Skip to main content

General decay for a wave equation of Kirchhoff type with a boundary control of memory type

Abstract

A nonlinear wave equation of Kirchhoff type with memory condition at the boundary in a bounded domain is considered. We establish a general decay result which includes the usual exponential and polynomial decay rates. Furthermore, our results allow certain relaxation functions which are not necessarily of exponential and polynomial decay. This improves earlier results in the literature.

MSC: 35L05; 35L70; 35L75; 74D10.

1 Introduction

In this article, we study the asymptotic behavior of the energy function related to a nonlinear wave equation of Kirchhoff type subject to memory condition at the boundary as follows:

u t t - M | | u | | 2 2 Δ u + l ( t ) h ( u ) - Δ u t + a ( x ) f ( u ) = 0 in  Ω × ( 0 , ) ,
(1.1)
u=0 on  Γ 0 × ( 0 , ) ,
(1.2)
u + 0 t g ( t - s ) M | | u ( s ) | | 2 2 u ν ( s ) + u t ν ( s ) d s = 0 on  Γ 1 × ( 0 , ) ,
(1.3)
u ( x , 0 ) = u 0 ( x ) , u t ( x , 0 ) = u 1 ( x ) in  Ω,
(1.4)

where Ω is a bounded domain with smooth boundary ∂Ω = Γ0 Γ1. The partition Γ0 and Γ1 are closed and disjoint, with meas0) > 0, ν represents the unit normal vector directed towards the exterior of Ω, u is the transverse displacement, and g is the relaxation function considered positive and nonincreasing belonging to W1,2 (Ω).

From the physical point of view, we know that the memory effect described in integral equation (1.3) can be caused by the interaction with another viscoelastic element. In fact, the boundary condition (1.3) signifies that Ω is composed of a material which is clamped in a rigid body in the portion Γ0 of its boundary and is clamped in a body with viscoelastic properties in the portion of Γ1.

When Γ1 = ϕ, problem (1.1) has its origin in describing the nonlinear vibrations of an elastic string. More precisely, we have

ρ h 2 u t 2 = p 0 + E h 2 L 0 L u x 2 d x 2 u x 2 + f
(1.5)

for 0 < × < L, t ≥ 0; where u is the lateral deflection, x the space coordinate, t the time, E the Young modulus, ρ the mass density, h the cross section area, L the length, p0 the initial axial tension and f the external force. Kirchhoff [1] was the first one who introduced (1.5) to study the oscillations of stretched strings and plates, so that (1.5) is called the wave equation of Kirchhoff type after him. In this direction, problem (1.1) with ∂Ω = Γ0 and l(t) = 0 has been investigated by many authors in recent years, and many results concerning existence, nonexistence and asymptotic behavior have been established, see [213].

On the other hand, regarding the viscoelastic wave equations with memory term acting in the boundary or in the domain, there are numerous results related to asymptotic behavior of solutions. For example, in the case where M(s) = 1, Cavalcanti et al. [14] investigated the existence and uniform decay of strong solutions of wave equation (1.1) with a nonlinear boundary damping of memory type and a nonlinear boundary source when l(t) = 0. Cavalcanti and Guesmia [15] considered the following system:

u t t -Δu+F ( x , t , u , u ) =0 in  Ω× ( 0 , ) ,
(1.6)
u=0 on  Γ 0 × ( 0 , ) ,
(1.7)
u + 0 t g ( t - s ) u ν ( s ) d s = 0 on  Γ 1 × ( 0 , ) ,
(1.8)
u ( x , 0 ) = u 0 ( x ) , u t ( x , 0 ) = u 1 ( x ) , in  Ω,
(1.9)

where Ω is a bounded domain with smooth boundary ∂Ω = Γ0 Γ1. They obtained the general decay result which depends on the relaxation function g. In particular, if the relaxation function g decays exponentially (or polynomially), then the solution also decays exponentially (or polynomially) and with the same decay rate. Moreover, when u0 = 0 on Γ1, they obtained exponential or polynomial decay of solutions, even if the relaxation function g does not converge to 0 at ∞. Later, Messaoudi and Soufyane [16] generalized this result to the case of a system of Timoshenko type. They established general decay rate results, from which the usual exponential and polynomial decay rates are only special cases. Recently, Messaoudi and Soufyane [17] studied the following problem:

u t t -Δu+f ( u ) =0

in a bounded domain with boundary conditions (1.7)-(1.9). They improved the results of [15] by applying the multiplier techniques. Indeed, they obtained not only a general decay result, but their works also allowed certain relaxation functions which are not necessarily of exponential or polynomial decay. For other related works, we refer the reader to [1820] and references therein.

Conversely, in the case where M is not a constant function, Santos [21] considered

u t t - μ ( t ) u x x = 0 , ( x , t ) ( 0 , 1 ) × R + , u ( 0 , t ) = 0 , u ( 1 , t ) = - 0 t g ( t - s ) μ ( s ) u x ( 1 , s ) d s , t > 0 , u ( 0 ) = u 0 , u t ( 0 ) = u 1 , x ( 0 , 1 ) ,

where μ(t) is a nonincreasing function satisfying μ(t) ≥ μ0 > 0. By denoting k the resolvent kernel of g', he showed that the solution decays exponentially (or polynomially) to zero provided k decays exponentially (or polynomially) to zero. Later on, Santos et al. [22] generalized this result to a nonlinear n-dimensional equation of Kirchhoff type of the form

u t t - M | | u | | 2 2 Δ u - Δ u t + f ( u ) = 0
(1.10)

in a bounded domain with boundary conditions (1.2)-(1.3). In that article, they proved that the energy decays with the same rate of decay of the relaxation function. This latter result improved an earlier one by Park et al. [23], where the authors considered (1.10) in a bounded domain with nonlinear boundary damping and memory term and M(s) = 1 + s and f = 0.

