Elastic-Plastic Microcontact Model for Elliptical Contact Areas and Its Application to a Treillis Point in Overhead Electrical Conductors

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Frédéric Lévesque ◽  
Sylvain Goudreau ◽  
Louis Cloutier
Keyword(s):  
Contact Force ◽  
Critical Points ◽  
Contact Area ◽  
Transmission Lines ◽  
Electrical Transmission ◽  
Contact Areas ◽  
Elastic Plastic ◽  
Elliptical Contact ◽  
Rigid Plane ◽  
Electrical Conductors

Aeolian vibrations represent a threat to the integrity of electrical transmission lines. The fretting fatigue of conductors is thus a major concern. The modelization of the contact conditions at critical points is an important tool in assessing the life of conductors. Treillis points around the last point of contact between the conductor and the pieces of equipment are such critical points. We observe a fully plastic contact condition at these points. Finite element results for the contact between an ellipsoid and a rigid plane and between two wires at different angles are compared with an elastic-plastic microcontact model for elliptical contact areas. These numerical results are then compared with experimental ones for the contact between two wires of a conductor (ACSR Bersfort), showing a very similar relationship between the contact force and the observed contact area. We have a good correlation between the microcontact model and the finite elements ones in the fully plastic contact regime on both the contact area and the contact force for a given interference between bodies. The use of the elastic-plastic microcontact model for elliptical contacts presented in this paper proves to be a strong tool in getting a better understanding of the mechanical behavior at those critical points.

scholarly journals A Finite Element-Based Elastic-Plastic Model for the Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Contact Area ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Element Model ◽  
Tangential Component ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Force Components

Three-dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity constitutive relations from a finite element model of the elastic-plastic interaction proposed by Kogut and Etsion (2002), in which asperity scale constitutive relations are derived using piecewise approximate functions. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. Shoulder-shoulder asperity contact yields a slanted contact force consisting of two components, one in the normal direction and a half-plane tangential component. Statistical summation of the asperity level contact force components and asperity level contact area results in the total contact force and total contact area formulae between two rough surfaces. Approximate equations are developed in closed form for contact force components and contact area.

Unloading Process in Elastic-Plastic Contact of a Rough Surface With a Flat

2008 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Contact Force ◽  
Contact Area ◽  
Three Dimensional ◽  
Integral Form ◽  
Real Contact Area ◽  
Elastic Plastic ◽  
Real Contact ◽  
Approximate Equations

Three dimensional elastic-plastic contact of a nominally flat rough surface and a flat is considered. The asperity level Finite Element based constitutive equations relating contact force and real contact area to the interference is used. The statistical summation of asperity interaction during unloading phase is derived in integral form. Approximate equations are found that describe in closed form contact load as a function of mean plane separation during unloading. The approximate equations provide accuracy to within 6 percent for the unload phase of the contact force.

Elastic-Plastic Contact Analysis of a Deformable Sphere and a Rigid Flat with Friction Effect

2013 ◽  
Vol 644 ◽  
pp. 151-156 ◽  
Author(s):  
Li Wang ◽  
Yang Xiang
Keyword(s):  
Plastic Deformation ◽  
Contact Area ◽  
Contact Load ◽  
Deformation Analysis ◽  
Elastic Plastic ◽  
Friction Effect ◽  
Finite Element Software ◽  
Plastic Deformation Process ◽  
Rigid Plane ◽  
The Impact

Elastic-plastic deformation analysis of the deformable sphere and the rigid plane was studied using the finite element software,this paper was focused on the impact of the friction effects on the deformation of the elastic-plastic deformation under considering the material strain stiffening properties,studies have shown that，the strain stiffening feature increases the contact load while reducing the contact area，the friction effect reduce both the contact load and contact area during elastic-plastic deformation process of the deformable sphere with increasing contact interference.

Approximate Macroscale Constitutive Relations Using a Finite Element Based Constitutive Equations for Microscale Contact

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Cumulative Effect ◽  
Element Model ◽  
Tangential Component ◽  
Total Force ◽  
Asperity Contact ◽  
Elastic Plastic

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity-asperity constitutive relations from a finite element model of their elastic-plastic interaction. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Multiscale modeling of the elastic-plastic rough surface contact is presented in which asperity-level FE-based constitutive relations are statistically summed to obtain total force in the normal and tangential direction. The equations derived are in the form of integral functions and provide expectation of contact force components between two rough surfaces. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. This is shown to yield upon statistical summation the cumulative effect resulting in the contact force between two rough surfaces with two components, one in the normal direction and a half-plane tangential component.

