Mohd Imran Ghazali

The effects of bolted joints on dynamic response of structures

Joint is an universal fastening technology for structural members; in particular bolted joints are extensively used in mechanical structures due to their simple maintenance and low cost. However, the components of bolted joints are imperative because failure could be catastrophic and endanger lives. Hence, in this study, the effects of bolted joints on vibrating structures are investigated by determining the structural dynamic properties, such as mode shapes, damping ratios and natural frequencies, and these are compared with the monolithic structures (welding). Two approaches of experimental rigs are developed: a beam and a frame where both are subjected to dynamic loading. The analysis reveals the importance of bolted joints in increasing the damping properties and minimizing the vibration magnitude of structures, this indicates the significant influence of bolted joints on the dynamic behaviour of assembled structures. The outcome of this study provides a good model for predicting the experimental variable response in different types of structural joints.

Vibration Characteristics of Composite Plate Embedded with Shape Memory Alloy at Elevated Temperature

Unique functional material of shape memory alloy has attracted tremendous interest from researches, thus has been broadly investigated for a wide range application. Current research effort extends the use of SMA for the design of smart composite structures due to its shape memory effect, pseudo-elasticity and high damping capability. This paper presents an assessment of applications of the SMA materials for structural vibration controls, where the influences of SMA as reinforcement in the composite plate at different temperature are investigated. Four cases of composite plate are studied, which two of them are SMA-based composite fabricated at 0° and 45° angles, and the other two plates are neat (without SMA wires) and built with local stiffener. By using modal testing, the free vibration analysis is carried out to determine the vibration characteristics of composite plates. The results show that infusing SMA wires into composites increased the natural frequencies of the plate considerably, while decreased slightly for damping percentage. However, when SMA wires are heated, the damping percentage improved tremendously due to the phase transformation temperature of SMA from martensite to austenite. The outcome of this study reveals the potential of SMA materials in active vibration control.

A Preliminary Study on Acoustical Performance of Oil Palm Mesocarp Natural Fiber

As the population increases, the demand of a comfortable environmental such as sound pollution is getting higher. Sound pollutions also have become worsen and creating concerns for many peoples. Due to this problem, synthetic materials as acoustic absorbers still applied as commonly acoustical panels and this material may hazardous to human health and contribute significantly a pollution to the environments. However, researchers have interested in conducting their research on natural fiber to be an alternative sound absorber. This study investigated the potential of oil palm Mesocarp fiber for sound absorbing material. The Mesocarp fibers were mixed with polyurethane (PU) as binder with ratio of 70:30. The thickness was varied in 10mm, 20mm, 30mm, and 40mm. This study also investigated the air gap of 5mm and 10mm in the sound absorption performance. Impedance Tube Method was used to measure sound absorption coefficient (a). The measurement was done on accordance with ASTM E1050-98, which is the standard test method for impedance and absorption of acoustical materials using a tube. The results showed that the optimum value for Mesocarp fiber is 0.93. The optimum value obtained at 5000 Hz. The influence of air gap increases the sound absorption especially from 250 Hz to 4000 Hz. These results indicate that fiber from Mesocarp is promising to be used sound absorbing material.

Hybrid Bat-BP: A New Intelligent Tool for Diagnosing Noise-Induced Hearing Loss (NIHL) in Malaysian Industrial Workers

Noise-Induced Hearing Loss (NIHL) has become a major health threat to the Malaysian industrial workers in the recent era due to exposure to high frequency noise produced by the heavy machines. Recently, many studies have been conducted to diagnose the NIHL in industrial workers but unfortunately they neglected some factors that can play a major role in speeding-up NIHL. In this paper, a new Hybrid Bat-BP algorithm which is based on the trio combination of BAT based metaheuristic optimization, back-propagation neural network, and fuzzy logic is proposed to diagnose NIHL in Malaysian industrial workers. The proposed Hybrid Bat-BP will use heat, body mass index (BMI), diabetes, and smoking along with the century old audiometric variables (i.e. age, frequency, and duration of exposure) to better predict NIHL in Malaysian workers. The results obtained through Hybrid Bat-BP will be able to help us identify and reduce the NIHL rate in the workers with high accuracy.

Surface Modification of Pure Titanium by Nitrogen Ion Implantation at Different Beam Energy and Dose

The implantation of nitrogen ion is one of the important techniques for modifying the surface characteristics to improve wear and corrosion resistance of commercially pure (cp) Titanium. Although nitrogen ions implanted titanium in various dose demonstrated significant changes of the wear and corrosion resistance, the variable energy implanted is still not yet fully studied. Nitrogen ions were implanted in cp Titanium surface with varies of both dose of 0.5; 1.0 and 2.0 x1017 ions cm-2 and energy of 80, 100 and 115 keV. The nitrogen ion implanted cp Titanium demonstrated an increase in the surface hardness and improvement in corrosion behavior. The maximum surface hardness was delivered by the specimens implanted with the dose of 2.0x1017 ions cm-2 at energy of 80 keV. Grazing incidence x-ray diffraction studies indicated that TiN phase was formed on near surface substrate. Electrochemical tests in 3.5%-wt NaCl solution depicted significant improvements in corrosion resistance for specimens implanted with dose of 0.5x1017 and 1.0x1017 ions cm-2 at energy of 80 keV, dose of 1.0x1017 and 2.0x1017 ions cm-2 at energy of 100 keV. The dose of 2.0x1017 ions cm-2 and energy of 100 were the best implantation parameter in this study.

