طراحی، ساخت و کارآیی تستر اصطکاک پد ترمز جدید Design, construction and performance of a novel brake pad friction tester

1. Introduction A vast number of traffic accidents today can be blamed on problems related to the brake systems of the vehicles. Specifically, brake pads and the friction materials used in them are the most important components in the brake systems affecting driving security and braking performance [1]. In this regard, brake pads should meet the criteria of driving safety, comfort, and high strength and exhibit a constant friction coefficient, low wear rate, low noise and anti-vibration properties under adverse conditions [2,3]. Brake performance is affected not only by the materials and vehicle hardware design, but also significantly by driver behavior, the vehicle usage, the state of adjustment of the brake system, and the overall environment in which the vehicle is driven. In addition to these considerations, engine braking and the aerodynamics in the wheel system are possible influences on braking control systems. No laboratory test can simulate driving conditions precisely and accurately. In the literature, four different test methods for evaluating automotive brake pads and wear amount have been reported: (1) vehicle road tests, (2) inertial dynamometers, (3) vehicle sliding-pad tests and (4) laboratory tribometers. Among these, the tests conducted using laboratory-type friction devices are generally used. These test devices are of four types: (1) the friction assessment and screening test (FAST) machine, (2) the Chase-type machine, (3) pin-on disc tribometers and (4) inertial dynamometers (ECE R-90 standard test) [4–6]. The basic elements of these friction machines include a means to apply a force, use of conformal contact, and a means to measure frictional torque. Some tests involve constant speed, while others involve deceleration. The use of multiple-load applications is common, as is temperature measurement deceleration. Although a number of researchers are using the laboratory-type devices for determining the wear and friction characteristics of automotive brake pads composed of natural and metal powders, some researchers conduct their experiments by using the simpler friction devices designed for specimen-type pads. Qui et al. [7], Bahari et al. [8], Saffar et al. [9] and Matejka et al. [10] investigated the wear and friction performance of asbestos-free eco-friendly pads. The friction-wear properties of the prepared composites were tested by using a Chase friction performance testing device. For this type of device, the amount of wear and the friction coefficients were determined according to SAE J-661standard recommendations. On the other hand, some other researchers [11,12] tested these properties using FAST-type friction devices. Tayeb et al. [13], Kim et al. [14] and Liew et al. [15] conducted a number of studies on the determination of wear rate with regards to the friction coefficients and weight-loss of small brake pad specimens by using pin-on disc tribometers. This type of device was developed on the basis of the wearing of a material on a pre-determined path by an abrasive material.