Complex Dynamic Modulus Research Articles

Soft material characterization through surface wave elastography using a laser Doppler vibrometer

This paper provides a comprehensive investigation into characterizing viscoelastic properties in soft materials, focusing on silicone. Conventional measurement techniques such as tensile testing and dynamic mechanical analysis prove inadequate for soft materials. The proposed method utilizes Rayleigh surface wave propagation, employing a laser Doppler vibrometer to measure phase speed and amplitude, induced by air jet pulses in a contactless manner. Usually, a contact probe is used for excitation, which results a higher signal to noise ratio. The study involves a regression analysis to obtain dispersion curves, filtering outcomes with a coefficient of determination threshold above 95% as a quality indicator for the measurements. Mechanical parameters, including complex dynamic modulus and shear modulus components, are determined from Rayleigh and shear complex wave-numbers. Repeatability assessments, including changes in measuring direction, underscore the stability of the experimental setup and sample uniformity. Noteworthy is the comparison of results from the Surface Wave Elastography (SWE) method through an experimental test, a novel aspect in this study. The evaluation method, based on a spring–damper model rooted in the exact solution of Newton’s second law differential equation, serves as a reference. The comparison of mean storage modulus values between the SWE method and the free-loading mass method revealed errors of 6.36% and 10.23% for two tested samples.

An alternative approach for characterization of the linear viscoelastic behavior of asphalt binders

This study aimed to develop an alternative approach to characterise the linear viscoelastic behaviour of asphalt binders. A rheogram model was firstly proposed based on the Carreau–Yasuda model; its accuracy was substantiated by high R 2 values. The dynamic shear modulus master curve model was then obtained using the relationship between the magnitude of complex viscosity and dynamic shear modulus and the two definitions of the time-temperature shift factor. Afterwards, the phase angle master curve model was derived according to the approximate Kramers–Kronig relation. The proposed approach was demonstrated to be capable of accurately characterising the linear viscoelastic behaviour of selected asphalt binders. In addition, the predicted zero shear viscosity (ZSV) could be potentially employed to evaluate the asphalt binder rutting resistance. Compared with the widely-used Christensen-Anderson-Marasteanu (CAM) model, the developed master curves models were better at constructing the phase angle master curves of selected asphalt binders.

Fatty acid amides of plant origin in elastomeric compositions

One of the strategic directions of chemical technology eco-modernization is the use of renewable natural raw materials to create ingredients for elastomeric composites. The use of fatty acids amides of sunflower oil, such as monoethanolamide and diethanolamide of sunflower oil fatty acids, and oleic acid amide, has been proposed for the rubber industry; their main characteristics have been determined. The effectiveness of the action of fatty acid amides in sulfur vulcanization system has been studied in unfilled and filled elastomeric composites of a model type based on butadiene--methylstyrene rubber with the presence of the investigated substances at a dosage of 1.5 phr per 100.0 phr of the rubber base. Using the rheometry method, it has been shown that the investigated fatty acid amides significantly activate and deepen the degree of sulfur vulcanization, and their activity in the composition of accelerated sulfur vulcanization activators depends on the structure. Fatty acid diethanolamide with a tertiary nitrogen atom exhibited the maximum activity. A positive effect of fatty acid amides on the gain coefficient, complex dynamic modulus, and mechanical loss tangent of rubber has been established.

Laboratory Characterization of Additive-Modified Asphalt Concrete Mixtures

There is a need for a more rapid system of evaluation and implementation for new and existing asphalt additives, especially because of the prohibitive cost of full-scale performance evaluations. To help to meet this need, the Additive Group (AG) experiment at the National Center for Asphalt Technology (NCAT) was developed and began in 2021. A comprehensive laboratory evaluation of six mixtures, each modified with a popular additive type selected by the AG state DOT sponsors, was conducted. Simultaneously, full-scale test sections were constructed at the NCAT test track to evaluate the field performance and structure behavior of each modified mixture. Trafficking of these test sections is currently underway, and estimated to be completed in 2024, at which point an investigation linking the laboratory and field results will be done. This paper presents the completed laboratory evaluation of each AG mixture via complex dynamic modulus (E*), direct tension cyclic fatigue, and bending beam fatigue testing. The wet-process rubber modified mixture was found to have reduced E* and initial flexural stiffness, but increased fatigue resistance, relative to the styrene-butadiene-styrene (SBS)-modified control mixture. The dry-process rubber-modified mixture displayed similar trends, though to a lesser degree. Conversely, the dry-process plastic-modified mixture was found to have increased E* and initial flexural stiffness, but reduced fatigue resistance, relative to the SBS-modified control mixture. The other AG mixtures—a dry-process fiber and a wet-process plastic-modified mixture—were found to display E*, initial flexural stiffness, and fatigue resistance similar to that of the SBS-modified control mixture.

