Inverse calculation of material parameters for a thin-layer system using transient elastic waves

2002 ◽  
Vol 112 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Chien-Ching Ma ◽  
Shaw-Wen Liu ◽  
Chen-Ming Chang
Keyword(s):  
Thin Layer ◽  
Elastic Waves ◽  
Layer System ◽  
Material Parameters

scholarly journals Research on the Shock Response Characteristics of a Threaded Connection Using the Thin-Layer Element Method

2021 ◽  
Vol 11 (12) ◽  
pp. 5611
Author(s):  
A’min Yan ◽  
Xiaofeng Wang ◽  
He Yang ◽  
Fenglei Huang ◽  
Aiguo Pi
Keyword(s):  
Dynamic Response ◽  
Thin Layer ◽  
Contact Stiffness ◽  
Maximum Error ◽  
Elastic Model ◽  
Material Parameters ◽  
Response Characteristics ◽  
Threaded Connection ◽  
Constraint Method ◽  
Element Method

Nonlinear factors such as the contact stiffness and friction damping at the threaded interface of a projectile–fuse system significantly affect the dynamic response characteristics. To obtain the dynamic response of the fuse body accurately during penetration, it is necessary to characterize these nonlinear factors reasonably. Because the existing structural dynamics software cannot effectively deal with nonlinear factors, the thin-layer element method was used to represent the nonlinear factors in this study. By combining the thread elastic model with thin-layer element principles, an effective method for determining the material parameters of the thin-layer element was established theoretically, which provided a different method of determining material parameters, not just relying on experiments. The accuracy of the material parameters was verified based on modal experiments with threaded tubes having different specifications. The errors were within 5%, indicating the reliability of the theoretical determination method for the material parameters. In addition, projectile penetration into a semi-infinite concrete target was tested to verify the accuracy of the thin-layer element modeling. Compared with the ‘TIED’ constraint method, the resonant frequency obtained with the thin-layer element method was in better agreement with that of the experimental data. The maximum error decreased from 15.7 to 7.8%, indicating that the thin-layer element method could accurately represent the nonlinear factors. Thus, this study serves as a reference for accurately evaluating the dynamic response of the fuse body of a penetrator.

Arbitrary shaped acoustic omnidirectional absorber based on transformation theory

2020 ◽  
Vol 34 (11) ◽  
pp. 2050111
Author(s):  
Weikai Xu ◽  
Yingchun Tang ◽  
Meng Zhang ◽  
Wuchao Qi ◽  
Wei Wang
Keyword(s):  
Numerical Simulations ◽  
Elastic Waves ◽  
Sound Absorption ◽  
Acoustic Absorption ◽  
Two Dimensional ◽  
Acoustic Path ◽  
Transformation Theory ◽  
Material Parameters ◽  
Arbitrary Geometries ◽  
Transformation Acoustics

In this study, an arbitrary shaped acoustic omnidirectional absorber (AOA) is achieved for absorbing incoming acoustic/elastic waves in the ambient environment. Using the transformation acoustics theory, we present a theoretical framework for two-dimensional acoustic path guidance around arbitrary shapes for which the material parameters in the transformed space can be obtained analytically. Results indicate that the transformed space is distorted rather than compressed; numerical simulations confirm that these absorbers exhibit a remarkably large absorption and that the proposed method can control acoustic absorption for arbitrary geometries of interest. This method can potentially be applied to sound absorption and noise control.

ADHESION BETWEEN AN AFM PROBE AND AN INCOMPRESSIBLE ELASTIC FILM

2004 ◽  
Vol 03 (04n05) ◽  
pp. 599-608 ◽  
Author(s):  
Z. W. ZHENG ◽  
I. SRIDHAR ◽  
K. L. JOHNSON ◽  
W. T. ANG
Keyword(s):  
Thin Layer ◽  
Empirical Equation ◽  
Surface Force ◽  
Contact Radius ◽  
Layer System ◽  
Atomic Force ◽  
Elastic Film ◽  
Afm Probe ◽  
Range Of Values ◽  
Contact Size

