Viscoelastic Disc Research Articles

The Anteroposterior Positioning of Viscoelastic Cervical Disc Prosthesis Does Not Alter the Outcomes.

While first-generation articulated disc prostheses had an ideal positioning schematically as posterior as possible because of their geometrically determined center of rotation, the dogma may change for viscoelastic implants, whose center of rotation is free. Our hypothesis was to assess whether the anteroposterior positioning (APP) of a viscoelastic implant may influence the clinical or radiological outcomes at follow-up. Twenty-five patients (mean age 47 years) were evaluated, with an average follow-up of 25.9 months. The primary outcome was the implants' APP on lateral radiographs. APP between 0% and 49% meant anterior centering, 50% perfect centering, and 51% to 100% posterior centering. The cohort was divided into 2 groups: anterior positioning and posterior positioning. Measurements were performed blindly to the functional outcomes. Visual analog scale for neck pain and radicular pain and the Neck Disability Index were assessed. Range of motion was measured at the last follow-up. The C2 to C7 Cobb angle and the spinocranial angle were also measured. The median crude offset from the vertebral endplate center was 0.4 mm (mean: 0.3 mm, Q1: -1.5 mm, Q3: 2 mm; range, -2.9 to 4 mm). The mean overall APP was 49%, 45.2% (95% CI, 43.2%-47.1%) in the anterior group, and 54.1% (95% CI, 51.4%-55.3%) in the posterior group. Fifteen patients were in the group anterior positioning and 10 in the group posterior positioning. The mean spinocranial angle was 79° preoperatively and 74° preoperatively (P = 0.04). Functional outcomes were significantly improved at the last follow-up (P < 10-4). There was no significant correlation between the APP, functional outcomes, and range of motion. The APP of the CP-ESP viscoelastic disc arthroplasty does not significantly influence the clinical or radiological outcomes at follow-up. This study suggests that this type of implant tolerates greater variability in its implantation technique.

Computer simulation for stability analysis of the viscoelastic annular plate with reinforced concrete face sheets

This article deals with the frequency analysis of viscoelastic sandwich disk with graphene nano-platelets (GPLs) reinforced viscoelastic concrete (GPLRVC) face sheets and honeycomb core. The honeycomb core is made of aluminum due to its low weight and high stiffness. The rule of the mixture and modified Halpin–Tsai model are engaged to provide the effective material constant of the concrete. By employing Hamilton's principle, the governing equations of the structure are derived and solved with the aid of the Generalize Differential Quadrature Method (GDQM). In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Afterward, a parametric study is carried out to investigate the effects of the outer to inner radius ratio, hexagonal core angle, thickness to length ratio of the concrete, the weight fraction of GPLs into concrete, and the thickness of honeycomb core to inner radius ratio on the frequency of the viscoelastic sandwich disk with honeycomb core and FGGPLRVC face sheet.

Деформирование вязкоупругого диска, вращающегося с ускорением

Рассматривается деформирование вязкоупругого диска, вращающегося с изменяющейся скоростью (разгон, торможение и вращение с постоянной скоростью). Для математического моделирования процесса деформирования используется теория течения. При предположении плоского напряженного состояния получена система дифференциальных уравнений для определения полей напряжений, обратимых и необратимых деформаций и перемещений. Численное решение этой системы уравнений найдено с помощью конечно-разностного метода. В случае решения осесимметричной задачи используется метод конечных элементов, реализованный в пакете Freefem++. Рассмотрено деформирование полого диска и диска с жестким включением, как постоянной толщины, так и переменной. The deformation of a viscoelastic disk rotating with a changing speed is considered. Within the framework of the theory of flow, relations are obtained that allow one to calculate the fields of stresses, strains, displacements, and velocities. To solve these equations in the case of a plane stress state, the finite-difference method is used, in the case of an axisymmetric problem, the finite element method implemented in the Freefem ++ package is used. Acceleration, braking and rotation at a constant speed are considered. The deformation of a hollow disk and a disk with a hard inclusion of both a constant thickness and a variable is considered.

