Damping of Flexural Waves With Imbedded Viscoelastic Materials

1998 ◽  
Vol 120 (1) ◽  
pp. 188-193 ◽  
Author(s):  
E. R. Marsh ◽  
L. C. Hale
Keyword(s):  
Finite Element ◽  
Design Parameters ◽  
Constrained Layer Damping ◽  
Structural Components ◽  
Flexural Waves ◽  
Viscoelastic Materials ◽  
The Common ◽  
Damping Treatments ◽  
The Relationship ◽  
Insight Into

This paper considers a passive damping method that can be applied to beam-like structures such as machine tool bases and columns. The method uses viscoelastic materials to dissipate energy in the manner of classic constrained-layer damping; however, the layers are embedded within the structure as opposed to being applied externally. This provides a robust means of incorporating damping without encountering several of the common disadvantages associated with external damping treatments. An analytical solution to the amount of damping that can be achieved using embedded layers is available, but is known to be inaccurate when the viscoelastic stiffness approaches that of the structural components. Therefore, a new prediction of the maximum damping level that can be expected in a structure is developed and presented here. This prediction gives good results in a wide variety of applications, and offers insight into the relationship between key design parameters. Finite element and experimental verification of the maximum damping predictor are also presented.

Damping Machine Tools With Imbedded Viscoelastic Materials Constrained by Shear Tubes

1995 ◽  
Author(s):  
Eric R. Marsh ◽  
Layton C. Hale
Keyword(s):  
Finite Element ◽  
Machine Tools ◽  
Design Parameters ◽  
Constrained Layer Damping ◽  
Structural Components ◽  
Viscoelastic Materials ◽  
The Common ◽  
Damping Treatments ◽  
The Relationship ◽  
Insight Into

Abstract This paper considers a passive damping method that can be applied to beam-like structures such as machine tool bases and columns. The method uses viscoelastic materials to dissipate energy in the manner of classic constrained-layer damping; however, the layers are embedded within the structure as opposed to being applied externally. This provides a robust means of incorporating damping without encountering several of the common disadvantages associated with external damping treatments. An analytical solution to the amount of damping that can be achieved using embedded layers is available, but is known to be inaccurate when the viscoelastic stiffness approaches that of the structural components. Therefore, a new prediction of the maximum damping level that can be expected in a structure is developed and presented here. This prediction gives good results in a wide variety of applications, and offers insight into the relationship between key design parameters. Finite element and experimental verification of the maximum damping predictor are also presented.

Vibration Analyses of Cylindrical Hybrid Panel with Viscoelastic Layer Based on Layerwise Finite Elements

2006 ◽  
Vol 324-325 ◽  
pp. 699-702 ◽  
Author(s):  
Il Kwon Oh ◽  
Tai Hong Cheng
Keyword(s):  
Finite Element ◽  
Virtual Work ◽  
Structural Parameters ◽  
Element Model ◽  
Viscoelastic Layer ◽  
Normal Strain ◽  
Constrained Layer Damping ◽  
Damping Characteristics ◽  
Viscoelastic Layers ◽  
Damping Treatments

Based on full layerwise displacement shell theory, the vibration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modeling. The layerwise finite element model is formulated by using Hamilton’s virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factor and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

Labour Market Segmentation: Standard and Non-Standard Employment in Germany

2013 ◽  
Vol 14 (3) ◽  
pp. 349-371 ◽  
Author(s):  
Marcel Garz
Keyword(s):  
Labour Market ◽  
Market Segmentation ◽  
Market Theory ◽  
Standard Work ◽  
Labour Market Segmentation ◽  
Economic Barriers ◽  
The Common ◽  
The Relationship ◽  
Insight Into

Abstract Data from the German Socio-Economic Panel provide insight into the relationship between standard and non-standard work, from the perspective of dual labour market theory. We identify two segments that largely correspond to the common distinction between these forms of employment and find substantial differences in the determination of wages, as well as the composition of worker and job characteristics. These differences tend to increase after the Hartz reforms. The estimates also indicate the existence of a primary sector wage premium and job rationing, as well as specific patterns of labour mobility due to (partly non-economic) barriers between segments.

