Papers by Author: Ahmad Kamal Ariffin

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Authors: N.A. Akeel, Z. Sajuri, Ahmad Kamal Ariffin
Abstract: Fatigue crack propagation in two-dimensional rail track model under constant amplitude loading was analyzed using finite element method. The stress intensity factor was predicted using the displacement correlation method that was written in FORTRAN code and exported to Post2D to run the program and utilizing the singular elements around the crack tip area with automatic remeshing model. The fatigue crack propagation is modeled through the successive linear extensions under the linear elastic assumption. To simulate the propagation a single edge angled-crack was introduced to calculate the accurate values of stress intensity factors. The fatigue crack propagation for rail track under four point bend loading model was successfully simulated. The crack was initially propagated in direction inclined to the rail head surface but changed its direction 90° to rail head surface after certain crack length. The mix mode stress intensity factors were also successfully determined through the proposed model.
Authors: Ahmad Kamal Ariffin, M.R.M. Akramin, Syifaul Huzni, Shahrum Abdullah, Mariyam Jameelah Ghazali
Abstract: This paper presents a probabilistic approach for fracture mechanics analysis of cracked structures. The objective of this work is to calculate the rigidity of cracked structures based on failure probability. The methodology consists of cracked structures modelling, finite element analysis with adaptive mesh, sampling of cracked structure including uncertainties factors and probabilistic analysis using Monte Carlo method. Probabilistic analysis represents the priority of proceeding either suitable to repair the structures or it can be justified that the structures are still in safe condition. Therefore, the combination of finite element and probabilistic analysis represents the failure probability of the structures by operating the sampling of cracked structures process. The uncertainty of the crack size can produce a significant effect on the probability of failure, particularly for the crack size with large coefficient of variation. The probability of failure caused by uncertainties relates to loads and material properties of the structure are estimated using Monte Carlo simulation technique. Numerical example is presented to show that probabilistic analysis based on Monte Carlo simulation provides accurate estimates of failure probability. The comparisons of simulation result, analytical solution and relevant numerical results obtained from other previous works shows that the combination of finite element analysis and probabilistic analysis based on Monte Carlo simulation provides accurate estimation of failure probability.
Authors: M.R. Jamli, Ahmad Kamal Ariffin, D.A. Wahab, A.E. Ismail, I.A. Shah
Abstract: The aim of this paper is to examine the modeling sensitivity of the three-point bending test by using finite element method (FEM). Three-point bending test has been frequently used to determine the material hardening parameters of sheet metal. As a part of the parameter identification, three-point bending has been simulated and analyzed using FEM. To minimize the computation time, shell element was used to model the sheet metal. The analysis includes implicit and explicit procedures. In particular, this study examines the effect of FEM results by varying the element type, mesh density, and number of integration point. It is shown that the implicit procedure analyze the simulation with very less computation time compared to the explicit procedure. The results also show that only the number of integration point has significant effect on the simulation in both implicit and explicit procedures.
Authors: S.M. Beden, Shahrum Abdullah, Ahmad Kamal Ariffin, N.A. Al-Asady
Abstract: The problem of crack growth is a major issue in the prediction and maintenance of engineering structural elements. Prediction of expected life of a structural element due to constant (static) and alternating loading (fatigue) is of major concern to the designers. Prediction of remaining life of the structural elements influences the decisions of maintenance engineers (checking intervals, corrections, and replacements).The fatigue crack growth rate, which determine the fatigue life of the components after crack initiation need to be experimentally and theoretically investigated. In this study, fatigue crack growth tests were conducted under constant amplitude loading at a stress ratio of 0.1, using three-point bend (TPB) specimens of ASTM A533 steel material. For the simulation part of this study, three fatigue crack growth models, i.e. the Paris, modified Forman and Austen were examined. None of the models has a fit for the fatigue crack growth rate data in a similar behaviour compared to others. The modified Forman model provided a closer fit than the Paris model with respect to the experimental results. However, the Austen model provided the best fit to the fatigue crack growth rate data as compared with the other two models. Therefore, this model is suggested for use in critical applications.
Authors: A. Zulkifli, Ahmad Kamal Ariffin, A.E. Ismail, Ruslizam Daud, M.R.M. Akramin
Abstract: The objectives of this study were to determine the stress concentration of the lumbar vertebra and the probability of failure associated with finite element method. The lumbar vertebra model was constructed in SolidWorks software and imported by ANSYS software for the analysis. In this work, all the model components were meshed using the tetrahedral solid element (SOLID186). In order to simplify the model, all the spinal components were modeled as an isotropic and elastic material. Monte Carlo Simulation (MCS) technique was performed to conduct the probabilistic analysis using a built-in probabilistic module in ANSYS with attempt for 100 trials. The results were observed that the highest stress concentrations were found in the adjacent posterior vertebral body with 1.2117 MPa and the corresponding probability of failure for the model is 3%. Sensitivity analysis had been revealed that the force applied to the facet (FORFCT) variable was sensitive to the stress and displacement output parameters and need to be emphasized. The current probabilistic study was very useful as a tool to understand the inherent uncertainties and variations in biological structures.
