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Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformation theory
Mohammad Javad REZVANIL, Mohammad Hossein KARGARNOVIN, Davood YOUNESIAN
Front Mech Eng. 2011, 6 (4): 409-418.
https://doi.org/10.1007/s11465-011-0245-8
The response of an infinite Timoshenko beam subjected to a harmonic moving load based on the third-order shear deformation theory (TSDT) is studied. The beam is made of laminated composite, and located on a Pasternak viscoelastic foundation. By using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained. The solution is directed to compute the deflection and bending moment distribution along the length of the beam. Also, the effects of two types of composite materials, stiffness and shear layer viscosity coefficients of foundation, velocity and frequency of the moving load over the beam response are studied. In order to demonstrate the accuracy of the present method, the results TSDT are compared with the previously obtained results based on first-order shear deformation theory, with which good agreements are observed.
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Ultrasonic assisted EDM: Effect of the workpiece vibration in the machining characteristics of FW4 Welded Metal
Mohammadreza SHABGARD, Hamed KAKOLVAND, Mirsadegh SEYEDZAVVAR, Ramin Mohammadpour SHOTORBANI
Front Mech Eng. 2011, 6 (4): 419-428.
https://doi.org/10.1007/s11465-011-0246-7
This paper presents the results of experimental studies carried out to conduct a comprehensive investigation on the influence of ultrasonic vibration of workpiece on the characteristics of Electrical Discharge Machining (EDM) process of FW4 Welding Metal in comparison with the conventional EDM process. The studied process characteristics included the material removal rate (MRR), tool wear ratio (TWR), and surface roughness (Ra and Rmax) of the workpiece after the EDM and ultrasonic assisted EDM (US-EDM) processes. The experiments performed under the designed full factorial procedure and the considered EDM input parameters included pulse on-time and pulse current. The experimental results show that in short pulse on-times, material removal rate in the US-EDM process is approximately quadruple than that of the EDM process. On the contrary, in the long pulse on-times, ultrasonic vibration of work??piece leads to the reduction in the MRR. On the other hand, in short pulse on-times, the TWR in the US-EDM process is lower than that of in the EDM process, and this condition reverses with increase in the pulse on-time. Furthermore, the surface roughness of the workpiece machined by EDM process is slightly lower than that of applied to the US-EDM process.
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Gray-box modeling and QFT control for precision servo transmission systems
Xiulan BAO, Xuedong CHEN, Xin LUO, Haocheng ZUO
Front Mech Eng. 2011, 6 (4): 442-448.
https://doi.org/10.1007/s11465-011-0242-y
Precision servo transmission systems have widely been applied in industrial equipment to achieve high accuracy and high speed motion. However, due to the presence of friction and uncertainty, the characteristics of precision servo transmission systems are variant depends on the working conditions, leading to oscillation and instability in the system performances. In this paper, a grey-box model of the system is established, the model structure derived from the theoretical modeling and the model parameters are obtained by experiments using set membership identification method. This paper proposes two-degrees of freedom (2-DOF) robust position controller for a precision servo transmission system, based on the quantitative feedback theory (QFT), to achieve high accuracy and consistent tracking performance even in presence of considerable system uncertainties and friction disturbances. The results of simulate and experiment validate the effectiveness of the proposed controller.
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Identification of abnormal operating conditions and intelligent decision system
Xiuliang LI, Junjie JIANG, Hongye SU, Jian CHU
Front Mech Eng. 2011, 6 (4): 456-462.
https://doi.org/10.1007/s11465-011-0224-0
In earth pressure balance (EPB) shield construction, the “plastic flow state” is difficult to form using the soil dug in the capsule because it can cause three abnormal operating conditions, including occlusion, caking in the capsule, and spewing at the outlet of the dump device. These abnormal operating conditions can, in turn, trigger failure in tunneling, cutter-device damage, and even catastrophic incidents, such as ground settlement. This present paper effectively integrates the mechanism of abnormal operating conditions and knowledge of soil conditioning, and establishes a uniform model of identifying abnormal conditions and intelligent decision support system based on the belief rule-base system. The model maximizes knowledge in improving the soil, construction experience, and data to optimize the model online. Finally, a numerical simulation with specific construction data is presented to illustrate the effectiveness of the algorithm.
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A redundantly actuated PRPRP radial mechanism in the segment erector of a shield machine for synchronization control
Wanghui BU, Zhenyu LIU, Jianrong TAN, Jin CHENG
Front Mech Eng. 2011, 6 (4): 463-467.
https://doi.org/10.1007/s11465-011-0225-z
The shield machine is a heavy construction machine for tunnel excavation, and the segment erector is an important subsystem of the shield machine. It is difficult to achieve precise control in the 6-DOF (degree of freedom) erector in the 2-DOF 5-bar radial mechanism. Hence, this paper proposes a redundantly actuated PRPRP radial mechanism for the segment erector. When the redundant actuator is unlocked, the radial mechanism is able to adjust its posture, which has two degrees of freedom. On the other hand, when the redundant actuator is locked or produces enough pre-tightening tensile force, the PRPRP mechanism can ensure the synchronization of the two driving hydraulic cylinders along the radial direction based on the mechanical structure, which has one degree of freedom. The redundant actuator also facilitates the equal application of two flexural torques at the hydraulic cylinders; thus, preventing the overload of a single cylinder.
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11 articles
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