Papers by Keyword: Dynamic Analysis

Abstract: The suspension system is crucial for durability testing, vibration analysis, and evaluating the smoothness and stability of vehicles. Leaf springs are commonly used in suspension systems of heavy-duty trucks. This study analyzed the durability using finite element analysis (FEA) and modeled a dual-leaf spring system on the HOWO truck, a popular vehicle in Vietnam. The research team compared the stress, displacement, and vibration of dual leaf springs made from two materials: steel and E-glass. Durability testing was conducted using HyperWorks software, and the team successfully built a vibration simulation model of the leaf spring suspension system using Matlab-Simulink software. The results showed that the stress in the E-glass material was lower, but its displacement was larger compared to steel, indicating that E-glass provides better smoothness than steel. The auxiliary springs only engage when the load on the main springs exceeds their capacity. Leaf springs made of E-glass showed slower damping of vibrations than steel but provided better smoothness.

Abstract: This paper involves a fundamental study of a numerical method for progressive collapse resistance design of floor-to-floor joints in precast cross-wall structures. It presents a 3D numerical study of a floor-to-floor system with longitudinal and transverse ties. The model is also used to derive the post-bond behavior and the mechanism of forming catenary action concerning the bond behavior in precast cross-wall structures. The obtained results indicated the adequacy and applicability of the code specifications in British Standard, Euro Codes, and DoD 2013. Discrepancies in the tie-force between the numerical results and codified specifications have suggested an inappropriate use of the current TF method, hence, an improved model based on the numerical results has been proposed to address this concern. To the authors’ best knowledge, this is the first numerical study to investigate the behavior of floor-to-floor joints following the removal of wall support in typical precast cross-wall structures when considering bar fracture and pull-out failure mode..

Abstract: The dynamics of the micro-cantilever with linearly varying width under electrostatic actuation is presented. The restraining displacement and voltage dissociating the unstable and stable operating region are determined by Bubnov-Galerkin approach. The influence of the variation in geometry of micro-beam and change in material parameters on the pull-in conditions is investigated. The increase of 24.27% is obtained in pull-in displacement when the tip width is reduced to 0.

Abstract: With no beams, reinforced concrete flat slab buildings are typically built to advance urban growth and to meet the architectural needs of large spans and low storey heights. Its behaviour to avoid a progressive collapse must therefore be investigated. In this research, the progressive collapse resistance of six-storey RC flat slab buildings with varying span lengths and floor heights is assessed by subjecting the building to three different instances of instantaneous removal of columns in the first storey, performing dynamic progressive collapse analysis as per GSA guidelines, and comparing the evaluated joint displacements and chord rotations at column removal locations with the permissible chord rotation for flat slab buildings as per DoD guidelines. The results have shown that the studied flat slab building with all different span lengths and floor heights is prone to progressive collapse. It is also observed that the vertical displacements and chord rotations at column removal positions increase as the span lengths and storey heights are increased alternately.

Abstract: Wavelet Transform (WT) and Wavelet Packet Transform (WPT) approaches have shown great promise in the field of signal analysis in recent decades. The main merit of these methods is their capability in localization of each signal in distinct time or space interval. However, the frequency resolution of such transformation is relatively poor in high frequency regions. The WPT, which is an extended form of the WT, provides a complete level-by-level signal decomposition. Therefore, a frequency analysis creates an arbitrary time. In this study, dynamic transient analysis is performed employing a finite element software (ANSYS) on a beam and acceleration time history of various points is investigated. Then, the captured signals are decomposed to the wavelet packet components using MATLAB and energy rate index is calculated for each component utilizing a wavelet packet rate index (WPERI). The results indicate that not only are the obtained index values sensitive, but they also are precise for the crack identification.

