Viscoelastic Mechanical Model Research Articles

A Fractional Viscoelastic Mechanical Model for Speed Optimization of Robotic Cell Microinjection

A Fractional Viscoelastic Mechanical Model for Speed Optimization of Robotic Cell Microinjection

Viscoelastic Mechanical Models of the Peel Strength of Adhesives

Viscoelastic Mechanical Models of the Peel Strength of Adhesives

Theoretical solutions of short glass fiber/polyurethane composite beams based on Hamiltonian principle

AbstractShape memory polymers (SMP) and its composites (SMPC) have gained popularity for their potential in intelligent structures fields. Developing a reliable mechanical model to accurately describe mechanical behavior of its intelligent structures is important for both theory and practice. This paper presents a novel mechanical model for describing the mechanical behavior of short glass fiber/polyurethane (GF/PU) composite beams, based on a constitutive model of SMP and incorporating principles from composite mechanics theory, the Hamiltonian principle and Euler–Bernoulli beam theory. The model includes kinematic equations and material parameter equations. Based on the constitutive equations of SMP, coupled with Euler–Bernoulli beam theory and Hamilton's principle, the kinematic equations of GF/PU composite beam are established. Additionally, a correction factor was proposed and employed to modify the material parameter equation of SMP, which was then combined with the mechanics theory of composite materials to establish a material parameter equation for composite beams. Taking a simply supported beam as an example, we solve the model using Fourier method and simulate and analyze the material parameters properties, static and viscous mechanical behaviors properties, and shape memory behavior properties of the GF/PU composite beam. The results show that the GF volume fraction, temperature correction coefficient, regularization parameter, and contact parameter have a significant impact on the material parameters of GF/PU composite materials and the material parameters of composite beams have important effects on their mechanical properties. By adjusting material parameters, ideal mechanical properties can be obtained for the GF/PU composite beam. This study provides a theoretical foundation for intelligent beam design and analysis based on SMP and SMPC.Highlights A novel viscoelastic mechanical model for GF/PU composite beam is proposed. Effect of composite components on GF/PU composite is studied. Kinematic equations based on Hamiltonian principle is established. Material parameter equation including corrected parameter is established.

Microscopic double-chain sawtooth model and macroscopic four-parameter fractional-order derivative viscoelastic model based on magnetorheological elastomers

In order to restore the distribution of ferromagnetic particles in magneto-rheological elastomers to the greatest extent, the magnetotropic effect of magneto-rheological elastomers is more accurately represented, and the dynamic mechanical properties of magneto-rheological elastomers are more accurately reflected. In this paper, based on the dipole theory, a new microscopic model of magnetorheological elastomer, the double chain sawtooth model, is proposed based on the chain model and the main chain adsorption model, and a macroscopic viscoelastic mechanical model of magnetorheological elastomer, the four-parameter fractional order derivative improvement model, is proposed based on the classical macroscopic mechanical parametric model and the fractional order derivative model. A microscopic model of magnetorheological elastomer was combined with a macroscopic model to describe its mechanical properties. Isotropic and anisotropic magnetorheological elastomers with different mass fractions and different silicone oil contents were prepared using silicone rubber as the matrix and carbonyl iron powder as the filling phase, and dynamic shear tests were conducted to verify the validity of the model.

Investigation into Viscoelastic Properties of Fiber-Reinforced Asphalt Composite Concrete Based on the Burgers Model

Asphalt composite concrete pavement is one of the common pavement forms in China. However, due to the influence of design, materials, construction quality, and other aspects, asphalt composite concrete pavement develops various degrees of cracks after being put into use, which affects the service performance and life of asphalt pavement. The Burgers model is used to examine the effects of fiber-volume-fraction and length–diameter-ratio on the viscoelastic mechanical behavior model parameters and viscoelastic properties of asphalt composite concrete through the bend test for creep of polyester fiber asphalt composite concrete beam. The findings indicate that the fiber’s ability to control asphalt composite concrete bending creep deformation increases initially and subsequently diminishes as fiber-volume-fraction and length–diameter-ratio increase. Fiber-volume-fraction and length–diameter-ratio effects can be fully reflected by fiber amount characteristics. A viscoelastic mechanical behavior model of fiber-reinforced asphalt composite concrete is developed on this foundation while taking into account the influence of fiber amount characteristic factors. Theoretical study and practical research indicate that the ideal fiber volume ratio of polyester fiber asphalt composite concrete is 0.35 percent, the ideal length-to-diameter ratio is 324, and the ideal fiber amount characteristic parameter is 1.13. The test results can provide a certain reference value for the improvement of the long-term durability of fiber asphalt composite concrete pavement of road engineering.

