Published: June 8, 2026

Propagation of three-dimensional boundary waves in thin viscoelastic cylindrical shells

Botir Usmanov1
Ismoil Safarov2
Bekzod Mirzakabilov3
Tulkin Ruziyev4
Nozimbek Shomurodov5
Sherzodjon Ablokulov6
1Department of Automation and Digital Management, Tashkent Chemical-Technological Institute, Navoi St. 32, Tashkent, 100011, Uzbekistan
2, 3, 6Department of Higher Mathematics, Tashkent Chemical-Technological Institute, Navoi St. 32, Tashkent, 100011, Uzbekistan
3Higher Mathematics Department, Tashkent Chemical-Technological Institute, Navoi St. 32, Tashkent, 100011, Uzbekistan
4Bukhara State Pedagogical Institute, Piridastgir St. 2, Bukhara, 200100, Uzbekistan
5Department of Higher Mathematics, Tashkent State Transport University, Temiryulchilar St. 1, Tashkent, 100167, Uzbekistan
Corresponding Author:
Bekzod Mirzakabilov
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Abstract

This paper examines the propagation of three-dimensional boundary waves in an infinite, thin, viscoelastic cylindrical shell. The governing equations are formulated using the three-dimensional theory of viscoelasticity in cylindrical coordinates. The problem is reduced to an eigenvalue problem using separation of variables and potential functions. A numerical solution is obtained using the Muller method, and dispersion relations are analyzed. The influence of viscoelastic parameters on natural frequencies is studied. The results indicate that material viscosity has a significant impact on wave attenuation and frequency characteristics. Comparisons with the classical Kirchhoff-Love theory demonstrate good agreement at low wave numbers, while deviations increase at higher frequencies.

1. Introduction

The dynamic properties of extended axially symmetrical structures are primarily dictated by the mechanical characteristics and geometric dimensions of the cylindrical shell [1]. However, several challenges remain regarding their geometric properties. The inherent axial symmetry and significant length of these structures allow for the derivation of theoretical dispersion relations in specific cases [2]. Previous studies based on the Kirchhoff-Love theory demonstrate that a natural boundary wave is not attenuated by propagating modes [3]. Numerical calculations have further shown that the frequencies corresponding to this wave consistently remain below the first cut-off frequency [4].

It is important to note that eigenwaves derived from both three-dimensional theory and Kirchhoff-Love theory accurately describe wave behavior only at low frequencies, while providing qualitatively inaccurate results at higher frequencies. For instance, in [5], the first mode value of the angular wave velocity for elastic cylindrical shells was determined. Despite these advancements, the viscoelastic properties of the material have received limited attention in existing literature. This study aims to address this gap by accounting for viscoelastic effects in the analysis.

2. Materials and methods

Let us consider the non-axially symmetrical harmonic oscillations of a semi-infinite hollow viscoelastic cylinder (cylindrical shell). To describe cylindrical oscillations, we adopt a three-dimensional viscoelastic framework, expressed in cylindrical coordinates (r, θ,z), in which the area occupied by the cylinder (see Fig. 2). 1) is determined by the inequalities.

Fig. 1Calculation scheme

Calculation scheme

arb, 0θ2π, 0z. The dynamic equation of wave propagation in a viscoelastic cylindrical shell satisfies the Lame operator equation [6], which has the form:

1
μ~12u+(λ~1+μ~1)graddiv u=ρ12ut2,

where u(ur,uθ,uz) – displaced points of the cylindrical shell; ρ1 – density of the shell material. The coefficients of the Lame operator have the following form:

2
λ~1ft=ν1E0(1+ν1)(1-2ν1)f(t)-0tRλ1(t-τ)f(t)dτ,
μ~1ft=ν1E021+ν1ft-0tRμ1t-τftdτ,

where f(t)an arbitrary function of time; Rλt-τ and Rμt-τ – relaxation kernel [7], ν1 – Poisson’s ratio of the shell, E0 – instantaneous modulus of elasticity. Enter dimensionless variables:

3
r=Rr-, z=Rz-,  ur,uθ,uz=R u-r,u-θ,u-z,    ϖ=Rωcs-1,    R=(a+b)/2,σrr,σθθ,σzz,σrθ,σrz,σθz=E02(1+ν)-1σ-rr,σ-θθ,σ-zz,σ-rθ,σ-rz,σ-θz.