Abstract: It is important to improve dynamic performance of rotating machinery by reducing the mass of shaft and increasing the natural frequency. Many studies have focused on dynamic characteristics of shaft in rotating machinery with the utilization of composite material. This paper mainly investigates the structural design and dynamic analysis of a CFRP/Metal hybrid shaft. The finite element method (FEM) has been used to determine the selection of design variables include fiber orientation angle, layers stacking sequence and layers thickness. Also, experimental test was carried out using a FFT analyzer with impact hammers. The differences between the FEM analysis result and the experiment test result were respectively less than 4.5% and 6.3% for the first two natural frequencies; therefore, the results of FEM analysis are acceptable. The results reveal that the fiber orientation angle is the most significant factor affecting the dynamic characteristics of CFRP/Metal hybrid shaft. In addition, there have some effect of the layer stacking sequence on natural frequency.

Abstract: The publication outlines the issue of the experimental determination of modal parameters of structures using a method called operational modal analysis. The principle of the method and possible approaches of calculation of modal parameters are presented. An example of the method’s application is the determination of mode shapes and frequencies of the repaired footbridge in Kroměříž where the dynamic test was performed twice – before and after reinforcement of the structure. The results of both dynamic tests and their comparisons with the results of the calculation model performed in the ANSYS environment are presented in this article. Additionally, and integral to this article is a description of the completed footbridge reconstruction.

Abstract: This research focuses on studing the main points that concern on the behavior of reactive powder concrete (RPC) slab reinforced by smeared steel fibers subjected to impact load. The rectangular pulse force is used to represent an impact load. The material properties of the reactive powder concrete with the smeared reinforcement are simulated in the range of elastic behavior. The numerical modeling of the RPC slab structure with smeared steel fibers reinforcement is implemented by using ANSYS-LS-DYNA-software. The mode shapes and frequencies values of the RPC slab model are extracted by modal analysis. Impact load analysis of the RPC slab model with smeared steel fibers reinforcement is carried out for different cases. The effect of different amounts of smeared reinforcement and different locations of impact load are investigated. The results show that the first mode shape is governing impact load problems. Also, the effect of smeared reinforcement is so small within elastic range. In addition, it is observed there is a simple ratio between amount of smeared reinforcement and maximum displacement in force vibration.

Abstract: A new approach of mechanical driving-gear dynamic analysis, which includes several modelling stages is observed in the article. On the first stage driving-gear is represented in the form of consistently connected rotation bodies. The driving-gear is represented in a graphic kind by means of the marked graph. On the second stage mathematical model of driving-gear performance with using of mnemonic rule is created. Mathematical model of mechanical driving-gear is a system of second-order regular differential equations (RDEs). The system of second-order regular differential equations is transformed into a system of first-order regular differential equations. There is a standard method for writing a higher-order RDE as a system of the first-order RDEs. On the third stage computer model of driving-gear performance using system Mathcad is created and initial data is defined. On the fourth stage the mechanical driving-gear modelling is performed and calculation data in numerical and graphical forms is obtained. This approach provides high level of the driving-gear dynamic analysis, including the received results presentation, which is especially important on the earliest stages of mechanical driving-gear design. The proposed procedure of mechanical driving-gear dynamic analysis using Mathcad software significantly decreases time and working costs on execution of such computations and helps to execute investigations related with changing of driving-gear elements parameters efficiently.

Abstract: Robot simulation has developed quickly in recent decades. Along with the development of computer science, a lot of simulation soft-wares have been created to perform many purposes such as studying kinematic, dynamic, and off-line program to avoid obstacle on manipulator robots. The main objective of this study is therefore to analyze kinematic, dynamic characteristics of an R-R robotic manipulator in order to control this robot. Newton-Euler method was used to calculate the torque acting on each joint of the robot. Then, a numerical model of the robot was established by a multi-body dynamics software to compare with the results obtained by Newton-Euler theory. After that, a feed-forward control system was created by RecurDyn/CoLink to control the end-effector of the robot following a desired trajectory. The results showed that this research can be used for efficient simulation of structural kinematics, dynamics as well as control of the real manipulator robot with the robot structure in a virtual environment.