Utilization of viscoelatic models with non-linear springs and dashpots in delamination study of multilayered beams

This paper analyzes delamination of multilayered inhomogeneous beam structure by utilization a non-linear viscoelastic mechanical model. The non-linear time-dependent response is treated by a non-linear spring and a non-linear dashpot connected in series to a system of two linear springs and two linear dashpots. The model is under stress that is a linear function of time. The constitutive law of the model representing a non-linear dependence between stress, strain and time is derived. The main goal of the paper is to obtain a solution of the strain energy release rate for the delamination in the multilayered inhomogeneous beam by applying the non-linear viscoelastic model. Solutions are derived by using the complementary strain energy and by analyzing the balance of the energy with taking into account the non-linear viscoelastic behaviour. For this purpose, the constitutive law of the non-linear viscoelastic mechanical model is used. The solutions are applied to obtain results for multilayered beams with non-linear variation of material properties in longitudinal direction. The influence of different parameters on the time-dependent strain energy release rate is assessed. The study indicates the effectiveness of the viscoelastic mechanical models with non-linear springs and dashpots in time-dependent delamination analyses of multilayered inhomogeneous beam structures.

The Effect of Ultraviolet Aging Duration on the Rheological Properties of Sasobit/SBS/Nano-TiO2-Modified Asphalt Binder

In recent years, nanoparticles have been introduced into warm-mix-modified asphalt to improve asphalt performance after sustaining ultraviolet (UV) aging, yet the evaluation of aging performance is often a descriptive characterization of rheological properties. This study extends rheological characterization with viscoelastic mechanical modeling to evaluate resistance to UV aging using Sasobit and SBS compound-modified binder blended with nano-titanium dioxide (TiO2). The extended method comprises characterizations using several rheological properties and a viscoelastic mechanical model, named the 2S2P1D model, on modified asphalt after 3 days, 6 days and 9 days of ultraviolet (UV) aging. The rheological properties of the UV-aged binders were tested at high and medium temperatures in terms of viscosity, complex modulus, phase angle and fatigue factor. Rheological test results showed that nanoparticles generally had no apparent effect on the complex modulus of aged binders regardless of UV aging times. However, the aged binder with nanoparticles showed better fatigue resistance than aged binders without nanoparticles after 3 days of UV aging. As an extension, the black space diagram and 2S2P1D model were used to investigate the viscoelastic properties of these aged binders. The k and h values, as important model parameters, were almost the same and less than one for all UV-aged binders. All investigated aged asphalt binders showed characteristics of a viscoelastic solid in terms of the master curves of the complex modulus and phase angle, and the master curves of the phase angle for all UV-aged binders did not meet the time–temperature equivalence. Moreover, these observations from the 2S2P1D model revealed that aging durations did not affect the viscoelastic mechanical characteristics of warm mix asphalt in this study. The method adopted in this study may promote a comprehensive evaluation of asphalt properties after UV aging, especially considering the viscoelastic mechanical performance.

Research and Application of "Concentric Ring" Reinforcement and Sealing Technology for Gas Drainage Boreholes in Soft-Coal Seams.

The problems of lack of stability and difficult sealing of gas drainage boreholes in soft-coal seams directly affect the efficient extraction of gas in these soft-coal seams. After the holes are drilled, the collapsed holes lead to the failure to seal in time, which brings hidden dangers to mine production and causes time and economic waste. In this paper, the viscoelastic mechanics model is used to solve the force of the coal body in the fractured area of the orifice, combined with the theory of the external conditions affecting the collapse of the orifice of the soft-coal seam. The reason for the easy collapse of the borehole of the soft-coal seam is studied, and a reasonable solution is proposed. “Concentric ring” reinforced sealing technology, elaborated from the physical model, technical principles, and processes, was finally carried out in an on-site application test at the N2106 working face of a mining area in Shanxi. The results show that the fracture zone of the soft-coal seam easily enters a stage of rapid deformation under the effect of time. Its strong adsorption behavior, easy expansion, and other characteristics, combined with the violent disturbance of the drill pipe when the drilling is offset, eventually cause the hole to retreat, making it easy to deform and collapse afterward. The test boreholes reinforced and sealed with “concentric rings” have no problem of collapsed holes after retreating. The gas concentration remained above 30% in the first 30 days. The maximum gas purity of the borehole on the 30th day of extraction flow rate reached 0.053 m3/min. It is found that the sealing effect of the “concentric ring” reinforced seal drilling technology is better than that of the traditional sealing technology.

