Strain measurements in tubular specimens under combined tensile-torsional loading

0464424 - ÚTAM 2017 RIV CZ eng A - Abstract
Doktor, Tomáš - Koudelka_ml., Petr - Černý, Miloš - Wolf, Benjamin - Drdácký, Miloš
Strain measurements in tubular specimens under combined tensile-torsional loading.
Book of abstracts. International symposium on experimental methods and numerical simulation in engineering sciences 2016. Praha: Czech Technical University in Prague, Faculty of Transportation Sciences, 2016 - (Kytýř, D.; Zlámal, P.; Jiroušek, O.). s. 14-14. ISBN 978-80-01-06009-4.
[International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences 2016. 18.09.2016-21.09.2016, Liblice]
R&D Projects: GA ČR(CZ) GBP105/12/G059
Institutional support: RVO:68378297
Keywords : biaxial loading * cultural heritage * tension * torsion
Subject RIV: JM - Building Engineering
http://www.itam.cas.cz/exnum2016/BofA.php

Failure induced by shear stress plays an important role in analysis of failure in many building materials. To analyse shear stress in the building materials, e.g. bricks, sandstone or mortar, a loading mode composed of uniaxial tension and torque was used. For description of the entire deformation behaviour under combined loading, in this case not only the ultimate shear stress or the maximum distortion angle, but the strain fields occurring at the specimen surface, full-field strain mapping was employed. A unique tension-torsion loading frame was developed at the Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences. The loading frame is equipped with two force transducers to be able to measure both axial force and the torque. The deformation behaviour is assessed by optical measurement setup. For the capturing of the surface displacements a CCD camera was used with a bi-telecentric zoom lens. In the loading scene an array of tracking features is defined and the tracking is performed using Digital Image Correlation (DIC) algorithm. Tubular specimens with dimensions 36 × 65 × 4mm were tested. To ensure proper boundary conditions of the loading, i.e. to transmit axial forces in vertical direction and torque along the same axis, the specimens were attached to the fixing plates using epoxy resin at both top and bottom end. To prove the stability of the prescribed loading paths calibration measurements were performed prior the loading of the tested specimens. During these measurements, only rigid body motions were prescribed to the specimens (only one fixed grip) and the DIC algorithm was used to check if the strains meet the expected zero values. Then combined loading was prescribed to the specimen and strain fields were assessed using DIC. Based on the observed strain maps the developed loading device with a custom optical strain measurement system is suitable to track displacements on the cylinder’s surface and to develop the strain maps.
Permanent Link: http://hdl.handle.net/11104/0263297