We note that stability of problems with the nonlinear term h(u) requires a careful treatment because we do not have any information about the influence of the integral Ω h ( u ) u t dx about the sign of the derivative E'(t). Although the subject is important, there are few mathematical results in the presence of the nonlinearity given by h(u), see [2426]. In light of this and previous articles [17, 22], it is interesting to investigate whether we still have the similar general decay result as in [17] for nondissipative distributed system (1.1) with the memory-type damping acting on a part of the boundary. Hence, the main purpose of this article is to answer the above question for system (1.1)-(1.4). Consequently, by following the arguments close to the one in [17] with necessary modification required the nature of our problem, we establish a general decay result which includes the usual exponential and polynomial decay rates. Furthermore, our results allow a larger class of relax functions which are not necessarily of exponential and polynomial decay. Therefore, this improves earlier results in the literature [22, 27].

In order to obtain our results, we consider system (1.1)-(1.4), under some assumptions on a(x), l(t), M and f. Precisely, we state the general assumptions:

(A1) a(x): Ω → R+ is a function.

(A2) f C1(R) is a function and satisfies

uf ( u ) βF ( u ) 0forβ>2,
(1.11)

where F ( u ) = 0 u f ( s ) ds with

F ( u ) d|u | p for all  uR,

d > 0 and 1p n n - 2 .

(A3) M is a C1 function on [0, ∞) satisfying

M ( λ ) m 0 > 0 and M ( λ ) λ M ^ ( λ ) for all λ 0 ,
(1.12)

Where M ^ ( λ ) = 0 λ M ( s ) ds.

(A4) h : RnR is a C1 function such that h is bounded and there exists β1 > 0 such that

|h ( ξ ) | β 1 |ξ| for all  ξ R n ,
(1.13)

and l(t) is a positive and nonincreasing function.

The remainder of this article is organized as follows. In Section 2, we introduce some notations, present Lemma 2.1 to describe more general relations between the relaxation function g and the corresponding resolvent kernel k and state the existence result to system (1.1)-(1.4). In Section 3, we give the proof of our main result Theorem 3.5.

2 Preliminaries

In this section, we introduce some notations and establish the existence of solutions of the problem (1.1)-(1.4). In what follows, let ||·|| p denote the usual Lp (Ω) norm ||| | L p ( Ω ) , for 1 ≤ p ≤ ∞. We define the convolution product operator by

( g * u ) ( t ) = 0 t g ( t - s ) u ( s ) d s ,
(2.1)

and set

( g ϕ ) ( t ) = 0 t g ( t - s ) | | ϕ ( t ) - ϕ ( s ) | | 2 2 d s ,
(2.2)
( g ϕ ) ( t ) = 0 t g ( t - s ) ( ϕ ( t ) - ϕ ( s ) ) d s .
(2.3)

Using Hölder's inequality, we observe that

| g ϕ ( t ) | 2 0 t | g ( s ) | d s ( | g | ϕ ) ( t ) .
(2.4)

Next, we shall use Equation 1.3 to estimate the boundary term M | | u ( s ) | | 2 2 u ν + u t ν . Differentiating (1.3), we obtain

M | | u ( t ) | | 2 2 u ν ( t ) + u t ν ( t ) + 1 g ( 0 ) 0 t g ( t - s ) M | | u ( s ) | | 2 2 u ν ( s ) + u t ν ( s ) d s = - 1 g ( 0 ) u t .

Assume the function k is the resolvent kernel of the relaxation function g, then

k+ 1 g ( 0 ) k* g =- 1 g ( 0 ) g .

Applying Volterra's inverse operator yields

M | | u ( t ) | | 2 2 u ν ( t ) + u t ν ( t ) =- 1 g ( 0 ) ( u t + k * u t ) ,

which implies that

M | | u ( t ) | | 2 2 u ν ( t ) + u t ν ( t ) = - τ { u t + k ( 0 ) u - k ( t ) u 0 + k * u } on  Γ 1 × ( 0 , ) ,
(2.5)

where τ= 1 g ( 0 ) . Reciprocally, taking u0 = 0 on Γ1, identity (2.5) implies (1.3). As we are interested in relaxation functions of more general decay and the resolvent k appeared in Equation 2.5, we want to know if the resolvent k has the same property with the relaxation function g involved in (1.3). The following lemma answers this question. Let h be a relaxation function and k its resolvent kernel, that is

k ( t ) =h ( t ) + ( k * h ) ( t ) .

Lemma 2.1. [15, 17, 22] If h : [0, ∞) → R+is continuous, then k is also a positive continuous function. Moreover,

(1) If there exists a positive constant c0such that

h ( t ) c 0 e - 0 t γ ( s ) d s ,

where γ : [0, ∞) → R+, is a nonincreasing function satisfying, for some positive constant ε < 1,

c 1 = 0 e - 0 t ( 1 - ) γ ( s ) d s dt< 1 c 0 .

