纳秒激光毫米级光斑辐照典型金属材料冲量耦合特性

利用纳秒脉冲激光器对典型金属材料在毫米级烧蚀光斑尺寸下的冲量耦合特性进行了实验研究。基于典型扭摆测量系统测量激光烧蚀产生的冲量特性，采用局部最小二乘法平移拟合的方法，对扭摆振动产生的微小位移实验数据进行了预处理，避免了噪声对冲量测量的干扰。设计了一种毫米量级烧蚀光斑尺寸测量方法。在此基础上，实验获得了毫米量级光斑辐照金属靶材Al 5A06、TC₄、30CrMnSiA的冲量，研究结果表明，在相同能量密度的情况下，钛合金TC₄对应的冲量最大，TC₄获得的最大冲量耦合系数大于Al 5A06和30CrMnSiA，其对应的最优能量密度却是三种材料中最小的。为了分析烧蚀羽流对冲量耦合特性的影响，估算了不同能量密度对应的羽流透射率，计算结果表明，当羽流透射率低于0.3时，大量的入射激光能量被羽流吸收，导致冲量耦合系数的下降。

Impulse coupling characteristics of typical metal materials irradiated by nanosecond laser with a millimeter-scale spot size

A nanosecond pulsed laser was used to study the impulse coupling characteristics of typical metal materials with millimeter ablation spot size. The impulse characteristics of laser ablation were studied based on a typical torsion pendulum measuring system. By using the method of translational fitting of the local least square method, the experimental data of small-displacement generated by torsion pendulum vibration were preprocessed, and the interference of noise to impulse measurement was avoided. A measurement method of millimeter scale ablation spot size was designed. On this basis, the impulse of millimeter scale spot irradiating metal target Al 5A06, TC4, 30CrMnSiA was obtained in the experiment. The results showed that the impulse generated by irradiating titanium alloy TC₄ was the largest at the same laser fluence. And the maximum impulse coupling coefficient generated by irradiating TC₄ was greater than that of Al 5A06 and 30CrMnSiA. However, the optimal laser fluence of TC₄ was the smallest among the three materials. In order to analyze the influence of the ablation plume on the impulse coupling characteristics, the plume transmittance at different laser fluences was estimated. The results indicated that a large amount of incident laser energy was absorbed by the ablation plume when the plume transmittance was lower than 0.3, which caused a decrease of the impulse coupling coefficient.