Mechanical Behavior Of Viscoelastic Materials Research Articles

Isogeometric FE-BE method with non-conforming coupling interface for solving elasto-thermoviscoelastic problems

The isogeometric finite element (FE) and boundary element (BE) coupling method with non-conforming interface is applied to solve 3D elasto-thermoviscoelastic problems. The thermoviscoelastic constitutive relation is expressed by Stieltjes integral, and the equivalent integral weak form of the problem is derived according to the principle of virtual work, in which the time integral is discretized by the trapezoidal difference approximation formula. The parameters of viscoelastic material are described by Prony series, and the discrete formula can be simplified by recursive relationship to avoid storing all solutions in time steps. The equilibrium and compatibility conditions of FE and BE subdomains on the coupling interface are used to couple two different system matrices, and the coupling of non-conforming non-uniform rational B-splines (NURBS) surfaces in different subdomains is achieved by using virtual knot insertion technique. In addition, the time-temperature equivalent principle is applied to observe the mechanical behavior of viscoelastic materials over a wide temperature range in a short time. Through several numerical examples, the effects of different working conditions and geometrical parameters of combustion chamber on the structure of the solid rocket motor (SRM) are studied, and the correctness and robustness of this method are verified.

Fractional viscoelastic model with a non-singular kernel for a rotating semiconductor circular cylinder permeated by a magnetic field and due to heat flow pulse heating

To investigate the mechanical behavior of viscoelastic materials, a variety of linear and nonlinear constitutive models have been developed to characterize the viscoelastic deformation process. However, it has been demonstrated that the constitutive relation in the integer-order of stress–strain available in traditional viscoelastic models may fail in some cases and does not match justifications well. This work provides an innovative mathematical model for viscoelastic processes that is compatible with thermodynamic principles, including Caputo–Fabrizio fractional-order derivatives. In addition to the exponential form, the Caputo–Fabrizio kernel possesses a number of properties, including nonlocality and non-singularity. Additionally, by connecting thermoelasticity to photothermal processes, the photothermal action was considered for incorporation into a magneto-thermoelastic semiconductor material. The suggested model was used to evaluate the photothermal, thermal, and elastic waves in a rotating solid cylinder of viscoelastic semiconductor material. The surface of the viscoelastic cylinder was assumed to be fixed and exposed to a time-dependent pulsed heat flow. The physical fields were studied for their sensitivity to the angular velocity, phased delays, laser pulse length, and fractional parameters. The physical fields were studied in terms of their sensitivity to angular velocity, phase delays, laser pulse length, and fractional parameters.

Nonlinear Schapery viscoelastic material model for thermoplastic polymers

AbstractThe nonlinear mechanical behavior of viscoelastic materials is modeled based on the Schapery integral model containing internal variables. In this context, a new approach for the strain‐dependent material properties is introduced considering a one‐dimensional formulation with strain‐dependent nonlinear functions for an oscillatory load case. In addition to the viscoelastic storage and loss modulus, the higher order harmonic oscillations in the stress response are computed and compared to experimental data from Fourier transform rheology of Polyamide 6 (PA6). The comparison reveals a good agreement between the predictions of the nonlinear model and the experimental data for the higher harmonic intensity .

Viscoelastic mechanical behavior of periodontal ligament: Creep and relaxation hyper-viscoelastic constitutive models

In this contribution, creep and relaxation hyper-viscoelastic constitutive models of periodontal ligament (PDL) was proposed to define PDL as a steady state rheology (linear)-nonlinear viscoelastic fluid biomaterial. The physical elements of the hyperelastic spring, non-Newtonian fluid damper and strain gap were proposed. The hyperelastic spring, linear elastic spring, linear viscous damper, stress lock, and strain gap constituted the creep and relaxation models. The qualitative energy analysis was made in the viscoelastic zone between the instantaneous elastic element and the infinite elastic element in the creep and relaxation models. The mechanical behavior of viscoelastic materials is qualitatively unified. The universal static, creep, and relaxation mechanical behaviors of materials were explained from the energy point of view (graphische viscoelastic). After defining a virtual “infinite elastic curve of viscoelastic solid” in the viscoelastic fluid model, the universal creep recovery mechanical behavior was analyzed. The unity of the opposites between viscoelastic solid and viscoelastic fluid was clarified. In addition, A physical thinking of “anchored” was proposed to qualitatively modify the Boltzmann superposition principle. Instantaneous/infinite elastic-plastic-fracture curve, yield curve and fracture curve were defined to distinguish viscoelastic zone and viscoplastic zone. Finally, the unsteady-rheological (nonlinear) behavior of nonlinear viscoelastic fluid materials and the hyper-viscoelastic-plastic behavior of nonlinear viscoelastic solid materials were predicted.