Improving the whey protein foam structures by using novel acetylated triglycerides: A response surface methodology (RSM) approach

AbstractProtein foams are common to foods, such as meringue, whipped cream and mousses. Stability is a challenging issue determined by fat and sugar content. We hypothesize that acetyl‐triacylglycerols (acetyl‐TAG) that possess sn‐3 acetate group with high oleic content can provide stability to the foam at reduced sugar concentrations by increasing the surface viscosity and minimizing serum drainage. A fractional factorial Box‐Wilson design was used to investigate the effects of whey protein concentration (WPI) (2–10 wt%), sucrose concentration (SC) (10–30 wt%) and acetyl‐TAG concentration (ATC) (0–1 wt%) on overrun (FO), stability against serum drainage (FD) and surface dilatational rheology. Each response was analyzed by linear regression model fitting and a backward elimination algorithm for significance (α = 0.01). FO was significantly affected (p < 0.01) by WPI and ATC, but not sucrose concentration. The optimum overrun (nearly 700%) was obtained at 9 wt% WPI and 0.6 wt% ATC. Drainage and viscoelastic properties were significantly (p < 0.01) affected by all process variables. Dynamic complex modulus (|E|) as measured using an optical tensiometer was around 30–40 mN/m when acetyl‐TAG was higher than 0.5 wt%. Our findings indicated that the acetyl‐TAG can be used to enhance the stability of protein foams in reduced sugar food products, however, not at high sugar concentrations (30 wt%).

A time-temperature-ageing shift model for bitumen and asphalt mixtures based on free volume theory

ABSTRACT This paper aims to develop a general form of the time-temperature-ageing shift model for bituminous materials based on free volume theory and validate its application in the Finite Element (FE) modelling for predicting aged asphalt mixtures’ mechanical responses. The frequency sweep, dynamic modulus, and Fourier Transform Infrared Spectroscopy (FTIR) tests were used to validate the proposed time-temperature-ageing shift model. A generalised Maxwell model incorporating the proposed shift model of asphalt mixtures was used to predict the mechanical responses of aged asphalt mixtures using FE modelling, verified via laboratory cyclic load tests. Results indicate that the time-temperature-ageing shift function can model the complex shear modulus and dynamic modulus master curves of bituminous materials, addressing the modulus dependency of temperature and ageing. Temperature dominates the modulus change of bituminous materials in the ageing process. The coefficients of the time-temperature-ageing shift model have clear physical meanings and can potentially quantify the effects of asphalt mixtures’ air voids on their temperature and ageing susceptibilities. The time-temperature-ageing shift model can be incorporated into the constitutive relations of the FE model to effectively couple and efficiently predict the effects of temperature and ageing on the mechanical responses of aged asphalt mixtures.

A NUMERICAL ANALYSIS OF FORCED STEADY-STATE VIBRATIONS OF AN ELECTRO-VISCOELASTIC SYSTEM IN CASE OF A JOINT IMPACT OF ELECTRICAL AND MECHANICAL LOADS

