Publications by authors named "Trevor Bird"

2 Publications

  • Page 1 of 1

A high magnification UV lens for high temperature optical strain measurements.

Rev Sci Instrum 2019 Apr;90(4):045117

Department of Mechanical and Aerospace Engineering, Utah State University, 4130 Old Main Hill, Logan, Utah 84322-4130, USA.

Digital Image Correlation (DIC) measures full-field strains by tracking displacements of a specimen using images taken before and after deformation. At high temperatures, materials emit light in the form of blackbody radiation, which can interfere with DIC images. To screen out that light, DIC has been recently adapted by using ultraviolet (UV) range cameras, lenses, and filters. Before now, UV-DIC had been demonstrated at the centimeter scale using commercially available UV lenses and filters. Commercial high-magnification lenses using visible light have also been used for DIC. However, there is currently no commercially available high-magnification lens that will allow images to be taken (a) in the UV range, (b) at a submillimeter scale, and (c) from a relatively long working distance separating a specimen inside a test chamber and a camera outside the chamber. In this work, a custom UV high-magnification lens is demonstrated to perform high-magnification, high-temperature DIC measurements. To demonstrate the capabilities of this lens, a series of thermo-mechanical tests was run on a stainless-steel ring specimen. Two UV cameras performed simultaneous measurements: one at lower magnification using a commercial UV lens, and one with the custom high-magnification UV lens. At room temperature, the custom lens produces sufficiently bright images to perform DIC, while at high temperature (demonstrated to 900 °C) the images retained sufficient contrast while avoiding oversaturation. The lens can detect submillimeter rigid motion and tensile strains from long working distances and high magnification. These tests show that the custom lens is suitable for use in high-magnification UV-DIC measurements.
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http://dx.doi.org/10.1063/1.5081899DOI Listing
April 2019

Interglacial pollen and plant macrofossils from Langdon River, western Tasmania.

New Phytol 1989 Mar;111(3):531-548

CSIRO, Stowell Avenue, Hobart, Tas, 7000, Australia.

Pollen and plant macrofossils from Langdon liner give an interglacial floral record for western Tasmania. The location of the site between the ice limits of the Last or Margaret Glaciation and the Penultimate or Henty Glaciation indicate that it cannot be younger than the Last Interglacial. The sequence of vegetation changes shows the succession Casuarina Phyllocladus-Nothofagus with Casuarina as pioneer and Nothofagus as representing Maximum wet forest development. After the maximum the presence of Phyllocladus-Nothofagus-Eucalyptus-Microstrobos suggests deterioration to subalpine woodland/shrubland, and Compositae, Gramineae-Microstrobos to alpine shrubland and herbland. The sequence represents most of a glacial-interglacial-glacial cycle Of environmental changes that occurred before 43 000 C yr B.P. Very high Casuarina values occur in the early part at the interglacial sequence which contrasts with the Holocene where Eucalyptus is more important than Casuarina. Otherwise the sequence of Phyllocladus, Nothofagus, Eucryphia-Anodopetalum is the same as for Holocene forest development. The interglaeial 'optimum' is marked by the occurrence of Pomaderris apetala type and Dicksonia antarctica. There is some similarity with the Casuarina curves in the Lake George interglacials before the Last Interglacial. But, on the whole, there is more similarity with interglacial rainforest development in western South Island, New Zealand Only one cycle of vegetation change is recognized at Langdon River which is unlike New Zealand and central Chilean records from 40-42° S which in different ways record a mid Last Interglacial climatic deterioration.
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http://dx.doi.org/10.1111/j.1469-8137.1989.tb00716.xDOI Listing
March 1989