Quantitative Near Infrared Thermal Imaging of Laser Based Additive Manufacturing of Metals

研究问题：现有的热成像技术能否用于金属增材制造中的热场测量？金属的增材制造需要一个小的快速移动的热源，通常是激光或电子束。测量热源周围的热场对从事该领域工作的材料科学家来说是一个巨大的福音。热场的在线测量也有助于过程的闭环反馈控制。热场的精确测量具有挑战性。在整个博士课程中，我获得了在改进的商业和纯研究环境中实施高速热显微镜所需的技能和专业知识。我开发了新的方法来表征和克服市场上可用的热成像仪器组件的局限性。我使用了各种光学装置的商用硅基相机来获取金属增材制造过程的视频。我的论文关注的是将这些图像转换成精确的热场图所需的步骤。在尝试量化热场时，我使用了光学设计理论。辐射测温理论，包括辐射特性。成像系统特性。包括新方法二维数字信号处理，包括其他领域方法的新应用。我已经实现了坐标系统转换，以纠正几何扭曲。我使用图像处理技术提取定量测量，与增材制造领域相关。

Research question:Can existing thermal imaging technologies be used to measure the thermal fields in additive manufacturing of metals. Additive manufacturing of metals requires a small rapidly moving heat source, usually either a laser or an electron beam. Measurement of the thermal fields around the heat source would be a great boon to materials scientist working in the field. An online measurement of the thermal field would also facilitate closed loop feedback control of the process. Accurate measurement of the thermal fields is challenging. Throughout the course of the PhD I have gained the skills and expertise necessary to implement high speed thermal microscopy in a modified commercial and pure research environment. I have developed novel methodologies to characterise and overcome limitations of the thermographic instrument components available on the market. I have used commercial silicon based cameras with various optical arrangements to acquire videos of the metal additive manufacturing process. My thesis is concerned with the steps required to convert these images into accurate maps of the thermal fields. In attempting to quantify the thermal fields I have utilised:Optical design theory.Radiometric temperature measurement theory including radiative properties.Imaging system characterisation. Including novel methodologiesDigital signal processing in two dimensions, including novel applications of methodologies from other fields.I have implemented coordinate system transforms to correct for geometric distortions.I have used image processing techniques to extract quantitative measurements, pertinent to the field of additive manufacturing.