Abstract
In aircraft engineering, an increase of internal pressure in a hydraulic pipe increases the probability of pipe damage, leading to crack propagation becoming a serious issue. In this study, the extended finite element method (XFEM) is applied to simulate initial crack propagation in hydraulic pipes and to investigate the influence factors. Stress intensity factors are extracted to verify the mesh independence of XFEM, which is based on the level set method and unit decomposition method. A total of 30 finite element models of hydraulic pipes with cracks are established. The distribution of von Mises stress under different initial crack lengths and internal pressures is obtained to analyze the change of load-carrying capacity in different conditions. Then, a total of 300 finite element models of hydraulic pipes with different initial crack sizes and locations are simulated under different working conditions. The relationship between the maximum opening displacement and crack length is analyzed by extracting the opening displacement under different initial crack lengths. The length and depth of the initial crack are changed to analyze the factors affecting crack propagation. The opening size and crack propagation length are obtained in different directions. The results show that radial propagation is more destructive than longitudinal propagation for hydraulic pipes in the initial stage of crack propagation.
Highlights
There are many industrial structures that are normally regarded as shells, such as reactor pressure vessels, natural gas pipelines, and aircraft hydraulic pipes
Results have shown that damage initiation and resistance ability against crack propagation are significant factors of XFEM that greatly affect the crack behavior and load-carrying capacity of hydraulic pipes
The advantages of the XFEM are obvious compared with the conventional finite element method in solving the crack propagation problem
Summary
There are many industrial structures that are normally regarded as shells, such as reactor pressure vessels, natural gas pipelines, and aircraft hydraulic pipes. In order to solve the above problems, a minimal re-meshing finite element method for crack growth was proposed by Belytschko and Black [9]. XFEM has a great advantage in simulating crack propagation and does not need to keep re-meshing At present, this method has been widely used to simulate crack propagation in an arbitrary path, in which a valid idea to update the value of the level set method and a developed penalty function is proposed. Results have shown that damage initiation and resistance ability against crack propagation are significant factors of XFEM that greatly affect the crack behavior and load-carrying capacity of hydraulic pipes. A method combining the classical global–local finite element method and the partition of unity approach was presented to solve fracture mechanics problems with multiple cracks in the domain [28]. Factors affecting crack propagation along the longitudinal and radial directions will be discussed further
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