In the current paper an estimation of a mechanical response of a structure on joint mechanical (force and kinematic) and electrical (voltage and current) impacts taking into account different options of their combinations was carried out. A mechanical response was esteemed basing on solution to the problem of natural vibrations for piecewise-homogeneous electro-viscoelastic bodies. A cantilever plate with piezoelectric element attached to its surface was chosen as an object under study. The plate was made of viscoelastic material the mechanical properties of which are described using complex dynamic moduli. A piezoelectric ceramic material was chosen as the one for piezoelectric elements. An amplitude of forced steady-state vibrations of a component of displacement vector that is perpendicular to the surface of the plate was chosen as a quantity that characterize a mechanical response. Variational equation of motion of the object under consideration is formulated based on relations of linear elasticity, linear viscoelasticity and Maxwell’s equations for a conducting media in a quasistatic approximation. Ranges of changing of values of excitation impacts for vibration modes taken into account were chosen on the basis of values of natural vibrations frequencies obtained from the solution to natural vibration problem for electro-viscoelastic bodies. Numerical implementation of the stated problem was performed in finite element software package ANSYS. Some characteristic peculiarities of a mechanical response depending on a type and magnitude of external impact were obtained as the result of the carried out numerical experiments. There was demonstrated that in case of joint impact of two loading factors there reveals an additional capability of control a mechanical response of an electro-viscoelastic system.

Laboratory performance of dense graded asphalt mixtures prepared using highly polymer modified binders containing corn oil as softening agent

• High Polymer Modified Asphalt (HPMA) with corn oil can resist short term aging. • Crack Propagation slows with HPMA and corn oil combination compared to Control. • Life Cycle Analysis shows the cost-effectiveness of the optimized combination of HPMA and Corn Oil. This study evaluated the impact of aging on High Polymer Modified Asphalt (HPMA) mixtures containing a softening agent (SA). The aging susceptibility was evaluated in terms of rutting, cracking, and durability. Four asphalt mixtures were prepared, one with PG 52–34 binder as control, and three others using modified PG 52–34 with varying dosages of Styrene Butadiene Styrene (SBS) and corn oil (SA). The tests performed to evaluate the impact of aging (short, long, extended long term) were the Dynamic Complex Modulus, Hamburg Wheel Tracking, Flow Number, Indirect Tension and semi-Circular Bend tests. Based on these testing results, SBS and SA increased the durability and rutting resistance of asphalt mixtures. Modified asphalt mixtures also showed better cracking resistance than the control mix (i.e. lowering of crack propagation). However, with aging, fatigue cracking performance diminished while remaining comparable to the control mix. A balanced dosage of SBS (7.5%) and SA (7%) led to the best improvement in durability, rutting, and short-term cracking performance.

Experimental determination of the dynamic elastic modulus of polymeric soft materials in an extended frequency range: A supported free loading-mass method

In this paper, an experimental test method to accurately measure the complex dynamic elastic modulus of soft materials designed for anti-vibration purposes over a wide frequency range with high resolution at low uncertainty levels is proposed and applied to six polymeric soft materials. The proposed experimental technique, based on standardized test set-up and laser-Doppler velocimetry, is conceived to provide the uniaxial dynamic modulus of these materials on the basis of the exact solution of the Newton’s second law differential equation of a free loading-mass supported by a spring-damper system and subjected to an underlying dynamic stress. After a preliminary characterization with different standard procedures, the dynamic elastic modulus and damping properties of the six materials are investigated over a frequency range of 25–1000 Hz. The overall expanded uncertainty, on average around 3 %, is determined from five repeated measurements including the instrumental uncertainty. Results are compared with the standard ones.

Rheological behavior of oil sludge from Algerian refinery storage tanks

The consumption and demand for petroleum are increasing dramatically with the rapid development of industry and energy sector. As a result, petroleum refineries produce the greatest amount of oily sludge formed at the bottom of storage tanks during oil storage operations, which has a severely negative impact on the storage capacity and the operational safety of the storage tank. The present study focuses on the rheology of this complex fluid from Algerian crude oil storage tanks. Rheological measurements were performed at different temperatures under steady shear and dynamic oscillometry using AR-2000 Rheometer. The results obtained show that the sludge exhibits yield-pseudoplastic flow behavior at low shear rates, which is adequately described by the Herschel Bulkley model based on the standard error and correlation coefficient values. However, quasi-Newtonian flow behavior occurs at very high shear rates. The increase in temperature had positive effects on the rheological properties of the sludge, including dynamic viscosity, shear stress, yield stress, complex modulus, elastic modulus and viscous modulus. The dynamic rheology studies have shown that the sludge material behaves more like a solid than a liquid under all experimental conditions studied.

