飞秒脉冲激光冲击强化中等离子体压力时空演化规律

为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律，利用考虑电子态密度（DOS）效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律，并与采用QEOS（quotidian equation of state）模型计算结果进行了对比；提出DOS飞秒脉冲激光冲击强化模型，计算得到电子温度、晶格温度、等离子体羽位置时间演化规律和等离子体压力时空演化规律，并与QEOS飞秒脉冲激光冲击强化模型结果进行了对比。结果表明：DOS飞秒脉冲激光冲击强化模型计算得到的等离子体羽位置随时间的演化规律与实验结果吻合程度更好；增加激光能量或功率密度、考虑电子DOS效应会增加电子、晶格温度和等离子体压力。

Plasma pressure over time-space evolution law for femtosecond pulses laser shock peening

The purpose of this research work is to look into the time-space evolution of plasma pressure for femtosecond pulse laser shock peening (fs-LSP). In this study, propose a model to understand plasma pressure over time-space process in fs-LSP based on the first principle, improved two temperature equations, and plasma hydrodynamic equations. Firstly analyze the plasma plume front location with respect to time by solving the plasma hydrodynamic equations. The simulated results by the electron DOS (density of state) femtosecond pulse laser shock peening model are in better agreement with the experiment results than the QEOS (quotidian equation of state) femtosecond pulse laser shock peening model. The DOS femtosecond pulse laser shock peening model was shown to be effective and superior. Then use the DOS model to calculate how the electron heat capacity and electron-phonon coefficient with respect to electron temperature. Electron heat capacity calculated by the QEOS model is larger than calculated by the electron DOS model, whereas the electron-phonon coefficient is the reverse. Moreover, the electron-phonon coefficient calculated by the QEOS model shows linear variation with respect to the electron temperature, which is the reverse of that calculated by the electron DOS model. Therefore, the electron DOS effect should be considered in two-temperature equations. Next see a graph of electron and lattice temperature with respect to time using the modified two-temperature equations to calculate. Increasing laser energy, decreasing pulse width, and considering the electron DOS effect will increase the electron’s peak temperature, and equilibrium temperature of electron and lattice systems, and reduce the electron-phonon relaxation time. Finally, we utilize the results of the two temperature equations as the initial condition to substitute into the plasma hydrodynamic equations to compute the plasma pressure. plasma peak pressure will rise as laser energy is increased, the pulse width is decreased, and the electron DOS effect is taken into account.