Effect of Loading Angle on Crack Propagation in 6005A-T6 Aluminum Alloy Under Different Degradation Levels
-
摘要:
为研究加载角度对6005A-T6铝合金在不同疲劳退化水平下的裂纹扩展寿命与损伤机理的影响，本文设计并开展了系统的疲劳裂纹扩展试验. 研究采用紧凑型拉伸剪切试样，在4种退化水平和4种加载角度条件下进行对比试验，并利用七点增量多项式法对裂纹扩展速率进行计算与评估. 首先，在无退化和不同程度预疲劳条件下获取裂纹扩展曲线；其次，在不同加载角度条件下对比剩余寿命的变化规律；最后，结合DIC（数字图像相关）技术分析裂纹尖端局部应变分布，并通过断口形貌观察揭示裂纹扩展机制. 研究结果表明：加载角度对裂纹扩展行为具有显著影响，随着加载角度增大，裂纹扩展速率明显降低，剩余寿命得到显著延长；在无退化条件下，寿命提升幅度可达186%，而在1.5 × 105周次退化条件下，寿命提升幅度下降至约140%，说明加载角度对寿命延长的作用随退化加深逐渐减弱；DIC结果显示，加载角度增加使裂纹尖端局部应变逐步减小，裂纹对主加载方向的敏感性降低，表现出更强的扩展迟滞效应；在断口形貌方面，随加载角度增大，断口粗糙度增强，解理台阶和撕裂棱由细密逐渐转为粗大，裂纹扩展路径更复杂，揭示了加载角度对裂纹失效模式的主导作用.
-
关键词:
- 6005A-T6铝合金 /
- 裂纹扩展 /
- 加载角度 /
- 疲劳退化 /
- 疲劳寿命
Abstract:To investigate the effects of loading angle on the crack propagation life and damage mechanisms of 6005A-T6 aluminum alloy under different fatigue degradation levels, a systematic fatigue crack propagation test was designed and conducted. The compact tension shear specimens were employed, and the comparative tests were performed under four degradation levels and four loading angles. The crack propagation rate was calculated and evaluated by using the seven-point incremental polynomial method. First, crack propagation curves were obtained under non-degraded and different degrees of pre-fatigue conditions. Second, the variation law of residual life at different loading angles was compared. Finally, the local strain distribution at the crack tip was analyzed by using digital image correlation (DIC) technology, and fracture morphology was observed to reveal the crack propagation mechanisms. The results show that the loading angle significantly affects the crack propagation behavior. As the loading angle increases, the crack propagation rate decreases significantly, and the residual life is greatly extended. Under the non-degraded condition, the degree of life extension can reach up to 186%. Under the 1.5 × 105 cycles of degradation, the degree of life extension drops to approximately 140%, indicating that the effect of loading angle on life extension diminishes as degradation deepens. DIC results show that increasing the loading angle reduces the local strain at the crack tip, decreases the sensitivity of the crack to the main loading direction, and exhibits a stronger propagation hysteresis effect. In terms of fracture morphology, as the loading angle increases, the fracture roughness increases, and the cleavage steps and tear ridges gradually become coarser, with the crack propagation path becoming more complex, revealing the dominant role of loading angle in the crack failure mode.
-
Key words:
- 6005A-T6 aluminum alloy /
- crack propagation /
- loading angle /
- fatigue degradation /
- fatigue life
-
图 6 不同疲劳退化水平时加载角度影响的a-N曲线
Figure 6. a–N curves illustrating effect of loading angle under different fatigue degradation levels
图 7 不同疲劳退化程度下加载角度对剩余寿命提高水平的影响
Figure 7. Effect of loading angle on improvement levels of residual life under different fatigue degradation levels
图 8 不同加载角度时试样表面应变响应
Figure 8. Surface strain response of specimen at different loading angles
图 9 不同疲劳退化水平时加载角度影响的da/dN-ΔKeq曲线
Figure 9. da/dN-ΔKeq curves illustrating effect of loading angle under different fatigue degradation levels
表 1 6005A-T6铝合金的合金成分（质量分数，%）
Table 1. Composition of 6005A-T6 aluminum alloy （mass fraction, %）
成分 Si Fe Cu Mn Mg Cr Zn Ti Al 质量分数 0.75 0.35 0.30 0.50 0.60 0.30 0.15 0.10 余量 
下载: 导出CSV
表 2 6005A-T6铝合金机械性能
Table 2. Mechanical properties of 6005A-T6 aluminum alloy
性能参数 弹性模量
E/GPa屈服强度
σy /MPa抗拉强度
σu /MPa伸长率
δ /%断面收缩率
Ψ /%泊松比$ \upsilon $ 值 69 222 270 12 34 0.33
下载: 导出CSV
表 3 6005A-T6铝合金Ⅰ + Ⅱ复合型疲劳裂纹扩展试验结果
