Identification of Crack Tip Positions Based on the Scaled Boundary Finite Element Method and the Grey Wolf Optimization Algorithm
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摘要: 基于比例边界有限元法(SBFEM)和灰狼优化(GWO)算法,提出了一种裂纹尖端识别方法。首先,借助SBFEM解决断裂力学问题特有的优势,快速准确地计算出反演所需的测点位移,并验证了正问题求解的正确性。其次,建立与裂纹尖端位置有关的目标函数,将求解裂纹尖端位置转换为求解目标函数最小值的优化问题。最后,采用GWO算法对目标函数进行了优化,进而搜索裂纹尖端的最佳位置。数值算例结果表明:利用SBFEM的高精度、半解析的优点,在反演过程中采用其求解正问题是非常有效的;GWO算法具有良好的全局收敛性,且相比经典的粒子群算法,能够更快速准确地搜索出裂纹尖端的位置;GWO算法具有较好的抗噪性。Abstract: Based on the scaled boundary finite element method (SBFEM) and the grey wolf optimization algorithm (GWO), an identification method for crack tips was proposed. Firstly, the special advantages of the SBFEM were used to solve the fracture mechanics problem, the displacements of measurement points required in the inversion process were quickly and accurately calculated, and the correctness of the solution to the forward problem was verified in advance. Then, the objective function related to the crack tip position was established, and the identification of the crack tip position was converted to the optimization problem of solving the minimum value of the objective function. Finally, the GWO was used to optimize the objective function, that is, to search for the optimal position of the crack tip. The numerical example results show that, it is very effective to solve forward problems in the inversion process with the high precision and semi-analytical advantages of the SBFEM. The grey wolf optimization algorithm has good global convergence property, and can search for the crack tip position more quickly and accurately compared with the classical particle swarm optimization. The grey wolf optimization algorithm has good noise resistance.
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表 1 中心裂纹应力强度因子
Table 1. The stress intensity factor of the center crack
SBFEM
KI / (MPa·m1/2)analytical solution KI / (MPa·m1/2) relative error
δ / %1.4886 1.4819 0.452 表 2 中心裂纹尖端识别结果
Table 2. Identification results of center crack tips
case crack tip position (x, y) / m objective function value 1 (−0.5001, 0.0096),(0.4999, 0.0086) 2.49×10−13 2 (−0.5000, 0.0119),(0.5007, 0.0273) 2.87×10−12 3 (−0.5013, 0.0419),(0.5008, 0.0131) 6.03×10−12 4 (−0.4997, 0.0245),(0.5003, 0.0473) 1.02×10−11 表 3 GWO和PSO算法识别边缘裂纹尖端位置结果
Table 3. The position of the edge crack tip identified with GWO and PSO algorithm
real position (x, y) / m (x, y)GWO / m (x, y)PSO / m (0, 0) (−1.953×10−12, 3.621×10−12) (−2.877×10−12, 2.886×10−12) 表 4 GWO和PSO算法识别斜裂纹尖端位置
Table 4. The position of the oblique crack tips identified with GWO algorithm and PSO algorithm
real position (x, y) / m (x, y)GWO / m (x, y)PSO / m (−0.5, 0) (−0.499 8, −9.2407×10−3) (−0.499 8, −1.0472×10−3) (0, 0.5) (2.2318×10−4, 0.503 0) (5.1873×10−4, 0.504 2) 表 5 考虑正则化时裂纹尖端识别结果
Table 5. Identification results of the crack tip in view of the regularization scheme
error ε 1% 3% 5% objective function value of GWO result 4.537×10−13 3.153×10−12 4.109×10−11 objective function value of PSO result 6.501×10−10 2.088×10−9 1.030×10−8 crack tip position of GWO result (x,y)GWO /cm (1.904×10−4, −4.229×10−5) (8.294×10−4, 8.427×10−4) (2.501×10−3, 5.543×10−4) crack tip position of PSO result (x,y)PSO /cm (−2.713×10−2, 5.981×10−3) (−6.183×10−2, 1.237×10−2) (8.414×10−2, −1.315×10−2) -
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