Mohd Shahrir Mohd Sani

Study of Passive Vibration Absorbers Attached on Beam Structure

Structural vibration is undesirable, wasting energy and possibly leading to excessive deflections and structure and machine’s failure. In order to reduce structural vibration, one of the common way is considering vibration absorber system attach to the structure. In this study, a vibration absorber is developed in a small scale size. The host structure selected for the study is a fixed-fixed ends beam. The effectiveness of vibration absorbers attached to a beam is investigated through experimental study. In prior to experiment, a finite element analysis of Solidworks® and analytical equations of Matlab® are produced in order to determine the structural dynamic response of the beam, such as the natural frequency and mode shapes. The preliminary results of finite element analysis demonstrate that the first five natural frequency of fixed-fixed end beam are 17Hz, 46Hz, 90Hz, 149Hz and 224Hz, and these results are in agreement with the beam’s analytical equations. However, there are slight discrepancies in experiment result due to noise and error occurred during the setup. In the later stage, the experimental works of beam are performed with attached vibration absorber. Result shows that the attachment of vibration absorber produces better outcome, which is about 45% vibration reduction. It is expected that by adding more vibration absorber to the structure, the vibration attenuation can significant.

A review on model updating in structural dynamics

This paper is a review of information and related studies concerning topic of model updating in structural dynamics. It is purposed to introduce and explain the important concept of the discussed subject in model updating area as well as to summarize the development and available guidance and method of conducting the study in this area. The review is structured by presenting an overview of general concept of finite element model updating in structural dynamics and the capabilities of finite element method as a tool in model updating. After the concept introduction, the reliable methodology to perform model updating, the limitation and the critical issues in model updating is discussed. The limitation and problems arise concerning correcting inaccurate finite element model is also discussed. This lead to issue of parameterization and regularization which the limitation and uncertainty in choosing the updating parameter is shown able to be overcome. Further studies on the elimination of systematic errors from both the measurements and the finite element model so that it can provide more reliable model updating is recommended.

Investigation on modal transient response analysis of engine crankshaft structure

The crankshaft is a very crucial part in an internal combustion engine. This paper presents the findings of the mode shape and natural frequency of 3 cylinder 4 stroke engine crankshafts. Both experimental and computational methods were carried out to determine the modal parameter or dynamic characteristics, which are natural frequency, damping factor and mode shape. The prediction of the dynamic properties of the chassis is of great significance in determining the natural frequencies of the structure. The experiment is done by using an impact hammer to excite the crankshaft and data is recorded using a data acquisition system (DAS) connected to a sensor located on the crankshaft. Computational modal analysis on the crankshaft structure is simulated using finite element software. It can be seen from the results that there is a good agreement between the experimental and computational results in terms of modal parameter with a small discrepancy. The modal analysis techniques are essential for automotive crankshaft structure design.

Theoretical Modelling of Plate with Attached Vibration Absorber

There are many ways to control the vibration of plate structure. Conventional approaches that include structural alterations are frequently time consuming and costly. One of the common schemes is using vibration absorber attached to a structure. In this paper, a mathematical model is developed to determine the frequency response of fixed-fixed ends plate with attached vibration absorber. A finite element analysis was performed and compared with the theoretical predictions and showed that there was good resemblance. The results demonstrated that the addition of vibration absorber onto plate can attenuate vibration considerably at a constant frequency.

Finite element model updating of riveted joints of simplified model aircraft structure

Thin metal sheets are widely used to fabricate a various type of aerospace structures because of its flexibility and easily to form into any type shapes of structure. The riveted joint has turn out to be one of the popular joint types in jointing the aerospace structures because they can be easily be disassembled, maintained and inspected. In this paper, thin metal sheet components are assembled together via riveted joints to form a simplified model of aerospace structure. However, to model the jointed structure that are attached together via the mechanical joints such as riveted joint are very difficult due to local effects. Understandably that the dynamic characteristic of the joined structure can be significantly affected by these joints due to local effects at the mating areas of the riveted joints such as surface contact, clamping force and slips. A few types of element connectors that available in MSC NATRAN/PATRAN have investigated in order to presented as the rivet joints. Thus, the results obtained in term of natural frequencies and mode shapes are then contrasted with experimental counterpart in order to investigate the acceptance level of accuracy between element connectors that are used in modelling the rivet joints of the riveted joints structure. The reconciliation method via finiteelement model updating is used to minimise the discrepancy of the initial finite element model of the riveted joined structure as close as experimental data and their results are discussed.Thin metal sheets are widely used to fabricate a various type of aerospace structures because of its flexibility and easily to form into any type shapes of structure. The riveted joint has turn out to be one of the popular joint types in jointing the aerospace structures because they can be easily be disassembled, maintained and inspected. In this paper, thin metal sheet components are assembled together via riveted joints to form a simplified model of aerospace structure. However, to model the jointed structure that are attached together via the mechanical joints such as riveted joint are very difficult due to local effects. Understandably that the dynamic characteristic of the joined structure can be significantly affected by these joints due to local effects at the mating areas of the riveted joints such as surface contact, clamping force and slips. A few types of element connectors that available in MSC NATRAN/PATRAN have investigated in order to presented as the rivet joints. Thus, the results obtain...

