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As of now, there are no standard guidelines for implementing data from Traffic Speed Deflection Devices (TSDDs) into Pavement Management Systems (PMS). This is primarily due to the complexities in analysing TSDD data. Several variables might potentially influence TSDD measurements. This study evaluates the effect of changing loading configurations, moving speed, temperature and pavement structure characteristics on the measurements of TSDDs through software modelling. The viscoelastic behaviour of the surface layer and the dynamic loads applied by all the vehicle axles are reflected in the modelling process. It is shown that pavement temperature can significantly affect TSDD measurements, primarily by changing the modulus of asphalt layer. At speeds exceeding 60 km/h, the effect of vehicle speed on TSDD measurements is negligible. Among the pavement structure characteristics, the subgrade modulus has a significant effect on TSDDs' deflection basin. Also, this study demonstrates device-specific models for estimating critical strains from TSDD data. The proposed models are validated using field measurements from a road in the Norwegian road network. [ABSTRACT FROM AUTHOR]

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In this study, we investigated the thermoresponsive behavior of two different binary wax compositions of commercially available natural candles. The chemical nature of carbon bonds in the fatty acid chains of the natural wax component effectuate a different hygroscopic behavior, as confirmed by NMR analysis. The phase transitions of polymorphic stearin‐rapeseed and stearin‐coconut wax composites were tracked by DSC‐TGA and VT‐XRD. The reduction in the eutectic temperatures of wax composites during the second heating cycles of DSC measurements was correlated with the length of fatty acid chains in rapeseed and coconut waxes, as well as their co‐crystallization kinetics with stearin. Mechanical and hygroscopic behavior of the binary waxes were examined at elevated temperatures between 23 °C and 45 °C using QCM‐D. Voigt viscoelastic model was employed to reveal the soft and rigid textures of wax composites. The hydrophilic behavior of the rapeseed wax composite changed to hydrophobic when the co‐crystallized and individual stearin melted above 35 °C. Activation energies required for melting wax crystals were calculated to be 51±3 kJ mol−1 for pure rapeseed wax, 373 kJ mol−1 for co‐crystallized rapeseed and stearin waxes, and 244 kJ mol−1 for co‐crystallized coconut and stearin waxes, using Arrhenius method with the QCM‐D data. [ABSTRACT FROM AUTHOR]

The semi-flexible pavement (SFP) has been used as a promising wearing course in heavy traffic roads. It is crucial to investigate the main failure mechanisms caused by different influencing factors on SFPs at medium and high temperatures. In this research, utilising a three-dimensional (3D) finite-element model (FEM), the performance of SFP and conventional pavement under realistic tire–pavement contact stresses was compared by computing the critical responses associated with rutting and top-down cracking (TDC). Besides, experimental studies were conducted on typical asphalt concrete (AC16) and four types of SFP mixtures grouted with cement paste and cement asphalt emulsion pastes (CAEPs) to evaluate their rutting resistance and fatigue cracking potential at medium and high temperatures. The numerical analysis results indicated that SFP mixtures with lower asphalt emulsion (AE) content enhanced rutting resistance significantly while TDC potential was reduced at higher percentages of AE. Compared to dual-tire assembly, the wide-base tire led to less TDC damage and asphalt layer (primary) rutting, but more subgrade (secondary) rutting once carrying the same load. Moreover, based on the findings of laboratory evaluation, SFP with CAEP presented the best performance in terms of fatigue life and permanent deformation when AE to cement by weight (AE/C) was no more than 0.4. [ABSTRACT FROM AUTHOR]

