Engineering Friction Characterization for CAE Modeling
In mechanical systems, friction and wear usually take place concurrently between two surfaces when they slide or roll relative to each other. Friction exhibits resistance to the relative motion which may vary with different normal loads and relative velocities, while wear is the removal and displacement of the materials from one or both surfaces. It is critical to define accurate coefficients of friction at contacts with relative motion in CAE models, especially when collision or impact is present. However, only textbook values of friction coefficients have been employed in most of the models, and often the values are deemed as adjustable parameters for model tuning. The use of textbook values many times leaves discrepancy between test and simulation!
Example: Pedestrian Headform Impact Model (Courtesy of Honda R&D Americas, Inc)
SIMCenter provides an in-house made pin-on-disc tribometer to measure friction forces between different materials.
The concept is to measure the friction between a stationary pin and a rotating disc using a load cell. Schematics of the set-up are shown below.
The test sample is placed and fixed on a platform which is rotated by a DC motor. The pin is held by a gymbal assembly which allows different normal loads applied at the interface by adding different weights. The friction force at the interface is measured by a load cell.
Example testing: PED Rubber vs. Painted steel sheets
Measured coefficient of friction is 10 times the textbook value! Using the measured values, the match between simulation and test has been greatly improved.
Get your materials tested and models improved!