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Zonal intelligent inversion of viscoelastic parameters of high arch dams using an HEST statistical model

JOURNAL OF CIVIL STRUCTURAL HEALTH MONITORING 2022年第1期12卷 207-223页

作者： Wang, Shaowei Xu, Cong Liu, Yi Xu, Bo Nanjing Hydraul Res Inst State Key Lab Hydrol Water Resources & Hydraul En Nanjing 210029 Peoples R China Changzhou Univ Sch Environm & Safety Engn Changzhou 213164 Peoples R China China Inst Water Resources & Hydropower Res Minist Water Resources Key Lab Construct & Safety Water Engn Beijing 100038 Peoples R China Yangzhou Univ Coll Hydraul Sci & Engn Yangzhou 225009 Jiangsu Peoples R China

To evaluate the real working behaviour of high arch dams, the in-situ monitoring data-based inversion of deformation parameters is essential. The frequently used hydraulic, seasonal, and time model cannot accurately interpret the viscoelastic deformation behaviour of concrete dams. The main purpose of this paper is to propose a hydraulic, exponential, seasonal, and time (HEST) statistical model to conduct the multi-point zonal intelligent inversion of viscoelastic parameters of high arch dams. The extreme learning machine (ELM) is used to establish the nonlinear relationship between viscoelastic parameters and finite element method-calculated total hydraulic displacement. The particle swarm optimization is improved by three strategies and is then used to search the optimal viscoelastic parameters from the ELM model, according to the HEST model-separated total hydraulic displacement. An engineering example of the Jinping-I arch dam has demonstrated the good performance of the proposed HEST model and inversion method. In the water level stable stage, the abnormal increase of dam radial displacement, which is measured by the plumb line monitoring system, can be reasonably interpreted by the air temperature annual drop effect and dam concrete's hysteretic deformation, and the latter can be reasonably represented by the step-type exponential function-based hysteretic hydraulic component, which occupies a proportion of 20-30%. The inverted instantaneous elastic moduli of concrete in the four clustered zones of the dam body are 44.8, 48.8, 30.8 and 41.0 GPa, respectively, and other viscoelastic parameters are linearly proportional to these. The inverted parameters in the central of the dam body are the highest, followed by the crest region, while smaller values are obtained for dam regions near the foundation. With the utilization of deformation spatial association, the zonal intelligent inversion can effectively avoid the interference of the location of used dam displacem

关键词： High arch dams viscoelastic deformation behaviour HEST statistical model Improved particle swarm optimization Zonal intelligent inversion viscoelastic parameters

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An equivalent method for predicting acoustic scattering of coated shell using identified viscoelastic parameters of anechoic coating

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APPLIED ACOUSTICS 2021年 179卷 108071-108071页

作者： Ke, Yibo Zhang, Lin Zhao, Xuefeng Tao, Meng Guizhou Univ Sch Mech Engn Guiyang Peoples R China

A novel method to identify the viscoelastic parameters of underwater anechoic coating has been proposed in this present study. Based on two sets of measured reflection coefficients, the viscoelastic parameters can be identified by using the combination of finite element method and Newton's iterative method. The identification method is used to obtain the viscoelastic parameters of polyurethane, and the effects of some experimental errors, including the mismatched amplitude responses and the mismatched phase responses of two hydrophones on the identified results are discussed. Then, an equivalent method is developed to predict the acoustic scattering performance of coated shell. The equivalence kernel is that the equivalent coating has the same reflection coefficient as the original perforated anechoic coating by using the genetic algorithm. In order to verify the accuracy of equivalent method, a direct finite element model (perforated coating - spherical shell) for acoustic scattering simulation is precisely modelled, where the material of coating is selected to be the identified polyurethane. Obtained results are compared to the acoustic scattering of equivalent method (homogenous coating - spherical shell). Good agreement between two models shows that the equivalent method is feasible and effective to predict the acoustic scattering of coated shell. Moreover, it is found that applying the equivalent method greatly reduces the computational expenses compared to the conventional direct model. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Anechoic coating viscoelastic parameters Identification method Acoustic scattering Equivalent method

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Investigation on the Effect of the Contact-Free Creep Test Loading Conditions on the Human Skin viscoelastic parameters 8th

Investigation on the Effect of the Contact-Free Creep Test L...

