Numerical Simulation Of The Polyethylene-aluminium Composite Pipe's Testing Process

The polyethylene-aluminium composite pipe is a kind of new pipe combining the advantages of metal and plastic. It consists of five-layer materials. The inner and outer plastic uncovered outside can prevent the pipe from erosion and well protect the mid-layer of aluminum as well. And the mid-layer of aluminum can contribute to the pipe' s capability of bearing the weight. Due to the advantages of anti-erosion and little weight, the new pipe is widely used in industry in our country.The polyethylene-aluminium composite pipe can be classified into two types according to the welding method used in the mid-layer of aluminum. The two types are respectively overlapped polyethylene-aluminium composite pipe and adjoining polyethylene-aluminium composite pipe. Due to the uneven structure of the pipe, during testing the pipe's capability by pushing the water pressure, the pipe always is destroyed near the overlapped joint. In order to explain the destruct mechanism and learn about the factors affecting the mechanical capability, the ANSYS software is used in this paper to simulate the type of 1216 pipe's testing process under the various geometrical structure parameters(mainly the thickness of the inner and outer layers and the length of the overlapped joint).The results demonstrates that firstly, the mid-layer of aluminium bears the weight and the destruct of the aluminium can directly result in the destruct of the whole pipe. The destruct mechanism is intensified stress near the overlapped joint which can result in the destruct of the pipe. Secondly, the intensified stress can result in the intensified strain of the inner and outer layers near the area of the intensified stress. The intensified strain plays an important role in the destruct of the pipe. Thirdly, the thickness of the various layers is the most important factor affecting the pipe's mechanical capability. The increase of the inner layer's thickness, on one hand can decrease the intensified stress of the mid-layer and on the other hand it can increase the strain of the inner layer and make the strain of the inner layer more complex. Therefore, it is necessary to conduct optimum design of the polyethylene-aluminium composite pipe to balance the effect of the inner and outer thickness. Finally the proper increase of the overlapped joint's length can decrease the stress intension as well as the strain of outer and inner layers.