The Performance Research of Automobile Disc Brake Based on Finite Element Technology

2011 ◽  
Vol 381 ◽  
pp. 90-93
Author(s):  
Ya Feng He
Keyword(s):  
Finite Element ◽  
Automotive Industry ◽  
Design Parameters ◽  
Disc Brake ◽  
Braking Performance ◽  
Finite Element Technology ◽  
Relationship Of ◽  
The Relationship ◽  
Performance Research ◽  
Automotive Brake

Due to good cooling and braking performance, it is widely used for disc brake in automotive industry. The numerical analysis of stress and strain field for automobile disc brake is done by using ANSYS finite element platform in this paper, the relationship of design parameters and braking performance is obtained by changing design parameters of the brake (braking force, friction coefficient, brake pad thickness).At the same time the modal of automobile disc brake is analyzed, which the results provide a theoretical basis and reference for the automotive brake designer.

scholarly journals Dimensionless Analysis of Segmented Constrained Layer Damping Treatments with Modal Strain Energy Method

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Shitao Tian ◽  
Zhenbang Xu ◽  
Qingwen Wu ◽  
Chao Qin
Keyword(s):  
Shear Strain ◽  
Strain Field ◽  
Strain Energy ◽  
Design Parameters ◽  
Viscoelastic Layer ◽  
Constrained Layer Damping ◽  
Modal Strain Energy ◽  
Modal Strain Energy Method ◽  
Damping Treatments ◽  
Strain Energy Method

Constrained layer damping treatments promise to be an effective method to control vibration in flexible structures. Cutting both the constraining layer and the viscoelastic layer, which leads to segmentation, increases the damping efficiency. However, this approach is not always effective. A parametric study was carried out using modal strain energy method to explore interaction between segmentation and design parameters, including geometry parameters and material properties. A finite element model capable of handling treatments with extremely thin viscoelastic layer was developed based on interlaminar continuous shear stress theories. Using the developed method, influence of placing cuts and change in design parameters on the shear strain field inside the viscoelastic layer was analyzed, since most design parameters act on the damping efficiency through their influence on the shear strain field. Furthermore, optimal cut arrangements were obtained by adopting a genetic algorithm. Subject to a weight limitation, symmetric and asymmetric configurations were compared. It was shown that symmetric configurations always presented higher damping. Segmentation was found to be suitable for treatments with relatively thin viscoelastic layer. Provided that optimal viscoelastic layer thickness was selected, placing cuts would only be applicable to treatments with low shear strain level inside the viscoelastic layer.

Geometry-Driven Finite Element for Four-Dimensional Printing

2017 ◽  
Author(s):  
Tsz-Ho Kwok
Keyword(s):  
Finite Element ◽  
Optimization Problem ◽  
Geometric Optimization ◽  
Reserve Design ◽  
The Finite Element Method ◽  
4D Printing ◽  
Shape Transformation ◽  
The Common ◽  
The Relationship ◽  
Dimensional Printing

Four-dimensional (4D) printing is a new category of printing that expands the fabrication process to include time as the forth dimension, and its process planning and simulation have to take time into consideration as well. The common tool to estimating the behavior of a deformable object is the finite element method (FEM). Although FEM is powerful, there are various sources of deformation from hardware, environment, and process, just to name a few, which are too complex to model by FEM. This paper introduces Geometry-Driven Finite Element (GDFE) as a solution to this problem. Based on the study on geometry changes, the deformation principles can be drawn to predict the relationship between the 4D-printing process and the shape transformation. Similar to FEM, the design domain is subdivided into a set of GDFEs, and the principles are applied on each GDFE, which are then assembled to a larger system that describes the overall shape. The proposed method converts the complex sources of deformation to a geometric optimization problem, which is intuitive and effective. The usages and applications of the GDFE framework have also been presented in this paper, including freeform design, reserve design, and design validation.

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