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Technical Paper

Investigation of Mid-Frequency Interior Noise due to Tyre-Road Interaction

Over the past twenty years, the automotive sector has increasingly prioritized lightweight and eco-friendly products. Specifically, in the realm of tyres, achieving reduced weight and lower rolling resistance is crucial for improving fuel efficiency. However, these goals introduce significant challenges in managing Noise, Vibration, and Harshness (NVH), particularly regarding mid-frequency noise inside the vehicle. This study focuses on analyzing the interior noise of a passenger car within the 250 to 500 Hz frequency range. It examines how tyre tread stiffness and carcass stiffness affect this noise through structural borne noise test on a rough road drum and modal analysis, employing both experimental and computational approaches. Findings reveal that mid-frequency interior noise is significantly affected by factors such as the tension in the cap ply, the stiffness of the belt, and the damping properties of the tyre sidewall.
Technical Paper

Piston and Guide-Pin Rattle Noise Mitigation in Electro-Mechanical Brake Caliper

The hydraulic brake caliper utilizes pressurized brake fluid to actuate one or multiple pistons generating friction between the brake pads and disc. Calipers are classified into floating and fixed type caliper. Floating caliper slides inboard/outboard direction to apply and release pressure on the outer pad. This type of caliper has rubber or spring components to maintain specific clearance for sliding characteristics. Therefore, caliper rattle noise could occur due to wheel vibrations when the vehicle is driven on unpaved roads or rough surfaces. Rattle noise is particularly pronounced in front calipers positioned closer to the driver and its susceptibility tends to increase with the weight of the caliper. The Electro-Mechanical Brake (EMB) caliper has gained substantial attention in automotive industry for its advantages features including reduced brake drag, optimized vehicle layout and precise brake control.
Technical Paper

Evaluation of friction torque in tapered roller bearings

A bearing is a mechanical component that facilitates rotation and supports loads. Bearings are differentiated into ball bearings and tapered roller bearings, depending on the rotating mechanism. Tapered roller bearings, known for their superior load-bearing capabilities compared to ball bearings, are utilized in high-load applications such as commercial vehicle and truck wheel bearings, aircraft and high-speed train components, and heavy machinery spindles. With the growing emphasis on CO2 emission reduction and fuel efficiency in the automotive industry, there's an increasing demand to minimize driving friction torque. This has highlighted the importance of research into the driving friction torque of bearings. Although numerous studies have explored lubrication, friction, and contact phenomena in tapered roller bearings, including aspects like lip friction and roller misalignment and skew, investigations into the effects of roller shape and material properties have been limited.
Technical Paper

Glow-discharge Optical Emission Spectroscopy Study of Cr(III) Sealing in Anodized Aluminium-Silicon Alloys for Brake Component

Calipers and pistons for high-end car braking systems are typically realized using anodized Aluminium-Silicon alloys. Indeed, Aluminium-Silicon alloys are light materials with optimal mechanical properties and, when anodized, excellent corrosion and wear resistances. To achieve these top-notch surface properties, the anodizing process is followed by a sealing post-treatment, which significantly improves the corrosion resistance and tunes the tribological properties (e.g., hardness and friction coefficient) of the anodized pieces. Sealing consists in the precipitation of insoluble hydroxides and functional compounds (e.g., corrosion inhibitors) inside the nano-pores of the anodic layer. Nevertheless, sealing might not penetrate through all the nano-porous structure of the anodic layer. Thus, in light of possible post-machining of sealed, anodized components, it appears fundamental to develop a tool to determine the depth penetration of sealing inside the anodic layer.