Initial Crack Propagation and the Influence Factors of Aircraft Pipe Pressure

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.

Initial structural damage detection approach via FE-based data augmentation and class activation map

“…The damage classification accuracy of the CAM network was calculated using the relative error between the damage classification result and actual damage. The damaged and undamaged subregions were trained to output [0, 1] and [1,0], respectively. Moreover, the CAM image of subregion C S 2 R M3M31 could also be obtained from the CAM network, and it is noted that the CAM image of the subregion was an output from the principal strain of subregion e S 1, 2 2 R (N s 3 n g ) 3 (N s 3 n g ) 3 2 .…”

“…When damage occurs in structures such as aircraft wings and rotorcraft blades, it occurs locally and spreads throughout the entire structure. 1 To prevent the destruction of the entire structure when a small amount of damage occurs in a local area, it is essential to detect and act on damage at an early stage through the real-time monitoring of the entire structure. 2 Techniques for detecting structural damage include modal-based and strain-based detection techniques.…”

Failure Mechanism of Tensile CFRP Composite Plates with Variable Hole Diameter

“…In addition, the study proposes a new method for determining the crack initiation and failure loads of the composite plate under tension, and the results obtained thereby are verified numerically. A review of the literature shows that many studies have used XFEM for isotropic materials [ 41 , 42 , 43 , 44 ]. However, there is a lack of studies describing the failure of real sandwich composites (CFRPs) using the numerical XFEM technique.…”

Numerical and Experimental Study of Crack Propagation in the Tensile Composite Plate with the Open Hole

“…The novelty of the research problem undertaken in this study is that it describes the phenomenon of fracture and the failure of composite structures using a currently popular XFEM. A literature review demonstrates that numerous studies were devoted to the application of XFEM for isotropic materials [50][51][52][53]. However, there is a lack of studies describing the failure of real layered composites (CFRP) using the numerical XFEM technique.…”