Semi-numerical simulation for vibrational responses of the viscoelastic imperfect annular system with honeycomb core under residual pressure

This composition investigates the frequency analysis of sandwich imperfect viscoelastic disks with graphene nano-platelets (GPLs)-reinforced viscoelastic composite (GPLRVC) face sheets and honeycomb core. The honeycomb core is made of aluminum because of its high stiffness and low weight. The modified Halpin-Tsai model and rule of the mixture have been utilized to provide the effective material constant of the composite layers. Through employing Hamilton's principle, the governing equations of the structure are accordingly discerned and resolved by utilizing the Generalized Differential Quadrature Method (GDQM). Throughout this investigation, viscoelastic properties have been modeled in accordance with Kelvin-Voigt viscoelasticity. The deflection as the function of time is capable of being resolved through employing the fourth-order Runge-Kutta numerical method. Afterwards, a parametric study is conducted to discern the effects of the FG patterns, outer to inner radius ratio, hexagonal core angle, thickness to length ratio of the GPLs, the weight fraction of GPLs, FG face sheet thickness ratio, the thickness of honeycomb core to inner radius ratio, tensile, imperfect coefficient, and in-plane force on the frequency of the sandwich viscoelastic disk with honeycomb core and FG-GPLRVC face sheet.

Axisymmetric and Non-Axisymmetric Vibration of Thin Growing Viscoelastic Disc

Axisymmetric and non-axisymmetric in-plane vibrations of thin radially growing disc are considered in the frame of the Kelvin–Voigt model of linear viscoelasticity. The main focus of the research is on asymptotic behavior of solutions to the model. Mixed boundary value problems are formulated and converted into standard form by means of time dependent coordinate transformation. The boundary value problems obtained are transformed into infinite systems of ordinary differential equations using the Galerkin-Kantorovich method. It is shown that both axisymmetric and non-axisymmetric problems can be considered in terms of the same mathematical model. The simplified single mode model of the growing disc vibration is formulated and analysed. In the frame of this model the exact solutions are obtained in some interesting special cases. In the general case, solutions are derived using the Wentzel–Kramers–Brillouin (WKB) method. Depending on the exponent of radial growth, the vibration amplitude of the disc demonstrates qualitatively different behavior: if the exponent is less than 0.5 the vibration amplitude decays, if it is more than 0.5 the amplitude increases without bound no matter what size of damping coefficient is assumed. If the exponent equals 0.5 the vibration behavior depends on damping, namely there exist the critical damping coefficient and if the damping coefficient of a particular mode is less than this coefficient, the vibration amplitude grows without bound. Otherwise, if the damping coefficient of the mode is larger than the critical damping coefficient the vibration amplitude decays to zero. In the case where damping coefficient equals to the critical damping one, the amplitude of vibration remains constant. All of the qualitative results obtained for the single mode model are numerically tested and verified using a truncated multimodal system.

RETRACTED ARTICLE: Chaotic simulation of the multi-phase reinforced thermo-elastic disk using GDQM

In this research, a mathematical derivation is made to develop a nonlinear dynamic model for the nonlinear frequency and chaotic responses of the multi-scale hybrid nano-composite reinforced disk in the thermal environment and subject to a harmonic external load. Using Hamilton’s principle and the von Karman nonlinear theory, the nonlinear governing equation is derived. For developing an accurate solution approach, generalized differential quadrature method (GDQM) and perturbation approach (PA) are finally employed. Various geometrically parameters are taken into account to investigate the chaotic motion of the viscoelastic disk subject to harmonic excitation. The fundamental and golden results of this paper could be that in the lower value of the external harmonic force, different FG patterns do not have any effects on the motion response of the structure. But, for the higher value of external harmonic force and all FG patterns, the chaos motion could be seen and for the FG-X pattern, the chaosity is more significant than other patterns of the FG. As a practical designing tip, it is recommended to choose plates with lower thickness relative to the outer radius to achieve better vibration performance.

Lumbar and cervical viscoelastic disc replacement: Concepts and current experience.

The ideal lumbar and cervical discs should provide six degrees of freedom and tri-planar (three-dimensional) motion. Although all artificial discs are intended to achieve the same goals, there is considerable heterogeneity in the design of lumbar and cervical implants. The “second generation total disc replacements” are non-articulating viscoelastic implants aiming at the reconstruction of physiologic levels of shock absorption and flexural stiffness. This review aims to give an overview of the available implants detailing the concepts and the functional results experimentally and clinically. These monobloc prostheses raise new challenges concerning the choice of materials for the constitution of the viscoelastic cushion, the connection between the components of the internal structure and the metal endplates and even the bone anchoring mode. New objectives concerning the quality of movement and mobility control must be defined.

How Osmoviscoelastic Coupling Affects Recovery of Cyclically Compressed Intervertebral Disc.

