Torsional Vibration Analysis of Complicated Multi-Branched Shafting Systems by Modal Synthesis Method

2003 ◽  
Vol 125 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Chun-Ping Zou ◽  
Duan-Shi Chen ◽  
Hong-Xing Hua
Keyword(s):  
Torsional Vibration ◽  
Vibration Analysis ◽  
Synthesis Method ◽  
Synthesis Methods ◽  
Elastic Coupling ◽  
Improved Method ◽  
Modal Synthesis ◽  
Rigid Connection ◽  
Flexible Connections ◽  
Fixed Interface

The torsional vibration calculations of the complicated multi-branched system with rigid connection and flexible connections made up of elastic-coupling parts are very difficult to perform using conventional methods. In this paper, a modal synthesis method of torsional vibration analysis for the system is proposed. This approach is an improved method of Hurty’s fixed-interface and Hou’s free-interface modal synthesis methods. Because of the introduction of flexible substructure, the improved modal synthesis method can effectively treat the complicated system in which there exists a rigid connection and a flexible connection that is formed by an elastic-coupling part. When the calculation is performed, the complicated multi-branched system is divided into several substructures that are analyzed by FEM (finite element method) except the special elastic-coupling part that is defined as flexible substructure and treated individually. The efficiency of modal synthesis is improved by choosing suitable number of lower-frequency modes in modal synthesis. As an example of an application of this method, the analysis of torsional vibration of a cam-type engine shafting system is carried out both numerically and experimentally. The results show that the above kind of multi-branched shafting system can be analyzed effectively by the proposed method.

Modal synthesis method of lateral vibration analysis for rotor-bearing system

2002 ◽  
Vol 80 (32) ◽  
pp. 2537-2549 ◽  
Author(s):  
Chun-Ping Zou ◽  
Hong-Xing Hua ◽  
Duan-Shi Chen
Keyword(s):  
Vibration Analysis ◽  
Synthesis Method ◽  
Lateral Vibration ◽  
Modal Synthesis ◽  
Rotor Bearing ◽  
Bearing System

COMPARING AND IMPROVING THE SYNTHESIS OF STATE-BASED SPECIFICATIONS FROM SCENARIO-BASED SPECIFICATIONS

2012 ◽  
Vol 22 (07) ◽  
pp. 867-890
Author(s):  
ZHIJIAN WANG ◽  
WENRUI LI ◽  
PENGCHENG ZHANG
Keyword(s):  
Synthesis Method ◽  
The State ◽  
Experimental Comparison ◽  
Synthesis Methods ◽  
User Requirements ◽  
State Machines ◽  
Analysis Method ◽  
Improved Method ◽  
Local Synthesis ◽  
Novel Algorithm

The scenario-based specifications are popularly used to capture user requirements. The state-based specifications are very appropriate to capture system design. Recently, there has been increased research interest in connecting these two kinds of specifications, called synthesis. Synthesis is a way to automatically construct the state-based specifications from the scenario-based specifications. There are two kinds of synthesis methods: global synthesis and local synthesis. Global synthesis means constructing a state-based specification for the whole system from the scenario-based specifications, while local synthesis means constructing a state-based specification for each object in the system. The two different synthesis methods have different uses and need to be systematically compared. The contributions of this paper are twofold. Firstly, we propose an improved method supporting the global and the local synthesis of state machines (a kind of state-based specifications) by using a novel algorithm for state machine execution and an algorithm similar to operator priority analysis method, which can fully automate the process of synthesis. Our synthesis method also satisfies two important properties: completeness and soundness. Secondly, to the best of our knowledge, our work does the first attempt to systematically compare global synthesis with local synthesis, and shows some insightful results of the experimental comparison between the two kinds of synthesis methods, which are valuable for the practitioners to choose an appropriate synthesis method for the analysis and verification of the system.

scholarly journals Fast structural dynamic modeling and analysis for horizontally folding wing

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
Y. Ni ◽  
W. Zhang ◽  
Y. Lv
Keyword(s):  
Dynamic Modeling ◽  
Structural Dynamics ◽  
Dynamic Characteristics ◽  
Synthesis Method ◽  
Finite Model ◽  
Dynamics Modeling ◽  
Structural Dynamic ◽  
Modal Synthesis ◽  
Folding Wing ◽  
Fixed Interface

To investigate the structural dynamic characteristics of a folding wing effectively, a fast structural dynamic modeling approach is proposed. Firstly, the interface compatible relationship of the traditional fixed interface component modal synthesis method is modified, and the internal force of the interface is completely expressed in the structural dynamic equation, so that the influence of the connection stiffness on the wing structure dynamics can be considered. Then, on the basis of the fixed interface component modal synthesis method, the main mode of fixed-loaded interface is introduced to establish the mixed-loaded interface component modal synthesis method, which makes it feasible to accurately reflect the influence of elasticity and inertia of fuselage and outer wing on inner wing. The structural dynamics modeling method based on two different kinds of component modal synthesis method analyzed and deduced in detail. The application of component modal synthesis method in the fast structural dynamics modeling of folding wing is achieved. The whole program is compiled in MATLAB. At the same time, the dynamic characteristics of the folding wing with different folding angles, different connections and different connection positions is investigated. The results of the method proposed in this paper are compared with the results of the repeated finite model established in MSC.NASTRAN to verify the effectiveness from the aspects of natural frequency and vibration mode.