Then, k satisfies

k ( t ) c 0 1 - c 0 c 1 e - 0 t ε γ ( s ) d s .

(2) Suppose that

h ( t ) c 0 ( 1 + t ) p

for c0 < p - 1. Then, there exists a positive constant ε < 1 such that

k ( t ) β ( 1 + t ) ε p ,

where β > 0 is a constant.

Based on this lemma, we will use (2.5) instead of (1.3), i.e., we can consider system (1.1)-(1.4) as follows:

u t t - M | | u | | 2 2 Δ u + l ( t ) h ( u ) - Δ u t + a ( x ) f ( u ) = 0 in  Ω × ( 0 , ) , u = 0 on  Γ 0 × ( 0 , ) , M | | u ( t ) | | 2 2 u ν ( t ) + u t ν ( t ) = - τ { u t + k ( 0 ) u - k ( t ) u 0 + k * u } on  Γ 1 × ( 0 , ) , u ( x , 0 ) = u 0 ( x ) , u t ( x , 0 ) = u 1 ( x ) in  Ω .

We notice that, due to the condition (1.2), the solution of system (1.1)-(1.4) must belong to the following space:

V= { v H 1 ( Ω ) ; v = 0 on  Γ 0 } ,

which endowed with the norm ||·||2 is a Hilbert space. Now, we are ready to give the well-posedness of system (1.1)-(1.4).

Theorem 2.2. Let k W2,1 (R+) ∩ W1,∞ (R+), (u0, u1) (H2 (Ω) ∩ V)2 and satisfy the compatibility condition

M | | u 0 | | 2 2 u 0 ν + u 1 ν +τ u 1 =0 on  Γ 1 .

Assume further that (A1)-(A4) hold. Then, there exists a unique solution u of system (1.1)-(1.4) such that

u L ( 0 , ; H 2 ( Ω ) V ) , u t L ( 0 , ; V ) , u t t L ( 0 , ; L 2 ( Ω ) ) .

Proof. Using the Galerkin method and procedures similar to that of [22, 28], we can obtain the result.    □

3 Decay of solutions

In this section, we study the asymptotic behavior of the solutions of system (1.1)-(1.4) when the resolvent kernel k satisfies

k ( 0 ) > 0 , k ( t ) 0 , k ( t ) 0 , k ( t ) - γ ( t ) k ( t ) ,
(3.1)

where γ : [0, ∞) → R+ is a function satisfying the following condition:

γ ( t ) > 0 , γ ( t ) 0 and 0 γ ( s ) d s = .
(3.2)

To get our result, we further assume that

0 < l ( t ) γ ( t ) for all  t 0 .
(3.3)

Let x0 be a fixed point in Rn. Set

m=m ( x ) =x- x 0 ,R ( x 0 ) =max | | m ( x ) | | 2 ; x Ω ̄

and partition the boundary ∂Ω into two sets

Γ 0 = { x Ω ; m ( x ) ν 0 } , Γ 1 = { x Ω ; m ( x ) ν > 0 } .
(3.4)

Define the first-order energy function of system (1.1)-(1.4) by

E ( t ) = 1 2 | | u t | | 2 2 + M ^ | | u | | 2 2 + Ω a ( x ) F ( u ) d x + τ 2 k ( t ) Γ 1 | u | 2 d Γ - τ 2 Γ 1 k u d Γ .
(3.5)

The following lemma is associated with the property of the convolution operator, which is used to estimate the energy identity.

Lemma 3.1. If g, ϕ C1(R+), then

( g * ϕ ) ϕ t = - 1 2 g ( t ) | ϕ ( t ) | 2 + 1 2 g ϕ - 1 2 d d t g ϕ - 0 t g ( s ) d s | ϕ ( t ) | 2 .
(3.6)

Proof. Our conclusion is followed by differentiating the term g ϕ.   □

Lemma 3.2. Under the assumptions of (A1)-(A4), the energy function E(t) satisfies

d d t E ( t ) - τ 2 Γ 1 | u t | 2 d Γ + τ 2 k 2 ( t ) Γ 1 | u 0 | 2 d Γ + τ 2 k ( t ) Γ 1 | u | 2 d Γ - τ 2 Γ 1 k u d Γ - Ω | u t | 2 d x - Ω l ( t ) h ( u ) u t d x .
(3.7)

Proof. Multiplying Equation 1.1 by u t , and integrating by parts over Ω, we get

d d t 1 2 | | u t | | 2 2 + M ^ | | u | | 2 2 + Ω a ( x ) F ( u ) d x = Γ 1 M | | u | | 2 2 u ν + u t ν u t d Γ - Ω | u t | 2 d x - Ω Δ l ( t ) h ( u ) u t d x .

Exploiting (2.5), (3.6) and the definition of E(t) by (3.5), we have

d d t E ( t ) - τ Γ 1 | u t | 2 d Γ + τ Γ 1 k ( t ) u 0 u t d Γ + τ 2 k ( t ) Γ 1 | u | 2 d Γ - τ 2 Γ 1 k u d Γ - Ω | u t | 2 d x - Ω l ( t ) h ( u ) u t d x .

Then, using Hölder's inequality and Young's inequality, the inequality (3.7) is obtained.    □

Next, we construct a Lyapunov functional which is equivalent to E(t). To do so, for N > 0 large enough, let

L ( t ) =NE ( t ) +ψ ( t ) ,
(3.8)

where

ψ ( t ) = Ω m u ( t ) + n 2 - θ u u t d x
(3.9)

for 0 < θ < 1.

