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Abstract Purpose The study of cracks behaviour in a composite plate is of significant importance in the dynamics of the Mechanical parts in order to avoid design failures due to resonance or high amplitude vibrations. Design/methodology/approach In this paper, a square glass-epoxy composite plate is adopted. The plate has four layers with symmetric and asymmetric lamination. Assuming the cracks are profound as defects. The results were obtained by using a numerical solution of mechanical APDL from ANSYS. Findings It has been found for different boundary conditions that the rank of natural frequencies is decreased by increasing the crack ratio due to the reduction of the plate’s stiffness, whereas the crack direction has no mentioned effect for a small angle of rotation. Research limitations/implications The accuracy of results is verified by comparing a single case of the current work with other previous investigations. Originality/value Evaluate the influence of the crack length ratio, angle of the crack rotation, boundary conditions and lamination angles on the natural frequencies of the square composite plate with glass-epoxy materials.

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Abstract: The Gough Stewart Robotic manipulator is a parallel manipulator with six-degree of freedom, whichhas six equations of Kinematics (Inverse and forward), with six variables (Lengths, Position, andOrientation). In this work derived the inverse equations, which used to compute the lengths of the linkagesand its changes depended on the position and orientation of the platform's center, then derived the forwardequations to calculate the position and orientation of the moving platform in terms of the lengths. Thistheoretical model of the kinematics analysis of the Gough Stewart has been built into the Simulink packagein Matlab to obtain the lengths, position, and orientation for the manipulator at any time of motion. The inputparameters (Position and Orientation) in inverse blocks compared with the output parameters (Position andOrientation) in the forward blocks, which show good results.

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Abstract: This work deals with Gough-Stewart robot manipulator, which has six degrees of freedom, six actuators, fixed base, and moving platforms. Here, the Jacobian matrix derived to detect the singular point in the workspace for manipulator at determinant of Jacobian matrix equal to zero, then derived the equation of motion from the dynamic analysis by Lagrange method to verify the singular points with Jacobian where the forces increase rapidly at this point. Finally, design blocks in Simulink include the Jacobian matrix and the equations of motion to detection the singularities at any time for current input parameters (X, Y, Z, α, β, γ), where the determinant of the Jacobian equal to zero at maximum forces.

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Abstract In the present work the effect of residual stress on the fatigue behavior of 2024 Aluminum alloy was studied experimentally and numerically using finite element method with aid of ANSYS-11 software. All the test specimens treated by annealing before any process to remove the internal stresses due to cold work. Residual stresses were imparted to the fatigue tests specimens by heat treatment, pre-strain and welding. X-Ray diffraction was used to measure the residual stress. The heat treatment; done on the test specimens with different temperature of (420, 450, 480, and 510) C. After heat treatment; alloy mechanical properties were improved. For the heat treated specimens as the temperature increased the compressive residual stress increased to (27.06, 41.43, 72.8 and 85.6) MPa. That leads to increase the endurance fatigue limit by (32.93%, 40.48%, 50.68% and 61.03%) respectively than other alloy as received. While in pre strain groups; the test specimens loaded to (265, 290, 315 and 340) MPa by a tension test machine. As the applied load series were increased the compressive residual stress increased to (16.51, 25.62, 51.54 and 62.44) MPa which improve the endurance fatigue limit by (7.68%, 16.19%, 24.98%, and 46.45%), respectively. An electrical arc and metal inert gas were used in welding series to weld the test specimens, that present a tensile residual stress of (76.93 and 72.66) MPa, which reduces the endurance fatigue limit by (23.45% and 16.08%), respectively. The numerical results present fatigue behavior, deflection and stress at any load, and show a reasonable agreement results with an experimental one. Keywords: Residual stresses, Fatigue, X-Ray diffraction. o

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Abstract In this paper, Gough Stewart parallel manipulator with six-degree of freedom used as a model to derived the inverse kinematics equations and inverse dynamic equations. The inverse kinematic problem is very simple to derive then used to computed the jacobian matrix and the lengths of the linkages to determine the path trajectory of the moving platform. The dynamic equation based on the Lagrange method by calculated the kinetic and potential energies for the model. The dynamic equation inserted in Simulink block as Matlab file lead to computed the forces of the linkages at any time of simulation and can be used to explain if the path contain a singularities where the forces increasing very quickly in singular point compare with other points during the path of the moving platform. Finally, these blocks can be used in the other models with different parameters inputs.

