Papers by Author: Jamaluddin Mahmud

Abstract: Silicone rubber is widely used in various fields but has low strength, whereas kenaf has higher strength. Therefore, this study aims to synthesise a new material that consists of both kenaf and silicone with three different variances and determine its properties using the three most common hyperelastic constitutive models: Neo-Hookean, Mooney-Rivlin and Ogden. In order to obtain the material constant of kenaf silicone biocomposite, experimental and numerical approaches are adapted. The xperimental approach involves synthesising of kenaf silicone biocomposite and uniaxial tensile test, while the numerical approach involves curve fitting method using an excel programme. Curve fitting method was used because the raw data from tensile test alone could not determine the material constant of agar silicone biocomposite. The results show that the numerical value of the material constant increases as the percentage of the reinforcement material (kenaf) increases. However, the tensile strength of the material decreases as the reinforcement material increases.

Abstract: The study presents the multi methods of determining mechanical properties and mechanical characterization under tensile loading of hybrid composite in the form of experimental technique involving measurement of strain using strain gauge and digital image correlation (DIC) technique utilizing open source platform Ncorr to compute the strain on surface of hybrid composite. The method of micro mechanical modelling using Finite Element Modelling (FEM) in the mode of representation volume element (RVE) method and macro scale FEM using commercial software Ansys have been performed to compute the modulus of elasticity in direction of uniaxial tensile loading. The four methods then compared which yields very consistent results with each other. It is observed that all four methods are reliable in determining mechanical properties of unidirectional single composite as well as hybrid composite. The experimental involved the use of ASTM D3039 standard tensile test for hybrid composite and strain are measured using strain gauges and DIC.

Abstract: Hyperelastic materials are unique materials that have high tendency to stretch and its highly non-linear behaviour is commonly investigated using hyperelastic constitutive models. The aim of this paper is to investigate the sensitivity of Mooney-Rivlin material constants; C₁ and C₂ values in order to observe the behavior and pattern of the stress-stretch graph for silicone-kenaf composite. There were no previous studies done in regards to assess the mechanical behaviour of the stress-stretch curve for silicone-kenaf biocomposite by varying the Mooney-Rivlin material constants. The material constant, C₁ and C₂ are varied into few cases and the patterns of stress-stretch curves are studied. It was found that variations of C₁ and C₂ material constants could contribute differently on the mechanical properties of silicone-kenaf composite. Thus, the results and findings of this study could be further enhanced by future study to gain deeper understanding on the hyperelastic materials behaviour and Mooney-Rivlin hyperelastic constitutive model.

Abstract: The development of a robotic exoskeleton to restore and rehab, hand and finger function is highly competitive nowadays. The robotic exoskeleton is an active actuated mechanism implemented in rehabilitation system, in which each finger attached to an instrumented lead screw mechanism allowing force and position control, according to the normal human setting. The robotic device is a direct driven actuated based on ergonomics measurements, capable to assist in flexion and extension motion. As an adaptation mechanism, it's also compatible with various sizes and shapes of anthropometric human‘s finger. The integration of DC servo motor and lead screw mechanism were the main features of the interface, which allows independent motion of the five fingers with small and lightweight actuators. The device is easily transportable, efficient safety performance, user friendly and offer multiple modes of training potentials. This paper presents the measurements implemented in the system to determine the requirements for finger and hand rehabilitation device, the design and characteristic of the whole system.

Abstract: Woven composite laminates have been widely used in various application and rapidly replacing unidirectional composite laminates. Thus, it is vital to understand clearly their material parameters and characteristic. Apparently, it is very difficult to analyse the design parameters of a unidirectional composite laminate, and thus due to its weaving structure, analysing numerically the parameters of a woven composite laminate is even more difficult. Therefore, this paper aims to review the work related to woven laminates with respect to its testing and simulations. During the initial stage, a tensile test is conducted according to ASTM D3039 on the 2×2 twill weave carbon fibre woven prepeg where the material constants (E_1, E_2, G₁₂ and ν₁₂) and the deformation behaviour will be obtained. The later stage will involve the development of a finite element modelling and simulation by means of commercial finite element package ANSYS 14.0 to replicate the experimental set-up. Ultimately, the outcomes and findings between the experimental and numerical approaches will be compared and reported.