Comparative Study on Complex Modulus and Dynamic Modulus of High-Modulus Asphalt Mixture

In the French high-modulus asphalt mixture design system, the complex modulus of the mixture under the conditions of 15 °C and 10 Hz is taken as the design index. However, in China, the dynamic modulus under the conditions of 15 °C, 10 Hz, 20 °C, 10 Hz and 45 °C, 10 Hz was taken as the stiffness modulus index of high-modulus asphalt mixture. The difference in modulus values between the two systems caused the pavement structure layer to be thicker and the construction cost to be higher in China. In order to find out the appropriate modulus value of high-modulus asphalt mixture suitable for China’s modulus parameter conditions to better carry out the reasonable design and evaluation of high-modulus asphalt mixture in China, the modulus of four types of high-modulus asphalt mixtures under the two systems through the two-point bending complex modulus test of the CRT-2PT trapezoidal beam and the SPT uniaxial compression dynamic modulus test were analyzed in this paper. Under the premise of meeting the stiffness modulus index of the French high-modulus asphalt mixture, the relationship conversion models between the dynamic modulus and complex modulus of high-modulus asphalt mixture under different temperatures were established. According to the conversion models, the design evaluation value range of dynamic modulus suitable for China’s condition was recommended. It is recommended that the dynamic modulus of China’s high-modulus asphalt mixture at 15 °C and 10 Hz is not less than 16,000 MPa, the dynamic modulus at 20 °C and 10 Hz is not less than 14,000 MPa, and the dynamic modulus at 45 °C and 10 Hz is not less than 2500 MPa. Five kinds of high-modulus asphalt mixtures used in actual road engineering were tested to verify the reliability of the recommended dynamic modulus values based on the modulus conversion model, and the results are consistent with the recommended value range of the model.

Characterization of the effect of dry-heat treatment on the gelation of alkaline dried egg whites using dynamic viscoelastic measurement and ultrasound spectroscopy

In the present study, the mechanism for gelation of dried egg whites (DEWs) samples, which were differentially pretreated with dry-heat treatment and alkaline pH, were investigated using dynamic viscoelastic measurements and ultrasound spectroscopy for gels formed with at high protein concentrations. Rheological measurements showed that DEW gels with dry-heat treatments have a higher dynamic complex modulus than DEW gels without dry-heat treatments. Furthermore, ultrasonic attenuation analyses showed that subjecting DEWs to dry-heat treatment and alkaline pH induced the formation of an increased number of DEW protein “soluble aggregates” compared with unheated and neutral DEWs. Our data suggests that pretreatment of DEW samples led to partially unfolded DEW proteins with more “soluble aggregates”, which were strongly correlated with the formation of gels with a more homogeneous and rigid texture. Understanding their structural properties at a molecular detail would enable desirable textural modifications for the development of new food products.

Viscoelastic Properties of Filled Polyurethane Auxetics

The paper presents experimental values of lateral and extension transmission ultrasonic waves speed and their absorbance coefficient obtained with the help of discrete immersed method in metal filled polymer auxetic samples with polyurethane matrix. Poisson’s ratio, real and imaginary parts of complex dynamic elastic modulus (Young’s modulus, shear modulus, bulk modulus) and mechanical losses tangent of angle for extension, lateral and bulk deformation have been calculated regarding paper’s results. Viscoelastic properties of polyurethane auxetic have been examined regarding different theoretical approaches. To support negative values of Poisson’s ratio, a filled polymer model with critical filler amount and auxetic deformation models have been used. Models structural characteristics for filled polyurethane auxetics have been defined. Systems modeling with solid bulky inclusions, that are able to absorb and to disseminate ultrasonic waves, enables to consider suchlike systems as complex density materials. It is shown that in certain ratio of wave parameters and environment structural and mechanical properties, resonance effects take place, regarding filler’s particles vibration as inclusions in general.