Microneedles, including dissolvable ones made from biocompatible and biodegradable materials, have been widely studied and can potentially be used for transdermal drug delivery, disease diagnosis (sampling), skin care, etc. Characterizing their mechanical properties is essential, as being mechanically strong enough to pierce the skin barrier is one of the most fundamental and crucial requirements for them. The micromanipulation technique was based on compressing single microparticles between two flat surfaces to obtain force and displacement data simultaneously. Two mathematical models had already been developed to calculate the rupture stress and apparent Young's modulus, which can identify variations of these parameters in single microneedles within a microneedle patch. In this study, a new model has been developed to determine the viscoelasticity of single microneedles made of hyaluronic acid (HA) with a molecular weight of 300 kDa loaded with lidocaine by using the micromanipulation technique to gather experimental data. The modelling results from the micromanipulation measurements suggest that the microneedles were viscoelastic and their mechanical behaviour was strain-rate dependent, which implies that the penetration efficiency of viscoelastic microneedles can be improved by increasing their piercing speed into the skin. [ABSTRACT FROM AUTHOR]

In this study, the early-age mechanical properties of a concrete mix containing ground granulated blast furnace slag (GGBFS) were investigated and incorporated in a finite-element model. The viscoelastic behavior caused by early-age tensile creep was considered using a viscoelastic analysis in which the creep strain increment was calculated using a strain superposition method. Subroutines for a FEM program (ABAQUS) were developed to predict the stress time-history considering early-age tensile and compressive creep during thermal loading and unloading. Three 1.2-m (4-ft) cubes were cast with a mix design containing 50% replacement by weight of the cement with GGBFS. The FEM predictions match well with the experimental strain measurements. The results indicate that using the proposed analysis and the measured mechanical properties obtains an accurate estimation of the maximum tensile stress for a concrete mix containing GGBFS. Engineers can use the estimated tensile stresses to take preventative measures to minimize the risk of thermal cracking on mass concrete structures. [ABSTRACT FROM AUTHOR]

In the present study, the viscoelastic analysis is investigated for composite laminated plates using a smoothed finite element method called cell/element based smoothed discrete shear gap method. Moreover, the hygrothermal effects is considered on the viscoelastic responses of composite laminated plates. The first-order shear deformation theory is employed due to its simplicity and accuracy. With the help of the convolution theorem in Laplace transformation, the complex stress-strain relationship in integral form is simplified to linear in transformed domain. Therefore, all computing procedures are performed in the transformed domain and then, using inverse techniques (Fast Fourier Transform) to converted back to the real-time domain. The study provides an effective computational tool to analyze the viscoelastic response of laminated composite taking into account the influence of the time and hygrothermal effects. [ABSTRACT FROM AUTHOR]

Orthotropic steel deck (OSD) bridges have gained increasing popularity around the world and the steel deck pavement is essential to extend the service life of the bridge. To optimise the design method for OSD pavements, this study evaluated the critical response of this type of pavement using the viscoelastic finite element (FE) model. Firstly, the FE model was elaborated and comprehensively complemented with field strain measurements to simulate the OSD pavement response. Secondly, the critical responses including critical strain, shear stress and deflection of the OSD pavement under various loading and pavement conditions were predicted via the proposed model. It was found that in FE model, a moving load better simulated the field truck loading than a pulse one, while quasi-static and dynamic analysis algorithms provided nearly identical response predictions. The positions of critical horizontal strains were temperature-dependent. Critical strains and deflections dropped with the load motion speed and rose with temperature, while the critical shear stresses exhibited the opposite trend. Moreover, the investigated three types of critical responses were found to be similarly influenced by the layer thickness variation but showed different patterns under varying bonding conditions. [ABSTRACT FROM AUTHOR]

Abstract The elasticity, soft consistency and similarity to the human body are important characteristics of the gels. Such similarities allow the hydrogels to be biocompatible and, as a consequence, they are very attractive to be applied as biomaterials. This study presents a new strategy for developing a biohybrid complex based on a natural/synthetic polymer conjugate as gel type structure enriched with quercetin, which can be a relevant biomaterial for its antimicrobial properties. There are evidenced the preparation possibilities for the natural/synthetic structure as complex gel based on hyaluronic acid conjugated with poly(itaconic anhydride‑co‑3,9‑divinyl‑2,4,8,10‑tetraoxaspiro[5.5] undecane) copolymer decorated with quercetin. The effects of the composition on various properties were assessed. The chemical composition of bioconjugate gels was confirmed by FTIR spectroscopy. It was established that the new gel structures have enhanced swelling capacity and a typical gel-like behavior. The investigations evidenced the gels responsiveness to stimuli and their high elasticity. The new structures were tested as drug delivery systems. The in vitro release shows the dependence of the mechanism of release on the composition of the gels, evidencing a transport behavior which varies from the Fickian to super case II. In vivo investigations demonstrated a good biocompatibility after systemic administration in mice. Graphical abstract Unlabelled Image Highlights • Hybrid gels with tunable characteristics were prepared using hyaluronic acid and a synthetic copolymer. • The bioconjugate compounds were realized by using a grafting-to strategy without using other chemical additives. • The physical properties including in vitro and in vivo study, swelling capacity, rheological properties were investigated. [ABSTRACT FROM AUTHOR]