An Extension of CEB Elastic-Plastic Contact Model

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Force Components ◽  
Plastic Parts

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is by developing the equations governing the shoulder-shoulder contact of asperities based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.

A Reexamination of the Extraction of Material Properties Using Nanoindentation

2008 ◽  
Author(s):  
B. Poon ◽  
D. Rittel ◽  
G. Ravichandran
Keyword(s):  
Contact Area ◽  
Material Properties ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Nanoindentation Test ◽  
Displacement Curve ◽  
Elastic Solids ◽  
Ratio Effect ◽  
Elastic Plastic ◽  
Tip Radius

The paper reexamines the extraction of material properties using nanoindentation for linearly elastic and elastic-plastic materials. The paper considers indentation performed using a rigid conical indenter, as follows. Linearly elastic solids: The reduction of nanoindentation test data of elastic solids is usually processed using Sneddon’s relation [1], which assumes a linearly elastic infinite half space and an infinitely sharp indenter tip. These assumptions are violated in practical indentation experiments. Since most of the research on the extraction of material properties relies heavily on numerical simulations, we used them to investigate the specimen dimensions required for it to qualify as an infinite body, and the indentation conditions for finite tip radius effect to be negligible. The outcome of this part is firstly, the definition of a “converged” 2D geometry so that additional magnification of the numerical model does not influence the load-displacement curve, and secondly, an explicit relationship between the measured load and displacement that takes into account the finite tip radius. Elastic-plastic solids: Here, the main data reduction technique was proposed by Pharr et al. [2], assuming elastic unloading of a plastic nanoindentation. We investigated the effects of finite tip radius in elastic-plastic indentations and found that the accuracy of the prediction is currently limited by the accurate determination of the projected contact area. This point will be discussed and a new experimental technique to measure the projected contact area will be proposed. The Poisson’s ratio effect in elastic-plastic indentations is found to be different from the linearly elastic case. This leads to the discussion on the applicability of the correction factor (for Poisson’s ratio effect) derived in linear elastic indentations, on elastic-plastic indentations. Finally, a technique to obtain an upper bound estimate of the yield stress for the indented elastic-plastic material (which is an exact estimation for non-hardening materials), will be presented.

scholarly journals STUDY ON EFFECT OF UPFC DEVICE IN ELECTRICAL TRANSMISSION SYSTEM: POWER FLOW ASSESSMENT

2013 ◽  
pp. 70-74
Author(s):  
CH. CHENGAIAH ◽  
R.V.S. SATYANARAYANA ◽  
G.V. MARUTHESWAR MARUTHESWAR
Keyword(s):  
Transmission Lines ◽  
Power Flow ◽  
Reactive Power ◽  
Power Transmission ◽  
Stability Limit ◽  
Transmission System ◽  
Real Time Control ◽  
Electrical Transmission ◽  
Transmission Systems ◽  
Time Control

The power transfer capability of electric transmission lines are usually limited by large signals ability. Economic factors such as the high cost of long lines and revenue from the delivery of additional power gives strong intensive to explore all economically and technically feasible means of raising the stability limit. On the other hand, the development of effective ways to use transmission systems at their maximum thermal capability. Fast progression in the field of power electronics has already started to influence the power industry. This is one direct out come of the concept of FACTS aspects, which has become feasible due to the improvement realized in power electronic devices in principle the FACTS devices should provide fast control of active and reactive power through a transmission line. The UPFC is a member of the FACTS family with very attractive features. This device can independently control many parameters. This device offers an alternative mean to mitigate transmission system oscillations. It is an important question is the selection of the input signals and the adopted control strategy for this device in order to damp power oscillations in an effective and robust manner. The UPFC parameters can be controlled in order to achieve the maximal desire effect in solving first swing stability problem. This problem appears for bulky power transmission systems with long transmission lines. In this paper a MATLAB Simulink Model is considered with UPFC device to evaluate the performance of Electrical Transmission System of 22 kV and 33kV lines. In the simulation study, the UPFC facilitates the real time control and dynamic compensation of AC transmission system. The dynamic simulation is carried out in conjunction with the N-R power flow solution sequence. The updated voltages at each N-R iterative step are interpreted as dynamic variables. The relevant variables are input to the UPFC controllers.

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