Experimental Study of Shear and Tensile Properties of LIGA Ni-Fe and Ni-Co Alloys at Quasi-static and Intermediate Strain Rates

Abstract

AbstractWe report the in-plane shear properties, to fracture, of 200 μm-thick LIGA nanocrystalline Ni-10%Fe and micrograined Ni-10%Co. Planar simple shear specimens were designed, fabricated and pulled to fracture using a miniature commercial tension test stage. Forces were measured with a load cell and displacements were measured via digital image correlation. A procedure was developed to extract the shear strains from the displacements. We show shear stress vs shear strain curves to fracture for each material, at strain rates 0.001/s and 30/s. Tensile tests were also performed on both materials at strain rates 0.001/s and 1/s. Increases in shear strength, tensile strength, and true strain to fracture were observed at the higher strain rate, but rate effects were inconclusive for the Young’s modulus, shear modulus, and yield strength due to large measurement uncertainties. Finally, the stress triaxiality and equivalent plastic strain at fracture for the tensile and shear specimens were estimated and used to construct part of the fracture locus for the Ni-10%Fe material. It is anticipated that this data may be used to facilitate failure prediction models for LIGA MEMS.KeywordsElectrodeposited nickelLIGAMEMSShearFracture locus