| 引用本文: | 金丹,刘壮,郭超越,李卓群,孙梦莹.激光冲击强化对FV520B钢疲劳寿命的影响[J].中国表面工程,2024,37(1):280~286 |
| JIN Dan,LIU Zhuang,GUO Chaoyue,LI Zhuoqun,SUN Mengying.Effect of Laser Shock Peening on Fatigue Life for FV520B Steel[J].China Surface Engineering,2024,37(1):280~286 |
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| 摘要: |
| 为提高叶轮的使用寿命，对叶片的抗疲劳性能提出了更高的要求，激光冲击强化（LSP）处理是提高材料抗疲劳性能的重要途径。针对 FV520B 钢棒状试样进行 LSP 试验和不同应变幅值下的单轴低周疲劳试验，并进行疲劳寿命预测。结果表明，LSP 后试样的表面硬度由 330 HV 提升至 490 HV，且 LSP 后试样表面产生约?90 MPa 的残余压应力。相比于未冲击试样， LSP 试样的疲劳寿命均有所提高，±0.5%应变幅值下试样的疲劳寿命提高 132.2%。SEM 结果表明，LSP 后试样表面产生的残余压应力抑制了疲劳裂纹的萌生和扩展，裂纹萌生位置由试样表面向次表面转移，且疲劳条纹的间距和韧窝尺寸减小，从而延长了试样的疲劳寿命。采用 Manson-Coffin 方程针对光滑试样和 LSP 试样进行疲劳寿命预测，总的来说，对于光滑试样预测结果与试验结果吻合较好；对于 LSP 试样，预测的疲劳寿命偏保守。考虑残余压应力的影响针对 Manson-Coffin 方程进行修正，得到了较好的预测结果。研究结果可为 FV520B 材料 LSP 处理工艺和疲劳失效研究提供理论依据。 |
| 关键词: 激光冲击强化 低周疲劳 残余应力 疲劳断口 疲劳寿命预测 |
| DOI：10.11933/j.issn.1007-9289.20230116001 |
| 分类号:TG156；TB114 |
| 基金项目:国家自然科学基金（11102119）；辽宁省教育厅项目（LJKZ0437） |
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| Effect of Laser Shock Peening on Fatigue Life for FV520B Steel |
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JIN Dan, LIU Zhuang, GUO Chaoyue, LI Zhuoqun, SUN Mengying
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School of Mechanical and Power Engineering, Shenyang University of Chemical Technology,Shenyang 110142 , China
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| Abstract: |
| FV520B steel is primarily used in the manufacturing of blades for various centrifugal compressors because of its high strength, good fatigue resistance, corrosion resistance, good toughness and plasticity, and excellent welding characteristics. The service life of impellers can be increased by improving the anti-fatigue performance. Several methods have been proposed to enhance the anti-fatigue performance of materials. Laser shock peening (LSP) is an important strengthening technology that can effectively improve the fatigue, wear, and corrosion resistance of metallic materials compared to the traditional surface treatment methods. To evaluate the effectiveness of LSP, experiments were conducted on FV520B steel-bar specimens by choosing the appropriate shock energy, laser wavelength, pulse width, circular spot diameter, shock frequency, laser power density, and spot overlap ratio. Surface hardness was measured using a digital microhardness tester (HVS-1000AT) before and after LSP. The results showed that LSP increased the surface hardness of the specimens from approximately 330 HV to 490 HV; the depth of hardening was 0.25 mm. The residual stresses of the LSP specimens were measured using a Proto-LXRD high-power residual stress tester—a residual compressive stress of approximately 90 MPa was generated on the surface of the specimens. The low cycle fatigue experiments for FV520B specimens with and without LSP were conducted for different strain amplitudes ±0.5%, ±0.6%, ±0.7%, ±0.8%, and ±1.0%, respectively. The fatigue life decreased with the increasing strain amplitude for all specimens with and without LSP. The fatigue life of all specimens improved after LSP for the five strain amplitudes. For the strain amplitudes between ±0.6% to ±1.0%, it was observed that the higher the strain amplitude, the more significant the improvement in fatigue life of specimens. The strain amplitude of ±0.5% showed the most significant improvement of 132.2%. Scanning electron microscopy (SEM) experiments for fatigue fractures on smooth and LSP specimens showed that all the fractures presented three typical regions—the crack source region, crack propagation region, and transient fracture region. Moreover, an obvious fatigue strip in the crack growth region and a secondary crack perpendicular to the direction of crack propagation were observed for the smooth specimen. On the contrary, for the LSP specimen, the fatigue source became fuzzy, and the residual compressive stress generated on the surface after LSP inhibited fatigue crack initiation and propagation. This caused the location of crack initiation to transfer from the surface to the subsurface, and the fatigue strip spacing and dimple size were reduced, which improved the fatigue life of the specimens. Further, the fatigue lives of the smooth and LSP specimens were predicted using the Manson–Coffin equation. Overall, the prediction results for the smooth specimens agreed well with the experimental results. For the LSP specimens, the predicted fatigue life was the same as that predicted for the smooth specimens, and the prediction results were conservative. Furthermore, considering the effect of residual compressive stress on the inhibition of fatigue crack initiation and propagation, a new fatigue life prediction method that can be used to predict the fatigue life with residual compressive stress is proposed by modifying the Manson–Coffin equation. The predictions for the LSP specimens using this method were in good agreement with the experimental results. The comparative analysis of the fatigue life between smooth and LSP specimens for different strain amplitudes in this study can be used to select the appropriate process parameters of LSP for FV520B materials. This fatigue prediction method provides a new concept for determining the fatigue life of materials with residual stress. |
| Key words: laser shock peening low cycle fatigue residual stress fatigue fracture fatigue life prediction |