Table 3. Test results of Ⅰ + Ⅱ mixed fatigue crack propagation in 6005A-T6 aluminum alloy
试样编号 退化水平/
（× 105周次）加载角度/
（°）剩余寿命/
周次BM1 0 0 72255 BM5 0 30 93087 BM9 0 45 123265 BM13 0 60 207018 BM2 0.5 0 62398 BM6 0.5 30 75652 BM10 0.5 45 92852 BM14 0.5 60 155662 BM3 1.0 0 57214 BM7 1.0 30 65124 BM11 1.0 45 81785 BM15 1.0 60 146562 BM4 1.5 0 52120 BM8 1.5 30 59964 BM12 1.5 45 76352 BM16 1.5 60 124985
下载: 导出CSV
-
[1] 吕可, 杨冰, 王栓程, 等. 6005铝合金激光-MIG复合焊接接头裂纹扩展行为[J]. 焊接学报, 2025, 46(4): 82-93.Lyu Ke, Yang Bing, Wang Shuancheng, et al. Crack propagation behavior of laser-MIG hybrid welded joints in 6005 aluminum alloy[J]. Transactions of the China Welding Institution, 2025, 46(4): 82-93. [2] Duan C H, Hao X J, Luo X P, et al. Microstructure and fatigue properties of laser-MIG hybrid welding of medium-thickness 6005A aluminum alloy[J]. Engineering Failure Analysis, 2024, 165: 108753. doi: 10.1016/j.engfailanal.2024.108753 [3] Jiang G Q, Zhou J Z, Huang S, et al. Microstructure response and bending fatigue characteristics of typical positions for the integral stiffened structure of 6005A-T6 aluminum alloy after laser peen forming[J]. Journal of Materials Research and Technology, 2024, 33: 1623-1639. doi: 10.1016/j.jmrt.2024.09.180 [4] Wu L J, Yang B, Han X H, et al. Improving liquation cracks and mechanical properties of 6005A aluminum alloy MIG welded joints via a hybrid milling-friction stir processing tool[J]. The International Journal of Advanced Manufacturing Technology, 2023, 127(1/2): 419-429. doi: 10.1007/s00170-023-11539-2 [5] Wu L J, Han X H, Ma G L, et al. Effects of welding layer arrangement on microstructure and mechanical properties of gas metal arc welded 5083/6005A aluminium alloy butt joints[J]. Transactions of Nonferrous Metals Society of China, 2023, 33(6): 1665-1676. doi: 10.1016/S1003-6326(23)66212-0 [6] 袁周致远, 吉伯海, 傅慧, 等. 疲劳裂纹气动冲击的维修机理及效果[J]. 西南交通大学学报, 2024, 59(2): 307-314.Yuan Zhouzhiyuan, Ji Bohai, Fu Hui, et al. Fatigue crack repair mechanism and effect by pneumatic impact treatment[J]. Journal of Southwest Jiaotong University, 2024, 59(2): 307-314. [7] 董丙杰, 陈光雄, 冯晓航, 等. 钢轨波磨激励下的e型弹条振动疲劳断裂机理[J]. 西南交通大学学报, 2025, 60(5): 1287-1295.Dong Bingjie, Chen Guangxiong, Feng Xiaohang, et al. Vibration fatigue fracture mechanism of e-type clip under rail corrugation excitation[J]. Journal of Southwest Jiaotong University, 2025, 60(5): 1287-1295. [8] 张继旺, 张浩楠, 杨冰, 等. 超声滚压EA4T车轴钢疲劳性能及寿命预测[J]. 西南交通大学学报, 2024, 59(6): 1305-1313.Zhang Jiwang, Zhang Haonan, Yang Bing, et al. Fatigue properties and life prediction of ultrasonic rolling EA4T axle steel[J]. Journal of Southwest Jiaotong University, 2024, 59(6): 1305-1313. [9] Calvín G, Escalero M, Zabala H, et al. A new effective stress intensity factor approach to determine thickness-independent fatigue crack growth rate curves[J]. Theoretical and Applied Fracture Mechanics, 2022, 121: 103505. doi: 10.1016/j.tafmec.2022.103505 [10] Mahtabi M, Roshan M, Shakil S I, et al. Crack initiation, small crack growth, and stress intensity factor in the very high cycle fatigue (VHCF) of wire arc additive manufactured (WAAM) nickel aluminum bronze (NAB)[J]. Engineering Fracture Mechanics, 2025, 313: 110671. doi: 10.1016/j.engfracmech.2024.110671 [11] Yang B, Zhang Z, Deng H, et al. Fatigue strength prediction and degradation behavior analysis of 6005A-T6 aluminum alloy considering fatigue aging effects[J]. Fatigue & Fracture of Engineering Materials & Structures, 2025, 48(6): 2669-2685. doi: 10.1111/ffe.14632 [12] Wang X R, Zhu T, Lu L T, et al. A damage sequence interaction model for predicting the mechanical