Nonlinear Constitutive Model of High-Temperature Viscoelastic Deformation of Gussasphalt Concrete

To accurately evaluate the high-temperature stability of cast asphalt concrete, based on the traditional viscoelastic mechanical model, this paper innovatively improves the traditional viscoelastic mechanical model considering the conditions of temperature and dynamic load and deduces the viscoelastic constitutive model of high-temperature deformation performance of cast asphalt concrete, using a dynamic penetration test (DPT) to regress improved the Burgers model parameters and verify the model’s applicability and reliability. The results show that for the modified Burgers model parameters, E1, E2, A, and η2 decrease with increasing temperature, while parameter B increases with the increase of temperature. The high-temperature deformation of cast asphalt concrete is mainly related to η1, and η1 decreases, and deformation increases with the increase in temperature. With the increase in loading times, the dynamic penetration of cast asphalt concrete (AC) gradually increases, that is, when the greater the permanent deformation is. When the specimen is loaded 3000 times, the dynamic penetration value at 60°C is about 1.237 mm, and the dynamic penetration value at 50°C is about 0.819 mm. Under other loading times, the permanent deformation of the specimen at 60°C is much greater than that at 50°C. There is a good fit between the mechanical model derived from the viscoelastic theory and the measured test data, and the correlation coefficient is greater than 0.98, indicating that the model can accurately describe the permanent deformation law of GA under periodic semivector sinusoidal pulse load at high temperatures. The research results of this paper provide a solid theoretical basis for the promotion and application of cast asphalt concrete, and the method has wide applicability in practical engineering.

Two-stage model of prepreg bonding interface formation in automated fiber placement process

While Automated Fiber Placement (AFP) of thermoset matrix composites are widely used in the aviation industry, there is little conclusive research on the relationship between the physical model of bonding interface formation process and the actual bonding strength between prepreg layers formed in AFP process. Although massive amounts of experimental data on prepreg tack have been achieved from existing research, engineers are unable to use these data as a decisive criterion in choosing process parameters. In this research, a prepreg layup physical model based on reptation model and viscoelastic mechanical model is built, in which the bonding interface formation process is divided into two stages, namely, diffusion and viscous stage. Layup-peeling experiments are conducted via a special designed high-speed layup experimental platform so that practical AFP process parameters can be imitated, and a logarithmic curve of layup velocity-peeling energy under different layup pressure is achieved. The slope of the logarithmic curve and the surface morphology of the sample after peeling prove the correctness of the established model. Simultaneously, the experimental data proves that when prepreg is peeled off, the transition from the cohesive failure mode to the interface failure mode occurs at the laying speed between 100 mm/s and 200 mm/s. These results can be used as a reference for choosing AFP process parameters to realize the balance between good bonding quality and harmless separation of adjacent prepreg layers.

Statically undetermined multilayered beam of non-linear viscoelastic behaviour: a delamination study

Delamination of a twice statically undetermined multilayered beam structure which has non-linear viscoelastic behaviour is studied analytically. The beam is made of layers whose time-dependent behaviour is treated by a non-linear viscoelastic mechanical model having equal number of springs and dashpots. The strain energy release rate is derived by analyzing the balance of the energy. The curvatures and the coordinates of neutral axes of the beam portions needed for obtaining of the strain energy release rate are found by resolving the static indeterminacy. The delamination is studied also by the method of J-integral to verify the strain energy release rate. In order to evaluate the effect of the static indeterminacy, an analysis of the strain energy release rate is carried-out also assuming that the beam under consideration is statically determinate structure.

Finite Volume Method for the Launch Safety of Energetic Materials

It is important to examine the ignition of energetic materials for launch safety. Given that there is a paucity of experimental tests, numerical simulations are important for analysing energetic materials. A computer program based on the finite volume method and viscoelastic statistical crack mechanics model is developed to study the ignition of energetic materials. The trends of temperature and stress of energetic materials subjected to projectile base pressure are studied by numerical examples. The results are compared with those in an extant study, which verified the correctness of the proposed method. Additionally, the relationships between the temperature increase and nonimpact ignition of energetic materials were analysed. The results show that when the temperature at the bottom of the explosive rises to a certain value, it will cause the explosive to ignite. This research has significance to the study of the base gap of explosives, and it provides a reference for launch safety evaluation of energetic materials.

