A predictive model for in situ distortion correction in laser powder bed fusion using laser shock peen forming
A predictive model for in situ distortion correction in laser powder bed fusion using laser shock peen forming
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DOI：
10.1007/s00170-020-06399-z
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发表时间：
2021-01
期刊：
影响因子：
--
通讯作者：
Sumair Sunny;Haoliang Yu;Ritin Mathews;A. Malik
中科院分区：
文献类型：
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作者：
Sumair Sunny;Haoliang Yu;Ritin Mathews;A. Malik
描述了一种混合金属增材制造（AM）方法，其将原位激光冲击喷丸（LSP）成形与激光粉末床熔合（PBF）集成以减轻部件构建期间的垂直变形。LSP最近被提出来减少在选择性激光熔化（SLM）过程中的拉伸残余应力。然而，LSP对部分失真的影响尚未得到严格的研究。本文提出SLM可以与原位LSP成形集成，以减少印刷期间或之后部件的上表面的变形。为了研究失真校正能力，创建了一个两阶段计算框架，其中包括SLM过程和LSP处理的基于物理的模型。第1阶段包括热机械SLM模拟，以预测表面几何形状，并应用于模拟具有4 mm × 4 mm足迹的316 L部件的四个50 μm层。框架的第二阶段包括弹塑性热机械冲击波模拟，以预测LSP表面处理成形效果。表面变形检查不同的激光光斑尺寸，重叠，和部分温度从300至500 K，使用纳秒脉冲红外激光。对于316 L SLM样品，预测在200 μm的4层构建上，上表面具有9 μm的垂直失真。在2 μm的允许变形下，只有44.13%的表面最初符合要求。在300 K下进行一次激光冲击成形处理后，共形率提高到84.75%。在第三次LSP成形后，随着50%的激光功率密度增加，表面一致性增加到91%，证明了混合AM-LSP工艺在减少精加工方面的潜力。
Described is a hybrid metal additive manufacturing (AM) method that integrates in situ laser shock peen (LSP) forming with laser powder bed fusion (PBF) to mitigate vertical distortions during part builds. LSP has recently been proposed to reduce tensile residual stresses during selective laser melting (SLM). The effects of LSP on part distortion, however, have not been rigorously examined. It is proposed here that SLM can be integrated with in situ LSP forming to reduce distortion of the upper surface of parts during or after printing. To study the distortion correction capability, a 2-stage computational framework is created, which includes physics-based models of the SLM process and LSP treatment. Stage 1 includes thermomechanical SLM simulation to predict surface geometry and is applied to model four 50-μm layers of a 316L part having a 4 mm × 4 mm footprint. Stage 2 of the framework includes an elastic-plastic thermomechanical shock-wave simulation to predict LSP surface treatment forming effects. Surface distortion is examined for varying laser spot size, overlap, and part temperatures from 300 to 500 K, using a nanosecond-pulsed infrared laser. For the 316L SLM sample, the upper surface is predicted to have9-μm vertical distortion on the 200-μm 4-layer build. With a 2-μm allowable distortion, only 44.13% of the surface initially conforms. After one LSP forming treatment at 300 K, conformance improves to 84.75%. After a third LSP forming, with 50% laser power-density increase, surface conformance increases to 91%, demonstrating potential of the hybrid AM-LSP process in reducing finish-machining.