鎔接殘留應力이 應力比에 따라 疲勞龜裂傳播에 미치는 影響 = The Effect of Welding Residual Stress in Fatigue Crack Propagation as Each Stress Ratio

다국어 초록 (Multilingual Abstract)

To examine the effects of the welding residual stress on Mode I fatigue crack propagation behavior, 3mm thickness SS41 steel plate was welded by an Auto-matic Submerged Arc Welding.
Initial residual stress and relaxation residual stresses according to each stress ratio were measured.
The fatigue crack propagation behavior from the region of compressive residual stress to region of tensile residual stress was analyzed.
The results predicted by the Forman's equation using the superposition approach of the respective stress intensity factors for the initial residual stress and for the applied stress according to each stress ratio were compared with experimental data.
The validity of the superposition approach was investigated.
The conclusion are summerized as follows:
1. When the component is subjected to a constant amplitude cyclic tensile loading, the welding residual stress is reduced as stress ratio increase.
2. As the fatigue crack is propagation through the compressive residual stress field, it was found that the effects of welding compressive residual stress on fatigue crack growth in weldments, and the stress ratio decreases, become larger and delay the fatigue crack growth rate.
3. For negative values of the effective stress ratio, R? in the welding compressive residual stress field, the prediction of fatigue crack growth rate by the Forman's equation were found to be corresponded to experimental data for stress ratio R?0.3, as the effective stress ratio R? approached zero, when the stress ratio R>0.3 the prediction of the fatigue crack growth rate by Forman's equation were found to be impossible.

목차 (Table of Contents)

• 1. 緖論
• 2. 基礎理論
• 2-1. 殘留應力에 依한 Crack先端에서의 應力擴大係數
• 2-2. 疲勞龜裂傳播와 應力比 影響
• 3. 實驗方法
• 4. 實驗結果 및 考察
• 4-1. 應力比에 따른 熔接殘留應力의 分布
• 4-2. Cycle數에 따른 Crack傳播
• 4-3. 疲勞龜裂成長率과 應力擴大係數幅과의 關係
• 5. 結論