The Johnson–Kendal–Roberts (JKR) adhesion theory is frequently applied to extract the surface energy of the contacting thin coating systems in micro or nanoprobe instruments such as Surface Force Apparatus (SFA) and Atomic Force Microscope (AFM). For thin-layer systems, the JKR theory may give rise to erroneous predictions as it is based on the elastic contact between a sphere and a half-space. Adhesion between the thin-layer surfaces has been analyzed by Sridhar et al. using a numerical SJF (Sridhar–Johnson–Fleck) model. In this paper, the adhesion between a spherical tip of an AFM and an incompressible thin elastic film is investigated. When the substrate is rigid, the normalised pull-off force may differ from the JKR value of -0.5 by as much as 90%. Computations of the contact size and pull-off force are presented for a range of values of adhesion energy. Finally, an empirical equation for the adhesive load was developed by curve fitting the compliance of the layer system as a function of contact radius.

scholarly journals Mass transport in water waves over a thin layer of soft viscoelastic mud

2007 ◽  
Vol 573 ◽  
pp. 105-130 ◽  
Author(s):  
CHIU-ON NG ◽  
XUEYAN ZHANG
Keyword(s):  
Mass Transport ◽  
Thin Layer ◽  
Water Waves ◽  
Stokes Equations ◽  
Steady Motion ◽  
Single Layer ◽  
Viscoelastic Layer ◽  
Layer System ◽  
Overlying Water ◽  
Viscoelastic Parameter

A theory is presented for the mass transport induced by a small-amplitude progressive wave propagating in water over a thin layer of viscoelastic mud modelled as a Voigt medium. Based on a sharp contrast in length scales near the bed, the boundary-layer approximation is applied to the Navier–Stokes equations in Lagrangian form, which are then solved for the first-order oscillatory motions in the mud and the near-bed water layers. On extending the analysis to second order for the mass transport, it is pointed out that it is inappropriate, as was done in previous studies, to apply the complex viscoelastic parameter to a higher-order analysis, and also to suppose that a Voigt body can undergo continuous steady motion. In fact, the time-mean motion of a Voigt body is only transient, and will stop after a time scale given by the ratio of the viscosity to the shear modulus. Once the mud has attained its steady deformation, the mass transport in the overlying water column can be found as if it were a single-layer system. It is found that the near-bed mass transport has non-trivial dependence on the mud depth and elasticity, which control the occurrence of resonance. Even when the resonance is considerably damped by viscosity, the mass transport in water over a viscoelastic layer can be dramatically different, in terms of magnitude and direction, from that over a rigid bed.

scholarly journals Nonlinear Modeling and Identification of an Aluminum Honeycomb Panel with Multiple Bolts

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Yongpeng Chu ◽  
Hao Wen ◽  
Ti Chen
Keyword(s):  
Thin Layer ◽  
Plastic Material ◽  
Experimental Tests ◽  
Bolted Joints ◽  
High Excitation ◽  
Material Parameters ◽  
Elastic Plastic ◽  
Aluminum Honeycomb ◽  
Elastic Plastic Material ◽  
Honeycomb Panel

This paper focuses on the nonlinear dynamics modeling and parameter identification of an Aluminum Honeycomb Panel (AHP) with multiple bolted joints. Finite element method using eight-node solid elements is exploited to model the panel and the bolted connection interface as a homogeneous, isotropic plate and as a thin layer of nonlinear elastic-plastic material, respectively. The material properties of a thin layer are defined by a bilinear elastic plastic model, which can describe the energy dissipation and softening phenomena in the bolted joints under nonlinear states. Experimental tests at low and high excitation levels are performed to reveal the dynamic characteristics of the bolted structure. In particular, the linear material parameters of the panel are identified via experimental tests at low excitation levels, whereas the nonlinear material parameters of the thin layer are updated by using the genetic algorithm to minimize the residual error between the measured and the simulation data at a high excitation level. It is demonstrated by comparing the frequency responses of the updated FEM and the experimental system that the thin layer of bilinear elastic-plastic material is very effective for modeling the nonlinear joint interface of the assembled structure with multiple bolts.

CW-laser-induced spherulitic recrystallization in Sb-Se thin layer system

1998 ◽  
Author(s):  
N. Starbov ◽  
V. Mankov ◽  
K. Starbova ◽  
Konstantin Kolev ◽  
Alain Jadin ◽  
...  
Keyword(s):  
Thin Layer ◽  
Layer System ◽  
Cw Laser
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