切向气流对激光加热金属板非熔化穿孔效应的影响

针对切向气流加载导致激光加热金属板在熔化前的穿孔效应,利用金属薄板的弹性弯曲理论,推导出了两种典型光束（方形和圆形）照射下的弯曲挠度表达式,利用Mises理论给出了非熔化穿孔的破坏判据。研究结果表明：激光加热下材料强度降低是出现非熔化穿孔破坏的主要机理;薄板在光斑区的最大变形与气流速度、光斑直径、板厚与弹性模量（U2a4/Eh3）相关,穿孔破坏温度与气流速度、光斑直径及板厚（Ua/h）2相关;与方形光斑辐照相比,圆形光斑辐照的破坏阈值稍高一些。数值计算结果表明：0.8 Ma切向气流作用下,铝合金壳体的激光破坏能量阈值大大降低（可达40%～50%）,典型不锈钢壳体的破坏阈值降低相对较小（20%左右）,气流作用导致金属板破坏阈值的下降是需特别关注的问题。

Influence of tangential airflows on burn-through effect with no-melting of metal heated by laser

On the basis of elastic bending theory, the bending deflection expression by both quadrate and cir- cinal facula irradiations is deduced for burn-through effect with no-melting of metal heated by a laser caused by tangential airflows. A rupture criterion for burn-through with no-melting is given out by the Mises theory. The study indicates that the material softened by laser heating is the primary mechanism for burn-through effect with no-melting. The maximal deflection of thin plate in the spot area is related to the airflow speed, spot di- ameter, plate thickness and the elasticity modulus（ expression is U2a4/Eh3）, the damage temperature is relat- ed to the airflow speed, spot diameter and the plate thickness （expression is （Ua/h）2）, and the damage threshold under the circinal facula irradiated is higher than that under the quadrate facula. The numerical re- suh indicates that for aluminum alloy shell, the damage threshold of laser energy can decrease much up to 40% - 50% under 0. 8 Ma tangential airflows, but it can decrease less （ about 20% ） for a stainless steel shell. The damage threshold decrease under airflows needs more attention.