Influence of thickness variation on the buckling load in plates made of functionally graded materials

n this paper, a simply supported plate made of Functionally Graded Materials (FGM) with linearly varying thickness is considered. The material properties are assumed to vary as a power law though the plate thickness. Based on higher-order theory assumptions, the equilibrium, stability equations and the relations for pre-buckling loads of the plate under mechanical load are obtained using a variational formulation. The equations are based on Love-Kirchhoff hypothesis and the Sanders non-liner strain-displacement relations. The closed form solution for the buckling load is obtained and the result is verified against known case i.e. a plate with constant thickness. The buckling load is derived by employing the weighted residual approach. Finally, different plots indicating the variation of buckling load vs. different FGM materials, geometries and loading conditions were obtained

Intelligent modelling and active vibration control of flexible manipulator system

Unwanted vibration of flexible manipulator results in unsatisfactory performance of any dynamic system using the flexile manipulator. This paper presents a robust control strategy in order to suppress undesirable vibration due to flexible manipulator maneuver. First, the appropriate model of the flexible manipulator is extracted by applying the control-model identification technique for linear and nonlinear model, namely, autoregressive with exogenous input (ARX) model and nonlinear ARX (NARX) respectively. The linear model is estimated by recursive least square method (RLS) and nonlinear model identified by artificial neural network (NN). Finally, the PID controller is designed for each proposed model to cancel the vibration of the flexible manipulator. The robustness of the controller is evaluated by imposing new disturbances into the linear and nonlinear systems. System identification and controller design is conducted by numerical and simulation approaches. The results from simulation indicate that performance of PID controller using linear model is satisfactory compared to nonlinear model

The post-buckling behavior of the composite plates with embedded shape memory alloy subjected to combined loading using finite element method

Thin composite structures that are used in aerospace applications can be subjected to buckling failure due to combined mechanical and thermal loadings. This paper presents the work on the thermal post-buckling improvement of composite plates previously subjected to mechanical loading. Pre-strained shape memory alloy wires were embedded within laminated composite plate so that the recovery stress that can improve strain energy of the plate can be induced when the wires were heated. A geometric non-linear finite element formulation of the shape memory alloy composite plate and its source codes were developed. The formulation is based on total strain for the case of mechanical loading and incremental strain for the case of thermal loading. Using the codes, post-buckling paths were determined for quasi-isotropic and anti-symmetric cross-ply composite plates. It was found that by embedding shape memory alloy wires within composite plates, thermal post-buckling paths can be improved significantly even after the degradation of the thermal buckling resistance of composite plates due to the application of the mechanical loading

Theoretical Analysis and Finite Element Simulation of Behavior of Laminated Hemispherical GRP Dome Subjected to Internal Pressure

Abstract. Finite element simulation employing ABAQUS software and theoretical approaches are used to analyze the behavior of hemispherical GRP dome subjected to internal pressure. Static internal pressure and fiber angle orientation effects on meridian stress values distribution at the middle of each ply are studied. Each ply is assumed to have same thickness. Composite layup is also assumed to be symmetrical. Moreover, Language of technical computing MATLAB software is used to acquire analytical results. Meanwhile, the analytical solutions are checked through finite element simulation for validation. Static internal pressure and fiber angle orientation both are proved to linearly effect on stress distribution values in a lamination

Factors that Influence the Quality of Life Among Undergraduate School of Quantitative Sciences (SQS) Students in Universiti Utara Malaysia (UUM)

