WARP - Modeling Sliding Wear: From Dry to Wet Environments

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Modeling Sliding Wear: From Dry to Wet Environments - Gaseous Environment Parameter: C_e(t)Parameter: C_c Parameter: V_ret(t)Parameter: C_e(t)Parameter: C_c Parameter: C_g Parameter: t_cg Parameter: C_g Parameter: t_cg Parameter: D Parameter: γ

Model Parameters

Name	Description	Parameter Type	Units	View Sub-Model
V(t)	Wear volume of the speciment at sliding time t	Variable	millimeter cube
t	sliding time	Constant (Dimensions Req.)	minutes
C_e(t)	Equivalent protective coverage of the wear surface	SubModel/Equation		View
N(t)	Quantity of wear debris particles generated per unit time on a unit area of the wear surface	Variable	Not Specified
A_a(t)	Fraction of the total apparent area of contact	Variable	Not Specified
D	Wear debris particle size	SubModel/Equation		View
f(D)	Function for the size of the newly generated wear debris particles	Variable	Not Specified
Pr(D)	Probability of a wear debris particle being removed from the wear track	Variable	Not Specified

Failure Mechanism

Name
Wear

Component / Technology Types

Name
Surface, Sliding Contact

Characteristics

Title	Description
Fatigue Approach to Wear	Model considers low cycle fatigue to be the mechanism responsible for the generation of wear debris.
Retained Wear Debris	This model considers the effects of wear debris particles that are retained between the contacting surfaces. This includes both the generation of additional wear debris as well as the cold-welding of hardened, wear-protective layers on the sliding surface.
Oxygen and Other Reactive Species	This model considers the effects of oxygen partial pressure and other reactive species in the determination of wear debris particle size (D) and surface energy (gamma) of the contacting surfaces).
Surface Energy	The surface energy is related to the partial pressure of the reactive species by the Gibbs' adsorption isotherm and the classical Langmuir gas adsorption isotherm.
Max Vertical Strain	The maximum vertical strain in the wear surface due to the frictional action (Emax) is approximately equal to the strain limit of the material at the formation of the wear debris.
Wear-Protective Layer	The model accounts for compact layers as well as glaze layers on the wear surface generated from debris particles, the latter being the most effective.
Vret(t) Parameter	The volume of wear debris retained between the sliding surfaces [Vret(t)] is a sub-model of this model. However, as it's value is required to solve one of it's own sub-models, it's described as a Constant(Testing Req'd) for that sub-model.

Assumptions

Title	Description
Wear Rate of Protective Layers	The wear rate of the protective layers formed by debris particles on the sliding surface is assumed to be negligible compared to other areas uncovered by such wear-protective layers.
Retained Particles	It's assumed that all retained particles are compacted eventually to form wear-protective layers of an average thickness ranging from 2-15 micrometers. This assumption is to establish the equation to determine the coverage of the wear surface by compact layers (Cc).

Limitations

Title	Description
N/A	N/A

Constraints

Title	Description
N/A	N/A

Uncertainty Limits

Type	Uncertainty
N/A	N/A

Data or Information Needed from Outside Sources

Category	Source	Description
Material Properties	User	Partial pressure of the reactive species (p_A)
Scaling Factor	User	Constant in the Langmuir isotherm representing the ratio between the rate constants for adsorption and desorption of a gas on a solid (b), testing required
Material Properties	User	Number of bonds per unit area along the crack-plane (N_A)
Material Properties	User	Surface energy of a solid in a vacuum (γ₀)
Material Properties	User	Maximum vertical strain in the wear surface due to frictional action (ε_max)
Material Properties	Manufacturer	Elastic modulus (E)
Mechanical Properties	Manufacturer	Poisson's Ratio (ν)
Material Properties	User	Critical glaze oxide thickness for effective wear protection (δ_c)
Physical Dimension(s)	User	An area of the compact layer that develops into a glaze layers after a period of tcg [dA_c(τ)]
Physical Dimension(s)	User	Fraction of the total apparent area of contact [A_a(t)]
Physical Dimension(s)	User	Average thickness of wear protective layers (δ)
Physical Dimension(s)	User	Quantity of wear debris particles generated per unit time on a unit area of the wear surface [N(t)]
Physical Dimension(s)	User	Function for the size of the newly generated wear debris particles [f(t)]
Material Properties	User	Probability of a wear debris particle being removed from the wear track [Pr(t)]

Bibliographic Citation

Published Status	Source Type	Title	Authors
Published	Article/Paper	Modelling Sliding Wear: From Dry to Wet Environments	Jiaren Jang, M. M Stack

Abstract/Summary
Corrosive species in various forms exist widely in the environment and can significantly affect wear behaviour of materials, usually accelerating wear. Under conditions where the environments are seemingly non-deleterious in terms of corrosivity, some species from the environment can still affect the tribological behaviour of materials. It is thus extremely important to recognise the roles of reactive species in affecting the tribological processes and to understand the processes of tribo-corrosion interactions. In this paper, the mechanisms of wear debris generation and the roles of reactive species in the generation of wear debris during sliding wear in gaseous or aqueous environments are discussed. The effect of environment on the development of wear-protective layers is described. Based on the proposed mechanisms, mathematical models for sliding wear in both dry and aqueous environments are outlined, and the validity of the models is assessed against experimental data in sliding conditions.

Abstract/Summary

Corrosive species in various forms exist widely in the environment and can significantly affect wear behaviour of materials, usually accelerating wear. Under conditions where the environments are seemingly non-deleterious in terms of corrosivity, some species from the environment can still affect the tribological behaviour of materials. It is thus extremely important to recognise the roles of reactive species in affecting the tribological processes and to understand the processes of tribo-corrosion interactions. In this paper, the mechanisms of wear debris generation and the roles of reactive species in the generation of wear debris during sliding wear in gaseous or aqueous environments are discussed. The effect of environment on the development of wear-protective layers is described. Based on the proposed mechanisms, mathematical models for sliding wear in both dry and aqueous environments are outlined, and the validity of the models is assessed against experimental data in sliding conditions.

Report #	Publication Name	Volume #	Publisher Name
N/A	Wear	2612006	N/A

Publication Date	Pages	Source URL	Copyright Info
2006-05-02	954-965	http://www.sciencedirect.com	2006 Elsevier B.V. All rights reserved

Technical Point of Contact (PoC)

Jiaren Jiang
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WARP-ADMIN
Apr 30 at 11:52 pm

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