property of in-service aluminium alloy 6005A-T6[J]. Engineering Fracture Mechanics, 2023, 291: 109565. doi: 10.1016/j.engfracmech.2023.109565 [13] Wang X R, Zhu T, Lu L T, et al. Rate-dependent damage sequence interaction model for predicting the mechanical property of in-service aluminum alloy 6005A-T6[J]. Mechanics of Materials, 2024, 191: 104959. doi: 10.1016/j.mechmat.2024.104959 [14] Yu Y F, Wang L Y, Wu J P, et al. An enhanced nonlinear fatigue cumulative damage model based on toughness exhaustion and strength degradation[J]. International Journal of Fatigue, 2025, 198: 109025. doi: 10.1016/j.ijfatigue.2025.109025 [15] Liu H B, Yang S L, Xie C J, et al. Mechanisms of fatigue crack initiation and propagation in 6005A CMT welded joint[J]. Journal of Alloys and Compounds, 2018, 741: 188-196. doi: 10.1016/j.jallcom.2017.12.374 [16] 耿庆涛, 杨丽, 曲凤娇, 等. 不同应力比对6005A铝合金裂纹扩展速率的影响研究[J]. 轨道交通材料, 2025, 4(2): 51-54.Geng Qingtao, Yang Li, Qu Fengjiao, et al. Influence of different stress ratios on the crack propagation rate of 6005A aluminum alloy[J]. Materials for Rail Transportation System, 2025, 4(2): 51-54. [17] Zhang X S, Ma Y E, Yang M, et al. Effects of biaxial residual stress components on mixed-mode fatigue crack propagation behavior in friction stir welded 7075-T6 aluminium alloy panel[J]. Theoretical and Applied Fracture Mechanics, 2022, 121: 103437. doi: 10.1016/j.tafmec.2022.103437 [18] Yu X B, Li L, Proust G. Fatigue crack growth of aluminium alloy 7075-T651 under proportional and non-proportional mixed mode I and Ⅱ loads[J]. Engineering Fracture Mechanics, 2017, 174: 155-167. [19] 刘源艺, 龚浩, 陈特, 等. 6061铝合金各向异性疲劳裂纹扩展研究[J]. 力学季刊, 2024, 45(4): 911-919.Liu Yuanyi, Gong Hao, Chen Te, et al. Investigation of the anisotropic fatigue crack propagation of 6061 aluminum alloy[J]. Chinese Quarterly of Mechanics, 2024, 45(4): 911-919. [20] 雷付煜, 徐小旭, 赵亚明, 等. 加载角度对6082铝合金自冲铆接接头疲劳性能及失效模式的影响[J]. 中国机械工程, 2025, 36(1): 141-151.Lei Fuyu, Xu Xiaoxu, Zhao Yaming, et al. Influences of loading angle on fatigue characteristics and failure modes of self-piercing riveted joints in aluminum alloy 6082[J]. China Mechanical Engineering, 2025, 36(1): 141-151. [21] Richard H A, Fulland M, Sander M. Theoretical crack path prediction[J]. Fatigue & Fracture of Engineering Materials & Structures, 2005, 28(1/2): 3-12. [22] Zhang Z, Yang B, Feng F, et al. Multiaxial fatigue model describing crack growth behavior and its application in welded structures of railway frames[J]. International Journal of Fatigue, 2025, 194: 108831. [23] Zhang Z, Yang B, Wang S C, et al. Mixed mode (I/Ⅱ) fatigue crack growth in butt-welded joints using actual stress intensity factors[J]. Theoretical and Applied Fracture Mechanics, 2025, 138: 104894. [24] Sajith S, Shukla S S, Murthy K S R K, et al. Mixed mode fatigue crack growth studies in AISI 316 stainless steel[J]. European Journal of Mechanics - A/Solids, 2020, 80: 103898. [25] Zhang Z, Yang B, Zhou S Q, et al. Investigation on fatigue crack growth behavior and remaining useful life prediction of 6005A-T6 aluminum alloy under fatigue aging[J]. International Journal of Fatigue, 2026, 206: 109448. [26] Jin P F, Liu Z, Chen H R, et al. Mixed-mode I&Ⅱ fatigue crack growth behaviors of 16MND5 steel: The role of crack driving forces and crack closure[J]. International Journal of Fatigue, 2024, 183: 108228. [27] Kim J S, Kim D J, Hong S P. Effect of Mode Ⅱ in the mixed-mode on the fatigue crack growth behaviour for SAPH440 material[J]. International Journal of Fatigue, 2024, 187: 108470. -
下载:
点击查看大图
计量
- 文章访问数: 1
- HTML全文浏览量: 0
- PDF下载量: 0
- 被引次数: 0