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8th International Congress on Design and Modeling of Mechanical Systems, CMSM 2019

作者： Azzez, Khouloud Abellan, Marie-Angèle Chaabane, Makram Bergheau, Jean-Michel Zahouani, Hassan Dogui, Abdelwahab Mechanical Engineering Laboratory University of Monastir ENIM MonastirLR99ES32 5000 Tunisia Laboratory of Tribology and Dynamics of Systems University of Lyon ENISE UMR 5513 CNRS Saint-Étienne42023 France

ISBN: (纸本)9783030271459

The present paper proposes an insight into the objective quantification of internal parameters through experimental tests and numerical simulations of contact-free creep tests. The study investigates effects of applied pressure and dwell-times of contact-free creep tests on the viscoelastic properties of human skin. The skin is seen as a homogeneous, quasi-incompressible, linear, isotropic and viscoelastic material modelled by the Zener’s rheological model. A Finite Elements model is developed and an inverse approach is used in order to identify the viscoelastic parameters. Analysis of variance (ANOVA) is carried-out to assess intra- and inter- related effects for two protocols. The analyzed results prove that the imposed pressure exhibits a major effect on the identified viscoelastic properties. However, the dwell time has no remarkable effects. Moreover, the major conclusion establishes that a loading pressure of 1 bar allows to distance objective quantifications from possible protocol influences. © 2020, Springer Nature Switzerland AG.

关键词： ANOVA Contact-free creep test Human skin Numerical simulation viscoelastic parameters

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viscoelastic parameters of Asphalt Mixtures Identified in Static and Dynamic Tests

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MATERIALS 2019年第13期12卷 2084-2084页

作者： Mackiewicz, Piotr Szydlo, Antoni Wroclaw Univ Sci & Technol Fac Civil Engn PL-50370 Wroclaw Poland

We present two methods used in the identification of viscoelastic parameters of asphalt mixtures used in pavements. The static creep test and the dynamic test, with a frequency of 10 Hz, were carried out based on the four-point bending beam (4BP). In the method identifying viscoelastic parameters for the Brugers' model, we included the course of a creeping curve (for static creep) and fatigue hysteresis (for dynamic test). It was shown that these parameters depend significantly on the load time, method used, and temperature and asphalt content. A similar variation of parameters depending on temperature was found for the two tests, but different absolute values were obtained. Additionally, the share of viscous deformations in relation to total deformations is presented, on the basis of back calculations and finite element methods. We obtained a significant contribution of viscous deformations (about 93% for the static test and 25% for the dynamic test) for the temperature 25 degrees C. The received rheological parameters from both methods appeared to be sensitive to a change in asphalt content, which means that these methods can be used to design an optimal asphalt mixture composition-e.g., due to the permanent deformation of pavement. We also found that the parameters should be determined using the creep curve for the static analyses with persistent load, whereas in the case of the dynamic studies, the hysteresis is more appropriate. The 4BP static creep and dynamic tests are sufficient methods for determining the rheological parameters for materials designed for flexible pavements. In the 4BP dynamic test, we determined relationships between damping and viscosity coefficients, showing material variability depending on the test temperature.

