Laser-based additive manufacturing is a technology for the production of freeform metallic parts. In order to produce parts with high quality, it is important for the manufacturing processes to be controllable with a high degree of precision. Current additive manufacturing systems attempt to reach this goal by carefully tuning the operational parameters, often in combination with a feedback control system. These systems are based on low order, empirical models of the process, which may limit the performance that can be achieved. This paper introduces a control system based on a high order physical heat conduction model of the melt pool dynamics. The control system serves as a framework which can be applied to many laser material processes in which high precision is required such as laser cladding and selective laser melting. The controller is able to regulate the melt pool size by modulating the laser power using a number of surface temperature measurements as the feedback signal. A hardware-in-the-loop (HIL) system was built to enable safe and cost-effective testing of the controller hardware in different simulation environments. The HIL setup includes a real-time image processing module for extracting the required temperature information from hyperspectral data generated by detailed numerical simulations of the melt pool dynamics. Hyperspectral measurements are performed on a laser cladding system to validate the simulation results.

Fatigue performance of additively manufactured (AM) components is still uncertain and inconsistent. Structural health monitoring (SHM) systems offer a solution to continuously monitor the structural integrity of a structure. The effective Structural Health Monitoring (eSHM) system is the first SHM principle developed with the principal purpose to monitor AM components. The eSHM principle exploits the design freedom offered by AM to integrate a capillary inside the component. The capillary is put under low vacuum and the pressure is monitored during the operation of the component. As-built AM surfaces report elevated surface roughness and are one of the principle causes of premature fatigue initiation and fatigue failure. The current study will investigate the effect of a chemical etching (CE) post-process on the capillary surface and evaluate its effect on the fatigue performance.

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Additive manufacturing (AM) of metals offers new possibilities for the production of complex structures. Up to now, investigations on the mechanical response of AM metallic parts show a significant spread and unexpected failures cannot be excluded. In this work, we focus on the detection of fatigue cracks through the integration of a Structural Health Monitoring (SHM) system in Ti-6Al-4V specimens. The working principle of the presented system is based on the integration of small capillaries that are capable of detecting fatigue cracks. Four-point bending fatigue tests have been performed on Ti-6Al-4V specimens with integrated capillaries and compared to the reference specimenswithout capillaries. Specimens were produced by conventional subtractive manufacturing of wrought material and AM, using the laser based Directed Energy Deposition (DED) process. In this study, we investigated the effect of the presence of the capillary on the fatigue strength and fatigue initiation location. Finite element (FEM) simulations were performed to validate the experimental test results. The presence of a drilled capillary in the specimens did not alter the fatigue initiation location. However, the laser based DED production process introduced roughness on the capillary surface that altered the fatigue initiation location to the capillary surface. The fatigue performance was greatly reduced when considering a printed capillary. It is concluded that the surface quality of the integrated capillary is of primary importance in order not to influence the structural integrity of the component to be monitored.

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