Viscoelastic Mechanical Model of Asphalt Concrete Considering the Influence of Characteristic Parameter of Fiber Content

This paper carries out bending creep tests on polyester fiber-reinforced asphalt concrete beams, and investigates how the volume ratio and aspect ratio of the fibers influence the parameters of viscoelastic mechanical model and the viscoelastic performance of the asphalt concrete. The results show that: with the growing volume ratio and aspect ratio of the fibers, the midspan deflection and bottom flexural-tensile strain of asphalt concrete beams first dropped and then rose over time; the characteristic parameter of fiber content (FCCP) could reflect the overall effects of the volume ratio and aspect ratio of the fibers. On this basis, a viscoelastic mechanical model was established for the asphalt concrete in the light of the influence of FCCP. The test and theoretical results show that, in our tests, the optimal volume ratio of fibers, optimal aspect ratio of fibers, and optimal FCCP are 0.348, 324, and 1.128 for polyester fiber-reinforced asphalt concrete.

Dynamic response properties of polymer bonded explosives under different excitation by deceleration

Based on the experimental method of projectile penetration into the concrete target, different excitation by deceleration of polymer bonded explosives (PBXs) was achieved by controlling the length of steel pillars behind PBXs. A series of impact tests were conducted to study the mechanical response of PBXs with different initial densities under different excitation by deceleration. A physical model was developed to describe the viscoelastic-plastic deformation of PBXs. The plastic part was added on the basis of the viscoelastic statistical crack mechanical model (Visco-SCRAM) model, and the compaction behavior of charge in different environments was characterized based on the Heckel compaction equation. The model was implemented in LS-DYNA, and the simulation results were verified by the experiments. The dynamic mechanical behavior of PBXs under different excitation by deceleration was studied from the macroscopic and mesoscale aspects. The stress curves, strain curves, the density change and the interaction between particles in deceleration environment were predicted. After comparison and analysis, the dynamic response law of the charge in the penetrating process was obtained. Macroscopic responses along with mesoscale modeling results are significantly important to have a better understanding of deformation mechanisms of PBXs.

Investigating the accuracy of ultrasound viscoelastic creep imaging for measuring the viscoelastic properties of a single-inclusion phantom

Ultrasound viscoelastic creep imaging is a noninvasive technique that has potential to measure the internal spatial distribution of viscoelastic properties of materials, based on inducing the creep response of the material and using a viscoelastic mechanical model to analyze the creep response. Since how viscoelastic creep imaging can be applied to accurately measure the viscoelastic properties of heterogeneous materials is still unclear, the purpose of this study is to use finite element computer simulation to quantitatively investigate the accuracy of compressional viscoelastography (viscoelastic creep imaging using external mechanical compression as the source of excitation) on measuring the viscoelastic properties of a single-inclusion phantom. The study intends to answer a question: can compressional viscoelastography accurately measure the viscoelastic properties of the inclusion as well as the background material within a single-inclusion phantom? Based on the simulation results, compressional viscoelastography could not accurately measure the viscoelastic properties of the inclusion. The measurement of a viscoelastic property (modulus of elasticity or relaxation time constant) of the inclusion is accurate if and only if the difference in that property between the inclusion and background material is very small, less than around 10%. On the other hand, compressional viscoelastography can accurately measure the viscoelastic properties of the background material regardless of the difference in the viscoelastic properties between the inclusion and background material. In a real biological tissue, the mechanical behaviors are much more complicated and unpredictable than those in a single-inclusion phantom like the one used in the present study. Hence, based on the simulation results of the present study, it could be more challenging to apply compressional viscoelastography to accurately measure the viscoelastic properties of a mass or a target tissue within a real biological tissue. The findings of the present study based on compressional viscoelastography may also be applicable to acoustic-radiation-force-based viscoelastic creep imaging. In the future, experiments are needed to justify the simulation results found in the present study.

Viscoelastic model to capture residual stresses in heat cured dissimilar adhesive bonded joints

The thermal loading during the curing process of an adhesive-bonded joint induces residual stresses in the joint, thereby affecting its performance. The problem becomes worse in the case of a multi-material joint involving varying coefficients of thermal expansion (CTE) for different parts. A novel approach was developed to model the properties of automotive grade structural adhesives during the heat curing process. The material model was divided into two components: curing kinetics model and viscoelastic mechanical model. The models were calibrated using experimental data from Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) tests performed on an epoxy-based single-component adhesive. The calibrated material model parameters were fed into a finite element simulation and the prediction results were compared to a unique set of experiments utilizing two substrate combinations of adhesive-bonded single lap shear joints. An excellent agreement between the simulated and experimental results (displacement across the bond, force applied by the adhesive) was achieved. The modeling results give a better understanding of the residual stresses and agree with the experimental trend on the effect of bondline thickness on the joint.

