scholarly journals An Independent-Flow-Field Model for a SDOF Nonlinear Structural System: Part II — Analysis of Complex Responses

2003 ◽  
Author(s):  
Huan Lin ◽  
Solomon C. S. Yim
Keyword(s):  
Flow Field ◽  
Field Model ◽  
Periodic Wave ◽  
Experimental Results ◽  
Experimental Result ◽  
Structural System ◽  
Frequency Domains ◽  
Wave Heights ◽  
System Part ◽  
Good Agreement

Complex responses observed in an experimental, nonlinear, moored structural system subjected to nearly periodic wave excitations are examined and compared with the simulations of a newly proposed independent-flow-field (IFF) model in this paper. Variations in wave heights are approximated by additive random perturbations to the dominant periodic component. Simulations show good agreement with the experimental results in both time and frequency domains. Noise effects on the experimental results including bridging and transition phenomena are investigated and interpreted by comparing with the simulations of its deterministic counterpart. Possible causes of a chaotic-like experimental result as previously observed are also inferred.

scholarly journals An Independent-Flow-Field Model for a SDOF Nonlinear Structural System–Part II: Analysis of Complex Responses

2005 ◽  
Vol 128 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Huan Lin ◽  
Solomon C. S. Yim
Keyword(s):  
Flow Field ◽  
Field Model ◽  
Periodic Wave ◽  
Experimental Results ◽  
Experimental Result ◽  
Structural System ◽  
Frequency Domains ◽  
Wave Heights ◽  
System Part ◽  
Good Agreement

Complex responses observed in an experimental, nonlinear, moored structural system subjected to nearly periodic wave excitations are examined and compared to the simulations of a newly proposed independent-flow-field (IFF) model in this paper. Variations in wave heights are approximated by additive random perturbations to the dominant periodic component. Simulations show good agreement with the experimental results in both time and frequency domains. Noise effects on the experimental results, including bridging and transition phenomena, are investigated and interpreted by comparing to the simulations of its deterministic counterpart. Possible causes of a chaoticlike experimental result as previously observed are also inferred.

Numerical modeling and experimental investigation of fiber diameter of melt blowing nonwoven web

2015 ◽  
Vol 27 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Bo Zhao
Keyword(s):  
Flow Field ◽  
Field Model ◽  
Fiber Diameter ◽  
Jet Flow ◽  
Experimental Result ◽  
Computer Assisted ◽  
Melt Blowing ◽  
Content Type ◽  
Air Jet ◽  
Computer Assisted Design

Purpose – The purpose of this paper is to varify, the air drawing model and the air jet flow field model of dual slot shape die for a polymer in a melt blowing process were established, by the experimental results obtained with experimental equipment. Design/methodology/approach – The air jet flow field model is solved by introducing the finite difference method. The air drawing model of polymers in the melt blowing process was studied with the help of the simulation results of the air jet flow field. Findings – The higher air initial velocity and air initial temperature can all yield finer fibers and causes the fibers to be attenuated to a greater extent. Originality/value – The predicted fiber diameter agrees well with the experimental result, which verifies the reliability of these models. At the same time, the results also reveal the great potential of this research for the computer-assisted design of melt blowing technology.

Simulation of Fracture Behavior of Elastomer Modified Polypropylene Based on Elastoviscoplastic Constitutive Equation With Craze and Tensile Softening Law

2005 ◽  
Author(s):  
Hiroyuki Mae
Keyword(s):  
Constitutive Equation ◽  
Crack Propagation ◽  
Strain Rate ◽  
Fracture Behavior ◽  
Experimental Results ◽  
Experimental Result ◽  
Load Displacement ◽  
Macroscopic Crack ◽  
Tensile Softening ◽  
Good Agreement

The strong strain-rate dependence, neck propagation and craze evolution characterize the large plastic deformation and fracture behavior of polymer. In the latest study, Kobayashi, Tomii and Shizawa suggested the elastoviscoplastic constitutive equation based on craze evolution and annihilation and then applied it to the plane strain issue of polymer. In the previous study, the author applied their suggested elastoviscoplastic constitutive equation with craze effect to the three dimensional shell issue and then showed that the load displacement history was in good agreement with the experimental result including only microscopic crack such as craze. For the future industrial applications, the macroscopic crack had to be taken into account. For instance, an airbag deployment simulation needed the macroscopic crack prediction. Thus, the main objective of this study was to propose the tensile softening equation and then add it to the elastoviscoplastic constitutive equation with craze effect so that the load displacement history could be roughly simulated during the macroscopic crack propagation. The tested material in this study was the elastomer blended polypropylene used in the interior and exterior of automobiles. First, the material properties were obtained based on the tensile test results at wide range of strain rates: 10−4 – 102 (1/sec). Next, the fast compact tension test was conducted and then the tensile softening parameters were fixed. Then, the fast bending test and the dart impact test were carried out in order to obtain the load displacement history and also observe the macroscopic crack propagation at high strain rate. Finally, the fracture behavior was simulated and then compared with the experimental results. It was shown that the predictions of the constitutive equation with the proposed tensile softening equation were in good agreement with the experimental results.