This study presents a novel approach for constitutive modeling of multi-part viscoelastic shell structures using a combination formulation of mixed MITC (MITC3 and MITC4) and interface shell elements with reduced computational cost. It focuses on accurate viscoelastic analysis, considering the time-dependent behavior of the multi-part shell structures. The use of the Laplace transform simplifies the integral-form constitutive equation, enabling efficient and accurate viscoelastic analysis. Moreover, by combining the advantages of MITC shell elements and interface shell elements, this approach comprehensively represents multi-part shell structures with non-matching interfaces. Hence, it allows the meshing of each component part independently when assembled. Furthermore, these methods also provide better resistance to shear and membrane locking, which can be problematic when modeling thin shell structures. In numerical examples, to validate the accuracy of the current study, we meticulously analyze multi-part shell models such as an elastic U-shaped beam and the viscoelastic propeller subjected to creep bending loads. This research contributes to improving the design and performance of shell structures in various engineering fields. • Combining mixed MITC elements with ISEs to analyze the viscoelastic multi-part shell structures. • Simplified viscoelastic formulation and reduced computational requirements by using the Laplace transform. • Enhanced accuracy and shear locking mitigation by using MITC formulation. • Integrating the hybrid MITC elements with ISEs to efficient non-matching meshing. [ABSTRACT FROM AUTHOR]

Owing to the pavement cracking of heightening and thickening levees (HTL) caused by differential settlement, it is necessary to study the settlement prediction and differential settlement criterion for HTLs. In this study, an HTL was taken as the study object. First, leveling observation and layered settlement observation were adopted, and a generalized settlement prediction model (GSPM) that can describe both S-shaped and hyperbolic settlement–time curves was proposed. The physical meanings of GSPM parameters were analyzed. Moreover, the effectiveness of the GSPM was verified using field monitoring data. Second, finite element analysis based on a viscoelastic constitutive model was used to reveal the quantitative relationship between the differential settlement and horizontal stress of the pavement. On this basis, the differential settlement criterion was obtained. The results showed that the GSPM can unify the logistic model and hyperbolic model by introducing two morphological change parameters. In addition, the GSPM can be more widely used, more accurate, and more stable than the traditional logistic model and hyperbolic model. When an asphalt concrete pavement (whose ultimate tensile stress is 0.12 MPa) is used, the corresponding differential settlement criterion is approximately 4.3 cm. The research results can provide a reference for reasonable differential settlement control for HTLs in order to prevent pavement cracking. [ABSTRACT FROM AUTHOR]

Energy piles are increasingly being exploited worldwide for their dual functions of bearing structural loads and utilizing geothermal energy. However, scarce knowledge is available on the time-dependent thermomechanical behavior of energy pile groups constructed in soft soils. In this paper, an analytical approach was proposed for the thermomechanical analysis of energy pile groups considering the time-dependent deformation of viscoelastic soils and validated against field test data. The impact of the soil creep behavior on the axial load–displacement response and pile-soil-pile interaction of the energy piles was further investigated. Finally, a simplified method and design charts were provided for displacement estimation and design of energy pile groups in soft soils. The results indicated that the displacement of energy piles would change with time until stabilization because of the viscous properties of the soil. The interaction between energy piles was directly related to the pile-soil stiffness ratio, the soil viscosity coefficient, the pile slenderness ratio, the pile spacing, and the number of piles. The soil creep behavior would result in a decrease in the displacement ratio of energy pile groups under thermal loading and an increase under mechanical loading. [ABSTRACT FROM AUTHOR]

