Development of in situ manufacturing and mechanical evaluation system for micromaterials

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In order to develop a reliable micromachine in a service operation, much care must be taken to micro mechanical evaluation, i.e., mechanical properties of μm-sized microelements including fatigue behavior. However, the evaluation method has not been well established yet. In this study, the evaluation system of metallic foil is developed, including in situ specimen machining, chucking and non-contact strain measurement. Using an electric discharge machine (PX-05 : Mitsubishi Co.Ltd.), micro specimens of stainless steel foil were machined and a suitable machining condition was found to minimize the roughness of machined surface : the minimum of the maximum roughness was 1.0μm. The micro specimen for tensile testing was designed to make easily handle and testing, which has the specimen supporting part and the specimen chucking part. To measure the strain of microelements, for which strain gages on the market are too large and strong, a laser speckle strain measurement method was applied, and non-contact strain measurement system for microelements was developed. Integrating these machining system and non-contact strain measurement system, tensile and fatigue tests of micro specimens of stainless steel foil (thickness : 50 μm, width : 1 mm) was successfully conducted, and the influence of anisotropy and machining method on the mechanical and fatigue strength was investigated. The elongation at break and fracture morphology of tensile tests were affected by specimen orientation, but fatigue strength was not.