Osmoviscoelastic behavior of cyclically loaded cervical intervertebral disc. The aim of this study was to evaluate in vitro the effects of physiologic compressive cyclic loading on the viscoelastic properties of cervical intervertebral disc and, examine how the osmoviscoelastic coupling affects time-dependent recovery of these properties following a long period of unloading. The human neck supports repetitive loadings during daily activities and recovery of disc mechanics is essential for normal mechanical function. However, the response of cervical intervertebral disc to cyclic loading is still not very well defined. Moreover, how loading history conditions could affect the time-dependent recovery is still unclear. Ten thousand cycles of compressive loading, with different magnitudes and saline concentrations of the surrounding fluid bath, are applied to 8 motion segments (composed by 2 adjacent vertebrae and the intervening disc) extracted from the cervical spines of mature sheep. Subsequently, specimens are hydrated during 18 hours of unloading. The viscoelastic disc responses, after cyclic loading and recovery phase, are characterized by relaxation tests. Viscoelastic behaviors are significantly altered following large number of cyclic loads. Moreover, after 18-hour recovery period in saline solution at reference concentration (0.15 mol/L), relaxation behaviors were fully restored. Nonetheless, full recovery is not obtained whether the concentration of the surrounding fluid, that is, hypo-, iso-, or hyper-osmotic conditions. Cyclic loading effects and full recovery of viscoelastic behavior after hydration at iso-osmotic condition (0.15 mol/L) are governed by osmotic attraction of fluid content in the disc due to imbalance between the external load and the swelling pressure of the disc. After removal of the load, the disc recovers its viscoelastic properties following period of rest. Nevertheless, the viscoelastic recovery is a chemically activated process and its dependency on saline concentration is governed by fluid flow due to imbalance of ions between the disc tissues and the surrounding fluid. 3.

Distribution Natural Waves on the Viscoelastic Cylindrical Body in Plane Strain State

In this paper the distribution of natural waves in the viscoelastic disc is discussed. The spectral problem is reduced to solving a system of ordinary differential equations of the first order with variable complex coefficients. The solution of differential equations is expressed by a special cylindrical Bessel functions and Hankel. The frequency equations are solved by numerical methods Muller and Gauss. The problem is solved numerically by the Godunov orthogonal sweep method and Mueller. Compares the numerical results.

Five-year follow-up of clinical and radiological outcomes of LP-ESP elastomeric lumbar total disc replacement in active patients

Background contextThe surgical treatment of degenerative disc disease at the lumbar spine may involve fusion. Total disc replacement (TDR) is an alternative treatment to avoid fusion-related adverse events, specifically adjacent segment disease. New generation of elastomeric non-articulating devices has been developed to more effectively replicate the shock absorption and flexural stiffness of native disc. PurposeTo report 5 years clinical and radiographic outcomes, range of motion (ROM), and position of the center of rotation after a viscoelastic lumbar TDR. Study DesignProspective observational cohort study Patient sampleSixty-one patients Outcome MeasuresThe clinical evaluation was based on visual analog scale (VAS) for pain, Oswestry disability index (ODI) score, short form-36 (SF-36) including the physical component summary (PCS) and the mental component summary (MCS), and general health questionnaire-28 (GHQ28). The radiological outcomes were ROM and position of the center of rotation at the index and the adjacent levels and the adjacent disc height changes. MethodsOur study group included 61 consecutive patients with monosegmental disc replacement. We selected patients who could provide a global lumbar spine mobility analysis (intermediate functional activity according to the Baecke score). Hybrid constructs had been excluded. Only the cases with complete clinical and radiological follow-up at 3, 6, 12, 24, and 60 months were included. ResultsThere was a significant improvement in VAS (3.3±2.5 vs. 6.6±1.7, p<.001), in ODI (20±17.9 vs. 51.2±14.6, p<.001), GHQ28 (52.6±15.5 vs. 64.2±15.6, p<.001), SF-36 PCS (58.8±4.8 vs. 32.4±3.4, p<.001), and SF-36 MCS (60.7±6 vs. 42.3±3.4, p<.001). The mean location centers of the index level and adjacent discs were comparable to those previously published in asymptomatic patients. According to the definition of Zigler and Delamarter, all of our cases remained grade 0 for adjacent level disc height (within 25% of normal). ConclusionsThis series reports significant improvement in midterm follow-up after TDR, which is consistent with previously published studies but with a lower rate of revision surgery and no adjacent level disease pathologies. The radiographic assessment of the patients demonstrated the quality of functional reconstruction of the lumbar spine after LP-ESP viscoelastic disc replacement.