Authors: Syifaul Huzni, M. Ridha, Ahmad Kamal Ariffin
Abstract: Stress distribution analysis on four types of stress corrosion cracking (SCC) specimen is presented in this paper. This work was performed using commercial finite element based software, ANSYS. Two types of mesh arrangements, fixed mesh with different mesh size and adaptive mesh, were employed in this work to study the effect of mesh size on stress distribution of SCC specimen. Four types of SCC specimen were studied in this work, i.e. C-ring specimen, tensile test specimen, pre-crack cantilever beam specimen and U-bend specimen. Simulation result shows that stress distribution on the SCC specimen much affected by mesh size and arrangement, especially for specimen with notch. By performing the stress analysis, less effort needed in order to determine the location of corrosion potential measurement on the SCC specimen. This will be very helpful for future work of SCC study.
Authors: Ruslizam Daud, M.S. Abdul Majid, Mohd Afendi, N.A.M. Amin, Ahmad Kamal Ariffin, Shahrum Abdullah
Abstract: Numerical accuracy in assessing the strong shielding interaction that promotes cracking process based on continuum mechanics is presented in this paper. Crack interaction limit (CIL) and crack unification limit (CUL) are investigated based on strain energy release rate approach. The case of two interacting edge crack in finite body is simulated using finite element analysis and J-integral. As a result, the trend of CIL and CUL is presented to prove the limit and unification of energy release can be numerically shown at higher and lower crack-to-width ratio at two crack interval ratio b = 1 and b = 0. It can be concluded that the CIL and CUL is geometrically dependent.
Authors: M. Ridha, M. Safuadi, Syifaul Huzni, Israr Israr, Ahmad Kamal Ariffin, Abdul Razak Daud
Abstract: Cathodic protection system is one of corrosion protection systems that well acknowledged protecting infrastructure such as pipeline and storage tank. Early damage of the infrastructure can be caused by improper design of the protection system. Currently, many cathodic protection systems are designed only based on the previous experiences. It is urgently needed the tool that can be used to simulate the effectiveness of any design of cathodic protection system before the system is applied to any structure. In this study, the three-dimensional boundary element method was developed to simulate the effectiveness of sacrificial anode cathodic protection system. The potential in the domain was modeled using Laplace equation. The equation was solved by applying boundary element method, hence the potential and current density on the metal surface and at any location in the domain can be obtained. The boundary conditions on the protected structures and sacrificial anode were represented by their polarization curves. A cathodic protection system for liquid storage tank and submersible pump were evaluated in this study. The effect of placement of sacrificial anode were examined to optimize the protection system. The result shows that the proposed method can be used as a tool to simulate the effectiveness of the sacrificial anode cathodic protection system.
Authors: Ahmad Kamal Ariffin, Syifaul Huzni, Nik Abdullah Nik Mohamed, Mohd Jailani Mohd Nor
Abstract: The implementation of inter-element model to simulate crack propagation by using finite element analysis with adaptive mesh is presented. An adaptive finite element mesh is applied to analyze two-dimension elastoplastic fracture during crack propagation. Displacement control approach and updated Lagrangean strategy are used to solve the non-linearity in geometry, material and boundary for plane stress crack problem. In the finite element analysis, remeshing process is based on stress error norm coupled with h-version mesh refinement to find an optimal mesh. The crack is modeled by splitting crack tip node and automatic remeshing calculated for each step of crack growth. Crack has been modeled to propagate through the inter-element in the mesh. The crack is free to propagates without predetermine path direction. Maximum principal normal stress criterion is used as the direction criteria. Several examples are presented to show the results of the implementation.
Authors: Syarizal Fonna, M. Ridha, Syifaul Huzni, Ahmad Kamal Ariffin
Abstract: Particle Swarm Optimization (PSO) has been applied as optimization tool in various engineering problems. Inverse analysis is one of the potential application fields for PSO. In this research, the behavior of PSO, related to its inertia weight, in boundary element inverse analysis for detecting corrosion of rebar in concrete is studied. Boundary element inverse analysis was developed by combining BEM and PSO. The inverse analysis is carried out by means of minimizing a cost function. The cost function is a residual between the calculated and measured potentials on the concrete surface. The calculated potentials are obtained by solving the Laplace’s equation using BEM. PSO is used to minimize the cost function. Thus, the corrosion profile of concrete steel, such as location and size, can be detected. Variation in its inertia weight was applied to analyze the behavior of PSO for inverse analysis. The numerical simulation results show that PSO can be used for the inverse analysis for detecting rebar corrosion by combining with BEM. Also, it shows different behavior in minimizing cost function depending on inertia weight.
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