激光特性对金属基底激光熔化内部流动行为的影响
The influence of laser characteristics on internal flow behaviour in laser melting of metallic substrates
AI总结：
本研究采用考虑激光特性、入射角、表面温度和材料成分的增强吸收模型，预测不锈钢316L激光熔化的内部热流与流体流动，揭示了吸收率对内部流动物理机制的关键影响及不同激光源下熔池形状差异。
摘要：
材料的吸收率是激光焊接和增材制造数值模拟中的一个主要不确定性因素，其值通常通过试错法进行校准。这会对数值模拟预测加工过程行为的能力产生不利影响，并最终阻碍完全数字化制造工艺的实现，而这是“工业4.0”的目标。在本研究中，采用了一种考虑激光特性、入射角、表面温度和材料成分影响的增强吸收模型，用于预测不锈钢316L激光熔化过程中的内部热流和流体流动。采用这种吸收模型在物理上比假设恒定吸收率更真实，并且可以降低与校准合适值相关的成本。使用可变和恒定吸收率模型进行了高保真三维数值模拟，并将预测结果与实验数据进行了比较。本研究的结果揭示了吸收率对激光材料加工中内部流动物理机制的关键影响。解释了使用光纤和CO$_2$激光源获得的熔池形状之间的差异，并讨论了影响局部能量吸收的因素。
英文摘要：
The absorptivity of a material is a major uncertainty in numerical simulations of laser welding and additive manufacturing, and its value is often calibrated through trial-and-error exercises. This adversely affects the capability of numerical simulations when predicting the process behaviour and can eventually hinder the exploitation of fully digitised manufacturing processes, which is a goal of "industry 4.0". In the present work, an enhanced absorption model that takes into account the effects of laser characteristics, incident angle, surface temperature, and material composition is utilised to predict internal heat and fluid flow in laser melting of stainless steel 316L. Employing such an absorption model is physically more realistic than assuming a constant absorptivity and can reduce the costs associated with calibrating an appropriate value. High-fidelity three-dimensional numerical simulations were performed using both variable and constant absorptivity models and the predictions compared with experimental data. The results of the present work unravel the crucial effect of absorptivity on the physics of internal flow in laser material processing. The difference between melt-pool shapes obtained using fibre and CO$_2$ laser sources is explained, and factors affecting the local energy absorption are discussed.
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