Adhesion, Friction and Lubrication of Viscoelastic Materials

The mechanical behavior of viscoelastic materials is a key factor of many physical phenomena occurring at the interface of contacting bodies [...]

Experimental and Numerical Sensitivity Assessment of Viscoelasticity for Polymer Composite Materials

Viscoelastic polymer composites are widely used for vibration control in different fields of engineering like aerospace, mechanical, and structural engineering. The viscoelastic properties of these materials are strain rate-dependent and are highly related to frequency. Yet to date, less attention has been paid to quantifying the effects of these parameters and their interactions on damping properties and providing an approximation method for further applications. In the present research, a series of experimental tests was conducted on a viscoelastic material and the experimental data were numerically analyzed in detail. Sensitivity analyses are usually applied to quantify uncertainty using sampling techniques. However, in this study a method was proposed to derive a closed-form solution using the response surface function and a derivative-based global sensitivity analysis to evaluate the output contribution of each parameter. These effects were quantified and several approximation statistics were provided for future engineering implementations. The computational evaluation conducted in this study gives a detailed insight into the mechanical behavior of viscoelastic materials.

Visuo-Haptic Discrimination of Viscoelastic Materials.

In our daily lives, we interact with different types of deformable materials. Regarding their mechanical behavior, some of those materials lie in a range that is between purely elastic and purely viscous. This range of mechanical behavior is described as viscoelasticity. In certain types of haptic interactions, such as assessment of ripeness of fruit, firmness of cheese, and consistency of organ tissue, we rely heavily on our haptic perception of viscoelastic materials. The relationship between the mechanical behavior of viscoelastic materials and our perception of them has been investigated in the field of psychorheology. However, our knowledge on how we perceive viscoelastic materials is still quite limited though some research work has already been done on purely elastic and purely viscous materials. History- and frequency-dependent behavior of viscoelastic materials result in a complex time-dependent response, which requires relatively more sophisticated models to investigate their behavior than those of purely elastic and viscous materials. In this study, we model viscoelasticity using a "springpot" (i.e., fractional-order derivative element) and express its behavior in the frequency domain using two physical parameters-"magnitude" and "phase" of complex stiffness. In the frequency domain, we are able to devise signal detection experiments where we can investigate the perception of viscoelastic materials using the perceptual terms of "firmness" and "bounciness," corresponding to the physical parameters of "magnitude" and "phase." The results of our experiments show that the just-noticeable difference (JND) for bounciness increases linearly with increasing "phase," following Weber's law, while the JND for firmness is surprisingly independent of the level of "phase."

The development of the formalism of movable cellular automata for modeling the nonlinear mechanical behavior of viscoelastic materials

The paper is devoted to the development of the formalism of the computational method of discrete elements (DEM) for describing the mechanical behavior of consolidated viscoelastic materials. We considered an advanced implementation of DEM, namely, the method of movable cellular automata (MCA). A feature of this implementation of DEM is the use of a generalized many-body formulation of the relations for the forces of element-element interaction. 3D numerical models of viscoelastic material with a spectrum of relaxation times (Kelvin and Maxwell models, the standard model of elastomers, and others) were developed within the formalism of MCA. The correctness of the developed discrete element formalism and its applicability for modeling the processes of deformation and fracture of viscoelastic materials under dynamic loading are shown using the standard model of elastomers as an example. The relevance of the results is determined by the prospects for the further development of DEM and its application to study and predict the mechanical response of viscoelastic materials of various nature under dynamic loading including contact problems.

Modelling water hammer in viscoelastic pipelines: short brief

The model of water hammer in viscoelastic pipelines is analyzed. An appropriate mathematical model of water hammer in polymer pipelines is presented. An additional term has been added to continuity equation to describe the retarded deformation of the pipe wall. The mechanical behavior of viscoelastic material is described by generalized Kelvin-Voigt model. The comparison of numerical simulation and experimental data from well known papers is presented. Short discussion about obtained results are given.

A Three-Dimensional Boundary Element Approach for Transient Anisotropic Viscoelastic Problems

This paper presents a three-dimensional direct boundary element approach for solving transient problems of linear anisotropic elasticity and viscoelasticity. In order to take advantage of the correspondence principle between viscoelasticity and elasticity the formulation is given in the Laplace domain. Anisotropic viscoelastic fundamental solutions are obtained using the correspondence principle and anisotropic elastic Green’s functions. The standard linear solid model is used to represent the mechanical behavior of viscoelastic material. Solution in time domain is calculated via numerical inversion by modified Durbin’s method. Numerical example is provided to validate the proposed boundary element formulation.

