Mixed-EHL Simulator For Rolling-Sliding Line-Contacts
The simulation app for mixed-EHL rolling-sliding line-contacts has been developed based on the capabilities of the Cam-Roller-Interface Tribotester (CRT-01) shown in Figure 1. The CRT-01 as well as the simulation app, allow the user to evaluate the resulting slide-to-roll ratio (SRR) and traction coefficient (among others) generated in a lubricated roller-on-roller (i.e., disc-on-disc) configuration when a load torque (i.e., braking torque) is applied to the driven roller (see figure above).
Figure 1. The CRT-01 is a novel test setup that can be used to perform a wide variety of tribological tests where the behavior of rolling-sliding interfaces can be simulated. The interested user can refer to this article for more information about the testing method and the test setup.
Differently from classic twin disc machines, the CRT-01 allows the generation of slippage throughout the application of a load torque (i.e., braking torque) to the top roller (Roller II). This means that slippage is not a fixed variable during the test but, a result of the applied braking torque. In this way, changes in the tractive behavior of surfaces produced by wear (or other factors) can be studied based on the changes in the slide-to-roll ratio during the test.
Mixed-EHL Simulator for Rolling-Sliding Line Contacts
The calculations performed by the mixed-EHL simulator for rolling-sliding line-contacts are carried out based on the model for evaluation of traction in mixed EHL contacts presented by [1]. The main goal of the simulator is to allow the user to estimate the slide-to-roll ratio and the traction coefficient, as a function of the applied braking torque (for a given set of conditions). The results can be also used to estimate the amount of resistance (i.e., braking torque) that a lubricated interface can tolerate before the onset of high slip levels.
Figure 2 shows the forces acting at the contact between the rollers. L is the load (in kN), R1 Speed is the rotational velocity of the driving roller (in RPM), τL is the load torque applied to the driven roller in (Nm) and Ѱ is the offset angle between the centers of the rollers (in °). Fc and Ft are the contact force and the traction force respectively (in N). Note that when Ѱ=0, the load (L) is equal to the contact force Fc (i.e., L is normal to the contact). When a load torque τL is applied, a traction force Ft is generated at the interface and the traction coefficient is given by Ft/Fc.
Figure 2. forces at the contact between rollers.
Instructions for use:
The mixed-EHL simulator for rolling sliding line contacts is divided into 3 different panels. The reference conditions, the controls, and the results (see Figure 3).
Figure 3. Mixed-EHL Simulator for Rolling Sliding Line Contacts
- Reference Conditions:
A set of reference conditions is given by default. They include contact conditions, material properties, and lubricant properties. The user can modify these values and click “Run” to display the results.
- Control Panel:
The app allows the adjustment of 5 parameters for the simulation, namely, the load (L), the rotational velocity (R1 Speed), the temperature of the lubricant, the load torque, and the offset angle (Ψ). Note that with Ψ=0, the contact force is equal to the load (L). After adjusting the controls, the results can be obtained by clicking “Run”.
- Results
The results panel displays several tribological quantities that can be used to evaluate the behavior of the simulated contact. They include the lambda ratio, the traction coefficient, the slide-to-roll ratio, among others. Note that the slide-to-roll ratio and the traction force increase when higher load torques (i.e., braking torques) are applied.
References
- M. Masjedi and M. M. Khonsari, “An engineering approach for rapid evaluation of traction coefficient and wear in mixed EHL,” Tribol. Int., vol. 92, pp. 184–190, Dec. 2015.
