power of around 100MW. To analyze the influence of the added mass, both experimental tests and numerical simulations have been carried out. The experiment has been performed in air and in water. From the frequency response functions the modal characteristics such as natural frequencies and mode shapes have been obtained. A numerical simulation using FEM (Finite Elements Model) was done using the same boundary conditions as in the experiment (impeller in air and surrounded by a mass of water). The modal behaviour has also been calculated. The numerical results were compared with the available experimental results. The comparison shows a good agreement in the natural frequency values both in air and in water. The reduction in frequency due to the added mass effect of surrounding fluid has been calculated. The physics of this phenomenon due to the fluid structure interaction has been investigated from the analysis of the mode-shapes.

High Amplitude Sound Propagation at Low Frequencies in a Flow Duct Lined With Resonators: A Time Domain Solution

1988 ◽  
Vol 110 (4) ◽  
pp. 545-551 ◽  
Author(s):  
A. Cummings ◽  
I.-J. Chang
Keyword(s):  
Time Domain ◽  
Internal Combustion Engines ◽  
Sound Propagation ◽  
Sound Field ◽  
High Amplitude ◽  
Combustion Engines ◽  
Low Frequencies ◽  
The Time Domain ◽  
Flow Duct ◽  
Good Agreement

A quasi one-dimensional analysis of sound transmission in a flow duct lined with an array of nonlinear resonators is described. The solution to the equations describing the sound field and the hydrodynamic flow in the neighborhood of the resonator orifices is performed numerically in the time domain, with the object of properly accounting for the nonlinear interaction between the acoustic field and the resonators. Experimental data are compared to numerical computations in the time domain and generally very good agreement is noted. The method described here may readily be extended for use in the design of exhaust mufflers for internal combustion engines.

scholarly journals Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding?

2021 ◽  
Vol 11 (9) ◽  
pp. 3734
Author(s):  
Jian Dong ◽  
Youhai Guo ◽  
Long Jiao ◽  
Chao Si ◽  
Yinbo Bian ◽  
...  
Keyword(s):  
Rough Surface ◽  
Contact Angle Hysteresis ◽  
Minimum Energy ◽  
Contact Angles ◽  
Microfluidic Chips ◽  
Motion State ◽  
Receding Contact ◽  
Novel Design ◽  
Minimum Energy Dissipation ◽  
Good Agreement

The motion state of a droplet on an inclined, hydrophilic rough surface in gravity, pinned or sliding, is governed by the balance between the driving and the pinned forces. It can be judged by the droplet’s shape on the inclined hydrophilic rough surface and the droplet’s contact angle hysteresis. In this paper, we used the minimum energy theory, the minimum energy dissipation theory, and the nonlinear numerical optimization algorithm to establish Models 1–3 to calculate out the advancing/receding contact angles (θa/θr), the initial front/rear contact angles (θ1−0/θ2−0) and the dynamic front/rear contact angles (θ1−*/θ2−*) for a droplet on a rough surface. Also, we predicted the motion state of the droplet on an inclined hydrophilic rough surface in gravity by comparing θ1−0(θ2−0) and θ1−*(θ2−*) with θa(θr). Experiments were done to verify the predictions. They showed that the predictions were in good agreement with the experimental results. These models are promising as novel design approaches of hydrophilic functional rough surfaces, which are frequently applied to manipulate droplets in microfluidic chips.

On the receding contact between a graded and a homogeneous layer due to a flat-ended indenter

2021 ◽  
pp. 108128652110431
Author(s):  
Rui Cao ◽  
Changwen Mi
Keyword(s):  
Finite Element ◽  
Contact Problem ◽  
Integral Equations ◽  
Singular Integral ◽  
Functional Dependence ◽  
Singular Integral Equations ◽  
Homogeneous Layer ◽  
Cauchy Type ◽  
Receding Contact ◽  
Contact Pressures

This paper solves the frictionless receding contact problem between a graded and a homogeneous elastic layer due to a flat-ended rigid indenter. Although its Poisson’s ratio is kept as a constant, the shear modulus in the graded layer is assumed to exponentially vary along the thickness direction. The primary goal of this study is to investigate the functional dependence of both contact pressures and the extent of receding contact on the mechanical and geometric properties. For verification and validation purposes, both theoretical analysis and finite element modelings are conducted. In the analytical formulation, governing equations and boundary conditions of the double contact problem are converted into dual singular integral equations of Cauchy type with the help of Fourier integral transforms. In view of the drastically different singularity behavior of the stationary and receding contact pressures, Gauss–Chebyshev quadratures and collocations of both the first and the second kinds have to be jointly used to transform the dual singular integral equations into an algebraic system. As the resultant algebraic equations are nonlinear with respect to the extent of receding contact, an iterative algorithm based on the method of steepest descent is further developed. The semianalytical results are extensively verified and validated with those obtained from the graded finite element method, whose implementation details are also given for easy reference. Results from both approaches reveal that the property gradation, indenter width, and thickness ratio all play significant roles in the determination of both contact pressures and the receding contact extent. An appropriate combination of these parameters is able to tailor the double contact properties as desired.

scholarly journals Waste heat recovery from Refrigeration machine

2019 ◽  
Vol 9 (2) ◽  
pp. 185-190
Keyword(s):  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Sea Water ◽  
Waste Heat ◽  
Experimental Tests ◽  
Air Conditioner ◽  
Heat Exchanges ◽  
Refrigeration Machine ◽  
New System ◽  
Good Agreement

With the aim of saving energy and to reduce global warming effect, our work focuses on the valorization of the waste heat evacuated by the condenser of a refrigeration machine (air-conditioner) for the desalination of sea water. In this paper, the conception of a new system combining airconditioning and desalination is realized. The modelling of the heat exchanges of each part of the system is realized. To improve the performance of the system, various experimental tests are represented and discussed. Comparison between simulation and experimental results shows a good agreement and present a courageous motive for the system application.

Vibrations of an Intermediately Supported U-Bend Tube

1975 ◽  
Vol 97 (1) ◽  
pp. 23-32 ◽  
Author(s):  
L. S. S. Lee
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Experimental Tests ◽  
Bending Stiffness ◽  
Stiffness Ratio ◽  
Plane Vibration ◽  
Straight Beam ◽  
Out Of Plane ◽  
Straight Segments ◽  
Good Agreement

Vibrations of an intermediately supported U-bend tube fall into two independent classes as an incomplete ring of single span does, namely, the in-plane vibration and the coupled twist-bending out-of-plane vibration. Natural frequencies may be expressed in terms of a coefficient p which depends on the stiffness ratio k, the ratio of lengths of spans, and the supporting conditions. The effect of the torsional flexibility of a curved bar acts to release the bending stiffness of a straight beam and hence decrease the natural frequency. Some conclusions for an incomplete ring of single span may not be equally well applicable to the U-tube case due to the effects of intermediate supports and the presence of the supporting straight segments. Results of the analytical predictions and the experimental tests of an intermediately supported U-tube are in good agreement.

Sign in / Sign up

Export Citation Format

Share Document