DSpace Program:http://hdl.handle.net/123456789/1252019-11-20T12:45:26Z2019-11-20T12:45:26ZVibration Reduction by Command Shaping on Flexible Rotating Beam Under the Effect of GravityWorood Al-Munayyeshttp://hdl.handle.net/123456789/8562019-05-14T08:51:44Z2018-01-01T00:00:00ZTitle: Vibration Reduction by Command Shaping on Flexible Rotating Beam Under the Effect of Gravity
Authors: Worood Al-Munayyes
Abstract: Multiple sources of vibration exist in the environment, and their presence usually lead to
undesired events. Input shaping is a technique developed for minimizing residual vibrations
in rest-to-rest maneuvers. In this work, a smooth sine based waveform command shaping
profile is proposed to reduce residual vibrations of a vertically rotating flexible beam in restto-
rest maneuvers under the effect of gravity. The system contains nonlinearities with infinite
modes of vibration. The equation of motion is determined and then discretized for simplicity.
Only the first mode is considered because it is the only effective mode in the system. The
system inputs include the maneuvering time, maximum velocity, and final rotational angle.
A comparison is performed between the uncontrolled system, double-step technique, smooth
command shaping technique with optimization, and the smooth command shaping technique
without optimization. The respective techniques were applied in different cases with varying
maximum velocities, flexible beam lengths, and maneuvering times. The smooth command
shaping technique with optimization provided the best result in terms of eliminating residual
vibrations in rest-to-rest maneuvers. Its performance is followed by that of the command
shaping technique without optimization, and then that of the double-step strategy. The
command shaping technique proved to be very effective when compared with the
uncontrolled system. The results showed that the effect of nonlinearities arises as the
maximum velocity and beam length increase or maneuvering time decreases. Additionally,
the results show that optimizing the shaper parameters considerably reduces the residual
vibrations.2018-01-01T00:00:00ZAnalysis of Multi-Sectioned Beam VibrationsAbdullah A. Al Ajeelhttp://hdl.handle.net/123456789/7552019-03-28T08:50:58Z2018-01-01T00:00:00ZTitle: Analysis of Multi-Sectioned Beam Vibrations
Authors: Abdullah A. Al Ajeel
Abstract: Beams are widely used in the industrial sectors where they usually have an uneven shape, multi-sections, different densities, and varying widths and thicknesses. Many re-searchers tend to simplify the system by assuming even shapes or by using Finite Element Methods (FEM) to predict the dynamic behavior or to control such systems. It is well known that, these methods might find a solution but it is either inaccurate or mathematically chal-lenging. Finding reduced order equations greatly simplifies the prediction of the dynamic be-havior and the choice of proper control scheme.
In this work, a mathematical method to reduce the partial differential equation of mul-ti-sectioned beams to ordinary differential equation is proposed. The beam nonlinear equation of motion is derived by utilizing Hamilton’s principle. This equation is linearized and then reduced by adopting Galerkin’s Method. The linear natural frequenciesarecalculated analyti-cally by using Maple and validated numerically using FEM.The generated analytical solution isdesigned to solve complex models fora multi-thicknesses cantilever beam which is separat-ed into multiple segments. Each segment can have different thickness, density, or shape but with common width. The change in density has been utilized to determine the effect of piezo-electric actuator dimensions and locations on a beam’s natural frequencies. Finally In order to study the effect of beam segmentsonthe natural frequencies,multi-sectioned examples are cal-culated analytically using the proposed method and validated numerically using FEM.
The results show that the analytical and FEM natural frequencies are almost identical for both uniform and non-uniformed cantilever beams with a minor percentage error. The same results are found as per changing the segment density. In fact, the percentage error is found to be less than 10%. The results confirm that the proposed analytical technique is suc-cessfully predicted the linear natural frequencies and can be used to predict the dynamical behavior of multi-sectioned beams with different used materials2018-01-01T00:00:00ZThe Effect of Durability and Corrosion Behavior on the Concrete Treated with Chemical InhibitorTahani Ahmad Al-Ghareebhttp://hdl.handle.net/123456789/7532019-03-28T08:51:01Z2018-01-01T00:00:00ZTitle: The Effect of Durability and Corrosion Behavior on the Concrete Treated with Chemical Inhibitor
Authors: Tahani Ahmad Al-Ghareeb
Abstract: Chloride-induced corrosion of steel reinforcement and the reaction of atmospheric carbon dioxide with cement paste are the most important causes of premature failure in marine-reinforced concrete structures. Among the available methods, corrosion inhibitors offer a simple and cost-effective technique in reducing the chloride-induced corrosion on the steel reinforced concrete. This study was conducted to evaluate the efficacy of adding two commercial concrete admixtures named Migrating Corrosion Inhibitor (MCI) and Waterproofing Concrete Admixture (HCA) to Ordinary Portland Cement (OPC) in order to protect steel reinforcement from corrosion in seawater environment, and was aimed at studying the effect of using sulphate resistant cement (SRC) in concrete mix for marine structures. The effectiveness of the inhibitors was evaluated both in the field and in the laboratory using long-term rebar corrosion monitoring in reinforced concrete, electrochemical corrosion testing techniques, corrosion potential and also through rebar visual inspection. The evaluation was performed on two different types of concrete mixes and two different water cement (w/c) ratios of 0.4 and 0.6 with regular steel rebar. From the tests and study, the compressive strength and water absorption of the concretes cured with fresh water is better performance than those cured with seawater. The concretes mixed with admixtures (MCI and HCA) have lower water absorption than the control mix, which have an OPC and no inhibitors. The HCA mixed concrete samples showed the better compressive strength and water resistance than the MCI mixed concrete samples at same w/c ratios. The concrete samples injected with MCI and HCA have higher corrosion resistivity compared to the concrete samples without admixture chemicals. Whilst injection of HCA in OPC Concretes improved the corrosion resistivity than injection of MCI.2018-01-01T00:00:00ZA Modified Smooth Wave-Form Shaped Command for Overhead Cranes with HoistingSara A. Barghashhttp://hdl.handle.net/123456789/7472019-03-28T08:50:51Z2016-01-01T00:00:00ZTitle: A Modified Smooth Wave-Form Shaped Command for Overhead Cranes with Hoisting
Authors: Sara A. Barghash
Abstract: A method of reducing the residual vibrations in rest-to-rest crane maneuvers and
smoothing crane operating input is proposed. Several researchers have discussed this
problem and implemented different methods and various input functions. Optimization
techniques were also applied to find the optimal performance according to their own
models. A smooth input command profile using a harmonic function is proposed in this
work. The modified input shaped-command profile is analytically generated, and
numerically simulated and validated, on an overhead crane considering both the payload
hoisting and no-hoisting cases. The new input was tested for different maneuvering
times, different cable lengths, and different hoisting speeds. The input function
parameters were determined to satisfy system constraints, and to optimize system
performance. The generated input was compared with the command profiles obtained by
earlier works to prove the improvement of the new input over the earlier ones. The
obtained results showed that the new input shaper produces a smoother output, and
transfers the payload in less time. Also, the proposed input has a lower sensitivity to
changes in the crane cable length. The proposed input command profile is more efficient
and easier to apply, and it reduces the swing angle regardless of the cable length or the
maneuvering time.2016-01-01T00:00:00Z