Papers by Keyword: Dynamic Characteristics

Abstract: The article examines the impact of nanodefects on the reduction of the crystals strength. A summary of the authors research results is illustrated by the analysis example of the NaCl crystal destruction process from the standpoint of strength quantum theory. As the base experiment is seen testing the dry and wet a salt crystal made by academician A. Ioffe. The authors research aim was a little-studied patterns of the crystal lattice destruction quantum mechanism. The article gives a brief historical background of the research in this area. The first section discusses the rystal cell dynamic characteristics change as a result of destruction. Assesses self-resonant frequency of an atom at a lattice point of the crystal before and after the destruction. In the second section of the article examines the relationship between the natural frequencies of the atoms in the lattice and elastic energy wich accumulated in the crystal body in the force loading process. The main attention is paid to theoretical modeling of the links strength between atoms in the crystal surface layer. We study the strength dependence of these relationships to the availability of nanodefects on the crystal surface. There are modeled bond strength to clean the crystal surface, as a result of the surface lattice electrification when atoms capture free electrons and for the case when jobs of atoms in the crack are filled with the external environment atoms. The calculations confirm the validity of the proposed theoretical model of reduction or the hanging of the crystals strength by the atoms interaction with the external environment.

Abstract: In a hierarchical system, grading wheel plays a very important role in material scattering and classifying. This article calculates the critical speed of the grading wheel rotor, a small part of the SZ spin flash dryer, based on finite element analysis software ANSYS. Meanwhile, in order to provide a theoretical evidence for the design of the grading wheel’s dynamic performance, analyze the influence of the bearing’s radial stiffness and some geometry parameters of the structure on the critical speed, including bearing stiffness, bearing span, cantilever length and wheel’s weigth. The result indicates that bearing span is approximately proportional to the critical speed, the cantilever length and runner quality are inversely proportional to the critical speed and the bearing span and the cantilever length have a greater impact on the critical speed.The final purpose of this paper is to find a set of proper parameters on the basis of the analysis result and optimize the rotor’s structure.

Abstract: This paper dedicated of introduction of dynamic model of improved mechanical system of sensor of atomic force microscope. The subject of the research is enhancement of dynamic characteristics of cantilever - main mechanical part of sensor. These characteristics defines frequency of oscillations of mentioned cantilever and are main limitations of the speed of scanning procedure of the microscope. Modification of original dynamic system of atomic force microscope made adding nonlinear additional stiffness, created by stream of compressed air. In order to determine dynamic characteristics of modified system there are necessary to create corresponding dynamic model. Parameters of such model were defined using experimental research and theoretically from 3-D model of microscope cantilever. Solution of this model brings dependencies between air gap, pressure of compressed air and oscillation frequency of cantilever. Finally, results there are presented and conclusions are drawn.

Abstract: A thermal/vibration test system was established in this paper, using which the key vibration characteristic parameters of a plate structure made of high-temperature-resistant nickel-based stainless steel in a thermal vibration coupled environment up to 1100°C (e.g., the modal frequency and modal vibration shape) were experimentally obtained. A self-developed extension configuration of a high-temperature-resistant ceramic pole was used to transfer the vibration signals of the structure to a non-high temperature zone, and the acceleration sensors were applied to identify the vibration signals. The test data were analyzed using a time-frequency joint analysis technique. The research results can provide an important basis for the dynamic performance analysis and safety design of structure under high-temperature thermal vibration conditions for hypersonic flight vehicles.

Abstract: The underwater glider is a new type of autonomous underwater vehicle driven by buoyancy. The glider hydrofoil is the key driving element of the glider, it works under complex alternative load and determines the safety of navigation of the underwater glider. This paper takes the hydrofoil as the research object, a finite element model of hydrofoil has been established and the dynamic load of hydrofoil has been calculated. Finite element model analysis was conducted to the glider hydrofoil in free and restrained states, and the preceding few orders natural frequency of the glider hydrofoil and the corresponding vibration model and the vibration amplitude in the conditions were conducted respectively. The dangerous area of the glider hydrofoil was found out, which could provide data for optimal dynamic design and dynamic modification of hydrofoil.

Abstract: According to the structure and production processing requirements of polyester filament winding head, a finite element dynamic model of the winding system in parameters time-varying was established. By using the method of numerical calculation, the dynamic characteristics of the winding head were analyzed in three processes: rapid starting-up in empty volume, winding filament process and stopping in full volume. By studying the influence of the three processing under large stiffness coupling and soft stiffness coupling in the winding head, the role of the coupling stiffness and spindle structure was revealed in different working process.

Abstract: The dynamic characteristic is one of the important indicators which determine the performance of a machine tool, in this paper, the finite element model of a plane grinder is established with consideration of the behavior of joint, the static dynamic characteristics of machine tools are analyzed to reveal the vibration weak link, the column structure is topology optimized and redesigned based on the variable density degradation method. Static and dynamic characteristics of the original and new column are compared, and the dynamic characteristics of the machine tool before and after modification are discussed. The results indicate that the static and dynamic characteristics of the plane grinder are all improved after optimization.

Abstract: This paper resolved CNC turret punch cause vibration phenomenon in the course of processing sheet,analysis of its dynamic characteristics of the beam servo feed mechanism, using the method of constrained modal analysis.Through the establishment of finite element model exactly for the servo beam and setting the boundary elastic restraint stiffness, solving the natural frequencies and mode shapes of the servo beam under boundary constraints and loading conditions. Constraints modal analysis results are consistent with experimental monitoring results of CNC turret punch servo beam. This modeling methodology and results of the analysis has a high practical value for CNC turret punch dynamic characteristics analysis and structural optimization design.

Abstract: Historical Churches in Armenia may have many experiences of earthquake ground motion. Thus, some of them have been damaged partially or severely. We had carried out the microtremor survey at a historical churches, which is Cathedral at Etchimiadzin around 5th century, to identify the dynamic characteristic. Four sensors are used simultaneously for the observations and modes of vibration are identified from some methods such as the Fourier spectrum and coherence function, and frequency domain decomposition (FDD) technique.

Abstract: The unequal leg transmission tower in mountainous areas of 5B-ZBC4 is based to establish the finite element model of three transmission tower and four wire line system. To further study the transmission tower under wind load displacement response, firstly using ANSYS analysis of the dynamic characteristics of the tower-line system. Then, taking the power spectrum of Kaimal wind speed and simulating the curve of wind speed of transmission tower line system in mountainous areas, considering the different elevation and different sizes of wind load, to analysis the wind vibration response for the tower-line coupling system. The results indicates that the tower top displacement means of 1# tower, 2# tower, 3# tower is increasing along with the elevation changes in 0 degrees wind load; The 37 m/s is the critical wind speed of 3# tower of transmission tower line system.