Study on long-term rheological characteristics of polymer gel and prediction of its creep fracture time

Conformance control by using the polymer gel is an important stimulation technique of heterogeneous oil reservoirs. After operation of the conformance control, the water channeling of heterogeneous oil reservoirs can be plugged, which can force the follow-up injected water to divert into the area with high oil saturation. Thus, under the action of water injection pressure, the polymer gel is deformed. Because this is a long-term process, the ability to resist the long-term deformation and resist damage of polymer gel is important for the long-term plugging effect. However, there are few reports on the effect of long-term rheological characteristics of the polymer gel on its plugging ability. Therefore, it is of great significance to study the rheological characteristics of the polymer gel under the long-term action of a stress, which can be used to accurately predict the effective period of plugging the water channeling. In this paper, taking the Hook body and the viscous pot as the basic elements, and considering the Maxwell model and the Kelvin model as the basic models, a combined viscoelastic mechanical model of the polymer gel is established, which can be used to simulate the creep deformation of polymer gel. At the rheological damage stage of the polymer gel, the strain is increased exponentially and the mechanical parameters is decayed exponentially with time. By introducing the damage variable, based on the stress - time equivalence principle of polymer materials, the time of creep fracture of the polymer gel can be accurately calculated. Since then, the polymer gel is started to break obviously and lost its ability for plugging. This study can provide an important guidance to optimizing the scheme of conformance control and predicting the validity period.

The viscoelastic mechanical property and constitutive models of 3D printed photopolymer

Purpose The purpose of this paper is to study the mechanical property of three-dimensional (3D) Printed photopolymer (Vero Yellow and Tango Black) with different constant strain rate. According to the experimental results, three constitutive models are used to describe the stress-strain and stress-time relation in the tension and stress relaxation process. Design/methodology/approach The Stratasys Objet 260 was used to prepare the four groups of samples with different photopolymers (Vero Yellow and Tango Black). The stress-strain and stress-time relations are obtained by the uniaxial tensile tests and relaxation tests performed at room temperature with different constant strain rates. The generalized Kelvin model (GKM), standard linearized model (SLM) and fractional order model (FOM) are used to describe experimental data by means of the curve-fitting approach. Findings Experimental results show that the tension stress increases faster at a higher strain-rate for tensile tests. Relaxation stress is influenced by the preload strain-rate for relaxation tests. For the theoretical fitting, the error comparison between three constitutive models and experimental data are calculated to demonstrate the high accuracy in describing the stress-strain relationship for tension. For stress relaxation, the error comparison confirms higher accuracy of FOM with the largest error within 3%, while the error of GKM and SLM up to 10%. Originality/value The paper confirms the viscous-elastic mechanical property of 3D printed photopolymer composites (Vero Yellow and Tango Black) for Stratasys PolyJet. As FOM shows high accuracy both in describing stress-strain and stress-time relation for tension and stress relaxation process, it can be directly used as a constitutive model to predict mechanical properties for engineering application.

Comparison between Viscoelastic Mechanical and Chemical Kinetic Aging Model of Asphalt Concrete

The objective of this study was to fully characterize and validate the mechanical-based aging model parameters and compared with the chemical kinetic model. This study found that level of aging applied to both asphalt binder and asphalt concrete showed differences, as verified by all of the p-values from regression analysis test, were greater than 0.05. The aging variable value decreased with the aggregate involved. The aging history dependent (k2) could be simulated the actual aging behavior as a polynomial curve. The Pearson correlation test showed that there is a strong relationship between the carbonyl content and the aging model variable.

Fibrous inductance strain sensors for passive inductance textile sensing

Stretchable strain-sensitive textiles that can detect human motion and physiological information in real time have considerable potential for application in next-generation wearable electronic devices. However, the application of such textiles has been hindered largely by their vulnerability to magnetic and electrical interference, wear and tear, and baseline drift. In this article, we report a new type of highly retractable and stretchable inductive sensor with a notable reciprocal change in inductance during stretching and recovery. Our experiments indicate that yarn sensors with a small diameter (627.4 μm) have high sensitivity (0.4 μH/%), fast response (<0.1 s), and stable performance without baseline drift after 4000 cycles of testing. The mechanical performance of the strain sensors was analyzed based on a viscoelastic mechanical model. From the derived effective stress-lifespan curve, the strain sensors can undergo 2.2 × 106 cycles of stretching and recovery with only a 5% reduction in performance. Our flexible yarn sensors can be used for monitoring motion in different parts of the body using the self-inductance effect. On the other hand, by employing mutual inductance to couple the sensors and an external readout coil, strians can also be monitored passively. Thus, these capabilities facilitate new methods for all-in-one wearable motion sensing with potential applications in the field of passive sensing in electronic textiles.