scholarly journals Damping Performance Analysis of Magnetorheological Damper Based on Multiphysics Coupling

Actuators ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 176
Author(s):  
Guoliang Hu ◽  
Lifan Wu ◽  
Yingjun Deng ◽  
Lifan Yu ◽  
Bin Luo
Keyword(s):  
Flow Field ◽  
Field Model ◽  
Dynamic Performance ◽  
Mr Damper ◽  
Experimental Results ◽  
Structural Stress ◽  
Applied Current ◽  
Damping Force ◽  
Multiphysics Coupling ◽  
Simulation Results

Magnetorheological (MR) damper performance is evaluated only by single-field analysis in the design process, which can easily lead to larger design errors. Based on this, a simulation method of MR damper considering multiphysics coupling was proposed. According to a certain automobile shock absorber requirement, an MR damper suitable for automobile suspension was designed. The mechanical model, electromagnetic field model, flow field model, and structural stress field model of the MR damper were deduced and established. To investigate the damping performance of the MR damper more accurately, the multiphysics coupling simulation model was established by COMSOL software, and coupling analysis of the electromagnetic field, flow field, and structural stress field was also carried out. The static magnetic field characteristics, dynamic flow field characteristics, stress distribution, and dynamic performance of the proposed MR damper under the action of multiphysics coupling were obtained. The simulation results show that the damping force is 1134.6 N, and the damping adjustable coefficient is 9.1 at an applied current of 1.4 A. A test system was established to analyze the dynamic performance of the MR damper, and the simulation results were compared with the experimental results. The results show that the simulated and experimental results have the same change rule. Moreover, the damping force increases with the applied current, and different external excitations have little effect on the damping force. The damper can output appropriate damping force and has a wide adjustable damping range. The experimental results illustrate that the damping force is 1200.0 N, and the damping adjustable coefficient is 10.1 when the current is 1.4 A. The error between simulation and experiment of the damping force and damping adjustable coefficient is only 5.5% and 9.9%, respectively.

Delamination Evaluation Approach for Bimaterial Structure Considering Interfacial Layer

2007 ◽  
Author(s):  
Qiang Yu ◽  
Tadahiro Shibutani ◽  
Masaki Shiratori ◽  
Tomio Matsuzaki ◽  
Tsubasa Matsumoto
Keyword(s):  
Interfacial Layer ◽  
Interfacial Strength ◽  
Interfacial Fracture ◽  
Experimental Results ◽  
Interfacial Structure ◽  
Experimental Result ◽  
Bonding Layer ◽  
Mechanical Fracture ◽  
Uf Resin ◽  
Good Agreement

In recent years, interfacial fracture is one of the most important issues in the assessment of reliability of electronics packaging. In particular, underfill (UF) resin is used to prevent thermal fatigue of solder joints in flip chip packaging. Interfacial fracture between components/substrates and UF resin also affects the reliability of electronic devices. In general, the interfacial strength can be evaluated with the concept of interfacial fracture mechanics. However, as new materials and new processes using in the devices increase, it becomes clear that the fracture concept is difficult to evaluate the interfacial strength quantitatively. Many researches assumed that the interface is bonded perfectly. However, the interface has the micro-scale structure and the bonding may be imperfect. Specially interfaces of the resin have complicated structure. In this study, an alternative approach for evaluating the mechanical fracture of the interfacial structure of resin in electronic components was proposed. The basic mechanical behavior of the new interfacial model with imperfect bonding layer was examined by using finite element analysis. The stress field around the interfacial layer depends not only on the properties of interfacial layer but also on the micro structure of the interfacial layer. In addition, based on the experimental result of the tensile and the shearing test from the reference, the mechanical models of the interfacial structure were constructed. The conditions of delamination were examined by using FEA Furthermore, the new model and approach was confirmed quantitatively. It was found that the basic properties of the interfacial layer can be tuned to the proper values by two different delamination tests, and the new approach could show good agreement with the experimental results from the initial delaminaiton to the instability fracture process qualitatively. The simulation results were in good agreement with the experimental results.