For the purpose of achieving our main result, we need the following lemmas.

Lemma 3.3. There exist two positive constants α1 and α2 such that the relation

α 1 E ( t ) L ( t ) α 2 E ( t )

holds for all t ≥ 0.

Proof. From (3.9) and using Young's inequality, we get

| ψ ( t ) | R ( x 0 ) + B 1 n 2 - θ | | u t | | 2 | | u | | 2 2 m 0 R ( x 0 ) + B 1 n 2 - θ E ( t ) ,

where we have used the fact that || u t | | 2 2 2E ( t ) by (3.5) and

| | u | | 2 2 2 m 0 E ( t )
(3.10)

due to M ^ ( λ ) m 0 λ>0 by (A3) and (3.5). Here B1 > 0 is the smallest constant such that

| | u | | 2 B 1 | | u | | 2 , u V .
(3.11)

Thus, from (3.8), we deduce that

|L ( t ) -NE ( t ) |=|ψ ( t ) | 2 m 0 R ( x 0 ) + B 1 n 2 - θ E ( t ) .

Hence, selecting

N > 2 m 0 R ( x 0 ) + B 1 n 2 - θ ,
(3.12)

there exist two positive constants α1 and α2 such that the relation

α 1 E ( t ) L ( t ) α 2 E ( t )

holds.    □

Lemma 3.4. Let (A1)-(A4) and (3.1)-(3.3) hold, with β1 (given by (A4)) small enough and

lim t k ( t ) = 0 .
(3.13)

Then, for some t0 large enough, the functional L(t) verifies, along the solution u of (1.1)-(1.4) ,

L ( t ) - α 2 E ( t ) + c 4 k 2 ( t ) Γ 1 | u 0 | 2 d Γ - c 5 Γ 1 k u d Γ + Ω n + α - n 2 - θ β a ( x ) + m a F ( u ) d x
(3.14)

for all tt0, where α = min {2θ, 1 - θ} and c i are positive constants given in the proof, i = 4, 5.

Proof. First, we are going to estimate the derivative of ψ(t). From (3.9) and using Equation 1.1, we have

d d t ψ ( t ) = 1 2 Γ 1 ( m ν ) | u t | 2 d Γ - θ Ω | u t | 2 d x + Ω m u ( t ) + n 2 - θ u M | | u | | 2 2 Δ u d x + Ω m u ( t ) + n 2 - θ u Δ u t d x - Ω l ( t ) h ( u ) m u ( t ) + n 2 - θ u d x - Ω m u ( t ) + n 2 - θ u a ( x ) f ( u ) d x .

Performing integration by parts and using Young's inequality, we obtain

d d t ψ ( t ) 1 2 Γ 1 ( m ν ) | u t | 2 d Γ - θ Ω | u t | 2 d x + Γ 1 M | | u | | 2 2 u ν + u t ν m u ( t ) + n 2 - θ u d Γ - M | | u | | 2 2 2 Γ 1 ( m ν ) | u | 2 d Γ - ( 1 - θ ) M ( | | u | | 2 2 ) | | u | | 2 2 + ε c 0 M | | u | | 2 2 | | u | | 2 2 + C ε Ω | u t | 2 d x - Ω l ( t ) h ( u ) m u ( t ) + n 2 - θ u d x - Ω m u ( t ) + n 2 - θ u a ( x ) f ( u ) d x ,
(3.15)

where ε > 0, c ε and c0 are some positive constants. In the following, we will estimate the last two terms on the right-hand side of (3.15). It follows from (1.13), Hölder's inequality, (3.11), (3.3) and (3.10) that

Ω l ( t ) h ( u ) m u ( t ) + n 2 - θ u d x γ ( 0 ) β 1 R ( x 0 ) + B 1 n 2 - θ | | u | | 2 2 2 γ ( 0 ) β 1 c 1 m 0 E ( t ) ,
(3.16)

where c 1 =R ( x 0 ) + B 1 ( n 2 - θ ) . Taking (1.11) and (3.4) into account, we have

- Ω m u ( t ) + n 2 - θ u a ( x ) f ( u ) d x = - Ω a ( x ) m F ( u ) d x - n 2 - θ Ω a ( x ) u f ( u ) d x Ω ( n a ( x ) + m a ) F ( u ) d x - Γ 1 a ( x ) ( m ν ) F ( u ) d Γ - n 2 - θ β Ω a ( x ) F ( u ) d x Ω n - n 2 - θ β a ( x ) + m a F ( u ) d x .
(3.17)

A substitution of (3.16)-(3.17) into (3.15), we obtain

d d t ψ ( t ) 1 2 Γ 1 ( m ν ) | u t | 2 d Γ - θ | | u t | | 2 2 - ( 1 - θ - ε c 0 ) M | | u | | 2 2 | | u | | 2 2 + Γ 1 M | | u | | 2 2 u ν + u t ν m u ( t ) + n 2 - θ u d Γ + C ε Ω | u t | 2 d x - M | | u | | 2 2 2 Γ 1 ( m ν ) | u | 2 d Γ + 2 γ ( 0 ) β 1 c 1 m 0 E ( t ) + Ω ( n - n 2 - θ β ) a ( x ) + m a F ( u ) d x .
(3.18)