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AbstractThe Gough Stewart Robotic manipulator is a parallel manipulator with six-degree of freedom, which has six equations of inverse and forward with six variables. This paper model of the Gough Stewart has been built into the MSC ADAMS software and its motion based on the inverse equations of the Stewart. Then compare the obtained results from the software with the results, which obtained from theoretical model.

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A general investigation was done in the present work to study the effect of the residual stresses on the fatigue behavior for 2024 aluminum alloy. The residual stresses were introduced from different sources (heat treatment, pre-strain, and welding) and measured by X-Ray diffraction. All the test specimens were treated by annealing before any test. For heat treatment, groups were heated to (420, 450, 480, and 510) oC up 30 min, then quenched in water (at room temperature), and followed by natural aging (stayed at room temperature for seven days(. After heat treatment at 510 oC, an 85.6 MPa compressive residual stress has been introduced, leading to improve the mechanical properties (yield stress, ultimate stress, and hardness) by (45.83%, 42.53%, and 72.88%), respectively, while the elongation was decreased by (40%). The fatigue strength at 106 for this alloy was improved by (61.03%) as compared with the same alloy as received. For pre strain, groups were loaded to (265, 290, 315 and 340) MPa by a tensile testing machine. All these loads were between the yield and ultimate strengths. When loaded to 340 MPa, a compressive residual stress of 62.448 MPa was generated, which leads to improve the fatigue strength by (46.453%), while for welding series, the fatigue strength decreased by (23.452%) due to the 76.9345 MPa of residual stress with using arc welding in width direction. A finite element model was used to compare and satisfy the results of (fatigue life, deflection, and stress) at any load. The comparison exhibits that the error is not more than 13% between the experimental results and numerical analysis, These errors due to the condition of expermental work were not exact and can not be controlled at this condition, such as the environment, equipments, and surface finishing.

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Real-time motion control is basically dependent on robot kinematics analysis where there is no unique solution of the inverse kinematics of serial manipulators. The predictive artificial neural network is a powerful one for finding appropriate results based on training data. Therefore, an artificial neural network is proposed to implement on Arduino microcontroller for a 4-DOF robot manipulator where the inverse kinematics problem was partitioned to suit the low specification of the board CPU. With MATALB toolbox, multiple neural network configuration based were trained and experienced for the best fit of the dimensionless feedforward data that is obtained from the forward kinematics of reachable workspace with average MSE of 6.5e-7. The results showed the superior of the proposed networks reducing the joints error by 90 % at least with comparing to traditional one. An Arduino on-board program was developed to control the robot independly based on pre validated parameters of the network. The experimental results approved the proposed method to implement the robot in real time with maximum error of (± 0.15 mm) in end effector position. The presented approach can be applied to achieve a suitable solution of n-DOF self-depend robot implementation using micro stepping actuators.

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Purpose: This paper aims to improve an active suspension system of vehicles by developing an optimal control strategy. Design/methodology/approach: This work proposes a Linear Matrix Inequality (LMI) hybrid based on Liner Quadratic Integral LQI. The LMI-LQI hybrid closed-loop control is used to enhance the main parameters for the closed-loop control of the active suspension system to compensate for the dead zone nonlinearity effect in the actuator and enhance the dynamic performance of the system. An active suspension system of a quarter-vehicle with 3 DOF is considered to examine the system. Findings: MATLAB/Environment was used to simulate a comparison between the proposed active control LMI-LQI system with dead zone input performance and active control LMI-LQI system performance with passive system performance. Research limitations/implications: It is concluded that the proposed hybrid control improves the system performance in terms of ride comfort and safety by reducing the RMS (root mean square) seat acceleration by 93% for the LMI-LQI control system with dead zone input and 97% for the LMI-LQI system compared to the passive system. In addition, the suspension travel is reduced by 82% compared to the passive system. Originality/value: The LMI-LQI control technique is proposed to design active suspension systems. According to the simulated results, the controller action is robust and realisable because it has the potential to minimise the nonlinear effect of the dead zone and the vertical acceleration, thus enhancing ride comfort. © by International OCSCO World Press. All rights reserved. 2023.