Numerical Simulation of the Flow Field in a Statically and Dynamically Eccentric Annular Seal With Non-Circular Whirl Orbits

2010 ◽  
Author(s):  
Anand Vijaykumar ◽  
Gerald Morrison
Keyword(s):  
Flow Field ◽  
Wall Pressure ◽  
Dynamic Mesh ◽  
Experimental Results ◽  
Pressure Distributions ◽  
Mesh Model ◽  
Pressure Fields ◽  
Annular Seal ◽  
Velocity Pressure ◽  
Good Agreement

The flow field in an annular seal is simulated for synchronous circular whirl orbits with 60Hz whirl frequency and a clearance/radius ratio of 0.0154 using the Fluent CFD code. Fluent’s Moving Reference Frame model (MRF) is used to render the flow quasi-steady by making transformations to a rotating frame. The computed flow fields for velocity, pressure and shear stress measurements are compared with the experimental data of Winslow (1994), Thames (1992) and Cusano (2006). The CFD predictions are found to be in good agreement with the experimental results. The present CFD methodology can be extended to other whirl frequencies and clearances. The dynamic wall pressure distributions in an annular seal for non-circular whirl orbits was obtained using CFD. The simulations were performed using a time dependant solver utilizing Fluent’s Dynamic Mesh model and User Defined Functions (UDFs). The wall pressure distributions obtained from the simulations are compared with data of Cusano (2006). The CFD simulations over predicted the pressure field when compared to experimental results however the general trends in pressure contours are similar. The flow field for varying rotor eccentricities are also studied by performing coordinate transformations and rendering the flow quasi-steady at set eccentricities using Fluent’s MRF model. The computed velocity and pressure fields are compared with the time dependant solution obtained using Fluent’s Dynamic Mesh model and UDFs for the same eccentricity. Good agreement in the velocity fields is obtained however the pressure fields require further investigation.

Modeling of Dryout in Core Debris Beds of Conical and Cylindrical Geometries

2012 ◽  
Author(s):  
Eveliina Takasuo ◽  
Ville Hovi ◽  
Mikko Ilvonen ◽  
Stefan Holmström
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Flow Field ◽  
Nuclear Power ◽  
Experimental Results ◽  
Severe Accident ◽  
Accident Analysis ◽  
Simulation Results ◽  
Particle Bed ◽  
Good Agreement

A porous particle bed consisting of core debris may be formed as a result of a core melt accident in a nuclear power plant. The coolability of conical (heap-like) and cylindrical (evenly-distributed) ex-vessel debris beds have been investigated in the COOLOCE experiments at VTT. The experiments have been modeled by using the MEWA severe accident analysis code. The main objectives of the modeling were (1) to validate the simulation results against the experiments by comparing the dryout power density predicted by the code to the experimental results and (2) to evaluate the effect of geometry on the coolability by examining the flow field and the development of dryout in the two geometries. In addition to the MEWA simulations, 3D demonstration calculations of the particle bed dryout process have been performed using the in-house code PORFLO. It was found that the simulation and experimental results are in a relatively good agreement. The results suggest that the coolability of the conical debris bed is poorer than that of the cylindrical bed due to the greater height of the conical configuration.

Enhanced Photoyield with Decreasing Film Thickness on Metal-Semiconductor Structures

1996 ◽  
Vol 448 ◽  
Author(s):  
V. Hoffmann ◽  
M. Brauer ◽  
M. Schmidt
Keyword(s):  
Quantum Yield ◽  
Film Thickness ◽  
Layer Thickness ◽  
Experimental Results ◽  
Experimental Result ◽  
Model Calculations ◽  
Hot Carrier ◽  
Semiconductor Structures ◽  
Carrier Scattering ◽  
Good Agreement

AbstractExperimental results of the internal quantum yield Yi associated with the internal photoemission on Au/n-Si structures are presented. The samples were prepared on Si(100) and Si(111) substrates with photoemitter layer thicknesses ranging from 5 nm to 50 nm. The Yi was measured at temperatures between 165 K and 300 K with the photoexciting energy varying from 0.72 eV to 1.07 eV. It was found that the Yi increases with decreasing Au layer thickness with a strong enhancement (40 times) in regard to the conventional Fowler theory. This experimental result is in good agreement with model calculations taking account of hot carrier scattering in the photoemitter layer. Barrier energies are larger than deduced from the Fowler plot.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

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