激光冲击选区强化对2024铝合金叶片振动响应特性的影响

Effect of Selective Laser Shock Peening on Vibration Response of 2024 Aluminum Alloy Blade

目的探究激光冲击强化技术对2024铝合金叶片振动性能的影响,并探寻最理想的冲击参数。方法运用Johnson-Cook动态塑性本构模型模拟激光冲击选区强化过程,对强化后的2024航空铝合金叶片的振动特性进行分析。将2024铝合金在激光冲击强化过程中产生的残余应力场和梯度密度分布导入模型,量化激光冲击强化对2024铝合金叶片振动特性的提高效果,研究激光冲击参数对叶片振动响应的影响规律。结果激光冲击强化产生的残余压应力场并非均匀分布在表面,而是只存在于冲击区域,冲击区域外为拉应力。其中,最大残余压应力为273.5 MPa。选取第六阶振型为目标振型,在同样冲击工况下,模拟和实验结果吻合较好。在模型中引入激光冲击强化产生的残余应力与梯度密度结构会使2024铝合金叶片的振动特性发生改变,其中,残余应力对振动特性影响更为显著。结论激光冲击强化工艺调控分析表明,采用较大圆形光斑,施加较大功率密度冲击模型中部,可获得最显著的振动特性改善效果。最适合的激光冲击强化参数可将振动特征频率降低118.87 Hz,将振幅降低94.37%。

This work aims to investigate the influence of laser shock peening on the vibration performance of the 2024 aluminum alloy blade and to find the optimal shock parameters.The Johnson-Cook model was used to simulate the selective laser shock peening process.The residual stress field and gradient density generated in the laser shock peening process of 2024 aluminum alloy were imported into the finite element simulation to analyze the vibration response.The effect of laser shock peening on the vibration characteristics was quantified,and the influence of laser shock parameters on the vibration response was studied.The residual compressive stress field generated by laser shock peening is distributed in a nonuniform way on the surface that it only exists in the impact area,while the residual tensile stress exists in the regions out of the impact area.The maximum residual compressive stress is 273.5 MPa.Selecting the sixth vibration mode as the target mode,the finite element simulation matches the vibration test well at the same laser shock peening condition.The contribution of the residual stress is larger than gradient mass density on the change of the frequency and amplitude of the sixth vibration mode.By manipulating the laser shock peening parameters,the most significant improvement of vibration characteristics can be obtained when a larger circular laser spot with larger peak pressure is applied in the middle of the model;the most appropriate laser shock peening parameters can reduce the frequency of vibration by 118.87 Hz,the amplitude can be reduced by 94.37%.