Dynamic Study of Bicycle Frame Structure

Bicycle frames have to bear variety of loads and it is needed to ensure the frame can withstand dynamic loads to move. This paper focusing on dynamic study for bicycle frame structure with a purpose to avoid the problem regarding loads on the structure and to ensure the structure is safe when multiple loads are applied on it. The main objectives of dynamic study are to find the modal properties using two method; finite element analysis (FEA) and experimental modal analysis (EMA). The correlation between two studies will be obtained using percentage error. Firstly, 3D model of mountain bike frame structure has been draw using computer-aided design (CAD) software and normal mode analysis using MSC Nastran Patran was executed for numerical method meanwhile modal testing using impact hammer was performed for experimental counterpart. From the correlation result, it show that percentage error between FEA and EMA were below 10% due to noise, imperfect experiment setup during perform EMA and imperfect modeling of mountain bike frame structure in CAD software. Small percentage error differences makes both of the method can be applied to obtain the dynamic characteristic of structure. It is essential to determine whether the structure is safe or not. In conclusion, model updating method is required to reduce more percentage error between two results.

Frequency response function (FRF) based updating of a laser spot welded structure

The objective of this paper is to present frequency response function (FRF) based updating as a method for matching the finite element (FE) model of a laser spot welded structure with a physical test structure. The FE model of the welded structure was developed using CQUAD4 and CWELD element connectors, and NASTRAN was used to calculate the natural frequencies, mode shapes and FRF. Minimization of the discrepancies between the finite element and experimental FRFs was carried out using the exceptional numerical capability of NASTRAN Sol 200. The experimental work was performed under free-free boundary conditions using LMS SCADAS. Avast improvement in the finite element FRF was achieved using the frequency response function (FRF) based updating with two different objective functions proposed.

Design Analysis of Mechanical Jack for Assembling Canopy

The canopy has been used widely all over the world due to the ability of the canopy to provide protection to human from the scorching sun or rain. However, the erection of the canopy is a tedious work. It needs four or manpower in order to lift a canopy frame at the same time, thus requires more spending in order to hire a worker. The canopy jack was designed to make the erection of canopy easier at the same time to reduce the usage of workers. There are several mechanical jack that available in the market, but there is no specification of design analysis. This research is conducted to design canopy jack and determine the static analysis by using SolidWorks software. The design process was done by following the design engineering process which consisted of four main phases; defined task, conceptual design, embodiment design and lastly is the detail drawing. The static analysis was carried out by using SolidWorks to determine the maximum stress and strain, displacement and the safety factor of the canopy jack. The main bolt was the critical part of the canopy jack. Based on the result of static analysis, it shows that the maximum stress analysis reading is 362 MPa and the minimum factor of safety reading of the main bolt is 1.71, thus shows the main bolt was safe to be used. Overall, it can be concluded that the canopy jack was safe and strong enough to be use in order to lift the maximum load of 200 kg.

Modelling of Rigid Walled Enclosure Couple to a Flexible Wall using Matlab and Ansys APDL

Generally, solutions to improve the noise problems in enclosure are to redesign or modifying the system such as increasing the thickness of the wall panels, enhancing the elasticity of the structure, and increase the damping mechanism of the wall structure. In this paper, the application of vibroacoustic modelling of enclosure coupled to a flexible wall was presented. The sound pressure characteristics of rigid walled enclosure, such as natural frequency and mode shape were determined using two approaches which are finite element simulation of Ansys® and mathematical model. The mathematical equations derived in Matlab® such as rigid walled enclosure and rigid walled enclosure coupled to flexible wall were used to validate finite element analysis (FEA). The result indicates that the theory and FEA display in a good agreement. Thus, proved that the FE model was accurate and can be applied in further research such as sound pressure and noise attenuation in enclosure.

A Comparison of Muscular Activity among European, Korea and Malaysian During Seating Using Musculoskeletal Computational Analysis Method

Sitting is the most common posture in any industry field either in office work, manufacturing or even automotive. Sit for a long time lead to musculoskeletal disorder which causes muscle fatigue. However, different size of people will have a different level of muscle activation. The objective of this paper is to analyse and compare the muscle activation during sitting among European, Korean, and Malaysian. The human size employed for this study is by 95th percentile male. The AnyBody Modelling Software is used to simulate and analyse the human muscle activity of the seating posture of these respective countries. Our finding showed that the trunk of the human body has the highest muscle activity. The Malaysian anthropometry showed the highest muscle activity in sitting posture; followed by Korean and European.