Analysis of the effect of vibration from footfalls on office building

Human footfalls are the main source of vibration in office building and it could affect the structure of the building as well as causing discomfort and annoyance to the occupants of the building when the vibration level inside the building exceeds the recommended level. The objectives of the study are to determine the level of vibration on each floor of a multi-storey building due to footfalls and to perform structural response on the multi-storey building due to footfalls input. The selected building for this study is Registrar Office building located in Universiti Tun Hussein Onn Malaysia (UTHM). The scope of study is focused on the effect of vibration induced by footfalls on multi-storey building and analyzing the data using MATLAB and ANSYSv14. The real inputs of vibration induced by footfalls were measured and obtained using Laser Doppler Vibrometer (LDV). The vibration level induced by footfalls on the multi-storey office building can be determined using Vibration Criteria (VC) guidelines. Finally, from the study, the vibration level achieved for this Registrar Office building is in ISO level range which is still under the acceptable limit for office building.

The Acoustical Characteristics Analysis on Different Type of Natural Fibres

Natural fibres are fibre that can be directly obtained from an animal, mineral, or vegetable sources. Recently natural materials are becoming a good alternative for synthetic material as they provide good health to a greener environment. This aim of this study to investigate and compared the acoustic characteristics of three natural fibres; Kenaf fibre (Hibiscus Cannabinus), Ijuk fibre (Arenga Pinnata), and Coconut coir fibre, where each material is qualified for acoustical absorption. During the processing stage, each fibre is reinforced with 60:40 ratio of pure latex separately. The fibres are then compressed after the pure latex treatment into circular samples, of 28 mm and 100 mm diameters respectively. The thickness of each sample is fixed at 50mm. The acoustical performances were evaluated by using an impedance tube instrument. This study also investigates the effect of air gap of 10mm and 50mm in the sound absorption performance. The results show that, all the three fibres have reached an optimum level of sound absorption value of more than 0.7. The frequency peak value of Kenaf is obtained in a range of 700 Hz – 800 Hz, while for coconut coir is at 1000 Hz – 1075 Hz frequency range. Only Ijuk has obtained the highest frequency range of 3200 Hz – 3400 Hz. The results demonstrate that these three fibres are a promising light and environment-friendly sound absorption material as they are ready to replace the common synthetic fibre.

Appraisal on Rail Transit Development: A Review on Train Services and Safety

The ever increasing problems faced by population around the world have made demands that transportation need to be improved as an effective and efficient communication means. It is considered as a necessity especially when rapid development and economic growth of a country is the agenda. Among the transportation modes being focused as critical facilities are the bus system, rail system, road network, shipping system and air transportation system. Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In Malaysia, the railway network has evolved tremendously since its inception in the early 19th century. It has grown proportionally with the national development. Railway network does not only mean for rural transportation, but it also considered as a solution to urban congestion challenges. Currently, urban rail transit is the most popular means of urban transportation system especially as big cities such as Kuala Lumpur. This paper presents the definition of rail transportation system and its role in urban or sub-urban operation. It also describes the brief history of world railway transportation including a discussion on Malaysian rail history perspective. As policy and standard are important in operating a railway system, this paper also illustrates and discusses some elements which have an impact on the effectiveness and efficiency of train operation. Towards the end, this paper also shares the importance of railway safety based on real case studies around the world. Thus, it is hoped that this paper will enable the public to understand the rail transit development and appreciate its existence as a public transportation system.

Hand-arm vibration disorder among grass-cutter workers in Malaysia.

Introduction. Prolonged exposure to hand-transmitted vibration from grass-cutting machines has been associated with increasing occurrences of symptoms and signs of occupational diseases related to hand–arm vibration syndrome (HAVS). Methods. A cross-sectional study was carried out using an adopted HAVS questionnaire on hand–arm vibration exposure and symptoms distributed to 168 male workers from the grass and turf maintenance industry who use hand-held grass-cutting machines as part of their work. The prevalence ratio and symptom correlation to HAVS between high and low–moderate exposure risk groups were evaluated. Results. There were positive HAVS symptoms relationships between the low–moderate exposure group and the high exposure group among hand-held grass-cutting workers. The prevalence ratio was considered high because there were indicators that fingers turned white and felt numb, 3.63, 95% CI [1.41, 9.39] and 4.24, 95% CI [2.18, 8.27], respectively. Less than 14.3% of workers stated that they were aware of the occupational hand–arm vibration, and it seemed to be related to the finger blanching and numbness. Conclusion. The results suggest that HAVS is under-diagnosed in Malaysia, especially in the agricultural sectors. More information related to safety and health awareness programmes for HAVS exposure is required among hand-held grass-cutting workers.

Condition Monitoring of Variable Speed Worm Gearbox Lubricated with Different Viscosity Oils

Over the years, condition monitoring of gear transmission systems have captured significant worldwide attention from both industries and academia. This is in light of the fact that an effective condition monitoring techniques will unquestionably extend the life span of the rotating equipment. In this research, both the vibration and temperature monitoring techniques were utilized to characterize the vibration behavior of worm gear as function of gear lubricant’s viscosity. Three different types of lubricant’s viscosity; VG100, VG460 and VG680 were used in the study to serve the sliding friction of worm gears. The predetermined speeds of electric motor at 900, 1150 and 1400 rpm were introduced to the gearbox prior to the measurement of vibration signal and temperature profile. The results revealed that a lubricant with higher viscosity contributes to less vibration amplitude. At 1150 rpm, it was recorded that the vibration amplitudes are higher compare to the other motor speeds, for all lubricants types. In this case, VG100 showed the highest vibration amplitude followed by VG460 and VG680. This result was corroborated well with the obtained temperature profiles which are 35.0°C, 35.7°C and 39.3°C for the respective VG100, VG460 and VG680. Thus, concludes the correlation between the lubrication’s viscosity, vibration level, temperature profile and worm gear speed.