Papers by Author: Shahrum Abdullah

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Authors: Mahfodzah M. Padzi, Shahrum Abdullah, Mohd Zaki Nuawi
Abstract: This paper discussed on an application of the statistical based analysis approach on fatigue failure of carbon steel. A new statistical based method known as Integrated Kurtosis-based Algorithm for Z-filter (I-kaz) and the quadratic mean were used in this fatigue failure assessment. Fatigue tests were performed according to the ASTM E466-96 standard with the attachment of a strain gauge to the tested specimen. Test was performed at a constant loading leading to the collection of strain data throughout the test. A fatigue based data acquisition system was used in this work. All obtained data were analysed using specific software. Fatigue failure behaviour was observed through the strain signal analysis to investigate significant correlation between I-kaz coefficient, root mean square value and the fatigue failure behaviour. It was found that I-kaz coefficient and root mean square value are proportional to life cycle.
Authors: Ahmad Mubarak Tajul Arifin, Shahrum Abdullah, Rozli Zulkifli, Dzuraidah Abd Wahab
Abstract: This paper focuses on the characteristic study of polymer matrix composites using a statistical approach, in terms of difference experimental and reflected to difference stacking sequence and orientation of composite lamination. Composite material, have an excellent characteristic and behavior, but with a difference application and materials used, it have a difference phenomenon occurred before the composite structure are collapsed. Therefore, in order to understand the characteristic of polymer matrix composites, it needs to investigate the phenomenon that influences the structure of composite lamination before failures. In this research, polymer matrix composites are produced using difference material and stacking sequence of lamination. The matrix used is thermoset epoxy and polyester resin with chopped strand mat (CSM) and woven roving (WR) as reinforcement materials. It has been produced using hand lay-up technique. The experimental work is carried out using the tension and flexural test accordance to ASTM-D3039 and D-D790 standard. By using a statistical approach, it can clearly show the differential between materials used with a characteristic of composite materials. It is noted, based on this investigation it also showed difference phenomenon failures and damage structure of polymer matrix composites with difference type of experimental.
Authors: Mohd Noor Baharin, Zulkifli Mohd Nopiah, Shahrum Abdullah, Mohd Jailani Mohd Nor
Abstract: This paper presents the comparative study on two types of the clustering technique for decomposing Variable Amplitude (VA) loadings signals based on its amplitude. These two techniques are used to recognize clusters or patterns of fatigue damaging events in the record which will bring aboutthe majority of fatigue damage. However, one of the problems that existswhencomparing which technique will produce better clusters is the fact thata clustering validation index isneeded. In this study, techniques that were used were theFuzzy C-means and C-means. At first, the VA data weresegmented using the Running Damage Extraction (RDE) technique. Then, each segment produced wasanalysed using the strain life approach and global statistical signal values. Finally, the accuracy of each clustering technique wasmeasured based on the OV coefficient index. From the study, the index shows that the Fuzzy C-means technique produced much better clusters rather than the C-mean clustering technique.
Authors: Shahrum Abdullah, Ahmad Kamal Ariffin
Abstract: This paper describes the laboratory accelerated fatigue tests of BS 080A42 steel using the shortened variable amplitude (VA) loading produced by the Wavelet Bump Extraction (WBE) algorithm. In this study, a VA strain loading which was measured on the lower suspension arm of a vehicle while driven over a pavé road surface was used. The WBE shortened loading was validated based on the fatigue life comparison to the original loading using four strain-life fatigue damage models. Experimental fatigue tests were performed using a cylindrical shape specimen with the 6- mm gauge length smooth surface made from BS 080A42 steel. The experimental findings showed that the fatigue tests were accelerated from 78.8 hours to 32.5 hours, preserving at least 99% of the original fatigue damage in the mission loadings. Finally, it is suggested that the WBE algorithm is suitable for the application of automotive accelerated fatigue tests.
Authors: Zainudin Kornain, Azman Jalar, Rozaidi Rashid, Shahrum Abdullah
Abstract: Underfilling is the preferred process to reduce the impact of the thermal stress that results from the mismatch in the coefficient of thermal expansion (CTE) between the silicon chip and the substrate in Flip Chip Packaging. Voids formation in underfill is considered as failure in flip chip manufacturing process. Voids formation possibly caused by several factors such as poor soldering and flux residue during die attach process, voids entrapment due moisture contamination, dispense pattern process and setting up the curing process. This paper presents the optimization of two steps curing profile in order to reduce voids formation in underfill for Hi-CTE Flip Chip Ceramic Ball Grid Array Package (FC-CBGA). A C-Mode Scanning Aqoustic Microscopy (C-SAM) was used to scan the total count of voids after curing process. Statistic analysis was conducted to analyze the suitable curing profile in order to minimize or eliminate the voids formation. It was shown that the two steps curing profile provided solution for void elimination.