In this paper, a new finite element formulation based on the enhanced first-order shear deformation theory (EFSDT) is developed for the efficient and accurate viscoelastic analysis of multilayered composite and sandwich plates. The main objective herein is to systematically establish the relationship between two independent theories (i.e., third order zigzag model and conventional FSDT) in the Laplace domain via the strain energy transformation. For viscoelastic problems, the complexity of dealing with viscoelastic materials can be simplified by introducing the concept of Laplace transform. Based on the predefined relationship, the proposed finite element model has the same computational advantage as that of the conventional FSDT (5-DOFs), while allowing the improved local layer-wise distributions of viscoelastic responses via the recovery procedure. In the model, a simple eight-noded isoparametric plate element is employed to analyze the viscoelastic response of multilayered composite and sandwich plates. Furthermore, for the isotropic material, a reference solution based on the three-dimensional finite element model is newly introduced to evaluate the accuracy of the viscoelastic behavior. To demonstrate the perforance of the proposed finite element model, the results obtained are compared to those of the conventional FSDT and three-dimensional finite elements with commercial software (i.e., ABAQUS). [ABSTRACT FROM AUTHOR]

An exact solution for simply supported two-layer plate sandwiching a thin viscoelastic interlayer under transverse load is proposed. The deformation of each plate layer is described by the exact three-dimensional linear elasticity equations. The viscoelastic characteristic of interlayer is simulated by the standard linear solid model, considering the memory effect of the material. The shear and transverse normal strains in the interlayer are simultaneously considered in the analysis. The analytical approach is presented to obtain the solution of stresses and displacements in the plate. The present solution can be used as a benchmark to access other simplified solutions for the problem aforementioned. The comparison analysis shows that the finite element solution has a close agreement with the present solution. However, the solution based on Kirchhoff-Love hypothesis is greatly different from the present solution for thick plates. It is indicated that the effect of the transverse normal strain in the interlayer increases with the increase of the interlayer thickness, especially for thick plates. Finally, the influences of geometric and material parameters on the plate deflections are investigated in detail. [ABSTRACT FROM AUTHOR]

Owing to the pavement cracking of heightening and thickening levees (HTL) caused by differential settlement, it is necessary to study the settlement prediction and differential settlement criterion for HTLs. In this study, an HTL was taken as the study object. First, leveling observation and layered settlement observation were adopted, and a generalized settlement prediction model (GSPM) that can describe both S-shaped and hyperbolic settlement⁻time curves was proposed. The physical meanings of GSPM parameters were analyzed. Moreover, the effectiveness of the GSPM was verified using field monitoring data. Second, finite element analysis based on a viscoelastic constitutive model was used to reveal the quantitative relationship between the differential settlement and horizontal stress of the pavement. On this basis, the differential settlement criterion was obtained. The results showed that the GSPM can unify the logistic model and hyperbolic model by introducing two morphological change parameters. In addition, the GSPM can be more widely used, more accurate, and more stable than the traditional logistic model and hyperbolic model. When an asphalt concrete pavement (whose ultimate tensile stress is 0.12 MPa) is used, the corresponding differential settlement criterion is approximately 4.3 cm. The research results can provide a reference for reasonable differential settlement control for HTLs in order to prevent pavement cracking.