Viscoelastic Relaxation Modulus Characterization Using Prony Series

THE MECHANICAL BEHAVIOR OF VISCOELASTIC MATERIALS IS INFLUENCED, AMONG OTHER FACTORS, BY PARAMETERS LIKE TIME AND TEMPERATURE. THE PRESENT PAPER PROPOSES A METHODOLOGY FOR A THERMORHEOLOGICALLY AND PIEZORHEOLOGICALLY SIMPLE CHARACTERIZATION OF VISCOELASTIC MATERIALS IN THE TIME DOMAIN BASED ON EXPERIMENTAL DATA USING PRONY SERIES AND A MIXED OPTIMIZATION TECHNIQUE BASED ON GENETIC ALGORITHMS AND NONLINEAR PROGRAMMING. THE TEXT DISCUSSES THE INFLUENCE OF PRESSURE AND TEMPERATURE ON THE MECHANICAL BEHAVIOR OF THOSE MATERIALS. THE RESULTS ARE COMPARED TO EXPERIMENTAL DATA IN ORDER TO VALIDATE THE METHODOLOGY. THE FINAL RESULTS ARE VERY PROMISING AND THE METHODOLOGY PROVES TO BE EFFECTIVE IN THE IDENTIFICATION OF VISCOELASTIC MATERIALS.

11th International Conference on the Mechanical Behavior of Materials Analysis of Defects in Viscoelastic Solids by a Transformed Boundary Element Method

Due to the inclusion of time as an independent variable to describe the mechanical behavior of viscoelastic materials, the available analytical solutions have been obtained only for a few simplified problems. To study the mechanical behavior of viscoelastic solids, the numerical approaches such as finite element method (FEM) and boundary element method (BEM) are normally needed. The main advantages of BEM are the reduction of the problem dimension by one and the exact satisfaction of certain boundary conditions for particular problems if their associated fundamental solutions are embedded in boundary element formulation. Through the use of correspondence principle, the viscoelastic solids can be effectively treated in Laplace domain. To take advantage of the available fundamental solutions for the defects in anisotropic elastic materials, in this paper we use the transformed BEM to treat the problems of viscoelastic solids containing defects such as holes, cracks, or inclusions. By using the subregion technique, the problems with simultaneous existence of multiple holes, cracks, and inclusions can also be treated. The main feature of this proposed method is that no meshes are needed along the boundary of defects and the boundary conditions are satisfied exactly, which means that the present approach should be more efficient and correct.

1450 釣り糸の引張り強度評価(S20-1 材料特性評価(1),S20 実験力学的手法による材料・製品の評価)

Among fishing tackle, fish line has the simplest structure, however, its quality is very critical to overall performance. Thus, we evaluated tensile strength of fishing line. Most commercially available fishing line is made from polymer materials, such as nylon, Fishing line made of nylon was used in this study. It is known that, unlike that of metals, the mechanical behavior of viscoelastic materials shows significant time-temperature dependence. Therefore, the effects of displacement speed and cross-sectional area on tensile strength were investigated.

Viscoelastic constants of a soda-lime-silica glass

A complete development of the viscoelastic constants is given in the framework of the viscoelastic theory using the definition of Tschoegl and the notion of moment introduced by Gy et al. for the linear viscoelasticity. Viscoelastic constants were considered as ‘constant’ because these dimensionless parameters do not change with loading level for a linear viscoelastic material. In addition, for a thermorheologically simple viscoelastic material, some of them are temperature-independent, whereas others follow the temperature-dependence of the Poisson ratio. Since some of them have a simple physical meaning, all models have to take them into account for simulating mechanical behavior of viscoelastic materials. Experimental measurements for some of viscoelastic constants under shear and uniaxial loadings allow determination of bulk equilibrium elastic modulus and other viscoelastic constants, used for describing hydrostatic pressure and biaxial behavior.

Finite amplitude oscillations of viscoelastic fluids

Finite amplitude oscillatory shear experiments are used to study the mechanical behavior of viscoelastic materials. Four rheological relations are derived which can be used to determine both linear and nonlinear rheological properties of simple fluids from data obtained using large amplitude oscillatory experiments. Two consistency conditions are derived for a fluid which obeys the K-BKZ constitutive equation, and these relations are used in conjunction with data from a finite amplitude oscillatory experiment to check the validity of the K-BKZ equation.

Boundary element analysis of viscoelastic structures involving fractional operators

The boundary element method (BEM) is applied to solve viscoelastic structural problems. The viscoelastic characteristic of the structure is represented using the fractional integrodifferential operators. The fractional operator representation of viscoelasticity provides a means to more accurately describe the mechanical behavior of viscoelastic materials. In this paper, a direct BEM formulation for the transient dynamic analysis of three‐dimensional viscoelastic structures modeled by the fractional operator constitutive equations is presented. The BEM formulation is developed in the Laplace transformed domain. The transient problem is first solved in the Laplace transformed domain and the time domain solutions are obtained by using an FFT based numerical inversion procedure. Example problems are solved using this BEM formulation and the results are compared.

粘弾性体の力学的挙動

粘弾性体の力学的挙動