Abstract: Finite element analysis (FEA) has become an increasingly important tool in evaluating structural performance of platforms. This includes the use of this tool to perform strength, stability checks, optimisation of structural design upon subjected to design loads as well as to perform failure investigation of platforms upon subjected to special loading conditions such as impacts. Traditionally, small and medium enterprises utilises laboratory (physical) testing and heuristic experience to fabricate and test the platforms, nonetheless this approach is deemed too time consuming and cost demanding. Therefore, this study aims at reconstructing the actual design based on engineering drawings as well as performing stress analysis by means of a commercial FEA software package, ANSYS v14.0 by investigating the effects of two distinct loading impacts on a mild steel platform. The maximum stress and maximum displacement values obtained via the FEA simulation was then compared with values obtained via theoretical computation. The results obtained via the FEA simulation was found to be in good agreement with the exact solution. The present study is non-trivial as it contributes towards the knowledge in the design and optimisation of complex steel structures.

Abstract: Skin is an important organ which provides multiple functions. Thus, if skin fails i.e. due to burns or diseases, body will lose the protection provided by skin against infections and the harmful outer environment. Due to that, synthetic skin is seen as a very important alternative in the future. A number of studies have been carried out to understand skin’s basic functions and behaviour as its mechanical properties and behaviour are important in various fields. Nevertheless, to date no breakthrough has been reported. Therefore, this paper aims to briefly review and outline a framework which ultimately will lead to the synthesising silicone-hydrogel materials that potentially becoming a skin substitute. The newly synthesised composite materials will be tested mechanically to characterise its behaviour based on Ogden hyperelastic model. It could be emphasised that the present study is significant and will contribute to the body of knowledge in the area of skin mechanics.

Abstract: The designing of composite structures for modern and precision application is complicated due to its anisotropic and inhomogeneous material behaviour. Therefore, reliable methodology for fully predicting the performance of composite structures must be developed. Hence, analytical and numerical solution will be implemented in order to perform failure analysis of composite laminates under biaxial loading. There are many approaches developed in order to study the failure behaviour of composites materials. This paper reviews and proposes a research framework that employs analytical method, numerical method using MATLAB programming and finite element method using ANSYS 14.0 to investigate the failure behaviour of composite structures. The First Ply Failure (FPF) and Last Ply Failure (LPF) analysis will be performed to determine the failure curves. Finally, the failure curves obtained from both analytical and finite element simulation will be compared with results published from previous experiments.

Abstract: Kaedah A is a fend off technique engaged in Seni Silat Cekak Malaysia, upon confronting a punch force exerted within the vicinity of the thorax area. Hitherto, there is still lack of biomechanical analysis on the execution of Kaedah A. Therefore, this study aims at analysing the effectiveness of Kaedah A based on the total execution time as well as to describe the kinematic characteristics of the hand movement upon its execution. The experiment was carried out by means of motion capture. Microsoft Kinect was utilised to detect the hand movement whilst the post processing of the captured motion was performed via Virtual Sensei Lite. Kaedah A was executed five times by an experienced Seni Silat Cekak Malaysia practitioner to investigate the accuracy and repeatability of the system. The data obtained serves as an input for the trajectory mapping for both initial and end point identification. The time difference, Δt between the points demonstrates that the total time execution for Kaedah A is less than 0.1 s. Further analysis involves filtering the coordinate data obtained in order to generate the polynomial function of the hand movement during the execution of Kaedah A. It could be concluded that the Kaedah A execution has the features of a ballistic movement. The findings provides useful data for reliability prediction as well as further enhancement of the Kaedah A itself.

Abstract: Virtual Sensei Lite (VS Lite) is an inexpensive user-friendly motion analysis system. As an alternative motion capture system, it is a must for VS Lite’s user to assess the accuracy of the measurement system capability. To date, such analysis to observe the reliability and accuracy of VS Lite has not been reported. Therefore, this study proposes a procedure for assessing the accuracy and capability of the Virtual Sensei Lite using ANOVA Gage Repeatability and Reproducibility (Gage R&R) designed experiments. In this procedure, a gage R&R study is conducted to obtain replicate measurements on nine parts by three operators. The total variation due to measurement error is then observed to identify the accuracy of measurement. The study able to demonstrate on the accuracy of VS Lite as the value of total variation due to measurement error is within 10%-30%.