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Development of Microtesting Systems: I. Tensile Testing of Metallic Microsamples

Seyed M. Allameh, Morteza Sadat Hossieny and Mark Rajai

Northern Kentucky University

Abstract

This paper describes procedures adopted for the development of microtesters, including microtensile and microfatigue testing systems. Small structures are known to exhibit superior mechanical properties attributed to their finer microstructure. This includes stress-life response at low and high cycle fatigue. The fatigue life of small structures involves crack initiation and crack propagation stages. While the crack initiation stage is known to be a significant component of fatigue life, experimental verification of its impact has not been performed. Using the compliance response of small LIGA Ni structures in load control mode and under cyclic loading conditions, the contributions of crack initiation and propagation to fatigue life were quantified. Instrumentation details of the development of microtesters, including the use of PID functions of Labview®, IMAQ Vision®, a piezoelectric actuator, and the results of fatigue tests will be discussed.

Introduction

The advent of micro- and nanotechnology and their emerging applications in various fields has prompted actions on the testing and characterization of such materials and devices used in micro and nanoelectromechanical systems (M/NEMS). The mechanical properties of materials have been shown to be different at the micro- and nano-scale, as compared to those at the macro- scale1. Variation of properties, across scales, originates mainly from the difference in microstructure; however, there are other contributing factors, such as size effect. Moreover, the mechanisms of failure at the micro-scale may differ from those at the macro-scale purely due to dimensional differences. For example, the fatigue crack growth component of fatigue life has been shown to be orders of magnitude smaller than that of the crack initiation component.

With the development of new microfabrication techniques, reliability becomes a critical issue for microdevices that have applications where human lives are at stake. Microdevices used in triggering weaponry systems, or those used in life-supporting devices are examples of such applications. Factors that affect reliability of such devices and structures must be explored to help optimize their design and manufacturing processes. Since properties do vary across scales, mechanical tests must be performed on structures that are used in real-size applications, e.g. at

Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition Copyright © 2005, American Society for Engineering Education

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Allameh, S., & Sadat-Hossieny, M., & Rajai, M. (2005, June), Development Of Microtesting Systems: I. Tensile Testing Of Metallic Microsamples Paper presented at 2005 Annual Conference, Portland, Oregon. 10.18260/1-2--14141