Flow stress characterization using piezo-actuated micro-compression machine

• Main Author: Ng, Caine Jianyuan.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/53430
• Institution: Nanyang Technological University

With the increase in demand for smaller and more powerful electronic and mechanical devices the demand for parts made in the micro scale increases. Typically parts with two dimensions smaller than 1mm are considered micro scale are manufactured by lithography techniques or by machining, which is suitable for such high precision parts however time consuming. An alternative means of production is required. Looking towards macro forming methods, metal forming of blank parts to final shape seems suitable to meet the demands of micro parts; however scaling macro-forming processes to micro scale poses certain challenges and difficulties. One of the challenges is the issue of size effects. With the decrease in size, all forming variables can be proportionally scale down with the exception of grain structure and surface topography. This creates problems such as process scatter and the inability to directly transfer knowledge of macro forming to the micro scale. In order to gain a better understanding of materials in the micro scale a piezo actuated micro compression machine was built in house to determine the stress-strain characteristics of micro scale parts. Currently the machine is in improvement stages and preliminary test were conducted to determine the capabilities of this machine and provide data for further improvement. At the end of this project it is shown that at the current stage the machine is capable to conducting basic flow stress studies. Samples made of copper and stainless steel of two sizes, diameter 2mm by 2.5mm and diameter 1mm by 1.25mm were tested at 3 different strain rates. The results show that grain sizes have a significant role in flow stress of the material. Decreasing the scale of the sample from 2mm to 1mm increased spread of flow stresses. The increase in flow stress with increase in strain rate was observed in copper samples.