Rotation in a gravitational billiard

Gravitational billiards composed of a viscoelastic frictional disk bouncing on a vibrating wedge have been studied previously, but only from the point of view of their translational behavior. In this work, the average rotational velocity of the disk is studied under various circumstances. First, an experimental realization is briefly presented, which shows sustained rotation when the wedge is tilted. Next, this phenomenon is scrutinized in close detail using a precise numerical implementation of frictional forces. We show that the bouncing disk acquires a spontaneous rotational velocity whenever the wedge angle is not bisected by the direction of gravity. Our molecular dynamics (MD) results are well reproduced by event-driven (ED) simulations. When the wedge aperture angle [Formula: see text], the average tangential velocity [Formula: see text] of the disk scales with the typical wedge vibration velocity [Formula: see text], and is in general a nonmonotonic function of the overall tilt angle [Formula: see text] of the wedge. The present work focuses on wedges with [Formula: see text], which are relevant for the problem of spontaneous rotation in vibrated disk packings. This study makes part of the PhD Thesis of G. G. Peraza-Mues.

Viscoelastic Disc Arthroplasty Provides Superior Back and Leg Pain Relief in Patients with Lumbar Disc Degeneration Compared to Anterior Lumbar Interbody Fusion.

Lumbar disc degeneration (LDD) is one of the most frequently diagnosed spinal diseases. The symptoms these disorders cause are anticipated to increase as the population in Western countries ages. Compare back and leg pain alleviation in patients with LDD and a viscoelastic disc prosthesis documented in the SWISSspine registry versus patients with anterior lumbar interbody fusion documented in the Spine Tango registry. Prospectively collected clinical and outcome data in two independent spine registries. Outcome Measures were back and leg pain relief on 0 to 10 numerical rating scales. The analysis included a single surgeon series of 48 patients with viscoelastic total disc replacement (VTDR) from the SWISSspine registry which were compared to 131 patients with anterior lumbar interbody fusion (ALIF) from the Spine Tango registry. Two linear multivariate regression models were built to assess the associations of patient characteristics with back and leg pain relief. The following covariates were included in the models: patient age and sex, disc herniation as additional diagnosis, number of treated segments, level of treated segment, treatment type (VTDR, ALIF), preoperative back and leg pain levels and follow-up interval. Both models showed VTDR to be associated with significantly higher back (2.76 points; 95% confidence interval (CI) 1.78 - 3.73; p < 0.001) and leg pain (2.12 points; 95% CI 1.12 to 3.13; p < 0.001) relief than ALIF. Other influential factors for higher back pain relief were female sex compared with male sex (1.03 additional points; 95% CI 0.27 to 1.78; p = 0.008), monosegmental surgery compared with bisegmental surgery (1.02 additional points; 95% CI 0.21 to 1.83; p = 0.014), and higher back pain at baseline (0.87 points additional pain relief per level of preoperative back pain; 95% CI 0.70 to 1.03; p < 0.001). Other influential factors for leg pain relief were monosegmental surgery (0.93 additional points; 95% CI 0.10 to 1.77; p = 0.029) and higher leg pain at baseline (0.83 points additional pain relief per level of preoperative leg pain; 95% CI 0.70 to 0.96). In both models the L3/4 segment showed 2.36 points (95% CI -4.27 to -0.45; p = 0.016) and 3.69 points (95% CI -5.66 to -1.71; p < 0.001) less pain relief than L5/S1. Significantly higher back and leg pain relief were observed after viscoelastic total disc replacement in comparison with anterior lumbar interbody fusion. The new less rigid materials used in the second generation total disc replacements (TDRs) may make artificial disc replacement an increasingly attractive option for patients with degenerative lumbar disc disease. Further controlled and long-term follow-up studies are required for more detailed comparisons of the outcomes of these types of disc implants. The Freedom Lumbar Disc is limited by U.S. federal law to investigational use only.