Here σrr, σθθ, σzz, σrθ, σrz, σθz – components of the stress tensor. Enter the thickness parameter: η=h/R, h=(b-a)/2.

The thickness parameter is always less than one η1. On the composite surface, without stress b, conditions r=a are established:

4
σrr=0,    σrθ=0,    σrz=0.

Conditions of the free edge at the end-of-shell free edge conditions: z=0, σzz=0, σrz=0; σθz=0, z meets nonhomogeneous boundary conditions at θ:

5
σzz=Pgrcosnθ,    σrz=0,    σθz=0,

where, n is a Pg(r) given function of the variable p, where n =  1, 2,…. We choose the function Pg(r) so that the resonance of the wave of interest to us is excited most effectively. The condition of the absence of energy sources is established z. Taking into account the perturbations, using the integral operators in Eq. (2), we define ft=ψte-iωRt a slowly changing time ψt function, ωR – a real constant. The freezing technique [8] allows us to predict these relationships as follows: E-f=E01-ΓECωR-iΓESωRf.

Introduction of the Fourier transforms of the relaxation nucleus of the material. We accept a three-parameter kernel Rt=Ae-β t/t1-α for a viscoelastic medium, which requires that the kernel Rt-τ be integrable according to standard hereditary mechanics.

Here:

6
ГsωR=0RτcosωRτ dτ,  ГsωR=0RτsinωRτ dτ.   

t=τ continuity (excluding), precision, and monotony:

7
R>0,  dRtdt0,       0<0Rtdt<1.

u , j – layer medium displacement vector.

Then Eq. (1) takes the form:

8
μ-12u+(λ-1+μ-1)graddiv u=ρ12ut2,

where:

λ-1ft=ν1(1+ν1)(1-2ν1)E01-ΓECωR-iΓESωR,    μ-1f(t)=ν12(1+ν1)E01-ΓECωR-iΓESωR.

It is convenient to express displacements and stresses in terms of Lame’s elastic potentials φ and ψ. We have the following relationships:

9
u=gradφ+rotψ,  divψ=0.

Consequently, we obtain the next set of partial differential equations in the form φ and ψ (ψr,ψθ,ψz) with respect to:

10
Δφ1-1c-p122φ1 t2=0,  Δψz1-1c-s122ψz1 t2=0,
Δψr1-ψr1r2+2r2 ψθ1 θ-1c-s122ψr1 t2=0,     Δψθ1-ψθ1r2+2r2 ψz1 θ-1c-sk22ψr t2=0,
Δ=2 t2+1r r+1r22 θ2+2 z2,     ur1= φ1 r+1r ψz1 θ- ψθ1 z,
uθ1=1r φ1 θ+ ψz1 z- ψθ1 r,      uz1= φ1 r+ ψθ1 r+ ψz1 r-1r ψr1 θ,

where:

c-p12=cp12Γλμp,  c-s12=cs12Γμs,       cp12=λ1+2μ1ρ1,     cs12=μ1ρ1, 
Γλμp=1-Γλμc(ωR)-iΓλμs(ωR),Γμs=1-Γμc(ωR)-iΓμs(ωR),
ΓλμсωR=0(Rλτ+2Rμτ)cosωRτ dτ,
ΓλμsωR=0(Rλτ+2Rμτ)sinωRτ dτ,
ΓμсωR=0RμτcosωRτ dτ,       ΓμsωR=0RμτsinωRτ dτ.

To satisfy the boundary Eq. (5), the solution of the system of differential Eq. (10) is taken as follows:

11
φ1r,θ,z,t=n=0RφnrZφn(z)Φφn(θ)Tn(t),ψz1r,θ,z,t=n=0RψznrZψzn(z)Φψzn(θ)Tn(t),ψr1r,θ,z,t=n=0RψrnrZψrn(z)Φψrn(θ)Tn(t),ψθ1r,θ,z,t=n=0RψθnrZψθn(z)Φψθn(θ)Tn(t).