There are many various rheological models which are used for modeling of asphalt layers in flexible pavement structures. It can be expected that the use of various models may affect different results of mechanical pavement calculations and analysis. The paper presents comparison of the use of Burgers’ and Huet-Sayegh's viscoelastic models and Hooke's elastic model to calculate pavement deflections and strains at the bottom of asphalt layers at high temperatures (from 20 °C to 50 °C). The authors assumed Polish typical flexible pavement structure and standard wheel loading. The analysis were performed under the central point of pavement loading area. Performed calculations showed that the effect of the use of rheological models may be, from practical point of view, more significant for strains at the bottom of asphalt layers than for the pavement displacements at high temperatures. [ABSTRACT FROM AUTHOR]

Objective To assess the utility of population-based reference intervals (PRIs) for interpreting thromboelastography (TEG) variables in horses using biological variation data. Design Prospective cohort biologic variation study conducted over a 5-week period. Setting Veterinary teaching hospital and research facility. Animals Ten clinically healthy horses randomly selected from a veterinary school research and teaching herd. Interventions Horse health was determined using physical examination, CBC, and biochemical and coagulation profiles prior to the start of the study. Subsequently, once weekly blood sampling for TEG testing was performed for 5 weeks. Measurements and Main Results The 4 TEG variables reaction time ( R), clot formation time ( K), angle, and maximum amplitude (MA) were measured, and coefficient of variation representing within- and between-horse biological variation (CVi and CVg, respectively) and coefficient of variation representing analytical variation (CVa) were calculated using a nested ANOVA after removing outlier data. The CVi, CVg, and CVa for R were 26.8%, 5.2%, and 5.9%; for K were 31.0%, 0.0%, and 5.9%; for angle were 9.4%, 6.2%, and 21.7%; and for MA were 3.4%, 4.1%, and 4.4%, respectively. Index of individuality (IOI) was then calculated for each variable using the formula [ABSTRACT FROM AUTHOR]

In the paper, the analysis of composite and prestressed beams using the matrix stiffness method is presented. The stiffness matrix for the frame element with a moment release at one end and the vector of equivalent nodal forces for the frame element with and without a moment release are derived. In the presented method, concrete is assumed to behave as viscoelastic material and the relaxation of the prestressing steel is also considered. Therefore, the relations between the generalized element displacements and the generalized element forces are integral and, here, are presented using the mathematical operators. Applying the linear integral operators, the solution to the problem is derived without introducing additional mathematical approximations and simplifications, besides the inevitable approximations related to the rheological properties of constitute materials, i.e., steel, concrete, prestressing and reinforcement steel. The derived relations can be applied with any concrete creep functions and for the element with a variable cross section. [ABSTRACT FROM AUTHOR]

The paper presents the viscoelastic analysis of composite and prestressed beams using the slope deflection method. For the fixed-end frame element, considering the viscoelastic behavior of concrete and relaxation of prestressing steel, the integral relation between the generalized element forces and the generalized element displacements, i.e., the element stiffness matrix, is derived and presented using the mathematical operators. From the element and system equilibrium equations, the integral equations of the problem with unknown displacements are formulated. Comparing to the analysis of homogeneous elastic structures, the governing equations of the problem are similar, but with integral equations instead of algebraic equations. In the presented method, the solution to the problem is derived using the linear integral operators without introducing any additional mathematical approximations, apart from the adopted rheological relations for constitute materials. In addition, the obtained expressions are general in a sense that any concrete creep functions can be used and the element can be with a variable cross section. [ABSTRACT FROM AUTHOR]

Permanent deformation is one of the most important types of distress in flexible pavement. Currently and based on the Australian Mechanistic-Empirical Pavement Design Procedure, the indirect tensile test (IDT) is conducted in New Zealand in order to determine the asphalt modulus. This test is carried out on a 100 mm diameter by 50 mm height specimen. However, the current Simple Performance Test (SPT) procedure requires the dynamic modulus to be obtained from the axial compression test performed on 100 mm diameter by 150 mm height specimen. One issue related to the axial compression test is that it is often impossible to obtain this size specimen from actual pavement since a typical asphalt layer thickness is less than 150 mm in New Zealand. Therefore, IDT becomes more appropriate for existing pavement evaluation due to its privilege of testing on cored size specimens. The objective of this research is to perform an experimental and analytical study on the dynamic modulus parameters derived from the aforementioned test methods to improve design accuracy. In this research, two common types of asphalt cement are tested at three different air void percentages. Graphical and statistical comparisons of results from the axial compression and IDT test methods are presented in order to assess their interrelationships. The findings show that, the dynamic modulus determined form IDT test is in good agreement with that form axial compression tests. Based on the statistical analysis, more than 90% of data showed complete similarity for the dynamic modulus calculated from these two tests. [ABSTRACT FROM AUTHOR]