关键词： viscoelastic parameters creep test fatigue tests asphalt mixtures Burgers model four point bending beam

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Multistage Frequency-Domain Transient-Based Method for the Analysis of viscoelastic parameters of Plastic Pipes

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JOURNAL OF HYDRAULIC ENGINEERING 2020年第3期146卷

作者： Pan, B. Duan, H. F. Meniconi, S. Urbanowicz, K. Che, T. C. Brunone, B. Hong Kong Polytech Univ Dept Civil & Environm Engn Hung Hom Kowloon Hong Kong 999077 Peoples R China Univ Perugia Dept Civil & Environm Engn G Duranti 93 I-06125 Perugia Italy West Pomeranian Univ Technol Szczecin Dept Mech Engn & Mechatron Piastow 19 PL-70310 Szczecin Poland

Plastic/viscoelastic pipes such as polyvinyl chloride (PVC), polyethylene (PE), and high-density polyethylene (HDPE) pipes have been increasingly applied in fluid piping systems. The understanding of the hydrodynamic behavior and features of such pipe materials are important in their practical applications. This paper develops an effective frequency-domain transient-based method (FDTBM) for the efficient and accurate identification of viscoelastic parameters of plastic pipes. The analytical expression of transient frequency response in a typical viscoelastic pipeline system is first derived to describe the dependence relationship among different factors and coefficients in the system (e.g., pipe and fluid properties). The obtained result is then applied to inversely identify the viscoelastic parameters of plastic pipes under different flow and operational conditions. A multistage analysis framework is proposed to enhance the robustness and effectiveness of the proposed FDTBM to obtain accurate and unique solutions of viscoelastic parameters for the plastic pipes used in this study. The proposed method and analysis framework have been validated and evaluated through various experimental tests and numerical simulations.

关键词： Transients Plastic pipes viscoelastic parameters Multistage analysis Frequency-domain method

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Quantitative Study of the Effects of Dehydration on the viscoelastic parameters in the Vocal Fold Mucosa

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JOURNAL OF VOICE 2017年第3期31卷 269-274页

作者： Yang, Shuai Zhang, Yu Mills, Randal D. Jiang, Jack J. Xiamen Univ Coll Ocean & Earth Sci Dept Appl Marine Phys & Engn Xiamen Fujian Peoples R China Xiamen Univ Minist Educ Key Lab Underwater Acoust Commun & Marine Informa Xiamen 361005 Fujian Peoples R China Chinese Acad Sci Inst Acoust State Key Lab Acoust Beijing Peoples R China Univ Wisconsin Sch Med & Publ Hlth Dept Surg Div Otolaryngol Head & Neck Surg Madison WI USA

Objectives. The goal of this study was to quantify the viscoelastic parameters of the vocal fold mucosa at varying dehydration levels. Study Design and Methods. Healthy canine larynges were obtained postmortem, and the samples were separated from the subglottal wall. The samples were dehydrated in a vacuum dryer. According to the total dehydration time per sample, dehydration levels were divided into four degrees: 0%, 40%, 60%, and 80%. The stepper was set to stretch the sample to a level of 35% strain at the same rate (0.5 mm/s). Data collection was repeated five times under each dehydration condition. The compression resilience, RC% = S'/S* 100%, and the hysteresis area were measured according to the stress-strain curves. The varying properties of the samples under different dehydration levels were investigated by fitting the curves. Results. The area of the hysteresis loops observed in the stress-strain curves increased exponentially with dehydration levels, whereas the RC% decreased linearly. For all curves, low-strain stages can be explained by Hooke's law (sigma= E-0*epsilon). With increasing levels of dehydration, E-0 was shown to increase, whereas the linear range was shortened. High-strain stages resembled exponential rather than the linear curves. And the nonlinear stage of the curve became increasingly apparent in the stress-strain curves of increased dehydration levels. Conclusions. The quantitative results in this study not only provide a numerical reference for future experimental measurements, but also can be used to verify the biphasic model in future studies.

