Improvement of Damping at the Micromechanical Level in Polymer Composite Materials Under Transverse Normal Loading by the Use of Special Fiber Coatings

1998 ◽  
Vol 120 (2) ◽  
pp. 623-627 ◽  
Author(s):  
I. C. Finegan ◽  
R. F. Gibson
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Plane Strain ◽  
Composite Structure ◽  
Element Model ◽  
Acrylic Polymer ◽  
Normal Loading ◽  
Fiber Coating ◽  
Parametric Studies ◽  
Fiber Coatings

This paper describes preliminary results from a systematic analytical study of the improvement of damping in polymer composites at the micromechanical level under transverse normal loading by the use of special fiber coatings. Since shear deformations are important in damping of viscoelastic polymers, and large shear strains are generated in the region of the fiber/matrix interface, one idea for improving damping is to put a fiber coating made from a highly dissipative material in this region. A finite element model based on a “representative volume element” or repeating element of a continuously reinforced coated fiber composite is used to study damping under transverse normal loading. The micromechanical composite model investigated is a unidirectional graphite/epoxy with an acrylic polymer as the fiber coating material. Both two and three dimensional finite element models are analyzed in order to compare the influence of plane stress and plane strain conditions on the damping and stiffness properties of the composite micromechanical model. Parametric studies are conducted by using a two dimensional plane strain finite element model in order to illustrate how the coating applied to the fiber influences dynamic properties of the composite structure. The parametric studies are done with particular emphasis on the effects of frequency, temperature, and fiber coating thickness on the damping of the composite structure.

Wear Modeling of Nanometer Thick Protective Coatings

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Jungkyu Lee ◽  
Youfeng Zhang ◽  
Robert M. Crone ◽  
Narayanan Ramakrishnan ◽  
Andreas A. Polycarpou
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Protective Coatings ◽  
Element Model ◽  
Disk Surface ◽  
Magnetic Storage ◽  
Theoretical Frameworks ◽  
Storage Devices ◽  
Parametric Studies ◽  
Magnetic Storage Devices

Use of nanometer thin films has received significant attention in recent years because of their advantages in controlling friction and wear. There have been significant advances in applications such as magnetic storage devices, and there is a need to explore new materials and develop experimental and theoretical frameworks to better understand nanometer thick coating systems, especially wear characteristics. In this work, a finite element model is developed to simulate the sliding wear between the protruded pole tip in a recording head (modeled as submicrometer radius cylinder) and a rigid asperity on the disk surface. Wear is defined as plastically deformed asperity and material yielding. Parametric studies reveal the effect of the cylindrical asperity geometry, material properties, and contact severity on wear. An Archard-type wear model is proposed, where the wear coefficients are directly obtained through curve fitting of the finite element model, without the use of an empirical coefficient. Limitations of such a model are also discussed.

Design and characterization of a hybrid soft gripper with active palm pose control

2020 ◽  
Vol 39 (14) ◽  
pp. 1668-1685 ◽  
Author(s):  
Vignesh Subramaniam ◽  
Snehal Jain ◽  
Jai Agarwal ◽  
Pablo Valdivia y Alvarado
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structure ◽  
Element Model ◽  
Open Loop ◽  
Aspect Ratios ◽  
Maximum Payload ◽  
Wide Range ◽  
Pose Control

The design and characterization of a soft gripper with an active palm to control grasp postures is presented herein. The gripper structure is a hybrid of soft and stiff components to facilitate integration with traditional arm manipulators. Three fingers and a palm constitute the gripper, all of which are vacuum actuated. Internal wedges are used to tailor the deformation of a soft outer reinforced skin as vacuum collapses the composite structure. A computational finite-element model is proposed to predict finger kinematics. Thanks to its active palm, the gripper is capable of grasping a wide range of part geometries and compliances while achieving a maximum payload of 30 N. The gripper natural softness enables robust open-loop grasping even when components are not properly aligned. Furthermore, the grasp pose of objects with various aspect ratios and compliances can be robustly maintained during manipulation at linear accelerations of up to 15 m/s2 and angular accelerations of up to 5.23 rad/s2.

