Mohd Kameil Abdul Hamid

Effects of Pad Surface Topography on Disc Brake Squeal

Brake squeal has always been a major NVH problem to many car makers due to significant number of warranty claims. Brake squeal is a high frequency noise (above 1 kHz) emanating from car disc brakes that get excited due to one or more mechanisms such as mode coupling, stick-slip, hammering and sprag-slip. This paper attempts to investigate the effects of brake pad surface topography on squeal generation. Two pairs of a non-asbestos organic (NAO) brake pad will be tested on a brake dynamometer test rig. Surface topography of the brake pad will be analyzed through microscopic techniques using energy dispersive X-ray analysis (EDX), and optical microscope.

Effects of External Hard Particles on Brake Noise of Disc Braking System

The open design and position of disc brake that is closed to road surfaces enable contaminants to enter the brake gap and caused noise and tribological disturbance at the brake interface. Contaminants such as dirt and soil can be present and are expected to influence the occurrence of brake squeal that produce an annoying sound during braking action. The objective of this study was to examine the effect of external hard particles at different disc sliding speed on generation of brake squeal using a brake dynamometer. Different rotational speed of disc brake was selected and the experiments squeal noise data was collected and analyzed using the Fast Fourier Transformation (FFT) analyzer. From the experiments, the presence of external particle and the rotation speed of disc brake promotes the generation of brake squeal phenomenon by changing the surface roughness and effective contact of brake interface. Results obtained from the experiment also showed that higher rotating disc generate higher sound level meter or squeal frequency and increase numbers of squeal noise generated.

Humidity and Water Effect on Wear Characteristics of Disc Braking System

A series of wet braking tests has been performed using two different pad materials. Brake tests were conducted in different operating conditions i.e. dry, humid air and wet environment in which both pad samples were tested against grey cast iron disc at certain sliding speed and contact pressure. Wear analysis was performed to find correlation between presence of water and changes in brake pad wear characteristics. The results revealed that regardless of the frictional behaviour, wear rate for both pad materials tested at humid air and wet braking is significantly lower than in dry results.

The Road Particle Effect on Squeal Noise of Disc Braking System

This experimental work was carried out to examine the effect of road particle on squeal noise exerted at different load and sliding speed. The test was performed under dry sliding condition by utilizing brake test rig and commercial brake pad and discs. Squeal measurement was taken based on frequency, sound pressure level (SPL) value, vibration and brake torque measurement. The output signal from microphone and accelerometer was processed by Fast Fourier Transform analyzer to synchronize value SPL and vibration in the power spectrum graph. Simultaneous increase at the same value of frequency and SPL values showed the squeal occurrence for value above 70dBa and 1000Hz respectively. Result for test with road particle showed number of squeal tends to increase compared to test without road particle. SPL also showed high pitch of noise on squeal with road particle presence. Brake torque significantly increased with increasing brake line pressure and exaggerated with road particle. Higher brake torque resulted in higher coefficient of friction and showed high squeal generation.

Application of sustainable integrated process design and control for four distillation column systems

The objective of this paper is to present the application of sustainable integrated process design and control methodology for distillation columns systems. The sustainable integrated process design and control methodology is developed and able to find the optimal solution for a single distillation column to ensure the design is more cost efficient, controllable and sustainable to meet the product quality. The sustainable integrated process design and control problem for a distillation column system is typically formulated as a mathematical programming (optimization with constraints) problem, and solved by decomposing it to six sequential hierarchical sub-problems: (i) pre-analysis, (ii) design analysis, (iii) controller design analysis, (iv) sustainability analysis, (v) detailed economics analysis and (vi) final selection and verification. In the pre-analysis sub-problem, the concept of driving force is used to locate the optimal design-control-sustainable solution targets, which are defined at the maximum point of the driving force diagram. The sustainability analysis sub-problem was analysed by using the three-dimensional sustainability index. The results through separation of n-Pentane, n-Hexane, n-Heptane, n-Octane and n-Decane mixtures with four distillation column systems shows the methodology is capable to find the optimal solution for multiple distillation column systems that satisfies design, control and sustainability criteria in a simple and efficient way.

Influence of Silica Sand Particles on Disc Brake Squeal Noise

Researchers in recent years begin to explore on tribological behavior of automotive brake squeal phenomena which covers the morphology, chemical composition, friction and wear, phase composition and third body or friction film distribution. However less effort has been made to study the tribological on the influence of small particles on brake squeal. During braking condition, both rotor and pads are exposed to road environmental particle which may affect pads surface condition. In order to assess the influence of this particle on brake squeal a series of squeal tests were performed. Silica sand grit particles with a size range between 400 to 200 μm which most available on the road surface were used in this experiment. Brake pad and disc surface characteristics were analyzed before and after squealing condition using Scanning Electron Microscope (SEM) and Energy dispersive X-ray analysis (EDX). The result shows that the silica sand particles had influence the squeal and surface behavior of the brake pad.

Experimental Investigation of Low Speed Disc Brake Judder Vibration

Brake judder is defined as disc or drum deformation-induced vibration which typically occurs at frequency less than 200 Hz. There are two types of brake judder namely, low speed (cold) judder and high speed (hot) judder. These two types of judder are often causing the brake pedal, steering wheel, suspension or chassis to vibrate. Consequently, it will affect comfort level of the driver and passengers. This paper focuses on the experimental investigation of low speed brake judder. In doing so, a laboratory test rig consists of disc brake unit, steering and suspension systems was used to assess level of brake judder vibration at different wheel turning angles. It was found that brake judder generated slightly high vibration at the steering wheel in the axial direction which led to a little uncomfortable feeling to the driver.

Structural modification of disc brake judder using finite element analysis

Brake judder is a phenomenon of noise which its vibration can be felt physically by the driver of a vehicle. If this vibration is exposed to the driver for a long period it can lead to tiredness during driving. There are two types of judder which is cold judder and hot judder. This paper will be focusing on the hot judder. As a disc surface heats up during braking it causes both sides of the disc distort and hence produce a sinusoidal waviness around its edges. In this paper finite element analysis of hot judder is performed using a commercial software package, ABAQUS. An existing brake disc design is simulated and will be used as a baseline model. Various structural modifications made on the disc are proposed in an attempt to reduce brake judder in a disc brake assembly.

The effects of grit particle size on frictional characteristics of automotive braking system

The effect of grit particle size on frictional characteristics was investigated using a vertically oriented brake test rig. Silica sand of grit sizes 50-180 µm, 180-355 µm and 355-500 µm were used in drag mode application. Results showed that the presence of hard particles from environment can influence the friction response significantly. Basically, once the hard particles enter the gap, the value and amplitude of friction coefficient tend to decrease. However, slight increase in friction with smaller particles was recorded due to more hard particles involved in mixing and changing the effective contact area. Better friction stability was related to the presence of smaller grit particles and compacted wear debris to form frictional film on the braking interface.