Three-dimensional contact patch strain measurement inside rolling off-Road tyres

The forces generated in the tyre contact-patch are important for vehicle dynamics analysis. The tyre contact patch is not directly visible due to the terrain. Measuring the strain in the contact patch region may give insight into the forces generated by the tyre as it deforms. Strain measurement in the contact patch is often limited to discrete points, using strain gauges or other techniques which limits data capture to once per revolution. In this study stereovision cameras are used to capture unique features in the pattern painted on the tyres inner surface. An in-tyre mechanically stabilized camera system allows the contact patch to be captured continuously and the stereovision cameras allow for full field measurement of the tyre inner surface. In post processing the features are tracked and triangulated to form point-clouds for each time step. Point-clouds are compared to determine the strain of common points in two directions. The system is applied to an agricultural tyre with large tread-blocks. The wheel is instrumented to measure pressure and forces. The tyre is tested statically in a series of tyre tests where the lateral, longitudinal and vertical displacement is controlled. The strain measured in the tyre contact patch region is compared to the forces measured at the wheel centre. It is noticed that as the measured forces increases so too does the magnitudes of the strains. Unique patterns are found in the contact patch strain for each test type. These patterns could be used to identify the type of forces experienced by the wheel while the strain magnitude could give an indication of the magnitude of the forces. Future work could allow for strain measurement in the contact patch as the tyre rolls over deformable terrain where displacement is not easily controlled.Dissertation (MEng)--University of Pretoria, 2019.Mechanical and Aeronautical EngineeringMEngUnrestricte

Three-dimensional contact patch strain measurement inside rolling off-Road tyres

The forces generated in the tyre contact-patch are important for vehicle dynamics analysis. The tyre contact patch is not directly visible due to the terrain. Measuring the strain in the contact patch region may give insight into the forces generated by the tyre as it deforms. Strain measurement in the contact patch is often limited to discrete points, using strain gauges or other techniques which limits data capture to once per revolution. In this study stereovision cameras are used to capture unique features in the pattern painted on the tyres inner surface. An in-tyre mechanically stabilized camera system allows the contact patch to be captured continuously and the stereovision cameras allow for full field measurement of the tyre inner surface. In post processing the features are tracked and triangulated to form point-clouds for each time step. Point-clouds are compared to determine the strain of common points in two directions. The system is applied to an agricultural tyre with large tread-blocks. The wheel is instrumented to measure pressure and forces. The tyre is tested statically in a series of tyre tests where the lateral, longitudinal and vertical displacement is controlled. The strain measured in the tyre contact patch region is compared to the forces measured at the wheel centre. It is noticed that as the measured forces increases so too does the magnitudes of the strains. Unique patterns are found in the contact patch strain for each test type. These patterns could be used to identify the type of forces experienced by the wheel while the strain magnitude could give an indication of the magnitude of the forces. Future work could allow for strain measurement in the contact patch as the tyre rolls over deformable terrain where displacement is not easily controlled.Dissertation (MEng)--University of Pretoria, 2019.TM2019Mechanical and Aeronautical EngineeringMEngUnrestricte

Full-field strain measurements of the inside of an agricultural tyre using digital image correlation

This paper investigates strain measured on the inside of an agricultural tyre with large tread-blocks during a series of static tests using a novel measuring system. The full field strain measurements may be used in the development of a tyre which is capable of estimating tyre forces from strain measurements. The strain measurement system makes use of a calibrated stereo camera system on a mechanical stabilizing system that keeps the cameras pointed at the inside surface of the tyre in contact with the road while the wheel rotates. A static tyre test rig is used to displace the road surface relative to the tyre in the vertical and longitudinal direction. The large tread-blocks caused strain concentrations on the inner surface as the tyre deforms to comply with the road surface. Vertical and longitudinal tests each produce unique strain patterns in the contact patch region. Relationships between the applied forces and strain measurements were developed and showed that these relationships are near linear with R2 values above 0.97. The strain measurements also show that the location where strain gauges, for single point strain measurements, are placed inside the tyre is very important on large lugged tyres.http://www.elsevier.com/locate/jterra2022-09-19hj2021Mechanical and Aeronautical Engineerin