Thermal cracking is a critical pavement issues in the cold regions and has been of a major concern in asphalt pavements. The paper presents a viscoelastic modeling work using pure power law, generalized power law, and Prony series functions to characterize low temperature performance of asphalt mixtures. The bending beam rheometer (BBR) using asphalt mixture beams was employed to obtain creep compliance and further viscoelastic analyses were performed to determine relaxation moduli and thermal stresses of asphalt mixtures. The objective of this paper is to provide a better understanding on low temperature viscoelastic behavior of asphalt mixtures by quantifying creep compliance errors and differences among these representation models (pure power law, generalized power law, and Prony series functions) in the predictions of relaxation moduli and thermal stresses. Based on the comparison of viscoelastic analyses at low temperatures, the generalized power law function shows a better agreement with the experimental data and has the least creep compliance error as compared with other two representation functions. [ABSTRACT FROM AUTHOR]

An investigation of the existence of predominant frequency, (or frequencies), and the ability to predict critical pavement responses in asphalt layers using those predominant frequencies has been presented. The study used an extensive database of computed pavement response histories of four different asphalt pavement structures (thin and thick) at two temperatures (21 and 40°C) subjected to a tandem axle load at three speeds (16, 65, and ) using the pavement response analysis program 3D-Move Analysis. The conversion of load duration to frequency and the validity of using one response component () alone in the estimation of the pulse time () were explored. Instead of focusing on only , attention is given to all pavement response components (stresses and strains). In addition, verification of whether the use of a consistent set of value(s) can in fact adequately capture all components of pavement response has also been undertaken. The viscoelastic properties that are representative for the predominant (or equivalent) frequencies from frequency sweep data were used. A major contribution of the study is that the critical responses and performance in a flexible pavement system can be successfully simulated with a static multilayer elastic analysis (within ) by assigning elastic modulus to hot-mix asphalt (HMA) based on appropriately selecting the corresponding predominant or equivalent frequency, (or frequencies). Generalized equations for estimating those values for all pavement structures, temperatures, and vehicle speeds under consideration have been developed. Good fitting parameters () were observed for all evaluated cases. The impact of loading frequency on predicted asphalt distresses was assessed for rutting and bottom-up fatigue cracking following the AASHTO mechanistic-empirical pavement design guide approach. The study showed that the proposed procedure for estimating values resulted in rut depths and bottom-up fatigue cracking that are within of those determined using the viscoelastic dynamic responses. [ABSTRACT FROM AUTHOR]

In this article, we performed a numerical analysis of dielectric ceramic and Ni electrode layers with voids in a multilayer ceramic capacitor using the finite element method. To numerically analyze a multilayer ceramic capacitor composed of several hundred ceramic and Ni layers, we defined a unit cell, and equivalent material properties from the ceramic and Ni layers were calculated by the homogenization method. We predicted the deformation of the overall multilayer ceramic capacitor from that of a unit cell with equivalent material properties. Voids in the Ni layer, produced during the manufacturing process, were taken into consideration. Because both ceramic and Ni layers are viscoelastic and are in contact with each other, viscoelastic and contact analyses were carried out using the commercial software ANSYS. Dynamic mechanical analysis was used to determine the viscoelastic material properties of the ceramic and Ni layers. We compared the elastic results with the viscoelastic results to determine the viscoelastic characteristics of a multilayer ceramic capacitor. The surface roughness of a multilayer ceramic capacitor was measured by confocal microscopy to verify the reliability of the numerical analysis. The experimental results showed reasonable agreement with the model-based results. [ABSTRACT FROM PUBLISHER]

