Vietnam Journal of Mechanics

Response analysis and control of plates induced by piezoelectric actuators using finite element method

Thien M. Tran, Trieu L. Vo, Son H. Nguyen — Mon, 20 Jan 2025 00:00:00 +0700

In this article, the shape deformation of the plate bonded to the piezoelectric actuators and sensors is analyzed using the finite element method, and then controlled by an algorithm. It expresses the need to conduct the comparison between non-controllable and controlled ways with low-order finite element methods because of the low cost of investigation. The proposed method is investigated in three cases studied to compare and prove the feasibility and verification. To do these tasks, the effects of coupling between the electric and mechanical properties of piezoelectric materials draw significant attention to the material’s potential applications such as actuators and sensors. Firstly, a rectangular piezoelectric actuator with symmetrically bonded three sensors is considered. The piezoelectric actuator of the injector is implemented in the second experiment. Finally, this study is applied to control the diving board in diving sports. As the simulated results, the deformed shape of piezoelectric actuators can be computed accurately using the finite element method, demonstrating the relation between the central displacement of the piezoelectric actuator in the injector and the voltage level, being linear. An algorithm controls the shape and position of sheet metal to make a foundation and premises for the empirical process and applies it in production.

Dynamical behavior of damaged railway sleeper subjected to moving loads: Parametric study of crack properties

Thuy-Duong Le, Le-Hung Tran — Tue, 07 Jan 2025 00:00:00 +0700

This study investigates the dynamic responses of cracked beams placed on a visco-elastic foundation and subjected to moving loads. Utilizing the Euler–Bernoulli beam model, the behavior of the beams is characterized, accounting for multiple open cracks on one side with varying depths. Through the application of Fourier transform techniques and Green's function, the dynamic response of the beam is analytically determined in the frequency domain. Furthermore, an analytical model for railway sleepers is developed by integrating them with a periodically supported beam model. This integrated model enables efficient computation of the dynamic behavior of damaged sleepers, where cracks are present at specific locations. Additionally, a calculation model utilizing the finite element method is established and compared with the analytical model. The parametric study shows the influence of crack properties on the dynamic beam responses.

Investigating design parameter effects on the curvature of composite soft actuators by automated numerical simulation with Python integration

Trinh Xuan Hiep, Van Binh Phung — Tue, 21 Jan 2025 00:00:00 +0700

In the realm of soft robotics, investigating the effect of design parameters on the deformation of complex structures like soft composite actuators is a challenging task. Existing mathematical models often rely on limiting assumptions, while traditional simulation approaches demand substantial computational time and resources, hindering concurrent investigations of multiple design parameters. To address these issues, this paper introduces a new technique to expedite the deformation simulation of composite soft actuators. This automation program enables automatic modification of input parameters while preserving critical properties, constraints, and boundary conditions, resulting in a significant reduction in simulation time. Compared to traditional methods requiring approximately 60 minutes for a single task, our technique achieves the same in merely 10 minutes. The developed program is applied to analyze the impact of design parameters on the curvature of composite soft actuators, leading to the identification of optimal parameters. Through experimental verification, the reliability and efficiency of our technique are demonstrated, showing simulation results with less than a 10% error when compared to physical experiments. The proposed approach enables swift investigation of design parameter influence, facilitating the identification of optimal soft robotic structures for specific objectives. As a result, it has the potential to become a promising tool for advancing soft robotics design and analysis.

An application of the dynamic stiffness concept for vibration of three-dimensional cracked overhead crane

Dang Xuan Trong, Nguyen Tien Khiem — Fri, 15 Nov 2024 00:00:00 +0700

A simplified model is proposed for modal analysis of cracked 3D-framed overhead crane of H-form frame using the well-known dynamic stiffness method. First, the dynamic stiffness of a cracked beam is derived as the inverse of the frequency response function and used for establishing a model of the cracked beam called dynamic stiffness one. Then, the dynamic stiffness model of cracked beams is employed for representing two supporting beams in the H-form frame crane. So that a simplified model of the overhead crane is conducted as a beam with artificial elastic supports of stiffness obtained above for supporting beam. Finally, the free vibration problem of the simplified overhead crane is formulated and solved for the crane fundamental frequency analysis in dependence upon crack parameters and supporting positions. Numerical computation is accomplished for illustrating the proposed theory and providing some conclusions on the simplified model of 3D overhead cranes.

Dynamic analysis of functionally graded viscoelastic beams on the elastic foundation under multiple moving loads

Tran Van Lien, Le Thi Ha — Wed, 12 Mar 2025 00:00:00 +0700

In this paper, the dynamic analysis of the Functionally Graded (FG) simply supported beam resting on the Winkler–Pasternak elastic foundation under multiple moving loads is investigated by using Timoshenko beam theory and the Kelvin–Voigt damping model. The material properties of the FG beam vary continuously in the thickness direction. The Mori–Tanaka homogenization model is used to determine the effective material properties of the FG beam. Equations of motion for the beams are established based on the Finite Element Method (FEM). The effects of different material distributions, velocities of multiple moving loads, distances between loads, and damping on the dynamic responses of the beam are discussed.

Prof. Nguyen Van Khang: A lifetime of dedication to mechanics and educating the young generation

Nguyen Phong Dien, Nguyen Quang Hoang — Mon, 17 Mar 2025 00:00:00 +0700

With almost 60 years dedicated to the field of mechanics and the Department of Applied Mechanics, Hanoi University of Science and Technology, Prof. Dr. Sc., People's Teacher Nguyen Van Khang made a vital contribution to educating generations of outstanding students in mechanics and mechatronics, as well as to developing multi-body mechanics in Vietnam. His enthusiasm and passion for mechanical research lasted until the final days of his life. With a burning passion and endless creativity, he always strived hard and became the leading professor in Dynamics and Mechatronics in Vietnam. He also built and maintained close scientific cooperation with many famous professors in other countries. In the bottom of the hearts of colleagues, students and his family members, Prof. Khang remains a symbol of an excellent scientist with practical expertise, extensive knowledge and dedication, as well as a steadfast Party member with unwavering determination. The professor's spirit of dedication to science and teaching will always be a valuable lesson and a motivation for students and successors to follow.