Now, we analyze the boundary term on the right-hand side of (3.18). Applying Young's inequality and M(λ) ≥ m0 > 0 by (1.12), we have, for ε1 > 0,

Γ 1 M | | u | | 2 2 u ν + u t ν ( m u ( t ) + n 2 - θ u ) d Γ ε 1 Γ 1 | m u ( t ) | 2 + n 2 - θ 2 | u | 2 d Γ + C ε 1 Γ 1 M | | u | | 2 2 u ν + u t ν 2 d Γ ε 1 Γ 1 ( m ν ) | u | 2 d Γ + n 2 - θ 2 B * ε 1 | | u | | 2 2 + C ε 1 Γ 1 M | | u | | 2 2 u ν + u t ν 2 d Γ ε 1 Γ 1 ( m ν ) | u | 2 d Γ + n 2 - θ 2 B * ε 1 m 0 M | | u | | 2 2 | | u | | 2 2 + C ε 1 Γ 1 M | | u | | 2 2 u ν + u t ν 2 d Γ ,

where C ε 1 is a positive constant and B* > 0 is the constant such that

Γ 1 | u | 2 d Γ B * | | u | | 2 2 , u V .
(3.19)

Thus, (3.18) becomes

d d t ψ ( t ) 1 2 Γ 1 ( m ν ) | u t | 2 d Γ - θ | | u t | | 2 2 - 1 - θ - ε c 0 - n 2 - θ 2 B * ε 1 m 0 M ( | | u | | 2 2 ) | | u | | 2 2 - M ( | | u | | 2 2 ) 2 - ε 1 Γ 1 ( m ν ) | u | 2 d Γ + C ε Ω | u t | 2 d x + C ε Γ 1 M | | u | | 2 2 u ν + u t ν 2 d Γ + 2 γ ( 0 ) β 1 c 1 m 0 E ( t ) + Ω n - n 2 - θ β a ( x ) + m a F ( u ) d x .
(3.20)

By rewriting the boundary condition (2.5) as

M | | u | | 2 2 u ν + u t ν =-τ { u t + k ( t ) u ( t ) - k ( t ) u 0 - k u } ,

and, then, combining (3.7) and (3.20), we deduce that

L ( t ) = N E ( t ) + ψ ( t ) - N τ 2 - ( m ν ) 2 - 8 τ 2 c ε 1 Γ 1 | u t | 2 d Γ - ( N - c ε ) | | u t | | 2 2 - θ | | u t | | 2 2 - 1 - θ - ε c 0 - n 2 - θ 2 B * ε 1 m 0 M ( | | u | | 2 2 ) | | u | | 2 2 + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u | 2 d Γ + N τ 2 + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u 0 | 2 d Γ - N τ 2 Γ 1 k u d Γ - M | | u | | 2 2 2 - ε 1 Γ 1 ( m ν ) | u | 2 d Γ + 8 τ 2 c ε 1 Γ 1 | k u | 2 d Γ + 2 γ ( 0 ) β 1 c 1 m 0 E ( t ) - N l ( t ) Ω h ( u ) u t d x + Ω n - n 2 - θ β a ( x ) + m a F ( u ) d x .

Similarly as in deriving (3.16), we note that

l ( t ) Ω h ( u ) u t d x γ ( t ) β 1 1 2 | | u t | | 2 2 + 1 2 | | u | | 2 2 γ ( t ) β 1 c 3 E ( t ) γ ( 0 ) β 1 c 3 E ( t ) ,
(3.21)

where c 3 =1+ 1 m 0 . This implies that

L ( t ) - N τ 2 - ( m ν ) 2 - 8 τ 2 c ε 1 Γ 1 | u t | 2 d Γ - θ | | u t | | 2 2 - ( N - c ε ) | | u t | | 2 2 - 1 - θ - ε c 0 - n 2 - θ 2 B * ε 1 m 0 M | | u | | 2 2 | | u | | 2 2 + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u | 2 d Γ + N τ 2 + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u 0 | 2 d Γ - N τ 2 Γ 1 k u d Γ - M | | u | | 2 2 2 - ε 1 Γ 1 ( m ν ) | u | 2 d Γ + 8 τ 2 c ε 1 Γ 1 | k u | 2 d Γ + β 1 γ ( 0 ) N c 3 + 2 c 1 m 0 E ( t ) + Ω n - n 2 - θ β a ( x ) + m a F ( u ) d x .

At this point, we choose

ε= ε 1 <min m 0 4 , ( 1 - θ ) 2 c 0 + n 2 - θ 2 B * .

Once ε = ε1 is fixed (hence c ε and c ε 1 are also fixed), we pick N large satisfying (3.12) and

N > max max Γ 1 | m ν | + 16 τ 2 c ε 1 τ , c ε
(3.22)

at the same time. Then, from the properties of k(t) by (3.1) and noting that |gϕ ( t ) | 2 0 t |g ( s ) |ds ( | g | ϕ ) ( t ) by (2.4), we see that

L ( t ) - θ | | u t | | 2 2 - 1 - θ 2 M | | u | | 2 2 | | u | | 2 2 - k ( 0 ) Γ 1 k u d Γ + c 4 k 2 ( t ) Γ 1 | u 0 | 2 d Γ + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u | 2 d Γ + β 1 γ ( 0 ) N c 3 + 2 c 1 m 0 E ( t ) + Ω n - n 2 - θ β a ( x ) + m a F ( u ) d x .

