Inability of Free-Interface Modes in Representing Stress Resultants Near the Free Interface

2000 ◽  
Vol 122 (4) ◽  
pp. 409-411 ◽  
Author(s):  
Yoon Young Kim ◽  
Jeong Hoon Kang
Keyword(s):  
Theoretical Analysis ◽  
Synthesis Method ◽  
Normal Modes ◽  
Component Mode Synthesis ◽  
Coupling Method ◽  
Slow Convergence ◽  
Free Interface ◽  
Solution Convergence ◽  
Fundamental Cause ◽  
Convergence Problems

As the fundamental cause of the slow convergence of a direct free-interface component mode synthesis method, we point out the inability of free-interface normal modes in representing the stress resultants near the free interface of a substructure. Although the effects of the residual flexibility of a substructure on the solution convergence are well known, the present theoretical analysis would help understand more clearly the convergence problems of the direct free-interface substructure coupling method. [S0739-3717(00)01704-9]

A Novel Gap Element for the Coupling of Incompatible Interface in Component Mode Synthesis Method

2019 ◽  
Vol 17 (07) ◽  
pp. 1950033
Author(s):  
Ruoyu Li ◽  
Jianyao Yao ◽  
Linlin Wang ◽  
Chen Jiang ◽  
Fei Wu ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Natural Frequencies ◽  
Synthesis Method ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Compatibility Conditions ◽  
Free Interface ◽  
Numerical Errors ◽  
Gap Element ◽  
Finite Elements Model

The component mode synthesis (CMS) methods are often utilized for modal analysis to investigate the vibration characteristics of the complex structures which are commonly divided into several substructures. However, non-matching finite element meshes may occur at the interfaces between components and virtual gaps are easily produced along the curved interfaces, which limit the application of CMS and lead to larger numerical errors for vibration analysis. To overcome the problem, a novel gap element method (GEM) is employed into a free-interface CMS method in this paper, where both displacements and forces of the nodes on the incompatible interfaces are introduced by two independent Lagrange multipliers to enforce the compatibility conditions. Two-dimensional numerical examples are given to validate the effectiveness of the proposed method. The results of natural frequencies and modal shapes obtained using the proposed method agree very well with the ones obtained using full finite elements model, no matter the gaps along the interface exist or not. The influence of the number of nodes on the non-matching interfaces on the accuracy of frequencies is also discussed.

Component Mode Synthesis Method Using Partial Interface Modes: Application to Tuned and Mistuned Bladed Disk With Local Non-Linearity

2009 ◽  
Author(s):  
Duc-Minh Tran
Keyword(s):  
Synthesis Method ◽  
Normal Modes ◽  
Component Mode Synthesis ◽  
New Method ◽  
Reduced Order Models ◽  
Reduced Order ◽  
Generalized Coordinates ◽  
Bladed Disk ◽  
Static Condensation ◽  
Fixed Interface

A new fixed interface component mode synthesis method using partial interface modes is presented. Partial interface modes are the structure normal modes which result from the static condensation of the structure to the interface between the substructures and which are clamped at a part of this interface. This method is the generalization of the classical component mode synthesis method which keeps all the interface physical displacements in the assembled reduced system and the method using interface modes which eliminates all of them. It allows one to reduce the number of the interface generalized coordinates and at the same time to keep some of the physical displacements at the interface. This latter capability is very useful to build reduced order models in which the presence of physical displacements are essential, for example in order to impose prescribed motions or to take into account local non-linearities. The new method is applied to a bladed disk in both tuned and mistuned cases.

Component Mode Synthesis of a Vehicle System Model Using the Fictitious Mass Method

2006 ◽  
Vol 129 (1) ◽  
pp. 73-83 ◽  
Author(s):  
M. Karpel ◽  
B. Moulin ◽  
V. Feldgun
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Structural Model ◽  
Synthesis Method ◽  
Normal Modes ◽  
Low Frequency ◽  
Component Mode Synthesis ◽  
Response Analysis ◽  
Element Analysis ◽  
Local Boundary

A new procedure for dynamic analysis of complex structures, based on the fictitious-mass component mode synthesis method, is presented. Normal modes of separate components are calculated by finite-element analysis with the interface coordinates loaded with fictitious masses that generate local boundary deformations in the low-frequency modes. The original fictitious-mass method is extended to include three types of component interconnections: displacement constraints, connection elements, and structural links. The connection elements allow the introduction of springs and dampers between the interface points without adding structural degrees of freedom. The structural links facilitate the inclusion the discrete finite-element representation of typically small components in the coupling equations. This allows a convenient treatment of loose elements and the introduction of nonlinear effects and parametric studies in subsequent analyses. The new procedure is demonstrated with the structural model of a typical vehicle with four major substructures and a relatively large number of interface coordinates. High accuracy is obtained in calculating the natural frequencies and modes of the assembled structure and the separate components with the fictitious masses removed. Dynamic response analysis of the vehicle travelling over a rough road, performed by modal coupling, is in excellent agreement with that performed for the full model.

scholarly journals Free-Interface Component Mode Synthesis Method with Link Substructure as Super-Element

2011 ◽  
Vol 16 ◽  
pp. 685-694 ◽  
Author(s):  
Kai-Liang Lu ◽  
Yuan Liu ◽  
Wei-guo Zhang ◽  
Hui-qing Qiu ◽  
Wei-jian Mi
Keyword(s):  
Synthesis Method ◽  
Component Mode Synthesis ◽  
Free Interface

Dynamic Analysis of Cage Stress in Tapered Roller Bearings Using Component-Mode-Synthesis Method

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Tomoya Sakaguchi ◽  
Kazuyoshi Harada
Keyword(s):  
Rigid Body ◽  
Dynamic Analysis ◽  
Boundary Point ◽  
Axial Load ◽  
Synthesis Method ◽  
Load Condition ◽  
Component Mode Synthesis ◽  
Analysis Model ◽  
Tapered Roller ◽  
Tapered Roller Bearings

In order to investigate cage stress in tapered roller bearings, a dynamic analysis tool considering both the six degrees of freedom of motion of the rollers and cage and the elastic deformation of the cage was developed. Cage elastic deformation is equipped using a component-mode-synthesis (CMS) method. Contact forces on the elastically deforming surfaces of the cage pocket are calculated at all node points of finite-elements on it. The location and pattern of the boundary points required for the component-mode-synthesis method were examined by comparing cage stresses in a static condition of pocket forces and constraints calculated by using the finite-element and the CMS methods. These results indicated that one boundary point lying at the center on each bar is appropriate for the effective dynamic analysis model focusing on the cage stress, especially at the pocket corners of the cages, which are actually broken. A behavior measurement of a polyamide cage in a tapered roller bearing was conducted for validating the analysis model. It was confirmed in both the experiment and analysis that the cage whirled under a large axial load condition and the cage center oscillated in a small amplitude under a small axial load condition. In the analysis, the authors discussed the four models including elastic bodies having a normal eigenmode of 0, 8 or 22, and rigid-body. There were small differences among the cage center loci of the four models. These two cages having normal eigenmodes of 0 and rigid-body whirled with imperceptible fluctuations. At least approximately 8 normal eigenmodes of cages should be introduced to conduct a more accurate dynamic analysis although the effect of the number of normal eigenmodes on the stresses at the pocket corners was insignificant. From the above, it was concluded to be appropriate to introduce one boundary point lying at the center on each pocket bar of cages and approximately 8 normal eigenmodes to effectively introduce the cage elastic deformations into a dynamic analysis model.

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