Modeling and experimental analysis of the hyperelastic thin film nitinol

2011 ◽  
Vol 22 (17) ◽  
pp. 2045-2051 ◽  
Author(s):  
Youngjae Chun ◽  
Po-Yu Lin ◽  
Hsin-Yun Chang ◽  
Michael C. Emmons ◽  
K.P. Mohanchandra ◽  
...  
Keyword(s):  
Thin Film ◽  
Finite Element ◽  
Finite Element Model ◽  
Large Deformation ◽  
Experimental Analysis ◽  
Electronic Devices ◽  
Element Model ◽  
Elastic Response ◽  
Geometric Factors ◽  
Parametric Studies

Many flexible electronic devices or endovascular biomedical devices require large deformation; however, potential materials produce limited elastic response, that is, 10% when 400% is required. In this article, a finite element model is used to design a hyperelastic thin film nitinol structure containing geometric fenestrations. The hyperelastic response is dependent upon geometric factors that produce buckling. Parametric studies provide the influence-specific parameters have on buckling load. These results are used to select three designs to manufacture and test. Experimental results indicate that elongations greater than 700% are possible.

Assessment of a finite element model for plate shearing

2002 ◽  
Vol 216 (4) ◽  
pp. 519-529 ◽  
Author(s):  
J P Domblesky ◽  
L Zhao
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Plane Strain ◽  
Element Model ◽  
Experimental Results ◽  
Process Conditions ◽  
Initiation And Propagation ◽  
Model Predictions ◽  
Edge Wear ◽  
Strain Model

A study was conducted to assess the robustness of a plane strain finite element model that was developed to simulate plate shearing using the Cockroft-Latham fracture criterion and element deletion. Model predictions for blade gap, ductility and edge wear were compared with published experimental results. Results showed that the model was able to simulate initiation and propagation of fracture lines at the punch and die corners and the resultant break angle along the edge was found to be close to values observed in practice. Simulated edge geometry and microhardness were found to be in reasonable agreement with published experimental results for the steel plate considered although the model was unable to simulate double cutting at 0.8 per cent clearance. Results also suggest that edge hardness is independent of the starting ductility in the plate and that increasing the edge radii does not effectively simulate edge wear. Based on the results obtained, it may be concluded that the plane strain model is able to simulate plate shearing with sufficient accuracy in the range of normal process conditions.

Nonlinear Finite Element Analysis of FRP Strengthened RC Beams with Bond-Slip Effect

2017 ◽  
Vol 14 (03) ◽  
pp. 1750032 ◽  
Author(s):  
Prabin Pathak ◽  
Y. X. Zhang ◽  
Xiaodan Teng
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Structural Behavior ◽  
Slip Effect ◽  
Rc Beams ◽  
Element Analysis ◽  
Bond Slip ◽  
Research Findings ◽  
Parametric Studies

This paper investigates the structural behavior of fiber reinforced polymer (FRP) strengthened reinforced concrete (RC) beams by developing a new simple, efficient and accurate finite element model (FEM-B). In addition to the FRP, concrete and steel rebars, the adhesive and stirrups which have been generally ignored in the reported models from literatures are considered in the new models. At first, a finite element model (FEM-P) is developed assuming perfect bond between concrete, FRP and adhesive interfaces. Then the FEM-P model is expanded to form the FEM-B model by including the bond-slip effect between concrete, FRP and adhesive interfaces. The developed new finite element models (FEM-B and FEM-P) are validated against experimental results and demonstrate to be effective for the structural analysis of FRP strengthened RC beams. Furthermore, parametric studies are carried out to learn the effects of types and thickness of FRP on the structural behavior of FRP strengthened RC beams based on the FEM-B model. The research findings are summarized finally.

Rotordynamic Analysis of a Power Turbine Including Support Flexibility Effects

2008 ◽  
Author(s):  
Oscar De Santiago ◽  
Edward Abraham
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Oil And Gas ◽  
Transfer Functions ◽  
Element Model ◽  
Process Equipment ◽  
Gas Generator ◽  
Power Turbine ◽  
Parametric Studies ◽  
Function Information

Power turbines are commonly used in the oil and gas industries as mechanical drives of process equipment such as centrifugal compressors or electrical generators. Power turbine rotordynamic design analysis is important because there may be interaction between the rotor and the structure, including the baseplate where they are mounted. This paper presents the results of the dynamic analysis of a power turbine considering the turbine frame, gas generator and baseplate. A large finite element model (FEM) of the assembly is used to generate transfer functions representing the dynamics of these components acting at the rotor bearing locations. The transfer function information is then used in a dedicated rotordynamic program to perform parametric studies and provide recommendations for the optimum power turbine bearing and baseplate configurations that meet all applicable industrial specifications. Predictions from a complete rotor-structure finite element model confirm the results from the dedicated rotordynamic program using transfer functions, showing that this simplified model can be used to satisfactorily study the system dynamics.

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