Novel post-processing methods on additively manufactured thermal devices for high performance cooling

Uvodich, Kevin

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https://hdl.handle.net/2142/127504 Copy

Description

Title

Novel post-processing methods on additively manufactured thermal devices for high performance cooling

Author(s)

Uvodich, Kevin

Issue Date

2024-12-06

Director of Research (if dissertation) or Advisor (if thesis)

Miljkovic, Nenad

Doctoral Committee Chair(s)

Miljkovic, Nenad

Committee Member(s)

• Haran, Kiruba
• Cai, Lili
• Zhang, Winston

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Additive Manufacturing
• Etching
• Post-processing
• Heat Exchangers
• Heatsinks
• Etch Rates
• CT scanning
• Roughness
• Flow Etching
• Microchannels
• Dross

Abstract

Additive Manufacturing (AM) is becoming an established technology with high impact. The invention of Direct Metal Laser Sintering (DMLS) to produce solid metal parts layer by layer from a powder has altered the landscape of many industries, where increased design flexibility allows for more innovative designs. This creates opportunities in thermal management technology, which is a bottleneck for many systems such as computer and power electronics. Microchannel heat exchangers are a potential solution in many cases, such as conformal cooling applications of system components with large heat fluxes. However, several challenges with metal AM technology still limit its usefulness in practice. This work addresses the challenges and offers solutions using novel post-processing methods coupled with non-destructive analysis, providing a framework for reliable implementation of the suggested methods. Using a chemical flow etching process, metal AM parts are post-processed and evaluated in three different contexts. First, a method for resolving failed DMLS microchannels is demonstrated using chemical flow etching to clear obstructions and remove surface roughness. Experiments show clear trends of microchannel failure likelihood and severity increasing with parameters such as decreasing channel diameter, increasing aspect ratio, and increasing surface overhang. The post-process enables the creation of passable microchannels that initially fail as printed. X-ray Computed Tomography (CT scanning) is utilized as a powerful non-destructive tool to support analysis on the effects of the post-process, by revealing the extent and nature of microchannel obstructions. With the utility of flow etching established, the effects of such a process on the various forms of surface roughness present with metal AM are studied and quantified, as well as the effects on thermal-hydraulic performance. In the second study, single microchannel and parallel microchannel AlSi10Mg samples are characterized and measured using CT scanning, with thermal-hydraulic performance measured experimentally before and after post-processing. For the third context, the post-process is studied for positive feature creation, using the etching to achieve thin features below current metal AM capabilities. The influence of hydrodynamics, geometry, concentration, and temperature on etch rates of internal features during a flow etch are measured and compared to predictions. This research lays the groundwork for chemical flow etching to be used in metal AM post processing to elevate the technology and push the limits of what is possible. It also highlights key areas of importance for future development so the post-process can be applied reliably and consistently in a variety of situations.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127504

Copyright and License Information

Copyright 2024 Kevin Uvodich

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