Research of Numerical Algorithms for Structure's Fatigue Assessment in Random Waves Based on Fracture Mechanics

Abstract

Abstract:

Paris law gives a simple formula for offshore structure's fatigue assessment with fracture mechanics method. However, the input "stress" data are complex, because the offshore structure's response under random waves is complex. For structures exposed under long-term waves, it is important to find a numerical algorithm which is efficient, accurate and safe for calculating fatigue life. Structure's response stress is a random variable, so its equivalent constant value can be investigated for efficiency,and its loading sequence under long-term waves should be investigated for conservation.

Key words: random waves, fracture mechanics, fatigue, numerical algorithm

CLC Number:

TU973+.254

Yan-kun YIN, Shi CHEN, Ting-qian LI. Research of Numerical Algorithms for Structure's Fatigue Assessment in Random Waves Based on Fracture Mechanics[J]. Ocean Engineering Equipment and Technology, 2014, 1(3): 213-217.

Figures/Tables 12

Fig.1

Fig.2

Fig.3

Table 1

Table 2

Fig.4

Table 3

Table 4

Table 5

Table 6

Table 7

Fig.5

有效波高	跨零周期	持续时长	波浪谱
H_s/m	T_z/s	T/s
3.0	7.0	43 200	PM谱

裂纹初始尺寸	应力强度因子幅阈值	应力强度因子修正系数	裂纹扩展率常数
a/mm	Δk₀ /(MPa·m^1/2)	Y	A	m
2.0	63.0	2.0	1.32×10^-11	2.67

应力阈值	有效周期	有效应力	有效循环次数	裂纹扩展
σ₀/MPa	T_e/s	/MPa	N_e	Δa/mm
12.57	5	26.9	6 438	0.005 41

有效波高H_s /m	跨零周期T_z/s						总和
有效波高H_s /m	<2	2~3	3~4	4~6	6~10	>10	总和
0	0.139	0.269	0.104	0.003	-	-	0.515
0.0~0.5	1.844	26.065	17.719	5.802	0.090	-	51.52
0.5~1.0	1.172	8.545	15.523	7.394	0.347	-	32.981
1.0~1.5	0.486	2.170	3.134	4.245	0.208	-	10.243
1.5~2.0	0.075	0.871	0.744	1.499	0.211	-	3.400
2.0~2.5	0.006	0.165	0.148	0.521	0.194	-	1.034
2.5~3.0	-	0.006	0.029	0.096	0.096	-	0.227
3.0~3.5	-	-	0.012	0.017	0.029	-	0.058
3.5~4.0	-	-	-	0.003	0.003	-	0.006
4.0~4.5	-	-	-	0.003	0.003	-	0.006
>4.5	-	-	-	0.003	-	-	0.003
总和	3.722	38.091	37.413	19.586	1.181	-	100

组号	1	2	3	4	5	6
H_s/m	4	4	4	1	1	1
T_z/s	7	7	7	3	3	3
T/s	43200	43200	43200	43200	43200	43200