Clinical Outcome after Cervical Arthroplasty Using the Novel One-Piece Viscoelastic Freedom Prosthesis

Introduction The objective of this study was to evaluate the patients’ clinical condition after cervical arthroplasty using the Freedom Cervical Disc (AxioMed). Cervical arthroplasty is one possible treatment option for cervical degenerative disc disease (CDDD), offering an alternative to cervical decompression and fusion. As opposed to first generation ball and socket artificial disc devices, the freedom prosthesis is a one-piece viscoelastic artificial disc. This design is meant to re-establish the function of the spinal segment, mimicking the biomechanics of a healthy intervertebral disc and restoring segmental lordosis. Materials and Methods A total of 12 patients (women: 8; men: 4; mean age: 44.5 years, range: 37-59 years) received a prosthetic disc due to CDDD between April and September 2013. Follow-up assessment took place 6 weeks and 3 months after surgery and included clinical evaluation. The patients rated their clinical condition subjectively using the VAS for neck and arm pain, the North American Spine Society patient questionnaire for cervical pain and neurology (COSS), EuroQoL-5D, and the Neck Disability Index (NDI). Results All clinical indices indicated a clinically significantly improved condition of the patients after surgery. Mean VAS score for neck pain decreased from 6.36 preoperatively to 1.66 cm 3 months after surgery. Similarly, VAS score for radicular pain decreased from 6.81 to 1.33 cm. As expected, VAS for health state increased from 5.0 to 7.83 cm. Mean working capacity improved up to 75% at the 6 weeks and up to 91.66% at the 3 months follow-up. Furthermore, the COSS as well as the EuroQoL-5D and NDI showed an improvement of patients’ well-being. Mean improvement of the COSS for cervical pain and cervical neurology was 1.7 points. EuroQol-5D rose from 0.64 points preoperatively to 0.86 points 3 months after the procedure. NDI decreased from 48.6 to 16.3%. Conclusion At this early follow-up, our data indicate that the freedom prosthesis is a good treatment option in patients with CDDD. The clinical indices markedly improved after surgery. However, further data collection, as well as statistical analyses are needed to prove our preliminary results. Disclosure of Interest O. Boss: None declared B. Bäurle: None declared O. Hausmann: Conflict with Axiomed Spine Corporation

Application of the polynomial chaos expansion to approximate the homogenised response of the intervertebral disc

A possibility to simulate the mechanical behaviour of the human spine is given by modelling the stiffer structures, i.e. the vertebrae, as a discrete multi-body system (MBS), whereas the softer connecting tissue, i.e. the softer intervertebral discs (IVD), is represented in a continuum-mechanical sense using the finite-element method (FEM). From a modelling point of view, the mechanical behaviour of the IVD can be included into the MBS in two different ways. They can either be computed online in a so-called co-simulation of a MBS and a FEM or offline in a pre-computation step, where a representation of the discrete mechanical response of the IVD needs to be defined in terms of the applied degrees of freedom (DOF) of the MBS. For both methods, an appropriate homogenisation step needs to be applied to obtain the discrete mechanical response of the IVD, i.e. the resulting forces and moments. The goal of this paper was to present an efficient method to approximate the mechanical response of an IVD in an offline computation. In a previous paper (Karajan et al. in Biomech Model Mechanobiol 12(3):453-466, 2012), it was proven that a cubic polynomial for the homogenised forces and moments of the FE model is a suitable choice to approximate the purely elastic response as a coupled function of the DOF of the MBS. In this contribution, the polynomial chaos expansion (PCE) is applied to generate these high-dimensional polynomials. Following this, the main challenge is to determine suitable deformation states of the IVD for pre-computation, such that the polynomials can be constructed with high accuracy and low numerical cost. For the sake of a simple verification, the coupling method and the PCE are applied to the same simplified motion segment of the spine as was used in the previous paper, i.e. two cylindrical vertebrae and a cylindrical IVD in between. In a next step, the loading rates are included as variables in the polynomial response functions to account for a more realistic response of the overall viscoelastic intervertebral disc. Herein, an additive split into elastic and inelastic contributions to the homogenised forces and moments is applied.

Longitudinal wave propagation in multi cylindrical viscoelastic matching layers of airborne ultrasonic transducer: New method to consider the matching layer’s diameter (frequency

Wave propagation in viscoelastic disk layers is encountered in many applications including studies of airborne ultrasonic transducers. For viscoelastic materials, both material and geometric dispersion are possible when the diameter of the matching layer is of the same order as the wavelength. Lateral motions of the matching layer(s) that result from the Poisson effect are accounted by using a new concept called the “effective-density”. A new wave equation is derived for both metallic and non-metallic (polymeric) materials, usually employed for the matching layers of airborne ultrasonic transducer. The material properties are modeled by using the Kelvin model for metals and Linear Solid Standard model for non-metallic (polymeric) matching layers. The utilized model of the material of the matching layers has influence on amount and trend of variation in speed ratio. In this regard, 60% reduction in speed ratio is observed for Kelvin model for aluminum with diameter of 80mm at 100kHz while for a similar diameter but Standard Linear Model, the speed ratio increase to twice value at 15kHz, and then reduced until 70% at 67kHz for Polypropylene. The new wave theory simplifies to the one-dimensional solution for waves in metallic or polymeric matching layers if the Poisson ratio is set to zero. The predictions simplify to Love’s equation for stress waves in elastic disks when loss term is removed from equations for both models. Afterwards, the new wave theory is employed to determine the airborne ultrasonic matching layers to maximize the energy transmission to the air. The optimal matching layers are determined by using genetic algorithm theory for 1, 2 and 3 airborne matching layers. It has been shown that 1-D equation is useless at frequencies less than 100kHz and the effect of diameter of the matching layers must be considered to determine the acoustic impedances (matching layers) to design airborne ultrasonic transducers.

