Dr. Paul A. Hooper

Swiss Cheese: A Practical Tutorial on Assessing AM Build Quality
Dr. Paul A. Hooper, Department of Mechanical Engineering, Imperial College, London

Build quality in laser powder bed fusion (LPBF) can seem to vary from excellent to absolutely terrible with the slightest change in processing conditions. A quick and rough way to get some idea of the quality of a build is to check the density of the material. This gives rise to the question: how dense is dense enough? Is it >99% good enough? Or do we need >99.9% or >99.99%? In this tutorial we will take a more detailed look at porosity and outline the limitations of using density alone as a quality metric. We will learn about the concept of a critical flaw and the effect of size and shape on the failure mode of a part. We will then look at simple ways we can determine how likely our part is to contain a critical flaw based on data from a variety sources (e.g. sectioning, X-ray CT or in-situ monitoring). At the end of the tutorial you should be armed with practical ways to assess build quality in LPBF parts.

Biography: Dr. Paul A. Hooper is a Lecturer in the Mechanics of Materials Group in the Department of Mechanical Engineering at Imperial College London. He research focuses on additive manufacturing (AM) and he leads industry-funded projects focusing on certification of AM components. His specific interests include in-situ process monitoring, process-microstructure-performance relationships, simulation of AM processes, design for AM and new process development. He also has interests in high-strain rate material behaviour and structural integrity. He has authored over 30 journal publications, has an h-index of 16 and has one patent.