Strain Measurement with Nanometre Resolution by Transmission Electron Microscopy

Strain is routinely used in state-of-the-art semiconductor devices in order to improve their electrical performance. Here we present experimental strain measurements obtained by different transmission electron microscopy (TEM) based techniques. Dark field electron holography, nanobeam electron diffraction (NBED) and high angle annular dark field scanning electron microscopy (HAADF STEM) are demonstrated. In this paper we demonstrate the spatial resolution and sensitivity of these different techniques on a simple calibration specimen where the accuracy of the measurement can easily be assessed.

Hopkinson bar experimental technique: A critical review

A critical review of three classic papers by B Hopkinson, RM Davies, and H Kolsky, and the state-of-the-art in Hopkinson bar experimental techniques is presented. The validity and applicability of the assumption made in the 1D Hopkinson bar theory are discussed. Fundamentals of the Hopkinson bar experimental procedure are outlined including bar calibration, specimen design, pulse shaping, and data analysis following the essential dispersion correction methodology. Additional data tables necessary for dispersion correction are provided to cover a wide range of Poisson’s ratio. In addition to the elastic-plastic metals, methodologies for soft and hard materials are also discussed. This paper provides the necessary information for conducting a Hopkinson bar experiment and analyzing the experimental data. This review article cites 61 references.

Determination of Elastic Constants of Composites with a Circular Disk Specimen

The in-plane elastic constants of orthotropic composite materials need to be determined in order to perform stress analysis and design of composite structures. Several specimen configurations have been proposed and the majority suffer from one of two drawbacks: either multiple specimens are required or the experimental method involves a scientific rather than an engineering approach. In the present investigation a simple procedure involving a single calibration specimen is suggested. The method utilises a theoretical solution available in the literature for an orthotropic circular disk under diametral compression, measured strains at specific locations on a circular disk specimen, and a least squares procedure that gives average rather than localised elastic constants.

Development of a Method for Characterizing Joint Stiffness, Deadband, and Hysteresis

This article documents the development of a procedure for characterizing the stiffness, deadband, and hysteretic behavior of struts with pinned joints. A test setup utilized procedures recommended by other authors. The test results included a calibration specimen with linear stiffness and near zero hysteretic behavior that identified the capabilities and limitations of the procedure. Tension/compression pull tests of the truss joints were conducted. The load vs. displacement curves showed stiffness, deadband, and hysteresis loops consistent with theory. Vibration damping was inferred from the hysteresis loops and compared with measured data from a three bay truss.