Tire Rolling Excitations and Their Impacts

The vibration and noise generated by tires during rolling are core research areas for studying vehicle NVH (noise, vibration, and harshness) performance. The complexity of these excitation sources directly determines the diversity of transmission paths.

Road surface roughness: The primary excitation source

Road surface roughness, as the primary excitation source, encompasses everything from macroscopic road undulations to microscopic texture variations. At the macro level, joints in asphalt pavement, expansion joints in concrete pavement, and potholes create periodic impacts.

When a tire travels over a joint spaced 10 meters apart at 60 km/h, it experiences 6.7 pulses per second. This low-frequency vibration is transmitted to the vehicle body through the suspension system, potentially inducing structural resonance at 20-50 Hz.

At the micro level, the sharp corners and indentations of the pavement aggregate cause high-frequency bouncing in the tire tread. Especially on rough concrete pavement, vibration energy of 100-500 Hz is rapidly transmitted through the steel belts in the tire carcass, becoming the primary source of high-frequency noise within the vehicle.

The Impact of Tire Manufacturing Variations

Tire manufacturing variations are also not negligible. Uneven mass distribution creates eccentric excitation. When a tire has a 50g dynamic balance error, it generates a centrifugal force pulsation of approximately 80N at a speed of 100km/h. This cyclical load is converted into vibration through the wheel hub bearing, resulting in a noticeable noise peak in the 150-300Hz frequency range.

Uneven stiffness stems from variations in the sidewall ply splicing process. The tire carcass exhibits alternating "hard spots" and "soft spots" during rolling, resulting in sinusoidal fluctuations in radial stiffness. These fluctuations, when combined with road excitation, exacerbate the expansion and contraction of the suspension springs, thereby amplifying the vertical vibration of the vehicle body.

Dynamic Interaction between Tread Pattern and Road Surface: A Key Cause of Mid- and High-Frequency Noise

The dynamic interaction between the tread pattern and road surface is a key cause of mid- and high-frequency noise. The grooves of the longitudinal tread compress upon contact and rapidly rebound upon leaving the contact patch, creating an air pulse similar to a "vacuuming" sound. This aerodynamic noise is particularly noticeable in the 300-2000Hz frequency range and increases proportionally with the square of vehicle speed.

The block-shaped structure of the transverse tread generates high-frequency impact upon contact with the road. The shear deformation of the tread blocks induces vibrations of 1000-5000Hz, which are transmitted to the tire body through the elasticity of the tread rubber and ultimately radiate as a "hissing" sound inside the vehicle.

Vibration Caused by Localized Tread Bending

When a tire enters the contact patch, the tread transitions from a circular arc to a flat surface. This localized bending produces periodic stress release. The hysteresis of the tread rubber causes some of the kinetic energy during bending to be converted into heat, but 30%-40% of the energy is still transmitted as vibration.

The 200-800Hz vibration component is highly likely to resonate with the vehicle floor, generating a low-frequency rumble inside the vehicle. At the same time, the elastic deformation of the tire sidewall amplifies this vibration. Due to the transfer function of the suspension system, the vibration energy can be amplified 2-5 times before being transmitted into the vehicle cabin.

Vibration Energy Transfer Path and Its Impact on Ride Comfort

The vibration energy generated by these excitations exhibits a multi-stage amplification path: Tire vibration is first transmitted to the suspension arm through the wheel hub bearing. The arm's rigid vibration is attenuated by 10%-20% by the bushing before being transmitted to the body pillar. The pillar vibration excites the body panel through the welds, which ultimately propels air and generates interior noise.

Research shows that at a speed of 100 km/h, road surface roughness contributes approximately 45% to interior noise, tread pattern contributes 30%, and tire structural factors contribute 25%. The combined effects of these three factors result in a complex, multi-peaked interior noise spectrum, posing a significant challenge to ride comfort.