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Hub AI
Tire uniformity AI simulator
(@Tire uniformity_simulator)
Hub AI
Tire uniformity AI simulator
(@Tire uniformity_simulator)
Tire uniformity
Tire uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers.
These standards include the parameters of radial force variation, lateral force variation, conicity, ply steer, radial run-out, lateral run-out, and sidewall bulge. Tire makers worldwide employ tire uniformity measurement as a way to identify poorly performing tires so they are not sold to the marketplace. Both tire and vehicle manufacturers seek to improve tire uniformity in order to improve vehicle ride comfort.
The circumference of the tire can be modeled as a series of very small spring elements whose spring constants vary according to manufacturing conditions. These spring elements are compressed as they enter the road contact area, and recover as they exit the footprint. Variation in the spring constants in both radial and lateral directions cause variations in the compressive and restorative forces as the tire rotates. Given a perfect tire, running on a perfectly smooth roadway, the force exerted between the car and the tire will be constant. However, a normally manufactured tire running on a perfectly smooth roadway will exert a varying force into the vehicle that will repeat every rotation of the tire. This variation is the source of various ride disturbances. Both tire and car makers seek to reduce such disturbances in order to improve the dynamic performance of the vehicle.
Tire forces are divided into three axes: radial, lateral, and tangential (or fore-aft). The radial axis runs from the tire center toward the tread, and is the vertical axis running from the roadway through the tire center toward the vehicle. This axis supports the vehicle's weight. The lateral axis runs sideways across the tread. This axis is parallel to the tire mounting axle on the vehicle. The tangential axis is the one in the direction of the tire travel.
In so far as the radial force is the one acting upward to support the vehicle, radial force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the force will change. Consider a tire supporting a 4,000 N (900 lbf) load running on a perfectly smooth roadway. It would be typical for the force to vary up and down from this value. A variation between 3,900 and 4,100 N (880 and 920 lbf) would be characterized as an 200 N (40 lbf) radial force variation (RFV). The radial force variation can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described below.
Some tire manufactures mark the sidewall with a red dot to indicate the location of maximal radial force and runout, the high spot. A yellow dot indicates the point of least weight. Use of the dots is specified in Technology Maintenance Council's RP243 performance standard. To compensate for this variation, tires are supposed to be installed with the red dot near the valve stem, assuming the valve stem is at the low point, or with the yellow dot near the valve stem, assuming the valve stem is at the heavy point.
Radial force variation, as well as all other force variation measurements, can be shown as a complex waveform. This waveform can be expressed according to its harmonics by applying Fourier transform (FT). FT permits one to parameterize various aspects of the tire dynamic behavior. The first harmonic, expressed as radial force first harmonic (RF1H) describes the force variation magnitude that exerts a pulse into the vehicle one time for each rotation. Radial force second harmonic (RF2H) expresses the magnitude of the radial force that exerts a pulse twice per revolution, and so on. Often, these harmonics have known causes, and can be used to diagnose production problems. For example, a tire mold installed with 8 segments may thermally deform as to induce an eighth harmonic, so the presence of a high radial force eight harmonic (RF8H) would point to a mold sector parting problem. RF1H is the primary source of ride disturbances, followed by RF2H. High harmonics are less problematic because the rotating speed of the tire at highway speeds times the harmonic value makes disturbances at such high frequencies that they are damped or overcome by other vehicle dynamic conditions.
Insofar as the lateral force is the one acting side-to-side along the tire axle, lateral force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the lateral force will change. As the tire rotates it may exert a lateral force on the order of 100 N (22 lbf), causing steering pull in one direction. It would be typical for the force to vary up and down from this value. A variation between 90 and 110 N (20 and 25 lbf) would be characterized as a 20 N (5 lbf) lateral force variation (LFV). The lateral force variation can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described above. Lateral force is signed, such that when mounted on the vehicle, the lateral force may be positive, making the vehicle pull to the left, or negative, pulling to the right.
Tire uniformity
Tire uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers.
These standards include the parameters of radial force variation, lateral force variation, conicity, ply steer, radial run-out, lateral run-out, and sidewall bulge. Tire makers worldwide employ tire uniformity measurement as a way to identify poorly performing tires so they are not sold to the marketplace. Both tire and vehicle manufacturers seek to improve tire uniformity in order to improve vehicle ride comfort.
The circumference of the tire can be modeled as a series of very small spring elements whose spring constants vary according to manufacturing conditions. These spring elements are compressed as they enter the road contact area, and recover as they exit the footprint. Variation in the spring constants in both radial and lateral directions cause variations in the compressive and restorative forces as the tire rotates. Given a perfect tire, running on a perfectly smooth roadway, the force exerted between the car and the tire will be constant. However, a normally manufactured tire running on a perfectly smooth roadway will exert a varying force into the vehicle that will repeat every rotation of the tire. This variation is the source of various ride disturbances. Both tire and car makers seek to reduce such disturbances in order to improve the dynamic performance of the vehicle.
Tire forces are divided into three axes: radial, lateral, and tangential (or fore-aft). The radial axis runs from the tire center toward the tread, and is the vertical axis running from the roadway through the tire center toward the vehicle. This axis supports the vehicle's weight. The lateral axis runs sideways across the tread. This axis is parallel to the tire mounting axle on the vehicle. The tangential axis is the one in the direction of the tire travel.
In so far as the radial force is the one acting upward to support the vehicle, radial force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the force will change. Consider a tire supporting a 4,000 N (900 lbf) load running on a perfectly smooth roadway. It would be typical for the force to vary up and down from this value. A variation between 3,900 and 4,100 N (880 and 920 lbf) would be characterized as an 200 N (40 lbf) radial force variation (RFV). The radial force variation can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described below.
Some tire manufactures mark the sidewall with a red dot to indicate the location of maximal radial force and runout, the high spot. A yellow dot indicates the point of least weight. Use of the dots is specified in Technology Maintenance Council's RP243 performance standard. To compensate for this variation, tires are supposed to be installed with the red dot near the valve stem, assuming the valve stem is at the low point, or with the yellow dot near the valve stem, assuming the valve stem is at the heavy point.
Radial force variation, as well as all other force variation measurements, can be shown as a complex waveform. This waveform can be expressed according to its harmonics by applying Fourier transform (FT). FT permits one to parameterize various aspects of the tire dynamic behavior. The first harmonic, expressed as radial force first harmonic (RF1H) describes the force variation magnitude that exerts a pulse into the vehicle one time for each rotation. Radial force second harmonic (RF2H) expresses the magnitude of the radial force that exerts a pulse twice per revolution, and so on. Often, these harmonics have known causes, and can be used to diagnose production problems. For example, a tire mold installed with 8 segments may thermally deform as to induce an eighth harmonic, so the presence of a high radial force eight harmonic (RF8H) would point to a mold sector parting problem. RF1H is the primary source of ride disturbances, followed by RF2H. High harmonics are less problematic because the rotating speed of the tire at highway speeds times the harmonic value makes disturbances at such high frequencies that they are damped or overcome by other vehicle dynamic conditions.
Insofar as the lateral force is the one acting side-to-side along the tire axle, lateral force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the lateral force will change. As the tire rotates it may exert a lateral force on the order of 100 N (22 lbf), causing steering pull in one direction. It would be typical for the force to vary up and down from this value. A variation between 90 and 110 N (20 and 25 lbf) would be characterized as a 20 N (5 lbf) lateral force variation (LFV). The lateral force variation can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described above. Lateral force is signed, such that when mounted on the vehicle, the lateral force may be positive, making the vehicle pull to the left, or negative, pulling to the right.