关键词： vocal fold mucosa dehydration levels quantify viscoelastic parameters

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Active microrheology to determine viscoelastic parameters of Stokes-Oldroyd B fluids using optical tweezers

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JOURNAL OF PHYSICS COMMUNICATIONS 2019年第3期3卷 035002-035002页

作者： Paul, Shuvojit Kundu, Avijit Banerjee, Ayan Indian Inst Sci Educ & Res Kolkata India

We use active microrheology to determine the frequency dependent moduli of a linear viscoelastic fluid in terms of the polymer time constant (lambda), and the polymer (mu(p)) and solvent viscosity (mu(s)), respectively. We measure these parameters from the response function of an optically trapped Brownian probe in the fluid under an external perturbation, and at different dilutions of the viscoelastic component in the fluid. This is an improvement over bulk microrheology measurements in viscoelastic Stokes-Oldroyd B fluids which determine the complex elastic modulus G(omega) of the fluid, but do not, however, reveal the characteristics of the polymer chains and the Newtonian solvent of the complex fluid individually. In a recent work (Paul et al 2018 J. Phys. Condens. Matter 30, 345101), we linearized the Stokes-Oldroyd B fluid model and thereby explicitly formulated the frequency dependent moduli in terms of mu(p), mu(s) and lambda which we now extend to account for an external sinusoidal force applied to the probe particle. We measure lambda, mu(p), and mu(s), experimentally, and compare with the existing A values in the literature for the same fluid at some of the dilution levels, and obtain good agreement. Further, we use these parameters to calculate the complex elastic modulus of the fluid again at certain dilutions and verify successfully with existing data. This establishes our method as an alternate approach in the active microrheology of complex fluids which should reveal information about the composition of such fluids in significantly greater detail and high signal to noise.

关键词： viscoelastic Stokes-Oldroyd B optical tweezer microrheology viscoelastic parameters

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Tabletop magnetic resonance elastography for the measurement of viscoelastic parameters of small tissue samples

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JOURNAL OF MAGNETIC RESONANCE 2015年第1期251卷 13-18页

作者： Ipek-Ugay, Selcan Driessle, Toni Ledwig, Michael Guo, Jing Hirsch, Sebastian Sack, Ingolf Braun, Juergen Charite Dept Radiol D-12200 Berlin Germany Pure Devices GmbH Wurzburg Germany Charite Inst Med Informat D-12200 Berlin Germany

We demonstrate the feasibility of low-cost tabletop MR elastography (MRE) for quantifying the complex shear modulus G* of small soft biological tissue samples as provided by pathologists. The MRE system was developed based on a tabletop MRI scanner equipped with a 0.5 T permanent magnet and a tissue sample holder mounted to a loudspeaker. A spin echo sequence was enhanced with motion-encoding gradients of 250 mT/m amplitude synchronized to acoustic vibration frequencies. Shear wave images suitable for elastography were acquired between vibration frequencies of 0.5 and 1 kHz in agarose, ultrasound gel, porcine liver, porcine skeletal muscle, and bovine heart with a spatial resolution of 234 mu m pixel edge length. The measured frequency dependence of G* agreed well with previous work based on high-field MR systems. The ratio between loss and storage moduli was highest in liver and ultrasound gel, followed by muscle tissue and agarose gel while ultrasound gel and liver showed similarly low storage moduli compared to the other samples. The shear wave to noise ratio is an important imaging criteria for MRE and was about 4.2 times lower for the preliminary setup of the 0.5 T tabletop system compared to a 7 T animal scanner. In the future, the new tabletop MRE system may serve as a low cost device for preclinical research on the correlation of viscoelastic parameters with histopathology of biological samples. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Tabletop magnetic resonance elastography Tissue samples viscoelastic parameters Soft biological tissue Liver Muscle Heart Complex shear modulus

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Energy absorption in composite structure reinforced with advanced functionally graded nano-materials: Artificial intelligence and numerical approaches

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MECHANICS OF ADVANCED MATERIALS AND STRUCTURES 2024年第28期31卷 10264-10278页