Utilizing the inequality M ( λ ) λ M ^ ( λ ) by (1.12) and the definition of E(t) by (3.5), we obtain

L ( t ) - α - β 1 γ ( 0 ) N c 3 + 2 c 1 m 0 E ( t ) + τ α 2 k ( t ) + 8 τ 2 c ε 1 k 2 ( t ) Γ 1 | u | 2 d Γ - τ α 2 + k ( 0 ) Γ 1 k u d Γ + c 4 k 2 ( t ) Γ 1 | u 0 | 2 d Γ + Ω n + α - n 2 - θ β a ( x ) + m a F ( u ) d x ,

which together with (3.19) and (3.10) infers that

L ( t ) - α - β 1 γ ( 0 ) N c 3 + 2 c 1 m 0 E ( t ) + 2 B * m 0 τ α 2 k ( t ) + 8 τ 2 c ε 1 k 2 ( t ) E ( t ) - τ α 2 + k ( 0 ) Γ 1 k u d Γ + c 4 k 2 ( t ) Γ 1 | u 0 | 2 d Γ + Ω n + α - n 2 - θ β a ( x ) + m a F ( u ) d x ,

where α = min{2θ, 1 - θ}. Besides, we note that there exists t0 large enough satisfying

k ( t ) m 0 2 B * min α 64 τ 2 c ε 2 , 1 4 τ for t t 0 ,
(3.23)

because of limt→∞ k(t) = 0 by (3.13). Therefore, taking β1 small enough such that

0 < β 1 < α 4 γ ( 0 ) N c 3 + 2 c 1 m 0 ,
(3.24)

then,

L ( t ) - α 2 E ( t ) + c 4 k 2 ( t ) Γ 1 | u 0 | 2 d Γ - c 5 Γ 1 k u d Γ + Ω n + α - n 2 - θ β a ( x ) + m a F ( u ) d x
(3.25)

for all tt0, where c i are positive constants, i = 4, 5. This completes the proof.    □

Theorem 3.5. Given that (u0, u1) (H2 (Ω) ∩ V)2, assume that (A1)-(A4), (3.1)-(3.3) and (3.13)hold, with β1 (given by (A4)) small enough. Assume further that

n + α - n 2 - θ β a ( x ) + m a < 0 , x Ω .
(3.26)

Then, for some t0 large enough, we have, tt0,

E ( t ) cE ( t 0 ) e - a 1 0 t γ ( s ) d s if u 0 =0on Γ 1 ,
(3.27)

otherwise (if u0 ≠ 0 on Γ1),

E ( t ) c E ( t 0 ) + Γ 1 | u 0 | 2 d Γ t 0 t k 2 ( s ) e a 1 t 0 s γ ( ζ ) d ζ d s e - a 1 0 t γ ( s ) d s ,
(3.28)

where a1 is a fixed positive constant and cis a generic positive constant.

Proof. Multiplying (3.25) by γ(t) and exploiting (3.26), (3.1) and (3.7), we derive that

γ ( t ) L ( t ) - α 2 γ ( t ) E ( t ) + c 4 k 2 ( t ) γ ( t ) Γ 1 | u 0 | 2 d Γ - c 5 γ ( t ) Γ 1 k u d Γ - α 2 γ ( t ) E ( t ) + c 4 k 2 ( t ) γ ( t ) Γ 1 | u 0 | 2 d Γ + c 5 Γ 1 k u d Γ - α 2 γ ( t ) E ( t ) + c 6 k 2 ( t ) Γ 1 | u 0 | 2 d Γ - c 7 E ( t ) - c 7 l ( t ) Ω h ( u ) u t d x ,
(3.29)

where c6 = c4γ(0) + c5 and c 7 = 2 c 5 τ . Employing (3.21) again, (3.29) becomes

F 1 ( t ) - γ ( t ) L ( t ) - γ ( t ) α 2 - β 1 c 7 c 3 E ( t ) + c 6 k 2 ( t ) Γ 1 | u 0 | 2 d Γ ,

where

F 1 ( t ) =γ ( t ) L ( t ) + c 7 E ( t ) ,

which is equivalent to E(t) due to Lemma 3.3 and γ(t) is nonincreasing by (3.2). In addition to (3.24), we further require

0< β 1 < α 8 c 7 c 3 ,

then, we have

F 1 ( t ) - a 1 γ ( t ) F 1 ( t ) + c 6 k 2 ( t ) Γ 1 | u 0 | 2 d Γ , t t 0 ,
(3.30)

where a1 is a positive constant.

Case I: If u0 = 0 on Γ1, then (3.30) reduces to

F 1 ( t ) - a 1 γ ( t ) F 1 ( t ) ,t t 0 .

Integrating the above inequality over (t0, t) to get

F 1 ( t ) F 1 ( t 0 ) e - a 1 t 0 t γ ( s ) d s ,t t 0 .

Then, using the fact F1(t) is equivalent to E(t), we obtain, for some positive constant c,

E ( t ) c E ( t 0 ) e - a 1 t 0 t γ ( s ) d s = c E ( t 0 ) e a 1 0 t 0 γ ( s ) d s e - a 1 0 t γ ( s ) d s , t t 0 .

Thus, (3.27) is proved.

