Vibration analysis of a plate with an arbitrarily orientated surface crack

This research presents a vibration analysis for a thin isotropic plate containing an arbitrarily orientated surface crack. The work has been motivated by the well known applicability of various vibrational techniques for structural damage detection in which the detection and localisation of damage to thin plate structures at the earliest stage of development can optimise subsystem performance and assure a safer life, and is intended to be an enhancement to previous work on cracked plates for which the orientation of the crack angle was not included. The novelty of this research activity has been in the assimilation of a significantly enhanced crack model within the analytical model of the plate, in modal space, and taking the form of a specialised Duffing equation. The governing equation of motion of the plate model with enhanced crack modelling is proposed to represent the vibrational response of the plate and is based on classical plate theory into which a developed crack model has been assimilated. The formulation of the angled crack is based on a simplified line-spring model, and the cracked plate is subjected to transverse harmonic excitation with arbitrarily chosen boundary conditions. In addition, the nonlinear behaviour of the cracked plate model is investigated analytically from the amplitude-frequency equation by use of the multiple scales perturbation method. For both cracked square and rectangular plate models, the influence of the boundary conditions, the crack orientation angle, crack length, and location of the point load is demonstrated. It is found that the vibration characteristics and nonlinear characteristics of the cracked plate structure can be greatly affected by the orientation of the crack in the plate. The dynamics and stability of the cracked plate model are also examined numerically using dynamical systems tools for representing the behaviour of this system for a range of parameters. Finally the validity of the developed model is shown through comparison of the results with experimental work and finite element analysis in order to corroborate the effect of crack length and crack orientation angle on the modal parameters, as predicted by the analysis. The results show excellent predictive agreement and it can be seen that the new analytical model could constitute a useful tool for subsequent investigation into the development of damage detection methodologies for generalised plate structures

Neuro modelling and vibration control of flexible rectangular plate structure

The demand for soft computing techniques in the modeling and control of dynamic system has increased in recent years especially for flexible structures. Flexible plate structures are extensively used in many space applications, however this type of structure leads to high vibration problems. The aim of this investigation is to modelling and control of two dimensional flexible plate structures. This will involve an identification system including least squares, recursive least squares, and neural networks within an active vibration control framework. A thin rectangular plates with all edges clamped is considered. A simulation algorithm characterising the dynamic behaviour of the plate is developed through a discretisation of the governing partial differential equation formulation of the plate dynamics using finite difference methods. The simulation algorithm thus developed and validated forms a suitable test and verification platform in subsequent investigations for development of vibration control techniques for flexible plate structures. The design and analysis of an active vibration control (AVC) system utilizing conventional and soft computing methods with single-input single-output AVC structure is presented to suppressing the vibration of the flexible plate structures. Finally a comparative performance of the algorithm in implementing AVC system using recursive least square (RLS), Multilayer perceptron neural networks (MLP-NN) and Elman Neural networks (ENN) is presented and discussed

Correlation of design parameters of lattice structure for highly tunable passive vibration isolator

The purpose of this study is to correlate the influence of multiple size-based design parameters of lattice structure, namely, the unit cell (UC) and strut diameter (SD) through the static and dynamics analyses for passive vibration isolation application. The lattice structures were prepared by utilizing the fused deposition modeling (FDM) additive manufacturing (AM). The samples were designed to retain lattice structure’s unique advantages while also conserving material consumption to fulfill the energy and cost demand. Through the static test, the crush behavior, failure mechanism, and mechanical properties were determined. The stiffness of lattice structure exhibited an increasing relationship with the unit cell and strut diameter where smaller unit cell and bigger strut diameter produced higher strength, and with that, higher load can be sustained. Through the dynamic vibration transmissibility test, it was found that the dynamic vibration results follow closely the trend in the static analysis. Lattice structure with larger unit cell and smaller strut diameter showed larger effective isolation region due to lower natural frequency value. The trade-off limit between stiffness for a lower natural frequency of the proposed design parameters was determined from the two parts analyses. The results suggest that most lattice isolators from the pool of design parameter combinations in this study have sufficient strength to withstand the predefined mass load and provide the most region for vibration isolation. The two proposed design parameters can later be used for a major or minor tuning of lattice isolators for other specific applications

Lattice Structure Design Parameters Optimization For The Structural Integrity Of Passive Vibration Isolator