作者： Chen, Guang Xia, Lingqin Wu, Yaofeng Alshamrani, Ahmad M. Zhejiang Inst Mech & Elect Engn Coll Addit Mfg Hangzhou Peoples R China NingboTech Univ Sch Mechatron & Energy Engn Ningbo Peoples R China King Saud Univ Coll Sci Stat & Operat Res Dept Riyadh Saudi Arabia

The energy absorption characteristics of materials and structures are crucial for ensuring the safety of structures when subjected to mechanical forces. This study focuses on the significance of energy absorption in composite structures. Specifically, it examines the energy absorption in composite structures that are reinforced using sophisticated functionally graded nano-materials. The analysis is conducted using both mathematical modeling and artificial intelligence methods. The Halpin-Tsai micromechanics method is employed to simulate the material properties of the advanced composite construction, taking into account the role of the mixture. Within the realm of mathematical modeling, the energy method, higher-order Taylor's Formula, viscoelastic formula, and differential quadrature method (DQM) are employed to extract and solve the governing equations of composite structures reinforced with advanced functionally graded nano-materials. The Deep Neural Networks Model (DNNM) is a highly popular supervised machine learning approach that may be employed for both regression and classification tasks. The objective of regression analysis is to determine the correlation between independent variables and dependent responses by identifying the function of optimal decision that can accurately explain the fluctuations in the response parameter depending on the dependent variables. In the second phase, the findings acquired from mathematical modeling are trained and evaluated for the aim of DNNM. Upon receiving the results, recommendations for enhancing the energy absorption in composite structures reinforced with advanced functionally graded nano-materials will be provided for inclusion in future publications on advanced structures.

关键词： Energy absorption advanced FGM artificial intelligence composite structure viscoelastic parameters

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Effects of storage and toothbrush simulation on Martens hardness of CAD/CAM, hand-cast, thermoforming, and 3D-printed splint materials

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CLINICAL ORAL INVESTIGATIONS 2023年第12期27卷 7859-7869页

作者： Rosentritt, Martin Hickl, Verena Rauch, Angelika Schmidt, Michael UKR Univ Hosp Regensburg Dept Prosthet Dent D-93042 Regensburg Germany

ObjectivesTo investigate Martens hardness parameters of splint materials after storage in liquids and toothbrush *** and methodsTen specimens per material and group were fabricated (hand-cast CAST, thermoformed TF, CAD/CAM-milled CAM, 3D-printed PS, PL, PK, PV), stored in air, water, coffee, red wine, and cleaning tablets and investigated after fabrication, 24 h, 2- and 4-week storage or toothbrushing. Martens hardness (HM), indentation hardness (HIT), indentation modulus (EIT), the elastic part of indentation work (eta IT), and indentation creep (CIT) were calculated (ISO 14577-1). Statistics: ANOVA, Bonferroni post hoc test, between-subjects effects, Pearson correlation (alpha = 0.05).ResultsHM varied between 30.8 N/mm2 for PS (water 4 weeks) and 164.0 N/mm2 for CAM (toothbrush). HIT values between 34.9 N/mm2 for PS (water 4 weeks) and 238.9 N/mm2 for CAM (toothbrush) were found. EIT varied between 4.3 kN/mm2 for CAM (toothbrush) and 1.8 kN/mm2 for PK (water 2 weeks). eta IT was found to vary between 16.9% for PS (water 4 weeks) and 42.8% for PL (toothbrush). CIT varied between 2.5% for PL (toothbrush) and 11.4% for PS (water 4 weeks). The highest impact was identified for the material (p <= 0.001).ConclusionsStorage and toothbrushing influenced Martens parameters. The properties of splints can be influenced by the choice of materials, based on different elastic and viscoelastic parameters. High HM and EIT and low CIT might be beneficial for splint *** relevanceMartens parameters HM, EIT, and CIT might help to evaluate clinically relevant splint properties such as hardness, elasticity, and creep.

关键词： Hardness Martens Elastic behavior viscoelastic parameters Creep

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