Directed energy deposition (DED), also known as laser cladding, is one type of additive manufacturing where a high-power laser combined with a coaxial powder delivery system is used to produce metal components layer-by-layer. Despite many advancements in DED, little work has been accomplished in online estimation of mechanical properties, such as Young's modulus and Poisson's ratio, during the DED process. In this study, an online mechanical properties estimation technique was developed for the DED process using femtosecond laser ultrasonics and laser polishing. The unique contributions of this study are the following: (1) the development of a fully noncontact and nondestructive technique for the estimation of Young's modulus and Poisson's ratio using a femtosecond laser, (2) layer-by-layer estimation of mechanical properties accomplished by achieving micrometer-level spatial resolution, (3) laser ultrasonic measurement from a deposited metal layer using laser polishing instead of mechanical polishing, and (4) potential for online operation during the DED process. The performance of the proposed technique was examined using specimens fabricated under various DED operation conditions. The Young's modulus and Poisson's ratio values estimated by the proposed technique were consistent with those obtained from independent tensile tests performed after the completion of the DED process.

定向能量沉积（DED），也称为激光熔覆，是一种增材制造类型，其中将高功率激光与同轴粉末输送系统结合使用来逐层生产金属部件。尽管DED取得了许多进步，但是在DED过程中，在线评估机械性能（例如杨氏模量和泊松比）的工作还很少。在这项研究中，使用飞秒激光超声和激光抛光技术为DED工艺开发了一种在线机械性能评估技术。这项研究的独特贡献如下：（1）开发了一种完全非接触式和非破坏性的技术，用于使用飞秒激光估算杨氏模量和泊松比，（2）通过达到微米级的空间分辨率来逐层评估机械性能，（3）使用激光抛光代替机械抛光从沉积的金属层进行激光超声测量，以及（4）在加工过程中在线运行的潜力DED过程。使用在各种DED操作条件下制造的样品检查了所提出技术的性能。通过提出的技术估算的杨氏模量和泊松比值与从DED过程完成后进行的独立拉伸试验获得的值一致。（4）DED过程中在线运行的潜力。使用在各种DED操作条件下制造的样品检查了所提出技术的性能。通过提出的技术估算的杨氏模量和泊松比值与从DED过程完成后进行的独立拉伸试验获得的值一致。（4）在DED过程中具有在线运行的潜力。使用在各种DED操作条件下制造的样品检查了所提出技术的性能。通过提出的技术估算的杨氏模量和泊松比值与从DED过程完成后进行的独立拉伸试验获得的值一致。