讨论了热应力在短脉冲激光清洗油漆过程中的作用,从一维热传导方程出发,计算了由热膨胀产生的热应力以及根据粘附力公式计算出了油漆的粘附力。通过比较热应力与粘附力大小,得到激光清洗油漆的条件,进而建立一维短脉冲激光除漆模型。根据此模型可计算出：波长为1064 nm,脉宽为10 ns的激光清除铁基底上厚度为40 μm橙色漆的清洗阈值为0.5 J/cm2;不同能量密度下使得油漆脱落所需的激光作用时间;激光脉冲作用过程中铁基底的温度变化情况。实验所测得的清洗阈值为0.57 J/cm2,与理论结果接近。实验与理论都表明当能量密度过高时,铁基底的温度升高很大,超过其熔点,铁基底被损坏。并考虑了激光清洗铝基底上油漆的情况。

The thermal stress model was put forward in the paint removal from substrate by Q-switched laser pulses. With the one-dimensional equation of heat conduction, the thermal stress generated by thermal expansion was calculated. The adhesion force between the paint and the substrate was calculated according to adhesion formula. If the thermal stress is greater than the adhesion force, the paint will be removed from the substrate by the laser action. When the Nd∶YAG laser with wavelength of 1064 nm and pulse width of 10 ns is used to remove orange paint from Fe substrate, the cleaning threshold is 0.5 J/cm2 and the irradiation time required for paint removal and the temperature change of Fe substrate were calculated according to the theoretical model. The experimental cleaning threshold is 0.57 J/cm2, which is in accordance with the theoretical result. From the experiments and theoretical model it is found that if the laser fluence is too high, the temperature of Fe substrate will exceed the melting point of Fe and the Fe substrate will be broken. And the paint removal on Al substrate by laser was taken into account.