Applied Mechanics and Materials Vol. 471

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: The objectives of this study are to determine the stress intensity factor (SIF) for different surface crack size of the lumbar vertebra and the probability of failure associated with finite element method. In this work, all the model components were meshed using the tetrahedral solid element. 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 probabilistic module in ANSYS with attempt for 100 trials. The results are observed that the maximum SIF were found in the end of crack path with 0.53 MPa.m^1/2 and the corresponding probability of failure for the model is 1.22%. Sensitivity analysis had been revealed that the crack size was sensitive to the maximum stress and maximum SIF output parameters with correlation 0.989 and 0.811 respectively. The current probabilistic study is useful as a tool to understand the inherent uncertainties and variations in biological models.

Abstract: The main requirement in designing a structure is to ensure the structure is reliable enough to withstand loading and the reliability study of structure. Classical and probability approach was introduced to analyse structural reliability. However, the approaches stated above are unable to take into account and counter the uncertainties arising from the natural of geometry, material properties and loading. This leads to the reduction in accuracy of the result. The goal of this study is to assess and determine the reliability of structures by taking into consideration of the epistemic uncertainties involved. Since it is crucial to develop an effective approach to model the epistemic uncertainties, the fuzzy set theory is proposed to deal with this problem. The fuzzy finite element method (FFEM) reliability analysis conducted has shown this method produces more conservative results compared to the deterministic and classical method espacially when dealing with problems which have uncertainties in input parameters. In conclusion, fuzzy reliability analysis is a more suitable and practical method when dealing with structural reliability with epistemic uncertainties in structural reliability analysis and FFEM plays a main role in determining the structural reliability in reality.

Abstract: The effectiveness of the cathodic protection system is very important to be maintained for the submersible pump structure. Early damage of the infrastructure can be caused by improper design of the protection system. However, nowadays the effectiveness of the cathodic protection system could not be evaluated before the system applied in the field. This study is conducted on development of 3D infinite domain boundary element method (BEM) to evaluate the cathodic protection system for submersible pump structure using aluminum sacrificial anode. In this study, the potential in the domain was modeled using Laplace equation. The equation was solved by applying BEM, hence the potential distribution and current density on the metal surface and at any location in the domain can be obtained. The numerical analysis result shows that the 3D infinite domain BEM can be used to simulate the cathodic protection system. Moreover, the execution time for infinite domain BEM is less than the finite domain for the evaluated case.

Abstract: This paper presents the comparison of the two optimization methods, particle swarm optimization (PSO) and genetic algorithm (GA) in boundary element inverse analysis that applied to detect the corrosion location of rebar in the concrete. This comparison focuses at analyzing the performance of both methods in reaching the global optimum, considering that both heuristics are based on population search techniques. The model of 2-dimension rectangular reinforced concrete was used as a case example to compare both methods in boundary element inverse analysis. The boundary element inverse analysis was developed by combining Boundary Element Method (BEM) and PSO or GA. 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 Laplaces equation using BEM. The GA or PSO is used to minimize the cost function. Thus, the corrosion location of reinforcing steel in concrete can be detected. The numerical simulation results showed that one of PSO or GA can be used for the inverse analysis for detecting rebar corrosion by combining with BEM. However, it shows that PSO seem numerically superior compared to GA in term of consistency and accuracy in finding global optimum solution for such a problem.

Abstract: The finite element modeling and analysis have been performed to investigate the effects of nitriding, cold rolled and shot peening on fatigue life of an automotive lower suspension arm component which fabricated of SAE1045 steel. The finite element analysis (FEA) results indicate a great effect for all surface finish parameters on fatigue life. It shows that nitriding increased the fatigue life of the component better than shot peening, while cold rolled effect was between them. In a nut shell, nitriding can be considered as the best surface treatment to improve the fatigue life of the automotive lower suspension arm which fabricated of SAE1045 steel.

Abstract: The competency of acoustic emission (AE) technique in order to predict the fatigue life of SAE 1045 carbon steel was discussed in this paper. The correlation of the AE parameter and the number of cycles to failure of the tested specimens were established via the statistical approach. In this paper, The AE hits were selected as the functional parameter. The fatigue life values were calculated using the strain-life approach of three models; Coffin-Manson, Smith-Watson Topper and Morrow. Both AE and strain signals used in the analysis were captured using the AE sensor and strain gauge that were attached to the specimen during the fatigue test. The results show that the AE technique has a good potential in assessing the fatigue life with the designed H-N curve (AE hits-number of cycles to failure curve).

Abstract: This paper presents the investigation of composite materials lamination using different materials in the structure of lamination. The main purpose of the study is to evaluate the behaviour of characteristics in composite materials subjected to difference of fatigue loading, leading to understand the criteria that influence the behaviour of composite lamination structure. Therefore, in this research, the orientation of lamination structure used is 0⁰/90⁰ and the material selected for the study were chopped strand mat (csm) and woven roving fabric (wr) as a reinforcement and the matrix used were polyester and epoxy resin. The composite lamination structure was produced using hand lay-up technique. The fatigue condition experiment of composite materials in this research was carried under tension-tension loading. With difference in fatigue loading condition, the lifetime of composite structure will be different and the cracking phenomenon in the structure will also be different. It is suggested that, different number of lamination and amount of reinforcement and matrix, produce a variety of materials characteristic with respect to elasticity of material. An implication of the study in this research showed various behaviour of composite materials with different materials used and it showed a difference phenomenon in comparison to metalic materials.

Abstract: Introduction of holes into plat-like structures is commonly found as one of practical noise control measures to reduce sound radiation. However, perforation into the panel also reduces the panel stiffness and hence increases its vibration. Since the discussion and also the analytical model to quantify this effect are lacking, this paper discusses the dynamics of a perforated panel from the results obtained using Finite Element Method (FEM). Different hole geometries are simulated to investigate their effect on the plate mobility. It is found that increasing the perforation ratio increases the plate mobility particularly at off-resonance peaks. The effect of hole size and number are also discussed in this report.

Abstract: This paper presents some preliminary studies on the frequency-up conversion method for low frequency application energy vibration based harvesting device, mainly from human body motion, by employing the translation to rotary mechanism. Vibration signals from different parts of the human body were first measured when the human subject was walking at 5 km/h. The signals obtained from the measurement were then reconstructed using Fourier Transform and it was found that frequency content of human body motion was in the range of 1 Hz 25 Hz. A preliminary experiment was conducted to check on the ability of the mechanism to amplify the low excitation frequency. Although the experiment was not optimized, it is found that the device was able to amplify input frequency up to 3.6 times.