作者: Shahrum Abdullah, Ahmad Kamal Ariffin

摘要: 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.

1023

作者: Mohd Basri Ali, Shahrum Abdullah, Mohd Zaki Nuawi, Ahmad Kamal Ariffin

摘要: 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.

130

作者: M. Ridha, Syarizal Fonna, Syifaul Huzni, Fachrizal, Ahmad Kamal Ariffin

摘要: The earthquake and tsunami that struck Aceh region on December 2004 caused many public buildings submerged by seawater. In long periods, it will promote the premature failure of the existing buildings constructed by reinforced concrete structure due to corrosion. Early detection of the corrosion is urgent. The corrosion assessment using haft-cell potential mapping has been conducted to understand the current status of public buildings after five years tsunami Aceh 2004. The results for four existing public buildings in the region show that the corrosion level of steel in concrete of the buildings was already at intermediate risk. However, these results show only the corrosion risk instead of the actual corrosion of the steel. To improve the corrosion assessment, BEM was employed by simulating some factors that might affect the measured potential on the concrete surface. Laplace equation is used to model the potential in concrete structure. The steel surfaces were represented by using polarization curves. BEM is employed to solve the Laplace equation; hence the potential and current density in the whole domain can be obtained. The simulation results show that the potential corrosion on concrete surface was significantly affected by corrosion of steel, concrete conductivity and concrete cover. Accordingly, by employing BEM, more precise corrosion of steel in concrete can be identified from the measured potential on the concrete surface. Moreover, further study is needed to apply the proposed method in the field.

413

作者: Saber Rashid, N. Islami, Ahmad Kamal Ariffin, M. Ridha, Syarizal Fonna

摘要: The aim of this paper is to investigate the effects of elastic stress for a C-ring specimen with an18.974-mm outer diameter and a 1.244-mm wall thickness. Tests are conducted on Type 304L SS material. Half-cell potential measurement specimens are used as methods of exposure and inspection The C-ring specimen for quantitatively determining the stress corrosion. Applying ASTM G38, which is a standard practice for making and using C-Ring Stress-Corrosion, was performed for elastic stress analysis. The results show that the effects of stress on the polarization curve are due to the magnitude of stress level in the speciﬁc corrosive environment.

355

作者: Syarizal Fonna, M. Ridha, Syifaul Huzni, Israr Israr, Ahmad Kamal Ariffin

摘要: Boundary element inverse analysis (BEIA) by using genetic algorithm (GA) to identify corrosion location has been introduced by many researchers. However, the BEIA using GA is more complex to be programmed since it involved with genetic operators such as crossover and mutation. Recently, Particle Swarm Optimization (PSO) already takes researcher’s attention because of its simplicity to be programmed and comparable accuracy. This study is conducted to develop BEIA by combining Boundary Element Method (BEM) and PSO to identify the corrosion location of the steels in concrete structure from some potential data on concrete surface. The potential in the concrete domain was modeled by Laplace’s equation. The anode and cathode are represented by each polarization curve. The inverse problem is carried out by means of minimizing a cost function i.e. a difference between the calculated and measured potentials on the concrete surface. The calculated values of potential are obtained by solving the Laplace’s equation using boundary element method (BEM). Numerical simulation results show that the developed BEIA has proven that it can identify the corrosion location on the surface of reinforcement steel precisely.

171

作者: Mohd Zaki Nuawi, Abdul Rahim Bahari, Shahrum Abdullah, Ahmad Kamal Ariffin

摘要: This paper presents an alternative statistical signal analysis method to characterise and determine Youngs modulus property of metallic materials. For this characterisation purpose, we propose an alternative method called Integrated Kurtosis-based Algorithm for Z-notch filter (I-kazTM) and Mesokurtosis Zonal Nonparametric (M-Z-N). Impulsive excitation test has been performed according to ASTM E1876 on three metallic materials of medium carbon steel S50C, stainless steel AISI 304 and brass to measure the piezoelectric and acoustic signals. The transient acoustic signal has been analysed using M-Z-N analysis while I-kazTM has been used to analyse the impulsive piezoelectric signal. Correlation expression between Youngs modulus property and the calculated statistical parameters has been discussed and the accuracy of these two methods has been identified using cast iron FCD 500 specimen.