Passive vibration isolator with lower natural frequency has always been a challenge due to structural integrity issues. This study presents the use of RSM statistical tool to analyze and optimize the mechanical responses of BCC lattice structure for structural integrity in a passive vibration isolator application. The optimization was done to obtain low stiffness for low natural frequency but high yield stress for optimum load-bearing capability with unit cell size and strut diameter design parameters tweak. From the results, the significance and contribution of each design parameter on each mechanical response through compression test can be understood. Results indicated changes in strut diameter produced linear growth while changes in the unit cell size produced inverse exponential responses. From optimization, a combination of 3.9 mm strut diameter with 10 mm unit cell size produced the optimum result. Therefore, it was demonstrated that RSM can provide statistical importance and contribution between input factors and their influence on each mechanical response with minimal test and cost

Numerical Analysis On Static And Dynamic Behavior Of Additively Manufactured BCC Lattice Structures

This research aims to investigate the effect of the strut diameter of lattice structures on their vibration characteristic numerically. The finite element analysis (FEA) method was validated beforehand in experimental work with lattice structure fabricated using fused deposition modeling (FDM) additive manufacturing (AM). From the comparison, good agreement was achieved with less than 11% error. From numerical results, it was found the stiffness values decrease with strut diameter from 1.8 mm to 1.0 mm. The first three vibration modes show steady increment around 12 Hz, 20 Hz, and 70 Hz in natural frequency respectively for acrylonitrile butadiene styrene (ABS) material and roughly 35 Hz, 60 Hz, and 200 Hz for both stainless steel and titanium as the strut diameter increase by 0.2 mm each. The validated FEA models can be used for exploration on many other materials and design parameters without having to conduct experimental work which helps for sustainability

Effect of fabric layer on sound absorption of micro-perforated panel

Micro-Perforated Panel (MPP) absorber becomes an alternative to common fibrous porous absorber without owning health and environmental issues. The system is considered as the next generation of absorber in noise control. However, such a system suffers from narrow absorption bandwidth so that its application becomes limited. Theoretically, the frequency range with effective absorption is determined by the surface acoustic impedance controlled by the perforation ratio, hole diameter and cavity depth. Hence, by keeping those parameters to be constant, an intervention to the change of impedance is expected to be useful in widening the absorption bandwidth. In this research, textile materials from woven fabrics namely cotton fabric, plain fabric and satin fabric were used to cover the surface of Micro Perforated Panel (MPP) absorber either at the front or at the back surface. The sound absorption coefficients were measured for the normal incidence using an impedance tube. From the measured results, it is found that the presence of the fabric on MPP surface can improve the MPP absorber in terms of amplitude as well as the frequency bandwidth of absorption. Moreover, the placement of the woven fabric at downstream area is more beneficial than at the upstream are

Static And Dynamic Analysis Of FDM Printed Lattice Structures For Sustainable Lightweight Material Application

This study investigated the effect of strut diameter size of fused deposition modelling (FDM) printed lattice structure on compressive performance and its relation to dynamic behaviour of the lattice structure using vibration analysis.The lattice structure samples were fabricated using FDM 3D printing/additive manufacturing (AM) technique with three sizes of strut diameters:1.2 mm,1.4 mm and 1.6 mm.Findings from compression test showed that increased in size of strut diameter would increase the compressive strength performance as well as better energy absorptions.Similar increased trend was shown in the vibration analysis as the strut diameter size increased.This study provides information that lattice structure is suitable for use in dynamic load bearing applications

Investigation On Process-Properties Relationship With Load-Bearing Performance Of Lattice-Structured Cellular Material For Lightweight Applications

Lattice structure is a periodic cellular structure which can become lightweight materials with good mechanical properties. This study characterized and examined the manufacturability of lattice structure geometry that was produced by FDM CubePro 3D-printer. The effect of process parameters on ABS lattice-structure's geometry were evaluated and their relationships were derived by using experimental approach. Dynamic behaviour of the material was explored for a better understanding of the material in real applications. The BCC lattice structure specimens were subjected with quasi-static compression and dynamic vibration loadings. Significant process parameter that influenced mechanical performance and geometrical properties for the FDM printer machine was found to be the layer thickness at 200 pm. Vibration test results show that the material's natural frequency was greatly affected by strut diameter sizes due to increase in stiffness as the strut diameter increases. The natural frequency values increase as induced damage location became farthest from clamped edge. With respect to both compression deformation and vibration behaviours of the lattice structure in this study, the material is found to be more suitable in energy absorption applications such as in car engine hood or arm parts of drone due to its bending dominated behaviour when subjected to loading