The Experts below are selected from a list of 107919 Experts worldwide ranked by ideXlab platform
Lingtao Mao - One of the best experts on this subject based on the ideXlab platform.
-
interior 3d strain mapping in opaque materials using digital volumetric speckle photography and x ray micro computer tomography
Applied Mechanics and Materials, 2015Co-Authors: Lingtao Mao, Qian Wen Sun, F P ChiangAbstract:Developing a true 3D Experimental Stress Analysis technique has been the holy grail of solid mechanics researchers since the genesis of the field. Combined the high-resolution x-ray computer tomography (Micro CT) with the 2D speckle photography technique developed by one of us (Chiang), we recently proposed a new 3D strain Analysis technique called Digital Volumetric Speckle Photography (DVSP). The elements of DVSP technique are as follows. A reference volumetric image of the specimen is recorded by a Micro-CT scan and stored as a reference. Under load the deformed CT image of the specimen is also recorded. Both volume images are divided into subimages of certain voxel arrays. Each corresponding pair of the subimages are ‘compared’ via a two-step 3D Fourier Transform Analysis. The result is a 3D map of displacement vectors representing the collective displacement experienced by all the speckles within the subset of voxels. Strain distribution of the entire specimen can then be calculated using appropriate displacement strain relations. Application of this technique to strain mapping of red sandstone and composite are presented.
-
development of interior strain measurement techniques using random speckle patterns
Meccanica, 2015Co-Authors: Fupen Chiang, Lingtao MaoAbstract:Experimental Stress Analysis is a well established mechanics discipline dealing with measuring Stress/strain in solids under load. Most techniques can only be applied to measuring strain of the surface. In this paper we review the development of techniques of using a random speckle patterns as a quantitative tool to mapping interior strain field of solids. After some elementary treatment of the basic principles of the speckle photography technique we describe three approaches that can probe the interior strain field of a transparent object. They are followed by a newly developed 3D strain measurement technique called digital volumetric speckle photography which can probe the interior of opaque materials as well.
Francesco Ginesu - One of the best experts on this subject based on the ideXlab platform.
-
A temporal phase unwrapping algorithm for photoelastic Stress Analysis
Optics and Lasers in Engineering, 2007Co-Authors: Antonio Baldi, Filippo Bertolino, Francesco GinesuAbstract:Photoelastic Stress Analysis is a full-field optical technique for Experimental Stress Analysis whose automation has received considerable research attention over the last 15 years. The latest developments have been made possible largely due to the availability of powerful calculators with large memory capacity and colour, high resolution, cameras. A further stimulus is provided by the photoelastic resins now used for rapid prototyping. However, one critical aspect which still deserves attention is phase unwrapping. The algorithms most commonly used for this purpose have been developed in other scientific areas (classical interferometry, profilometry, moire, etc.) for solving different problems. In this article a new algorithm is proposed for temporal phase unwrapping, which offers several advantages over those used today.
R E Rowlands - One of the best experts on this subject based on the ideXlab platform.
-
Experimental Stress Analysis of unsymmetrical irregularly shaped structure containing an arbitrarily shaped hole
2018Co-Authors: B Kalayciogli, A. Alshaya, R E RowlandsAbstract:This paper describes the ability to process load induced temperature information with an Airy Stress function in real polar coordinates and some local known boundary conditions to determine the Stresses Experimentally in an isotropic linear elastic finite arbitrarily-shaped structure containing an irregularly-shaped hole. The proposed method simultaneously smooths the measured data, separates the Stress components, and evaluates the individual Stress components full-field, including at the boundary of the hole (location of highest tensile Stress).
-
separating Stresses thermoelastically in a central circularly perforated plate using an airy Stress function
Strain, 2009Co-Authors: S J Lin, D R Matthys, R E RowlandsAbstract:: Thermoelastic Stress Analysis (TSA) is a contemporary full-field, non-contacting method of Experimental Stress Analysis. In a cyclically loaded structure which experiences adiabatic and reversible conditions, the measured local change in temperature is proportional to the change in Stress. Under isotropy, the technique measures information on the sum of the principal Stresses. As engineering analyses often necessitate knowing the individual components of Stress, additional Experimental methods or information are frequently required to ‘separate the Stresses’. The ability to evaluate individual Stresses reliably in a uniaxially loaded finite plate with a central circular hole from TSA-recorded information without supplementary Experimental data is demonstrated here. Measured temperature data are combined with an Airy Stress function and some limited traction-free conditions. The present inverse technique does not presuppose knowledge of the external geometry or boundary conditions, overcomes the traditional difficulties of unreliable edge data, and reduces the number of coefficients needed by satisfying the traction-free conditions analytically on the edge of the hole. Particular attention is paid to determining a realistic value for the needed number of Airy coefficients.
David Rowlands - One of the best experts on this subject based on the ideXlab platform.
-
thermoelastic Stress Analysis with a compact low cost microbolometer system
Quantitative InfraRed Thermography, 2013Co-Authors: Nik Rajic, David RowlandsAbstract:This article describes the development and validation of a novel thermoelastic Stress Analysis (TSA) system based on a low-cost microbolometer device. The use of a microbolometer for a highly synchronous and delicate temperature measurement breaks a longstanding and exclusive reliance on high performance, cooled photon detectors for thermoelastic applications. It is shown that despite markedly inferior noise equivalent temperature detectivity and dynamic response specifications, microbolometers are capable of achieving comparable levels of Stress measurement performance. The practical implications for Experimental Stress Analysis are significant. Microbolometers are relatively low in capital cost, small in size, have good tolerance to shock and vibration and consume less power than their photon counterparts, attributes that confer enormous practical advantages. It is argued that the emergence of TSA systems that are more affordable and better suited to in-service application could help to promote a much b...
Antonio Baldi - One of the best experts on this subject based on the ideXlab platform.
-
A temporal phase unwrapping algorithm for photoelastic Stress Analysis
Optics and Lasers in Engineering, 2007Co-Authors: Antonio Baldi, Filippo Bertolino, Francesco GinesuAbstract:Photoelastic Stress Analysis is a full-field optical technique for Experimental Stress Analysis whose automation has received considerable research attention over the last 15 years. The latest developments have been made possible largely due to the availability of powerful calculators with large memory capacity and colour, high resolution, cameras. A further stimulus is provided by the photoelastic resins now used for rapid prototyping. However, one critical aspect which still deserves attention is phase unwrapping. The algorithms most commonly used for this purpose have been developed in other scientific areas (classical interferometry, profilometry, moire, etc.) for solving different problems. In this article a new algorithm is proposed for temporal phase unwrapping, which offers several advantages over those used today.