Substituting this expression into the wave equation and dividing the result by RZFT, we get:

12
1Rφn2Rφnr2+1r1RφnRφnr+1r2Φφn2Φφnθ2+1Ζφn2Ζφnz2=1c-p21Tn2Tnt2.

Eq. (12) is formulated for the longitudinal displacement potentials. Other potentials are defined in a similar manner. The terms in the first and ik second parentheses depend on (r, θ) and z, respectively, while the right-hand side depends only on t. Consequently, Eq. (12) is satisfied for all independent variables r, θ, z, and t only if each term is equal to a separation constant. Thus, we obtain the following system of ordinary differential equations:

13
1c-p2Tnd2Tndt2=-kφ2,        1Zd2Zφndt2=-kφz2,  1Rd2Rdr2+1RdRdr+1r2ψzd2Φφndθ2=-kφr2.

Arbitrary constants -kφ2, -kφz2 and -kφr2 are defined as the negative squares of the corresponding quantities. The resulting solutions are simplified and take a convenient form for the present analysis. We express Eq. (13) in the following form:

14
r2Rd2Rdr2+1RdRdr+kφr2r2=-1ψzd2ψzdθ2.

Here, the variables θ and r are assumed to be independent of each other. Substituting Eq. (13) into the differential Eq. (12), we obtain the following separated equations:

15
1ψzd2ψzdθ2=-m2,        1Rd2Rdr2+1RdRdr+kφr2-m2r2=0.

The constants m, kφz and kφr are interdependent. Substituting Eq. (13) into differential Eq. (12), we obtain the following relationship:

16
kφz2=kφ2-kφr2.

The general solution for the initial Eq. (13) is expressed as follows: Tn(t)=Aneiωt+Bne-iωt.

The second and third governing relations in Eq. (13) give solutions determined by the following expressions:

17
Znz=Cneikzφz+Dne-ikzφz,    Φφnθ=Eneimθ+Fne-imθ.

The set of solutions Eq. (17) represents a standing wave formed by the superposition of two waves propagating in opposite directions along the θ-axis. The functions representing these waves take the following form: F(r,θ,z,t)=F0(r,z)ei(ωt±nθ).

As observed from the previous expression, the constant-phase surface in this case does not move parallel to itself, unlike in planar structures; instead, it undergoes angular rotation over time. In this study, the velocity of the outer waves is determined by the formula c=ω/p , where p represents the wave number [8]. Eq. (13) defines the solution involving Bessel  (Zn1) and Neumann (Zn2) functions with complex arguments. Substituting the obtained solutions Eqs. (13-15) into the boundary conditions yields a homogeneous system of linear equations with nine unknown parameters [9]:

18
CX=0.

3. Results and discussion

For a solid cylindrical body of infinite length, the characteristic determinant Eq. (16) reduces to the third order. For elastic bodies, a similar equation was previously derived in [10]. Notably, the equations obtained by the proposed method demonstrate good agreement with the results presented in the work of V. T. Grinchenko.

The transcendental characteristic Eq. (17) is solved numerically using the Muller method [10]. The material parameters adopted for calculations are: ν1= 0.25, R= 0.75. The relaxation kernel is modeled using the Rzhanitsyn-Koltunov three-parameter weak singular kernel: REt=A1e-β1 t/t1-α1, with A1= 0.048, β1= 0.05, and α1= 0.1. The comparative numerical results are illustrated in Fig. 2.

Fig. 2Comparison of dispersion results between three-dimensional shell theory and Kirchhoff-Love hypothesis: 1, 3 – Kirchhoff-Love hypothesis; 2, 4 – three-dimensional theory; A= 0.1, A= 0.02

Comparison of dispersion results between three-dimensional shell theory and Kirchhoff-Love hypothesis: 1, 3 – Kirchhoff-Love hypothesis; 2, 4 – three-dimensional theory; A= 0.1, A= 0.02

Fig. 2 distribution of natural frequencies, ka= 0.1. As can be seen, natural frequencies initially decrease, and then increase with growth.

