External particle shape analysis and its effect on tribological performance of disc brake

The open design of disc brake and its location close to the road surface may lead the road particles of various sizes and shapes to enter in between brake pads and disc rotor. This study presents an experimental approach to determine the particle shape effect on friction and wear characteristics of OEM disc brake under different operating condition. Two types of external particles which are road particles and silica sand with two range of size of 200 μm and 400 μm were used. Testing was conducted for variable load and sliding speed. Presence of external particle with various size and shape affect the wear rate, friction coefficient and surface topography of the brake pad. Smaller particle generated more wear. Moreover, the particles which have sharped shape or high angularity resulted in higher weight loss of the pad and contribute to greater formation of compacted wear debris. Wear rate and friction coefficient also increase with contact pressure

Disc brake squeal occurrences under dry and wet brake pad conditions

This paper investigates the effect of water absorption in the brake pad on squeal noise occurrences. A series of brake noise tests is performed at different hydraulic pressure and rotating speed conditions using the laboratory brake test rig, Four brake pad conditions are examined and tested, namely dry, low water absorption, medium water absorption and high water absorption, The test results show that the dry brake pad produces fewer numbers of squeal occurrence compared to the other three wet pad conditions, These three wet pads are also generating high sound pressure level, i.e. 100 dBA and above. than that recorded by the dry pad

Wear characteristic of RBD palm olein using four-ball tribotester

Palm oil shows a great potential to be used as a lubricant. It is a vegetable oil which is environmentally friendly and has a high biodegradability in comparison to mineral oil. However, the research of the properties of palm oil based lubricant from the industrial point of view has never been widely conducted. In this research, the tribological properties of RBD palm olein; which is one of the palm oil refine product, was tested with four-ball tribotester to investigate its wear resistance. The testing method followed the ASTM D4172. The investigation was continued with 40kg, 80kg and 120 kg normal loads. For comparison, similar experimental and analytical works were done with additive-free paraffinic mineral oil and their results were compared with RBD palm olein. The analysis focused on the temperature properties, friction coefficient and wear observation. Results show that RBD palm olein has a good wear resistance performance in high and low temperature compared to additive free paraffinic mineral oil, especially at high normal load

Tribological behavior of organic anti-wear and friction reducing additive of ZDDP under sliding condition: synergism and antagonism effect

The effect of eichhornia crassipes carbon nanotubes (EC-CNTs) as additives in both base mineral oil (MOO) and vegetable rapeseed oil (ROO) alone and also together with ZDDP additive under sliding condition was studied. The investigation shows that both on individual and in combine state enhanced tribological properties. The coefficient of friction reduction was 40 % and 37.5 % for EC-CNT inclusion against ROO and MOO respectively under 80 N. The study revealed that enough tribofilm were generated thereby separating the two surfaces leading to low COF. In the case of wear effect, combination of the two additives gives substantial reduction of 65.5 % and 70.2 % against MOO and ROO respectively. The study shows that more reduction was obtained with RO + EC-CNT + ZDDP than the other. The use of two additives in combine lubrication shows synergistic effect, however, observed antagonistic effect if MO + EC-CNT + ZDDP is used for long period of time. The study further revealed that EC-CNT does more of anti-wear service while ZDDP improves friction reducing effect as well as anti-wear

Study on water hammer effect in turbulent flow through the pipe system

The purpose of this research is to study water hammer effect in turbulent flow through the pipe system. The water hammer occurs when the water flow in the pipeline is suddenly stopped by the valve. Water hammer can cause the pipe to break if the pressure is high enough. An experimental method has been conducted to investigate the effect of design parameters such as difference kind of material properties of pipes and the effect of the flow rate of fluid on the frequency (Hz) and the maximum acceleration of vibration signal (m/s2) during water hammer effect, the vibration signal is captured by using the DEWE-41-T-DSA signal analysis and piezoelectric accelerometer sensor. Data signal is transferred to DEWESoft software to be analyzed using the Fast Fourier Transform (FFT) method. We found that the maximum acceleration vibration signal will increase the flow rate of fluid increase. Besides, the maximum acceleration vibration signal of UPVC pipe is higher than HDPE pipe. Meanwhile, for the frequency, the experimental result shows that the larger frequency is the UPVC pipe compare with the HDPE pipe. This is due to the compressibility of fluid and elasticity of the pipe. Therefore, it can be concluded that the UPVC pipe deal with more water hammer effect compares to the HDPE pipe due to the mechanical properties difference of UPVC and HDPE pipe

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

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

A new prediction methodology for dynamic contact pressure distributions in a disc brake

The dynamic contact pressure distribution in a disc brake system remains impossible to measure through experimental methods. This makes numerical analysis using the finite element method an indispensable alternative tool to its prediction. However, the finite element model must first be validated through appropriate analyses so that realistic predicted results can be obtained. This paper proposes and carries out a three-stage validation methodology: validating the dynamic aspect of each brake component and the brake assembly using modal testing data and the contact aspect using the experimental results of static contact pressure. A detailed 3-dimensional finite element model of an actual disc brake was developed. Brake pad surface topography is also taken into consideration. Good agreement is achieved between predicted and experimental results both in modal analysis and static contact pressure distributions. Once a validated model was obtained, contact analysis for dynamic condition of the disc brake is performed