Majed Majeed
Kuwait University, Mechanical Engineering Department, Faculty Member
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Deformations of In-plane Loaded Unsymmetrically Laminated Composite Plates by Majed A. Majeed This study focuses on the response of flat unsymmetric laminates to an inplane compressive loading that for symmetric laminates are of... more
Deformations of In-plane Loaded Unsymmetrically Laminated Composite Plates by Majed A. Majeed This study focuses on the response of flat unsymmetric laminates to an inplane compressive loading that for symmetric laminates are of sufficient magnitude to cause bifurcation buckling, postbuckling, and secondary buckling behavior. In particular, the purpose of this study is to investigate whether or not the concept of bifurcation buckling is applicable to unsymmetric laminates. Past work by other researchers has suggested that such a concept is applicable for certain boundary conditions. The study also has as an objective the determination of the response of flat unsymmetric laminates if bifurcation buckling does not occur. The finite-element program ABAQUS is used to obtain results, and a portion of the study is devoted to becoming familiar with the way ABAQUS handles such highly geometrically nonlinear problems, particularly for composite materials and particularly when instabilities a...
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Supplemental Material for Analytical study of thermal variation impact on dynamics of a spindle bearing system by Mohammed Alfares, Omar Saleem and Majed Majeed in Proceedings of the Institution of Mechanical Engineers, Part K: Journal of... more
Supplemental Material for Analytical study of thermal variation impact on dynamics of a spindle bearing system by Mohammed Alfares, Omar Saleem and Majed Majeed in Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics
The geometrically nonlinear deformation response of initially flat unsymmetric cross-ply laminates subjected to an inplane compressive load and two sets of boundary conditions is studied. Stability of the deformations is considered. At... more
The geometrically nonlinear deformation response of initially flat unsymmetric cross-ply laminates subjected to an inplane compressive load and two sets of boundary conditions is studied. Stability of the deformations is considered. At issue is whether or not the plate remains flat with increased compressive loading, and whether it buckles. A semi-infinite unsymmetric cross-ply laminate is used to show the combined effects of geometric nonlinearities and bending-stretch coupling. Finite element results for finite laminates are then presented, and it is shown that to a large degree the boundary conditions control the character of the deformation response. It appears that clamped boundary conditions support buckling behavior, in the classic sense of bifurcation, whereas simply-supported conditions do not.
Multi-mode vibration control using single actuator and single sensor is considered as a difficult control scheme. Most researchers use multi actuators and multi controllers to control multimode structural vibrations. In the present work,... more
Multi-mode vibration control using single actuator and single sensor is considered as a difficult control scheme. Most researchers use multi actuators and multi controllers to control multimode structural vibrations. In the present work, a multi-mode control model consists of a single actuator and single sensor, both attached at the top of simply supported thin plate, is developed. A piezoelectric actuator is used and it is assumed to be perfectly bonded to the plate, which means the bonding thickness is neglected. The sensed accelerometer signal is integrated and then filtered to include only the first and the second vibration modes. The linear equations of motion of the plate are derived and discretized using Galerkin’s Method. The resulting coupled equations are combined with velocity delay feedback controller to reduce the structure vibration. Genetic Algorithm is then used to optimize controller parameters using the root mean square of the input signal as an objective function....
Changes in the thermal status of machine tools spindle-bearing system can have a noticeable effect on the performance of the machine itself, and therefore studying the thermal effect on the performance ball bearing during service is... more
Changes in the thermal status of machine tools spindle-bearing system can have a noticeable effect on the performance of the machine itself, and therefore studying the thermal effect on the performance ball bearing during service is important. For this purpose, a study was carried out where a simple rotating shaft system supported by two angular contact ball bearings was taken into consideration. Heat was generated due to the contact between the balls and rings of the bearing. This thermal effect on the dynamics of the system was studied using a transient thermal model. The system was divided into nodes; each was assumed to be a uniform temperature. Thermal energy balance was used on each node to obtain a set of differential equations. ODE solver in MATLAB was used to solve the resulting system of differential equations. The thermal model considered an initial preload as well as the thermal preload that is caused by the uneven expansion of bearing components. In this research, a 5 D...
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Great amount of work has been dedicated to eliminate residual vibrations in rest-to-rest motion. Considerable amount of these methods is based on convolving a general input signal with a sequence of timed impulses. These impulses usually... more
Great amount of work has been dedicated to eliminate residual vibrations in rest-to-rest motion. Considerable amount of these methods is based on convolving a general input signal with a sequence of timed impulses. These impulses usually have large jumps in their profiles and are chosen depending on the system modal parameters. Furthermore, classical input shaping methods are usually used for constant cable length and are sensitive to any change in the system parameters. To overcome these limitations, polynomial command shapers with adjustable maneuvering time are proposed. The equation of motion of a simple pendulum with the effect of hoisting is derived, linearized, and solved in order to eliminate residual vibrations in rest-to-rest maneuvers. Several cases including smooth, semi-smooth and unsmooth continuous shapers are simulated numerically and validated experimentally on an experimental overhead crane. Numerical and experimental results show that the proposed polynomial comma...
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Research Interests: Materials Engineering, Mechanical Engineering, Civil Engineering, Materials Science, Scanning Electron Microscopy, and 10 moreFailure Analysis, Cyclic Loading, Service Life, Brittle Fracture, Engineering Failure Analysis, Tensile Strength, Fatigue Crack Propagation, Tensile Test, Corrosion Resistance, and Post Weld Heat Treatment
Controlling multimode vibrations using a single actuator and a single sensor is challenging. Most researchers use multiactuators and multisensors to control multimode structural vibrations. In the present work, a multimode delayed... more
Controlling multimode vibrations using a single actuator and a single sensor is challenging. Most researchers use multiactuators and multisensors to control multimode structural vibrations. In the present work, a multimode delayed feedback control using a single actuator and a single sensor, both attached at the top surface of a simply supported thin plate, is developed. The linear equations of motion of the plate are derived and then discretized using Galerkin’s method. The resulting coupled equations are controlled with a velocity-delay feedback control to mitigate multimode structural vibrations. A sensed accelerometer signal is integrated and then filtered to include only the effect of the targeted vibration frequency. A global optimization method is then used by minimizing the root mean square of the total controlled response of the system. Many parameters, such as size, location, and orientation of the sensor/actuator as well as time delay and controller gain, play an essentia...
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ABSTRACT
This study focuses on the response of flat rectangular unsymmetric cross-ply laminates to a uniaxial inplane compressive edge displacement that for symmetric laminates are of sufficient magnitude to cause bifurcation buckling,... more
This study focuses on the response of flat rectangular unsymmetric cross-ply laminates to a uniaxial inplane compressive edge displacement that for symmetric laminates are of sufficient magnitude to cause bifurcation buckling, postbuckling, and secondary buckling ...
ABSTRACT
abstract Pipelines conveying gas under pressure exhibit turbulence-induced vibrations. The current work is concerned with extracting useful power from pipelines operating well within their stability region. At such regions, the pipe... more
abstract Pipelines conveying gas under pressure exhibit turbulence-induced vibrations. The current work is concerned with extracting useful power from pipelines operating well within their stability region. At such regions, the pipe vibrations exist in small magnitudes and are unlikely to cause structural failure, yet can be exploited to provide useful energy for low-power electronic devices. Accordingly, emphasis in the present work is placed on the development of an energy harvesting technique employing the omnipresent and ...
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ABSTRACT
Research Interests:
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ABSTRACT
Research Interests:
ABSTRACT