The numerical results, obtained for ka= 0, 1, indicate that an increase in the wave number causes the real part of the wave frequency to initially decrease before subsequently increasing. This phenomenon aligns with the observations reported by Mikhail A. Koltunov for elastic thin and cylindrical shells. Furthermore, incorporating the material viscosity leads to a reduction in the real frequency components by up to 5 %. A comparison shows that the results based on the Kirchhoff-Love hypothesis and the three-dimensional theory are in close agreement for small wave numbers (n =  5), with a discrepancy of approximately 2-3 %. However, this difference becomes more pronounced as the wave number increases.

Table 1Key parameters of three-dimensional boundary waves in a thin viscoelastic cylindrical shell

Parameter
Value / range
3D viscoelastic theory
Kirchhoff-love theory
Remark
Poisson’s ratio (ν1)
0.25
Applied in calculations
Applied in calculations
Shell material property
Mean radius ratio (R)
0.75
Applied in calculations
Applied in calculations
R=(a+b)/2
Relaxation kernel parameters
A= 0.048, β1= 0.05,
α1= 0.1
Used in Rzhanitsyn-Koltunov kernel
Not applicable
3-parameter weakly singular kernel
Natural frequency behavior (low wave numbers)
n5
Decreases first, then increases
Agrees within 2-3 % deviation
Low-frequency range
Natural frequency behavior (high wave numbers)
n>5
Provides accurate results
Deviation increases significantly
High-frequency range
Effect of viscosity on frequency
≈ 5 % reduction
Real frequency reduced by ~5 %
Not accounted for
Due to material viscosity
Complex frequency (damping)
Complex
ω=ωr+iωi
Non-zero imaginary part present
Damping not considered
Viscoelastic attenuation
Numerical method
Muller method
Solves transcendental characteristic equation
Corresponding method applied
Stable and accurate computation

4. Conclusions

In this study, the propagation of three-dimensional boundary waves in a long viscoelastic cylindrical shell has been rigorously analyzed within the framework of the three-dimensional theory of viscoelasticity. The governing equations, formulated using the Lamé operator, were reduced to a spectral (eigenvalue) problem by employing potential functions and the method of separation of variables.

The analytical solutions, represented in terms of exponential functions and higher-order special functions (Bessel, Neumann, and Hankel functions with complex arguments), provide a comprehensive description of wave processes in cylindrical geometries. The viscoelastic behavior of the material was successfully incorporated using the Boltzmann-Volterra hereditary integral with a three-parameter weakly singular Rzhanitsyn-Koltunov relaxation kernel.

A robust numerical algorithm based on the Muller method was developed to solve the resulting transcendental characteristic equations. This approach enables an efficient transformation of complex functional determinants into polynomial forms, ensuring stable and accurate computation of complex eigenfrequencies.

The main quantitative and qualitative findings of the study can be summarized as follows:

The dispersion analysis shows that the real part of the natural frequency exhibits a non-monotonic behavior, decreasing at low wave numbers and increasing at higher values.

The inclusion of viscoelastic effects leads to a noticeable reduction in natural frequencies (up to approximately 5 %) and introduces damping, characterized by the emergence of a non-zero imaginary component of the frequency.

A comparative analysis demonstrates that the classical Kirchhoff-Love shell theory provides accurate results only in the low-frequency range (n5), with deviations increasing significantly as the wave number grows.

The influence of the viscoelastic parameters on wave attenuation and dispersion characteristics is substantial, indicating the necessity of using three-dimensional models for accurate predictions in practical applications.

The proposed methodology and obtained results significantly extend existing models of wave propagation in cylindrical shells by incorporating viscoelastic effects and providing a reliable computational framework. The findings of this study have important implications for the design and analysis of engineering structures subjected to dynamic loading, including pipelines, aerospace shells, and mechanical systems where vibration control and wave attenuation are critical.

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About this article

Received
January 27, 2026
Accepted
March 19, 2026
Published
June 8, 2026
SUBJECTS
Mathematical models in engineering
Keywords
viscoelastic shell
boundary waves
eigenvalue problem
dispersion relation
natural frequency
Acknowledgements

The authors have not disclosed any funding.

Data Availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflict of interest

The authors declare that they have no conflict of interest.