Fabrication of Thin Walls with and without Close Loop Control as a Function of Scan Strategy Via Direct Energy Deposition

Direct Energy Deposition (DED) is a technique used to fabricate metallic parts and is a subcategory of metal additive manufacturing. Despite of its vast advantages over traditional manufacturing the deployment at industrial level is still limited due to underlaying concerns of process stability and repeatability. In-situ monitor- ing, therefore, is indispensable while depositing via DED. The present experiment is a step towards enhancing our current understanding of the DED when coupled with a closed loop control system to control melt pool width for deposition of thin- walled structures, and as a function of scan strategy. 316L stainless steel powder was deposited on S235JR substrate. A total of 6 iterations are reported, out of many performed, of which 3 were without the closed loop control. Also, to understand the effect of scan strategy as a function of laser power. Two different scan strategies were employed for understanding of the issue i.e., unidirectional, and bidirectional. Apart from the geometrical consistency of the wall, microhardness, density calcula- tions and microstructure were investigated. The geometric consistency was found to be almost perfect with the bidirectional scan strategy. In case of unidirectional scan strategy, the wall shows a negative slope along the other extreme regardless of the closed loop control system. Dilution zone shows the hardness greater than both the substrate and the wall. The specimens fabricated without the use of closed loop con- trol were found to be denser than their counterparts. This was found to be true also in case of manual reduction of power during each layer

Laser cladding and its potential to reduce particulate matter emissions from the automotive and locomotive sector

Laser Cladding (LC) is an emerging technology which is used both for coating applications as well as near-net shape fabrication. Despite its significant advantages, such as low dilution and metallurgical bond with the substrate, it still faces issues such as process control and repeatability, which restricts the extension to its applications. The following thesis evaluates the LC technology and tests its potential to be applied to reduce particulate matter emissions from the automotive and locomotive sector. The evaluation of LC technology was carried out for the deposition of multi-layer and multi-track coatings. 316L stainless steel coatings were deposited to study the minimisation of geometric distortions in thin-walled samples. Laser power, as well as scan strategy, were the main variables to achieve this goal. The use of constant power, reduction at successive layers, a control loop control system, and two different scan strategies were studied. The closed-loop control system was found to be practical only when coupled with the correct scan strategy for the deposition of thin walls. Three overlapped layers of aluminium bronze were deposited onto a structural steel pipe for multitrack coatings. The effect of laser power, scan speed and hatch distance on the final geometry of coating were studied independently, and a combined parameter was established to effectively control each geometrical characteristic (clad width, clad height and percentage of dilution). LC was then applied to coat commercial GCI brake discs with tool steel. The optical micrography showed that even with preheating, the cracks that originated from the substrate towards the coating were still present. The commercial brake discs emitted airborne particles whose concentration and size depended on the test conditions used for simulation in the laboratory. The contact of LC cladded wheel with rail emitted significantly less ultra-fine particles while maintaining the acceptable values of coefficient of friction

Employing diffusion of innovation theory for ‘not missing the mass’ in community-engaged research

Introduction Engaging with minority communities, such as immigrants and ethnic minorities, often involves adopting top-down approaches, wherein researchers and policymakers provide solutions based on their perspective. However, these approaches may not adequately address the needs and preferences of the community members, who have valuable insights and experiences to share. Therefore, community-engaged approaches, which involve collaborative partnerships between community members and researchers to identify issues, co-create solutions, and recommend policy changes, are becoming more recognized for their effectiveness and relevance. Yet, prevailing community engagement efforts often focus on easily reachable and already engaged segments of the community, sometimes overlooking the broader population.Methods When working with immigrant and racialized communities, we encountered difficulties in engaging the wider community through traditional researcher-led approaches. We realized that overcoming these challenges required innovative strategies rooted in community-based participatory research principles and the diffusion of innovation theory. We recognized that a nuanced understanding of the community's dynamics and preferences was crucial in shaping our approach and building trust and rapport with the community members.Results The need to bridge the gap between researcher-led initiatives and community-driven involvement has never been more pronounced. Our experience, chronicled in this article, highlights the journey of our research program with an immigrant/racialized community. This reflection enhances our comprehension of community engagement that deliberately strives to reach a larger cross-section of the community. By providing practical methods for reaching the broader community and navigating the intricacies of engagement, we aim to assist fellow researchers in conducting effective community-engaged research across various minority communities.Conclusion In sharing our insights and successful strategies for community engagement, we hope to contribute to the field's knowledge. Our commitment to fostering meaningful collaboration underscores the importance of co-creating solutions that resonate with the diverse voices within these communities. Through these efforts, we envision a more inclusive and impactful approach to addressing the complex challenges faced by minority populations