Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 31 Aug 2020

Using a New 3D-Printing Method to Investigate Rubber Friction Laws on Different Scales

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Page Range: 250 – 286
DOI: 10.2346/tire.20.190218
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ABSTRACT

Rubber friction is a complex phenomenon that is composed of different contributions. Because it always consists of a friction pairing, the road surface topology has a main impact on the adhesive and sliding characteristics in the rubber-road interaction. New manufacturing processes offer the means to develop specific road surfaces. By using a modified three-dimensional (3D) printing method based on selective laser melting with stainless steel, it is possible to create any desired surface up to a resolution of 20 μm. In this work, several metallic surfaces are built for two separate purposes. First, the rubber-road interaction is analyzed and compared for metal and asphalt. Second, theoretical friction laws are investigated with synthetic surfaces. Toward this aim, the friction coefficients are measured in both dry and wet conditions. A multiscale approach for friction properties on different length scales is implemented to accumulate the micro and mesoscopic friction into a macroscopic friction coefficient. On each length scale, a homogenization procedure generates the friction features as a function of slip velocity and contact pressure for the next coarser scale. Within the multiscale approach, adhesion implemented as nonlinear traction separation law is assumed to act only on microscopic length scales. By using the finite element method, the sensitivity of the influencing factors, such as macroscopic slip and load conditions, is investigated. The friction loss from dry to wet conditions cannot be explained by loss of adhesion alone. Hysteresis has to be affected as well. A possible hypothesis for this is the trapped water pools in the texture. The road surface is effectively smoothed and thus hysteresis reduced. To verify this hypothesis, a hysteretic friction model is calibrated to dry measurements. The cavities in the modeled texture are then filled incrementally to simulate various amounts of trapped water.

Keywords: tire-road interaction; selective laser melting; rubber friction; surface roughness; multiscale homogenization; wet friction theory
FIG. 1
FIG. 1

Scheme of experimental setup.

FIG. 2
FIG. 2

Simplified system of the fringe projection method [7].

FIG. 3
FIG. 3

Sketch of the used SLM method [8].

FIG. 4
FIG. 4

Overview of the SLM-printed test surfaces.

FIG. 5
FIG. 5

Mobile linear friction tester [10].

FIG. 6—
FIG. 6—

Rubber sample information and wet friction testing.

FIG. 7
FIG. 7

Example of a friction coefficient as a function of sliding displacement.

FIG. 8
FIG. 8

3D scan of the SLM-printed surface B.

FIG. 9
FIG. 9

3D scan of the SLM-printed surface C.

FIG. 10
FIG. 10

Radially averaged power spectral density of surfaces B and C.

FIG. 11
FIG. 11

Qualitative comparison of the asphalt specimen and its replica.

FIG. 12
FIG. 12

Friction maps of “standard” for replica and original in dry condition.

FIG. 13
FIG. 13

Friction maps of “standard” for replica and original in wet condition.

FIG. 14
FIG. 14

Relative deviation between frictions maps of original asphalt and its replica for “e-mobility” in dry and wet condition.

FIG. 15
FIG. 15

Course of the friction value for one measuring point with different surface conditions.

FIG. 16
FIG. 16

Averaged friction coefficients for all measurement series.

FIG. 17
FIG. 17

Relative velocity in the footprint of the “standard” tire in the FTire simulation at 3 kN.

FIG. 18
FIG. 18

Averaged friction coefficients for all measurement series for high load and velocity.

FIG. 19
FIG. 19

Patch test for adhesion model.

FIG. 20
FIG. 20

Damage and reaction forces during the patch test.

FIG. 21
FIG. 21

Time homogenization of the friction coefficient (p = 2 N/mm2, v = 10 mm/s).

FIG. 22
FIG. 22

Friction map generated by piecewise cubic spline interpolation.

FIG. 23
FIG. 23

Macroscopic friction using microscopic scale z1,I.

FIG. 24
FIG. 24

Macroscopic friction using microscopic scale z1,II.

FIG. 25
FIG. 25

Macroscopic friction using microscopic scale z1,III.

FIG. 26
FIG. 26

Micro scale roughness visualized by a scan of SLM-printed test surface B.

FIG. 27
FIG. 27

Finite element model is virtually sliding over the sinusoidal rigid surface.

FIG. 28
FIG. 28

Friction during experiment and simulation using load of 50 kg and velocity of 10 mm/s.

FIG. 29
FIG. 29

Contact shear stresses in first tangential direction during simulation applying load of 50 kg and velocity of 10 mm/s.

FIG. 30
FIG. 30

Test results of friction measurements under wet conditions on surface C.

FIG. 31
FIG. 31

Simulation results of multiscale approach using test surface C (only hysteresis friction).

FIG. 32—
FIG. 32—

Schematics of the Prony series.

FIG. 33—
FIG. 33—

Surface texture in the model with the location of the chosen profile (black line).

FIG. 34—
FIG. 34—

Surface texture (top) and tire rubber (low, red) in the simulation.

FIG. 35—
FIG. 35—

Geometry of discretization point forces.

FIG. 36—
FIG. 36—

Result of experiment (a), uncalibrated simulation (b), and calibrated simulation (c) with 200 N to 500 N vertical load.

FIG. 37—
FIG. 37—

Dry (a) and wet (b) friction by Persson [23].

FIG. 38—
FIG. 38—

Schematic illustration of different water amounts. The texture on the left is about 20% filled and on the right about 50 % filled.

FIG. 39 —
FIG. 39 —

Comparison of the experiments of real asphalt and replicated asphalt texture in dry (a) and wet (b) conditions with 200 N load.

FIG. 40 —
FIG. 40 —

Wet friction experiment result (top left) and simulation results with various water levels with 200 to 500 N vertical load.

Contributor Notes

1 Institute for Automotive Engineering, RWTH Aachen University, Steinbachstrasse 7, Aachen, 52074, Germany
2 Corresponding author. Email: jan.friederichs@ika.rwth-aachen.de
3 Institute for Structural Analysis, Technische Unversität Dresden, Dresden, 01062, Germany
4 Institute for Road and Transport Science, Stuttgart University, Pfaffenwaldring 7, Stuttgart, 70569, Germany
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