Strain rate sensitivity of nanocrystalline Au films at room temperature

The effect of strain rate on the inelastic properties of nanocrystalline Au films was quantified with 0.85 and 1.76 lm free-standing microscale tension specimens tested over eight decades of strain rate, between 6 106 and 20 s1. The elastic modulus was independent of the strain rate, 66 ± 4.5 GPa, but the inelastic mechanical response was clearly rate sensitive. The yield strength and the ultimate tensile strength increased with the strain rate in the ranges 575–895 MPa and 675–940 MPa, respectively, with the yield strength reaching the tensile strength at strain rates faster than 101 s1. The activation volumes for the two film thicknesses were 4.5 and 8.1 b3, at strain rates smaller than 104 s1 and 12.5 and 14.6 b3 at strain rates higher than 104 s1, while the strain rate sensitivity factor and the ultimate tensile strain increased below 104 s1. The latter trends indicated that the strain rate regime 105–104 s1 is pivotal in the mechanical response of the particular nanocrystalline Au films. The increased rate sensitivity and the reduced activation volume at slow strain rates were attributed to grain boundary processes that also led to prolonged (5–6 h) and significant primary creep with initial strain rate of the order of 107 s1

Full-field identification of interfaces in microelectronic devices

To improve the integrity of densely stacked multilayers in microelectronic systems, e.g., Light Emitting Diodes (LED), and thereby overcome the currently experienced problems related to interface failure during manufacturing of such devices, accurate identification of interface properties is essential. The behavior of the interface is only measurable through kinematic information from adjacent materials. The goal of this research is to identify interface parameters by Integrated Digital Image Correlation (IDIC), in which experimental images of a deformation process are correlated by utilizing the mechanical response from finite element (FE) simulations. An interface is herein modeled by cohesive zone (CZ) elements exhibiting constitutive traction-separation laws. The versatility of FE simulations and the kinematic richness of the full-field measurements are thereby exploited. Comprising an elastic hinge system, a small-scale mechanical test-setup is designed from two 3-axes (XYZ) piezo stages, with which micrometer displacements and realistic interface loading conditions (shear, normal, and mixed-mode loading) can be applied to an LED specimen. This allows to, in a well-controlled manner, mechanically mimic interface delamination that is typically induced during fabrication steps by thermal expansion. This setup and the IDIC method are integrated to identify the CZ parameters of the critical interface of an LED specimen

Identification of interparticle contacts in granular media Using mechanoluminescent materials.

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