Michael Silverstein

Previous articleNext article No AccessObituaryMichael Silverstein (1945–2020)Greg Urban and Benjamin LeeGreg UrbanDepartment of Anthropology, University of Pennsylvania. Email: [email protected] Search for more articles by this author and Benjamin LeeDepartments of Anthropology and Philosophy, New School for Social Research Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Journal of Anthropological Research Volume 77, Number 2Summer 2021 Article DOIhttps://doi.org/10.1086/713648 Views: 210Total views on this site Citations: 1Citations are reported from Crossref HistorySubmitted December 23, 2020Accepted December 24, 2020Published online April 15, 2021 © 2021 by The University of New Mexico. All rights reserved.PDF download Crossref reports the following articles citing this article:Fabian Urban, Bo Armbruster, Peter Middendorf Development and validation of a method for linear-viscoelastic characterization of the dynamic complex modulus of short-fiber reinforced plastics using flexural resonances, Polymer Testing 94 (Feb 2021): 107055.https://doi.org/10.1016/j.polymertesting.2021.107055

Controlling the Vibration Amplitude of a System with a Piezoelectric Element by Applying an Electric Voltage to it

The article is devoted to the study of the mechanical response of an electro-viscoelastic structure if an electric voltage with given characteristics supplied to a piezoelectric element attached to the surface of the structure. A cantilever plate made of a viscoelastic material is considered as a structure under study. The amplitude of displacements of the free end of the plate in resonance modes occurring at forced steady-state vibrations is considered as the mechanical response. Excitation of vibrations is realized by a harmonic movement applied to the clamped end of the plate. The control of the mechanical response within the framework of this work is supposed to be performed by supplying an electric signal to the piezoelectric element. This signal changes harmonically and has the form of a potential difference which changes according to a harmonic law. The magnitude of the vibration amplitude of the structure is determined numerically by the finite element method implemented in the ANSYS software package. The viscoelastic properties of the plate material are described according to the relations of hereditary theory of viscoelasticity in terms of complex dynamic moduli. Within the framework of this work, the relations between the mechanical response of the structure and the magnitude and polarity of the electric voltage applied to the piezoelectric element were obtained. It is shown that by a proper selection of the characteristics of the electric voltage, it is possible to control the magnitude of the amplitude of forced steady-state vibrations.

Effect of Temperature on Phase Angle and Dynamic Modulus of Asphalt Mixtures Using SPT

The Simple Performance Test (SPT) can be used to characterize the strength and load resistance of asphalt mixtures. The objectives of this study are to determine the effect of temperature on the phase angle and dynamic complex modulus of the asphalt mixtures tested at 30°C, 35°C, 40°C, 45°C and 50°C at 25Hz, 20Hz, 10Hz, 5Hz, 1Hz and 0.5Hz frequencies. The asphalt mixtures of NMAS 12.5mm are prepared using asphalt binder PEN 80/100 and PEN 60/70. The asphalt mixtures are designed using the Superpave system and compacted using the Superpave Gyratory Compactor (SGC). The dynamic modulus test results showed that at a higher temperature, the stiffness of the asphalt mixtures is affected. The dynamic modulus of the mixtures is highest at 30°C and gradually decrease at 35°C, 40°C, 45°C and 50°C respectively. The dynamic modulus values for asphalt mixtures with bitumen grade PEN 60/70 are also higher compared to the asphalt mixtures with bitumen grade PEN 80/100. Results also showed that the low phase angle values indicate low viscosity of the asphalt binder due to increase in temperature. The present study is meaningful in understanding the asphalt mixture behaviour at different temperature and loading frequencies.

Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis

Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) deflection measurements; however, the stationary nature of the FWD requires lane closure and traffic control. In recent years, traffic speed deflection devices such as the traffic speed deflectometer (TSD), which can continuously measure pavement surface deflections at traffic speed, have been introduced. In this study, a mechanistic-based approach was developed to convert TSD deflection measurements into the equivalent FWD deflections. The proposed approach uses 3D-Move software to calculate the theoretical deflection bowls corresponding to FWD and TSD loading configurations. Since 3D-Move requires the definition of the constitutive behaviors of the pavement layers, cores were extracted from 13 sections in Louisiana and were tested in the laboratory to estimate the dynamic complex modulus of asphalt concrete. The 3D-Move generated deflection bowls were validated with field TSD and FWD data with acceptable accuracy. A parametric study was then conducted using the validated 3D-Move model; the parametric study consisted of simulating pavement designs with varying thicknesses and material properties and their corresponding FWD and TSD surface deflections were calculated. The results obtained from the parametric study were then incorporated into a Windows-based software application, which uses artificial neural network as the regression algorithm to convert TSD deflections to their corresponding FWD deflections. This conversion would allow backcalculation of layer moduli using TSD-measured deflections, as equivalent FWD deflections can be used with readily available tools to backcalculate the layer moduli.