186

作者: Ruslizam Daud, Ahmad Kamal Ariffin, Shahrum Abdullah, A.E. Ismail

摘要: This paper presents the extensions of newly developed finite element (FE) formulation to evaluate fracture behavior of parallel edge cracks problems. The numerical formulation used Barsoum singular finite elements to compute fracture parameters in two dimensional finite element models subjected to different crack-width ratio and cracks interval ratio. Mixed mode stress intensity factors (SIFs) of parallel edge cracks are computed in extending of FE formulation for pure Mode I formulation proposed by authors. In 2D linear elastic problem under mixed mode condition, the variation of SIF value near crack tips are discussed comprehensively. The newly finite element formulations are resulted with remarkable agreement with energy release rate based method compared to analytical solution available in the literatures.

1326

作者: Ruslizam Daud, Ahmad Kamal Ariffin, Shahrum Abdullah, Al Emran Ismail, A. Zulkifli

摘要: The simplification of two dimensional approaches in singular finite elements has promoted the method to be used in the formulation of stress intensity factor (SIF) of multiple cracks in finite body. The effect of shielding and amplification are considered in defining the SIF. As been observed, the current available analytical approximations are more restricted to several assumptions. The more accurate and less restricted method has motivated this study. This paper presents the investigation of singular finite elements applied in two dimensional finite element models subjected to different crack-width ratio and cracks interval ratio. The newly finite element formulations are resulted with good agreement with theoretical statement compared to analytical solution. The weak points of presented analytical solution are discussed regards to the influence of crack width ratio and cracks interval ratio.

75

作者: M. Abdul Razzaq, Ahmad Kamal Ariffin, Shahrum Abdullah, Z. Sajuri

摘要: In this paper, fatigue crack growth rate (FCGR) analyses were conducted on compact specimens of an AISI 4340 alloy to study the behavior over a range in load ratios (0.1 ≤ R ≤ 0.95) and constant maximum stress intensity factor (Kmax) condition. Previous study had indicated that high R > 0.7 and constant Kmax test conditions near threshold conditions were suspected to be free of crack-closure and that any differences were caused by Kmax effects, from threshold to near fracture conditions. Cracks in high-cycle fatigue (HCF) components spend a large portion of their fatigue life near threshold conditions. In order to characterize the evolution of damage and crack propagation during these conditions, fatigue crack growth rate (FCGR) data at threshold and near-threshold conditions are essential in predicting service life and in determining the proper inspection intervals. Fatigue crack growth model, namely the Forman model were examined, this model implicit the effect of R ratio and ease of curve fitting to measured data. The Forman model may be suggested for use in critical applications in studying fatigue crack growth for different load ratios.

54

作者: Mashitah Mahmud, Shahrum Abdullah, Ahmad Kamal Ariffin, Z.M. Nopiah, M.F.M. Yunoh, Nor Izan Izura Mansor

摘要: The evaluation of fatigue behavior of real components under service loading is important in reliability analysis. The present paper investigates the characteristics of two strain signals spectrum by using statistical inferences. The data used in this study are obtained from strain gauges installed on coil spring component of car suspension system driven over two different road surfaces. The coil springs are made of SAE 5160 carbon steel materials. The strain signals are explored to produce the summary statistics (i.e. root-mean-square, kurtosis, skewness etc.) and the rainflow cycle counting is performed to obtain total number of cycles and damage per cycle. Further, distribution fitting is applied to the cycle-counted strain ranges data. The results show that both signals fit well to a mixed Weibull distribution with three subpopulations.

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