A new model was developed for the simulation of the friction coefficient in lubricated sliding li... more A new model was developed for the simulation of the friction coefficient in lubricated sliding line contacts. A half-space-based contact algorithm was linked with a numerical elasto-hydrodynamic lubrication solver using the load-sharing concept. The model was compared with an existing asperity-based friction model for a set of theoretical simulations. Depending on the load and surface roughness, the difference in friction varied up to 32 %. The numerical lubrication model makes it possible to also calculate lightly loaded contacts and can easily be extended to solve transient problems. Experimental validation was performed by measuring the friction coefficient as a function of sliding velocity for the stationary case.
In this paper the transition from mild wear to severe wear of lubricated, concentrated contacts i... more In this paper the transition from mild wear to severe wear of lubricated, concentrated contacts is dealt with. It is suggested that this transition is thermally induced. The transition from a mild wear to severe adhesive wear occurs when more then 10% of the surface transcends a predefined, critical temperature. A method for determining this critical temperature is presented. Using a BIM based numerical model including the local implementation of Archard's wear law, for the contact pressure and temperature the transition diagram for a model system is calculated and validated by experiments. The transition predicted by numerical calculations is in very good agreement with the experimental determined transition.
In the current study a physical based threshold is used to calculate the transition from mild to ... more In the current study a physical based threshold is used to calculate the transition from mild to severe wear. This threshold is formed by using a local coefficient of friction, which is split into two regimes: one high friction regime with a coefficient of friction of in the range of 0.1-0.15 and a high frictional regime in the range of 0.3-0.4. The transition from one to another is determined by the local transition of the predetermined critical contact temperature. To validate the model an experimental transition diagram is determined. The experimental results agree with the simulation for both the location of the transition as for the severity of the adhesive wear.
During the running-in of surfaces a change in roughness takes place. The presented model predicts... more During the running-in of surfaces a change in roughness takes place. The presented model predicts this change for concentrated contacts using an elasto-plastic contact model based on a semi-analyticalmethod recently developed. Combining this method with a local coefficient of friction, which is determined using a mechanical threshold on the protective nature of the lubricant, and a strain related failure to model the smoothening of surfaces protected by a lubricant, the surface topography can be calculated. Multiple examples using concentrated contacts are simulated using real engineering surfaces and realistic values for the properties of the chemical reaction layer as well as the nano crystalline layer present at and underneath the surface. The results obtained are realistic, indicating the usefulness of the developed method.
In this paper, a wear model is introduced for the mild wear present in boundary-lubricated system... more In this paper, a wear model is introduced for the mild wear present in boundary-lubricated systems protected by additive-rich lubricants. The model is based on the hypothesis that the mild wear is mainly originating from the removal of the sacrificial layer formed by a chemical reaction between the base material and the additive packages present in the lubricant. By removing a part of this layer, the chemical balance of the system is disturbed and the system will try to restore the balance for which it uses base material. In this study, mechanical properties reported throughout literature are included into the wear model based on observed phenomena for this type of systems. The model is validated by model experiments and the results are in very good agreement, suggesting that the model is able to simulate wear having a predictive nature rather than on empirical-based relationships as Archard’s linear wear model. Also a proposal is made to include the transition from mild to severe wear into the model creating a complete wear map.
A new model was developed for the simulation of the friction coefficient in lubricated sliding li... more A new model was developed for the simulation of the friction coefficient in lubricated sliding line contacts. A half-space-based contact algorithm was linked with a numerical elasto-hydrodynamic lubrication solver using the load-sharing concept. The model was compared with an existing asperity-based friction model for a set of theoretical simulations. Depending on the load and surface roughness, the difference in friction varied up to 32 %. The numerical lubrication model makes it possible to also calculate lightly loaded contacts and can easily be extended to solve transient problems. Experimental validation was performed by measuring the friction coefficient as a function of sliding velocity for the stationary case.
In this paper the transition from mild wear to severe wear of lubricated, concentrated contacts i... more In this paper the transition from mild wear to severe wear of lubricated, concentrated contacts is dealt with. It is suggested that this transition is thermally induced. The transition from a mild wear to severe adhesive wear occurs when more then 10% of the surface transcends a predefined, critical temperature. A method for determining this critical temperature is presented. Using a BIM based numerical model including the local implementation of Archard's wear law, for the contact pressure and temperature the transition diagram for a model system is calculated and validated by experiments. The transition predicted by numerical calculations is in very good agreement with the experimental determined transition.
In the current study a physical based threshold is used to calculate the transition from mild to ... more In the current study a physical based threshold is used to calculate the transition from mild to severe wear. This threshold is formed by using a local coefficient of friction, which is split into two regimes: one high friction regime with a coefficient of friction of in the range of 0.1-0.15 and a high frictional regime in the range of 0.3-0.4. The transition from one to another is determined by the local transition of the predetermined critical contact temperature. To validate the model an experimental transition diagram is determined. The experimental results agree with the simulation for both the location of the transition as for the severity of the adhesive wear.
During the running-in of surfaces a change in roughness takes place. The presented model predicts... more During the running-in of surfaces a change in roughness takes place. The presented model predicts this change for concentrated contacts using an elasto-plastic contact model based on a semi-analyticalmethod recently developed. Combining this method with a local coefficient of friction, which is determined using a mechanical threshold on the protective nature of the lubricant, and a strain related failure to model the smoothening of surfaces protected by a lubricant, the surface topography can be calculated. Multiple examples using concentrated contacts are simulated using real engineering surfaces and realistic values for the properties of the chemical reaction layer as well as the nano crystalline layer present at and underneath the surface. The results obtained are realistic, indicating the usefulness of the developed method.
In this paper, a wear model is introduced for the mild wear present in boundary-lubricated system... more In this paper, a wear model is introduced for the mild wear present in boundary-lubricated systems protected by additive-rich lubricants. The model is based on the hypothesis that the mild wear is mainly originating from the removal of the sacrificial layer formed by a chemical reaction between the base material and the additive packages present in the lubricant. By removing a part of this layer, the chemical balance of the system is disturbed and the system will try to restore the balance for which it uses base material. In this study, mechanical properties reported throughout literature are included into the wear model based on observed phenomena for this type of systems. The model is validated by model experiments and the results are in very good agreement, suggesting that the model is able to simulate wear having a predictive nature rather than on empirical-based relationships as Archard’s linear wear model. Also a proposal is made to include the transition from mild to severe wear into the model creating a complete wear map.
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