Papers by Author: Ahmad Kamal Ariffin

Abstract: 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.

Abstract: Solder joints are exposed to drop impact, vibration loading, bending, and twisting of PCBs. Study on this matter will lead to prediction of fracture load, prevalent fracture mode, exact joint interconnect size and life of joints under brittle and fatigue failure. This paper presents a finite element modeling of intermetallic compounds solder joints failure based on displacement extrapolation method. Based on conceptual FE model of intermetallic IMC solder joints, this paper present the full model of IMC model for intermetallic Mode I and Mode II fracture prediction.

Abstract: Solder joints failure due to thermal loads and mechanical loads is a significant reliability concern in electronic devices. From literatures, little attention is paid to the development of methods on predicting fracture behavior of solder joint under mixed-mode loading. This paper presents a finite element modeling of intermetallic compounds solder joints failure based on displacement extrapolation method (DEM). Conceptual study on single edge crack on intermetallic IMC solder joints is presented.

Abstract: 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.

Abstract: This paper presents a numerical investigation on semi-elliptical surface cracks in round bars subjected to mode III loadings. Lack of information can be found in open literature regarding to the J-integral solution especially the surface crack subjected to mode III loadings. Therefore, this work investigates and analyzes crack behavior using J-integral approach. On the other hand, a mathematical model is also developed to predict the J-integral along the crack front. It is found that the J-integral can be used to predict well along the crack front. However, the prediction is strongly influenced by whether the material is elastic-or plastic dominated region.

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.

Abstract: 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.

Abstract: The aim of this paper is to present the simulation technique and experimental work for surface crack in a structure. For the sake of test apparatuss feasibility, a semielliptical surface crack in a structure was converted into small specimen size. The specimens represented semielliptical surface crack problem in real application of engineering structure. The specimens with semielliptical surface crack were tested by experiment and simulation. The S-version Finite Element Model (S-FEM) was implemented in simulation, and verification was performed through experimental works. The S-FEM consists of virtual crack closure method and Paris law as a crack growth criterion for 3-dimensional problem with hexahedron elements was used. Auto-mesh generation technique with a fully automatic crack growth simulation system was employed in S-FEM simulation. Specimens with 0^o of crack surface angle were prepared and analysed for the mode I loading. A four-point bending fatigue test was conducted and simulated in order to gain crack path, fatigue crack growth and stress intensity factors value. Results from simulation and experiment showed good agreement with a certain condition. The implications from the results were discussed through the analysis of fatigue crack growth.

Abstract: Stress shielding interaction effect of two parallel edge cracks in finite body under uniaxial loading is analysed using developed finite element (FE) analysis program. In present study, the stress shielding interaction is formulated as a mathematical model called stress shielding damage (SSD) model. SSD model used to define the combination and re-characterization of crack interaction from multiple cracks to single crack. Focus is given to weak crack interaction state as the crack interval exceed the length of cracks (b > a). The crack interaction factors are evaluated based on Griffith strain energy release rate and mode I SIF using J-integral analysis. For validation, the stress shielding factor parameters are compared to single edge crack SIF as a state of zero interaction in a form of crack unification limit (CUL) and crack interaction limit (CIL).

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.