The concept of quality of life broadly encompasses on how an individual measures the goodness of multiple aspects of their life, as there are number of challenges to develop a meaningful understanding of the quality of life. The purpose of this study is to identify the factors that contribute to the quality of life among undergraduate SQS students. The respondents of this cross-sectional study were 273 undergraduate students from School of Quantitative Sciences, which was selected via convenient and snowball non-probability sampling method. The collection of the primary data was performed using a questionnaire including demographic and quality of life questions. Analysis of the data was conducted through Statistical Package for the Social Sciences (SPSS) version 2.6. All the 32 items are tested for its’ reliability using the Cronbach’s alpha, and KMO’s. The values are 0.891 and 0.876 respectively. According to the results, there are six factors that contribute/ influence the QoL for the undergraduate SQS students that involved in this study, which are family, friends, academic, social wellbeing, physical and financial, and environment. The value of Cronbach alpha for each factor indicates that the reliability of internal consistency is high and reliable and the KMO’s value for the factor pattern is meritorious and the Bartlett's test of sphericity also resulted with a significant value of p < 0.05

Factors that Influence the Quality of Life Among Undergraduate School of Quantitative Sciences (SQS) Students in Universiti Utara Malaysia (UUM)

The concept of quality of life broadly encompasses on how an individual measures the goodness of multiple aspects of their life, as there are number of challenges to develop a meaningful understanding of the quality of life. The purpose of this study is to identify the factors that contribute to the quality of life among undergraduate SQS students. The respondents of this cross-sectional study were 273 undergraduate students from School of Quantitative Sciences, which was selected via convenient and snowball non-probability sampling method. The collection of the primary data was performed using a questionnaire including demographic and quality of life questions. Analysis of the data was conducted through Statistical Package for the Social Sciences (SPSS) version 2.6. All the 32 items are tested for its’ reliability using the Cronbach’s alpha, and KMO’s. The values are 0.891 and 0.876 respectively. According to the results, there are six factors that contribute/ influence the QoL for the undergraduate SQS students that involved in this study, which are family, friends, academic, social wellbeing, physical and financial, and environment. The value of Cronbach alpha for each factor indicates that the reliability of internal consistency is high and reliable and the KMO’s value for the factor pattern is meritorious and the Bartlett's test of sphericity also resulted with a significant value of p < 0.0

Dynamic response of aluminium sheet 2024-T3 subjected to close-range shock wave: experimental and numerical studies

Abstract This present study investigates experimentally and numerically the behaviour of 1 mm thick aluminium 2024-T3 alloy sheets from near field shock waves. A comparison and examination are undertaken with respect to global deformation and plastic damage formation from two different stand-off distances of 4 mm and 50 mm that were exposed to a constant charged mass. A 4-cable instrumented pendulum blast set-up was used to carry out and monitor the blast test. The results of the blast test were subsequently used to simulate the pressure history for different stand-off distances. The simulation involved implementing a user subroutine in ABAQUS/Explicit solver to model non-uniform pressure fields for use in finite element simulation. The results provided a strong alignment of the numerical method when compared with the experimental data. The main outcome of this study is to show the significant effect of the changing damage from highly localised perforation to global deformation when the stand-off distance is changed from 4 mm to 50 mm

Stress analysis of torispherical shell with radial nozzle

The high stresses at intersections are caused by discontinuity shear stresses and moments which exist to maintain compatibility at the junction. The finite element method was used to determine the stress field at the intersection of a radial nozzle attached to a torispherical crown of a cylindrical vessel. The mechanical loads acting on the stru c t u re consisted of nozzle thrust, bending moment, torsion and internal pre s s u re. A comparison between predicted and measured readings gave acceptable results for internal pre s s u re loading but fair for other loadings. A computer program was written to calculate interaction between any two combining loads. The results, presented graphically, could be used to predict first yield for vessels of this configuration

Transmission conditions between carbon fiber and epoxy matrix for thin interphases

Fiber/matrix adhesions are most likely to control of the overall mechanical behavior of fiber-reinforced composite materials. In this work, non-linear transmission conditions have been evaluated for a thin intermediate layer which can be considered to be the interphase in an elastoplastic epoxy matrix. The intermediate layer which is situated between two carbon fibers is assumed to be very small in thickness in comparison with those of the surrounding materials. Verification with the numerical simulation based on finite element method (FEM) has shown high accuracy of the derived transmission conditions