Abstract: External bonding of FRP plates or sheets has become a popular method for strengthening reinforced concrete structures. Stresses along the FRP-concrete interface are critical to the effectiveness of this technique because high stress concentration along the FRP-concrete interface can lead to the FRP debonding from the concrete beam. Although the short-term stress distribution along the FRP-concrete interface has been studied extensively, very few studies have been conducted on the long-term stress distribution, which closely simulates the behavior of the structure during the service-life. In this study, we develop a viscoelastic solution for the long-term interface stress distribution in a FRP plate strengthened reinforced concrete beam. In this solution, the RC beam and the FRP plate are modeled as elastic materials; while the adhesive layer is modeled as a viscoelastic material using the Standard Linear Solid model. Closed-form expressions of the interface stresses and deflection of the beam are obtained using Laplace transform and calculated using the Zakian’s numerical method. The validation of this viscoelastic solution is verified by finite element analysis using a subroutine UMAT based on the Standard Linear Solid model. [Copyright &y& Elsevier]

Abstract: To predict the warpage behaviour of an anode-supported half-cell of a solid oxide fuel cell (SOFC), a viscoelastic analysis has been made for a system with Gd-doped ceria (GDC) and NiO–yttria stabilized zirconia (NiO–YSZ) bi-layers. The viscoelastic properties of each component at 1573K are measured by discontinuous sinter forging (for GDC) and continuous sinter forging (for NiO–YSZ) techniques. Using the measured uniaxial viscosities and the viscous Poisson ratio, the warpage during the co-firing of a GDC/NiO–YSZ bi-layer is calculated for the continuum mechanical models of Cai et al. and Kanters et al. The warpage predicted by the two models, in particular that of Cai et al., is shown to be in good quantitative agreement with the experimental observation. This result demonstrates that the warpage of bi-layer samples during co-firing can be suitably predicted when the viscoelastic properties of each component are properly measured and estimated. The present investigation also provides a useful methodology for optimizing the design of planar asymmetric half-cells for the SOFC industry. [Copyright &y& Elsevier]

Abstract: This paper utilized the viscoelastic theorem to derive thermoviscoelastic stress in a thin film/substrate structure, and obtain a closed-form expression of the stress. In this viscoelastic analysis, the Maxwell model is assumed and the Laplace transformation is applied to the variables of time-space followed by the calculation of the viscoelastic stress of the thin film in the transformation domain. Finally, after the inverse Laplace transformation, the normalized stress at any depth and at any time was obtained analytically and expressed as a function of the relaxation times, the biaxial moduli ratio, and the ratio of thickness between the film and the substrate. The effects of the different thickness ratio values on the normalized viscoelastic stress were analyzed and the results showed that the effects were significant. In addition, the distribution of the viscoelastic stress varies with different depths of the film and the maximum stress induced on its surface. [Copyright &y& Elsevier]

This paper presents constitutive modeling of dynamically loaded elastomeric products such as power transmission belts. During the normal operation of the belts certain segments of the belt structure are loaded with a tooth-like periodic (cyclic) loading. When the time-dependent properties of the elastomeric material “match” the time-scale of the dynamic loading a strain accumulation process occurs. The critical angular velocity is proportional to the ratio of the belt length to the common diameters of the pulleys. The magnitude of the strain accumulated in each loading cycle decreases with an increase in belt length. For a given belt geometry the critical angular velocity increases with the number of loading cycles. At the same time the magnitude of the accumulated strain decreases non-linearly as the number of loading cycles increases. However if the belt operates at or in the close vicinity of its critical angular velocity it will almost certainly fail! The critical angular velocity depends on the material retardation time (location in the frequency spectrum), while the magnitude of the accumulated strain is dictated by the strength of the corresponding discrete spectrum lines. Thus, the mechanical spectrum of the elastomeric material from which the belt is constructed is the most important material function for predicting the durability of drive belts and similarly dynamically loaded elastomeric products. [ABSTRACT FROM AUTHOR]

