We know that viscoelastic materials have memory effects. These properties are due to the mechanical response influenced by the history of the materials. As these materials have a wide application in the natural science, their dynamics are of great importance and interest. The memory effects can be modeled by a partial differential equation. In recent years, the behaviors of solutions for the PDE system have been studied extensively, and many achievements have been obtained. Many authors have focused on the problem of existence, decay and blow-up for the last two decades, see [1] -[5] . And the attractors are still important contents that are studied.

In [6] , R.O. Araújo, T. Ma and Y.M. Qin studied the following equation

and they proved the global existence, uniqueness and exponential stability of solutions and existence of the global attractor.

In [7] , Y.M. Qin, B.W. Feng and M. Zhang considered the following initial-boundary value problem:

where is a bounded domain of with a smooth boundary, (the past history of u) is a given datum which has to be known for all, the function g represents the kernel of a memory,

is a non-autonomous term, called a symbol, and ρ is a real number such that if; if

. They proved the existence of uniform attractors for a non-autonomous viscoelastic equation with a past history. For more related results, we refer the reader to [8] -[14] .

In this work, we intend to study the following initial-boundary problem:

where and is a bounded domain with smooth boundary,

if; if, for the problem (1.3), the memory term

replaces, and we consider the strong damping term, the li-

near damping term and source terms. We define

A direct computation yields

Thus, the original memory term can be written as

and we get a new system

with the initial conditions

and the boundary conditions

The rest of this paper is organized as follows. In Section 2, we first obtain the priori estimates, then in Section 3, we prove the existence of the global attractors.

For convenience, we denote the norm and scalar product in by and, let,.

In this section, we present some materials needed in the proof of our results, state a global existence result, and prove our main result. For this reason, we assume that

(G1) is a differentiable function satisfying;

(G2);

(G3) There exists a constant such that,;

Lemma 1. Assume (G1), (G2) and (G3) hold, let

and, , , then the solution of Equation (1.3) satisfies

and

here, thus there exists and, such that

Proof. We multiply with both sides of equation and obtain

By using Holder inequality, Young’s inequality and Poincare inequality, we get

and

and

For the first term on the right side (2.5), by using (G1), (G2) and (G3), we have

where

For the second term on the right side (2.5), by using Holder inequality and Young’s inequality, we get

So, we have

By using Poincare inequality, we obtain

and

and

By using Holder inequality and Young’s inequality, we obtain

Then, we have

That is

Next, we take proper, such that

Taking, then

where, by using Gronwall inequality, we obtain

From, according to Embedding Theorem then, let, so we have

Then

So, there exists and, such that

Lemma 2. Assume (G1), (G2) and (G3) hold, let

and, , , then the solution of Equation (1.3) satisfies and

Here, thus there exists and, such that

Proof. We multiply with both sides of equation and obtain

By using Holder inequality, Young’s inequality and Poincare inequality, we get

and

and

For the first term on the right side (2.23), by using (G1), (G2) and (G3), we have

where

For the second term on the right side (2.23), by using Holder inequality and Young’s inequality, we get

so, we have

By using Poincare inequality, we have

and

And using Interpolation Theorem, we have

By using Holder inequality and Young’s inequality, we have

Then, we have

That is

Next, we take proper, such that

Taking, then

where, by Gronwall inequality, we have

From, according to Embedding Theorem, then, let, so, we have

then

So, there exists and, such that

Theorem 1. Assume (G1), (G2) and (G3) hold, let

and, , , so Equation (1.3) exists a unique smooth solution

Proof. By the method of Galerkin and Lemma 1 and Lemma 2, we can easily obtain the existence of solutions. Next, we prove the uniqueness of solutions in detail.

Assume that are two solutions of equation, let, then, the two equations subtract and obtain

where

By multiplying the equation by and integrating over, we get

here

and

by using (G1), (G2) and (G3), we have

By using Poincare inequality, we have

and

By using Holder inequality, Young’s inequality and Poincare inequality, we have

then, we have

That is

Taking, then

By using Gronwall inequality, we have

So we get, the uniqueness is proved.

Theorem 2. Let X be a Banach space, and are the semigroup operator on X., , , here I is a unit operator. Set satisfy the follow conditions.

1) is bounded, namely, , it exists a constant, so that

2) It exists a bounded absorbing set, namely, , it exists a constant, so that

3) When, is a completely continuous operator A.

Therefore, the semigroup operators exist a compact global attractor.

Theorem 3. Under the assume of Theorem 1, equations have global attractor

where, is the bounded absorbing set of

and satisfies

1),;

2), here and it is a bounded set,

Proof. Under the conditions of Theorem 1, it exists the solution semigroup, here,.

1) From Lemma 1 to Lemma 2, we can get that is a bounded set that includes in

the ball,

This shows that is uniformly bounded in.

2) Furthermore, for any, when, we have

So, we get is the bounded absorbing set.

3) Since is tightly embedded, which means that the bounded set in is the tight set in, so the semigroup operator is completely continuous.

So, the semigroup operators exist a compact global attractor A. The proof is completed.

The authors express their sincere thanks to the anonymous reviewer for his/her careful reading of the paper, giving valuable comments and suggestions. These contributions greatly improved the paper.

This work is supported by the National Natural Sciences Foundation of People’s Republic of China under Grant 11161057.