| Author: | Tong, Xu |
| Title: | Study on size effect affected deformation behavior in microembossing of multi-channel structures |
| Advisors: | Fu, Mingwang (ME) |
| Degree: | M.Sc. |
| Year: | 2021 |
| Subject: | Production engineering Manufacturing processes Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | xii, 93 pages : color illustrations |
| Language: | English |
| Abstract: | Although the manufacturing industry is constantly developing and innovating in recent years, metal forming still is of particular importance in many industrial clusters such as consumer electronics, automobiles, biomedical equipment, and aerospace. With the increasing demand for product miniaturization, explosive growth in the use of micro-scale materials and structures drives the exploration of micro-manufacturing technologies and related size-dependent behaviors. The embossing process plays an essential part because of its high precision and high efficiency. However, the physics behind these researches is still not fully understood. An in-depth understanding of the deformation mechanism of microparts and designing methods to avoid dimensional accuracy and undesirable geometries during microembossing process will contribute to the development of micromanufacturing. In this dissertation, the size effect affected deformation behavior in microembossing of multi-channel structures is well investigated. The T2 pure copper sheets with different thicknesses and grain sizes were fabricated to multi-channel structure, and the related deformation behaviors were extensively studied. In addition, the flow stress curves obtained from uniaxial tensile tests were used in FE simulations to verify the experimental results. Correlations between the channel quality evaluation indicators and grain size and workpiece size are investigated experimentally and numerically. Size effects occur with the changes of part feature size and grain size, significantly affecting the quality of the microchannel structure in terms of deformation load, dimensional accuracy, material flow, surface quality, and mechanical properties. Thickness reduction, height variation and other inhomogeneous deformation become more significant in coarse-grained and thinner microparts. A worse forming quality appeared on the multichannel structure, where the defects including microvoids, micro-scratches, wrinkles, and grooves in grain boundaries were observed. The origin of inhomogeneous deformation and surface defects can be attributed to grain boundary strengthening, crystal plasticity, surface roughening, etc. This investigation thus provides an in-depth understanding of the size effects in the multi-channel structure fabricated by microembossing process from the aspects of deformation behaviors and product quality control and enriching the knowledge of this unique microforming process. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 5937.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 8.58 MB | Adobe PDF | View/Open |
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