基于小裂纹理论的航空材料疲劳全寿命预测

 综述了基于小裂纹理论的疲劳全寿命预测方法。该方法把断裂力学的ΔK分析与裂纹闭合概念结合起来,应用于自然萌生的小裂纹和长裂纹的扩展,并全部基于对起源于材料初始缺陷的裂纹扩展分析预测疲劳全寿命。这一方法已被作者成功地应用于多种航空材料,包括:4种高强度铝合金、2种高强钢和2种钛合金,载荷类型涉及恒幅、Mini-Twist和直升机旋翼谱等。结果表明,预测的疲劳全寿命与实验结果吻合良好,从而为把基于断裂力学裂纹扩展的损伤容限方法向传统的疲劳领域(S-N曲线,安全寿命)延伸开辟了可行的途径。

Total Fatigue Life Prediction for Aeronautical Materials by Using Small-Crack Theory

The paper presents a review of a fatigue life prediction method by using the small-crack theory. The approach is to apply continuum mechanics, the fracture-mechanics-based ΔK analyses, and the crack-closure concept to naturally occurring small cracks and large crack growth, and to make total-fatigue-life predictions solely based on crack growth from the assumed initial materials defects. The methodology has been successfully verified by experiments for a wide variety of aeronautical materials including two high-strength steels: 9310 and 30CrMnSiNi2A, four high-strength aluminum alloys: 7075-T6, 7075-T73 (forged), LC9cs and LY12, and two titanium alloys: Ti-6Al-4V and TC11, and the load types include constant amplitude, Mini-Twist and a helicopter rotor spectrum. Results show that the predicted total fatigue lives are in good agreement with the experimental data. Thus, the feasibility for the establishment of a link between the classical S-N fatigue (safe-life) and the modern damage-tolerance methodologies is demonstrated.