Authors: Mohd Basri Ali, Shahrum Abdullah, Mohd Zaki Nuawi, Ahmad Kamal Ariffin
Abstract: Dynamic fracture properties of most engineering materials are evaluated using Charpy test. The dynamic responses of the standard Charpy impact machine are experimentally studied using the relevant data acquisition system in order to obtain the impact response. For this reason, strain gauges were connected to the data acquisition set and it was then attached to the striker for the signal collection. The numerical analysis by mean of the finite element method has been used to obtain the findings. The standard Charpy modelling using the aluminium 6061 material was used in order to obtain strain responses on the striker during the impact simulation. A standard Charpy specimen aluminium 6061 was used for the experimental impact testing. A power spectrum density (PSD) approach is then used to convert a signal from the time domain to the frequency domain using the fast Fourier transform (FFT) method. Related parameters on strain signals, power spectrum density (PSD), comparison between experiment and finite element analysis, and the relationship between all the parameters were finally correlated and discussed. It was found that the finite element results are validated to show simulated time histories and its PSD compared with experimental work.
Authors: Muhammad Nubli Zulkifli, Azman Jalar, Shahrum Abdullah, Norinsan Kamil Othman
Abstract: The evaluation of the strength and bondability of gold, Au ball bond requires a new approach to provide a more detail data. Nanoindentation test was used as a new approach to evaluate the strength distribution and bondability of Au ball. Au ball bonds that experienced different value of wire bonding parameter namely bonding force, bonding time, bonding power, and stage temperature were used as samples for the present analysis. The distribution of strength based on hardness and reduced modulus values located at the bonding area of Au ball bonds were found to be related with the values of the wire bonding parameter. Nanoindentation test was found to be a suitable approach to analyze and evaluate the bondability of Au ball bond in a localized and detailed manner. In addition, the responsible mechanism for the thermosonic Au wire bonding can be identified and analyzed by using the results obtained from the nanoindentation test.
Authors: Abdul Rahim Bahari, Mohd Zaki Nuawi, Shahrum Abdullah, Ahmad Kamal Ariffin Mohd Ihsan, Mohd Basri Ali
Abstract: Dynamic response of automotive component materials which are carbon steel S50C and cast ironon its sound and vibration characteristichas been studied. This paper shows that I-kaz analysis method can be applied to characterise this dynamic behavior problem. In the present work, an excitation has been performed by an impact hammer at the center of a rectangular bar specimen instrumented with accelerometer and microphone to obtain sound and vibration time-histories. From the experimental results, it was found that the recorded sound and vibration signal has a transient characteristic with high oscillation. Frequency spectrum analysis shows that impact testing on any material will generate its own characteristic of frequency peak and constantboth for sound and vibration signal. From I-kaz analysis method, it can be concluded that I-kaz coefficient, for sound signal is proportional to the modulus of elasticity, density and Poissons ratio. It is also shown that for vibration signal is inversely proportional to these mechanical properties.Data scattering representation supported this pattern of .
Authors: Mariyam Jameelah Ghazali, S.E. Mat Kamal, Shahrum Abdullah
Abstract: This work aims to characterise a Cu-based coating material on Al-7075 by using a plasma-spray technique in order to enhance the surface properties of components for automotive applications. Plasma-spray is a process for formation coating on substrates whereby a feedstock is rapidly heated to a molten or near-molten state, and a gas are use to propel the material toward suitably prepared substrate. The most prominent advantages of this method are virtually any coating material can be used and any substrate material can be coated with low thermal stress on substrate parts and high deposition rates [1]. The coating characteristic can be controlled by varying the process variables such as input powers, material feed rates, gas pressures, surface preparation of the substrate and spray distance [2]. The effect of crucial parameters like the electric power input to plasma, spray rate and substrate roughness were studied. The experiments of spraying were design using a 23 fractional factorial plan. The plan allows studying the effect of each factor on the response variables, as well as the effect of interactions between factors on the response variable at the least number of experiment runs. The coating layers have been characterised with respect to the structure by using a scanning electron microscopy (SEM). The result indicates that sprayed particles cool and built up into pancake-like shapes splat, characteristic a plasma spray electric process products. It was found that the optimum parameters were obtained at a power of 24.6 kW, with a powder feed rate of 1 rpm and substrate roughness of 0.5µm.
Authors: Mohd Zahrin A. Wahab, Azman Jalar, Shahrum Abdullah, Hazian Mamat
Abstract: This paper presents Time Dependent Dielectric Breakdown (TDDB) testing of gate oxide on 0.5µm BiCMOS Technology. The gate oxide quality for the technology has been investigated and furthermore to qualify the whole set up of the foundry from the process, equipment, cleanroom control and raw material used to produce high quality gate oxide and hence good quality of BiCMOS devices. TDDB test is the most widely used testing to check the quality of gate oxide and in this paper the TDDB test done on MOS capacitors fabricated using 0.5 µm BiCMOS Technology. Seven consecutive qualification lots have been tested and the data shown that TDDB measurement is capable to differentiate between accepted wafer and rejected wafer. The data also shown that TDDB test was capable to characterise 0.5 µm BiCMOS gate oxide with higher yield and comparable with reference lot from other foundry fab.
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