Component Modal Synthesis Methods Based on Hybrid Models, Part I: Theory of Hybrid Models and Modal Truncation Methods

1994 ◽  
Vol 61 (1) ◽  
pp. 100-108 ◽  
Author(s):  
L. Jezequel ◽  
H. D. Seito
Keyword(s):  
Synthesis Method ◽  
Integral Operators ◽  
Hybrid Models ◽  
Force Distribution ◽  
Synthesis Methods ◽  
Displacement Distribution ◽  
New Methods ◽  
Modal Synthesis ◽  
Intermediate Problem ◽  
Modal Truncation

The assembly of structures along continuous boundaries poses great difficulties for expressing generalized boundary coordinates in modal synthesis, especially in the context of experiments. In order to solve such problems, a hybrid modal synthesis method is proposed in this study. This approach is based on the intermediate problem theory of Weinstein and brings out the duality between the formulation in displacement and the formulation in force. Generalized boundary coordinates are defined by introducing static deformations resulting from force distribution or displacement distribution along the boundaries depending on which formulation is to be used. By introducing integral operators associated with intermediate problems, two new methods of modal truncation can be proposed.

scholarly journals A Combination of Modal Synthesis and Subspace Iteration for an Efficient Algorithm for Modal Analysis within a FE-Code

2003 ◽  
Vol 10 (1) ◽  
pp. 27-35 ◽  
Author(s):  
M.W. Zehn
Keyword(s):  
Eigenvalue Problem ◽  
Modal Analysis ◽  
Efficient Algorithm ◽  
Degrees Of Freedom ◽  
Synthesis Method ◽  
Problem Solver ◽  
Synthesis Methods ◽  
Combined Method ◽  
Subspace Iteration ◽  
Modal Synthesis

Various well-known modal synthesis methods exist in the literature, which are all based upon certain assumptions for the relation of generalised modal co-ordinates with internal modal co-ordinates. If employed in a dynamical FE substructure/superelement technique the generalised modal co-ordinates are represented by the master degrees of freedom (DOF) of the master nodes of the substructure. To conduct FE modal analysis the modal synthesis method can be integrated to reduce the number of necessary master nodes or to ease the process of defining additional master points within the structure. The paper presents such a combined method, which can be integrated very efficiently and seamless into a special subspace eigenvalue problem solver with no need to alter the FE system matrices within the FE code. Accordingly, the merits of using the new algorithm are the easy implementation into a FE code, the less effort to carry out modal synthesis, and the versatility in dealing with superelements. The paper presents examples to illustrate the proper work of the algorithm proposed.

Component Modal Synthesis Methods Based on Hybrid Models, Part II: Numerical Tests and Experimental Identification of Hybrid Models

1994 ◽  
Vol 61 (1) ◽  
pp. 109-116 ◽  
Author(s):  
L. Jezequel ◽  
H. D. Setio
Keyword(s):  
Synthesis Method ◽  
Hybrid Models ◽  
Synthesis Methods ◽  
Mass Loading ◽  
Frequency Range ◽  
Compatibility Conditions ◽  
Experimental Identification ◽  
Numerical Tests ◽  
Modal Synthesis ◽  
Vibration Tests

A double modal synthesis method in which compatibility conditions at substructure interfaces are ensured by the introduction of loaded modes is presented in this study. These loaded modes, which are obtained by introducing mass loading or stiffness loading along the boundaries, are used to define generalized boundary coordinates. Thus the hybrid models presented in the first part of this study are developed so that they can be derived from test data as results of independent modal identifications. Unlike in classical modal synthesis methods, in this double modal synthesis method, it is not necessary to clamp the interfaces, which is always difficult to carry out during vibration tests. By introducing loaded modes, generalized boundary coordinates which represent boundary deformability in the frequency range under study can be defined.

Structural Dynamics Optimization Based on a Hybrid Inverse Synthesis Method Using a Quadratic Approximation

2004 ◽  
Vol 126 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Alain Schorderet ◽  
Thomas Gmu¨r
Keyword(s):  
Structural Dynamics ◽  
Shape Factor ◽  
Synthesis Method ◽  
Synthesis Methods ◽  
The Novel ◽  
Synthesis Algorithm ◽  
Numerical Examples ◽  
Dynamic Constraints ◽  
Modal Synthesis ◽  
Synthesis Approach

This paper lies within the framework of the so-called redesign problem of structures subjected to dynamic constraints. A hybrid synthesis algorithm is developed, combining the truncated modal basis of the initial system and the spatial or material co-ordinates of an added component, which is modelled with shell-type finite elements parameterized with respect to a shape factor. Based upon a quadratic inverse formulation, the proposed technique shows several advantages in comparison to other synthesis methods, such as a refined sensitivity strategy, a powerful modal synthesis approach and a simplified optimization phase. Numerical examples are provided illustrating the capabilities of the novel procedure.

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