The purposes of the paper are to analyze the fracture phenomenon by delamination and cracking when the encapsulant of plastic IC package with polyimide coating shows viscoelastic behavior under hygrothermal loading in the IR soldering process and to suggest more reliable design conditions by the approaches of stress analysis and fracture mechanics. The model is the plastic SOJ package with the polyimide coating surrounding chip and dimpled diepad. On the package without cracks, the optimum position and thickness of polyimide coating to decrease the maximum differences of strains at the bonding surfaces of parts of the package are studied. For the model delaminated fully between the chip and the dimpled diepad, C (t)-integral values are calculated for the various design variables. Finally, the optimal values of design variables to depress the delamination and crack growth in the plastic IC package are obtained. [ABSTRACT FROM AUTHOR]

The viscoelastic response of a chopped strand mat E-glass fibre reinforced vinylester resin has been studied over a wide range of applied stress levels. At low applied stress levels, the material exhibited a linear viscoelastic response well represented by Schapery's power law model with constant C and n terms. At higher stresses nonlinear behaviour was observed which apparently is caused by the multiplicity of complex local phenomena associated with and preceding damage development (plastic deformation of the matrix, interfacial slippage, fiber-matrix debonding). The limits of linear viscoelastic behaviour and of damage initiation – about 0.48% strain or 42 MPa – coincide for this material. However, for successful modelisation of uniaxial creep strain in the nonlinear range a modified power law is proposed which uses stress-dependent creep parameters C and n. [ABSTRACT FROM AUTHOR]

The isogeometric boundary element method (IGABEM) has a broad application prospect due to its exact geometric representation, excellent field approximation and only boundary discretization property. In this paper, IGABEM based on radial integration method (RI-IGABEM) is used for viscoelastic analysis of solid propellant grain. The memory stress, as the initial stress, leads to the boundary-domain integral equations and thus eliminates the only boundary discretization advantage of boundary element method (BEM). The radial integration method (RIM) is applied to transform the domain integral into an equivalent boundary integral by means of the applied points. The usage of RIM makes it possible to only store the strains on the applied points. Meanwhile, Prony-series is used to discretize the general integrals and to store the two most recent time-step strains rather than the time-step strains of the entire process. The combination between RIM and Prony-series will help reduce the storage space and computational time. In addition, by using the fundamental solutions for linear elastic problems and the regularized technologies, the singular integrals can be solved through the previous methods, such as the Telles scheme and element sub-division method. In order to validate the accuracy and robustness of RI-IGABEM in viscoelastic analysis, the influence of the number and position of applied points as well as the time interval on viscoelastic analysis is discussed through comparing with cell discretization methods. A set of numerical examples demonstrates the ability of the scheme to simulate the viscoelastic problems. • The regularized time boundary integral equation for viscoelasticity is proposed. • The IGABEM is applied to solve viscoelastic problems. • RIM is applied to transform the domain integral into a boundary integral. • The combination of RIM and Prony series saves storage space and computing time. • The influence of time interval and position of inner points in RIM is discussed. [ABSTRACT FROM AUTHOR]

3D printed polycaprolactone (PCL)-blended scaffolds have been designed, prepared, and evaluated in vitro in this study prior to the incorporation of a polyvinyl alcohol–polyacrylic acid (PVA–PAA) hydrogel for the delivery of in situ-formed sodium indomethacin. The prepared PCL–PVA–PAA scaffold is proposed as a potential structural support system for load-bearing tissue damage where inflammation is prevalent. Uniaxial strain testing of the PCL-blended scaffolds were undertaken to determine the scaffold’s resistance to strain in addition to its thermal, structural, and porosimetric properties. The viscoelastic properties of the incorporated PVA–PAA hydrogel has also been determined, as well as the drug release profile of the PCL–PVA–PAA scaffold. Results of these analyses noted the structural strength, thermal stability, and porosimetric properties of the scaffold, as well as the ability of the PCL–PVA–PAA scaffold to deliver sodium indomethacin in simulated physiological conditions of pH and temperature. The results of this study therefore highlight the successful design, fabrication, and in vitro evaluation of a 3D printed polymeric strain-resistant supportive platform for the delivery of sodium indomethacin. [ABSTRACT FROM AUTHOR]