Case II: If u0 ≠ 0 on Γ1, then (3.30) gives

F 1 ( t ) - a 1 γ ( t ) F 1 ( t ) + c 8 k 2 ( t ) ,t t 0 ,

where c 8 = c 6 Γ 1 | u 0 | 2 dΓ. Direct computations give

e a 1 t 0 t γ ( s ) d s F 1 ( t ) c 8 k 2 ( t ) e a 1 t 0 t γ ( s ) d s .

An integration over (t0, t) yields

F 1 ( t ) F 1 ( t 0 ) + c 8 t 0 t k 2 ( s ) e a 1 t 0 s γ ( ζ ) d ζ d s e - a 1 t 0 t γ ( s ) d s , t t 0 .

Again using the fact F1(t) is equivalent to E(t), we obtain, for some positive constant c,

E ( t ) c E ( t 0 ) + Γ 1 | u 0 | 2 d Γ t 0 t k 2 ( s ) e a 1 t 0 s γ ( ζ ) d ζ d s e a 1 0 t 0 γ ( s ) d s e - a 1 0 t γ ( s ) d s , t t 0 .

This completes the proof of Theorem 3.5.    □

4 Conclusion and suggestions

Santos et al. [22] considered problem (1.1)-(1.4) with a = 1 and without a function of the gradient term. They showed the solution decays exponentially (or polynomially) to zero provided the kernel decays exponentially (or polynomially) to zero. Recently, Messaoudi and Soufyane in 2010 [17] considered a semi-linear wave equation, in a bounded domain, where the memory-type damping is acting on the boundary. They established a general decay result, from which the usual exponential and polynomial decay rate are only special cases. Motivated by this, we intended to investigate the decay properties of problem (1.1)-(1.4) using the work of Messaaoudi and Soufyane [17]. Since stability of problems with the nonlinear term h(u) requires a careful treatment, it is interesting to investigate whether we still have the similar general decay result as that of [16] in the presence of a function of the gradient term. This is our motivation to consider problem (1.1)-(1.4). And, this problem is not considered before.

By adopting and modifying the method proposed by Messaoudi and Soufyane in 2010 [17], we establish a general decay result, from which the usual exponential and polynomial decay rate are only special cases. Further, our result allows certain kernels which are not necessarily of exponential or polynomial decay. In this way, we improved the results of Santos et al. [22], in which they considered problem (1.1)-(1.4) with a = 1 and in the absence of l(t)h (u). Moreover, we note that our result also holds for problem (1.1)-(1.4) with a = 1 and l(t) = 0 and without imposing strong damping term, thus our result improves the one of Bae et al. [27]. More precisely, the estimate (3.27) and (3.28) generalizes the exponential and polynomial decay result given in [22, 27]. Indeed, we obtain exponential decay for γ(t) = c and polynomial decay for γ(t) = c(1 + t)-1, where c is a positive constant. Additionally, as in [17], our result allows kernels which satisfy k″(t) ≥ c (-k′)1+q, for 0 < q < 1 instead of the usual assumption 0<q< 1 2 . It suffices to take, for example, k(t) = (1 + t)-λ, for λ > 0. Direct computations yield

k ( t ) =c ( - k ( t ) ) 1 + 1 1 + λ .

It is clear that 0< 1 1 + λ <1, for λ > 0.

Though we consider the conditions on the term involving the gradient are too restrictive and we combine some known ideas to obtain our result, our findings extend those decay results in [22, 27] and these findings are interesting to those with closely concerns. For future work, we will consider not necessarily decreasing kernels and relax the condition of h(u).

References

  1. Kirchhoff G: Vorlesungen über Mechanik. Leipzig Teubner 1883.

    Google Scholar 

  2. Biler P: Remark on the decay for damped string and beam equations. Nonlinear Anal TMA 1984, 9: 839-842.

    Google Scholar 

  3. Brito EH: Nonlinear initial boundary value problems. Nonlinear Anal TMA 1987, 11: 125-137. 10.1016/0362-546X(87)90031-9

    Article  Google Scholar 

  4. Ikerata R: On the existence of global solutions for some nonlinear hyperbolic equations with Neumann conditions. TRU Math 1988, 24: 1-17.

    MathSciNet  Google Scholar 

  5. Ikerata R: A note on the global solvability of solutions to some nonlinear wave equations with dissipative terms. Differential Integral Equations 1995, 8: 607-616.

    MathSciNet  Google Scholar 

  6. Matos MP, Pereira DC: On a hyperbolic equation with strong damping. Funkcial Ekvac 1991, 34: 303-311.

    MathSciNet  Google Scholar 

  7. Matsuyama T, Ikerata R: On global solutions and energy decay for the wave equations of Kirchhoff type with nonlinear damping terms. J Math Anal Appl 1996, 204: 729-753. 10.1006/jmaa.1996.0464

    Article  MathSciNet  Google Scholar 

  8. Nishihara K, Yamada Y: On global solutions of some degenerate quasilinear hyperbolic equations with dissipative terms. Funkcial Ekvac 1990, 33: 151-159.