Analytical solution of transient in-plane vibration of a thin viscoelastic disc and its multi-precision evaluation

The analytical solution of transient in-plane vibration of a thin viscoelastic disc caused by a radial pressure load is presented. Using the multi-precision implementation of FFT based algorithm, the inverse Laplace transform is carried out and the spatio-temporal distributions of displacement components are obtained. The efficiency and the accuracy of the process of analytical solution evaluation are discussed in detail and the consequences in context of the application of results are mentioned. Finally, the results of numerical simulation are presented. They are used for the verification of the correctness of the derived analytical formulae and their evaluation and for the determination of numerical model capabilities.

Mechanical Characterization of a Viscoelastic Disc for Lumbar Total Disc Replacement

A viscoelastic artificial disc may more closely replicate normal stiffness characteristics of the healthy human disc compared with first-generation total disc replacement (TDR) devices, which do not utilize viscoelastic materials and are based on a ball and socket design that does not allow loading compliance. Mechanical testing was performed to characterize the durability and range of motion (ROM) of an investigational viscoelastic TDR (VTDR) device for the lumbar spine, the Freedom® Lumbar Disc. ROM data were compared with data reported for the human lumbar disc in the clinical literature. Flexibility and stiffness of the VTDR in compression, rotation, and flexion/extension were within the parameters associated with the normal human lumbar disc. The device constrained motion to physiologic ranges and replicated normal stress/strain dynamics. No mechanical or functional failures occurred within the loads and ROM experienced by the human disc. Fatigue testing of the worst case VTDR device size demonstrated a fatigue life of 50 years of simulated walking and 240 years of simulated significant bends in both flexion/extension and lateral bending coupled with axial rotation, with no functional failures. These results indicate that the VTDR evaluated in this mechanical study is durable and has the ability to replicate the stiffness and mechanics of the natural, healthy human lumbar disc.

Numerical Analysis of a Rotating Viscoelastic Body under Repeated Contact Load.

Polygonal type wear is often seen on a circumference of a rotating viscoelastic disk under contact load. This phenomenon is caused by a combination of physical and mechanical features, such as a dynamic behavior of the material, a heat generation due to loss energy, a heat conduction and various modes of vibrations in the viscoelastic disk including the loading system. The authors had already discussed about the dominant factor of the peculiar phenomenon using an experimental-theoretical hybrid type simulation. In this study, numerical analyses were attempted by using four simplified numerical models, namely a multistage modeling, for a finite element analysis in order to investigate a dominant factor and an opportunity of the periodic stress and temperature distribution of the rotating viscoelastic disk. The criterion of the occurrence of the periodic stress and temperature distribution in a rotating viscoelastic disk was investigated accurately, comparing the results of the experimental/theoretical hybrid simulations and FE analysis.

An Approach to Peculiar Vibration Observed in a Rotating Viscoelastic Disk under Contact Load.

Wavy patterns of stress and temperature distribution are occasionally observed along the circumference of a rotating viscoelastic disk under a contact load. This phenomenon is caused by a combination of physical and mechanical features such as dynamic behavior, heat generation due to loss energy, heat conduction and various modes of vibrations in the viscoelastic disk including the loading system. This study attempts to give a rational explanation of the phenomenon, through experimental and theoretical approaches, by means of dynamic modeling of the entire vibrating system. The study by means of dynamic analysis revealed that the wavy stress pattern results from the resonant vibration of the loading mechanism which corresponded to its natural frequency. It is emphasized that the peculiar vibration is strongly influenced by temperature-dependent dynamic properties of the viscoelastic disk.

Energy analysis of the stress-strain state of a viscoelastic disk with rigidly fixed ends under cyclic compression

Energy analysis of the stress-strain state of a viscoelastic disk with rigidly fixed ends under cyclic compression