Papers by Author: Mohd Zaki Nuawi

Abstract: The prevalence of work related musculoskeletal problems with respect to vibration is prominent. This review paper gather recent studies related to objective assessment among work force from all over the world. The three main objectives of this review are: to analyse published objective assessment related to vibration among the work force; to extract and understand in detail the process of each assessment; and to identify whether or not there is a relationship between each variables. Twenty relevant studies were identified and chosen from electronic databases, dating as far back as 2001. “Vibration”, “musculoskeletal problem”, “worker”, and “objective measures” were the keyword search terms for this paper. Past studies demonstrated various purposes and implementation of objective assessment among the work force in evaluating vibration effects. It provides better understanding for the future researchers and industry to deal with vibration issues among work force. Many objective assessment methods among the work force have been applied in the past studies. However, they are still many concerns found in past studies that need to be investigated in the future studies. Therefore, there is a need to perform and apply different objective assessment for evaluating human vibration issues.

Abstract: Motorcycle riders are exposed to extreme riding discomfort due to engine inertial imbalances, improper structural motorcycle design, and road excitation. This paper presents a survey on the perception regarding riding discomfort among motorcycle riders in Malaysia. The survey aims to gather information from motorcycle riders regarding the sources and effects of discomfort in the form of vibration and noise exposure. This survey highlights the components and factors that are related to all aspects of discomfort when riding a motorcycle. Thirty respondents with a mean age of 19 years old from two private universities in Selangor participated in this study. All respondents ridevarying types and sizes of motorcyclesas their main transportation to and from their homes and offices. The resultsindicatethat the vibration source on the foot pedal is the main factor that contributes to the highest discomfort level among motorcycle riders in Malaysia. Despite the small current sample, this studyobtained results that agree with those of previous literature.

Abstract: Material play an important role in engineering design and the characterisation of material property has become an essential requirement for their successful application as structural elements. In this paper, the development of material property characterisation method has been presented. Impulsive excitation test has been performed on rectangular bars (medium carbon steel S50C, cast iron FCD 500, stainless steel AISI 304and brass). The transient vibro-acoustic signals generated during the excitation test have been captured using data acquisition system consist of accelerometer-microphone combination. A new method for reducing the noise components from the recorded signals is introduced by an extensive process of a new Z-stem filtering technique. The filtered signals have been analysed using an alternative statistical method known as Integrated Kurtosis-based Algorithm for Z-notch filter (I-kaz^TM) to determine the pattern of the signal and to estimate the significance differences among those materials. The representation of the experimental curves obtained by the determination of I-kaz coefficient, Z^∞ for various impact forces and materials revealed that the results are statistically significant and can be successfully used for determining the correlation between the curves and material property. Implications of this research to material property characterisation will be discussed.

Abstract: An experimental study on the effect of panel density on the sound absorption properties of a date palm fiber panel has been presented in this paper. The experiments were carried out by using impedance tube at the Acoustic Lab, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia. The date palm fiber was tested for densities of 77 kg/m³, 100 kg/m³ and 125 kg/m³.The results show that the values of absorption coefficient improve when increasing the density of the panel. Noise reduction coefficient (NRC) was computed to compare the performance of the palm date fiber samples for the different densities. The NRC increases by increasing the density.

Abstract: Non-destructive characterization of material is given more attention due to its advantages in cost of research, procedure of experiment, accuracy of results and time taken to undergo experiment. As compare to other non-destructive characterization method, non-contact ultrasonic method does not need physical contact with specimen, surface specimen no need special preparation, analysis of any stage of formation of specimen and non-hazardous.This study is to carry out the experiment of material characterization by using non-contact ultrasonic method. First, the grid on the specimen is identifying by plot the chart grid in 5x5 mm size grid. Next, ‘surfer’software will generate a contour map, specimenimage and wire-frame image for each specimen by using the data taken. According to the specimenimage and wire-frame image, the shape, position of the defects of specimen and the change of density of defects can be identified. The area of defects of specimen is calculated by using the mean value calculation method. The accuracy of calculation area of defects is calculated by comparing the area of defects by experimental and theoretical. The result of this study shows the accuracy of this study depend of the ratio of size of defects which is the area of defects and grid size which is the area of data be taken.

Abstract: The Fuel injector is an important component in a vehicle engine for determining the performance of an engine. It is believed that, by knowing the current state of the injector, one can take any prior safety measure and ensuring the optimal performance of the engine. However, it is very difficult to study and analyse the fuel injection system in real time during the operation of the vehicle. A study was conducted in developing a method to monitor the fuel injector using the strain signal generated from the strain gauge sensors installed on the fuel injector. This method is practically implementable and can be used on the actual operation of the engine. A research rig was developed in order to visualise the behaviour of the injector at any instant by obtaining the three key parameters from the strain gage sensors which are the pulse width (ms), frequency (Hz) and pressure (bar). All data obtained from this experiment will be analysed using the Matlab software, where the I-kaz (Z^∞) will be applied as the main method to clearly visualize the operation of the machine. The result shows that for the same pulse width and pressure, the series have the same pattern for I-kaz coefficient. They have a consistent trend compared to the Skewness and Kurtosis parameters. This method serves to predict and describe the behaviour of the fuel injector to ease the monitoring task at any instant throughout the engine operation.

Abstract: Exposure to high levels of hand-arm vibration (HAV) from the steering wheels can present risks to health and safety to drivers. This study aim to do HAV comparison analysis on the Malaysian Army (MA) three-tonne truck steering wheels in three different speeds, when the truck is stationary with the engine switched on and when truck is moving at speed of 40 km/h and 80 km/h. HAV from the steering wheel were measured by using single axis piezoelectric accelerometer and was connected to Brüel & Kjær Vibration Analyser Type 3649, which is which is capable to produce tangential direction acceleration time discrete continuous raw data in units of meters per second squared (m/s²). The raw data were analyzed using statistical analysis I-kaz method to determine the HAV in relation to difference speed of the truck. Based on the results, HAV experienced by the drivers can be presented in frequency weighted HAV_hwz, I-kaz coefficient (Z^∞) and I-kaz display which the value will increase proportional to the truck speed.

Abstract: An electromagnetic braking system using eddy current experiment was conducted to study the behaviour of the system in terms of vibration. Brake disc used which is Al6061 has a displacement in z-axis direction which occurred because of the repulsive force generated on both sides of the disc as drag force from electromagnetic braking. This study aims to analyze the vibration behaviour when braking occurred in different initial speeds of DC motor and different air-gap cases. Smaller air-gap will produce high braking torque due to the increasing of magnetic field density. The higher the force generated, the vibration of the disc may illustrates different behaviour of the vibration in the structure. Test rig was developed using sensor of accelerometer and data acquisition of NI-DAQ with the use of Dasylab for the measurement and instrumentation purposes. Findings shows that the electromagnetic braking force generated in smaller air-gap between electromagnetic poles and rotating conductive disc during the braking using eddy current has damped the vibration occur in the structure of bearing cage.

Abstract: This paper presents the statistical analysis that was used to define optimized parameter for the electromagnetic braking using eddy current study. It illustrates parametric study on four different parameters affecting the braking performance using eddy current which are air-gap, number of electromagnet turns, current induced and disc thickness. These four parameters are defined as the factors which contribute to the reduction of RPM speed as the effect. Fully nested ANOVA was used as the first analysis to determine two most significant factors to eddy current braking system. Then, two-way ANOVA was applied to clarify the most significant factors to be used as the controllable parameters in the verification study. Results from both ANOVA test shows that current induced and air-gap are the two most significant factors that affected braking using eddy current.