    MathSciNet  Google Scholar 

  9. Nishihara K: Exponentially decay of solutions of some quasilinear hyperbolic equations with linear damping. Nonlinear Anal TMA 1984, 8: 623-636. 10.1016/0362-546X(84)90007-5

    Article  MathSciNet  Google Scholar 

  10. Ono K: On global existence, asymptotic stability and blowing up of solutions for some degenerate nonlinear wave equations of Kirchhoff type with a strong dissipation. Math Methods Appl Sci 1997, 20: 151-177. 10.1002/(SICI)1099-1476(19970125)20:2<151::AID-MMA851>3.0.CO;2-0

    Article  MathSciNet  Google Scholar 

  11. Ono K: On global solutions and blow-up solutions of nonlinear Kirchhoff strings with nonlinear dissipation. J Math Anal Appl 1997, 216: 321-342. 10.1006/jmaa.1997.5697

    Article  MathSciNet  Google Scholar 

  12. Wu ST, Tsai LY: Blow-up of solutions for some nonlinear wave equations of Kirchhoff type with some dissipation. Nonlinear Anal TMA 2006, 65: 243-264. 10.1016/j.na.2004.11.023

    Article  MathSciNet  Google Scholar 

  13. Yamada Y: On some quasilinear wave equations with dissipative terms. Nagoya Math J 1982, 87: 17-39.

    MathSciNet  Google Scholar 

  14. Cavalcanti MM, Domingos Cavalcanti VN, Prates JS, Soriano JA: Existence and uniform decay of solutions of a degenerate equation with nonlinear boundary memory source term. Nonlinear Anal TMA 1999, 38: 281-294. 10.1016/S0362-546X(98)00195-3

    Article  Google Scholar 

  15. Cavalcanti MM, Guesmia A: General decay rates of solutions to a nonlinear wave equation with boundary condition of memory type. Differential Integral Equations 2005, 18: 583-600.

    MathSciNet  Google Scholar 

  16. Messaoudi SA, Soufyane A: Boundary stabilization of solutions of a nonlinear system of Timoshenko system. Nonlinear Anal TMA 2007, 67: 2107-2121. 10.1016/j.na.2006.08.039

    Article  MathSciNet  Google Scholar 

  17. Messaoudi SA, Soufyane A: General decay of solutions of a wave equation with a boundary control of memory type. Nonlinear Anal Real World Appl 2010, 11: 2896-2904. 10.1016/j.nonrwa.2009.10.013

    Article  MathSciNet  Google Scholar 

  18. Cavalcanti MM, Domingos Cavalcanti VN, Prates JS, Soriano JA: Existence and uniform decay rates for viscoelastic problems with nonlinear boundary damping. Differential Integral Equations 2001, 14: 85-116.

    MathSciNet  Google Scholar 

  19. Cavalcanti MM, Domingos Cavalcanti VN, Santos ML: Existence and uniform decay rates of solutions to a degenerate system with memory conditions at the boundary. Appl Math Comput 2004, 150: 439-465. 10.1016/S0096-3003(03)00284-4

    Article  MathSciNet  Google Scholar 

  20. Jiang S, Muñoz Rivera JE: A global existence for the Dirichlet problems in nonlinear n-dimensional viscoelasticity. Differential Integral Equations 1996, 9: 791-810.

    MathSciNet  Google Scholar 

  21. Santos ML: Asymptotic behavior of solutions to wave equations with a memory condition at the boundary. Electronic J Differential Equations 2001, 73: 1-11.

    Google Scholar 

  22. Santos ML, Ferreira J, Pereira DC, Raposo CA: Global existence and stability for wave equation of Kirchhoff type with memory condition at the boundary. Nonlinear Anal TMA 2003, 54: 959-976. 10.1016/S0362-546X(03)00121-4

    Article  MathSciNet  Google Scholar 

  23. Park JY, Bae JJ, Hyo Jung IL: Uniform decay of solution for wave equation of Kirchhoff type with nonlinear boundary damping and memory term. Nonlinear Anal TMA 2002, 50: 871-884. 10.1016/S0362-546X(01)00781-7

    Article  Google Scholar 

  24. Aassila M, Cavalcanti MM, Domingos Cavalcanti VN: Existence and uniform decay of the wave equation with nonlinear boundary damping and boundary memory source term. Calc Var 2002, 15: 155-180. 10.1007/s005260100096

    Article  MathSciNet  Google Scholar 

  25. Guesmia A: A new approach of stabilization of nondissipative distributed systems. SIAM J Control Optim 2003, 42: 24-52. 10.1137/S0363012901394978

    Article  MathSciNet  Google Scholar 

  26. Park JY, Ha TG: Energy decay for nondissipative distributed systems with boundary damping and source term. Nonlinear Anal TMA 2009, 70: 2416-2434. 10.1016/j.na.2008.03.026

    Article  MathSciNet  Google Scholar 

  27. Bae JJ, Yoon SB: On uniform decay of wave equation of carrier model subject to memory condition at the boundary. J Korean Math Soc 2007, 44: 1013-1024. 10.4134/JKMS.2007.44.4.1013

    Article  MathSciNet  Google Scholar 

  28. Santos ML, Junior F: A boundary condition with memory for Kirchhoff plate equations. Appl Math Comput 2004, 148: 475-496. 10.1016/S0096-3003(02)00915-3

    Article  MathSciNet  Google Scholar 

Download references

Acknowledgements

The author would like to thank the anonymous referees for their valuable and constructive suggestions which improve this work.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Shun-Tang Wu.

Additional information

Competing interests

The author declare that they have no competing interests.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Wu, ST. General decay for a wave equation of Kirchhoff type with a boundary control of memory type. Bound Value Probl 2011, 55 (2011). https://doi.org/10.1186/1687-2770-2011-55

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/1687-2770-2011-55

Keywords