Assessment of the Impact of Fiber Types on the Performance of Fiber-Reinforced Hot Mix Asphalt

This study aims to evaluate the impact of fiber types on the performance of hot mix asphalt (HMA) mixtures. Specifically, the impacts of fiber type on HMA mix design and laboratory performance are investigated. Four types of fiber (fiberglass, basalt, carbon, and polyolefin/aramid blend) were used to produce four fiber-reinforced HMA mixes, and a control mix without fibers was also prepared. The fiber dosage rates used in this study were 0.16% (fiberglass, basalt, and carbon) and 0.05% (polyolefin/aramid) by total mixture weight, based on manufacturer recommendations. Two mixing procedures for introducing fibers into HMA were also evaluated: dry and 15-s dispersion methods. The dry method involved mixing the fibers with aggregates before the addition of asphalt binder while the 15-s dispersion method involved adding the fibers into the mix every 15 seconds (as aggregates were coated by asphalt binder during the mixing process). All the HMA mixtures (unreinforced and fiber-reinforced) were then subjected to several different laboratory performance tests: dynamic complex modulus, Cantabro durability, asphalt pavement analyzer, flow number, and indirect tensile strength. Analysis of variance was conducted to evaluate statistically the impact of fibers on mix performance. Results showed that fibers affected the volumetric properties, mix durability, and rutting resistance of HMA mixes. It was also found that the process for introducing fibers into the mix (i.e., mixing method) affected the consistency of fiber-reinforced HMA samples. Overall, the results of this study showed that the use of fibers improved the rutting and durability performance of asphalt mixtures in the laboratory.

Evaluation of the complex dynamic modulus of asphaltic concretes manufactured with construction and demolition waste (CDW) aggregates.

Currently, there is an overexploitation of natural resources worldwide due to the need to build various types of civil engineering infrastructure, such as buildings, bridges, housing and, in particular, roads. A large number of countries, including Mexico, additionally do not apply adequate treatment to the material resulting from the demolition of this type of work. Both situations generate significant environmental damage and contribute to the non-sustainability of the road construction sector. This research assesses the linear viscoelastic (LVE2) behavior of asphalt concrete specimens made with different combinations of mineral aggregate and construction and demolition waste (CDW). Complex dynamic modulus tests were performed in compression on cylindrical samples at different temperatures and frequency loading. The ANOVA analysis of test results indicate that the stiffness of the different asphalt concretes evaluated, represented by the complex dynamic modulus, tends to decrease with the temperature and increase with load frequency, which are typical of materials with viscous characteristics. The stiffness of the asphalt concrete evaluated does not show significant changes as the CDW aggregate content varies.

A comparative analysis of two approaches to damping of vibrations

In the current paper a comparison between two approaches to damping of vibrations is presented. A comparative analysis was carried-out on the example of a cantilever plate. In the first case, the surface of the plate was covered with a layer of viscoelastic material. Its mechanical behavior is described by equations of the linear theory of viscoelasticity based on complex dynamic moduli. In this case, the complex dynamic moduli can increase or decrease as the oscillation frequency increases, or remain constant. It is assumed that the thickness of the viscoelastic layer is equal to the thickness of the plate.In the second case piezoelectric elements shunted with resistive (R) or resonant (RL) electric circuits were applied for damping of vibrations. In this case, for each vibration mode, the optimal location of the piezoelectric element and the parameters of the external electrical circuit are determined. The comparison is carried out on the basis of analysis of the vibration damping coefficients determined by the value of the complex natural vibration frequencies obtained from the solution to the problem of natural vibrations for electro-viscoelastic bodies with external electric circuits. Numerical implementation was performed using finite element method.