Identification of Damping and Dynamic Young’s Modulus of a Structural Adhesive Using Radial Basis Function Neural Networks and Modal Data

Rezaee

2021

Proc Inst Mech Eng H

In this paper, mechanical parameters of a calf heart muscle are identified and a gel-type material as the representative of the cardiac muscle in dynamic tests is introduced. The motivation of this study is to introduce a replacement material of the heart muscle to use in experimental studies of the leadless pacemaker. A particular test setup is developed to capture the experimental data based on the stress relaxation test method where its outputs are time histories of the force and displacement. The standard linear solid model is used for mathematical modeling of the heart muscle sample and a gel-type material specimen namely α-gel. Five tests with different strain history [Formula: see text] are performed by regarding and disregarding the influence of the initial ramp of the loading. The mechanical parameters of the standard linear solid model were identified with precise curve fitting. Consideration of the initial ramp significantly influences the consequences and they are so close to their experimental counterparts. The identified parameters of the standard linear solid model by regarding the influence of the initial ramp for the gel-type material are within an acceptable range for the viscoelastic properties of the calf heart tissue. These results show that the gel-type material has the potential to represent the cardiac muscle in the leadless pacemaker experimental studies. Dynamic mechanical analysis is used to characterize the dynamic viscoelastic properties for the gel by utilizing the identified parameters with taking into account the initial ramp in the frequency domain. Results show that Storage modulus, Loss modulus, and Loss tangent are strongly frequency-dependent especially at low-frequency around the heartbeat frequency range (0–2 Hz).

“…Generally, the relation between stress and strain in viscoelastic materials is expressed utilizing complex modulus. 52,53 Therefore, the stress-strain relation can be written as follows…”

Section: Analytical Modelingmentioning

confidence: 99%

Identifying the parameters of viscoelastic model for a gel-type material as representative of cardiac muscle in dynamic tests

Siami

Rezaee

2021

Proc Inst Mech Eng H

“…where P(t) is an unknown function of time and f z ( ) is an eigenfunction of the linear problem. By substituting equations (11) and (12) into equation (10), multiplying the resultant equation by f z ( ) and then integrating over z =0 to 1, the final equation will be of the following form: g P g P g P g V g PV g t sin 13…”

Section: Electromechanical Modeling and Governing Equations (With Rig...mentioning

confidence: 99%

“…From the point of view of structural dynamics, joints have an important role in the vibrational behavior of assembled structures, so that if joints are not modeled correctly, the dynamic behavior of the structure cannot be evaluated properly [4][5][6]. Extensive research has been conducted to identify the characteristics of the joint region in assembled structures using different techniques [7][8][9][10]. Depending on the accuracy of modeling and the frequency range of interest, one may consider the stiffness, damping and mass characteristics of joint media, or the stiffness and dissipation, or just the elasticity of the joint region in predicting the dynamic behavior of the assembled structure.…”

Section: Introductionmentioning

confidence: 99%

How joint characteristics between a piezoelectric beam and the main structure affect the performance of an energy harvester

Rafiei

Aghazadeh

2017

Smart Mater. Struct.

In this paper, the influence of the joint region between a piezoelectric energy harvesting beam and the vibratory main structure is studied. The investigations are conducted in two separate sections, namely numerical and experimental studies. In numerical studies, the effects of nonlinear parameters on generated power are investigated while the joint characteristics the between vibrating base and a piezoelectric energy harvester are taken into consideration. A unimorph beam with a tip mass and a nonlinear piezoelectric layer that undergoes a large-amplitude deflection is considered as an energy harvester. By applying the Euler–Lagrange equation and Gauss’s law the mechanical and electrical equations of motion are obtained, respectively. The excitation frequency is assumed to be close to the first natural frequency. Thus, a unimodal response is considered to be like that of a system with a single degree of freedom (SDOF). The joint between the vibrating main structure and the cantilevered beam is then added to the SDOF model. The joint characteristics are simulated with a light mass, mj, linear spring stiffness, kj, and equivalent viscous damper, cj. In two scenarios, i.e. with a rigid joint and with a flexible one, a numerical approach is followed to investigate the effects of each nonlinear parameter of the harvester (stiffness, damping and piezoelectric coefficient) on the harvested power. In experimental studies, the influence of a bolted joining technique and a flexible adhesive bonding method on the harvested power is investigated. The results achieved experimentally confirm those obtained numerically, i.e. a stiffer joint leads to a greater power produced by the harvester. In other words, neglecting the joint characteristics will cause the performance (maximum output power and the range of excitation frequency) of the harvester to be overestimated in numerical simulations.

“…To determine the dynamic mechanical characteristics of elastomers, in most of the documented methods the elastic and storage moduli (or elastic modulus and loss factor) have been used as material properties where, these properties extracted from resonant tests (Gupta et al, 1999, Jahani and Nobari, 2010, Wismer and Gade, 1997. However, there are a few publications about dynamic material constants of the hyperelastic models for elastomers at broad frequency range.…”

Section: Introductionmentioning

confidence: 99%

Predicting the dynamic material constants of Mooney-Rivlin model in broad frequency range for elastomeric components

Lat. Am. j. solids struct.

Mahmoodzade

2014

In this paper, dynamic material constants of 2-parameter Mooney-Rivlin model for elastomeric components are identified in broad frequency range. To consider more practical case, an elastomeric engine mount is used as the case study. Finite element model updating technique using Radial Basis Function neural networks is implemented to predict the dynamic material constants. Material constants of 2-parameter Mooney-Rivlin model are obtained by curve fitting on uni-axial stress-strain curve. The initial estimations of the material constants are achieved by using uni-axial tension test data. To ensure of the consistency of dynamic response of a real component, frequency response function of three similar engine mounts are extracted from experimental modal data and average of them used in the procedure. The results showed that this technique can successfully predict dynamic material constants of Mooney-Rivlin model for elastomeric components.