Engineers at theTokyo University of Science(TUS) have developed a mathematical model capable of predicting the performance of Directed Energy Deposition (DED)-produced parts before they’re ever 3D printed.
使用他们的方法，该团队发现有可能在温度分布，变形状态和残余应力分布方面确定DED过程的性能。通过进一步的调整，研究人员说，他们的模型可以部署以提高技术的效率，尤其是在维修应用程序中。
“Using our technique, the surface shape of a metal structure can be completely restored on-site, and the disposal of the metal powder required for repair can be significantly reduced,” explains TUS Professor Masayuki Arai. “However, the optimum forming conditions required for the widespread application of this technology in industry had to be hitherto determined by a trial-and-error process.”
DED: an industrial repair solution?
As you’d expect, when mechanical parts used in industrial machinery begin to thin or develop cracks, they need to be replaced with new ones. However, while 3D printing has shown potential as a means of making these repairs, the TUS researchers say that many current laser or electron beam-based 3D printing technologies “require the use of bulky equipment, and waste metal powder.”
That said, with industrial sustainability increasingly becoming a hot topic, significant R&D is being poured into identifying new solutions to the issue. One technology that continues to gain traction as an industrial and aerospace repair tool is DED. Typically, the process involves the deposition of a powder or wire feedstock onto a surface, which is melted as it’s deposited by a focused energy source.
Given that the nozzle depositing these materials isn’t fixed to a specific axis, it can be fitted to multi-axis machines and deployed at various angles. This not only makes the technology ideal for depositing materials onto existing surfaces in repair applications, but according to the TUS team, enables it to do so with a significantly-reduced footprint.
然而，尽管作为一种工业维修工具而获得了吸引力，但它尚未在该领域获得广泛的采用。As identified by the TUS team, this is somewhat down to how difficult it is to find the optimal parameters for producing a part that’ll meet end-use requirements, and some early adopters have therefore been forced into a ‘trial and error’ approach.
采用数值模拟方法
为了使DED 3D打印结果更具可预测性，TUS工程师提出了一个数值处理分析系统，以自动确定构建的最佳形成条件。该软件是通过称为“死亡 - 出生算法”的东西来做到的，该算法通过数值模拟修复过程并创建正在维修的区域的“数字双胞胎”来起作用。
“The thermal radiation-thermal conduction model and the viscoplastic-thermoplastic constitutive model are applied to the stacked elements that constitute the deposited region, so that a wide range of state changes from melting to solidification of the deposited layer of metal powder can be faithfully simulated,” adds Professor Arai. “By incorporating these models into a finite element analysis program, we have developed a new machining analysis system that has never been used before.”
在将模型部署在测试中后，该团队发现其温度历史和应变行为估计是“与他们的实验结果一致”。还可以证实，沉积层中形成的残余应力略高于基本材料的屈服强度，并且明显低于焊接叠加过程中形成的残余应力，这是另一个工业维修过程。
Utilizing their model, the researchers reckon it’ll ultimately be possible to make DED a more effective repair technology, “with efficient resource management to improve its sustainability.” In terms of applications, they see their software being deployed to repair cavitation thinning on power plant blades, and gas turbine rotor blades impacted by residual deformation.
尽管尚未在能源和航空航天上进行大规模应用，但DED仍继续获得吸引力，作为修复这些行业的涡轮刀片的手段。在2021年底，据透露，一个长期的客户已经开始使用Optomec 3D printing for turbine blade repairs。The firm has also previously been awarded $500,000 to deploy its LENS DED technology forUS Air Force turbine blade repairs。
在其他地方，在与TUS团队类似的项目中，一个德国 - 加拿大的财团已经开始使用AI自动维修3D打印。As part of the ‘AI-SLAM’ initiative, the team is developing software that algorithmically manages the DED process to more effectively repair irregular surfaces on damaged components, without any need for human input.
研究人员的发现在其论文中详细介绍了“Three-Dimensional Numerical Simulation of Repairing Process by Laser Direct Energy Deposition”，由Masayuki Arai，Toshikazu Muramatsu，Kiyohiro Ito，Taisei Izumi和Hiroki Yokota合着。
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Featured image shows Optomec’s LENS DED technology in-action. Photo via Optomec.
